scholarly journals Low-Cycle Fatigue of FRP Strips Glued to a Quasi-Brittle Material

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7753
Author(s):  
Enzo Martinelli ◽  
Antonio Caggiano
Keyword(s):  
Bond Length ◽  
Low Cycle Fatigue ◽  
Cyclic Behavior ◽  
Pure Mode ◽  
Geometric Quantity ◽  
Bond Slip ◽  
Frp Strips ◽  
Interface Bond ◽  
Fracture Processes

This paper aims at further advancing the knowledge about the cyclic behavior of FRP strips glued to quasi-brittle materials, such as concrete. The results presented herein derive from a numerical model based on concepts of based on fracture mechanics and already presented and validated by the authors in previous works. Particularly, it assumes that fracture processes leading to debonding develop in pure mode II, as is widely accepted in the literature. Starting from this assumption (and having clear both its advantages acnd shortcomings), the results of a parametric analysis are presented with the aim of investigating the role of both the mechanical properties of the interface bond–slip law and a relevant geometric quantity such as the bond length. The obtained results show the influence of the interface bond–slip law and FRP bond length on the resulting cyclic response of the FRP-to-concrete joint, the latter characterized in terms of S-N curves generally adopted in the theory of fatigue. Far from deriving a fully defined correlation among those parameters, the results indicate general trends that can be helpful to drive further investigation, both experimental and numerical in nature.

Damage Parameter Assessment for Energy Based Fatigue Life Prediction Methods

2012 ◽  
Author(s):  
Casey M. Holycross ◽  
John N. Wertz ◽  
Todd Letcher ◽  
M.-H. Herman Shen ◽  
Onome E. Scott-Emuakpor ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Energy Dissipation ◽  
Strain Energy ◽  
Life Prediction ◽  
Low Cycle Fatigue ◽  
Cyclic Strain ◽  
Damage Parameter ◽  
Fatigue Life Prediction ◽  
Cyclic Behavior ◽  
Fracture Processes

An energy-based method used to predict fatigue life and critical life of various materials has been previously developed, correlating strain energy dissipated during monotonic fracture to total cyclic strain energy dissipation in fatigue fracture. This method is based on the assumption that the monotonic strain energy and total hysteretic strain energy to fracture is equivalent. The fracture processes of monotonic and cyclic failure modes can be of stark contrast, with ductile and brittle fracture dominating each respectively. This study proposes that a more appropriate damage parameter for predicting fatigue life may be to use low cycle fatigue (LCF) strain energy rather than monotonic energy. Thus, the new damage parameter would capture similar fracture processes and cyclic behavior. Round tensile specimens machined from commercially supplied Al 6061-T6511 were tested to acquire LCF failure data in fully reversed loading at various alternating stresses. Results are compared to both monotonic and cyclic strain energy dissipation to determine if LCF strain energy dissipation is a more suitable damage parameter for fatigue life prediction.

scholarly journals Experimental and Numerical Investigation on the Steel Reinforced Grout (SRG) Composite-to-Concrete Bond

2020 ◽  
Vol 4 (4) ◽  
pp. 182
Author(s):  
Luciano Ombres ◽  
Salvatore Verre
Keyword(s):  
Bond Length ◽  
Failure Modes ◽  
Peak Load ◽  
Element Model ◽  
Test Results ◽  
Shear Tests ◽  
Bond Slip ◽  
Bond Behavior ◽  
Direct Shear Tests ◽  
Inorganic Matrix

In the paper, the bond between a composite strengthening system consisting of steel textiles embedded into an inorganic matrix (steel reinforced grout, SRG) and the concrete substrate, is investigated. An experimental investigation was carried out on medium density SRG specimens; direct shear tests were conducted on 20 specimens to analyze the effect of the bond length, and the age of the composite strip on the SRG-to-concrete bond behavior. In particular, the tests were conducted considering five bond length (100, 200, 250, 330, and 450 mm), and the composite strip’s age 14th, 21st, and 28th day after the bonding. Test results in the form of peak load, failure modes and, bond-slip diagrams were presented and discussed. A finite element model developed through commercial software to replicate the behavior of SRG strips, is also proposed. The effectiveness of the proposed numerical model was validated by the comparison between its predictions and experimental results.

The role of inclusion-matrix boundaries in steels fracture processes

2021 ◽  
pp. 42-47
Author(s):  
S. I. Gubenko ◽  
E. V. Parusov ◽  
O. V. Parusov
Keyword(s):  
Fracture Processes ◽  
Inclusion Matrix

Experimental study on the bond behavior of the CFRP-steel interface under the freeze–thaw cycles

2019 ◽  
Vol 54 (1) ◽  
pp. 13-29 ◽  
Author(s):  
Yu-Yang Pang ◽  
Gang Wu ◽  
Hai-Tao Wang ◽  
Zhi-Long Su ◽  
Xiao-Yuan He
Keyword(s):  
Carbon Fiber ◽  
Bond Length ◽  
Ultimate Load ◽  
Fiber Reinforced Polymer ◽  
Carbon Fiber Reinforced Polymer ◽  
Fiber Reinforced ◽  
Bond Slip ◽  
Freeze Thaw ◽  
Reinforced Polymer ◽  
Carbon Fiber Reinforced

The bond–slip degradation relationship between carbon fiber-reinforced polymer and steel in a freeze–thaw environment is crucial to evaluate the long-term service performance of steel structures strengthened with carbon fiber-reinforced polymer plates. However, limited studies on the durability and long-term performance of the carbon fiber-reinforced polymer-steel-bonded interface are the major obstacle for the application of carbon fiber-reinforced polymer plates in strengthening steel structures. This paper reports an experimental study to investigate the effects of the carbon fiber-reinforced polymer bond length and the freeze–thaw cycles on the bond behavior of the carbon fiber-reinforced polymer-steel-bonded interface. The three-dimensional digital image correlation technique is applied to obtain displacements and strains on the surface of the single-shear specimen. The experimental results present herein include the failure mode, the ultimate load, the carbon fiber-reinforced polymer strain distribution, the displacement distribution, and the bond–slip relationship. The results show that the ultimate load increases with increasing bond length until a certain bond length value is reached, after which the ultimate load remained approximately constant, and the ultimate loads of carbon fiber-reinforced polymer-steel interface decrease gradually under freeze–thaw cycles. The bond–slip parameters degradation models are proposed, and the bond–slip degradation relationship under the freeze–thaw cycles is established. Finally, the bond–slip degradation relationship is confirmed through comparisons with the experimental results.

scholarly journals An Assessment of Computational Methods for Calculating Accurate Structures and Energies of Bio-Relevant Polysulfur/Selenium-Containing Compounds

Molecules ◽  
2018 ◽  
Vol 23 (12) ◽  
pp. 3323 ◽  
Author(s):  
Sahar Nikoo ◽  
Paul Meister ◽  
John Hayward ◽  
James Gauld
Keyword(s):  
Inorganic Chemistry ◽  
Bond Length ◽  
Gas Phase ◽  
Electron Correlation ◽  
Negative Charge ◽  
Basis Set ◽  
Proton Affinities ◽  
Selenium Compounds ◽  
Gas Phase Basicities

The heavier chalcogens sulfur and selenium are important in organic and inorganic chemistry, and the role of such chalcogens in biological systems has recently gained more attention. Sulfur and, to a lesser extent selenium, are involved in diverse reactions from redox signaling to antioxidant activity and are considered essential nutrients. We investigated the ability of the DFT functionals (B3LYP, B3PW91, ωB97XD, M06-2X, and M08-HX) relative to electron correlation methods MP2 and QCISD to produce reliable and accurate structures as well as thermochemical data for sulfur/selenium-containing systems. Bond lengths, proton affinities (PA), gas phase basicities (GPB), chalcogen–chalcogen bond dissociation enthalpies (BDE), and the hydrogen affinities (HA) of thiyl/selenyl radicals were evaluated for a range of small polysulfur/selenium compounds and cysteine per/polysulfide. The S–S bond length was found to be the most sensitive to basis set choice, while the geometry of selenium-containing compounds was less sensitive to basis set. In mixed chalcogens species of sulfur and selenium, the location of the sulfur atom affects the S–Se bond length as it can hold more negative charge. PA, GPB, BDE, and HA of selenium systems were all lower, indicating more acidity and more stability of radicals. Extending the sulfur chain in cysteine results in a decrease of BDE and HA, but these plateau at a certain point (199 kJ mol−1 and 295 kJ mol−1), and PA and GPB are also decreased relative to the thiol, indicating that the polysulfur species exist as thiolates in a biological system. In general, it was found that ωB97XD/6-311G(2d,p) gave the most reasonable structures and thermochemistry relative to benchmark calculations. However, nuances in performance are observed and discussed.

Role of Internal Damage Mechanisms in Controlling Bond-Slip Behavior in Pullout Tests in Concrete

2019 ◽  
Vol 31 (12) ◽  
pp. 04019284 ◽  
Author(s):  
Orit Leibovich ◽  
David Z. Yankelevsky ◽  
Avraham N. Dancygier
Keyword(s):  
Internal Damage ◽  
Damage Mechanisms ◽  
Bond Slip ◽  
Pullout Tests

scholarly journals Effect of change in role of an aircraft on engine life

2013 ◽  
Vol 117 (1196) ◽  
pp. 1053-1070
Author(s):  
A. Gad-Briggs ◽  
A. Haslam ◽  
P. Laskaridis
Keyword(s):  
Life Cycle ◽  
Life Cycle Cost ◽  
Low Cycle Fatigue ◽  
Operating Conditions ◽  
Significant Life ◽  
European Theatre ◽  
Harsh Climate ◽  
Performance Conditions ◽  
Dust Ingestion

Abstract New aircraft require years of development from concept to realisation and can be prone to delays. Consequently, military operators take existing fleets and operate them in a different role. The objective of this study is to examine the effect of operating a typical low bypass military fast jet engine, originally designed for a European theatre, in a hot and harsh climate. The specific purpose is to determine the effect on the high-pressure turbine blade life and the life- cycle cost of the engine. A mission profile and respective performance conditions were analysed and modelled using an in-house performance tool. The flow conditions were simulated using ANSYS® FLUENT. A conjugated heat transfer solution was adopted to determine the blade metal temperature. The blade was modelled physically in 3D using SIMULIA® ABAQUS FEA software. The stresses were derived and used to calculate the temperature coupled low cycle fatigue and creep life. A deterioration case was also studied to evaluate the effect of sand and dust ingestion. There was a significant life reduction of approximately 50% due to creep. The reduction in life was inversely proportional to the life cycle cost of the engine depending on the operating conditions. The results were compared with similar engines and summarised in the context of airworthiness regulations and component integrity.

The Fatigue Properties of Duplex Stainless Steels: Role of Microstructure

2008 ◽  
Vol 378-379 ◽  
pp. 101-114 ◽  
Author(s):  
Jean Bernard Vogt
Keyword(s):  
Fatigue Resistance ◽  
Stainless Steels ◽  
Load Transfer ◽  
Volume Fraction ◽  
Low Cycle Fatigue ◽  
Fatigue Behaviour ◽  
Cyclic Softening ◽  
Duplex Stainless Steels ◽  
Fatigue Properties

The paper analyzes the role of microstructure on the low cycle fatigue behaviour of duplex stainless steels. The alloys are investigated in their as received condition and after ageing at 475°C. The fatigue resistance and the cyclic accommodation of these DSS are strongly controlled by the volume fraction of α and γ "phases which is related to the chemical composition in particular nitrogen. It is shown that DSS with a high fraction of austenite present a good combination of fatigue resistance and cyclic softening especially in the aged condition. The mutual interaction between ferrite and austenite referred to load transfer is beneficial for increasing the fatigue resistance. Alloying with nitrogen appears to be a promising way to master an optimised microstructure leading to high mechanical resistant DSS.

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