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Assessment with indentation techniques of the local mechanical behavior of joints in polymer parts

Lach R, Hutař P, Veselý P, Nezbedová E, Knésl Z, Koch T, Bierögel C, Grellmann W

Polimery

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2013

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T. 58, nr 11-12

900--905

EN

The paper summarizes our investigations performed with micro- and nanoindentation techniques and results presented in literature, concerning local mechanical behavior of welded joints [polyamide 6, polypropylene, polyethylene (high density and crosslinked polyethylene), poly(vinyl chloride)] and weld lines (polypropylene, polycarbonate, polystyrene) of amorphous and semicrystalline polymers. For amorphous polymers, minimum of hardness and indentation modulus in the joint are found or no change in the properties were stated, whereas for semicrystalline polymers, hardness and indentation modulus mostly pass through a maximum in the weld line, the welded joint or the heat-affected zones.

PL

W pracy podsumowano wyniki badań wykonanych metodą wciskania wgłębnika w zakresie mikro i nano oraz wyniki przedstawione w literaturze, dotyczące lokalnych właściwości złączy spawanych [poliamidu 6, polipropylenu, polietylenu (dużej gęstości i usieciowanego), poli(chlorku winylu)] i linii spoiny polimerów amorficznych i semikrystalicznych (polipropylenu, poliwęglanu, polistyrenu). W przypadku polimerów amorficznych wykazano w złączu minimum twardości i modułu sprężystości przy wciskaniu wgłębnika lub stwierdzono brak zmian tych właściwości. W przypadku polimerów semikrystalicznych twardość i moduł sprężystości osiągają maksimum w linii spoiny, złączu spawanym lub w strefach wpływu ciepła.

2

Evaluation of the threshold values for the propagation of a fatigue crack starting at a V-notch

Klusák J., Knésl Z.

Computer Assisted Mechanics and Engineering Sciences

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2002

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Vol. 9, No. 4

459-468

EN

This paper presents a simple method for evaluating the threshold value for fatigue cracks that emanate from a V-notch. The proposed method is based on the similarities between the elastic-stress fields around the tip of a crack and the tip of a V-notch. Threshold values for fatigue cracks that emanate from a V-notch are expressed by means of the threshold value for the propagation of a high-cycle-fatigue crack and the opening angle of the V-notch. The corresponding calculations were performed by the finite-element method.

3

Estimation of the driving force acting on the interface edge

Knésl Z., Vrbka J., Vilímek D.

Computer Assisted Mechanics and Engineering Sciences

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1998

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Vol. 5, nr 2

185-192

EN

This paper introduces a simple and approximate of calculating the elastic driving force acting on the interface in two-phase materials. The method is based on considerations of the elastic energy connected with the change in the shape of the interface. The two phases are considered to be elastically isotropic media with different elastic constants. The procedure is developed in the framework of the finite element method and is applied to the estimation of the local driving force in the case of the edge of an interface with a singular distribution of stress. The application of T-stress to the problem is suggested.