Femtosecond Laser-Pulse-Induced Surface Cleavage of Zinc Oxide Substrate

The induction of surface cleavage along the crystalline structure of a zinc oxide substrate (plane orientation: 0001) by femtosecond laser pulses (wavelength: 1030 nm) has been reported; a scanning electron microscope image of the one-pulse (pulse energy: 6–60 μJ) irradiated surface shows very clear marks from broken hexagons. This cleavage process differs from the general laser-induced melt process observed on the surfaces of narrower-bandgap semiconductors and other metal materials. This phenomenon is discussed using a multi-photon absorption model, and the pulse-energy dependence of the cleavage depth (less than 3 μm) is quantitatively analyzed. Laser-induced cleavage is found not to occur under multi-pulse irradiation; when more than four pulses are irradiated upon the same spot, the general laser-induced melt process becomes dominant. This cleavage–melt shift is considered to be caused by the enhancement of absorption due to the initial pulses, which is supported by our measurement of cathodoluminescence

Study on Cage Wear of Railway Traction Motor Bearings Based on Analysis of Rolling Element Motion

Cylindrical roller bearings used in traction motors for railway vehicles are used at high rotational speeds and under light loads. Under these operating conditions, the life due to cage wear is much shorter than the life due to raceway fatigue. Therefore, bearing life can be extended by reducing cage wear. The authors thought that to reduce cage wear, it is necessary to establish a dynamic analysis method for the contact between the roller and the cage, and to identify the wear mode of the cage. If cage wear follows Archard’s equation, then cage wear is proportional to the impulse caused by the contact between the rollers and the cage. Therefore, in this paper, a simple model consisting only of a roller and a cage was constructed, and the impulse was obtained via dynamic analysis. The impulses calculated by the dynamic analysis were in good agreement with those measured. In addition, the experiments showed that cage wear is proportional to the impulse and revealed the wear mode of the cage. These allow the method proposed in this paper to be used to predict cage wear and to determine bearing specifications to reduce cage wear

IMECE2004-61767 MICRO-EDM DEPOSITION ALLOYING PROCESS

ABSTRACT A new deposition alloying process using Micro-EDM was developed. Using the energy released by the electrical discharge, material from the tool electrode is melted and deposited over the work surface. When a rotating bi-metal tool electrode is fed towards the work surface, the alloying between its elements occurs during process. The obtained results of the alloying between nickel and iron are presented in the present paper, when the components of the bi-metal tool electrode are made of YNi-1 (nickel alloy used in TIG welding -JIS standard) and medium carbon steel (S45C -JIS standard). X-ray and EDS analysis have shown that the chemical composition of the obtained deposit can be controlled and is proportional to the cross sectional area of each element present in the bi-metal electrode. With this process, a material with the same composition of Invar was successfully deposited

Static Hydrophobic Cuprous Oxide Surface Fabricated via One-Step Laser-Induced Oxidation of a Copper Substrate

In this study, we developed a one-step method for fabricating hydrophobic surfaces on copper (Cu) substrates. Cuprous oxide (Cu2O) with low free energy was successfully formed after low-fluence laser direct irradiation. The formation of Cu2O enhanced the hydrophobicity of the Cu substrate surface, and the contact angle linearly increased with the proportion of Cu2O. The Cu2O fabricated by low-fluence laser treatment showed the same crystal plane orientation as the pristine Cu substrate, implying an epitaxial growth of Cu2O on a Cu substrate