C. Braccesi¹, F. Cianetti¹, G. Lori¹, D. Pioli¹

Structural Durability & Health Monitoring, Vol.1, No.4, pp. 277-290, 2005, DOI:10.3970/sdhm.2005.001.277

Abstract This paper describes an original frequency method for fatigue life estimation of mechanical components subjected to random inputs. Currently mechanical components life design under random loads is an important task of the research, due to the increasing importance of virtual simulation in opposition to the experimental tests. The frequency domain approach, in this context, seems to be able to supply reliable estimations with small computational effort. The proposed method belongs to the class of corrective coefficient to narrow-band formula methods and it has been thought for bimodal PSDs. The definition of the generalized bimodal processes and the research of the… More >

S. Baragetti¹, A. Terranova²

Structural Durability & Health Monitoring, Vol.1, No.4, pp. 267-276, 2005, DOI:10.3970/sdhm.2005.001.267

Abstract Aim of this work is to investigate into the possibility of enhancing the fatigue resistance of CrN PVD coated components. In particular PVD coated spur gears were tested and numerical simulation of crack propagation was carried out. The coating layer micro-hardness and the residual stresses characterising the surface film were measured and the obtained results were introduced in a numerical modelling predicting fatigue life procedure of coated gears used in gearboxes for automotive applications. The number of cycles necessary to reach specified crack depths of coated and uncoated samples was numerically determined and represents a powerful tool to predict fatigue… More >

C. Colombo¹, M. Guagliano^1,2, L. Vergani¹

Structural Durability & Health Monitoring, Vol.1, No.4, pp. 253-266, 2005, DOI:10.3970/sdhm.2005.001.253

Abstract In this paper the fatigue crack growth properties of a nitrided and shot-peened steel is dealt with: different peening intensities were considered and the resulting residual stresses measured by means of an X-ray diffractometer. Rotating bending fatigue tests were executed on specimens including a blind micro hole, acting as a pre-existent crack. The fracture surface of broken specimens was observed with a SEM to detect the crack growth initiation point. The run-out specimens were broken after the test and the presence of non-propagating cracks detected. The results allowed to determine the propagation threshold of the nitrided and shot peened material. More >

L. Fratini¹, S. Pasta²

Structural Durability & Health Monitoring, Vol.1, No.4, pp. 245-252, 2005, DOI:10.3970/sdhm.2005.001.245

Abstract In the last years friction stir welding (FSW) has reached a quite large diffusion in the welding of aluminium alloys, difficult to be welded with traditional technologies. The objective of this investigation was to investigate the influence of FSW process parameters on the fatigue strength of the developed joints. Moreover, in order to improvement the strength of joint, the effect of a post-welding treatment has been highlighted; what is more a surface finish treatment has been developed with the aim to eliminate the stress concentration caused by welding process on the surface of the joints. Finally, the fracture locations have… More >

S. Glodež¹, B. Aberšek¹, G. Fajdiga², J. Flašker²

Structural Durability & Health Monitoring, Vol.1, No.3, pp. 215-224, 2005, DOI:10.3970/sdhm.2005.001.215

Abstract A computational model for simulation of surface and subsurface initiated fatigue crack growth due to contact loading is presented. The model is based on fracture mechanics theory where the required materials properties are obtained from common fatigue tests. For computational simulations an equivalent model of two contacting cylinders is used instead of simulating the actual contact of mechanical elements. The discretised model with the initial crack on or under the surface is then subjected to normal contact pressure, which takes into account the elasto-hydro-dynamic (EHD) lubrication conditions, and tangential loading due to friction between contacting surfaces. The model considers also… More >

A. Rama Ch,ra Murthy¹, G.S. Palani¹, Nagesh R. Iyer¹

Structural Durability & Health Monitoring, Vol.1, No.3, pp. 203-214, 2005, DOI:10.3970/sdhm.2005.001.203

Abstract This paper presents an improved Wheeler residual stress model for remaining life prediction of the cracked structural components under variable amplitude loading. The improvement to the Wheeler residual stress model is in two folds. One is expressions for the shaping exponent, which are generally obtained through experiments. Another is calculation of effective plastic zone size to incorporate the sequent effects under tensile-compressive overloading. The remaining life prediction has been carried out by employing the linear elastic fracture mechanics (LEFM) principles. Studies on remaining life prediction of cracked plate panels subjected to tensile-compressive overloading have been carried out for validating the… More >

G. Minak¹, F. E. G. Chimisso², H. S. Costa Mattos³

Structural Durability & Health Monitoring, Vol.1, No.3, pp. 193-202, 2005, DOI:10.3970/sdhm.2005.001.193

Abstract Cyclic plasticity and damage of a metal matrix composite have been studied in the framework of continuum damage mechanics. The material was considered as macroscopically homogeneous and a model incorporating damage gradient was applied. Strain-controlled fully reversed low-cycle fatigue uniaxial tests were performed to identify material parameters related to yield stress, isotropic and kinematic hardening, fatigue life and damage diffusion. From previous studies it has been found that in the most general case the parameters of the model are constant or depend exponentially on total strain so that only two or three tests are needed for the characterisation. The results… More >

G. Bertrand¹

Structural Durability & Health Monitoring, Vol.1, No.3, pp. 185-192, 2005, DOI:10.3970/sdhm.2005.001.185

Abstract Each maintenance strategy demands for the definition of an inspection threshold and further inspection intervals. A general criterion for the calculation of the time to first inspection is high probability of detection of a certain crack size and low failure probability in case a predicted crack size was not detected. The proposed method demonstrates that a top down analysis of crack development from critical sizes to detectable sizes reveals an economic benefit with respect to the frequency of inspections. The dispersion of fatigue stress cycles at rupture obtained from component tests at riveted lap joints is transformed to the distribution… More >

M. S. Alam¹, M.A. Wahab^1,2

Structural Durability & Health Monitoring, Vol.1, No.3, pp. 171-184, 2005, DOI:10.3970/sdhm.2005.001.171

Abstract Fatigue life of curved structural joints in ship structures under constant amplitude cyclic loading has been studied in this research. A new approach for the simulation of fatigue crack growth in welded joints has been developed and the concept has been applied to welded curved butt-joints. The phenomena of crack propagation and interface debonding can be regarded as the formation of new surfaces. Thus, it is possible to model these problems by introducing the mechanism of surface formation. In the proposed method, the formation of new surface is represented by interface element based on the interface surface potential energy. The… More >

M. M. Rahman¹, A. K. Ariffin¹, N. Jamaludin¹, C. H. C. Haron¹

Structural Durability & Health Monitoring, Vol.1, No.2, pp. 121-130, 2005, DOI:10.3970/sdhm.2005.001.121

Abstract The focus of this paper is to design a new two-stroke linear generator engine. This paper describes the finite element based vibration fatigue analysis techniques that can be used to predict fatigue life using total life approach. Fatigue damage in traditionally determined from time signals of loading, usually in the form of stress and strain. However, there are scenarios when a spectral form of loading is more appropriate. In this case the loading is defined in terms of its magnitude at different frequencies in the form of a power spectral density (PSD) plot. A power spectral density function is the… More >