Papers by Author: Rui Ting Tong

Abstract: To improve the car's active safety, studies on electromechanical brake (EMB) system have been taken in recent years. The principle and characteristics of EMB are investigated in this paper. An EMB system is designed, and a ballscrew/ballnut assembly is used as the transmission device. The comparison of hydraulic brake (HB) and EMB shown that EMB could regulate brake force more quickly and accurately.

Abstract: Based on the current study of planetary roller screw(PRS), a summary of how to match the main parameters of the PRS is obtained. A mathematic model for contact analysis is developed, where series of equivalent balls are used to replace the rounded profile of the roller. At the same time, the formula of axial contact deformation of the PRS is derived. Then a simplified finite element model of the PRS is established and the contact analysis is conducted by FEA. The FEA results and the theoretical ones agree well with each other, so the accuracy of the calculation method and the validity of the equivalent method are verified.

Abstract: Coupled molecular dynamics simulation and finite element method, a multiscale method is used to model nanoscale sliding contacts problems. According to an experimental sample, 4 textured surfaces with different asperity shapes are designed. Through the friction forces comparisons between smooth surface and textured surfaces, the effects of texture shapes are investigated, and 2 better textured surfaces are discovered to reduce friction forces.

Abstract: Based on the meshing principle of Planetary Roller Screw (PRS), the meshing clearance of screw pair is minimized by taking the half of thread angle, and the pitch diameter tooth thickness, e, as the optimization variables. Optimal structural parameters are obtained by using optimization module of the software Matlab. The 3D model of PRS structures are established with Solidworks and the finite element contact analysis is carried out with Ansys. The contact deformation and stress distribution are calculated among screw, rollers and nut. The results can be used for PRS design.

Abstract: A multiscale method coupled molecular dynamics simulation and finite element method is used to investigate two dimensional nanoscale sliding contacts between a rigid cylindrical tip and an elastic face centered cubic copper substrate with textured surface, in which adhesive effects are considered. Two series of nanoscale surface textures with different asperity shape, different asperity heights and different spacing between asperities are designed. Through the friction forces comparisons between smooth surface and textured surfaces, a better shape is advised to indicate that asperity shape plays an important role in friction force reduction. With proper asperity height and proper spacing between asperities, surface textures can reduce friction forces effectively.

Abstract: Surface texture, as one of the typical surface integrity characteristics, plays a vital part in efficiently and systematically evaluating the surface integrity and relevant mechanical properties of machined parts. Commonly used 2D surface roughness parameters are formularized and discussed in this paper. And 3D characterization technique is also illustrated through measuring and describing a machined surface with an optical profiling system. The relationship between surface texture and the fatigue property of final machined parts are discussed by employing the quantity of effective stress concentration factor which could be expressed by the standard surface roughness parameters and measured averaged root radius of surface texture’s valleys. This research emphasizes the indispensable role of the surface texture in evaluating surface integrity and corresponding functional performance of machined parts.

Abstract: Groundbreaking work and past standard of surface integrity regarding description, measurement and evaluation of machined components are retrospected. Typical surface integrity characteristics such as surface topography, macro and microstructure, microhardness and residual stress distribution are preferentially adopted for quantitatively describing and systematically evaluating of surface integrity. Corresponding processing conditions and fatigue performance along with surface integrity characteristics are also detailedly classified and digitally defined through meaningful data sets. A framework of surface integrity model for machined components is subsequently proposed and preliminarily established by understanding the nature of surface integrity and its relation with processing parameters and fatigue properties. This pilot study offers a conceptual model as well as some feasible operational approaches for control of surface integrity in cutting technology and consequent improvement of the fatigue life for machined components.

Abstract: A thermal elasto-plastic asperity contact model is investigated in this paper, which takes into account the steady-state heat transfer and the asperity distortion due to thermal elasto-plastic deformations. A hard coating and a soft coating are applied to study the correlations between contact area and contact pressure, average gap and contact pressure, coating thickness and contours of the contact stress distribution et al. The effects of material properties, the coating thickness, frictional coefficient, and the heat input combinations on the stress distribution are investigated and discussed. The results may help to make an appropriate choice of the hard coating thickness.