Design, finite life

The first gear of a gear box in a car is another example. As it is used only for a small amount of time, it is also designed for finite life only. 

Fatigue strength in the finite-life range is a very important consideration in designing engineering steel chains. Loads sometimes exceed the fatigue Unfit in some heavily loaded conveyors and drives. 

Guard columns and in-line filters alone will not ensure long life for the analytical column. They are designed to perform a specific function for a finite period of time. They, too, will be short-lived if shortcuts are taken in sample preparation and mobile phase quality control. Use of a guard column does not mean that other good analytical practices can be neglected. Shortcuts mean shorter life for any column. 

Lines 1, 2, and 3 (investments) in Table 2 would normally only be filled in for the first column (discount factor of 1.000) which is designated as the zero year for the operation, with the unit actually going into operation at the start of the so-called first year. It is assumed that working capital and salvage value will be recovered in a lump sum at the end of the estimated service life, so these values are listed on lines 1, 2, and 13 as positive (incoming funds) numbers in the end-of-life column. Since these are lump-sum instantaneous values, the discount factor to apply to them is the finite (year-end) cash flow factor as shown in line 14 in the end-of-life column. 

Traditional tensile, compression, and flexural tests are being supplemented by newer and more exacting requirements that include much more action in formabihty, instrumented impact, pressure, thermal environment simulation, and fatigue and fracture testing that can provide product life prediction. Data from these exhaustive tests are fed back to designers using finite element analysis and to customers as proof of quality. 

As discussed in the last section, the engineer has to make decisions about all aspects of his design solution. He has to ensure that the structure will be constructed successfully, and that it will be successfully used for its desired life span. The small, but unfortunately from the designer s viewpoint, finite chance that an accident will happen has to be considered. Some of these undesirable events are listed in Table 1.2. The risk or probability that any of these events will happen has to be kept acceptably low. 

Introduction to Precision Machine Design and Error Assessment, Edited by Samir Mekid Introductory Finite Element Method, Chandrakant S. Desai and Tribikram Kundu Large Energy Storage Systems Handbook, Edited by Frank S. Barnes and Jonah G. Levine Machine Elements Life and Design, Boris M. Klebanov, David M. Barlam, and Frederic E. Nystrom... 

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