Michał Böhm

Opole University of Technology · Department of Mechanics and Machine Design

The paper presents experimental static and fatigue tests results under random loading conditions for the bending of 0H18N9 steel. The experimental results were used in performing calculations, according to the theoretical assumptions of the spectral method of fatigue life assessment, including elastoplastic deformations. The presented solution exte...

The problem with fatigue lifetime estimation of explosive cladded transition joints under random loading conditions has been described. The paper presents the fatigue test results performed for the random state of tension-compression under a generated spectrum according to the Pierson-Moskowitz model. The obtained spectrum has a non-Gaussian charac...

The paper presents the experimental fatigue test results for cyclic constant amplitude loading conditions for the case of the torsion of the PA4 (AW-6082-T6), PA6 (AW-2017A-T4) and PA7 (AW-2024-T3) aluminum alloy for a drilled diabolo type test specimen. The tests have been performed for the stress asymmetry ratios R = −1, R = −0.7, R = −0.5 and R...

The paper presents a new fatigue damage assessment model defined for the strain energy density parameter. The model is defined for calculations in the frequency domain for the case of narrowband loading. Analytical expressions are derived for the probability density function of peaks, the level crossing spectrum, and for the expected damage that is...

The paper describes the problem of fatigue life assessment for the case of explosive cladded transition joints under random loading. Such elements are usually used in the lightweight automobile industry as well as in the marine industry. Due to this, they are undergoing random loading conditions in terms of road surface quality and the change of se...

Optimizing the geometry for material savings, or heat transfer, can yield thin-walled additively manufactured parts. A wall thickness of only a few hatching spaces can be fabricated using laser powder bed fusion (LPBF). However, the unmachined surface quality and subsurface defects in the low-thickness wall put the load-bearing capacity of the manu...

The paper presents the results of tension-compression fatigue tests of a new steel-aluminum welding transition joint with a titanium Grade 1 interlayer. The new explosive welded transition joint prototype used as a connector in the shipbuilding industry has been developed by the Explomet company situated in Opole-Poland. The paper discusses the adv...

At present, due to advanced fatigue calculation models, it is becoming more crucial to find a reliable source for design S–N curves, especially in the case of new 3D-printed materials. Such obtained steel components are becoming very popular and are often used for important parts of dynamically loaded structures. One of the commonly used printing s...

A contemporary challenge for the construction industry is to develop a technology based on natural building materials which at the same time provides high energy efficiency. This paper presents the results of an airtightness test and a thermal imaging study of a detached house built with technology using cross laminated dowelled timber panels. The...

Random loading conditions can be rarely defined by a pure gaussian process. Due to this when we are using methods which are based on the concept of pure gaussian distributions of loading we must have a tool to take into account any distortions of the gaussian process. The paper presents a short review of the models for determination of the moment o...

This paper presents the analysis of the influence of the shape of the probability distribution of the load course on the computational fatigue life. The literature on the subject shows that the main parameter describing the deviation from the normal (Gaussian) distribution is kurtosis and skewness. The authors proved that kurtosis parameter alone i...

Dear Colleagues, Our goal is to attract quality papers related to recently developed experimental methodologies, theoretical and applied fracture and fatigue theories, advanced numerical models, and examples of real life applications related to advanced materials and composites that are affected with variable loading, especially due to the crystal...

Fatigue life assessment under multiaxial loading requires the use of multiaxial fatigue failure criteria which are defined in time and frequency domain. Frequency domain criteria are created via formulations using former criteria in the time domain. Therefore, there is a need for a general approach to formulate criteria in the frequency domain base...

The paper presents a new damage assessment model defined for the strain energy density parameter. The model is defined for calculations in the frequency domain for the case of narrow-band loading. The strain energy density parameter is described as well as the process of determination of the proposed model. The general probability density and the p...

This article presents the analysis of the influence of the shape of the probability distribution of the load course on the computational fatigue life. The literature on the subject shows that the main parameter describing the deviation from the normal (Gaussian) distribution is kurtosis. The authors proved that this parameter is not sufficient for...

The results of fatigue tests of samples made of S355JR steel under random tension-compression with nonzero mean stress are presented. The procedure of experimental research is described. The obtained experimental results are presented with the use of Wöhler fatigue graphs. The algorithm for the determination of the fatigue life uses, among other th...

The paper discusses presently experienced problems concerned with forecasting the fatigue life of welded joints in terms of the spectral method defined in the frequency domain. In addition, the article presents the primary assumptions of the spectral method and describes the issue related to the recognition of the mean stress value and loads above...

The main goal of the paper is to calculate the heat conductivity for three experimental hemp–lime composites used for structural construction purposes with the use of the experimental stand inside two compartments. Due to current construction trends, we are constantly searching for eco-friendly materials that have a low carbon footprint. This is th...

This paper describes the current state-of-the-art in fatigue life assessment for lightweight composite structures with the use of the frequency domain fatigue life calculation method. Random stationary gaussian loading signals have been generated and served in the process of fatigue calculation. The material information that is being used in the ca...

The paper presents the results of the welding simulation performed for S235JR-Aluminum A5083 transition joint with the use of finite element method. Paper presents FEM model properties including nonlinear material data and heat source parameters. Results of the first calculations were presented in the form of the residual stresses patterns in and t...

The problem with the use of the energy parameter lying in its indirect definition in frequency domain is discussed. Modification of the fatigue life assessment method defined in the frequency domain with the use of the energy parameter (stress-strain relation) is presented. The modification is based on the direct use of power spectral densities (PS...

Fatigue life assessment under multiaxial loading conditions needs the use of multiaxial fatigue failure criteria. There are many formulations of such criteria which are usually divided in the groups of critical plane criteria and invariants based criteria. Other classifications refer to the parameter that determines fatigue, and these are stress, s...

Fatigue life assessment for random loading can be divided into two groups, defined in time or frequency domain. In this paper we are within the range of calculations in the frequency domain. The paper deals with the problem of fatigue life assessment of materials subjected to wind loading spectrum. The paper analyses three types of standardized spe...

Many computer aided design methods that are being presented in the literature are using advanced fatigue life assessment methods. The problem with the assessment is especially interesting in the moment when the calculations are performed for random loads. In such cases it is common to use one of two calculation methods. The first one is based in th...

The paper presents a first attempt to calculate fatigue life for random loading with single overloads with the use of the spectral method of fatigue life assessment. The proposed modification of the fatigue life assessment algorithm is based on the transformation of the power spectral density of the loading signal with the use of the correction fac...

The objective of the paper is to calculate fatigue life with the use of the spectral method for 10HNAP steel under non-Gaussian loading conditions with the use energy parameter and non-Gaussian correction. The energy parameter has not yet been used in the frequency domain for fatigue calculations under non-Gaussian loading conditions. Some calculat...

Most of the models used for taking into account the influence of mean stress on fatigue life work on the basis of the correction of stress amplitudes of particular loading cycles. This can be done directly on the amplitudes or through the modification of the reference S-N curve. The mentioned procedure is also applicable for variable amplitude load...

The well-known problem with the fatigue lifetime assessment of non-Gaussian loading signals with the use of spectral method has been presented in the paper. A correction factors that transform the non-Gaussian signal into an equivalent Gaussian signal proposed by Bracessi et al. (2009) has been used for the purpose of lifetime calculations together...

Two frequency-domain fatigue life calculation methods are presented which take into account the impact of the mean stress effect. The emphasis is set on the algorithm for fatigue life assessment of the method proposed by the authors. It is supplemented with a mean stress effect correction. Correction method is based on the direct transformation of...

Two fatigue life calculation methods are presented. One defined in the time domain and the second one defined in the frequency domain – both supplemented with a mean stress effect correction. The method is verified on the basis of own results for the S355JR steel. The authors analyze six models for the designation of the probability density functio...

To describe the impact of multiaxial service loads a power spectral density matrix of the strain tensor components has been taken into account. To determine the fatigue life some selected multiaxial fatigue failure criteria have been used. The main focus of this paper is set on the comparison of the cycle counting method and the spectral method. An...

The paper presents the concept of fatigue test stand designed for multiaxial tests. The main advantage of the test stand is the possibility to perform fatigue tests under any combination of bending and torsional moments – from constant amplitude loading with different loading frequency, phase shifts and amplitudes ratio to advanced tests under rand...

Spectral method is one of the most effective methods of fatigue life estimation. In this method fundamental parameters characterizing the load process are determined on the basis of Power Spectral Density (PSD) function. PSD function can be obtained in many ways. Several functions from parametric methods, nonparametric methods and subspace method f...

The paper presents a new formula for fatigue life determination with the use of the spectral method for fatigue life assessment on the basis of fatigue strain characteristics. The spectral method is widely used together with the stress characteristics, but the literature does not contain a case where it is used together with strain characteristics....

You can find here some code lines written in Matlab script which supplements the paper: A. Niesłony and M. Böhm, “Mean stress effect correction using constant stress ratio S–N curves,” International Journal of Fatigue, vol. 52, pp. 49–56, Jul. 2013.

This paper presents a stress based approach to take into account the influence of the mean stress value on fatigue strength of constructional materials. Elaborated model uses two S–N curves, i.e. for alternating stress (R = −1) and another one obtained under stress ratio R ≠ −1, for calibrating the equations of boundary condition. Two particular eq...

The paper deals with a comparison of fatigue life calculations, obtained on the basis of classical Basquin diagrams and approximated diagrams acquired with the use of the section method, which allows us to fit the diagrams shape to real material properties. While comparing the calculation results, literature data concerning fatigue tests of welded...

The purpose of this paper is to provide a simple approach for indication of those places of machine parts, where the fatigue crack initiation begins. This method uses FEM and the cyclic stress-strain curve for calculating the stress state on specimens. The multiaxial fatigue failure criterion based on the critical plane approach was used for reduct...

The paper presents a proposal of account of mean stress value in the process of the determination of the fatigue life, using the spectral method. The existing approaches have been described and some chosen stress models used to take into account the influ-ence of the mean value in the process of the determination of fatigue life have been introduce...