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Development of New Material Rapid Evaluation Technology with the Aid of Mechanics Models.

The progress of materials science has provided the world with a multitude of new materials with outstanding mechanical properties, including lightweight and high-strength materials. However, each new material requires an evaluation to determine whether it satisfies the strength reliability required for a mechanical structure, and this normally takes some time. At this laboratory, we have implemented mechanics to develop a technology that can be used to evaluate the strength reliability of new materials rapidly, and it has been applied to the utilization of newly developed non-combustible magnesium alloys.

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A defect (blow hole) shown on the fracture surface
of the non-combustible magnesium alloy with silicon.

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Definition of √area


Although steel is widely used as a material in mechanical structures, 100 years has passed since its appearance. Some structures are old, and have been in long use while supporting various loads, which has an effect on the mechanical structure. The shape of each structure also has a bearing on its strength, as do various environmental influences. Since conventional material testing examines a combination of various parameters, it is a time-consuming process. Although principle clarification of the microscale (atomic level) using materials science as another approach has been mentioned, since the target scale is very different from the mechanical structure's scale, it is not easily to put into practical use. So, in this study, through mesoscale observation and property evaluation at a level somewhat greater than microscale, a mechanics model of a phenomenon is built, the strength-of-materials technique of evaluating macroscopic characteristics is used, and a technology for rapidly evaluating the strength reliability of new materials is being developed.

Since a new magnesium alloy has an outstanding specific tensile strength (ratio of weight to strength), and offers superior recycling efficiency and damping capacity, it is a material that is expected to be widely used in automobile engines. However, the previous magnesium alloy suffered from strength loss and even ignition at high temperatures. The new non-combustible magnesium alloys have displayed greater strength at high temperatures because silicon is added to the alloy. The ignition point was also raised by adding calcium to the magnesium alloy. However, problems remain when casting with silicon-enhanced non-combustible magnesium alloys. These include the oxide that is an unavoidable by-product, and blowhole defects, both of which remain to be addressed. In this study, we are constructing a mechanics model to promptly evaluate the strength reliability of the material containing a defect, and working to develop a technique for utilization of the material.

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Evaluation method for defects in material.

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Micrographs around fatigue crack from an artificial defect.


Solid Mechanics Laboratory,
Department of Mechanical Engineering, Faculty of Engineering, Kyushu University
Professor Hiroshi Noguchi
Associate Professor Shigeru Hamada
Assistant Professor Motomichi Koyama
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