Abstract
Understanding the mechanical behavior of materials at extreme conditions, such as high temperatures, high strain rates, and very large strains, is fundamental for applications where these conditions are possible. Although tensile testing has been used to investigate material behavior under high strain rates and elevated temperatures, it disregards the occurrence of localized strains and increasing temperatures during deformation. The objective of this work is to combine synchronized full-field techniques and an electrical resistive heating system to investigate the thermomechanical behavior of commercially pure titanium under tensile loading at high temperatures and high strain rates. An electrical resistive heating system was used to heat dog-bone samples up to 1120 °C, which were then tested with a tensile Split Hopkinson Pressure Bar at strain rates up to 1600 s−1. These tests were monitored by two high-speed optical cameras and an infrared camera to acquire synchronized full-field strain and temperature data. The displacement and strain noise floor, and the stereo reconstruction error increased with temperature, while the temperature noise floor decreased at elevated temperatures. A substantial decrease in mechanical strength and an increase in ductility were observed with an increase in testing temperature. The localized strains during necking were much higher at elevated temperatures, while adiabatic heating was much lower or non-existent at elevated temperatures.
Highlights
Titanium alloys are consistently employed in aerospace and racing engineering applications, due to their high mechanical resistance and low density
The objective of this work is to combine synchronized full-field techniques and an electrical resistive heating system to investigate the thermomechanical behavior of commercially pure titanium under tensile loading at high temperatures and high strain rates
An electrical resistive heating system was used to heat dog-bone samples up to 1120 ◦C, which were tested with a tensile Split Hopkinson Pressure Bar at strain rates up to 1600 s−1
Summary
Titanium alloys are consistently employed in aerospace and racing engineering applications, due to their high mechanical resistance and low density. A temperature gradient in the Split Hopkinson Pressure Bar (SHPB) distorts elastic wave propagation, changes the particle velocity, and causes additional dispersion to the loading pulses [8] These factors interfere with the precision of the stress and strain measurements made during mechanical testing. There is more to a tensile test than what a single average value over the gauge volume can describe, as materials can display strain localization and localized adiabatic heating in phenomena such as necking [6], shear bands [2,5], and Portevin–Le Chatelier (PLC) bands [9] For this reason, it is interesting to pursue the acquisition of full-field measurements during testing so that such phenomena can be properly described and investigated
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