Loading...

Development of Inverse Isogeometric Formulations in Simulation of Sheet Metal Forming Processes

Shamloofard, Mansoor | 2021

494 Viewed
  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 53614 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Assempour, Ahmad
  7. Abstract:
  8. This research presents inverse isogeometric models based on the deformation theory of plasticity to predict the blank and strain distribution in sheet metal forming processes. In this study, the NURBS functions are utilized for both modeling of a final part and analysis of the forming process. Therefore, the developed models require only one modeling and analysis representation, in contrast to finite element models which deal with two separate modeling and analysis representations. In this research, a membrane one-step inverse isogeometric model is initially presented to analyze sheet metal forming processes. This method has various advantages such as solving the governing equations in two-dimensional space without any concern about pre-estimation results; however, major sources of errors in this method include (i) neglecting the bending effects, (ii) considering small strains for estimation of the blank, and (iii) applying the deformation theory of plasticity in one step between the blank and final part. To decrease the errors, (i) bending-dependent, (ii) nonlinear and (iii) multi-step inverse isogeometric models are developed, respectively. The performance of the presented models is experimentally and numerically evaluated in several problems such as forming analysis of square and rectangular boxes. The bending-dependent model improves the accuracy of the membrane model with a slight increase in the computation time. This accuracy enhancement is mainly achieved in the punch and die profile radii where the bending effects are dominant. Comparison of results in forming analysis of a rectangular box reveals that the average of calculated error in the bending-dependent model for prediction of thickness at the middle of punch radius zone is around half of that in the membrane model. The nonlinear model, considering large strains for prediction of the initial blank, improves the accuracy of the linear models in the entire domain. For instance, in forming analysis of a square box, the error in prediction of minimum thickness is reduced from 11.9% to 6.7% by considering large strain effects. The one-step inverse isogeometric models are not capable of analyzing forming processes which require severe deformation and/or several forming stages. In these cases, for example forming analysis of a rectangular box with high drawing depth and a two-step drawing of a circular cup, the results confirm that only the multi-step model can predict the forming parameters with acceptable accuracy. After verification of the developed one-step and multi-step inverse isogeometric methods, an efficient isogeometric-based framework is presented to integrate optimum design and formability analysis of sheet metal forming processes. For this purpose, the presented inverse models are used as forming solvers of the genetic global optimization algorithm. In this framework, addendum surfaces of the formed parts and also tools of the middle forming operation are optimally designed to achieve the desired qualities of the final parts. The results of the developed NURBS-based framework confirm the credibility of this approach in rapid optimum design of addendum surfaces and intermediate tools with acceptable accuracy
  9. Keywords:
  10. Bending Effect ; Sheet Metal Forming ; Process Analysis ; Finite Strains ; Process Optimization ; Deep Drawing ; Addendum Geometry ; One-Step Inverse Isogeometric Analysis ; Multi-Step Inverse Isogeometric Analysis

 Digital Object List

 Bookmark

No TOC