Magnitude Of Thermal Stresses Research Articles

Effect of intermediate layer composition upon the structural changes in and mechanical properties of VK-VK, TK-TK, AND VK-U8-Steel welds

1. It has been found that in the diffusion welding of hard alloys to themselves the magnitude of residual stress depends on the amount of cobalt in the hard alloys. The greater the difference in cobalt content in welded hard-alloy pairs, the higher is the stress and the lower is the transverse rupture strength. 2. In the diffusion welding of VK15 hard alloy to U8 steel the best results are obtained with iron-nickel intermediate layers containing 2 wt.% of VK3 hard alloy. 3. In the diffusion welding of TK hard alloys to themselves the magnitude of thermal stress is much less with nickel than with iron intermediate layers.

The Clamped Plate Analogy for Thermoelasticity

A method is described for determining the thermal stresses in plane systems with free boundaries. The method makes use of the analogy between the problems of the bending stresses in clamped plates and those of plane thermoelasticity. The analogy is illustrated for both simply and multiply connected regions. The method allows the simple solution of thermal stress problems for which the analogous plate bending problem has already been solved; and provides a means of easily visualizing the distribution and magnitude of thermal stresses in terms more familiar to many engineers.

Residual stresses in the leaves of automobile springs

1. Quenching of spring steel with a section of 6×25 mm from 950–1100°C in oil and in a stream of air creates tensile stresses of 4–19 kg/mm2 in the surface layers. Tempering at 500°C almost completely relieves these stresses. 2. Cooling in water after tempering creates insignificant compression stresses in the surface layer (0.3–3.6 kg per mm2). 3. These stresses increase with the tempering temperature, but reach only 8.4 kg/mm2, even after tempering at 650°C followed by cooling in water. 4. The magnitude of thermal stresses depends very much on the structure and the hardness of the steel. When the hardness, i.e., the resistance to plastic deformation, decreases, then the thermal stresses increase sharply, reaching 36.4 kg/mm2. 5. Shotblasting creates considerable compression stresses (up to 110 kg/mm2) in the surface layer. 6. Tempering at 200°C after shotblasting decreases the residual stresses very little—to about 93 kg/mm2. The corrosion resistance of the surface layer improves but, according to the preliminary data, the fatigue limit changes very little.

鋼種による熱応力亀裂の発生度合を比較するための高温弾性率および熱膨脹率の測定

According to the kinds of steels there are some differences in the frequency of thermal stress crackings which occur in the heating process of ingots. In this report, we measured Young's modulus and the coefficient of thermal expansion of typical steels, within the temperature range of room tempereature to 1000°C, because they influence the thermal stress. And using the results we compared the rate of frequency of thermal stress crackings according to the kinds of steels.The results obtained are as follows:(1) It was found that the Young's modulus decreases rectilinearly up to 400°C and curvilinearly over about 500°C to 600°C in all the steels tested. And the modulus is not influenced greatly by a small change of the components, the inclusions heat treatment, etc. of steels, but there is some difference among the kinds of steels classified roughly.(2) As for the coefficient of thermal expansion there is little difference with a small change in heat treatment for the same kind of steels but a considerably large difference according to the components of steels. This influence of the components is not very great under the transformation point but it becomes very great above the point (i. e. Austenite range). Especially when carbon content increases, the coefficient of thermal expansion increases heavily.(3) To estimate the magnitude of thermal stress which occurs when steels complete the transformation we utilized Young's modulus and coefficient of thermal expansion, and found that thermal stress increases chiefly in accordance with the increase of carbon content.It follows from this that thermal stress is greatest in hyper-eutectoid steel of JIS SK2, SUJ 2, 3. Consequently we can conclude that thermal stress crackings are most liable to occur in these kinds of high-carbon steel.

Thermal stresses in reactor constructions

Conditions for the appearance of thermal stresses in reactors are investigated; also their magnitude and the danger they create are estimated. The influence of the form of the heat-generating elements (HGE) on the temperature drop and magnitudes of thermal stresses is analyzed; recommendations are given with the aim of decreasing the harmful effect of thermal stresses.

Certain problems in measuring the temperature of rotating objects

The described method of experimental temperature determination in rotating structural parts of high-speed turbines under actual operating conditions provides the possibility of obtaining a clear idea about their actual thermal state, which makes it possible to determine the character and magnitude of thermal stresses in these structural elements. This method is also of interest for further improvements of methods for temperature measurements in rotating parts of various machines.

Design of Transparencies

Summary:—A study of engineering problems encountered in the design of transparencies for supersonic aircraft is presented with a special emphasis on the effects of kinetic heating. The paper is written primarily with optical transparencies in mind but many of the general principles discussed are equally applicable to the design of radomes for elevated temperature applications.The first parts of the paper consider briefly the methods of calculating temperature distribution in transparent panels subjected to kinetic heating (or cooling) and this leads naturally to discussion of the effects of the non-uniform temperature distribution, differential expansion and the edge restraints preventing thermal deformations. Methods of calculating thermal stresses are suggested through the concept of the “ self-equilibrating ” temperature distribution; the main attention, however, being concentrated on the derivation of simple engineering formulae rather than on the mathematical rigour of the solution.The choice of design cases for combined pressure and thermal loading is considered and it is shown that, in general, deceleration manoeuvres combined with outward pressure constitute the design criteria for transparencies. The effects of various parameters on the magnitude of thermal stresses are analysed; these include the effects of altitude, temperature, deceleration and material properties. It is shown that, for given material and panel geometry, the thermal stresses depend mainly on the following parameters: total temperature change, acceleration (or deceleration), and the Biot number based on the panel thickness.Practical design aspects are also considered, such as choice of materials, strength, panel geometry, mounting of panels and the fail-safe design. Finally, testing of transparencies under pressure and thermal loading is briefly discussed, together with possible methods of strain measurements, and a tentative proving procedure for transparencies is suggested.