International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

Additive manufacturing approach is thought to be a key element to meet the needs of Industry 4.0. Selective laser melting (SLM) is a powder bed fusion additive manufacturing method for producing fully functional components. It is critical to determine the fatigue behavior of components produced by selective laser melting in order to fulfill the needs of industries with rigorous norms and criteria, such as the aviation industry. However, the rapid heating and cooling cycle caused by the nature of the SLM process has a negative mechanical effect on the components manufactured by this process.. Mechanical properties such as hardness and fatigue behavior should be disclosed for Co-Cr-Mo alloy manufactured by SLM technique. In this study, hardness and fatigue tests were performed on Co-Cr-Mo alloy components manufactured by SLM, and microstructure images were acquired and evaluated. When the microstructure of the samples was analyzed, tiny precipitates localized at the grain boundaries were discovered, along with the dominating γ phase. The average hardness value of the samples subjected to the Vickers microhardness test was 482±10. The fatigue life of the samples at the maximum stress of 800 MPa was 47,351 cycles. At the minimum stress of 400 MPa, the fatigue life exceeded 107 cycles. When fatigue fracture surfaces were examined, flat fracture surfaces similar to semi-cleavage were detected. The results will contribute to the literature on the mechanical characterization of SLM manufactured Co-Cr-Mo alloy components.

The fatigue strength of 40X steel at 25 oC was determined following ASTM E606M standard for strain-controlled tests. The studied experimental dependence was modelled with a power function as well as with the functions and coefficients described in the standard. The material expresses plastic properties for cyclic loadings above 0.2% strain amplitude.

During the combustion processes of fuels, fuel gasses are created which flow over the heat exchanger. The flow of fuel gasses brings ash particles which are deposited on heat exchanger surfaces and thus reduce the heat exchange efficiency. The removal of ash deposits from the heat exchanger is performed by a striker. Striker indirectly strikes the floor of the lower chamber of the heat exchanger via the mandrel and transmits kinetic energy to it. The impact results in inertial forces on the layer of deposits that are greater than those of adhesion forces between the surface of the exchanger pipes and the ash deposits. The pipes are loaded with displacement caused by the impact of a mandrel used to clean the heat exchanger, displacement caused by the operating pressure inside the pipe, and thermal elongation. The load of the pipes is cyclic, and calculation was performed according to the standards: EN 12952-3:2012-03 and EN 13445-3:2009. The calculation was performed at critical pipe cross-sections. The Abaqus/CAE2016 software package was used to determine the critical cross-sections of pipes and stress that occur in them. The model was created using beam finite elements. After analyzing the stress and applying the standards, a conclusion is reached on the fatigue strength of the drainage pipes. The heat exchanger pipes are made of austenitic W.Nr.2.5956 and 16Mo3 steels. The pipe with maximum fatigue stress of 208 MPa is made of 16Mo3 steel, which has a tensile strength from 450 to 600 MPa. Young modulus of elasticity at an operating temperature of 383 ° C is E = 173,9 GPa. The permanent strength diagram is taken from EN 12952-3: 2011 standard shows that this material can withstand 107 cycles with such fatigue stress, and the required number of cycles is determined based on the customer’s request which is the projected number of years. The plant is projected on operating 5 years. The designed number of cycles is 350400 cycles, so it is concluded that the pipes satisfy the conditions of exploitation.

This paper deals with a change of states of power transmission system elements up to the achievement of boundary conditions based on a material fatigue. Depending on the level of change in states of elements, an estimation of a remaining working life of a power transmission system was given. Additionally, an estimation of a change of conditions of power transmission system elements , as well as the impact of states of elements on a power efficiency of a vehicle are presented . Besides an analytical consideration, the simulation models were created and the results of simulations presented.

The paper presents a method for calculating the durability of structure regular zones in view of working stresses and aircraft routine flight profile. Application of the method is advisable at the early design stages. The method is based on the discrete atmospheric turbulence model and dependence model for durability calculation by nominal stresses. Fatigue damage for a routine flight has been determined as the amount of damage due to accidental loads and the damage resulting from enveloping ground-air-ground cycle, naturally repeated during each flight. It has been noted that the consideration of the fatigue curve break point in the low-stress area leads to an increase in the calculated durability by 10-15%. A comparison has been made of the calculated durability values for two airplanes with the experimental data of TsAGI. The correlation is satisfactory enough.

The paper deals with an experimental measurement of the fatigue operating life of a specimen from the aluminium AlMgSi07 alloy on a built testing equipment, into which the welded joint was implemented. An importance of the measurement is in a comparison of achieved results with the same material, which was not subjected to welding. The result of the research is verification of the influence of welding on the fatigue operating life of the concrete material at torsion stress.

The research paper presents the improvement on the mechanical and service properties of the austenitic stainless 0.07% C-17% Cr-9% Ni-0.7%-Ti steel in the fully austenitic state obtained by equal-channel angular pressing (ECAP) at the temperatures of 200 °C and 400 °C. Subgrain oriented structure in the Cr-Ni-Ti steel after ECAP significantly enhances the strength characteristics of steel at satisfactory plasticity. The fatigue limit of steel after ECAP at T = 200 ° C is higher than that after ECAP at T = 400 ° C, increasing in comparison with the initial state by 2.2 and 1.7 times, respectively. It was revealed that severe plastic deformation by ECAP increases the friction coefficient of the material by the 1.1 and 1.7 times at T = 200 ° C and 400 ° C, respectively. Despite this, the wear rate after ECAP at T = 200 ° C and 400 ° C decreases by 7 and 40 times, respectively, compared to initial state.