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Kumulacja uszkodzeń zmęczeniowych dla obciążeń blokowych z wykorzystaniem pamięci materiału

100%

Böhm E.

tom z. 105

21-22

The paper presents a new model to calculate the degree of fatigue damage. It is based on the memory of the material. The model is verified on the basis of the block loads (High-Low, Low-High).

Wpływ eksploatacji na wybrane właściwości mechaniczne stali X10CrMoVnB9-1 (P91)

84%

Grzywna P. , Kukla D.

tom R. 85, nr 12

75--77

Przedstawienie wyników badań stali P91 w stanie dostawy i po 80 000 h przepracowanych na rurociągu pary świeżej oraz wskazanie parametrów porównawczych stanowi treść niniejszego opracowania. W pracy przedstawione zostały wyniki badań składu chemicznego, mikrostruktury, statycznej próby rozciągania oraz charakterystyki Wöhlera. Nawiązano też do wyników badań nieniszczących otrzymanych przy użyciu metody prądów wirowych umożliwiających ilościową ocenę stopnia degradacji zmęczeniowej stali P91.

Tests results of P91 steel taken from a scrap of a new pipeline and a pipeline after 80 000 h of its exploitation in real steam conditions were presented. Additionally, in the present paper comparative parameters were indicated. Chemical composition analysis, microstructural observations, static tensile tests were carried out; also Wöhler’s characteristics were outlined. Moreover, there were considered results of nondestructive methods such us eddy currents that allow quantitative assessment of fatigue damage evolution of P91 steel.

Application of X-ray tomography to assess fatigue structural changes in asphalt mixtures

84%

Mackiewicz P. , Szydło A.

tom Vol. 67, nr 2

307--315

The article presents an analysis of the change in air voids in asphalt mixtures subjected to fatigue tests at three temperatures of 0°C, 10°C and 25°C. The X-ray computerized tomography imaging method, XCT, was used to identify the air voids in the samples. The research allowed to determine changes in the content of air voids in subsequent fatigue cycles in the sample area. The relationship between air voids volume and the stiffness modulus value was also determined during fatigue for three temperatures. The largest changes were found in samples with notches at 0°C. The analysis of the change in the content of air voids showed that the micro-cracking nucleation processes develop with the number of fatigue cycles. Using the numerical model finite element method we determined the distribution and change in fatigue damage in the extreme areas of the sample during various stages of fatigue. We found clear relationship between the damage and the increased content of air voids.

Evaluation of fatigue life calculation algorithm of the multiaxial stress-based concept applied to S355 steel under bending and torsion

84%

Macek W. , Mucha N.

tom Vol. 21, nr 4

935--951

This paper presents the results of a study into the stress-based fatigue life calculation algorithm applied to cyclic and random multiaxial proportional and non-proportional loading. This method for high-cycle fatigue, covers both infinite and finite life region, and is based on a critical plane approach combined with rain flow cycle counting and linear damage accumulation. Algorithm based on the method for equivalent scaling of the normal stress in material planes in dependence on the stress state, proposed by Gaier and Danbauer. For analysis the calculated fatigue lives are compared to the experimental results for steel S355 under proportional and non-proportional bending with torsion.

Experimental study on fatigue failure evolution in composite plate monitored by wave propagation method

84%

Stawiarski A. , Barski M. , Muc A.

2020

tom Vol. 31, nr 2

art. no. 2020227

In this study, the elastic wave propagation method is used to observe the initiation and evolution of the fatigue failure form in the multilayered composite plate with an elliptical hole. The experimental tests with the use of active, pitch-catch elastic wave measurement techniques are used during the fatigue test of the composite specimens. The fatigue tests were preceded by the numerical, finite element analysis of the elastic wave propagation phenomenon in a composite plate with an elliptical hole. The sequential measurement related to the number of cycles during the fatigue tests was assumed. The time of flight (ToF) and amplitude change was monitored by piezoelectric sensors localized in the area of predictable failure form evolution. The analysis of the dynamic response of the structure under fatigue loading conditions by a relatively small number of piezoelectric transduces allows us to build cost-effective Structural Health Monitoring (SHM) system for damage detection and monitoring of the failure form evolution.