Failure by fracture or yielding in strain hardening materials according to the t-criterion

In designing prosthetics for amputees, quality and quantity of materials determine device tensile, flexural, extension and compression strength as well as energy distribution when load is applied. Biomechanical properties contribute in combination to any device longevity and resolution force effect to gait expression. Four different dry rattan canes were sampled and subjected to biomechanical analysis, and sample 3 had highest tensile strength with ultimate tensile strength of 11.5N/mm2 revealed when load at break of 668.18N applied, and modulus 1033.90MPa with ductility of 7.33mm were resultant. While average ultimate tensile strength of 8.68N/mm2 was sustained by load at break of 396.66N, modulus of 1119MPa and ductility of 9.5mm was confirmed of rattan cane. Highest flexural strength of 34.43N/mm2 resulted from load at break of 32.82N, modulus 255.65MPa and elongation of 66.81mm was dictated of sample 3, and an average Flexural strength of 26.4 N/mm2 occurred when load at break of 16.04N, modulus 229.16MPa produced elongation (ductility) of 55.1mm on rattan cane. The highest load resistance was shown by sample 3 at compressive strength of 8.79MPa when on load at break of 330N, modulus 622.53MPa resulted. While sample 4 had the highest compressive strength of 9.94MPa when load break at 309N exerted modulus 283.14MPa. Gait analysis revealed terminal swing and heel strike of chosen height 8cm and deformity 0cm while early and mid stance of 0.3cm and 7.7cm were respectively for deformity and height.

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“…Failure can be determined in two ways (i.e. dilatational and distortional), and nonlinear material can be generally captured by [32][33]…”

Section: Flexural Test (3 Point Bend Test)mentioning

confidence: 99%

The Biomechanical Properties of Rattan Cane in the Design and Fabrication of Prosthetic Foot

Kelechi

Ndubuka

Onwukamuche³

et al. 2020

AJAS

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“…A launching point was the first version of the so-called T-criterion, which proved adequate to predict failure conditions for precracked [16,17] or uncracked geometries [18,19]. It was based on the von Mises [20] criterion and an addendum giving an answer to the question: What happens with the dilatation of the material?…”

Section: Introductionmentioning

confidence: 99%

On the Failure Locus of Isotropic Materials in the Stress Triaxiality Space

Manolopoulos

Andrianopoulos

2015

Journal of Engineering Materials and Technology

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The aim of this paper is to contribute to the prediction of the failure of materials (ductile and brittle) with a single criterion (rule) not violating the assumptions of continuum mechanics. In this work, the failure behavior of isotropic materials is connected with the ability of a material to store elastic strain energy from the very start of loading until its fracture. This elastic strain energy is known that is separated in a distortional and a dilatational part. So, when one of these quantities takes a critical value, then the material fails either by slip or by cleavage. The behavior of a material is described with regard to the secant elastic moduli depending on both unit volume expansion 0 and equivalent strain eeq. This dependence enlightens, in physical terms, the different reaction of materi als in normal and shear stresses. T-criterion is applied for the prediction of failure in a series of experiments that took place to an aluminum alloy (AI-5083) and to PMMA (Plexiglas). A single criterion was used for two totally different materials and the predic tions are quite satisfactory. This work is a step toward the direction of using one criterion in order to explain and predict failure in materials independently of the plastic strain that developed before fracture.

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“…A criterion based on elastic strain energy density in case of linear elasticity was the first version of the socalled T-criterion which has been proved adequate to predict failure conditions for pre-cracked (Theocaris and Andrianopoulos 1982a, b) or uncracked geometries (Andrianopoulos 1993;Andrianopoulos and Boulougouris 1994). It was based on the von Mises's (1913) criterion and an addendum giving an answer to the question: 'What happens with the, not covered by von Mises, dilatation of the material?'…”

Section: Introductionmentioning

confidence: 99%

Elastic strain energy density decomposition in failure of ductile materials under combined torsion-tension

Andrianopoulos

Manolopoulos

2014

Int J Mech Mater Eng

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The constitutive behavior and failure of ductile materials are described in the present work for a general case of loading in terms of the secant moduli, which depend on the first (dilatational) and second (deviatoric) strain invariants. This approach exposes the distinct behavior of materials to the equivalent normal and shear stresses. The secant moduli enable the establishment of two (instead of one) constitutive equations necessary for the complete description of these materials. Emphasis is given in the accuracy of the resulting constitutive equations in terms of their predictions relative to actual experimental data for two materials systems. Failure predictions, according to T-criterion, are derived for two materials under combined torsion and tension, which are in good agreement with experimental data. Finally, the associated failure surfaces in a stress space are presented as well.

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Failure by fracture or yielding in strain hardening materials according to the t-criterion

Cited by 8 publications

References 9 publications

The Biomechanical Properties of Rattan Cane in the Design and Fabrication of Prosthetic Foot

The Biomechanical Properties of Rattan Cane in the Design and Fabrication of Prosthetic Foot

On the Failure Locus of Isotropic Materials in the Stress Triaxiality Space

Elastic strain energy density decomposition in failure of ductile materials under combined torsion-tension

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