Fatigue Damage Behavior of a Structural Component Made of P355NL1 Steel Under Block Loading

Abstract

The common design practice of pressure vessels subjected to variable amplitude loading is based on the application of a linear damage summation rule, also known as the Palmgren–Miner’s rule. Even though damage induced by small stress cycles, below the fatigue limit, are often taken into account in design codes of practice by two-slope stress-life curves, the sequential effects of the load history have been neglected. Several studies have shown that linear damage summation rules can predict conservative as well as nonconservative lives depending on the loading sequence. This paper presents experimental results about the fatigue damage accumulation behavior of a structural component made of P355NL1 steel, which is a material usually applied for pressure vessel purposes. The structural component is a rectangular double notched plate, which was subjected to block loading. Each block is characterized by constant remote stress amplitude. Two-block sequences were applied for various combinations of remote stress ranges. Three stress ratios were considered, namely, R=0, R=0.15, and R=0.3. Also, constant amplitude fatigue data are generated for the investigated structural component. In general, the block loading illustrates that the fatigue damage evolves nonlinearly with the number of load cycles and is a function of the load sequence, stress levels, and stress ratios. In particular, a clear load sequence effect is verified for the two-block loading, with null stress ratio. For the other (higher) stress ratios, the load sequence effect is almost negligible; however the damage evolution still is nonlinear. This suggests an important effect of the stress ratio on fatigue damage accumulation.

Vibration Fatigue Damage Accumulation of Ti–6Al–4V under Constant and Sequenced Variable Loading Conditions

“…The fatigue lives under the one-way two-level loading conditions are compared with the CAV results ( Figure 5). The equivalent stress is calculated according to the cycle fraction of the two blocks [6]. Under a specific stress level the two-level data follows a pattern: taking the CAV results as reference, the data from the H-L case concentrates on the left side and that from the L-H case locates on the right side.…”

“…Aid [5] conducted a series of variable loading experiments of 6082 T6 Aluminum alloy including four blocks loading and random loading conditions. Pereira [6] carried out multi-level loading tests with different sequences (high-low and low-high) and a constant loading test using P355NL steel under various cyclic ratios. However, a common feature of the above studies is that the loading sequences used are either in ascending order (e.g., low-high loading) or in descending order (e.g., high-low loading).…”

Nonlinear fatigue damage accumulation and life prediction of metals: A comparative study

“…In the current analysis, fatigue experiments of smooth specimens of P355NL1 steels were conducted. [39][40][41] This steel is a normalized fine grain low alloy carbon steel normally utilized for pressure vessels. These tests were carried out under fully reversed strain-controlled mode.…”

Crack Closure Effects on Fatigue Crack Propagation Rates: Application of a Proposed Theoretical Model

“…The P355NL1 steel is a pressure vessel steel and is a normalized fine grain low alloy carbon steel. Its fatigue behaviour has been investigated [16,23,24]. A steel plate 5 mm thick was used to prepare specimens for experimental testing.…”

“…This paper proposes a theoretical model based on Walker's propagation law [15] to estimate the quantitative parameter, , important for the evaluation of the fatigue crack opening stress intensity factor, op , taking into account the stress ratio and crack closure and opening effects. The current study is applied to the P355NL1 steel using experimental fatigue crack propagation test results under constant amplitude loading [16]. The proposed model is applied using an inverse analysis of the experimental results.…”