فهرس المقالات Time-dependent creep

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  1 - Thermo-Elastic and Time-Dependent Creep Evolution Behaviour of Ferritic Steel Rotating Disks using Theta Projection Concept
  H. Daghigh V. Daghigh
  In this article, thermo-elastic and creep evolution behaviour of ferritic steel rotating disks with variable thickness are investigated. Four thickness profiles of uniform, convex, concave and linear are considered for the disk geometry. The material creep constitutive أکثر

  In this article, thermo-elastic and creep evolution behaviour of ferritic steel rotating disks with variable thickness are investigated. Four thickness profiles of uniform, convex, concave and linear are considered for the disk geometry. The material creep constitutive model is defined by the Θ projection concept, based on the experimental results existing in the literature. Loading applied is due to the inertial body force caused by the rotation and a constant temperature field throughout the disk. To achieve history of stresses and displacements, a numerical procedure using finite difference and Prandtl-Reuss relations is used. Stress and deformation histories are calculated using successive elastic solution method. In order to verify the solution approach, both composite and aluminum rotating disks were taken into account and the thermo-elastic and time-dependent creep behaviours for composite as well as the former for aluminum were obtained. Results from the current study were found to be in very good agreement with those available from literature in the area. It was shown that convex thickness profile disks display the least creep displacement, creep effective and circumferential stresses. Additionally, constant and concave thickness profiles were positively correlated with time while for linear and convex ones, it was found to have an inverse trend. تفاصيل المقالة
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  2 - Hygrothermal Creep and Stress Redistribution Analysis of Temperature and Moisture Dependent Magneto-Electro-Elastic Hollow Sphere
  M Saadatfar
  10.22034/jsm.2019.582849.1371
  In this article, the time-dependent stress redistribution analysis of magneto-electro-elastic (MEE) thick-walled sphere subjected to mechanical, electrical, magnetic and uniform temperature gradient as well as moisture concentration gradient is presented. Combining cons أکثر

  In this article, the time-dependent stress redistribution analysis of magneto-electro-elastic (MEE) thick-walled sphere subjected to mechanical, electrical, magnetic and uniform temperature gradient as well as moisture concentration gradient is presented. Combining constitutive equations of MEE with stress-strain relations as well as strain-displacement relations results in obtaining a differential equation in which there are the creep strains. At the first step, discounting creep strains in the mentioned equation, an analytical solution for the hygro-thermo-magneto-electro-elastic behavior is achieved at the initial state. After that, the creep stress rates can be achieved by keeping only the creep strains in the differential equation for the steady-state condition. The analysis is done by applying the Prandtl-Reuss equations as well as Norton’s law in creep behavior modeling. Finally, the history of stresses, displacement as well as magnetic and potential field, at any time, is achieved using an iterative method. Results show that the increase in tensile hoop stress resulted from creep progress must be considered in design progress. Also, the effect of hygrothermal loading is more extensive after creep evolution. تفاصيل المقالة
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  3 - Creep Evolution Analysis of Composite Cylinder Made of Polypropylene Reinforced by Functionally Graded MWCNTs
  A Loghman H Shayestemoghadam E Loghman
  Polypropylene is one of the most common, fastest growing and versatile thermoplastics currently used to produce tanks and chemical piping systems. Even at room temperature creep is considerable for polypropylene products. The creep behavior of strains, stresses, and dis أکثر

  Polypropylene is one of the most common, fastest growing and versatile thermoplastics currently used to produce tanks and chemical piping systems. Even at room temperature creep is considerable for polypropylene products. The creep behavior of strains, stresses, and displacement rates is investigated in a thick-walled cylinder made of polypropylene reinforced by functionally graded (FG) multi-walled carbon nanotubes (MWCNTs) using Burgers viscoelastic creep model. The mechanical properties of the composite are obtained based on the volume content of the MWCNTs. Loading is composed of an internal pressure and a uniform temperature field. Using equations of equilibrium, stress-strain and strain-displacement, a constitutive differential equation containing total creep strains is obtained. Creep strain increments are accumulated incrementally during the life of the vessel. Creep strain increments are related to the current stresses and the material uniaxial Burgers creep model by the well-known Prandtl-Reuss relations. A semi-analytical solution using Prandtl-Reuss relation has been developed to determine history of stresses, strains and displacements. The results are plotted against dimensionless radius for different volume content of MWCNTs. It has been found that the creep radial and circumferential strains of the cylinder reduce with increasing content of carbon nanotubes. It has also been concluded that the uniform distribution of MWCNTs reinforcement does not considerably influence on stresses. تفاصيل المقالة
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  4 - Non-Axisymmetric Time-Dependent Creep Analysis in a Thick-Walled Cylinder Due to the Thermo-mechanical loading
  M Moradi A Loghman
  In this study, the non-linear creep behaviour of a thick-walled cylinder made of stainless steel 316 is investigated using a semi-analytical method. The thick-walled cylinder is under a uniform internal pressure and a non-axisymmetric thermal field as a function of the أکثر

  In this study, the non-linear creep behaviour of a thick-walled cylinder made of stainless steel 316 is investigated using a semi-analytical method. The thick-walled cylinder is under a uniform internal pressure and a non-axisymmetric thermal field as a function of the radial and circumferential coordinates. For the high temperature and stress levels, creep phenomena play a major role in stress redistributions across the cylinder thickness. The Bailey-Norton creep constitutive equation is used to model the uniaxial creep behaviour of the material. Creep strain increments are accumulated incrementally during the life of the vessel. Creep strain increments are related to the current stresses and the material uniaxial creep model by the well-known Prandtl-Reuss relations. Considering the mentioned non-axisymmetric boundary conditions, the heat conduction equation and the Navier partial differential equations has been solved using the separation of variables and the complex Fourier series methods. The corresponding displacement, strain and stress functions are obtained. Considering the non-axisymmetric loadings, the distribution of the radial, circumferential and shear stresses are studied. Furthermore, the effects of internal pressure and external temperature distribution on the effective stress history are investigated. It has been found that the non-axisymmetric thermal loading has a significant effect on stress redistributions. تفاصيل المقالة