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Articles 1 - 8 of 8
Full-Text Articles in Mechanical Engineering
Width-Wise Variation Of Magnetic Tape Pack Stresses, Jonathan A. Wickert, Y.M. Lee
Width-Wise Variation Of Magnetic Tape Pack Stresses, Jonathan A. Wickert, Y.M. Lee
Jonathan A. Wickert
A model is developed for predicting the stress and displacement fields within a magnetic tape pack, where those quantities are allowed to vary in both the pack's radial and transverse (cross-tape) directions. As has been the case in previous analyses based upon one-dimensional wound roll models, the present approach accounts for the anisotropic and nonlinear constitutive properties of the layered tape, and the incremental manner in which the pack is wound. Further, such widthwise variation effects as differential hub compliance and nonuniform winding tension, which can be significant in data cartridge design, are also treated in the model. The pack …
Toward Improved Film Cooling Prediction, G. Medic, Paul A. Durbin
Toward Improved Film Cooling Prediction, G. Medic, Paul A. Durbin
Paul A. Durbin
Computations of flow and heat transfer for a film-cooled high pressure gas turbine rotor blade geometry are presented with an assessment of several turbulence models. Details of flow and temperature field predictions in the vicinity of cooling holes are examined. It is demonstrated that good predictions can be obtained when spurious turbulence energy production by the turbulence model is prevented.
Toward Improved Prediction Of Heat Transfer On Turbine Blades, G. Medic, Paul A. Durbin
Toward Improved Prediction Of Heat Transfer On Turbine Blades, G. Medic, Paul A. Durbin
Paul A. Durbin
Reynolds averaged computations of turbulent flow in a transonic turbine passage are presented to illustrate a manner in which widely used turbulence models sometimes provide poor heat transfer predictions. It is shown that simple, physically and mathematically based constraints can substantially improve those predictions.
Stress Field In Finite Width Axisymmetric Wound Rolls, Jonathan A. Wickert, Y.M. Lee
Stress Field In Finite Width Axisymmetric Wound Rolls, Jonathan A. Wickert, Y.M. Lee
Jonathan A. Wickert
A model is developed for predicting the stress field within a wound roll of web material, in which the radial, circumferential, transverse, and shear stresses can vary in both the roll's radial and cross-web (transverse) directions. As has been the case in previous wound roll stress analyses based on one-dimensional models, the present approach accounts for the anisotropic and nonlinear material properties of the layered web material, and the incremental manner in which the roll is wound. In addition, the present development accounts for arbitrary cross-sectional geometry and material of the core, and the presence of nonuniform tension across the …
Low-Pressure Phase Transformation From Rhombohedral To Cubic Bn: Experiment And Theory, Valery I. Levitas, Leonid K. Shvedov
Low-Pressure Phase Transformation From Rhombohedral To Cubic Bn: Experiment And Theory, Valery I. Levitas, Leonid K. Shvedov
Valery I. Levitas
An irreversible phase transformation (PT) from the rhombohedral phase of boron nitride rBN to cubic cBN was recently recorded at the surprisingly low pressure of 5.6 GPa at room temperature. In this paper, a very nontrivial and unexpected explanation of this phenomenon is found, based on our criterion for the PT in plastic materials and approximate solution of corresponding plastic problems. It is found that due to orientational plastic instability and rotational softening in rBN and the higher yield stress of cBN, stresses grow drastically in the transforming region during the PT (despite a volume decrease by a factor of …
Three-Dimensional Landau Theory For Multivariant Stress-Induced Martensitic Phase Transformations. Ii. Multivariant Phase Transformations And Stress Space Analysis, Valery I. Levitas, Dean L. Preston
Three-Dimensional Landau Theory For Multivariant Stress-Induced Martensitic Phase Transformations. Ii. Multivariant Phase Transformations And Stress Space Analysis, Valery I. Levitas, Dean L. Preston
Valery I. Levitas
In this paper, the three-dimensional Landau model of austenite-martensite transformations constructed in Part I is generalized to include transformations between an arbitrary number of martensitic variants. The model can incorporate all temperature-dependent thermomechanical properties of both phases for arbitrary crystal symmetries, including higher-order elastic constants, and it correctly describes the characteristic features of stress-strain curves for shape-memory alloys and steels, namely, constant transformation strain tensors, constant or weakly temperature dependent stress hysteresis, and transformation at nonzero tangent moduli. Geometric representations of the conditions for phase equilibrium and phase transformations in six-dimensional stress space are developed. For the cubic-tetragonal phase transformation, …
Three-Dimensional Landau Theory For Multivariant Stress-Induced Martensitic Phase Transformations. I. Austenite↔Martensite, Valery I. Levitas, Dean L. Preston
Three-Dimensional Landau Theory For Multivariant Stress-Induced Martensitic Phase Transformations. I. Austenite↔Martensite, Valery I. Levitas, Dean L. Preston
Valery I. Levitas
A three-dimensional Landau theory of stress-induced martensitic phase transformations is presented. It describes transformations between austenite and martensitic variants and transformations between martensitic variants. The Landau free energy incorporates all temperature-dependent thermomechanical properties of both phases. The theory accounts for the principal features of martensitic transformations in shape memory alloys and steels, namely, stress-strain curves with constant transformation strain and constant, or weakly temperature dependent, stress hysteresis, as well as nonzero tangent elastic moduli at the phase transformation point. In part I, the austenite↔martensite phase transformation is treated, while transformations between martensitic variants are considered in part II.
Piezoelectric In Situ Transmission Electron Microscopy Technique For Direct Observations Of Fatigue Damage Accumulation In Constrained Metallic Thin Films, Xiaoli Tan, T. Du, J.K. Shang
Piezoelectric In Situ Transmission Electron Microscopy Technique For Direct Observations Of Fatigue Damage Accumulation In Constrained Metallic Thin Films, Xiaoli Tan, T. Du, J.K. Shang
Xiaoli Tan
A piezoelectricin situtransmission electron microscopy(TEM) technique has been developed to observe the damage mechanism in constrained metallic thin films under cyclic loading. The technique was based on the piezoelectric actuation of a multilayered structure in which a metallic thin film was sandwiched between a piezoelectric actuator and a silicon substrate. An alternating electric field with a static offset was applied on the piezoelectric actuator to drive the crack growth in the thin metallic layer while the sample was imaged in TEM. The technique was demonstrated on solder thin films where cavitation was found to be the dominant fatigue damage mechanism.