Pull-Out and Push-Out Tests for Rubber-to-Metal Adhesion

摘要

A steel rod embedded in a rubber block can be debonded either by pulling it out or by pushing it out. A comparison is made between the two failure forces. It is shown that friction, aggravated by the tendency of rubber to undergo Poissonian contraction as the block is stretched, makes the pull-out force much higher for rods of large diameter, deeply embedded in the block. On the other hand, the push-out experiment is difficult to carry out because of the inherent instability of tall blocks in compression. Thus, pull-out is still the preferred way of measuring adhesion, but the product aL, where a is the rod radius and L the depth of embedment, should be made much smaller than the cross-sectional area of the block in order to minimize frictional contributions to failure force. (jes)