Static analysis of rectangular nanoplates using trigonometric shear deformation theory based on nonlocal elasticity theory

In this article, a new higher order shear deformation theory based on trigonometric shear deformation theory is developed. In order to consider the size effects, the nonlocal elasticity theory is used. An analytical method is adopted to solve the governing equations for static analysis of simply supported nanoplates. In the present theory, the transverse shear stresses satisfy the traction free boundary conditions of the rectangular plates and these stresses can be calculated from the constitutive equations. The effects of different parameters such as nonlocal parameter and aspect ratio are investigated on both nondimensional deflections and deflection ratios. It may be important to mention that the present formulations are general and can be used for isotropic, orthotropic and anisotropic nanoplates

Three Dimentional Finite Element Simulation of Welding of a Thick Plate Flange by Using Anand Viscoplastic Model

Common and important problems associated with the welding of large structures are induced distortion and residual stresses, both difficult to simulate accurately given the intensive computational demands of such severely nonlinear processes. In this paper, temperature distribution and variation of stresses and deformations in welding of a thick plate flange have been evaluated by using a three dimensional (3D) model. For modeling of molten puddle motion (speed of welding) in numerical model, birth and dead element method have been employed. By using 3D nonlinear-transient-heat flow finite element analysis, temperature distribution versus time, during welding and after cooling, is obtained. Then by applying these results and viscoplastic condition (Anand viscoplastic model), stress distribution during welding and residual stresses and final deformations are determined

Global Buckling Investigation in Welding of a Thin Wall Aluminum T Joint

In this paper global welding buckling distortion of a thin wall aluminum T joint is investigated. A thermo-elastoplastic model is employed to determine longitudinal residual stresses; analysis of thermal model and elastic-viscoplastic (Anand) model are decoupled. Molten puddle motion (speed of welding) is modeled by using birth and death element method and time dependent model. Three dimensional nonlinear-transient heat flow analysis has been used to obtain temperature distribution, and then by applying thermal results and using three dimensional Anand elastic-viscoplastic model, stress and deformation distributions are obtained. By applying residual stresses on a structural model and using eigenvalue methods, global buckling instability of the welded structure is determined

Prediction of Welding Buckling Distortion in a Thin Wall Aluminum T Joint

In this paper, local and global welding buckling distortion of a thin wall aluminum T joint is investigated. A thermo-elastic-viscoplastic model is employed to determine longitudinal residual stresses; analysis of thermal model and elastic-viscoplastic (Anand) model are uncoupled. Molten puddle motion (speed of welding) is modeled by using time dependent birth and death element method. Three dimensional nonlinear-transient heat flow analysis has been used to obtain the temperature distribution, and then by applying thermal results and using three dimensional Anand elastic-viscoplastic model, stress and deformation distributions are obtained during welding and after cooling. Local buckling is investigated by analyzing the history of stress and strain relations. Local buckling is assumed to occur at a point if a small change in the magnitude of stress causes large deformation during of the welding process. By applying residual stresses on a structural model and using eigenvalue methods, global buckling instability of the welded structure is determined

Investigation of Global Buckling Distortion in Welding of a Thin Wall Aluminum T Joint

In this paper global welding buckling distortion of a thin wall aluminum T joint is investigated. A thermo-elastoplastic model is employed to determine longitudinal residual stresses; analysis of thermal model and elastic-viscoplastic (Anand) model are decoupled. Molten puddle motion (speed of welding) is modeled by using birth and death element method and time dependent model. Three dimensional nonlinear-transient heat flow analysis has been used to obtain temperature distribution, and then by applying thermal results and using three dimensional Anand elastic-viscoplastic model, stress and deformation distributions are obtained. By applying residual stresses on a structural model and using eigenvalue methods, global buckling instability of the welded structure is determined. Some experiments are done for validating the numerical results

SARS-CoV-2 vaccination modelling for safe surgery to save lives: data from an international prospective cohort study

Background: Preoperative SARS-CoV-2 vaccination could support safer elective surgery. Vaccine numbers are limited so this study aimed to inform their prioritization by modelling. Methods: The primary outcome was the number needed to vaccinate (NNV) to prevent one COVID-19-related death in 1 year. NNVs were based on postoperative SARS-CoV-2 rates and mortality in an international cohort study (surgical patients), and community SARS-CoV-2 incidence and case fatality data (general population). NNV estimates were stratified by age (18-49, 50-69, 70 or more years) and type of surgery. Best- and worst-case scenarios were used to describe uncertainty. Results: NNVs were more favourable in surgical patients than the general population. The most favourable NNVs were in patients aged 70 years or more needing cancer surgery (351; best case 196, worst case 816) or non-cancer surgery (733; best case 407, worst case 1664). Both exceeded the NNV in the general population (1840; best case 1196, worst case 3066). NNVs for surgical patients remained favourable at a range of SARS-CoV-2 incidence rates in sensitivity analysis modelling. Globally, prioritizing preoperative vaccination of patients needing elective surgery ahead of the general population could prevent an additional 58 687 (best case 115 007, worst case 20 177) COVID-19-related deaths in 1 year. Conclusion: As global roll out of SARS-CoV-2 vaccination proceeds, patients needing elective surgery should be prioritized ahead of the general population