G. Meneghetti¹

Structural Durability & Health Monitoring, Vol.8, No.2, pp. 111-130, 2012, DOI:10.3970/sdhm.2012.008.111

Abstract This paper deals with the local approach based on the Notch Stress Intensity Factors (NSIFs) to analyse the fatigue behavior of welded joints. In transverse load carrying fillet-welded joints, failure may occur either at the toe or at the root, depending on the geometry. At the toe, due to the flank angles that are usually encountered in practice, mode I local stresses are singular, while mode II stresses are not. Conversely, at the root of the particular joints analysed in the present paper both mode I and mode II stresses are singular and must be… More >

A. Risitano¹, D. Corallo¹, G. Risitano²

Structural Durability & Health Monitoring, Vol.8, No.2, pp. 91-110, 2012, DOI:10.3970/sdhm.2012.008.091

Abstract According to Miner's rule, the fatigue life of a material (or a mechanical component) is not a function of the order of the application of load. Many authors have already observed that the model proposed by Palmgren/Miner leads to underestimation of the damage and one of the reasons could be the disregard of the sequence of loads. Referring to the energy loss related to irreversible damage of the material, it was observed that the Miner's rule gives exact results only if the damage caused by the fatiguing load is low compared to the limit energy More >

G. Olmi¹

Structural Durability & Health Monitoring, Vol.8, No.1, pp. 61-90, 2012, DOI:10.3970/sdhm.2012.008.061

Abstract Turbogenerator rotors and coil retaining rings are highly loaded components, under low cycle fatigue at every machine switch on and switch off transient. Their failure during service may lead to very serious consequences. The present paper utilizes several experimental data, concerning the static, cyclic and fatigue behaviour of the rotor material, in order to perform a probabilistic analysis. All the main methodological issues are tackled, consisting in the experimental data processing, in the choice of the random variables that are involved in the fatigue process, in the determination of their distributions, in the practical computation More >

F. Curà¹, A. Gallinatti¹, R. Sesana¹

Structural Durability & Health Monitoring, Vol.8, No.1, pp. 45-60, 2012, DOI:10.3970/sdhm.2012.008.045

Abstract In this paper the effect of high cycle fatigue damaging on a commercial steel is investigated by means of experimental measurement of mechanical and dissipative parameters variation during fatigue testing. Experimental procedures for HCF damage incrementing on specimens and for parameter measurement have been defined. A statistical analysis of the significance of the results have been applied to select the parameters which best represent the damage progression on the specimen. More >

F. Berto¹, P. Lazzarin¹, D. Radaj²

Structural Durability & Health Monitoring, Vol.8, No.1, pp. 31-44, 2012, DOI:10.3970/sdhm.2012.008.031

Abstract The fictitious notch rounding concept is applied here for the first time to V-shaped notches with root hole subjected to in-plane shear loading. The fictitious notch radius ρ_f is determined as a function of the real notch radius ρ, the microstructural support length ρ* and the notch opening angle 2α, at first using the normal stress criterion in combination with the maximum tangential stress criterion for finding the crack propagation angle. An analytical method has been developed resulting in closed form expressions for the multiaxiality factor s in the well known relationship ρ_f=ρ+sρ*. It expresses the notch More >

F. Cianetti¹

Structural Durability & Health Monitoring, Vol.8, No.1, pp. 1-30, 2012, DOI:10.3970/sdhm.2012.008.001

Abstract This research activity refers to the problem of fatigue damage evaluation of mechanical components subjected to random loads. In detail, the present paper describes a procedure, developed by the author, that, starting from component modal modelling, can very quickly gives an answer to the request not only of a qualitative evaluation of its stress state but also of a quantitative and very reliable estimation of the component damage. This estimation is available (both in time and in frequency domain), regardless of the stress state recovery, only by an appropriate elaboration of lagrangian coordinates and elements stress More >

Ramamurty Raju P.¹, Rajesh S.¹, Satyanarayana B.², Ramji K.³

Structural Durability & Health Monitoring, Vol.7, No.1&2, pp. 139-152, 2011, DOI:10.3970/sdhm.2011.007.139

Abstract This paper presents the details of method of sample size determination to estimate the characteristic fatigue life of aluminum alloy, A356.2-T6. The characteristic fatigue life of the alloy has been estimated by assuming log normal distribution model. A step wise procedure is outlined to determine the number of specimens required at predetermined stress amplitude to estimate the fatigue life with an acceptable error at 50% probability and various confidence levels, 90%, 95% and 99%. Maximum percentage of errors has also been calculated for the above probability and confidence levels. Details of generation of S-N curve More >

P. Gayathri¹, R. Ganguli^1,2

Structural Durability & Health Monitoring, Vol.7, No.1&2, pp. 119-138, 2011, DOI:10.3970/sdhm.2011.007.119

Abstract The effect of random variation in composite material properties on the reliability of structural damage detection is addressed in this paper. A composite plate is considered as the structure and a finite element model is used for the simulation. Damage growth due to cyclic loading is addressed. Matrix crack induced delamination is emphasized in this paper. Thresholds for the damage accumulation are found using finite element simulations so that the structure can be subjected to inspections and removed from service safely. Uncertainty effects of composite material properties on the response of the structure are quantified More >

C. Braccesi¹, F. Cianetti^1,2

Structural Durability & Health Monitoring, Vol.7, No.1&2, pp. 83-118, 2011, DOI:10.3970/sdhm.2011.007.083

Abstract In this paper the problem of the correct evaluation of the stress state of mechanical components of non linear systems in the frequency domain was analysed. This is one of the most important steps in the frequency domain evaluation of the fatigue behaviour of components submitted to random loads. A new methodology to obtain an accurate representation in frequency domain of the non-linear behaviour of the system as well as of the stress state of the components both in terms of power spectral density (PSD) function and of frequency response function (FRF) was proposed and More >

Clyde K Coelho, Cristobal Hiche, Aditi Chattopadhyay

Structural Durability & Health Monitoring, Vol.7, No.1&2, pp. 65-82, 2011, DOI:10.3970/sdhm.2011.007.065

Abstract Low velocity impacts on composite plates often create subsurface damage that is difficult to diagnose. Fiber Bragg grating (FBG) sensors can be used to detect subsurface damage in composite laminates due to low velocity impact. This paper focuses on the prediction of impact loading in composite structures as a function of time using a support vector regression approach. A time delay embedding feature extraction scheme is used since it can characterize the dynamics of the impact using the sensor signals. The novelty of this approach is that it can be applied on complex geometries and… More >