Search results

This cross-sectional online survey in Oman in April 2021 aimed to assess university students' resilience, stress levels and meaning during the COVID-19 pandemic and identify characteristic profiles.

A cross-sectional survey design was used to collect data from full-time students at one University in Oman. Outcomes included sociodemographic information, the brief resilience scale, the perceived stress scale-4 and the meaning in life questionnaire to explore the students' profiles.

A total of 964 students participated (response rate = 34.8%), of which 35% had low resilience scores. The average perceived stress, presence of meaning in life and search for meaning in life scores were 7.9 ± 2.3, 24.2 ± 6.9 and 24.9 ± 7.7, respectively. Cluster analysis identified three groups: low-risk and fewer impacts (cluster A, n = 503, 523%), moderate-risk and moderate impacts (cluster B, n = 160, 16.6%) and high-risk and more impacts (cluster C, n = 301, 31.2%). Cluster C students experienced more psychological problems and were at high risk during the pandemic.

The respondents' honesty is a possible error that could influence the results. Low response rates limit its generalizability, and cause-effect relationships among mental health outcomes cannot be discerned.

This study identified three distinct groups of students, each with different levels of severity in their health problems. There is an increased need for education and counseling to support students during this period, and university management should focus on implementing personal precautionary measures and providing high-tech, user-friendly platforms for students to enhance their learning.

These findings suggest that tailored strategies should be developed to address the unique psychological needs of each group. The study provides important information for university management to understand the pandemic's psychological impact on students and develop effective interventions to support their well-being.

THE purpose of this paper is to examine the part that metal fatigue plays in the engineering of the helicopter, and to outline the methods used at present to estimate the safe fatigue life of the component parts of the helicopter.

The purpose of this paper is to study the effect of mean stress and stress amplitude on the asymmetric cyclic deformation behavior of SA333 Gr-6 C-Mn steel. Such type of loading may arise during the service period because of the load fluctuations, thermal gradients and sudden loading like seismic events. Tests were also carried out at different temperatures to understand the effect of it on sensitiveness of the materials deformation behavior.

Cylindrical specimen of 8-mm gauge diameter and 15-mm gauge length was fabricated from the pipe section along its axis. Stress controlled ratcheting tests were carried out by using triangular waveform for cyclic loading. The strain accumulations were measured using 12.5-mm gauge length extensometer. Ratcheting tests were carried out at fixed stress amplitude of 400 MPa and mean stress varying from 0 to 75 MPa, whereas at the fixed mean stress of 100 MPa and stress amplitude varies from 300 to 400 MPa at 300°C. To study the effect of temperature on ratcheting behavior, tests were carried out at a load of 100 MPa mean stress and 350 MPa stress amplitude, with a varying temperature between room temperature and 350°C. The stress rate of 115 MPas-1 was kept constant for all the tests.

Increase in mean stress and stress amplitude, ratcheting strain and plastic strain amplitude increases, whereas ratcheting life decreases. With an increase in temperature, ratcheting life increases and strain accumulation decreases up to 300°C, whereas on further increase in temperature, strain accumulation increases with reduction in ratcheting life. Minimum ratcheting rate was observed at 250°C and 300°C. The dynamic strain aging (DSA) phenomena lead to the hardening of the material. The investigated steel shows DSA temperature regime lies between 250°C and 300°C. The failure modes at 250°C and 300°C temperature was transgranular, whereas at 350°C complete ductile.

The stress rate and loading condition may vary to study the ratcheting behavior.

From this study, the critical cyclic load may be determined. The DSA temperature regime of this material is determined at this stress rate. This could help to evaluate the cyclic deformation behavior of the material with temperature changes.

In this investigation, the DSA temperature regime has been determined where maximum ratcheting life, minimum strain accumulation and ratcheting rate were observed. The critical load where the minimum life of the material occurred at elevated temperature is 100 MPa mean stress and 400 MPa stress amplitude.

Under multiaxial random loading, the material stress–strain response is not periodic, which makes it difficult to determine the direction of the critical plane on the material. Meanwhile, existing methods of constant loading cannot be directly applied to multiaxial random loading; this problem can be solved when an equivalent stress transformation method is used.

First, the Liu-Mahadevan critical plane is introduced into multiaxial random fatigue, which is enabled to determine the material's critical plane position under random loading. Then, an equivalent stress transformation method is proposed which can convert random load to constant load. Meanwhile, the ratio of mean stress to yield strength is defined as the new mean stress influence factor, and a new non-proportional additional strengthening factor is proposed by considering the effect of phase differences.

The proposed model is validated using multiaxial random fatigue test data of TC4 titanium alloy specimens and the results of the proposed model are compared with that based on Miner's rule and BSW model, showing that the proposed method is more accurate.

In this work, a new multiaxial random fatigue life prediction model is proposed based on equivalent stress transformation method, which considers the mean stress effect and the additional strengthening effect. Results show that the predicted fatigue lives given by the proposed model are in well accordance with the tested data.

THIS note proposes a new type of empirical alternating/mean stress diagram for plain fatigue specimens, which combines the merits of the Modified Goodman Line and the Gerber Parabola, with increased accuracy.

Stress damages us and our performance. It is a real part of most manager's experience and can be said to occur when significant demands exceed perceived management responsibilities and routines. Stress can be the essence of working life, and certainly need not always be damaging to us. But when it becomes excessive, it is something unwanted.

We demonstrate in a laboratory experiment that the effectiveness of performance-contingent incentives is inversely related to risk-aversion levels. For about 16.5% of participants, performance fails to improve under performance-pay, and the probability of such failure increases with risk-aversion. This phenomenon works in part through the reduced effort level of more risk-averse individuals when effort level is positively correlated with risk exposure. It is also associated with higher self-reported levels of stress by more risk-averse people working under performance-contingent pay. We find no evidence of such stress causing decrements in the quality of effort affecting performance after controlling for effort level. However, controlling for effort, more risk-averse participants perform better under a fixed salary, leaving less room for improvement under performance-pay.

Clad 2024‐T3 and 7075‐T6 sheet specimens were loaded at three different load amplitudes and three different mean loads. It turned out that the mean stress had an important influence on the crack propagation rate. The crack growth rate in the 7075 specimens was three to four times as large as in the 2024 specimens.

Recently, a new class of fatigue crack growth models based on elastoplastic stress‐strain histories at the crack tip region and strain‐life fatigue damage models have been proposed. The fatigue crack propagation is understood as a process of continuous crack initializations, over elementary material blocks, which may be governed by strain‐life data of the plain material. The residual stresses developed at the crack tip play a central role in these models, since they are used to assess the actual crack driving force, taking into account mean stresses and loading sequential effects. The UniGrow model fits this particular class of fatigue crack propagation models. The purpose of this paper is to propose an extension of the UniGrow model to derive probabilistic fatigue crack propagation data, in particular the derivation of the P–da/dN–ΔK–R fields.

An existing deterministic fatigue crack propagation model, based on local strain‐life data is first assessed. In particular, an alternative methodology for residual stress computation is proposed, based on elastoplastic finite element analysis, in order to overcome inconsistencies found in the analytical approximate approaches often used in literature. Then, using probabilistic strain‐life fields, a probabilistic output for the fatigue crack propagation growth rates is generated. A new probabilistic fatigue field is also proposed to take mean stress effects into account, using the Smith‐Watson‐Topper (SWT) damage parameter. The proposed models are assessed using experimental data available for two materials representative from old Portuguese bridges.

A new method to generate probabilistic fatigue crack propagation rates (P–da/dN–ΔK–R fields) is proposed and verified using puddle iron from old Portuguese bridges, usually characterized by significant scatter in fatigue properties. Also, a new probabilistic fatigue field for plain material is proposed to deal with mean stress effects.

A relation between the P–ε–N and the P–da/dN–ΔK–R fields is firstly proposed in this research. Furthermore, a new P–SWT–N field is proposed to deal with mean stress effects.

The nature of work has changed in the past 30 years but we do not know what these changes have meant for worker job stress. In this chapter we compare data from three surveys of the quality of work life from 1972 to 2002. At the most general level, work today is less stressful than it was in 1972. Workers report fewer job demands, more decision latitude, less job strain, more job security and greater access to job resources and job support. However, these changes have not affected all workers equally. Women, those with less education, non self-employed workers, blue collar workers and workers in manufacturing industries showed the greatest decreases in job stress although levels of job stress remain higher than for comparison groups (men, college educated, white collar, service workers). Changes were not always linear across time suggesting that some aspects of job strain are sensitive to economic cycles.