When performing structural analysis using CAE,
stresses and deformations can be calculated by setting constraint and load points.
The main constraint setting is probably the "fixed" condition.
This is because halfway constraint settings will cause rigid body movement in the model, which will not converge in the calculation and will be a source of error. Unless you have a particularly complicated constraint condition, you will probably use "fixed".
So, how can we reproduce "Fixed" in an actual test?
(1) Bolt fixation
This is the closest condition to fixation in analysis. Compared to the plastic products we handle, bolts are often made of metal, which is closer to a rigid body. Therefore, there is little change in the state of restraint during the test.
Therefore, it can be said that there is little difference between the analysis results and the results of the test. However, if the mating part to be fixed is resin, the mating part may be deformed, so the mating part must be metal to avoid differences.
In addition, bolt fixation requires a hole to be drilled, so the product shape is limited.
(2) Fixing with double-sided tape
If bolt fixing is not possible, double-sided tape is often used.
When measuring a product shape in 3D measurement, etc., if the product shape does not have a hole, the most flat surface and the measurement table are fixed with double-sided tape.
However, if the part to be measured is made of resin, it is desirable to use a metal material that is close to a rigid body because deformation of the part will be taken into account.
(3) Clamp Fixing
Another method is to use a special clamp to fix the product. This method may or may not be suitable depending on the contents of the test, since the clamping force may crush or destroy the resin product.
Also, if the surface to be secured by the clamp is small, stress is applied to the contact surface, and the product may be destroyed from the clamping point.
Thus, it is quite difficult to reproduce "fixation" under analytical conditions in an actual test, and the conditions are limited. Especially in the case of non-rigid plastic parts, the fixation itself is difficult to achieve, and this is the reason why there is a difference between the analytical and experimental values.
When setting restraint conditions, it is necessary to consider the actual test method.
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