The Experts below are selected from a list of 78 Experts worldwide ranked by ideXlab platform
Sylvester Abanteriba - One of the best experts on this subject based on the ideXlab platform.
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Analysis of the Lubrication Condition of a Crosshead Pin Bearing of a Large Marine Diesel Engine
Volume 1: Symposia Parts A and B, 2005Co-Authors: Sylvester AbanteribaAbstract:The main function of the crosshead bearing of a crosshead engine is to transmit the load from the connecting rod, which is directly attached to the piston of the engine, through a second rod to the Guide Shoe, which bears the entire crosshead. Apart from this function it enables the large normal forces, which are usually borne by the piston skirt in the case of a trunk piston engine, to be transmitted to the Guide Shoe from which it is subsequently transmitted to the rails along which the Guide Shoe glides. The dynamics of the crosshead bearing is such that the bearing pin is subjected to very low levels of incomplete rotation resembling that executed by a pendulum over a reduced arc. The bearing is also subjected to the load in only one direction. These operating conditions augur poorly for the formation of the hydrodynamic oil film necessary to support the imposed load. This type of bearing is therefore susceptible to considerable friction losses and significant wear as a result of lack of the capacity to generate lubrication film. This paper evaluates a model to determine the levels of achievable hydrodynamic film and the measures introduced to generate a hydrostatic squeeze lubricating film in the bearing as a result of the introduction of high pressure oil during part of the operating cycle of the engine.Copyright © 2005 by ASME
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The Analysis of the Lubrication Condition and Friction Losses of a Single Acting Cross Head Guide Shoe of a Low Speed Cross Head Diesel Engine: Part I—An Alogrithm For The Prediction of Oil Film Thickness
Tribology Transactions, 2000Co-Authors: Sylvester AbanteribaAbstract:The lubrication condition pertaining to the cross head Guide Shoe of a low speed cross head diesel engine is evaluated in this paper under the principles of hydrodynamic lubrication. The Reynolds differential equation which describes the pressure and oil film thickness distribution of the cross head Guide Shoe system operating under unsteady load will be solved using a finite difference method. The influence of the width to length ratio of the rectangular cross head Guide Shoe plate will be considered in terms of variation of the pressure distribution within the bearing and its load carrying capacity.
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The Analysis of the Lubrication Condition and Friction Losses of a Single Acting Cross Head Guide Shoe of a Low Speed Cross Head Diesel Engine: Part II — A Practical Model for the Determination of the Oil Film Thickness
Tribology Transactions, 2000Co-Authors: Sylvester AbanteribaAbstract:The cross head Guide Shoe plate of a large diesel engine operates under a large normal force which presses it against the rails between which it executes both axial and transverse motion. In order to ensure the safe operation of an unconventional bearing such as the Guide Shoe system of the cross head engine, an algorithm that can be used to predict accurately the oil film thickness that can be achieved for all the engine's operating regimes, is invaluable. A solution of the three dimensional form of Reynolds differential equation can provide the requisite oil film thickness. However, with even the availability of very fast computers and large computer storage capacity this solution for a large axial bearing such as the Guide Shoe becomes impractical in terms of computation time and computer core requirements. This paper describes alternative simplified algorithm for accurate prediction of the oil film thickness developed in the Guide Shoe bearing at different operating regimes of the engine.
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The Analysis of the Lubrication Condition and Friction Losses of a Single Acting Cross Head Guide Shoe of a Low Speed Cross Head Diesel Engine: PART III — Friction and Its Minimization
Tribology Transactions, 2000Co-Authors: Sylvester AbanteribaAbstract:This paper describes a model which can be used to analyze the friction losses in the Guide Shoe of the cross head bearing of a large two stroke diesel engine. It describes further methods by which the friction losses in this component can be significantly reduced.
Gerard T. Pittard - One of the best experts on this subject based on the ideXlab platform.
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SEALING LARGE-DIAMETER CAST-IRON PIPE JOINTS UNDER LIVE CONDITIONS
2004Co-Authors: Kiran M. Kothari, Gerard T. PittardAbstract:Utilities in the U.S. operate over 75,000 km (47,000 miles) of old cast-iron pipes for gas distribution. The bell-and-spigot joints that connect pipe sections together tend to leak as these pipes age. Current repair practices are costly and highly disruptive. The objective of this program is to design, test and commercialize a robotic system capable of sealing multiple castiron bell and spigot joints from a single pipe entry point. The proposed system will perform repairs while the pipe remains in service by traveling through the pipe, cleaning each joint surface, and installing a stainless-steel sleeve lined with an epoxy-impregnated felt across the joint. This approach will save considerable time and labor, avoid traffic disruption, and eliminate any requirement to interrupt service to customers (which would result in enormous expense to utilities). Technical challenges include: (1) repair sleeves must compensate for diametric variation and eccentricity of cast-iron pipes; (2) the assembly must travel long distances through pipes containing debris; (3) the pipe wall must be effectively cleaned in the immediate area of the joint to assure good bonding of the sleeve; and (4) an innovative bolt-on entry fitting is required to conduct repair operations on live mains. The development effort is divided into eleven tasks. Task 1 (Program Management) and Task 2 (Establishment of Detailed Design Specifications) were completed in prior quarters while Task 3 (Design and Fabricate Ratcheting Stainless-Steel Repair Sleeves) has progressed to installing prototype sleeves in cast iron test pipe segments. Efforts in this quarter continued to focus on Tasks 4-8, with significant progress made in each as well as field testing of the 4-inch gas pipe repair robot in cast iron pipe at Public Service Electric & Gas. The field tests were conducted August 23-26, 2004 in Oradell, New Jersey. The field tests identified several design issues which need to be implemented in both the small- and large-diameter cast iron repair robots to assure their commercial success. Task 4 (Design, Fabricate and Test Patch Setting Robotic Train) progressed to the design of the control electronics and pneumatic system to inflate the bladder robotic patch setting module in the last quarter 5. In this quarter, work has been concentrated on increasing the nitrogen bladder reservoir volume to allow at least two complete patch inflation/patch setting cycles in the event the sleeve does not set all ratchets in the same row on the first attempt. This problem was observed on a few of the repair sleeves that were recently installed during field tests with the small-diameter robotic system. For Task 5 (Design & Fabricate Pipe-Wall Cleaning Robot Train with Pan/Zoom/Tilt Camera) it was observed that it will be necessary to add a stiff brush to push debris away from the immediate vicinity of the bell and spigot joints in mains having low gas velocities. Otherwise, material removed by the cleaning flails (which were found to be very effective in cleaning bell and spigot joints) simply falls to the low side of the pipe and accumulates in a pile. This accumulation can prevent the sleeve from achieving a leak free repair. Similarly, it is also necessary to design a small magnet to capture existing service tap coupons and allow their removal from the inside of the pipe. These coupons were found to cause difficulty in launching and retrieving the small pipe repair robot; one coupon lodged beneath the end of the Guide Shoe. These new features require redesign of the pipe wall cleaning train and modification to the patch setting train. Task 6 (Design & Build Surface Control and Monitoring System) was previously completed with the control and computer display functions being operated through LabView. However, this must now be re-visited to add control routines for the coupon catcher to be added. This will most likely include a lift-off/place-on magnet translation function. Task 7 (Design & Fabricate Large Diameter Live Access System) progressed to completing the detailed design of the entry fitting for 12-inch diameter cast iron pipe in the previous quarter. Field tests with the 4-inch size fitting were completely successful and did not reveal any significant design issues. The primary suggestion from the PSE&G field crew was to produce a version which completely bolts together and does not require a long seam weld. This could be used in low-pressure cast iron mains to reduce installation time. A bolt-on version is now being designed based on this recommendation. Task 8 (System Integration and Laboratory Validation) continued with the development of the robot module inter-connects and of a master LabView-based system display and control software.
Gerard T. Pittard - One of the best experts on this subject based on the ideXlab platform.
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SEALING LARGE-DIAMETER CAST-IRON PIPE JOINTS UNDER LIVE CONDITIONS
2005Co-Authors: Kiran M. Kothari, Gerard T. PittardAbstract:Utilities in the U.S. operate over 75,000 km (47,000 miles) of old cast-iron pipes for gas distribution. The bell-and-spigot joints that connect pipe sections together tend to leak as these pipes age. Current repair practices are costly and highly disruptive. The objective of this program is to design, test and commercialize a robotic system capable of sealing multiple cast-iron bell and spigot joints from a single pipe entry point. The proposed system will perform repairs while the pipe remains in service by traveling through the pipe, cleaning each joint surface, and installing a stainless-steel sleeve lined with an epoxy-impregnated felt across the joint. This approach will save considerable time and labor, avoid traffic disruption, and eliminate any requirement to interrupt service to customers (which would result in enormous expense to utilities). Technical challenges include: (1) repair sleeves must compensate for diametric variation and eccentricity of cast-iron pipes; (2) the assembly must travel long distances through pipes containing debris; (3) the pipe wall must be effectively cleaned in the immediate area of the joint to assure good bonding of the sleeve; and (4) an innovative bolt-on entry fitting is required to conduct repair operations on live mains. The development effort is divided into eleven tasks. Task 1 (Program Management) and Task 2 (Establishment of Detailed Design Specifications) were completed in prior quarters while Task 3 (Design and Fabricate Ratcheting Stainless-Steel Repair Sleeves) has progressed to installing prototype sleeves in cast-iron test pipe segments. Efforts in the current quarter continued to focus on Tasks 4-8. Highly valuable lessons were learned from field tests of the 4-inch gas pipe repair robot in cast-iron pipe at Public Service Electric & Gas. (These field tests were conducted and reported last quarter.) These tests identified several design issues which need to be implemented in both the small- and large-diameter repair robots for cast-iron pipe to assure their commercial success. For Task 4 (Design, Fabricate and Test Patch Setting Robotic Train), work has been directed on increasing the nitrogen bladder reservoir volume to allow at least two complete patch inflation/patch setting cycles in the event the sleeve does not set all ratchets in the same row on the first attempt. This problem was observed on a few of the repair sleeves that were recently installed during field tests with the small-diameter robotic system. For Task 5 (Design & Fabricate Pipe-Wall Cleaning Robot Train with Pan/Zoom/Tilt Camera), the recent field tests showed clearly that, in mains with low gas velocities, it will be necessary to improve the system's capacity to remove debris from the immediate vicinity of the bell and spigot joints. Otherwise, material removed by the cleaning flails (the flails were found to be very effective in cleaning bell and spigot joints) falls directly to the low side of the pipe and accumulates in a pile. This accumulation can prevent the sleeve from achieving a leak-free repair. Similarly, it is also deemed necessary to design an assembly to capture existing service-tap coupons and allow their removal from the inside of the pipe. These coupons were found to cause difficulty in launching and retrieving the small pipe repair robot; for example, one coupon lodged beneath the end of the Guide Shoe. Designs for new features to accomplish these goals for the large robotic system were pursued and are presented in this report. Task 6 (Design & Build Surface Control and Monitoring System) was previously completed with the control and computer display functions being operated through LabVIEW. However, this must now be revisited to add control routines for the coupon catcher to be added. This will most likely include a lift-off/place-on magnet translation function. Task 7 (Design & Fabricate Large Diameter Live Access System) progressed to completing the detailed design of the entry fitting for 12-inch diameter cast iron pipe in the previous quarter. Field tests with the 4-inch size fitting were completely successful and did not reveal any significant design issues. The primary suggestion from the PSE&G field crew was to produce a version which completely bolts together and does not require a long seam weld. This could be used in low-pressure cast iron mains to reduce installation time. A bolt-on version is being designed based on this recommendation. Task 8 (System Integration and Laboratory Validation) continued with the development of the robot module inter-connects and of a master LabVIEW-based system display and control software
F. J. Martínez - One of the best experts on this subject based on the ideXlab platform.
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Application of wear modelling methodology to the design of a lift car installation by means of finite element simulation
Meccanica, 2014Co-Authors: F. J. Martínez, M. A. Jiménez, M. A. MartínezAbstract:The aim of this work is to study the applicability of a numerical-experimental methodology for wear modelling to the design of a lift car installation by means of finite element simulations. The study focuses on the sliding of Guide Shoe inserts, made of thermoplastic polyurethane, TPU, over fixed lift car Guides, made of steel. This component includes the same polymer-metal contact pair formerly studied in a tribometer test, working under sliding conditions in reciprocating relative movement. This simulation allows to get final wear predictions in the component considering real installation parameters, as well as the wear distribution in the contact faces of the Guide Shoe inserts with the counterpart. Additionally, the work also includes a numerical sensitivity analysis of how several design variables determine the wear amount of the component.
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Finite element implementation and validation of wear modelling in sliding polymer–metal contacts
Wear, 2012Co-Authors: F. J. Martínez, M. A. Jiménez, M. Canales, Salvador Izquierdo, Miguel Ángel MartínezAbstract:Abstract The objective of this work is to present an integral methodology to numerically model the wear phenomena by friction in a polymer–metal contact pair, showing the development of a numerical tool to implement a wear model in the commercial finite element code Abaqus. The contact pair in which this work is based corresponds to the contact between a Guide Shoe insert for an elevator, made of thermoplastic polyurethane elastomers (TPU), and the corresponding Guide, made of steel. Tribometer tests are planned to fit the numerically implemented wear model as well as to validate it. These tests are briefly described as an introduction to the numerical fitting of the data from which the wear model is obtained. The numerical tool in which the wear model in a polymer–steel contact pair is implemented is based on a methodology that combines the use of the user subroutine Umeshmotion, which offers the possibility of implementing a wear model in any general form, several routines to result access, and the adaptive meshing technique, a mesh smoothing tool available in Abaqus based on ALE (Augmented Lagrangian Eulerian) methods. With this technique, it is possible to eliminate material during the simulation as well as to maintain a high-quality mesh throughout an analysis by allowing the mesh to move independently of the material. As the tests that are carried out in the tribometer to fit and to validate the wear model require long travel distances and a large number of cycles, a real simulation of those tests would require a huge calculation time. Therefore, to simulate the wear process equivalent to the travelled distances in the tests in an affordable simulation time, an accelerated numerical procedure of the wear process is also proposed in this work. To numerically implement the wear model, and as it is usually stated in polymers, it is previously necessary to set up a procedure for determining the relationship between the friction coefficient and the contact pressure for the material and countermaterial contact pair. Finally, a validation of the methodology with a new wear tribometer test under different conditions to those stated to characterise the model is also presented.
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Relationship between wear rate and mechanical fatigue in sliding TPU–metal contacts
Wear, 2010Co-Authors: F. J. Martínez, M. Canales, J.m. Bielsa, M. A. JiménezAbstract:The present paper reports the process for obtaining a law of wear by friction that reproduces the behaviour of a contact pair between a Guide Shoe insert, made of TPU, and the corresponding Guide, made of steel, in a lift Guide Shoe application. After an initial identification of the TPU wear type as fatigue wear, the wear law is fitted from tests carried out in a tribometer, obtaining a relationship between the TPU worn volume and two fundamental variables: the travelled distance and the applied load. Archard's law, a relationship commonly used by many authors in the literature, is taken as a starting point, analysing its validity in this case and proposing an improved fitting by means of a potential law.Additionally, in order to analyse in depth the physical phenomena that Guide the wear process present in the contact pair under study, and corroborating what was stated by the law fitted previously, the wear process is studied by means of observations by SEM and confocal microscopy by finite element simulations at micro-level, analysing the interaction between material and countermaterial. The results from these analyses are compared with conclusions stated by several authors in the literature in similar studies of other polymers. Finally, this study is completed with an analysis of the analogy between wear and mechanical fatigue, relating both phenomena, in order to confirm the assertion stated in previous studies: the wear process in TPU occurs as a result of repeated crack propagation in the subsurface layer of the material at small scale.
M. A. Martínez - One of the best experts on this subject based on the ideXlab platform.
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Application of wear modelling methodology to the design of a lift car installation by means of finite element simulation
Meccanica, 2014Co-Authors: F. J. Martínez, M. A. Jiménez, M. A. MartínezAbstract:The aim of this work is to study the applicability of a numerical-experimental methodology for wear modelling to the design of a lift car installation by means of finite element simulations. The study focuses on the sliding of Guide Shoe inserts, made of thermoplastic polyurethane, TPU, over fixed lift car Guides, made of steel. This component includes the same polymer-metal contact pair formerly studied in a tribometer test, working under sliding conditions in reciprocating relative movement. This simulation allows to get final wear predictions in the component considering real installation parameters, as well as the wear distribution in the contact faces of the Guide Shoe inserts with the counterpart. Additionally, the work also includes a numerical sensitivity analysis of how several design variables determine the wear amount of the component.