Evolution of real area of contact due to combined normal load and sub-surface straining in sheet metal
- PDF / 4,083,283 Bytes
- 16 Pages / 595 x 791 pts Page_size
- 92 Downloads / 152 Views
ISSN 2223-7690 CN 10-1237/TH
RESEARCH ARTICLE
Evolution of real area of contact due to combined normal load and sub-surface straining in sheet metal Meghshyam SHISODE1,*, Javad HAZRATI1, Tanmaya MISHRA2, Matthijn DE ROOIJ2, Ton VAN DEN BOOGAARD1 1
Nonlinear Solid Mechanics, Faculty of Engineering Technology, University of Twente, Enschede 7522 NB, The Netherlands
2
Surface Technology and Tribology, Faculty of Engineering Technology, University of Twente, Enschede 7522 NB, The Netherlands
Received: 12 April 2020 / Revised: 10 July 2020 / Accepted: 18 August 2020
© The author(s) 2020. Abstract: Understanding asperity flattening is vital for a reliable macro-scale modeling of friction and wear. In sheet metal forming processes, sheet surface asperities are deformed due to contact forces between the tools and the workpiece. In addition, as the sheet metal is strained while retaining the normal load, the asperity deformation increases significantly. Deformation of the asperities determines the real area of contact which influences the friction and wear at the tool–sheet metal contact. The real area of contact between two contacting rough surfaces depends on type of loading, material behavior, and topography of the contacting surfaces. In this study, an experimental setup is developed to investigate the effect of a combined normal load and sub-surface strain on real area of contact. Uncoated and zinc coated steel sheets (GI) with different coating thicknesses, surface topographies, and substrate materials are used in the experimental study. Finite element (FE) analyses are performed on measured surface profiles to further analyze the behavior observed in the experiments and to understand the effect of surface topography, and coating thickness on the evolution of the real area of contact. Finally, an analytical model is presented to determine the real area contact under combined normal load and sub-surface strain. The results show that accounting for combined normal load and sub-surface straining effects is necessary for accurate predictions of the real area of contact. Keywords: asperity flattening; real area of contact; sub-surface strain; zinc coating; sheet metal forming
1
Introduction
Evolution of sheet surface topography due to asperity flattening is one of the key parameters to predict friction and wear at the tool–workpiece interface. For example, friction models proposed by Bay [1, 2] and Wanheim et al. [3] include real area of contact as an important parameter. The real area of contact is much lower than the nominal contact area at the tool–workpiece interface. Therefore, the local contact pressure developed at the asperity level is much higher than the nominal pressure and yield strength of the material, which may plastically deform the asperities. The real area of contact for a given loading condition or a combination
of loads is generally determined either by dedicated experiments or physics based models. There are numerous models and experimental studies available for normal load flattening for un
Data Loading...
