Influence of the Sheet Edge Condition on the Fracture Behavior of Riv-Bonded Aluminum-Magnesium Joints

Abstract

This work investigates the influence of the sheet edge condition on the fracture behavior of riv-bonded aluminum-magnesium lap joints under monotonic-static and cyclic-dynamic shear-tensile loads. Therefore, sheets of 1.5 mm-thick EN AW-6016-T4 aluminum alloy were joined with sheets of 2.0 mm-thick AZ91 magnesium alloy using two C5.3×6.0-H4 rivets and epoxy-based adhesive. The side edges of the sheets were either shear-cut or milled after cutting. Before testing, the joints were heat-treated at about 180-200 °C for 20 min in order to cure the adhesive and to peak-age the aluminum alloy. The cyclic load maximum was about 40 % of the monotonic load maximum. The cyclic load minimum was 10 % of the cyclic load maximum, i.e., the load ratio was R = 0.1. The edge condition of the sheets did not have any significant influence in monotonic-static testing; however, in cyclic-dynamic testing the number of cycles to fracture was about four-times higher for samples with milled side edges than for samples with shear-cut side edges. Hence, the potential load capacity of riv-bonded aluminum-magnesium joints cannot be exploited under cyclic loading, if the magnesium sheet has edges with poor quality.