It has been found that pre-stressing samples at 0.95 of the 0.2% proof stress leads to early failure when they are fatigue-tested at stress levels of about 0.65 of the 0.2% proof stress.
However, HPPD will not occur when the peak stress is far below the proof stress.
The test specimens consisted of normal strength material (T5) with the 0.2% tensile proof stress (yield stress) ranging from 185 to 196 MPa, and high-strength material (T6) with the 0.2% tensile proof stress ranging from 226 to 317 MPa.
Strength increased monotonically with hot-rolling reduction, eventually reaching 1400 MPa in 0.2% proof stress, an exceptionally high value.
The 0.2% proof stress and tensile strength slightly increased after the wire-brushing, although the elongation decreased.
That it nevertheless has a proof stress 35 MPa lower can be qualitatively explained by the differences in martensite crystallography.
Attention has been focused on small fatigue crack growth at maximum stresses beyond the 0.2% proof stress of the material.
The other, containing 0.45 wt% carbon and 13.2 wt% nickel, had a 0.2% proof stress of 1000 MPa and a fracture toughness of 103.8MPam12.
The 0.2% proof stress is comparatively more reasonable to predict the design strengths of stainless steel tubular X-joints for both ultimate limit state and serviceability limit state.
It was observed that cross-section slenderness λp and material properties such as non-dimensional proof stress e and strain hardening exponent n significantly influence column resistances.
Key stress strain parameters viz., Young's modulus, proof stress, ultimate strength, percentage elongation, strain hardening exponent etc. were generated based on flat, corner and weld coupon tests data.
