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Abstract: The influence of residual stresses as a result of the welding process in the overall stress state of the weld joint is of great importance because they significantly affect the creation and growth of cracks, the occurrence of brittle fracture, and material fatigue. Previous experiences indicate that it would be necessary to provide an assessment of the deformation and stress state in the critical zones of the weld joints using a suitable test method, which will not endanger the structural integrity of the tested places. There are different methods for measurement of residual stress in welded constructions: destructive, semi-destructive and non-destructive. To choose one method over another, it is necessary to take into account the advantages and limitations of these techniques for practical application. This paper considers and analyzes the residual stresses in the welded joint of high-strength steel S960QL. MAG welding was performed by a robot. Three methods were used to measure the residual stresses: the magnetic method (MAS), the X-ray diffraction method (XRD), and the hole drilling method (HD). By all three methods, the highest residual stresses were measured in the weld metal and in the heat-affected zones. Nevertheless, the measured values differed considerably. The differences can be contributed to (a) the kind of stress that the individual method measures, (b) to the volume of material from which each method captures the signal and averages it, and (c) to the different sensitivities of the applied methods to coarse-grained microstructure and microstructural gradients.
Keywords: welded joints, high-strength steel, residual stress, magnetic method, X-ray diffraction method, hole drilling method
Published in DKUM: 11.06.2025; Views: 0; Downloads: 4
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Abstract: This paper presents an experimental and numerical analysis of the mechanical behaviour of orthopaedic implants with crack-type defects, considering the principles and advantages of the modern X-FEM method, which was used due to limitations of traditional FEM in terms of crack growth simulation, especially for complex geometries. In X-FEM, the finite element space is enriched with discontinuity functions and asymptotic functions at the crack tip, which are integrated into the standard finite element approximation using the unity division property. Though rare, femoral component failures are well-documented complications that can occur after hip prosthetic implantation. Most stem fractures happen in the first third of the implant due to the loosening of the proximal stem and fixation of the distal stem, leading to bending and eventual fatigue failure. The main goal of this paper was to obtain accurate and representative models of such failures. Experimental analyses of the mechanical behaviour of implants subjected to physiological loads, according to relevant standards, using a new combined approach, including both experiments and numerical simulations was presented. The goal was to verify the numerical results and obtain a novel, effective methodology for assessing the remaining fatigue life of hip implants. For this purpose, the analysis of the influence of Paris coefficients on the total number of cycles was also considered. Hence, this simulation involved defining loads to closely mimic real-life scenarios, including a combination of activities such as ascending stairs, stumbling, and descending stairs. The tensile properties of the titanium alloy were experimentally determined, along with the Paris law coefficients C and m. The finite element software ANSYS 2022R2 version was used to develop and calculate the three-dimensional model with a crack, and the resulting stresses, stress intensity factors, and the number of cycles presented in the figures, tables, and diagrams. The results for the fatigue life of a partial hip implant subjected to various load cases indicated significant differences in behaviour, and this underscores the importance of analysing each case individually, as these loads are heavily influenced by each patient’s specific activities. It was concluded that the use of numerical methods enabled the preliminary analyses of the mechanical behaviour of implants under fatigue loading for several different load cases, and these findings can be effectively used to predict the possibility of Ti-6Al-4V implant failure under variable cyclic loads.
Keywords: structural integrity, fatigue fracture, extended finite element method (XFEM), experimental testing, DIC, numerical simulations, stress intensity factor, orthopaedic implants, crack-type defect
Published in DKUM: 21.03.2025; Views: 0; Downloads: 8
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Abstract: The objective of the research is to identify the different factors of Lebanese culture that interfere with weight loss therapy and assist the field of nutrition in homogenising in a standardised manner the protocol of Medical Nutrition Therapy (MNT). The first part of the study is based on a literature review, and, in the second part, quantitative analysis was used. The research was conducted on 514 Lebanese adults via questionnaire. The analysis was performed with the AMOS (Version 22, IBM®, Amonk, NY, USA) statistical tool. For the analysis of correlations, chi-square and non-parametric tests were used. Variables affecting weight loss management were identified with the aid of seven hypotheses using structural equation modelling (SEM). Body shape and Body Mass Index (BMI) were found to be inter-related to cognitive behaviours toward food, lifestyle practices, medical conditions, food and beverages. In parallel, and based on the research results, younger adults, in particular women, have better BMI and look better in terms of body shape. Ageing has a direct impact on weight gain. Older people have a lower activity level, which is more prevalent among women, and they also prefer to eat typical Lebanese food. Habits, such as smoking, drinking alcohol, are directly related to obesity and some medical conditions. Low physical activity influences the problems related to body shape. For further studies, one should also include types of physical activities in terms of intensity and number of hours. This would assist the study in being more specified and credible toward the effect of exercise on weight loss management.
Keywords: medical nutrition therapy, weight loss management, cost-effectiveness, anthropometry, culture, stress, physical activity
Published in DKUM: 24.01.2025; Views: 0; Downloads: 6
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Abstract: This article aims to analyse significant differences in four constructs: occupational stress, job satisfaction, work engagement, and work productivity among employees before and after the COVID-19 pandemic. The purpose of the paper is to develop a multidimensional model with these four constructs and analyse the differences in the strength of their effects on the model across two intersectional times: before the COVID-19 pandemic and during the COVID-19 pandemic. The research was implemented on a sample of 885 employees in Slovenian organisations. During COVID-19, Slovenia had one of the strictest lockdowns. Based on the research, we can confirm significant differences in the four analysed constructs among employees before COVID-19 and during COVID-19. Based on the results, we can confirm that occupational stress had a more negative effect on job satisfaction and work engagement during COVID-19 than before prior to it. Our research and conclusions highlight the measures with which organisations can reduce the problem of occupational stress and with which organisations can increase job satisfaction, work engagement and work productivity among employees during COVID-19. Based on this, organisations may be able to build a more supportive work environment during, and after, COVID-19.
Keywords: organisational sustainability, work engagement, work environment, COVID-19, stress, satisfaction, productivity, wellbeing
Published in DKUM: 06.12.2024; Views: 0; Downloads: 6
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Abstract: The organizational culture is a significant construct in a time of change during the organizational transition, and it plays an important role in achieving goals of social responsibilities, which is an important part of sustainability. The literature shows the gap of socially responsible transfer of organizational culture with the impact on employee’s well-being. The cultural changes of the organization during the transition are particularly in connection with the impact on internal communication where organizational culture presents a part of values, norms, and ethics, which influences successfully implemented changes and in such a way has an influence on the stress and work satisfaction. The main purpose of the presented study is the development of the model of socially responsible transfer of organizational culture to the foreign subsidiaries on a basis of adjusted internal communication, which reduces stress and increases work satisfaction. Impacts of organizational culture on internal communication, stress, and work satisfaction are clearly presented, as well as inter-related impacts of the constructs concerning national culture, leadership, and organizational knowledge. Thus, the new holistic model of socially responsible transfer of the parent organization culture to foreign subsidiaries clearly defines steps of organizational culture, internal communication, stress management, and work satisfaction. Managerial implications are discussed.
Keywords: organizational culture, internal communication, work stress, work satisfaction, organizational change, organizational transfer, social responsibility, sustainability
Published in DKUM: 16.09.2024; Views: 14; Downloads: 16
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