The aim of this paper is to determine the critical buckling load for simply supported thin shallow spherical shells made of functionally graded material (FGM) subjected to uniform External pressure. A metal-ceramic functionally graded (FG) shell with a power law distribution for volume fraction is considered, where its properties vary gradually through the shell thickness direction from pure metal on the inner surface to pure ceramic on the outer surface. First, the total potential energy functional is obtained using the first-order shell theory of Love and Kirchhoff, Donnell-Mushtari-Vlasov kinematic equations and Hooke's Law. Then, equilibrium equations are derived through the minimization of the total potential energy functional by employing the Euler equations. The stability equations are derived by application of the adjacent-equilibrium criterion. As the nonlinear strain-displacement relations are employed, so the presented analysis is nonlinear with high accuracy. The Galerkin method is used to determine the critical buckling load. The present problem is also analyzed numerically by simulating it in Abaqus software. For validation, the present analytical results are compared with the present numerical results and with the known data in the literature. Also, the effects of some important geometrical and mechanical parameters on the hydrostatic buckling pressure are investigated.

Buckling and post buckling of cylindrical shells under hydrostatic pressure is regarded as important issue in structure of submarines. These cylindrical shells have variable thickness due to construction process which effected by pressure of buckling and its destruction. In this paper, effects of changing thickness on buckling and destruction pressure under External hydrostatic pressure of a shell are studied. Results of buckling pressure of cylindrical shell have been obtained with theoretical relations and finite element method. Then, using machining process a sample of cylindrical shell with variable thickness has been produced. Buckling pressure and post buckling of the constructed sample have been obtained with the reservoir under closed-ended hydrostatic pressure. Changes of the test sample size have been considered with closed-ended testing apparatuses which are used for new evaluation of buckling. In this research, results of the pressure have been obtained in terms of the volume change. At the end, results of the finite element method have been compared with results of the analytical solutions and experimental data. Results show that the shell with variable thickness has buckling pressure close to shell bucking pressure with mean thickness.

Grid-stiffened composite shells are one of the most important structures in many industries. These structures based on their fabrication method, provide both high strength and light structural weight. In this study, buckling analysis under External hydrostatic pressure is performed to obtain critical buckling pressure and the optimum values of parameters for stiffeners. First-order shear deformation theory (FSDT) based on the Ritz method is used to calculate the critical buckling load of these structures. The effects of shell thickness, angle of helical stiffeners, rib section area, and the stiffeners number into the buckling load are determined. Comparing the calculated buckling load for stiffened and non-stiffened structures shows that stiffeners significantly optimize structural performance. Furthermore, optimization of stiffener parameters is done by Genetic Algorithm. The results show that the introduced structure has the minimum mass. So, the stiffener parameters would be better. According to the results, the optimum dimensions for stiffener buckling load for the optimal stiffener have been increased by about 80% compared to non-stiffened.

This study focuses on investigating how grid-stiffened composite shells behave under External hydrostatic pressure. The critical buckling load is calculated using the first-order shear deformation theory (FSDT) and the Ritz method. Various factors, including shell thickness, angle of helical stiffeners, rib section area, and the number of stiffeners, are examined to understand their impact on the buckling load. To optimize the design, three multi-objective optimization algorithms are employed: Nondominated Sorting Genetic Algorithm II (NSGAII), Multiobjective Particle Swarm Optimization (MOPSO), and a hybrid method that combines NSGAII and MOPSO. The hybrid method intelligently divides the population into two groups and uses NSGAII and MOPSO to efficiently explore and exploit the solution space. The results yield a Pareto optimal front that showcases diverse solutions across different regions, providing decision-makers with the flexibility to select the solution that best fits their preferences. The solutions obtained through these algorithms are compared based on their diversity and distribution throughout the Pareto front.

Introduction: Parthenogenesis is production of offspring by a female and without genetic contribution from a male and meiotic chromosome reduction. hydrostatic pressure can act as a mechanical stimulator that rearranges egg contents, leading to new structural or molecular combinations.Alternatively, mechanical stimulation could stimulate a mechanically-gated process, such as the opening or closing of stretch-activated ion channels. Such alterations to ion channels can lead to ionic changes. In this study, we induced the parthenogenetic activation in the mouse oocyte by hydrostatic pressure.Materials and Methods: Six to 8-week-old female NMRI mice were superovulated by an injection of 10 IU of pregnant mare's serum gonadotropin (PMSG), followed 48 hr later by an injection of 10IU of human chorionic gonadotropin (hCG) 48-52 hours apart. Metaphase II oocytes were collected from oviducts 15-18 hours after hCG injection. The oocytes transferred to T6 medium and divided into treatments. There were four treatments; oocytes subjected to 20 mmHg hydrostatic pressure in pressure chamber for 10, 20 and 30 min were treatments I, II, III, respectively. Oocytes without pressure exposure considered as treatment IV. Oocytes from all treatments were cultured for 72 hr and embryo development was assessed.Results: Our results showed that, the best cleavage rates were better. After 24h, the highest cleavage rates was associated with treatment II (21.4%) which were significantly different with treatments I, III and IV (10.7, 6.5 and 4.33%) respectively, (p<0.05). After 48 hr, the cleavage rates was highest in treatment II (43%) compared to treatments I, III and IV (16, 16.9 and 10.26 %) respectively, (p<0.05). After 72 hr, the cleavage rates increased in treatment II (52.79) in comparison with 48 hr (p<0.05). It was constant in treatments I, III and IV.Conclusion: It is concluded that partenogenetic activation can be induced by hydrostatic pressure in a time and dose manner in mouse oocytes.