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

This study investigates the influence of distance and relative orientation of semi-elliptical twin surface cracks in cylindrical bars under tensile loading on the stress intensity factors (SIF). Finite element analysis was used to analyze the interactions between two identical cracks with different spacing (5-20 mm) and rotation angles (0°-180°). The results show that the crack orientation has a significant effect on the stress distribution patterns and stress intensity factor values, with a 45° rotation producing the highest SIF values, while a parallel orientation has a favorable shielding effect with significantly lower values. All configurations gradually converge to the reference value for a single crack at larger distances (20 mm), indicating decreasing interaction effects. These results can provide insights for the assessment of structural integrity, especially for components with multiple closely spaced defects, and provide a basis for the development of more accurate predictive models for fracture behavior in engineering applications.

In this paper, the tensile strength of the composite material made of onyx and carbon fibers was investigated. Onyx is a material manufactured by the company Mark Forged, which is used for 3D printing of composite materials. It is a thermoplastic filled with carbon fibers used for printing solid and rigid parts. The tensile test according to the standard ISO 527 was carried out experimentally and the numerical results were obtained by numerically modelling the test specimen and simulating the test in Ansys, after which the results obtained experimentally and numerically were compared.

The present work deals with the analysis of the influence of internal forces and moments on the nozzle of the main boiler of a steam boiler used in the waste incineration industry. The analysis is carried out analytically by performing calculations using standards, and later numerically using finite element method software. As results of the analyses, equivalent von Mises stresses, displacements and buckling eigenvalues are obtained and compared with analytical solutions.

This paper presents the calculation of the stress and stability of a third-cycle module of a steam boiler during the lifting process. A steam boiler is a key element of a cogeneration plant, so all calculations are performed according to prescribed standards. Before the numerical analysis of the steam boiler, the characteristics, components and function of the boiler are described, as well as the required standards. The 3D model of the boiler was created using the Abaqus/CAE 2016 program package according to the manufacturer’s technical documentation. Using the finite element method, the stresses and stability during lifting of the boiler from the horizontal and vertical positions were calculated and presented. It was found that when lifting from a horizontal position, the structural stress values of the main elements do not exceed the allowable values. On the other hand, when lifting from a vertical position, the stresses exceed the allowable values. In this case, the connection point between the lug and the profile was checked and analytically dimensioned. The obtained values of the stability analysis of the boiler module are satisfactorily defined and there is no risk of buckling in both cases of lifting. The boiler conforms with the standard and fulfils the requirements handed over to the engineer.

This paper shows the approach of submodeling in finite element analysis in process of designing the horizontal tank for storing petroleum products. Those kinds of tanks are made at exact standards or slightly altered by customers’ demands. Before the numerical analysis of the tank, the tank standards are described as well as numerical analysis. In the paper, the methods which will be used in obtaining solutions by finite element method were described. 3D finite elements have been used for numerical analysis. After getting the results of full tank model meshed with 3D tetrahedral final elements, the technique of submodeling has been used to achieve more accurate results in critical locations of the tank. In the final aspect, result analysis was conducted, where the results were confirmed so that the tank complies with the standard and meets all the criteria given to the designer.

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.