Plastic deformation of sheet metals during forming induces complex residual stresses in the component owing to its geometry and material anisotropy. The residual stresses affect the durability of the components. Fatigue life estimation incorporating the forming-induced residual stresses is limited. In the present work, the state-of-the-art in modelling sheet metal forming, residual stress estimation and fatigue life prediction are reviewed. The challenges in integrating the residual stress owing to forming and fatigue life prediction are brought out. The parameters influencing the sheet metal forming, residual stresses and fatigue are discussed to emphasize the complexity of the present problem. © IMechE 2012.

K Hariharan

Department of Mechanical Engineering

Raghu V. Prakash

FATIGUE LIFE ESTIMATION

Fatigue life prediction

Material anisotropy

plastic anisotropy

STRESS ESTIMATION

Anisotropy

Fatigue damage

Fatigue of materials

finite element method

Sheet metal

Residual stresses

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IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Integrating effect of forming in fatigue life prediction: review of present scenario and challenges

Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture

In this study, Hill 48 and Barlat 89 yield criteria are evaluated by simulating the Limiting Dome Height test of the Numisheet 96 benchmark problem [1] for a commercial D-grade steel and the results are validated with experimental data. Three strain modes, viz. biaxial, plane strain, and uniaxial strain modes, are used in the simulation studies. The yield criteria are evaluated based on the strain distribution in forming and residual stress distribution after springback. The results show that the Hill 48 and Barlat 89 yield criteria do not show a good match with predicted results of strain distribution in the plane strain mode. The difference between predicted results and experiments can be attributed to the combined influence of friction coefficient and draw bead boundary condition. The prediction of residual stress distribution differed considerably with the yield criteria. The residual stress predicted is validated for selected locations using X-ray diffraction techniques. Copyright © Taylor &amp; Francis Group, LLC.

Materials and Manufacturing Processes

Influence of yield criteria in the prediction of strain distribution and residual stress distribution in sheet metal formability analysis for a commercial steel

Process induced anisotropy in sheet metal is accounted for in analytical modeling by anisotropic yield criteria. The suitability of a yield criterion for predicting sheet metal forming process is generally validated by way of its ability to predict surface strains. However, the sensitivity of surface strains to yield criteria is dependent upon strain modes, with plane strain mode exhibiting higher sensitivity. To eliminate dependency on strain modes, stresses are used to evaluate yield criteria, since forming stresses are less sensitive to strain modes. In the study, the residual stresses remaining in a hemispherical cup formed in plain strain mode is predicted using Hill48 and Barlat89 criteria. The residual stresses are experimentally characterized by using X-Ray diffraction method. Suitable yield criterion for forming simulation is validated based on the correlation of theoretical predictions with experimental residual stress values. © 2010 Springer-Verlag France.

International Journal of Material Forming

Evaluation of yield criteria for forming simulations based on residual stress measurement

Room-temperature total strain-controlled low-cycle fatigue tests were carried out on AISI 304LN austenitic stainless steel specimens that were cold worked by swaging to different levels (10, 20 and 30% reduction in area) prior to testing. Cyclic softening was mostly noticed. A crossover in the total strain-life plots for the material with different degrees of prior cold work is explained in terms of the differences in strength and ductility. Prior cold work increased the total strain fatigue resistance at total strain amplitudes less than about 0.50%. A reduction in the transition fatigue life with an increase in the percentage of prior cold work was observed. Masing behaviour was observed only in the 30% prior cold worked material.

International Journal of Fatigue

Effect of prior cold work on the room-temperature low-cycle fatigue behaviour of AISI 304LN stainless steel

Journal of Materials Science Letters

On the correlation between annealing textures and formability in an extra-deep drawing low-carbon steel

Residual stress evolution in cold-rolled steels

Integrating effect of forming in fatigue life prediction: Review of present scenario and challenges

Journal	Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture
ISSN	09544054
Open Access	No