What is the ratio between the ultimate strength and the allowable stress called?

The ratio between the ultimate strength and the allowable stress is known as the safety factor. This concept is critical in engineering design, particularly in fields like refrigeration, where structures and components must withstand various operating conditions without failing.

The ultimate strength refers to the maximum stress a material can withstand before it fails, while the allowable stress is the maximum stress that a material is permitted to endure during regular operations, typically calculated with a margin of safety in mind. The safety factor provides an essential value that ensures the structure or component operates safely under expected loads and conditions.

A safety factor greater than one implies that the design has considered additional stress that might occur, offering a buffer against unforeseen circumstances. By using the safety factor, engineers can account for uncertainties in material properties, potential overloading, and inaccuracies in loading estimations, ensuring that the system remains safe and functional throughout its intended lifespan.