Non-Rigid Rotating Motion Effect on Creep Behavior for Infinite Cylinders under Thermomechanical Loading

2021 ◽  
Vol 105 ◽  
pp. 137-143
Author(s):  
Hamideh Seddighi ◽  
Mohammad Parhizkar Yaghoobi ◽  
Mehdi Ghannad
Keyword(s):  
Creep Behavior ◽  
Radial Displacement ◽  
Rigid Motion ◽  
Structural Behavior ◽  
Uniform Heat Flux ◽  
Kinematic Equation ◽  
Rigidity Parameter ◽  
Material Creep ◽  
Rate Form ◽  
History Of

The effect of non-rigid motion on creep analysis for cylinders have been investigated. inner surface of the cylinder is exposed to a uniform heat flux and for cooling the outer surface of the cylinder an air steam is applied to it. The cylinder is subjected to a body force. That produced by rotating cylinder about its own axis. It is assumed the cylinder is not rigid. Therefore, using equations of equilibrium, stress–strain and kinematic equation, governed equation which includes redial displacement and creep strains, is obtained. The material creep constitutive model is defined by the Bailey-Norton time-dependent creep law. From a solution consisting of analytical solution and iteration method has been used to obtain history of stresses and deformations during creep evolution of rotating cylinders. Therefore, Prandtle-Ruess equation substituted in equilibrium equation in the rate form, the radial displacement rate is obtained for plane strain condition. To investigate the effect of non-rigidity, the non-rigidity parameter (ζ) is defined and its effect on the creep behavior of the structure is investigated. It was revealed that Considering the structure as rigid does neglect the amount of stresses and radial displacement. History of stresses and displacement during 20 years are studied and it is observed that the changes have not accrued in recent years. The effect of velocity is another parameter that is investigated its effect on structural behavior during the time. it was revealed that, velocity has significant effect on structural behavior which cause trend of variation behavior change from linear to polynomial curve.

scholarly journals On the Connections between Thermodynamics and General Relativity

2021 ◽  
Author(s):  
◽  
Jessica Santiago Silva
Keyword(s):  
General Relativity ◽  
Hawking Radiation ◽  
Rigid Motion ◽  
Irreversible Thermodynamics ◽  
Temperature Gradients ◽  
Type I ◽  
Killing Vectors ◽  
Proper Distance ◽  
Perfect Fluids ◽  
History Of

<p>In this thesis, the connections between thermodynamics and general relativity are explored. We introduce some of the history of the interaction between these two theories and take some time to individually study important concepts of both of them. Then, we move on to explore the concept of gravitationally induced temperature gradients in equilibrium states, first introduced by Richard Tolman. We explore these Tolman-like temperature gradients, understanding their physical origin and whether they can be generated by other forces or not. We then generalize this concept for fluids following generic four-velocities, which are not necessarily generated by Killing vectors, in general stationary space-times. Some examples are given.  Driven by the interest of understanding and possibly extending the concept of equilibrium for fluids following trajectories which are not generated by Killing vectors, we dedicate ourselves to a more fundamental question: can we still define thermal equilibrium for non-Killing flows? To answer this question we review two of the main theories of relativistic non-perfect fluids: Classical Irreversible Thermodynamics and Extended Irreversible Thermodynamics. We also take a tour through the interesting concept of Born-rigid motion, showing some explicit examples of non-Killing rigid flows for Bianchi Type I space-times. These results are important since they show that the Herglotz–Noether theorem cannot be extended for general curved space-times. We then connect the Born-rigid concept with the results obtained by the relativistic fluid’s equilibrium conditions and show that the exact thermodynamic equilibrium can only be achieved along a Killing flow. We do, however, introduce some interesting possibilities which are allowed for non-Killing flows.  We then launch into black hole thermodynamics, specifically studying the trans-Planckian problem for Hawking radiation. We construct a kinematical model consisting of matching two Vaidya spacetimes along a thin shell and show that, as long as the Hawking radiation is emitted only a few Planck lengths (in proper distance) away from the horizon, the trans-Plackian problem can be avoided.  We conclude with a brief discussion about what was presented and what can be done in the future.</p>

Creep Relaxation of an Elastic–Perfectly Plastic Hemisphere in Fully Plastic Contact

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Andreas Goedecke ◽  
Randolf Mock
Keyword(s):  
Creep Behavior ◽  
Contact Area ◽  
Geometrical Parameters ◽  
Second Phase ◽  
Perfectly Plastic ◽  
Area Increase ◽  
Accelerated Creep ◽  
Material Creep ◽  
Evolution Laws ◽  
Elastic Perfectly Plastic

A set of finite element simulations was performed to analyze the creep behavior of an elastic–perfectly plastic hemisphere in contact with a rigid flat. This study focuses on the time-dependent stress relaxation of a fully plastic asperity. Assuming a Garofalo (hyperbolic sine) type material creep law, the asperity shows two distinct phases of relaxation. In the first phase, the asperity creeps with an accelerated creep rate and shows a contact area increase similar to that of a cylindrical geometry. In the second phase, no contact area change can be measured and the asperity creeps with a slower rate. Empirical evolution laws for the asperity creep behavior are presented, analyzing the influence of both material and geometrical parameters. The results are interpreted in terms of transient friction.

Analysis of the Thermo-Structural Behavior of Polyethylene Using Simultaneous DSC/XRD

1985 ◽  
Vol 29 ◽  
pp. 315-322 ◽  
Author(s):  
C. E. Crowder ◽  
S. Wood ◽  
B. G. Landes ◽  
R. A. Newman ◽  
J. A. Blazy ◽  
...  
Keyword(s):  
Thermal Conditions ◽  
Atmospheric Environment ◽  
Structural Behavior ◽  
X Ray Diffraction ◽  
Heating Rates ◽  
Scanning Calorimetry ◽  
X Ray ◽  
The Past ◽  
Polymer Properties ◽  
History Of

Over the past 25 years, numerous studies of polymers utilizing both X-ray diffraction (XRD) and differential scanning calorimetry (DSC) have been reported in the literature. These studies have suffered because the two techniques must be performed on separate samples and under conditions that are often dissimilar. By combining the two techniques into one instrument, typical problems encountered with variations in sample preparation and thermal and atmospheric environment are eliminated. This is quite important in the study of polymers since one must match not only temperatures between the two techniques, but also heating rates as well. Matched thermal conditions are necessary because polymer properties such as crystallinity and crystallite size depend on both the temperature and thermal history of the sample under study.

Fitness for Service of Degraded Grade 91 Pipe

2012 ◽  
Author(s):  
Marvin J. Cohn ◽  
Steve R. Paterson
Keyword(s):  
Power Plants ◽  
Thermal Stresses ◽  
Creep Rupture ◽  
Piping System ◽  
Principal Stresses ◽  
Support Costs ◽  
Material Creep ◽  
History Of ◽  
Grade 91 ◽  
Life Consumption

The use of creep strength enhanced ferritic alloys such as Grade 91 in fossil power plants has become popular for high temperature piping applications. Since Grade 91 has higher stress allowables than Grade 22, a designer can specify thinner component wall thicknesses, resulting in lower through-wall thermal stresses during transient events and lower material and piping support costs. During the past two decades, Grade 91 has been used successfully in fossil power plants. However, this alloy has had some incidents of non-optimal weldment microstructure. In this case study, Brinell hardness tests of an ASME A182 Grade F91 (F91) wye block, including upstream and downstream F91 spools, revealed several readings of soft material, as low as 168HB. A study of creep rupture tests of degraded Grade 91 specimens revealed that the lower bound creep rupture curve of the degraded Grade 91 material is above the average creep rupture curve of Grade 22 material for the range of the specific piping operating stresses. Based on the empirical evidence that the average Grade 22 material creep rupture curve is conservative for the creep rupture of degraded Grade 91 material, a life consumption evaluation was performed for the degraded Grade 91 weldments using Grade 22 creep rupture properties. A life fraction analysis was performed considering the redistributed maximum principal stresses, based on simulation of piping displacements obtained from the hot and cold walkdowns. This study also considered the recent history of the specific piping system operating pressures and temperatures. This study also considered dissimilar metal welds, from ASME A182 Grade F91 (F91) to ASME A335 Grade P22 (P22) materials. It was determined that the Grades F91-to-F91 weldments had about 30% life consumption and the remaining lives were at least 7 years. The Grades F91-to-P22 weldments had less than 40% life consumption and the remaining lives were at least 15 years.

Creep Modeling of Polyvinyl Chloride Bolted Flange Joints

2017 ◽  
Author(s):  
Zijian Zhao ◽  
Rahul Palaniappan Kanthabhabha Jeya ◽  
Abdel-Hakim Bouzid
Keyword(s):  
Polyvinyl Chloride ◽  
Creep Behavior ◽  
Compressive Load ◽  
Dissimilar Materials ◽  
Operating Conditions ◽  
Relaxation Behavior ◽  
Creep Model ◽  
Compression Creep ◽  
Material Creep ◽  
Bolted Flange

Alike other polymer material, PolyVinyl Chloride (PVC) shows a clear creep behavior, the rate of which is influenced by temperature, load and time. Polyvinyl chloride bolted flange joints undergo relaxation under compression for which the material creep properties are different than those under tension. Since the sealing capacity of a flanged gasketed joint is impacted by the amount of relaxation that takes place, it is important to properly address and predict the relaxation behavior due to flange creep under compression and reduce the chances of leakage failure of PVC flange joints. The main objective is study the creep behavior of PVC flanges under the influence of normal operating conditions. This is achieved by developing a PVC creep model based on creep test data under various compressive load, temperature and time. A simulation of a PVC flange relaxation behavior bot numerically and experimentally is conducted on an NPS 3 class 150 bolted flange joint of dissimilar materials one made of PVC material and the other one by steel SA105. The study also provides a clear picture on how the compression creep data on Ring specimen may be utilized for predicating the flange performance under various operating temperatures with time.

Load-Deformation Behavior of Elastic Beam-Columns on Yielding Foundations

1978 ◽  
Vol 100 (1) ◽  
pp. 182-188
Author(s):  
C. Shahravan ◽  
A. I. Soler
Keyword(s):  
Tube Bundle ◽  
Compressive Load ◽  
Elastic Beam ◽  
Beam Columns ◽  
Support Plate ◽  
Perfectly Plastic ◽  
Load Carrying ◽  
Rate Form ◽  
History Of ◽  
Elastic Perfectly Plastic

The effect of an elastic-perfectly plastic foundation on compressive load carrying capacity of beam columns is considered. The configuration studied simulates a power plant condenser support plate acting as a column member to support the condenser walls against excessive deformation due to vacuum pressure. The yielding foundation represents the effect of the condenser tube bundle which can resist support plate bending through frictional action between the plate and the tubes. The equation governing lateral motion of the beam column is developed in rate form using the Green’s function for an elastic beam column. An approximate incremental solution is obtained enabling the load-deformation history of the beam column to be studied incorporating elastic-plastic loading and unloading of the foundation. “Failure” is assumed to occur when the maximum stress in the beam column reaches a preset allowable design value.

scholarly journals Some Issues on Crystal Plasticity Models Formulation: Motion Decomposition and Constitutive Law Variants

Crystals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1392
Author(s):  
Peter Trusov ◽  
Alexey Shveykin ◽  
Nikita Kondratev
Keyword(s):  
Coordinate System ◽  
Crystal Plasticity ◽  
A Priori ◽  
Deformation Gradient ◽  
Rigid Motion ◽  
Constitutive Law ◽  
Current Configuration ◽  
Treatment Processes ◽  
Rate Form ◽  
Moving Coordinate

In this paper, kinematic relations and constitutive laws in crystal plasticity are analyzed in the context of geometric nonlinearity description and fulfillment of thermodynamic requirements in the case of elastic deformation. We consider the most popular relations: in finite form, written in terms of the unloaded configuration, and in rate form, written in terms of the current configuration. The presence of a corotational derivative in the relations formulated in terms of the current configuration testifies to the fact that the model is based on the decomposition of motion into the deformation motion and the rigid motion of a moving coordinate system, and precisely the stress rate with respect to this coordinate system is associated with the strain rate. We also examine the relations of the mesolevel model with an explicit separation of a moving coordinate system and the elastic distortion of crystallites relative to it in the deformation gradient. These relations are compared with the above formulations, which makes it possible to determine how close they are. The results of the performed analytical calculations show the equivalence or similarity (in the sense of the response determined under the same influences) of the formulation and are supported by the results of numerical calculation. It is shown that the formulation based on the decomposition of motion with an explicit separation of the moving coordinate system motion provides a theoretical framework for the transition to a similar formulation in rate form written in terms of the current configuration. The formulation of this kind is preferable for the numerical solution of boundary value problems (in a case when the current configuration and, consequently, contact boundaries, are not known a priori) used to model the technological treatment processes.

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