Symmetric Interface (/INTER/TYPE3)

This interface is used to simulate symmetric impacts between two surfaces.

Both surfaces are defined through the use of oriented segments; therefore, contacts can only occur on one side. Each node on both surfaces is considered as a secondary node, and each surface is considered as a main segment.


Figure 1. Interface TYPE3

Contrary to interface TYPE5, interface TYPE3 has two main surfaces; therefore, the contact algorithm is performed twice. The first pass solves the penetration of nodes from the first surface with respect of the second surface. The second pass solves the penetration of nodes from the second surface with respect of the first surface. This leads to higher accuracy compared to interface TYPE5, but more CPU time is needed.

When contact is detected, an elastic spring is added and the spring stiffness is calculated using both surfaces stiffness. Based on material and geometric properties, stiffness is attributed to each surface, then the overall interface stiffness is computed:(1)
K=s K 1 K 2 K 1 + K 2 MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbbG8FasPYRqj0=yi0dXdbba9pGe9xq=JbbG8A8frFve9 Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeaaeaaakeaacaWGlbGaey ypa0Jaam4CamaalaaabaGaam4samaaBaaaleaacaaIXaaabeaakiaa dUeadaWgaaWcbaGaaGOmaaqabaaakeaacaWGlbWaaSbaaSqaaiaaig daaeqaaOGaey4kaSIaam4samaaBaaaleaacaaIYaaabeaaaaaaaa@411B@

The default value for the stiffness scale factor(s) is 0.2, for stability reason this value should not be modified. However, if the ratio of K 1 MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbbG8FasPYRqj0=yi0dXdbba9pGe9xq=JbbG8A8frFve9 Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeaaeaaakeaacaWGlbWaaS baaSqaaiaaigdaaeqaaaaa@3816@ over K 2 MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbbG8FasPYRqj0=yi0dXdbba9pGe9xq=JbbG8A8frFve9 Fve9Ff0dmeaabaqaciGacaGaaeqabaWaaeaaeaaakeaacaWGlbWaaS baaSqaaiaaigdaaeqaaaaa@3816@ is greater than 100 (or lower than 0.01), it is recommended to increase the stiffness scale factor to avoid too many penetrations. The spring stiffness is constant, allowing secondary nodes to pass through the mid-plane of the main segment.

This interface does not enable auto-contact simulation, as a node cannot belong to both surfaces.
Note: This interface is mainly used for shell plates initially in contact. If the two plates are modeled with a gap between the two meshes, it is better to use interface TYPE7; unless, if the two plates are modeled without a gap, interface TYPE3 is a good choice.