assignment5

OBJECTIVE

• Create the mesh for bumper assembly,mesh size should be 6mm.

1. Run the crash tube model as it is.
2. Change the Inacti=6 and run.
3. Create the type 11 contact and run.
4. Remove both notches and remove boundary condition on rigid body node then run.
5. Create a new notch in the middle ,select the whole section and run.
6. Create a new notch with nodes only from opposing 2 faces and run.HYPERCRASHHyperCrash is a pre-process for RADIOSS which is tailored to meet the needs of automotive crash users. HyperCrash enables the users to build the highest quality model, with significant decrease in modeling time, and with highest level of homogeneity. Also, HyperCrash has an Automotive Safety module which consists of the following tools: Dummy Positioner, SeatBelt Generator, Airbag Folder and Seat Deformer. HyperCrash has various quality checks, including it most powerful intersection/penetration checking and fixing routine, which enables the users to setup a model that is perfectly consistent with the RADIOSS solver. HyperCrash has built-in automated routines that allow the users to significantly reduce the modeling time. Also, it allows the users in a specific group to build a homogeneous model by allowing these users to access the same databases like materials, properties, spotweld connections, dummies, barriers, same checks and etc.

Type 7()

General purpose interface and can simulate all types of impact between the set of nodes and the master surface.

a slave can belong to the master surface and auto impact possible. a gap is defined around the master segment and slave nodes.the gap can be constant or variable.resistive force are applied to keep slave nodes out of the contact gap.

type 11(edge to edge )

in the case of edge crossing th etype 11 interface can be added to capture geometry correctly.for type 11 master surface are generally coarser mesh and bodyundergoing zero deformation like a rigid body.slave are finer and moving body.

INTERFACE PARAMETERS

IGAP : determine how the size of the gap is calculated.

GAPmin : minimum gap for activation of the interface

Inacti : action to be taken if initial penetrations exist. it should be set to 6 or 1

Istf : affects how the stiffness of the interface is calculated.

Iform : frictionformulation is of two types.viscous and stiffness types.for all structural analysis stiffness types are used.

Istf : minimum stiffness to use in the interface.

Idel : what to do with slave nodes and master segments if elements deleted.that they are attached to

• Create the mesh for bumper assembly,mesh size should be 6mm.

CASE 1

1. Run the crash tube model as it is.

the crush tube model is run as it is.default parameter for the contact defined as to prevent penetration.

• rigid wall force increasing smoothly at starting and achieve maximum value at 26ms.then decreases zero at end

CASE-2

in this case open inacti which deals with initial penetraion is set to 6 which compensate the gapfor such contact is any.

• maximum internal energy 42500l. internal energy continously increases with time and achieve maximumvalue at 30ms.
• rigid wall force increasing smoothly at starting and achieve maximum value at 26ms.then decreases zero at end.

case -3

• open crush_tube_000.rad file in hypercrash and apply type 11 contact and applied below parameter.
• the recommended parameters are defined for the already present type 7contact type 11 edge to edge contact with similar parameters is defined for better coverage.the gap minimum is kept lowerin type 11 than that in type 7 compensate for bigger than elem size.

• maximum internal energy 42500l.internal energy continously increases with time and achieve maximumvalue at 30ms

case- 4

• removed both notch and removed boundary condition on rigid body
• the notches are removed with help of align node option.the boundary condition dof applied on the rigid node at the upper end are removed.

• less contact force as compared to previous case due to removal of notch.
• the maximum rigid wall force 1200 KN.The rigid wall forces increase smoothly at staring and achieve maximum value at 26ms,then decrease to zero due to removal of notch.
• the internal energy is 42500J.internal energy continously increases with time and achieve maximum value at 30ms.

CASE-5

create a new notch in middle of thecrushtube on whole section by using align node command.

CASE-6

create new notch only on opposing face.

using the move node option a square set of nodes was pushed inwards on one of the faces approximately in the middle of the tube.all the other analysis parameters and inputs were kept the same .

conclusion

in the case of single notch tube without any bcdue to th excessive crushing action of only one face the vertical force due to intial velocity applied act as a leaverage firsh pushing the tube sideways 13ms,and rotating whole tube about at around 17ms.maximum forces and stresses are acquired.

the plastic strain across the cases is within limit as no deletion of elements is recorded.

when input with recommended parameters ,a zero notched crush tube with both type 7 and type 11 contct interfaces gives out best/realistic resuts.

notches are responsible for the deviation and increases in the dynamic value obtained during the simulation thus the better element alignment should be preffered to get the desired output.