Embedded Files
Final Design
The fatigue testing machine produces a relatively high stress on a large section of material. As illustrated in Figure 9, this machine requires the use of a sturdy testing frame, an electric motor, mounted bearings, etc. This poses a challenge to the structural design of the apparatus, as everything will need to be strong and stiff enough to support the loads we require. The fatigue test illustrated in figure 1 is going to be the basic design that will be submitted the ATA In ten weeks. As illustrated in Figure 4, the final design is composed of four components: Four Concentric bearing and mounts, a load frame, a self reacting frame, and a drive assembly.
Overall view of the fatigue tester
One of the most important components of the entire design are the concentric bearings. For this design we used mounted ball bearings. The mounted bearings consist of a spherical bearing insert that allowed a larger tolerance for misalignment. This allows the bearing to function even under large misalignment. Through our [1] analysis we have determined that there will be over two degrees of misalignment due to the test article bending. The concentric bearing design is illustrated in Figure _.
Concentric bearings aligned concentrically
Cross sectional view of pillow block bearing and test article (red)
Another important component is the Load Frame. To provide 207 MPa of stress it was [2] calculated that about120 N must be applied. To do that, our team developed a simple design compose of two steel plates, a 1in cap screw, and a crowned nut. This is illustrated in figure 3. [3] To increase the weight the two nuts will be tightened to create bending in the test article. To prevent vibrations from loosening the nut, a secondary hex nut was be added.
Since there is an large amount of stresses throughout this design, a strong and stable support structure was needed. This was why our team decided to use 7.62 mm thick C-channels. To keep the C-channels in place, Aluminum square pipes were integrated into the design. The wooden supports at the base of the structure allow an affordable way to keep stability. Also a metal plate was also place on top of the supports to insure that the bolts stay perfectly aligned. See Figure 16below.
The Support Structure
A belt drive is used to rotate the test article about 600 rpm. For this design, a 248.6 W (1/3 HP) 3-Phase AC Electric Motor was used. The motor was integrated with a timing belt to prevent belt slippage and did not require much tensioning. (See Figure 11)
m
Pulley and Belt Drive System
The reduced tension needed for the timing belt made designing the motor mount easier without a belt tensioning device. In order to insure that the belt pulleys were aligned and at the correct distance relative to each other the motor mount was made height adjustable. The motor was placed in an adjustable aluminum platform supported as a cantilever by two aluminum angles as shown in Figure 7.
The Belt Drive
Page updated
Report abuse