Rigid-plastic FEM Analysis Research Articles

Rigid-Plastic FEM Simulation of Orthogonal Cutting Process

This paper presents a rigid-plastic finite element method for orthogonal cutting process by adopting Lagrange method. The rigid-plastic FEM analysis model is established and the rigid-plastic FEM analysis toolkit was developed. Meanwhile, two relevant key problems are discussed systematically, including the rule of chip-workpiece separation and the criterion of tool-chip separation. At last, a simulation example of planing an aluminium alloy (ZL-301) workpiece was conducted. The effects of the cutting stroke, the tool rake angle and the friction coefficient on chip were observed. The numerical simulation results have a good agreement with their experimental ones. It is indicated that the presented FEM model and algorithm are efficient and correct.

Elastic-Plastic FEM Analysis for Piercing of Small Holes.

Experiments and FEM analysis on the piercing of small holes were carried out. Small hole, in this paper, means that the diameter is smaller than the thickness of the material. Material deformation in the piercing differs from that of conventional shearing. So, the piercing processes were calculated by rigid-plastic FEM analysis and elastic-plastic FEM analysis, experimental and FEM analytical results were compared, and material deformations and piercing forces were investigated. The results of elastic-plastic FEM analysis showed good agreement with the experiment results even more than the results of rigid-plastic FEM analysis.

Slope Stability Analysis with Rigid-Plastic Finite Element Method

Rigid plastic finite element method was formulated for slope stability assessment by introducing the shear strength reduction coefficient to define the factor of safety used in slope stability. The framework of the proposed method was clarified in comparison with the limit equilibrium method based on slice method. The limit equilibrium method was shown to coincide with the upper bound theory in limit analysis and the process of minimizing the factor of safety for possible slip line was clarified to be important from the viewpoint of limit analysis. Rigid plastic FEM analysis has the advantages of (1) no need to assume the failure mode prior to analysis, (2) mathematical minimization of factor of safety, (3) use of constitutive equation and (4) taking account of dilatancy property of geo-material. The factor of safety was examined with simple slope for various conditions. It shows the good agreement with conventional methods and the applicability of proposed method was clarified. Case studies shows non-linear slip lines were well obtained corresponding to geometry and geology of slopes in the analysis. In some cases the sliding mass included several shearing zones inside and this fact suggests the existence of complicated failure mode not to be covered in the conventional methods.

FEM Simulation of a Friction Testing Metliod Based on Combined Forward Conical Can-Backward Straight Can Extrusion

A new friction testing method based on combined forward conical can-backward straight can extrusion is proposed in order to evaluate friction characteristics in severe metal forming operations. By this method the friction coefficient along the conical punch surface is determined knowing the friction coefficient along the die wall. The latter is determined by a combined forward and backward can extrusion of straight cans. Calibration curves determining the relationship between punch travel, can heights, and friction coefficient for the two tests are calculated based on a rigid-plastic FEM analysis. Experimental friction tests are carried out in a mechanical press with aluminium alloy A6061 as the workpiece material and different kinds of lubricants. They confirm that the theoretical analysis results in reasonable values for the friction coefficient.

Calculation of Isothermal Flow Stress by the Combination of FEM and a Simple Compression Test.

In forging of parts with complicated shapes or of high strength materials, it is important to predict the accurate load and the tool pressure, and thus it is essential to evaluate the exact flow stress of materials. In the practice, nominal flow stress calculated from a simple compression test, which is derived by diving the load by the cross-sectional area, is often used for approximate evaluation of forming load. This nominal flow stress contains the effects of the frictional force, the change in ternperature caused by plastic deformation, and the heat transfer between the tool and the material. These effects are especially significant in a high swain range. To obtain an accurate flow curve, the rigid-plastic FEM-analysis is carried out by using the approximate value of flow stress obtained from a simple compression test and the effects of friction and heat transfer are eliminated. Then, isothermal flow stress which corresponds to the strain, strain rate and temperature at each point of material is derived from this result. It is concluded that the ratio of nominal stress to isothermal flow stress ranges from 0.75 to 2.0.

Proposal of Lubricant Test for Thick Sheet Forming.

The purpose of this research is to develop a new method for the evaluation of lubricant performance with regard to the plastic deformation forming of thick sheets. A series of procedures for the new method are described and the feasibility of the method confirmed. Attention is focused on the compression of a disk-shaped blank by a ring-type punch, and the formation mechanism of the 'dome' that is generated in the center of the blank. This mechanism is assessed by considering a nomograph (constructed through rigid plastic FEM analysis), and the height of the dome is related to the friction coefficient. In an experimental approach, the disk and ring-punch compression tests were performed with 5 types of lubricant, the actual friction coefficients being obtained from a nomograph.

三次元切削機構の剛塑性有限要素法による解析(第2報)

三次元切削機構の剛塑性有限要素法による解析(第2報)

Rigid-Plastic FEM Analysis of Three-Dimensional Deformation Field in Chip Formation Process

Summary A three-dimensional deformation field in the chip formation process is analyzed by the Rigid-Plastic Finite Element Method. By developing a three-dimensional model of the work material, the deformation field in oblique cutting is continuously analyzed for the transition process from the beginning of the cutting until the steady state. The variations in the chip geometry and cutting forces due to the inclination angle of the cutting edge are simulated for a carbon steel. The simulation results are compared with in-situ scanning electron microscope observations of the cutting experiments, and good correlation between them is found.

Shape Control in CNC Rotary Swaging Machine

To obtain sound products with good shape accuracy in the computer controlled rotary swaging machine, the effects of working conditions and the methods for improving the accuracy after forming process are investigated by experiment and FEM analysis. The rigid-plastic FEM analysis with an assumption of generalized plane strain can be employed for predicting the shape of products. Optimum incremental angle of billet rotation is found to be about 10 degrees when 4 dies are used. It is clarified that slow retreat of dies and finishing blows after forming are effective to suppress the shape distortion.

Densification of iron compacts with various initial porosities under hydrostatic pressure

This study evaluated the effects of hydrostatic pressures up to 1104 MPa on densification of porous iron containing 0.3–11.1% porosity. For the porosities studied, densification as a result of pressurization increased with hydrostatic pressure and initial porosity. The 0.3% porosity iron was the only one whose density did not increase with pressurization up to 1104MPa. Current deformation models of ductile porous materials based on Gurson's yield criterion and rigid-plastic FEM analysis predicted much faster densification with pressurization than observed for porosity contents of 6.2% or less. A reason proposed for this behavior is the omission in the models of an internal pressure which builds up in the pores during the compaction process. A modification is introduced to Gurson's model to take account of internal pressure effects. The modified model exhibited excellent agreement with the experimental observations and provides a constitutive relation for the simulation of compaction and forming processes of P/M parts.