Motion Viewにおけるパラメータ調整方法

Armstrong

現在，MotionViewを用いて衝突吸収機構のシミュレーションモデルを構築しており，シミュレーション結果を確認しながら，減衰や接触力の挙動を検証しています．

相談したい点

① ゴムシート（SGNB）とアルミ合金容器の接触設定について

質量(約３ kg)を持つ構造体が0.5 m高さから落下し，SGNB製のゴムシートに着地（着地面は）する構成です．接触対象はSGNBゴムとA6016-T6相当のアルミ容器で，ゴムは固定，容器側は落下側です．MotionViewの Contact 機能を用いて，Impactモデルにより接触を定義しています．

相談内容：

このような「ゴムとアルミ合金の接触」において，StiffnessやDampingなどの設定値をどのように決定・調整していくべきか，MotionSolve上での設計方針や推奨される手順などがあればご教示いただけますでしょうか．

② ピアノ線ばねの設定について

現在，ばね定数はピアノ線の仕様に基づいて決定していますが，ばねの挙動を確認すると適切な値ではない気がして，シミュレーション結果を見ながら手動で調整している状況です．

相談内容：

MotionView／MotionSolveでばねのパラメータを設定する場合，どのように決めていくべきか，設計上の考え方やバランスの取り方についてアドバイスをいただけますと幸いです．

お忙しいところ恐縮ですが，ご確認のほどよろしくお願いいたします．

GTT Adam

Translated using Google Translate:

"We are currently using MotionView to build a simulation model of a shock absorption mechanism, and are verifying the behavior of damping and contact force while checking the simulation results. What I would like to discuss:

① About the contact settings between a rubber sheet (SGNB) and an aluminum alloy container

A structure with a mass (approximately 3 kg) is dropped from a height of 0.5 m and lands (the landing surface) on a rubber sheet made of SGNB. The contact objects are the SGNB rubber and an aluminum container equivalent to A6016-T6, with the rubber fixed and the container side being the falling side. The contact is defined using the Impact model using the Contact function of MotionView.

What I would like to discuss: In this type of "contact between rubber and aluminum alloy," how should I determine and adjust the settings such as stiffness and damping? Could you please tell me if there are any design guidelines or recommended procedures in MotionSolve?

② Piano wire spring settings

Currently, the spring constant is determined based on the piano wire specifications, but when checking the behavior of the spring, it doesn't seem to be an appropriate value, so I'm manually adjusting it while looking at the simulation results.

Consultation content: I would appreciate some advice on how to decide on spring parameters in MotionView/MotionSolve, as well as design considerations and how to balance them. I apologize for bothering you during your busy schedule, but I would appreciate your help in checking."

Hi @Armstrong,

Thank you for reaching out regarding your shock absorption mechanism. For questions related to Contact tuning, there is a handy guide in our Help Documentation that speaks to best practices. Below is an excerpt from that guide:

"General guidelines for changing these parameters are below.

1. Initially set "low" values for stiffness (penalty) for the normal force. This will enable fast simulations. Review the contact overview table for the maximum penetration seen in the simulation result. If these are higher than expected, increase the stiffness. While using large values for stiffness (penalty) if the contact force is noisy, reduce the simulation step size.
2. Set damping to be about 0.1%-1% of the stiffness or set the coefficient of restitution around 0.4. Models with no damping are prone to undamped high frequency vibration, which will lead to small step sizes. Conversely, models with high damping can also be problematic as the damping force can dominate the overall response."

Typically, if the material types are known for the objects in contact, then you can implement the Poisson Model for contact as you can usually find a table for the Coefficient of Restitution for those materials. Alternatively, the Contact Model will also work just fine if you steadily increase the stiffness and damping until the contact generates little penetration and does not oscillate significantly.

As for spring stiffness, it is based purely on your application. If this was for automotive purposes, you would set the spring stiffness such that the nominal position of the strut is approximately in the middle of the stroke when the vehicle is at its Gross Vehicle Weight (GVW). In some other applications, where a spring will be unloaded and then loaded, the ideal stiffness is such that when under load, it does not reach a compression stop (reach full stroke).

If you are using manufacturer data for spring stiffness and finding it is not providing enough stiffness, then maybe the amount of load you are placing on it is too high. This could be due to improper mass/COG/inertia settings for the contact objects.

Hope this helps!

Adam Reid