Failure Analysis

 It is imperative to realize that there are period in which no falure could occur,which also affects the performance of machine,such period is called d,when d <0 failure occur before time equal 0,machine/engine performance could  either be positive (+) or negative(-) index.this might sound  surprise and radiculous but a negative location is caused by failed unit.Failure during transportation and shelf life affects materials and cause delay in maintenance logistics,But generally the location parameters would be assume to be zero.(wellbull,1951).