Dense Silicon nitride was investigated to determine the effect of its microstructural parameters and densification on thermo-mechanical properties and THERMAL STRESS resistance to fracture initiation during a hot or cold mechanical and THERMAL shock testing. The different materials and microstructures were obtained by changing the parameters such as the type of the powder, additive, forming process and sintering condition. Maximum crack growth and THERMAL shock resistance of dense Si3N4 are achieved after complete conversion of the a®b transformation, and after the change in grain morphology towards elongated grain and the relative crystallization of the second phases have been obtained. The characteristics are obtained by a high a phase content of the starting powder, high Y2O3 and sintering condition of higher temperature (2000o C), longer soaking times (1h) and load application at the beginning of the THERMAL cycle.

In the present study, the effect of hyperthermia on GH3\B6 cells has been investigated. These cells are derived from rat anterior-pituitary tumor cells with the ability of Prolactin secretion. They are used as endocrinology tools and some previous studies were done on different secretion conditions in these cells. THERMAL effect, in a controlled condition makes some morphological changes in these cells. These changes depend on the period of heat shock and also its amplitude. It was seen that cells can tolerate 41°C well, but higher temperature made changes in cells’ attachment, morphology and viability.

Temperature change is one of the major factors that causes cracks in concrete pavements. Temperature change causes expansion or contraction and thus creates a movement in the concrete slab. Friction between the concrete slab and the sub-base layer resists this movement, and induces THERMAL STRESS in the concrete. In this research study, the THERMAL STRESS created in concrete pavement due to drop in temperature and other intensifying factors (such as friction changes in layers interface), are investigated using numerical analysis method. In current research, two finite element models are used to analyze the friction and temperature drop STRESSes. The first concrete slab model does not have a dowel bar and the second includes the dowel bar with or without misalignment. Finite element models using ABAQUS software are created for concrete pavement with or without dowel bars, and with various friction factors between the concrete slab and the sub-base layer. The effects of friction factor between the concrete slab and the sub-base layer and temperature changes on frictional and tensile STRESSes in the concrete slab are analyzed for various cases. The results obtained in this research study indicate that the high temperature drop (about 30 ° C) during the 7 to 8 initial hours of construction of concrete pavement and a high friction factor in the layers interface are the main causes of cracks in concrete pavements. The combined effects of these factors, high temperature drop and high friction factor in the layers interface, worsen the conditions. The low tensile strength of concrete during the initial days of the concrete formation is the main reason for increasing chance of occurring cracks during this period. In second part of the research, the THERMAL STRESS created in the concrete pavement with dowel bars deviating from the horizontal (a vertical tilt in the bars) is analyzed too. The research results show that the amount and the distribution of frictional and tensile STRESSes in the concrete slab when the dowel bars have no misalignment and are well lubricated, have conditions similar to the concrete pavements without dowel bars. Meanwhile numerical analysis results show that misalignment of the dowel bars and temperature drop, increase the tensile STRESS around the dowel bars and increase the threat of concrete disintegration. Ultimately, the results of numerical analysis are compared with the tensile strength of concrete during the initial hours of concrete construction. Results show that a 33˚ C drop in temperature and a friction factor about 3, create a tensile STRESS of 124000 Pascal in the concrete slab, which can cause cracks in the concrete pavement during the initial 7-8 hours of concrete pavement construction. Furthermore, a vertical tilt in the dowel bars causes a considerable increase in tension STRESS around the dowel bars. In order to prevent cracks during the initial days and hours of forming concrete pavements, the friction factor in the layers interface should be reduced using bond breaker, such as polyethylene sheets, concrete pavement should not be made in conditions with severe temperature drop, and dowel bars should be implemented with no or allowable misalignment.

Dimensional accuracy in machined parts depends on the precision of spindle, which is highly affected by applied forces, itself. This precision of spindle becomes more serious when it is used for a period of long times. Therefore, STRESS and strain analysis of spindle is very important in the behavior and preservation of its precision. In this paper, the forces applied to the spindle of a turning machine are calculated and analyzed. Afterwards, the spindle is simulated with MSc Visual Nastran software and analyzed due to the application of boundary conditions. According to the spindle's STRESS and strain, the modal analysis has been done and the natural frequencies of the spindle are determined. The results show that, the front  bearing of the spindle is the critical section and its STRESS and strain will be increased with feed and depth of cut. When these feed rates and depths of cut become less, the created STRESSes at the least speed of spindle are more in comparison with the other speeds.

Purpose: Application of heavy forces to maxillary dentition during treatment with headgear, induces high concentration of STRESSes in periodontal tissue. Quantification of this STRESS is of great concern in orthodontics. This study was designed to investigate the quantity and quality of STRESS response in the PDL of maxillary first molar which was subjected to high pull headgear traction using Finite Element method.Methods and Material: In an experimental study, a three-dimensional finite element model of maxillary dentition, consisting of 17096 elements and 23013 nodes, was developed based on a young human skull. The forces were applied to the maxillary first molar in the stabilized Arch by means of a rectangular full size arch wire in (022) slot bracket. Mechanical properties of this model were based on previous studies. A 350 gram force was used for high pull headgear to affect the dentition (+30 degree) and STRESS distribution was investigated in buccal, palatal, mesial and distal side and in cervical, middle, apical sections of the PDL. The quantity of STRESSes were expressed as principal STRESSes (1,2,3), while the negative and positive signs indicated compressive and tensile STRESSes.Results: The buccal surface of PDL of mesiobuccal root and the buccal, palatal and distal surface in cervical region of PDL of distobuccal root and the distal surface of the PDL of palatal root had received a great deal of STRESSes, in addition, the over all STRESS distribution in roots of molar had intrusive nature.Conclusion: The extension of high STRESS concentration areas observed after using high pull headgear is limited to some root surfaces specially the distobuccal root.

This paper presents an analytical and computational approach for investigating the behavior of a simply supported carbon nanotube-reinforced composite shell that has been exposed to temperature variations. The equations are solved using the Ritz energy method for the analytical solution and ABAQUS finite element software for numerical solution. The displacement field is the first-order shear deformation theory, and the linear equations were solved using the rule of the mixture to determine the mechanical properties of carbon nanotube-reinforced composites. A uniform distribution of temperature with no heat flux in the shell and nanotubes in five distinct shapes classified as V, A, X, and O have been considered in this study. The support conditions are the same in all cases, but the temperature, THERMAL boundary conditions, and carbon nanotube volume function values vary. The findings are illustrated in a detailed manner in the form of diagrams, which perfectly demonstrate the differences between both of the carbon nanotube distribution material models. Validation of the results shows great compatibility in energy solution and finite element methods. The results show that increasing the volume function of the carbon nanotubes increases the STRESS values and THERMAL gradients, and on the other hand, reduces the displacement, and by increasing the temperature the number of STRESS increases.