AGMA 09FTM09-2009 pdf download.AGMA Technical Paper Designing for Static and Dynamic Loading of a Gear Reducer Housing with FEA by M. Davis, Y.S. Mohammed,and A.A. Elmustafa, Old Dominion University and P.F. Martin,C. Ritinski, Sumitomo Machinery Corporation America.
With the model constrained at the torque arm location-1 (see Figure 6) with zero degrees of free- dom in every direction, high stresses were seen on the structural tubing in Figure 7(a). This tubing and the area surrounding show stresses above failure. Figure 7(a) shows that stress concentration in two major areas; the circular mounting hole and the round corners of the structural tubing. The maximum stress on the structural tubing is 543 MPa, and it occurred on the outermost edges of the exterior of the tubing. This stress concentration area is very small and should be omitted due to stress singularities at those points.
A local maximum stress occurred near the edge of the mounting hole of 400 MPa. Because A36 steel tubing has an ultimate tensile strength of around 450 MPa, this stress could cause this tubing to yield. With the weight of the system, and the external torque applied, the structural tubing of the motor adapter could fail in those areas of high stress.
Figure 7(b) shows the mounting hole that was constrained during the analysis. High stresses were seen on the edge of this mounting bar due to a pinching effect. When the loads are applied while that location is held fixed, a significant amount of bending stress is created in the area where the mounting bar meets the structural tubing and outermost motor plate shown in Figure 7(b). The local maximum stresses of this outermost plate are around 200 MPa, and thereby will not cause failure.
Similar analyses were conducted with counterclockwise torque and the two locations of the torque arm. These analyses, however, showed lower stresses, and were disregarded. In this way a worst case loading scenario was obtained.
In the static analysis, the plate at this interface, between the motor adapter and the reducer box, exhibited much higher stresses than the reducer, and is thereby the limiting factors of the design. The greater thickness of the reducer housing at the interface allowed that area to produce little stress.
In order to get lower stresses, many of the parts were redesigned in an iterative process. The plates were thickened, the structural tubing was thickened, but the stresses were still high and the cost of these modifications would increase the production cost. Eventually, the solution that proved to be easy and cost effective in terms of manufacturing was to extend the bottom bar to the entire width of the coupling box. This causes the reaction forces from the torque arm to act over the entire coupling box instead of a small region thereby lowering the stresses.
Figure 8 shows the results from the static analysis with the extended bar. With this bar extended the stresses were around 60 MPa. These stresses were located on the bar mounting hole. With this small modification a significant reduction in stresses was achieved.AGMA 09FTM09 pdf download.