Thermal Stress

The aim of this work was to study, using the finite element method (FEM), the distribution of thermal residual stresses arising in metal-ceramic dental restorations after cooling from the processing temperature. Three different interface configurations were studied: with conventional sharp transition; one with a 50% metal-50% ceramic interlayer; and one with a compositionally functionally gradated material (FGM) interlayer. The FE analysis was performed based on experimental data obtained from Dynamic Mechanical Analysis (DMA) and Dilatometry (DIL) studies of the monolithic materials and metal/ceramic composites. Results have shown significant benefits of using the 50% metal-50% ceramic interlayer and the FGM interlayer over the conventional sharp transition interface configuration in reduction of the thermal residual stress and improvement of stress profiles. Maximum stresses magnitudes were reduced by 10% for the crowns with 50% metal-50% ceramic interlayer and by 20% with FGM int...

Based on human-biometeorological measurements at two different sites within a street canyon in the city of Freiburg (southwest Germany), the shading influence of the canopy of street trees on human thermal comfort was investigated for a typical Central European summer day ...

All electric equipment in a power system has to be designed to withstand the mechanical and thermal stresses of potential short-circuit currents. Any reduction of these currents can lead to significant cost savings. Among all current limiting devices, superconducting fault current ...

Exposure of superalloy surfaces to jet fuel at elevated temperatures leads to the formation of carbonaceous deposits and metal sulfides. The formation of stable oxide layers on alloy surfaces can reduce the activity of the constituent transition metals that catalyze the dehydrogenation of hydrocarbons and the subsequent carbon deposit growth. The metals Ni, Cr, Fe, Mn, Al, Ti and Nb + Ta

Twenty single male Assaf lambs were divided into two groups and housed in semi-open barns. Air temperature averaged 35°C. For 9 weeks after parturation, one group was cooled by fan between 1000 and 1600 hours and the other group was not cooled. Rectal and skin (head and testis) temperatures, respiration rate, and pulse rate were recorded twice daily. Lambs were weighed individually every week and levels of T3 and thyroxin were determined. Differences in rectal, head, and testis temperatures (P < 0.05) and respiration rates (P < 0.01) between the two groups were significant. Growth was affected positively by fan treatment, live weight increased by 15%, and cooled lambs had higher thyroxin levels.

Numerous studies have confirmed that performance can be impaired when athletes are dehydrated. Endurance athletes should drink beverages containing carbohydrate and electrolyte during and after training or competition. Carbohydrates (sugars) favor consumption and Na(+) favors retention of water. Drinking during competition is desirable compared with fluid ingestion after or before training or competition only. Athletes seldom replace fluids fully due to sweat loss. Proper hydration during training or competition will enhance performance, avoid ensuing thermal stress, maintain plasma volume, delay fatigue, and prevent injuries associated with dehydration and sweat loss. In contrast, hyperhydration or overdrinking before, during, and after endurance events may cause Na(+) depletion and may lead to hyponatremia. It is imperative that endurance athletes replace sweat loss via fluid intake containing about 4% to 8% of carbohydrate solution and electrolytes during training or competition....

Within the framework of the ‘Component Specific Analysis of Mechanical Behaviour’, the nuclear codes and standards, e.g. KTA Standard KTA 3201.2 on Components of the Reactor Coolant Pressure Boundary of Light Water Reactors (Design and Analysis) allow a simplified stress and fatigue analysis for piping by applying the stress index method. The equations supplementary to present KTA Standard given in this context can be used for the consideration of the thermal loads arising from piston flow but not of those from thermal stratification. Thermal stratification occurs e.g. in the surge line of pressurised water reactors during start-up and shut-down processes. This phenomenon is explained and its effects are described. The equations supplementary to the present KTA Standard are derived which enable the consideration of the load case ‘thermal stratification’ in the simplified stress and fatigue analysis. Their applicability is demonstrated by a numeric example.