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Vol. 14, No. 1 (1958)

1958-01-05
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CONTENT
THE FRICTION-FIELD OF LEAST RESISTANCE
LIU SHU-I
1958, 40 (1): 1-8. doi: 10.7498/aps.14.1
Abstract +
The contact surface in plastic deformation is considered as a field, whose field-line is given by the "generalized rule of gradient" based upon the condition of least resistance applied both to effective and ineffective direction of "relative" slip on solid and liquid surfaces, as shown by equation (1),which is the formulation of the sta tement that the direction of field-lines is the direction of (most rapidly) decreasing frictional resistance [equation (2) ]. The main results are:(1 )The rule of field lines is given by equation (l)and(2). Accordingly, for dry friction, the"resistant" field is divergent; for plastic lubrication, the "lubricating" field is convergent (Fig. 1). There may be combination of both types, as shown in Fig.l(c) and Fig. 4 for the case of plate-rolling. (2)The two field functions, the unit friction (τ) and the unit pressure (p) are governed by equations (3), (4), (8), (9), (11), given in this work, by equations (5), (6), (7), (15) of classical theory and by equations (6), (12), (14), (16)and Fig. 6, all based upon classical concept, but first used in our work. Fig. 6 deals with range of variation of what is termed the "point of friction", that is, (τ, p) point in the stress plane. Equation (12) reads: The point of friction (Q) must be on the segments of the curve τ=Fp, merged in the closed field limited by the three stress circles where F is the "friction-function" defined by equation (6). In these equations, S is are-length of field lines. The other designations are self-evident. (3) A region of sticking in plate-rolling is determined by equation (15) as shown in Fig.6. It is pointed out that the value of the coefficient of friction can be measured by two separate experiments on pressure distribution and on friction-lines.The friction-field of least resistance provides a new fundation for plasticity under pressure.
LONG RANGE AND SHORT RANGE FRICTIONAL SLIP-LINES ON PLANE CONTACT SURFACE IN PLASTIC COMPRESSION (THE RULE OF ISOCLINIC GRADIENT)
LIU SHU-I
1958, 40 (1): 9-16. doi: 10.7498/aps.14.9
Abstract +
In the recent years, the theory related to friction-lines has been independently developed both in Europe and here, according the information reached the author in 1956. These investigations are based on the condition of least frictional resistance at a point.In 1954, a variational equation (2a) on classical basis was given on a meeting for the related research. This equation was based on the frictional work at point. In as much as the condition of least force at a point has became acceptable, there seems no reason to object the condition of least work at a point, that is, the frictional work along the path of an element of area. Thus, the above equation are further investigated in this paper.For the case of short range slip occuring in processes such as plane forging under small reduction, the last term of this equation is zero, the rule of gradient follows. Therefore, the rule of gradient holds only for short range slip or instantaneous friction-lines.For long range slip, this equation leads to the "rule of isoclinic-gradient", (equation 9), which states that the gradient line of pressure (p) is the isoclinic curve for frictional force τ(Fig. 2). The angle of inclination (φ) changes along the pressure contour according equation (11), and along the friction-line according to equaiion (14). The function (τ) has the general nature of equation (16). Examples for long range slip is given in Fig. 3 and 4. Continuous divergent long range slip can only be generated by point or line-sourse in extrusion. The singularities in the case of short range slip are not real sourses.In this analysis, the frictional force is regarded as a shear stress on pure mechanical basis, without assuming its physical nature.For complete details of the paper, see[10].
THE ROLLING AND RECRYSTALLIZATION TEXTURES OF ARMCO IRON
TAT LI-CHI, CHANG SIN-YU
1958, 40 (1): 17-22. doi: 10.7498/aps.14.17
Abstract +
A study of the preferred orientations and microstructure of armco iron after cold reduction and recrystallization has been made.The treatments consisted of hot-rolling the material into strips and (1) a cold reduction of 98.8 percent or ( 2 ) two cycles of cold reduction of about 64 percent with an intermediate anneal. All these specimens for recrystallization were treated in hydrogen at 650° and 1000℃.The components after deformation for material (1) were found to be (100) [011] +(112) [110] + (111) [112] . The primary orientations of the specimens treated in a and γ regions were determined as (100) [011] and (111) [112] .The cold rolling textures of material ( 2 ) were found to be the same as those of (1), the deviation angle being larger. The surface texture was different from the texture possessed by inside of the sheet. The microstructure showed the phe-namena of secondary recrystallization for the samples treated at higher temperature.
ULTRAPHOTOMETER USING MAGNETICALLY MODULATED PHOTOMULTIPLIER
G. O. STRIKER
1958, 40 (1): 23-36. doi: 10.7498/aps.14.23
Abstract +
Theoretical considerations indicate that by applying the Magnephot principle to photomultipliers, a simple and rugged industrial microphotometer may be built in the range of extremely low light intensities. The requirements for a low input impedance and a conservative input signal level can be successfully combined with a satisfactory signal-to-noise ratio without the use of mechanical light chopping. The external-shield method of dark current suppression may be usefully employed to extend the sensitivity limit to lowest light values, limited only by the discontinuous nature of the light flux.Experimental investigation confirmed these assumptions and led to the construction of a sturdy and simple ultra-photometer of inherent electrical stability. The limit of useful sensitivity is around 10-12 Lumen, corresponding to the light collected by a 24" telescope from a star of the 14th order. Experiments with scintillating crystals yielded data about the use of the new instrument as a quantitative sensing device for nuclear radiation. The experimental instrument gave satisfactory performance as to zero stability, independence from leakage currents and the exclusion of dark current without cooling. The use of a.c. amplification assured convenient range-switching and the possibility to amplify the signal further for registration or control purposes. The new ultra-photometer will now be investigated in conjunction with spectrophotometry, astronomic and other low-level photometry as well as the indirect measurement of X-ray and nuclear radiation.
THE INTERFERENCE PHENOMENA OF LIGHT AT VERY LOW INTENSITY
L. JANOSSY, Zs. NARAY
1958, 40 (1): 37-53. doi: 10.7498/aps.14.37
Abstract +
An interference pattern is obtained with a Michelson interferometer; the intensity distribution in the pattern is determined by counting the rate of photons by means of a photomultiplier. It is shown that the pattern obtained for very low intensities of light does not differ outside the margin of experimental error from the pattern obtained for normal intensities. At low intensities about 106 photons enter the interferometer per second thus for these low intensities in average at any time much less than one photon is contained inside the interferometer.
THE RELATION BETWEEN SPECTRAL LINE INTENSITY AND CONCENTRATION OF THE CONSTITUENT IN THE PRESENCE OF SELF-ABSORPTION
HO I-DJEN, HSU SHENG-MEI
1958, 40 (1): 54-63. doi: 10.7498/aps.14.54
Abstract +
The functional relationship between intensity(I) of an emitted line and concentration ( C ) of emitting atoms serves as the physical basis for quantitative spe-ctrochemical analysis. The presence of self-absorption in spectral lines of most laboratory light sources, however, makes the dependence of I on C complicated.A study of variation of slope ( b )of the calibration curve (Si 2516-Fe 2518) with concentration of silicon in cast iron samples by the "transfer method" of spectral analysis was carried out under the condition that within the range of Si content studied, Si 2519 was free from self-absorption and Si 2516, the most intense component of the multiplet was showing self-absorption. A straight line has been obtained by plotting 6 versus log I2519 which was used as a measure of log C. From the slope ( k ) of this straight line, following relationships were derived: b=klogC+β+1,(1) and logI=k/2(logC)2+(β+1)logC+α, (2) where β and α are experimental constants. In the case of Si 2616, the value of k has been found to be about-(1/2) The change of spectral intensity with concentrationin the presence of self-absorption expressed by equation ( 2 ) was found to be in agreement with laboratory observations in general.
APPLICATION OF γ RAYS EXCITED BY HEAVY CHARGED PARTICLES IN THE DETERMINATION OF ISOTOPIC ABUNDANCES
YEH MING-HAN, LI CHENG-WU
1958, 40 (1): 64-70. doi: 10.7498/aps.14.64
Abstract +
Possibilities of using the γ rays excited by bombardment of an element with heavy charged particles to determine its isotopic abundances are discussed. With necessary facilities, this method, essentially a microanalytical or ultramicroanalytical method, would be convenient, especially if. a sample containing definite isotopic abundances is used as a standard for comparison. Nuclear reactions and γ rays suitable for the determination of isotopic abundances of Li, B, C and N are enumerated.
THEORY OF INTERNAL FRICTION IN A FACE-CENTRED CUBIC LATTICE
CHENG KAI-CHIA, CHANG SHEN-KWAI
1958, 40 (1): 71-81. doi: 10.7498/aps.14.71
Abstract +
It is now well-established that stress-induced micro-diffusion of carbon atoms in the interstitial lattice points will take place in body-centred cubic lattices such as in α-iron. This is the result of the lattice asymmetry introduced by an oscillating strain in the crystal. In a pure face-centred cubic metal, this phenomenon could not happen, namely, not in γ-iron. Nevertheless experimental evidences show to the contrary.The present note advances a criterion concerning the possible types of mechanisms which would give rise to internal friction in a face-centred cubic crystal. By the application of the general thermodynamical theory of internal friction, proposed by one of the present authors, we have calculated the relaxation strength for two important cases. If the asymmetry in the interstitial lattice points is to be ascribed to the presence of impurity or alloying atoms, then it can be shown that the relaxation strength will be proportional to the expression CxA (1-xA) , where xA. is the density in atom percentage of the impurity or alloying atoms and C is the density of the carbon atoms. However, recent experimental result of Ke and Tsien indicates that there is nothing like this sort of density dependence, i. e. it is rather structure insensitive. Hence, it is not likely that this micro-diffusion can be ascribed to the action of the alloying (substitutional) atoms.A second possible mechanism is proposed in the text. The asymmetry is due to the presence of the Schottky defects, in which a pair of carbon atoms settle down and orientates itself in accordance with the direction of external strain; the possible location of the pair may be such that one carbon atom is located in the centre of the hole while the other is in an interstitial point immediate to the hole. The calculated relaxation strength is proportional to the expression AC2/(B +C), where A and B are such constants that B is structure insensitive. A comparison of the calculated and the experimental curve for the internal friction strength is made in the text, which shows a remarkable agreement. Furthermore, one can thereby estimate the free energy evolved in trapping a carbon atom in a Schottky hole to about the order of 0.14 eV. It seems that the above proposed vacancy-induced asymmetry might be a possible correct explanation.The authors like to tend their appreciation to Dr. Ke Ting-sui and his collaborators for the kindness to communicate to us their results before publication and to their valuable discussions.
ON THE THEORY OF INJECTION OF MINORITY CARRIERS IN p-n ALLOY JUNCTIONS
WANG SHOU-WU
1958, 40 (1): 82-94. doi: 10.7498/aps.14.82
Abstract +
A general theory of injection of minority carriers in p-n alloy junctions was developed by using one-dimensional model. It was assumed that the recombination rate is proportional to the density of injected carriers. Two extreme cases of low injection levels and high injection levels were first considered, and the result of which was then used as the zero-order approximation in calculating the distribution of the injected minority carriers in p-n junctions. By the method of successive approximation, an analytical expression for the relationship between the injection efficiency and the injection level (i. e. the ratio of the density of injected minority carriers to that of original majority carriers) was obtained. A similar expression for the relationship between the total current density flowing through the junction and the injection level was developed on the same basis. The results of the present theory show that for an ordinary alloy junction transistor, the injection efficiency of the emitter decreases gradually as the emitter current increases. At very highinjection levels, the injection efficiency approaches a limiting value of 1/(1+b) , where6 is the ratio of electron mobility to hole mobility. For a p-n alloy junction with very low injection efficiency, the injection efficiency is proportional to the total current flowing through the junction when the injection current is small, and itapproaches a limiting value of 1/(1+b) as the injection current becomes very large. Itwas also shown that for low injection levels, the total current flowing through a p-n alloy junction is proportional to the injection level, while for high injection levels, it is proportional to the square of the injection level.