ORIGINAL ARTICLE Investigation of the viscous and thermal effects on ductile fracture in sheet metal blanking process Ahmad Rafsanjani & Saeed Abbasion & Anoushiravan Farshidianfar & Nilgoon Irani Received: 9 July 2008 / Accepted: 18 February 2009 / Published online: 10 March 2009 # Springer-Verlag London Limited 2009 Abstract In this paper, a methodology is proposed to predict the ductile damage in the sheet metal blanking process using a coupled thermomechanical finite-element method. A constitutive material model combined with the ductile fracture criteria was used. The effect of material softening due to the heat generated during plastic work in a specimen was considered in blanking simulations. To verify the validity of the proposed model, several blanking simulations are performed and the results compared with those obtained from an experimental study. The interaction of fracture initiation and temperature distribution in the sheet metal during the process was studied. The effect of velocity and the clearance on the product shape were examined. It was seen that at high punch speeds the viscous and thermal effects have significant effects on product quality. Keywords Blanking . Thermal . Viscous . FEM Nomenclature " p effective plastic strain Á " effective strain rate s flow stress s 1 maximum tensile stress s h hydrostatic stress A G Goijaerts criterion constant A RT Rice and Tracey criterion constant A O Oyane criterion constant B G Goijaerts criterion constant C i critical damage values T temperature 1 Introduction Sheet metal blanking process is one of the most widely used manufacturing processes. The complex nature of this process involving separation and material fracture makes the design and realization of the metal blanking process an empirical effort. As a result, the appropriate process settings must be determined by time-consuming trial and error, and uncontrollable variations in product dimension often still arise during production. Finite-element technique is an appropriate method to take over the restrictions of the process simulation. Due to improvement of computational resources, the blanking simulation has been developed considerably in recent years and many researchers devoted their consideration to study this process in details. The early works on numerical simulation of the blanking process has been done by Lee et al. [1]. They studied the rigid-plastic analysis of the fine-blanking process with the finite-element method. Faura et al. [2] proposed a method- ology to predict the optimum punch–die clearance accord- Int J Adv Manuf Technol (2009) 45:459–469 DOI 10.1007/s00170-009-1988-9 A. Rafsanjani (*) Member of Young Researchers Club of Islamic Azad University, Tehran-Center Branch, Tehran, Iran e-mail: rafsanjani@mecheng.iust.ac.ir S. Abbasion Department of Mechanical Engineering, Iran University of Science and Technology, Tehran, Iran A. Farshidianfar Department of Mechanical Engineering, Ferdowsi University of Mashhad, Mashhad, Iran N. Irani Department of Mechanical Engineering, Amir Kabir University of Technology, Tehran, Iran