The Bathtub Curve
The bathtub curve describes the shape of aggregated failure rates for a given product. Also known as a hazard function, it’s a rule-of-thumb that generally states:
- random failure is likely to happen at all stages of a product’s lifecycle
- early failure decreases over time as problems in a product are resolved. These are typically characterised as design flaws
- wear-out failure increases over time as components wear out. These typically occur after the warranty period of a product, and are either repaired or the product is replaced with the newer version.
Example applications
The bathtub curve is widely used in reliability engineering. It provides a way of thinking about the likelihood of failure during a product’s lifecycle.
Building a bathtub curve
In order to replicate the bathtub curve, whole-of-system data is required. This is often difficult to find, so the practical value of understanding the bathtub curve in the context of this course is knowing that there are the three failure modes, and accounting for them in the planning about a design.
Key concepts
- an overview of the bathtub curve, and the three types of failure
- a practical example of the three types of failure (may be different examples)
- advice to the student engineer on how understanding the bathtub curve can lead to better engineering decisions