Ultimate Load Test Rig
This ultimate load test rig was custom designed by Jamtech to validate design calculations for the maximum deflection of a glider wing spar component.
Jamtech carried out the following:
- Design of test rig
- Design/implement load measurement instrumentation
- Author test report
The wing spar is subject to flying loads as a result of lift. Given the spar is restrained at points A and B by the air frame, the resulting stress can be visualized using finite element analysis as shown below. Deflection has been exaggerated for illustration purposes.
Having an understanding of the flying loads now allows a test rig to be devised to reproduce the loads and observe the deflection on a test specimen. The general arrangement of the test rig is shown below (test rig structure has been omitted for clarity).
Here a known force is applied at F and the deflection of the spar measured.
What is the Ultimate load?
Before defining the ultimate load, we need to first look at working load. Working load is defined as the maximum load in normal use that produces a deflection without causing the structure to distort (i.e. yield).
The ultimate working load is the product of maximum working load and a safety factor. In general the ultimate working load ensures that structural integrity is maintained (i.e. nothing breaks) but acceptable distortion may occur.
Jamtech consultants designed a test rig for validating the wind spar conformed to the expected deflection when the ultimate load was applied.
Stress calculations and instrumentation were also carried out by Jamtech.