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Fatigue Modeling/Testing & CAE Durability Analysis, 2017

This collection of papers focus on state-of-the-art fatigue theory and advanced development in fatigue testing, material behavior under cyclic loading, and fatigue analysis methodology & research in the ground vehicle industry. Studies and discussions on innovative and improved fatigue theory/methods in will be discussed along with and engineering applications of CAE durability analysis.

Monitoring the Progression of Micro-Pitting in Spur Geared Transmission Systems Using Online Health Monitoring Techniques

Micro-pitting is a fatigue effect that occurs in geared transmission systems due to high contact stress, and monitoring its progression is vital to prevent the eventual failure of the tooth flank. Parameter signature analysis has been successfully used to monitor bending fatigue failure and advanced phases of gear surface fatigue failure such as macro-pitting and scuffing. However, due to modern improvements in steel production the main cause of gear contact fatigue failure can be attributed to surface micro-pitting rather than sub-surface phenomena. Responding to the consequent demand to detect and monitor the progression of micro-pitting, this study experimentally evaluated the development of micro-pitting in spur gears using vibration and oil debris analysis. The paper presents the development of an online health monitoring system for use with back-to-back gear test rigs.

SAE Fatigue Design Handbook

Prepared under the auspices of the SAE Fatigue Design and Evaluation Committee. The SAE Fatigue Design Handbook covers, in a single source, current technologies and procedures on all of the major elements of fatigue design. Intended as a handbook for industrial use, this book describes the major elements of the fatigue design process and how those elements must be tied together in a comprehensive product evaluation. Using this handbook will save the design engineer time, while ensuring understanding of the important elements of the fatigue design process. Significant Updates On: Fatigue Life Prediction (New sections on multiaxial effects and statistical aspects) Vehicle Simulation Structural Life Evaluation Material Properties Fatigue Performance
Technical Paper

Bodily Steadiness-A Riding-Comfort Index

This is the fourth report by Dr. Moss on the investigation of riding comfort at the George Washington University and is a progress report on the measurement of automobile riding-qualities. The previous reports were published in the S.A.E. JOURNAL as follows: September, 1929, p. 298; January, 1930, p. 99; and April, 1930, p. 513. In this report, which was presented at the 1930 Semi-Annual Meeting, the author describes improvements made in two wabblemeters for measuring physiological fatigue caused by riding and the use of two accelerometers to correlate the behavior of the automobile with the physiological results. Results obtained with two groups of subjects, one consisting of taxicab drivers and the other of university students, are summarized, and the results of preliminary tests of the comparative riding-qualities of different cars as shown by their effects on the subjects are also given.
Technical Paper

Measurement of Comfort in Automobile Riding

EXPERIMENTS that have been in progress since the 1929 Semi-Annual Meeting to measure the fatigue caused by an automobile ride, using the human body as a measuring instrument, and to predict there-from the possible effects of various types of spring-suspension, shock-absorber and other comfort-giving components are described. Initially, the problem was approached from the physiological standpoint because fatigue is definitely known to be a physiological phenomenon and, if the physiological changes are sufficiently marked to be measured, physiological tests are definite and quantitative. Changes in the human body are a good index of relative comfort, and, if the normal reactions of an individual or any group of individuals before a test are known, similar measurements at the end of a test or at the end of an automobile ride should show an appreciable difference.
Technical Paper

Cageless Roller Bearings Develop High Carrying Capacities

A ROLLER having the same diameter as a corresponding ball and a length equal to the ball diameter has approximately four times the carrying capacity of a ball, according to Mr. Hermann. The data presented on cageless roller bearings are based upon knowledge of the carrying capacity and life of the ball bearing. The reason for the increased carrying capacity of a roller over that of a ball is due to the distribution of the load over a line of contact rather than at a point of contact. The roller bearing increases the number of such line contacts and therefore further distributes the load to the raceways. By increasing the number of line contacts, the cageless rollers reduce the stress per roller and failure due to fatigue. The fatigue factor is reduced 40 per cent, comparing a cageless with a caged roller.
Technical Paper


Disc wheels are the answer to a demand for something better at a more reasonable price. The art of making wood wheels has been established, the machinery has become standardized and further reduction in cost is improbable; whereas the cost of suitable wood is steadily advancing and the trend, consequently, is upward. When the wire wheel was first introduced its use was a mark of distinction and to it can be traced the origin of the sport model, but its price cannot be reduced and it cannot compete, therefore, with the disc wheel on a price basis. The development of the disc wheel brought an equal distinctiveness of design and of pleasing appearance, but its progress has been different. The initial expenditure involved in the production of disc wheels is large; but the output also is large, and, as the volume increases, the prices become lower.
Technical Paper

Preliminary Report on Fatigue Produced by Automobile Riding

THIS IS a preliminary report of the results obtained to date in the study of fatigue incident to motor travel, which is part of the Society's Riding-Qualities Research program. A series of physiological tests were conducted after muscular fatigue had been induced by a known amount of work, with the hope of finding some tests sufficiently sensitive to measure less pronounced types of fatigue. These fatigue tests conducted on subjects after riding showed that a decrease in the carbon-dioxide combining power of the blood and an increase in metabolism are fairly satisfactory indications of muscular fatigue, but the results led to the conclusion that the fatigue which accompanies riding in automobiles does not represent a very marked muscular fatigue, and suggested that it may represent a condition more closely similar to nerve fatigue. Consequently, a rather extensive study of various tests of nerve fatigue was undertaken.
Technical Paper


Substitution of scientific data obtained by experiment for the mere opinions long since prevailing about the respective values of arguments pro and con in regard to the interleaf friction of springs, the effectiveness of many leaves versus few leaves, the lubrication of springs and kindred subjects, was the objective of the author and the results he has secured since the start of the experimental work early in 1924 are set forth. Tests were conducted with springs having leaves varying in number from 1 to 14 and, in all cases, both when dry and when copiously lubricated with thin oil. All the variable factors were included during the progress of the experiments, the number of combinations possible being indicated by the fact that about 250 tests were made and more than 50 different springs were used.
Technical Paper


PROBLEMS of suspension spring design that have been of major interest in recent years, such as spring life and reliability, hardness and settling, fatigue, shot peening, and presetting, are presented here. Various types of springs are discussed by Mr. Schilling, who concludes that no one type is superior in all respects, hence commercial applications of different types have remained competitive. He feels that this picture will not change in the future, that is, no one type will be used exclusively. Considering the great superiority of some types in economy of material, however, he expects that the less economical springs will gradually be replaced unless their weight can be substantially reduced.
Technical Paper


TORSION-BAR suspension is of great military importance, Col. Colby says, because its large shock-absorbing capacity gives the following advantages: 1. Higher sustained speed over adverse battlefield terrain. 2. Greater comfort of tank operating personnel and reduction of fatigue. 3. More reliable vehicle because components are cushioned from shock. 4. More stable firing platform for delivery of effective firepower. 5. Improved obstacle-crossing ability. 6. Better traction. 7. More reliable track operation through the use of the compensator. 8. Greater protection because much of the mechanism is behind armor plates.
Technical Paper

Improved Method for Estimating Fatigue Life of Bevel and Hypoid Gears

IN this paper the author explains a new method for the determination of the fatigue life of bevel and hypoid gears. This method is said to offer a means for comparing various tooth forms and gear mountings. Briefly, it consists of making a layout in the mean normal section of the tooth, and of calculating the tensile stress in the fillet when the maximum load is applied at its highest position on the tooth. Consideration is given to the fact that in cases where the contact ratio is sufficient to ensure at least two teeth in contact at all times the load will be divided between the teeth. Such factors as impact, inertia, and temperature are given consideration. A graph is plotted using this calculated stress and the number of cycles to failure resulting from extensive bending fatigue tests on both bevel and hypoid gears. With the aid of this graph the fatigue life of new gear designs may be estimated.
Technical Paper

Current Practice in Tractor Bevel Gears

THE design and application of tractor bevel gears is covered in this paper. The authors discuss the problems involved, under the following headings: 1. Basic bevel-gear systems in use, based upon the method of cutting. 2. Method of calculation and selection of factors determining the static and maximum tensile stresses. 3. Summary of static and maximum tensile stresses, and fatigue life analysis. 4. Materials and heat-treatment.
Technical Paper

Survey of Engine Combustion-Chamber Envelope

THE author states that his purpose in presenting this paper before the Student Branch is to suggest a few unsolved problems concerning the diesel engine. His effort to stimulate student thinking into channels which may lead to acceptable solutions has been summarized in four pertinent points: 1. Stressing the importance of mixture formation to the end that each fuel particle, when properly prepared for the chemistry of combustion, may find its necessary equivalent of oxygen as quickly and conveniently as possible. 2. More definite controls for heat extraction of regions subject to thermal fatigue in combustion-chamber envelope. 3. Better knowledge of distortion control to give added life to critical parts required to channel heat or seal pressures. 4. Need to develop a real supercharger preeminently matched to diesel field operating conditions.
Technical Paper

Today’s Aluminum Aircraft Alloys

INASMUCH as new developments in the field of aluminum alloys are immediately reflected in the aircraft industry, the author of this paper reviews past and present achievements which relate directly to aviation needs of the future. The alloys in use today are described as satisfactory. They have been brought to this point by intensive research leading to high strength, resistance to corrosion and fatigue, and ease of fabrication. A clearer understanding of the problems associated with present alloys is responsible for the presentation of successful new alloys. The author describes how a recent newcomer, 75S, has already attained dominance in the extrusion field, and has made measurable inroads in the sheet, plate, and forging fields. He also describes how military demands for alloys of higher and higher strengths have led to a complete revision of concepts concerning elongation, followed by a reappraisal of the need for artificial aging.
Technical Paper


STATIC fatigue of rubber is defined by the authors as a progressive breakdown under the influence of a static load, whereas dynamic fatigue is defined as the progressive loss of strength due to successive cycles of stress. The static fatigue life is the time required for rupture under a static load. Test data presented on the tension static fatigue of rubber indicate that the static fatigue lives of the samples are functions of the stresses acting on them; that the static fatigue lives fall off rapidly with increasing stresses; and that the dependents of static fatigue life on the stress is a function of the stock, among other things. Curves of reduction of tensile due to static fatigue show that the tensiles of samples under load actually decrease and that the decrease is greater, the greater the time under load.