Final Design

Note:  Engineering drawings and  part specifications are located in Appendix C of Final Report. 

In the current design (Figure 3-20), the tester can be configured to act as a tensile fatigue tester, a rotating-bending fatigue tester, or a combination of the two. The horizontally mounted motor will provide the rotation (at up to 30 cycles/second) for the rotating-bending mode of operation. Looking from the side and moving left-to-right in Figure 3-20, a motor is mounted to the base. The shaft of the motor is connected to the 1” main rotating shaft my means of a spider coupling. A spider coupling was chosen in place of a rigid coupling in order to allow for minor misalignment between the main shaft and the motor. The main rotating shaft passes through a set of pillow mounted ball bearings to ensure that no significant bending of the shaft is transmitted to the coupling between the main shaft and the motor.

Two flange mounted bearings are placed on the outside of an aluminum block.  The aluminum block has a pin connected on each side which in turn fits into a guide block that is fitted into the vertical track.  In this way, the bearings can both pivot and translate vertically if desired.  The vertical bending load is applied by tightening a screw down onto an aluminum block which is attached to the top of the vertical assembly.  The screw is set in another aluminum block above the top of the vertical assembly which has two guide rods on each side of the screw that is connected to the top of the two guide blocks.  When the screw is tightened the guide blocks will move up and the force applied to the system will be measure with a force transducer that is placed under the screw applying the force.

The vertical assembly has a half inch steel plate mounted to the rear.  The vertical plate is pulled on by a magnetic force produced by an electromagnet mounted at the rear of the assembly.  This electromagnet is adjustable via a screw which runs through the rear support and mounts to the electromagnet.  Below the electromagnet on the rear support is a load cell which is depressed by an adjustable bolt on the steel plate.

Figure 3-21: Final Assembled Machine