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Bartosz Madejski and Grzegorz Socha

Abstract

Static tension test allows characterization of material strength properties. This simple test provides input data for numerical calculation of structural components made of the tested alloy. Elastic, plastic and failure behavior of the structural component in question is simulated, using, for example, the FEM package, based on parameters obtained as the result of tensile testing. When using the results of the tensile test for modeling the material failure it is important to estimate correctly plastic strain corresponding to failure. It is common practice to use elongation of the specimen gage part for the calculation of failure strain. On the other side, the most popular ductile failure criterion used by engineers performing numerical simulation of the material’s behavior relies on the equivalent plastic strain as the criterial quantity. Those two parameters can differ significantly. In order to calculate the equivalent plastic strain correctly, we have to remember about strain localization (necking) appearing during tensile tests and take into account the fact that during tensile testing we have three non-zero strain tensor components. Ignoring this fact, and using only elongation as the criterial quantity can lead to enormous simulation error. This error is analyzed in this paper for nickel based superalloy tested at elevated temperatures.

Open access

Józef Krysztofik, Wojciech Manaj and Grzegorz Socha

Abstract

Structural properties of materials change under stress, temperature and work environment. These changes are generally unfavorable. They cause a reduction in strength of materials. This has an impact on the safety and service life of machines and constructions.

In the chemical and petrochemical industry the destruction of a structure can be activated by chemical substances. In the energy industry, a key element in assisting the destruction is temperature. In aviation, the typical cause of damage is the process of fatigue. Regardless of the differences regarding/concerning the mechanisms of degradation, typical of the sectors of industry, the end result is the emergence of microvoids and microcracks in the material. In the final phase of the process, dominant cracks are formed.

The term of measure of material damage, introduced by Kachanov and Rabotnow, can be effectively used also when considering the impact of microdamages on measurable macroscopic acoustic quantities. A damage parameter proposed by Johnson allows to correlate changes in acoustic birefringence of the material with the parameter describing the degree of damage.

In this article the authors presented the nondestructive tests results concerning Inconel 718 alloy subjected to damage caused by plastic deformation. This paper focuses on the evaluation of acoustic properties in relation to the degradation of the materials tested.

Open access

Arkadiusz Denisiewicz, Krzysztof Kula, Tomasz Socha and Grzegorz Kwiatkowski

Abstract

The article presents the results of laboratory tests of selected mechanical and physical properties of fine-grained concrete. The tests were carried out on samples with varying degrees of microsilica addition. The consistency class, shrinkage, compressive and bending strength, water resistance and frost resistance were determined for the designed concrete mixtures and made samples.

Open access

Grzegorz B. Durło, Stanisław Małek and Jarosław Socha

Abstract

An increase in frequency of weather phenomena in the Western Beskids that are disadvantageous for natural environment caused an upset of ecologic balance, especially within the scope of water management and retention. Concerns referring to forest groups maintaining their stability are fully justified, regarding that in many areas of the Beskids, there is an intensive reconstruction of stands of trees in the lower subalpine region. In turn, young generations of trees are continuously stresses, which arise from periodic shortages of precipitation within the course of the whole vegetation process. The presented work encompasses characteristics of extreme rainfall events that might have a negative impact on growth and development of Norway spruce stands in the Silesian Beskid in recent decades.

The article makes use of meteorological data from a multiannual period (1951–2010), gathered in 26 meteorological stations of the Polish Institute of Meteorology and Water Management (IMGW) in Silesian Beskid one station located in the Carpathian regional gene bank and two under canopy posts located in Wisła forestry inspectorate area. Special attention was devoted to the presence of extreme phenomena and their repeatability. The analysis of parameters of rainfall sequences was complemented with indexes determining ecological requirements of spruce, such as: Schmuck moisture indicator, Vogel-Daniels habitat dryness index and abundance of rainfall indicator developed in this study.

Results of climatological analysis confirmed that weather phenomena with, especially dynamic course may lead to destabilisation of even a properly formed and adequately developed forest ecosystem, and as a consequence, disturb stability in the natural environment. Diminishment of the index of precipitation size, which has been observed in recent years, may be one of the most crucial causes that limit the number of spruces in the stands of trees of the lower subalpine region in Silesian Beskid. The climatological analysis confirmed that during 60 years in Silesian Beskid, there were over 20 extreme weather (precipitation) episodes of different courses, intensity and surface reach, out of which at least 9 played a key role in lowering the health condition of the trees, as a consequence, it influenced destabilisation of the spruce stands in the lower subalpine region, regardless of their age or location within the area.