Thermal Instability in High-Speed Gearing

1961 ◽  
Vol 83 (1) ◽  
pp. 91-103 ◽  
Author(s):  
W. P. Welch ◽  
J. F. Boron
Keyword(s):  
Thermal Expansion ◽  
Steady State ◽  
Experimental Verification ◽  
Thermal Effects ◽  
High Speed ◽  
Thermal Instability ◽  
Point Of View ◽  
State Point

Thermal-expansion effects in gearing have usually been considered from a steady-state point of view. A theory of thermal instability is developed which takes into account the tendency of the thermal effects to be regenerative. This theory provides an adequate and complete explanation for several previously unexplained cases of tooth failure in high-speed high-horsepower reduction gears. Experimental verification of the theory is presented and some of the conditions for avoiding thermal instability are described.

Periodic Motions of a Two-Body System Subjected to Repetitive Impact

1969 ◽  
Vol 91 (4) ◽  
pp. 931-938 ◽  
Author(s):  
David L. Sikarskie ◽  
Burton Paul
Keyword(s):  
Steady State ◽  
High Speed ◽  
Equations Of Motion ◽  
Point Of View ◽  
State Behavior ◽  
State Response ◽  
Stability Of Solution ◽  
Straightforward Method ◽  
Parametric Studies ◽  
Repetitive Impact

The dynamics of a widely used class of hammer impact machines are investigated on the basis of a two-degree-of-freedom idealization. The difficulty in the problem is due to the repetitive impact which introduces a nonlinearity in the system. It is the purpose of the analysis to develop a solution for the steady-state behavior of the system. There are several ways this can be done. One of the most efficient ways, from the point of view of ease of parametric studies of the system, is to convert the problem to a “boundary” value problem. With this technique, the system is governed by the equations of motion between impacts, and further satisfies additional conditions at the beginning and end of each impact cycle. Since the solution is obtained in only one cycle, it thus represents a straightforward method of studying the effect of various system parameters. A fundamental assumption in the analysis is that the steady-state response of the system has a period equal to the forcing period. This is verified for one set of parameters through the use of high-speed movies of an actual machine. There are several other interesting features in the analysis, including multivaluedness of the solution, allowable solution domain, and stability of solution, which have not been completely resolved to date.

The Redistribution of Load in Bolted Gasketed Joints Subjected to Steady State Thermal Loading

2002 ◽  
Author(s):  
Akli Nechache ◽  
Abdel-Hakim Bouzid
Keyword(s):  
Mechanical Properties ◽  
Thermal Expansion ◽  
Steady State ◽  
Thermal Effects ◽  
Thermal Loading ◽  
Operating Temperature ◽  
Theoretical Models ◽  
Joint Analysis ◽  
Effects Of Temperature

Pressure vessel joints operating at high temperature are often very difficult to seal. The existing flange design methods do not address thermal effects other than the variation of flange material mechanical properties with temperature. It is possible to include the effects of temperature loading in joint analysis, however, presently very few guidelines exist for this type of analysis. This paper outlines the theoretical analysis used for the determination of the steady state operating temperature and the induced loads in flange joints. It details the theoretical equations necessary to predict the temperature and the redistribution of load due to the thermal expansion of the joint components for the case of a pair flange and the case of a flange with a blind-cover. The results from the theoretical models are verified by comparison to finite element results.

Thermal instability in drawing viscous threads

2007 ◽  
Vol 570 ◽  
pp. 1-16 ◽  
Author(s):  
JONATHAN J. WYLIE ◽  
HUAXIONG HUANG ◽  
ROBERT M. MIURA
Keyword(s):  
Steady State ◽  
Thermal Effects ◽  
Thermal Instability ◽  
Radiative Heat ◽  
Physical Mechanism ◽  
Surprising Result ◽  
Downstream Location ◽  
The Stability ◽  
Steady State Solutions ◽  
Oscillatory Instabilities

We consider the stretching of a thin viscous thread, whose viscosity depends on temperature, that is heated by a radiative heat source. The thread is fed into an apparatus at a fixed speed and stretched by imposing a higher pulling speed at a fixed downstream location. We show that thermal effects lead to the surprising result that steady states exist for which the force required to stretch the thread can decrease when the pulling speed is increased. By considering the nature of the solutions, we show that a simple physical mechanism underlies this counterintuitive behaviour. We study the stability of steady-state solutions and show that a complicated sequence of bifurcations can arise. In particular, both oscillatory and non-oscillatory instabilities can occur in small isolated windows of the imposed pulling speed.

The Effect of Steady State Thermal Loading on the Deflections of a Flanged Joint With a Cover Plate

2002 ◽  
Author(s):  
Abdel-Hakim Bouzid ◽  
Akli Nechache ◽  
Warren Brown
Keyword(s):  
Thermal Expansion ◽  
Steady State ◽  
Temperature Profile ◽  
Thermal Effects ◽  
Thermal Loading ◽  
Cover Plate ◽  
Asme Code ◽  
Effects Of Temperature ◽  
Bolted Flange

It is well recognized that bolted flange joints operating at high temperature are often very difficult to seal. The existing flange design methods including that of the ASME code do not address thermal effects other than the variation of flange and bolt material mechanical properties with temperature. It is possible to include the effects of temperature loading in the flexibility analysis of the joint. However, the temperature profile to be known to determine the radial and axial thermal expansion displacements of the joint elements to be used in the analysis. This paper outlines the theoretical analysis used for the determination of the steady state operating temperature profile, the thermal expansion displacements of the joint components and the bolt load changes for the case of a flange joint with a blind cover. The results from the proposed analytical model are verified by comparison to finite element results of three different sizes of bolted joints.

Resistance to Outflow of Cerebrospinal Fluid Determined by Bolus Injection Technique and Constant Rate Steady State Infusion in Humans

Neurosurgery ◽  
1985 ◽  
Vol 16 (3) ◽  
pp. 336-340 ◽  
Author(s):  
Michael Kosteljanetz
Keyword(s):  
Cerebrospinal Fluid ◽  
Steady State ◽  
Bolus Injection ◽  
Point Of View ◽  
Injection Technique ◽  
Communicating Hydrocephalus ◽  
Constant Rate ◽  
High Degree ◽  
Infusion Technique

Abstract Two methods for the determination of resistance to the outflow of cerebrospinal fluid, the bolus injection technique and the constant rate steady state infusion technique, were compared. Thirty-two patients with a variety of intracranial diseases (usually communicating hydrocephalus) were studied. There was a high degree of correlation between the resistance values obtained with the two methods, but values based on the bolus injection technique were systematically and statistically significantly lower than those obtained with the constant rate infusion test. From a practical point of view. both methods were found to be applicable in a clinical setting.

Comparison of the reluctance laminated and solid rotor synchronous machine operating at high temperatures

2019 ◽  
Vol 38 (4) ◽  
pp. 1111-1119 ◽  
Author(s):  
Marcin Lefik ◽  
Krzysztof Komeza ◽  
Ewa Napieralska-Juszczak ◽  
Daniel Roger ◽  
Piotr Andrzej Napieralski
Keyword(s):  
High Speed ◽  
Design Methodology ◽  
Three Dimensional ◽  
Synchronous Machine ◽  
Point Of View ◽  
Heat Sources ◽  
Model Calculations ◽  
Content Type ◽  
Thermal Phenomenon ◽  
Practical Implications

Purpose The purpose of this paper is to present a comparison between reluctance synchronous machine-enabling work at high internal temperature (HT° machine) with laminated and solid rotor. Design/methodology/approach To obtain heat sources for the thermal model, calculations of the electromagnetic field were made using the Opera 3D program including effect of rotation and the resulting eddy current losses. To analyse the thermal phenomenon, the 3D coupled thermal-fluid (CFD) model is used. Findings The presented results show clearly that laminated construction is much better from a point of view of efficiency and temperature. However, solid construction can be interesting for high speed machines due to their mechanical robustness. Research limitations/implications The main problem, despite the use of parallel calculations, is the long calculation time. Practical implications The obtained simulation and experimental results show the possibility of building a machine operating at a much higher ambient temperature than it was previously produced for example in the vicinity of the aircraft turbines. Originality/value The paper presents the application of fully three-dimensional coupled electromagnetic and thermal analysis of new machine constructions designed for elevated temperature.

Steady-state point-defect diffusion profiles in solids during irradiation

1974 ◽  
Vol 23 (1) ◽  
pp. 53-59 ◽  
Author(s):  
Nghi Q. Lam ◽  
Steven J. Rothman ◽  
Rudolf Sizmanns
Keyword(s):  
Steady State ◽  
Point Defect ◽  
Defect Diffusion ◽  
State Point ◽  
Diffusion Profiles

STAND-UP MOTION SUPPORT BY A MOBILE MANIPULATOR SYSTEM WITH HIGH SPEED TACTILE SENSORS

2011 ◽  
Vol 08 (03) ◽  
pp. 181-195
Author(s):  
ZHAOXIAN XIE ◽  
HISASHI YAMAGUCHI ◽  
MASAHITO TSUKANO ◽  
AIGUO MING ◽  
MAKOTO SHIMOJO
Keyword(s):  
Fuzzy Logic ◽  
Feedback Control ◽  
Experimental Verification ◽  
High Speed ◽  
Center Of Pressure ◽  
Tactile Sensor ◽  
Mobile Manipulator ◽  
Tactile Sensing ◽  
Robot Arm ◽  
Tactile Sensors

As one of the home services by a mobile manipulator system, we are aiming at the realization of the stand-up motion support for elderly people. This work is charaterized by the use of real-time feedback control based on the information from high speed tactile sensors for detecting the contact force as well as its center of pressure between the assisted human and the robot arm. First, this paper introduces the design of the tactile sensor as well as initial experimental results to show the feasibility of the proposed system. Moreover, several fundamental tactile sensing-based motion controllers necessary for the stand-up motion support and their experimental verification are presented. Finally, an assist trajectory generation method for the stand-up motion support by integrating fuzzy logic with tactile sensing is proposed and demonstrated experimentally.

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