A New Method for Testing Formability in Sheet Metal Forming at Biaxial Tensile State

2014 ◽  
Vol 626 ◽  
pp. 275-280 ◽  
Author(s):  
Rong Shean Lee ◽  
Ta Wei Chien
Keyword(s):  
Experimental Data ◽  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Experimental Results ◽  
New Method ◽  
Dome Height ◽  
Uniaxial Tensile ◽  
Biaxial Tensile ◽  
Theoretical Predictions

This paper presents a new method concerning testing formability in sheet metal forming, especially focuses on clarifying the divergence of the experiment and a variety of theoretical predictions on biaxial tensile state. Up to now, there are many different fracture criteria appeared. All researches have presented their experimental data which could justify the criterion they presented. However, the experimental results and predictions in the first quadrant of the forming limit diagram (FLD) often diverge. Today, limiting dome height test is commonly used for FLD experiment, but specimens are rubbed and bended during the test, both influencing the experimental results.In order to provide for convincible experimental data, this paper presents a new experimental method to establish the first quadrant of FLD. In this method, cruciform biaxial tensile specimen and biaxial tensile apparatus have been developed. The proposed specimen has the feature of thickness reduction and contour design to ensure the fracture location is in the central region, so that accurate biaxial tensile state can be obtained. Through this method, there is an opportunity to obtain the whole FLD using uniaxial tensile testing machine, which is a low-cost alternative in compared with limiting dome height test. Besides, the experimental results can be utilized to clarify the divergence between various theoretical predictions and experimental results in the first quadrant of the FLD.

scholarly journals Investigation of Sheet Metal Forming Using a Rapid Compression Machine

Materials ◽  
2019 ◽  
Vol 12 (23) ◽  
pp. 3957 ◽  
Author(s):  
Sandeep P. Patil ◽  
Yann Fenard ◽  
Shridhar Bailkeri ◽  
Karl Alexander Heufer ◽  
Bernd Markert
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Peak Pressure ◽  
Experimental Results ◽  
Maximum Height ◽  
Outer Diameter ◽  
Rapid Compression Machine ◽  
Damage Initiation ◽  
Rapid Compression

The primary goal of this work is to understand the deformation behavior of an aluminum alloy (Al) workpiece by using a rapid compression machine (RCM). The primary novelty in this work is that this is the first study on sheet metal forming using RCM. Numerical simulation and experimental results are in excellent agreement, e.g., the dome-shape, the maximum height, the final outer diameter, and the thickness distribution of the deformed workpiece. We demonstrate that the maximum deformation height grows linearly with the peak pressure with an intercept tending to zero. The proposed linear relationship can be effectively used for designing new components for a specific application. Moreover, the proposed numerical model was competent in reproducing the experimental results of damage initiation and evolution in case of high peak pressure as well as the initial misalignment of the workpiece. The results of this investigation revealed that a rapid compression machine can be utilized efficiently for the controlled forming of complex shapes of metal sheets.

Study on Parameters for Affecting SCI of Sheet Metal Forming

2010 ◽  
Vol 44-47 ◽  
pp. 2862-2866
Author(s):  
Ji Tao Du
Keyword(s):  
Mechanical Property ◽  
Surface Quality ◽  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Friction Condition ◽  
Experimental Results ◽  
Forming Defect ◽  
Punch Radius

The surface contact impression(SCI) is the neglected forming defect and seriously affects surface quality and mechanical property of stamping parts. The technology parameters and affective degree which alleviate or eliminate SCI are researched , four factors including die radius(DR) , die clearance(DC), punch radius(PR) and friction condition(FC) , which each factor chooses three levels are designed and constitute a L9（34）orthogonal table. The experimental results indicate that the significances order of technology parameters affecting SCI is DR> PR > DC >FC. The analyzed result shows that the superior parameter affecting SCI is DR ,the inferior is FC, adapted DC greatly removes SCI. the research puts forward a reference for improving surface quality of stamping parts.

Formability and Surface Finish Studies in Single Point Incremental Forming

2011 ◽  
Author(s):  
A. Bhattacharya ◽  
Samarjit Singh ◽  
K. Maneesh ◽  
N. Venkata Reddy ◽  
Jian Cao
Keyword(s):  
Surface Roughness ◽  
Sheet Metal ◽  
Surface Finish ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Incremental Forming ◽  
Experimental Results ◽  
Wall Angle ◽  
Incremental Sheet Metal Forming ◽  
Tool Diameter

Incremental sheet metal forming (ISMF) has demonstrated its great potential to form complex three-dimensional parts without using a component specific tooling. The die-less nature in incremental forming provides a competitive alternative for economically and effectively fabricating low-volume functional sheet parts. However, ISMF has limitations with respect to maximum formable wall angle, geometrical accuracy and surface finish of the component. In the present work, an experimental study is carried out to study the effect of incremental sheet metal forming process variables on maximum formable angle and surface finish. Box-Behnken method is used to design the experiments for formability study and full factorial method is used for surface finish study. Analysis of experimental results indicates that formability in incremental forming decreases with increase in tool diameter. Formable angle first increases and then decreases with incremental depth and it is also observed that the variation in the formable angle is not significant in the range of incremental depths considered to produce good surface finishes during the present study. A simple analysis model is used to estimate the stress values during incremental sheet metal forming assuming that the deformation occurs predominantly under plane strain condition. A stress based criterion is used along with the above mentioned analysis to predict the formability in ISMF and its predictions are in very good agreement with the experimental results. Surface roughness decreases with increase in tool diameter for all incremental depths. Surface roughness increases first with increase in incremental depth up to certain angle and then decreases. Surface roughness value decreases with increase in wall angle.

Formability Evaluation Using Modified Cockcroft Criterion with Strain Paths for Sheet Metal Forming

2014 ◽  
Vol 626 ◽  
pp. 495-501 ◽  
Author(s):  
Rong Shean Lee ◽  
Ta Wei Chien
Keyword(s):  
Tensile Test ◽  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Strain Path ◽  
Dome Height ◽  
Bulge Test ◽  
Cruciform Specimen ◽  
Strain Paths ◽  
Good Agreement

In most situations, original Cockcroft criterion underestimates material formability in the first quadrant of FLD. So far, some modified Cockcroft criteria have been reported for different applications. This presentation will focus on the modified Cockcroft criterion which takes strain-path effect into consideration. This paper demonstrates the accuracy of this criterion through limiting dome height test, free bulge test, and the biaxial tensile test using cruciform specimen respectively. The results showed that the modified Cockcroft criterion with strain path effect has good agreement with experimental results.

Effect of Ductile Damage Evolution in Sheet Metal Forming: Experimental and Numerical Investigations

2010 ◽  
Vol 446 ◽  
pp. 157-169 ◽  
Author(s):  
Fethi Abbassi ◽  
Olivier Pantalé ◽  
Sébastien Mistou ◽  
Ali Zghal ◽  
Roger Rakotomalala
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Rolling Direction ◽  
Constitutive Law ◽  
Image Correlation ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Plastic Behavior ◽  
Marquardt Algorithm

The numerical simulation based on the Finite Element Method (FEM) is widely used in academic institutes and in the industry. It is a useful tool to predict many phenomena present in the classical manufacturing forming processes such as necking, fracture, springback, buckling and wrinkling. But, the results of such numerical model depend strongly on the parameters of the constitutive behavior model. In the first part of this work, we focus on the traditional identification of the constitutive law using oriented tensile tests (0°, 45°, and 90° with respect to the rolling direction). A Digital Image Correlation (DIC) method is used in order to measure the displacements on the surface of the specimen and to analyze the necking evolution and the instability along the shear band. Therefore, bulge tests involving a number of die shapes (circular and elliptic) were developed. In a second step, a mixed numerical–experimental method is used for the identification of the plastic behavior of the stainless steel metal sheet. The initial parameters of the inverse identification were extracted from a uniaxial tensile test. The optimization procedure uses a combination of a Monte-Carlo and a Levenberg-Marquardt algorithm. In the second part of this work, according to some results obtained by SEM (Scaning Electron Microscopy) of the crack zones on the tensile specimens, a Gurson Tvergaard Needleman (GTN) ductile model of damage has been selected for the numerical simulations. This model was introduced in order to give informations concerning crack initiations during hydroforming. At the end of the paper, experimental and numerical comparisons of sheet metal forming applications are presented and validate the proposed approach.

A new method for circular grid analysis in the sheet metal forming test

2000 ◽  
Vol 40 (2) ◽  
pp. 190-196 ◽  
Author(s):  
C. -C. Wang ◽  
J. Lee ◽  
L. -W. Chen ◽  
H. -Y. Lai
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
New Method ◽  
Grid Analysis ◽  
Circular Grid

Formability and Surface Finish Studies in Single Point Incremental Forming

2011 ◽  
Vol 133 (6) ◽  
Author(s):  
A. Bhattacharya ◽  
K. Maneesh ◽  
N. Venkata Reddy ◽  
Jian Cao
Keyword(s):  
Surface Roughness ◽  
Sheet Metal ◽  
Surface Finish ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Incremental Forming ◽  
Experimental Results ◽  
Wall Angle ◽  
Incremental Sheet Metal Forming ◽  
Tool Diameter

Incremental sheet metal forming (ISMF) has demonstrated its great potential to form complex three-dimensional parts without using a component specific tooling. The die-less nature in incremental forming provides a competitive alternative for economically and effectively fabricating low-volume functional sheet parts. However, ISMF has limitations with respect to maximum formable wall angle, geometrical accuracy, and surface finish of the component. In the present work, an experimental study is carried out to study the effect of incremental sheet metal forming process variables on maximum formable angle and surface finish. Box–Behnken method is used to design the experiments for formability study and full factorial method is used for surface finish study. Analysis of experimental results indicates that formability in incremental forming decreases with increase in tool diameter. Formable angle first increases and then decreases with incremental depth and it is also observed that the variation in the formable angle is not significant in the range of incremental depths considered to produce good surface finishes during the present study. A simple analysis model is used to estimate the stress values during incremental sheet metal forming assuming that the deformation occurs predominantly under plane strain condition. A stress-based criterion is used along with the above mentioned analysis to predict the formability in ISMF and its predictions are in very good agreement with the experimental results. Surface roughness decreases with increase in tool diameter for all incremental depths. Surface roughness increases first with increase in incremental depth up to certain angle and then decreases. Surface roughness value decreases with increase in wall angle.

A new method to get initial guess configuration for multi-step sheet metal forming simulations

2020 ◽  
Vol 110 (9-10) ◽  
pp. 2651-2668
Author(s):  
Yongcai Liu ◽  
Wenliang Chen ◽  
Qingwan Hu ◽  
Chunhui Yang ◽  
Yidong Bao
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Initial Guess ◽  
New Method ◽  
Forming Simulations

Forming Limits Prediction of the Sheet Metal Forming Process by the Energy-Based Damage Model

2006 ◽  
Vol 22 (1) ◽  
pp. 43-50 ◽  
Author(s):  
H.-Y. Yeh ◽  
J.-H. Cheng
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
Damage Model ◽  
Uniaxial Tensile ◽  
Strain History ◽  
Forming Process ◽  
Forming Limits ◽  
Metal Forming Process ◽  
Strain Paths

AbstractAn energy-based damage model is proposed and applied to predict the fracture initiation of the sheet metal forming process. The fracture mechanism is investigated through the plastic energy dissipation. The concepts of the damaging work and the fracture energy are proposed for the quantitative description of damage evolution and crack initiation. The developed formulations are implemented into the finite element program ABAQUS to simulate the biaxial stretching of sheet metals and to predict the fracture strains. The material parameter needed in the damage model for fracture prediction is determined by the stress-strain history of the uniaxial tensile test. The forming limits for aluminum alloy sheets under various strain paths are predicted by the present approach and then compared to the measured data quoted from the literatures [1,2]. Good agreements are found between this study and the previous results.

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