The bonding state of the asphalt layers in a road pavement structure significantly affects its fatigue life. These bondings, therefore, require detailed tests and optimization. In this paper, the analyses of the correlation between the results of laboratory static tests and the results of fatigue tests of asphalt mixture interlayer bondings were performed. The existence of the relationships between selected parameters was confirmed. In the future, the results of these analyses may allow for assessment of interlayer bondings' fatigue life based on the results of quick and relatively easy static tests.

The paper analyses the influence of seasonal temperature variations on fatigue strength of flexible and semi-rigid pavement structures chosen for KR4 traffic flow category. The durability of pavement determined assuming a yearly equivalent temperature of 10˚C and assuming season-dependent equivalent temperatures was compared. Durability of pavement was determined with the use of Asphalt Institute Method and French Method. Finite Element Method was applied in order to obtain the strain and stress states by the means of ANSYS Mechanical software. Obtained results indicate a considerable drop in pavement durability if seasonal temperature variations are considered (up to 64% for flexible pavements and up to 80% for semi-rigid pavements). Durability obtained by the French Method presents lower dependence on the analysed aspect.

The paper there presents the analysis of low-cycle fatigue test results of 30 HGSA alloy steel obtained with the use of two methods. In the standard method, fatigue tests were performed with the use of many specimens, and in the simplified method, the results were defined in an incremental step test using one specimen. Test results were analysed taking into account the influence of loading form on the course of a stabilization process with defined material data. The analysis of the stabilization process in diversified conditions of loading was performed by comparison of the stress amplitude CTa and strain amplitude Eap for the same levels of total strain amplitude Eac• Basing on the tests, one could state that both methods of defining the cyclic properties lead to qualitatively and quantitatively convergent results. The results exhibit qualitative similarity as far as the character of courses of changes determined in different periods of life of n' and K' parameters of the cyclic strain chart is concerned, and quantitative similarity of the values of determined parameters.

In this present study, the effect of the shot peening process on fatigue life, surface hardness and corrosion properties of a low carbon alloy steel is examined at room temperature. The research article addresses the effect of shot peening by varying the process parameters such as peening distance and pressure with amachrome as shots. The experiment is designed by means of full factorial design. The experimental result reveals that the pressure and distance are the most significant factors in the shot peening process. The results illustrate that the average pressure of 7 bar and distance of 100 mm improves fatigue life by 1.5% of unpeened material under 20 Hz frequency while corrosion resistance improves by 4% with unpeening of the low carbon alloy steel by using amachrome as a shot.

Results and low-cycle fatigue tests analysis of 45 steel in conditions of block programmed loading with a different sequence of levels were presented in the paper. During tests four types of programs were applied: gradually increasing, gradually decreasing, gradually increasing and decreasing, and irregular. The sequence of levels in the block loading program was the parameter, which diversified the applied programs. The results of tests were analysed in the aspect of influence of loading program character on the course of the stabilization process. The analysis of the stabilization process was performed by comparing the stress loading amplitude for the chosen levels of the program in the following blocks. The hardening index was proposed as a description of the stabilization process. The comparative analysis showed similarity of the stabilization processes both under the programmed and the constant - amplitude loading.

Thermo-chemical treatments are known to increase the fatigue life of industrial parts. Due to the imprecise consideration of residual stresses in predicting the durability of components subjected to cyclic loading and their effect on the fatigue life, the authors developed a numerical model combining the influence of residual stresses with stresses caused by bending. The authors performed the numerical simulation with the use of Finite Element Method to analyse material behaviour during cyclic loading. The residual stress state developed during nitriding was introduced onto cross-section of the numerical specimen. The goal of this work was better understanding of the real conditions of the nitride steel fatigue processes and improving the knowledge about numerical predicting of the fatigue life for parts with residual stresses. The results of simulation were compared with plane bending fatigue tests. The presented method indicates the possibility of increasing the accuracy of the fatigue analysis of elements after surface treatment, increasing its certainty and the ability to perform better optimization of service life.

In the paper, on the basis of the performed tests, low-cycle fatigue characteristics (LCF) of selected light metal alloys used among others in the automotive and aviation industries were developed. The material for the research consisted of hot-worked rods made of magnesium alloy EN-MAMgAl3Zn1, two-phase titanium alloy Ti6Al4V and aluminium alloy AlCu4MgSi(A). Alloys used in components of means of transport should have satisfactory fatigue, including low-cycle fatigue, characteristics. Low-cycle fatigue tests were performed on an MTS-810 machine at room temperature. Low-cycle fatigue tests were performed for three total strain ranges Δεt = 0.8%, 1.0% and 1.2% with a cycle asymmetry coefficient R = –1. On the basis of the obtained results, characteristics of the fatigue life of materials, cyclic deformation σa = f(N) and cyclic deformation of the tested alloys were developed. The tests showed that titanium alloy Ti6Al4V was characterised by the highest fatigue life Nf, whereas the lowest fatigue life was found in the tests of the aluminium alloy AlCu4MgSi(A).

This paper presents the results of an extensive investigation of asphalt concrete beams with geosynthetics interlayer. The subject of the research is an evaluation of infl uence of geosynthetics interlayer applied to bituminous samples on their fatigue life. The results of the tests evidences that when geosynthetics are used, the fatigue life depends mainly on the type of bituminous mixture, the type of geosynthetics, and the type and the amount of bitumen used for saturation and sticking. The amount of bitumen used to saturate and fix the geosynthetic signifi cantly changes the samples fatigue properties. Essential positive correlation between fatigue and parameters of interlayer bonding (shear strength, shear stiffness) occurs in both testing temperatures.

For riveted joints with eccentricities of the load path, bending moments referred to as secondary bending are induced under nominally tensile loading conditions. Two simple theoretical models proposed in the literature to estimate the associated bending stresses are evaluated in the paper. Both approaches have been implemented in computer programs and applied to estimate the effect of several variables on the calculated bending stresses in the lap joint. Possibilities of the experimental and numerical verification of the models are also considered. Finally, a correlation between the secondary bending computed by one of the simple models and the observed fatigue properties of riveted specimens, as reported in the literature, is investigated. It is shown that deviations of the experimental results from the theoretical expectations stem from additional to secondary bending factors, like the inhomogeneous load transmission through the joint and the residual stresses induced by riveting process. These phenomena are known to be relevant to the fatigue behaviour of riveted joints, but they are not accounted for by the simple models. A conclusion from the present study is that despite the limitations and approximations inherent in the simple models, they provide reliable estimates of nominal bending stresses at the critical rivet rows and can be utilized in currently used semi-empirical concepts for predictions on the fatigue life of riveted joints.

The paper presents the method of determination of two-dimensional probability distribution P_f of crack initiation versus fatigue life N and the fatigue damage parameter : P_f − N − ϭ. The proposed distribution P_f uses parameters of the standard fatigue characteristics and allows calculating fatigue life of elements with heterogeneous stress fields at any probability level. The model was successfully verified on experimental test results.

The paper presents the results of research on low cycle properties of high-chromium martensitic GX12CrMoVNbN9-l (GP91) cast steel. The tests of fatigue strength were carried out at two temperatures: room temperature and at 600 degrees centigrade. At both temperatures the occurrence of cyclic softening of the cast steel was observed, revealing no clear stabilization period. Moreover, it has been proved that the fatigue life is influenced by the temperature which depends on the level of strain. The greatest influence was observed for the smallest strain levels applied in the research.

The paper presents comparative analysis of the results of low- cycle fatigue experiments on specimens made of 45 steel under uniaxial loading and bending. The analysis involves, among other things, the cyclic properties and the fatigue life of the specimens in a wide range of loading conditions. The experimental techniques used during bending enabled us to estimate the influence of strain distribution on fatigue life. The materials data obtained under the loading conditions mentioned above were employed to estimate the fatigue life of the structural elements. The results of experiments and calculations are presented in the form of fatigue curves. They also show the influence of axial loading and bending on the accuracy of the calculations.

Asphalt mixtures are commonly used for the pavement construction for national roads with a high traffic load, as well as local roads with low traffic load. The constructions of local road pavement consisting of thinner, more flexible layers located on less stable subbase than the pavement of national roads, require reinforcement with asphalt layers characterized by increased fatigue life. Technologies that allow quick repairs and reinforcements, while improving the durability of the road pavement are being sought. Such technologies include the use of modifications of asphalt mixtures with special fibers. The paper presents the results of investigations of the properties of asphalt mixtures modified with innovative basalt-polymer fibers FRP. On the basis of the obtained test results according to the Marshall method, stiffness modulus and fatigue durability, the technical properties of asphalt mixtures with FRP fibers addition were improved. This technology significantly increases the fatigue life of asphalt concrete dedicated for repairs and reinforcements of road pavements.

In this study, Al 2024-T3 alloy plates were joined by using friction stir welding. Welding was performed at a rotational speed of 930, 1450, 2280 rpm and a welding feed rate of 180 mm min ⁻¹. The welded samples were analyzed at the microstructural level. Moreover, both bending fatigue tests and tensile tests were performed on samples. At the end of the microstructural examination of the samples welded at the rotational speed of 930 rpm and the welding feed rate of 180 mm min ⁻¹, the formation of tunnel defects was observed. The highest fatigue life was obtained at 2280 rpm and 180 mm min ⁻¹. The lowest fatigue life was obtained at 930 rpm and 180 mm min ⁻¹. The highest ultimate tensile stress was obtained at 2280 rpm/180 mm min ^–1 sample, which shows about a 12% reduction relative to the base material. The lowest ultimate tensile stress was obtained at 930 rpm/180 mm min ^–1 sample. The ultimate tensile stress value of the 930 rpm/180 mm min ^–1 sample decreased by approximately 25%.

The introduction of new road pavement materials causes the need to verify whether the existing pavement design methods enable correct incorporation of their properties. In the case of asphalt pavements, the origins of contemporary methods may be traced back to the mid-20th century, when solely unmodified binders were used. The introduction of highly SBS-modified binders in 2009 significantly changed the behaviour of the asphalt mixtures and the entire pavement structure. Asphalt courses are now characterised by very high flexibility, elasticity and fatigue resistance, with simultaneous high resistance to rutting. The aim of the article is to present the effect of the use of asphalt mixtures with HiMA (Highly Modified Asphalt) binders in different variants of flexible pavement structures – including one, two or three courses containing HiMA. Fatigue life calculations were performed using the “Similarity Method”, which enables estimation of the fatigue life of the structure based on its relationship with the results of laboratory fatigue tests. The layer system with HiMA in the asphalt base course proved the most advantageous, combining excellent fatigue properties of the mixture containing HiMA with greater stiffness of the wearing and binder courses containing classic binders. The other aspect taken into account in the calculations was the effect of changing the mixture in the asphalt base course from AC 22 to AC 16. This change proved advantageous in all the analysed structures. The deflections and critical strains decreased, while pavement life, determined by fatigue and permanent deformation criteria, increased.

Pavements made of cement concrete, used for road constructions, are damaged during use. This applies to both the pavements of rural and forest roads with very low traffic loads, as well as road pavements with high traffic loads. One of the most effective ways of repairing damaged concrete cement pavements is through placing an asphalt overlay on a concrete slab. In order to increase the fatigue life of the asphalt overlay, asphalt mixtures are modified with fibres. One technological solution is to use FRP (Fiber Reinforced Polymer), an innovative material with improved properties.

The aim of this paper is to assess the impact of asphalt overlays modified with a new type of fibres to strengthen the durability of weakened cement concrete pavement structures.

On the basis of the conducted analyses, it was shown that the use of an asphalt layer reinforcement increases fatigue life, for both 15 cm thick prefabricated slabs and a typical road pavement for average traffic made of 25 cm doweled and anchored concrete slabs. There was a significant increase in the fatigue life of the concrete pavement structure as a result of modifying the overlaid asphalt mixture with FRP fibres.

In order to improve the toughness of traditional epoxy resin, dibutyl phthalate (DBP) was introduced into the epoxy resin. The static mechanical performance of plasticized and unplasticized epoxy resin was evaluated. The test results showed that the DBP modified epoxy resin can obtain a higher toughness than conventional epoxy resin, but the elastic modulus and the tensile strength were slightly reduced. The low cycle fatigue test results indicated that the stress ratio and the stress level were two critical factors of fatigue life, which was increased with the growth of stress ratio. It was also found that the fatigue life of plasticized specimen was much less than that of the unplasticized specimen because of the plastic deformation. A logarithmic linear relationship was then established to predict the fatigue life for plasticized epoxy resin. The strain energy density was also applied to demonstrate the accumulation of energy loss. In addition, the fatigue toughness can be obtained by the hysteresis loop area method.