Pressure-dependent Yield Criterion Research Articles

On the physical basis for a pressure‐dependent yield criterion for polymers. Comments on a paper by R. E. Lyon

Polymer Engineering & ScienceVolume 31, Issue 12 p. 924-925 Article On the physical basis for a pressure-dependent yield criterion for polymers. Comments on a paper by R. E. Lyon J. C. M. Li, J. C. M. Li Department of Mechanical Engineering, University of Rochester, Rochester, New York 14627Search for more papers by this authorC. C. Chau, C. C. Chau Advanced Composites Laboratory, Dow Chemical Company, Midland, Michigan 48674Search for more papers by this author J. C. M. Li, J. C. M. Li Department of Mechanical Engineering, University of Rochester, Rochester, New York 14627Search for more papers by this authorC. C. Chau, C. C. Chau Advanced Composites Laboratory, Dow Chemical Company, Midland, Michigan 48674Search for more papers by this author First published: June 1991 https://doi.org/10.1002/pen.760311212AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume31, Issue12June 1991Pages 924-925 RelatedInformation

A void growth-based failure model to describe spallation

A new dynamic failure model to describe void nucleation, growth, and coalescence in ductile metals is reported. The model is based on a pressure-dependent yield criterion for compressible plastic flow. This three-dimensional, plasticity-based continuum damage model is incorporated into a finite difference, wave propagation code. A procedure to determine the failure model parameters is proposed. In this procedure, the model parameters are calibrated based on the ability to match the experimental free-surface velocity history with code simulations. Model parameters for oxygen-free high-conductivity copper have been determined successfully using this procedure.

A formula which fits the pressure dependence of the torsional yield of polypropylene

A mathematical formula, which takes into consideration the physical aspects of both the pressure-modified von Mises and the modified non-linear pressure-dependent yield criteria, has been constructed. The proposed formula shows a very good fit to the experimental data.

The effect of high pressure on the mechanical behavior of short fiber composites

AbstractThree types of pressure dependent deformation processes have been observed for the short glass fiber reinforced composites of poly(vinyl chloride) (PVC). A unique deformation behavior, observed for the first time, features a sharp drop in stress followed by shear yielding in the matrix. Competitive pressure dependent failure processes in the composites are strongly affected by “debonding” at the fiber‐matrix interface. A new general pressure dependent yield criterion for PVC and its composites was elucidated.

The Stress-Strain Behaviour of Axially-Loaded Butt Joints

The effects of the stress distribution in the adhesive layer of axially loaded butt joints have been examined theoretically and experimentally. It has been shown that the measured stress–strain behaviour of a butt joint is dependent on the triaxial stress state induced in the adhesive by the restraint of the adherends. This causes a butt joint to yield at a stress which is greater than the uniaxial yield stress of the adhesive. Conversely, the presence of stress concentrations can cause a butt joint to fail at a lower tensile stress than the failure stress of a bulk specimen tested in uniaxial tension. Therefore, the relationship between the strength of a butt joint and that of a bulk specimen of the same adhesive depends on the ductility of the adhesive. Furthermore, if the adhesive obeys a pressure-dependent yield criterion, the compressive yield stress of a butt joint can be much greater than the tensile yield stress of a similar joint and, under some circumstances, compressive yielding of a butt joint...

Variation of yield stress with orientation in oriented polyethylene

AbstractHigh density polyethylene with a single crystal texture has been used to examine the variation of yield stress with orientation in both tension and compression. The Coulomb yield criterion, which has previously been applied to yield data in oriented polyethylene, must be rejected since the experimental data can only be fitted over a limited range of orientation in tension only. The von Mises criterion, as modified by Hill 12 for anisotropic materials, appears to give a reasonably good fit to the tensile data. However, further consideration of the theory with respect to the compressive data shows that the criterion is not applicable. The pressure dependent yield criterion proposed by Caddell et al13 also appears unable to predict the experimentally observed tensile and compressive behaviour. A three‐part criterion previously applied to fibre‐composites 11 gives a good fit to the tensile data; this model also predicts the changeover from ductile to brittle behaviour observed in tensile specimens with θ > 70d̀ (θ is the angle between the tensile axis and the molecular axis). None of the yield criteria examined have been able to explain satisfactorily the lack of any marked degree of anisotropy in compression.

Macroscopic yielding of oriented polymers

Uniaxial and biaxial stress states were employed to compare the measured macroscopic yield behaviour of oriented polycarbonate, polyethylene, and polypropylene with a proposed anisotropic and pressure-dependent yield criterion. A good correlation between theory and experiment was found for each material.

Deformation, yield and fracture of polymers at high pressure

AbstractThe effects of hydrostatic pressure on the shear, compressive, and tensile stress‐strain behavior of both amorphous and crystalline polymers are reviewed and illustrated. For polymers with Tg near to but below ambient temperature, there is a steep increase of modulus with pressure and, above some critical pressure, there is a lower rate of increase. The critical pressure is a linear function of the test temperature and, from its slope, one can deduce the pressure coefficient of Tg. For many other polymers, there is a linear increase, over a wide pressure range, of elastic and shear moduli with pressure, and this is in accord, to a first approximation, with predictions of finite strain theory. Most all polymers investigated show a strong pressure coefficient of yield stress and in many cases this variation is linear over a wide pressure range, in accord with several pressure dependent yield criteria. To a considerable extent, the yield stress rise with pressure parallels that of the modulus, and this behavior is predicted by some yield theories. The effects of pressure on fracture stress and fracture strain are discussed. The results obtained depend on the polymer composition and structure and on the pressure medium. Consideration is also given to the effects of pressure on crazing and stress‐whitening.

The flow of solid polymers under high pressure

The deformation and flow properties of solid polymers under uniaxial tensile and compressive loading have been determined for a variety of both crystalline and amorphous polymers at hydrostatic pressures to about 7 , kb. For some polymers, like polytetrafluoroethylene, cold drawing is inhibited by increasing pressure, and scanning electron micrographs show that local plastic deformation is greatly reduced. However, the true flow stress and the true fracture stress both increase with pressure, as does, also, the elastic modulus. The increase is greatest in the low-pressure range below 2 kb. This behavior is attributed to the pressure-induced shifting of a lowtemperatureβ′-transition. The influence of polymer composition and of the initial elastic constants on the pressure dependence of the elastic modulus and the yield stress is discussed. The observed behavior can be analyzed in terms of finite strain effects and a pressure-dependent yield criterion. It is shown that some amorphous polymers undergo a pressure-induced brittle-ductile transition, and these findings are used to explore the hydrostatic extrusion of polyimide and polysulfone at room temperature.

Analyses of Solid State Extrusion Process of Polymeric Materials by Pressure Dependent Yield Criteria

Abstract Among various methods to estimate extrusion pressure in solid state extrusion, Sachs's method1 is one of the most convenient and widely used ones. According to this method the equation for extrusion pressure is derived by taking accounts of the equilibrium of the forces in the tapered die part and of the yield criterion of the material being extruded. Analytical solutions have easily been obtained in the cases that the yielding behavior of the material obeys Tresca or von Mises yield criterion and where the yield stress does not depend on strain or the strain dependence of yield stress is represented in a simple analytical form. The yielding behavior of metallic materials satisfies these conditions.