What is an expected outcome when loads exceed the limit load but do not reach ultimate load?

When loads exceed the limit load but do not reach the ultimate load, one expected outcome is the potential for permanent deformation of the structure. Limit load is defined as the maximum load that an aircraft structure is designed to safely carry without experiencing permanent or significant deformation. When this limit is surpassed, the structure may begin to undergo changes that do not recover once the load is removed, which is referred to as plastic deformation.

The distinction between limit load and ultimate load is critical; ultimate load is the maximum load that can be applied before the failure occurs. If the structure exceeds the limit load but does not reach the ultimate load, it means that while it is subjected to excessive stress, it has not yet failed completely, causing the material to yield in a way that affects its shape or strength characteristics permanently. This is important for safety assessments and maintenance considerations since even if the structure remains intact, its ability to perform under future loads could be compromised. Understanding these consequences is essential for proper aircraft operation and maintenance practices.