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 . 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 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 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
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.
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.
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.
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.
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 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 Kc 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).
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 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.