Integral bending moment absorber system for mechanical testing of materials

摘要

An apparatus is invented that accurately determines the failure or fracture stress of materials that behave in a brittle manner while under static or dynamic loadings that applies a stress to a test specimen in tension, compression, shear, or combination thereof, or in the case of cyclic loading stressing a fatigue sample. The bending and twisting of the test specimen due to the inherent misalignments in conventional test systems are drastically reduced by this device, which utilizes a hollow cylinder, termed a bending moment absorber whose ends are fitted and fixed to the ends of a dumbbell or flat specimen. This assembly, in turn, is clamped at each end by commercially available hydraulically-operated grips within the load train. This device causes the combined cross- sections of the hollow cylinder and the specimen to act in concert so as to markedly increase the moment of inertia of the system and thus reduce both the imposed bending stress and the error during testing. If the bending moment absorber and the specimen are of dissimilar materials and their modulus of elasticity ratio is less than 1. 0, while their fracture strength ratio is greater than their modulus ratio, then failure will occur in the specimen, and the moment absorber will be reusable. In addition, this apparatus can be operated at cryogenic, ambient, or elevated temperatures.