Self-limiting stress, in the context of engineering and specifically pressure vessel design, refers to a type of stress that, once it exceeds the material's yield point in a localized area, ceases to increase proportionally with the applied load. This is because the material's post-yield stiffness decreases, breaking the direct relationship between applied load and stress. In simpler terms, the stress limits itself. This contrasts with primary stress, which continues to increase with the load even after yielding begins.
Understanding Self-Limiting Stress:
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Mechanism: Self-limiting stress often arises from secondary stresses caused by factors like thermal expansion or misalignment. When these stresses exceed the material's yield strength, localized plastic deformation occurs. This deformation accommodates the initial stress, preventing further stress increase. The ASME code categorizes these as self-limiting.
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Examples: A heated pipe expanding will generate a self-limiting stress. The expansion initially causes stress, but once the pipe yields locally and deforms, the stress increase plateaus.
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Contrast with Primary Stress: Unlike self-limiting stresses, primary stresses are caused by direct load applications (like internal pressure) and are not self-limiting. They continue to increase even if the material yields, potentially leading to catastrophic failure.
Key Characteristics of Self-Limiting Stress:
- Localized yielding: The stress is limited by plastic deformation concentrated in specific areas.
- Reduced post-yield stiffness: The material's ability to resist further stress is reduced after yielding.
- Accommodation of stress: Plastic deformation "takes up" the stress, preventing further accumulation.
- Common in secondary stresses: Often associated with thermal effects, misalignment, or other non-direct load sources.
The concept of "self-limiting stress" within a psychological or personal development context, as described in some search results, refers to self-limiting beliefs or behaviors that restrict a person's potential. This is a separate and distinct concept from the engineering definition.
