Cracked Shaft Detection Using the Unbalance Excitation Technique

1995 ◽  
Author(s):  
Farokh H. Kavarana ◽  
R. Gordon Kirk
Keyword(s):  
Crack Detection ◽  
Direct Result ◽  
Response Characteristics ◽  
The Past ◽  
Promising Tool ◽  
Complete Test ◽  
Vibration Signature ◽  
Complete Failure ◽  
Cracked Shafts ◽  
Cracked Shaft

Abstract The ever-growing interest of the modern rotordynamicist in the early detection of rotor cracks in turbomachinery has been the direct result of multiple catastrophic experiences that industry has faced in recent times due to cracked rotors. The complete failure of the rotor due to crack propagation is easily recognized as one of the most serious modes of plant failure. Even though the past decade has witnessed some laudable attempts that have been moderately successful in detecting cracked rotors, this aspect has not received the attention it warrants. A complete test rig has been designed and constructed for experimental research on the response characteristics of cracked rotors, the results of which will permit increased confidence in detecting the presence of rotor cracks in turbomachinery. The rig is capable of testing cracked shafts under the effect of lateral and coupled lateral/torsional vibrations. Conventional vibration signature analysis has been employed for the purpose of crack detection. This paper presents the details of the rig capabilities and results from the unbalance excitation technique applied for crack detection. The response of a cracked shaft differs markedly from that of an uncracked shaft when subjected to a known unbalance. This paper shows that unbalance excitation is a promising tool for cracked shaft detection.

Crack Detection in Shafts of Rotating Machinery Using Active Sensing With an External Excitation on a Bearing

2008 ◽  
Author(s):  
Jose´ M. Machorro-Lo´pez ◽  
Douglas E. Adams ◽  
Julio C. Go´mez-Mancilla
Keyword(s):  
Power Plants ◽  
Crack Detection ◽  
Experimental Tests ◽  
Element Model ◽  
Rotating Machinery ◽  
Mode Shapes ◽  
External Excitation ◽  
Transverse Cracks ◽  
Cracked Shafts ◽  
Cracked Shaft

Because several power plants have undergone burst shafts with catastrophic consequences, methods for detecting cracks in the shafts of rotating machinery are of great interest to the research community. Cracked shafts represent a very small percentage of the vibration issues in machinery (less than 2%) compared with other faults such as misalignment and mass imbalance, which are responsible for 85% of these issues. However, if a cracked shaft is not detected early enough, it can jeopardize the safety of operators and result in high costs for replacement. A method sensitive enough to detect cracks in the shafts of rotating machinery is investigated in this paper. It is shown that changes in the natural frequencies and/or mode shapes are not sensitive enough indicators to detect transverse cracks at the mid-span of shafts in rotating machinery. An exhaustive numerical analysis using a finite element model of a simple machine is conducted to consider many different measurements of the machinery vibratory responses that most clearly detect cracking. It is shown that external excitations applied on a bearing enhance the sensitivity of vibration measurements to cracking. Experimental tests are also used to validate several of the numerical simulation findings.

Performance Assessment of the Lead User Idea-Generation Process for New Product Development

2002 ◽  
Vol 48 (8) ◽  
pp. 1042-1059 ◽  
Author(s):  
Gary L. Lilien ◽  
Pamela D. Morrison ◽  
Kathleen Searls ◽  
Mary Sonnack ◽  
Eric von Hippel
Keyword(s):  
New Product Development ◽  
Idea Generation ◽  
New Product ◽  
Major Product ◽  
Product Line ◽  
Direct Result ◽  
Target Market ◽  
Generation Process ◽  
The Past ◽  
Lead User

Traditional idea generation techniques based on customer input usually collect information on new product needs from a random or typical set of customers. The “lead user process” takes a different approach. It collects information about both needs and solutions from users at the leading edges of the target market, as well as from users in other markets that face similar problems in a more extreme form. This paper reports on a natural experiment conducted within the 3M Company on the effect of the lead user (LU) idea-generation process relative to more traditional methods. 3M is known for its innovation capabilities— and we find that the LU process appears to improve upon those capabilities. Annual sales of LU product ideas generated by the average LU project at 3M are conservatively projected to be $146 million after five years—more than eight times higher than forecast sales for the average contemporaneously conducted “traditional” project. Each funded LU project is projected to create a new major product line for a 3M division. As a direct result, divisions funding LU project ideas are projecting their highest rate of major product line generation in the past 50 years.

Choosing Surgery: Identifying Factors Leading to Increased General Surgery Matriculation Rate

2017 ◽  
Vol 83 (3) ◽  
pp. 290-295 ◽  
Author(s):  
David T. Pointer ◽  
Matthew D. Freeman ◽  
James R. Korndorffer ◽  
Peter C. Meade ◽  
Bernard M. Jaffe ◽  
...  
Keyword(s):  
General Surgery ◽  
Role Models ◽  
Medical Student Education ◽  
Direct Result ◽  
Factors Affecting ◽  
The Past ◽  
Education Experience ◽  
Surgical Career ◽  
Core Rotation ◽  
Question Survey

Tulane graduates have, over the past six years, chosen general surgical residency at a rate above the national average (mean 9.6% vs 6.6%). With much of the recent career choice research focusing on disincentives and declining general surgery applicants, we sought to identify factors that positively influenced our students’ decision to pursue general surgery. A 50-question survey was developed and distributed to graduates who matched into a general surgery between the years 2006 and 2014. The survey evaluated demographics, exposure to surgery, and factors affecting interest in a surgical career. We achieved a 54 per cent (61/112) response rate. Only 43 per cent considered a surgical career before medical school matriculation. Fifty-nine per cent had strongly considered a career other than surgery. Sixty-two per cent chose to pursue surgery during or immediately after their surgery clerkship. The most important factors cited for choosing general surgery were perceived career enjoyment of residents and faculty, resident/faculty relationship, and mentorship. Surgery residents and faculty were viewed as role models by 72 and 77 per cent of responders, respectively. This study demonstrated almost half of those choosing a surgical career did so as a direct result of the core rotation experience. We believe that structuring the medical student education experience to optimize the interaction of students, residents, and faculty produces a positive environment encouraging students to choose a general surgery career.

New Rights – New Laws: South African Legal Literature in a Time of Transition

2004 ◽  
Vol 32 (2) ◽  
pp. 390-416
Author(s):  
Amanda Barratt
Keyword(s):  
South African ◽  
Political System ◽  
Direct Result ◽  
The Political ◽  
The Past ◽  
Legal Literature ◽  
Substantive Law

The title of this paper follows the 2003 Meeting theme: Law in a Time of Transition. Speakers thus far have discussed the various ways in which South African substantive law has changed since 1990. With such far-reaching changes in the political and legal landscape, one would expect to see some changes in the legal literature. There have indeed been profound changes in the forms of legal publication over the past few years, some of which would seem to be a direct result of the new legal and political system. I refer in this context not so much to the content and substance of our statutes and decided cases, but rather to the forms in which they are made available.

Transplantation is the best treatment for hypoplastic left heart syndrome

2004 ◽  
Vol 14 (S1) ◽  
pp. 109-111 ◽  
Author(s):  
Leonard L. Bailey
Keyword(s):  
Hypoplastic Left Heart Syndrome ◽  
Reconstructive Surgery ◽  
Cardiac Transplantation ◽  
Direct Result ◽  
Left Heart ◽  
Hypoplastic Left Heart ◽  
Surgical Strategies ◽  
The Past ◽  
Left Heart Syndrome

Thank you for asking me to make the case for cardiac transplantation in this debate. Marshall, that was a truly comprehensive and spectacular defense of the value of reconstructive surgery in babies born with hypoplastic left heart syndrome. It is clear that the potential for babies born with this complex and lethal malformation has improved dramatically over the past 2 decades. The improvement in outcome is a direct result of complementary surgical strategies. Marshall Jacobs has constructed a stellar review outlining the important issues relating to the ever-evolving staged palliative reconstruction for hypoplastic left heart syndrome. And, he appealed to those present at the Symposium with some images of extraordinary children who represent the most favorable outcomes seen today after staged reconstructive surgery. It would be inappropriate for me to criticize or condemn any feature of these favorable outcomes.

scholarly journals The Great War and popular modernism: Pat Hanna's Louis XI

2016 ◽  
Vol 23 (2) ◽  
pp. 133-142
Author(s):  
Richard Fotheringham
Keyword(s):  
Real Life ◽  
Direct Result ◽  
Great War ◽  
High Culture ◽  
Shell Shock ◽  
Popular Theatre ◽  
Avant Garde ◽  
The Past ◽  
First Time ◽  
The Great War

AbstractPat Hanna's Famous Diggers, a professional vaudeville theatre troupe comprising ex-Great War Anzac soldiers (initially, mainly New Zealanders, as Hanna was himself) played for nearly two years (1923–24) at the old Cremorne Theatre in Brisbane. One item Hanna premiered at the Cremorne was Louis XI, a short (ten-minute) comic sketch he wrote himself. Modernism in the inter-war years, given its usual location within avant-garde aesthetics, high culture, internationalism and radical politics, is not — with the notable exception of Brecht's cabaret work in the 1920s — usually associated with popular theatre. While one comic playlet hardly challenges that positioning, Louis XI was a direct result of the Great War's profound reshaping of modern life. Many of the dramatised sketches performed by Hanna's company, including Louis XI, were structured around a contrast between events as they had occurred in the trenches and as they were portrayed in a utopian or dystopian fantasy, sometimes triggered by shell shock or a dream. Several, again including Louis XI, involve the past, and express the curiosity and cultural dislocation Australian- and New Zealand-born soldiers felt as they moved for the first time through real-life landscapes and architecture they had known only from popular history and romance.

Dynamic Response Analysis of Rotor-Bearing Systems With Cracked Shaft

2002 ◽  
Vol 124 (4) ◽  
pp. 690-696 ◽  
Author(s):  
M. A. Mohiuddin ◽  
Y. A. Khulief
Keyword(s):  
Large Scale ◽  
Crack Detection ◽  
Equations Of Motion ◽  
Response Analysis ◽  
Reduced Order ◽  
Stepped Shaft ◽  
Rotor Bearing ◽  
Element Approach ◽  
Detection Schemes ◽  
Cracked Shaft

A general dynamic model for a large-scale rotor-bearing system with a cracked shaft is introduced. A finite shaft element with a crack is developed using a consistent finite element approach. The model accommodates shafts with tapered portions, multiple disks and anisotropic bearings. The formulation is applicable to rotor-bearing systems with different practical design configurations including intermediate bearings, shaft overhang, and stepped shaft assemblies. A reduced order form of equations of motion is obtained by invoking the actual non-planar (complex) modal transformations. The time-response due to different excitations are calculated, and comparisons are presented to establish the validity and efficiency of the reduced order model. It is hoped that the developed computational scheme offers an efficient and essential core module in establishing other specialized crack detection schemes for rotor-bearing systems.

Dynamic Analysis of Flapper/Nozzle Electrohydraulic Servovalve Considering the Influence of the First-Stage Parameters

2014 ◽  
Vol 687-691 ◽  
pp. 316-321
Author(s):  
Wei Zhang ◽  
Song Jing Li
Keyword(s):  
Dynamic Response ◽  
Dynamic Analysis ◽  
Simulation Model ◽  
Discharge Coefficient ◽  
Mathematic Model ◽  
Viscous Damping ◽  
Response Characteristics ◽  
The Past ◽  
Simulation Results ◽  
Dynamic Response Characteristics

The mathematic model of flapper/nozzle electrohydraulic servovalves is rearranged, many factors are reconsidered which have been omitted in the past analysis which are for the purposes of convenience or on the assumption that they are of no particular significance. According to the rearranged mathematic model, the simulation model of the servovalve is established using the Matlab/simulink software, dynamic response characteristics of the servovalve is simulated when the parameters of the discharge coefficient of nozzles and the viscous damping constant of torque motor and flapper are changed. Simulation results show that the change of the parameters influence the dynamic response of the spool displacement.

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.

A Kineto-Static Model for a Cracked Shaft Flexible Bearing System With Linear-Angular Coupled DOF in Bending

2007 ◽  
Author(s):  
Alfayo Anyika Alugongo ◽  
Josiah Lange Munda
Keyword(s):  
Crack Detection ◽  
Linear Time ◽  
Time History ◽  
Frequency Spectra ◽  
Rotating Speed ◽  
Shallow Crack ◽  
Bearing System ◽  
Variant System ◽  
Cracked Shaft ◽  
Vector Approach

In this paper, a model for vibration of a cracked rotor shaft flexible bearing system with linear-angular coupled DOF in bending is proposed. A vector approach on the change of the system’s angular momentum at a steady state has been used to derive the equation of motion leading to a linear time-variant system. By considering the forces and moments in the kinematic pairs of the shaft and bearing, an equivalent coupled 4-DOF complex spring is analytically introduced to simulate the system at a low rotating speed with the crack as an external force. Consequently, the Kineto-static response has been obtained by restricting the system to strong parameters. Viability of the model for investigating the complex response of a shallow-crack rotor bearing system has been demonstrated by analysis and features in time history and frequency spectra explored for crack detection. Various scenarios are considered, and the presented results concur with the published literature.

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