Media transport

The verification test in this section is a media transport analysis of a periodic media consisting of nine blocks modeled using M3D4R and C3D8R elements. The membrane elements are used to model the conveyor belt, and the brick elements are used to model the packages on top of the belt. The packages are tied to the belt with a tie constraint. The model is pre-stretched using Abaqus/Standard and imported to Abaqus/Explicit, where the periodic media is defined and activated. The belt is set in motion at the beginning of the Abaqus/Explicit analysis by specifying a uniform initial velocity. The model is illustrated in Figure 1.

Figure 1. Periodic media transport analysis.

Because the periodic media analysis technique is not available in Abaqus/Standard, the ties between blocks must be defined explicitly using a tie constraint and the boundary conditions at the inlet and outlet must be defined directly at the nodes. In addition, the front end nodes of the inlet block must be constrained to have identical displacements as their corresponding nodes in the back end of the inlet. This is accomplished by defining an equation constraint between corresponding nodes that forces the y-direction displacements to be equal. The belt is stretched by fixing the inlet nodes and displacing the outlet nodes in the x-direction.

In the Abaqus/Explicit analysis the periodic media is defined using element sets and node sets. Two rollers are added with general contact defined between the belt and the rollers. Both the inlet and outlet control nodes are fixed in the y- and z-directions and given a velocity of 1000 in the x-direction. All of the belt and package nodes are given an initial velocity of 1000 in the x-direction. Block shuffling takes place when the back end of the inlet passes the trigger plane. The trigger plane is located at an x-coordinate of –200 and is normal to the x-direction.

The verification test in this section is the same model described in the previous section, except that the pre-stretching step is defined directly in the Abaqus/Explicit analysis and the packages are fixed to the belt using cohesive contact instead of a tie constraint. The periodic media is inactive during the pre-stretching step. The stretching is achieved by applying velocity boundary conditions with different amplitudes at both inlet and outlet control nodes. The velocity amplitudes ramp up from zero to one in a span of 0.2 seconds; however, one amplitude starts ramping at the start of the step and the other is delayed by 0.2 seconds. At the end of the step the inlet and outlet control nodes have uniform velocity boundary conditions. The periodic media is activated in the second step, allowing block shuffling to take place when the back end of the inlet block passes the trigger plane. The model is illustrated in Figure 1.