scholarly journals Fatigue life research of welded joints in railway girder

2020 ◽  
Vol 7 (2) ◽  
Author(s):  
Kirill Zhunev ◽  
Jurij Murovannyj ◽  
Andrey Yashnov
Keyword(s):  
Fatigue Life ◽  
Welded Joints ◽  
High Cycle Fatigue ◽  
Crack Formation ◽  
Fatigue Cracks ◽  
Moving Load ◽  
Moving Loads ◽  
Reliable Prediction ◽  
Strain Monitoring ◽  
Complex Tensor

Progressive crack formation in welded joints of railway girders requires a reliable prediction of the fatigue life. It was found that the most common fatigue cracks are T-9 and T-10, which are formed in welded joints of vertical stiffeners to the beam web. The service life calculation of such joints, according to guideline, shows overestimated results. To reduce the error, the operational features of these joints were investigated under a moving loads. Stress-strain monitoring was carried out with the help of a small-sized automated tensometric complex «Tensor-MS». In total, 13 trussed and solid-web girders were investigated. As a result, it was found that the beam web near the welded ends of stiffeners subjected to bending deformations, but fatigue curves, obtained under tensile-compressive, are used to calculate the durability of such joints. To increase the reliability of fatigue calculation, laboratory tests were carried out for a high-cycle fatigue of welded specimens, simulating joints with T-9, T-10 cracks. The design and materials of laboratory specimens were assigned similarly to that of the main beams or the floor beams. Analysis of the actual stresses under the moving load revealed the necessary loading conditions for laboratory specimens. Totally, 42 laboratory samples were tested for bending. As a result of the tests, fatigue curves of welded joints were obtained. The results show a decrease in the joints durability by 20–50 % in comparison with the samples tested in tensile-compressive. In addition, as a result of the tests, the dependences of the fatigue cracks growth rate on the maximum cycle stresses were obtained.

Fatigue Life Prediction of Microstructures

2012 ◽  
Author(s):  
Gustavo M. Castelluccio ◽  
David L. McDowell
Keyword(s):  
Grain Size ◽  
Life Prediction ◽  
High Cycle Fatigue ◽  
Crack Formation ◽  
Fatigue Cracks ◽  
Fatigue Crack Initiation ◽  
Modeling Framework ◽  
Small Cracks ◽  
Engineering Alloys ◽  
Bimodal Grain Size

The formation and early growth of fatigue cracks in the high cycle fatigue regime is influenced by microstructuctural features such as grain size and morphological and crystallographic texture. However, most fatigue models do not predict the influence of the microstructure on early stages of crack formation, or they employ parameters that should be calibrated with experimental data from specimens with microstructures of interest. These post facto strategies are adequate to characterize materials, but they are not fully appropriate to aid in the design of fatigue-resistant engineering alloys. This paper presents a modeling framework that facilitates relative assessment of fatigue resistance among different microstructures. The scheme employs finite element simulations that explicitly render the microstructure and a methodology that estimates transgranular fatigue growth for microstructurally small cracks on a grain-by-grain basis, including consideration of growth within grains (embedded analytically) and stress redistribution as the cracks extend. The methodology is implemented using a crystal plasticity algorithm in ABAQUS and calibrated to study fatigue crack initiation of a bimodal grain size distribution found in RR1000 powder processed Ni-base superalloys for turbine disk applications.

Fatigue Life of Welded Joints of High-Strength Structural Steel S960QL

2016 ◽  
Vol 250 ◽  
pp. 169-174 ◽  
Author(s):  
Tomasz Slezak ◽  
Lucjan Sniezek
Keyword(s):  
Fatigue Life ◽  
Structural Steel ◽  
Welded Joints ◽  
Low Cycle Fatigue ◽  
Fatigue Cracks ◽  
Fatigue Cracking ◽  
High Strength ◽  
Propagation Rate ◽  
Total Strain Amplitude ◽  
Fatigue Life Analysis

The article presents the results of research on low cycle fatigue strength of welded joints of structural steel S960QL. Two types of butt welds were analysed: I-joints and V-joints. The tests were performed under load controlled using the total strain amplitude εac. Fatigue life analysis was conducted based on the Manson-Coffin-Basquin equation, which made it possible to determine fatigue parameters. High concordance was found of the adopted description model with experimental results. Studies have shown differences in the fatigue life of the various joints analysed, wherein I-joints showed about 20-50% higher fatigue life. Fractographic tests of fatigue fractures in joints revealed the details of fatigue cracking and differences in the propagation rate of fatigue cracks.

Fatigue crack growth behavior of rib-to-deck double-sided welded joints of orthotropic steel decks

2020 ◽  
pp. 136943322096175
Author(s):  
Yang Liu ◽  
Fanghuai Chen ◽  
Da Wang ◽  
Naiwei Lu
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Crack Growth ◽  
Welded Joints ◽  
Mixed Mode ◽  
Fatigue Cracks ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Fatigue Crack Growth Behavior ◽  
Orthotropic Steel Decks

Innovative double-sided welding is expected to improve the fatigue resistance of rib-to-deck welded joints of orthotropic steel decks (OSDs). Welding crack-like defects are the crucial issue affecting the fatigue performance of rib-to-deck double-sided welded joints. This study presents a numerical simulation of three-dimensional (3D) mixed mode fatigue crack growth behavior of rib-to-deck double-sided welded joints of OSDs. Maximum tensile stress theory and equivalent stress intensity factor (SIF) were used to simulate mixed mode fatigue cracks growth. The Paris law model was employed to predict the fatigue life. Fatigue cracks of rib-to-deck double-sided welded joints were characterized by the presence of mixed mode cracks of modes I (open), mode II (shear), and mode III (tear), which was dominated by mode I. The equivalent SIF was found to be complex at the growth stage with the maximum value at the two ends of the crack front and the minimum value at the midpoint of the crack front. The crack shape became flatter in the later phase of the crack growth. The fatigue crack surface underwent deflections during crack growth, making the final crack shape exhibiting the characteristic of a spatial curved surface. The initial crack geometry showed a significant impact on the fatigue life.

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.

Very High Cycle Fatigue Properties of Welded Joints under High Frequency Loading

2013 ◽  
Vol 647 ◽  
pp. 817-821
Author(s):  
Chao He ◽  
Yong Jie Liu ◽  
Qing Yuan Wang
Keyword(s):  
Base Metal ◽  
Welded Joints ◽  
High Cycle Fatigue ◽  
Low Cycle Fatigue ◽  
Fatigue Cracks ◽  
Ambient Air ◽  
Cycle Fatigue ◽  
Very High Cycle Fatigue ◽  
Ultrasonic Fatigue ◽  
Very High

Very high cycle fatigue (VHCF) properties of welded joints under ultrasonic fatigue loading have been investigated for titanium alloy (TI-6Al-4V) and bridge steel (Q345). Ultrasonic fatigue tests of base metal and welded joints were carried out in ambient air at room temperature at a stress ratio R=-1. It was observed that the fatigue strength of welded joints reduced by 50-60% as compared to the base metal. The S-N fatigue curves in the range of 107~109 cycles of base metal and welded joints for both materials exhibited the characteristic of continually decreasing type. The fatigue failure still occurred after 107 cycles of loading, and the fatigue limit in traditional does not exist. The fatigue facture mainly located in the weld metal region at low cycle fatigue range, but in the fusion area in HCF and VHCF. Analysis of fracture surfaces analyzed by SEM revealed that the fatigue cracks initiated from welding defects such as pores, cracks and inclusions.

Simulation and Prediction Method of the Fatigue Cracks Life for Remanufacturing Shaft Parts

2014 ◽  
Vol 684 ◽  
pp. 291-296
Author(s):  
Yan Feng ◽  
Shou Xu Song ◽  
Qing Di Ke
Keyword(s):  
Fatigue Life ◽  
Life Prediction ◽  
Crack Formation ◽  
Fatigue Cracks ◽  
Prediction Method ◽  
Service Condition ◽  
Simulation Method ◽  
Element Analysis ◽  
Relationship Of ◽  
The Relationship

Combining the method of finite element analysis with fatigue life prediction, fatigue cracks on the shaft parts is analyzed with cyclic loading. Analyzing the shafts with different sizes of cracks in different locations, a simulation modal is established. Informed by analytical and numerical simulation method, the crack formation and propagation life could be calculated. With considering the relationship of "Frequency - crack - fatigue life - remanufacturing ", the remanufacturability of the shaft parts might be evaluated based on service condition. And in this paper, a more convenient way to detecting and predicting the fatigue cracks on shaft parts is given.

Very high cycle fatigue behavior of dissimilar martensitic stainless-steel diffusion-bonded joints

2019 ◽  
Vol 9 (9) ◽  
pp. 1120-1126
Author(s):  
Baohua Nie ◽  
Zihua Zhao ◽  
Dongchu Chen ◽  
Fangjun Liu ◽  
Jishi Zhao ◽  
...  
Keyword(s):  
Fatigue Life ◽  
High Cycle Fatigue ◽  
Fatigue Behavior ◽  
Fatigue Cracks ◽  
Fatigue Property ◽  
Bonded Joints ◽  
Cycle Fatigue ◽  
Shape Characteristic ◽  
Very High Cycle Fatigue ◽  
Very High

Very high cycle fatigue (VHCF) behavior of the diffusion bonded joints between 3Cr13 and 2Cr13 were investigated. Results showed that the diffusion bonded joints obtained a comparable fatigue property of 2Cr13, and the S–N curves exhibited a decreasing shape characteristic. However, fatigue life was dramatically decreased by occasional non-diffusion defects. Fatigue cracks in diffusion bonded joints occurred at specimen's surface in high cycle regimes, whereas VHCF cracks were originated from inclusions on the side of 2Cr13 based materials, in which the fine granular area (FGA) characteristics were observed around the internal inclusion. Furthermore, fatigue strength of the diffusion joints was interpreted based on the Murakami model. The crack propagation life estimated by Paris-Hertzberg-McClintock model mainly contributed for the fatigue life of the specimens with occasional non-fusion defects, in which non-fusion defects acted as pre-cracks.

scholarly journals Prediction of Fatigue Life of Welded Joints Made of Fine-Grained Martensite-Bainitic S960QL Steel and Determination of Crack Origins

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Tomasz Ślęzak
Keyword(s):  
Experimental Data ◽  
Fatigue Life ◽  
Welded Joints ◽  
Life Prediction ◽  
Notch Root ◽  
Fatigue Cracks ◽  
Strain Range ◽  
Carbon Steels ◽  
Fatigue Life Prediction ◽  
The Impact

Due to growing requirements connected with the utilization of advanced structures, nowadays the modern design processes are developed. One of the crucial issues considered in these processes is proper design of the joints against fatigue in order to fulfill a stated life of operation. In this study, the method of fatigue life prediction based on the criterion of permissible strain range in the notch root is presented. An engaged simplified model of fatigue life prediction was previously developed for mild and carbon steels. The evaluation made during the research has proven that this method can also be used for S960QL high-strength steel characterized by entirely different properties and structure. A considered theoretical model demonstrates satisfactory correlation with experimental data and safely describes the fatigue life of weldments. Furthermore, the predicted fatigue life of studied steel without welds shows great comparability with experimental data. The limit value of the strain range in the notch root was estimated. Below this value of strain, the fatigue life of welded joints is infinite, theoretically. Finally, the impact of the surface imperfections on the fatigue crack initiation was revealed. For paternal material, the origins of cracking were discovered at the places of nonmetallic scale particles. In welded joints, the fatigue cracks initiated at the whole length of the fusion line.

Improve the Fatigue Performance of Welded Joints with Undercuts by TIG Dressing Treatment

2012 ◽  
Vol 472-475 ◽  
pp. 1300-1304 ◽  
Author(s):  
Liang Chen Wu ◽  
Dong Po Wang
Keyword(s):  
Fatigue Life ◽  
Fatigue Strength ◽  
Adverse Effects ◽  
Dynamic Loading ◽  
Weld Joint ◽  
Welded Joints ◽  
Fatigue Cracks ◽  
Fatigue Property ◽  
Fatigue Performance ◽  
Weld Toe

Undercuts often exists in the surface at weld toe. Undercuts affects the capability of weld subjected to dynamic loading greatly and fatigue cracks usually initiate from these zones with undercuts. Combining with low-alloy middle strength steel 16Mn，study of increasing the fatigue strength and the fatigue life was carried out. Compared with specimen without defects, the fatigue strength of specimen with undercuts has been increased by 10~20%. Study also shows that comparing with as-welded specimen with defects, with TIG dressing treatment, fatigue strength of cruciform weld joint of steel 16Mn has been increased by 70%, fatigue life by 5~8 times. Compared with as-welded specimen without defects, fatigue strength has been increased by 34%, fatigue life by 3~4 times. Undercuts have no adverse effects on fatigue property of welded joints under TIG dressing.

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