Distribution of residual stress in a plate may be determined by the stress analysis using X-ray. In this connection, the present authors propose two kinds of method to obtain two principal components of residual stress in a plate. A plate having residual stress is electrolysed only on one side to remove thin layers successively, and two methods are applied to it for obtaining two principal components of residual stress. One of them consists of that the residual stresses are calculated from the stress distributions in two principal directions measured by using X-ray on the electrolysed surface successively (front surface method). In the other method, residual stress distributions are calculated from the stresses successively measured by using X-ray on the surface opposite to the electrolysed or chemically etched surface (back surface method). In these two methods, theoretical formulas are derived respectively from the corresponding integral equations of Volterra type. As examples of the two methods proposed by the present authors, principal components of residual stress in a thin steel plate are measured, and the results are compared with those obtained by the usual methods, curvature method and strain gauge method.

View full abstract

This paper is concerned with the limit analysis of shells of revolution made of a rigid-perfectly-plastic material that obeys Tresca's yield condition. The four-dimensional yield hypersurface for shells of revolution was once presented by E.T. Onat and W. Prager. Using this yield surface, a numerical solution for simply supported conical shells was obtained by R.H. Lance and E.T. Onat. Fundamentally based on their method and considering more precisely the yield hypersurface, a numerical method is presented that can be applied to general shells of revolution. As numerical examples, the solutions for truncated conical shells, and pressure vessels with rigid circular plates are presented. These solutions verify that this method is correct.

View full abstract

The Problem of bending deformation of U-shaped bellows has not been treated hitherto except by an approximate energy method, and the presentation of the data for this problem is being looked forward to by the designers in piping engineering at the present time. In this paper, the numerical method proposed by B. Budiansky and P.P. Radkowski for problems of unsymmetrical bending of axisymmetric shells, is applied to the problem mentioned above, and the design data for it are presented.

View full abstract

The problem of a corrugated plate under a uniformly distributed load is studied in this paper, and the deformations and stresses produced are discussed. The cross section of the corrugated plate is considered as a combination of two cylindrical shells with the same radius, and using the differential equations of thin shell theory introduced by Dr. Mizoguchi, an exact solution is obtained, and the results are compared with the experimental ones. In the numerical calculation, we took into account various values of the length of shells, and two forms of the cross section. The results show that the deformations and stresses have considerably various features according to the length of the shell and the forms of the cross section. For instance, in the case of long shells, we can say the results are similar to those of the elementary beam theory, but, as the length of shells turns out to be smaller, the results become complicated gradually.

View full abstract

The authors proposed a hypothesis of cumulative damage due to the low cycle fatigue and gave the following formula for fatigue fracture criterion for the multi-stage loading test; Σ^^p__(i=1)(n_iΔW_ci)(σ_maxi)^α=C(σ_maxp)^β where n_i and ΔW_ci are number of cycles and plastic strain energy per cycle in the i-th stage, respectively; σ_maxi and σ_maxp denote maximum tensile stresses in the i-th and final stages, respectively; α, β and C are material constants. Experimental data on stainless steel show that the above formula approximately holds good. The above formula is transformed into Σ^^p__(i=1)a_i(n_i/N_fi)=1 for multi-stage constant strain cycling test. Deviations in the experimental value of Σ(n_i/N_fi) from Miner's damage rule may be explained by this formula.

View full abstract

This paper describes the analyzing method in a complicated vibration system as in the machine tools structure, which makes possible the improvements and compensations of the dynamic characteristics of these machines in the predesign stage. This method utilizes the signal flow graphs reducing to the direct simulation by the analogue computers, so that the physical meaning of the vibratory phenomena occurring in real systems can be easily recognized and the nonlinear feedback oscillations as observed when the machine tools are cutting the metal, can be handled successfully. In this paper, how to construct the signal flow graphs of the machine element considered as a distributed parameter system, is described by use of typical examples. After that, the results of the computation and experiments are compared to indicate the precision of this method.

View full abstract

In this paper, the author analytically investigates a second order control system with dead time and saturation and he elucidates selective occurrence of self-oscillation in the system. The conclusions obtained are as follows: The system has several pairs of unstable characteristic roots in some intervals of dead time. Among a number of self-excited modes of oscillations which correspond to unstable roots, only one mode of oscillation develops and settles down to a steady state periodic oscillation under the effect of saturation (the oscillation is referred to as self-oscillation). Although occurrence of two or more modes of self-oscillations may be possible in some intervals of dead time, these modes of oscillations can never occur simultaneously, but only one mode of them can occur depending upon the initial condition. The condition of occurrence of self-oscillation is analytically expressed and also amplitudes and frequencies of self-oscillations are theoretically obtained. The theoretical results are in good agreement with the experimental results by analog computer.

View full abstract

Experimental and theoretical studies of the fluctuation of air-water two-phase slug flow in a vertical tube, have been described in three papers. Among them, the experimental results are presented in this paper. It was verified that the time variation of pressure drop is predicted by the variation of lengths of gas bubble and liquid slug flowing in the tube. It was also shown that the probability distribution of pressure drop in long segments of tube is normal distribution, and that in short segments, distribution has generally two peaks at Δp^* (i.e., dimensionless pressure drop) =0 and 1. The maximum amplitude of the pressure drop was given by the following empirical equation δΔp_max^*/Δp_m^*=0.7L_T^-0.62w_l0^-0.62w_g0^0.9 where, δΔp_max^* and Δp_m^* are the maximum amplitude and the mean value of dimensionless pressure drop, respectively; w_l0 and w_g0 superficial liquid and gas velocity, respectively; and L_T is the length of segment of tube.

View full abstract

The fluctuation of pressure drop was analyzed theoretically, and the basic equations were derived. The probability distribution of the pressure drop was obtained from the equations by means of Monte-Carlo method, and was verified to approximated the experimental results described in the 1st report. In order to generalize the characteristics of pressure drop, the correlation among three dimensionless numbers, namely, Δp⁺, L_T⁺ and L_gm, has been proposed, where, Δp⁺ is the dimensionless pressure drop, L_T⁺ the dimensionless length of segment of tube L_T/(L_lm+L_gm), and L_gm and L_lm the mean lengths of bubble and slug, respectively. Also, the calculated results of the probability distribution of Δp⁺ have been shown. Using the above numbers, the maximum amplitude δΔp⁺_<max> of dimensionless pressure drop is expressed by δΔp⁺_<max>=1.05[L_T+(L_gm/L_lm+L_lm/L_gm}]^-0.62

View full abstract

The variation of pressure difference in a vertical tube when a single gas bubble rose in still water, was investigated experimentally and theoretically, as a fundamental study of two-phase slug flow. The pressure recovery Δp_R due to the momentum of liquid film around a gas bubble was studied experimentally. It was shown that Δp_R is about 30 kg/m² or less theoretically, and agrees with the experimental value. Moreover the theory was extended to the general two-phase flow, and the results that Δp_R takes a value of 40∼50 kg/m², was obtained experimentally and theoretically. And also the statistical characteristics of the lengths of bubble and slug were described, which were used in the analysis of the fluctuation of pressure drop in the 1st and 2nd reports.

View full abstract

The velocities of the inlet air, the exhaust gas and the air flow in the cylinder of crankcase scavenged two-stroke cycle engines were measured successfully by the method utilizing the property of electric discharge. The test results are as follows: The inlet air velocity varies mainly due to the natural oscillation in the system consisting of inlet pipe and crankcase, and it is influenced by the compressibility of the air. It is also recognized that the maximum charge is obtained by making the port opening period equal to 3/4 of period of the natural oscillation. The velocities in the transfer passage and the exhaust pipe during the scavenging process are influenced by the oscillation system consisting of crankcase, transfer passage, cylinder and exhaust pipe and are also influenced remarkable by the air column oscillation in the exhaust pipe when the engine speed is high.

View full abstract

A crankcase-scavenged two-stroke engine with piston controlled ports has inevitable backflow of inlet charge at low speed in case where the inlet port timing is designed to be suitable for high speed operation. This paper describes an attempt that was made to prevent the backflow by a fluidic device which has diode characteristics, namely a fluid diode. A comparison of the effects on delivery ratio produced by two typical types of fluid diodes, i.e. a scroll diode and a vortex diode, is made and it is shown that the former is more effective than the latter. Experimental evidence of prevention of backflow by the scroll diode is provided showing the data compared with those for its acoustically equivalent device. The inlet system with the scroll diode is theoretically analyzed to give the trend of the delivery ratio with engine speed, by simulating the engine having a straight inlet pipe with an acoustically equivalent length and with flow resistance which varies with flow direction.

View full abstract

In this paper, a new cycle concept is presented, that is, the suction cooling gas turbine cycle using the bleed air has been devised in order to improve the part-load performance characteristics of gas turbine. Then, the analysis of this cycle has been made thermodynamically from both the design point and the part-load performance. The results of analysis have revealed: (1) at the design point this cycle gives little advantages in both thermal efficiency and specific power for the given conditions over the conventional cycle. (2) The part-load thermal efficiency can be highly improved in the constant speed operation for the fixed turbine inlet temperature owing to application of the higher value of an air bleed rate.

View full abstract

The purpose of this paper is to show dissimilarities between the Marform process and the hydroforming. Firstly, the forming pressure distribution over the rubber die surface is clarified from the measurement. Secondly, it is emphasized that the deformed profile at the forming radius portion determined theoretically agrees fairly well with the experiment considering the above pressure distribution and the frictional force between a sheet metal and a rubber die. Finally, it should be noted that the frictional force at the side wall portion does not always play so important a role as in the hydroform method in preventing the concentration of the forming force at the punch profile portion. The product of the drawing ratio 2.76, however, can safely be obtained by regulating the forming pressure so as to make good use of the frictional force.

View full abstract