A contact surface may be modeled using gap (compression-only) link objects and large-displacement time-history analysis. To demonstrate, the sequence of a sphere dropping onto a flexible deck is modeled as follows:

Use traditional modeling techniques to create a sphere and a deck.

Use a gap (compression-only) link to connect the sphere and the deck. The gap joints on each object, which will create the contact point upon impact, must align exactly. By using a gap link, the resultant deck displacement may be modeled.

Run a nonlinear large-displacement direct-integration time-history analysis which amplifies gravity load, causing the sphere to impact the deck. Mass- and stiffness-proportional damping should be included, along with small time steps and a Hilber-Hughes-Taylor alpha value of less than zero.