Case Studies 0: A Two Level Strain History Applied to
Axial Kt=1 SAE 1045 Steel Samples



Fatigue Design and Evaluation Committee member: J. Bonnen
Web Page: https://fde.uwaterloo.ca/Fde/CaseStudies/TwoLevel/bonnen_2level.html
Data Reference: J.J.F. Bonnen, "Multiaxial Fatigue Response of Normalized 1045 Steel Subjected
to Periodic Overloads: Experiments and Analysis," PhD Thesis, U. Waterloo, 1998.
Moderator comment: It could be argued that if one cannot predict these
simple (Kt=1.0) axial specimen results well, that it will be very difficult
to expect good predictions for the variable amplitude tests documented in
the other case studies.

Material

The material is a normalized SAE1045 steel. 

    Hardness         203 BHN
    Engr. Strain at fracture=    0.432
    Reduction in area %RA=       48.2
    Strength Coeffiecient, K    1370 mpa
    Strain Hardneing Expo., n   0.261
    Upper Yield Stress,          476 mpa
    Lower Yield Stress,          397 mpa
    Ultimate Stress              703 mpa
    Elastic Modulus           203000 mpa
The constant amplitude axial fatigue specimens were tested by Bonnen and
Chernenkoff and were denoted as "Phase II" material of the FD+E bending/torsion
test program.

Constant Amplitude tests SAE 1045 PhaseII Axial Samples

Geometry



                 Kt = 1.0
Test Specimen: (J.Bonnen PhD thesis)



Load/Strain History (repeated):




The periodic overload strain level was close to the cyclic yield stress
i.e.: mostly elastic behavior; thus after a few sets of these cycles the
tests were switched to load control. The individual test histories are
further described: 


      Detailed Histories

Test Results



        Results  ( See "Bf" blocks to failure column )