Modeling the effect of laser heating on the strength and failure of 7075-T6 aluminum

Abstract

a b s t r a c tThe effect of rapid laser heating on the response of 7075-T6 aluminum has been characterized using 3-D digital image correlation and a series of thermocouples. The experimental results indicate that as the samples are held under a constant load, the heating from the laser profile causes non-uniform temperature and strain fields, and the strain-rate increases dramatically as the sample nears failure. Simulations have been conducted using the LLNL multi-physics code ALE3D, and compared to the experiments. The strength and failure of the material was modeled using the Johnson-Cook strength and damage models. In order to capture the response, a dual-condition criterion was utilized which calibrated one set of parameters to low temperature quasi-static strain rate data, while the other parameter set is calibrated to high temperature high strain rate data. The thermal effects were captured using temperature dependent thermal constants and invoking thermal transport with conduction, convection, and thermal radiation.

Transient Thermomechanical Simulation of 7075 Aluminum Contraction around a SiO2 Microparticle

“…The purpose of the present simulation was to observe the stress increment during the contraction of the 7075 aluminum [39][40][41], and according to a predefined cooling sequence in which the thermal and mechanical properties change. These properties are shown in Tables 2 and 3.…”

Mechanical Response and Failure Evolution of 304L Stainless Steel under the Combined Action of Mechanical Loading and Laser Heating

“…The mechanism for the primarily slow strength degradation is the low sensitivity of strengthening species in 304L stainless steel to modest temperature increases. Later, with the further increase in temperature, the strengthening species start to lose coherency, and favor mechanical degradation [23][24][25][26]. When the continually-heated specimen with limited thermally activated dynamics continually attains strain energy from the preload, it eventually becomes energetically supportive, to relieve the load through fractures in the specimen.…”

Failure Response of Simultaneously Pre-Stressed and Laser Irradiated Aluminum Alloys

“…The reason behind the initially slow strength degradation is the less sensitivity to modest temperature increases of strengthening precipitates in Al-6061 specimens, until a temperature where precipitates start to lose coherency [10]. When the preload continues to add strain energy to the continually-heated specimen with limited possibilities for dislocation movement, it eventually becomes energetically favorable to ease the load by fracturing.…”

“…Considering the combined effect of mechanical load and laser irradiation, a brief review of studies on aluminum alloys and other structural materials is presented here. Florando et al [10] investigated the effect of laser irradiation on the failure response of aluminum alloy (Al-7075) by using 3D digital image correlation and a series of thermocouples. The specimens were held under constant load and then irradiated by a diode laser (780 nm, 5 kW).…”