Residual Stresses Induced by Dry and Cryogenic Cooling during Machining of AZ31B Magnesium Alloy

The major challenge of the Mg alloys has been their unsatisfactory corrosion resistance, which can be enhanced by improving the surface integrity. Cryogenic machining, where liquid nitrogen was used during machining, has been reported to improve the surface integrity of machined components, including compressive residual stresses. This paper analyses the influence of several cutting parameters, tool geometry and cryogenic conditions on the surface and subsurface residual stresses distribution

Residual Stresses in Machining of AISI 52100 Steel under Dry and Cryogenic Conditions: A Brief Summary

17th Conference on Material Forming (ESAFORM) - FinlandResidual stress is one of the most important surface integrity parameter that can significantly affect the service performance of a mechanical component, such as: contact fatigue, corrosion resistance and part distortion. For this reason the mechanical state of both the machined surface and subsurface needs to be investigated. Residual stress induced by dry and cryogenic machining of hardened AISI 52100 steel was determined by using the X-ray diffraction technique. The objective was to evaluate the influence of the tool cutting edge geometry, workpiece hardness, cutting speed, microstructural changes and cooling conditions on the distribution of the residual stresses in the machined surface layers. The results are analysed in function of the thermal and mechanical phenomena generated during machining and their consequences on the white layer formation

Influence of cutting process mechanics on surface integrity and electrochemical behavior of OFHC copper

The authors gratefully acknowledge the support received from IC ARTS and CEA ValducSuperfinishing machining has a particular impact on cutting mechanics, surface integrity and local electrochemical behavior. In fact, material removal during this process induces geometrical, mechanical and micro-structural modifications in the machined surface and sub-surface. However, a conventional 3D cutting process is still complex to study in terms of analytical/numerical modeling and experimental process monitoring. So, researchers are wondering if a less intricate configuration such as orthogonal cutting would be able to provide information about surface integrity as close as possible to that one generated by a 3D cutting process. For that reason, in the present paper, two different machining configurations were compared: face turning and orthogonal cutting. The work material is oxygen free high conductivity copper (OFHC) and the cutting tools are uncoated cemented carbide. The research work was performed in three steps. In the first step, the process mechanics of superfinishing machining of OFHC copper was performed. In the second step, the surface integrity and the chemical behavior of the machined samples were analyzed. Finally, in the third step, correlations between input parameters and output measures were conducted using statistical techniques. Results show that when applying low ratios between the uncut chip thickness and the cutting edge radius, the surface integrity and cutting energy are highly affected by the ploughing phenomenon. Otherwise, the most relevant cutting parameter is the feed. In order to compare face turning with orthogonal cutting, a new geometrical parameter was introduced, which has a strong effect in the electrochemical behavior of the machined surface

Surface integrity predictions and optimisation of machining conditions in the turning of AISI H13 tool steel

Surface integrity (SI) plays a very important role in functional performance. It is dependent on a large number of machining parameters. The major concern of industry is to know which combination of machining parameters provides the best SI of machined components. Traditionally, surface roughness is considered to be the principal parameter to assess the SI of a machined part. However, residual stresses also become an important parameter because they control the lifetime of components (moulds, dies, etc.) and their abilities to withstand severe thermal and mechanical cyclic loadings (fatigue) during service. Therefore, significant improvements in the quality of the mould/die can be achieved with the control of residual stresses and surface roughness, both induced by machining. This paper examines both residual stresses and surface roughness induced by the dry turning of AISI H13 tool steel with different hardnesses. SI parameters were evaluated experimentally with respect to tool geometry, cutting speed, feed and depth of cut. A modelling and optimisation procedure based on artificial neural network (ANN), response surface methodology (RSM) and genetic algorithm (GA) approaches was developed and applied to identify the optimum combination of cutting parameters, leading to the best SI for machined components

Sport participation analysis: an empirical study on two small communities

Information about Sport Participation Index (SPI) is a critical factor in the sport development process. Sociodemographic data can be a cost effective instrument to increase effi ciency of local policies that promote sport participation (SP). Although bibliography about SP is vast, the analysis and comparison of previous works is complex due to heterogeneity in methodologies. There is an enormous disparity in SP results in Portugal: Marivoet (2001) refers that SPI in Portugal is 27%; Almeida, & Graça (1998) refer that the non participation percentage in Portugal is 60%; and according to the Eurobarometer report (2004) Portugal presents the lowest fi gure of SPI, 22%, followed by Greece 26%, while the European average is 38%. There is a limited availability of data about SP in small cities. The presented study intended to: a) characterise SP in two small cities; b) identify target groups in order to increase the effi ciency local authority efforts’

Tool life and surface integrity in hard milling of hot work tool steels

Machinability enhancement of hot work tool steels can be achieved intrinsically through tailoring of alloying elements and steel processing route but also externally through the use of adequate tooling. The aim of the present investigation was to identify the limitations in hard milling of AISI H13 (50HRC) with respect to different strategies for microstructure control. Accordingly, tool life tests in face and cavity milling were performed using modern PVD-coated carbide inserts where subsequent investigation of tool wear mechanisms and surface integrity were carried out. A modified tool life model derived from Taylor’s approach was employed for the assessment of tool life. The results indicate that traditional improvement in machinability through additives and inclusion control appears not always adequate and the role of primary carbides distribution needs also to be considered. Surface integrity studies, namely residual stress, indicate the predominance of compressive residual stress in the machined surfaces

Tool life and surface integrity in hard milling of hot work tool steels

Machinability enhancement of hot work tool steels can be achieved intrinsically through tailoring of alloying elements and steel processing route but also externally through the use of adequate tooling. The aim of the present investigation was to identify the limitations in hard milling of AISI H13 (50HRC) with respect to different strategies for microstructure control. Accordingly, tool life tests in face and cavity milling were performed using modern PVD-coated carbide inserts where subsequent investigation of tool wear mechanisms and surface integrity were carried out. A modified tool life model derived from Taylor’s approach was employed for the assessment of tool life. The results indicate that traditional improvement in machinability through additives and inclusion control appears not always adequate and the role of primary carbides distribution needs also to be considered. Surface integrity studies, namely residual stress, indicate the predominance of compressive residual stress in the machined surfaces

Sensitivity Analysis of Cryogenic Cooling on Machining of Magnesium Alloy AZ31B-O

Improving the corrosion resistance of magnesium alloys has gained special focus in recent years, and cryogenic machining has been one of the successfully used techniques. The current study presents a sensitivity analysis of cryogenic cooling effects on process mechanics, when cutting AZ31B-O magnesium alloy. Finite element modelling was used to simulate orthogonal cutting of AZ31B-O under dry and cryogenic conditions, where different parameters (cutting forces, temperatures, shear angle, chip compression ratio and plastic deformation) were investigated. Also, orthogonal cutting tests were performed on a CNC lathe, under dry and cryogenic conditions, where cryogenic cooling was applied to the clearance side using an LN2 jet

Process Mechanics and Surface Integrity Induced by Dry and Cryogenic Machining of AZ31B-O Magnesium Alloy

The corrosion resistance of magnesium alloys depends mainly on its surface integrity. Previous experimental studies have shown that machining can induces small (nano-scale) grain size, compressive residual stresses and basal plane crystallographic texture, which significantly improve the corrosion resistance of magnesium alloy. These studies have focused on the positive effects of cryogenic cooling and tool edge radius preparation. In this paper, the influence of a wide range of cutting process parameters (including cut-ting speed, feed, tool rake angle, tool edge radius and cooling conditions) acting on the cutting mechanics and surface integrity produced during machining of AZ31B-O magnesium alloy have been studied experimentally and numerically

On the selection of Johnson-Cook constitutive model parameters for Ti-6Al-4V using three types of numerical models of orthogonal cutting

Johnson-Cook constitutive model is still the most used model in metal cutting simulation, although several drawbacks reported in the literature. A high number of Johnson-Cook model parameters can be found in the literature for the same work material. One question that may arise is “What is the most suitable set of Johnson-Cook model parameters for a given material?”. The present paper puts in evidence some issues related with the selection of these parameters from the literature. In this contribution, two sets of Johnson-Cook model parameters for Ti-6A-4V are evaluated, using three types of metal cutting models. These models are based on three different formulations: Lagrangian, Arbitrary Eulerian-Lagrangian (ALE) and Couple Lagrangian-Eulerian (CEL). This evaluation is based on the comparison between measured and predicted chip geometry, chip compression ratio, forces, plastic deformation and temperature distributions