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To obtain qualitative and quantitative indicators of changes in the stress-strain state of the nodes of steel bar structures, we identified four characteristic types of nodes. On the basis of modeling in the "Lira-CAD" software package, we analyzed the stress-strain state of four types of nodes for steel trusses with a symmetric and asymmetric design solution. For the research, a calculation of volumetric models of nodes according to the fourth strength theory was performed. At the current moment, the choice of the required thickness of the truss gusset is performed according to the value of the maximum force in the rods. During the nodes modeling it was found that the safety factors depending on the node type for the symmetrical design solution are more than 40 %. The obtained data allow us to reduce the thickness of the gusset taking into account design constraints. It was found that the safety factors depending on the node type for the asymmetric design solution are 7–90 %. The simulation results substantiated the possibility of reducing the gusset thickness for node type 3, and for node types 1, 2 and 4, they showed the necessity of increasing the thickness taking into account design constraints. We derived the refined dependences between the gusset thickness and the maximum force in the attached rods for each structural type of nodes. Based on results of the analysis, we developed recommendations for calculating the most typical types of nodes and presented them in the form of tables and dependencies. For a constructive solution of fastening of gusset braces at an acute angle, we analyzed the influence of the eccentricity value on the stress in gussets. We determined that the main parameter influencing to the stress-strain state of the gusset is the displacement of attached element relative to the axis of the elements fastening. We derived dependences and made graphs of the displacement influence on stresses for different values of gusset thickness.

This research provides a thorough examination of ball bearings from various brands, with a specific focus on 6207 type bearings, using ANSYS simulation software. The bearings under study are sourced from five different brands: KOYO, NSK, Nachi, NTN, and SKF. The study includes a series of tests, with a primary emphasis on assessing static stress when subjected to a 1000 MPa pressure load. Key parameters evaluated in these tests encompass total deformation, equivalent stress, bearing life, and safety factor. The findings from the analyses reveal significant differences among the tested bearings. Notably, KOYO brand bearings demonstrate superior performance compared to their counterparts, characterized by reduced levels of deformation and stress. However, it's important to acknowledge that each brand of bearings possesses distinctive characteristics, comprising both strengths and weaknesses, contingent upon the specific application context. In conclusion, this study underscores the critical importance of thorough testing and analysis in the process of selecting bearings tailored to precise operational requirements. The research highlights the exceptional performance of KOYO bearings under the examined conditions, while also emphasizing the necessity for a nuanced decision making process that takes into account diverse user preferences and varied application demands. [ABSTRACT FROM AUTHOR]

Copyright of Lubrication Engineering (0254-0150) is the property of Editorial Office of LUBRICATION ENGINEERING and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Manny disc brake are produced at conventional machinery workshop. But, the optimum value of disc brake based on heat dissipation, and the safety is unknown. One of the causes of vehicle accidents is the vehicle factor (brake failure). Prolonged and continuous braking on the disc brake can result in fadding. Continuous stress generation can decrease fatigue life. The required material and the right number of holes are needed to solve this problem. The Purpose of this research is to get the optimum temperature and stress value. In this study, simulations were carried out with CAE software on disc brakes with materials Al 7075- T6, SS 304, gray cast iron and the number of ventilation holes 36, 48, 60. The results show that the disc brake with Al 7075-T6 material and 60 ventilaton holes has the best heat dissipation with 38,005ᴼC temperature value. Material gray cast iron with number of ventilation holes 48 produces the lower equivalent stress with 89,272 Mpa. From the research it can be concluded, disc brake with higher density,has higher temperature too. The greater tensile strength of disc brake material, resulting the lower equivalent stress. The gray cast iron material and the number of ventilation holes 48 is the most optimal in temperature absorption, the longest fatigue life, and the highest fatigue safety factor, with a temperature value of 54.99ᴼC, a fatigue life of 100000000 cycles, and an FOS of 3.34.The more number of ventilation holes, has the lower of temperature result but the higher stress concentration.

Hydropower plant can be expected gradually undertake the task of peak shaving and frequency modulation in the power grid, in order to reduce the impact from the renewable energy, such as the solar, and wind energy. In the switch operating conditions of hydraulic turbines, it is a high demand to fully meet the grid requirements during power generation. Consequently, the turbine can be required to work at the off-design conditions, particularly with the high operation stability. This study aims to explore the flow and structure characteristics of Francis turbine under different conditions (0.35Qr, Qr, and 1.09Qr). The turbulence model of SST k-ω was used to solve the internal fluid, whereas the method of fluid-solid coupling was adopted in the structure field. There was the deviation between the relative velocity direction angle of flow and the inlet angle of blade at the off-design points, where the maximum eddy viscosity at 0.35Qr and 1.09Qr were 3.97 and 2.23 times of Qr, respectively. Some parameters were analyzed quantitatively, including the velocity, pressure, eddy viscosity, equivalent stress, and deformation extent. The results show that both Smax and dmax increased with the increasement of load. The large values of Smax appeared at the outlet edge of blade, which was close to the upper crown, whereas the dmax appeared in the middle region of blade outlet edge, under all three conditions. The axial vortex generated by the impact flow at the runner inlet was the main reason for the increment of eddy viscosity, equivalent stress, and deformation extent under off-design conditions, wherein the Smax at Qr is larger than that of 0.35 Qr and smaller than 1.09 Qr, respectively. Stress concentration occurred at the connection area between the blades and the crown, due to the strong constraint at the connection position, where deformation extent was small. However, the dmax appeared at the center position of blades that caused by the strong constraint of upper crown, In addition, the combination of theoretical analysis and numerical simulation was applied to investigate the runner performance, with the different manufacturing materials. The results illustrated that the frequency of Q345 runner at the wet modal shared the highest decrease rate. Among them, the maximum decreasing ratio was 24.5%, which frequency drop rate is bigger than that of ZG00Cr13Ni5Mo. Thus, the fluid damping effect should be fully considered, when using Q345, but Q345 was lighter form the aspect of weight. The critical speed of each material runner was much higher than the working speed of turbine. There was no resonance during this time. The critical speed of ZG00Cr13Ni5Mo runner was the lowest. The runner presented the strongest ability of deformation resistance, when it was made of Q345 and 1Cr18Ni9Ti materials. Therefore, the Q345 was more suitable for the runner manufacture. Moreover, there were the similar developments of static characteristics on the equivalent stress and deformation extent for runners with different materials. Furthermore, all runners with different materials showed the similar vibration modes. Hence, each material can be extended to the other common materials. This finding can provide some reference and guidance for the design and operation of hydraulic turbine. [ABSTRACT FROM AUTHOR]

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This study explores a super-fast magnetic abrasive finishing (MAF) process for polishing the surface of an Inconel 625 bar workpiece for a hydrogen solenoid valve stem. The Inconel 625 bar was chosen to replace the existing STS 316 bar material, previously used for a hydrogen solenoid valve stem. The cylindrical surface of Inconel 625 bars was polished by a super-fast MAF process with high rotational speeds of 1000, 5000, 15,000, and 25,000 RPM and a super-strong magnetic field of 550 mT. The polishing characteristics of this process were evaluated according to the type of abrasives, rotational speeds of the workpiece and processing time. As a result, a super-smooth Inconel 625 bar was successfully achieved, with a surface roughness (Ra) reduced from 0.31 μm to 0.02 μm under the optimal conditions (15,000 RPM, CNT particles (0.04 μm), PCD diamond abrasive (1 μm), Fe (#200), 0.5 g of light oil, and 16 min of processing time). Also, the Ansys analysis results showed suitable strain, equivalent stress, and safety factor of the Inconel 625 bar. This confirmed that, after a super-fast MAF process, an Inconel 625 bar is feasible for application in Hydrogen (H2) tanks instead of a conventional STS 316 bar.

The behavior of composite materials under tensile and bending loading differs, and material designs optimized for tensile loading may not be suitable for applications subjected to bending loading. In this study, the bending behavior of two different composite materials, namely glass and carbon fiber-reinforced composites, was analyzed under a three-point bending load. The output from the analysis of these two materials was compared, revealing that, in addition to longitudinal direction strength, transverse and through-thickness directional strength, as well as shear strength in all planes of the composite, are essential to minimize deformations, normal stress, and shear stress. In the study, under the same loading and boundary conditions, the carbon epoxy composite exhibited 84% more deformation than the FR-4 composite at the maximum load considered for the study. Furthermore, the strength of the FR-4 composite in the loading direction was 2.4 times greater than that of the carbon epoxy composite. The present work is used for the effective design of the composite material under bending loading.

Abstract Background The objective is to clarify the effect of alveolar cleft bone graft on maxillofacial biomechanical stabilities, the key areas when bone grafting and in which should be supplemented with bone graft once bone resorption occurred in UCCLP (unilateral complete cleft lip and palate). Methods Maxillofacial CAD (computer aided design) models of non-bone graft and full maxilla cleft, full alveolar cleft bone graft, bone graft in other sites of the alveolar cleft were acquired by processing the UCCLP maxillofacial CT data in three-dimensional modeling software. The maxillofacial bone EQV (equivalent) stresses and bone suture EQV strains under occlusal states were obtained in the finite element analysis software. Results Under corresponding occlusal states, the EQV stresses of maxilla, pterygoid process of sphenoid bone on the corresponding side and anterior alveolar arch on the non-cleft side were higher than other maxillofacial bones, the EQV strains of nasomaxillary, zygomaticomaxillary and pterygomaxillary suture on the corresponding side were higher than other maxillofacial bone sutures. The mean EQV strains of nasal raphe, the maximum EQV stresses of posterior alveolar arch on the non-cleft side, the mean and maximum EQV strains of nasomaxillary suture on the non-cleft side in full alveolar cleft bone graft model were all significantly lower than those in non-bone graft model. The mean EQV stresses of bilateral anterior alveolar arches, the maximum EQV stresses of maxilla and its alveolar arch on the cleft side in the model with bone graft in lower 1/3 of the alveolar cleft were significantly higher than those in full alveolar cleft bone graft model. Conclusions For UCCLP, bilateral maxillae, pterygoid processes of sphenoid bones and bilateral nasomaxillary, zygomaticomaxillary, pterygomaxillary sutures, anterior alveolar arch on the non-cleft side are the main occlusal load-bearing structures before and after alveolar cleft bone graft. Alveolar cleft bone graft mainly affects biomechanical stabilities of nasal raphe and posterior alveolar arch, nasomaxillary suture on the non-cleft side. The areas near nasal floor and in the middle of the alveolar cleft are the key sites when bone grafting, and should be supplemented with bone graft when the bone resorbed in these areas.

Based on the wind turbine data provided by the American National Renewable Energy Laboratory (NREL), the manuscript was used ProE to establish a 5 MW offshore semi-submersible wind turbine model. A two-way fluid-structure coupling simulation through simulation software was conducted. The research was based on the deformation and equivalent stress of the two-way fluid-structure coupling semi-submersible wind turbine blade during the coupling action. The shutdown state of the wind turbine and the operation of the wind turbine under different wind and wave conditions were analyzed. The analysis shows that the blade is the most important part of the wind turbine. As the speed of impeller increases, the deformation increases, and the peak value shifts to the left. The maximum equivalent stress of the wind wheel appears in the initial stage of operation. As time goes by, the stress finally stabilizes within a certain range. The degree of deformation of the blade increases with the increase of wind speed. During the operation of the wind turbine, the mooring line moves periodically with the float foundation. This research provides a reference for the safe and stable operation of offshore semi-submersible wind turbines, and at the same time provides a reference for the design of offshore semi-submersible wind turbines.

Jacketed pressure vessels are pressure vessels used for either heating or cooling the vessel. This type of pressure vessel is subjected to several loads under its operating conditions which generates maximum stress at the jacket closure. The maximum stress at the jacket closure affects the performance and life cycle of the jacketed vessel. The present study aims to optimize the jacket closure design to which minimum or a considerable amount of equivalent stress is generated. The numerical model of jacket closure was developed in Ansys Workbench in order to optimize the design of jacket closure. The Taguchi method with orthogonal L27 array is adopted to experimentally analyze the effect of jacket closure thickness, closure angle, and closure radius. S/N ratio smaller-the-better is used to study the influence of these parameters on maximum equivalent stress-induced and to get the optimum design parameter set for jacket closure. ANOVA is used to find the parameter which affects the equivalent stress significantly. The prediction model of the maximum stress induced at the jacket closure has been developed and validated with the virtual experiments of stress analysis. The current study provides the pressure vessel industry a prediction model for the accurate selection of jacket closure design parameters without the need for trial experiments with various jacket closure materials. It was observed that jacket closure thickness has the maximum influence on the stress induced followed by jacket closure angle. However, inner closure radius has very less influence on the stress generated at the jacket closure. [ABSTRACT FROM AUTHOR]

Copyright of Water Conservancy Science & Techonlogy & Economy is the property of Water Conservancy Science & Technology & Economy Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The current research is focused on the design and development of auxetic woven structures. Finite element analysis based on computational modeling and prediction of axial strain as well as Poisson’s ratio was carried out. Further, an analytical model was used to calculate the same parameters by a foldable zig-zag geometry. In the analytical model, Poisson’s ratio is based on the crimp percentage, bending modulus, yarn spacing, and coefficient of friction. In this yarn, properties and fabric parameters were also considered. Experimental samples were evaluated for the actual performance of the defined auxetic material. Auxetic fabric was developed with foldable strips created in a zig-zag way in the vertical (warp) direction. It is based on the principle that when the fabric is stretched, the unfolding of the folds takes place, leading to an increase in transverse dimensions. Both the analytical and computational models gave close predictions to the experimental results. The fabric with foldable strips created in a zig-zag way in the vertical (warp) direction produced negative Poisson’s ratio (NPR), up to 8.7% of axial strain, and a maximum Poisson’s ratio of −0.41 produced at an axial strain of around 1%. The error percentage in the analytical model was 37.14% for the experimental results. The computational results also predict the Poisson’s ratio with an error percentage of 22.26%. Such predictions are useful for estimating the performance of auxetic woven structures in composite reinforcement. The auxetic structure exhibits remarkable stress-strain behavior in the longitudinal as well as transverse directions. This performance is useful for energy absorption in composite reinforcement.

Fourteen-gauge solar PV mounting structure installations represent 60% of total solar PV installations in Pakistan. At least 34 (1.72%) structures were damaged on 13 June 2021 with an average 56 km/h wind speed on that day. Therefore, a need arose for a thorough analysis of the 14-gauge solar PV mounting structure. Computational analysis was carried out for 14-gauge solar PV mounting structures. The equivalent stress and total deformation in the structure were calculated computationally. Using computational analysis, it was found that 14-gauge solar PV mounting structures deformed at an 80 km/h wind velocity and broke at a 110 km/h wind velocity. Hence, 14-gauge solar PV mounting structures do not fulfil the building code of Pakistan.

This paper investigated the stress distribution of an adhesive layer for GFRP–steel bonded joints under 22.48 kN tensile loading using a three-dimensional numerical simulation. Firstly, a stress analysis of three paths was conducted, and after comparison, path II (through the middle layer of the bonding layer) was adopted as the analyzing path. Furthermore, a systemically parametric study of the effects of the FRP stiffness (i.e., elastic modulus and thickness), bonding length, adhesive thickness, and adhesive modulus was conducted. For the joints with different FRP elastic moduli, the minimum value of normal peeling stress was calculated as −3.80 MPa by the FRP for 10 GPa, showing a significantly severe stress concentration of FRP for 10 GPa. An analysis of the von Mises stresses proved that the increase in FRP stiffness could reduce the stress concentration of the adhesive layer effectively. The study of the effect of bonding lengths indicated that a more uniform peeling stress distribution could result from the longest bonding size; the largest peeling stress of 6.54 MPa was calculated for a bonding length of 30 mm. Further parameter analysis showed that the stress concentration of the adhesive layer could be influenced by the FRP thickness, bonding thickness, and elastic modulus of the adhesive layer. [ABSTRACT FROM AUTHOR]

Objective: This study intended to ascertain the dimensional effects of labial bone thickness and height on the mechanobiological stimuli distribution of maxillary anterior labial bone through biomechanical analysis. Material and methods: Twelve 3D finite element models of an anterior maxillary region with an implant were computer‐simulated, including four levels of labial bone thicknesses (2, 1.5, 1.0, and 0.5 mm) and three levels of labial bone heights (normal, reduced by 1/3, reduced by 1/2). A 45° buccolingual oblique load of 100 N was applied to the implant restoration. Results: Equivalent stress and principal strain mainly concentrated on crestal bone around the implant neck. The maximum equivalent stress in bone decreased as labial bone mass decreased, while the maximum principal strain and the displacement of dental implant increased as labial bone mass decreased. No significant difference of these three indicators was observed, when the labial bone thickness changed in the range of 2.0–1.0 mm with sufficient labial bone height. Conclusions: In terms of biomechanics, the thickness of labial bone plate was recommended ≥1 mm. Sufficient labial bone height was warranted to prevent the stability of the implants from being seriously affected. The labial bone heights were more effective than thicknesses on the mechanobiological stimuli response of the dental implant‐bone system. Clinical significance: For this 3D finite element study, the biomechanical responses under different bone mass conditions were explored, in order to predict the process of bone remodeling and provide valid clinical recommendations for the decision‐making process regarding the choices of tissue augmentation for some specific esthetic implantation cases for future clinical applications. [ABSTRACT FROM AUTHOR]

In recent years, the use of unmanned aerial vehicles (UAVs) has increased significantly. Asymmetrical factors, or frictional studies on the disc brake of UAVs, are one of the safety considerations taken into consideration during the design process because UAVs and their components have been built with the best safety in mind. This study focuses on choosing the optimal material for a UAV's disc brake by using transient structural and thermal models. In order to compare the asymmetry-based frictional force produced by the two ways; the processes used in the transient simulation are validated using pin-on-disc (POD) testing. The foundation for this validation investigation is a metal matrix composite made of an aluminum alloy, and the basis tool is an ASTM G99-based computational test specimen. Steel-EN24 and carbon ceramic matrix composites testing are expanded using the same POD tests. A range of 3 percent to 8 percent error rates is found. As a result, the calculation techniques are applied to the UAV's disc brake after they have proven to be trustworthy. This fixed-wing UAV's extensions have a 5 kg payload capacity. The weight, avionics components, tire dimensions, and disc brake dimensions of the other UAV design parts are calculated using analytical formulas. The final designs are made using CATIA as a result. The grid convergence experiment is organized using a traditional finite element analysis tool. Finally, at its maximum rotational speed, a UAV's disc brake is put through asymmetrical friction testing based on structural and thermal consequences. The correct materials for critical applications, such as carbon fiber-woven-wet-based reinforced polymer and Kevlar unidirectional-49-based reinforced polymer composites for changing rotating speeds, have now been made possible by fixed-wing UAVs. [ABSTRACT FROM AUTHOR]

Simufact Forming covers the complete spectrum of working on forming technologies like rolling, forging, and sheet metal forming. In this paper, finite element comparative analysis was performed on two chromium- and molybdenum-alloyed steel billets, namely 42CrMo4 and 16CrMo4 alloyed steels, using multi-step forming process of hot closed die forging process using Simufact Forming software. 42CrMo4 alloy steel is most commonly used in making of automobile components, and 16CrMo4 alloyed steels are commonly utilised in the area of ship building, airplanes, etc. While working with these materials, with the help of forging process, lot of stresses, strains and temperatures will develop. In this paper, three state variables, namely effective plastic strain, equivalent stress and temperature, for two materials at the end of multi-step forming processes like chamfering, preforming and final forging stages are evaluated and compared. In cooling process, the initial temperature of billet is maintained at 1250°C for both materials. Finally, comparative analysis of two alloyed steel billets was done by considering three-state variables. [ABSTRACT FROM AUTHOR]

The fluctuating wind pressure generated when a high-speed train passes through the noise barrier will cause deformation and damage to the noise barrier, affecting the safety of train operation and causing serious economic losses. In this paper, a research method for the dynamic response of noise barriers is proposed, and a comparative study of vertical noise barriers and semi-enclosed noise barriers is carried out. The study shows that when trains pass through the noise barrier, the fluctuating wind pressure on the surface of the two different types of noise barriers both exhibit the characteristics of head and tail waves; the time course curve of fluctuating wind pressure has the same change rule, the wind pressure reaches the maximum value at the bottom measuring point, the maximum value of fluctuating wind positive pressure and negative pressure of the semi-closed noise barrier is larger than that of the vertical noise barrier. In terms of natural frequency, the natural frequency range of the vertical noise barrier is 16~85 Hz, and the natural frequency range of the semi-enclosed noise barrier is 3~13 Hz. The natural frequency of the semi-enclosed noise barrier partially coincides with the main frequency of fluctuating wind pressure, which may lead to resonance damage. When the train speed is raised from 200 km/h to 350 km/h, the maximum equivalent force of the semi-enclosed noise barrier reaches 17.21 Mpa, which is much larger than the maximum equivalent force of the vertical noise barrier. At the same time, the displacement of the two noise barriers increases with the height of the noise barrier, and the maximum displacement of the semi-closed noise barrier unit board reaches 3.63 mm, which is much larger than that of the vertical noise barrier unit board. [ABSTRACT FROM AUTHOR]

• This paper intends to adopt the method of setting temperature gradient to analyze the influence of temperature on its dynamic characteristics. • This paper takes CAP1400 RCP as the research object to carry out effective dynamic characteristics analysis of the RCP impeller. • The presence of water environment and the increase of temperature will reduce the modal frequency of the RCP. Because the dynamic characteristics of the reactor coolant pump (RCP) impeller working in high temperature and high pressure environment are difficult to determine, this paper analyzes the dynamic characteristics of the RCP impeller under different temperatures, in order to explore the correlation between its dynamic characteristics and temperature. In this paper, CAP1400 RCP is taken as the research object. Firstly, the rationality of the method is verified by normal temperature test. Then, the pressure pulsation of RCP without temperature is analyzed, and the correlation law between pressure pulsation and temperature is summarized. Based on the fluid-thermal-solid coupling, the rotor prestress mode and the dynamic stress of the impeller are studied respectively. The results show that the natural frequency of the structure will decrease with the increase of temperature. The Campbell diagram proves that the structure will not have resonance caused by the operation of the structure. The increase of temperature will also lead to the decrease of dynamic stress of the impeller, and the change law of dynamic stress and temperature is found. [ABSTRACT FROM AUTHOR]

In this paper, the stress and the local liquid residue of the diaphragm plug valve were simulated. Simulation of the diaphragm plug valve opening process was performed by using a bidirectional fluid-structure interaction based on dynamic mesh technique. The pressure and velocity distribution of the internal flow were obtained with boundary conditions for the fluid–structure interaction during the opening process. The finite element method was used to compare the equivalent stress with FSI method. The results indicate that mechanical tensile stress plays a prominent role in determining the equivalent stress of the diaphragm, with the highest stress concentration occurring in the root region. The electrolyte flow in the valve tends to be stable when reaching an opening degree of 56.6 %. Crystallization accumulation will occur due to the existence of vortices in the flow field around the diaphragm which affects the fluidity of the fluid, this area needs to be focused on. • Simulation of the diaphragm plug valve opening process was performed by using a bidirectional fluid-structure interaction based on dynamic mesh technique. • The finite element method was used to compare the equivalent stress with FSI method. It's found that mechanical tensile stress plays a prominent role in determining the equivalent stress of the diaphragm. [ABSTRACT FROM AUTHOR]

In the conventional gas seal analysis of special threaded joints, the influence of temperature stress caused by the difference between formation temperature and fluid temperature in casing is often neglected. However, the influence mechanism of temperature stress is prerequisite information for accurately predicting the safe operating conditions that prevent a premium connection from being damaged. In this paper, we propose a model that includes these effects to predict the safe operating pressures and temperatures that will prevent seal failure. For the temperature stress, we propose a finite element model of thermal solid coupling. Subsequent stress changes are evaluated by a fully coupled model of thermal solid coupling to analyze the mechanical behavior of the premium connection. We predict the safe operating envelope (SOE) for premium connection failures caused by pressure and temperature perturbations after make-up. Our model predicts that radial pressure is a key factor for connection failure, especially for rapid temperature changes. If the formation temperature is high and the casing fluid temperature is low, the influence of temperature stress will increase under this working condition, resulting in an increase in the probability of failure of premium connections. Compared with conventional premium connection models, the model of thermal solid coupling predicts a smaller SOE when heating the internal casing fluid and a larger envelope when cooling the internal casing fluid. Finally, the heating rate was considered with respect to field applications. The heating rate was also considered, and slower heating/cooling rates can prevent damage to the seal integrity. Finally, the model was applied to explain several laboratory and field experiments and achieved good matches. [ABSTRACT FROM AUTHOR]

Background: Pubic nonunion after curved periacetabular osteotomy (CPO) reportedly occurs in 1%-17% of patients and causes pubic pain in 21%. Furthermore, pubic nonunion is associated with a risk of ischial ramus stress fracture, but the mechanical influence of pubic nonunion has not been fully clarified.Methods: Patient-specific finite element (FE) analysis was performed using Mechanical Finder software. Three FE models (pre-CPO, union, and nonunion models) were constructed from preoperative and postoperative computed tomographic data. The contact area (mm2) and contact pressure (MPa) in the hip joint as well as the equivalent stress (MPa) at the ischial ramus were evaluated among the 3 FE models.Results: Patient-specific FE models were generated using 18 consecutive hips treated with CPO. The mean contact pressure in the hip joint was not significantly different between the union and nonunion models (0.50 ± 0.10 vs 0.50 ± 0.09 MPa, P = .88). However, the mean equivalent stress at the ischial ramus in the nonunion models was 1.7 times higher than that in the union models (1.13 ± 0.77 vs 0.64 ± 0.45 MPa, P < .01).Conclusion: FE analysis revealed that pubic nonunion did not affect the mechanical distribution in the hip joint itself but increased the mean equivalent stress at the ischial ramus. This finding suggests the importance of achieving pubic union after CPO to avoid the risk of ischial ramus stress fracture. [ABSTRACT FROM AUTHOR]

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Introduction. Cylindrical and spherical shells are extensively used in engineering. They face internal and/or external pressure and heat. Stresses and strains distribution in elastoplastic shells has been studied by many scientists. Numerous works involve the use of the von Mises yield conditions, maximum shear stress, maximum reduced stress. These condi- tions do not include the dependence on the first invariant of the stress tensor and the sign of the third invariant of the stress deviator. In some cases, it is possible to obtain numerical-analytical solutions for stresses, displacements and de- formations for bodies with spherical and cylindrical symmetry under axisymmetric thermal and force action.Materials and Methods. The problem on the state of a thick-walled elastoplastic shell is solved within the framework of the theory of small deformations. A plasticity condition is proposed, which takes into account the dependence of the stress tensor on three independent invariants, and also considers the sign of the third invariant of the stress deviator and translational hardening of the material. A disconnected thermoelastoplastic problem is being solved. To estimate the stresses in the region of the elastic state of a spherical shell, an equivalent stress is introduced, which is similar to the selected plasticity function. The construction of the stress vector hodograph is used as a method for verification of the stress state.Results. The problem has an analytical solution for linear plasticity functions. A solution is obtained when the strength- ening of the material is taken into account. Analytical and graphical relationships between the parameters of external action for the elastic or elastoplastic states of the sphere are determined. For a combined load, variants are possible when the plastic region is generated at the inner and outer boundaries of the sphere or between these boundaries.Discussion and Conclusions. The calculation results have shown that taking into account the plastic compressibility and the dependence of the plastic limit on temperature can have a significant impact on the stress and strain state of a hollow sphere. In this case, taking into account the first invariant of the stress tensor under the plasticity condition leads to the fact that not only the pressure drop between the outer and inner boundaries of the spherical shell, but the pressure values at these boundaries, can vary within a limited range. In this formulation of the problem, when there is only thermal action, the hollow sphere does not completely pass into the plastic state. The research results provide predicting the behavior of an object (a hollow sphere) that experiences centrally symmetric distributed power and thermal external influences.

Background: The objective is to clarify the effect of alveolar cleft bone graft on maxillofacial biomechanical stabilities, the key areas when bone grafting and in which should be supplemented with bone graft once bone resorption occurred in UCCLP (unilateral complete cleft lip and palate).Methods: Maxillofacial CAD (computer aided design) models of non-bone graft and full maxilla cleft, full alveolar cleft bone graft, bone graft in other sites of the alveolar cleft were acquired by processing the UCCLP maxillofacial CT data in three-dimensional modeling software. The maxillofacial bone EQV (equivalent) stresses and bone suture EQV strains under occlusal states were obtained in the finite element analysis software.Results: Under corresponding occlusal states, the EQV stresses of maxilla, pterygoid process of sphenoid bone on the corresponding side and anterior alveolar arch on the non-cleft side were higher than other maxillofacial bones, the EQV strains of nasomaxillary, zygomaticomaxillary and pterygomaxillary suture on the corresponding side were higher than other maxillofacial bone sutures. The mean EQV strains of nasal raphe, the maximum EQV stresses of posterior alveolar arch on the non-cleft side, the mean and maximum EQV strains of nasomaxillary suture on the non-cleft side in full alveolar cleft bone graft model were all significantly lower than those in non-bone graft model. The mean EQV stresses of bilateral anterior alveolar arches, the maximum EQV stresses of maxilla and its alveolar arch on the cleft side in the model with bone graft in lower 1/3 of the alveolar cleft were significantly higher than those in full alveolar cleft bone graft model.Conclusions: For UCCLP, bilateral maxillae, pterygoid processes of sphenoid bones and bilateral nasomaxillary, zygomaticomaxillary, pterygomaxillary sutures, anterior alveolar arch on the non-cleft side are the main occlusal load-bearing structures before and after alveolar cleft bone graft. Alveolar cleft bone graft mainly affects biomechanical stabilities of nasal raphe and posterior alveolar arch, nasomaxillary suture on the non-cleft side. The areas near nasal floor and in the middle of the alveolar cleft are the key sites when bone grafting, and should be supplemented with bone graft when the bone resorbed in these areas. [ABSTRACT FROM AUTHOR]

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Tubular turbines have been widely used to develop low-head hydraulic resources and tidal energy, due to their compact structure, straight flow channels, large flow capacity, and high hydraulic efficiency. However, the hydraulic vibration, fatigue damage and cracks of overflow components inevitably occur in actual operation, particularly for the low number of runner blades, the large blade area, and simple structural support. Previous studies are focused mainly on the hydraulic design and performance evaluation of tubular turbines for the prototypes using experiments or numerical simulation. Less reports remain on the free-surface fluctuations in the reservoir and the influence of water gravity on the performance of the turbine. It is a high demand to accurately reveal the internal flow state of tubular turbines for the direct causes of blade vibration and fatigue damage. Taking the tubular turbine (including the upstream and downstream reservoir areas) as the research object, a numerical simulation was performed on the internal-flow performance in a prototype machine considering the free surface and water gravity. The one-way fluid-structure coupling calculation was implemented for the stress-strain analysis of the runner blade under different operating conditions, in order to reveal the distribution along the circumferential direction during the rotation of the runner. The results were as follows. 1) The pressure in the tubular turbine increased significantly under the free surface and the water gravity, with the increase of the submerged depth. The blades experienced periodic pressure fluctuations in the process of rotation. The magnitude of pressure fluctuations on the blade surface also increased accordingly, when the submerged depth of the runner increased, as the water head decreased. Therefore, there was severe vibration on the blade surface, when the tubular turbine operated under the condition of ultra-low head. 2) There was a gradually increased deformation at different positions of the blade from the hub to the chamber of the runner along the radial direction. The maximum deformation position was located at the geometric lowest point of the blade near the shroud. There was consistent running in the direction of hydrostatic pressure and the dynamic water pressure on the blade along the entire circumferential direction, leading to the increased deformation of the blade, where the blade overcame the hydrostatic pressure with the rotation of the runner. Once the hydrostatic pressure was promoted the rotation of the blade, the dynamic water pressure on the blade surface and the hydrostatic pressure were in opposite directions, indicating a counteracting effect on the dynamic water pressure for the reduced deformation of the blade. Therefore, the maximum deformation of the blade occurred at the blade rim, when the blade was running in a horizontal position during bottom-to-top rotating from the bottom to the top of the runner chamber. 3) Since the blade of the tubular turbine was supposed as a cantilever beam structure with the fixed constraints at the hub, the stress on the blade near the shroud was relieved by a larger amount of deformation. There was no deformation of the blade near the hub, due to the fixed constraint of the pivot. As such, the maximum stress occurred at the root of the blade pivot. Therefore, the distribution of the equivalent stress on the blade increased, as the radius decreased. The water head can greatly contribute to the decrease in the submerged depth of the runner, which was reduced the hydrostatic pressure on the blade surface, where the load on the blade surface tended to decrease for the reduced maximum deformation and maximum equivalent stress on the blade at different positions of circumferential direction. The blades were prone to deformation and fatigue damage at the low operating head of the tubular turbine. The finding can provide theoretical support to the severe vibration of tubular turbines in the ultra-low head operation, particularly for the hydraulic design, operation, and maintenance of tubular turbines. [ABSTRACT FROM AUTHOR]

Copyright of China Journal of Oral & Maxillofacial Surgery is the property of Shanghai Jiao Tong University, College of Stomatology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The purpose. The aim of the present study is the Finite Element Analysis (FEA) of a reconstruction model of a molar restored with an entirely ceramic crown, using 3 types of ceramic cemented with 3 different types of adhesive systems in order to identify equivalent stress and shearing values, as well as the deformations in accordance with the direction of the applied stress. Material and method. The geometric model used in FEA is based on one reconstructed from CT scans. Following the CT scan of the dental images and their processing, the structure of an intact molar was made, which was later modified to only select the area of the crown and dental trunk. The FEA analysis aimed to identify both the values of equivalent stress and shear, as well as the deformations of the structure in accordance with the defined materials and the direction of the applied stress. In the present simulation, a single stress value of 170 N was chosen, but applied in sequence at 6 angles: 0°, 30°, 45°, 60°, 75°, 90°. This way the shearing effects are discreetly simulated up to pure compression of the structure. Results and discussions. The stress peaks for both the crown and the cement appear at the level of the horizontal walls, following a sudden decrease of the values recorded on the vertical walls. The change of sign at the level of the shearing stress is normal and is due to the change in orientation of the applied force in relation to the plane in which the stress is studied. Regarding cements, the equivalent stresses indicate that it is possible to reach values that can lead to the appearance of fissures on the dental interface. Conclusions. The values of the mechanical resistances of the 3 ceramics exceed the values of the equivalent and shearing stresses analysed by at least one order of magnitude. Therefore, the application of a similar stress value cannot produce mechanical fractures on any of the ceramics, but fissures can occur in the cement or dentin.

Abstract In antiquity, amphorae served as standard transport containers for diverse goods. For packaging of large numbers of amphorae, the basically ovoid‐shaped amphora bodies were stacked in several layers placing their pointed bases into the spaces between the shoulders of the amphorae in the respective lower layer. Thus, particularly during transport in cargo ships they had to withstand considerable mechanical loads at their contact points. This required high mechanical performance concerning the actual ceramic materials as well as the vessel design. In the present paper, the performance of different types of amphorae will be assessed. On the basis of mechanical tests of specimens of East Aegean transport amphorae of the Hellenistic and Roman Period, the material properties of the ceramics have been estimated. These properties are used in three‐dimensional models, simulating the performance of different amphora types under typical loads by using the finite element method (FEM). In this way, specific design features of different vessel types can be assessed for their performance particularly during transport. On the other hand, the simulations provide information toward the interpretation of typical damages observed in archaeological finds and allow for a realistic assessment of amphora function and the risk of its failure.

It is known that for metal components of aircraft structures, "equivalent stress" is one of the most important parameters used to assess the fatigue damage resistance of a structural element for a given program of its fatigue tests. The method and the procedure for estimating the values of this parameter for metal elements of aircraft structures are presented It is noted that for aircraft structural elements made of polymer composite materials, neither the concept of the "equivalent stress" parameter nor the methods for calculating estimates of the values of this parameter are currently defined in domestic and foreign studies of the fatigue strength of such elements. In order to achieve particular progress in the considered area, the definition of the "equivalent stress" parameter of fatigue test programs for composite aircraft structural elements is proposed. For the case of uniaxial tension-compression load of laminates from layered composites representing the upper and lower panels of composite wings of transport category aircraft, a method for calculating the estimation of this parameter is proposed. It is shown that using the "equivalent stress" parameter, the following main tasks can be solved: assessment of the damage resistance of a structural element with a given program of its fatigue tests; comparison of damages resistance of various programs, calculation of equivalents between the programs; calculation of fatigue life of layered composites samples and elements using the fatigue curve under regular load. It is noted that the fundamental meaning of the proposed method for calculating the equivalent stresses and equivalents of fatigue test programs is the use of a special hypothesis of a fatigue damage accumulation rule. An example of calculating the equivalent stresses and equivalents of various modifications of the quasi-random program for CFRP T300/5208 [45/0/-45/90] 2s samples of fiber-carbon composite with the open hole is presented. The fatigue life of these samples under load with the considered modifications was calculated using the obtained values of equivalent stresses and equivalents. Good agreement between the calculated results and experimental data is shown.