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Amirkabir Journal of Mechanical Engineering (20086032) (1)pp. 180-186
High-speed planetary gears, or more generally, gyroscopic systems are not preserve energy and therefore subjected to instability. In this research, the dynamic equations for double- helical planetary gear system in 3-D space and considering 6-DOF for each member are extracted. Then, the system stability in the range of critical speed is investigated. In the extraction of equations, the constant mesh stiffness is assumed and the gyroscopic effects due to rotating carrier are considered. The critical speeds of gyroscopic systems occur at speeds in which one or more natural frequencies are zero. To calculate the critical speeds, the eigenvalue problem of the system is solved by numerical methods. In order to validate the equations and the process of extraction of critical speed, the obtained results for a high-speed spur planetary gear system are compared with the results of the existing research. Finally, by plotting the variations of the real and imaginary parts of the Eigenvalues of the double-helical planetary gear system versus a range of carrier speeds investigate the system stability near critical speeds. The results of the current study indicate that the double- helical planetary gear system is stable at some critical speeds and in others subjected to divergence instability.
Amirkabir Journal of Mechanical Engineering (20086032) (3)pp. 61-70
The aim of this study is an investigate the effect of design parameters and profile modification on static transmission error and load sharing factor of helical gears using analytical method with Matlab software. In the first step, we define the concept of transmission error that is the source of noise in the gear pair. Then load sharing factor and static transmission error are calculated using the gear mesh stiffness. In this paper the total stiffness of helical gear’s and the load sharing factor is determined using an accumulated integral potential energy method. In the next, results are verified and the effect of design parameters on avarege and pick to pick of the helical gears transmission error and load sharing factor is investigated. This parameter is called macro-geometric parameters of gear pairs. At the end, we write a Matlab code to modify the tip relif of tooth to optimize the load sharing factor and static transmission error. The results of this study show that the simultaneous correction of macro-geometric modifications and profile modification (micro-geometric modifications) cause a more uniform load distribution and significantly reduce the transmission error of the helical gear and consequently reduce the noise and vibration of the gearboxes.
International Journal of Engineering, Transactions B: Applications (1728144X) 39(1)pp. 44-58
Bevel gears are a kind of gears that transmit power between two intersecting shafts. Bevel gears with Octidal and spherical involute profiles are the most common types of bevel gears. The profile of spherical involute teeth is a three-dimensional complex surface, requiring an accurate geometric definition calculation. Due to this complex geometry, modeling, stress-strain analysis, and mesh stiffness calculation are very difficult. In this study by extracting Napier’s Equations from the tooth profile geometry, geometric parameters of the spherical involute curve have been calculated. The results show that the pitch cone angle has an important effect on the shape of the spherical involute curve, so choosing the correct angle is particularly important. A significant increase in the azimuthal angle is observed by increasing the polar angle. In addition, increasing the angle of the pitch cone reduces the curvature of the side surfaces of the teeth and facilitates the manufacturing process. On the other hand, reducing the pressure angle will result in flat lateral surfaces and a tooth shape similar to the octoidal tooth. The sphere radius variations do not affect the shape of the tooth and only change the size of the tooth. Finally, a gear system comprising a pinion and gear was made from Polylactic Acid (PLA) utilizing the calculated angles to verify the accuracy of computed angles. Also, experimental and finite element methods determined the pinion and gear contact pattern. There was a good agreement between the finite element simulation and the experimental observation. ©2026 The author(s).
Arabian Journal for Science and Engineering (21914281) 50(4)pp. 2663-2689
Parametric study of ductile material forming processes for optimization of damage that occurs in the production stages of the parts will lead to better quality, performance, durability, and reduced production costs. Additionally, implementing an appropriate criterion that accurately predicts and simulates damage growth in the production of a part is an essential step in the optimization process. This research investigates the optimization and minimization of the final damage in a gudgeon pin produced by a two-stage cold extrusion process. First, numerical simulations are performed using the modified Lemaitre’s damage criterion, which provides an accurate estimate of damage growth in combined tensile and compressive loads. In the following, two methods for optimizing the parameters of each extrusion cold die are examined, and the magnitude of the final damage in the product is compared. In the first method, the design of the Taguchi experiment is implemented. In the second method, by implementing and training an artificial neural network and transferring the results to the genetic algorithm, the optimization of the die parameters is investigated to minimize the final damage in the product. A comparison of the results in the two mentioned methods shows that the final damage in the product is less than the critical damage value in both methods. Also, the neural network method will lead to less final damage in the product in comparison with the design method of the Taguchi experiment. © King Fahd University of Petroleum & Minerals 2024.
Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science (20412983)
The spherical involute is one of the most important profiles used in bevel gear design. Spherical involute bevel gears have excellent features, such as insensitive to shaft angle variations, low sensitivity to transmission errors, and favorable wear conditions compared to planar involute bevel gears. These unique characteristics will establish the spherical involute as the standard for bevel gears. In this study, the mesh stiffness of spherical involute bevel gears has been calculated for the first time using three approaches: analytical, finite element, and experimental methods. The results of all three methods are consistent with each other. The maximum difference between the results of the proposed analytical and the experimental procedure is about 8.4%, which shows the high accuracy of the proposed experimental method. Also, the mesh stiffness of the spherical involute gear has been compared with the planar involute bevel gears. Furthermore, the impact of contact ratio and pressure angle on variations of mesh stiffness has been examined. The results indicate that increasing the pressure angle and contact ratio enhances the mesh stiffness in bevel gears with a spherical involute profile. © IMechE 2025
Measurement: Journal of the International Measurement Confederation (02632241) 224
The mesh stiffness is a necessary and influential parameter in system dynamics modeling and vibration analysis of straight bevel gear systems (SBG). A new experimental method, employing a laser extensometer (LE) and an innovative setup, is developed to calculate the mesh stiffness in both healthy and cracked systems. An analytical method based on potential energy and tooth root crack modeling is also proposed. Both methods were implemented on healthy and cracked gear systems with varying crack depths. The new LE experimental method's results are compared with those obtained from the proposed analytical method. The results showed good agreement between both methods, indicating that the newly proposed experimental method considers all parts of mesh stiffness and is suitable for measuring mesh stiffness in both healthy and cracked SBG systems. © 2023
Measurement: Journal of the International Measurement Confederation (02632241) 238
The mesh stiffness plays a crucial role in influencing the performance and behavior of straight bevel gear (SBG) systems. Precisely determining the mesh stiffness enables to assess the SBG system's dynamic behavior more accurately and anticipate potential concerns such as crack identification and noise reduction. A novel experimental method is developed, employing experimental modal analysis associated with metaheuristic algorithms and an innovative setup. This method effectively determines the mesh stiffness in healthy and cracked systems. Additionally, an analytical method based on the potential energy associated with crack modeling is proposed. Both methods are implemented on SBG systems with varying crack depths. The results obtained from the experimental method are compared with those from the analytical method, revealing good agreement between them. This demonstrates that the newly proposed experimental method effectively considers all parts of mesh stiffness and is appropriate for determining the mesh stiffness in healthy and cracked SBG systems. © 2024
Nonlinear Dynamics (0924090X) 112(14)pp. 11945-11970
The tooth crack identification through the effect of the tooth root crack on nonlinear vibration behaviors in a straight bevel gear (SBG) system is sought. The mesh stiffness is evaluated through an analytical method based on the potential energy and Tredgold approximation associated with tooth root crack modeling. A 10-dof model is developed for the SBG system where the backlash nonlinearity is of concern. To assess the nonlinear vibration behaviors of the SBG system, first, the dynamic response is extracted analytically with the proposed dynamic model, and experimentally with a designed setup, then the extracted response is assessed based on the different crack identification statistical factors. Results indicate that the Skewness is the most effective factor in identifying the crack in the SBG system with backlash nonlinearity, compared to other investigated factors. The nonlinear vibration response as a time history, phase diagram, Poincaré map, modal analysis, and mesh stiffness FFT spectrum is analyzed and recommended as an appropriate indicator for tooth root cracks. The modeled mesh stiffness and simulated SBG system are verified by applying FEM and the experimental method. Graphical abstract: (Figure presented.) © The Author(s), under exclusive licence to Springer Nature B.V. 2024.
International Journal of Material Forming (19606206) 16(3)
The material properties of the strip play a vital role in the power consumption and the damage evolution in a tandem cold rolling mill. Therefore, the strip tearing or power consumption level of importance is not the same for different materials. Besides, various reduction schedules can be proposed for the specified total reduction and initial strip thickness in the tandem cold rolling process. An important goal that the reduction patterns should be met is to minimize power consumption and damage evolution simultaneously. Firstly, the level of importance of saving energy and strip tearing should be calculated for each material to find a reduction schedule. For this purpose, the Bao-Wierzbicki (BW) ductile damage criterion is selected and calibrated by the hybrid experimental–numerical method for five widely used carbon steel alloys. Then, the fracture loci of selected materials are constructed and implemented into an explicit finite element code. A five-stand tandem rolling mill is simulated numerically in which the flattening phenomenon of the rollers is considered. By comparing the simulation results, an indicator is introduced for the comparison of steel grades in terms of the rolling power consumption and damage evolution in a specified rolling program. Afterward, the Pareto optimality is undertaken to optimize the power-damage objective function. This paper presents a new method for determining the importance of damage evolution and power consumption based on material properties. This method significantly reduces energy consumption and the probability of strip tearing simultaneously in a tandem cold rolling mill. © 2023, The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature.
Mechanics Based Design of Structures and Machines (15397742) 51(8)pp. 4452-4466
Continuum damage mechanics (CDM) studies the deterioration of mechanical properties in materials that leads to material failure. The Lemaitre’s ductile damage model is known as a suitable criterion for damage growth in ductile materials. The standard Lemaitre’s model cannot accurately predict the damage growth in most of bulk metal forming processes with a combination of tension and compression loadings. In this paper, first, an explicit step-by-step algorithm of the Lemaitre’s ductile damage model conjugated with the crack closure effect in compressive loadings is provided and directly presented for the computational implementations. Then, employing the proposed algorithm, a user-defined material subroutine is developed and implemented. In the following, a few bulk metal forming processes under compressive loadings are numerically simulated. Finally, the numerical simulation results are compared with the prediction results of the standard model and also experimental tests. The comparison confirms the high precision of the modified model vs. the standard model. Hence, it is concluded that the modified Lemaitre’s model can truly predict the damage behavior of ductile materials in bulk metal forming processes with combined tensile and compressive loadings. © 2021 Taylor & Francis Group, LLC.
Mechanical Systems and Signal Processing (08883270) 164
A stochastic interpretation of the stick/slip mechanism is proposed to model and mitigate the complicated friction interaction that occurs between surfaces, with direct implications on the stability of dynamic mechanical systems involved. Most investigations dealt with the estimation of such stability regions in a deterministic framework. A realistic approach is to consider random aspects in the analysis of complex dynamic behaviors. In the present article, a stick–slip nonlinear model possessing multiple periodic solutions is considered under fluctuating random excitations. The time evolution of the probability density function is studied by employing an adaptive path integration method and then compared through Monte-Carlo simulations. A parametric study is performed on characteristics such as noise intensity and initial distribution. The physical example employed will permit to assume the entrance of noise through a first-order linear filter. Results reveal that the randomness factor extremely affects the probability of occurrence of each solution, justifying the application of such analyses in reliability-related studies and situations where sensitivity to randomness is acute. © 2021 Elsevier Ltd
Archive of Applied Mechanics (14320681) 91(4)pp. 1859-1878
During tandem cold rolling mill process, strip tearing reduces production rate, damages the rollers, and consequently decreases efficiency of production. Predicting and postponing of this phenomenon leads to less expensive trial and errors in rolling industries. In this research first, DIN1623 St12 steel which is frequently applied in metal forming industries and also Bao–Wierzbicki ductile damage criterion is selected. Then, six curve fitting methods are employed to calibrate the material and are presented in 2D space of equivalent plastic strain to fracture and stress triaxiality. Finally, the achieved fracture loci are validated by comparing corresponding simulation results with experimental tests and the best curve fitting method with aims of high accuracy for tracking the strip tearing in a tandem cold rolling mill process and fewer numbers of required tests is revealed. Eventually, due to engaging this innovative approach, it is possible to trace the strip tearing in tandem cold rolling mill process by performing only two simple tensile tests. Therefore, it is concluded that strip tearing phenomenon can be precisely predicted in tandem cold rolling mill processes by a special focus on calibration of the Bao–Wierzbicki damage criterion in the range of low positive stress triaxiality which causes less number of needed tests. © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH, DE part of Springer Nature.
Archive of Applied Mechanics (14320681) 91(10)pp. 4163-4177
The damage of materials is the progressive or unexpected deterioration of mechanical strength because of loadings, thermal or chemical effects. The micromechanical damage process of ductile materials is generally studied by the continuum damage mechanics (CDM). One of the most well-known damage models is the Lemaitre’s ductile damage criterion. This model only requires one material-dependent parameter to represent damage evolution. In this investigation first, a novel numerical approach is proposed to determine the Lemaitre’s ductile damage parameter. Then, a user-defined material subroutine founded on the Lemaitre’s ductile damage model is developed. Following, numerical results are achieved for a standard round tensile test specimen. Finally, to validate the suggested method, experimental tests are carried out and compared with the numerical results. The comparison reveals a good agreement and excellent correlation between the numerical and practical results. Hence, it is concluded that the offered numerical approach can accurately determine the Lemaitre’s ductile damage parameter as well as the damage behavior of ductile metals. © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.
Journal of Mechanical Science and Technology (1738494X) 35(10)pp. 4617-4625
Internal ring gears have a wide application in planetary gearboxes and transmission systems. The mesh stiffness of planetary gearboxes is an essential parameter for dynamic and vibration analysis. No direct practical method for calculating the stiffness of the internal ring gear rim has been investigated yet to the authors’ knowledge. For the first time in this research, a practical method is presented to determine the stiffness of the internal ring gear rim with an appropriate accuracy based on strain energy. To accomplish this goal, every part of the internal ring gear rim, which is between two consecutive pins or bolts, is modeled as a curved beam. The deflection of the curved beam is determined according to Castigliano’s theorem. Then, the stiffness of the internal ring gear rim is obtained through this deflection. Fourier’s series of deflections are calculated to make analytical results more comfortable to use. Finally, the analytical results are validated by FEM using ABAQUS software. © 2021, The Korean Society of Mechanical Engineers and Springer-Verlag GmbH Germany, part of Springer Nature.
Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications (20413076) 235(10)pp. 2266-2275
Gear systems are the most useful and essential power transmission systems in the high-speed industry due to their accuracy. It is necessary to make sure that these systems work without defects such as tooth cracks. Therefore, detecting the location and depth of cracks in gear systems is very important. In this research, a new approach is proposed to detect the crack location, and accordingly, some statistical indicators are used to estimate the crack depth in the helical gear tooth. To this end, after explaining the helical gear mesh stiffness and tooth-root crack modeling, the helical gear pair dynamic is modeled. Then, the vibration data of a helical gear system is obtained by an experimental test rig, and the moving average method is undertaken to precisely detect the crack location. The crack depth ratio is estimated using the crest factor, impulse factor, clearance factor, and (Formula presented.) and (Formula presented.) which are applied to the simulation results and the experimental signal. According to these results, the crest factor, impulse factor, and clearance factor calculated the crack depth ratio with a good agreement, and the indicators (Formula presented.) and (Formula presented.) estimated it with a more significant error. Also, the average of estimated values is calculated, indicating a better result than each indicator alone. © IMechE 2021.
International Journal of Non-Linear Mechanics (00207462) 131
In this study, the stochastic dynamic response of a spur gear pair model under the excitation of filtered noise is investigated. The spur gear pair is modeled as a single degree of freedom (SDOF) system in which nonlinear and non-smooth backlash and time-varying mesh stiffness as well as stochastic excitation are concurrently considered. Four cases are addressed, based on how the noise is incorporated in the loading terms. A first order filter is employed to generate various filtered noises with the same energy but different power spectrum. The combination of the SDOF gear model and the shaping filter leads to a (3D) Markov model. The numerical path integration (PI) technique is adopted to obtain the probabilistic response of the gear model using an adaptive time-stepping method in order to increase the accuracy of the time integration. A 4D system is also considered by applying a second order filter to model a narrow-band noise. The results are verified by comparing with Monte Carlo simulations. The effect of the noise spectrum on the probabilistic response is evaluated for different loading cases. The response PDF is of key importance in relation to reliability assessment of gear systems. © 2021 Elsevier Ltd
International Journal of Engineering, Transactions A: Basics (17281431) 33(10)pp. 2079-2086
Gear systems are one of the most functional power transmission systems in the industry. Crack is one of the common defects in gears which is caused by excessive loading, sudden impact and shortcomings in the gears construction. Initially, the crack will not result in structure collapse, but its growth can lead to irreparable damage. Therefore, detecting the crack and determining its location and depth are very important in this respect. In this paper, two encoders are used to obtain the spur gear pair transmission error speed. Moreover, the short-time averaging method (STAM) has been proposed thereby detecting the crack location and some statistical indicators have been used to estimate the crack depth in the spur gear tooth. For this purpose, a dynamical model in which mesh stiffness varying with time has been deployed to achieve the transmission error speed of the gear system. Additionally, a gear test rig including a single-stage gearbox, two encoders, and also an electronic board has been used. Encoders were installed on input and output shafts and the angular position of each shaft in time was saved in the computer using the electronic board. In addition, the transmission error speed was obtained by analyzing the received signals. Then, short-time averaging method was used to identify the crack location. Ultimately, some indicators such as ABS-max, FM0, Energy Ratio (ER) and Residual Signal Average were applied to the simulated results and experimental signals to fine the crack depth ratio. According to the results of this study, it seems safe to conclude that the STAM is a useful method in cracked tooth detection and the indicators have acceptable accuracy to find the crack depth ratio. © 2020 Materials and Energy Research Center. All rights reserved.
Jordan Journal Of Mechanical And Industrial Engineering (19956665) 13(2)pp. 69-74
Spur gear systems are widely used in power transmission systems in the industry. One of the common defects of the gears is tooth crack. Tooth crack increases the vibration and also generates noise. Previous studies have shown that tooth stiffness will decrease due to any crack and it is important to estimate the magnitude of reduction of tooth stiffness. This research suggests a new analytical approach for crack modeling and determining the reduction of time-varying gear mesh stiffness by Elastic Spring Method (ESM). Based on this approach, two or more cracks can be considered in one tooth. However, previous studies have primarily concentrated on one crack. In addition, it should be voted that each crack is replaced by one linear and one torsional spring in the present study. The results that were obtained from this method are validated through a comparison with Limit Line Method (LLM) and Finite Element Method (FEM). © 2019 Jordan Journal of Mechanical and Industrial Engineering. All rights reserved.
Journal of Mechanical Science and Technology (1738494X) 33(3)pp. 1115-1121
Gear systems are used to transmit power in the industry when accuracy and synchrony are needed and helical gear systems are used in more accurate and high-speed industries. It is important to ensure that these systems work faultlessly, therefore the detection of the crack location and situation is very efficient in the gear systems. In this research, a new approach is proposed to detect the multi crack location and length in the helical gear teeth. To this end, after giving an explanation of helical gear mesh stiffness and demonstrating the helical gear pair dynamic modeling, the transmission error ratio method is used to detect the cracks locations and lengths. Then, according to solved examples, when the cracks locations are far enough that their effects on the transmission error are completely separated, the cracked teeth and the lengths of cracks can be detected exactly, and when the cracks are in adjacent teeth, according to the cracks lengths and depths and their effects overlap, the number of cracks and their lengths can be detected exactly, approximately or absolutely undetectable. © 2019, KSME & Springer.
Journal of Sound and Vibration (10958568) 447pp. 170-185
This study is purposed to enhance conventional spur gear models by moving from a deterministic to a stochastic representation, based on adding a Gaussian white noise in the loading terms while including the effect of both backlash and time-varying mesh stiffness. Meanwhile, an efficient numerical path integration (PI) technique is used to obtain the probability distribution functions (PDFs) of the response. A novel adaptive time-stepping scheme is proposed for the PI method that momentarily increases its accuracy in order to detect the edge of transition when dealing with the non-smoothness due to backlash. The results demonstrate good agreement with Monte Carlo simulation (MCS). It is observed that if the initial distribution covers a region containing the basins of attraction of coexisting solutions, the stationary PDF will be formed around both of their deterministic solutions. The resulting response PDF contains subtle information about the system, which is essential in the design of its parts and its reliability assessment. The generality of the approach is such that the new path integration method can be implemented for the stochastic analysis of other non-smooth random dynamical systems. © 2019 Elsevier Ltd
Journal of Mechanical Science and Technology (1738494X) 32(8)pp. 3537-3545
Time-dependent mesh stiffness is a most important reason of vibration and dynamic excitation in gear sets. In this research, analytical formulas of the helical gear set and the planetary gear system are combined to calculate the time-dependent mesh stiffness of the helical planetary gear system. For this purpose, at the first step, the analytical equations are derived for the spur gear pair. Then by dividing a helical tooth into the several independent thin spur tooth slices, the helical gear pair mesh stiffness is extracted. Finally, these equations are extended to the helical planetary gear system. The suggested analytical results and those which obtained by the finite element method (FEM) are compared and are in good agreement when the helix angle is less than 15 degrees. Also, the helical planetary gear system mesh stiffness in different cases such as fixed carrier, fixed sun gear and fixed ring gears is calculated. These results show that the value of mesh frequency ratio in each case scales the mesh stiffness shapes in the rotation angle direction. In other words, mesh frequency ratio parameter determines the number of meshing period in each rotation of planets. © 2018, The Korean Society of Mechanical Engineers and Springer-Verlag GmbH Germany, part of Springer Nature.
Aboutalebi, F.H. ,
Poursina, M. ,
Nejatbakhsh h., H. ,
Khataei m., M. Engineering Fracture Mechanics (00137944) 192pp. 276-289
In this research, first DIN1623 St12 steel is selected because of its remarkable formability and wide application in metal forming industries. As the main contribution and objective of the current study, a ductile damage model is proposed and calibrated for the selected material. For this goal, then damage parameters and fracture locus of the material are experimentally and numerically determined. Various convenient tensile tests on flat-grooved, pure tension and shear-tension specimens are employed, as the novelty of the investigation. Based on the experimental and numerical results, a relation between equivalent fracture strain and stress triaxiality is obtained. Finally, in order to validate the fracture locus, the determined damage parameters, and the damage model, extra tensile tests are experimentally performed on notched specimens and compared with numerical simulations. Comparison of the numerical results and observation tests reveals good conformity. Therefore, it is concluded that the presented ductile damage model can successfully and reliably predict damage initiation, propagation, and fracture of the material in metal forming processes. © 2017 Elsevier Ltd
Proceedings of the Institution of Mechanical Engineers, Part K: Journal of Multi-body Dynamics (20413068) 232(2)pp. 199-223
Gyroscopic effects may change the stability, dynamic behaviour and vibratory responses of the systems at high-speed applications in a significant manner. In this study, a new linear time-invariant lumped mass model in three-dimensional space is developed with a high emphasis on gyroscopic effects for a double-helical planetary gear system. In the developed model, each member has six degrees of freedom where both the mesh and the bearing stiffness are considered. The forced responses, due to gear mesh transmission error excitations, are calculated through the modal summation technique. The natural modes are extracted from the corresponding eigenvalue problem for the undamped system. The obtained results indicate the reduction in most of the natural frequencies by applying the gyroscopic effects in double-helical planetary gear systems. By considering the gyroscopic effects in this newly proposed model, the root mean square (RMS) amplitudes of vibration are changed in different directions. To verify this developed model and solution method, the obtained natural frequencies and forced responses are compared with those obtained in other studies. © IMechE 2017.
Journal of Mechanics in Medicine and Biology (17936810) 16(3)
The dynamic study of frog's swimming style contributes to the modeling of the nature-inspired robots. To study the torque matrix produced in the joints during continuous modeling, the dynamic model of the Xenopus laevis swimming is reproduced in the coronal plane. The necessary kinematic data for the modeling is extracted from the frog movement graphs and diagrams during swimming. In the dynamic model, legs are considered as a group of rigid links. In order to verify this method, the generated forward force in half a cycle is studied. Unlike the previous studies, the role of geometry, dimensions and mechanical properties of the legs' fundamental links in generating thrust force is modeled in this study, leading to finding the most proper form for this mechanism design. © 2016 World Scientific Publishing Company.
International Journal of Advanced Manufacturing Technology (02683768) 78(9-12)pp. 1827-1835
A new method for prediction of forward slip in the tandem cold rolling mill without the velocity meter sensors based on rolling geometry is proposed here. According to this proposed method, an algorithm is developed for online estimation of friction coefficient and strip’s behavior. Online exertion of friction coefficient and strip’s behavior in the rolling’s program results in better control. So, the unsaturated actuators are satisfied and the possibility of strip tearing is decreased. The strip’s material is st12. The material is considered elastic-plastic, homogenous, and it follows the Ludwick’s constitutive equation law. The yield stress of strip and Young modulus are determined by simple tension test on a specimen of strip before rolling. For validation of the developed scheme, two operating samples are considered and the results are compared with the available literature. © 2015, Springer-Verlag London.
International Journal of Engineering, Transactions B: Applications (1728144X) 28(8)pp. 1247-1254
Radial forging is an open die forging process used in reducing the diameters of shafts, tubes, stepped shafts and axles in addition to creating internal profiles such as rifling the gun barrels. The radial forging of tube is usually performed over a mandrel to create an internal profile and/or size the internal diameter. Most of the previous studies conducted on the radial forging process have used axisymmetric models. In this study, the residual stresses of a short hollow tube in a cold radial forging process is assessed through 3-D finite element simulation. The mandrel used here contains six helical grooves and two steps along its length. This kind of mandrel is innovated in this research. The workpiece is modeled as an elastic-plastic material and the commercial finite element software, ABAQUS is used to simulate the process. The accuracy of the finite element model is tested by comparing the predicted results with available experimental works and is validated by both the slab and upper bound methods. Residual stresses in the radial forged product and influence of the process parameters on stress distribution, such as workpiece motions, friction and percentage of reduction are studied to determine the optimized parameters of simulation and improve the condition of this process.
Neural Computing And Applications (09410643) 24(5)pp. 1123-1133
The superposition of work roll initial crown, the work roll bending and flattening crown, the work roll wearing crown and the work roll thermal crown makes the final hot strip. In this paper, new models based on numerical method have been obtained to predict the roll force, the work roll wearing crown and the work roll thermal crown utilizing experimental data provided by Mobarake Steel Complex. Meanwhile, the work roll bending and flattening crown has been obtained from finite element method as well as elasticity approach. Then, a computer programing has been written to obtain the work roll initial crown in order to get desired strip profile. This program is called Initial Crown Prediction Software (ICPS). Finally, the obtained initial crowns from ICPS were applied for different stands of hot strip mill of Mobarake Steel Complex, and the strip profile shows a good agreement with the desired one for the mentioned mill. © 2013 Springer-Verlag London.
Neural Computing And Applications (09410643) 25(3-4)pp. 849-858
The application of finite element method and intelligent systems techniques to predict the applied force during the radial forging process is studied. Radial forging is a unique process used for the precision forging of round and tubular components, with or without an internal profile. More than 800 radial forging machines are currently operating worldwide. Since the maximum forging force per die is constant, determining the die force before the process can prevent die damage and material wastage. Then, the results of the FE simulation are applied for two intelligent forecasting systems in artificial neural network and adaptive neuro-fuzzy inference system. Initial billet temperature, die inlet angle, feed rate, and reduction in cross-section are applied as input parameters, and radial forging force is applied as the output parameter. Finally, the results of these two intelligent systems are compared with the multiple regressions method. A sensitivity analysis is carried out to determine how the radial forging force is influenced by the input parameters. © 2014 Springer-Verlag London.
Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science (20412983) 227(8)pp. 1633-1649
In many modern continuous production lines of steel sheets, a twist roll machine is used to change the strip direction for shortening the production line. A twist roll machine typically consists of a cylindrical body on which some guide rollers are mounted in rows to gradually change the traveling direction of the strip when passes over the guide rollers. In this article, quality of the sheets after exiting an industrial twist roll machine is first investigated. The amount and distribution of wear on the guide rollers are also assessed by measuring and comparing diameter at different sections of selected worn and new guide rollers. The specific wear rate as well as friction coefficient for guide rollers made of two different popular polymers is measured by pin-on-disk wear tests. Details of the strip path on the twist roll machine as well as contact between the strip and all the guide rollers are specified, and stress distribution in strip and the guide rollers is studied by finite element analysis. Effects of the guide rollers material and arrangement, the bridle rolls tension, and width and thickness of the strip on the amount and distribution of wear on the guide rollers as well as the elasto-plastic response of the strip are studied. The results are utilized to propose techniques for reducing defects on the sheet and the guide rollers, and finite element simulations show the effectiveness of these techniques. © 2012 IMechE.
Journal of Mechanical Science and Technology (1738494X) 27(3)pp. 783-792
Rotary draw tube bending is one of the most complex tube forming processes subject to different process parameters such as material properties and geometry. This process is being practiced in more and more applications in industry due to its high efficiency, high forming precision and quality. However, improper process parameters can lead to wrinkling which restrict the thin walled tube bending. Therefore, the prediction and prevention of wrinkling is very important. Despite its importance, the effect of anisotropy on the occurrence of wrinkling was not considered in the literature up to now. In this investigation, a quantitative study on the wrinkling of thin walled tube bending is carried out through a finite element model of the process using velocity integral parameter, which is used for the detection of wrinkles. The other methods usually warn the wrinkling initiation with no precise location prediction. In addition, the effects of some process parameters, specially normal and planar anisotropy on the tube wrinkling are investigated. It is shown that increasing normal and planar anisotropy (increasing r0 and r90 values) result in a decrease in tube wrinkling. © 2013 The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg.
International Journal of Engineering, Transactions A: Basics (17281431) 26(1)pp. 83-89
Thin-walled tube bending has common applications in the automobile and aerospace industries. The rotary-draw-bending method is a complex physical process with multi-factor interactive effects and is one of the advanced tube forming processes with high efficiency, high forming precision, low consumption and good flexibility for bending angle changes. However, it may cause a wrinkling phenomenon, over thinning and cross-section distortion if the process parameters are inappropriate. Wrinkles propagate in thin-walled tube, but in some cases, localize in a finite zone and lead to failure. Wrinkling prediction in thin-walled tube bending processes has been an important and challenging subject in the related industry. In this paper, the plastic deforming behavior and wrinkling mechanism for a thin-walled tube is simulated and the results are compared with the available experimental ones. Next, the effect of anisotropy on ovalization, thickness and wrinkling of tube is investigated using Finite Element Method (FEM). Numerical results are presented showing the effects of various kinds of materials and geometric parameters on wrinkling using anisotropic yield function.
Simulation Modelling Practice and Theory (1569190X) 22pp. 61-73
It is well known that tandem cold rolling is one of the most widely used processes in the manufacture of various sheet products with high accuracy and production rate. This paper deals with an optimization problem for tandem cold rolling. A genetic algorithm is developed to optimize the reduction schedules from the power consumption and damage evolution points of view. Damage-coupled finite element simulations are employed to determine the damage objective function. The dominant parameters of the rolling process are calculated using an experimental-analytical model, obtained from an industrial tandem rolling mill. Generally, in rolling process damage and power have conflicting natures and none of them can be improved without degrading the other. In this paper, in the first step, power and damage are optimized independently and some reduction schedules are introduced to minimize power consumption or damage evolution during the process and the results are compared with the experimental observations. Afterwards power and damage are optimized simultaneously by defining a multi-objective function and employing the Pareto optimality; a set of optimized reduction schedules are provided to optimize the power and damage based on the preference ordering of the decision makers in tandem mill. This multi-objective optimization enables the mill operators to select the most appropriate optimized schedule according to the mill necessities. Finally the optimal schedules are numerically simulated to investigate the efficiency of the damage optimized schedule. © 2011 Elsevier B.V. All rights reserved.
Simulation Modelling Practice and Theory (1569190X) 19(2)pp. 612-625
Strip tearing during tandem cold rolling is one of the manufacturing issues in the rolling industry that can significantly increase production costs. In this paper, an explicit finite element code coupled with the improved Lemaitre damage model is developed to predict strip tearing in a five-stand tandem rolling mill. The simulation results are validated using experimental data from an industrial rolling mill, and there is good agreement between the numerical and experimental results. Some factors related to strip tearing, such as friction coefficient variations, thickness difference between two welded strips and reduction schedule, are introduced, and their influence on the damage evolution through the strip during the process is investigated by using damage-coupled finite element simulations. © 2010 Elsevier B.V. All rights reserved.
Journal of Mechanical Science and Technology (1738494X) 25(7)pp. 1675-1685
Impact is very common source of noise in the industries. The impacts can be visible, such as forging, and can be invisible, such as impacts due to clearance of hinges. As a result of this generality, the control of impact noise needs more attention. Reduction of this tiresome noise needs enough perception about the impact. A study of this noise sources presents difficult problems both theoretically and experimentally. This is partly due to the many complex interconnected mechanical phenomena that occur and partly due to the fact that usual steady-state techniques of analysis cannot be applied. In such complex problems numerical techniques can help to acousticians. To gain some insight into this source of sound, in this paper collision of two steel spheres are studied with finite element method (FEM). Then the FEM results were compared with experiments to show authority of this numerical method to simulate impact noises. FEM results show that if the vibrational modes are excited by impact, the vibrational modes can be as effective as rigid body motion. © 2011 The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg.
International Journal of Advanced Manufacturing Technology (02683768) 53(1-4)pp. 157-165
St14 steel (DIN 1623) is widely used in sheet metal forming industries because of its remarkable formability and also its low price. In this paper, damage behaviour of St14 steel is studied in order to be used in complex forming conditions with the goal of reducing the number of costly trials. Damage parameters of St14 steel have been determined by using standard tensile and Vickers micro-hardness tests. A fully coupled elastic-plastic-damage model has been developed and implemented into an explicit code. With this model, damage propagation and crack initiation, and ductile fracture behaviour of drilled and notched specimens are predicted. The model can quickly predict both deformation and damage behaviour of the part because of using plane stress algorithm, which is valid for thin sheet metals. Experiments are also carried out to validate the results. It is concluded that finite element analysis (FEA) in conjunction with continuum damage mechanics (CDM) can be used as a reliable tool to predict ductile damage and fracture of St14 steel.
AIP Conference Proceedings (0094243X) 1383pp. 477-483
In the deep drawing process, determination of the drawing depth and prediction of the time and the place that fracture occurs has been one of the important case studies which engineers tend to take into account. Because of a drastic reduction in design and manufacturing expenditures, numerical methods are extended to calculate the drawing depth during the process. In this paper, ductile damage model in which the stress triaxiality and equivalent strain are the most effective parameters on the damage growth and fracture of the material is used to predict fracture. For prediction the place and time of ductile fracture, according to ductile damage criteria, the fracture strain for various stress triaxiality values should be determined. To obtain the parameters of ductile damage model for St12 steel, some tensile tests have been performed on the notched specimens. Numerical simulation of deep drawing was performed using commercial finite element ABAQUS. Results obtained from simulation are in good agreement with the experimental ones and emphasize that using ductile damage model is appropriate to anticipate the place and time of the fracture during the deep drawing process. © 2011 American Institute of Physics.
AIP Conference Proceedings (0094243X) 1383pp. 187-193
Thin-walled tube bending has found many of its applications in the automobile and aerospace industries. The rotary-drawbending method which is a complex physical process with multi-factor interactive effects is one of the advanced tube forming processes with high efficiency, high forming precision, low consumption and good flexibility for bending angle changes. However it may produce a wrinkling phenomenon, over thinning and cross-section distortion if the process parameters are inappropriate. Wrinkles propagate permanently in thin-walled tube, but finally, localize in a finite zone and lead to failure. The prediction of wrinkling in thin-walled tube bending processes has been a challenging topic. In this paper, firstly, the plastic deforming behavior and wrinkling mechanism for a thin-walled tube is simulated and the results will compare with the available experimental ones. Then, the effect of anisotropy on ovalization, thickness and wrinkling of tube will be investigated using FEM. Extensive numerical results are presented showing the effects of the various kinds of materials and geometric parameters on wrinkling using anisotropic yield function. © 2011 American Institute of Physics.
AIP Conference Proceedings (0094243X) 1252pp. 1303-1308
In a metal forming process, the state of stress is one of the most important parameters on forming and behavior of the material. According to ductile damage criteria, the magnitudes of fracture strain for various stress triaxiality values should be determined for prediction of the place and time of ductile fracture. In this paper, the magnitudes of fracture strain of St12 steel is measured using several tensile tests on notched samples. Johnson-Cook equation for fracture strain as a function of stress triaxiality is calibrated for St12 steel, using the obtained experimental data. The accuracy of this function is achieved by comparison of the FEM results with experimental data which are achieved during simple tension and Erichsen tests. The simulation results have shown that the ductile damage model is a suitable criterion for prediction of fracture in St12 steel. In addition, notched samples tensile tests are suitable for calibration of Johnson-Cook equation for St12 steel. © 2010 American Institute of Physics.
International Journal of Engineering, Transactions B: Applications (1728144X) 23(3-4)pp. 233-241
Fullering process is a type of open die forging. In this research, elongation and maximum sideways spread in final shape of a billet after the first blow of a fullering process are predicted by designing a back propagation multilayer perceptron neural network. Several experiments are conducted using lead as the model material. Billets with three different square cross-sections are used in these experiments. These fullering physical investigations are performed to simulate the elongation and maximum sideways spread in the final shape of the billet at the end of the first blow of the process. In addition, ring compression tests are undertaken in the quantitative determination of the friction coefficient for three kinds of lubricants. In the training of neural network width of billet, friction coefficient, height of the final shape, and die length are used as the input data. Elongation and maximum sideways spread in the final shape of the billet are the specified outputs. As a result of the specified parameters, the program is able to estimate the elongation and maximum sideways spread for any given input variables instead of time consuming experimental processes or finite element simulations.
In this paper, an approach for prediction deformation of upsetting processes is developed. The approach combines the finite element method and Neural Network to view the resultant deformation changes in upsetting. Because real time deformation simulation is a time consuming repeated analysis, the neural networks are employed in this work as numerical devices for substituting the finite element code needed for the upsetting deformation. The input data for the artificial neural network are a set of parameters generated randomly (aspect ratio d/h, material properties , temperature and coefficient of friction). The output data are the coefficient of polynomial that fitted on barreling curves. Neural network was trained using barreling curves generated by finite element simulations of the upsetting and the corresponding material parameters. This technique was tested for three different specimens and can be successfully employed to determine barreling curve.
Chinese Journal of Polymer Science (English Edition) (02567679) 27(2)pp. 221-229
Preform permeability is an important process parameter in liquid injection molding of composite parts. This parameter is currently determined with time consuming and expensive experimental procedures. This paper presents the application of a back-propagation neural network to predicting fiber bed permeability of three types of reinforcement mats. Resin flow experiments were performed to simulate the injection cycle of a resin transfer molding process. The results of these experiments were used to prepare a training set for the back propagation neural network program. The reinforcements consisted of plain-weave carbon, plain-weave fiberglass, and chopped fiberglass mats. The effects of reinforcement type, porosity and injection pressure on fiber bed permeability in the preform principal directions were investigated. Therefore, in the training of the neural network reinforcement type, these process parameters were used as the input data. Fiber bed permeability values were the specified output of the program. As a result of the specified parameters, the program was able to estimate fiber bed permeability in the preform principal directions for any given processing condition. The results indicate that neural network may be used to predict preform permeability. © 2009 World Scientific Publishing Company.
International Journal of Material Forming (19606206) 1(SUPPL. 1)pp. 371-374
Radial forging is an incremental forming process, where the total deformation is achieved by successive individual forming steps. Most researchers investigating radial forging processes have used axisymmetric models. In this research, multi-pass hot radial forging of short hollow and solid products are investigated using a 3-D finite element simulation. The workpiece is modeled as an elastic-viscoplastic material. Three-pass radial forging of solid cylinder and tube products are simulated. Temperature, stress, strain, and metal flow distributions are obtained in each pass through a 3D thermo-mechanical simulation. Finally, the results of 3D FEM models are compared with results obtained by axisymmetric FEM models from previous work and with available experimental data. © Springer/ESAFORM 2008.
International Journal of Material Forming (19606206) 1(SUPPL. 1)pp. 17-20
In this paper both back-propagation artificial neural network (BPANN) and regression analysis are employed to predict the maximum downward deflection of the exit profile in roll-forming of symmetric channel section. To prepare a training set for BPANN, some finite element simulations were carried out. Sheet thickness, flange width, fold angle and friction coefficient were used as the input data and the maximum downward deflection as the specified output used in the training of neural network. As a result of the specified parameters, the program will be able to estimate the maximum downward deflection of the exit profile for any new given condition. Comparing FEA and BPANN results, an acceptable correlation was found. © Springer/ESAFORM 2008.
Journal of Materials Processing Technology (09240136) 199(1)pp. 287-294
This paper considers re-assessment of the material behavior of stainless steels 1.4021 and 1.4841 using the compression test at medium strain and high temperature (1100 °C), for forming simulation, and compares the result of the forging test with the finite element simulation predictions using the derived constitutive equations; thus making a link between the numerical simulation and the experimental results that can justify both the modeling hypotheses of the simulation, and the assumptions used for measurements in the experimental test. Tests are carried out using a dilatometer for different strain rates. To decrease the role of friction, both the geometry of specimens and the lubricant used should be optimized. Norton-Hoff, logarithmic, Perzyna and Peirce constitutive equations are examined to find out the best coverage of the flow stress curves. The validity of the suggested constitutive equation is reconfirmed by comparing the geometrical deformation of the specimens and numerical simulation of the compression test. © 2007 Elsevier B.V. All rights reserved.
AIP Conference Proceedings (0094243X) 908pp. 963-968
Radial forging is an open die forging process used for reducing the diameter of shafts, tubes, stepped shafts and axels, and creating internal profiles for tubes such as rifling of gun barrels. In this work, a comprehensive study of multi-pass hot radial forging of short hollow and solid products are presented using 2-D axisymmetric finite element simulation. The workpiece is modeled as an elastic-viscoplastic material. A mixture of Coulomb law and constant limit shear is used to model the die-workpiece and mandrel-workpiece contacts. Thermal effects are also taken in to account. Three-pass radial forging of solid cylinders and tube products are considered. Temperature, stress, strain and metal flow distribution are obtained in each pass through thermo-mechanical simulation. The numerical results are compared with available experimental data and are in good agreement with them. © 2007 American Institute of Physics.
AIP Conference Proceedings (0094243X) 907pp. 487-492
One of the main objectives of forging process design is to ensure adequate metal flow in the dies so that the desired finished part geometry can be obtained without any internal or external defects. This paper presents a preform design method which employs a new criterion based on shape complexity factor to determine the necessity of preform stages for axisymmetric forging parts. The presented criterion was tested on several examples using finite element method to verify the models. Comparison of the new shape complexity factor with the other ones shows that the new criterion is more accurate in estimating the number of preform stages. © 2007 American Institute of Physics.
International Journal of Mechanical Sciences (00207403) 49(5)pp. 622-634
Slab analysis of asymmetrical sheet rolling is presented by considering non-uniform normal and shear stress profiles across the section of product. An important phenomenon considered in this paper is the deflection of plate at entry to the deformation zone and the amount of which is predicted by using a genetic algorithm (GA). In the utilized GA, the elimination/replacement operator and a new operator called "the adaptive mutation" are developed in order to increase the efficiency of the search. Shear stresses are taken into account in applying the Von-Mises yield criterion, and it is shown that this improves the accuracy of the model. Rolling force and pressure distribution predicted by the present model are shown to be in good agreements with the experimental and theoretical results of other investigators. © 2006 Elsevier Ltd. All rights reserved.
AIP Conference Proceedings (0094243X) 907pp. 951-956
Resin flow analysis in the injection cycle of an RTM process was investigated. Fiberglass and carbon fiber mats were used as reinforcements with EPON 826 epoxy resin. Numerical models were developed in ANSYS finite element software to simulate resin flow behavior into a mold of conical shape. Resin flow into the woven fiber mats is modeled as flow through porous media. The injection time for fiberglass/epoxy composite is found to be 4407 seconds. Required injection time for the carbon/epoxy composite is 27022 seconds. Higher injection time for carbon/epoxy part is due to lower permeability value of the carbon fibers compared to glass fiber mat. © 2007 American Institute of Physics.
AIP Conference Proceedings (0094243X) 908pp. 1597-1602
This research focuses on the determination of thermal conductivity of single-walled carbon nanotube (SWCNT) composite materials using Finite Element Methods (FEM). The effects of SWNT array distribution on effective thermal conductivity of composites are investigated. The composite is analyzed at a microscopic scale by considering two fiber distribution patters: 1- a moderately aligned nano-array distribution, and 2- a random SWCNT nano-array distribution. A thermal conduction problem is solved in the composite domain to obtain the effective thermal conductivity in each case. A composite lamina with 12 percent SWCNT fiber volume fraction is investigated. ANSYS finite element software is used to perform the analysis. The results of FEM models are compared to thermal conductivities obtained using the weight-average formulations. Weight average formulations under-estimate the value of composite thermal conductivity. The effective thermal conductivity values obtained using the FEM models turned out to be much higher than the weight averaged results. © 2007 American Institute of Physics.
Journal of Materials Processing Technology (09240136) 174(1-3)pp. 325-333
Since 1980s the problem of manufacturing defect-free parts has been tackled with simulation tools. In this paper, a numerical method for shape optimisation of pre-form dies in a two-stage hot forging is presented. The object of optimisation is to eliminate work-piece defects that may arise during the forging process. A two dimensional finite element code has been developed for the simulation of the mechanical process and prediction of the defects. The material is incompressible and it follows the Norton-Hoff law. To deal with contact constraint, the velocity-projection algorithm is used. The optimisation method is based on a genetic algorithm supported by an elitist strategy. The developed scheme is used to design optimal pre-form dies for two axi-symmetric examples. The objective function is associated with the quality of the final product. Comparing the obtained optimal results with other articles justifies the proposed optimisation method. © 2006 Elsevier B.V. All rights reserved.
Poursina, M. ,
Antonio c.a.c., ,
Castro c.f., ,
Parvizian j., ,
Sousa l.c., Engineering Computations (02644401) 21(6)pp. 631-650
A numerical method for shape optimisation in forging is presented. The god of the optimisation is to eliminate work-piece defects that may arise during the forging process. A two-dimensional finite element code has been developed for the simulation of the mechanical process. The material is incompressible and it follows the Norton-Hoff law. To deal with contact constraint the velocity projection algorithm is used. The optimisation process is conducted using a genetic algorithm supported by an elitist strategy. A new genetic operator called adaptive mutation has been developed to increase the efficiency of the search. The developed scheme is used to design optimal preform shapes for several axisymmetric examples. Continuous and discrete design variables are considered. The objective function of the optimisation problem is associated with the quality of the final product. Comparing the obtained optimal results with the literature validates the proposed optimisation method.
