Papers by Keyword: Surface Integrity

Abstract: This paper presents a diagram of maximum contact zone temperature T_max versus contact time Δt, based on the analysis of workpiece surface layer properties after cylindrical grinding experiments. Apart from resulting surface layer properties, process quantities (T_max, normal and tangential grinding forces F_n, F_t) are investigated with reference to the resulting workpiece surface layer state as well. Ground workpieces are analyzed by performing Barkhausen noise level measurements together with subsequent metallographic and X-ray diffraction investigations. By mapping characteristic values T_max and the contact time Δt to corresponding surface layer properties, a general analysis of workpiece material response to the thermo-mechanical load during grinding is possible.

Abstract: The abrasive-wear resistance and the lifetime of tribologically stressed free-formed surfaces of forming tools can be increased by thermally sprayed tungsten carbide coatings. In order to improve the surface quality and the shape accuracy, the workpieces must be machined prior to industrial application. A suitable machining process is NC grinding on five-axis machining centres using abrasive mounted points. However, the high hardness of the applied coatings and the small diameter of the utilized tools pose a great challenge for the process design. In order to optimize the grinding process and predict the resulting surface topography, a geometric-kinematic simulation based on the modelling of individual grains using Constructive Solid Geometry techniques was developed. In this paper, the results of fundamental investigations on grinding tungsten carbide coatings and the developed process simulation are presented.

Abstract: A variety of current scientific work shows the importance and possibilities of an effective conditioning of tribological contacts to minimize friction and wear, respectively an increase in performance of tribological highly stressed components. By slight modifications of the finishing process positive effects like the increase of lifetime or increase of power can therefore be generated. Based on this approach the tribological system piston ring/cylinder running surface of internal combustion engines is an example with high potential for optimization of production. This paper introduces alternative production and conditioning processes. The evaluation of chemical modifications of boundary layers, which are used in addition to the topography as a representative indicator for the description of the functionalities of produced surfaces is considered to be a special aspect. The present paper combines considerations of manufacturing technology with tribological tests showing the relationships and dependencies between the process characteristics of finishing and the operational behavior of the examined components.

Abstract: Surface integrity is widely used for evaluating the quality of machined components. It has a set of various parameters which can be grouped as: (a) topography parameters such as surface roughness, textures and waviness (b) mechanical parameters such as residual stresses and hardness, and (c) metallurgical state such as microstructure, phase transformation, grain size and shape, inclusions etc. Surface roughness and residual stresses are among the most significant parameters of surface integrity, so that it is worth investigating them particularly. Many factors affect the surface integrity of machined components, including cutting parameters, tool parameters, material properties and vibrations. We can make prediction and optimization for surface integrity by taking advantage of these factors. This paper reviews previous studies and gives a comprehensive summary of surface integrity in the following order: introduction of surface integrity, main parameters of surface integrity, factors affecting surface integrity, prediction and optimization for surface integrity.

Abstract: The use of GH4169 nickel-based superalloy for the manufacture of gas turbine engines components for aerospace/energy applications has become a routine exercise. However, components with complex designs specifications might pose manufacturing challenges especially when grinding processes are needed to enable their compliance with tight industrial standards for workpiece surface integrity. Information on grinding processes for such sensitive industrial applications is scarce. The paper reports on the influence of grinding methods/strategies on the quality and integrity of workpiece surfaces obtained after abrasive belt grinding methods on GH4169 nickel-based superalloy. The influences of grinding speed, contact pressure and oscillation frequency on surface roughness were discussed. The performance of the abrasive belt and surface topography were discussed. As a result, the maximum surface roughness of Ra is 0.072μm, and have a good performance of the abrasive belt, it could be concluded that abrasive belt grinding might be considered as a viable process for grinding aero-engine components.

Abstract: Machining of advanced aerospace materials have grown in the recent years although the difficult-to-machine characteristics of alloys like titanium or nickel based alloys cause higher cutting forces, rapid tool wear, and more heat generation. Therefore, machining with the use of cooling lubricants is usually carried out. To reduce the production costs and to make the processes environmentally safe, the goal is to move toward dry cutting by eliminating cutting fluids. This objective can be achieved by using coated tool, by increasing cutting speed and by improving the product performance in term of surface integrity and product quality. The paper addresses the effects of cutting speed and feed on the surface integrity during dry machining of Waspaloy using coated tools. In particular, the influence of the cutting conditions on mechanical power consumption, the tool wear and some important indicator of the surface integrity (surface roughness, affected layer, microhardness, grain size and microstructural alteration) were investigated. Results show that cutting conditions have a significant effect on the parameters related to the surface integrity of the product affecting its overall performance.

Abstract: In order to investigate the impact of cutting parameters on surface integrity when high-speed turning 58SiMn without cutting fluid, three-factor three-level orthogonal experiments and single factor experiments based on cutting speed and feed rate are employed, and an empirical model is established. The results of analysis of variance (ANOVA) revealed that feed rate is the dominant factor affecting the surface roughness. With the increase of cutting speed and feed rate, residual tensile stress on the surface becomes larger. Along the depth, micro hardness first decreases and then increases.

Abstract: This paper presents finite element method (FEM) and experimental analysis on high-speed milling for thin-wall machining of Al7075-T651. Changes in cutting forces, temperature, and chip morphology according to cutting conditions are analyzed using FEM. Results of machining experiments are analyzed in terms of cutting forces and surface integrity such as surface roughness and surface condition. Variables of cutting conditions are feed per tooth, spindle speed, and axial depth of cut. Cutting conditions to improve surface integrity were investigated by analysis on cutting forces and surface roughness, and machined surface condition.

Abstract: The high cycle fatigue life of machined parts is affected by the so-called surface integrity induced by the machining process. To model the high cycle fatigue behaviour of turned parts a probabilistic two-scale continuum damage model is developed. While the macroscopic behaviour of the material is assumed to remain elastic during the fatigue loading, the fatigue prediction is based on the incremental evolution of micro-plasticity and damage. The non-standard initial mechanical state of the material in the sub-surface, viz. the plastic strains and residual stresses fields induced by the machining process are taken into account via an initial step prior to the fatigue loading. As far as the micro-geometry of the surface is concerned, an initial micro-crack distribution depending on the depth and shape of the micro-defects observed is introduced.

Abstract: This article is for the integrity of the cutting surface, explaining the reason for the cutting residual stress generated from the mechanism, proposed several typical methods to reduce the residual stress. According to some experimental researches on cutting parameters which have been done by previous scholars, this article gives some analysis of the effects of cutting parameters of residual stress. And preliminary summary of the influence of residual stress on cutting parameters, it also provides a way for further discussion of cutting parameters and material effect on the machined surface residual stress distribution law.