摘要:

With the aid of a phase diagram, a theoretical principle is developed to calculate the stress in the matrix phase and the overall volume change of dual-phase metals during a cooling process involving martensitic transformation. The cooling process may start from a pure austenite phase or from a mixture of austenite and ferrite, resulting in a two- or a three-phase system during the phase transformation. The transformed martensites in the former case are taken to be randomly oriented spheroids. In the latter case, ferrite is taken as the matrix, whereas austenite will transform into martensite, both existing as randomly oriented spheroidal inclusions. The theory is developed using Eshelby's inhomogeneity and transformation principle, by which the influence of elastic heterogeneity, thermal expansion coefficients, phase-transformation strain, and inclusion shape can all be accounted for. When applied to the iron—carbon system, it is found that, for a typical cooling path, the thermal stress developed in the matrix is hydrostatically tensile in both two- and three-phase systems, with a magnitude that is strongly sensitive to the inclusion shape and carbon content. After the martensite transformation starts, the volume of the system is found to increase first, indicating the stronger contribution of the phase-transformation strain over the thermal contraction. Subsequently, the transformation rate decreases and thermal contraction becomes a more dominant factor to the volume change. Finally, it is demonstrated that the theory can be used to predict the transition of martensite morphology from the lath to the twinned structure as the carbon content increases.

ISSN:0149-5739    

DOI:10.1080/01495739208946117

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The response of a thin composite plate constructed of piezothermoelastic layers and subject to stationary thermal and electric fields is examined. Solutions based on classical lamination theory, extended here to include piezoelectric effects, are obtained for a “free” plate of arbitrary contour and for a simply supported, rectangular plate. Numerical results illustrate that thermally induced deformation of a structural laminate can be reduced significantly through the addition of a layer of piezoelectric material under an applied electric potential.

ISSN:0149-5739    

DOI:10.1080/01495739208946118

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Determination of thermal stress concentration factor (TSCF) due to a circumferential groove possessing a transverse plane of symmetry in a long hollow cylinder is discussed. It is shown that integrated photoelastic data in conjunction with a single measurement of radial displacement on the transverse plane of symmetry is adequate to obtain TSCF. An interesting offshoot concerning a photoelastic method of obtaining the temperature profile on the transverse plane of symmetry is demonstrated for a thermally stressed hollow cylinder with an external circumferential groove.

ISSN:0149-5739    

DOI:10.1080/01495739208946119

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A new computer model for welding by surface heating is used to predict the residual stresses in the weldment. By incorporating both solid and fluid phases during melting and solidification it is possible to monitor the complete history of the stress field, as well as the residual stress field. Predicted results when compared to an available experiment show qualitative agreements.

ISSN:0149-5739    

DOI:10.1080/01495739208946120

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Two-dimensional electrothermal crack problems are treated. Steady temperature distribution near the lip of a crack is analyzed for a homogeneous isotropic conductive material with the steady dc current. A path-independent integral jtis newly introduced and is used for the analysis together with the jeintegral, which has been introduced by the authors for electric crack problems. Based on the analysis, the mode it stress intensity factor KII, which is attributed to thermal stresses caused by Joule heating, is shown to be a function of the two path-independent integrals.

ISSN:0149-5739    

DOI:10.1080/01495739208946121

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The Stroh formalism for two-dimensional deformations of anisotropic elastic solids has been extended to include the effects of heat conduction. The formalism is employed here to study stress singularities in anisotropic elastic bimaterials with the presence of interface cracks. It is known that, without the effects of heat conduction, there are three singularities of the formr−½r−½+γwhere r is the radial distance from the crack tip and γ is a positive constant that depends on the mismatch of elasticity constants of the two materials. With the inclusion of heat effects, there is arδksingularity in which —1 < δk< 0 depends on the heat conduction coefficientskij. The special case δk= —½, which occurs in particular whenkijin the two materials are identical or when the Onsager reciprocal relations are invoked so thatkij=kij, is studied here. We show that therδksingularity may convert into ar−½(ln r) singularity. The conditions for the existence ofr−½(ln r)singularity are presented explicitly.

ISSN:0149-5739    

DOI:10.1080/01495739208946122

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Creep life predictions are based on the assumption that the life-to-rupture of a structure differs only insignificantly from the creep failure time,i.e., the time at which the strain reaches infinity. The reason for this is to be sought in the circumstance that, toward the end of its life, a structure creeps very rapidly. In case of a rotating thin-walled cylinder there are two effects that contribute: first, the continuing reduction of wall thickness; and second, the increase of centrifugal loading due to an increasing diameter.

ISSN:0149-5739    

DOI:10.1080/01495739208946123

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Coupled equations governing temperature and stress fields incorporating solidification in a growing body with a moving boundary are developed based on the thermomechanics of a mixture of liquid and solid, and a finite-element method for stress analysis as well as temperature distribution is formulated, where a unified inelastic constitutive relationship capable of describing both elastic-viscoplastic solids and viscous fluids is employed. Examples of numerical calculation of temperature affected by solidification and stresses are presented for some practical cases of centrifugal casting processes. In order to verify the results of simulation, calculated temperatures were compared with the measured data.

ISSN:0149-5739    

DOI:10.1080/01495739208946124

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A uniformly heated, anisotropic, thermoelastic solid undergoes distortion as well as volume change because it experiences differential expansions in different directions. This effect is compounded if, in addition to being anisotropic, the material is in-homogeneous, as is the case with laminated materials. We consider a circular cylindrical tube or channel section, composed of an arbitrary number of laminae, each of which is of anisotropic, thermoelastic material. The only material symmetry assumed is reflectional symmetry with respect to concentric circular cylindrical surfaces; orthotropy and transverse isotropy are included as special cases. We consider a class of deformations that includes torsional shear, torsion, bending, and warping, as well as radial expansion and axial extension. An exact analysis is given that defines a procedure for determining the deformation and stress due to uniform heating of the tube or channel.

ISSN:0149-5739    

DOI:10.1080/01495739208946125

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

This article examines the application of a numerical method of transient stress analysis for the study of a crack located in a viscoelatic layer bonded to an elastic substrate. The layered structure containing the defect is subjected to heat conduction and associated thermo-viscoelastic effects. The finite-element technique is used to examine the time-dependent variation in the stress intensity factor at the crack tip due to a sudden reduction in the temperature at the surface of the layered structure. Numerical results presented in the article illustrates the influence of the thermo-viscoelastic coupling on the crack behavior.

ISSN:0149-5739    

DOI:10.1080/01495739208946126

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor