scholarly journals Probabilistic Analysis of Fatigue Behavior of Single Lap Riveted Joints

2020 ◽  
Vol 10 (10) ◽  
pp. 3379 ◽  
Author(s):  
Enrico Armentani ◽  
Alessandro Greco ◽  
Alessandro De Luca ◽  
Raffaele Sepe
Keyword(s):  
Fatigue Life ◽  
Stress Level ◽  
Fatigue Behavior ◽  
Crack Size ◽  
Probabilistic Methods ◽  
Critical Crack ◽  
Riveted Joints ◽  
Anderson Darling ◽  
Critical Crack Size ◽  
Through Hole

This research deals with the fatigue behavior of 200 small single lap multiple-riveted joint specimens, widely used for aeronautic structures. The tests were performed with three different levels of stress with stress ratio R = 0.05; three levels were set: 90 MPa, 120 MPa and 160 MPa. The fatigue life and critical crack size for all tested specimens were analyzed. According to the results’ analysis, two types of fracture, through-hole and in proximity of the hole, were observed, depending on the level of stress: the higher the applied stress, the more through-hole cracking. Indeed, under the fatigue load with a stress level of 90 MPa, less than 30% of specimens showed cracks propagating through the hole, while, at the stress level of 120 MPa, the percentage reaches 36.3%. At the stress level of 160 MPa, 100% of specimens failed through the hole. Moreover, aimed to use experimental data for probabilistic methods, a statistical analysis was performed according to the Anderson–Darling test. This method allowed the analysis of the datasets, in terms of both fatigue life and critical crack size, providing information about the best distribution function able to fit experimental results.

On The Mechanism of Fatigue in Micron-Scale Structural Films of Polycrystalline Silicon

2001 ◽  
Vol 697 ◽  
Author(s):  
C. L. Muhlstein ◽  
E. A. Stach ◽  
R. O. Ritchie
Keyword(s):  
Thin Film ◽  
Polycrystalline Silicon ◽  
Fatigue Behavior ◽  
Crack Size ◽  
Native Oxide ◽  
Self Assembled Monolayer ◽  
Critical Crack ◽  
Thin Film Silicon ◽  
Transmission Electron ◽  
Critical Crack Size

Abstract2-μm thick structural films of polycrystalline silicon are shown to display “metal-like” stress-life fatigue behavior in room air, with failures occurring after > 1011 cycles at stresses as low as half the fracture strength. Using in situ measurements of the specimen compliance and transmission electron microscopy to characterize such damage, the mechanism of thin-film silicon fatigue is deduced to be sequential oxidation and moisture-assisted cracking in the native SiO2 layer. This mechanism can also occur in bulk silicon but it is only relevant in thin films where the critical crack size for catastrophic failure can be exceeded within the oxide layer. The fatigue susceptibility of thin-film silicon is shown to be suppressed by alkene-based self-assembled monolayer coatings that prevent the formation of the native oxide.

On the Mechanism of Fatigue in Micron-Scale Structural Films of Polycrystalline Silicon

2001 ◽  
Vol 687 ◽  
Author(s):  
C. L. Muhlstein ◽  
E. A. Stach ◽  
R. O. Ritchie
Keyword(s):  
Thin Film ◽  
Polycrystalline Silicon ◽  
Fatigue Behavior ◽  
Crack Size ◽  
Native Oxide ◽  
Self Assembled Monolayer ◽  
Critical Crack ◽  
Thin Film Silicon ◽  
Transmission Electron ◽  
Critical Crack Size

Abstract2-νm thick structural films of polycrystalline silicon are shown to display “metal-like” stress- life fatigue behavior in room air, with failures occurring after >1011 cycles at stresses as low as half the fracture strength. Using in situ measurements of the specimen compliance and transmission electron microscopy to characterize such damage, the mechanism of thin-film silicon fatigue is deduced to be sequential oxidation and moisture-assisted cracking in the native SiO2 layer. This mechanism can also occur in bulk silicon but it is only relevant in thin films where the critical crack size for catastrophic failure can be exceeded within the oxide layer. The fatigue susceptibility of thin-film silicon is shown to be suppressed by alkene-based self- assembled monolayer coatings that prevent the formation of the native oxide.

Effect of Rotational Stiffness Evolution at Crack Part on Critical Crack Size in SFR

2012 ◽  
Author(s):  
Takashi Wakai ◽  
Hideo Machida ◽  
Shinji Yoshida
Keyword(s):  
Evaluation Method ◽  
Large Diameter ◽  
Crack Size ◽  
Evolution Model ◽  
Piping System ◽  
Rotational Stiffness ◽  
Critical Crack ◽  
Rotational Spring Model ◽  
Size Evaluation ◽  
Critical Crack Size

This paper describes the efficiency of the deployment of rotational stiffness evolution model in the critical crack size evaluation for Leak Before Break (LBB) assessment of Sodium cooled Fast Reactor (SFR) pipes. The authors have developed a critical crack size evaluation method for the thin-walled large diameter pipe made of modified 9Cr-1Mo steel. In this method, since the SFR pipe is mainly subjected to displacement controlled load caused by thermal expansion, the stress at the crack part is estimated taking stiffness evolution due to crack into account. The stiffness evolution is evaluated by using the rotational spring model. In this study, critical crack sizes for several pipes having some elbows were evaluated and discuss about the effect of the deployment of the stiffness evolution model at the crack part on critical crack size. If there were few elbows in pipe, thermal stress at the crack part was remarkably reduced by considering the stiffness evolution. In contrast, in the case where the compliance of the piping system was small, the critical crack size could be estimated under displacement controlled condition. As a result, the critical crack size increases by employing the model and LBB range may be expected to be enlarged.

Determination of Critical Crack Size Utilizing a Fracture Mechanics Test in Equipment Under Fatigue

2009 ◽  
Author(s):  
Irene Garcia Garcia ◽  
Radoslav Stefanovic
Keyword(s):  
Heat Treatment ◽  
Fracture Mechanics ◽  
Crack Size ◽  
Operational Experience ◽  
Element Analysis ◽  
Critical Crack ◽  
Circumferential Welds ◽  
Fea Model ◽  
Critical Crack Size

Equipment that is exposed to severe operational pressure and thermal cycling, like coke drums, usually suffer fatigue. As a result, equipment of this sort develop defects such as cracking in the circumferential welds. Operating companies are faced with the challenges of deciding what is the best way to prevent these defects, as well as determining how long they could operate if a defect is discovered. This paper discusses a methodology for fracture mechanics testing of coke drum welds, and calculations of the critical crack size. Representative samples are taken from production materials, and are welded employing production welding procedures. The material of construction is 1.25Cr-0.5Mo low alloy steel conforming to ASME SA-387 Gr 11 Class 2 in the normalized and tempered condition (N&T). Samples from three welding procedures (WPS) are tested: one for production, one for a repair with heat treatment, and one for repair without heat treatment. The position and orientation of test specimen are chosen based on previous surveys and operational experience on similar vessels that exhibited cracks during service. Fracture mechanics toughness testing is performed. Crack finite element analysis (FEA) model is used to determine the path-independed JI-integral driving force. Methodology for the determination of critical crack size is developed.

Critical crack size in the fracture of metals

2007 ◽  
Vol 52 (7) ◽  
pp. 937-939
Author(s):  
V. A. Ivanskoĭ
Keyword(s):  
Crack Size ◽  
Critical Crack ◽  
Critical Crack Size

scholarly journals On the fracture toughness of snow

2004 ◽  
Vol 38 ◽  
pp. 1-8 ◽  
Author(s):  
Jürg Schweizer ◽  
Gerard Michot ◽  
Helmut O.K. Kirchner
Keyword(s):  
Fracture Toughness ◽  
Crack Size ◽  
Laboratory Measurements ◽  
Critical Crack ◽  
Arrhenius Relation ◽  
Linear Fracture ◽  
Different Temperatures ◽  
Increasing Temperature ◽  
Critical Crack Size ◽  
Key Parameter

AbstractThe release of a dry-snow slab avalanche involves brittle fracture. It is therefore essentially a non-linear fracture mechanics problem. Traditional snow-stability evaluation has mainly focused on snow strength measurements. Fracture toughness describes how well a material can withstand failure. The fracture toughness of snow is therefore a key parameter to assess fracture propagation propensity, and hence snows lope stability. Fracture toughness in tension KIc and shear KIIc was determined with notched cantilever-beam experiments in a cold laboratory. Measurements were performed at different temperatures and with different snow types of density ρ = 100–300 kgm–3, corresponding to typical dry-snow slab properties. The fracture toughness in tension KIc was found to be larger (by about a factor of 1.4) than in shear KIIc. Typical values of the fracture toughness were 500–1000 Pam1/2 for the snow types tested. This suggests that snow is one of the most brittle materials known to man. A power-law relation of toughness KIc on relative density was found with an exponent of about 2. The fracture toughness in tension KIc decreased with increasing temperature following an Arrhenius relation below about –8°C with an apparent activation energy of about 0.16 eV. Above –6°C the fracture toughness increased with increasing temperature towards the melting point, i.e. the Arrhenius relation broke down. The key property in dry-snow slab avalanche release, the critical crack size under shear at failure, was estimated to be about 1 m.

Fracture Resistance in GFRP-BMC Composites Induced by Sub-Millimeter Length Fiber Dispersion

2012 ◽  
Vol 706-709 ◽  
pp. 907-913
Author(s):  
Michael C. Faudree ◽  
Yoshitake Nishi
Keyword(s):  
Fracture Resistance ◽  
Unsaturated Polyester ◽  
Glass Fibers ◽  
Acoustic Emissions ◽  
Crack Size ◽  
Critical Crack ◽  
Fiber Dispersion ◽  
Static Tensile ◽  
Styrene Butadiene ◽  
Critical Crack Size

Based on previous results of both an increase of nearly 40% in static tensile strain by shortening fiber length from commercial 6.4 mm to 0.44 mm in an unsaturated polyester/styrene-butadiene GFRP-BMC composite containing 20 mass% short E-glass fibers and their acoustic emissions (AE), the fracture resistance mechanics of sub-mm length fiber dispersion reinforcement is proposed. Since the 40% strain increase acts to improve strength and toughness, the mechanics is useful. This paper aims to present the mechanism of strain-driven improvement where microcracks are prevented from propagating beyond the critical crack size (2ac) for thermoset polymers, resulting in an increased and more dispersed total microcrack surface area as recorded by AE raising fracture strain.

NUMERICAL METHODS RESEARCH AND FRACTURE FAILURE ANALYSIS FOR CRITICAL CRACK SIZE

2019 ◽  
Vol 2019.27 (0) ◽  
pp. 1542
Author(s):  
Kaikai SHI ◽  
Xiaoming BAI ◽  
Yanli YUAN ◽  
Liangang ZHENG ◽  
Jianguo CHEN ◽  
...  
Keyword(s):  
Numerical Methods ◽  
Failure Analysis ◽  
Crack Size ◽  
Critical Crack ◽  
Fracture Failure ◽  
Critical Crack Size

Interfacial properties and fatigue behavior of carbon fiber epoxy laminate composites

2013 ◽  
Vol 33 (2) ◽  
pp. 173-179 ◽  
Author(s):  
Hsien-Tang Chiu ◽  
Yung-Lung Liu ◽  
Kuo-Chuan Liang ◽  
Peir-An Tsai
Keyword(s):  
Fatigue Life ◽  
Carbon Fiber ◽  
Fatigue Fracture ◽  
Stress Level ◽  
Fatigue Behavior ◽  
Cyclic Stress ◽  
Matrix Cracking ◽  
Stacking Sequence ◽  
Carbon Fiber Laminate ◽  
Carbon Fiber Epoxy

Abstract The study elucidated the relationship between the stacking sequence and physical properties, by investigating mechanical properties, fatigue life and the morphology, after fatigue fracture of carbon fiber/epoxy composites. The results show that the unidirectional carbon fiber laminate has the maximum tensile stress. Moreover, the laminate with ±45° plies can improve the tensile strain. The fatigue life of all specimens was shorter than 103 cycles under high cyclic stress level, and longer than 106 cycles under low cyclic stress level. Laminates with [908]s stacking sequence had the shortest fatigue life under high and low cyclic stress, while the unidirectional carbon fiber laminate had the highest fatigue life. A number of fatigue damage models, including delaminating, matrix cracking and fiber failure, have been identified by scanning electron microscopy (SEM). The SEM micrographs showed that the morphology on the cross section, after fatigue fracture, was significantly correlated to the stacking sequence.

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