Transient responses of a fluid-saturated poroelastic cut-ring subjected to sudden moments or sudden opening at its ends are analyzed in the Laplace space and the analytical results are inverted into the time space. The numerical results are given in the form of curves. Four cases for the boundary conditions at the inner and outer surfaces of the ring are considered but only the case of free drainage there is described here. In addition, the multi-valued displacement in the tangential direction is somewhat discussed with respect to its stress function.
This paper deals with the stress concentration problem of an elastic infinite plate with a circular rigid inclusion under harmonic vibration loads. Applying a fundamental solution of the two dimensional elastodynamics for harmonic vibration problems, we present a method of solution for the inclusion problem. It is assumed that the infinite elastic plate is under a plane strain conditions. Stress distributions around the inclusion are investigated.
This paper deals with the stress distributions of an elastic thick plate subjected to torsion by a rigid circular cylinder inserted in any depth into a circular hole of the thick plate. The problem was considered in a previous paper where the stress singularity was discussed few. The stress singularity at a contact point with the bottom corner of the rigid cylinder on the cylindrical surface of the thick plate is investigated in this paper. We use a body force distribution method by a new Green functions for torsional body force problems of an infinite elastic thick plate.
The classical body-force analogy for static or quasi-static problems of thermoelasticity is extended towards coupled dynamic problems of thermoelasticity. We consider two dynamic problems, namely a thermal problem without body forces, but with a given distribution of transient sources of heat, and a force problem without sources of heat, but with body forces. Both problems are treated within the context of the coupled dynamic thermoelasticity. We show that, given suitable boundary and initial conditions, a distribution of body forces can be constructed, such that the dynamic displacements or transient temperature in both problems become equal.
Subaru telescope has been leading the world as the best instrument for astronomical observation in the visible and infrared region. Before Subaru, Japan had almost no experience to engineer and design such a large and accurate optical telescope. At the development stage, various state-of-the-art technologies were studied. It is, however, the basis of "The mechanics of materials" that played one of the most important roles in the study. The important roles include 1) how to make the huge and complicated telescope structure behave as an elastic body so as to show almost perfect repeatability of the deformation, and 2) how to obtain force vectors to correct the deformation of primary mirror with 8.3m diameter. This is to simplify the drive control system of the telescope structure and the figure control system of the primary mirror. The author learnt "The mechanics of materials" and "The theory of elasticity" from Prof. Atsumi in Tohoku University late in the 1970s, and led the Subaru telescope project as a system engineer and project manager in Mitsubishi Electric from 1987 to 2001. The basis of the learning was fully utilized in the design of Subaru with some additional application which Prof. Atsumi would have not taught. Some differences of the practical engineering from the academic learning and some key technologies which led the success of Subaru are introduced.
Mechanical behavior of the metal matrix composite is affected by microscopically distributed residual stress owing to interaction of fibers. A periodical cluster model is made to analyze both macro- and microscopic behavior of the composite. The fiber-matrix interface of the composite is modeled as Coulomb frictional contact under compressive residual stress. To solve for the perturbed displacement field of the composite, boundary integral formulation is introduced into the interface contact problem. The formulation enables simultaneous numerical calculations for macro- and microscopic fields to evaluate nonlinear mechanical behavior of composite.
This paper is concerned with the theoretical treatment of transient piezothermoelastic problem is developed for a smart composite hollow cylinder constructed of an isotropic elastic layer and a piezoelectric layer due to uniform heat supply. The transient one-dimensional temperature in a smart composite hollow cylinder is analyzed by the method of Laplace transformation. By using the exact solutions for isotropic hollow cylinder and piezoelectric hollow cylinder, the theoretical analysis of transient piezothermoelasticity is developed for a smart composite hollow cylinder. As an example, numerical calculations are carried out for an isotropic elastic hollow cylinder made of steel, bonded to a piezoelectric layer of cadmium selenide. Some numerical results for the temperature change, the displacement, the stress and the electric potential distributions in a transient state are shown.
This study is concerned with a theoretical treatment of plane thermoelastic problem of an inhomogeneous medium. We assume that a medium has inhomogeneous material properties which are changed in a form of power of coordinate variable y. In the present report we consider a plane thermoelastic problem of an inhomogeneous slab whose material inhomogeneity is symmetrical with a middle plane, and which is subjected to nonuniformly distributed and symmetrical heat supply on boundary surfaces. Making use of fundamental equations system of thermoelasticity for the inhomogeneous medium which have already been formulated by one of authors, we attempt to derive analytical solutions of temperature change, thermal displacement and thermal stresses in the slab. Thereafter, carrying out numerical calculations, we discuss an effect of material inhomogeneity upon the thermoelastic behavior in the slab and material inhomogeneity to secure material strength against thermal loading.
This paper presents plane thermal stresses in a functionally graded plate (FGP) with the slanting boundary to the functional gradation subjected to a partial heating. The heat conductivity, Young's modulus and the coefficient of the linear thermal expansion are expressed by exponential functions of the position in the functionally graded coordinate. The steady thermal stresses in the FGP with the slanting boundary to the functional gradation under two-dimensional temperature distribution are obtained by use of the stress function method. The numerical calculations are carried out for ZrO_2/Ti-6Al-4V and ZrO_2/stainless (SUS304) functionally graded plates, when the ceramic surface is partially heated.
Bacterial Cellulose is one of the eco-friendly materials, and is synthesized by the acetic bacterium Acetobacter xylinum. In this paper, the mechanical behavior of Bacterial Cellulose (BC) composites is investigated. The BC composite specimens are prepared under the test method of JIS K7113. The matrix of composites is BC and their reinforcements are powdered paper (PP), CaCO_3, and clay of 35%, 60% and 70% by weight. Tension tests were performed in the atmospheric condition. From the experimental results for BC composites, the recorded σ-ε curve for the PP/BC composite specimen indicates significant non-linear behavior from the earlier stage of loading, and the mechanical behavior of the PP/BC specimen is similar to that of the CaCO_3/BC and/or Clay/BC specimens. The effects of material properties and configurations on the mechanical properties of BC composites were discussed, and the method of molding was evaluated.
Thermal barrier coating (TBC) of a gas turbine blade suffers from high temperature oxidation. Delamination damages of interface between ZrO_2-8%Y_2O_3 top-coating and CoNiCrAlY undercoating are reported. It is important to clarify the delamination mechanism. It is known that thermally growth oxidation (TGO) grows at the interface between ZrO_2-8%Y_2O_3 and CoNiCrAlY, and the TGO degrades the adhesive strength. The purpose of this study is to clarify the TGO growth process. Thermal aging tests of ZrO_2-8%Y_2O_3/CoNiCrAlY TBC systems under various temperature conditions were carried out. TGO growth process was observed by the electron probe micro analyzer (EPMA). Both TGO of Al and TGO of Cr were mapped, and the thickness of the TGOs were measured. Results are summarized as follows. (1) The delamination occurred at a ZrO_2-8%Y_2O_3 layer beside the interface. (2) The delamination occurred if the thickness of Al TGO layer increased over about 3μm. (3) The TGO of Cr didn't affect the delamination life, but affect the growth of Al TGO. (4) TGO growth rate was dependent of temperature. Taking into account of the temperature dependency, the thickness of Al TGO could be predicted with good agreement.
In order to investigate the influence of stress on growth of an oxide at an interface between a thermal barrier coating (TBC) and a bond coating, a creep test was carried out. The TBC of 300-μm thick Yttria stabilized Zirconia (YSZ) and 100-μm thick CoNiCrAlY was plasma sprayed on the surface of the Ni base superalloy substrate. The creep test was performed under various conditions of temperature and axial stress. It was found that the TGO grew following a parabolic law and it consisted of an Al_2O_3 layer. Both the composition and the shape of the oxide did not change regardless of the applied stress at temperatures below 950℃. However, the thickness of the TGO clearly increased with increases of the applied stress and temperature. It was about 23% when the applied stress was increased from 0MPa to 205MPa at 900℃ and was about 29% when the stress was increased from 0MPa to 150MPa at 950℃.
The two-way shape memory effect is expected as unique mechanical property for new engineering applications of shape memory alloys such as micro actuators. The two-way shape memory effect occurs by giving internal stress field to shape memory alloys. The mechanical loading training is the method to give internal stress field. The mechanism of the two-way shape memory behavior have not been understood yet. In this study, the two-way shape memory behavior obtained by the mechanical loading training was investigated experimentally. The obtained results are presented and discussed in this paper.
The shape memory alloys have been expected from a view point of engineering applications because of its unique mechanical properties. When the shape memory alloy which was deformed at low temperature is heated in the condition with the restriction of strain, the recovery stress occurs by a reverse transformation. In this study, the recovery stress after the torsional loading condition was experimentally investigated in TiNi shape memory alloy tube manufactured by the sintering synthetic method. The obtained results are discussed in this paper.
To develop high temperature shape memory alloys, TiPt and TiIr are noted because of their possibility of phase transformation above 1273K. Then, the effects of Iridium (Ir) into TiPt on the constituent phases and the phase transformation temperature were investigated. It was found that the B19 phase appeared up to 37.5at% Ir in Ti (Pt, Ir) and the phase transformation temperature raised from 1303K in TiPt to 1473K in the Ti-12.5Pt-37.5Ir. Shape recovery and superelasticity of Ti-50 (Pt, Ir) were investigated by thermal expansion measurement in dilatometer and loading-unloading compression test. The shape recovery was found in all compounds in at least one of the testing methods. The highest shape recovery, about 4% was found in Ti-25Pt-25Ir using loading-unloading compression test. On the other hand, superelasticity was found in only ternary compounds. Larger superelasticity was observed in ternary compounds with higher Ir contents. Potential of Ti-50 (Pt, Ir) as high-temperature shape memory alloys is discussed.
The influence of strain ratio on bending fatigue properties of TiNi shape-memory alloy thin wires and the process of fatigue crack growth were investigated. The results obtained are summarized as follows. (1) The maximum bending strain of fatigue limit is the martensitic-transformation starting strain. (2) The plane-bending low-cycle fatigue life curve is expressed by a power function between maximum strain ε_max and the number of cycles to failure. The smaller the strain ratio, the shorter the fatigue life.
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