The uncertainties involved in a structural system are discussed in conjunction with the resultant fluctuation of structural response. The methodology studied is a stochastic finite element method which is based on the mean-centered second order perturbation technique. Small probabilistic variables are assigned to finite elements in order to represent the uncertainties, and the rates of change of the finite element solution with respect to the probabilistic variables are evaluated by means of the perturbation technique. A way is described to estimate the variance of structural response in relation to the variance of the uncertainties. Numerical examples are given in regard to inply stresses of an FRP laminated plate with uncertain stacking parameters and natural frequencies of spatial pipe whose restraint locations are uncertain.

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The flow field near the tip of compressor rotor blades is distorted by leakage through the tip clearance and the performance of the compressor is deteriorated. The literature regarding the tip clearance of compressor blades consists of computational fluid mechanics and experimental studies on the flow field and the pressure loss. Empirical equations expressing the pressure loss and the efficiency drop are varied. They relate to the lift coefficient in different ways, such as proportional to C_L, C_L^1.5, C_L², or the sum of two terms, depending upon the ways of understanding the mechanics of pressure losses. These methods are examined and compared. Also, a brief discussion is made on the optimum value of the tip clearance.

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The fretting fatigue strength of a low strength medium carbon steel (JIS S45C) under two-step block loading was examined by using contact pads of the same material. The linear cumulative damage rule did not always hold for fretting fatigue under two-step block loading, while it held for plain fatigue. when the number of cycles in the block were large enough and the number of blocks to failure were smaller than 5 or 6, tow-step block loading reduced the fretting fatigue life by a factor of five to ten. The coefficient of friction and the relative slip amplitude reached constant values within a few hundred cycles after changing the stress level. Prediction of fatigue life was made on the basis of the analysis proposed in a previous paper, where the frictional force between the fretting pad and the specimen was taken into consideration. The predicted lives were in good agreement with the experimental results.

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Fatigue strength design techniques for spot-welded car body structures are studied. The load-carrying property per spot of a spot-welded structure is estimated by the finite element method. The validity of this method is confirmed by fatigue strength design procedure for spot-welded car body structures is shown.

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The influences of small vibratory stresses and the loading axis against grain flow directions on the initiation behavior of stress corrosion cracking (SCC) were investigated in high-strength aluminum alloys sensitive to active path corrosion type SCC. Irrespective of loading direction, the strength of dynamic SCC under a sustained load with small superimposed vibratory stresses (≧59MPa) was considerably lower than that of static SCC under a sustained load, σ_scc. The static SCC resistance in the TT orientation, where the loading axis is normal to the rolling direction, was superior to that in the LL orientation, where the loading axis is parallel to the rolling direction. Under dynamic loading, on the contrary, the strength in the LL orientation was higher than that in the TT orientation. Static SCC cracks under a sustained load were initiated at grain boundaries, whereas dynamic SCC cracks were initiated at grain boundaries, hydrogen-induced {111} plain cleavages, and transgranular sites associated with corrosion fatigue.

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A reliability evaluation system for ceramic gas turbines was developed. This system combined the results of a finite element stress analysis with a probabilistic analysis of ceramic structures. In this system, a new probabilistic method was used to estimate time and cycles to failure of multiaxially stressed ceramic structures. Using this system, fast fracture, static fatigue and dynamic fatigue can be evaluated. Also, the effect of the proof test on these failure modes can be evaluated quantitatively.

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This paper describes the characteristics of a turbulent slug and the velocity field in the inlet region for pulsatile pipe flow. Experimental conditions of the present study were arranged systematically by pulsation frequency and velocity amplitude ratio A₁. The experimental results regarding the onset of a turbulent slug, the propagation behavior of the slug, and the distributions of velocity and turbulence intensity inside the slug were compared with those for a turbulent patch in a pulsatile boundary layer on a flat plate. A close analogy was shown between them. When A₁ was smaller than 0.608, the velocity distribution for the laminar region outside a slug was approximated by an analytical solution previously presented for pulsatile laminar flow with a smaller A₁.

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This paper is concerned with the laminar-turbulent transition of three-dimensional boundary layers on cones rotating in external axial flow. The experiment was carried out for three cone angles of 15°, 30° and 60° in a range of free-stream turbulence (0.04% to 3.5%) using a hot-wire anemometer and a flow-visualization technique. The transition region was determined with the critical Reynolds number and the transition Reynolds number in relation to the rotational speed ratio. The spiral vortices were found to fix relative to the rotating surface. The relation of the direction of the spiral vortices to the rotational speed ratio remains unchanged as the cone angle becomes larger, while the number of vortices increases with increased cone angle. These experimental results were compared with the present numerical results based on the linear stability theory. The free-stream turbulence has no effect on the transition Reynolds number, while the effect becomes more sensitive to the critical Reynolds number as the cone angle is increased.

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When metering the flow rate of fluid in a pipeline, it is most important that the flow approaches the orifice flowmeter in a normally turbulent state. When the approach piping of an orifice flowmeter is shorter than that recommended by JIS Z 8762, it leads to a noticeable error. Hence, the rectifying device investigated in the first report was tested for its ability to reduce the error. This device was installed just behind single, double, and triple bends. The effects of bent pipes on the discharge coefficient of an orifice flowmeter were examined, experimentally. It was found that this device could reduce the minimum required lengths of a straight pipe on the inlet side of the orifice flowmeter to a large extent without sacrificing its accuracy.

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The shape of a horizontal slender jet of a liquid metal issuing from non-contacting circular nozzles under a non-uniform magnetic field is discussed. Our primary interests are to determine the shape of the free surface of the jet under such a field, and to demonstrate the possibility of the magnetic shape control of liquid metal jets. The basic equations of MHD flows are simplified by neglecting the terms concerning the viscosity, and solutions of the approximate analysis are presented. Parameters on which the magnetic shaping of jets are dependent are made clear. A jet with a circular initial shape forms a thin sheet, but maintains the same cross-sectional area. The shapes obtained by the approximate analysis are shown to be in good agreement with those of the experimental results using mercury.

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The motion of a spark-induced cavitation bubble is examined near a solid boundary by high-speed photography and the impulsive pressure generated at its collapse-reexpansion stage is detected by a local pressure sensor with four small sensor elements. As a result, the impulsive pressures of a shock wave and of a water microjet are separately measured by the local pressure sensor. The result is ascertained by high-speed photographs of the cavitation bubble, which indicate that a microjet is generated at the top surface of the collapsing bubble and collides against one of the pressure sensor elements through the interior of the bubble at its collapsing stage. Moreover, the diameter of the generated microjet tip and its travelling velocity through the interior of the bubble are evaluated to be about 0.5mm and 100110 m/s, respectively.

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This paper deals with the transient vibration of a rotating shaft with nonlinear spring characteristics during constant acceleration passing through a major critical speed. In a theoretical analysis, we solve the equations of motion numerically and discuss this phenomenon. paying attention to the nonlinear components represented by polar coordinates. As a result, it is clarified that when the angular acceleration λ and to a large extent at a certain value of λ=λ₀. This characteristic is different from that of a linear system, where the maximum amplitude decreases markedly in the range of small angular accelerations. We verified these phenomena in experiments. Generally speaking, it is more difficult to pass through a critical speed in a nonlinear system than in a linear system.

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The nonstationary response of an elastic circular cylindrical tank, partially filled with liquid, to lateral earthquake excitation is investigated by modeling the earthquake acceleration as an amplitude modulated nonwhite random process. The differential equation governing the displacement of the tank wall due to the finite amplitude liquid surface oscillation is solved directly and the results are compared with those obtained by Galerkin's method reported previously. A fairly good agreement is found between the previous and the present results.

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Many kinds of curve fit techniques have been developed for the estimation of the modal parameters of a mechanical structure, using the theory of modal analysis. As one of the most popular curve fit techniques which correspond to the multiple input vibration test, Vold's method in the time domain (Poly-reference) is well-known and used extensively. In this paper, a new method which results from improving Vold's method in the time domain is proposed to obtain global modal parameters. In Vold's method, residues are determined by using every column of the transfer function matrix. Then, any two columns of residue matrix contradict each other. In the proposed method, the residues are obtained at the same time by using all of the transfer function matrix. And such contradiction can be solved. With this method, modal parameters of the fly wheel of an automobile are identified. Comparing this new method with former methods, the validity of the new method is confirmed.

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Exact solutions of the autonomous Duffing equation, including the so-called snap-through spring system, are obtained in the Fourier expansion using elliptic functions. The characteristic parameter J in Fourier coefficients and/or the governing parameter m (or the complementary parameter m₁) of the complete elliptic integral of the first kind, K(m), must be determined to satisfy conditions which are characterized by the situation of the system as well as the natural (non-dimensional) frequency ν. In this paper, three algorithms are established to compute parameter m or m₁ exactly, by a trial method, and also three approximate formulae to express J are proposed. The solutions are grouped into five classes according to the characteristics of the spring system and the type of wave form of the vibration. The frequency responses and some salient features of the solutions are examined and illustrated generally. The numerical results of J(ν) are shown in tabular form, in which the relative error is about 10^-14.

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Large pulsations cause engineering problems such as piping vibrations, which may impede plant operations. Therefore, a pulsation study should be carried out during the design stage and the results should be incorporated into the piping design in order to minimize pulsations. This paper proposes a method of digital simulation, which takes the dynamic interaction between the reciprocating compressors and the piping systems into account, so as to accurately predict pulsations in a piping system. The digital simulation method is composed of two interactive models: a Compressor Simulation Model for calculating the pressure and temperature in the cylinder, etc., and a Piping Model for calculating pulsations by applying the modal analysis method. Comparisons between the calculations and experimental or field data have proven that accurate predictions of pulsations can be made using the digital simulation method proposed in this report.

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This paper presents a study on the effect of radial clearance between a planet gear and shaft on the root stress of a planet gear. The stress analysis of planet gears with various radial shaft clearances by the finite element method (FEM), in which the elastic contact between a planet gear and shaft was taken into consideration, was carried out under different normal tooth loads, and the relation between the root stress and normal tooth load, the effect of radial shaft clearance on root stress, the position of maximum root stress and the cyclic stress under running conditions were examined. Furthermore, the stress analysis of planet gears with various radial shaft clearances and rim thickness was carried out and the stress state of a planet gear with radial shaft clearance was clarified to a considerable extent.

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A new method of displacement analysis for complex six-link mechanisms of the Stephenson-type, which are composed of only turning pairs or one sliding and six turning pairs, is developed for the purpose of automatic calculations of kinematic properties. First, the displacements of the links of twenty-three kinds of mechanisms are calculated by the formulas for the geometric analysis of two kinds of five-link structures. Then, the equation of sixth degree is solved by the Strum theorem and the Ferrari method. Second, the composition loops and domains of motion of the driving link are discriminated by domains on four number lines, which are separated on the basis of the limit-positions of motion of the driving link and the special positions of component four- and two-link chains. This discrimination algorithm can also be used as the Grashof condition of complex six-link mechanisms.

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The number and dimensional syntheses of mechanical grippers with multiple degrees of mobility are presented systematically. Several types of contacts of fingers with a grasped body are considered as kinematic pairs, and number conditions for grasping a body are derived by applying Grubler's mobility equation to the gripper-body kinematic system. A number synthesis of a gripper with one input and three degrees of mobility, as an example, is carried out, and dimensions of parameters of such a gripper are determined by considering action forces and transmissibilities. Moreover, the graspable size of a circular cylinder by such a gripper is obtained, and is compared numerically to that with the use of a conventional parallel-two-finger-type gripper. Also, characteristics such as shapes, sizes, and masses of the bodies are obtained with respect to a circular cylinder, a regular square prism, and a hexagonal prism.

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Failure of a cutting tool is one of the most serious problems in machining systems. Therefore, several methods have been proposed so far to detect cutting tool failure. However, most of them have some problems from the viewpoint of practical application. In this study, an acoustic emission sensor is used to detect cutting tool failure and a monitoring system which has high reliability is developed. The failure of single-point as well as multipoint cutting tools is successfully detected with the monitoring system developed in this study.

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