Richard M. Christensen's blog

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Failure Theory Applications

A new section on applications has been added to the website on failure criteria.  Six examples of failure applications are given which span the range from very ductile to very brittle isotropic and homogeneous materials.  Summarizing two of the examples, first a very ductile polymer is examined wherein its tensile, compressive, and shear strengths are determined as influenced by a state of superimposed hydrostatic pressure. An interesting fallout from the example shows just how seriously in error the Mises criterion can be, even when applied to a ductile material.

 


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Critical Experimental and Theoretical Tests for Failure Criteria

 A new section has been added to the website http://www.failurecriteria.com/.  This is on critical tests for failure criteria.  It summarizes most of the previous entries to the website and provides evaluations of the most salient of the failure criteria by comparing with high quality experimental data.

 


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Failure Surface Graphics in Stress Space

 A new section has been added to the website on failure criteria for engineering materials.  This new work displays many different three-dimensional computer graphics of failure criteria surfaces in stress space. The full range of isotropic materials are covered from ductile metals to brittle ceramics and glasses and beyond.  All of these computer generated graphics can be seen at www.failurecriteria.com/failuresurfacegr.html.

 


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Fatigue and Creep Failure Models for Variable Amplitude Loading Programs

A new section on fatigue and creep rupture has been added to the website:    http://www.FailureCriteria.com

This is Section IV entitled “Cumulative Damage Leading to Fatigue and Creep Failure for General Materials”.  It is shown that a general formalism can be taken which applies to either fatigue or creep rupture through suitable notational changes.  The basic problem is to predict the lifetimes under variable amplitude loading programs based upon knowledge of the data base of lifetimes under constant amplitude loading conditions.  The problem is analogous to that of viscoelasticity where creep or relaxation functions combined with convolution integrals can be used to predict the response for a general loading history.  However, the viscoelasticity problem admits a linear constitutive formulation, whereas the failure problems of interest here are by definition nonlinear.


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Fiber Composites Failure Criteria

  A new failure criterion has been formulated for fiber composite materials.  It is the anisotropic counterpart of a recently derived isotropic criterion.  The targeted applications are for carbon fiber, polymeric matrix (or equivalent) types of materials.   The complete treatment can be accessed at the new website:                                                                 http://www.failurecriteria.com


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FailureCriteria.com

     A new website http://www.failurecriteria.com has been initiated which surveys mechanics type failure criteria for homogeneous materials.  Although later additions will be concerned with anisotropic materials, the first topic of attention is that of yield and failure criteria for isotropic materials.  A brief review of  the Mises, Tresca, and Coulomb-Mohr criteria is given, along with the need for a more general form which spans the various  materials classes including metals, polymers and ceramics. Using results from the recent literature, a new two property failure form is


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