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Firefighters are faced with numerous work-related demands and stressors, including exposure to potentially traumatic events, and are thus at an increased risk for poor mental health outcomes. To better understand the mental health of trauma-exposed firefighters, the current study sought to examine the association of fatigue sensitivity with posttraumatic stress disorder (PTSD), anxiety, and depressive symptom severity in a cross-sectional study design. Participants included 107 (Mage = 40.8 years; SDage = 8.95; age range: 21–67 years; 95.0% male) trauma-exposed firefighters. Findings from the current study indicated that fatigue sensitivity was a statistically significant clinical correlate of PTSD, anxiety, and depressive symptom severity. The statistically significant incremental effects were small to medium across the mental health variables, but evident after accounting for years in the fire service, sleep quality, and trauma load. The present data provide initial empirical evidence for the role of fatigue sensitivity in terms of a broad range of mental health indices among trauma-exposed firefighters. [ABSTRACT FROM AUTHOR]

Fatigue sensitivity, or the misattribution that fatigue symptoms will lead to negative personal consequences, is one individual difference factor related to adverse behavioral health consequences. The current study investigated whether fatigue sensitivity was related to panic symptoms, depression, as well as fatigue severity among 166 persons of diverse racial/ethnic backgrounds with severe fatigue. As hypothesized, fatigue sensitivity was statistically significantly related to greater panic symptoms, general depression, and fatigue severity. These results were evident over the variance explained by age, sex, neuroticism, and somatic symptoms. This work is the first to evaluate fatigue sensitivity in terms of behavioral health outcomes among a racial/ethnically diverse sample with severe fatigue. [ABSTRACT FROM AUTHOR]

Porous asphalt concrete (PAC) is prone to fatigue cracking and moisture damage due to its open gradation and high air voids. This study presented a systematic evaluation of the role of moisture damage on the fatigue performance of PAC. The mixture was designed with a high-viscosity modified asphalt and target air void of 20%. Moisture damage was induced into the compacted specimens via different numbers of freeze–thaw (F–T) cycles, and was quantified by the parameter Dm defined as loss in the indirect tensile (IDT) strength. Fatigue characterization adopted both the single- and two-stage loading patterns and was approached by phenomenological modeling. Results indicated that the PAC strength reduced with the F–T cycle number at a decreasing rate, following an exponential decay function. The single-stage fatigue characterization yielded an S–N relationship where the intercept and slope both depended exponentially on Dm. In the two-stage characterization, the Miner's sum declined with Dm indicating the weakening effect of the moisture conditioning. Fatigue life results from the high-low sequence seemed to suggest the presence and escalation of material sensitivity to the load level change between the two stages for F–T cycle ≥ 3. The Corten–Dolan model was adapted and applied to the two-stage loading. For both the high-low and low–high sequences, a unified expression for the parameter d in terms of Dm and the first cycle ratio α was derived. The investigation revealed that the fatigue performance of PAC became more sensitive to stress level with higher moisture damage, and exhibited higher dependence on moisture damage under larger load levels. [ABSTRACT FROM AUTHOR]

Objective: Chronic low back pain is the second leading cause of disability in the United States and is frequently related to increased risk of opioid and alcohol misuse. Depression is associated with poor substance use outcomes among persons with chronic low back pain. Theoretically, the influence of depression on opioid and alcohol misuse among those with chronic low back pain may vary as a function of fatigue sensitivity. Method: To empirically test this theorized model, the current study examined fatigue sensitivity as a moderator for the relation between depression and opioid and alcohol misuse among 291 adults (69.1% female, Mage = 45.77 years, SD = 11.22) with chronic low back pain currently using opioids. Results: Results suggested that fatigue sensitivity moderated the effect of depression on opioid misuse (β = 0.60, p =.001, 95%CI [0.02, 0.06]) and alcohol misuse (β = 0.45, p =.025, 95%CI [0.002, 0.03]). Examination of simple slopes revealed that the association between depression and opioid and alcohol misuse was statistically significant for those with higher levels of fatigue sensitivity, but not lower levels of fatigue sensitivity. Conclusions: Overall, the current investigation provides initial empirical support for the moderating role of fatigue sensitivity in the relation between depression and alcohol and opioid misuse among adults with chronic low back pain. [ABSTRACT FROM AUTHOR]

Currently, there is poor understanding of fatigue and the possible psychological conditions that may underlie chronic fatigue. Although substantial work has been directed to better clinically address fatigue, no work has explored individual differences in expectations or perceptions of the negative consequences associated with fatigue-related symptoms. The goals of this study were to (a) develop and (b) validate a measure of expectations or perceptions of the negative consequences associated with fatigue-related symptoms (e.g. fatigue sensitivity) across two independent samples (N = 1,827; 73.1% female; Mage = 21.68; SD = 4.54) of young adults. Results supported a 10-item measure of fatigue sensitivity, entitled the Fatigue Sensitivity Questionnaire (FSQ). The FSQ demonstrated unidimensionality, excellent internal consistency, and strong convergent and discriminant validity. Overall, the 10-item scale offers a single score that can be employed to measure fatigue sensitivity. Clinically, the FSQ may be a brief, informative, and easily disseminated measure in better understanding and capturing expectations or perceptions about the negative consequences of fatigue. As a research tool, the use of the FSQ may provide broader understanding of vulnerability factors that may influence fatigue-related health outcomes. Future research is needed to test the validity of the FSQ in other samples. [ABSTRACT FROM AUTHOR]

The transient dynamics analysis of the new driving drum is carried out by using ANSYS,its maximum equivalent stress cloud pictures and maximum principal stress time history in different work conditions are obtained. The rain-flow counting,the load extrapolation and superposition of the maximum equivalent stress time history of the dangerous area of the driving drum are carried out by using Rainflow module in n Code Glyph Works. Based on the relative theory of fatigue life prediction,stress life module is used to analyze the fatigue life and fatigue sensitivity of the driving drum. The damage histogram of the driving drum and the minimum fatigue life curves of the driving drum under the different inputted parameters are obtained. The results show that the driving drum has a good mechanical property,the minimum fatigue life of the driving drum is about 783 days to meet use requirements. The overload and residual stress have obvious influence on the fatigue life of the driving drum.

Fibre metal laminate (FML) with the carbon, flax and sugar palm fibres were prepared by hand layup and hot press technique. Their tensile and fatigue properties were studied. Results indicate that both the tensile properties and fatigue behaviour was dependent on the natural fibre type and their stacking sequence in the laminate. Flax based FML showed promising results with superior tensile properties and fatigue life. It also displayed fibre bridging mechanism, a phenomenon responsible for the higher fatigue life. Introducing flax in combination with sugar palm fibre resulted in slightly higher fatigue life than the sugar palm fibre based FML. FML with the sugar palm fibres showed the least fatigue life below 1000 cycles and did not exhibit fibre bridging effect. This behaviour indicates that sugar palm fibre may not be a suitable fibre for applications requiring fatigue resistance. [ABSTRACT FROM AUTHOR]

In this paper, the questions concerning the investigation of fatigue characteristics of composite materials are discussed and the changes in their static deformation and strength properties caused by preliminary cyclic actions are estimated. The aim of the work was to obtain new experimental data on damage accumulation processes in GFRP composite materials under combined cyclic and quasistatic loadings. An analysis of processes of fatigue damage accumulation in the composite materials is performed, and stages of change in the residual mechanical properties of the materials during cyclic loadings are noted. Temperature fields in the working section of samples are analyzed, and the characteristics features of temperature distribution in their destruction zone are revealed. Functions describing damage accumulation and changes in the strength and stiffness properties of the composites are introduced, which can be used to describe the behavior of the materials under fatigue loadings. A new form of representation of experimental data in the form of a fatigue sensitivity diagram is proposed, which can be employed to analyze the residual strength of structures made from composite materials. The characteristic stages of change in their residual static strength are presented in relation to the degree of preliminary cycling. It is proposed to use new material characteristics — the fatigue sensitivity threshold and the coefficient of static strength preservation. [ABSTRACT FROM AUTHOR]

The fatigue mechanics and mechanisms of cemented carbides (composites usually referred to as hardmetals) are reviewed. The influence of microstructure on strength lessening and subcritical crack growth for these ceramic-metal materials when subjected to cyclic loads are highlighted. The simultaneous role of the ductile metallic binder as a toughening and fatigue-susceptible agent for hardmetals results in a tradeoff between properties measured under monotonic and cyclic loading: fracture strength and toughness on one hand, as compared to fatigue strength and crack growth resistance on the other one. Toughness/fatigue−microstructure correlations are analyzed and rationalized on the basis of specific crack−microstructure interactions, documented by the effective implementation of advanced characterization techniques. As a result, it is concluded that the fatigue sensitivity of cemented carbides may be reduced if either toughening mechanisms beyond ductile ligament bridging, such as crack deflection, are operative, or strain localization within the binder is suppressed. In this regard, grades exhibiting metallic binders of a complex chemical nature and/or distinct microstructural assemblages are proposed as options for effective microstructural tailoring of these materials.

By transforming the platform response obtained from coupled hydrodynamic analysis to the top motions of steel catenary riser (SCR), the nonlinear dynamic analysis of the SCR is carried out in Abaqus/Aqua. In this analysis, the SCR-seabed interaction is well taken into account by introducing the seabed trench model and hysteretic seabed model. The fatigue damage of the SCR near touchdown point (TDP) is calculated using rain-flow counting methodology, and the sensitivity of the fatigue damage to the seabed and wave parameters are investigated. The results indicate that as seabed stiffness increases, the fatigue life and its sensitivity to seabed stiffness decrease. Seabed trenching may benefit the fatigue life of the SCR and the trench position should be elaborated for realistic fatigue damage prediction. Due to the induced platform response, significant wave height and spectral peak period have significant effects on the fatigue damage, thus the short-term sea state bins should be carefully selected from the wave scatter diagram. [ABSTRACT FROM AUTHOR]

Increasing the knowledge about the fatigue performance of thermoplastic-based fibre metal laminate is crucial for further extending their applications. In this study, the density and tension-tension fatigue performances of laminate structures with different hybrid layups are investigated. The fibre metal laminate structure is formed by bonding the composite laminate to annealed aluminium 5052 by using polypropylene adhesive through the hot press moulding compression method. The fatigue test was conducted at force controlled constant amplitude loading in accordance with ASTM E466. The results show that hybrid composite laminates layups of kenaf/glass/kenaf reinforced metal laminate improve the tensile and fatigue strength by 9%, compared to composite laminates layups of kenaf/kenaf/kenaf fibre reinforced metal laminate. Meanwhile, the hybrid composite laminates layups of glass/kenaf/glass reinforced metal laminate show an increase in tensile strength and fatigue strength by 30% and 4% respectively. In terms of fatigue sensitivity, a hybrid laminate system with kenaf/glass/kenaf composite construction had better performance than other layups. [ABSTRACT FROM AUTHOR]

In this work, functionally graded cemented carbides (FGCCs) with CoNiFeCr multi-principal-element alloy (MPEA) binder were prepared by pre-sintering and carburizing. The microstructure and mechanical behavior of WC-CoNiFeCr FGCCs with different carbon contents obtained at different carburization temperatures were studied. The results showed that a higher carbon content simultaneously accelerated the diffusion rate of carbon and increased the diffusion channel of carbon. The FGCC with a carbon content of 4.55% obtained at a carburizing temperature of 1450 °C exhibited the thickest gradient layer and the highest extreme hardness difference, TRS, and fracture toughness. Moreover, as the thickness of the gradient layer increased, the fatigue sensitivity of FGCCs enhanced, approaching the characteristics of metallic materials. • The extreme hardness difference, TRS, and fracture toughness for FGCCs with CoNiFeCr MPEA binder increase with the carbon content and the carburizing temperature. • As the thickness of the gradient layer of FGCCs increases, the fatigue sensitivity increases, exhibiting a transition from ceramic-like to metal-like behavior. [ABSTRACT FROM AUTHOR]

This article examines the suitability of vertical jump and 20-m sprint (SPRINT) testing for detecting neuromuscular fatigue in athletes. Data were collected immediately after zeroing until the jump was completed. Large widespread decreases in neuromuscular function were apparent immediately postexercise.

There is a major interest in replacing cobalt binder in hardmetals (cemented carbides) aiming for materials with similar or even improved properties at a lower price. Nickel is one of the materials most commonly used as a binder alternative to cobalt in these metal-ceramic composites. However, knowledge on mechanical properties and particularly on fatigue behavior of Ni-base cemented carbides is relatively scarce. In this study, the fatigue mechanics and mechanisms of a fine grained WC–Ni grade is assessed. In doing so, fatigue crack growth (FCG) behavior and fatigue limit are determined, and the attained results are compared to corresponding fracture toughness and flexural strength. An analysis of the results within a fatigue mechanics framework permits to validate FCG threshold as the effective fracture toughness under cyclic loading. Experimentally determined data are then used to analyze the fatigue susceptibility of the studied material. It is found that the fatigue sensitivity of the WC–Ni hardmetal investigated is close to that previously reported for Co-base cemented carbides with alike binder mean free path. Additionally, fracture modes under stable and unstable crack growth conditions are inspected. It is evidenced that stable crack growth under cyclic loading within the nickel binder exhibit faceted, crystallographic features. This microscopic failure mode is rationalized on the basis of the comparable sizes of the cyclic plastic zone ahead of the crack tip and the characteristic microstructure length scale where fatigue degradation phenomena take place in hardmetals, i.e. the binder mean free path. [ABSTRACT FROM AUTHOR]

In this study, we prepared WC-CoNiFe and WC-Co with different grain sizes by sintering-hot isostatic pressing (SHIP) and evaluated their fracture behavior. The results showed that WC-CoNiFe has a higher fracture toughness (between 13.16 and 17.82 MPam1/2) than WC-Co (between12.08 and 16.21MPam1/2). Moreover, fracture toughness and fatigue crack growth (FCG) were closely related to the corresponding microstructural characteristics. The fracture toughness increased via ductile ligament bridging and crack deflection as the mean free path of the binder phase (λ Co) increased, or the contiguity of the carbide phase (C WC) decreased. The fatigue fracture mode showed a transition from a cleavage-like brittle fracture to a ductile dimple-like fracture. The fatigue sensitivity of cemented carbides was positively related to the fracture toughness. As the fracture toughness increased, cemented carbides exhibited a transition from ceramic-like material to metal-like material. Considering two important controlling parameters of FCG behavior, the effect of maximum stress intensity factor (K max) on FCG was dominant compared to the stress intensity factor range (∆K). However, the difference in the relative influence of these two parameters diminished as the fracture toughness increased. Moreover, with the rise in K max value, we defined three stages of the FCG process: crack initiation, stable crack growth, and unstable crack growth. The results suggest that CoNiFe medium entropy alloy is a promising material for application as a binder phase of cemented carbides with high toughness. • WC-CoNiFe and WC-Co with different particle sizes (from fine grain to ultra-coarse grain) were prepared by sintering-hot isostatic pressing (SHIP) to evaluate the fracture behavior. • WC-CoNiFe has higher fracture toughness and fatigue sensitivity compared to WC-Co. • As the toughness increases, the material's fatigue sensitivity increases, showing a transition from ceramic to metal-like material. [ABSTRACT FROM AUTHOR]

The fatigue mechanics and mechanisms of cemented carbides (composites usually referred to as hardmetals) are reviewed. The influence of microstructure on strength lessening and subcritical crack growth for these ceramic-metal materials when subjected to cyclic loads are highlighted. The simultaneous role of the ductile metallic binder as a toughening and fatigue-susceptible agent for hardmetals results in a tradeoff between properties measured under monotonic and cyclic loading: fracture strength and toughness on one hand, as compared to fatigue strength and crack growth resistance on the other one. Toughness/fatigue–microstructure correlations are analyzed and rationalized on the basis of specific crack–microstructure interactions, documented by the effective implementation of advanced characterization techniques. As a result, it is concluded that the fatigue sensitivity of cemented carbides may be reduced if either toughening mechanisms beyond ductile ligament bridging, such as crack deflection, are operative, or strain localization within the binder is suppressed. In this regard, grades exhibiting metallic binders of a complex chemical nature and/or distinct microstructural assemblages are proposed as options for effective microstructural tailoring of these materials. [ABSTRACT FROM AUTHOR]