The LORD Corporation, MicroStrain Sensing Systems has developed a blade bolt with embedded load sensor (Bolt-Link) for wireless load measurement and control. The Bolt-Link was strength tested to examine its potential use for wind turbine applications.
Ultimate loads are same as standard bolt
Fatigue loads (20 year life) determined from 1.5 MW turbine model and modified to a single load applied one-million times
Calibrate sensor to the limit of the test machine (50,000 lb = 50 kip)
Design/build lever system to double load capacity (100 kip)
Test six Bolt-Links to maximum load failure
Test six Bolt-Links (two instrumented) in fatigue to one-million cycles, continue and stop at two-million cycles (two lifetimes)
Evidence of bolt bending during ultimate load testing
Range of ultimate loads from 97 kip to 102 kip (criteria 99.3 kip)
Six bolts tested to two-lifetimes with no failures
Two bolts with sensors tested to two-lifetimes with no sensor failures
Test results confirm the structural integrity and sensor reliability within a wind turbine application
Cannot determine true ultimate load due to bending from lever system; however, Bolt-Link expected to meet ultimate load criteria
Bolt-Link should be tested in a complete blade fatigue test for further verification
Available at: http://works.bepress.com/scott-larwood/27/