Page 5: BeltFit

Purpose:

This interface can be used to create seatbelts and fit them to dummy models. The seatbelt fitting algorithm uses segment sets for defining the contact surface between the seatbelt and the dummy. This provides a more flexible way of defining which element faces should be included in the contact search for the seatbelt/dummy interaction while position the belt. One or several segments sets can be seleted for defining the contact surface on the dummy. If no segment sets exists in the dummy, they can easily be created using the SetD Interface on Page 5.

Usage:

An initial belt path has to be specified in order to fit a belt on a dummy. The first and last node selected will be the belt end nodes. In nearly all cases, it is sufficient to pick only one node between the end nodes. The initial belt path nodes can be picked from the graphics window when the Pick nodes toggle is activated. Alternately, the node IDs can be entered into the adjacent text field and confirmed by typing Enter. The belt path nodes are visible in the list . The complete list of belt path nodes can be cleared with the Clear button. Individual nodes can be removed from the list by selecting the node and click the Rm button.

The initial belt path is displayed as a white line going along the selected nodes in sequential order. When the belt path node selection is done, the Fit button can be clicked. This displays a preview of what the belt will look like if the elements are created. The Stretch button stretches the belt on the dummy in an attempt to make the belt shorter while preventing penetration of the contact segments. The program tries to find a shorter belt each time the Stretch button is pressed, so it should be pressed until no additional improvment is visually noticable. The number of elements will automatically be changed to obey the desired element length. The length of the belt is reported in the message field after each stretch operation. To create elements from the preview state, the Accept button can be clicked.

Belt Types:

Two types of belts can be created: simple and mixed. An optional clearance between the belt and the dummy can be created for both simple and mixed belt types when positioning the belt. The desired clearance distance is typed in to the Offset field. Element size in the belt path direction is given in the Elem size field.

Simple belt – The simple belt option only creates *ELEMENT_SEATBELT elements between the belt path end nodes. Part ID specifies the part ID for the new seatbelt elements. By default, this will be set to last_part_ID+1.

Mixed belt – The mixed belt creates elements of type *ELEMENT_SEATBELT at the ends of a belt and *ELEMENT_SHELL in between as shown in Figure 2. In the transitions between the two element types, *CONSTRAINED_NODAL_RIGID_BODY entities are created.

Figure 3 shows the default vaules if the model appears to be in meters. If the model appears to be in millimeters or inches, the Belt width, Offset, N1->Shell, and Nlast->Shell are scaled accordingly. N1->Shell is the distance from the first node in the belt path to where shell elements should begin. Nlast->Shell is the distance from the last node in the belt path list to where shell elements should begin. Elem/width is the number of shell elements across the width of the belt. Values of 2, 4, 6, or 8 are the avilable options. 1D Part ID is the part ID for the 1D elements (*ELEMENT_SEATBELT). 2D Part ID is the part ID for the 2D elements (*ELEMENT_SHELL). The defaults are last_part_ID+1 and last_part_ID+2 respective.