摘要:

AbstractThe bulging of continuously cast steel between the support rolls has been computed using a viscoplastic finite element model. Both two‐dimensional and three‐dimensional models are based on the minimization of the functional associated with the Norton–Hoff law and use the streamlines integration to calculate the bulging. By using industrial data, the influence of both numerical parameters and process parameters on the extent of the calculated bulging values has been investigated. The comparison of our results with experimental measurements confirms the relevance of the hypothesis of viscoplastic beha

ISSN:0029-5981    

DOI:10.1002/nme.1620250113

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractThe boundary element method is applied to large deformation problems typical in industrial forming problems. A form of Betti's theorem relevant to an updated Lagrangian type of solution procedure is established as the basis for the boundary element formulation. Equilibrium iterations are needed in each load step. All non‐linear terms are moved to the right‐hand side and the boundary element method can be used. Cross‐anisotropy is assumed where Hill's yield criterion is adopted together with isotropic hardening. The investigation has shown that the boundary element method is applicable to this type of problem, giving good results within reasonable computer

ISSN:0029-5981    

DOI:10.1002/nme.1620250114

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractThe pseudo‐concentration method is used to follow the flow of metal during the transient analysis of an axisymmetric forging problem. The technique requires a minimum of user interaction and appears to be ideal for computer aided design of dies. An analysis of an engine disc blocker die is presented and compared with experimental results. The same problem is analysed using a Newtonian fluid which is shown to give good qualitative results which would be acceptable in the initial stages of die desig

ISSN:0029-5981    

DOI:10.1002/nme.1620250115

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractRate form constitutive equations of elasto‐viscoplastic type are expressed in a manner similar to that of classical metals, but the viscoplastic part, which is no longer incompressible, is related to the rate of variation of porosity. An incremental and implicit algorithm has been implemented in a finite element program in order to simulate hot isostatic pressing of an Astroloy powder. Temperature distributions are shown to induce strong density variations in real parts during hot isostatic pressing (HIP). For one particular turbine disk, we tested the sensitivity of the final shape to different processing parameters. Computed final shapes compare well with experimental one

ISSN:0029-5981    

DOI:10.1002/nme.1620250116

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractA numerical method is introduced which is based on metal flow theory and simulates the densification of metal powder during hot isostatic pressing.The method, in which nodal velocities are variables, takes into consideration the dependence of flow stress on the temperature, strain rate and relative density of the material. The compressibility of porous metal as well as the incompressibility of fully dense metal are also taken into account.Porous specimens of the superalloy MERL76 were subjected to uniaxial compression tests at high temperature in order to determine the parameters of the equations on which the method is based. The densification behaviour of a turbine disk and two cylindrical components was numerically simulated and compared with experimental results.

ISSN:0029-5981    

DOI:10.1002/nme.1620250117

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractA formal analogy between the equations of pure plastic and viscoplastic flow theory for void‐containing metals and those of standard non‐linear elasticity is presented. The formulation is particularized for the analysis of axisymmetric sheet metal forming problems using simple two node linear finite elements. Details of the treatment of friction and strain hardening phenomena, time increment computation and elastic effects are also given. Examples of the effect of void porosity on the hemispherical stretching of a circular sheet are presen

ISSN:0029-5981    

DOI:10.1002/nme.1620250118

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractThe majority of work in numerical analyses of sheet metal forming operations is based on the simple membrane‐shell theory which neglects the effect of sheet bending. While useful information can be extracted from these analyses, especially for stretch‐dominated operations, the membrane theory is basically inadequate for analysing the draw‐type operations where sheet metal bends, slides and unbends over a draw radius.This paper presents axisymmetric and plane‐strain finite element analyses of stretch/draw of sheet metal over a die corner radius. Numerical solutions obtained from a total Lagrangian formulation of a finite‐strain thin shell theory are used to indicate the relative significance of including the bending effects in various simple forming operations. Comparisons of the calculated results with available experimental data are a

ISSN:0029-5981    

DOI:10.1002/nme.1620250119

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractThe goal of mathematical modelling of sheet metal forming processes is to provide predictive tools for use in the design of stamping processes and the selection of sheet materials. Most current approaches to finite element modelling of large deformation, elastic–plastic sheet metal forming problems use a rate form of the virtual work (equilibrium) equations, and a single‐field finite element representation of the displacement components. Called the incremental method, this approach does not produce approximations which satisfy the discrete equilibrium equations at all times, and consequently it demands small time steps to insure stability and numerical accuracy. This paper describes a variant of the mixed method in which displacements, stresses, effective strain and pressures are all given separate finite element representations. The equilibrium equations in non‐rate form are discretized to produce a system of algebraic equations which are coupled with the constitutive equations and then integrated using state‐of‐the‐art numerical software. When used to model rate sensitive sheet materials in hydrostatic bulging, plane strain punch stretching and hemispherical punch stretching, the new approach proved to be between 6 and 26 times as fast as the old increme

ISSN:0029-5981    

DOI:10.1002/nme.1620250120

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

摘要:

AbstractA finite element simulation code of the sheet metal forming process has been developed. This simulation code plays an important role in the computer aided engineering (CAE) system for an automobile parts forming process, which includes the pre‐ and post‐processes. The paper presents the development of an updated Lagrangian type finite element modelling, based on the elastic–plastic (J2 flow law) membrane shell theory. An attempt is made to calculate the strain distribution incurred by peripherally clamped or non‐clamped square plates when impressed by rigid punches. These are the cases of square box‐shape punch drawing and arbitrary shaped panel stretc

ISSN:0029-5981    

DOI:10.1002/nme.1620250121

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY

ISSN:0029-5981    

DOI:10.1002/nme.1620250102

出版商:John Wiley&Sons, Ltd    

年代:1988

数据来源: WILEY