Closure to “Discussion of â€کMechanical Anisotropy and Strain Rate Dependency Behavior of Ti6Al4V Produced Using E Beam Additive Fabrication’†(Pettit, C., Mullen, J., Bhave, T., and Kraft, F. F., ASME J. Eng. Mater. Technol., 137(3), p. 031006)
Abstract
According to classical mechanics definition, if the material properties are the same in all direction, material is called isotropic. The word isotropy means uniformity in all orientations and it is derived from the Greek isos “equal†and tropos “way.†Consequently, if material properties are not isotropic, they are called anisotropic. This is a general definition of isotropy. What Pettit et al. [1] in their discussion mean most likely is what is so called “plastic anisotropy,†using Lankford coefficient, which is used to evaluate the distortion in yield surface in metal forming operations and is used for materials that have experienced large plastic deformation during a process. This is a measure of plastic anisotropy, rather than a general measurement of variation of properties in different orientations.