Glossary term
Yield Criterion
A material model rule used to predict the onset of plastic deformation under multiaxial stress.
Definition
modelA yield criterion is a mathematical rule that predicts when a material begins plastic deformation under a multiaxial stress state.
Yield criteria reduce a stress tensor to a condition for the onset of irreversible deformation. They are used in structural design, pressure vessels, forming simulation, crash analysis, geotechnical modelling, plasticity models, and finite-element analysis, with the chosen criterion depending on material class, ductility, pressure sensitivity, anisotropy, and calibration data.
A yield criterion defines the boundary between elastic response and plastic deformation for a given stress state. In uniaxial tension, yielding can be compared directly with yield strength. In real components, stresses are usually multiaxial, so the criterion determines how normal stress, shear stress, hydrostatic pressure, and material directionality combine.
For many ductile metals, the von Mises criterion is widely used because it correlates yielding with distortional energy and is relatively insensitive to hydrostatic stress. Other criteria may be more appropriate for brittle materials, polymers, soils, rocks, foams, composites, anisotropic sheet metals, or pressure-sensitive materials.
Engineering use
Yield criteria are used in finite-element analysis, design codes, pressure-vessel checks, plastic collapse assessment, metal forming, crashworthiness, bolted joints, shafts, welded structures, and failure investigation. They help answer whether a local stress state is expected to remain elastic, yield locally, redistribute load, or enter a plastic-collapse mechanism.
The criterion must be calibrated with material data. Yield strength, hardening law, temperature, strain rate, loading path, residual stress, anisotropy, and manufacturing history can change the yield surface. A simulation using an unsuitable criterion may look numerically precise while representing the wrong physics.
Common mistakes
A common mistake is applying one yield criterion to every material. A ductile metal, a pressure-sensitive polymer, a concrete element, and a fiber composite do not necessarily yield by the same rule. Another mistake is comparing a single principal stress with yield strength when the actual state includes shear and multiple normal components. A strong plasticity review states material class, stress measure, yield criterion, calibration tests, hardening model, temperature and strain-rate range, mesh sensitivity, and validation evidence.