Experimental study on static/dynamic local buckling of ping pong balls compressed onto a rigid plate

Ping-pong balls were employed to experimentally study the deformation and buckling behaviors of thin-walled spherical shells compressed onto a rigid plate. First, the quasi-static tests were conducted on an MTS tester, in which the ball was compressed onto a PMMA plate. The compression force and displacement of the crosshead were obtained by the MTS, while the evolution of the contact zone between the ball and the plate was recorded by a digital camera. Two transition points were identified from the load-displacement curve and a snap-through buckling gradually happened after the contact zone reaches a critical size. By correlating the evolution in the contact zone and the load-displacement curve, it is found that the two transition points are corresponding to the traveling of the plastic hinges around the contact zone and the unrecoverable buckling, respectively. In dynamic tests, the ping pong ball accelerated by an air-gun impacted onto a PMMA plate with the velocity ranging 10-50m/s, whilst the dynamic deformation process of the contact zone was captured by a high-speed digital camera. As a result, the impact duration, the maximum contact diameter, and the contact diameter at buckling under different impact velocities were obtained. It is revealed that when contact diameter is the same the energy absorbed by the ping-pong ball is much larger than that in quasi-static tests.