07. Basic mathematics of reliability and basic concepts of reliability
1) Definition of reliability: the ability of the product to complete the specified functions under the specified conditions and within the specified time.
The elements of product reliability definition are three "stipulations": "stipulation condition", "stipulation time", and "stipulation function".
◼ The specified conditions include the environmental conditions and working conditions when the product is used;
◼ The specified time refers to the time specified by the product to perform tasks;
◼ The specified functions refer to the required functions and technical indicators specified by the product.
◼ The products here generally refer to systems, subsystems, complete machines, sub-machines, equipment, components, parts and components.
2) Failure and its classification
The opposite of reliable is failure. It is a basic skill for designers to analyze the nature of faults and classify them correctly.
◼ Failure is defined as the loss of the product's specified function. For non-repairable products, also known as failure, the terms failure and failure are often used interchangeably.
◼ Failure Mode: The manifestation of the failure.
◼ Failure mechanism: internal reasons such as physical and chemical changes that cause failure.
◼ Cause of failure: design, manufacture, use, maintenance and other related factors that cause the failure.
◼ Fault classification: According to different classification standards, there are various classification methods for product fault classification. For example, the following set of categories:
failure rate
bathtub curve
Mean Time Before Failure (MTTF) Mean Time Between Failure (MTBF)