This video showcases how kdFlex can be used to simulate a system with constraints and flexible bodies as well as how kdFlex can be used to post-process and obtain stress data vs. time for a flexible body. The slider crank system shown has one link replaced by a flexible body (the one visualized as a set of spheres with changing colors). First, a simulation was run that logged the modal coordinates, modal velocity coordinates, and modal acceleration coordinates of the link vs. time. Then, FEMBridge was used to post-process this data and calculate the stress vs. time on the link. Finally, the simulation was re-run using this data to color the spheres based on their stress (red is tensile and blue compressive). This system does not have any friction modeled between the block and channel, so the only forces on the flexible link are inertial forces from moving the block and constraint forces that propagate to the link from keeping the block in the channel.