Design and Stress Analysis of Extraterrestrial ... - The Black Vault

Yield' limit a a is the stress which corresponds to the
T 0.2
appearance of permanent sets of a certain magnitude. Usually yield
limit is defined as the stress at which residual relative elongation
e = 0'.2% occurs. Yield limit is widely used in calculations as a
characteristic of the material's resistance to stati.o loads when the
operating capability of the part or design element Is determined by
its deforming ,properties, for example, when rotating parts interfer
with nonrotating parts or when the elongation of an element leads to
the overlapping of important ducts for passage of the working medium.
Beyond the plastic limit is the hardening modulus D, which
characterizes the resistance of the material to small elasticplastic
deformations:
where
D =tg= dolde.
The substantial difference between D and E is the fact that the
quantity D is a variable. In approximate calculations it is
frequently assumed to be constant.
The hardering modulus D with an increase in stresses from y
to aT can be de'zreased by a factor of 100 and more.
The strength limit or tensile strength of the material ao1 is
the arbitrary stress corresponding to maximum load duriiig extension
or compression tests on the sample.
For most structural materials tensile strength is the main
strength characteristic of metal during static loading, the quantity
determining strength reserve of the structure.
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