2. Determining viscoplastic properties

2.1 Definition of viscoplastic behavior

Various types of loading characterize such behavior. Under constant load, the material creeps: its deformation increases at a rate that may be decreasing or, on the contrary, increasing. If, instead of keeping the load constant, it is the elongation that is stabilized, the stress applied to this end decreases over time: this is a relaxation test. After unloading, material deformation is likely to decrease, a phenomenon known as recovery. In a test where the rate of elongation is kept constant, the material's behavior depends on this rate.

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