scholarly journals Defects of steel crane beams and methods of their strengthening

2020 ◽  
Vol 212 ◽  
pp. 02016
Author(s):  
Andrei Shuryn ◽  
Anatoli Mukhin ◽  
Alexandr Bryantsev
Keyword(s):  
Fatigue Damage ◽  
Fatigue Cracks ◽  
Negative Influence ◽  
Truss Structure ◽  
Shear Stresses ◽  
Building Structures ◽  
Technological Processes ◽  
Local Stresses ◽  
Damaged Beams ◽  
Main Factors

Crane structures are the most vulnerable in buildings and structures because of their early wear in comparison with other building structures. The wear of crane structures is because of the appearance and the development of fatigue damage nature. The article presents the constructive solutions developed by the authors for strengthening the structures of steel crane beams with conventional and corrugated walls which allow to reduce the influence of the negative influence of installation, operation and technological processes on their operational durability. The most dangerous installation defect is the displacement of the crane rail axis relative to the axis of the crane beams wall. Value of this shift is exceeded several times in the cases considered below. It is proposed to use crane beams with corrugated walls to solve this problem. The authors have developed and implemented a project to restore the performance of steel crane beams by strengthening the walls of damaged beams without stopping production. Strengthening was performed on the outside of the eccentricities of the application of loads from crane rails by creating a truss structure parallel to the I-beam with chords of I-beams, which made it possible to significantly reduce the magnitude of local stresses from moments, the magnitude of transverse forces and consequently shear stresses, which are the main factors in the appearance and development of fatigue cracks in their walls.

Modeling Multiaxial Fatigue Damage Using Polar Equations

2017 ◽  
Author(s):  
Jafar Albinmousa ◽  
Syed Haris Iftikhar ◽  
Mustafa Al-Samkhan
Keyword(s):  
Fatigue Damage ◽  
Fatigue Cracks ◽  
Closed Form Solution ◽  
Damage Parameter ◽  
Multiaxial Fatigue ◽  
Loading Path ◽  
Shear Stresses ◽  
Critical Plane ◽  
Stress Strain ◽  
Loading Paths

It is estimated that more than 70% of failures in engineering components are associated with fatigue loading. Therefore, fatigue is a major design tool for mechanical components. These components are usually subjected to multiaxial cyclic loading. In fact, multiaxial state is very common as tension specimen is under triaxial strain state even though its stress state is uniaxial. There are three approaches to modeling fatigue damage: stress, strain and energy. Critical plane concept is established based on the fact that fatigue cracks initiate at specific plane(s), therefore, multiaxial fatigue damage parameter is evaluated at these plane(s). Critical plane fatigue models such as Fatemi-Socie is among the popular strain-based models. Because it was shown to provide estimation mostly within two factors of life for different materials and different multiaxial loading conditions. This paper presents a new method for analyzing critical plane damage parameters. Using plane stress-strain transformation, maximum values of normal and shear stresses and strains from hysteresis loops are obtained at 360 planes. Plotting these values on polar diagrams shows that multiaxial cyclic responses represent polar curves that can successfully be fitted with definitive known polar equations. In principle, this means that both critical plane and fatigue damage can be determined analytically for a given loading path. However, fitting constants must first be determined. A systematic analysis is performed on different experimental data that were obtained by testing two extruded magnesium alloys at proportional and 90° out of phase loading paths. A closed-form solution for Fatemi-Socie damage parameter is presented for these two loading paths.

Plastic Slip and Early Stage of Fatigue Damage in Polycrystals: Comparison between Experiments and Crystal Plasticity Finite Elements Simulations

2014 ◽  
Vol 891-892 ◽  
pp. 1711-1716 ◽  
Author(s):  
Loic Signor ◽  
Emmanuel Lacoste ◽  
Patrick Villechaise ◽  
Thomas Ghidossi ◽  
Stephan Courtin
Keyword(s):  
Fatigue Crack ◽  
Finite Elements ◽  
Crack Initiation ◽  
Fatigue Damage ◽  
Crystal Plasticity ◽  
Early Stage ◽  
Low Cycle Fatigue ◽  
Fatigue Cracks ◽  
Fatigue Crack Initiation ◽  
Plastic Slip

For conventional materials with solid solution, fatigue damage is often related to microplasticity and is largely sensitive to microstructure at different scales concerning dislocations, grains and textures. The present study focuses on slip bands activity and fatigue crack initiation with special attention on the influence of the size, the morphology and the crystal orientation of grains and their neighbours. The local configurations which favour - or prevent - crack initiation are not completely identified. In this work, the identification and the analysis of several crack initiation sites are performed using Scanning Electron Microscopy and Electron Back-Scattered Diffraction. Crystal plasticity finite elements simulation is employed to evaluate local microplasticity at the scale of the grains. One of the originality of this work is the creation of 3D meshes of polycrystalline aggregates corresponding to zones where fatigue cracks have been observed. 3D data obtained by serial-sectioning are used to reconstruct actual microstructure. The role of the plastic slip activity as a driving force for fatigue crack initiation is discussed according to the comparison between experimental observations and simulations. The approach is applied to 316L type austenitic stainless steels under low-cycle fatigue loading.

scholarly journals Improvement of trawler hull structure under condition of ensuring fatigue strength

2021 ◽  
Vol 4 (7(112)) ◽  
pp. 50-59
Author(s):  
Leontii Korostylov ◽  
Dmytro Lytvynenko ◽  
Hryhorii Sharun ◽  
Ihor Davydov
Keyword(s):  
Fatigue Strength ◽  
Fatigue Damage ◽  
Hot Spot ◽  
Fatigue Cracks ◽  
Bending Moment ◽  
Theoretical Method ◽  
Corrosive Wear ◽  
Hot Spot Stress ◽  
Hull Structure ◽  
Internal Forces

The structure of the hull of the project 1288 trawler in a region of fore hold was improved to ensure fatigue strength of assemblies of the intersection of main frames with the second bottom. To this end, a study of the fatigue strength of these assemblies was carried out for the original side structure and two versions of its modernization. Values of internal forces at the points of appearance of fatigue cracks in the compartment have been determined for three design versions of the side. It was found that the greatest forces act in the middle of the fore half of the compartment. Calculations of parameters of the long-term distribution of magnitudes of ranges of total equivalent operating stresses according to the Weibull law in the points of occurrence of fatigue cracks for different design versions of the side grillage have been performed. These parameters were determined for the middle of the fore hold of the vessel and for the areas in which maximum values of bending moment ranges are in effect with and without corrosive wear. Values of total fatigue damage and durability of the studied assemblies were determined. Calculations were carried out by nominal stress method, hot spot stress method, and experimental and theoretical method. It was shown that in order to ensure fatigue strength of the assembly under consideration, it is necessary to extend the intermediate frames of the original version of the side structure to the level of the second bottom fixing them to the deck. It is also necessary to attach a cargo platform to the side thus reducing the frame span. As a result, the level of fatigue damage over 25 years of operation will decrease by about 3.5 times. As it was found, approximate consideration of the slamming effect does not significantly increase the amount of fatigue damage to the assembly. The results of the development of recommendations for modernization of the side structure can be implemented both on ships of the 1288 project and on other ships with a transverse side framing system.

Investigation of Thermal Fatigue Characteristics of Charging Line of RCV in PWR

2017 ◽  
Author(s):  
Naeem Ahmad ◽  
XiangBin Li ◽  
Iftikhar Ahmad ◽  
Nan Li ◽  
Shahroze Ahmed ◽  
...  
Keyword(s):  
Fatigue Damage ◽  
Thermal Fatigue ◽  
Nuclear Power ◽  
Thermal Loading ◽  
Structural Model ◽  
Fatigue Cracks ◽  
Volume Control ◽  
Piping System ◽  
Thermal Transients ◽  
Fatigue Evaluation

Nuclear Power Plant (NPP) components need to tolerate thermal constraints, internal pressure and thermal transients. These thermal transients being repeated again and again can lead to thermal fatigue of the component. It has significant effect on the degradation of the NPP components in long term. Studies of thermal fatigue on different NPP components such as mixing tees and valves have been carried out before but the charging line in the chemical and volume control system (RCV) of the NPP seems to have been ignored for thermal fatigue analysis. Charging Line is the connection from RCV towards Reactor Coolant System (RCP). To enhance the safety of the charging line, thermal fatigue evaluation of piping system was performed using the Fluid Structure Interaction (FSI) analysis. Temperature distributions in the pipes were determined via thermal hydraulic analysis (CFX) and the results were applied to the structural model of the piping system to determine the thermal stress (Transient Structural). Results revealed the location of fatigue cracks. Types of stress were identified that caused the fatigue damage. The CFD analysis enabled us to clarify the role of turbulence with respect to the thermal loading of the structure. The study will provide valuable information for establishing a permanent methodology to help minimize thermal fatigue damage in NPP components.

Using deformation modes to identify cracks in turbine engine compressor disks

2009 ◽  
Vol 113 (1150) ◽  
pp. 811-819
Author(s):  
R. A. Brockman ◽  
R. John ◽  
M. A. Huelsman
Keyword(s):  
Fatigue Damage ◽  
Fatigue Cracks ◽  
Measurement Techniques ◽  
Analytical Models ◽  
Worst Case ◽  
Turbine Engine ◽  
Combined Use ◽  
Engine Compressor ◽  
Extent Of Damage ◽  
Vibration Signatures

Abstract Recent studies show that analytical predictions of crack growth in rotating components can be used in conjunction with displacement measurement techniques to identify critical levels of fatigue damage. However, investigations of this type traditionally have focused on the detection of damage at known flaw locations. This paper addresses the related problem of estimating damage associated with flaws at unknown locations, through the combined use of analytical models and measured vibration signatures. Because the measured data are insufficient to identify a unique solution for the location and severity of fatigue cracks, the function of the analytical model is to bound the extent of damage occurring at life-limiting locations. The prediction of remaining life based on estimates of worst-case fatigue damage and crack locations also is discussed.

Micromechanics of an Extrusion in High-Cycle Fatigue With Creep

1990 ◽  
Vol 57 (4) ◽  
pp. 815-820 ◽  
Author(s):  
T. H. Lin ◽  
S. R. Lin ◽  
X. Q. Wu
Keyword(s):  
Crack Initiation ◽  
Tensile Strain ◽  
High Cycle Fatigue ◽  
Elevated Temperatures ◽  
Fatigue Cracks ◽  
Fatigue Crack Initiation ◽  
Tensor Component ◽  
Shear Stresses ◽  
Cycle Fatigue ◽  
Thin Slice

Extrusions and intrusions often are sites of fatigue cracks. The extent of extrusions is important in fatigue crack initiation. Metals often are subject to fatigue loadings at elevated temperatures. At temperatures below one half of the melting temperature slip is the main mechanism of inelastic deformation. In this study, an aluminum polycrystal loaded in this temperature range is considered. A most favorably oriented crystal located at a free surface of a f.c.c. polycrystal subject to creep under cyclic tension and compression of high-cycle fatigue is considered. An extrusion in this crystal is shown to be produced by a positive slip in one thin slice “P” and a negative slip in a closely located slice “Q”. An initial tensile strain εααI in the thin slice “R” sandwiched between P and Q causes a positive initial shear stress ταβI in P and a negative one in Q. It is shown that the extrusion growth causes a tensile strain in R, which can activate a second slip system giving a creep strain with a tensor component εαα. It has the same effect as the initial strain εααI in causing this difference in shear stresses in P and Q and gives much additional extrusion growth. The extent of intrusion and extrusion is important in this study of crack initiation.

Development of a Quantifiable Approach in Monitoring the Fatigue Cracks Using Digital Image Correlation

2016 ◽  
Vol 701 ◽  
pp. 211-215
Author(s):  
Sze Wei Khoo ◽  
Saravanan Karuppanan ◽  
Ching Seong Tan
Keyword(s):  
Digital Image Correlation ◽  
Fatigue Damage ◽  
Digital Image ◽  
Fatigue Cracks ◽  
Image Correlation ◽  
Correlation Technique ◽  
Digital Image Correlation Technique ◽  
Deformation Parameters ◽  
Industrial Grade ◽  
Number Of Cycles

From the viewpoint of engineering, fatigue is an important issue as most of the mechanical failures are associated with fatigue damage. In fact, these disastrous events had occurred unexpectedly during the regular working conditions and most of the time the applied stresses are well below the yield strength of the material. Thus, it makes the prediction of fatigue damage a challenging task in the field of engineering, especially when the manmade structures and machines are getting more complex than before. Even though fatigue has been studied extensively in the past 170 years, many limitations are still being found within the current fatigue analysis, testing and the non-destructive inspection. Hence, there is a great need to develop a precise and yet efficient inspection technique in quantifying the fatigue cracks. Therefore, the objective of this study is to develop a quantifiable approach in monitoring the fatigue cracks using digital image correlation technique. This can be achieved by using a developed two-dimensional sub-pixel accuracy deformation measurement algorithm which determines the deformation parameters of the first-order shape function of a material subjected to cyclic loading. Next, fatigue tests for samples made of mild steel (Grade: JIS G 3101 SS400) were conducted in accordance to the ASTM E466. Simultaneously, an industrial grade camera was used to capture the fatigue crack’s region at a specific interval until the sample broke into two pieces. The captured images were then analysed and the deformation parameters such as translations, normal and shear strains values were determined by using the developed digital image correlation algorithm. Based on the determined deformation patterns, a specific trend was observed throughout the graphs of respective deformation parameters against the number of cycles. Besides, drastic changes were observed when the average number of cycles was approaching 95.5% (min. loading) and 93.8% (max. loading) of the total fatigue life. In conclusion, the digital image correlation technique was proven to be capable in monitoring the severity of a fatigue crack and the proposed monitoring system would serve as an inspection technique in examining the fatigue damage of a structural component throughout its operational period.

Analysis of Factors Influencing the Performance of Q460 Steel

2014 ◽  
Vol 599-601 ◽  
pp. 7-11
Author(s):  
Zhu Ling Yan
Keyword(s):  
Mechanical Properties ◽  
Engineering Application ◽  
Steel Structures ◽  
Building Structures ◽  
Practical Application ◽  
Widespread Application ◽  
Factors Influencing ◽  
Steel Building ◽  
Practical Engineering ◽  
Main Factors

With the development of technology, steel structures have been gaining increasingly widespread application, and the scope of research of steel types is also becoming increasingly broad. In addition to the four common steels used in construction, various mechanical properties and practical application of Q460 steel have also been studied at home and abroad at present. This paper introduces the research status of Q460 steel, describes its mechanical properties and the requirements for steels used in steel building structures, and analyzes the main factors influencing the properties of Q460 steel, providing some reference for practical engineering application of Q460 steel.

scholarly journals What Are the Most Important Factors Influencing Springtail Tetrodontophora bielanensis?

Insects ◽  
2021 ◽  
Vol 12 (10) ◽  
pp. 858
Author(s):  
Strahinja Mladenović ◽  
Jan Materna ◽  
Tereza Brestovanská ◽  
Jakub Horák
Keyword(s):  
Spatial Distribution ◽  
Czech Republic ◽  
Negative Influence ◽  
Positive Influence ◽  
Cold Climate ◽  
The Czech Republic ◽  
Soil Layers ◽  
Factors Influencing ◽  
Main Factors ◽  
Landscape Level

The springtail, Tetrodontophora bielanensis, dwells in the litter and upper soil layers. This arthropod mainly inhabits humid litter and soil and prefers a cold climate. We determined the main factors influencing this springtail in forests at the landscape level in Krkonoše and site level in Orlické hory in the Czech Republic. We used passive trunk-tree traps. These traps are highly effective for sampling flightless fauna. We used 128 traps in Krkonoše and 17 traps in Orlické hory. The springtail was significantly positively influenced by the presence of Norway spruce (Picea abies) at the landscape level. Springtails’ abundance was, furthermore, influenced by the spatial distribution of the sampling sites. The negative influence of bark coverage and the presence of fungi, and positive influence of an increasing dimension of trees were significant at the site level. We argue for a more diversified management of mountainous forests with respect to forest history. This appears to be also important for mountainous forests in protected areas.

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