scholarly journals Study on Fatigue Degradation Behavior of a Cracked Rotor Subjected to Lateral Vibration

2018 ◽  
Vol 2018 ◽  
pp. 1-21 ◽  
Author(s):  
Qian Niu ◽  
Shi-xi Yang
Keyword(s):  
Nonlinear Vibration ◽  
Crack Growth ◽  
Coupling Effect ◽  
Coupling Model ◽  
Degradation Behavior ◽  
Cracked Rotor ◽  
Multiple Parameters ◽  
Degradation Failure ◽  
Degradation Behaviors ◽  
Unstable Vibration

Fatigue crack in a rotary shaft is a common failure observed in rotor systems. Since vibration of the shaft causes alternating fatigue loads, the crack propagates slowly. Meanwhile, the propagating crack may cause nonlinear or unstable vibration of the rotor system. In fact, growth of the crack and vibration of the shaft are coupled with each other. Hence, it is necessary to study the fatigue degradation behavior of the cracked rotor accounting for this coupling effect. In this paper, a coupling model of rotor vibration and crack growth is established through dynamic theory and fracture mechanics, and a sequential iterative procedure is proposed to solve the coupling model. Then, the competing degradation failure mode of the cracked rotor is analyzed with regard to the rapid crack growth failure and the unstable vibration failure. And degradation measures are proposed based on the competing degradation failure criterion. At last, degradation behaviors with the coupling effect of nonlinear vibration behavior and multiple parameters including rotation speed, unbalance eccentricity and orientation angle, and damping are investigated by numerical simulation. The results indicate that nonlinear vibration behavior and multiple parameters have considerable influence on the degradation behaviors, which present complex regularity. The findings are of significance to guide the safety design of the rotor system for long time operation and help to the further research on prognostics and lifetime prediction.

Research on Degradation Behavior of Airborne Rubber Products

2012 ◽  
Vol 466-467 ◽  
pp. 127-131
Author(s):  
Xiao Jie Zhang ◽  
Tong Min Jiang ◽  
Hua Luo ◽  
Xiao Rui Zhang
Keyword(s):  
Detailed Analysis ◽  
Failure Mechanism ◽  
Aging Process ◽  
Degradation Behavior ◽  
Degradation Model ◽  
Electronic Products ◽  
Rubber Seal ◽  
Degradation Behaviors ◽  
Conducting Research ◽  
And Storage

Due to the complex working and storage environment for airplanes, the consumptive failures of airborne products are unavoidable. Aiming at the problem that degradation behaviors that cause this kind of failures are frequently neglected, based on the concept of degradation for airborne products, a new method of conducting research that treats aging process as a critical degradation behavior is presented. According to the characteristics of airborne mechano-electronic products, steering engine is defined as a critical airplane airborne mechano-electronic product. Through detailed analysis of the vulnerable area of steering engine, the failure mechanism of aging of steering engine rubber seal is discussed. The degradation model of steering engine rubber seal is presented. Finally, feasibility of the method that replaces the research of degradation behavior of the airborne mechano-electronic products with that of aging is verified.

An Experimental Investigation of Sample–Fluid Heat Coupling Effect in Thermal Lens Technique

2020 ◽  
Vol 74 (10) ◽  
pp. 1274-1279
Author(s):  
Gustavo V.B. Lukasievicz ◽  
Leandro S. Herculano ◽  
Elizandra Sehn ◽  
Marcos P. Belançon ◽  
Stephen E. Bialkowski ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Thermal Lens ◽  
Coupling Effect ◽  
Coupling Model ◽  
Theoretical Description ◽  
Photothermal Effect ◽  
Wavefront Distortion ◽  
Absorbing Materials ◽  
Heated Area ◽  
Long Rod

Laser-induced wavefront distortion is detectable by several techniques based on the photothermal effect. The effect is probed by monitoring the phase shift caused by the bulging of the heated area, the photoelastic effects, and the spatial distribution of the refractive index within the sample and in the fluid surrounding it. A simple analytical solution for the wavefront distortion was only possible for low absorbing materials, with the assumption that the stresses obey either the thin-disk or the long-rod type distributions. Recently, a unified theoretical description for the laser-induced optical path change was proposed to overcome part of this limitation for weakly absorbing materials, regardless of its thickness. In this work, we perform an experimental investigation taking the sample–fluid heat coupling effect into account using the thermal lens technique. The experimental investigation presented here validates the unified model. In addition, we show that the heat-coupling model provides an alternative method to obtain physical properties of non-absorbing fluid by using a reference solid sample.

Detection of a Rotor Crack Based on the Nonlinear Vibration Diagnosis Using Periodic Excitation

2005 ◽  
Author(s):  
Yukio Ishida ◽  
Tsuyoshi Inoue
Keyword(s):  
Nonlinear Vibration ◽  
Equations Of Motion ◽  
Frequency Component ◽  
Dominant Frequency ◽  
Vibration Characteristics ◽  
Periodic Excitation ◽  
Cracked Rotor ◽  
On Line ◽  
Linear And Nonlinear ◽  
Excitation Force

Detection of a rotor crack based on the nonlinear vibration diagnosis using periodic excitation force is investigated. Due to the open-close mechanism of the crack, the equations of motion of a cracked rotor have linear and nonlinear parametric terms. When a periodic excitation force is applied to the cracked rotor, various kinds of resonances due to the unique vibration characteristics of a crack. Furthermore, types of resonances, resonance points and dominant frequency component of these resonances are clarified theoretically and experimentally. These results enable us to detect a crack on-line without stopping the system.

Research on Numerical Simulation Model for Crack Growth Driven by Detonation Gas in High-Deep Rock Strata

2012 ◽  
Vol 170-173 ◽  
pp. 824-829
Author(s):  
Li Jing Chen ◽  
Jian Zheng ◽  
Cheng Ke Zhang
Keyword(s):  
Crack Growth ◽  
Rock Fracture ◽  
Coupling Model ◽  
Fracture Length ◽  
Finite Element Software ◽  
Deep Rock ◽  
Dynamic Growth ◽  
Analysis Platform ◽  
Geometric Morphology ◽  
Rock Strata

The effect of detonation gas upon rock fracture is the cross-frontier research project of fluid dynamics coupling and rock dynamics of crack dynamic growth, having the important scientific significance and explicit application value. In the process of detonation gas driven fracture growth, the varying law of the denotation gas pressure distribution in cracks is inter-influent with the geometric morphology variations in crack growth. This paper analyzes the denotation gas flowing behaviors, establishes the flowing model for denotation gas in rock cracks and the models for the rock crack dynamic response. Also suggests the fluid-solid coupling model for the denotation gas flowing, rock crack response and the numerical model for simulating crack growth driven by the denotation gas. The simulation program is developed on the large-sized rock engineering finite element software (FINAL platform). This numerical analysis platform is used to carry out the systematic numerical experimental study of several main influencing factors of core problems concerning pressure fracture length.

An Analytical Method for Vibration Fatigue of Cracked Beams

2012 ◽  
Vol 479-481 ◽  
pp. 783-786
Author(s):  
Wen Guang Liu ◽  
Hong Lin He
Keyword(s):  
Fatigue Crack ◽  
Crack Growth ◽  
Analytical Method ◽  
Loss Factor ◽  
Coupling Effect ◽  
Structural Response ◽  
Exciting Frequency ◽  
Vibration Fatigue ◽  
Damping Loss Factor ◽  
Cracked Beams

A new analytical method for vibration fatigue life of cracked beams was proposed with the structural response changes as crack growth. In analysis, the damping loss factor was introduced by the complex elastic modulus, and the crack growth was simulated by employing a Paris equation, and the coupling effect of vibration and crack growth was considered through vibration analysis and estimation of fatigue crack propagation cycles by cycles. Results indicate that impacts of exciting frequency and damping on the crack growth are obvious. The resonance fatigue crack growth rate decreases rapidly when big damping is involved, and the first mode is more important to the crack growth than that of other mode.

Degradation Behaviors of β-TCP/PLGA Composites Prepared with Microwave Energy

2007 ◽  
Vol 342-343 ◽  
pp. 205-208 ◽  
Author(s):  
Hong Chae Park ◽  
Hyeong Ho Jin ◽  
Yong Taek Hyun ◽  
Won Ki Lee ◽  
Seog Young Yoon
Keyword(s):  
Molecular Weight ◽  
In Situ Polymerization ◽  
Morphological Changes ◽  
Microwave Energy ◽  
Degradation Behavior ◽  
Soaking Time ◽  
Biodegradable Scaffolds ◽  
Degradation Behaviors ◽  
Sbf Solution

The β-tricalcium phosphate (β-TCP)/ poly(lactide-co-glycolide) (PLGA) composites for biodegradable scaffolds in bone tissue engineering were synthesized by in situ polymerization with microwave energy. The degradation behavior of β-TCP/PLGA composite was investigated by soaking in simulated body fluid (SBF) for 4 weeks. The molecular weight of the β-TCP/PLGA composites decreased with soaking time until week 2, whereas the loss rate of molecular weight reduced after week 2. The incubation time was needed for the degradation of the β-TCP, indicating that the β-TCP should be detached from the PLGA matrix and then degraded into SBF solution. The studies of mass loss of the composites with the soaking time revealed that the degradation behavior of PLGA would be processed with the transformation from the polymer to the oligomer followed by the degradation. Morphological changes, whisker-like, due to transformation and degradation of polymer in the composites were observed after week 2. On the basis of the results, it found that the degradation behavior of β-TCP/PLGA composites was influenced by the β-TCP content in the composite and the degradation rate of the composite could be controlled by the initial molecular weight of PLGA in the composite.

A Mathematical Thermal Hydraulic-Mechanical Coupling Model for Unsaturated Porous Media

2014 ◽  
Vol 602-605 ◽  
pp. 365-369
Author(s):  
Jun Yan ◽  
Yin Qi Wei ◽  
Hong Cai
Keyword(s):  
Porous Media ◽  
Solid Mechanics ◽  
Coupling Effect ◽  
Coupling Model ◽  
Unsaturated Porous Media ◽  
Liquid Pressure ◽  
Mechanical Coupling ◽  
The Earth ◽  
Highly Nonlinear ◽  
Pore Liquid

s: Temperature, seepage and deformation are the important parts of the engineering geological mechanics both in water conservancy and hydropower engineering since there are highly nonlinear complex coupling effect between each other. In this paper, the earth and rock mass are classified as continuous porous media. The thermal constitutive relation of porous media and motion regularity of pore fluid are deduced from the basic theory of solid mechanics, hydraulics, and thermodynamics. Based on momentum, mass and energy conservation equations, the multi-field controlling equations of unsaturated porous media are given, in which the unknown variables include displacements, pore liquid pressure, pore gas pressure, temperature, and porosity.

scholarly journals Hydrolytic Degradation of Comb-Like Graft Poly (Lactide-co-Trimethylene Carbonate): The Role of Comonomer Compositions and Sequences

Polymers ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 2024
Author(s):  
Xuefei Leng ◽  
Wenwen Zhang ◽  
Yiying Wang ◽  
Yanshai Wang ◽  
Xiaoqing Li ◽  
...  
Keyword(s):  
Block Copolymers ◽  
Hydrolytic Degradation ◽  
Gel Permeation Chromatography ◽  
Random Copolymers ◽  
Degradation Behavior ◽  
Weight Retention ◽  
Trimethylene Carbonate ◽  
Degradation Rates ◽  
Degradation Behaviors ◽  
Property Changes

The effect of sequence on copolymer properties is rarely studied, especially the degradation behavior of the biomaterials. A series of linear-comb block, gradient, random copolymers were successfully achieved using hydroxylated polybutadiene as the macroinitiator by simple ring-opening polymerization of l-lactide (l-LA) and 1,3-trimethylene carbonate (TMC). The hydrolytic degradation behaviors of the copolymers were systemically evaluated by using nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), differential scanning calorimeter (DSC), and scanning electron microscopy (SEM) to illustrate the influences of comonomer compositions and sequence structures. The linear-comb block copolymers (lcP(TMC-b-LLA)) with different compositions had different degradation rates, which increased with l-LA content. Thermal property changes were observed with decreased Tm and increased ΔHm in all block copolymers during the degradation. To combine different sequence structures, unique degradation behaviors were observed for the linear-comb block, gradient and random copolymers even with similar comonomer composition. The degradation rates of linear-comb PLLA-gradient-PTMC (lcP(LLA-grad-TMC)) and linear-comb PLLA-random-PTMC (lcP(LLA-ran-TMC)) were accelerated due to the loss of regularity and crystallinity, resulting in a remarkable decrease on weight retention and molar mass. The hydrolysis degradation rate increased in the order lcP(TMC-b-LLA), lcP(LLA-ran-TMC), lcP(LLA-grad-TMC). Therefore, the hydrolytic degradation behavior of comb-like graft copolymers depends on both the compositions and the sequences dramatically.

Roll-Yaw Coupling Effect of Jeffcott Rotor With Breathing Crack

2015 ◽  
Author(s):  
J. Zhao ◽  
H. A. DeSmidt ◽  
M. Peng ◽  
W. Yao
Keyword(s):  
Coupling Effect ◽  
Rotor System ◽  
Crack Model ◽  
Breathing Crack ◽  
Cracked Rotor ◽  
Lagrange Principle ◽  
Jeffcott Rotor ◽  
Vibration Responses ◽  
Cracked Rotor System ◽  
Rotor Model

A new rotor model is developed in this paper to explore the dynamic coupling effect of roll-yaw motion. The rotor model employs a 6 degree-of-freedom Jeffcott rotor with a breathing crack. Based on the energy method and Lagrange principle, equation of motion is derived in yawing coordinate system with consideration of unbalance mass. The breathing crack model is established by Zero Stress Intensity Factor (SIF) method based on the crack released strain energy concept in fracture mechanics. SIF method is used to determine the crack closure line by computing SIF for opening mode. The vibration responses of the cracked rotor system are solved by Gear’s method. The coupling effect of yawing and rolling motion is studied in this paper to investigate vibration response of cracked rotor system. With the yawing motion, the dynamics of the rotor-bearing system is changed by additional stiffness and force terms. The parametric study is conducted to analyze the effect of yawing rate and acceleration on the crack breathing behavior. Finally, the vibration responses of the nominal and damaged rotor systems are analyzed to find out the indication for the damage detection and health monitoring.

Research on Multi-Disciplinary Behavior Coupling Model in IC Engine

2010 ◽  
Vol 44-47 ◽  
pp. 2075-2079
Author(s):  
Xu Dong Dai ◽  
Zheng Shan Zhang ◽  
Xiang Hui Meng ◽  
Zhi Nan Zhang ◽  
You Bai Xie
Keyword(s):  
Coupling Effect ◽  
Dynamical Behavior ◽  
Cylinder Liner ◽  
Coupling Model ◽  
State Equation ◽  
The State ◽  
Analysis Model ◽  
Coupling Analysis ◽  
Ic Engine ◽  
Cylinder Piston

The paper analyzes the coupling of multi-disciplinary behaviors, including system dynamical behavior, combustion behavior and tribological behavior, of the cylinder liner-piston-rod-crank system in IC engine. Based on the state equation method, multi-disciplinary behavior coupling model of the Cylinder-Piston-Rod-Crank system is constructed and a multi-disciplinary behavior coupling analysis method in IC engine is presented on the basis of the state equation. With the coupling analysis model, the coupling effect of multi-disciplinary behaviors can be considered in the two sequential state calculations. By means of state calculation in time domain, the coupling effect of multi-disciplinary behaviors on life performance of IC engine can be predicted.

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