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.

The paper presents experimental results of creep and low cycle fatigue (LCF) tests carried out on the as-received cast aluminium alloys with different chemical composition and porosity. The test programmes contain creep investigations under step-increased stresses at different temperatures, and cyclic plasticity under different strain amplitudes and temperatures.

The paper presents a new method of lifetime calculations of steam turbine components operating at high temperatures. Component life is assessed on the basis of creep-fatigue damage calculated using long-term operating data covering the whole operating period instead of representative events only. The data are analysed automatically by a dedicated computer program developed to handle big amount of process data. Lifetime calculations are based on temperature and stress analyses performed by means of finite element method and using automatically generated input files with thermal and mechanical boundary conditions. The advanced lifetime assessment method is illustrated by an example of lifetime calculations of a steam turbine rotor.

The paper presents low-cycle fatigue (LCF) characteristics of selected magnesium alloys used, among others, in the automotive and aviation industries. The material for the research were bars of magnesium alloys AZ31 and WE43 after hot plastic working. Due to their application(s), these alloys should have good/suitable fatigue properties, first of all fatigue durability in a small number of cycles.

Low-cycle fatigue tests were carried out on the MTS-810 machine at room temperature. Low-cycle fatigue trials were conducted for three total strain ranges Δεt of 0.8%, 1.0% and 1.2% with the cycle asymmetry factor R = –1. Based on the results obtained, fatigue life characteristics of materials, cyclic deformation characteristics σa = f(N) and cyclic deformation characteristics of the tested alloys were developed. The tests have shown different behaviors of the tested alloys in the range of low number of cycles. The AZ31 magnesium alloy was characterized by greater fatigue life Nf compared to the WE43 alloy.

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.

The paper presents the results of comparative tests of the fatigue properties conducted on two non-ferrous alloys designated as Al 6082 and

Al 7075 which, due to the satisfactory functional characteristics, are widely used as engineering materials. The fatigue tests were carried

out using a proprietary, modified low cycle test (MLCF). Particular attention was paid to the fatigue strength exponent b and fatigue

ductility exponent c. Based on the tests carried out, the results comprised within the range defined by the literature were obtained. These

results prove a satisfactory sensitivity of the method applied, its efficiency, the possibility of conducting tests in a fully economical way

and above all the reliability of the obtained results of the measurements. Thus, the thesis has been justified that the modified low cycle

fatigue test (MLCF) can be recommended as a tool used in the development of alloy characteristics within the range of low-cycle variable

loads

The article presents the analysis of properties of the high-strength AlZnMgCu (abbr AlZn) aluminium alloy and estimates possibilities of

its application for responsible structures with reduced weight as an alternative to iron alloy castings. The aim of the conducted studies was

to develop and select the best heat treatment regime for a 7xx casting alloy based on high-strength materials for plastic working from the

7xxx series. For analysis, wrought AlZnMgCu alloy (7075) was selected. Its potential of the estimated as-cast mechanical properties

indicates a broad spectrum of possible applications for automotive parts and in the armaments industry. The resulting tensile and fatigue

properties support the thesis adopted, while the design works further confirm these assumptions.

In this study, the mechanical tests were carried out on ductile iron of EN-GJS-600-3 grade and on grey cast iron of EN-GJL-250 grade. The fatigue life was evaluated in a modified low-cycle fatigue test (MLCF), which enables the determination of parameters resulting from the Manson-Coffin-Morrow relationship. The qualitative and quantitative metallographic studies conducted by light microscopy on selected samples of ductile iron with spheroidal graphite and grey cast iron with lamellar graphite (showing only small variations in mechanical properties,) confirmed also small variations in the geometrical parameters of graphite related with its content and morphological features.

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).

The effect of hydrogen on short-term strength, low-cycle durability and planestress fracture toughness of 10Cr15Ni27 steel, 04Cr16Ni56 and 05Cr19Ni55 alloys at pressure up to 35 MPa and temperature 293. . . 773 K was investigated. The modes of hydrogen action for which the elongation δ, reduction of area ψ, low-cycle durability N and crack resistance parameters K_c of alloys are minimal were established: hydrogen pressure above 10 MPa (non-hydrogenated specimens of 04Cr16Ni56 alloy) and above 15 MPa (hydrogenated specimens of 10Cr15Ni27 steel and 05Cr19Ni55 alloy, hydrogen concentration 15 and 19 wppm, respectively).

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.

Since fatigue cracks nucleate and initiate generally at the surface of the rotary components such as blades and discs, the surface condition is the most important factor affecting the fatigue life. Surface scratches are suitable sites for stress concentrations and therefore the nucleation stage of fatigue cracks will be shortened. In the present work, the influence of surface roughness on the low cycle fatigue life behavior of nickel-based superalloy Rene®80 at the temperature of 900°C was evaluated. Results of low cycle fatigue tests (LCF) under strain-controlled condition at 900°C for R = _εmin/εmax = 0 and strain rate of 2×10 ^–3 s ^–1, at a total strain range of 1.2% showed an inverse relationship between fatigue strength and surface roughness of the specimens. In this study, increasing the surface roughness of Rene®80 from 0.2 μm to 5.4 μm led to the decline in the final LCF life from 127 cycles to 53 cycles which indicated a 58.3% reduction in fatigue life at the same condition. Fractography evaluation also exhibited that fatigue cracks initiated from the notch in the rough specimens, whereas in the smooth specimen fatigue cracks nucleated from the internal imperfections and carbides.

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.

Paper presents the assessment of impact of heat treatment on durability in low-cycle fatigue conditions (under constant load) in castings

made using post-production scrap of MAR-247 and IN-713C superalloys. Castings were obtained using modification and filtration

methods. Additionally, casting made of MAR-247 were subjected to heat treatment consisting of solution treatment and subsequent aging.

During low-cycle fatigue test the cyclic creep process were observed. It was demonstrated that the fine-grained samples have significantly

higher durability in test conditions and , at the same time, lower values of plastic deformation to rupture Δϵpl. It has been also proven that

durability of fine-grained MAR-247 samples can be further raised by about 60% using aforementioned heat treatment.

This study discloses the characteristic features of the modified low-cycle fatigue test used for the determination of the mechanical

properties of two types of cast iron, i.e. EN-GJL-250 and EN-GJS-600-3. For selected materials, metallographic studies were also

conducted in the range of light microscopy and scanning microscopy.

Turbogenerator coil retaining rings are shrunk-fitted onto the rotor over the coils, in order to restrain them against the centrifugal force. They are typically subjected to low cycle fatigue, with a cycle being completed at every machine switch-on and switch-off. The subject of this paper consists in the determination of the failure probability of a coil retaining ring. The failure mode of the ring cracking, when it swells in tension, due to the centrifugal force is here considered. The reliability assessment is preceded by the study of the input variables affecting the low-cycle fatigue load and of their stochastic distributions. This question is tackled by the experimental determination of the static, cyclic and fatigue curves of the involved material and by the application of a statistical model to compute related parameters and their standard deviations. Upon the determination of variable distributions, the probability of failure is estimated in the form of a cumulative distribution function by a computationally efficient methodology, based on the Advanced Mean Value approach. The obtained results account for the material response and the local stressstrain states at the most loaded coil retaining ring region. The determined probability at the end of the machine life, in the order of 10^-12, is compatible with reference values for structures under fatigue in the mechanical and aeronautical fields.

The paper presents the possibility of using FSW technology for joining elements of a landing gear beam of the M28 aircraft. The FSW process was performed on a 4-axis numerical machine under industrial conditions. However, before welding was carried out under industrial conditions, preliminary experimental tests were carried out under laboratory conditions. Preliminary research was carried out for AA2024-T3 aluminum sheets of 1 mm and 3 mm in thickness, joined in a lap configuration. The influence of technological and geometric parameters of the process on the quality and strength of the weld was examined. Sheet metal arrangement was analyzed. Tests were carried out for two configurations. The first of which with 1 mm sheet on the top and 3 mm sheet on the bottom and in reverse order. It has been shown that setting a thicker plate on the top gives a 40% better strength. The microhardness and microstructure of the weld were tested. During the laboratory tests, low-cycle fatigue tests of the FSW lap joint were performed. It has been shown that the FSW method can be an alternative to the riveting process in the production of aviation structure elements.

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.

The paper presents a detailed analysis of the material damaging process due to lowcycle fatigue and subsequent crack growth under thermal shocks and high pressure. Finite Element Method (FEM) model of a high pressure (HP) by-pass valve body and a steam turbine rotor shaft (used in a coal power plant) is presented. The main damaging factor in both cases is fatigue due to cycles of rapid temperature changes. The crack initiation, occurring at a relatively low number of load cycles, depends on alternating or alternating-incremental changes in plastic strains. The crack propagation is determined by the classic fracture mechanics, based on finite element models and the most dangerous case of brittle fracture. This example shows the adaptation of the structure to work in the ultimate conditions of high pressure, thermal shocks and cracking.

The paper presents the results of research work on linear FSW (Friction Stir Welding) joining aluminum alloys AA2024-T3 of 0.5 mm in thickness. The study was conducted on properly adapted numerical controlled 3 axis milling machine using a ceramic tool and special designed fastening device. The tool dimensions have been estimated according to the algorithm shown in the literature [4]. All joints were made of end-to end (butt) configuration under different welding speed. The rotational speed of the tool and tool offset was constant. The effect of selected technological parameters on the quality of the joint was analyzed. Produced butt joint have been subjected to a static tensile testing to identify mechanical features of the materials of joints compared to parent materials. Measurements of micro hardness HV in the plastically formed stir zone of joint and in the parent material have been carried out. Axial and radial welding forces in the joining region were recorded during the tests and their dependency from the welding parameters was studied. Based on the results of strength tests the efficiency of joints for sheets of 0.5 mm in thicknesses oscillated up to 96% compared to the parent material. It has been found that for given parameters the correct, free of defects joints were obtained. The paper also presents the results of low-cycle fatigue tests of obtained FSW joints. The use of a ceramic tool in the FSW process allows to obtain welds with higher strength than conventional tools. The results suggests that FSW can be potentially applied to joining aluminum alloys.

In this paper, four full-scale concrete columns with high-strength spiral stirrups (HSSS) are constructed and tested under low-cycle repeated loading. The specimens consisted of two castin- place columns and two precast concrete columns encased by a partly square steel pipe and bolt bars.The structural analysis of the HSSS columns of precast concrete conducted here is novel, and past experimental data for this are not available.To assess the seismic behavior and failure mechanisms of the new connections, quasi-static tests were carried out on columns prefabricated with them and cast-in-place specimens.The responses of all columns were compared, and the results showed that the failure modes of all columns are the large eccentric damage, and the destruction of all specimens occur at the column foot. The anti-seismic property of the precast HSSS concrete columns was comparable to that of the HSSS cast-in-place columns. A comparison of such performance parameters as energy dissipation and coefficient of ductility revealed that the precast HSSS concrete columns are suitable for use in earthquake zones.