Global Self-Esteem and Stress Intensity in a Group of Polish Nurses—A Mediatory Role of a Sense of Coherence

(1) Owing to their resistance resources, nurses can reduce the effects of stress, increase their commitment to work and improve their functioning in the face of challenges in the workplace. The aim of this study was to determine the mediatory role of a general sense of coherence and a sense of comprehensibility, manageability and meaningfulness correlated with global self-esteem and the perceived stress intensity in a group of Polish nurses aged 45–55 years. (2) The research using the diagnostic survey method was conducted on a group of 176 nurses (M = 49.1; SD = 3.1) working in seven hospitals located in Olsztyn (Poland). The following were used for data collection: Perceived Stress Scale - PSS-10, Rosenberg’s Self-Esteem Scale and Antonovsky’s Sense of Coherence (SOC-29) Questionnaire. (3) According to 21.02% of the nurses, their stress level at the workplace was low, 44.89% reported it was medium and 34.09% reported it was high. The self-esteem of nearly half of the nurses included in the study (48.30%) was at a medium level, 31.82% felt it was high and 19.89% felt it was low. The mediation analysis showed that a general sense of coherence and a sense of comprehensibility, manageability and meaningfulness have a mediator status in a correlation between global self-esteem and stress intensity. However, their mediatory role is partial. It is desirable for safe work environment promotion programmes to reinforce nurses’ personal resources, which can be helpful in coping with stressors.

Simulation of Deformation Process Failure of Jointed Rock Masses Based on the Numerical Manifold Method

On the basis of the numerical manifold method, this work introduces the concept of stress intensity factor at the crack tip in fracture mechanics and proposes the utilisation of artificial joint technology to ensure the accuracy of joint geometric dimensions in the element generation of the numerical manifold method. The contour integral method is used to solve the stress intensity factor at the joint tip, and the failure criterion and direction of crack propagation at the joint tip are determined. Element reconstruction and crack tracking are implemented in crack propagation, and a simulation programme of the entire process of deformation, failure, propagation and coalescence of jointed rock masses is developed. The rationality of the proposed method is verified by performing the typical uniaxial compression test and direct shear test.

Numerical Determination of Paris Law Constants for Carbon Steel Using a Two-Scale Model

For most engineering alloys, the long fatigue crack growth under a certain stress level can be described by the Paris law. The law provides a correlation between the fatigue crack growth rate (FCGR or da/dN), the range of stress intensity factor (ΔK), and the material constants C and m. A well-established test procedure is typically used to determine the Paris law constants C and m, considering standard specimens, notched and pre-cracked. Definition of all the details necessary to obtain feasible and comparable Paris law constants are covered by standards. However, these cost-expensive tests can be replaced by appropriate numerical calculations. In this respect, this paper deals with the numerical determination of Paris law constants for carbon steel using a two-scale model. A micro-model containing the microstructure of a material is generated using the Finite Element Method (FEM) to calculate the fatigue crack growth rate at a crack tip. The model is based on the Tanaka-Mura equation. On the other side, a macro-model serves for the calculation of the stress intensity factor. The analysis yields a relationship between the crack growth rates and the stress intensity factors for defined crack lengths which is then used to determine the Paris law constants.

Integrated modelling method of bonding strength and residual life prediction for selective repair structure of aluminium alloy

To accurately describe and predict the overall strength and residual life of selective repair bonded structures, an integrated simulation model of crack propagation including bonding strength is established. Based on two methods, an integrated simulation model including a cohesive zone method model for predicting the residual life of a selective repair structure is established. By comparing the computational efficiency and accuracy of both the stress intensity factor and residual life of selective repair structures using different calculation methods, the modelling scheme is optimised. Based on this optimised scheme, the effect of adhesive thickness on the stress intensity factor and residual life of the repair structure is analysed. FM94 adhesive measuring 0.2–0.4 mm thickness is used to decrease the stress intensity factor and improve the remaining life such that material utilisation efficiency is guaranteed.

The effect of disbond on the efficiency and durability of a composite patch repair in mode I and mixed mode considering different patch materials

In this paper, considering different parameters and various patch materials, the effect of disbond on the efficiency and durability of a composite patch repair is investigated in mode I and mixed-mode. One of the most important aspects of the composite patch repair is the bond strength. Repair patch disbond may occur at the patch edges or the crack site. At first, the effect of different parameters such as repair patch material and Young’s modulus and thickness of the adhesive on the efficiency and durability of the patch is investigated. Then, the effect of the disbond site on the stress intensity factor (patch efficiency) and adhesive stress (patch durability) is analyzed in both modes I and II. The results show that disbond at the crack site leads to a further reduction in patch efficiency compared to the patch edge disbond, but when separation occurs at the patch edge, the adhesive stress and the disbond growth rate are higher. Also, when 15% of the patch is separated in the crack site, for the longitudinal and transverse disbond modes, the mean KI is increased by 8 and 4%, respectively, compared to the state without disbond. Thus, the longitudinal disbond mode is more critical.