Simultaneous and Synchronous Full Field Deformation and Temperature Measurements in High Rate Events
Abstract
High strain rate deformation is very important for military and civilian applications. Various impact events, blast, and explosions are military examples where high rate deformation occurs. For civilian applications, numerous forming and machining operations of metals induce large strains at a high rate on materials. The material behavior, strength, ductility, shear localizations, and energy absorption are strongly influenced by the deformation rate. Engineers and scientists have tried to collect quality data from high temperature dynamic tests, but with rather poor success. A precise measurement must contain accurate information of forces, deformation, and temperature at high spatial resolution with microsecond time resolution. The optical strain measurements using Digital Image Correlation and fast Infrared thermal cameras show potential for full field simultaneous deformation and strain measurements. The typical instrument used for dynamic tensile testing is the Hopkinson Split Pressure Bar device, which however, has some inherent problems related to the deformation measurements. The sample simply deforms inhomogeneously due to its dog bone shape and strain hardening of the gage section. Nowadays it is recommended that the strains and the strain rates are obtained using an independent measurement device. Our objective is to develop simultaneous full field strain and temperature measurement method, and to use this method to study high strain rate tension behavior of selected materials up to the melting temperature of the metal at strain rates above 1000-s. We will investigate what are the effects of testing temperature and strain rate on the strain rate sensitivity, strain localization, and necking behavior of the selected wrought and 3D printed titanium and Inconel alloys at extreme conditions. We will also determine the Taylor Quinney coefficient of the test material as a function of strain, strain rate, and test temperature at high spatial resolutions.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jan 14, 2022
- Source ID
- FA95501917016
Entities
People
- Mikko Hokka
Organizations
- Air Force Office of Scientific Research
- United States Air Force