Recent advances in modelling of metal machining processes

Cutting edge geometries

https://hal.archives-ouvertes.fr/hal-02272886/document

SPH method applied to high speed cutting modelling

This paper proposes a methodology to identify the material coefficients of constitutive equation within the practical range of stress, strain, strain rate, and temperature encountered in metal cutting. This methodology is based on analytical modeling of the orthogonal cutting process in conjunction with orthogonal cutting experiments. The basic mechanics governing the primary shear zone have been re-evaluated for continuous chip formation process. The stress, strain, strain rate and temperature fields have been theoretically derived leading to the expressions of the effective stress, strain, strain rate, and temperature on the main shear plane. Orthogonal cutting experiments with different cutting conditions provide an evaluation of theses physical quantities. Applying the least-square approximation techniques to the resulting values yields an estimation of the material coefficients of the constitutive equation. This methodology has been applied for different materials. The good agreement between the resulting models and those obtained using the compressive split Hopkinson bar (CSHB), where available, demonstrates the effectiveness of this methodology.

From the basic mechanics of orthogonal metal cutting toward the identification of the constitutive equation

This paper presents a finite element model for white layer formation in orthogonal machining of hardened AISI 52100 steel under thermally dominant cutting conditions that promote martensitic phase transformations. The model explicitly accounts for the effects of stress and strain, transformation plasticity and the effect of volume expansion accompanying phase transformation on the transformation temperature. Model predictions of white layer depth are found to be in agreement with experimental values. The paper also analyzes the effect of white layer formation on residual stress evolution in orthogonal cutting of AISI 52100 hardened steel. Model simulations show that white layer formation does have a significant impact on the magnitude of surface residual stress and on the location of the peak compressive residual stress.

Modeling of white layer formation under thermally dominant conditions in orthogonal machining of hardened AISI 52100 steel

In the present study, two-dimensional orthogonal slot milling experiments in conjunction with an analytical-based computer code are used to determine flow stress data as a function of the high strains, strain rates and temperatures encountered in metal cutting. The workpiece materials selected for the present study are AISI P20 mold steel (DIN 1.2330, 35CrMo4) hardened to 30 HRC, AISI H13 tool steel (DIN 1.2344, X40CrMoV51) hardened to 46 HRC and Aluminum EN AW 2007 (DIN 1725 T1: AlCuMgPb, 3.1645) cold hardened to 100 HB. The methodology of flow stress determination for metal cutting, suggested in the present study, has advantages when compared with methods such as the Hopkinson's bar technique. This paper summarizes the first part of the study, conducted to estimate process variables in machining operations. The second part of the study, summarized in a different paper, addresses the application of flow stress data for predicting forces, stresses and temperatures in machining.

Process modeling in machining. Part I: determination of flow stress data

The flow stress data, determined in Part I of the present study, is validated by using it as an input to the finite element method and analytical based computer programs to predict process variables in metal cutting. The predicted process variables in two-dimensional orthogonal turning and three-dimensional face milling operations, are compared with the published experimental data and the results of experiments conducted in the present work. The majority of the predictions have been found to be in reasonable agreement with the measured results. The comparisons have been discussed and, in the case of unsatisfactory agreement, the reasons for inaccurate predictions are reviewed. The flow stress data of AISI H13 tool steel (46 HRC), determined in Part I is used in this study to investigate the influence of edge preparation on forces in the cutting and feed directions, tool stresses and cutting temperatures. It has been concluded that the hone-radius edge with a hone radius of 0.1 mm provides the maximum resistance to chipping and the chamfered edge (20°×0.1 mm) has the minimum flank and crater wears for the conditions used in the present study.

Christian Kerk

Papers

Process modeling in machining. Part I: determination of flow stress data

Process modeling in machining. Part II: validation and applications of the determined flow stress data