Experimental research on influence on single overloadon fatigue life of constructional steels under complex load

The paper presents the results of fatigue life tests under complex load conditions (proportional bending with torsion) with single overload for the different overload ratios (kj=1.5; kj = 2). Specimens of square sections made of costructional steels: 10HNAP and 18G2A with unilateral sharp notches were tested. The tests were performed at the fatigue test stand MZGS-100; amplitude of resultant moment was Ma=16 N.m (proportion of bending and torsion moments was Mag/Mas =1.73). Fatigue crack growth was measured with a microscope magnifying 25x. It was found that a single overload causes an essential change of fatigue life. It has been shown that the overload factor strongly influences those changes

Fatigue life of constructional materials under bending with torsion for crack propagation

The paper presents description of the equivalent range of the stress intensity factor in the case of bending with torsion of specimens where initiation and propagation of fatigue cracks are observed. Calculations with the Matlab-Simulink program were performed in order to estimate fatigue life. The calculations were realized for variable amplitudes of the resultant moment 13 and 16 N×m. The Forman’s relation was also used for the calculations. It has been shown that the Forman’s relation is suitable for description of fatigue life in the tested range of fatigue crack propagation

Experimental analysis of the state of stress in a steel – titanium perforated plate loaded with concentrated force

The paper presents an experimental analysis of the state of stress, free supported on the edge of a steel – titanium circular perforated plate loaded with a centrally concentrated force, created in the technological process of explosion welding. For this purpose, a special test stand was designed and a methodology for testing the perforated plate was developed. Resistance strain gauges were used to measure the state of strain. The load was applied in the center of the plate to a pressure stamp. As a result of the research, the values of radial, circumferential and equivalent von Mises stress were obtained as a function of the radius of the plate perforation circle and its load. The stress distribution topography revealed the zones of maximum stress of the steel – titanium perforated plate. The proposed method of experimental research can be used by engineers to verify the state of stress, e.g. in the designed tube sheet walls of reactors for ammonia synthesis

Numerical analysis of life of notched specimens subjected to complex bending with torsion

The authors analyzed life of specimens with rectangular sections and with notches (crack initiators). The specimens were loaded by amplitudes of bending and torsional moments, Mg and Ms respectively. The analysis was performed with use of the finite element method and the MSC Patran program using a modulus for fatigue calculations Fatigue. The analysis was done in order to select amplitudes of torsional and bending loading and determine fatigue life of the specimens made of 18G2A steel

Influence of the applied layer on the state of stress in a bimetallic perforated plate under two load variants

The paper presents the results of the analysis of the influence of the applied plate layer on the state of stress in the bimetallic perforated plate. The finite element method ANSYS program was used for numerical calculations. The paper presents the results of stress tests for a single-layer clad plate made of S355J2 steel and a bimetallic perforated plate consisting of layers made of S355J2 steel and titanium. In addition, the study presents the results of the research on the influence of the method of loading, i.e. the concentrated force P in the geometric center of the plate and the external pressure q on the entire surface of the plate, and the method of support, i.e. free support and fixed, on the location of stress concentration zones in the bimetallic circular perforated plate. It has been shown that the presence of a perforated layer in the plate reduces the value of the equivalent von Mises stress by a minimum of approximately 30% in the base (steel) layer

Research of stress distribution in the cross-section of a bimetallic perforated plate perpendicularly loaded with concentrated force

The paper presents the stress distribution along the plate thickness in a bimetallic steel – titanium circular, axially symmetrical perforated plate produced in the technological process of explosion welding. The steel layer is the layer that transfers the load in the plate, while the titanium layer is used to improve the properties of the plate, e.g. corrosion resistance, thermal transmittance, etc. in the plate. Two cases of fastening were considered, i.e. a freely supported and fixed plate. Such plates are used in various engineering structures, e.g. simply supported plates can be used in loose material screens, while plates are fixed in heat exchangers. The load was assumed as a concentrated force applied perpendicularly to the plate surface. The results obtained numerically using the finite element method were compared with the results calculated according to the analytical equations. It has been shown that the difference in the results of equivalent von Mises stress calculations does not exceed 13%. The research results presented in the paper can be used by engineers to design bimetallic perforated plates perpendicularly loaded to their surface

ANALYSIS OF THREAD COIL EFFORT IN THE SCREW – NUT JOINT

The paper concerns optimization of screws in the unit including connectingrod – connecting rod big end of the SW 680 Leyland motor related to uniform distribution of loading on all the thread coils. Optimization of screw geometry insists in partial turning of the thread coil at a determined angle. The stress state calculations were performed with the finite element method and the Nastran/Patran program. It has been shown that the angle 3o is the optimum angle of partial turning of the thread contour. At that angle, when the screw was loaded by the tensile force 29 kN, we obtained the reduced stress decreased by 12%, and more uniform distribution of the thread coil as compared with the traditional screw (not optimized)

Analysis of thread coil effort in the screw-nut joint

Przedmiotem artukułu jest optymalizacja śrub w zespole korbowód-stopa korbowodu silnika SW 680 Leyland, z uwagi na równomierny rozkład obciążenia na wszystkie zwoje gwintu. Optymalizacja geometrii śruby polegała na częściowym stoczeniu zwoi gwintu pełnego pod określonym kątem. Obliczenia stanu naprężenia prowadzono metodą elementów skończonych, przy użyciu programu Nastran/Patran. Wykazano, że optymalnym kątem częściowego stoczenia pełnego zarysu gwintu okazał się kąt 3⁰, przy którym obciążając śrubę siłą rozciągającą 29 kN, uzyskano obniżenie naprężenia redukowanego o 12% oraz bardziej równomierny rozkład obciążenia zwoi gwintu w porównaniu do śruby klasycznej o pełnym zarysie gwintu.The paper concerns optimization of screws in the unit including connecting-rod – connecting rod big end of the SW 680 Leyland motor related to uniform distribution of loading on all the thread coils. Optimization of screw geometry insists in partial turning of the thread coil at a determined angle. The stress state calculations were performed with the finite element method and the Nastran/Patran program. It has been shown that the angle 3⁰ is the optimum angle of partial turning of the thread contour. At that angle, when the screw was loaded by the tensile force 29 kN, we obtained the reduced stress decreased by 12%, and more uniform distribution of the thread coil as compared with the traditional screw (not optimized)