Stress Intensity
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2022 ◽  
Vol 149 ◽  
pp. 107854
Reza Masoudi Nejad ◽  
Danial Ghahremani Moghadam ◽  
Khalil Farhangdoost ◽  
Filippo Berto

2022 ◽  
Vol 9 ◽  
Xing-Chao Lin ◽  
Qiang Zhang ◽  
Jiufeng Jin ◽  
Guangming Chen ◽  
Jin-Hang Li

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.

Yashi Liao ◽  
Xuhui Zhang ◽  
Zhineng Wang ◽  
Miaolei He

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.

2021 ◽  
Vol 12 (1) ◽  
pp. 326
Axel Pössl ◽  
David Hartzke ◽  
Peggy Schlupp ◽  
Frank E. Runkel

Bioprinting with cell-laden hydrogels (bioink) requires the careful mixing of cells with the hydrogel carrier to ensure that the bioink is homogeneous and functional, and the printing results are reproducible. Bioink preparation is therefore a critical process step that must accommodate the specific rheological properties of different bioinks. Here, we developed a reproducible method for the optimized mixing of cells and hydrogel carriers that can be integrated into current bioprinting processes. First, we tested and optimized different mixing devices for their effect on bioink homogeneity and rheological properties, resulting in a low-shear process for the preparation of homogenous bioinks. Based on these findings, we evaluated the impact of different cell densities on the rheological profile of bioinks according to shear and temperature, and estimated the impact of shear stress intensity and duration on 1.1B4 cells. Finally, we integrated the optimized mixing method into a current printing process and monitored the printed construct for 14 days to confirm cell viability. We found that the cell viability in the printed cell-laden constructs remained in excess of 91% after 14 days.

Aerospace ◽  
2021 ◽  
Vol 9 (1) ◽  
pp. 17
Chenchun Chiu ◽  
Shaochen Tseng ◽  
Chingkong Chao ◽  
Jheyuan Guo

The failure analysis of a non-circular hole with an inclusion layer embedded in an infinite cracked matrix under a remote in-plane uniform load is presented. In this study, a series solution of stress functions for both the matrix and inclusion layer is obtained using the complex variable theory in conjunction with the method of conformal mapping. The stress intensity factor (SIF) can then be determined numerically by solving the singular integral equation (SIE) for the interaction among different crack sites, material properties, and geometries of irregular holes with an inclusion layer. In particular, the failure behavior of composite structures associated with an approximately triangular hole and an approximately square hole with inclusion layers, such as those of oxides, nitrides, and sulfides, is examined in detail. The results demonstrate that a softer layer would enhance the SIF and a stiffer layer would restrain the SIF when a crack is near the inclusion layer. It can be concluded that crack propagation would be suppressed by a stiffer layer even when a micro-defect such as a hole resides in the inclusion layer.

Grażyna Puto ◽  
Maria Jurzec ◽  
Anna Leja-Szpak ◽  
Joanna Bonior ◽  
Marta Muszalik ◽  

Introduction: Working during the COVID-19 pandemic is a particular challenge for nurses because, while performing their daily routines, they are exposed to physical and social consequences of the SARS-CoV-2 virus, which is accompanied by intensified stress. The aim of this study was to assess the intensity of stress and coping strategies applied by nurses working with both infected and non-infected patients with SARS-CoV-2 virus during the COVID-19 pandemic. Materials and Methods: The study was conducted between January and March 2021. Due to the epidemiological situation, the questionnaire was posted on Facebook in nurses’ groups and sent out via the “Messenger” and “WhatsApp” applications. Stress intensity was assessed by means of the Perceived Stress Scale (PSS-10), whereas coping strategies were assessed using the Mini-COPE stress coping inventory. Results: Among 151 surveyed nurses, more than half (52.3%) worked with infected patients and the remaining ones (47.7%) worked with non-infected patients. The level of stress perceived by nurses working with infected patients was higher than among nurses working with patients without SARS-CoV-2 infection (22.22 ± 5.94 vs. 20.21 ± 5.68, p = 0.03). The nurses working with infected patients were most likely to choose coping strategies focused on the problem (2.00 ± 0.62) and emotions (2.01 ± 0.69), whereas those working with non-infected patients usually chose strategies focused only on the problem (2.11 ± 0.58). Conclusions: During the COVID-19 pandemic, nurses working with SARS-CoV-2 patients experienced more intense stress than those working with non-infected patients. Nurses working with SARS-CoV-2 patients tended to cope with stress using strategies focused on the problem and on emotions, while those working with non-infected patients were more likely to choose strategies focused only on the problem.

Md Mizanur Rahman ◽  
Khalid Hasan ◽  
Wenchang Liu ◽  
Xinming Li

A new zero-equation model (ZEM) is devised with an eddy-viscosity formulation using a stress length variable which the structural ensemble dynamics (SED) theory predicts. The ZEM is distinguished by obvious physical parameters, quantifying the underlying flow domain with a universal multi-layer structure. The SED theory is also utilized to formulate an anisotropic Bradshaw stress-intensity factor, parameterized with an eddy-to-laminar viscosity ratio. Bradshaw’s structure function is employed to evaluate the kinetic energy of turbulence k and turbulent dissipation rate epsilon  . The proposed ZEM is intrinsically plausible, having a dramatic impact on the prediction of wall-bounded turbulence. 

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