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AssigneeBayer Aktiengesellschaft
InventorsBahman Sarabi, Martin Wanders, Dietmar Wächtler, Andreas Wende
Estimating the term…
The relationship between the stress σ and the strain ε is firstly established in step 100 with short-term tests as a function of the temperature T. In steps 101 to 104, a Findley model is extended in such a way as to obtain a relationship between the strain ε and the stress σ as a function of the time t and the temperature T. The two models are combined in steps 105 and 106, so as to obtain overall a relationship between the stress σ and the strain ε as a function of the time t and the temperature T.
A method for establishing a relationship between a strain ε and a stress σ as a function of a loading time t of the stress σ and a temperature T, comprising the steps:
A method for establishing a relationship between a strain ε and a stress σ as a function of a loading time t of the stress σ and a temperature T, comprising the steps:
Dependencies are inferred from the claim text.
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Design optimisation, verification or simulation: using finite element methods [FEM] or finite difference methods [FDM]
Theories, calculations: calculations a priori without experimental data
Details relating to the type or aim of the analysis or the optimisation: thermal analysis or thermal optimisation
Computing and data processing
Term ended 27 Mar 2022 (estimated)
The invention relates to a method for establishing a relationship between a stress σ and a strain ε and more particularly to a computer system useful therefor.
A method is disclosed comprising first establishing the relationship between the stress σ and the strain ε is firstly established in step 100 with short-term tests as a function of temperature T. In steps 101 to 104, a Findley model is extended to obtain a relationship between strain ε and stress σ as a function of time t and temperature T. The two models are combined in steps 105 and 106, to obtain a relationship between the stress σ and the strain ε as a function of the time t and the temperature T.
From the prior art, it is known for the relationship between the forces acting in the short term and displacements resulting therefrom to be represented by stress/strain curves. Especially in the field of plastics, such stress/strain curves form an important basis for the design of plastic parts.
An exemplary embodiment of the invention will be explained in more detail below with the aid of the figures, in which:
FIG. 1 shows a curve family of stress/strain curves for different temperatures under short-term tensile loading,
FIG. 2 shows a schematic representation of a Findley power function for a creep test,
FIG. 1 shows a family of stress/strain curves 1 to 6. The curves were respectively measured for the material Durethan-BKV 130 (polyamide modified with glass fibre and rubber) with a 4 mm-thick tensile rod in a tensile test at a tensile rate of 5 mm per minute in the freshly injected state.
The stress/strain curve 1 was measured at a temperature of 150° C.; the other stress/strain curves 2 to 6 were measured at temperatures of 120° C., 90° C., 40° C., 23° C. and −20° C., respectively. A calculation using the method according to the invention also gives the same curves. To describe the relationship between the stress σ and the strain ε as a function of the temperature T under short-term tensile loading—as represented in FIG. 1—the following model is in this case selected:
σ(T,ε)=A1+A2+A3+A4