Double-nut tightening fastening is widely known as one of the methods for preventing loosening. However, it is also well known that unless a self-locking state is properly realized the effect of loosening prevention is lost. There are not many precedents where double-nut performance was verified on the basis of these features. For this reason it is believed that it is very important to consider the loosening-prevention mechanism of these fasteners. In this paper, we analyze and explain the locking mechanism of a double-nut tightening system by three-dimensional finite element method. In addition, we also analyzed the loosening under shear loading and investigated the relation between locking state and loosening-prevention performance. Qualitative accordance with experimental results of tightening analysis presented by Yamamoto et al. was obtained. What was also made clear was that if the locking is properly realized, double-nut fastening is a very effective loosening-perevention method. On the other hand, if locking is not achieved properly, this method cannot be relied upon for loosening-prevention.

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The extended finite element method (X-FEM), which can model the domain without explicitly meshing the crack surface, can be used to perform stress analyses for efficiently solving fracture mechanics problems. In this study, the constraint condition enforcement for X-FEM analysis considering symmetry is presented. Since the interpolation functions utilized in X-FEM analysis include the enrichment basis functions, the freedoms of the node on the symmetric plane should be constrained properly in X-FEM model with symmetric conditions. Moreover evaluation of the energy release rate by the domain integral method should be performed considering symmetry conditions. In this paper the constraint conditions for three-dimensional X-FEM analysis considering symmetric conditions are summarized and the numerical examples using symmetric X-FEM models are shown. The proposed procedure can be used to perform efficient X-FEM analyses of practical fracture problems.

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In this paper, discussions on B-spline wavelet Galerkin method are presented for its mathematical formulations and numerical implementations. Scaling function and wavelet are used as the trial and the test functions in Galerkin formulation. Quadratic and Cubic B-spline scaling function/ wavelet are adopted as the basis functions. These basis functions have simple forms and are easy to integrate and differentiate. Furthermore, they have the so called multiresolution properties. The stress and strain solutions are continuous throughout the analysis domain. However, there are some difficulties in dealing with external boundaries. They are due to the loss of linear independence of the basis functions. To circumvent these problems, we introduce the boundary scaling functions/ wavelets or eliminate particular basis functions that can be expressed by the linear superpositions of the other basis functions. Numerical results are presented for the problems of tensile plate with a circular hole.

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This paper presents an analytical solution for an, infinite strip having a circular inclusion when the strip is subjected to tension at infinity. In the analysis, the inclusion is assumed to be perfectly bonded and be allowed to slide. The analysis is based on the Papcovich-Neuber stress function approach and the solution is obtained by the proper combination of harmonic function in integral forms and infinite series. The boundary conditions at the interface uniting the strip and the inclusion are satisfied using the relations between the polar and Cartesian harmonics. The numerical results obtained from the proposed method are illustrated for various stiffness ratio and sizes of the inclusion.

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Many literatures have been given for the stress intensity factors of a crack emanating from a hole or notch in infinite or semi-infinite body. However, there has been few detailed discussion about applicability of such stress intensity factors for the finite body. In this study, the stress intensity factors of a crack emanating from a U-shaped center notch in finite plate are analyzed for various crack lengths and parameters characterizing plate dimensions and notch shape on the bases of the body-force method. These results are then compared with those for the center-cracked plates. Also, the relationship between the variations of such stress intensity factors and the fatigue crack's behavior are discussed. The stress intensity factor of center cracked specimens can approximate that of center notched specimens with crack when an equivalent crack length is used for calculations in the cases of p/W<0.1 and c/p<1, where c, p and W are crack length measured from notch bottom, notch root radius and semi-width of specimen, respectively.

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Energy release rate for a 3-dimensional crack was examined by a virtual crack closure integral method in a FEM analysis where virtual extension for a part of crack tip element was used instead of a full element in usual procedure. Limiting case of zero crack extension was found to give a fairly well approximation of exact energy release rate and, hence, to relax the restriction of finite element arrangement around a crack front line because only nodal forces on a crack front line are needed. New method using zero virtual crack extension was proposed and applied to an embedded elliptical crack, semi-elliptical surface crack and one-quarter elliptical corner crack under tensile load. Estimated Mode I stress intensity factors were found to approximate Raju & Newman's results within several percent discrepancy for wide range of ratios of major to miner axes of ellipse.

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Plastic deformation and work-hardening of a crystal are caused by dislocation motions and dislocation accumulations, respectively. Recently, studies of crystal plasticity with the dislocation information have actively been done by many researchers. In this paper, both densities of isolated dislocation and dislocation pair corresponding respectively to the conventional GN and SS dislocation densities are uniformly defined as geometrical quantities, i.e., GN dislocation density and GN incompatibility tensors by extending Kröner's dislocation density and incompatibility tensors so that they are suitable for a crystal plasticity framework. Furthermore, we newly introduce a term of dynamic recovery that occurs in stage III of work-hardening of a single crystal into the expression of dislocation density. A new model of dislocation-crystal plasticity coupling deformation field with dislocation field is developed by introducing these dislocation densities into a hardening modulus matrix of crystal plasticity through the Bailey-Hirsch relation.

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Behavior of fatigue crack that grows to the rolling direction about 30 degrees to the loading direction as a mixed mode I + II crack in peculiar anisotropic commercial pure aluminum sheets (A 11110 p) was investigated using CCT specimens. From fatigue tests, it was found that the crack started to change the direction from mode I to the rolling direction when mode I stress intensity factor range was 4.2 MPa·mm^1/2 and crack grew continuously to the rolling direction when mode II stress intensity factor range was 4.3 MPa·mm^1/2 under small scale yielding state. However, in the case of specimen annealed in 563 k, 30 minutes, the crack did not grow to the rolling direction. The crack that grew on the rolling direction changed direction to mode I direction, due to the nominal stress which was about 80 percent of yield stress. According to the measurement on crystal planes using X ray diffraction, it was found that the slip plane of aluminum. (III) plane dominantly existed on the fracture surface of the crack that grew to the rolling direction. From pole figures, it was also verified that strong textures of (III) planes existed in rolling direction, so that the shear strength on the rolling direction was low as confirmed by shear test. Due to the strong textures of (III) planes that exist around the maximum shear stress region, the mode II crack component becomes easily to occur that makes the mixed mode I+II crack to grow to the rolling direction around 30 degrees towards loading direction.

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This paper proposes a new method for evaluating mode I, mode II and mixed-mode stress intensity factors from displacement fields around a crack tip obtained by experimental or numerical methods. Using two displacement components on an orthogonal coordinate system, not only stress intensity factors but crack tip location, higher order terms in the series expansion of displacement fields and rigid body displacement components are determined simultaneously using nonlinear least-squares based on Newton-Raphson method. The validity is demonstrated by applying the proposed method to mixed-mode displacement fields obtained by digital image correlation, elasto-plastic displacement fields obtained by finite element method, and displacement fields around a fatigue crack obtained by electronic speckle pattern interferometry. The results show that the stress intensity factors are evaluated accurately from the displacement fields by the proposed method. Furthermore, they can be determined even if the material exhibits small scale plastic deformation. As stress intensity factors can be evaluated easily and accurately, it is expected that the proposed method can he applied to various fracture problems during experimental and numerical evaluation of structural components.

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The new approximate evaluation method was proposed for thermal transient stress under variable heat transfer coefficient. The proposed method uses Green functions and convolution integral. The proposed method was applied to the calculations of thermal transient stresses of a skirt-structure and a tube-sheet structure of IHX (intermediate heat exchanger) in commercialized fast reactor. It was verified that the proposed method gave good estimations for thermal transient stresses of those structures

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This paper deals with fatigue damage and life prediction of CFRP cross-ply laminates. Fatigue tests are carried out on CFRP unidirectional and cross-ply laminates under the on-axis and off-axis directions. On the unidirectional laminate, fiber breakage and fiber-peeling develop before the final fracture under on-axis fatigue, while the final fracture suddenly occurs by cracking along the fiber direction under off-axis fatigue. On the cross-ply laminates, ply-cracking in 90° plies and fiber-peeling in 0° plies develop under on-axis fatigue, while ply-cracking and delamination lead to the final fracture under off -axis fatigue. Based on the comparison of damage behavior and S-N curves between unidirectional and cross-ply laminates, possibility of fatigue life prediction of CFRP cross-ply laminates is discussed.

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Due to low impact strength of C/C, it's important to evaluate impact damage properties and impact strength. In this study, the estimating method for impact damage is used to evaluate the relationship between the impact load and displacement, absorbed energy of C/C specimens on a drop weight impact test. The measured impact load is decomposed in approximation components and detail components by multiple resolution analysis in wavelet transform. The results are as follows : (1) The Daubechies' wavelet is useful for smoothing the impact load signals by multiple resolution analysis in wavelet transform. (2) In the low impact energy that most of the damage does not produce, the approximation component demanded by wavelet analysis accords with the wave pattern of the numerical computation result that is removed free vibration component.

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Due to low impact strength of C/C composites, it's important to evaluate impact damage properties and impact strength. In this study, the estimating method for impact damage is used to evaluate the relationship between the impact load and displacement, absorbed energy of UD-C/C specimens on a drop weight impact test. The measured impact load is decomposed in approximation components and detail components, and is reduced higher mode of vibration by multiple resolution analysis in wavelet transform. The results are as follows : (1) It is effective for evaluating the damage zone and the initiation by using the impact load-deflection diagram and the absorbed energy. (2) The Daubechies' wavelet is useful for smoothing the impact load signals by multiple resolution analysis in wavelet transform. (3) In the low impact energy that most of the damage does not produce, the approximation component demanded by wavelet analysis accords with the wave pattern of the numerical computation result that is removed free vibration component.

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A computational modeling is established for the electrochemical-poroelastic behavior of conducting polymers (CPs) such as polypyrrole. The three-dimensional continuum modeling given by Della Santa et al. for the passive, poroelastic behavior of CPs is extended to the formulation for the active, electrochemical-poroelastic formulation according to Onsager-like laws, which is combined with the one-dimensional equation for ionic transportation. The validity of the finite element formulation for these governing equations has been demonstrated by numerical studies for the passive and active responses of polypyrrole films.

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This study presents a method to evaluate anisotropic mechanical properties of a bone tissue using a scanning acoustic microscope (SAM). The measurement theory was constructed based on transverse isotropy of the bone tissue. Density and elastic modulus of it were analyzed via distributions of leaky surface wave velocity and acoustic impedance of micro parts of bone tissue measured using SAM. Velocity of the leaky surface wave was measured in the directions from longitudinal axis to transverse axis of long bone by rotating a lens slit attached to the front of a point focus acoustic lens. Anisotropic elastic modulus were determined by using orthotropic elastic constitutive equations and wave equations. Femur bones of elderly human and young beagle dog were measured by this method. It was found that the elastic modulus of femur bone of young canine showed more anisotropy than that of elderly human.

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High-temperature tensile tests were repeatedly conducted for a TZP specimen at 1, 400°C in air at intervals of about 2% of the true plastic strain up to 17.4%. After each deformation, displacement vectors of the specified 760 grains were measured from their position vectors obtained by FE-SEM micrographs. In a short time period during plastic deformation, grains moved gradually turing to the tensile axis in a zigzag way. At an early stage of deformation, the length of displacement vector distributed in a wide range because of their initial configuration after sintering. Further plastic deformation, however, grains tended to have their own movements depending on the constraint of the surroundings. In a middle time period during plastic deformation, a group of grains moved to the same direction so that several domains were formed. However, the domains disappeared due to constraint by the surrounding matrix, and other domains were formed by re-combination of grains. In a long time period during plastic deformation, grains seemed to be moving along path lines of a non-compressive fluid subjected to uniaxial tensile loading.

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We focused our attention on microstructure control and improvement of mechanical properties of induction tempering carbon steel using super rapid induction heating system. We examined the effect of tempering time on tensile properties. The tempering time was changed in two steps of 0.35 s and 1.15 s. As a result, it was found that the QT steel obtained super rapid induction tempering had both high strength and high ductility. The ductility of the super rapid induction tempering steel was 10% larger compared with the usual tempering steel. The reason for this phenomenon was explained in that cementite particle of super rapid induction tempering steel became small and dispersed finely in comparison with usual tempering steel.

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This paper reports on a new technique for measuring of birefringence to obtain stress fields using laser photoelasticity. This technique provides for the measurements of magnitude and the azimuth of the birefringence without the necessity of sample rotation. In order to check the validity of the technique, birefringence of a quartz waveplate was examined. Good quantitative agreement was obtained between measured values and the theoretical calculations. The cause of the error of the experimental results here is also discussed. It was confirmed that the error is consistent with the imperfection of a crossed state of polarizing prisms and with the tolerances of quarter-wave plates.

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The shape of a stress wave in a thin viscoelastic rod changes as it propagates because of attenuation and dispersion that mainly depend on the material damping. In a thick viscoelastic rod, however, the shape of the stress wave is also affected by a geometrical factor, such as a rod diameter. Pochhammer-Chree theory as well as Love theory is developed for viscoelastic rods of finite thickness in order to study geometrical effects on the attenuation and dispersion properties. Applying the Fourier transformation to both theories, attenuation and dispersion properties are evaluated in the frequency domain. Several wave propagation experiments are performed on polymethyl methacrylate (PMMA) rod specimens to evaluate the analytical results. Analytical solutions of the transient response are obtained to examine three-dimensional effects on axial strain-time histories. In addition, the applicability of Elementary theory is discussed.

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Cavitation erosion tests were carried out by using Ti-Ni base SMA (shape memory alloy) with the addition of the third element (Co, Fe, V and Cu) to Ti-Ni SMA. The erosion resistance and the mechanism were discussed. Erosion resistance of Ti-Ni base SMAs is about 1/4 to 1/2 as compared with that of Ti-Ni SMA, but it is about 6 to 16 times as high as that of SUS 304. It was found that the erosion resistance for martensite phase is superior to that for austenite phase. It was concluded that the erosion resistance of Ti-Ni base SMAs depends mainly on the defect density and the removal rate of eroded area.

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