scholarly journals High-Strength Reinforcing Steel Bars: Low Cycle Fatigue Behavior Using RGB Methodology

2021 ◽  
Vol 15 (1) ◽  
Author(s):  
Jorge E. Egger ◽  
Fabian R. Rojas ◽  
Leonardo M. Massone
Keyword(s):  
Fatigue Life ◽  
Strain Amplitude ◽  
Low Cycle Fatigue ◽  
High Strength ◽  
Image Correlation ◽  
Total Strain ◽  
Total Strain Amplitude ◽  
Reinforcing Steel ◽  
Cycle Fatigue ◽  
Steel Bars

AbstractLow cycle fatigue life of high-strength reinforcing steel bars (ASTM A706 Grade 80), using photogrammetry by RGB methodology is evaluated. Fatigue tests are performed on specimens under constant axial displacement with total strain amplitudes ranging from 0.01 to 0.05. The experimental observations indicate that buckling of high-strength reinforcing bars results in a damaging degradation of their fatigue life performance as the slenderness ratio increases, including an early rebar failure as the total strain amplitude increases since it achieves the plastic range faster. In addition to this, the results show that the ratio of the ultimate tensile strength to yield strength satisfies the minimum of 1.25 specified in ASTM A706 for reinforcement. On the other hand, the RGB methodology indicates that the axial strains measured by photogrammetry provide more accurate data since the registered results by the traditional experimental setup do not detect second-order effects, such as slippage or lengthening of the specimens within the clamps. Moreover, the RGB filter is faster than digital image correlation (DIC) because the RGB methodology requires a fewer computational cost than DIC algorithms. The RGB methodology allows to reduce the total strain amplitude up to 45% compared to the results obtained by the traditional setup. Finally, models relating total strain amplitude with half-cycles to failure and total strain amplitude with total energy dissipated for multiple slenderness ratios (L/d of 5, 10, and 15) are obtained.

High Temperature Low Cycle Fatigue Characteristics of Grit Blasted Polycrystalline Ni-Base Superalloy

2015 ◽  
Vol 665 ◽  
pp. 73-76 ◽  
Author(s):  
Ivo Šulák ◽  
Karel Obrtlík ◽  
Ladislav Čelko
Keyword(s):  
Fatigue Life ◽  
Strain Amplitude ◽  
Low Cycle Fatigue ◽  
Total Strain ◽  
Material Surface ◽  
Total Strain Amplitude ◽  
Cycle Fatigue ◽  
Stress Strain ◽  
Fatigue Characteristics ◽  
Base Superalloy

The present work is focused on the study of low cycle fatigue behavior of grit blasted nickel-base superalloy Inconel 713LC (IN 713LC). Grit blasting parameters are obtained. Button end specimens of IN 713LC in as-received condition and with grit blasted surface were fatigued under strain control with constant total strain amplitude in symmetrical cycle at 900 °C in air. Hardening/softening curves, cyclic stress-strain curve and fatigue life data of both materials were obtained. Both materials exhibit the same stress-strain response. It has not been observed any improvement or reduction of low cycle fatigue life in representation of total strain amplitude versus number of cycles to failure of grit blasted material in comparison with as-received material. Surface relief and fracture surface were observed in SEM. The little effect of surface treatment on fatigue characteristics is discussed.

Influence of Heat Treatment Condition on Low Cycle Fatigue Life of a Rolled AZ80 Magnesium Alloy Sheet

2011 ◽  
Vol 239-242 ◽  
pp. 1309-1312
Author(s):  
Zhong Jun Wang
Keyword(s):  
Fatigue Life ◽  
Magnesium Alloy ◽  
Strain Amplitude ◽  
Low Cycle Fatigue ◽  
Solution Treatment ◽  
Alloy Sheet ◽  
Total Strain ◽  
Total Strain Amplitude ◽  
Cycle Fatigue ◽  
Az80 Magnesium Alloy

In this paper, the influence of ageing and solution treatment on the low cycle fatigue behavior of a rolled AZ80 magnesium alloy sheet was investigated at constant total strain amplitudes between 0.003 and 0.01. It was observed that fatigue life of the alloy sheet at as-rolled, ageing and solution treatment conditions can be described well by Coffin-Manson and Basquin’s equations. The fatigue parameters follow the two equations were evaluated. With increasing total strain amplitude, the fatigue life of the three conditions decreased. At the lowest total strain amplitude of 0.003, the fatigue life of the as-rolled alloy sheet was the biggest. However, at the highest total strain amplitude of 0.01, the fatigue life of solution treated alloy sheet was the biggest, and that of the ageing treated alloy sheet was the shortest.

Effect of Gd and Y on the Low Cycle Fatigue Properties of AZ91D-0.4Ca-0.3Sr

2011 ◽  
Vol 197-198 ◽  
pp. 1536-1539
Author(s):  
Yong Chang Zhu ◽  
Shou Fan Rong ◽  
S. N. Shukayev ◽  
Jun Wang
Keyword(s):  
Fatigue Life ◽  
Magnesium Alloy ◽  
Strain Amplitude ◽  
Low Cycle Fatigue ◽  
Total Strain ◽  
Fatigue Properties ◽  
Total Strain Amplitude ◽  
Cycle Fatigue ◽  
Gravity Casting

The properties of gravity casting AZ91D-0.4Ca-0.3Sr alloy with Gd and Y in metal mould were studied by controlling the total strain amplitude ranged from 0.05mm to 0.25mm.under the conditions of the stress of ratio R equal to –1. In addition, the microstructure, phases, chemical constitute, fracture and low cycle fatigue behaviors of the magnesium alloy were primarily researched by means of SEM, EDAX and XRD and so on. The results showed that 3.0wt%Gd and 3.0wt%Y introduced the AZ91D-0.4Ca-0.3Sr alloy can refine α-Mg, and that Gd cooperating with Y can significantly improve the low cycle fatigue life. The low cycle fatigue times can be up to approximately 9874.

scholarly journals Low-cycle fatigue behaviour of laser welded high-strength steel DOMEX 700 MC

2018 ◽  
Vol 157 ◽  
pp. 05013 ◽  
Author(s):  
Peter Kopas ◽  
Milan Sága ◽  
František Nový ◽  
Bohuš Leitner
Keyword(s):  
Fatigue Life ◽  
Welded Joints ◽  
High Strength Steel ◽  
Fatigue Testing ◽  
Low Cycle Fatigue ◽  
High Strength ◽  
Fatigue Behaviour ◽  
Total Strain Amplitude ◽  
Cycle Fatigue ◽  
Fatigue Life Analysis

The article presents the results of research on low cycle fatigue strength of laser welded joints vs. non-welded material of high-strength steel DOMEX 700 MC. The tests were performed under load controlled using the total strain amplitude ɛac. The operating principle of the special electro-mechanic fatigue testing equipment with a suitable clamping system was working on 35 Hz frequency. Fatigue life analysis was conducted based on the Manson-Coffin-Basquin equation, which made it possible to determine fatigue parameters. Studies have shown differences in the fatigue life of original specimens and laser welded joints analysed, where laser welded joints showed lower fatigue resistance. In this article a numerical analysis of stresses generated in bending fatigue specimens has been performed employing the commercially available FEM-program ADINA.

scholarly journals Low Cycle Fatigue Properties of Sc-Modified AA2519-T62 Extrusion

Materials ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 220 ◽  
Author(s):  
Robert Kosturek ◽  
Lucjan Śnieżek ◽  
Janusz Torzewski ◽  
Marcin Wachowski
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Fatigue Strength ◽  
Strain Amplitude ◽  
Low Cycle Fatigue ◽  
Total Strain ◽  
Fatigue Properties ◽  
Total Strain Amplitude ◽  
Cycle Fatigue ◽  
Scanning Electron

This investigation presents the results of research on low cycle fatigue properties of Sc-modified AA2519-T62 extrusion. The basic mechanical properties of the investigated alloy have been established in the tensile test. The low cycle fatigue testing has been performed on five different levels of total strain amplitude: 0.4%; 0.5%; 0.6%; 0.7% and 0.8% with cycle asymmetry coefficient R = 0.1. For each level of total strain amplitude, the graphs of variations in stress amplitude and plastic strain amplitude in the number of cycles have been presented. The obtained results allowed to establish Ramberg-Osgood and Manson-Coffin-Basquin relationships. The established values of the cyclic strength coefficient and cyclic strain hardening exponent equal to k’ = 1518.1 MPa and n’ = 0.1702. Based on the Manscon-Coffin-Basquin equation, the values of the following parameters have been established: the fatigue strength coefficient σ’f = 1489.8 MPa, the fatigue strength exponent b = −0.157, the fatigue ductility coefficient ε’f = 0.4931 and the fatigue ductility exponent c = −1.01. The fatigue surfaces of samples tested on 0.4%, 0.6% and 0.8% of total strain amplitude have been subjected to scanning electron microscopy observations. The scanning electron microscopy observations of the fatigue surfaces revealed the presence of cracks in striations in the surrounding area with a high concentration of precipitates. It has been observed that larger Al2Cu precipitates exhibit a higher tendency to fracture than smaller precipitates having a higher concentration of scandium and zirconium.

Effects of Thermal Exposure on Low Cycle Fatigue Behavior of Ti600 Titanium Alloy

2010 ◽  
Vol 118-120 ◽  
pp. 611-615
Author(s):  
Teng Yu ◽  
Lei Wang ◽  
Yong Qing Zhao ◽  
Yang Liu
Keyword(s):  
Titanium Alloy ◽  
Strain Amplitude ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Thermal Exposure ◽  
Cyclic Softening ◽  
Total Strain ◽  
Total Strain Amplitude ◽  
Cycle Fatigue ◽  
Α2 Phase

Effects of thermal exposure on low cycle fatigue behavior of Ti600 alloy were investigated by LSCM, SEM and TEM. The results demonstrated that both the NTE specimens and the TE specimens showed the cyclic softening, within a total strain amplitude range from ±0.45% to ±1.00%. Since the α2 phase precipitated in the αp phase during thermal exposure, the resistance of fatigue crack propagation of αp phase could be increased by the precipitation of α2 phase. Therefore, the low cycle fatigue (LCF) lives of Ti600 alloy after thermal exposure were longer than those without thermal exposure, at the same total strain amplitude.

Low Cycle Fatigue Behavior of Spray Formed Superalloy Rings

2011 ◽  
Vol 399-401 ◽  
pp. 1937-1941 ◽  
Author(s):  
Wen Yong Xu ◽  
Guo Qing Zhang ◽  
Zhou Li
Keyword(s):  
Strain Amplitude ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Hysteresis Loops ◽  
Cyclic Strain ◽  
Cyclic Hardening ◽  
Cyclic Stress ◽  
Total Strain ◽  
Total Strain Amplitude ◽  
Cycle Fatigue

Low cycle fatigue behavior of spray formed superalloy GH738 at 650°C has been investigated under fully reversed total strain-controlled mode. When strain amplitude (Δεt/2) is between 0.32% and 0.4%, cyclic stress response is stable under fully reversed constant total strain amplitude. The stabilized hysteresis loops narrowing sharply to a straight line indicates that the alloy exhibits typical elastic strain. The crack initiates single site from the surface. When strain amplitude is between 0.6% and 1.0%, cyclic hardening is observed until fracture. The tendency for hardening is found to increase with strain amplitude. The hyperesis loops expand gradually, which indicates that plastic deformation happens during cyclic deformation process. The crack initiates multi-sites from the surface. The cyclic strain-stress relationship of spray formed GH738 at 650°C can be illustrated by Δσ/2 =2017(Δεp/2)0.1489.The total strain-life function can expressed by Δεt/2=0.0071(2Nf)-0.0781+0.0647(2Nf) )-0.4914.

Deformation and Fracture Analysis of a Duplex γ-TiAl Alloy during Low Cycle Fatigue

2007 ◽  
Vol 539-543 ◽  
pp. 1571-1576
Author(s):  
Wen Fang Cui ◽  
Chun Ming Liu ◽  
V. Bauer ◽  
Hans Jürgen Christ
Keyword(s):  
Strain Amplitude ◽  
Test Temperature ◽  
Tial Alloy ◽  
Low Cycle Fatigue ◽  
Fatigue Cracks ◽  
Total Strain ◽  
Fracture Mechanisms ◽  
Total Strain Amplitude ◽  
Cycle Fatigue ◽  
Test Conditions

Isothermal low cycle fatigue (LCF) behaviours of a third generation titanium aluminide based γ-TiAl alloy with duplex microstructure were investigated under the various test conditions, including temperature (550°C-750°C), total strain amplitude (0.3%-0.6%) and environment (air and vacuum), in order to clarify the fatigue life, deformation characters and fracture process of the alloy during LCF. The plastic strain accumulation has a great contribution to LCF damage. With increasing total strain range, LCF life decreases distinctly. Under the small total strain amplitude (≤0.4%), the increase of test temperature enforces microstructure resistance to LCF fracture. However, the increase of test temperature together with large total strain amplitude (>0.5%) accelerates the microstructural degradation, which behaves the dissolution of α2 lamellae and recrystallization of γ phase, resulting in great LCF damage. Moreover, environment brittlement during high temperature exposure to air influences the initiation process of fatigue cracks. The fracture mechanisms at various test conditions were analyzed.

scholarly journals Effects of Grain Refinement on the Low-Cycle Fatigue Behavior of IN792 Superalloys

Crystals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 892
Author(s):  
Beining Du ◽  
Liyuan Sheng ◽  
Chuanyong Cui ◽  
Ziyang Hu ◽  
Xiaofeng Sun
Keyword(s):  
High Temperature ◽  
Grain Refinement ◽  
Fatigue Test ◽  
Strain Amplitude ◽  
Mechanical Performance ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Total Strain ◽  
Total Strain Amplitude ◽  
Cycle Fatigue

The Ni-based IN792 superalloy is widely applied as a component in industrial turbines and aircraft engines due to its good high-temperature properties and excellent corrosion resistance. Since these components have to suffer from cyclic thermal and mechanical stresses during service, the high-temperature fatigue failure becomes one of the major factors affecting their service lives. Grain refinement has been considered as an effective way to improve the mechanical performance of superalloys. However, due to the complexity of alloy composition, microstructure and service condition, there is no unified theory about the influence of grain refinement on the fatigue performance and fracture mechanism of superalloys. In the present research, the IN792 superalloy with different grain sizes was manufactured. Then, fully reversed, strain-controlled, low-cycle fatigue (LCF) tests with four different total strain amplitudes were carried out on the alloy at 700 °C and 800 °C to clarify the effects of grain refinement on its LCF behavior. The results show that grain refinement improved the fatigue life significantly, which is mainly attributed to increasing the grain boundary content and refining MC carbides, eutectic structures and dendritic structures. During fatigue test under lower strain amplitude, the alloy exhibits a pronounced initial fatigue hardening followed by a continuous well-defined stability stage, which is caused by the formation of dislocation networks and coarsening of primary γ’ phases. However, during fatigue test under higher strain amplitude, the alloy exhibits continuous hardening response because the dislocations could shear primary γ’ phases, which could give rise to resistance to dislocation movement. In addition, the fracture surface observation shows that the fatigue fracture mode is mainly affected by the total strain amplitude. Under lower total strain amplitude, the fatigue microcracks mainly initiate at the porosities near the specimen surface, while under higher total strain amplitude, the fatigue microcracks tend to form at the interior of the specimen.

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