Materials safety and selection for the application of metals in high-pressure hydrogen storage of fuel cell vehicles were introduced based on the hydrogen gas embrittlement (HGE) examinations using the materials testing equipment. Testing steps are as follows; the 1st step is the tensile test in high-pressure hydrogen by slow strain rate technique to evaluate the effect of hydrogen and divide the materials into five categories based on stress-strain curves. The materials of type III, IV and V are picked up and their yield points and ultimate tensile strengths are collected. The 2nd step is the fracture mechanics test to obtain KICs and KIHs of type III, IV and V materials. The materials of type IV and V are considered to be applicable as usual. The 3rd step is the crack growth test to obtain the fatigue crack growth data. A special consideration of HGE is taken for the design of the equipment with limited operation period or cycles for the materials of type III. The issue of the Kth’s reproducibility remains unresolved, which calls another testing method and design concept. Candidate materials are then nominated following the procedure of materials selection.
Abrasive slurry jet (ASJ) is a promising technology to process a variety of materials with advantages of high flexibility, no heat affected zone and high cutting efficiency. In this paper, the impressions generated on a quartz crystal specimen by the impacts of micro-particles laden in a water flow and the associated impact erosion mechanisms are presented and discussed in order to effectively and efficiently control the machining quality. Both brittle and ductile mode erosions coexist in the machining process due to the influence of the fluid motion on the trajectories of particles near the target surface. Large-scale craters produced by brittle conchoidal fractures associated with crashed zone, radial and lateral cracks, dominate the erosion process at large jet impact angles while small-scale craters involving micro-ploughing and micro-cutting are produced by the ductile mode erosion at small jet impact angles. The relation between the process parameters and the overall average volume of craters has also been quantitatively analyzed. A combination of small jet impact angle and abrasive particles and low water pressure is preferred for improving the surface quality after the ASJ machining process caused by the more formation of ductile mode induced craters on the target material, but it is at the sacrifice of the material removal rate as well.
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