Distributions and fitting of stress amplitude spectra for railway vehicle structures

2019 ◽  
Vol 234 (1) ◽  
pp. 43-53 ◽  
Author(s):  
Dekun Liu ◽  
Jun Zhang ◽  
Qiang Li ◽  
Jie Chen
Keyword(s):  
Weibull Distribution ◽  
Lognormal Distribution ◽  
Stress Amplitude ◽  
Railway Vehicle ◽  
Distribution Fitting ◽  
Structural Fatigue ◽  
Amplitude Data ◽  
Stress Spectrum ◽  
Measured Stress ◽  
Truncated Normal

Stress spectra are essential for estimating the structural fatigue and the fatigue life of railway vehicle structures. However, the data grouping and distribution fitting approaches employed by previous empirical data processing methods are excessively coarse and contain distinctive defects. To address these shortcomings, general theoretical distributions are herein corrected according to the requirements presented by lower stress amplitude data bounds, and converted into a Weibull distribution, truncated lognormal distribution, and truncated normal distribution for comparison. In addition, an innovative distribution consisting of a combined Weibull distribution and truncated lognormal distribution is proposed. The results of fitting to measured stress spectra suggest that the combined distribution has remarkable advantages. Stress spectrum extrapolation and fatigue damage calculation verify that the stress spectrum derived from the combined distribution provides the closest match of all distributions considered to that obtained from the measured spectrum, and therefore best represents the stress distribution at critical points during the practical operation of railway vehicles.

Statistical Analysis of Loader’s Drive Axle Housing Random Load Spectrum

2011 ◽  
Vol 338 ◽  
pp. 456-459 ◽  
Author(s):  
Bu Zheng Wen ◽  
Jian Min Li ◽  
Zhong Tao Pei ◽  
Sheng Yu ◽  
Cuan Yang Sun ◽  
...  
Keyword(s):  
Statistical Analysis ◽  
Weibull Distribution ◽  
Fatigue Reliability ◽  
Load Spectrum ◽  
Distribution Fitting ◽  
Random Load ◽  
Structural Fatigue ◽  
History Of ◽  
Drive Axle ◽  
Drive Axle Housing

Statistical analysis of load spectrum is an important part on structural fatigue life and reliability research, it is generally considered that axle’s load spectrum follows Weibull distribution. This paper tested ZL50 loader’s loading history of different working conditions , and obtained the corresponding load spectrum by rain-flow counting method, then analyzed three distributions’ (normal distribution, lognormal distribution, Weibull distribution) fitting degree of load spectrum and effect on the fatigue reliability. Results show that the highest fitting degree of distribution function should be used to fit load spectrum, which can reduce the error in structural fatigue reliability prediction.

Analyses for Statistic Distribution of the Welded Joint Fracture Toughness about X65 Pressure Pipe Steel

2013 ◽  
Vol 791-793 ◽  
pp. 346-349
Author(s):  
Bo Lin He ◽  
Ying Xia Yu ◽  
Si Yong Lei ◽  
Li Xing Huo
Keyword(s):  
Fracture Toughness ◽  
Weibull Distribution ◽  
Normal Distribution ◽  
Lognormal Distribution ◽  
Pipe Steel ◽  
Welded Joint ◽  
Fracture Toughness Test ◽  
Structure Reliability ◽  
Pressure Pipe ◽  
Joint Fracture

It is important for the design engineer to realize that scatter and variability of materials properties are inevitable and must be dealt with appropriately. On occasion, data must be subjected to statistical treatments and probabilities determined. The fracture toughness of pipe steel has great effect on the safety of welded pressure pipe. The fracture toughness test of circumferential welded joint was carried out in this paper for X65 pressure pipe steel. The fracture toughness experimental results were analyzed by using computer program developed by ourselves. The distribution of weld fracture toughness of X65 pressure pipe steel which may accord with normal distribution, lognormal distribution or weibull distribution can be determined by calculating the results only one time. The program, which plays an important role in structure reliability analysis, can be used to determine the probability statistic distribution of the mechanical properties. The calculated results indicate that the weld fracture toughness of the X65 pressure pipe steel can either accord with normal distribution, lognormal distribution or weibull distribution, but the optimum fitting distribution of the fracture toughness is weibull distribution.

Nondestructive Detection of Cartilage Degeneration Using Electromechanical Surface Spectroscopy

1994 ◽  
Vol 116 (4) ◽  
pp. 384-392 ◽  
Author(s):  
Scott I. Berkenblit ◽  
Eliot H. Frank ◽  
Evan P. Salant ◽  
Alan J. Grodzinsky
Keyword(s):  
Stress Amplitude ◽  
Excitation Frequency ◽  
Piezoelectric Sensor ◽  
Cartilage Degeneration ◽  
Surface Probe ◽  
Electromechanical Transduction ◽  
Measured Stress ◽  
Surface Spectroscopy ◽  
Surface Measurements ◽  
Poroelastic Model

We have constructed an electrokinetic surface probe capable of applying small sinusoidal currents to the surface of articular cartilage and measuring the resulting current-generated stress with a piezoelectric sensor. Using the probe, we have characterized the electromechanical response of excised discs of normal and chemically modified adult bovine femoropatellar groove cartilage. The measured stress amplitude was proportional to the applied current density and inversely proportional to the excitation frequency, consistent with a poroelastic model. As a function of bath pH, the stress amplitude exhibited a minimum in the range pH 2.4–2.8 and the phase underwent an abrupt 180° transition in the same range, consistent with an electrokinetic mechanism as the origin of the current-generated mechanical stress. Digestion of the tissue with trypsin resulted in a progressive loss of highly charged proteoglycan molecules from the tissue, with a concomitant decrease in the measured stress amplitude. These results support the feasibility of surface measurements as a means of assessing electromechanical transduction in cartilage and of detecting subtle molecular-level degradative changes in the extracellular matrix. This technique of surface spectroscopy provides a new means of nondestructively measuring the material properties of cartilage on intact joints and detecting degradative changes such as those seen in the earliest stages of osteoarthritis.

scholarly journals Fitting Probability Distribution Function to Malaria Incidence Data

2019 ◽  
pp. 1-12
Author(s):  
Drinold Mbete ◽  
Kennedy Nyongesa ◽  
Joseph Rotich
Keyword(s):  
Weibull Distribution ◽  
Lognormal Distribution ◽  
Malaria Incidence ◽  
Science And Technology ◽  
Incidence Data ◽  
Technology Students ◽  
Complex Interactions ◽  
A Value ◽  
Best Fitting ◽  
Over Dispersion

Abstract: Malaria remains a major infectious disease that affects millions of people. Once infected with Plasmodium parasites, a host can develop a broad range of clinical presentations, which result from complex interactions between factors derived from the host, the parasite and the environment. Malaria has historically been a very serious health problem and currently poses the most significant threat to the health of Masinde Muliro University of Science and Technology students, data shows that more than 70% percent of pediatric cases are due to malaria. Methodology: Hence, the study aimed to fit malaria incidences dataset for the period 1st January, 2013 to 31st December, 2015. Data on monthly malaria incidence was obtained from the Masinde Muliro University of Science and Technology health service. Gamma, Weibull and Lognormal Distributions were employed to fit the malaria incidence dataset using R-software. Results: High malaria incidences were observed in the months of August, September and November. AIC values results showed that lognormal distribution had the lowest AIC value of 185.9875 followed by the Gamma distribution with a value of 187.8815 and then the Weibull distribution with a value of 188.7271. This confirmed the lognormal distribution to be the best fitting distribution for the malaria incidence dataset Conclusion: The Poisson regression model did not accurately fit the data on malaria incidences due to over dispersion in the data but lognormal distribution was a better fit compared to gamma and Weibull distribution.

Extrapolation Techniques for Very Low Cycle Fatigue Behavior of a Ni-base Superalloy

2011 ◽  
Vol 133 (2) ◽  
Author(s):  
Brian R. Daubenspeck ◽  
Ali P. Gordon
Keyword(s):  
Stress Amplitude ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Full Range ◽  
Turbine Blades ◽  
High Stress ◽  
Cycle Fatigue ◽  
Data Set ◽  
Amplitude Data ◽  
Base Superalloy

A combination of extrapolation and estimation techniques from both prior and current studies has been explored with the goal of developing a method to accurately characterize high-stress amplitude low cycle fatigue of a material commonly used in gas turbine blades with the absence of such data. This paper describes innovative methods used to predict high-temperature fatigue of IN738LC, a dual-phase Ni-base superalloy. Three sets of experimental data at different temperatures are used to evaluate and examine the validity of extrapolation methods such as anchor points and hysteresis energy trends. High-stress amplitude data points approaching the ultimate strength of the material were added to pre-existing base data with limited plastic strain to achieve a full-range data set that could be used to test the legitimacy of the different prediction methods. Each method is evaluated at a number of temperatures.

Constant Amplitude Fatigue Calculative Method of Welded Hollow Spherical Joint with Cross-Board in Steel Plate-Type Grid Structure

2012 ◽  
Vol 166-169 ◽  
pp. 180-186
Author(s):  
Jin Feng Jiao ◽  
Hong Gang Lei ◽  
Han Wu ◽  
Yong Liu
Keyword(s):  
Fatigue Failure ◽  
Stress Amplitude ◽  
Fatigue Curve ◽  
Use Of Self ◽  
Spherical Joint ◽  
Constant Amplitude ◽  
Grid Structure ◽  
Structural Fatigue ◽  
Plate Type ◽  
Welded Hollow Spherical Joint

The fatigue of grid structures with welded hollow spherical joint under suspending cranes is an issue in both academic and engineering fields at home and abroad. The structural fatigue is mainly caused by the fatigue failure of welded hollow spherical joint with cross-board. In this paper, 16 specimens categorized in KQ-4、KQ-5 and KQ-7were tested stably and efficiently under constant amplitude stress by use of self-designed loading equipment. The testing results show that the form and mechanism of fatigue failure were clarified elementarily. A fatigue curve of welded hollow spherical joint with cross-board, S-N curve, was suggested in this paper based on the statistic regression analysis of the 16 testing results. The constant amplitude fatigue calculation method was established for welded hollow spherical joint with cross-board in grid structure with welded hollow spherical joint by use of allowable stress amplitude method.

Total-Probability Method in Reliability Design of Gear Strength

2010 ◽  
Vol 37-38 ◽  
pp. 1604-1614
Author(s):  
Yan Li ◽  
Wei Xiao ◽  
Hai Yang Huang ◽  
Ying Cai Yuan
Keyword(s):  
Mathematical Model ◽  
Weibull Distribution ◽  
Lognormal Distribution ◽  
Extreme Value Distribution ◽  
Probability Method ◽  
Total Probability ◽  
Interference Theory ◽  
Reliability Design ◽  
Reliability Calculation ◽  
The Mathematical Model

Total probability method is based on stress-strength interference theory. There are four acceptable distribution types for gear (strength, stress), which are normal distribution, lognormal distribution, Weibull distribution and the smallest extreme value distribution. Based on the four distribution types, 16 different stress-strength distributions were obtained through permutation respectively. The results show that they summarize the mathematical model of reliability calculation for the gear actual failure mode and get the exact solutions of gear reliability.

Probability Distribution Analysis of Structural Response under Non-Gaussian Wind Loads

2010 ◽  
Vol 163-167 ◽  
pp. 4356-4362
Author(s):  
Jing Li ◽  
Xin Wang
Keyword(s):  
Weibull Distribution ◽  
Structural Response ◽  
Likelihood Estimation ◽  
Wind Pressure ◽  
Distribution Analysis ◽  
Distribution Fitting ◽  
Roof Structure ◽  
Speed Up ◽  
Non Gaussian ◽  
Determination Of Parameters

Based on the theory of maximum likelihood estimation, a set of nonlinear equations is first derived for determination of parameters of Weibull distribution. To speed up convergence, an efficient algorithm is proposed for solving the parameters. Further, a large-span roof structure is taken to demonstrate the proposed method. It is proved that the responses of a nonlinear structure have non-Gaussian properties under the excitation of non-Gaussian stochastic wind pressure field. By Weibull distribution fitting, the maximum and minimum values of structural response with a certain assurance rate are computed, and the results are compared with those obtained from normal distribution.

Evaluation of Fatigue Failure Risk Based on On-Track Tests

2016 ◽  
Author(s):  
Lara Erviti Calvo ◽  
Gorka Agirre Castellanos
Keyword(s):  
Fatigue Failure ◽  
Maximum Stress ◽  
Railway Vehicle ◽  
Stress History ◽  
Normal Behaviour ◽  
Operational Life ◽  
Measured Stress ◽  
Stress Levels ◽  
Systematic Failure ◽  
Multiple Conditions

When a mechanical component of a railway vehicle experiences failure due to fatigue, it is necessary to determine whether it has been an isolated failure or it is a systematic failure that may affect the whole fleet. The present work presents the methodology to be followed for the application of on-track tests to determine the probability of fatigue failure. By simulating a normal commercial service in one or multiple conditions, the stress levels experienced by the component are recorded. These stress levels are combined and extrapolated in order to determine the typical global stress history that the component will experience during its operational life. From this stress history, the risk of fatigue failure can be estimated by means of the cumulative damage method also known as Miner’s rule. For this calculation the measured stress levels have to be compared with an S-N curve. The problem arises because the S-N curves presented in the standards correspond to stresses in the direction perpendicular or longitudinal to the weld. The peculiarities of on-track tests imply that the direction of principal stress may vary continuously and the maximum stress value may be present in specific points of the record with directions that do not represent the normal behaviour of the piece. Different forms of dealing with the projection of the rosettes have been analyzed, and the influence of these considerations on the damage calculation has been studied.

Finite Element Analysis on the Fatigue Stresses of a Railway Vehicle Roller Bearing

2008 ◽  
Vol 44-46 ◽  
pp. 935-941 ◽  
Author(s):  
Feng Lin ◽  
Yong Xiang Zhao
Keyword(s):  
Finite Element ◽  
Stress Amplitude ◽  
Equivalent Stress ◽  
Roller Bearing ◽  
Fe Analysis ◽  
Local Analysis ◽  
Interactive System ◽  
Railway Vehicle ◽  
Load Spectrum ◽  
Equivalent Stress Amplitude

The distributed fatigue stresses of 353130B roller bearing of China freight car with K5 type titling bogie are investigated using an elastic-plastic finite element (FE) analysis. Policy of two steps is applied. First, an integral FE analysis is performed on adapter-bearing-axle-wheel-track interactive system. Second, local analysis is applied to the local axle-bearing-adapter part, in which on the section of axle is with the bound condition obtained from the integral analysis. Wheel contact force spectrum on a curved railway line by on-line inspection is used for the present study. Previous proposed multivariate quadratic regression approach is applied for transferring the load spectrum to the dynamic stress spectrum at a special position of the bearing. Results reveal that the rollers, innerand outer-rings of bearing are subjected to distribute axially equivalent stress amplitude. The closer to axle side, the larger the equivalent stress amplitude. The equivalent stress amplitude of outer ring at the position close to the seal seat is relative larger to that of inner ring. The results are consistency with the shell failures of the bearings in production. Availability of present study is indicated.

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