The effect of loading rate on the elasto-plastic flexure of steel beams

Abstract

The plastic behaviour of structural elements subjected to dynamic bending is discussed in relation to the strain-rate dependence of the flow stress. Theoretical and experimental work based on the concept of a dynamic fully plastic moment is summarized, with special reference to the yield behaviour of mild steel. A new dynamic loading machine is described which permits the deformation of a beam specimen in pure bending at speeds giving maximum strain rates up to 20 s -1 . The apparatus incorporates transducers which permit the recording of bending moment and deformation rate throughout the test. The paper gives the results of dynamic flexure tests on a 0.10 % carbon steel and also the results of dynamic compression tests on the same material. The relation between the two sets of results is discussed, and it is concluded that the behaviour in bending exhibits features which are not predictable from the compression test data.