scholarly journals Mechanical and Mesoscale Analyses of Cement Stabilized Macadam Prepared by Vibratory and Nonvibratory Mixing Techniques

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Jijing Wang ◽  
Zhihua Tan
Keyword(s):  
Fatigue Life ◽  
Stress Ratio ◽  
Cement Mortar ◽  
Stress Sensitivity ◽  
Fatigue Tests ◽  
X Ray ◽  
Loading Rates ◽  
Stress States ◽  
Mixing Techniques ◽  
Fatigue Equation

The objective of this study is to analyze the effects of mixing techniques on the mechanical behavior and meso-structure of cement-treated aggregate. Different specimens were prepared by vibratory and nonvibratory mixing techniques. X-ray CT scans were performed to illustrate the distribution of cement mortar on aggregate. The strength, modulus, and fatigue tests under different stress states were tested to reveal the impacts of mixing techniques. Then, the relationships between strengths and loading rates and that between moduli and stress levels were established. Hereafter, the S-N fatigue equation that modified with stress ratio related to loading rates was used to describe the fatigue performance. The results indicate that the cement mortar of specimens prepared by vibratory mixing was well-distributed on aggregates. The strength, modulus, and fatigue life of the specimens prepared by vibratory mixing were higher under the test condition threshold. Moreover, the growth rate of strength and modulus with loading for specimens prepared by vibratory mixing was slightly larger than that for specimens prepared by nonvibratory mixing. Compared with the cement-treated aggregates specimens prepared by nonvibratory mixing, the fatigue life of cement-treated aggregates specimens prepared by vibratory mixing had more stable stress sensitivity.

scholarly journals Multiaxial fatigue study on steel transversal attachments under constant amplitude proportional and non-proportional loadings

2018 ◽  
Vol 165 ◽  
pp. 16007
Author(s):  
Martin Garcia ◽  
Claudio A. Pereira Baptista ◽  
Alain Nussbaumer
Keyword(s):  
Fatigue Life ◽  
High Strength ◽  
Fatigue Tests ◽  
Multiaxial Fatigue ◽  
Life Assessment ◽  
Experimental Program ◽  
Proportional Loading ◽  
Load Carrying ◽  
Stress States ◽  
Experimental Values

In this study, the multiaxial fatigue strength of full-scale transversal attachment is assessed and compared to original experimental results and others found in the literature. Mild strength S235JR steel is used and an exploratory investigation on the use of high strength S690QL steel and the effect of non-proportional loading is presented. The study focuses on non-load carrying fillet welds as commonly used in bridge design and more generally between main girders and struts. The experimental program includes 33 uniaxial and multiaxial fatigue tests and was partially carried out on a new multiaxial setup that allows proportional and non-proportional tests in a typical welded detail. The fatigue life is then compared with estimations obtained from local approaches with the help of 3D finite element models. The multiaxial fatigue life assessment with some of the well-known local approaches is shown to be suited to the analysis under multiaxial stress states. The accuracy of each models and approaches is compared to the experimental values considering all the previously cited parameters.

Fatigue Life Properties of Circumferentially-Notched Bar of Austenitic Stainless Steel With Various Concentration Factors

2018 ◽  
Author(s):  
Naoaki Nagaishi ◽  
Michio Yoshikawa ◽  
Saburo Okazaki ◽  
Hisao Matsunaga ◽  
Junichiro Yamabe ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Fatigue Life ◽  
Stress Concentration ◽  
Austenitic Stainless Steel ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Stress Ratio ◽  
Ambient Air ◽  
Fatigue Tests ◽  
Concentration Factors

Fatigue tests were performed using three types of round-bar specimens of Type 304, meta-stable, austenitic stainless steel. The specimens had circumferential notch with stress concentration factors, Kt, of 2, 3 or 6.6. Load controlled fatigue tests were conducted at stress ratio, R, of 0.1 and −1 in ambient air at room temperature. At R of 0.1, fatigue life was decreased with an increase in the stress concentration factor. Conversely, at R of −1, the stress concentration factor had little influence on the fatigue life. To understand the mechanism of the stress ratio effect, local deformation behavior at and beneath the notch root during the fatigue test was computed by means of finite element analysis considering that the plastic constitutive model describes the cyclic stress-strain response.

Fatigue of Zirconia - Bioglass Dental Ceramics

2008 ◽  
Vol 591-593 ◽  
pp. 628-633 ◽  
Author(s):  
Luiz A. Bicalho ◽  
R.C. Souza ◽  
Claudinei dos Santos ◽  
M.J.R. Barboza ◽  
Carlos Antonio Reis Pereira Baptista
Keyword(s):  
Fracture Toughness ◽  
Fatigue Life ◽  
Bending Strength ◽  
Cyclic Fatigue ◽  
Fatigue Tests ◽  
Modulus Of Rupture ◽  
Dental Ceramics ◽  
X Ray Diffraction ◽  
X Ray ◽  
Four Point Bending

In this work the cyclic fatigue life of 3mol.%Y2O3-stabilized zirconia polycrystalline ceramics, doped with 5%wt 3CaO.P2O5,-SiO2-MgO, has been investigated. Samples with 5 and 10%wt were cold uniaxial pressed (80MPa) and sintered in air at 1200 and 1300oC for 120 minutes. Sintered samples were characterized by X-Ray diffraction and Scanning Electronic Microscopy. Hardness and fracture toughness were determined using Vicker’s indentation method, and Modulus of Rupture was determined by four-point bending testing. Furthermore, the cyclic fatigue tests were also realized by four-point bending tests, under frequency of 25 Hz and stress ratio, R, of 0.1, for the best condition. In this condition, highly dense samples were obtained and presented values of hardness, fracture toughness and bending strength of 11.3 ±0.1GPa, 6.1±0.4MPa.m1/2 and 320±55MPa, respectively. The increasing of stress level leads to decreasing of the number of cycles and the number of run-out specimens. The stress induced tetragonal-monoclinic (t-m)-ZrO2 transformation, observed by X-Ray diffraction, contributes to the increasing of the fatigue life. Samples 3Y-TZP presents clearly a range of loading conditions where cyclic fatigue can be detected.

Safety Assessment of Steels and Welds Under Cyclic and Monotonic Loadings at Low Temperatures

1984 ◽  
Vol 106 (4) ◽  
pp. 473-479
Author(s):  
N. Urabe ◽  
A. Yoshitake ◽  
H. Kagawa
Keyword(s):  
Fracture Toughness ◽  
Fatigue Life ◽  
Brittle Fracture ◽  
Low Temperatures ◽  
Safety Assessment ◽  
Loading Rate ◽  
Fracture Initiation ◽  
Fatigue Tests ◽  
Loading Rates ◽  
Wide Range

In order to investigate the mechanisms and the factors to govern the brittle fracture initiation during the fatigue crack propagation at low temperatures, fracture toughness tests under wide range of loading rates, fatigue tests at low temperatures and fracture toughness tests after having been given pre-loading were performed on steels and weld junctions. The fatigue fracture toughness Kfc was estimated as equivalent as the fracture toughness Kc under the monotonic tensile loading if they were compared at the same loading rate, since the residual stress due to the cyclic loading was less effective on the brittle fracture initiation. The calculated fatigue life based on Paris’s formula taken into consideration of the crack closure phenomena showed a good one-by-one agreement with the observed fatigue life up to the brittle fracture initiation. Therefore, a design curve was preliminarily drawn to determine the fatigue life at low temperatures.

scholarly journals Effect of Post-Heat Treatment Cooling Conditions on Microstructures and Fatigue Properties of Cobalt Chromium Molybdenum Alloy Fabricated through Selective Laser Melting

Metals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1005
Author(s):  
Hla Htoot Wai Wai Cho ◽  
Atsushi Takaichi ◽  
Yuka Kajima ◽  
Hein Linn Htat ◽  
Nuttaphon Kittikundecha ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Fatigue Life ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Cobalt Chromium ◽  
Laser Melting ◽  
Post Heat Treatment ◽  
X Ray ◽  
Cooling Conditions ◽  
Cobalt Chromium Molybdenum

Although post-heat treatment can improve the fatigue life of selective laser melting (SLM)-fabricated cobalt chromium molybdenum (CoCrMo) alloys, the effect of cooling conditions on the fatigue properties of such alloys remains unclear. In this study, we fabricated SLM CoCrMo alloy specimens and, after heat-treating them, cooled them either via furnace-cooling (FC) or air-cooling (AC). Subsequently, we analyzed their microstructures using scanning electron microscopy combined with energy-dispersive X-ray spectroscopy, electron backscattered diffraction, confocal laser scanning microscopy, and X-ray diffraction. Tensile and Vickers hardness (HV) tests and axial-fatigue tests were also conducted to assess their mechanical and fatigue properties, respectively. The microstructures of all samples showed homogeneous equiaxed grains, with the grains and precipitates of the AC samples (grain size: 84.9 μm) smaller than those of the FC samples (grain size: 109.7 μm). The AC samples exhibited better ductility than the FC samples. However, we observed no significant differences in the 0.2% yield strength and HV tests. The S–N curve derived from the fatigue tests showed that the AC samples had greater fatigue life than the FC samples. Therefore, a high cooling rate during post-heat treatment is effective in reducing grain and precipitate sizes, resulting in improved ductility and fatigue life.

scholarly journals Energy-Based Approach to Predict Fatigue Life of Asphalt Mixture Using Three-Point Bending Fatigue Test

Materials ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 1696 ◽  
Author(s):  
Yazhen Sun ◽  
Chenze Fang ◽  
Jinchang Wang ◽  
Zuoxin Ma ◽  
Youlin Ye
Keyword(s):  
Fatigue Life ◽  
Mathematical Models ◽  
Strain Energy ◽  
Asphalt Mixture ◽  
Fatigue Tests ◽  
Bending Fatigue ◽  
Three Point Bending ◽  
Average Value ◽  
Bending Fatigue Test ◽  
Fatigue Equation

The three-point bending fatigue tests were carried out in order to accurately predict the fatigue life of an asphalt mixture based on the plateau value (PV) of the dissipated strain energy ratio (DSER). The relations of the dissipated strain energy (DSE) to the stress-strength ratio, temperature and loading rate were studied, and the constructions of the mathematical models of DSE and DSER were completed based on the change laws of the DSE. The relation of the fatigue life to the PV was determined based on the analysis of damage evolution, based on which the fatigue equation was established and used to predict the fatigue life. The results show that the change laws of DSE and DSER can be well described by the proposed mathematical models. The PV is defined as the average value of the DSER in the second stage and the fatigue life decreases in power function with the increase of PV, based on which the fatigue equation of Nf = A(PV)B was established, and the established fatigue equation is very close to that is used in the MEPDG. The fatigue equation can well predict the fatigue life asphalt mixture.

Estimation of total fatigue life for in-service asphalt mixture based on accelerated pavement testing and four-point bending beam fatigue tests

2019 ◽  
Vol 46 (7) ◽  
pp. 557-566
Author(s):  
Zexin Ma ◽  
Liping Liu ◽  
Yu Yuan ◽  
Lijun Sun
Keyword(s):  
Fatigue Life ◽  
Asphalt Mixture ◽  
Shift Factor ◽  
Fatigue Tests ◽  
Accelerated Pavement Testing ◽  
Four Point Bending ◽  
Seismic Property ◽  
Equivalent Factor ◽  
Pavement Testing ◽  
Fatigue Equation

The purpose of this study was to estimate the total fatigue life for in-service asphalt mixture fatigue with in situ accelerated pavement testing (APT) and laboratory four-point bending beam tests. On a selected expressway in Shanghai, China, a series of full-scale APT tests were conducted. During the APT tests, a portable seismic property analyzer was used to monitor the pavement deterioration through modulus reduction. An equivalent factor between the APT loading and equivalent single axle loads (ESALs) was estimated. Additionally, asphalt concrete slabs were cut from the APT test sections and then transferred to the laboratory for four-point bending beam fatigue tests. A new fatigue equation was proposed for the in-service asphalt mixtures. Furthermore, a shift factor between the laboratory fatigue life and field ESAL was recommended. Finally, the field total fatigue life of the in-service asphalt mixture was estimated based on all the work in this study.

scholarly journals Estimation of Notched Composite Plates Fatigue Life Using Residual Strength Model Calibrated by Step-Wise Tests

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2180 ◽  
Author(s):  
Paweł Romanowicz ◽  
Aleksander Muc
Keyword(s):  
Fatigue Life ◽  
Residual Strength ◽  
Stress Ratio ◽  
Composite Plates ◽  
Fatigue Tests ◽  
Strength Model ◽  
Damage Growth ◽  
Testing Frequency ◽  
Fatigue Model ◽  
Layer Orientation

The proposed new technique of fatigue life prediction for notched composite plates is based on a residual strength model calibrated with the use of step-wise fatigue tests. It was proposed to calibrate the fatigue model with fatigue tests in which load conditions are in a step-wise fashion. The adopted fatigue model takes into account the most important loading parameters such as testing frequency, stress ratio, layer orientation and maximal fatigue stress. It was demonstrated that with the use of step-wise fatigue tests, it is possible to calibrate the fatigue model for a particular material and structure with the use of fewer samples. In the experimental tensile and fatigue tests TVR 380 M12/26%/R-glass/epoxy composite plates [+45°/−45°]4 with circular and elliptical cut-outs were used. The fatigue tests were performed under different loading conditions. The influence of testing frequency, stress ratio, maximal fatigue load and also geometry of the cut-out on damage growth rate and fatigue life were studied. The predicted fatigue life was in good agreement with the durability determined experimentally in all investigated samples.

Fatigue Life Parameter for Type 304 Stainless Steel Under Biaxial-Tensile Loading at Elevated Temperature

1999 ◽  
Vol 121 (3) ◽  
pp. 305-312 ◽  
Author(s):  
Abdelkrim Zouani ◽  
Thang Bui-Quoc ◽  
Marie Bernard
Keyword(s):  
Stainless Steel ◽  
Fatigue Life ◽  
Stress Ratio ◽  
Biaxial Stress ◽  
304 Stainless Steel ◽  
Biaxial Tensile ◽  
The Mean ◽  
Stress States ◽  
Type 304 ◽  
Type 304 Stainless Steel

This paper describes a damage Parameter for predicting fatigue life under biaxial-tensile loadings. Several studies have focussed in the past on the situations where the in-plane biaxial stress ratio is negative; however, little attention has been paid for the cases involving both principal stresses in tension. A new testing method is used to carry out biaxial fatigue tests, at room and 427°C, on Type 304 stainless steel for different positive values of the stress ratio. In the experimental procedure, a disk-shaped specimen was used in connection with a spatial-arms mechanism which converts the uniaxial force generated by a conventional testing machine to radial forces extending the disk specimen. A modified virtual strain energy parameter is then suggested to normalize fatigue data obtained under a wide range of stress states. The proposed parameter accounts for the mean stress and the mean strain effects in an explicit form. In addition, the COD equivalent stress and strain concepts are adopted to account for the stress state biaxiality. The predictions of the proposed parameter are compared with the obtained experimental data and the correlation between the applied stress states and the experimental fatigue lives is discussed.

AN ANALYSIS OF MECHANICAL PROPERTIES OF ANODIZED ALUMINUM FILM AT HIGH STRESS

2015 ◽  
Vol 22 (01) ◽  
pp. 1550002
Author(s):  
XIXI ZHAO ◽  
GUOYING WEI ◽  
YUNDAN YU ◽  
YUEMEI GUO ◽  
AO ZHANG
Keyword(s):  
Fatigue Life ◽  
Fracture Surface ◽  
Stress Ratio ◽  
High Stress ◽  
Fatigue Tests ◽  
Aluminum Film ◽  
Anodic Films ◽  
Anodized Aluminum ◽  
Al 2024 ◽  
Cycles To Failure

In this paper, a new environmental-friendly electrolyte containing sulfuric acid and tartaric acid has been used as the substitute of chromic acid for anodization. The work discussed the influence of anodizing voltages on the fatigue life of anodized Al 2024-T3 by performing fatigue tests with 0.1 stress ratio (R) at 320 MPa. Meanwhile the fatigue cycles to failure, yield strength, tensile strength and fracture surface of anodic films at different conditions were investigated. The results showed that the fatigue life of anodized and sealed specimens reduced a lot compared to aluminum alloy, which can be attributed to the crack sites initiated at the oxide layer. The fracture surface analyses also revealed that the number of crack initiation sites enlarged with the increase of anodizing voltage.

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