Testing
Testing Summary​
The testing of the bridge closely relates to the design criteria for its success, most important being the size constraints, the bridge weight, the bridge strength, and articulation functionality. The size of the bridge will be "tested" frequently throughout its design and construction, ensuring that each part that is designed and manufactured actually meets the specifications required. The bridge's weight will be tested by placing it on a weight scale and analyzing its weight. Although straightforward, this testing needs to be done often throughout the building process to test if certain parts are overweight. This portion is closely related to the improving and redesigning of the bridge. Upon failure to meet the weight requirement, weight needs to be shaved off without sacrificing strength and tested again, until it reaches 85 grams. The bridge strength will be tested by placing the bridge on two abutments 400mm apart, and then slowly adding weight applied at the center of the bridge (hanging below). One kg at a time, the load will be increased and deflection, defects, and the bridges behavior will be analyzed and taken into account. The articulation cycle of the bridge will be tested by examining the motor and ensuring its functionality, as well as its limits. To ensure that the bridge is able to open, the motor needs to be rated for a greater force than the bridges weight. This will be tested through calculations, as well as final testing by actually lifting the weight of the bridge.
Some issues faced during the articulation testing was that the motor would continue to run after the bridge reached maximum height, causing the bridge to jam into the articulation tower. This put unnecessary stress on the motor, since the bridge was restricted. This was solved by decreasing the articulation time in the Arduino code.
Figure 1
Pictured above is the second prototype of the bridge, laid on its side, ready for "dimension testing." This essentially meant that the bridge was checked for multiple dimension based criteria: the road length and width, the truss clearance, and tower geometry. This test was quick and only required a tape measure to complete.
Figure 2
Figure 3
Figure 4
The three pictures above show the balsa bridge while testing the articulation cycle. In the lower photo, it is at it's maximum articulation location, where it was held for 10 seconds before lowering back down. This test was largely successful and the results of the test showed that the articulation cycle could be done in under 15 seconds. Figures 2 and 3 show the bridge prior to articulation, where figure 2 shows the Arduino code being double checked (on monitor in back) and figure 3 shows the Arduino circuit being checked for any wiring errors or broken wires.
Figure 5
Figure 6
The two pictures seen above show the load test of the bridge. This was done on the instron machine (see figure 5), where the bridge was placed under a load equivalent to 190 Newtons, or roughly 19kg. The lower picture (figure 6), shows the maximum load and deflection of the bridge during the test. It reached 19 kg, and only deflected 3 mm.
Figure 7
The video above shows the Instron machine load testing the bridge. In this video, on the right hand side the data on the computer shows the load gradually increasing to 190 Newtons, and the "creaking" of the bridge as it sets in place can be heard. These creaks were not the bridge cracking or deforming, which was found from a post-test inspection for damages.