The use of digital processing in studying stretch-forming sheet metal

Joshi, R.; Bayoumi, Abdel; Zbib, Hussein M.

doi:10.1007/bf02324722

Cited by 8 publications

(7 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It seems that a more productive approach of obtaining a better estimate of plastic stress-strain curve for ductile sheet metals using a tapered tension coupon is to find an effective correction method for the estimated stress-strain curve based on ε 3 . Traditionally, the Bridgman correction method based on the certain assumption of the neck geometry may be used [10,11] but it requires the additional measurements of geometric parameters of the neck. Another method is an iterative correction method proposed by Tao et al [15] that may be used here as well but it needs the repeated finite element analyses and post-data processing steps.…”

Section: Resultsmentioning

confidence: 99%

“…The parameters k; R 0 ; R 1 ; and b used by the ANSYS finite element program can then be obtained via equation (11). Five different materials (two base metals D600a and D600b, two heat-affected zones HAZ_a and HAZ_b, and one weld metal) made of a dual-phase steel sheet were examined in this study.…”

Section: The Finite Element Simulation and Post Data Processing Procementioning

confidence: 99%

“…Using proper image magnifications and decorated surface contrast patterns, large plastic strains and high strain gradients over gage dimensions as small as only a fraction of the original sheet thickness within the necking region in a thin sheet can be easily mapped out in great detail [18,20]. The availability of such local plastic surface strain measurements by digital image correlation provides both a direct experimental estimate on the upper and lower bounds of the post-necking effective plastic stress-strain curves [6,21,22] and an improvement on the accuracy and reliability of some analytical or numerical methods in further correcting the post-necking effective stress-strain curves [11,14,15].…”

Section: Introductionmentioning

confidence: 99%

“…An experimental technique called digital image correlation (DIC) has been increasingly used in recent years for whole-field surface strain mapping applications in sheet metal testing, in part, due to a wider availability of many inhouse and commercial software tools [11,[16][17][18][19][20]. Using proper image magnifications and decorated surface contrast patterns, large plastic strains and high strain gradients over gage dimensions as small as only a fraction of the original sheet thickness within the necking region in a thin sheet can be easily mapped out in great detail [18,20].…”

Section: Introductionmentioning

confidence: 99%

“…Although the standard uniaxial tension test is often used to obtain the basic mechanical properties of the steel sheet metals, the valid plastic stress-strain data obtained for those low-strain hardening but ductile materials are rather limited to small strain ranges (say, a few percent) due to the earlier onset of the diffuse necking [8,9]. Some analytical and numerical methods have been developed over the years to address the problem of estimating the effective plastic stress-strain data beyond diffuse necking using a standard ductile metal tension coupon with certain corrections [10][11][12][13][14][15].…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

A Finite Element Analysis of a Tapered Flat Sheet Tensile Specimen

Yang

Tong

2009

Exp Mech

View full text Add to dashboard Cite

A uniaxial tension sheet metal coupon with a tapered instead of a straight gage section has been used for centering the location of diffuse neck and for measuring sheet stretchability in a non-uniform strain field. A finite element analysis of such a tensile coupon made of automotive steel sheet metals has been carried out to assess the effect of the tapered gage section geometry and material plastic strain hardening characteristics on the development of local plastic deformation pattern and local stress state, especially beyond the onset of diffuse necking but before localized necking. In particular, the finite element analysis was used in this study to evaluate the accuracy and reliability of an experimental data analysis method for estimating the post-necking effective plastic stress-strain curve based on the direct local surface axial plastic strain measurements for base metal, heat-affected zone, and weld metals of a dual-phase steel DP600. It is concluded that the estimated lower and upper bounds of the effective stress-strain curve at large strains are not satisfactory for low strain-hardening materials such as heat-affected zone and weld metals with the tapered tension coupons. A simple correction method utilizing only the additional local surface strain measurement in the transverse direction is proposed and it is shown to be effective in correcting the estimated effective stress-strain curve of dual-phase steel weld metals obtained for two tapered gage section geometries.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: The Finite Element Simulation and Post Data Processing Procementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

A Finite Element Analysis of a Tapered Flat Sheet Tensile Specimen

Yang

Tong

2009

Exp Mech

View full text Add to dashboard Cite

show abstract

An automatic and interactive large-deformation measurement system based on image processing

Septanika

Ernst

Hooff

1998

Experimental Mechanics

View full text Add to dashboard Cite

ABSTRACThThis paper describes an image-processingbased measurement system by which an automatic large deformation characterization and interactive force control can be realized. The system is provided by a servo-controlled CCD camera and a PC-based frame grabber. A tracking procedure based on the location of a target point is employed for guiding the camera movement. It is intended to monitor the local deformation in a relatively small moving area containing small globules. The globule positions are then used to determine the surface deformation characteristics. In this system, the momentary principal strains being computed online are immediately used to control the applied force. As an illustration, the present system is applied for observing a long-term homogeneous large deformation in SI-rubber specimens being subjected to a constant uniaxial true stress. Four solid, minuscule, relatively undeformable polystyrene globules are used as markers. A true stress control algorithm is developed based on the isotropy assumption in which the transverse area normal to the loading direction becomes determinable from the surface deformation data. It can be stated that the maximum speed of the true stress control is mainly related to the speed of image processing and analysis, which in turn is related to the chosen number of globules and the performance of the PC used. By using four globules, the true stress readjustment could be accomplished for roughly every 4 s. For a large-strain deformation of SI-rubber, it appears that the isotropy assumption is acceptable, since the resulting mean difference between out-of-plane contraction and in-plane contraction is restricted to about -4-8 percent.

show abstract