THE ABILITY TO CLINCHING AS A FUNCTION OF MATERIAL HARDENING BEHAVIOR

Tadeusz Balawender

doi:10.12776/ams.v24i1.940

Abstract

Mechanical clinching can be used to joining different metallic materials. The only restriction are their plastic properties. However some plastic materials, with good ductility, do not conform strong clinch joint, e.g. materials, featured by high strain hardening phenomena are difficult to clinching and do not create durable clinch joint. In case of others materials with limited ductility clinch forming generates the process-induced defects such as cracks. So, there are material’s features which are very important for the clinch forming process and among them the strain hardening properties seem to be in special importance. The clinch joints of different materials with diversified plastic and strength properties were tested. A single overlap clinch joints with one clinch bulge were realized in the tests. The joints were tested in the pull test. The obtained results showed the relation of the clinch joinability to the materials’ strain hardening exponent. The good quality and good strength joints, were obtained for materials with low value of strain hardening exponent below n = 0,22.

Highlights

The clinch joint forming process consists in localized cold forming of joined metallic materials with a punch and a die
The results of shear- tensile tests of clinch joints of tested materials are shown in Table 1, too
Strain hardening exponent and they are not clinchabele materials; the joint of CuZn37 brass sheets was very weak

Summary

Introduction

The clinch joint forming process consists in localized cold forming of joined metallic materials with a punch and a die. The stage proceeds when joined sheets reach the bottom of the die impression and further compression action between die and punch causes radial movement and additional reduction of sheets’ thickness During this stage, filling of the die cavity, i.e. the die groove placed in the bottom of impression and forming of the joint interlock proceed. Using of extensometer to measure the displacement let to confine a recorded deformation of the joint sample almost to the lap area range As it was shown in [8, 9] very important are friction conditions between working surfaces of tools and sheets. Low value of friction coefficient is favourable for plastic deformation, especially in the compression stage of clinching process, when thickness of the clinch joint bottom and interlock are formed. In all realized tests materials were clinched without any surface preparation

Results and discussion

Relative shear load of clinch joint aluminium

Conclusions