the dissipated heat energy as a fatigue damage index for experimental fatigue life estimations

Abstract In the last decade, the heat energy dissipated in a unit volume of material per cycle (the Q parameter) has been adopted by the authors as a fatigue damage indicator of metallic materials. The advantage of using such a parameter is that it can be readily and in-situ measured at a point or a component undergoing fatigue solicitations. Geometrical, mean stress and variable amplitude (limited to two stress-level tests) effects have been successfully analysed by using the Q parameter. Concerning geometrical effects, approximately 160 experimental results generated from constant amplitude, completely reversed, stress- or strain-controlled fatigue tests on plain or notched hot rolled as well as cold drawn stainless steel specimens have been rationalised. Afterwards, the heat-energy based approach was extended to include the mean stress effect, by using a thermodynamic fatigue damage variable that combines two parameters, i.e. Q and the thermoelastic temperature achieved by the material at the maximum stress of the load cycle. Finally, Q was used to rationalise two stress-level fatigue test results, by using the Q-based fatigue curve combined with Miner's rule. In this paper, the theoretical background and the application of the energy-based approach are reviewed in order to analyse all previously mentioned effects, focusing mainly on the mean stress and the variable amplitude, two stress-level effects

Experimental estimation of the heat energy dissipated in a volume surrounding the tip of a fatigue crack

Fatigue crack initiation and propagation involve plastic strains that require some work to be done on the material. Most of this irreversible energy is dissipated as heat and consequently the material temperature increases. The heat being an indicator of the intense plastic strains occurring at the tip of a propagating fatigue crack, when combined with the Neuber's structural volume concept, it might be used as an experimentally measurable parameter to assess the fatigue damage accumulation rate of cracked components. On the basis of a theoretical model published previously, in this work the heat energy dissipated in a volume surrounding the crack tip is estimated experimentally on the basis of the radial temperature profiles measured by means of an infrared camera. The definition of the structural volume in a fatigue sense is beyond the scope of the present paper. The experimental crack propagation tests were carried out on hot-rolled, 6-mm-thick AISI 304L stainless steel specimens subject to completely reversed axial fatigue loading

Analysis of the fatigue strength under two load levels of a stainless steel based on energy dissipation

In this paper the fatigue behaviour of a stainless steel AISI 304L is analysed. In the first part of the work the results obtained under constant amplitude fatigue are presented and synthesised in terms of both stress amplitude and energy released to the surroundings as heat by a unit volume of material per cycle, Q. Then some specimens have been fatigued in variable amplitude, two different load level tests: the first level was set higher while the second was lower than the constant amplitude fatigue limit. The Q values, evaluated during the second part of the fatigue test, have been compared with those calculated under constant amplitude fatigue at the same load level. The comparison allowed us to notice that the Q parameter is sensitive to the fatigue damage accumulated by the material during the first part of the fatigue test

Realism And Fantasy In Motion Pictures: Transportation Under Debate

Transportation is commonly presented in the context of realistic narratives. An important facet of transportation, which means being absorbed into the written narrative flow of a story, relies on its capacity to influence individuals’ beliefs. This research examines whether (i) the effects of transportation is replicable with movies; (ii) an individual difference, such as fantasy proneness, shapes the relationship between the realism of the movie and the transportation level of the individual. Two studies show that (a) movies have an impact on individuals’ transportation; (b) realistic movies have a greater impact on transportation than fantastic movies; (c) fantasy proneness increases the level of transportation; (d) transported individuals better evaluate movies

Quantifying the network connectivity of landscape mosaics: a graph-theoretical approach

Connectivity determines a large number of ecological functions of the landscape, including seed and animal dispersal, gene flow and disturbance propagation, and is therefore a key to understanding fluxes of matter and energy within land mosaics. Several approaches to quantifying landscape connectivity are possible. Among these, graph theory may be used to represent a landscape as a series of interconnected patches, where flows occur as a result of structural and/or functional patch connectivity. Within this context, we propose the use of a graph-theoretic index (i.e., the Harary index) as a measure of landscape connectivity. Results derived from the analysis of the vegetation map of Palmarola (central Italy) show that, from a statistical and ecological viewpoint, the Harary index may be a better measure of landscape connectivity than more traditional indices derived from transportation geography

Motivation Strategies for Improving Consistency in Live-Entertainment Employees\u27 Performances

The lack of discrete motivation strategies to improve the consistency of employees\u27 performances was the problem that instigated this research. The purpose of this single-case study was to explore the motivation strategies live-entertainment artistic directors (ADs) use to improve consistency in the artists\u27 performances. Data were collected within an international live-entertainment company to uncover whether artists self-determined the approach to improving consistency in performance or whether consistency occurred from strategies developed by the ADs. Data were collected from face-to-face interviews with ADs and senior ADs and performance evaluations of employees, and then analyzed using Miles, Huberman, and Saldana\u27s data analysis method. The 2 emergent themes indicated that the ADs achieved consistency from performers through strategies supporting well-being and technical proficiency. Analysis of employee evaluations indicated the use of alternative motivational strategies for achieving and improving consistency at the show level. Some ADs rely on artists to self-determine consistency when working in environments perceived as conducive to consistent behavior. These findings might result in a mutual understanding between employers and employees of the role of consistency in employees\u27 live performances, which may also improve employer-to-employee relationships in the live-entertainment sector. Such understanding might lead to positive social change by improving cultural output to the community and improving employees\u27 economic viability and ability to contribute to society

The heat energy dissipated in a control volume to correlate the crack propagation rate in stainless steel specimens

Metallic materials dissipate thermal energy when subjected to fatigue. Some of them, due a favorable combination of thermo-physical material properties, exhibit a significant temperature rise, which can be easily measured in-situ by means of thermocouples or infrared cameras. The heat energy dissipated in a unit volume of material per cycle (the Q parameter) has proven to be effective as a fatigue damage index in case of AISI 304L plain and notched specimens. Originally conceived and applied as a point-related quantity, recently Q has been averaged at the tip of propagating fatigue cracks (the Q* parameter) in order to correlate crack growth data gathered from fracture mechanics tests. The use of Q* seems interesting because (i) it can be evaluated in-situ from infrared temperature maps and (ii) crack acceleration due to excessive plasticity is likely to be accounted for

Experimental estimation of the heat energy dissipated in a volume surrounding the tip of a fatigue crack

Fatigue crack initiation and propagation involve plastic strains that require some work to be done on the material. Most of this irreversible energy is dissipated as heat and consequently the material temperature increases. The heat being an indicator of the intense plastic strains occurring at the tip of a propagating fatigue crack, when combined with the Neuber’s structural volume concept, it might be used as an experimentally measurable parameter to assess the fatigue damage accumulation rate of cracked components. On the basis of a theoretical model published previously, in this work the heat energy dissipated in a volume surrounding the crack tip is estimated experimentally on the basis of the radial temperature profiles measured by means of an infrared camera. The definition of the structural volume in a fatigue sense is beyond the scope of the present paper. The experimental crack propagation tests were carried out on hot-rolled, 6-mm-thick AISI 304L stainless steel specimens subject to completely reversed axial fatigue loading

Second-line treatment in renal cell carcinoma: clinical experience and decision making

Currently, conventional treatments for metastatic RCC (mRCC) include immune-based combination regimens and/or targeted therapies, the latter mainly acting on angiogenesis, a key element of the process of tumor growth and spread. Although these agents proved able to improve patients’ outcomes, drug resistance and disease progression are still experienced by a substantial number of VEGFR-TKIs-treated mRCC patients. Following the inhibition of the VEGF/VEGFRs axis, two strategies have emerged: either specifically targeting resistance pathways, at the same time continuing to inhibit angiogenesis, or using a completely different approach aimed at re-activating the immune system through the use of inhibitors of specific negative immune checkpoints. These two approaches, practically represented by the use of either cabozantinib or nivolumab, seem to remain a rational therapeutic approach also when first-line immune-based combinations are used. The objective of this study is to design a preferential therapeutic pathway for the second-line treatment of mRCC. The procedure applied in this project was a group discussion, based on the Nominal Group Technique (NGT) method in a meeting session, aimed at defining the therapeutic choice for the second-line treatment of mRCC. The NGT process defined the most relevant parameters that, according to the interviewed panelists, clinicians should consider for the selection of the second-line therapy in the context of advanced renal cell carcinoma of mRCC. The algorithm developed for the treatment selection as a result of this process should thus be considered by clinicians as reference for therapy selection. Plain language summary: The result of this paper was the definition of an algorithm intended to suggest a preferential therapeutic pathway considering both the outputs of the Nominal Group Technique (NGT) process and the actual clinical practice and the experience of selected panelists. During the NGT process and the discussion phase, panelists defined the most important parameters to be included in the algorithm that are important for the treatment definition. Cabozantinib and nivolumab are identified as the most reasonable therapeutic options for patients progressing after first-line treatment and are the medication options included in the algorithm for therapy selection