Load Sequence Effect on Fatigue Damage

2011 ◽  
Vol 488-489 ◽  
pp. 545-548 ◽  
Author(s):  
Y.G. Xu ◽  
L. Wang ◽  
Y. Chen ◽  
W. Tiu
Keyword(s):  
Fatigue Damage ◽  
Crack Closure ◽  
Life Prediction ◽  
Fatigue Cracks ◽  
Fatigue Loading ◽  
Sequence Effect ◽  
Complex Load ◽  
Load Sequence ◽  
Damage Tolerant ◽  
Spectrum Loading

Reliable damage tolerant design of airframe structures relies on the accurate life prediction of fatigue cracks propagating from a detectable size to the critical size, which is challenging due to the complex load sequence effect under spectrum loading. This paper aims at gaining a further understanding of the complex influence of the loading history on fatigue damage through a detailed numerical simulation of the near-tip crack behaviour using the crack closure concept. The spectrum loading is broken down into a number of simple yet representative loading scenarios with overload/underload superimposed onto the baseline constant amplitude fatigue loading. Detailed finite element (FE) simulation of the plasticity-induced crack closure (PICC) has been carried out to catch the transient behaviour of PICC and link it to the fatigue damage. The load interaction effect has been analysed with the aim to identify the possible dominant loading cycle which could simplify the fatigue life prediction process in the industry. It is concluded that more reliable damage tolerant design can be achieved if the load sequence effect on fatigue damage can be taken into account more accurately for a structure under spectrum loadings.

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

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Hélder F.S.G Pereira ◽  
Abílio M. P. De Jesus ◽  
Alfredo S. Ribeiro ◽  
António A. Fernandes
Keyword(s):  
Fatigue Damage ◽  
Structural Component ◽  
Stress Ratio ◽  
Sequence Effect ◽  
Block Loading ◽  
Fatigue Damage Accumulation ◽  
Load Sequence ◽  
Stress Ratios ◽  
Remote Stress ◽  
Damage Summation

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.

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

2007 ◽  
Author(s):  
He´lder F. S. G. Pereira ◽  
Abi´lio M. P. De Jesus ◽  
Anto´nio A. Fernandes ◽  
Alfredo S. Ribeiro
Keyword(s):  
Fatigue Damage ◽  
Structural Component ◽  
Stress Ratio ◽  
Sequence Effect ◽  
Block Loading ◽  
Fatigue Damage Accumulation ◽  
Load Sequence ◽  
Stress Ratios ◽  
Remote Stress ◽  
Damage Summation

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 S-N 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 non-conservative 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 is generated for the investigated structural detail which is applied for indirect damage calculations. 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 non-linear. This suggests an important effect of the stress ratio on fatigue damage accumulation.

Analysis of Cracks and Stresses of Welded Attachments on Full-Scale Plate Girder under Fatigue Loading

2006 ◽  
Vol 324-325 ◽  
pp. 459-462 ◽  
Author(s):  
Myung Gu Lee ◽  
Seung Yong Lee ◽  
Cheol Woo Park
Keyword(s):  
Fatigue Damage ◽  
Fatigue Cracks ◽  
Steel Structure ◽  
Fatigue Loading ◽  
Design Criterion ◽  
Full Scale ◽  
Parent Metal ◽  
Girder Bridges ◽  
Fatigue Design ◽  
Plate Girder

In steel structure systems such as plate girder bridges and framed structures, fatigue damage used to occur at welded areas rather than primary structural members. These damages and behaviors of the welded attachments need to be extensively investigated so that the fatigue design criterion can effectively control the fatigue damage of steel structure systems. This study utilized a full-scale plate girder on which various welding attachments were mounted. The welded attachments investigated herein included flange gussets, web gussets, vertical stiffeners, and cover plates. The fatigue cracks initiated at the longitudinal end of joint area of the weld bead and the parent metal where stress was significantly concentrated. The initiated fatigue cracks developed along the weld path and then, propagated to the parent metal in the direction perpendicular to the principal stress. The fatigue cracks developed even under a compressive stress when a significant residual stress was experienced from the welding. The fatigue strengths of the each welded attachment were evaluated and compared with the current fatigue design specifications in AASHTO [1] and JSSC [2].

Life prediction of wind turbine blades using multi-scale damage model

2021 ◽  
pp. 073168442199588
Author(s):  
Sepideh Aghajani ◽  
Mohammadreza Hemati ◽  
Shams Torabnia
Keyword(s):  
Wind Turbine ◽  
Turbine Blade ◽  
Fatigue Damage ◽  
Life Prediction ◽  
Turbine Blades ◽  
Damage Model ◽  
Fatigue Loading ◽  
Multiaxial Fatigue ◽  
Wind Turbine Blade ◽  
Wind Turbine Blades

Wind turbine blade life prediction is the most important parameter to estimate the power generation cost. Due to the price and importance of wind blade, many experimental and theoretical methods were developed to estimate damages and blade life. A novel multiaxial fatigue damage model is suggested for the life prediction of a wind turbine blade. Fatigue reduction of fiber and interfiber characteristics are separately treated and simulated in this research. Damage behavior is considered in lamina level and then extended to laminate; hence, this model can be used for multidirectional laminated composites. The procedure of fatigue-induced degradation is implemented in an ABAQUS user material subroutine. By applying the fatigue damage model, life is estimated by the satisfaction of lamina fracture criteria. This model provides a comprehensive idea about how damage happens in wind blades regarding a multi-axis fatigue loading condition.

scholarly journals Experimental and theoretical evidence for the load sequence effect in the compressive fatigue behavior of concrete

2021 ◽  
Vol 54 (2) ◽  
Author(s):  
Abedulgader Baktheer ◽  
Rostislav Chudoba
Keyword(s):  
Fatigue Life ◽  
Energy Dissipation ◽  
Cyclic Loading ◽  
Fatigue Behavior ◽  
Fatigue Loading ◽  
Theoretical Explanation ◽  
Life Assessment ◽  
Efficient Design ◽  
Sequence Effect ◽  
Load Sequence

AbstractA realistic prediction of the concrete fatigue life exposed to high-cycle loading scenarios with variable amplitudes is of utmost importance for a reliable and economically efficient design of civil engineering infrastructure for transport and energy supply. Current design codes estimate the fatigue life under variable amplitudes using the Palmgren–Miner rule, which assumes a linear scaling between lifetimes measured for uniform cyclic loading scenarios. Several experimental series conducted in the past, however, indicate that this assumption is not valid and that it may lead to unsafe design. In this paper, an experimental and theoretical investigations of the fatigue loading sequence effect in normal- and high-strength concrete behavior are presented, which confirm this observation. In particular, a test campaign with 135 cylinder specimens, including three concrete grades and six different loading scenarios has been conducted. Several response characteristics of the fatigue behavior including Wöhler curves, fatigue creep curves and evolving shapes of hysteretic loops have been evaluated. To substantiate the experimental results, a theoretical explanation of the observed sequence effect is formulated based on the assumption, that energy is dissipated uniformly within the volume of a test specimen during subcritical, compressive cyclic loading. Then, superposition of energy dissipation profiles along the lifetime measured for constant amplitudes becomes possible and a theoretical justification of the experimentally observed sequence effect can be provided. Moreover, a reverse sequence effect reported in the literature for bending fatigue of concrete can then be explained by an unevenly distributed energy dissipation over a cracked specimen. Supported by the theoretical consideration, the processed experimental data is used to validate existing fatigue life assessment rules by testing their ability to reflect the load sequence effect.

scholarly journals Damage Tolerant Design of Turbine Engine Disks

1982 ◽  
Author(s):  
C. H. Cook ◽  
C. E. Spaeth ◽  
D. T. Hunter ◽  
R. J. Hill
Keyword(s):  
Crack Growth ◽  
Life Prediction ◽  
Damage Tolerance ◽  
Fatigue Cracks ◽  
Design System ◽  
Crack Growth Behavior ◽  
Analytical Prediction ◽  
Turbine Engine ◽  
Damage Tolerant ◽  
The Impact

This paper describes a USAF sponsored effort to develop, apply, test, and evaluate Pratt & Whitney’s Damage Tolerant Design System for cold-section gas turbine engine disks. The design system includes a Damage Tolerance Specification proposed for new USAF engine programs, material characterization for crack-growth behavior, design procedures, and analytical life prediction methodology for consideration of large flaws. To evaluate and refine the design system, a current engine fan disk was redesigned to operate safely for a specified time after the occurrence of 0.030-inch (0.76 mm) surface length fatigue cracks. The redesigned disk was tested to failure while monitoring crack growth and correlating observed measurements with analytical prediction. Test results were used to refine the design system. Current work involves extending Damage Tolerant Design capability to hot-section powder-metallurgy disks. The impact of these efforts is twofold; current designs will benefit from improved life prediction capability in applying Retirement-for-Cause philosophy, and future designs can take advantage of the Life-Cycle-Cost benefit of designing for damage tolerance.

scholarly journals Low-Cycle Fatigue Crack Initiation Simulation and Life Prediction of Powder Superalloy Considering Inclusion-Matrix Interface Debonding

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4018
Author(s):  
Shuming Zhang ◽  
Yuanming Xu ◽  
Hao Fu ◽  
Yaowei Wen ◽  
Yibing Wang ◽  
...  
Keyword(s):  
Finite Element ◽  
Crack Initiation ◽  
Life Prediction ◽  
Damage Mechanics ◽  
Low Cycle Fatigue ◽  
Fatigue Crack Initiation ◽  
Fatigue Loading ◽  
Interface Debonding ◽  
Damage Evolution Equation ◽  
Finite Element Software

From the perspective of damage mechanics, the damage parameters were introduced as the characterizing quantity of the decrease in the mechanical properties of powder superalloy material FGH96 under fatigue loading. By deriving a damage evolution equation, a fatigue life prediction model of powder superalloy containing inclusions was constructed based on damage mechanics. The specimens containing elliptical subsurface inclusions and semielliptical surface inclusions were considered. The CONTA172 and TARGE169 elements of finite element software (ANSYS) were used to simulate the interfacial debonding between the inclusions and matrix, and the interface crack initiation life was calculated. Through finite element modeling, the stress field evolution during the interface debonding was traced by simulation. Finally, the effect of the position and shape size of inclusions on interface debonding was explored.

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