peteroznewman
Subscriber
nYou want to simulate this landing gear as it touches down and supports the weight of an aircraft that is not modelled. I see a triad in the top picture, so it looks like Z is up, and X is forward, while Y is lateral.nLet's assume that you only care about the maximum stress during the first touchdown. Aircraft often bounce back up into the air after the first touchdown. You can make a model to show the bounce, but it is more complicated. If you only want to simulate the downward followed by some upward displacement and end the simulation before the craft moves above the initial touchdown height, that lets you build a simpler model.nLet's also assume that the rest of the aircraft provides the stability to prevent the landing gear from rotation about the X, Y and Z axes as well as any lateral motion.nIf you were simulating a crash landing where the landing gear is going to be destroyed, then you would want to use Explicit Dynamics.nIf you are simulating a normal landing, then all the stresses should remain in the elastic range, then you should use Transient Structural. Let's go with that.nDelete all the loads and supports from the model.nSelect the top faces where you had the fixed support, but insert a Remote Displacement Support. Set X and Y components to 0., leave Z Component Free, and set all Rotations to 0. This constraint represents the airframe supporting all motion of the landing gear except for the vertical displacement. We won't simulate the forward motion of the craft in this model. In the Details window, set the Behavior to Rigid. Right click on this Remote Displacement and Promote to Remote Point.nRight click on the Geometry line in the Outline and Insert Point Mass. Set the Scoping Method to Remote Point and choose the Remote Point that was just created. Type in the Mass of the aircraft.nSelect the hole where the wheel axle went labeled C above. Insert a Remote Displacement on that face. Set Z = 0. and leave all other DOF Free. Repeat this on the other hole. These two constraints represent contact with the ground.nOn the Initial Conditions folder, insert a Velocity. Select the body and type in the downward velocity as a negative number in the Z Component.nBefore you finish this Transient Structural model, it's best to know the Natural Frequency of this model. In Workbench, Drag and Drop a Modal analysis onto the Model cell of the Transient Structural. In Mechanical, drag and drop the three Remote Displacements from the Transient Structural to the Modal. Solve the Modal. What is the first natural frequency? Call that value F. Back in the Transient Structural Analysis Settings, set the End Time to 2/F. That means you should see the downward and upward motion of the landing gear in the simulated time.nWhen you mesh this solid body, you must have at least 2 quadratic elements or 4 linear elements across the thickness of the landing legs. A better model would replace that with a surface model and shell elements.n