The Problem of Failures

The officer candidate course differed from all other service school courses in that the OCS student was constantly subjected to searching personal scrutiny. The candidate had to satisfy the staff and faculty as to his aptitude for eventual commissioned rank. At best, the initial selection of candidates had been provisional it was the responsibility of the school to determine finally, as a result of close observation over an extended period of time, those who actually were qualified, both mentally and physically, to assume the responsibilities of military leadership. In OCS training the function of separating the fit from the unfit ranked barely second in importance to the function of pedagogy. 

Under War Department policy, no candidate was relieved from an officer candidate school before completion of one third of the course, except for disciplinary action or at his own request. During the last two thirds of each 

Among failures attributable to leadership deficiency, the largest number were rooted in lack of force, aggressiveness, or an unimpressive military 

Demerits assessed for conduct delinquencies were also taken into consideration in determining a candidate s ability to accommodate himself to the disciplinary requirements of the course. Delinquencies were grouped into four classes, each carrying appropriate demerit values. These were published for the information of candidates in an OCS instruction circular. Serious offenses w ere in most cases brought before an Honor Committee of the student body which recommended to the director of the Officer Candidate School whether the offense merited dismissal. Misconduct, however, accounted for only a small number of separations on the whole the behavior of officer candidates was exemplary. 

When the cumulative class record of the candidate, either academic or nonacademic, definitely fell below the standard set by the school, appearance before the Status Board was mandatory. This board consisted of three officers, at least one being of field grade. The board interviewed the individual, considered the records, and, where deficiency in leadership was involved, discussed the matter with his platoon commander. The personal impression made by the candidate upon the board obviously carried considerable weight in the determination of each case. After the hearing, the Status Board recommended to the commandant, Chemical Warfare School, that the candidate either be relieved from the course, be turned back to a succeeding class, or in exceptional cases be continued on probationary status. The action of the commandant on these recommendations was final. 

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Equations (8.32) and (8.33) describe what we call the normal or no failure operation of the system of interest. The problem of failure detection is concerned with the detection of abrupt changes in a system, as modeled in Eqs. (8.32) and (8.33). Changes in (8.33) will be referred to as sensor failures. The main task of failure detection and compensation design is to modify the normal mode configuration to add the capability of detecting abrupt changes and compensating for them. In order to do that, we need to formulate what is called the failure model system ... 

Because coated fabrics are generally dealt with in separate standards committees, and because the thinner coatings are not strong enough to allow the use of the peel methods described above, separate standards have been developed for these products. The problem of failure in the coating is overcome by using reinforcements of fabric or cement. These methods are really product tests and outside the scope of this book but the appropriate references can be noted. The international standard for coated fabrics is ISO 241144, the British methods are identical as BS EN ISO 2411 and the ASTM methods are in D75145. There are also methods for conveyor belts in ISO 252-146. 

Frank and Hagenmaier suggested an alternative to both solid- and liquid-phase peptide synthesis by creating the solid-liquid-phase method in order to overcome the problem of failure and truncated sequences [105, 106], To this end, poly(ethylene glycol) monoalkyl ethers were used as carboxy protecting poups. The principle of this method is depicted in Scheme 2. 

There was a relationship, as has been indicated, between the type of selectee sent to the Officer Candidate School and the size of the student quotas. In the first six CWS classes, enrolling an average of thirty-six students, losses from all causes were negligible. The problem of failures began with the Seventh Class, which had 226 students. It became acute late in 1942 under the simultaneous impact of two adverse factors—an accentuated demand for officer candidates and an overrapid development of the instructional staff. 

For many years, companies and countries have lived with the problem of inflation, or the faUing value of money. Costs—in particular, labor costs—tend to rise each year. Failure to account for this trend in predicting future cash flows can lead to serious errors and misleading profitabihty estimates. 

The closer one is to the failure, the more its direct effects are apparent. The cumulative effects of failure are often overlooked in the rush to fix the immediate problem. Too often, the cause of failure is ignored or forgotten because of time constraints or indifference. The failure or corrosion is considered just a cost of doing business. Inevitably, such problems become chronic associated costs, tribulations, and delays become ingrained. Problems persist until cost or concern overwhelm corporate inertia. A temporary solution is no longer acceptable the correct solution is to identify and eliminate the failure. Preventative costs are almost always a small fraction of those associated with neglect. 

Measures to minimize safety problems must be initiated at the start of the life cycle of any product, but too often determinations of criticality are left to production or quality control personnel who may have an incomplete knowledge of which items are safety critical (Hammer, 1980). Any potential non-conformity that occurs with a severity sufficient to cause a product or service not to satisfy intended normal or reasonably foreseeable usage requirements is termed a defect (Kutz, 1986). The optimum defect level will vary according to the application, where the more severe the consequences of failure the higher the quality of conformance needs to be. 

For statie design to be valid in praetiee, we must assume situations where there is no deterioration of the material strength within the time period being eonsidered for the loading history of the produet. With a large number of eyelie loads the material will eventually fatigue. With an assumed statie analysis, stress rupture is the meehanism of failure to be eonsidered, not fatigue. The number of stress eyeles in a problem eould... 

The theory is concerned with the problem of determining the probability of failure of a part which is subjected to a loading stress, L, and which has a strength, S. It is assumed that both L and S are random variables with known PDFs, represented by f S) and f L) (Disney et al., 1968). The probability of failure, and hence the reliability, can then be estimated as the area of interference between these stress and strength functions (Murty and Naikan, 1997). 

Most hydrocarbon gases are more soluble in cold oil than in hot oil and may lower the viscosity to a dangerous level. The problems of thrust-bearing failures during startup due to low-viscosity oil can be eliminated by equipping the reservoir with oil heaters to raise the oil to the normal operating temperatures before starting the machine. 

In the event of failures due to lubrication problems, the failures should be thoroughly analyzed to determine if they were indeed caused by lubricant failure or incorrect maintenance procedures. Once the problem has been isolated, corrective action can be initiated to prevent subsequent similar failures—whether it requires changing lubricants or procedures. 

A lrLL[uently encountered problem requires estimating a failure probability based on the number of failures, M, in N tests. These updates are assumed to be binomially distributed (equation 2.4-10) as p r N). Conjugate to the binomial distribution is the beta prior (equation 2.6-20), where / IS the probability of failure. 

In early times 70/30 brass condenser tubes failed by dezincification and Admiralty brass (70Cu-29Zn-lSn) was brought into use. This proved little better, but some time later the addition of arsenic was found to inhibit dezincification. Failures of Admiralty brass by impingement attack became a serious problem, particularly as cooling water speeds increased with the development of the steam turbine. The introduction of alloys resistant to this type of attack was a great step forward and immediately reduced the incidences of failure. 

The process of analyzing designs includes the modes of failure analysis. At an early stage the designer should try to anticipate how and where a design is most likely to fail. A few examples of potential problems due to loading conditions on products are reviewed. 

The example of the roof structure represents the simplest type of problem in static loading in that the loads are clearly long term and well defined. Creep effects can be easily predicted and the structure can be designed with a sufficiently large safety factor to avoid the probability of failure. 

This type of caution approach is essential in high risk applications since only certain plastics can be used as the basis for such applications. This chapter has been concerned with the problems of the product in use under the types of environments and potential abuse that may be encountered, and how the designer can prevent premature product failure which is one of their major responsibilities. 

Does increased agitator speed improve performance in the pilot plant If so, there is a potential scaleup problem. Installing a variable-speed drive with a somewhat over-sized motor can provide some scaleup insurance, the cost of which is apt to be minor compared with the cost of failure. 

The senior author first became interested in acid-base cements in 1964 when he undertook to examine the deficiencies of the dental silicate cement with a view to improving performance. At that time there was much concern by both dental surgeon and patient at the failure of this aesthetic material which was used to restore front teeth. Indeed, at the time, one correspondent commenting on this problem to a newspaper remarked that although mankind had solved the problem of nuclear energy the same could not be said of the restoration of front teeth. At the time it was supposed that the dental silicate cement was, as its name implied, a silicate cement which set by the formation of silica gel. Structural studies at the Laboratory of the Government Chemist (LGC) soon proved that this view was incorrect and that the cement set by formation of an amorphous aluminium phosphate salt. Thus we became aware of and intrigued by a class of materials that set by an acid-base reaction. It appeared that there was endless scope for the formulation of novel materials based on this concept. And so it proved. 

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