Papers by Author: Megumi Uryu

Abstract: In this work, wear of reinforced poly-ether-ether-ketone (PEEK containing PTFE, graphite and carbon fibres) polymer bushes in friction against 7075 aluminium alloy cam plates is investigated in order to establish the application possibilities in transmission parts in humanoid robot joints. The PEEK bush surface conditions as well as the input axis-output axis transmission error (backlash) require close examination. Sliding wear tests were performed on bushes under 900 kgfcm loaded torque, while the cam plate oscillated. Based on the wear observation, it was found that PEEK wear fragments in the interface between PEEK bush and aluminium alloy cam plate formed a PEEK film.

Abstract: Failure of dies and molds is caused by wear and deformation during the metal sheet forming process. Die wear takes various forms, and the contact conditions in die-parts affect the strength of the components. Non-destructive methods that can be related to contact conditions are necessary to study and understand the phenomena caused by the contact stresses. In the present work, a newly developed scanning Hall probe microscope (SHPM) equipped with a GaAs film sensor was used to observe the three-dimensional magnetic fields in tool steel plates before and after contact tests at room temperature in air. It was found that the intensity of three-dimensional magnetic fields is only slightly affected by the spherical Hertzian contact. However, all of the three-dimensional components of the magnetic fields change significantly. The extent of the changes depends not on the distribution of stress under spherical Hertzian contact but on the initial distribution of the magnetic fields.

Abstract: Fatigue failure of steel occurs when cracks form in a component and continue to grow to a size large enough to cause rupture. In order to understand the crack initiation and propagation phenomena, non-destructive evaluation methods that can be correlated to in-situ measurements around the crack tips are necessary. In the present work, we developed a scanning Hall probe microscope (SHPM) equipped in a GaAs film sensor to observe fatigue cracks at room temperature in air while they were growing. Medium carbon low alloy steels specimens (JIS S45C) were used in the experiments. Only the area around the crack tip was magnetized and the changes at the crack tips were observed.