Investigation of surface residual stress distribution in deformation machining process for aluminum alloy (original) (raw)
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Study of Residual Stresses from Two Machining Protocols Using an Indentation Method
International Journal of Mechanical Engineering and Applications, 2013
Although high-speed machining offers a number of advantages over conventional machining, it is possible that the residual stress distributions generated by the former can affect the service life of the processed components. In this paper, a newly developed micro-indent method is used to evaluate different residual stress states, which were introduced in samples of AA 7075-T6 aluminum alloy milled at low and high-speed. Different surfaces were generated by varying the cutting speed in one order of magnitude, from 100 m/min to 1000 m/min. Two machining protocols, which consist of using different machine tools, were evaluated. The results show that it is possible to generate and to evaluate very small residual stresses. Finally, the values and levels obtained for normal components were analyzed in function of mechanical and thermal effects that generated the residual stresses.
Evaluation of Residual Stresses Induced by High Speed Milling Using an Indentation Method
Modern Mechanical Engineering, 2012
In this work, a recently developed method based on the change of distance between collinear indents is used to evaluate different states of residual stress, which were generated in samples of AA 6082-T6 and AA 7075-T6 aluminium alloys milled at high speed. One of the advantages of this method, which needs a universal measuring machine, is not requiring neither the use of specific equipment nor highly skilled operators. Also, by integrating an indentation device to the mentioned machine, the absolute error of measurement can be reduced. In results obtained in samples subjected to different cutting conditions it is observed a correlation between the stress values and the depth of cut, showing the AA 6082-T6 alloy higher susceptibility to be stressed. Furthermore, the high sensitivity of the method allowed detecting very small differences in the values reached by different normal components in the zones corresponding to climb and conventional cutting. It is important to note that these differences were similar for both evaluated alloys. Finally, the directions associated with the principal components of residual stress, where maximum local plastic stretching occurs, were found to be strongly dependent on the rolling direction prior to machining.
Monolithic aluminium alloy parts are highly required in aeronautical industry, but they show significant geometrical distortion after the machining process. This work investigated the distortion attributed by the initial residual stress of raw material and the machining induced residual stress during the milling process, as well as explored the effects of the machining toolpath strategy. Single-/multi-pocket parts were milled from 7050-T7451 aluminium blocks with different initial residual stress, and an element deletion method was developed for numerical study to simulate different sequences of material removal. It was revealed that the toolpath parallel to the long side of block caused more distortion on the side surfaces of final part. The value of distortion was positively correlated to the magnitude of initial residual stress of raw material. The simulation results indicated that the distortion attributed by machining induced residual stress accounted for about 15% of final dis...
Numerical Assessment of Residual Stress Induced by Machining of Aluminum Alloy
Advanced Materials Research, 2014
A numerical approach has been developed to predict the near surface residual stresses induced by turning in orthogonal cutting configuration of aluminum alloy AA7075-T651. This approach is based on a Lagrangian formulation using the finite element software Abaqus–Explicit. The calculated residual stress profiles were validated by experimental measurements using X-ray diffraction method on samples turned under different cutting conditions. Using this method, the effect of the cutting speed and the feed on the machining residual stress has been established.
2011
Through a proper analysis of residual strain and stress distributions obtained at the surface of high speed milled specimens of AA 6082–T6 aluminium alloy, the performance of an improved indentation method is evaluated. This method integrates a special device of indentation to a universal measuring machine. The mentioned device allows introducing elongated indents allowing to diminish the absolute error of measurement. It must be noted that the present method offers the great advantage of avoiding both the specific equipment and highly qualified personnel, and their inherent high costs. In this work, the cutting tool geometry and high speed parameters are selected to introduce reduced plastic damage. Through the variation of the depth of cut, the stability of the shapes adopted by the residual strain and stress distributions is evaluated. The results show that the strain and stress distributions remain unchanged, compressive and small. Moreover, these distributions reveal a similar ...
Effect Of Machining Parameters On Residuel Stresses Distribution
The high level of strain imposed by machining changethe structural state of materials, this change appear by the birth of residual stress field caused by the incompatibility of plastic strain between the different layers of the material beneath the finished surface. A number of questions remain about the causes and mechanisms of generation of residual stresses during machining and how these residual stresses can be controlled to achieve a desired distribution. The aim of this work is to create a numerical model using Abaqus software to verify residual stresses induced by machining in aluminum alloy 2024-T3 for different cutting parameters (cutting speed, feed rate and cutting angle). The effect of each cutting parameter used on the distribution of residual stresses induced by machining has been shown.
Experimental Mechanics, 2009
An improved method of indent pairs is utilised to determine residual stresses in high speed milling specimens of AA 6082-T6 and AA 7075-T6 aluminium alloys. To carry out the measurement procedure, this approach does not need specific equipment but only requires a universal measuring machine and an oven. An indentation device is incorporated to the measuring machine, which allows reducing the absolute error of measurement to just ±0.9 MPa. The geometry of the tool and cutting parameters are selected to evaluate the sensitivity of the method. The residual stress distributions generated by high speed milling are exhaustively evaluated taking into account orthogonal components of cutting speed and tangential force, which are parallel and perpendicular to feed direction.
A Review in Machining-Induced Residual Stress
Due to friction, chip forming, and the induced heat in the cutting area, produced parts by using machining operations have residual stress. Residual stresses caused by machining processes have a major effect on the fatigue life of machined components, which can shorten their service life. In order to increase the performance of machined parts in real-world applications, such as fatigue life, corrosion resistance, and component distortion, residual stress should be investigated and minimized. As a result, predicting and controlling residual stresses caused by machining operations is important in terms of quality enhancement of machined parts. This paper reviews the recent achievements in the machining-induced residual stress in order to be analyzed and decreased. Different methods of the residual stress measurement Destructive Methods, Semi-Destructive Methods and Non-Destructive Test (NDT) Methods are reviewed and compared in order to be developed. In order to minimize residual stress in machined parts, the study examines the effects of machining process parameters, highspeed machining conditions, coolant, cutting tool wear, edges, and radius on residual stress. Analytical and semi-analytical modeling, numerical and FEM simulation techniques of residual stress are reviewed to include advanced methods of residual stress modeling methodology to predict residual stress in machined components. Residual stress in various alloys such as AL alloys, biomedical implant materials, hard to cut materials such as nickel-based alloys, Titanium Based Alloys, Inconel Based Alloys, and stainless-steel alloys is investigated in order to provide efficient residual stress minimization methods in machined components. It has been realized that evaluating and analyzing recent advances in published papers will contribute to develop the research field.
Effect of machining-induced residual stress on the distortion of thin-walled parts
One of the main problems in the machining of thin-walled parts made of high-strength aluminum alloys is distortion and dimensional instability after machining, which leads to an increase in scraped parts and the cost of production. In general, distortion and dimensional instability in machined parts made of aluminum alloy is a function of the residual stresses. In this article, the correlation between machining-induced residual stresses and distortion in a thin-walled work pieces is investigated. Several experiments are carried out under different machining conditions using two carbide and polycrystalline diamond (PCD) tools on a thin-walled cylinder made of AL7075-T6 alloy. Rates of variations in geometrical tolerances and distortion for all work pieces are measured. To study the effect of mechanical and thermal loads on the residual stresses and distortion, the machining force and temperature of cutting area are measured. Finally, the correlation between the residual stress and distortion is studied by measurement of residual stress on some work pieces. Similarly, in order to investigate the effect of work pieces thickness on distortion, several tests are carried out on three work pieces with different thicknesses. The results indicate that the force and temperature have direct effect on the residual stresses and distortion in the thin-walled parts.