Zbigniew Marciniak

Energy Parameter Control System of Strength Machine for Material Tests under Cyclic Bending and Torsion

The paper presents strength machine control system for characterization of fatigue properties of materials based on a new, recently defined, energy fatigue damage parameter. It is used in new procedure for precise determination of the fatigue characteristics of materials with the controlled strain energy density parameter. The new parameter distinguishes positive and negative values strain energy density histories during variable loading. In case of modern, cyclically unstable materials the new closed-loop control system of strength machine allows to univocally establish the relevant stress-strain based fatigue characteristic under bending and torsion. This control system has been implemented with the use of National Instruments LabVIEW software. The mechatronic stand based on fatigue machine for material testing under bending moment and torsion moment has been described and preliminarily material tests have been done.

Fatigue Characteristic of Aluminium Alloy 2024 under Cyclic Bending with the Controlled Energy Parameter

In this paper the results of fatigue tests under cyclic bending of 2024 aluminium alloy with amplitude of strain energy density parameter control are presented. Based on these tests, energy fatigue characteristic of the tested material was elaborated.

Energy Fatigue Characteristic of C45 Steel Subjected to Cyclic Bending

The paper contains the results of fatigue tests under cyclic bending of C45 steel with amplitude of energy parameter control. The tests were performed on the smooth specimens. Based on these tests, energy fatigue characteristic of the tested material was elaborated.

Energy response of S355 and 41Cr4 steel during fatigue crack growth process

In this research, a novel approach of the fatigue crack growth rate description has been proposed. Based on theoretical and experimental approach, the mean stress effect expressed by R-ratio is present in classical da/dN–ΔK diagram. According to energy approach – based on the irrevocably dissipated energy accumulated in material (hysteresis loop) during fatigue process – the mean stress effect can be minimalized. Experimental validation of the proposed model was performed using results of fatigue crack propagation data for S355 and 41Cr4 steels in terms of strain energy density parameter ΔS or cyclic J-integral range –ΔJ. In contrast to the force approach based on Kmax (or ΔK), the energy parameters ΔS or ΔJ represent unambiguously the fatigue crack propagation rate, without influence of mean stress effect –R-ratio. However, in near threshold range of kinetic fatigue fracture diagram, the energy parameter displays a slight dispersion of the experimental data. According to the crack closure theory and its U-Elber parameter, the dispersion of experimental data is decreased. Therefore, the crack closure effects have a high significance in energy model – similar to the ‘force approach’ based on ΔK concept.

Comparison of C45 Steel Fatigue Characteristics Carried out at Controlled Stress and Energy Parameter, Subjected to Fully Reversed Bending

The work presents fatigue characteristics of C45 steel that have been obtained at controlled energy parameter and nominal stress. The tested material has been subjected to fully reversed bending on MZGS-100Ph fatigue test stand.

Fatigue Crack Growth Rate under Different Bending to Torsion Ratios in 10HNAP Steel

The paper contains the fatigue test results of rectangular cross-section specimens made of 10HNAP steel. The specimen height to width ratio was 1.5. Bending with torsion tests were carried out for the following ratios of bending to torsional moments MaB / MaT = 0.47, 0.94, 1.87 and the loading frequency 26.5 Hz. The tests were performed in a high cycle fatigue regime for the stress ratio R = - 1 and phase shift between bending and torsion loading equal to  = 0.