Block Fatigue Testing Techniques Considering Hold Time, Frequency, and Residual Stress-Strain Curves
Abstract
Block fatigue testing is a technique that can be used to accelerate the damage accumulation of a specimen by using high load tensile-tensile fatigue first to consume a certain percentage of the fatigue life of a specimen prior to dropping to a lower load to failure. Damage accumulation theory allows for partial life consumption analysis which would provide a simple percentage-based extrapolation to generate an S-N curve in a fraction of the time of a traditional fatigue testing campaign. Results from previous testing demonstrated that such a methodology correlates with a correction multiplier. To better understand the effect of block testing, three additional aspects were examined. The use of a hold time between blocks to allow for polymer chain relaxation prior to resuming fatigue testing at a lower tensile load. Traditional S-N curve generation can rely on a constant frequency, which would result in a slightly different strain rate at different max-min loading combinations due to more displacement in the same cycle time. This aspect was examined by using block testing at the same loads with different frequencies. The final damage mechanism that was examined was how the stress-strain curve changed as a function of fatigue life. These experiments provided additional insight into the possible use of block fatigue testing to accelerate meaningful fatigue curve generation.
College
College of Science & Engineering
Department
Composite Materials Engineering
Campus
Winona
First Advisor/Mentor
Eric Kerr-Anderson
Location
Ballroom - Kryzsko Commons
Start Date
4-18-2024 10:00 AM
End Date
4-18-2024 11:00 AM
Presentation Type
Poster Session
Format of Presentation or Performance
In-Person
Session
1b=10am-11am
Poster Number
28
Block Fatigue Testing Techniques Considering Hold Time, Frequency, and Residual Stress-Strain Curves
Ballroom - Kryzsko Commons
Block fatigue testing is a technique that can be used to accelerate the damage accumulation of a specimen by using high load tensile-tensile fatigue first to consume a certain percentage of the fatigue life of a specimen prior to dropping to a lower load to failure. Damage accumulation theory allows for partial life consumption analysis which would provide a simple percentage-based extrapolation to generate an S-N curve in a fraction of the time of a traditional fatigue testing campaign. Results from previous testing demonstrated that such a methodology correlates with a correction multiplier. To better understand the effect of block testing, three additional aspects were examined. The use of a hold time between blocks to allow for polymer chain relaxation prior to resuming fatigue testing at a lower tensile load. Traditional S-N curve generation can rely on a constant frequency, which would result in a slightly different strain rate at different max-min loading combinations due to more displacement in the same cycle time. This aspect was examined by using block testing at the same loads with different frequencies. The final damage mechanism that was examined was how the stress-strain curve changed as a function of fatigue life. These experiments provided additional insight into the possible use of block fatigue testing to accelerate meaningful fatigue curve generation.
