Mehdi Karimi Firouzjaei, Hassan Moslemi Naeini, Hamidreza Farahmand, Behnam Abbaszadeh, Mohammadmehdi Kasaei,
Volume 17, Issue 10 (1-2018)
Abstract
In this paper, cold roll forming process of a high strength steel pipe using four types of flower pattern including circular, edge, double radius and reverse bending is simulated with finite element method in MSC Marc Mentat software. Due to importance of quality of final pipe and in order to achieve the desired geometry in high strength steel pipes, selecting the appropriate flower pattern to design the pipe roll forming production line is considered. Using finite element simulation results, deformation of sheet in this process is studied and effect of flower pattern type on geometry of final product, which includes curvature distribution, spring back and thickness distribution of pipe, is investigated. Results show that implementing reverse bending flower pattern, leads to reduction in deviation from mean curvature at edge of the sheet up to about 65 percent. Thickness distribution analysis shows that circular and edge flower patterns cause upsetting and thinning of edge of the sheet up to 0.2 millimeters, respectively. But, use of double radius and reverse bending patterns cause average thickness of edge to be well adjusted to reach 2.8 millimeters. Also, circular flower pattern has the lowest value of spring back in terms of variation of mean relative curvature of 0.69 percent and edge deviation of 0.15 millimeters. To validate the finite element simulation, experimental tests were designed and conducted using one forming stand. By comparing resultant data of experimental tests with simulation results, validity of finite element simulation confirmed.
Mehdi Karimi Firouzjaei, Hassan Moslemi Naeini, Mohammad Mehdi Kasaei, Mohammad Javad Mirnia,
Volume 22, Issue 8 (August 2022)
Abstract
The deformation behavior of the material in micro-forming processes is different from macro-scale due to the size effect. The size effect in micro-scale appears due to few grains in the deformation region and causes the material behavior to be affected by the thickness and grain size of the sheet. Because of this, conventional constitutive models are not suitable for predicting the material behavior in micro-forming processes. In this paper, a new constitutive model based on the Swift equation and considering size effect in micro-scale is presented to describe the strain-hardening behavior of the stainless steel 304 foil. Comparison of flow stress curves of specimens with different grain sizes showed that the prediction of material flow stress with the new constitutive model is improved compared to the existing model, especially at high strains, so that the average and maximum error of the new model is less than one-third and less than half of the conventional model error, respectively. Finite element simulation of the micro-tensile test was performed using the new constitutive model to investigate the size effect on the deformation behavior of the specimens. The new constitutive model was verified by comparing the results of experimental tests and finite element simulation of sheets with different grain sizes. Also, the results revealed that the estimation of the forming force using the new constitutive model is done with higher accuracy than the conventional and existing model for sheets with different grain sizes and high strain ranges.
