Asymmetrical transient thermoelastic problems in a composite hollow circular cylinder

The present paper is concerned with the transient thermal stresses in a bonded composite hollow circular cylinder under an arbitrary asymmetrical heat supply. Numerical work is carried out using Laplace transforms and is given for the composite cylinder made of the different materials under three, band heat sources on its outer surface.     

Preloaded RC columns strengthened with high-strength concrete jackets under uniaxial compression

Although use of high-strength reinforced concrete (RC) jackets has become common practice worldwide, there are still two unresolved issues regarding the contribution of the original concrete and the effects of existing loads. Twelve RC-jacketed columns were tested with and without preloading under uniaxial compression. Tests showed the entire core to contribute to the capacity of the jacketed column, as long as adequate confinement is provided. Also, preloading does not adversely affect the capacity of the jacketed column, while it may increase its deformability, especially in square sections. Transverse reinforcement in the jacket directly improves ductility of the strengthened column, especially in circular sections.     

TRANSIENT THERMAL STRESSES OF A HOLLOW SPHERE DUE TO ROTATING HEAT SOURCE

Abstract

A three-dimensional theoretical treatment for the thermal-stress problems in spherical coordinates is developed. The first part is devoted to the relations of stress components in terms of thermoelastic displacement potential and a harmonic function. Next, a hollow sphere with a rotating heat source is considered as an illustrative example. The numerical calculations are then also carried out and the results shown graphically.     

Coupled thermal stress problem in a hollow sphere under a partial heating

In a precise analysis of transient thermal stress problem, this requires the corrected heat equation taking into account of the thermo-mechanical coupling term. In this report, we deal with the transient thermal stress problem in a hollow sphere accompanied by the simultaneous determination of stress and temperature distributions. A new technique is developed in this report and numerical works are carried out. From our results, it should be concluded that the small lag can be found in case of ordinal practical materials.     

A new numerical method for transient thermal stress problems

A new numerical method of calculating unsteady-state heat conduction and thermal stresses by using improved coefficient matrix patterns on the nodal points of a structure is given. Good agreement is obtained between our results and the rigorous results, and this method seems to yield better accuracy than other well-known approximate methods for two-dimensional transient thermal stress problems.     

THERMAL-STRESS PROBLEMS IN INDUSTRY. 3: TEMPERATURE DEPENDENCY OF ELASTIC MODULI FOR SEVERAL METALS AT TEMPERATURES FROM -196 TO 1000° C

The temperature dependency of the dynamic moduli of elasticity of steel and aluminum and copper alloys was investigated experimentally by an ultrasonic-wave method, in the temperature range from —196 to 1000°C. The results are compared with those obtained by the resonant-frequency method and are represented as empirical formulas. Useful data for commercial alloys are given in tables, by chemical composition.     

FOUNDATIONS FOR COUPLED THERMOELASTICITY

This article outlines a basic view of coupled thermoelasticity through the application of the first two laws of thermodynamics to thermal-stress problems in general continuous solids subject to moderately large temperature variations.     

Fabrication of silicon field-emission arrays using masks of amorphous hydrogenated carbon films

A fabrication process of silicon field-emission arrays is reported, in which thin films of amorphous hydrogenated carbon (a-C:H) are employed as masks in a two-step plasma-etching process, using pure SF₆ and a mixture of SF₆ and O₂. In comparison with processes that involve SiO₂ masks, the use of a-C:H improved the selectivity of the plasma etching, particularly in the case of pure SF₆. An estimation of Utsumi's figure of merit showed that a significant enhancement in electric field can be achieved, as a result of the sharp tips fabricated through this process.     

Unsteady thermal stresses in fuel elements under heat generation

In designing some types of fuel elements, it is necessary to find the thermal stresses in a continuous medium performated by cylindrical channels of circular cross-section. In order to set up the problem, assume that the strength and heat transfer calculation are based on the phenomena that occur in a typical unit lattice cell, and that the heat generation is uniform over the whole section: Therefore, the problems reduce to solve the temperature and thermal stresees in a polygonal prism with a central circular hole under uniform heat generation and for insulated outer boundary. In out previous papers we obtained the steady thermal stress distribution in such formed regions by use of the five elementary functions method.

In starting up or shutting down of the reactor, however, the problem becomes one of the unsteady state. It is felt that no analysis has been given to the transient thermoelastic problem of the multiply-connected region. The problems considered here are concerned with unsteady thermal stresses in a polygonal prism with a circular hole under a uniform heat generation. The solving process is divided into two basic steps. First, the heat conduction equation is solved by the technique of Laplace transform. Secondly, the plane thermoelastic problem is solved by use of the five elementary functions method. Throughout the treatment of both problems, in order to satisfy the boundary conditions, we use the point-matching technique in conjunction with the least square method.     

THERMAL-STRESS PROBLEMS IN INDUSTRY. 1: ON THERMOELASTIC DISTORTION IN MACHINING METALS

Abstract

This paper is a theoretical analysis of the thermoelastic effect upon accuracy in the machining of metals. The problem is reduced to the unsteady thermoelastic analysis of a solid cylinder heated on the surface axisym-metrically by a moving heat source under an axial restraint. The thermal and elastic distortions of the workpiece are computed, and the error in the shape is plotted.