Bertin Soh Fotsing - Academia.edu (original) (raw)
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Papers by Bertin Soh Fotsing
Most of mechanical components in the engineering are frequently subjected to the fatigue damaging... more Most of mechanical components in the engineering are frequently subjected to the fatigue damaging process because of the great number of stress cycles they have to undergo. This paper presents an elaboration of two of the most studied methods for the computation of fatigue life in multiaxial fatigue. We describe the reformulation of Sines and Crossland fatigue criteria, which have been adapted so that they could preserve the observed detrimental influence of a tensile mean stress and the observed beneficial effect of a compressive mean bending stress. The proposed reformulation of Crossland and Sines criteria is applied to a general sinusoidal in-phase or out-of-phase bending and torsion stress state, for which analytical formulae can be derived. From the theoretical results calculated according to the present propositions, the criterion proposed by Sines was found to be the most precise in preserving the detrimental influence of a tensile mean stress and the observed beneficial eff...
Reed valves in a compressor are critical parts that have a high fatigue failure potential due to ... more Reed valves in a compressor are critical parts that have a high fatigue failure potential due to cyclic bending and impact caused by the cyclic nature of the compression process. A sudden failure of a valve renders the compressor useless. Although the refining process of methods of fatigue design has already taken more than 50 years, older criteria such as Gerber and Goodman models are still attractive for engineering design of high cycle fatigue components. This paper presents an investigation on the effect of nonzero mean stress on the design of valve reeds that are widely used in compressors. The investigation relates the choice of a mean stress compensation models, with the predicted fluctuating bending fatigue strength and estimated safety coefficient values. The calculations have been performed using Gerber, Goodman, Soderberg, ASME, Crossland, and Tsapi-Soh models. The most relevant goal of this paper is to verify the efficiency of classical and advanced stress based multiaxi...
International Journal of Innovation and Scientific Research, Jun 2, 2015
Most of mechanical components in the engineering are frequently subjected to the fatigue damaging... more Most of mechanical components in the engineering are frequently subjected to the fatigue damaging process because of the great number of stress cycles they have to undergo. This paper presents an elaboration of two of the most studied methods for the computation of fatigue life in multiaxial fatigue. We describe the reformulation of Sines and Crossland fatigue criteria, which have been adapted so that they could preserve the observed detrimental influence of a tensile mean stress and the observed beneficial effect of a compressive mean bending stress. The proposed reformulation of Crossland and Sines criteria is applied to a general sinusoidal in-phase or out-of-phase bending and torsion stress state, for which analytical formulae can be derived. From the theoretical results calculated according to the present propositions, the criterion proposed by Sines was found to be the most precise in preserving the detrimental influence of a tensile mean stress and the observed beneficial effect of a compressive mean bending stress. On the other hand, the criterion proposed by Crossland was found to be precise in the multiaxial fatigue limit prediction. This analysis shows that the proposed procedure is very efficient, suggesting that Sines and Crossland fatigue criteria remain valuable fatigue evaluation tools for the mechanical design industry.
International Journal of Innovation and Scientific Research, Jun 2, 2015
In many situations encountered in engineering practice, structures or structural elements are und... more In many situations encountered in engineering practice, structures or structural elements are under thermomechanical cycles of loading. The use in this condition of traditional fatigue criteria in high cycle fatigue is no more advisable because on structures, these criteria are formulated for the prediction of the number of cycles for the nucleation of cracks in the isothermal situation. In this paper, we propose an extension of stress invariants based criteria, for the anisothermal high cycle fatigue. Our proposal is essentially based on the hypothesis of accommodation at macroscopic and microscopic levels. The simulation made from the fatigue strength of the proposed ansiothermal criterion reproduced qualitatively the expected results. The proposed modified criteria will enhance the account the account of the multiaxial and anisothermal character of thermomechanical loadings.
Latin American Journal of Solids and Structures, 2015
This paper is concerned with the fatigue prediction models for estimating the multiaxial fatigue ... more This paper is concerned with the fatigue prediction models for estimating the multiaxial fatigue limit. An equivalent loading approach with zero out-of-phase angles intended for fatigue limit evaluation under multiaxial loading is used. Based on experimental data found in literatures, the equivalent stress is validated in Crossland and Sines criteria and predictions compared to the predictions of existing multiaxial fatigue; results over 87 experimental items show that the equivalent stress approach is very efficient.
European Scientific Journal, Jul 30, 2014
The change of geometries, heterogeneities, degradation of components and the increase of maintena... more The change of geometries, heterogeneities, degradation of components and the increase of maintenance cost of the railway track are due to the phenomenon of vibrations, which is the main problem of structural dynamic. The aim of this work is to propose a dynamic model for the prediction of rail vibrations during starting and steady state response. The DEM (Discret Elements Method) is adopted for the modeling of the vehicle. Thus components are assumed as rigid bodies mounted on series of springs and dampers with several degrees of freedoms. The rail road is discretized and modeled using FEM (Finite Elements Method). Rail-pad is modeled as a massless series of springs-dampers connected along the total contact area in between the rail and the m th sleepers. The sleepers are modeled as rigid elements connected by spring-damper. The ballast is modeled as separate vibrating mass connected by spring-damper coupled together vertically and horizontally while only the stiffness and damping effects of the subgrade is taken into account. The wheel-rail contact is modeled according to Herzian theory. Newmark time discretization and Newton Raphson iteration method have been used for models simulation in MATLAB. Displacements, velocities and accelerations of each modeled subsystem of components during starting and steady state response of the vehicle are calculated. The evolution of the wheel-rail contact load is also evaluated. Proactive maintenance actions are proposed in design.
Déchets, sciences et techniques, 1998
International Journal of Engineering Research in Africa, 2015
Compressors suspension made up of helical suspension spring system has a significant importance o... more Compressors suspension made up of helical suspension spring system has a significant importance on the operation of hermetic compressors, considering the aspects of noise and vibration. These springs are loaded by harmonic forces very often. High cycles fatigue damage and failure can be found during its service loading. The severity of lading regime has been studied for three typical loading regimes of springs using the fatigue safety factor. The spring fails by fatigue not yielding; infinite life is not predicted. All cases are demonstrated in the Haigh diagram. Finite life is predicted. It has been showed that loading cases with constant mean shear give lowest safety factor than the proportional or constant middle stress regimes.
Mécanique & Industries, 2007
Most of mechanical components in the engineering are frequently subjected to the fatigue damaging... more Most of mechanical components in the engineering are frequently subjected to the fatigue damaging process because of the great number of stress cycles they have to undergo. This paper presents an elaboration of two of the most studied methods for the computation of fatigue life in multiaxial fatigue. We describe the reformulation of Sines and Crossland fatigue criteria, which have been adapted so that they could preserve the observed detrimental influence of a tensile mean stress and the observed beneficial effect of a compressive mean bending stress. The proposed reformulation of Crossland and Sines criteria is applied to a general sinusoidal in-phase or out-of-phase bending and torsion stress state, for which analytical formulae can be derived. From the theoretical results calculated according to the present propositions, the criterion proposed by Sines was found to be the most precise in preserving the detrimental influence of a tensile mean stress and the observed beneficial eff...
Reed valves in a compressor are critical parts that have a high fatigue failure potential due to ... more Reed valves in a compressor are critical parts that have a high fatigue failure potential due to cyclic bending and impact caused by the cyclic nature of the compression process. A sudden failure of a valve renders the compressor useless. Although the refining process of methods of fatigue design has already taken more than 50 years, older criteria such as Gerber and Goodman models are still attractive for engineering design of high cycle fatigue components. This paper presents an investigation on the effect of nonzero mean stress on the design of valve reeds that are widely used in compressors. The investigation relates the choice of a mean stress compensation models, with the predicted fluctuating bending fatigue strength and estimated safety coefficient values. The calculations have been performed using Gerber, Goodman, Soderberg, ASME, Crossland, and Tsapi-Soh models. The most relevant goal of this paper is to verify the efficiency of classical and advanced stress based multiaxi...
International Journal of Innovation and Scientific Research, Jun 2, 2015
Most of mechanical components in the engineering are frequently subjected to the fatigue damaging... more Most of mechanical components in the engineering are frequently subjected to the fatigue damaging process because of the great number of stress cycles they have to undergo. This paper presents an elaboration of two of the most studied methods for the computation of fatigue life in multiaxial fatigue. We describe the reformulation of Sines and Crossland fatigue criteria, which have been adapted so that they could preserve the observed detrimental influence of a tensile mean stress and the observed beneficial effect of a compressive mean bending stress. The proposed reformulation of Crossland and Sines criteria is applied to a general sinusoidal in-phase or out-of-phase bending and torsion stress state, for which analytical formulae can be derived. From the theoretical results calculated according to the present propositions, the criterion proposed by Sines was found to be the most precise in preserving the detrimental influence of a tensile mean stress and the observed beneficial effect of a compressive mean bending stress. On the other hand, the criterion proposed by Crossland was found to be precise in the multiaxial fatigue limit prediction. This analysis shows that the proposed procedure is very efficient, suggesting that Sines and Crossland fatigue criteria remain valuable fatigue evaluation tools for the mechanical design industry.
International Journal of Innovation and Scientific Research, Jun 2, 2015
In many situations encountered in engineering practice, structures or structural elements are und... more In many situations encountered in engineering practice, structures or structural elements are under thermomechanical cycles of loading. The use in this condition of traditional fatigue criteria in high cycle fatigue is no more advisable because on structures, these criteria are formulated for the prediction of the number of cycles for the nucleation of cracks in the isothermal situation. In this paper, we propose an extension of stress invariants based criteria, for the anisothermal high cycle fatigue. Our proposal is essentially based on the hypothesis of accommodation at macroscopic and microscopic levels. The simulation made from the fatigue strength of the proposed ansiothermal criterion reproduced qualitatively the expected results. The proposed modified criteria will enhance the account the account of the multiaxial and anisothermal character of thermomechanical loadings.
Latin American Journal of Solids and Structures, 2015
This paper is concerned with the fatigue prediction models for estimating the multiaxial fatigue ... more This paper is concerned with the fatigue prediction models for estimating the multiaxial fatigue limit. An equivalent loading approach with zero out-of-phase angles intended for fatigue limit evaluation under multiaxial loading is used. Based on experimental data found in literatures, the equivalent stress is validated in Crossland and Sines criteria and predictions compared to the predictions of existing multiaxial fatigue; results over 87 experimental items show that the equivalent stress approach is very efficient.
European Scientific Journal, Jul 30, 2014
The change of geometries, heterogeneities, degradation of components and the increase of maintena... more The change of geometries, heterogeneities, degradation of components and the increase of maintenance cost of the railway track are due to the phenomenon of vibrations, which is the main problem of structural dynamic. The aim of this work is to propose a dynamic model for the prediction of rail vibrations during starting and steady state response. The DEM (Discret Elements Method) is adopted for the modeling of the vehicle. Thus components are assumed as rigid bodies mounted on series of springs and dampers with several degrees of freedoms. The rail road is discretized and modeled using FEM (Finite Elements Method). Rail-pad is modeled as a massless series of springs-dampers connected along the total contact area in between the rail and the m th sleepers. The sleepers are modeled as rigid elements connected by spring-damper. The ballast is modeled as separate vibrating mass connected by spring-damper coupled together vertically and horizontally while only the stiffness and damping effects of the subgrade is taken into account. The wheel-rail contact is modeled according to Herzian theory. Newmark time discretization and Newton Raphson iteration method have been used for models simulation in MATLAB. Displacements, velocities and accelerations of each modeled subsystem of components during starting and steady state response of the vehicle are calculated. The evolution of the wheel-rail contact load is also evaluated. Proactive maintenance actions are proposed in design.
Déchets, sciences et techniques, 1998
International Journal of Engineering Research in Africa, 2015
Compressors suspension made up of helical suspension spring system has a significant importance o... more Compressors suspension made up of helical suspension spring system has a significant importance on the operation of hermetic compressors, considering the aspects of noise and vibration. These springs are loaded by harmonic forces very often. High cycles fatigue damage and failure can be found during its service loading. The severity of lading regime has been studied for three typical loading regimes of springs using the fatigue safety factor. The spring fails by fatigue not yielding; infinite life is not predicted. All cases are demonstrated in the Haigh diagram. Finite life is predicted. It has been showed that loading cases with constant mean shear give lowest safety factor than the proportional or constant middle stress regimes.
Mécanique & Industries, 2007