Strain-Level Determination Procedure for Small-Specimen Cyclic Fatigue Testing in the Asphalt Mixture Performance Tester

2019 ◽  
Vol 2673 (11) ◽  
pp. 824-835
Author(s):  
Kangjin “Caleb” Lee ◽  
Sonja Pape ◽  
Cassie Castorena ◽  
B. Shane Underwood ◽  
Y. Richard Kim
Keyword(s):  
Fatigue Testing ◽  
Asphalt Mixture ◽  
Cyclic Fatigue ◽  
Fatigue Tests ◽  
Strain Level ◽  
Small Specimen ◽  
Asphalt Mixture Performance Tester ◽  
Number Of Cycles ◽  
Cycles To Failure ◽  
Step Strain

With an increase in small-specimen cyclic fatigue testing using the Asphalt Mixture Performance Tester (AMPT), researchers have observed that the strain-selection guidelines in AASHTO TP 107-14 that are intended for large AMPT cyclic fatigue tests are inadequate for testing small specimens. The machine compliance factor is significantly different for testing small specimens compared with large specimens because of different required load levels, resulting in a significant offset in the relationship between the input strain and the number of cycles to failure. To this end, this paper presents the development and verification of a phenomenological model that relates strain levels to dynamic modulus and number of cycles to failure for small-specimen AMPT cyclic fatigue tests, as well as the development of a corresponding stepped strain-level determination procedure that takes into account cases when the initially selected strain-level results in an unexpected number of cycles to failure. The final procedure includes a table with input strain levels and step strain increments for a wide range of dynamic modulus values as well as a flow chart to guide the use of the step strain adjustment procedure.

Combination of Cyclic Fatigue Testing and Materials Characterisation to Investigate Ageing of Elastomers

2017 ◽  
Vol 44 (4) ◽  
pp. 1-8 ◽  
Author(s):  
T. Kroth ◽  
D. Lellinger ◽  
I. Alig ◽  
M. Wallmichrath
Keyword(s):  
Fatigue Life ◽  
Molecular Mass ◽  
Fatigue Testing ◽  
Cyclic Fatigue ◽  
Chain Scission ◽  
Thermal Ageing ◽  
Fatigue Tests ◽  
Additive Package ◽  
Number Of Cycles ◽  
Cycles To Failure

Cyclic fatigue testing and elastomer characterisation were combined to study changes in material properties and network structure of elastomers during thermal ageing. Natural rubber containing a typical additive package with carbon black was studied as a model material. The samples were aged at different temperatures in air or under a nitrogen atmosphere. The fatigue life in number of cycles to failure (S-N curves) was determined from force- and displacement-controlled fatigue tests on tensile bar specimens after different thermal ageing times. Changes in mechanical properties and crosslink density were studied by tensile tests, dynamic mechanical analysis, stress relaxation experiments, compression set measurements, swelling measurements and solid-state NMR. Changes in network density during thermal ageing are related to the interplay between the formation of new crosslinks and chain scission. The average molecular mass of the network chains was found to be a suitable parameter for comparing different characterisation methods. An initial decrease in the molecular mass between two crosslinking points due to post-curing is followed by an increase due to chain scission. A similar trend was found for fatigue life in number of cycles to failure (N) in force-controlled fatigue tests: an increase in N for short ageing times is followed by a decrease after longer ageing times.

Practical Method to Determine Strain Level for Cyclic Direct Tension Fatigue Testing in the Asphalt Mixture Performance Tester

2017 ◽  
Vol 2631 (1) ◽  
pp. 133-143 ◽  
Author(s):  
Sean (Xinjun) Li ◽  
David J. Mensching ◽  
Nelson Gibson
Keyword(s):  
Phase Angle ◽  
Fatigue Testing ◽  
Asphalt Mixture ◽  
Practical Method ◽  
Fatigue Tests ◽  
Strain Level ◽  
Direct Tension ◽  
Experimental Database ◽  
Asphalt Mixture Performance Tester ◽  
Peak Phase

This paper presents a practical procedure for estimating strain levels in the asphalt mixture performance tester cyclic direct tension fatigue test and provides practitioners with guidance for selecting a strain value for testing materials with unknown fatigue characteristics. A large variety of plant-produced and laboratory-prepared mixtures were analyzed. These included hot- and warm-mix asphalt, reclaimed asphalt pavement, and recycled asphalt shingles and various gradations and air void contents; all were tested following the AASHTO TP 107 procedure. The experimental results from a segregated material illustrate that AASHTO TP 107 could produce repeatable results and was sensitive to field variations in binder content. Data for satisfactorily performing and poorly performing mixtures were clustered on the plot of cycles to peak phase angle versus actuator strain level and a Black Space diagram evaluated at the AASHTO TP 107 test temperature. Curves of cycles to peak phase angle versus actuator strain level were built from the experimental database, with each curve representing one ideal mixture that followed a particular power function. The dynamic modulus data are used to determine a recommended actuator strain level to start the set of fatigue tests for each cluster.

Optimization of the Laboratory Fabrication of Small Specimens for Asphalt Mixture Performance Testing

2018 ◽  
Vol 2672 (28) ◽  
pp. 438-450 ◽  
Author(s):  
Sonja Pape ◽  
Kangjin Lee ◽  
Cassie Castorena ◽  
Y. Richard Kim
Keyword(s):  
Dynamic Modulus ◽  
Fatigue Testing ◽  
Extraction Procedure ◽  
Asphalt Mixture ◽  
Performance Testing ◽  
Cyclic Fatigue ◽  
Fatigue Tests ◽  
Void Content ◽  
Multiple Test ◽  
Air Void

The use of 38-mm-diameter small specimens for uniaxial dynamic modulus and cyclic fatigue asphalt mixture performance testing offers a significant opportunity to improve the efficiency of laboratory-fabricated specimen testing because multiple test specimens can be extracted per Superpave gyratory-compacted (SGC) sample. This study seeks to optimize the procedure used for the extraction of small specimens from SGC samples for dynamic modulus and cyclic fatigue tests. To this end, small cylindrical specimens were cored horizontally and vertically from SGC samples and subjected to performance testing. The dynamic modulus and fatigue test results indicate that the effects of anisotropy are minimal. However, all of the horizontally extracted small specimens exhibited fatigue failure at the specimen ends, outside the range of the gauges; the failure was likely due to the peripheral air void gradients in the SGC samples. Therefore, the authors concluded that small specimens should be vertically cored from SGC samples for the laboratory fabrication of small specimens. Specifically, four small specimens were cored vertically from the inner 100 mm of SGC samples where the air void content is relatively uniform. Four mixtures with different nominal maximum aggregate sizes (NMASs) were used to prepare small specimens using the proposed extraction procedure. These specimens were subjected to dynamic modulus and cyclic fatigue testing. The results demonstrate an increase in specimen-to-specimen variability with an increase in NMAS, which also is expected in large specimen testing.

scholarly journals Cyclic Fatigue Comparison of TruNatomy, Twisted File, and ProTaper Next Rotary Systems

2020 ◽  
Vol 2020 ◽  
pp. 1-4
Author(s):  
Abdullah Mahmoud Riyahi ◽  
Amr Bashiri ◽  
Khalid Alshahrani ◽  
Saad Alshahrani ◽  
Hadi M. Alamri ◽  
...  
Keyword(s):  
Standard Deviation ◽  
Fatigue Resistance ◽  
Fatigue Testing ◽  
Clinical Performance ◽  
Cyclic Fatigue ◽  
Tooth Structure ◽  
Multiple Comparison Test ◽  
Continuous Rotation ◽  
Number Of Cycles ◽  
Cycles To Failure

TruNatomy (TN; Dentsply Sirona, Maillefer, Ballaigues, Switzerland) is a newly released system that was not tested in any previous studies. The objective of this work is to evaluate cyclic fatigue resistance of the new file and compare it with the Twisted Files (TF) and ProTaper Next (PTN). Forty-five files were distributed into 3 groups: PTN X2 (size 25 and taper 0.06), TF (size 25 and taper 0.06), and TN prime file (size 26 and taper 0.04). Each group included 15 files. Lengths of all files were 25 mm. Cyclic fatigue testing was done using artificial stainless-steel canals with 60-degree curvature and 5 mm radius. Continuous rotation movement at 300 rpm was used until the file fractures. Time for file separation was recorded in seconds. The number of cycles to failure (NCF) mean and standard deviation for each group was calculated. For statistical analysis of data, ANOVA and Tukey’s multiple comparison test were used. Mean and standard deviation (SD) of NCF were 259 ± 37.2, 521.67 ± 63.07 and 846.67 ± 37.16 for PTN, TF, and TN respectively. TN on average had significantly the highest NCF compared with PTN (p<0.05) and TF (p<0.05). TruNatomy file showed superior cyclic fatigue resistance. With its potential to preserve tooth structure, this file offers a good cyclic fatigue advantage. However, future studies are required to evaluate other properties of this file and to examine its clinical performance.

A Criterion for Minimum Scatter in Fatigue Testing

1955 ◽  
Vol 22 (3) ◽  
pp. 427-431
Author(s):  
F. A. McClintock
Keyword(s):  
Statistical Analysis ◽  
Experimental Technique ◽  
Crack Detection ◽  
Fatigue Testing ◽  
Fatigue Tests ◽  
Radius Of Curvature ◽  
Definite Relation ◽  
Number Of Cycles ◽  
Cycles To Failure

Abstract When a number of fatigue tests are run on specimens with a longitudinal radius of curvature, there results a scatter in both the number of cycles to failure and the position of failure. A previous statistical analysis showed that if the variations in life are due solely to local inhomogeneities in the specimen, then there is a definite relation between the scatter in position of failure and the scatter in the number of cycles to failure. If the scatter in life significantly exceeds that corresponding to the scatter in position of failure, then there is some factor other than local inhomogeneities contributing to the scatter in life. Such other factors can be eliminated by improving the experimental technique. The usefulness of this criterion is illustrated by its application to crack detection tests on polycrystalline ingot iron.

Fatigue Testing of Polymeric Hollow Fibre Heat Transfer Surfaces by Pulsating Pressure Loads

2016 ◽  
Vol 821 ◽  
pp. 3-9 ◽  
Author(s):  
Tereza Brožová ◽  
Tomáš Luks ◽  
Ilya Astrouski ◽  
Miroslav Raudenský
Keyword(s):  
Heat Transfer ◽  
Fatigue Testing ◽  
Fatigue Loading ◽  
Hollow Fibre ◽  
Fatigue Tests ◽  
Outer Diameter ◽  
Hollow Fibres ◽  
Different Temperatures ◽  
Hot Bath ◽  
Number Of Cycles

This article deals with fatigue tests of polymeric hollow fibre heat transfer surfaces. The hollow fibres have an outer diameter between 0.5-0.8 mm and wall thickness 10 % of the outer diameter. These plastic heat transfer surfaces have some limitations but also many benefits. One of the limitations is the durability of plastic under fatigue loading. The heat transfer surfaces were subjected to pulsating pressure loads under different conditions (level of pressure, ambient temperature, number of cycles). Firstly, only an internal hydraulic pulsating load was applied and the behaviour of the hollow fibres was observed, focusing especially on the presence of leaks, ruptures, etc.Then, other conditions of operations were added. The heat transfer surfaces were immersed in a hot bath and loaded by internal pulsating pressure and high temperature simultaneously. Testing under different temperatures is important because the temperature significantly affects the material properties. The presence of leaks, ruptures and other possible damage was monitored as with previous tests.

scholarly journals Determination of the Creep-Fatigue Interaction Diagram for Alloy 617

2016 ◽  
Author(s):  
J. K. Wright ◽  
L. J. Carroll ◽  
T.-L. Sham ◽  
N. J. Lybeck ◽  
R. N. Wright
Keyword(s):  
Fatigue Testing ◽  
Hold Time ◽  
Strain Range ◽  
Fatigue Tests ◽  
Alloy 617 ◽  
Interaction Diagram ◽  
Creep Fatigue ◽  
Intermediate Heat Exchanger ◽  
Cycles To Failure

Alloy 617 is the leading candidate material for an intermediate heat exchanger for the very high temperature reactor (VHTR). As part of evaluating the behavior of this material in the expected service conditions, creep–fatigue testing was performed. The cycles to failure decreased compared to fatigue values when a hold time was added at peak tensile strain. At 850°C, increasing the tensile hold duration continued to degrade the creep–fatigue resistance, at least to the investigated strain–controlled hold time of up to 60 minutes at the 0.3% strain range and 240 minutes at the 1.0% strain range. At 950°C, the creep–fatigue cycles to failure are not further reduced with increasing hold duration, indicating saturation occurs at relatively short hold times. The creep and fatigue damage fractions have been calculated and plotted on a creep–fatigue interaction D–diagram. Test data from creep–fatigue tests at 800 and 1000°C on an additional heat of Alloy 617 are also plotted on the D–diagram.

Effect of Extended Aging on Asphalt Materials Containing Re-Refined Engine Oil Bottoms

2017 ◽  
Vol 2632 (1) ◽  
pp. 60-69 ◽  
Author(s):  
David J. Mensching ◽  
Adrian Andriescu ◽  
Christopher DeCarlo ◽  
Xinjun Li ◽  
Jack S. Youtcheff
Keyword(s):  
Low Temperature ◽  
Fatigue Testing ◽  
Asphalt Mixture ◽  
Field Performance ◽  
Cyclic Fatigue ◽  
Engine Oil ◽  
Short Term ◽  
Bending Beam Rheometer ◽  
The Difference

The use of re-refined engine oil bottoms (REOBs) in asphalt pavements is a topic of much debate because the aging susceptibility and quantity of the additive in the binder may affect field performance. In this study, four mixtures with varying REOB contents (up to 15%) were long-term oven aged by using a high-temperature, short-duration method (135°C, 24 h) and compared with existing data on mixtures aged with more conventional short-term and long-term oven-aging procedures. The recovered binders underwent Superpave® grading, double-edge notched tension, and extended bending beam rheometer testing, and the binders were subjected to dynamic modulus, cyclic fatigue testing in the asphalt mixture performance tester, and thermal stress restrained specimen testing. Results showed a general insensitivity when short-term oven-aged (135°C, 4 h) materials were compared with long-term oven-aged (85°C, 5 days) materials, whereas the aging process at 135°C over 24 h resulted in substantial changes to the stiffness and relaxation properties across high-, intermediate-, and low-temperature modes. The difference between the stiffness-based and slope-based low-temperature performance grades appears to be an indicator for REOB modification, with the test for physical hardening of the binder being more sensitive than standard bending beam rheometer testing. The details in this paper provide information for the asphalt pavement community to consider as specifications. Standard practices are developed to address REOB modification.

Microstructure and Properties Characterization of Polycrystalline Ni-Fe-Cr-Based Superalloy EP-718E after Electric Upsetting

2016 ◽  
Vol 721 ◽  
pp. 467-472 ◽  
Author(s):  
Lembit Kommel
Keyword(s):  
Mechanical Properties ◽  
Room Temperature ◽  
Energy Dispersive Spectrometry ◽  
Fatigue Testing ◽  
Tension Stress ◽  
Tension Testing ◽  
Electric Upsetting ◽  
Number Of Cycles ◽  
Cycles To Failure

The purpose of this study is to analyze the effect of electric upsetting on the microstructure defects eliminating and mechanical properties evolution of the Ni-Fe-Cr-based polycrystalline superalloy EP718E. The microstructure was examined by scanning electron microscope and energy dispersive spectrometry techniques. The material mechanical properties were characterized by nanoindentation, by tension testing of micro samples and high cycle fatigue testing at room temperature. The results show, that the microstructure defects on confluence of grain boundaries (depending on the processing stages) were step-by-step eliminated. The tension stress was lowered but elongation was increase. As a result of such changes in microstructure and mechanical properties of alloy the fatigue strength (δ-1) was increased from δ-1 = 300 MPa to δ-1 = 540 MPa and the number of cycles to failure was increased from N1 = 2·107 up to N4 = 4 x (2·107), respectively.

scholarly journals Comparison of cyclic fatigue resistance of XP-endo Shaper, HyFlex CM, FlexMaster and Race instruments

2018 ◽  
Vol 12 (3) ◽  
pp. 208-212 ◽  
Author(s):  
Mehmet Adiguzel ◽  
Ipek Isken ◽  
Ismail Ilker Pamukcu
Keyword(s):  
Body Temperature ◽  
Fatigue Resistance ◽  
Cyclic Fatigue ◽  
Radius Of Curvature ◽  
Rotary Instruments ◽  
Recorded Data ◽  
The Difference ◽  
Number Of Cycles ◽  
Cycles To Failure ◽  
One Way Anova

Background. The aim of this study was to compare the cyclic fatigue resistance of XP-endo Shaper, HyFlex CM, FlexMaster and Race rotary instruments at body temperature (37±1°C). Methods. Twenty XP-endo Shaper (#30/.01), 20 HyFlex CM (#30/.04), 20 FlexMaster (#30/.04) and 20 Race (#30/.04) instruments were tested at body temperature (n=20). The instruments were evaluated in artificial canals with a 3-mm radius of curvature and 60° angle of curvature to the center of the 1.5-mm-wide canal. Each instrument was rotated until fracture occurred and the number of cycles to failure (NCF) recorded. Data were analyzed using one-way ANOVA and Tukey HSD tests (P<0.05). Results. The difference in the NCF of all the instruments was statistically significant (P<0.05). The order of the instruments from the highest to the lowest NCF was as follows: XP-endo Shaper (3064.0±248.1), HyFlex CM (1120.5±106.1), FlexMaster (569.8±48.4) and Race (445.5±53.5). Conclusion. Under the limitations of the present study, XP-endo Shaper instruments were more resistant to cyclic fatigue than the #30/.04 nickel-titanium rotary instruments immersed in water at simulated body temperature.

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