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Previous studies on corrugated metal gaskets have established that the contact width, contact stress, and surface roughness are important design parameters for optimizing gasket performance. However, the contact stress and contact width considering the surface roughness when the leakage occur did not defined yet. In this study, we determined the real contact stress and contact width when leakage started on 25A-size metal gasket. The contact width determined through a comparison between simulation and experimental results. The contact stress determined through a simulation analysis. The experiment involves a helium leakage test using new metal gaskets having different surface roughness levels. The result justified that the real contact width and average contact stress when the leakage started occur were 0.195mm and 800MPa, respectively. There is a good agreement for contact width both by simulation and experiment result. The contact width for flange having surface roughness 1.5μm is longest than the others.

Although many investigations on the mechanical properties of aluminum alloy castings have been performed, there have been few investigations that make positively good use of the effect of impurities reduction. In this study, the influence of impurities on the tensile properties of aluminum alloy casting has been investigated by using aluminum alloy castings of different purity.Al Si Mg alloy castings were melted by cold crucible furnace using the commercial high purity metals. The chemical composition of the melted aluminum alloy casting was same as that of JIS AC4CH. The melted aluminum alloy castings have no strontium modification. Solution treatment and age hardening treatment of the ingot was performed in atmosphere. After the heated treatment, the test pieces for tensile test ware made by machine. Quasi static and impact tensile test were performed in atmosphere at room temperature. The usual AC4CH T6 which has strontium modification was used for comparative material.In both cases of quasi static and impact tensile tests, the tensile strength of Al Si Mg alloy casting melted by cold crucible furnace was lower than that of usual Al Si Mg alloy casting by about some percents and the elongation of Al Si Mg alloy casting melted by cold crucible furnace was bigger than that of usual Al Si Mg alloy casting by more than one and half times. Because there was very little difference in dendrite arm spacing and size, shape, distribution of eutectic silicon between the Al Si Mg alloy castings used in this experiment, it is expected that the impurities reduction is very effective to improve the tensile properties of aluminum alloy casting (AC4CH) from these results.

Contact width is important design parameter for optimizing design of new metal gasket. The contact width was found have relationship with helium leak quantity. Increasing axial force, the contact width will increase and helium leakage will decrease. This study we conducted the surface roughness evaluation of 25A-size metal gasket before and after use. The results denote the real contact width after contact with flange having different surface roughness. The real contact width for the flange having smoother surface roughness is wider than the rougher one.