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This paper presents a method for the acoustic analysis of electric motors in noisy industrial environments. Acoustic
signals were measured via acoustic camera 48-microphone array, which has the capability to localize a sound
(or sounds) source and, in turn, separate those sounds from intrusive background noise. These acoustic analysis results are then compared with vibration measurements; vibration monitoring is a well-known and established technique used in condition monitoring, and in this work vibration measurements were used as a reference signal for assessment of the value of the acoustic measurements. Vibration signals were measured by piezoelectric accelerometers. Two induction motor cases were examined — a healthy motor case, and a combination of static eccentricity with soft foot case. As shown, acoustic analysis appears to be a valuable technique for condition
monitoring of electric motors — particularly in noisy industrial environments.
When a power transmission component fails, it can adversely affect the performance of the assembly, often
making the machine inoperable. Such failures can not only harm the reputation of the manufacturer, but can lead to litigation, recalls and delays in delivery due to quality concerns. Some failures can even result in bodily injury or
death. Understanding why a part failed is critical to preventing similar failures from reoccurring. In the study of a failed part, the analyst must consider a broad range of possibilities for the failure. Although some failures can be
attributed to a single primary cause, it is common for multiple secondary factors to contribute. The failure analyst must evaluate all of the evidence available to prepare a hypothesis about the causes of failure.
Asymmetric tooth gears and their rating are not described by existing gear design standards. Presented is a rating approach for asymmetric tooth gears by their bending and contact stress levels, in comparison with symmetric tooth gears, whose rating are defined by standards. This approach applies finite element analysis (FEA) for bending stress definition and the Hertzian equation for contact stress definition. It defines equivalency factors for
practical asymmetric tooth gear design and rating. This paper illustrates the rating of asymmetric tooth gears with
numerical examples.
The performance of high-speed helical geartrains is of particular importance for tiltrotor aircraft drive systems.
These drive systems are used to provide speed reduction/torque multiplication from the gas turbine output shaft and provide the necessary offset between these parallel shafts in the aircraft. Four different design configurations have been tested in the NASA Glenn Research Center, High-Speed Helical Geartrain Test Facility. The design configurations included the current aircraft design, current design with isotropic superfinished gear surfaces, double-helical design (inward and outward pumping), increased pitch (finer teeth), and an increased helix angle. All designs were tested at multiple input shaft speeds (up to 15,000 rpm) and applied power (up to 5,000 hp).
Also two lubrication, system-related, variables were tested: oil inlet temperature (160–250° F) and lubricating jet pressure (60–80 psig). Experimental data recorded from these tests included power loss of the helical system under study, the temperature increase of the lubricant from inlet to outlet of the drive system and fling-off temperatures
(radially and axially). Also, all gear systems were tested with and without shrouds around the gears.
During the past 10 years, the PM industry has put a lot of focus on how to make powder metal gears for automotive transmissions a reality. To reach this goal, several hurdles had to be overcome, such as fatigue data generation on gears, verification of calculation methods, production technology, materials development, heat treatment recipes, design development, and cost studies.
All of these advancements will be discussed, and a number of vehicles with powder metal gears in their
transmissions will be presented. How the transmissions have been redesigned in order to achieve the required stress levels while minimizing weight and inertia, thus increasing efficiency, will also be discussed.
This paper provides a mathematical framework and its implementation for calculating the tooth geometry of
arbitrary gear types, based on the basic law of gear kinematics. The rack or gear geometry can be generated
in two different ways: by calculating the conjugate geometry and the line of contact of a gear to the given
geometric shape of a known geometry (e.g., a cutting hob), or by prescribing the surface of action of two gears in contact and calculating the correspondent flank shapes.
As gear efficiency is improved in small steps, it is important to be able to distinguish actual improvements from scatter that can occur while testing. An FZG back-to-back gear test rig was used
to investigate how the assembly and re-assembly of the same test setup affects the measurements. A spread in torque loss between one assembly and another of the same test setup were observed. Rig conditions also affected the spread in input torque. With knowledge of how the spread in torque loss varies due to assembly, test results could be distinguished between changes due to assembly and
actual differences between tests.
A thermo-mechanical model of a splash lubricated one-stage gear unit is presented. This system corresponds to a first step towards the design of a hybrid vehicle gearbox that can operate up to 40,000 rpm on its primary shaft. The numerical model is based on the thermal network method and takes into account power losses due to teeth friction, rolling-elements bearings and oil churning. Some calculations underline that oil churning causes a high amount of power loss. A simple method to reduce this source of power losses is presented, and its influence on the gear unit efficiency and its thermal capacity is computed.
The U.S. Space Shuttle fleet was originally intended to have a life of 100 flights for each vehicle, lasting over a 10-year period, with minimal scheduled maintenance or inspection.
The first space shuttle flight was that of the Space Shuttle Columbia
(OV-102), launched April 12, 1981. The disaster that destroyed Columbia occurred on its 28th flight, February 1, 2003, nearly 22 years after its first launch.
In 1991, Needelman and Zaretsky presented a set of empirically
derived equations for bearing fatigue life (adjustment) factors (LFs) as a function of oil filter ratings.