High temperature fatigue tests and crack growth in 40CrMoV13.9 notched components

The present paper addresses experimentally the high temperature fatigue of 40CrMoV13.9 steel and the effect of surface roughness on fatigue strength and crack initiation. The 40CrMoV13.9 steel is widely used in different engineering high temperature applications among which hot- rolling of metals, where, in order to assure a constant temperature, the rolls are provided with cooling channels. These are the most stressed zone of the rolls where cracks systematically initiate. In order to completely characterize the high temperature behaviour of this steel, firstly uniaxial-tension load controlled fatigue tests have been conducted at different temperatures up to 650°C. Two geometries are considered: plain specimens and plates weakened by symmetric V-notches. Subsequently, with the aim to investigate the influence of the cooling channels roughness on the high temperature behaviour and the cracks initiation, uniaxial-tension load controlled fatigue tests have been conducted on plate with central hole at the service temperature of 650°C varying the surface roughness. After a brief review of the recent literature, the experimental procedure is described in detail and the new data from un-notched and notched specimens are summarized in terms of stress range, at the considered temperatures. Finally, fatigue data from un-notched and notched specimens are re-analysed by means of the mean value of the Strain Energy Density (SED) approach extended at high temperature

Asymptotic residual stresses in butt-welded joints under fatigue loading

If a weld toe is modelled as a sharp V-notch angle, the stress distribution near the notch tip is singular. Its intensity can then be quantified by means of Notch Stress Intensity Factors (NSIF), which have been proven to be capable of summarising the high-cycle fatigue strength of welded joints having very different global and local geometries. In presence of a singular residual stress field near the weld toe, the local load ratio is modified making the fatigue strength sensitive to residual stresses in the high-cycle regime. However, for an accurate estimation of the fatigue performance of welded joints, it is necessary to consider not only the initial residual stress field but also its variation under load, as both of these may play an important role. In this work the effect of fatigue loading on the asymptotic residual stress redistribution near the weld toe of a butt-welded joint is studied by means of numerical simulations. A model is then proposed to estimate the influence of residual stresses on the fatigue strength of welded joints. Experimental results taken from the literature were found in good agreement with those predicted by the proposed model

Recent developments in multi-parametric three-dimensional stress field representation in plates weakened by cracks and notches

The paper deals with the three-dimensional nature and the multi-parametric representation of the stress field ahead of cracks and notches of different shape. Finite thickness plates are considered, under different loading conditions. Under certain hypotheses, the three-dimensional governing equations of elasticity can be reduced to a system where a bi-harmonic equation and a harmonic equation have to be simultaneously satisfied. The former provides the solution of the corresponding plane notch problem, the latter provides the solution of the corresponding out-of-plane shear notch problem. The analytical frame is applied to some notched and cracked geometries and its degree of accuracy is discussed comparing theoretical results and numerical data from 3D FE models

Notch Stress Intensity Factors Applied to U and V-Shaped Radiused Notches under In-plane Shear Loading

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Asymptotic residual stress distribution induced by multipass welding processes

publisher: Elsevier articletitle: Asymptotic residual stress distribution induced by multipass welding processes journaltitle: International Journal of Fatigue articlelink: http://dx.doi.org/10.1016/j.ijfatigue.2016.11.022 content_type: article copyright: © 2016 Elsevier Ltd. All rights reserved

Fracture Assessment of Blunt V-Notches under Prevalent Mode II Loading by Means of Local Energy

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How much is the indoor comfort of a residential building worth? A discrete choice experiment

Generally, people spend most of their time indoors, and the COVID-19 pandemic has further increased the amount of time people spent at home, owing to the widespread adoption of remote work. Consequently, there has been a heightened interest in indoor comfort, including thermal, visual, and acoustic comfort and indoor air quality. This interest has prompted a need to understand the economic value of each aspect of indoor comfort. To address this, a discrete choice experiment (DCE) was performed to estimate the willingness to pay (WTP) for advanced technological solutions that provide greater comfort than basic solutions in residential housing. The research showed a significant WTP for all aspects of comfort, with the greatest appreciation for thermal comfort. Additionally, the WTP for each aspect of comfort was greater than the additional costs required to implement advanced technological solutions to enable the desired comfort. The findings demonstrated that the sample population, mostly comprising people under the age of forty, was highly sensitive to comfort considerations and the related benefits derived from energy-efficient solutions. Specifically, comparing the WTP of the different aspect of comfort and the total one identified, the following relative importance was found: 51 % for thermal comfort (WTP = 377.94 EUR/m2); 22 % for visual comfort (WTP = 166.83 EUR/m2); 16 % for acoustic comfort (WTP = 119.60 EUR/m2) and 11 % for indoor air quality (WTP = 79.21 EUR/m2). These motivations can guide future decision-making and designers in the building market