Lateral release effect in shock-loaded specimens during soft recovery process

Under shock loading a specimen undergoes a uniaxial-strain loading process and a lateral release process, both of which have an influence on the residual structure, while the influence of the latter is often underestimated or even totally neglected. The plastic work generated in these two processes is calculated in this paper, and the stress history from the beginning of the shock loading to the specimen entering the recovery bin is given. It is found that after the lateral release process begins, the specimen experiences cyclic tension and compression load and the amplitude of the cyclic load reaches its maximum under moderate impact pressure. If the amplitude of the cyclic load is larger than the spall strength, the center of the specimen will be destroyed and the specimen cannot be recovered successfully. The ratio of the plastic work produced during the lateral release to that produced during the uniaxial-strain loading decreases as the impact velocity increases. When the impact velocity reaches a certain critical value, the plastic work produced during the lateral release is equal to that produced during the uniaxial-strain loading. At a certain impact velocity, decreasing the initial yield stress of the materials reduces the lateral release effects. Theoretical analysis of the ideally plastic material shows that the ratio of the plastic work produced during the lateral release to that produced during the uniaxial-strain loading decreases as the ratio of the impact velocity to the yield strength increases, which is consistent with the numerical results.