Finite element modeling plasticity

Finite-element techniques can cope with large, highly non-linear deformations, making it possible to model soft tissues such as skin. When relatively large areas of skin are replaced during plastic surgery, there is a problem that excessive distortion of the apphed skin will prevent adequate adhesion. Finite-element models can be used to determine, either by rapid trial-and-error modelhng or by mathematical optimisation, the best way of... 

H. G. deLorenzi and H. F Nied, Blow Molding and Thermoforming of Plastics Finite Element Modeling, Compu. Struct. 26, 197-206 (1987). 

We present recent results on the analysis of the interaction between plasticity and crazing at the tip of a preexisting crack under mode I loading conditions. Illustrations of the competition between these mechanisms are obtained from a finite element model in which a cohesive surface is laid out in front of the crack. 

From the perspective of the present discussion, our key objective is to uncover the detailed crystallographic underpinnings of single crystal plasticity. From the standpoint of a finite element model of such plasticity, what distinguishes the kinematic treatment of fee A1 from that of hep Zn In a word, the primary distinction is the presence of different slip systems in these different materials. The notion of a slip system refers to a partnership between two directions, the slip plane normal and the slip direction. 

Teoh, S. H. et al, A Elasto-Plastic Finite Element Model for Polyethylene Wear in Total Hip Arthoplasty, /. Biomechanics, 35, 323-330, 2002. 

The mechanism of stress transfer from the plastic matrix to the wood particles and vice versa was investigated by Sretenovic et al. [68]. They measured the strain distribution around the particle using electronic speckle pattern interferometry (ESPI). They also conducted an analytical analysis and finite element modelling of strain and stress distribution in the wood plastic composite. 

Of particular importance is the assumption of thin-walled geometry. From Eq. (7.3) we see that the pressure is independent of the z coordinate. Consequently, the finite element utilized for pressure calculation need have no thickness. That is, the element is a plane shell—generally a triangle or quadrilateral. This has great implications for users of plastics CAE. It means that a finite element model of the component is required that has no thickness. In the past this was not a problem. Almost all common CAD systems were using surface or wireframe modeling and thickness was never shown explicitly. The path from the CAD model to the FEA model was clear and direct. 

Hackett, R. M. andZhu, S.Z. (1992), Two-dimensional finite element model of the pultrusion process . Journal of Reinforced Plastics and Composites, 11,1322-1351. 

Plastics with their inherent complex geometries are typically better suited to boundary representation models. Also functions such as finite element modeling or numerical control tool paths require explicit surface definitions which are only available with boundary representations. With constructive solid geometry systems, surface information must be evaluated before it is user accessible. Wireframe models again may be used as the base and are easily transferred to a boundary representation system. Conversely a boundary representation model may be readily converted to a wireframe. Many current commercial systems combine the features of both constructive solid geometry and boundary representation. A project consisting of simple machineable shapes may be done faster in a constructive solid geometry mode while a sculptured surface model would be more easily created in a boundary representation mode. The separate models can... 

The finite element models used in this study have combined both elastic-plastic solid elements, used for soils, and elastic and elastic-plastic structural elements, used for concrete piles, piers, beams and superstructure. In this section described are material and finite element models used for both soil and structural components. In addition to that, described is the methodology used for seismic force application and staged construction of the model. 

Kang, S.-H. Im, Y.-T. (1987). Three dimensional thermo-elastic-plastic finite element modeling of quenching process of plain-carbon steel in couple with phase transformation. Int.. Mech. Sci., Vol. 49,423-439. 

Finite element modeling is a technique whereby a material continuum is divided into a number of patches, or finite elements, and the appropriate engineering theory is applied to solve a variety of problems. The initial (and probably still dominant) use of finite element modeling was for the solution of structural engineering problems. The technique is currently being applied by a number of companies and research institutions in the design of plastic products. CAD/CAM systems provide the means to create a mesh of finite elements directly from a product model database, by automatic and semiautomatic means. 

Finite element modeling (FEM) can be invaluable in developing and/or applying acceleration models for thermal and mechanical tests. Two-dimensional nonlinear modeling capability will usually be required in order to get meaningful results. Models can be constructed to estimate the stresses and strains in the material (e.g., the Cu in a PTH barrel or the solder in a surface-mount or through-hole joint) under operating conditions as well as under test conditions. These estimates will be far more accurate than the simple models provided in this overview because they can account for the interactions between materials in a complex structure and both elastic and plastic deformation. 

Finite element modelling on a macroscopic scale using the Tresca criterion matches the observed size and shape of the plastic zone and also the shape of the indentation stress-strain curves indicating that the physical characteristics of the microstructure determine its yield strength. The use of the Tresca criterion implies a zero coefficient of friction on the microstructural scale. The range of macroscopic yield stresses for the materials studied here is 750 MPa to 2000 MPa. 

With the remanent potential specified, it is possible to derive the back stresses and finally solve for the plastic multiplier yielding the incremental form of the constitutive law. For the implementation within the finite element model presented... 

Dean, G., McCartney, L.N., Crocker, L. and Mera, R. (2009) Modelling long term deformation behaviour of polymers for finite element analysis. Plastics, Rubber and Composites, 38,433-443. 

Figure 10.18 Finite element modeling of hot extrusion. Evolution of strain rate (left) and of cumulated plastic strain (right) [52].

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