Low-Velocity Spall Testing of TI-6AL-4V Alloy and New Spall Criterion Based on Mesoscale

摘要

This Interim Report covers the contract period from Sept 17/2002 to Dec. 16/2003 (the second period of three months). The research in this Project is directed toward better understanding of the fracture process due to the local plastic fields occurring in mesoscale during spalling of Ti-6Al-4V alloy. Preliminary planar impact tests have been performed using specimens in the form of disks of different thickness and DIA 57.0 mm delivered by AMSRL-WM-TA, APG aberdeen, MD. The plate-plate facility is in the stage of functioning after some period of preparation. A methodology of observation of the fracture surfaces after spalling on the mesoscale has been prepared More exactly, the surface topography after spall fracture has already been analyzed for an aluminum alloy (preliminary analysis) and some statistics programs were tested. A new, high resolution profilometer, based on the light interference: WYKO NT1000 by VEECO has been applied in this part of the Project The profilometer is equipped with a software which permits for variety of statistical analyses. This software permits for a detailed analysis of profiles in 3D. The 3D profiles will be compared with the scanning microscope data for the same areas An additional series of the improved Direct Impact Shear Test has been performed for Ti-6A- 4Valloy. The test results obtained from DIST at high strain rates -l0(3) I/s will be applied to identify the material constants in new temperature coupled model of spalling based on mesoscale.