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Technical Paper

A New Robust Design Methodology to Improve the Reliability of Structural Beams

Safety factors have been used widely in the design of beams for many years. It is still the major design method used in the industry. The advantage of using safety factors is that it is simple and easy to understand by the designer. However, the disadvantages of using it are that the product may be under-designed or over-designed depending on the safety factor value chosen, and the designers do not know what reliability they have designed into the product. In this paper, a new Robust Engineering Design-By-Reliability method is introduced. Using this method, the designers are able to know the designed-in reliability of their beams at the outset, thus avoiding the under- or over- design situations. Also in this paper, the safety factor based method and the Robust Engineering Design-By-Reliability method are compared. From the comparison it can be seen that the Robust Engineering Design-By-Reliability method is much more cost effective.
Technical Paper

An Approach to Reliability Determination of a Rotating Component Subjected to Complex Fatigue

A methodology for determining the reliability of mechanical components is given. The necessary design data are pointed out. Complex fatigue research machines are described, which are generating the required fatigue strength data in terms of cycles to failure and endurance strength. The test loading is that of alternating bending combined with steady torque. The design data obtained are presented. The design by reliability methodology and data are applied to the design of an actual alternator rotor inner shaft, and the results are compared with those obtained by conventional design procedure.
Technical Paper

An Unified Approach to System Classification and Optimum Maintenance Scheduling

Authors in this paper propose a new approach for system classification, for the purpose of facilitating optimum maintenance decision making, in terms of the economic dependency of replacements among preventively replaceable items (PRI) within a system. This classification divides the existing systems into three categories; i.e., Independent-PRI Systems, Dependent-PRI Systems and Mixed-PRI Systems. Accordingly, the existing replacement policies are classified according to their math structures and compositions, and a multi-mode-replacement-policy idea is presented for modern large-scale industrial systems. Cost, reliability and spares requirement models under each policy are given. Conditions for the existence of each policy are also discussed. Finally, the application strategies of these policies in modern industries are investigated.
Technical Paper

Distributions of Strength in Simple Fatigue and The Associated Reliabilities

A method for determining fatigue strength distributions at specific cycles of finite life, given cycles-to-failure data, is presented and applied to steel and aluminum wire fatigue data. Methods for calculating the reliability designed into a part for a specified cycle of finite life are given and are illustrated for the cases when the level of the maximum alternating operating stress is kept essentially constant, or has a normal or a Weibull distribution.
Technical Paper

Keynote Address: Robust Engineering Design-by-Reliability

This Keynote Address compares the deterministic design methodology, which is being used predominantly currently, with the probabilistic design methodology which enables the designer to design components to a desired reliability goal at a desired confidence level. It is demonstrated that the probabilistic design-by-reliability methodology is more economical plus it assures that there will be fewer product failures, fewer product recalls and more satisfied customers. It is urged that, henceforth, this design-by-reliability methodology be taught in our Colleges of Engineering instead of the inefficient deterministic one.
Technical Paper

Much Needed Attention to Car Reliability Demonstration Testing and Test Sample Size Determination

The automotive industry is suffering from massive recalls, even after many developments have occurred in the fields of Reliability and Quality Engineering. The cost of recalls has been devastating to the industry's profits and product reputation in terms of the bad image to the customer, which is spread to more customers by the dissatisfied customers. Furthermore, the Test Sample Size is often too small to provide useful results concerning the actual designed-in Reliability. The manufacturers do not seem to use sufficient sample sizes in their product Reliability Demonstration Tests, which yield large errors in the test results. In this paper we seek to stress the importance of adequate Testing prior to shipment as a measure to avoid recalls and increase Car Reliability. Millions of recalls every year would have been avoided if adequate Testing had been conducted and the Reliability of the Sample had thus been improved, based on the test results.
Technical Paper

The Reliability Engineering Education Program at The University of Arizona

The need for formally educated Reliability Engineers is pointed out. The Reliability Engineering Education Program developed at The University of Arizona in Tucson is described, and its present and future objectives are discussed. An appeal is issued to other educational institutions of higher learning to start and/or expand such programs to meet the great need for formally educated Reliability Engineers.