Fatigue Endurance Limit for Highway and Airport Pavements

2003 ◽  
Vol 1832 (1) ◽  
pp. 131-138 ◽  
Author(s):  
Samuel H. Carpenter ◽  
Khalid A. Ghuzlan ◽  
Shihui Shen
Keyword(s):  
Endurance Limit ◽  
Fatigue Testing ◽  
Healing Process ◽  
Extended Period ◽  
Load Cycle ◽  
Material Behavior ◽  
Dissipated Energy ◽  
Normal Strain ◽  
Perpetual Pavement ◽  
Fatigue Endurance

The existence of a fatigue endurance limit has been postulated for a considerable time. With the increasing emphasis on extended-life hot-mix asphalt pavement, or perpetual pavement, verification of the existence of this endurance limit, a strain below which none or very little fatigue damage develops, has become a substantial consideration in the design of these new multilayered full-depth pavements. Fatigue data are presented that were collected on a surface mix and a binder mixture tested for an extended period from 5 million to 48 million load repetitions at strain levels down to 70 microstrain. The fatigue results are analyzed in the traditional manner and using the dissipated energy ratio. This analysis shows that there is a difference in the data at normal strain levels recommended for fatigue testing and at the low strain levels. This difference cannot substantiate an endurance limit using traditional analysis procedures, but the dissipated energy approach clearly shows a distinct change in material behavior at low flexural strain levels, which supports the fact that at low strain levels the damage accumulated from each load cycle is disproportionately less than what is predicted from extrapolations of fatigue testing at normal strain levels. This reduced damage may be attributed to the healing process. The conclusion of this study is that laboratory testing can verify the existence of a fatigue endurance limit in the range of 90 to 70 microstrain below which the fatigue life of the mixture is significantly extended relative to normal design considerations.

Fatigue Study of a Zr-Ti-Ni-Cu-Be Bulk Metallic Glass

2003 ◽  
Vol 806 ◽  
Author(s):  
G. Y. Wang ◽  
P. K. Liaw ◽  
A. Peker ◽  
B. Yang ◽  
M. L. Benson ◽  
...  
Keyword(s):  
High Speed ◽  
Endurance Limit ◽  
Fatigue Testing ◽  
Imaging System ◽  
Fatigue Cracks ◽  
High Stress ◽  
Temperature Evolution ◽  
Test Environment ◽  
R Ratio ◽  
Fatigue Endurance

ABSTRACTHigh-cycle fatigue (HCF) studies were performed on zirconium (Zr)-based bulk metallic glasses (BMGs): Zr41.2Ti13.8Ni10Cu12.5Be22.5, in atomic percent. The HCF experiments were conducted using an electrohydraulic machine at a frequency of 10 Hz with a R ratio of 0.1 and under tension-tension loading, where R = σmin./σmax., where σmin. and σmax. are the applied minimum and maximum stresses, respectively. The test environment was air. A high-speed and high-sensitivity thermographic-infrared (IR) imaging system has been used for nondestructive evaluation of temperature evolution during fatigue testing of BMGs. Limited temperature evolution was observed during fatigue. However, no sparking phenomenon was observed at the final moment of fracture of this BMG. At high stress levels (σmax. > 864 MPa), the fatigue lives of Batch 59 are longer than those of Batch 94 due to the presence of oxides in Batch 94. Moreover, the fatigue-endurance limit of Batch 59 (703 MPa) is somewhat greater than that of Bath 94 (615 MPa) in air. The fatigue-endurance limit of Ti-6–4 is greater than this BMG, but Al 7075 has the lowest fatigue life. The vein pattern with a melted appearance were observed in the apparent melting region. The fracture morphology indicates that fatigue cracks initiate from some defects.

Application of the Dissipated Energy Concept in Fatigue Endurance Limit Testing

2005 ◽  
Vol 1929 (1) ◽  
pp. 165-173 ◽  
Author(s):  
Shihui Shen ◽  
Samuel H. Carpenter
Keyword(s):  
Fatigue Life ◽  
Endurance Limit ◽  
Fatigue Behavior ◽  
Testing Procedure ◽  
Dissipated Energy ◽  
Long Time ◽  
Loading Modes ◽  
Damage Condition ◽  
Fatigue Endurance ◽  
Unique Relationship

A fatigue endurance limit has been postulated to exist in hot-mix asphalt pavement performance. It cannot be observed and studied with the use of traditional phenomenological approaches as seen by the totally different fatigue behavior at low strain–damage levels close to the fatigue endurance limit. The ratio of dissipated energy change succeeds in defining and investigating the existence of a fatigue endurance limit with a unique relationship between plateau value (PV) and fatigue life (Nf), regardless of strain–damage levels, mixture types, loading modes, and other testing conditions. To determine a fatigue endurance limit requires an extraordinarily long time to conduct testing. This paper applied the PV to the study of a fatigue endurance limit to validate a shortened laboratory testing procedure. Statistical analysis shows that the shortened test can predict the PV with sufficient accuracy. By applying the validated relationship between PV and Nf, the extremely long fatigue life under low strain–damage condition can be predicted without performing millions of loading cycles.

scholarly journals Enhancement of Fatigue Endurance Limit through Ultrasonic Surface Rolling Processing in EA4T Axle Steel

Metals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 830
Author(s):  
Xiaodi Wang ◽  
Liqin Chen ◽  
Peng Liu ◽  
Guobiao Lin ◽  
Xuechong Ren
Keyword(s):  
Residual Stress ◽  
Surface Roughness ◽  
Fatigue Limit ◽  
Compressive Residual Stress ◽  
Endurance Limit ◽  
Static Load ◽  
Fatigue Testing ◽  
Fatigue Property ◽  
Surface Characteristics ◽  
Fatigue Endurance

Fatigue property is a key evaluation index for the service reliability of railway axle. In this work, the effect of ultrasonic surface rolling processing (USRP) on the surface characteristic and fatigue property was investigated in an EA4T axle steel used on high speed trains by several characterization techniques and the staircase method fatigue testing. The surface characteristics were initially studied in EA4T axle steel under different static loads of 1.0 kN, 1.5 kN and 2.0 kN, and served as the important USRP parameter. It was found that the larger static load greatly improved the surface microstructure, microhardness and compressive residual stress, but also increased the surface roughness. Furthermore, the rotating bending fatigue endurance limit of the USRP specimen with a static load of 1.5 kN was obviously enhanced by ~14% (from ~352 MPa to ~401 MPa) relative to the untreated specimen. The enhanced fatigue limit induced by USRP was attributed to the synergistic effect of the grain refinement, as evidenced by transmission electron microscope (TEM) observation, work-hardening, the increased compressive residual stress and the reduced surface roughness. Moreover, the fatigue limit of the USRP specimen was ~4% higher than that of the rolling specimen with turning off the ultrasonic system, ~386 MPa, which showed that the role of the ultrasonic impact could enhance the fatigue property. These findings demonstrate the validity of this technique in modifying the surface characteristics and thus improving the fatigue resistance of axle material, further ensuring its service safety and reliability.

Energy-Derived, Damage-Based Failure Criterion for Fatigue Testing

2000 ◽  
Vol 1723 (1) ◽  
pp. 141-149 ◽  
Author(s):  
Khalid A. Ghuzlan ◽  
Samuel H. Carpenter
Keyword(s):  
Fatigue Testing ◽  
Fatigue Loading ◽  
Constant Stress ◽  
Material Behavior ◽  
Dissipated Energy ◽  
Initial Stiffness ◽  
Repeated Load ◽  
Definition Of ◽  
Selection Of

Determination of the failure limit in a repeated-load fatigue test in the laboratory has relied entirely on the arbitrary selection of a fixed criterion. The constant strain and constant stress modes of fatigue loading have been described by a consistent definition of failure in flexural fatigue testing because of the distinctly different application of energy during the loading history. The most widely accepted definition is a decrease in initial stiffness by 50 percent. Procedures examining energy input and dissipated energy have required different schemes for each mode in an attempt to describe similar states of damage in the mixture. A proposed method is presented for examining dissipated energy to select a consistent level of material behavior that is indicative of the damage accumulation in the mixture. This procedure shows the similarity between the constant stress and constant strain modes of testing and is shown to provide the potential for unifying the now phenomenological description of fatigue with a more rational energy-based description.

SANDVIK Ti-3Al-2.5V GRADE 9

Alloy Digest ◽  
1997 ◽  
Vol 46 (9) ◽  
Keyword(s):  
Corrosion Resistance ◽  
Endurance Limit ◽  
Weight Ratio ◽  
High Strength ◽  
Strain Ratio ◽  
Bend Strength ◽  
Aerospace Applications ◽  
Excellent Corrosion Resistance ◽  
Titanium Aluminum ◽  
Fatigue Endurance

Abstract Sandvik Ti-3Al-2.5V Grade 9 titanium-aluminum alloy offers excellent corrosion resistance, especially to chloride media, and has a high strength-to-weight ratio, which is especially suitable for use in aerospace applications. Tubing can be produced having a CSR (contractile strain ratio) that enhances the fatigue endurance limit. This datasheet provides information on composition, physical properties, elasticity, tensile properties, and bend strength as well as fatigue. It also includes information on corrosion resistance as well as forming, machining, and joining. Filing Code: TI-109. Producer or source: Sandvik.

Cyclic Mechanical Properties of 16MnR Welded Joint under Constant

2011 ◽  
Vol 197-198 ◽  
pp. 1658-1661
Author(s):  
Ying Xiong ◽  
Han Ying Zheng
Keyword(s):  
Mechanical Properties ◽  
Weld Metal ◽  
Endurance Limit ◽  
Welded Joint ◽  
Cyclic Softening ◽  
Fatigue Tests ◽  
Test Results ◽  
Control Test ◽  
Strain Control ◽  
Fatigue Endurance

Fatigue tests are carried out for 16MnR welded joint under constant strain control. Test results reveal that 16MnR weld metal exhibits characteristic of cyclic softening and non-masing obviously. The strain–life curve can be best described by the three-parameter equation. It shows the fatigue endurance limit in the heat-affecting zone (HAZ) of welded joint is lower than that in the weld metal.

Predictive Artificial Neural Network Laboratory Fatigue Endurance Limit Model for Asphalt Concrete Pavements Based on the Volumetric Properties and Loading Conditions

2021 ◽  
pp. 036119812199965
Author(s):  
Mayzan M. Isied ◽  
Mena I. Souliman ◽  
Waleed A. Zeiada ◽  
Nitish R. Bastola
Keyword(s):  
Neural Network ◽  
Artificial Neural Network ◽  
Asphalt Concrete ◽  
Endurance Limit ◽  
Volumetric Properties ◽  
Void Content ◽  
Loading Conditions ◽  
Ann Model ◽  
Artificial Neural ◽  
Fatigue Endurance

Asphalt concrete healing is one of the important concepts related to flexible pavement structures. Fatigue endurance limit (FEL) is defined as the strain limit under which no damage will be accumulated in the pavement and is directly related to asphalt healing. Pavement section designed to handle a strain value equivalent to the endurance limit (EL) strain will be considered as a perpetual pavement. All four-point bending beam fatigue testing results from the NCHRP 944-A project were extracted and utilized in the development of artificial neural network (ANN) EL strain predictive model based on mixture volumetric properties and loading conditions. ANN model architecture, as well as the prediction process of the EL strain utilizing the generated model, were presented and explained. Furthermore, a stand-alone equation that predicts the EL strain value was extracted from the developed ANN model utilizing the eclectic approach. Moreover, the EL strain value was predicted utilizing the new equation and compared with the EL strain value predicted by other prediction models available in literature. A total of 705 beam fatigue lab test data points were utilized in model training and evaluation at ratios of 70%, 15%, and 15% for training, testing, and validation, respectively. The developed model is capable of predicting the EL strain value as a function of binder grade, temperature, air void content, asphalt content, SR, failure cycles number, and rest period. The reliability of the developed stand-alone equation and the ANN model was presented by reasonable coefficient of determination (R2) value and significance value (F).

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