Machining Residual Stresses Research Articles

Finite element modeling of residual stresses in machining induced by cutting using a tool with finite edge radius

A thermal elastic-viscoplastic finite element model is used to evaluate the residual stresses remaining in a machined component. An improvement in the accuracy of the predicted residual stresses is obtained by: (a) using a modified Johnson–Cook material model that is augmented by a linearly elastic component to describe the material behavior as non-Newtonian fluid; (b) using a remeshing scheme to simulate the material flow in the vicinity of the rounded cutting tool edge without the use of a separation criterion; (c) properly accounting for the unloading path, and (d) considering the thermomechanical coupling effect on deformation. Case studies are performed to study the influence of sequential cuts, cutting conditions, etc., on the residual stresses induced by orthogonal machining.

Finite-element analysis and simulation of machining: a bibliography (1976–1996)

Abstract This paper gives a bibliographical review of the finite-element methods (FEMs) applied to the analysis and simulation of machining. The bibliography at the end of the paper contains references to papers, conference proceedings and theses/dissertations on the subject that were published in 1976–1996. The following topics are included: material removal and cutting processes in general, computational models for specific machining processes, effects of geometric and process parameters, thermal aspects in machining, residual stresses in machining, dynamic analysis and control of machine tools, tool wear and failure, chip formation mechanism, and optimization and other topics, respectively.

Determination of Surface Residual Stresses in Machined Ceramics Using Indentation Fracture

Machining produces surface residual stresses which significantly influence the strength and wear resistance of ceramic components. As new methods are developed for machining ceramics, a quick and reliable technique for measurement of residual stresses would be valuable in assessing the viability of these methods from a residual stress perspective. The residual stresses on ground and polished (i.e. machined) surfaces of soda-lime glass, Ni-Zn ferrite, and silicon nitride have been measured using an indentation technique with a Vickers indenter. In this technique, the surface extent of the median/radial cracks produced by the Vickers indenter in machined and in annealed ceramics are measured. These are then combined with a fracture mechanics analysis to estimate the surface residual stresses produced by machining. In order to determine the validity of the indentation technique for estimating machining residual stresses, these stresses were also measured using an X-ray diffraction and a deflection method. The residual stress values determined using the indentation technique in the machined ceramics were found to be reasonably close to those obtained from the X-ray diffraction and deflection methods. Since the indentation technique is relatively simple and easily applied, it offers a promising method for evaluating surface residual stresses in machined ceramics.

Das Abschnitt-Polynom-Verfahren zur zerstörungsfreien Ermittlung gradientenbehafteter Eigenspannungszustände in den Randschichten von bearbeiteten Keramiken

X-ray analyses allow the non-destructive determination of residual stress states in machined ceramic materials with steep subsurface gradients. One assumes that variations in the penetration depth of the X-rays enable an assessment of the distributions of machining residual stresses versus the distance from the surface. However, this requires the inversion of Laplace-transforms which, for physicals reasons, are very ill-conditioned. Therefore, the evaluation procedure chosen is crucial for the quality of the results. Based on the Polynomial Method, the Sectioned Polynomial Method was developed which, by describing the depth distributions of residual stresses using piecewise defined polynomials, provides improved flexibility of the solution scheme together with significantly better stability. The details of the evaluation procedure are described and discussed using model calculations. Residual stress analyses on ground ZrO2 ceramics are presented.

Effect of machining residual stresses on the repetitive impact behavior of silicon nitride

Silicon nitride is a candidate valve material for internal combustion engines. Its low density and attractive mechanical properties relative to conventional metallic alloys portend significant improvements in valve performance. The production of valves involves a significant amount of machining, especially grinding. Grinding of ceramic materials may result in surface and subsurface damage in the form of fracture or residual stresses which may affect impact behavior and, consequently, the behavior of silicon nitride ceramic materials as valves. The effects of residual stresses due to grinding on the impact wear behavior of one silicon nitride composition ground under various conditions have been investigated.

Residual stresses after orthogonal machining of AlSl 304: numerical calculation of the thermal component and comparison with experimental results

Residual stresses due to the thermal influence of orthogonal machining have been calculated with a finite element model using stationary workpiece temperatures during cutting calculated with the finite difference method. Calculated results are compared with experimental data obtained with the X-ray diffraction method. In this way, the thermal and mechanical/frictional influences of the machining operation on the workpiece residual stress state can be separated. The influence of cutting speed and cutting depth on machining residual stresses is discussed. It is shown that the thermal as well as the mechanical impact of the orthogonal cutting process causes tensile residual stresses. The mechanical impact of the machining operation causing tensile residual stresses is due to (a) compressive plastic deformation in the surface layer ahead of the advancing tool and (b) greater elastic relaxation upon unloading with respect to the underlying material of a thin, strongly work-hardened surface layer.

Assessment of residual stresses in friction weldments of aluminium tubes

Some of the fundamentals of the friction welding of commercially pure aluminium tubes were studied. A centre lathe was adapted for the welding operation. A special guide was designed to fix the stationary part of the pure aluminium tube to the tool post during welding. The test variables were the spindle speed, the tube thickness and the vertical chamfering angle of the tube end. The distribution of residual stresses at the midsection of the weldment was assessed by a layer removal technique using sharp orthogonal edges in the presence of ample cooling to minimize machining residual stresses. Generally, as the spindle speed increases, the value of the maximum tensile stress and the depth of the stressed layers increase. The level of residual stresses increases with increase in tube wall thickness. The vertical chamfering angle had no significant effect on the residual stresses. The depths of the stressed layers in all the tests ranged from 1250 to 1450 μm; this corresponds to a proportion of between 0.2 and 0.35 of the tube thickness. The stress ranged from tensile surface stresses to compressive internal stresses and internal tensile stresses. The area of tensile stresses was approximately equal to that of compressive stresses.

Relationship between cold working and residual stresses in machining of aluminum alloy V96ts

Relationship between cold working and residual stresses in machining of aluminum alloy V96ts