Pressure Distribution In Contact Area Research Articles

Edge effect and indentation depth-dependent contact behavior in contact of an elastic quarter-space

The edge effect in contact of an elastic quarter-space is numerically studied in this work. The extension of Hetényi’s approach of overlapping two elastic half-spaces is implemented in the boundary element method to obtain the solution of an elastic quarter-space whose top and side surfaces could be both loaded. In the study on the indentation test of a rigid sphere on an elastic quarter-space, the dependencies of the normal force, mean contact radius, and pressure distribution in contact area as well as the internal von Mises stress in relation to the position of the sphere from the side edge are obtained numerically and expressed by fitting the numerical results. These equations can be also used to interpret the indentation depth-dependent contact behavior: from Hertzian contact at the beginning of the indentation to the non-circular contact at large indentation depth.In addition, the results are compared with a contact case of a quarter-space in which the side surface of the quarter-space is not completely free: shear stresses on the side surface vanish but normal stress exists. The latter case generates very similar results, especially the contact area, but its solutions are much easier to achieve by applying a symmetrical loading on an elastic half-space, offering an effective way to approximate the solution of a quarter-space.

Simulation and experimental study on the concave influence function in high efficiency bonnet polishing for large aperture optics

A detailed study of the concave influence function (IF) of bonnet polishing (BP) has been carried out by using theoretical and experimental method. The material removal model of bonnet polishing is established based on Preston’s law. Finite element analysis (FEA) is used to study the pressure distribution in the contact area. Meanwhile, the difference between Gaussian shape and concave IF is studied. The fixed position and surface polishing experiments have been conducted to verify the material removal capacity of the concave IF. The results show that the shape of the IF is mainly affected by the pressure distribution in contact area, and the IF is changed from Gaussian to concave when the compression is larger than 1 mm. The material removal rate (MRR) of the concave IF is higher than that of the Gaussian IF, as the MRR of the concave IF could reach 6.84 mm3/min. The removal capacity of the concave IF is similar to the Gaussian IF, and the effectiveness of the concave IF in high efficiency bonnet polishing is validated.

Tread wear and footprint geometrical characters of truck bus radial tires

Wear and mileage performance are the foremost performances for truck bus radial (TBR) tires. There are a lot of researches about the tire wear performance as well as the contact patch phenomenon by using finite element analysis (FEA) method or testing. But there is little published data on the correlations between the footprint geometry and the tread wear performance of tires. In this paper, an experiment on tire-ground performance of TBR tires is carried out by using Tekscan. The real-time changes of contact-area pressure distribution that occurred during the process of continuous load and unload are recorded. Three types of tires that act differently in behavior under normal usage are analyzed. A new method of researching in tire tread wear, which focuses on the geometrical characters of the footprint, is put forward. The experimental results of the three tires are described by using footprint geometrical characters. On the basis of studying the changing laws of footprint geometrical characters during the loading process and considering consumer survey and factory feedback information, the correlations between the geometrical character of footprints and tread destruction form are built. The analyzed results show that a greater contact area coefficient and a steady coefficient of contact result in a better wear performance for TBR tires. The footprint-shape coefficient changing laws in the process of loading are found to have a very good coincidence with the tread wear of the three types of tires. Tires with a smaller footprint-shape coefficient are likely to have an average tread wear while avoiding the shoulder wear first. The proposed research provides a new solution to predict tire-ground performance at the point of footprint and several useful references for improving tire design.

2402 車輪フランジ接触面形状の評価手法(OS4 接触問題とトライボロジ,オーガナイズド・セッション(OS))

This paper describes the measurement method of the contact condition between the wheel flange and the rail gauge corner. One of the most essential factors causing the flange climb derailment is the increase of coefficient of friction which is closely related to the surface condition of wheel flange. The purpose of this study is to clarify the mechanism of the increase of coefficient of friction from the aspect of visualization of the contact condition. In this study, we have proposed the measurement method for the contact shape and pressure distribution between the wheel flange with complicated surface figure and the rail gauge corner using the ultrasonic technique and the subtraction imaging method. And, we have confirmed the shape and pressure distribution of contact area by this method.