Numerical Simulation of the Splitting Ring Benchmark Test

2000

2014

Sheet metal deformation is widely used in automotive industry. Nowadays the automakers try to reduce the weight of the cars by using high strength steel. The disadvantage of the high strength steel is its significant springback effect. One of the aims of this study is to utilize the springback compensation algorithm of the commercial software during the drawing simulation process. In this paper, we discuss how the sheet metal deformation was simulated by using DYNAFORM V5.5 software. The results of the simulations were compared with producers’ experience. The geometrical data of the simulated parts were provided in “.iges” file format by producers of machine components. The model prepared for the simulation was developed as a system of die, punch, addendum, binder, and blank. After sheet plastic forming analysis was done, springback was performed. LS-DYNA software was used as a solver in the simulations.

Journal of Materials Processing Technology, 2008

Sheet metal forming Springback Bauschinger effect Finite element method Kinematic hardening a b s t r a c t An accurate modeling of the sheet metal deformations including the springback is one of the key factors in the efficient utilization of FE process simulation in the industrial setting. In this paper, a rate-independent anisotropic plasticity model accounting the Bauschinger effect is presented and applied in the FE forming and springback analyses. The proposed model uses the Hill's quadratic yield function in the description of the anisotropic yield loci of planar and transversely anisotropic sheets. The material strain-hardening behavior is simulated by an additive backstress form of the nonlinear kinematic hardening rule and the model parameters are computed explicitly based on the stress-strain curve in the sheet rolling direction. The proposed model is employed in the FE analysis of Numisheet'93 U-channel benchmark, and a performance comparison in terms of the predicted springback indicated an enhanced correlation with the average of measurements. In addition, the stamping analyses of an automotive part are conducted, and comparisons of the FE results using both the isotropic hardening plasticity model and the proposed model are presented in terms of the calculated strain, thickness, residual stress and bending moment

Engineering with Computers, 2012

Computer-aided engineering methods are extensively applied to sheet metal forming integrated design. The adoption of a new class of materials, the advanced high strength steels, has increased the occurrence of springback, and consequently the request for tools oriented to springback reduction and optimization. This paper presents an approximated formulation to compute the springback field after stamping through the finite element analysis of the process. This can be found assuming that the residual field of nodal forces after stamping produces a springback shape referable to a linear combination of n modes of vibration of the nominal shape of the component. The aim of this formulation is not that of substituting the finite element analysis of the springback but rather to make use of the coefficients of the linear combination, so to define a global quality function for springback. In this way, Robust Design methods or other current optimization procedures to improve the stamping process as for structural defects (such wrinkling, necking and flatness) can be applied also for the reduction of springback. The meaning of these coefficients will be shown through three test cases and the consistency of the formulation will be discussed according to the number of modes of vibration included in the computation.

AURUM Journal of Engineering Systems and Architecture, 2021

Advances in Materials and Processing Technologies, 2020

In many manufacturing and forming industries, springback effect in case of sheet metals is a major cause of concern. Thus, an effort has been made in present work for analysing the spring back effect with the help of split-ring test in deep drawn cups. The uniaxial tensile test has been performed and flow stress has been found to be decreased while ductility of material increased with rise in temperature. Subsequently, the deep drawing experiments have been conducted and overall thickness deviation was found to be increased with increase in temperature and decrease in blank holding pressure. The springback in deep drawn cups are measured in terms of average opening gaps in cut ring portion. Furthermore, Sellar's-based constitutive model with different anisotropic yield criteria namely; Hill'48 and Barlat'89 have been developed for Inconel 625 alloy. The combination of Sellar's model with Barlat'89 yield criterion is found to be more accurate for deformation behaviour prediction. Finally, these models have been implemented in finite element (FE) analysis of split-ring test using user defined material (UMAT) script. The mean relative error between numerically and experimentally computed results was found to be less than 8.11% which is well within the 10% of acceptance level.

International Journal of Engineering Research and Technology (IJERT), 2014

https://www.ijert.org/a-review-on-springback-in-metal-forming https://www.ijert.org/research/a-review-on-springback-in-metal-forming-IJERTV3IS10285.pdf Springback occurs in metal forming after removal of the load due to elastic recovery. It is difficult to develop analytical formulae for spring back and it should be compensated iteratively by for which number of trials are required. Finite element analysis reduces the number of trials reducing the cost, effort and time. In the present paper the review of literature springback and on finite element analysis of spring back is presented. It is the dimensional change of the formed part after the pressure of the forming tool has been released. It results from the changes in strain produced by elastic recovery. During sheet metal forming processes such as stamping and deep drawing where bending/unbending is predominant, the region around the neutral plane in the material undergoes both elastic and plastic deformation. When the punch has reached the final draw depth and is removed, the elastic strain in the material is recovered, which produces springback in the part due to this nonuniform stress distribution in the sheet. The discrepancy of shapes between a deep drawn product and the designed one due to springback must be compensated for, at the tool design stage in order to guarantee its function and assembly with other parts. It is, however, so difficult to predict and estimate the amount of compensation for springback that tool modification relies on the experience or a trial-and-error procedure in the press shop. This compensation procedure requires extra try-out time, which increases the cost for the tooling and product development time. Partnership for a New Generation of Vehicles (PNGV), a wing of the United States Council for Automotive Research (USCAR), identified sixteen manufacturing technologies that need to be addressed in order to improve automotive manufacturing [1] The ‗‗springback challenge,'' is one of these crucial manufacturing areas. In a forming process such as deep drawing, it remains to this day one of the great challenges and one of the greatest problems for the manufacturer. The preferred use of high-strength materials such as dual phase steels in many modern manufacturing processes aggravates the problem of increased springback. Springback is however affected by the complex combination of bending, unbending, and stretching imposed on parts during deep drawing process. Therefore, the proper understanding of the effects of process parameters as well as material properties on springback is so useful to effectively design the processes. The magnitude of springback depends on the bending moment, which intern depends on the through thickness stress distribution at each point in the plane of the sheet at the end of the drawing operation. The accuracy of springback prediction depends on the development of the internal stress distribution through out the drawing operation, which makes it sensitive to a range of variables.

International Journal of Research in Engineering & Advanced Technology, 2016

One of the largest challenges in manufacturing is the consistency of final products. Two basic approaches have been investigated to achieve this goal. One is to use intelligent assembly methodologies to select a suitable set of parts to be assembled which is taking advantage of tolerance stack up. The other approach aims at each individual manufacturing process module, for example sheet metal forming process. The forming of sheet metal into a desired and functional shape is a process, which requires an understanding of materials, mechanics, and manufacturing principles. The major problem in fabrication of sheet metal parts is spring back effect i.e. the elastic strain recovery in the material after the tooling is removed. Spring back control is one of the key concerns of the sheet metal forming industry. The current trial-and-error method of testing and controlling for spring back is costly, time consuming, and remains as an obstacle in achieving shorter design production cycles. The elastic spring back at the end of a bending process plays an important role in determining the quality of final product thus in practice the constitutive relation that considers the elastic and plastic parts together has to be used. The factors have a non-linear interaction with each other so it is extremely difficult to develop an analytical model for spring back control including all these factors. So approach with FEA simulations are used to confront this difficulty.

International Journal of Mechanical Sciences, 2010

Variation in the incoming sheet material and fluctuations in the press setup is unavoidable in many stamping plants. The effect of these variations can have a large influence on the quality of the final stamping, in particular, unpredictable springback of the sheet when the tooling is removed. While stochastic simulation techniques have been developed to simulate this problem, there has been little research that connects the influence of the noise sources to springback. This paper characterises the effect of material and process variation on the robustness of springback for a semi-cylindrical channel forming operation, which shares a similar cross-section profile as many automotive structural components. The study was conducted using the specialised sheet metal forming package AutoForm TM Sigma, for which a series of stochastic simulations were performed with each of the noise sources incrementally introduced. The effective stress and effective strain scatter in a critical location of the part was examined and a response window, which indicates the respective process robustness, was defined. The incremental introduction of the noise sources allows the change in size of the stress-strain response window to be tracked. The results showed that changes to process variation parameters, such as BHP and friction coefficient, directly affect the strain component of the stress-strain response window by altering the magnitude of external work applied to forming system. Material variation, on the other hand, directly affected the stress component of the response window. A relationship between the effective stress-strain response window and the variation in springback was also established.

International Journal of Engineering Research and Technology (IJERT), 2013

https://www.ijert.org/sheet-metal-forming-analysis-with-an-emphasis-on-spring-back-deformation https://www.ijert.org/research/sheet-metal-forming-analysis-with-an-emphasis-on-spring-back-deformation-IJERTV2IS100016.pdf Stress analysis plays important role in structural design and manufacturing. Proper stress estimation helps to prevent objects from failing during working. Spring back is mainly due to nonlinear plasticity with friction and heat loss in the material. Bauschigner effect is the main cause of this spring back phenomenon. In the present work, an analysis is carried out to find the spring back on the metal forming process is. Initially a geometrical model in plane strain approach is built using ANSYS mixed approach. The geometry is split to form mappable areas to quad meshing. Later contact elements are defined between the punch and the sheet metal and second contact pair between sheet metal and die surface. The analysis is done using Newton raphson iterative method to find the cone angle effect on spring back phenomenon. The results shows with the reduction in the cone angle all these parameters are increasing. Increasing plastic strain and residual stress are the potential sources for crack formation and propagation and eventual failure of the members.