Curved bathtub is mainly used in engineering to describe the process by which engineering components fail. The curve may also have other applications outside of engineering, but that is the main field in which it is used. The curve refers to the failure rate of various components in relation to time. This is usually expressed relative to the number of hours that the component has been in service.
The theory of hot-shaped curved bathtub is an analogy that a theory, but often is described in more theoretical terms. The decay rate or fails to which appear engineering components is linked to the curve inside of a typical bath. In the first phase of system implementation failure rate drops significantly over time because any initial failure or problem is overcome with a solution.
During the next phase, the bottom of the curved bathtub, the failure rate becomes more constant over the course of time as the system components are in relatively good shape. Towards the end of its life, the curve rises sharply again as the wall of the tub, as the fault appears in an increased rate. This is similar to an old car that has one problem after another older that follows.