Analysis of the Elastic Wave Behavior in a Cracked Shaft

2007 ◽  
Author(s):  
Kelsen LaBerge ◽  
Maurice Adams
Keyword(s):  
Crack Detection ◽  
Acoustic Velocity ◽  
New Method ◽  
Proof Of Concept ◽  
Test Apparatus ◽  
Rotating Shaft ◽  
One Dimensional ◽  
Crack Location ◽  
The Impact ◽  
Cracked Shaft

A new method currently under development for rotating shaft crack detection is presented. The underlying approach is to utilize the impact inherent in the once-per-revolution closing of a shaft crack. The axially traveling elastic compression wave, which is initiated by this impact, propagates to both ends of the shaft at the governing acoustic velocity. Provided suitable measurement near the shaft ends can detect the wave’s arrival, then extracting both the crack location and size is thereby feasible. Proof-of-concept for this new method for shaft crack detection utilizes one-dimensional wave propagation simulations and a newly designed test apparatus, which are presented.

In-Plane Vibration and Crack Detection of a Rotating Shaft-Disk Containing a Transverse Crack

1998 ◽  
Vol 120 (2) ◽  
pp. 551-556 ◽  
Author(s):  
Ming-Chuan Wu ◽  
Shyh-Chin Huang
Keyword(s):  
Crack Detection ◽  
Transverse Crack ◽  
Rotation Speed ◽  
Crack Depth ◽  
Multiple Scale ◽  
Crack Identification ◽  
Response Curves ◽  
Rotating Shaft ◽  
Crack Location ◽  
Depth Rotation

Dynamic response and stability of a rotating shaft-disk containing a transverse crack is investigated. FFT analysis of response amplitudes showed that the 2Ω component (Ω: rotation speed) was excited by crack breathing and could serve as a good index for crack identification. Intensive numerical studies of crack location, crack depth, rotation speed, and sensing position on response amplitudes displayed a feasible technique for the identification of crack depth and crack location. It is achieved by intersecting the two equi-amplitude response curves of two separated sensing probes. Finally, the instability of the system caused by a crack is examined via Floquet theory and the multiple scale method. The stability diagrams, illustrated as functions of crack depth, rotation speed, and damping, are shown and discussed.

The Dynamics of a Rotor System with a Cracked Shaft

1986 ◽  
Vol 108 (2) ◽  
pp. 189-196 ◽  
Author(s):  
H. D. Nelson ◽  
C. Nataraj
Keyword(s):  
Computer Code ◽  
Fourier Series Expansion ◽  
Simulation Studies ◽  
Cracked Rotor ◽  
Rotating Shaft ◽  
Crack Location ◽  
Excited System ◽  
System Equations ◽  
Stiffness Variation ◽  
Cracked Shaft

A theoretical analysis of the dynamics of a rotor-bearing system with a transversely cracked rotor is presented. The rotating assembly is modeled using finite rotating shaft elements and the presence of a crack is taken into account by a rotating stiffness variation. This stiffness variation is a function of the rotor’s bending curvature at the crack location and is represented by a Fourier series expansion. The resulting parametrically excited system is nonlinear and is analyzed using a perturbation method coupled with an iteration procedure. The system equations are written in terms of complex variables and an associated computer code has been developed for simulation studies. Results obtained by this analysis procedure are compared with previous analytical and experimental work presented by Grabowski.

Dynamics of Large Power Rotating Machine with Cracked Shaft

2005 ◽  
Vol 293-294 ◽  
pp. 337-346
Author(s):  
Slawomir Banaszek
Keyword(s):  
Crack Detection ◽  
Crack Depth ◽  
Computer Code ◽  
Crack Model ◽  
Simulation Research ◽  
Large Power ◽  
Crack Location ◽  
Rotating Machine ◽  
Diagnostic Indicator ◽  
Cracked Shaft

The paper presents the course and results of crack propagation simulation research. The object taken into account is a large power turbo-set rotor. The computer code system NLDW is presented. It uses a non-linear model of journal bearings, and well known crack model. Crack depth is marked by a crack coefficient. It is shown the crack generates a coupled forms of lateral, axial and torsional vibrations in multi-support rotor. Their intensity depends on the axial and circumferential crack location on the shaft. The attempt at pointing a proper diagnostic indicator for crack detection in large rotating machine is made according to obtained results.

Approximate analytical method for damage detection in free–free beam by measurement of axial vibrations

2012 ◽  
Vol 22 (1) ◽  
pp. 133-142 ◽  
Author(s):  
FB Sayyad ◽  
B Kumar ◽  
SA Khan
Keyword(s):  
Crack Detection ◽  
Natural Frequencies ◽  
Preventive Measure ◽  
Theoretical Method ◽  
Crack Size ◽  
Structural Element ◽  
Global Parameter ◽  
Crack Location ◽  
Vibration Data ◽  
The Impact

Nowadays, sophisticated structures and machinery parts are constructed by using metallic beams. Beams are widely used as structural element in civil, mechanical, naval, and aeronautical engineering. In structures and machinery, one undesirable phenomenon is crack initiation in which the impact cannot be seen overnight. Cracks develop gradually through time that lead finally to catastrophic failure. Therefore, crack should be monitored regularly with more care. This will lead to more effective preventive measure and ensure continuous operation of the structure and machine. Damage in structure alters its dynamic characteristics. The change is characterized by change in modal parameters, that is, modal frequencies. Thus, vibration technique can be suitably used as a nondestructive test for crack detection of component to be tested. Mostly modal frequencies are used for monitoring the crack because modal frequencies are properties of the whole structure component. In this paper, efforts are made to develop suitable methods that can serve as the basis to detection of crack location and crack size from measured axial vibration data. This method is used to address the inverse problem of assessing the crack location and crack size in various beam structure. The method is based on measurement of axial natural frequencies, which are global parameter and can be easily measured from any point on the structure and also indeed, the advantage in modeling complexity. In theoretical analysis, the relationship between the natural frequencies, crack location, and crack size has been developed. For identification of crack location and crack size, it was shown that data on the variation of the first two natural frequencies is sufficient. The experimental analysis is done to verify the practical applicability of the theoretical method developed.

A new method showing the impact of pulp refining on fiber-fiber interactions in wet webs

2016 ◽  
Vol 31 (2) ◽  
pp. 205-212 ◽  
Author(s):  
Belle Jürgen ◽  
Kleemann Stephan ◽  
Odermatt Jürgen ◽  
Olbrich Andrea
Keyword(s):  
New Method ◽  
The Impact

scholarly journals A Natural Language Processing Approach to Measuring Treatment Adherence and Consistency Using Semantic Similarity

AERA Open ◽  
2021 ◽  
Vol 7 ◽  
pp. 233285842110286
Author(s):  
Kylie L. Anglin ◽  
Vivian C. Wong ◽  
Arielle Boguslav
Keyword(s):  
Natural Language Processing ◽  
Natural Language ◽  
Semantic Similarity ◽  
Language Processing ◽  
Intervention Implementation ◽  
Proof Of Concept ◽  
Coaching Intervention ◽  
Processing Techniques ◽  
Teacher Coaching ◽  
The Impact

Though there is widespread recognition of the importance of implementation research, evaluators often face intense logistical, budgetary, and methodological challenges in their efforts to assess intervention implementation in the field. This article proposes a set of natural language processing techniques called semantic similarity as an innovative and scalable method of measuring implementation constructs. Semantic similarity methods are an automated approach to quantifying the similarity between texts. By applying semantic similarity to transcripts of intervention sessions, researchers can use the method to determine whether an intervention was delivered with adherence to a structured protocol, and the extent to which an intervention was replicated with consistency across sessions, sites, and studies. This article provides an overview of semantic similarity methods, describes their application within the context of educational evaluations, and provides a proof of concept using an experimental study of the impact of a standardized teacher coaching intervention.

scholarly journals A Low-Cost Assistive Robot for Children with Neurodevelopmental Disorders to Aid in Daily Living Activities

2021 ◽  
Vol 18 (8) ◽  
pp. 3974
Author(s):  
Roberto J. López-Sastre ◽  
Marcos Baptista-Ríos ◽  
Francisco Javier Acevedo-Rodríguez ◽  
Soraya Pacheco-da-Costa ◽  
Saturnino Maldonado-Bascón ◽  
...  
Keyword(s):  
Neurodevelopmental Disorders ◽  
Low Cost ◽  
Children And Youth ◽  
Proof Of Concept ◽  
Robotic Platform ◽  
Assistive Robot ◽  
Technical Details ◽  
The Impact ◽  
Near Future ◽  
Everyday Living

In this paper, we present a new low-cost robotic platform that has been explicitly developed to increase children with neurodevelopmental disorders’ involvement in the environment during everyday living activities. In order to support the children and youth with both the sequencing and learning of everyday living tasks, our robotic platform incorporates a sophisticated online action detection module that is capable of monitoring the acts performed by users. We explain all the technical details that allow many applications to be introduced to support individuals with functional diversity. We present this work as a proof of concept, which will enable an assessment of the impact that the developed technology may have on the collective of children and youth with neurodevelopmental disorders in the near future.

scholarly journals A new method of inferring the size, number density, and charge of mesospheric dust from its in situ collection by the DUSTY probe

2019 ◽  
Vol 12 (3) ◽  
pp. 1673-1683 ◽  
Author(s):  
Ove Havnes ◽  
Tarjei Antonsen ◽  
Gerd Baumgarten ◽  
Thomas W. Hartquist ◽  
Alexander Biebricher ◽  
...  
Keyword(s):  
New Method ◽  
Production Model ◽  
Dust Particles ◽  
Bottom Plate ◽  
Charged Dust ◽  
Fundamental Parameters ◽  
Dust Charge ◽  
Analysis Technique ◽  
June July ◽  
The Impact

Abstract. We present a new method of analyzing measurements of mesospheric dust made with DUSTY rocket-borne Faraday cup probes. It can yield the variation in fundamental dust parameters through a mesospheric cloud with an altitude resolution down to 10 cm or less if plasma probes give the plasma density variations with similar height resolution. A DUSTY probe was the first probe that unambiguously detected charged dust and aerosol particles in the Earth's mesosphere. DUSTY excluded the ambient plasma by various biased grids, which however allowed dust particles with radii above a few nanometers to enter, and it measured the flux of charged dust particles. The flux measurements directly yielded the total ambient dust charge density. We extend the analysis of DUSTY data by using the impact currents on its main grid and the bottom plate as before, together with a dust charging model and a secondary charge production model, to allow the determination of fundamental parameters, such as dust radius, charge number, and total dust density. We demonstrate the utility of the new analysis technique by considering observations made with the DUSTY probes during the MAXIDUSTY rocket campaign in June–July 2016 and comparing the results with those of other instruments (lidar and photometer) also used in the campaign. In the present version we have used monodisperse dust size distributions.

A TWELFTH-ORDER FOUR-STEP FORMULA FOR THE NUMERICAL INTEGRATION OF THE ONE-DIMENSIONAL SCHRÖDINGER EQUATION

2003 ◽  
Vol 14 (08) ◽  
pp. 1087-1105 ◽  
Author(s):  
ZHONGCHENG WANG ◽  
YONGMING DAI
Keyword(s):  
Schrödinger Equation ◽  
Numerical Integration ◽  
Schrodinger Equation ◽  
Numerical Test ◽  
New Method ◽  
Step Method ◽  
One Dimensional ◽  
The Stability ◽  
The One ◽  
Order Four

A new twelfth-order four-step formula containing fourth derivatives for the numerical integration of the one-dimensional Schrödinger equation has been developed. It was found that by adding multi-derivative terms, the stability of a linear multi-step method can be improved and the interval of periodicity of this new method is larger than that of the Numerov's method. The numerical test shows that the new method is superior to the previous lower orders in both accuracy and efficiency and it is specially applied to the problem when an increasing accuracy is requested.

Sign in / Sign up

Export Citation Format

Share Document