Research on the Propagation Characteristics of Fatigue Cracks on Rail Surfaces

2021 ◽  
pp. 2050121
Author(s):  
Ruipeng Gao ◽  
Shanshan Fan
Keyword(s):  
Crack Growth ◽  
Fatigue Cracks ◽  
Three Dimensional ◽  
Cyclic Loads ◽  
Propagation Characteristics ◽  
Ansys Software ◽  
Expansion Curve ◽  
Simulation Results ◽  
The Law ◽  
Experimental Findings

To solve the problem of rail crack propagation, inadequate studies mainly use a two-dimensional (2D) model for macroscopic crack analysis owing to the failure of accurately reflecting the contact status between the wheel and rail. In this work, we use ANSYS software to establish a three-dimensional (3D) wheel–rail contact model to clarify the microcracks on the rail tread. The influence of the number of horizontal and vertical cyclic loads during the rail’s fatigue crack growth is analyzed. The results suggest that as the number of vertical and tangential cyclic loads increases, the length of the rail crack increases. Using experiments to verify the law between the number of cyclic loads and rail crack growth length, the experimental findings proved that the law of crack growth is basically consistent with the aforementioned simulation results and the outcome of the Paris expansion curve, verifying the validity of the simulation results.

The Law of Crack Growth Life Under Load Controlled Creep-Fatigue Conditions for W-Added 12% Cr Steel

2016 ◽  
Author(s):  
Yoshiko Nagumo ◽  
A. Toshimitsu Yokobori ◽  
Takahiro Fukuda ◽  
Yoshiki Takahashi ◽  
Ryuji Sugiura
Keyword(s):  
Crack Growth ◽  
Three Dimensional ◽  
Turbine Rotor ◽  
Resistant Steel ◽  
Heat Resistant Steel ◽  
Heat Resistant ◽  
Creep Fatigue ◽  
The Law ◽  
Cycle Dependent ◽  
Dependent Mechanism

W-added 12% Cr ferritic heat resistant steel has been used as a steam turbine rotor material. The turbine rotor material is damaged by high temperature creep and fatigue due to starts and stops and changing load of power generation, which results in crack initiation and growth. In the studies done before, the law of crack growth life under creep-fatigue conditions was characterized and clarified that the characteristics of crack growth life of various load frequencies under different temperatures change from fatigue to creep behavior through an inflection region. The law of crack growth life under creep-fatigue interactive conditions has been reported and evaluated by monotonous linear law. On the other hand, it has been indicated that the characteristics of crack growth life under creep-fatigue condition can be represented mathematically by a three dimensional characteristic curved surface based on non-equilibrium science. In this study, crack growth tests using standardized C(T) specimens of W-added 12% Cr ferritic heat resistant steel were conducted under various conditions of stress holding time, applied stress and temperature. To evaluate the effect of cycle dependent and time dependent mechanisms on crack growth life, a method of separate estimation of cycle dependent mechanism from the time dependent mechanism based on the concept of three dimensional characteristic curved surface based on non-equilibrium science were used. As a result, the effect of load frequency on crack growth life was characterized and the predictive law of crack growth life for W-added 12% Cr ferritic heat resistant steel under creep-fatigue interactive conditions based on the concept of Q* with the transition function of crack growth life was estimated.

The Influence of Stress Ratio on Changes in Magnetic Flux Density around Fatigue Crack Tips of Carbon Tool Steel

2011 ◽  
Vol 83 ◽  
pp. 210-215 ◽  
Author(s):  
Takashi Honda ◽  
Katsuyuki Kida ◽  
Edson Costa Santos ◽  
Hitonobu Koike ◽  
Justyna Rozwadowska ◽  
...  
Keyword(s):  
Magnetic Flux ◽  
Crack Growth ◽  
Flux Density ◽  
Tool Steel ◽  
Fatigue Cracks ◽  
Three Dimensional ◽  
Magnetic Flux Density ◽  
Hall Probe ◽  
Steel Component ◽  
Stress Ratios

Fatigue failure of steel occurs when cracks form in a component and continue to grow to a size large enough to cause fracture. In order to understand the strength of a steel component, it is important to locate these cracks. We developed a scanning Hall probe microscope (SHPM), equipped with GaAs film sensors to observe fatigue cracks at room temperature in air while they were growing. In our previous works [1,2], the correlation between crack growth and magnetic field in high carbon tool steels (JIS SKS93 and JIS SUJ2) were determined. We also reported the sensitivity of the SHPM equipped with a three-dimensional line-probe that was developed to decrease the sensor gaps. By using the line-probe sensor we succeeded to measure the magnetic flux density distributions in very close proximity to the specimen’s surface. However, in order to further understand the relation between magnetic flux density and crack growth, other materials, microstructures and fatigue test conditions should be evaluated. In the present work, we focus on the effect of stress ratios on the changes of the magnetic flux density in annealed carbon tool steel.

The Observation of Changes in the Magnetic Field due to the Crack Initiation under Different Stress Ratio Conditions

2011 ◽  
Vol 217-218 ◽  
pp. 1408-1413 ◽  
Author(s):  
Takashi Honda ◽  
Katsuyuki Kida ◽  
Edson Costa Santos ◽  
Justyna Rozwadowska ◽  
M. Uryu
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Crack Growth ◽  
Flux Density ◽  
Fatigue Cracks ◽  
Three Dimensional ◽  
Magnetic Flux Density ◽  
Hall Probe ◽  
Steel Component ◽  
Stress Ratios

Fatigue failure of steel occurs when cracks form in a component and continue to grow to a size large enough to cause fracture. In order to understand the strength of a steel component, it is important to locate these cracks. We developed a scanning Hall probe microscope (SHPM) equipped with GaAs films sensors and observed fatigue cracks at room temperature in air while they were growing. In our previous works, we determined the correlation between crack growth and magnetic field in high carbon tool steels (JIS SKS93 and JIS SUJ2). We also reported the sensitivity of the SHPM equipped with a three-dimensional line-probe that was developed to decrease the sensor gaps. By using the line-probe sensor we succeeded to measure the magnetic flux density distributions in very close proximity to the specimen’s surface. However, in order to further understand the relation between magnetic flux density and crack growth, other materials, microstructures and fatigue test conditions should be evaluated. In the present work, we focus on the effect of stress ratios on the changes of the magnetic flux density in annealed carbon tool steel.

Fatigue Crack Initiation and Propagation in SuperCMV Hollow Shafts with Transverse Holes

2011 ◽  
Vol 70 ◽  
pp. 141-146 ◽  
Author(s):  
Ran Li ◽  
W. Sun ◽  
Thomas H. Hyde ◽  
Edward J. Williams ◽  
Xing Guo Wang
Keyword(s):  
Fatigue Crack ◽  
Crack Initiation ◽  
Crack Growth ◽  
Fatigue Cracks ◽  
Fatigue Crack Initiation ◽  
Three Dimensional ◽  
Axial Loading ◽  
Maximum Principal Stress ◽  
Experimental Results ◽  
Three Dimensional Finite Element

A fatigue crack growth test program has been carried out on hollow, SuperCMV shaft specimens, with transverse holes, under combined torsional and axial loading. The experimental results show that fatigue cracks always initiated in the stress concentration areas, i.e., in the transverse holes. Up to four cracks were observed to be initiated at different positions near the holes in the shafts. The fatigue crack propagation was initially found to occur under Mode I conditions, followed by a period of mixed Mode II/III crack growth. Three dimensional, finite element, elastic-plastic analyses have also been conducted, in an attempt to predict the crack-initiation locations and lives. The predicted crack-initiation sites agree with the experimental observations, for a range of loading conditions. The initiation sites were found to be approximately on the planes of maximum principal stress. The predicted, torque-dominated, fatigue lives of the shafts, obtained by use of a stress-life (S-N) approach, correlate reasonably well with the experimental results.

Modeling and Simulation of Airflow Omnibearing Posture Sensor

2014 ◽  
Vol 889-890 ◽  
pp. 817-820
Author(s):  
Qi Rui Yang ◽  
Lin Hua Piao ◽  
Wen Jie Tian
Keyword(s):  
Finite Element Modelling ◽  
Three Dimensional ◽  
Ansys Software ◽  
Three Dimensional Modeling ◽  
Dimensional Modeling ◽  
Modelling Method ◽  
Dimensional Finite Element ◽  
Simulation Results ◽  
Three Dimensional Finite Element ◽  
Simulation Time

In order to improve the performance of sensor, Using ANSYS software, the three-dimensional finite element modelling method and simulation results of micromachined airflow omnibearing level posture sensor are presented. The results show that: (1)Using the sense organ’s symmetry characteristic, a half model is built first, which is convenient for modelling and observing the simulation results;(2) Gridding should be meshed more densely where fluid grads is large, which is helpful of saving simulation time and improving precision. Compared to two-dimensional modeling, the simulation results of three-dimensional modeling are more comprehensive and exact, which provides dependable basis for further research of the sensor.

Assessment of thermal behavior of a cooling system to reduce thermal fatigue cracks in aluminum injection molds

2020 ◽  
pp. 75-86
Author(s):  
Sergio Antonio Camargo ◽  
Lauro Correa Romeiro ◽  
Carlos Alberto Mendes Moraes
Keyword(s):  
Thermal Fatigue ◽  
Cooling System ◽  
Fatigue Cracks ◽  
Cooling Water ◽  
Thermal Conditions ◽  
Thermal Gradients ◽  
Ansys Software ◽  
Cooling Systems ◽  
Thermal Fatigue Cracks ◽  
Number Of Cycles

The present article aimed to test changes in cooling water temperatures of males, present in aluminum injection molds, to reduce failures due to thermal fatigue. In order to carry out this work, cooling systems were studied, including their geometries, thermal gradients and the expected theoretical durability in relation to fatigue failure. The cooling system tests were developed with the aid of simulations in the ANSYS software and with fatigue calculations, using the method of Goodman. The study of the cooling system included its geometries, flow and temperature of this fluid. The results pointed to a significant increase in fatigue life of the mold component for the thermal conditions that were proposed, with a significant increase in the number of cycles, to happen failures due to thermal fatigue.

scholarly journals Simulation and Nonlinearity Optimization of a High-Pressure Sensor

Sensors ◽  
2020 ◽  
Vol 20 (16) ◽  
pp. 4419
Author(s):  
Ting Li ◽  
Haiping Shang ◽  
Weibing Wang
Keyword(s):  
High Pressure ◽  
Pressure Sensor ◽  
Pressure Sensors ◽  
Original Model ◽  
Ansys Software ◽  
Nonlinear Error ◽  
Sensor Model ◽  
Optimized Model ◽  
Simulation Results ◽  
Better Than

A pressure sensor in the range of 0–120 MPa with a square diaphragm was designed and fabricated, which was isolated by the oil-filled package. The nonlinearity of the device without circuit compensation is better than 0.4%, and the accuracy is 0.43%. This sensor model was simulated by ANSYS software. Based on this model, we simulated the output voltage and nonlinearity when piezoresistors locations change. The simulation results showed that as the stress of the longitudinal resistor (RL) was increased compared to the transverse resistor (RT), the nonlinear error of the pressure sensor would first decrease to about 0 and then increase. The theoretical calculation and mathematical fitting were given to this phenomenon. Based on this discovery, a method for optimizing the nonlinearity of high-pressure sensors while ensuring the maximum sensitivity was proposed. In the simulation, the output of the optimized model had a significant improvement over the original model, and the nonlinear error significantly decreased from 0.106% to 0.0000713%.

scholarly journals 3D monitoring of the surface slippage effect on micro-particle sedimentation by digital holographic microscopy

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Majid Panahi ◽  
Ramin Jamali ◽  
Vahideh Farzam Rad ◽  
Mojtaba Khorasani ◽  
Ahamd Darudi ◽  
...  
Keyword(s):  
Slip Length ◽  
Particle Interaction ◽  
Three Dimensional ◽  
Digital Holographic Microscopy ◽  
Particle Sedimentation ◽  
Micro Particles ◽  
Slippage Effect ◽  
Holographic Microscopy ◽  
3D Information ◽  
Experimental Findings

AbstractIn several phenomena in biology and industry, it is required to understand the comprehensive behavior of sedimenting micro-particles in fluids. Here, we use the numerical refocusing feature of digital holographic microscopy (DHM) to investigate the slippage effect on micro-particle sedimentation near a flat wall. DHM provides quantitative phase contrast and three-dimensional (3D) imaging in arbitrary time scales, which suggests it as an elegant approach to investigate various phenomena, including dynamic behavior of colloids. 3D information is obtained by post-processing of the recorded digital holograms. Through analysis of 3D trajectories and velocities of multiple sedimenting micro-particles, we show that proximity to flat walls of higher slip lengths causes faster sedimentation. The effect depends on the ratio of the particle size to (1) the slip length and (2) its distance to the wall. We corroborate our experimental findings by a theoretical model which considers both the proximity and the particle interaction to a wall of different hydrophobicity in the hydrodynamic forces.

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