The design life of a component or product is the period of time during which the item is expected by its designers to work within its specified parameters; in other words, the life expectancy of the item. It is the length of time between placement into service of a single item and that items on-set of wear-out.
The design life of components and products differs from the items mean time between failure (MTBF), in that MTBF is a measure of the rate of occurrence of random failures in time where these failures are not due to a wear-out mechanism. For example, the MTBF of a device may be 100,000 hours and the design-life is 20,000 hours. In this example, across the population of products, one failure will occur, on average, every 100,000 population operating hours (100,000 units operating for 1 hour each = 100,000 population operating hours). None of these units will ever approach reaching 100,000 operating hours as it will fail due to wear-out and be replaced by a new unit. Aluminum electrolytic capacitors, fans, and batteries are classic examples of components that will fail due to wear-out well before they could achieve the operating time indicated by their individual MTBF.
Another use of the term design-life deals with consumer products. Many products employ design-life as one factor of their differentiation from competing products and components. A disposable camera is designed to withstand a short life, whilst an expensive single-lens reflex camera can be expected to have a design life measured in years or decades. (Clearly in this example there are other differentiators).
Read more about Design Life: Long Design Lives, Short Design Lives, Obsolescence
Famous quotes containing the words design and/or life:
“For I choose that my remembrances of him should be pleasing, affecting, religious. I will love him as a glorified friend, after the free way of friendship, and not pay him a stiff sign of respect, as men do to those whom they fear. A passage read from his discourses, a moving provocation to works like his, any act or meeting which tends to awaken a pure thought, a flow of love, an original design of virtue, I call a worthy, a true commemoration.”
—Ralph Waldo Emerson (1803–1882)
“Who does not see that I have taken a road along which I shall go, without stopping and without effort, as long as there is ink and paper in the world? I cannot keep a record of my life by my actions; fortune places them too low. I keep it by my thoughts.”
—Michel de Montaigne (1533–1592)