Download or read book Gear Crack Propagation Investigations written by David G. Lewicki and published by . This book was released on 1996 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Gear Crack Propagation Path Studies Guidelines for Ultra Safe Design written by and published by . This book was released on 2001 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt: Design guidelines have been established to prevent catastrophic rim fracture failure modes when considering gear tooth bending fatigue. Analysis was performed using the finite element method with principles of linear elastic fracture mechanics. Crack propagation paths were predicted for a variety of gear tooth and rim configurations. The effects of rim and web thicknesses, initial crack locations, and gear tooth geometry factors such as diametral pitch, number of teeth, pitch radius, and tooth pressure angle were considered. Design maps of tooth/rim fracture modes including effects of gear geometry, applied load, crack size, and material properties were developed. The occurrence of rim fractures significantly increased as the backup ratio (rim thickness divided by tooth height) decreased. The occurrence of rim fractures also increased as the initial crack location was moved down the root of the tooth. Increased rim and web compliance increased the occurrence of rim fractures. For gears with constant pitch radii, coarser-pitch teeth increased the occurrence of tooth fractures over rim fractures. Also, 250 pressure angle teeth had an increased occurrence of tooth fractures over rim fractures when compared to 200 pressure angle teeth. For gears with constant number of teeth or gears with constant diametral pitch, varying size had little or no effect on crack propagation paths.

Download or read book Consideration of Moving Tooth Load in Gear Crack Propagation Predictions written by and published by . This book was released on 2000 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: Robust gear designs consider not only crack initiation, but crack propagation trajectories for a fail-safe design. In actual gear operation, the magnitude as well as the position of the force changes as the gear rotates through the mesh. A study to determine the effect of moving gear tooth load on crack propagation predictions was performed. Two dimensional analysis of an involuted spur gear and three-dimensional analysis of a spiral-bevel pinion gear using the finite element method and boundary element method were studied and compared to experiments. A modified theory for predicting gear crack propagation paths based on the criteria of Erdogan and Sih was investigated. Crack simulation based on calculated stress intensity factors and mixed mode crack angle prediction techniques using a simple static analysis in which the tooth load was located at the highest point of single tooth contact was validated. For three-dimensional analysis, however, the analysis was valid only as long as the crack did not approach the contact region on the tooth.

Download or read book Investigation of the Effects of Manufacturing Variations and Materials on Fatigue Crack Detection Methods in Gear Teeth written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-18 with total page 118 pages. Available in PDF, EPUB and Kindle. Book excerpt: The fatigue life of a gear tooth can be thought of as the sum of the number of cycles required to initiate a crack, N(sub i), plus the number of cycles required to propagate the crack to such a length that fracture occurs, N(sub p). The factors that govern crack initiation are thought to be related to localized stress or strain at a point, while propagation of a fatigue crack is a function of the crack tip parameters such as crack shape, stress state, and stress intensity factor. During a test there is no clear transition between initiation and propagation. The mechanisms of initiation and propagation are quite different and modeling them separately produces a higher degree of accuracy, but then the question that continually arises is 'what is a crack?' The total life prediction in a fracture mechanics model presently hinges on the assumption of an initial crack length, and this length can significantly affect the total life prediction. The size of the initial crack is generally taken to be in the range of 0.01 in. to 0.2 in. Several researchers have used various techniques to determine the beginning of the crack propagation stage. Barhorst showed the relationship between dynamic stiffness changes and crack propagation. Acoustic emissions, which are stress waves produced by the sudden movement of stressed materials, have also been successfully used to monitor the growth of cracks in tensile and fatigue specimens. The purpose of this research is to determine whether acoustic emissions can be used to define the beginning of crack propagation in a gear using a single-tooth bending fatigue test. Wheitner, Jeffrey A. and Houser, Donald R. Unspecified Center ACOUSTIC EMISSION; ACOUSTIC MEASUREMENT; BENDING FATIGUE; CRACK PROPAGATION; FATIGUE LIFE; FATIGUE TESTING MACHINES; FRACTURE MECHANICS; GEAR TEETH; NONDESTRUCTIVE TESTS; BEND TESTS; CRACKS; DETECTION; FATIGUE TESTS; STIFFNESS; STRESS WAVES...

Download or read book Three Dimensional Gear Crack Propagation Studies written by and published by . This book was released on 1998 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt: Three-dimensional crack growth simulation was performed on a split-tooth gear design using boundary element modeling and linear elastic fracture mechanics. Initial cracks in the fillet of the teeth produced stress intensity factors of greater magnitude (and thus, greater crack growth rates) than those in the root or groove areas of the teeth. Crack growth simulation was performed on a case study to evaluate crack propagation paths. Tooth fracture was predicted from the crack growth simulation for an initial crack in the tooth fillet region. Tooth loads on the uncracked mesh of the split-tooth design were up to five times greater than those on the cracked mesh if equal deflections of the cracked and uncracked teeth were considered. Predicted crack shapes as well as crack propagation life are presented based on calculated stress intensity factors, mixed-mode crack propagation trajectory theories, and fatigue crack growth theories.

Download or read book Effect of Speed Centrifugal Load on Gear Crack Propagation Direction written by and published by . This book was released on 2001 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Crack Propagation Studies to Determine Benign Or Catastrophic Failure Modes for Aerospace Thin rim Gears written by David G. Lewicki and published by . This book was released on 1996 with total page 186 pages. Available in PDF, EPUB and Kindle. Book excerpt: Analytical and experimental studies were performed to investigate the effect of rim thickness on gear tooth crack propagation. The goal was to determine whether cracks grew through gear teeth (benign failure mode) or through gear rims (catastrophic failure mode) for various rim thicknesses. The computer program used had an automated crack propagation option in which cracks were grown numerically using an automated re-meshing scheme. In addition, experimental studies were performed in the NASA Lewis Spur Gear Fatigue Rig. Good correlation between the predicted number of crack propagation cycles and measured number of cycles was achieved using both the Paris fatigue crack growth method and the Collipfiest crack growth equation when fatigue crack closure was considered.

Download or read book Gear Crack Detection Using Tooth Analysis written by and published by . This book was released on 2002 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt: Gear cracks are typically difficult to diagnose with sufficient warning time. Significant damage must he present before algorithms detect the damage. A new feature extraction and two new detection techniques are proposed. The time synchronous averaging concept was extended from revolution-based to tooth engagement-based. The detection techniques are based on statistical comparisons among the averages for the individual teeth. These techniques were applied to a series of three seeded fault crack propagation tests. These tests were conducted on aerospace quality spur gears in a test rig. The tests were conducted at speeds ranging from 2500 to 7500 revolutions per minute and torque from 184 to 228 percent of design load. The inability to detect these cracks with high confidence may be caused by the high loading required to initiate the cracks. The results indicate that these techniques do not currently produce an indication of damage that significantly exceeds experimental scatter.

Download or read book An Investigation on Spur Gear Rolling Contact Fatigue Crack Initiation and Crack Propagation Under EHL Condition written by Vignesh Dharmarajan and published by . This book was released on 2019 with total page 111 pages. Available in PDF, EPUB and Kindle. Book excerpt: Pitting is a rolling contact fatigue phenomenon commonly observed in mechanical rolling elements, such as gears and bearings. In case of gear contacts, pitting usually takes place in the dedendum region, where both sliding and contact load are high. In this study, a model is developed to predict surface breaking crack formation fatigue lives, including both nucleation and propagation stages, for spur gear contacts operating under mixed elastohydrodynamic lubrication (EHL) condition. The model utilizes a gear load distribution model for tooth contact Analysis. A mixed EHL formulation is implemented to evaluate the surface normal pressure and tangential shear, incorporating the lubricant non-Newtonian behavior, which is influential on lubrication film thickness and surface tractions under high sliding condition. According to the surface tractions, a boundary element formulation is utilized to determine the stress fields, whose contribution to fatigue damage accumulation is assessed using a multi-axial fatigue criterion, predicting the crack nucleation life. As for the crack propagation life evaluation, the Paris and Erdogan's formula is adopted. With the developed contact fatigue model, a parametric investigation is performed considering a spur gear pair, operating under different loads and different surface roughness conditions.

Download or read book The Life of Cracks written by Srečko Glodež and published by Cambridge Scholars Publishing. This book was released on 2020-07-13 with total page 175 pages. Available in PDF, EPUB and Kindle. Book excerpt: Many people find the concept of fracture and damage mechanics to be somewhat problematic, mainly because, until recently, close attention in mechanics was focused especially on the strength and resistance of materials. In this sense, to speak of fracture is as uncomfortable for some as it is to speak of a deadly disease. In confronting and preventing a fatal disease, one must understand its complexity, symptoms, and behavior; by the same token, in securing the strength of an engineering structure, one must understand the reasons and type of its potential failure. This book will provide knowledge and insights on this matter to its readers.

Download or read book Frattura ed Integrit Strutturale Annals 2014 written by Luca Susmel and published by Gruppo Italiano Frattura. This book was released on 2014-09-12 with total page 1208 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Estimation of Gear Crack Size Using Embedded Modeling and Prognosis of Gear Crack Propagation Using Fracture Mechanics written by Hyungdae Lee and published by . This book was released on 2002 with total page 100 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Unique Methods for Analyzing Failures and Catastrophic Events written by Anthony Sofronas and published by John Wiley & Sons. This book was released on 2022-05-20 with total page 356 pages. Available in PDF, EPUB and Kindle. Book excerpt: A practical and accessible approach to machinery troubleshooting Unique Methods for Analyzing Failures and Catastrophic Events is designed to assist practicing engineers address design and fabrication problems in manufacturing equipment to support safe process operation. Throughout the book, a wealth of real-world case studies and easy-to-understand illustrated examples demonstrate how to use simplified failure analysis methods to produce insights for a wide range of engineering problems. Dr. Anthony Sofronas draws from his five decades of industry experience to help engineers better understand the science behind a particular problem, evaluate the failure analysis of an outside consultant, and recommend the best path forward to management. The author distills sophisticated engineering analysis approaches into compact, user-friendly methodologies that can be easily applied to the readers’ own situations to avoid costly failures. Each chapter includes a thorough summary of the topic, relatable technical examples, and a concluding section with key takeaways and expert tips and advice. This invaluable guide: Helps readers make better decisions while solving complex engineering problems Provides numerous illustrated examples from engineering and science that can be used to develop real-world solutions Features detailed descriptions of both basic and advanced engineering analysis techniques Covers essential technical subjects that facilitate safe facility design and effective troubleshooting Unique Methods for Analyzing Failures and Catastrophic Events: An Illustrated Guide for Engineers is a must-have for chemical, petroleum, and mechanical engineers, reliability managers and technicians, design contractors, and maintenance workers working in process industries.

Download or read book Probabilistic Prognostics and Health Management of Energy Systems written by Stephen Ekwaro-Osire and published by Springer. This book was released on 2017-04-25 with total page 273 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book proposes the formulation of an efficient methodology that estimates energy system uncertainty and predicts Remaining Useful Life (RUL) accurately with significantly reduced RUL prediction uncertainty. Renewable and non-renewable sources of energy are being used to supply the demands of societies worldwide. These sources are mainly thermo-chemo-electro-mechanical systems that are subject to uncertainty in future loading conditions, material properties, process noise, and other design parameters.It book informs the reader of existing and new ideas that will be implemented in RUL prediction of energy systems in the future. The book provides case studies, illustrations, graphs, and charts. Its chapters consider engineering, reliability, prognostics and health management, probabilistic multibody dynamical analysis, peridynamic and finite-element modelling, computer science, and mathematics.

Download or read book International Conference on Residual Stresses written by G. Beck and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 1043 pages. Available in PDF, EPUB and Kindle. Book excerpt: Residual stresses are always introduced in materials when they are produced, or when they undergo non-uniform plastic deformation during use. The circumstances that can cause residual stresses are therefore numerous. Residual stresses exist in all materials and, depending on their distribution, can playa beneficial role (for example, compressive surface stress) or have a catastrophic effect, especially on fatigue behaviour and corrosion properties. The subject of residual stresses took form around 1970 with the development of methods to measure macroscopic deformations during the machining of materials or on an atomic scale by X-ray diffraction. These techniques have made considerable progress in the last 20 years. The meetings organized in several countries (Germany, France, Japan, etc. ) have largely contributed to this progress, aided by the numerous exchanges of information and knowledge to which they have given rise. Studies of the formation of residual stresses began more slowly, but have progressed with the emergence of increasingly realistic models of materials behaviour and with access to ever more powerful codes for numerical calculations. Two successive meetings for discussing this topic have been held in Europe. The first, held in 1982 in Nancy (France), consisted of 30 participants from 5 countries. The second was held in Linkoping (Sweden) in 1984, with 80 participants of 16 nationalities. It was decided to hold a first International Conference, ICRS, to address all aspects of the problem. Held in 1986 in Garmisch-Partenkirschen (FRG), it was an assembly of neady 300 participants from 21 countries.

Download or read book Simulating Fatigue Crack Growth in Spiral Bevel Gears written by and published by . This book was released on 2000 with total page 128 pages. Available in PDF, EPUB and Kindle. Book excerpt: The majority of helicopter transmission systems utilize spiral bevel gears to convert the horizontal power from the engine into vertical power for the rotor. Due to the cyclical loading on a gear's tooth, fatigue crack propagation can occur. In rotor craft applications, a crack's trajectory determines whether the gear failure will be benign or catastrophic for the aircraft. As a result, the capability to predict crack growth in gears is significant. A spiral bevel gear's complex shape requires a three dimensional model of the geometry and cracks. The boundary element method in conjunction with linear elastic fracture mechanics theories is used to predict arbitrarily shaped three dimensional fatigue crack trajectories in a spiral bevel pinion under moving load conditions. The predictions are validated by comparison to experimental results. The sensitivity of the predictions to variations in loading conditions and crack growth rate model parameters is explored. Critical areas that must be understood in greater detail prior to predicting more accurate crack trajectories and crack growth rates in three dimensions are identified.

Download or read book An Investigation of Gear Mesh Failure Prediction Techniques written by and published by DIANE Publishing. This book was released on with total page 102 pages. Available in PDF, EPUB and Kindle. Book excerpt: