Thermoelastic Effects in Frictionally Heated Line Contact of Slablike Bodies

1978 ◽  
Vol 100 (1) ◽  
pp. 136-141 ◽  
Author(s):  
S. R. Heckmann ◽  
R. A. Burton
Keyword(s):  
Thermal Expansion ◽  
Elastic Deformation ◽  
Elevated Temperatures ◽  
Frictional Heating ◽  
Line Contact ◽  
Two Dimensional ◽  
Sliding Speed ◽  
Thermoelastic Effects ◽  
Dimensional Models ◽  
Realistic Geometry

Many sealing configurations incorporate the geometry of line contact on bluff, slablike bodies. When sliding speed is sufficiently high along or across the line of contact, instabilities may arise from interactions of thermal expansion, elastic deformation and frictional heating. These lead to concentrated contact with elevated temperatures and pressures. Previous studies have been largely restricted to two-dimensional models of such contact. The present study shows how those earlier results must be modified to apply to the more realistic geometry, and show also that the principal features of the interactions are the same in both geometries.

The Role of Wear in the Initiation of Thermoelastic Instabilities of Rubbing Contact

1973 ◽  
Vol 95 (1) ◽  
pp. 71-75 ◽  
Author(s):  
T. A. Dow ◽  
R. A. Burton
Keyword(s):  
Thermal Expansion ◽  
Contact Pressure ◽  
Material Properties ◽  
Frictional Heating ◽  
Oscillatory Behavior ◽  
Two Dimensional ◽  
Infinite Body ◽  
Operating Variables ◽  
Uniform Value

Thermoelastic instability of rubbing contact results from the interaction of thermal expansion, frictional heating, and conduction of heat away from the contact zone. These interactions are modified by wear, which is shown to damp the growth of disturbances in contact pressure from a nominal uniform value. In some cases the presence of wear is found to give rise to oscillatory behavior where portions of the rubbing surfaces alternately rise and drop in temperature. These effects are analyzed for the case of a two-dimensional scraper or blade moving normal to its edge, which presses against the surface of a stationary semi-infinite body. The roles of material properties and operating variables are delineated in terms of dimensionless parameters appropriate to the system.

scholarly journals Effect of Material Properties in Certain Thermoelastic Contact Problems

1998 ◽  
Vol 65 (4) ◽  
pp. 889-893 ◽  
Author(s):  
D. Joachim-Ajao ◽  
J. R. Barber
Keyword(s):  
Contact Area ◽  
Material Properties ◽  
Frictional Heating ◽  
Contact Problems ◽  
Plane Boundary ◽  
Two Dimensional ◽  
Sliding Speed ◽  
Transient Problems ◽  
Contact Loads ◽  
Single Material

When two conforming bodies slide against each other, frictional heating and thermoelastic distortion generally causes the contacting surfaces to become convex and hence leads to a reduction in the size of the contact area. It is shown that, under such circumstances, the contact area is independent of the applied contact loads and the thermal and mechanical fields are linearly proportional to these loads. For two-dimensional problems involving a plane boundary, it is shown that there is a reduced dependence on material properties and in the case of a single material, the solution depends only on a single parameter which can be interpreted as a dimensionless sliding speed. These results extend to both steady-state and transient problems and therefore also characterize the critical sliding speed above which the system is unstable.

Magnetoelastic coupling, negative thermal expansion, and two-dimensional magnetic excitations in FeAs

2021 ◽  
Vol 103 (9) ◽  
Author(s):  
J. L. Niedziela ◽  
L. D. Sanjeewa ◽  
A. A. Podlesnyak ◽  
L. DeBeer-Schmitt ◽  
S. J. Kuhn ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Negative Thermal Expansion ◽  
Two Dimensional ◽  
Magnetic Excitations ◽  
Magnetoelastic Coupling

Ultra-thin two-dimensional molecular crystals grown on a liquid surface for high-performance phototransistors

2021 ◽  
Author(s):  
Shuyuan Yang ◽  
Yu Zhang ◽  
Ying Wang ◽  
Jiarong Yao ◽  
Lijuan Zhang ◽  
...  
Keyword(s):  
Organic Semiconductor ◽  
High Performance ◽  
Elevated Temperatures ◽  
Liquid Surface ◽  
Molecular Crystals ◽  
Two Dimensional ◽  
Poor Solubility

Bilayer 2D molecular crystals of an organic semiconductor with poor solubility were grown on a liquid substrate at elevated temperatures. The molecularly thin crystals exhibited superior mobility and photoresponse.

Enlarging the Temperature Range for Maximum Wear Resistance of TiNi Alloy Using a NTE Phase

2007 ◽  
Vol 539-543 ◽  
pp. 3261-3266 ◽  
Author(s):  
Iulian Radu ◽  
Dong Yang Li
Keyword(s):  
Wear Resistance ◽  
Thermal Expansion ◽  
Internal Stress ◽  
Frictional Heating ◽  
Negative Thermal Expansion ◽  
High Wear Resistance ◽  
Tini Alloy ◽  
Wear Loss ◽  
Second Phase ◽  
Temperature Range

The near-equiatomic TiNi alloy has been demonstrated to possess high wear resistance, which largely benefits from its pseudoelasticity (PE). However, the PE occurs only in a small temperature range, which makes the wear resistance of this alloy unstable as temperature changes, caused by environmental instability or frictional heating. Therefore, enlarging the working temperature of PE could considerably improve this alloy as a novel wear-resistant material. One possible approach is to develop a self-built temperature-dependent internal stress field by taking the advance of the difference in thermal expansion between the pseudoelastic matrix and a reinforcing phase. Such a T-dependent internal stress could adjust the martensitic transformation temperature to respond changes in environmental temperature so that the temperature range of PE could be enlarged, thus leading to a wide temperature range in which the minimum wear loss is retained. Research was conducted to investigate effects of an added second phase having a negative thermal expansion (NTE) coefficient on the wear resistance of a near-equiatomic TiNi alloy. It was demonstrated that the temperature range of this modified material in which the wear loss dropped was enlarged. In addition, the wear resistance of such a TiNi-matrix composite was on one order of magnitude higher than that of unmodified TiNi alloy.

Mine Impact Burial Prediction From One to Three Dimensions

2008 ◽  
Vol 62 (1) ◽  
Author(s):  
Peter C. Chu
Keyword(s):  
Three Dimensional ◽  
Time History ◽  
Three Dimensions ◽  
Vertical Position ◽  
Burial Depth ◽  
Prediction Errors ◽  
Two Dimensional ◽  
Dimensional Model ◽  
One Dimensional ◽  
Dimensional Models

The Navy’s mine impact burial prediction model creates a time history of a cylindrical or a noncylindrical mine as it falls through air, water, and sediment. The output of the model is the predicted mine trajectory in air and water columns, burial depth/orientation in sediment, as well as height, area, and volume protruding. Model inputs consist of parameters of environment, mine characteristics, and initial release. This paper reviews near three decades’ effort on model development from one to three dimensions: (1) one-dimensional models predict the vertical position of the mine’s center of mass (COM) with the assumption of constant falling angle, (2) two-dimensional models predict the COM position in the (x,z) plane and the rotation around the y-axis, and (3) three-dimensional models predict the COM position in the (x,y,z) space and the rotation around the x-, y-, and z-axes. These models are verified using the data collected from mine impact burial experiments. The one-dimensional model only solves one momentum equation (in the z-direction). It cannot predict the mine trajectory and burial depth well. The two-dimensional model restricts the mine motion in the (x,z) plane (which requires motionless for the environmental fluids) and uses incorrect drag coefficients and inaccurate sediment dynamics. The prediction errors are large in the mine trajectory and burial depth prediction (six to ten times larger than the observed depth in sand bottom of the Monterey Bay). The three-dimensional model predicts the trajectory and burial depth relatively well for cylindrical, near-cylindrical mines, and operational mines such as Manta and Rockan mines.

The gauge technique and two dimensional models

1983 ◽  
Vol 131 (4-6) ◽  
pp. 385-389 ◽  
Author(s):  
George Thompson
Keyword(s):  
Two Dimensional ◽  
Dimensional Models

Soluble Two-Dimensional Models of Generally Covariant Field Theories

1973 ◽  
Vol 7 (8) ◽  
pp. 2309-2310
Author(s):  
Joseph Klarfeld ◽  
Alexander L. Harvey
Keyword(s):  
Field Theories ◽  
Two Dimensional ◽  
Dimensional Models ◽  
Generally Covariant ◽  
Covariant Field

scholarly journals Improved Reliability of Bladed Disks due to Friction Dampers

1997 ◽  
Author(s):  
Walter Sextro ◽  
Karl Popp ◽  
Ivo Wolter
Keyword(s):  
Dry Friction ◽  
Three Dimensional ◽  
Line Contact ◽  
Two Dimensional ◽  
Centrifugal Forces ◽  
Friction Damper ◽  
Blade Vibration ◽  
Friction Dampers ◽  
Bladed Disk ◽  
Bladed Disk Assembly

Friction dampers are installed underneath the blade platforms to improve the reliability. Because of centrifugal forces the dampers are pressed onto the platforms. Due to dry friction and the relative motion between blades and dampers, energy is dissipated, which results in a reduction of blade vibration amplitudes. The geometry of the contact is in many cases like a Hertzian line contact. A three-dimensional motion of the blades results in a two-dimensional motion of one contact line of the friction dampers in the contact plane. An experiment with one friction damper between two blades is used to verify the two-dimensional contact model including microslip. By optimizing the friction dampers masses, the best damping effects are obtained. Finally, different methods are shown to calculate the envelope of a three-dimensional response of a detuned bladed disk assembly (V84.3-4th-stage turbine blade) with friction dampers.

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