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Strain (ε) as a function of time due to constant stress over an extended period for a Class M material. Creep behavior can be split into three main stages. In primary, or transient, creep, the strain rate is a function of time. In Class M materials, which include most pure materials, primary strain rate decreases over time.
Creep is dependent on time so the curve that the machine generates is a time vs. strain graph. The slope of a creep curve is the creep rate dε/dt [citation needed] The trend of the curve is an upward slope. The graphs are important to learn the trends of the alloys or materials used and by the production of the creep-time graph, it is easier ...
When subjected to a step constant stress, viscoelastic materials experience a time-dependent increase in strain. This phenomenon is known as viscoelastic creep. At time , a viscoelastic material is loaded with a constant stress that is maintained for a sufficiently long time period. The material responds to the stress with a strain that ...
The Voigt model predicts creep more realistically than the Maxwell model, because in the infinite time limit the strain approaches a constant: =, while a Maxwell model predicts a linear relationship between strain and time, which is most often not the case.
Source: [6] can be obtained by accelerated creep test in which strain is recirded, interpolating the data (,) (˙) = ˙ + (˙) When adopting the Omega Method for a remaining life assessment, it is sufficient to estimate the creep strain rate at the service stress and temperature by conducting creep tests on the material that has been exposed to service conditions.
The classical creep curve represents the evolution of strain as a function of time in a material subjected to uniaxial stress at a constant temperature. The creep test, for instance, is performed by applying a constant force/stress and analyzing the strain response of the system.
Experiments can be made where either the stress or strain is held constant for a certain time. These are called quasi-static, and in this case, anelastic materials exhibit creep, elastic aftereffect, and stress relaxation. In these experiments a stress applied and held constant while the strain is observed as a function of time.
Toughness as defined by the area under the stress–strain curve. Materials that are both strong and ductile are classified as tough. Toughness is a material property defined as the area under the stress-strain curve. Toughness can be determined by integrating the stress-strain curve. [3]