Papers by Keyword: Orthogonal Cutting

Abstract: The reliability of the pertinent parameters set of Johnson-Cook constitutive model is highly linked with the friction condition at the tool-chip-workpiece interface. In the present work, a study on the influence of Coulomb’s friction coefficient on the observables such as forces, chip thickness and chip curvature by FE simulation of orthogonal cutting of Ti6Al4V alloy has been carried out. A FE model with an Arbitrary Lagrangian-Eulerian (ALE) approach is employed to simulate the cutting process for different cutting conditions. The simulated results, for a wide range of friction conditions, are analyzed and compared with experimental results. The analysis show that the Coulomb’s friction coefficient has a direct link with the observables. The paper reveals that for accurate prediction of observables an optimized value of the coefficient of friction in correlation with the parameters values of the constitutive model is imperative.

Abstract: The capability of the explicit numerical methods to simulate accurately the real cutting process is investigated in this research work. Smoothed particle hydrodynamics - SPH, classical Lagrangian finite element method - FEM and Multi-Material Arbitrary Lagrangian Eulerian - ALE methods are chosen for the modeling and simulation of the orthogonal metal cutting process of AISI H13 in LS-DYNA. The cutting tool is modeled as a rigid FEM body that incrementally penetrates into the flexible deformable workpiece. At each numerical model, the dynamic elastoplastic behavior of the workpiece material is investigated by taking into account the Johnson-Cook (J-C) constitutive strength material model. The influence of the J-C parameter values found in literature to the models is explored. The obtained numerical SPH, FEM and ALE results of the estimated cutting and thrust forces, stress, plastic strain and thermal distributions are compared with results found in the literature. This comparison, leads to valuable conclusions for the performance of the three methods, concerning the approximation accuracy, model development complexity and computational time demands. Based on these conclusions the SPH method is chosen to simulate the experimentally performed orthogonal cut of AISI 1045. The obtained SPH numerical results outline its advantages among the other explicit simulation methods.

Abstract: This paper introduces new damage criteria for cutting process analyses based on the Coulomb-Mohr theory. When the accumulated damage reaches a certain critical level, brittle fracture occurs close to the tool tip, which is affected by the hydrostatic pressure and the location of conventional failure plane. The position of this plane is determined by the geometry of the cutting tool and the angle of friction. Numerical validation of the proposed criteria was made by FE-method in the Deform 2D using user routine usrdmg (User defined damage models).

Abstract: This paper presents an empirical force model quantifying the effect of fibre volume fraction and fibre orientation on the cutting forces during orthogonal cutting of unidirectional composites. Glass fibre plates and high speed steel cutting tools are used to perform orthogonal cutting on shaping machine whereas cutting forces are measured using platform force dynamometer. The analysis of forces shows almost linear dependency of cutting forces on the fibre content for both cutting and thrust forces. High dependency of cutting forces is also observed on fibre orientation with high percentage contribution ratio (up to 95.31%). Lowest forces corresponded to 30^o and highest to 90^o fibre orientation. Multivariate regression technique is used to construct the empirical model.

Abstract: To predict accurate cutting forces and residual stresses while machining products or to design optimum machining conditions like friction stir welding (FSW), FEM analyses are effective because they can reduce the cost of product design and improve product qualities. In order to conduct these FEM analyses precisely, it is necessary to determine accurate flow stresses of workpieces used for the constitutive equations of analyses that generally have a wide range of temperatures and strain rates. Correct identification of flow stress can lead to better analysis results close to actual phenomenon. In this study, focusing on 6061-T6 aluminum alloy used for objects such as civil engineering structures and railway vehicle bodies, we investigated the properties for machining the material. For this, we carried out an inverse analysis to understand the flow stress of 6061-T6 machined at high-strain rates and high temperatures. Then, we used this identified flow stress in the constitutive equation of FEM models, and inspected the accuracy of material properties conducting verification experiments and analyses to check the cutting forces and chip temperature while machining. As a result, we obtained good correlations between verification experiments and an analysis, which means the identified flow stress can be used for precise FEM analyses when machining materials.

Abstract: High strength carbon fiber reinforced polymers (CFRP) with unidirectional laminate structure have gradually developed into major materials in load-bearing aerospace components, and the cutting demand of CFRP is increasing. In this work, orthogonal cutting tests were conducted on T700 high-strength CFRP laminates to get the mechanistic force model of special cutting tools. Also cutting force coefficients were obtained when cutting T700 high-strength CFRP laminates under different fiber orientations. Experimental results showed that the lowest cutting force was obtained when fiber orientation was between 120° and 150°.

Abstract: This paper reports the stress distribution inside the workpiece under ultrasonic vibration cutting (UVC) condition. Many researchers have reported the improvements of tool wear, burr generation and surface integrity by reduction of time-averaged cutting force under UVC condition. However general dynamometers have an insufficient frequency band to observe the ultrasonically varying processing phenomena induced by UVC. In this paper, stress distribution inside the workpiece was observed by combining the pulse laser as light source synchronized with ultrasonically vibrating cutting tool and the photoelastic method. The one shot of pulse laser with pulse width of 15nsec visualizes an instantaneous stress distribution. Sweeping the phase of emission against to ultrasonic oscillation, 360 frames for 35.7μs, one period of ultrasonic oscillation, are captured. Because UVC induced an intermittent cutting condition, the stress distribution changed periodically and disappeared when the tool leaved from the workpiece. The ideal chip-generating period is calculated by relative motion between tool and work. We found that the actual chip-generating period was extremely longer than ideal period.

Abstract: The current paper deals with the orthogonal cutting of Ti6Al4V alloy. Initially, the cutting process is simulated using the Finite Element Method (FEM). Various cutting conditions including cutting speed and feed rate are considered. Based on this computational analysis the chip creation mechanism is studied. The simulation results describe adequately the chip generation and flow, delivering quantitative data concerning temperature and stress distribution, as well as chip geometry. In addition, orthogonal cutting experiments are conducted on a CNC lathe machine with the same cutting conditions. The experimental results are compared with the analytical ones and useful conclusions regarding the chip formation can be drawn.

Abstract: A modern meshless method known as Smooth Particle Hydrodynamics (SPH) was involved in achieving numerical simulation of chip formatting during the orthogonal cutting of AA6060-T6 alloy with the aim of finding a convenient method for investigating the chip formation and reducing the costs of experimental research by involving numerical simulation in order to get information about the parameters describing the process. Based on a few experimental orthogonal cutting results the procedure to achieve a proper numerical simulation of the chip formation process is presented. The procedure and the results may be applied when simulation data and prognosis data about machining AA6060-T6 data are needed.

Abstract: The chip formation mechanism in orthogonal cutting is a phenomenon that attracts the attention of many researchers. This paper investigates experimentally the orthogonal cutting of Ti6Al4V at different cutting conditions aiming at the understanding of the chip formation mechanism. Serrated chip formation is obtained during orthogonal cutting of Ti6Al4V in a wide range of cutting speeds. The results are analyzed in order to extract useful indices relevant to chip geometry, as the adiabatic zone angle and other dimensions that describe the serrated chip. The cutting forces and the acoustic emission are measured. Finally, by the aid of 3D Computed Tomography (CT) the chip morphology is analyzed to better understand the segmentation process.