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Linkage Kinematics Finite Element Analysis:
Find the stresses in various linkage components on a skid loader given maximum lift weight and shock loading.

Special features:
Determining the load vectors using gravity, finite element beams and trusses and time-based actuators (hydraulic cylinders).

Output:
Stresses as a function of mass, acceleration, gravity, inertial, and shock loading.

Comments:
Modeling a complex equipment linkage taxes the horsepower of even modern computers due to the necessarily complex mesh with many elements. So, a way was found to dynamically load individual components of the linkage as they are loaded in the working assembly to significantly reduce the computation time and allow for more scenarios inexpensively. This method employs finite element beams, trusses and actuators to simulate the working mechanism and gather the force loading to be used as the inputs to the stress models of the individual parts.

The beams and trusses were laid out to connect all the pivots of the rigid structural components (2), linkages (2), and hydraulic cylinders (2). The rigid portions, representing the frame work of the skid loader, were laid out with beams arranged in connecting triangles. The beams have rotational degrees of freedom; consequently, where they connect together, the connections are rigid. The trusses don't possess rotational degrees of freedom and were used as the two links. Where they connect to beams, they are free to rotate. The same degrees of freedom applied to the linear actuators. The beams and trusses were given a cross-sectional area of one (1) inch. The beam and truss axial stress output in Algor can be displayed as P/A, in effect, directly displaying the axial force as a function of time. These axial forces are co-linear with the individual beam and truss elements and since their orientations are known, their force outputs become time-based (dynamic) vector inputs for the stress analysis.

The first figures above (click on the thumbnails) show the layout of the mechanism. The second picture shows the layout measurements used to set up the Autodesk Algor model for kinematic output. The weights assigned to the beams and trusses total the assembled weight of the mechanism and were distributed to correctly locate the actual centers of mass of the individual components. The third thumbnail activates an animation of one of the loading scenarios. The arrow at the end of the hypothetical bucket was a constant 750 lbf load. However, in other scenarios, this was governed by a curve simulating shock (magnitude variation as a function of time). One can now see the mechanism in action and see the vector forces (compression and tension) change with time. The third thumbnail shows the solid model of one of the links with weld fillets. The last thumbnail activates an animation showing a stress output of one of the links.