The Effect of Frictional Forces on Fatigue Crack Growth in Lugs
Abstract
In a previous Report by the author, experimental stress intensity factor range distributions derived from crack propagation rate measurements were presented for a pin-loaded lug. It was shown that crack growth rate at short crack lengths was much faster, by up to almost an order of magnitude, than predicted by available fracture mechanics solutions. It was proposed that this was due to the action of frictional forces between the pin and hole surface. These forces are normally ignored, it being assumed that load is transferred by radial pressure alone. Further crack propagation rate measurements have been made on lugs with normal clearance fit pins which confirm the earlier results. Experiments are described in which the frictional forces were reduced by lubricant and removed altogether from around the crack origin using pins with flats. It is found that crack propagation rate at short crack lengths is significantly reduced by both of these measures, indicating values of delta K nearer to those predicted ignoring frictional forces. It is found that the inclusion of the action of frictional forces in a fracture mechanics analysis of a lug leads to an increase in the predicted delta K at short crack lengths. Closer agreement with experimental results is obtained if it is assumed that these forces build up more in region of the crack origin and are therefore effective for the important region of short crack lengths.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 1984
- Accession Number
- ADA151994
Entities
People
- J. E. Moon
Organizations
- Royal Aircraft Establishment