Scan Science and Technology
Contact Leading Edge Experts & Companies
Adiabatic Process
The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform
Piotr Perzyna – 1st expert on this subject based on the ideXlab platform
-
Adiabatic shear band localization in single crystals under dynamic loading Processes
Archives of Mechanics, 1997Co-Authors: M K Duszekperzyna, K Korbel, Piotr PerzynaAbstract:THE MAIN OBJECTIVE of the paper is the investigation of Adiabatic shear band localization phenomena in inelastic single crystals under dynamic loading Processes. In the first part, a rate-dependent plastic model of single crystals is developed within the thermodynamic framework of the rate-type covariance constitutive structure. This model takes account of the effects as follows: (i) influence of covariance terms, lattice rotations and plastic spin; (ii) thermomechanical coupling; (iii) evolution of the dislocation substructure. An Adiabatic Process is formulated and examined. The relaxation time is used as a regularization parameter. The viscoplastic regularization assures the stable integration algorithm by using the finite element method. It has been shown that the evolution problem (the initial-boundary value problem) for rate-dependent plastic model of single crystals is well posed. The second part is devoted to the investigation of criteria of localization of plastic deformation in both single slip and symmetric double slip Processes. The Adiabatic shear band formation in elastic-plastic rate-independent single crystals during dynamic loading Processes is investigated. The critical value of the strain hardening rate and the misalignment of the shear band from the active slip systems in the crystal’s matrix have been determined. Particular attention is focused on the investigation of synergetic effects. Calculations have been obtained for aluminum single crystals. The results obtained are compared with available experimental observations.
-
Adiabatic shear band localization of inelastic single crystals in symmetric double-slip Process
Archive of Applied Mechanics, 1996Co-Authors: M. K. Duszek-perzyna, Piotr PerzynaAbstract:The main objective of the present paper is the development of a viscoplastic regularization procedure valid for an Adiabatic dynamic Process for multi-slips of single crystals. The next objective is to focus attention on the investigation of instability criteria, and particularly on shear band localization conditions. To achieve this aim, an analysis of acceleration waves is given, and advantage is taken of the notion of the instantaneous Adiabatic acoustic tensor. If zero is an eigenvalue of the acoustic tensor, then the associated discontinuity does not propagate, and one speaks of a stationary discontinuity. This situation is referred to as the ‘strain localization condition’, and corresponds to a loss of hyperbolicity of the dynamical equations. It has been proved that for an, Adiabatic Process of rate-dependent (elastic-viscoplastic) crystal, the wave speed of discontinuity surface always remains real and different from zero. It means that for this case the initial-value problem is well-posed. However, for an Adiabatic Process of rate-independent(elastic-plastic) crystal, the wave speed of discontinuity surface can be equal zero. Then the necessary condition for a localized plastic deformation along the shear band to be formed is as follows: the determinant of the instantaneous Adiabatic acoustic tensor is equal to zero. This condition for localization is equivalent to that obtained by using the standard bifurcation method. Based on this idea, the conditions for Adiabatic shear band localization of plastic deformation have been investigated for single crystals. Particular attention has been focused on the discussion of the influence of thermal expansion, thermal plastic, softening and spatial covariance effects on shear band localization criteria for a planar model of an f.c.c. crystal undergoing symmetric primary-conjugate double slip. The results obtained have been compared with available experimental observations. Finally, it is noteworthy that the viscoplasticity regularization procedure can be used in the developing of an unconditionally stable numerical integration algorithm for simulation of Adiabatic inelastic flow Processes in ductile single crystals, cf. [21].
-
instability phenomena and Adiabatic shear band localization in thermoplastic flow Processes
Acta Mechanica, 1994Co-Authors: Piotr PerzynaAbstract:The main objective of the paper is the development of the viscoplastic regularization procedure valid for a broad class of thermodynamic plastic flow Processes in damaged solids. The additional aim is to investigate instability phenomena and Adiabatic shear band localization criteria when spatial covariance, thermomechanical coupling, strain induced anisostropy and micro-damage softening effects are taken into consideration. This investigation is based on an analysis of acceleration waves and takes advantage of a notion of the instantaneous Adiabatic acoustic tensor. In the first part of the paper the formulation of an inelastic flow Process is given and particular attention is focussed on the thermomechanical coupling effects. The thermodynamic theory of elastic-viscoplastic damaged solids is presented within a framework of the rate type covariance material structure with a finite set of the internal state variables. A notion of covariance is understood in the sense of invariance under an arbitrary spatial diffeomorphism. Rate sensitivity effect is introduced by the assumption of the viscoplastic overstress conception. A notion of a relaxation time has been used to control the description of mechanical as well as thermal disturbances. By the assumption that the mechanical relaxation time is equal to zero the thermo-elastic-plastic (rate independent) response of the damaged material is accomplished. In the second part of the paper the existence of a solution to the initial-boundary value problem is examined and its stability property is investigated based on the application of nonlinear semi-group methods and an analysis of continuity of evolution operators. For an Adiabatic Process the investigation of acceleration waves is given. The determination of eigenvalues of the appropriate acoustic tensor is presented. This helps to assess the well-posedness of the initial-value problems which describe the thermodynamic plastic flow Processes. Differences for two constitutive assumptions, namely for rate dependent and rate independent responses, are examined. In the case of an Adiabatic Process and elastic-viscoplastic response of a material the conditions for the existence, uniqueness and well-posedness of the initial value problem have been investigated.
S Ferrazmello – 2nd expert on this subject based on the ideXlab platform
-
planetary migration and extrasolar planets in the 2 1 mean motion resonance
Monthly Notices of the Royal Astronomical Society, 2005Co-Authors: C Beauge, T A Michtchenko, S FerrazmelloAbstract:In this paper, we present a new set of corotational solutions for the 2/1 commensurability, including previously known solutions and new results. Comparisons with observed exoplanets show that current orbital fits of three proposed resonant planetary systems are consistent with apsidal corotations. We also discuss the possible relationship between the current orbital elements fits of known exoplanets in the 2/1 mean-motion resonance and the expected orbital configuration due to migration. We find that, as long as the orbital decay was sufficiently slow to be approximated by an Adiabatic Process, all captured planets should be in apsidal corotations. In other words, they should show a simultaneous libration of both the resonant angle and the difference in longitudes of pericenter.
-
planetary migration and extrasolar planets in the 2 1 mean motion resonance
arXiv: Astrophysics, 2004Co-Authors: C Beauge, S Ferrazmello, T A MichtchenkoAbstract:We analyze the possible relationship between the current orbital elements fits of known exoplanets in the 2/1 mean-motion resonance and the expected orbital configuration due to migration. It is found that, as long as the orbital decay was sufficiently slow to be approximated by an Adiabatic Process, all captured planets should be in apsidal corotations. In other words, they should show a simultaneous libration of both the resonant angle and the difference in longitudes of pericenter.
We present a complete set of corotational solutions for the 2/1 commensurability, including previously known solutions and new results. Comparisons with observed exoplanets show that current orbital fits of three known planetary systems in this resonance are either consistent with apsidal corotations (GJ876 and HD82943) or correspond to bodies with uncertain orbits (HD160691).
Finally, we discuss the applicability of these results as a test for the planetary migration hypothesis itself. If all future systems in this commensurability are found to be consistent with corotational solutions, then resonance capture of these bodies through planetary migration is a working hypothesis. Conversely, If any planetary pair is found in a different configuration, then either migration did not occur for those bodies, or it took a different form than currently believed.
Hui Dong – 3rd expert on this subject based on the ideXlab platform
-
achieve higher efficiency at maximum power with finite time quantum otto cycle
Physical Review E, 2019Co-Authors: Jin-fu Chen, Hui DongAbstract:: The optimization of heat engines was intensively explored to achieve higher efficiency while maintaining the output power. However, most investigations were limited to a few finite-time cycles, e.g., the Carnot-like cycle, due to the complexity of the finite-time thermodynamics. In this paper, we propose a class of finite-time engine with quantum Otto cycle, and demonstrate a higher achievable efficiency at maximum power. The current model can be widely utilized, benefitting from the general C/τ^{2} scaling of extra work for a finite-time Adiabatic Process with long control time τ. We apply the Adiabatic perturbation method to the quantum piston model and calculate the efficiency at maximum power, which is validated with an exact solution.
-
boosting the performance of the quantum otto heat engines
arXiv: Quantum Physics, 2019Co-Authors: Jin-fu Chen, Hui DongAbstract:To optimize the performance of a heat engine in finite-time cycle, it is important to understand the finite-time effect of thermodynamic Processes. Previously, we have shown that extra work is needed to complete a quantum Adiabatic Process in finite time, and proved that the extra work follows a \mathcal{C}/\tau^{2} scaling for long control time \tau. There the oscillating part of the extra work is neglected due to the complex energy-level structure of the particular quantum system. However, such oscillation of the extra work can not be neglected in some quantum systems with simple energy-level structure, e. g. the two-level system or the quantum harmonic oscillator. In this paper, we build the finite-time quantum Otto engine on these simple systems, and find that the oscillating extra work leads to a jagged edge in the constraint relation between the output power and the efficiency. By optimizing the control time of the quantum Adiabatic Processes, the oscillation in the extra work is utilized to enhance the maximum power and the efficiency. We further design special control schemes with the zero extra work at the specific control time. Compared to the linear control scheme, these special control schemes of the finite-time Adiabatic Process improve the maximum power and the efficiency of the finite-time Otto engine.
-
achieve higher efficiency at maximum power with finite time quantum otto cycle
arXiv: Quantum Physics, 2019Co-Authors: Jin-fu Chen, Hui DongAbstract:The optimization of finite-time thermodynamic heat engines was intensively explored recently, yet limited to few cycles, e.g. finite-time Carnot-like cycle. In this Letter, we supplement a new type of finite-time engine with quantum Otto cycle and show the better performance. The current model can be widely utilized benefited from the general \mathcal{C}/\tau^{2} scaling of extra work for finite-time Adiabatic Process with long control time \tau. Such scaling allows analytical optimization of the generic finite-time quantum Otto cycle to surpass the efficiency at maximum power for the Carnot-like engine. We apply the current perturbation method to the quantum piston model and calculate the efficiency at maximum power, which is validated with exact solution.