Fatigue Assessment of Existing Riveted Bridges

2018 ◽  
Author(s):  
Henrik Mehlsen
Keyword(s):  
Fatigue Life ◽  
Fatigue Failure ◽  
Visual Inspection ◽  
Fatigue Cracks ◽  
Repeated Loading ◽  
Fe Modelling ◽  
Railway Bridges ◽  
Loading And Unloading ◽  
Fatigue Failures ◽  
Thick Layers

Fatigue failure of bridges occurs after repeated loading and unloading and hence fatigue becomes more and more severe with time. A majority of all existing riveted bridges are not explicitly designed for fatigue failures. Bridge owners should therefore have focus on fatigue life of riveted bridges. It can be difficult to discover fatigue cracks by visual inspection due to thick layers of paint and the fact that the rivets themselves may hide the cracks. Hence, it may be necessary to determine critical joints and possible fatigue cracks by using FE-modelling. Identification of critical joints may also target future inspection efforts and highlight hidden details, which may call for special inspection measures to be implemented. This paper describes a fatigue study of 11 riveted railway bridges in Denmark that includes both visual inspections and FE-modelling of bridges.

Thermographic Determination of Fatigue Damage

1978 ◽  
Vol 100 (2) ◽  
pp. 200-203 ◽  
Author(s):  
J. A. Charles ◽  
F. J. Appl ◽  
J. E. Francis
Keyword(s):  
Fatigue Life ◽  
Mild Steel ◽  
Surface Temperature ◽  
Fatigue Damage ◽  
Fatigue Cracks ◽  
Temperature Distributions ◽  
Fatigue Failures

The energy released due to hysteresis effects in cyclically loaded materials can be used to predict where fatigue cracks are likely to initiate and to determine the stage of fatigue life. In the present study, thermography is used to monitor the surface temperature distributions on a series of double-notched, mild steel fatigue specimens cyclically loaded in bending. The results indicate that the fatigue life of the material encompasses three thermal stages, each of which is indicative of the fatigue damage the material has sustained. This information can be used to avoid in-service fatigue failures.

scholarly journals Influence of Welded Pores on Very Long-Life Fatigue Failure of the Electron Beam Welding Joint of TC17 Titanium Alloy

Materials ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 1825 ◽  
Author(s):  
Fulin Liu ◽  
Hong Zhang ◽  
Hanqing Liu ◽  
Yao Chen ◽  
Khan Muhammad Kashif ◽  
...  
Keyword(s):  
Titanium Alloy ◽  
Electron Beam ◽  
Fatigue Life ◽  
Base Metal ◽  
Fatigue Failure ◽  
Electron Beam Welding ◽  
Welded Joint ◽  
Fatigue Cracks ◽  
Failure Behavior ◽  
Long Life

The electron beam welding process is widely used in the connection among titanium alloy material parts of aero-engines. Its mechanical properties need to meet the requirements of long life and high reliability. In this paper, the static strength and the fatigue failure behavior of the electron beam weldments of TC17 titanium alloy were investigated experimentally under low amplitude high frequency (20 kHz), and the mechanical response and failure mechanism under different external loading conditions were analyzed. In summary, the samples were found to have anisotropic microstructure. The tensile strength of the PWHT of TC17 EBW joint was ~4.5% lower than that of the base metal. Meanwhile, compared with the base metal, the fatigue strength was reduced by 45.5% at 109 cycles of fatigue life. The fracture analysis showed that the fatigue failure of the welded joint of TC17 alloy was caused by the welded pores and the fatigue cracks initiated from the welded pores. A fine granular area (FGA) was observed around the crack initiation region. The existence of pores caused the stress intensity factor of the fine granular area (KFGA) to be inversely proportional to the fatigue life. The KFGA calculation formula was modified and the fatigue crack propagation threshold of the welded joint of TC17 alloy was calculated (3.62 MPa·m1/2). Moreover, the influences of the effective size and the relative depth of the pores on the very long fatigue life of the electron beam welded joint of TC17 titanium alloy were discussed.

Influence of Subjection to Plasma Nitriding Surface Modifications on Ultra-High Cycle Fatigue Behavior of Ti-6Al-4V

2011 ◽  
Vol 105-107 ◽  
pp. 1731-1735
Author(s):  
Yan Zeng Wu ◽  
Qing Yuan Wang ◽  
Qiao Lin Ouyang
Keyword(s):  
Fatigue Life ◽  
Fatigue Failure ◽  
High Cycle Fatigue ◽  
Plasma Nitriding ◽  
Fatigue Behavior ◽  
Fatigue Cracks ◽  
Surface Modifications ◽  
Test Method ◽  
Cycle Fatigue ◽  
Ultra High Cycle Fatigue

Using the ultrasonic fatigue test method, the influence of subjection to plasma nitriding surface modifications on the ultra-high cycle fatigue behavior of Ti-6Al-4V was investigated, then a comparison with corresponding behaviors of the normal Ti-6Al-4V was made. The results show the S-N curve of Ti-6Al-4V with plasma nitriding surface modifications still continuously declines, no conventional fatigue limit exists for Ti-6Al-4V. Plasma nitriding surface modifications enhance surface hardness, but they make the material fatigue strength decrease by about 17 %. The fractography of fatigue failure has been observed by scanning electron microscopy. The observation shows that fatigue failure initiates from internal of specimen after the fatigue life of 108cycles and fatigue cracks mainly initiate from the surface of specimen before the fatigue life of 108cycles.

A novel method to improve fatigue behaviors of holed structures based on electromagnetic force

2022 ◽  
pp. 095440622110641
Author(s):  
Guo Zheng ◽  
Zengqiang Cao ◽  
Minghao Zhang
Keyword(s):  
Residual Stress ◽  
Fatigue Life ◽  
Electromagnetic Force ◽  
Stress Measurement ◽  
Fatigue Cracks ◽  
Axial Direction ◽  
Novel Method ◽  
Fatigue Life Enhancement ◽  
Fatigue Failures ◽  
Improve Fatigue

In this study, a novel method stress wave strengthening (SWS) process based on electromagnetic force was proposed to improve the fatigue life of holed structures. Corresponding tests were carried out to explore the fatigue performance of SWS. Cold expansion (CE) was also investigated for comparison. The fatigue life of SWS and CE samples were evaluated, moreover, the mechanisms of fatigue failures and life enhancements were also discussed. Results showed that double-side SWS extended fatigue life significantly and reduced stiffness degradation more effectively with respect to CE process. Moreover, fatigue cracks commonly appeared at mid-planes of hole surfaces and horizontally grew in SWS samples, which differed a lot from CE samples. Through the residual stress measurement, it is seen that more uniform residual stress along axial direction can be obtained by SWS compared to CE, which can explain the fatigue life enhancement and failure mechanism of SWS method.

Experimental and Modeling Study of the Effect of Corrosion Pitting on Fatigue Failure Locations in Aircraft Components

2014 ◽  
Vol 891-892 ◽  
pp. 236-241 ◽  
Author(s):  
Bruce R. Crawford ◽  
Chris Loader ◽  
Qian Chu Liu ◽  
Timothy J. Harrison ◽  
P. Khan Sharp ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Fatigue Failure ◽  
Pitting Corrosion ◽  
Structural Integrity ◽  
Turbine Blades ◽  
Gauge Section ◽  
Stress Concentration Factors ◽  
Corrosion Pits ◽  
The Cost ◽  
Fatigue Failures

It is well established that corrosion pits reduce the fatigue life and structural integrity of aluminum alloy aircraft components. A great deal of research has been conducted in this area in the last 20 years. This problem is not unique to aluminum alloys or aircraft however. Similar problems have been observed in the steel components of other engineered structures such as steel pipelines and steam turbine blades. However the effect of pitting corrosion on the probable location of fatigue failures has been overlooked. This is problematic as corrosion pits have caused fatigue failures in locations and components where they were unexpected, such as the trailing edge flap lug of the F/A 18 fighter aircraft. DSTO have called this problem ‘Corrosion Criticality’. This paper reports the development of Monte-Carlo models of how pitting corrosion affects the location of fatigue failures in two fatigue specimen geometries that have different stress concentration factors (kt). These specimens are a low-kt fatigue life specimen and a high-kt fatigue life specimen with three holes arranged along its centerline. The modeling results for the low-kt specimen are then compared with experimental results for that specimen. The low-kt model produces good estimates of fatigue life and of the probability of fatigue failure at any given location in the specimen’s gauge section. The process that will be followed to develop the high-kt model is outlined. The paper includes a discussion of using the Corrosion Criticality models to reduce the cost of corrosion maintenance by (i) identifying areas in which corrosion inspections are critical and (ii) identify aircraft components for which pitting corrosion will not be a threat to airworthiness during the life of an aircraft.

Quantification of vertical, lateral, and longitudinal fastener demand in broken spike track: Inputs to mechanistic-empirical design

2021 ◽  
pp. 095440972110307
Author(s):  
Marcus S Dersch ◽  
Matheus Trizotto ◽  
J Riley Edwards ◽  
Arthur de Oliveira
Keyword(s):  
Fatigue Life ◽  
Design Principles ◽  
Lateral Load ◽  
System Component ◽  
Applied Loading ◽  
Component Design ◽  
Stress Reversals ◽  
Fatigue Failures ◽  
Empirical Design

To address a recent challenge related to broken spikes in premium elastic fastening systems that have led to at least ten derailments and require manual walking inspections as well as build upon mechanistic-empirical (M-E) design principles for future fastening system component design, this paper quantifies the vertical, lateral, and longitudinal fastening system loads under revenue service traffic in a curve that has regularly experienced spike fastener fatigue failures. Previous data has indicated that the high rail of Track 3 experienced the most failures at this location. The data from this investigation sheds light into why failures are more predominant at this location than others and how the vertical, lateral, and longitudinal loads cannot be considered independently. Specifically, while the magnitude of the applied loading was the lowest on the high rail of Track 3, the threshold for failure was also the lowest given the operations at this location led to unloading of the high rail, thus indirectly highlighting the importance of friction within a fastening system. The data also show the high rail of Track 3 was subjected to the highest L/V load ratios and was an outlier in the typical lateral load reversals applied likely leading to spike stress reversals and thus a shorter fatigue life. Finally, based upon the data, it is recommended that to mitigate spike failures, as well as similar fastener challenges in other track types (e.g. rail seat deterioration, etc.) railroads should ensure trains operate close to the balance speed and use fastening system that transfer loads through friction. This study also provides novel data for M-E design of fastening systems.

scholarly journals Quantitative Analysis of Inclusion Engineering on the Fatigue Property Improvement of Bearing Steel

Metals ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 476 ◽  
Author(s):  
Chao Gu ◽  
Min Wang ◽  
Yanping Bao ◽  
Fuming Wang ◽  
Junhe Lian
Keyword(s):  
Fatigue Life ◽  
Quantitative Analysis ◽  
Critical Size ◽  
Fatigue Behavior ◽  
Fatigue Cracks ◽  
Fatigue Property ◽  
Bearing Steel ◽  
Fatigue Properties ◽  
Bearing Steels ◽  
Inclusion Distribution

The fatigue property is significantly affected by the inner inclusions in steel. Due to the inhomogeneity of inclusion distribution in the micro-scale, it is not straightforward to quantify the effect of inclusions on fatigue behavior. Various investigations have been performed to correlate the inclusion characteristics, such as inclusion fraction, size, and composition, with fatigue life. However, these studies are generally based on vast types of steels and even for a similar steel grade, the alloy concept and microstructure information can still be of non-negligible difference. For a quantitative analysis of the fatigue life improvement with respect to the inclusion engineering, a systematic and carefully designed study is still needed to explore the engineering dimensions of inclusions. Therefore, in this study, three types of bearing steels with inclusions of the same types, but different sizes and amounts, were produced with 50 kg hot state experiments. The following forging and heat treatment procedures were kept consistent to ensure that the only controlled variable is inclusion. The fatigue properties were compared and the inclusions that triggered the fatigue cracks were analyzed to deduce the critical sizes of inclusions in terms of fatigue failure. The results show that the critical sizes of different inclusion types vary in bearing steels. The critical size of the spinel is 8.5 μm and the critical size of the calcium aluminate is 13.5 μm under the fatigue stress of 1200 MPa. In addition, with the increase of the cleanliness of bearing steels, the improvement of fatigue properties will reach saturation. Under this condition, further increasing of the cleanliness of the bearing steel will not contribute to the improvement of fatigue property for the investigated alloy and process design.

scholarly journals Experimental Study on the Effects of Stress Variations on the Permeability of Feldspar-Quartz Sandstone

Geofluids ◽  
2017 ◽  
Vol 2017 ◽  
pp. 1-15 ◽  
Author(s):  
Fugang Wang ◽  
Zhaoxu Mi ◽  
Zhaojun Sun ◽  
Xufeng Li ◽  
Tianshan Lan ◽  
...  
Keyword(s):  
Injection Pressure ◽  
Confining Pressure ◽  
Repeated Loading ◽  
Micropore Structure ◽  
Injection Process ◽  
Reservoir Permeability ◽  
Stress Changes ◽  
Cyclic Variations ◽  
Loading And Unloading ◽  
Stress Variations

The multistage and discontinuous nature of the injection process used in the geological storage of CO2 causes reservoirs to experience repeated loading and unloading. The reservoir permeability changes caused by this phenomenon directly impact the CO2 injection process and the process of CO2 migration in the reservoirs. Through laboratory experiments, variations in the permeability of sandstone in the Liujiagou formation of the Ordos CO2 capture and storage (CCS) demonstration project were analyzed using cyclic variations in injection pressure and confining pressure and multistage loading and unloading. The variation in the micropore structure and its influence on the permeability were analyzed based on micropore structure tests. In addition, the effects of multiple stress changes on the permeability of the same type of rock with different clay minerals content were also analyzed. More attention should be devoted to the influence of pressure variations on permeability in evaluations of storage potential and studies of CO2 migration in reservoirs in CCS engineering.

A new approach for pre-stressing of rail-end-bolt holes

2016 ◽  
Vol 231 (12) ◽  
pp. 2275-2283 ◽  
Author(s):  
JT Maximov ◽  
GV Duncheva ◽  
IM Amudjev ◽  
AP Anchev ◽  
N Ganev
Keyword(s):  
Fatigue Life ◽  
Fatigue Cracks ◽  
New Technology ◽  
Innovative Technology ◽  
Bolted Joint ◽  
Compressive Stresses ◽  
Process Formation ◽  
Technology Process ◽  
Bolt Holes ◽  
Hoop Stresses

Bolted joint railroad is the subject matter of this paper. Rail joint elements are subjected to cyclic and impact loads as a result of the passage of trains, which causes the origination and growth of fatigue cracks occurring, in most cases, around the bolt holes. Fatigue failure around rail-end-bolt holes is particularly dangerous because it leads to derailment of trains and, consequently, to inevitable accidents. Moreover, the cracking at rail-ends, which starts from bolt hole surface, causes premature rails replacement. The presence of residual compressive hoop stresses around the bolted holes, which is achieved by prestressing of these holes, extends the fatigue life of bolted joint railroads. This article presents an innovative technology for pre-stressing of rail-end-bolt holes, implemented on a vertical machining centre of Revolver vertical (RV) type. Two consecutive operations are involved in the manufacturing technology process: formation of the hole by drilling, reaming and making of a chamfer through a new combined cutting tool; cold hole working by spherical motion cold working through a new tool equipment, which minimizes the axial force on the reverse stroke. The new technology introduces beneficial residual compressive stresses around the bolted holes thereby preventing the fatigue cracks growth and increasing the fatigue life of these openings.

Energy Storing and Positional Tendon Fascicles Exhibit Different Fatigue Behaviour

2013 ◽  
Author(s):  
J. H. Shepherd ◽  
K. Legerlotz ◽  
T. Demirci ◽  
C. Klemt ◽  
G. P. Riley ◽  
...  
Keyword(s):  
Fatigue Failure ◽  
Potential Benefit ◽  
Fatigue Behaviour ◽  
Repeated Loading

Overuse tendinopathies are often considered to be the result of repeated microstrain below the failure threshold, analogous to the fatigue failure of materials under repeated loading [1, 2]. Investigation of tendon overuse in vitro is thus of potential benefit towards characterizing the progression of damage.

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