Page 145 - Biaxial Multiaxial Fatigue and Fracture

130 RJ? KAUFMAN AND TH. TOPPER

plane. A Mohr's circle representation in part (c) shows that the maximum shear plane is at 45'
to the principal axes. The strain state on the maximum shear plane is illustrated in (d).
A total of 15 pure shear tests were conducted on specimens of BHN 456. Table 1 lists the
alternating shear stress amplitudes that were applied on the maximum shear planes and the
resulting number of cycles until a crack depth of approximately 50 pm or final separation of the
specimen occurred. Specimens that reached 1x106 cycles without failing were removed and
deemed to be run-outs.

Table 1. Alternating shear test results for SAE 1045 steel, 456 BHN.

Zero mean stress fatigue tests for SAE 1045 steel, BHN 203, with varying levels of cyclic
alternating shear stress were reported by Bonnen 12.51.

Alternating Shear Stress with Superimposed Static Mean Stresses. A total of 47 (No 16 to No 62
in Table 2) alternating shear stress tests with static tensile mean stresses and 15 (No. 63 to No. 77
in Table 2) tests with static compressive mean stresses normal to the maximum shear planes
were performed for BHN 456. For BHN 203, a total of seven (No I to No. 7 in Table 3)
alternating shear stress tests with static normal tensile mean stresses and five (No. 8 to No. 12 in
Table 3) tests with static normal compressive mean stresses were performed. For the as received
SAE 1045 steel (BHN 203), a run-out was listed if the specimen did not fail before 2x106cycles.
Tables 2 and 3 list the results for the static mean stress fatigue tests with alternating shear
stress for the hardened and as received SAE 1045 steels.