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 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 Research Technology 2001 written by and published by DIANE Publishing. This book was released on with total page 251 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 Effect of Rim Thickness on Gear Crack Propagation Path written by David G. Lewicki and published by . This book was released on 1996 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Simulating Fatigue Crack Growth in Spiral Bevel Pinion written by and published by . This book was released on 2003 with total page 50 pages. Available in PDF, EPUB and Kindle. Book excerpt: New results for predicting crack trajectory and fatigue life for a spiral bevel pinion using the Finite Element Method (FEM) are reported. The predictions presented are based on linear elastic fracture mechanics combined with the FEM, incorporating plasticity induced fatigue crack closure and moving gear tooth loads. The analyses were carried out using a parallel FEM solver, which calculates stress intensity factors using equivalent domain J-integral method. Fatigue life predictions were made based on a modified Paris model incorporating crack closure. To obtain a more detailed understanding of the contact between a cracked pinion tooth in mesh with an uncracked gear tooth, three-dimensional contact analyses were performed on a spiral bevel gear set incorporating a crack. The goal in carrying out these analyses was to capture the redistribution of contact loads due to crack growth. Results of these analyses showed the expected trend of decreasing tooth loads carried by the cracked tooth with increasing crack length. It was also showed that this decrease in contact loads bad an impact on the stress intensity factor values and therefore would also affect the crack trajectory and fatigue life predictions.
Download or read book Journal of Mechanical Design written by and published by . This book was released on 2008 with total page 818 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 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 Journal of the American Helicopter Society written by American Helicopter Society and published by . This book was released on 2002 with total page 316 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Research and Technology 2001 written by and published by . This book was released on 2002 with total page 250 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Dynamic Loads on Gear Teeth written by American Society of Mechanical Engineers. Special research committee on the strength of gear teeth and published by . This book was released on 1931 with total page 82 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Simulating Fatigue Crack Growth in Spiral Bevel Gears written by Lisa Eron Spievak and published by . This book was released on 2000 with total page 122 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 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 Recent Advances in Solids and Structures written by and published by . This book was released on 2005 with total page 192 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Detecting Gear Tooth Fatigue Cracks in Advance of Complete Fracture written by and published by . This book was released on 1996 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt:
