Types of Contacts
Hi,
I was trying to simulate a roller body, vibrating on the road. So, i gave conatct between the roller and the road. Once when i simulate it, the roller is penetrating into the road. Later i understood, its the stiffness and damping of the contact.
Can anyone help me on understanding different types of contacts i.e.
1) Impulse
2) poissions
3) Volume
What are the different situations, there are employed. If possible the mathematical understanding on how these solve the inputs.
Best Answer
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Hi Bhuvana,
The 3 different contact formulations mainly boil down to what information you have available about the contact.
For a general formulation, the Impact (default) method treats the contact like a spring, where a stiffness coefficient, stiffness exponent, and damping coefficient is defined. The penetration depth is a way of delaying the maximum damping being applied until that depth is reached. This spring and damper analogy will be featured in all methods.
The Poisson method uses the coefficient of restitution, which describes the relative elasticity or or bounciness of a collision between two objects. The coefficient of restitution and penalty value are used to calculate the equivalent spring force. The transition velocity is used to smoothly engage the damping with respect to velocity instead of distance like the Impact method.
The Volume method uses material properties to define the spring force such as the bulk modulus, shear modulus, layer depth, and stiffness exponent. A damping coefficient is also used for damping, of course.
As these are common contact methods, there is lots of information about them online and in our help documentation. For best practices with respect to contacts, please see the link below.
Best Practices for Running 3D Contact Models in MotionSolve:
Hope this helps!
Adam Reid
1
Altair EmployeeAnswers
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Hi Bhuvana,
The 3 different contact formulations mainly boil down to what information you have available about the contact.
For a general formulation, the Impact (default) method treats the contact like a spring, where a stiffness coefficient, stiffness exponent, and damping coefficient is defined. The penetration depth is a way of delaying the maximum damping being applied until that depth is reached. This spring and damper analogy will be featured in all methods.
The Poisson method uses the coefficient of restitution, which describes the relative elasticity or or bounciness of a collision between two objects. The coefficient of restitution and penalty value are used to calculate the equivalent spring force. The transition velocity is used to smoothly engage the damping with respect to velocity instead of distance like the Impact method.
The Volume method uses material properties to define the spring force such as the bulk modulus, shear modulus, layer depth, and stiffness exponent. A damping coefficient is also used for damping, of course.
As these are common contact methods, there is lots of information about them online and in our help documentation. For best practices with respect to contacts, please see the link below.
Best Practices for Running 3D Contact Models in MotionSolve:
Hope this helps!
Adam Reid
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Hi Adam,
That is awesome, Thank you so much for the responce. so, all these 3 types of contacts work as Spring-damper system, but the parameters are different, depending on the known values. is that it?
Like, think i have all the values which can be used in all these types of contacts mentioned. Then on what factor should i choose the a type of contact for a particular application. How do i know which contact to use.
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Bhuvana Siva Teja said:
Hi Adam,
That is awesome, Thank you so much for the responce. so, all these 3 types of contacts work as Spring-damper system, but the parameters are different, depending on the known values. is that it?
Like, think i have all the values which can be used in all these types of contacts mentioned. Then on what factor should i choose the a type of contact for a particular application. How do i know which contact to use.
Hi Bhuvana,
You've got it. If you possess all of the information required to define all 3 methods, than the choice is up to you.
The default Impact Method is easiest tune in my opinion, where the correct contact behaviour can be found by simply modifying direct spring parameters (stiffness and damping). The other methods require a more thorough understanding of the formulations in order to tune properly.
Hope this helps!
Adam Reid
1