Why Failures Occur

All products are subject to failures. The time at which failures occur is dependent on the nature of the product design, materials used, the operating environment, and the stresses to which they are subjected. Materials and structures can fail in several different modes. Often more than one failure type may occur at the same time. Some products fail very early in life owing to what is termed as “infant mortality failure.” Others may fail during their useful life span, and some fail owing to wearout at the end of their useful life. The causes of failure are varied and many. Manufacturing defects may have escaped the quality inspection, or the design strength may be less than the expected stress encountered in the use environment. The choice of materials used may be unsuitable for the intended use. Contaminants may have been left on the product during its manufacture that may cause degradation of performance over time. These failures in various phases of a product life cycle have been studied extensively and are described by the well known failure distribution called the Weibull distribution.