Hiroki Endo

Research on the wear characteristics of hypereutectoid steel

Abstract In this research, the wear behavior of hyper-eutectoid steel was examined at ambient temperature ranging from room temperature to a high temperature of 400 °C. A common asymmetric test rig was used, where a pin specimen of hyper-eutectoid steel is pressed against a disk of carbon steel for machine structure use. Two types of pin specimen were prepared: an as-received specimen and a quenched specimen.. As a result, the following was clarified. The protective surface film of iron oxide is not a main factor in determining the wear behavior of the hyper-eutectoid steel of as-received pin specimens. The wear behavior is closely related to the separation of the oxide film from bulk material when the sliding conditions are severe. The wear behavior of a quenched pin specimen is strongly influenced by a microstructural transition and a reduction in hardness of the pin specimen at elevated temperature.

Some considerations of slideway friction characteristics by observing stick-slip vibration

It is important to clarify the frictional characteristics of a slideway and to prevent unstable vibration, such as stick-slip vibration, for the improvement of kinematic performance and for precise positioning. In this research, the relations among the dynamic friction characteristics, the pitching motion or the floating up of the slider, the surface roughness of a slideway, and the lubricant property are investigated experimentally. As a result, some points necessary for the kinematic performance improvement of the slider are clarified.

Effect of reciprocating and unidirectional sliding motion on the friction and wear of copper on steel

From the practical necessity to obtain the friction and wear characteristics of materials used in machinery, various types of wear-testing machines have been developed and used. To obtain useful data for practical application, it is desirable that the investigation is carried out by a full-scale wear-testing apparatus having approximately similar contact conditions. Generally speaking, the obtained wear characteristics are different for every wear-testing apparatus used. When the type of wear-testing machine is not suitable, one cannot obtain the required wear characteristics. There are various parameters in wear-testing machines, such as configuration of contact surface and form of the relative motion between the test specimens. Thus, in this report, the effect of relative motion between contacting pair and friction process on obtained test results is investigated, for the combination of a copper pin specimen and a flat steel specimen. The microscopic structure of the pin specimen may be varied due to the friction and wear process. An optical microscope is used for the observations. The pin specimen is made from pure copper, which can be deformed easily.

Prototype fretting-wear testing machine and some experimental results

Abstract A new prototype fretting-wear testing machine is developed, and its performance is evaluated. In this testing machine, a spherical specimen is oscillated by a lead-zirconate-titanate semiconductor (PZT) actuator, driven by means of computer control. Thus, an arbitratry input waveform, such as sinusoidal wave, triangular wave and so on, can be easily operated to a spherical specimen. This is the special feature of our testing machine. As an example, a fretting experiment is carried out, using a steel flat specimen and a bearing steel sphere specimen. A sinusoidal input wave is added by a PZT actuator. It is clarified that there is a boundary fretting amplitude, beyond which fretting wear mass or volume increases abruptly.

Fundamental studies on friction and wear of engineering plastics

Engineering plastics having good mechanical properties are at present frequently used as materials for various machine elements. In this research, experimental investigations have been carried out regarding tribological factors such as friction and wear for five kinds of fundamental engineering plastics: non‐reinforced polycarbonate, polyphenylene oxide, polyamide, polyacetal, and polybutylene terephthalate. It is clarified that the tribological properties, especially the wear properties of the engineering plastics are influenced by the friction conditions and heat transfer characteristics on contact surfaces. However, no clear effects of mechanical strength such as tensile strength or hardness are seen. Thus, the fundamental wear properties of engineering plastics are strongly influenced not only by their own thermal characteristics but also by those of contact surfaces.

Studies on fretting wear: influence of rubbing surface materials and some considerations

When a small tangential relative displacement is repeatedly made between surfaces to which a quasi-static normal force is applied, fretting fatigue or fretting wear are induced. There are many factors influencing these fretting phenomena. In this study, fretting wear is observed experimentally for various surface material combinations, and fretting wear volume is estimated through a newly proposed method. The influence of surface materials on fretting wear is made clear by estimating the fretting wear size, fretting wear volume and cross-sectional area configuration of the wear scar. Four plate specimen materials are used in the experiment. They are a carbon steel for machine structural use, aluminum alloy, cemented carbide and Sialon ceramics.

In-plane deformation observation of indentation along indenter surface

In this paper, the in-plane plastic deformation, which is perpendicular to the contacting load, of soft metal in contact with a hard spherical indenter is observed on a rolled aluminum surface. By measuring a displacement due to indentation of lattice points described on the aluminum surface, the in-plain deformation is obtained. Many small ferrous impurities are scattered on and in this aluminum specimen. When a hard spherical indenter is pressed onto this aluminum surface, the distance between impurities is changed by the surface plastic deformation. The change in distance between impurities is obtained using the image processing method, and it is demonstrated that the in-plane plastic deformation of surfaces caused by indentation can be observed. Results by both the lattice point method and the image processing method are compared quantitatively.

Transient rolling behaviour of a slider supported by two rollers

A rolling element has a spring characteristic in the transient displacement region from the stationary state to a continuous rolling motion. For this reason, a bearing having a rolling element is useful for constructing an ultra-precision positioning device. In this paper, a mechanism for the damping capacity generation of a rolling element is investigated, to improve the dynamic characteristic of this positioning device. A stage supported by two rollers is constructed, and its tangential displacement is measured accurately when the driving force is acting. As a result, it is confirmed that the rolling element has a nonlinear spring characteristic. Energy loss is generated by the reciprocating motion of the stage in the transient displacement region. This is the main cause of the damping capacity. Furthermore, this energy loss or damping capacity of the stage can be improved by using two rollers with different diameters.

Additional effect of electroless plating film (damping capacity improvement)

Electroless plating treatment is one surface modification technique. An added effect due to electroless plating is expected, and the vibration damping capacity of the structures may be improved by this technique. In the present study, the vibration damping capacity of such electroless plated structures is measured experimentally. Damping capacity can be improved regardless of the plated film materials. Improvement efficiency with an electroless plating film with dispersed foreign particles such as SiC ceramics is higher than with a uniform electroless plating film.

Deformation simulation of ground materials by coated abrasives (wear test)

Purpose – This study seeks to clarify the behavior of ground materials and the grinding mechanism corresponding to the wear of abrasives, in the grinding process by coated abrasives.Design/methodology/approach – Cemented carbide ball indenters for abrasive grains were used. Cemented carbide ball indenters have a definite shape. Grinding process is carried out using a wear‐testing machine with a reciprocating motion. This is an abrasive wear test. The deformation of the ground material is observed by the measurement of the worn groove and optical microscopic photograph of the worn ground surfaces.Findings – Grinding process regularly proceeds when indenter diameter is small, that is, abrasive has a good cutting quality. However, when abrasives are gradually worn and the cutting quality becomes worse, a groove formed by grinding process is again filled up by the re‐adhesion of the generated worn debris. So, the grinding process by coated abrasives is impossible.Research limitations/implications – To clarify...