Small specimen techniques for estimation of tensile, fatigue, fracture and crack propagation material model parameters

2021 ◽  
pp. 030932472110252
Author(s):  
Julija Kazakeviciute ◽  
James Paul Rouse ◽  
Davide Focatiis ◽  
Christopher Hyde
Keyword(s):  
Fatigue Fracture ◽  
Structural Integrity ◽  
Standard Specimen ◽  
Creep Behaviour ◽  
Parameter Determination ◽  
Model Parameters ◽  
Small Specimen ◽  
Testing Methods ◽  
Advantages And Disadvantages ◽  
Tensile Fatigue

Small specimen mechanical testing is an exciting and rapidly developing field in which fundamental deformation behaviours can be observed from experiments performed on comparatively small amounts of material. These methods are particularly useful when there is limited source material to facilitate a sufficient number of standard specimen tests, if any at all. Such situations include the development of new materials or when performing routine maintenance/inspection studies of in-service components, requiring that material conditions are updated with service exposure. The potentially more challenging loading conditions and complex stress states experienced by small specimens, in comparison with standard specimen geometries, has led to a tendency for these methods to be used in ranking studies rather than for fundamental material parameter determination. Classifying a specimen as ‘small’ can be subjective, and in the present work the focus is to review testing methods that utilise specimens with characteristic dimensions of less than 50 mm. By doing this, observations made here will be relevant to industrial service monitoring problems, wherein small samples of material are extracted and tested from operational components in such a way that structural integrity is not compromised. Whilst recently the majority of small specimen test techniques development have focused on the determination of creep behaviour/properties as well as sub-size tensile testing, attention is given here to small specimen testing methods for determining specific tensile, fatigue, fracture and crack growth properties. These areas are currently underrepresented in published reviews. The suitability of specimens and methods is discussed here, along with associated advantages and disadvantages.

Parameter Determination for Chloride and Tritium Transport in Undisturbed Lysimeters during Steady Flow

1992 ◽  
Vol 23 (2) ◽  
pp. 89-104 ◽  
Author(s):  
Ole H. Jacobsen ◽  
Feike J. Leij ◽  
Martinus Th. van Genuchten
Keyword(s):  
Experimental Data ◽  
Unsaturated Flow ◽  
Transport Model ◽  
Time Moment ◽  
Breakthrough Curves ◽  
Coarse Sand ◽  
Retardation Factor ◽  
Parameter Determination ◽  
Model Parameters ◽  
Water Fraction

Breakthrough curves of Cl and 3H2O were obtained during steady unsaturated flow in five lysimeters containing an undisturbed coarse sand (Orthic Haplohumod). The experimental data were analyzed in terms of the classical two-parameter convection-dispersion equation and a four-parameter two-region type physical nonequilibrium solute transport model. Model parameters were obtained by both curve fitting and time moment analysis. The four-parameter model provided a much better fit to the data for three soil columns, but performed only slightly better for the two remaining columns. The retardation factor for Cl was about 10 % less than for 3H2O, indicating some anion exclusion. For the four-parameter model the average immobile water fraction was 0.14 and the Peclet numbers of the mobile region varied between 50 and 200. Time moments analysis proved to be a useful tool for quantifying the break through curve (BTC) although the moments were found to be sensitive to experimental scattering in the measured data at larger times. Also, fitted parameters described the experimental data better than moment generated parameter values.

Genotypic Methods for HIV Drug Resistance Monitoring: The Opportunities and Challenges Faced by China

2019 ◽  
Vol 17 (4) ◽  
pp. 225-239 ◽  
Author(s):  
Lulu Zuo ◽  
Ke Peng ◽  
Yihong Hu ◽  
Qinggang Xu
Keyword(s):  
Drug Resistance ◽  
Virological Suppression ◽  
Testing Methods ◽  
Hiv Drug Resistance ◽  
Advantages And Disadvantages ◽  
Hiv Epidemic ◽  
Routine Surveillance ◽  
The World ◽  
Global Project ◽  
Hiv 1

AIDS is a globalized infectious disease. In 2014, UNAIDS launched a global project of “90-90-90” to end the HIV epidemic by 2030. The second and third 90 require 90% of HIV-1 infected individuals receiving antiretroviral therapy (ART) and durable virological suppression. However, wide use of ART will greatly increase the emergence and spreading of HIV drug resistance and current HIV drug resistance test (DRT) assays in China are seriously lagging behind, hindering to achieve virological suppression. Therefore, recommending an appropriate HIV DRT method is critical for HIV routine surveillance and prevention in China. In this review, we summarized the current existing HIV drug resistance genotypic testing methods around the world and discussed the advantages and disadvantages of these methods.

scholarly journals Why ability point estimates can be pointless: a primer on using skill measures from large-scale assessments in secondary analyses

2021 ◽  
Vol 3 (1) ◽  
Author(s):  
Clemens M. Lechner ◽  
Nivedita Bhaktha ◽  
Katharina Groskurth ◽  
Matthias Bluemke
Keyword(s):  
Measurement Error ◽  
Statistical Models ◽  
Test Scores ◽  
Large Scale ◽  
Equation Modeling ◽  
Model Parameters ◽  
Advantages And Disadvantages ◽  
Point Estimates ◽  
Secondary Analyses ◽  
Large Scale Assessments

AbstractMeasures of cognitive or socio-emotional skills from large-scale assessments surveys (LSAS) are often based on advanced statistical models and scoring techniques unfamiliar to applied researchers. Consequently, applied researchers working with data from LSAS may be uncertain about the assumptions and computational details of these statistical models and scoring techniques and about how to best incorporate the resulting skill measures in secondary analyses. The present paper is intended as a primer for applied researchers. After a brief introduction to the key properties of skill assessments, we give an overview over the three principal methods with which secondary analysts can incorporate skill measures from LSAS in their analyses: (1) as test scores (i.e., point estimates of individual ability), (2) through structural equation modeling (SEM), and (3) in the form of plausible values (PVs). We discuss the advantages and disadvantages of each method based on three criteria: fallibility (i.e., control for measurement error and unbiasedness), usability (i.e., ease of use in secondary analyses), and immutability (i.e., consistency of test scores, PVs, or measurement model parameters across different analyses and analysts). We show that although none of the methods are optimal under all criteria, methods that result in a single point estimate of each respondent’s ability (i.e., all types of “test scores”) are rarely optimal for research purposes. Instead, approaches that avoid or correct for measurement error—especially PV methodology—stand out as the method of choice. We conclude with practical recommendations for secondary analysts and data-producing organizations.

scholarly journals Flight crew diagnostic using aviation simulator training data

2016 ◽  
Vol 9 (3) ◽  
pp. 118-137
Author(s):  
L.S. Kuravsky ◽  
P.A. Marmalyuk ◽  
G.A. Yuryev ◽  
O.B. Belyaeva ◽  
O.Yu. Prokopieva
Keyword(s):  
Continuous Time ◽  
Goodness Of Fit ◽  
Training Data ◽  
Simulator Training ◽  
Model Parameters ◽  
Flight Crew ◽  
Advantages And Disadvantages ◽  
Goodness Of Fit Tests ◽  
Flight Simulators ◽  
Discrete States

This paper describes a new concept of flight crew assessment based on flight simulators training result. It is based on representation of pilot gaze movement with the aid of continuous-time Markov processes with discrete states. Considered are both the procedure of model parameters identification provided with goodness-of-fit tests in use and the classifier-building technique, which makes it possible to estimate degree of correspondence between the observed gaze motion distribution under study and reference distributions identified for different diagnosed groups. The final assessing criterion is formed on the basis of integrated diagnostic parameters, which are determined by the parameters of the identified models. The article provides a description of the experiment, illustrations, and results of studies aimed at assessing the reliability of the developed models and criteria, as well as conclusions about the applicability of the approach, its advantages and disadvantages.

Ultrasonic Testing in 25 Minutes

2003 ◽  
Author(s):  
William E. Blum ◽  
Thomas Gryba¨ck
Keyword(s):  
Power Generation ◽  
Quality Control ◽  
Nondestructive Testing ◽  
Ultrasonic Testing ◽  
Basic Theory ◽  
Testing Methods ◽  
Advantages And Disadvantages ◽  
Basic Understanding ◽  
Fundamental Understanding ◽  
Nondestructive Testing Methods

Nondestructive Testing (AKA NDT, NDI, NDE) is an integral part of any power generation program. Ultrasonic Testing (UT) is one NDT method used to determine the integrity of materials and components. Managers, engineers, quality control personnel and others often require a fundamental understanding of the nondestructive testing methods used in their operations. This paper introduces basic theory, advantages and disadvantages, typical equipment and applications of ultrasonic testing. It is designed to give the reader a basic understanding of ultrasonic testing.

Mathematical Models of Proprioceptors. I. Control and Transduction in the Muscle Spindle

2006 ◽  
Vol 96 (4) ◽  
pp. 1772-1788 ◽  
Author(s):  
Milana P. Mileusnic ◽  
Ian E. Brown ◽  
Ning Lan ◽  
Gerald E. Loeb
Keyword(s):  
Muscle Spindle ◽  
Motor Behavior ◽  
Realistic Model ◽  
Medial Gastrocnemius ◽  
Parameter Determination ◽  
Model Parameters ◽  
Data Sets ◽  
Temporal Properties ◽  
Single Set

We constructed a physiologically realistic model of a lower-limb, mammalian muscle spindle composed of mathematical elements closely related to the anatomical components found in the biological spindle. The spindle model incorporates three nonlinear intrafusal fiber models (bag1, bag2, and chain) that contribute variously to action potential generation of primary and secondary afferents. A single set of model parameters was optimized on a number of data sets collected from feline soleus muscle, accounting accurately for afferent activity during a variety of ramp, triangular, and sinusoidal stretches. We also incorporated the different temporal properties of fusimotor activation as observed in the twitchlike chain fibers versus the toniclike bag fibers. The model captures the spindle's behavior both in the absence of fusimotor stimulation and during activation of static or dynamic fusimotor efferents. In the case of simultaneous static and dynamic fusimotor efferent stimulation, we demonstrated the importance of including the experimentally observed effect of partial occlusion. The model was validated against data that originated from the cat's medial gastrocnemius muscle and were different from the data used for the parameter determination purposes. The validation record included recently published experiments in which fusimotor efferent and spindle afferent activities were recorded simultaneously during decerebrate locomotion in the cat. This model will be useful in understanding the role of the muscle spindle and its fusimotor control during both natural and pathological motor behavior.

scholarly journals Automated Parameter Determination for Horizontal Curves for the Purposes of Road Safety Models with the Use of the Global Positioning System

Geosciences ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 397
Author(s):  
Marcin Budzynski ◽  
Kazimierz Jamroz ◽  
Jerzy Pyrchla ◽  
Wojciech Kustra ◽  
Adam Inglot ◽  
...  
Keyword(s):  
Global Positioning System ◽  
Road Safety ◽  
Automated System ◽  
Parameter Determination ◽  
The Road ◽  
Horizontal Curves ◽  
Advantages And Disadvantages ◽  
Second Stage ◽  
Global Positioning ◽  
Safety Models

This paper presents the results of research conducted to develop an automated system capable of determining parameters for horizontal curves. The system presented in this article could calculate the actual course of a road by means of a two-stage positioning of recorded points along the road. In the first stage, measurements were taken with a Real-Time Network (RTN) receiver installed in a research vehicle. In the second stage, pictures from three cameras, also installed in the vehicle, were analyzed in order to correct the accuracy of the location of the measurement points along the road. The RTN messages and the pictures from the cameras were sent to a mobile workstation which integrated the received signals in an ArcGIS (Esri) environment. The system provides a way to quickly accumulate highly accurate data on the actual geometric parameters of a road. The computer scripts developed by the authors on the basis of the acquired data could automatically determine the parameters of the horizontal curves. The solution was tested in the field and some comments on its advantages and disadvantages are presented in this paper. The automation of data acquisition with regards to the run of a road provides effective data input for mathematical models that include the effect of horizontal curve parameters on road safety. These could be used to implement more effective ways of improving road safety.

Diagnostics of aviation equipment. Methods and means of non-destructive testing of the technical condition of the aircraft

2017 ◽  
Author(s):  
Мартыненко ◽  
Elena Martynenko
Keyword(s):  
Physical Nature ◽  
Optical Devices ◽  
Civil Aviation ◽  
Measuring Instruments ◽  
Non Destructive Testing ◽  
Testing Methods ◽  
Destructive Testing ◽  
Ray Method ◽  
Advantages And Disadvantages ◽  
Non Destructive

This manual contains information about the appointment and the physical nature of the application existing non-destructive testing methods, their advantages and disadvantages. The manual contains a brief historical information about the development of non-destructive testing methods in manufacturing aircraft devices, the classification and possible causes of occurrence of various defects on which the studied method of non-destructive testing are directed. The first part of the manual, of the main methods that are used to detect the defects in any instrument control. The detailed classification of measuring instruments and optical devices are given. Moreover, the construction and the ways (the principles) of work of complex measuring instruments and optical devices, including endoscopes are given. The current devices and systems for visual inspection of fiber-hidden objects and internal cavities are considered. More detailed consideration in the manual is given to the capillary, magnetic, acoustic, eddy current non-destructive testing methods and techniques of radiographic(X-ray and gamma-ray method). Particular attention is paid to the field of practical application of different methods. A lot of attention is given to modern means of non-destructive testing of domestic and foreign production. The manual contains a significant amount of drawings and diagrams, which allows to increase the visibility and the accessibility of presentation. It is drawn up with the interdisciplinary course program MDK 01.01.03 "Technical maintenance of aircraft and engines" and is intended for students of the above mentioned specialization 25.02.01 branches of secondary vocational education. The manual can also be used by the students of the training courses for engineering and technical personnel of the enterprises of civil aviation.

Peak-To-Peak Change in Magnetization Caused by Fracture

2013 ◽  
Vol 787 ◽  
pp. 755-758
Author(s):  
Jian Wei Li ◽  
Zhong Su ◽  
Gui Ping Lv ◽  
Li Jun Pang ◽  
Wei Jia
Keyword(s):  
Fatigue Fracture ◽  
Magnetic Dipole ◽  
Fracture Zone ◽  
Linear Increase ◽  
Tensile Fracture ◽  
Tensile Fatigue ◽  
Magnetization Change

To simulated the magnetization change at the instant of fracture, assume that the distribution of dislocation-magnetic dipole is consistent, the models of dislocation-magnetic dipole for tensile fracture and tensile-tensile fatigue fracture are established, respectively: The distribution of magnetic dipole for tensile fracture is linear increase from distant to the fracture zone, while the distribution of magnetic dipole for tensile-tensile fatigue fracture is converging only at the fracture zone. It is found that the established model can present the change of peak-to-peak in magnetization for tensile fracture and tensile-tensile fatigue fracture.

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