A failure mode is the manner in which a process could potentially fail to meet the process or customer requirements. In other words it refers to the specific ways in which failures could occur for the components/subsystems you are analyzing.
To calculate it is necessary to use the failure mode and effects analysis (FMEA), which is the process of reviewing as many components, assemblies, and subsystems as possible to identify potential failures in a system and their causes and effects. For each component, the modes and their resulting effects on the rest of the system are recorded in a specific FMEA worksheet. There are numerous variations of such worksheets. An FMEA can be a qualitative analysis, but may be put on a quantitative basis when mathematical failure rate models are combined with a statistical failure mode ratio database. It was one of the first highly structured, systematic techniques for failure analysis. An FMEA is often the first step of a system reliability study.
A few different types of FMEA analyses exist, such as:
A successful FMEA activity helps identify potential failure modes based on experience with similar products and processes—or based on common physics of failure logic. It is widely used in development and manufacturing industries in various phases of the product life cycle. Effects analysis refers to studying the consequences of those failures on different system levels.