The mechanical response of an A359/SiCp MMC and the A359 aluminum matrix to dynamic shearing deformations

The mechanical response of a metal-matrix composite to dynamic shearing deformations has been measured, using a new design of the thin-walled tubular specimen for the torsional Kolsky bar experiment that allows working with these difficult-to-machine materials. The advantages of using the new specimen design are as follows: (i) the thickness of the thin wall along the axial direction is very uniform; (ii) specimen machining is extremely simple; (iii) the cost of specimen machining is greatly reduced. The approach has been used to characterize the high shear strain rate (10(3) s(-1)) behavior of an A359/SiCp composite and its corresponding A359 monolithic alloy with the torsion Kolsky bar. The experimental results show that the flow stress of the composite in shear increases in the presence of SiC particles, whereas the failure strain is reduced. The shear failure strains of both the A359/SiCp composite and the A359 monolithic alloy appear to increase with increasing strain rate. Previous observations have shown that particle fracture develops during compressive deformations of this material. However, particle fracture is not a significant damage mode during the shearing deformations of the composite, and this is reflected in differences between the torsional and tension behaviors of the material. (C) 2004 Elsevier B.V. All rights reserved.