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1

An energy-based method in phenomenological description of mechanical properties of nonlinear materials under plane stress

Wegner T., Kurpisz D.

Journal of Theoretical and Applied Mechanics

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2017

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Vol. 55 nr 1

129--139

EN

A method based on energy is a very useful tool for description of mechanical properties of materials. In the current paper, on the base of geometrical interpretation of a deformation process, the strain energy density function for isotropic nonlinear materials has been constructed. On account of hydrostatic interpretation of the volumetric deformation, the elastic part of energy has been extracted. The initiation of the damage process due to plastic flow of the material under plane stress has been determined and the stability conditions have been formulated by using in the stability analysis the strain energy density function in addition to Sylvester’s theorem and assumption of zero volume change during pure plastic deformations. This concept is an original part of the work and continuation of the investigations previously carried out by Wegner and Kurpisz. The theoretical investigations have been illustrated on the example of aluminium.

2

Aluminum Alloy Welded Connection Tension Test and Energy Strain Investigation

Obst M., Kroczak J., Kurpisz D.

Machine Dynamics Research

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2014

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Vol. 38, No. 3

81-86

EN

Welded connections are very popular and applicable joints methods of materials. Welding technology and methods intensely developed in recent times and now its base technology is used in different industrial branches. Pressure vessels, boilers, working machines parts, plane bodies, ship hulls and other structures are made of metal, parts connected together by welding. Many welded connections work under complex stress and strain state also thermally loaded. Engineers apply typical, formulas during the design process of welded connections, some designers attempt also to use Finite Element Method in the modelling and design process of welded connections. It’s well known, welded connections zones enclose a place where materials have different properties than properties of parent materials of connected parts. In this area can cracks initiate and propagate. This paper presents tension test results of welded parts of aluminium alloy sighed as AL 5084. Authors investigated strain energy density and volume energy density dependence in the tension test process of welded specimens. Energy as an universal measure can be applied to investigate complex strength and exploitation problems. Presented results can be used as an introduction for more complicated problems of welded connections where strain energy is a base for mechanical modelling of welded connections.

3

Phenomenological modeling of mechanical properties of metal foam

Wegner T., Kurpisz D.

Journal of Theoretical and Applied Mechanics

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2013

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Vol. 51 nr 1

203--214

EN

In this paper, constitutive relations for metal foam under complex load are introduced using a phenomenological concept. On the basis of stress-strain and transversal-longitudinal strain dependencies in uniaxial tests, a form of the function for strain energy density is specified, and further, the criterion for loss of stability due to the occurrence of plastic flow is defined. The theoretical investigations are illustrated by a short numerical example.

PL

W niniejszej pracy, bazując na fenomenologicznym sposobie podejścia, wyprowadzono związki konstytutywne piany metalowej poddanej złożonemu stanowi obciążenia. Na podstawie zależności naprężenia oraz odkształcenia poprzecznego od odkształcenia podłużnego uzyskanych w jednoosiowych próbach, wyznaczono wzór opisujący funkcję gęstości energii wewnętrznej, a następnie sformułowano analityczną postać kryteriów zniszczenia materiału ze względu na wystąpienie plastycznego płynięcia. Rozważania teoretyczne zilustrowano prostym przykładem numerycznym.