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An electronic ear for certifying reliability
308
A B S T R A C T S ON M I C R O E L E C T R O N I C S AND R E L I A B I L I T Y
the necessity arises for a method of making as simply and quickly as possible---on the basis of data acquired from experimental investigations--a preliminary verification of the hypothesis on a life distribution functional form and preliminary evaluation of parameters of this distribution. This paper presents considerations on the feasibility of the described task with use of an exact (unequivocal) representation of the real life distribution by an exponential distribution in an imaginary time space - = y (t). Detailed considerations cover cases of application of this method to distributions: Gamma, Weibull and Rayleigh as a particular case of the Weibull distribution. Solutions are presented in the form suitable for programming of computations on an electronic digital computer. Finally, some examples are given illustrating the practical value of the described method.
Reliabilitywa practical approach. R. F. HURT, I S I Bulletin, Vol, 16, No. 1, January 1964, p. 8. The advent of mass production and assembly line techniques has underlined the importance of intensive t¢3tlng and inspection to ensure high product reliability. This is epcially true of systems of increasing precision and complexity. However, in order that goods may be produced at a reasonably low cost, a hard-headed economic approach to reliability is essential. Some aspects of reliability with particular reference to the statistical approach were discussed in an earlier article published in the last issue of this Bulletin. The key to the practical approach to reliability, as brought out in this article, is that the basic reliability requirements should state and define all conditions and enable achievement of these requirements to be demonstrated. An electronic ear for certifying reliability. R. F. SPAIN', N. W. SCHUBRINGand M. J. DIAMOND, ~Iaterials Evaluation, March 1964, p. 113. Sonic instrumentation for certifying the reliability of General Motors Corporation foundry products has proven to be a valuable tool. Through the co-operative efforts of the Central Foundry Division and the Research Laboratories, a line of modular type instruments has been constructed, which achieves the flexibility necessary for simple and rapid adaptation to a variety of testing applications: the inspection of yokes, hinges, crankshafts, gear blanks, camshafts and rocker arms. Developments to date make possible the measurement of frequency changes to 1/30 c/s for ringing modes, and time as a function of decrement to a msec. This paper discusses the details of the various modular units and how they are used to advantage in the solution of typical production problems. RELIABILITY OF COMPONENTS, TUBES AND TRANSISTORS
Reliability and redundancy considerations in selecting spacecraft batteries. J. M. SHERFEY and K. JOHANNSEN, N A S A Technical Note D-1425, October 1962, p. 6. One of the problems in designing a spacecraft power supply is the selection of a suitable configuration for the cells which form the electrical storage battery. The usual practice is to connect in series the number of cells necessary to obtain the desired voltage; two or more of the "strings" thus formed are then connected in parallel to form the battery. In some instances the number of parallel strings is dictated by system constraints or some extraneous consideration. In other cases, however, the designer is free to choose the number of strings, provided that he makes a suitable choice of cell capacity. This paper gives a mathematical approach to the problem of making an optimum choice of the number of strings. The probability of system success is expressed as a sum of terms of a binomial distribution, and is plotted and tabulated as a function of P for various values of n and k. It is pointed out that a spacecraft battery may be designed either with the objective of a maximum probability of functioning for a given fixed time, or with that of a maximum expected lifetime. Whichever criterion is used, the tabulated data enable an optimum choice to be made among various cell configurations.
Microwave tube repair. J. F. HULL, ~Vlicrowaves, Vol. 2, October 1963, pp. 22-26. Failures involving tubes can be generally classified into two classes: equipment failures that result in tube failures and tube-based failures. Common equipment failures are: (1) loss of cooling, (2) faulty electrical contact fingers at the r.f. output or d.c. input, and (3) accidental breakage due to handling. Typical failures within the tube are: (1) arcing, (2) loss of vacuum, (3) loss of thermionic emission. (4) window failures and (5) excessive wear of moving parts. Each of these problems is discussed, including design methods for its elimination.
A B S T R A C T S ON M I C R O E L E C T R O N I C S AND R E L I A B I L I T Y
the necessity arises for a method of making as simply and quickly as possible---on the basis of data acquired from experimental investigations--a preliminary verification of the hypothesis on a life distribution functional form and preliminary evaluation of parameters of this distribution. This paper presents considerations on the feasibility of the described task with use of an exact (unequivocal) representation of the real life distribution by an exponential distribution in an imaginary time space - = y (t). Detailed considerations cover cases of application of this method to distributions: Gamma, Weibull and Rayleigh as a particular case of the Weibull distribution. Solutions are presented in the form suitable for programming of computations on an electronic digital computer. Finally, some examples are given illustrating the practical value of the described method.
Reliabilitywa practical approach. R. F. HURT, I S I Bulletin, Vol, 16, No. 1, January 1964, p. 8. The advent of mass production and assembly line techniques has underlined the importance of intensive t¢3tlng and inspection to ensure high product reliability. This is epcially true of systems of increasing precision and complexity. However, in order that goods may be produced at a reasonably low cost, a hard-headed economic approach to reliability is essential. Some aspects of reliability with particular reference to the statistical approach were discussed in an earlier article published in the last issue of this Bulletin. The key to the practical approach to reliability, as brought out in this article, is that the basic reliability requirements should state and define all conditions and enable achievement of these requirements to be demonstrated. An electronic ear for certifying reliability. R. F. SPAIN', N. W. SCHUBRINGand M. J. DIAMOND, ~Iaterials Evaluation, March 1964, p. 113. Sonic instrumentation for certifying the reliability of General Motors Corporation foundry products has proven to be a valuable tool. Through the co-operative efforts of the Central Foundry Division and the Research Laboratories, a line of modular type instruments has been constructed, which achieves the flexibility necessary for simple and rapid adaptation to a variety of testing applications: the inspection of yokes, hinges, crankshafts, gear blanks, camshafts and rocker arms. Developments to date make possible the measurement of frequency changes to 1/30 c/s for ringing modes, and time as a function of decrement to a msec. This paper discusses the details of the various modular units and how they are used to advantage in the solution of typical production problems. RELIABILITY OF COMPONENTS, TUBES AND TRANSISTORS
Reliability and redundancy considerations in selecting spacecraft batteries. J. M. SHERFEY and K. JOHANNSEN, N A S A Technical Note D-1425, October 1962, p. 6. One of the problems in designing a spacecraft power supply is the selection of a suitable configuration for the cells which form the electrical storage battery. The usual practice is to connect in series the number of cells necessary to obtain the desired voltage; two or more of the "strings" thus formed are then connected in parallel to form the battery. In some instances the number of parallel strings is dictated by system constraints or some extraneous consideration. In other cases, however, the designer is free to choose the number of strings, provided that he makes a suitable choice of cell capacity. This paper gives a mathematical approach to the problem of making an optimum choice of the number of strings. The probability of system success is expressed as a sum of terms of a binomial distribution, and is plotted and tabulated as a function of P for various values of n and k. It is pointed out that a spacecraft battery may be designed either with the objective of a maximum probability of functioning for a given fixed time, or with that of a maximum expected lifetime. Whichever criterion is used, the tabulated data enable an optimum choice to be made among various cell configurations.
Microwave tube repair. J. F. HULL, ~Vlicrowaves, Vol. 2, October 1963, pp. 22-26. Failures involving tubes can be generally classified into two classes: equipment failures that result in tube failures and tube-based failures. Common equipment failures are: (1) loss of cooling, (2) faulty electrical contact fingers at the r.f. output or d.c. input, and (3) accidental breakage due to handling. Typical failures within the tube are: (1) arcing, (2) loss of vacuum, (3) loss of thermionic emission. (4) window failures and (5) excessive wear of moving parts. Each of these problems is discussed, including design methods for its elimination.