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  Dependence of apparent modulus of elasticity on strain
- Dependence of apparent modulus of elasticity on strain -

There is hardly any portion where Hooke's law applies, i.e. where stress is directly proportional to strain, in the stress-strain relationship of plastic materials, as can be seen in the figure shown on the right side. Therefore, the modulus of elasticity changes depending on the amount of strain. In this case, the modulus of elasticity at each strain or stress level is called the secant modulus of elasticity(Es).
The above mentioned means that the secant modulus of elasticity(Es) has to be used for the precise designed calculation of plastic components, instead of the initial modulus of elasticity(Eo) usually shown in catalogs.

With regard to Duracon, the relation between the ratio of these two modulus of elasticity Es/Eo and the amount of strain is shown in the figure on the right side. When the amount of strain is less than 2%, this relation is not influenced by the retention time under load or temperature. It has been also known from the past experience that thus relation is not significantly influenced by the grades of Duracon or even by kinds of plastics.

Examples of calculation
by using Es/Eo --->