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Resin Product Development Support Using CAEDynamic Structural Analysis (Impact Analysis)

Technology that predicts an object response, such as stress or displacement, when a sudden force is applied to the object in a short time, such as an impact or a fall

FeaturesFeatures

When it is required to meet impact test and drop test standards in product development, special test equipment is required, resulting in a high test costs. If test results can be predicted at the design concept stage, development time and costs can be reduced. To achieve this, however, highly accurate simulation technology is essential.

A resin is a viscoelastic material, being solid but having liquid-like properties different from metal. One of the features is strain rate dependence. The graph on the right shows the stress-strain curve of our Leona 14G33 (polyamide 66 reinforced with 33% of glass fiber) with different tensile test speeds. As can be seen from this graph, the resin shows a hard response when pulled at high speed. Asahi Kasei has resin-specific simulation technology, which enables impact analysis by reflecting these unique properties of resins.

Strain rate dependence of polyamide 66ポリアミド66のひずみ速度依存性

Application of Asahi Kasei's Original Material Model to Impact Analysis Software

In order to predict the fracture behavior of resin products at high speed,numerical formulas (material models) that can accurately represent the mechanical response of resin materials (development of strain and damage, generated stress, etc.) are necessary in numerical analysis. Asahi Kasei has developed its own original material model considering microscopic damage and applied it to impact analysis software.

The above video shows a verification example comparing the simulation results with the experimental results of the punching test for resin plates. The simulation results using the conventional model and our own original model are shown on the right and center respectively. In the conventional model, the fracture starts from the part where the strain increased, but in the original model, the fracture progresses from the part where the strain rate is high.

In the experimental results on the left side, cup-shaped pieces were observed to be punched out, and the simulation results using the original model and the fracture form was confirmed to coincide with these results. The load-displacement graph also demonstrates that the original model is more consistent with the experimental results than the conventional model.

結晶性樹脂

Crystalline resin represented by polyamide has a mixture of crystalline and amorphous parts as shown above. Pulling unreinforced polyamide specimens causes necking, resulting in ductile fracture. This is due to the unique characteristic of the resin whereby the polymer in the amorphous part is stretched and breaks at the boundary between the crystalline part and the amorphous part.A material model in which microscopic damage is taken into account can reproduce this necking phenomenon in impact analysis.

ApplicationExample

An example is now introduced in which impact analysis is applied to an automobile oil pan chipping (flying stone) test, and the result is compared with the experimental result for verification.

活用例活用例

Impact location rib pitch Bullet impact angle Bullet speed [km/h] Fracture form / bullet state
CAE Experiment
Fine Vertical 100 Only rib fracture
No crack on base surface
Only rib fracture
No crack on base surface
Vertical 150 Fine fracture over large area
Penetration of the bullet
Fracture over large area
Penetration of the bullet
Fine Vertical 80 Rib fracture Cross crack on base surface
Bounce back of the bullet
Rib fracture Cross crack on base surface
Bounce back of the bullet
Diagonal 100 Rib fracture Bullet-shaped hole on the base surface
Almost halfway stop of the bullet
Rib fracture Bullet-shaped hole on the base surface
Halfway stop of the bullet
Diagonal 80 Only rib fracture Small round hole on the base surface
Bounce back of the bullet
Rib fracture Cross crack on base surface
Bounce back of the bullet

The chipping test is a test that assumes that a stone bounced up by the tire when the car is running impacts the oil pan. In the video above, a comparison is made between the simulation results of a test in which a metal bullet simulating a bounced stone impacts a resin oil pan at high speed and the actual test taken with a high-speed camera.
The table below shows a comparison between the simulation results with different oil pan rib shapes and bullet impact conditions, and the results of corresponding experiments. The parts indicated in blue letters are where the simulation and experimental results match.
In the experiment, the fracture form and the bullet behavior are observed to differ depending on the conditions, and it was confirmed that the results could be almost exactly reproduced by the simulation.

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