Spring-Back Evaluation of Stretch Bending Process Based on Chaboche Combined Isotropic-Kinematic Hardening Laws

2011 ◽  
Vol 204-210 ◽  
pp. 1745-1750 ◽  
Author(s):  
Jing Hu ◽  
Xiao Xing Li ◽  
Kwan Soo Chung ◽  
Rao Yao
Keyword(s):  
Kinematic Hardening ◽  
Spring Back ◽  
Stretch Forming ◽  
Forming Process ◽  
Hardening Law ◽  
Stretch Bending ◽  
User Subroutine ◽  
Bending Process ◽  
Chaboche Model ◽  
Simulation Results

We present a study on spring-back prediction in the stretching bending process using the Chaboche model combined isotropic-kinematic hardening law and Mises yielding criterion, and a material user subroutine (VUMAT, UMAT) program was developed base on the ABAQUS interface for the model. The effects of different hardening law on the spring-back in the stretch forming process was also analyzed and compared. The simulation results show that the combined isotropic-kinematic hardening law has the better spring-back prediction compared with the pure isotropic and kinematic hardening law in the stretch forming process, which is verified by the experimental results.

Effects of Part Geometry on Spring-Back/Spring-Go Feature in U-Bending Process

2013 ◽  
Vol 549 ◽  
pp. 100-107 ◽  
Author(s):  
Wiriyakorn Phanitwong ◽  
Arkarapon Sontamino ◽  
Sutasn Thipprakmas
Keyword(s):  
Laboratory Experiments ◽  
Fem Simulation ◽  
Work Piece ◽  
Spring Back ◽  
Forming Process ◽  
Bending Angle ◽  
Part Geometry ◽  
Bending Process ◽  
Metal Forming Process ◽  
Simulation Results

The U-bending process is a common sheet-metal forming process widely employed to fabricate sheet parts like channels, beams, and frames of various sizes applied in almost all industrial fields. In recent years, the precision requirements are increased on the U-bent parts. To achieve these requirements, in this study, the effects of part geometry on the spring-back/spring-go feature including work piece length, U-channel width, punch and die radii, and work piece thickness, were investigated by using the finite element method (FEM) and laboratory experiments. The FEM simulation results clearly revealed the influence of part geometry on spring-back/spring-go feature via the changes of stress distribution analyses on the bending allowance zone, the bottom of bent part, and the U-leg of bent part. Specifically, the part geometry affected on the bending characteristic on the bending allowance zone, as well as it affected on the spring-back feature. In addition, the part geometry also affected on the formation of reversed bending characteristic on the bottom and U-leg of bent parts, as well as it affected on the spring-go feature. The bending angle could be achieved by compensating these bending and reversed bending characteristics. Therefore, to meet the required bending angle, the suitable design of part geometry was strongly considered to maintain the balancing of the bending and reversed bending characteristics. The laboratory experiments were carried out to validate the accuracy of the FEM simulation results. The FEM simulation results showed good agreement with the experimental results with reference to the bending angle and bending force.

Numerical Evaluation of Crashworthiness of Automotive Sheets

2007 ◽  
Vol 345-346 ◽  
pp. 1537-1540
Author(s):  
Han Sun Ryou ◽  
Myoung Gyu Lee ◽  
Chong Min Kim ◽  
Kwan Soo Chung
Keyword(s):  
Crystal Structures ◽  
Yield Surface ◽  
Numerical Evaluation ◽  
Kinematic Hardening ◽  
Sheet Thickness ◽  
Back Stress ◽  
Yield Function ◽  
Chaboche Model ◽  
Simulation Results ◽  
Function Shape

Crash simulations were performed for automotive sheets. To understand the influence of crystal structures in sheet materials on crashworthiness, the effect of the yield function shape was studied by adopting the recently developed non-quadratic anisotropic yield surface, Yld2004-18p. The effect of the back-stress was also investigated by comparing simulation results obtained for the isotropic, kinematic and combined isotropic-kinematic hardening laws based on the modified Chaboche model. In addition, the effects of anisotropy and sheet thickness on crashworthiness were evaluated.

scholarly journals The Effect of Swinging Ball Heads with Different Arrangements in Multi-Point Stretch-Forming Process

Materials ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 337 ◽  
Author(s):  
Jian Xing ◽  
Yan-yan Cheng ◽  
Zhuo Yi
Keyword(s):  
Numerical Simulation ◽  
Finite Element ◽  
Sheet Metal ◽  
Strain Distribution ◽  
Finite Element Models ◽  
Stretch Forming ◽  
Forming Process ◽  
Forming Quality ◽  
Staggered Arrangement ◽  
Simulation Results

To improve the effect of multi-point stretch forming of sheet metal, it is proposed in this paper to replace a fixed ball head with a swinging ball head. According to the multi-point dies with different arrangements, this research establishes finite element models of the following stretch forming, i.e., fixed ball heads with conventional arrangement, swinging ball heads with conventional arrangement, swinging ball heads with declining staggered arrangement, and swinging ball heads with parallel staggered arrangement, and then numerical simulation is performed. The simulation results show that by replacing a fixed ball head with a swinging ball head, the surface indentation of the part formed was effectively suppressed, the stress and tension strain distribution of the part formed was improved, and the forming quality was improved; the thickness of the elastic pad was reduced, the springback was reduced and the forming accuracy was improved; and when the ball head was applied to a multi-point die with staggered arrangement, a better forming result was achieved, where the best forming result was achieved in combining the swinging ball heads with the multi-point die with a parallel staggered arrangement. Forming experiments were carried out, and the experimental results were consistent with the trend of numerical simulation results, which verified the correctness of the numerical simulation.

Comparison of Offset and Wiping Z-Die Designs for Precision Z-Bent Part Fabrication

2018 ◽  
Vol 140 (2) ◽  
Author(s):  
Sutasn Thipprakmas ◽  
Pakkawat Komolruji ◽  
Wiriyakorn Phanitwong
Keyword(s):  
Fem Simulation ◽  
The Finite Element Method ◽  
Spring Back ◽  
Bend Radius ◽  
Dimensional Precision ◽  
Bending Process ◽  
Simulation Results ◽  
Bend Angles ◽  
Selection Of ◽  
Good Agreement

In recent years, the requirements for high dimensional precision on Z-bent shaped parts have become increasingly stringent. To attain these requirements, the suitable selection of the Z-die bending type has to be considered much more strictly. In this research, two types of Z-bending processes, offset Z-die bending and wiping Z-die bending, were investigated using the finite element method (FEM) to identify the spring-back characteristics and dimensions of Z-bent shaped parts. In the case of offset Z-die bending, the spring-back characteristics on both bend angles were similar. In contrast, in the case of wiping Z-bending, the spring-back characteristics on both bend angles were different. In addition, the dimensions of the Z-bent shaped parts were investigated. It was found, in the case of wiping Z-bending, that web thinning was generated and the outer bend radius was out of tolerance. To validate the FEM simulation results, experiments were carried out. The FEM simulation results showed good agreement with the experimental results in terms of the bend angles and the overall geometry of the Z-bent shaped parts. To achieve precise Z-bent shaped parts, the suitable selection of Z-die bending type in the Z-die bending process is very important.

scholarly journals Method for Optimizing the Kinematic Scheme of Stretch-Forming Parts from Sheet Blanks

2021 ◽  
Vol 346 ◽  
pp. 01030
Author(s):  
Konstantin Bormotin ◽  
Anton Krivenok ◽  
Maria Pogartseva ◽  
Min Ko Hlaing
Keyword(s):  
Optimal Control ◽  
Optimal Control Problems ◽  
Optimization Criterion ◽  
Control Problems ◽  
Optimal Parameters ◽  
Kinematic Scheme ◽  
Stretch Forming ◽  
Forming Process ◽  
Residual Displacements ◽  
Simulation Results

The modeling of the stretch-forming process a sheet on a punch is considered. A numerical method has been developed for solving the optimal control problems of the stretch-forming process sheet blanks. The values of the residual displacements are considered as an optimization criterion. The algorithms implemented in CAE allow calculating the optimal parameters for the operation of the CNC stretch-forming press. The simulation results are compared with full-scale experiments on the shaping of sheet parts on a stretch-forming press T-600.

Numerically modeling spring back and spring go amounts and bending deformations of Cr-Mo alloyed sheet material

2020 ◽  
Vol 62 (12) ◽  
pp. 1265-1272
Author(s):  
Mustafa Özdemir ◽  
Hakan Dilipak ◽  
Bülent Bostan
Keyword(s):  
Heat Treatment ◽  
Mathematical Models ◽  
Deformation Zone ◽  
Sheet Material ◽  
Analysis Program ◽  
Spring Back ◽  
Forming Process ◽  
Bending Angle ◽  
Heat Treated ◽  
Bending Process

Abstract In the study conducted for this contribution, sheet material 4 mm thick, non-heat treated (II), normalized (NH) and tempering heat treatment implemented (TH), were formed at a bending angle of 90°. As a result of the forming process, the effects of the R2, R3, R4, R5, and R6 mm punch tip radii on spring back and spring go values were investigated. The bending operations were carried out by waiting for the punch in the material bending zone for 30 sec and then lifting. The samples were extracted from the middle deformation zone of the II, NH and TH applied sheet material, to which the bending process was applied, following which their ferrite phase, pearlite and martensite structures were microstructurally analyzed. A Minitab analysis program was used to investigate the effect of the bending parameters on the sheet material’s spring-back and spring-go behavior. Moreover, the effects of bending parameters were investigated by creating numerical and mathematical models. Thus, it was determined that spring-go behavior occurred on the II and NH applied sheet material, while spring-back behavior occurred on the TH applied material.

FEM-Based Simulation and Gripper Jaw Trajectory Fitting of Stretch-Bending Process for a Bending Beam of Railway Vehicles

2013 ◽  
Vol 372 ◽  
pp. 661-665
Author(s):  
Sheng Man Wang ◽  
Xin Hua Yang ◽  
Xing Lu
Keyword(s):  
Control Method ◽  
Die Design ◽  
Railway Vehicle ◽  
Fe Model ◽  
The Finite Element Method ◽  
Forming Process ◽  
Stretch Bending ◽  
Bending Process ◽  
Design Requirements ◽  
Displacement Control Method

The bending beam of railway vehicle is made of thin stainless steel, with large sizes and unsymmetrical section, and prone to defects during stretch-bending forming process, such as wrinkling, cross-section distortion and so on. A reasonable trajectory of gripper jaws could make for mitigating the mentioned defects. The Finite Element Method was employed to fit the trajectory as well as simulate the forming process. The FE model was built by using the commercial FE software Hypermesh and ABAQUS/CAE. The analysis was carried out based on dynamic explicit and displacement control method. On this basis, the actual stretch bending process was developed according to the fitted trajectory and simulated process. The actual production process indicates that the formed beam can meet the design requirements, and the method is feasible and economical, as well as can contribute to a better understanding of stretch bending process and die design.

How to Combine the Parameters of the Yield Criteria and the Hardening Law

2013 ◽  
Vol 554-557 ◽  
pp. 1195-1202 ◽  
Author(s):  
Pedro Prates ◽  
M.C. Oliveira ◽  
Nataliya A. Sakharova ◽  
José Valdemar Fernandes
Keyword(s):  
Numerical Simulation ◽  
Metal Forming ◽  
Forming Process ◽  
Accurate Identification ◽  
Material Parameters ◽  
Hardening Law ◽  
Out Of Plane ◽  
Simulation Results ◽  
The Hill ◽  
Constitutive Parameters

The numerical simulation of sheet metal forming processes needs the accurate identification of the material parameters, for a given constitutive model. This identification can follow different methodologies and different sets of experimental data can be used, which lead to distinct sets of material parameters. In order to accurately compare the results of several methodologies, it is necessary to guarantee uniformity of their presentation. In this work, the correspondence between sets of parameters of the Hill’48 criterion is explored. The meaning of the “isotropic values” of the parameters associated with the out-of-plane stresses components is discussed and a required condition is proposed, in order to properly compare numerical simulation results obtained by using different input sets of constitutive parameters, identified by different procedures. Finite element simulations of complex shaped forming process, involving strain-path changes, are carried out in order to support the analysis.

Numerical Simulation of Stretch Bending Process and Springback for T Section Aluminum Extrusions

2006 ◽  
Vol 315-316 ◽  
pp. 416-420
Author(s):  
Ming He Chen ◽  
Lin Gao ◽  
H.H. Mao ◽  
Dun Wen Zuo ◽  
Min Wang
Keyword(s):  
Numerical Simulation ◽  
Finite Element ◽  
Element Model ◽  
Major Effect ◽  
Experimental Results ◽  
Spring Back ◽  
Stretch Bending ◽  
Aluminum Extrusions ◽  
Bending Process ◽  
Forming Precision

In order to improve the forming precision of the stretch bending process for T section aluminum extrusions and meet the fine forming requirement of the aerostat blank parts, the elongation controlled stretch bending process finite element model is proposed, which is based on the basic principle of the stretch bending forming with respect to A-7B CNC Section Stretch Wrap Forming Machine by analyzing various factors that influence the qualities of stretch bending parts, and the numerical simulation of the stretch bending process and spring back for T section aluminum extrusions is carried out. The results of simulation show that the pre-stretching elongation has a major effect on stretch bending parts and finite post-stretching elongation helps to improve the forming qualities of the parts. Comparing with the experimental results, the spring back of the finite element simulation shows good agreement with that of the experimental results.

Study on the Spring-Back Effect with Stress Distribution According to Forming Sheet Width in the Roll Forming Process

2015 ◽  
Vol 789-790 ◽  
pp. 116-120
Author(s):  
Dong Hong Kim ◽  
Hao Yu ◽  
Dong Won Jung
Keyword(s):  
Stress Distribution ◽  
Roll Forming ◽  
Spring Back ◽  
Forming Process ◽  
Element Analysis ◽  
Forming Simulation ◽  
Sheet Width ◽  
Simulation Results ◽  
The Relationship ◽  
Roll Forming Process

This study, based on finite element analysis, analyzed the spring back phenomenon and stress distribution of forming sheets (HTS) in the roll forming process. By comparison of the stress distribution, this study analyzed two kinds of simulation. The first simulation performed simple bending simulation before roll forming simulation. With reference to the first simulation results, the second simulation analyzed the relationship between the stress distribution and the phenomenon of spring back. We also studied the stress distribution effect for spring back in the forming sheet.

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