Cumulative fatigue damage of stress below the fatigue limit in weldment steel under block loading

Abstract

To investigate the cumulative fatigue damage below the fatigue limit of multipass weldment martensitic stainless steel, and to clarify the effect of cycle ratios and high-stress level in the statement, fatigue tests were conducted under constant and combined high-and low-stress amplitude relative to stress above and below the fatigue limit. The outcomes indicate that neither modified Miner's nor Haibach's approach provided accurate evaluation under repeated two-step amplitude loading. Moreover, effect of cycle ratios has been determined. Additionally, the cumulative fatigue damage saturated model is established and validated. Cumulative fatigue damage contributed by lowstress below the fatigue limit in high stress of 700 MPa is higher than that with 650 MPa at identical conditions (fatigue limit 575 MPa). Thus, high stress affects fatigue damage behaviour below the fatigue limit. A new predicted approach has been proposed based on Corten-Dolan law, whose accuracy and applicability have been proven. K E Y W O R D S below fatigue limit, block loading, cumulative fatigue damage, fatigue life prediction, weldment stainless steel

Cumulative Damage and Life Prediction Models for High-Cycle Fatigue of Metals: A Review

“…Nonetheless, the effects of load interaction and low-amplitude loading are considered in the Corten-Dolan model, giving it a major advantage over Miner's rule. Recently, He et al [13] have shown that the Corten-Dolan model can be used to estimate the fatigue life for various multi-pass welded stainless steels whose S-N curves exhibit bilinear characteristics, including load spectra below the fatigue limit.…”

“…It has however been shown that both methods tend to be non-conservative in most variable amplitude experiments (e.g., Sonsino et al [10], Sonsino et al [11], and Schoenborn et al [12]). To overcome this, He et al [13] proposed the cumulative fatigue damage saturated model in which a critical number of cycles of below the fatigue limit in one block exists. When the value is exceeded, the remaining cycles below the fatigue limit become harmless.…”

Ductile fracture modeling of metallic materials: a short review

“…Finally, the third stage consists in the ultimate crack propagation the rate of which is roughly half of the speed of sound in the material [17]. Recent works on fatigue fracture with some numerical applications can be found in [18][19][20][21][22]. Creep fracture is particularly relevant in components that operate at high temperatures (e.g., turbine, petrochemical or nuclear plants, etc.).…”

Nonlinear fatigue life prediction model based on the theory of the S‐N fatigue damage envelope

“…7 This is due to the perspective that an accumulation model is required to design for VAL, that it is generally simple to follow, and that the formula yields acceptable life prediction for uniform random loading histories. [8][9][10][11] The inherent error or uncertainty in Miner's rule for decreasing load amplitude spectra could result in catastrophic consequences. However, it is commonly accounted for through the application of a Design Fatigue Factor, used in conjunction with a design S-N curve which already has a low probability of failure (2.3% in DNVGL), 12,13 resulting in a more conservative design due to the application of Miner's rule.…”