The original project was made by @stadlerj. The CAD is a courtesy of GrabCAD member Sankar Ram. The symmetry of the model was used to minimize the simulation domain. After that the model was prepared for each design version mainly in terms of removing and adding smaller features and parts. It was then uploaded as a STEP file to the SimScale Platform and meshed using the fully automatic tetrahedralization.
The strength of components is an important requirement in understanding a product’s performance lifecycle and possible failure modes. Tractors and other agricultural equipment are used in rough terrain and under tough conditions. Immense forces are created when the heavy equipment is in operation. The machinery must endure loads that can be possible miscreated by error of the operators. Those loads bring the tractors to operate outside of their normal operating conditions. So misuse loading simulations is a must in any product development cycle.
For the simulation a symmetric model was used to save computational time. Seven sliding contacts boundary conditions were made. One displacement constraint was used to generate the symmetry plane. For the connection of the arm with the two hydraulic cylinders with the chassis remote displacement boundary conditions were created. The load was then applied with a remote force. The 3 first runs are the ones with 16kN load, which is the normal operating load for this class of tractor (JCB Backhoe Loader). Then 3 runs were made with a misuse Load of 20kN, which would happen in case of the operator trying to load 400kg more in the shovel. Remembering that as we are using half of the model, each load has been applied accordingly.
For each load were simulated 3 different designs:
Design A - original design download from GrabCAD;
Design B - changes in thickness as in the picture below;
Design C - Design B plus material reduction
JCB Backhoe Loader with the arms in yellow and the shovel.
Three different designs proposed to simulate.
Mesh for each design.
Before prototyping the simulations guide the engineer or the designer to choose the best proposal that follows the design requirements and budget of the project.
The Von Mises Stress are shown for each case in the next table:
Results for operating load of 16kN.
Results for misuse load of 20kN.
It is clear from the results that the design can be improved as it didn’t reach Yield Stress for any proposal. Even under misuse load, if we consider the Design C which was the most aggressive in terms of material reduction, it didn’t reach the Yield Stress of the Steel. Of course this is a compromise between the design and its factor of safety. There will be a limit to material reduction in order to assure a desired factor of safety.
*FOS = Factor of Safety.
From the results above we see that the loader arms have not reached plastic deformation but we see that specially for the misuse load, the design C gets a FOS of 1.15 which can be considered too low for a tractor, so that shows us that a new design can be proposed investigating better where the material reduction can be applied in order to reduce weight but keeping the FOS in a higher value.
Every company in the agricultural or heavy machinery sector designs equipment to work reliably under normal and heavy operating conditions, even when the operator error or misuse occurs. Using SimScale platform as standard part of the design process, engineers have confidence to quickly and cost effectively develop robust equipment that works in the wide range of conditions that the Agricultural and Heavy Machinery market demands.
Obs: For each simulation we have also calculated the reaction forces for each hydraulic piston. So it is possible to investigate the forces needed for each hydraulic piston to work under the operating load and the misuse load as well.