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Effect of different machining processes on the tool surface integrity and fatigue life

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Abstract

Ultra-precision grinding, wire-cut electro discharge machining and lapping are often used to machine the tools in fine blanking industry. And the surface integrity from these machining processes causes great concerns in the research field. To study the effect of processing surface integrity on the fine blanking tool life, the surface integrity of different tool materials under different processing conditions and its influence on fatigue life were thoroughly analyzed in the present study. The result shows that the surface integrity of different materials was quite different on the same processing condition. For the same tool material, the surface integrity on varying processing conditions was quite different too and deeply influenced the fatigue life.

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... Some studies have reported surface softening in the near surface of components by hard turning with a sharp cutting tool [9]. These alterations have a large effect on the surface integrity and the subsurface residual stresses [10,11]. Thin white layers (WLs) and/or dark layers (DLs) appear on the finished surface and on the formed chip. ...
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Hard turning is more and more considered by the industry as a possible and good option for the process of grinding or pre-grinding. However, it is hurdled to a very great extent by surface integrity problems, to wit, for example, the microstructure transformations and the tensile residual stresses (white layers (WLs) and dark layers (DLs)), which are generally found to have negative effects on the stress corrosion, wear resistance, and fatigue life of machined parts. The optimization of this process has become the focus of experts. This paper presents a thermo-mechanical model able to predict the thicknesses of WLs and DLs during the orthogonal cuts of the hardened steel AISI 52100. The model combines the temperature, stress, and strain effects on the phase transformation mechanism to predict the thicknesses of layers. Unlike a similar model, presented in the literature, our developed approach firstly predicts the cutting forces for each tested condition. Secondly, it evaluates the thermo-mechanical loads on the machined surface. Thirdly, it evaluates the austenite transformation temperature. Therefore, it is possible to predict the WL and DL thicknesses for selected cutting conditions. This multi-physics model provides cutting force and layer thickness results close to those obtained experimentally in the literature. Analyzing the effect of the cutting conditions on the affected layer thickness reveals that the WL thickness increases with the rise in the cutting speed and the feed rate. Moreover, the flank wear has a greater effect on the thicknesses of layers.
... The machined product with better surface finish indicates good product quality (Liu, Chiang, and Hung 2013;Osman Zahid, Case, and Watts 2015;Paul, Varadarajan, and Gnanadurai 2016;Selvam and Senthil 2016). The machining parameters of the machining operation greatly influence the surface quality of the machined products (Bharathi Raja & Baskar, 2011;Roy, Ray, and Pradhan 2014;Tazehkandi, Shabgard, and Pilehvarian 2015;Cao and Zhang 2016;Nouioua et al. 2017). ...
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The objective of this study is to analyse the surface finish achieved during turning of AISI 4340 cylindrical steel components in three machining conditions namely, flooded, near-dry and dry conditions with three separate CNMG 431-PF 4325 80⁰ diamond finish Titanium Nitride (TiN) coated carbide cutting tool. The machining parameters considered in this study are cutting velocity, feed rate and depth of cut. The surface roughness of the machined components is measured using a surface roughness tester and subsequently, a mathematical model is developed for the average surface roughness values through regression analysis. The significance of the selected machining parameters and their levels on surface roughness is found by analysis of variance (ANOVA) and F-test. The results revealed that machining under near-dry condition provides better product surface quality in equivalence with the machined product surface quality under flooded condition.
... Microstructural transformations of hard-turned materials have a significant impact on the surface integrity [1,2]. These transformations can be summarized mainly on grain refinement [3,4], hardness modification [5,6], and phase transformations [7,8]. ...
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Surface integrity in material removal processes: Recent advances, CIRP Annals-Manufacturing Technology
  • I Jawahir
  • I. Jawahir