Abstract
The failure response of aluminum alloys (Al-6061 and Al-7075) under the condition of simultaneously pre-stressing and laser heating was investigated. Specimens were subjected to predetermined preloading states and then irradiated by continuous wave fiber (Yb) laser. For all specimens, it was found that the yield stress decreased with increasing laser power density. This implies that the load-bearing capacity of the specimens reduced under increased thermal or tensile loading. Consequently, the specimen’s failure time was shortened by increasing either laser power density or preloaded speed. For Al-6061, a remarkable reduction in failure time by the increase of laser power density is found. However, for Al-7075, under higher preloaded speeds, comparatively smaller impact of laser power density on the failure time is reported. Moreover, for Al-6061, relatively a more non-uniform variation in the average failure time with the increase of laser power density or preloaded speed is observed. The failure mode of Al-6061 turned from brittle to ductile at higher laser power densities; whereas for Al-7075, it changed from quasi-brittle to ductile. At higher preloaded speeds, a greater degree of melting and ablation phenomenon can be seen due to relatively higher temperatures and higher heating rates.
Highlights
The development of a general understanding for durability and damage analysis for structural components exposed to severe thermal heating is the most desirable knowledge in the defense and aerospace industry
The present study experimentally examined the failure behavior of aluminum alloys exposed to combined tensile loading and laser irradiation
The deformation of the specimen develops from thermoelastic effects including thermal expansion and modulus change through yielding to plastic deformation at high strain rates near failure
Summary
The development of a general understanding for durability and damage analysis for structural components exposed to severe thermal heating is the most desirable knowledge in the defense and aerospace industry. Automotive parts will face the load conditions where both high strain rate and rising temperature by adiabatic heating can be induced [3]. Structural reliability will be affected by the presence of thermal stresses, as well as the degradation of the strength properties at elevated temperatures caused by the heating. Since the modulus and yield stress of material generally decreases with the increase of temperature, material strength degrades under elevated temperature situations [4]. Dynamic failure processes are strongly influenced by the state of stress, the strain rate and loading history. The preloading or strain rate and temperature affect the material flow response significantly in deformation processes. Being subjected to quasi-static loading, strain hardening induces an enhancement in the force needed for the
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