STRAIN-BASED FATIGUE ANALYSIS OF WHEELCHAIRS ON A DOUBLE ROLLER FATIGUE MACHINE

Results are presented from an experimental program that recorded the o utputs of strain gages mounted on two wheelchair frames (one manual, o ne power) as the wheelchairs were run on a double roller fatigue machi ne. Rectangular strain gage rosettes were attached to the frames near the cross tube center pin and on the side frame behind a front easter. Thirty data sets were recorded from each rosette on each wheelchair f rame. The fatigue test machine and test protocol were in substantial c onformance with the recently published ANSI/RESNA Standard for wheelch air fatigue testing. Two analyses have been performed on the recorded strain data. The von Mises stress histories were computed from the str ain data and show that peak stresses are frequently twice the mean val ue. Also, estimates of the number of fatigue machine cycles to failure have been made using a strain-based fatigue analysis. These data will provide wheelchair designers with useful data to incorporate into the ir design process.