scholarly journals Optimization of Thick-Walled Viscoelastic Hollow Polymer Cylinders by Artificial Heterogeneity Creation: Theoretical Aspects

Polymers ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2408
Author(s):  
Anton Chepurnenko ◽  
Stepan Litvinov ◽  
Besarion Meskhi ◽  
Alexey Beskopylny
Keyword(s):  
Cylindrical Shell ◽  
Internal Pressure ◽  
High Density Polyethylene ◽  
Mechanical Characteristics ◽  
Optimization Technique ◽  
Creep Process ◽  
Mass Content ◽  
Shell Optimization ◽  
Relationship Of ◽  
The Relationship

A theoretical solution of the problem of thick-walled shell optimization by varying the mechanical characteristics of the material over the thickness of the structure is proposed, taking into account its rheological properties. The optimization technique is considered by the example of a cylindrical shell made of high-density polyethylene with hydroxyapatite subjected to internal pressure. Radial heterogeneity can be created by centrifugation during the curing of the polymer mixed with the additive. The nonlinear Maxwell–Gurevich equation is used as the law describing polymer creep. The relationship of the change in the additive content along with the radius r, at which the structure is equally stressed following the four classical criteria of fracture, is determined in an elastic formulation. Moreover, it is shown that a cylinder with equal stress at the beginning of the creep process ceases to be equally stressed during creep. Finally, an algorithm for defining the relationship of the additive mass content on coordinate r, at which the structure is equally stressed at the end of the creep process, is proposed. The developed algorithm, implemented in the MATLAB software, allows modeling both equally stressed and equally strength structures.

FEM Stress Analysis and Sealing Performance of Bolted Flanged Connections Using PTFE Blended Gaskets Under Internal Pressure

2015 ◽  
Author(s):  
Koji Sato ◽  
Akira Muramatsu ◽  
Takashi Kobayashi ◽  
Toshiyuki Sawa
Keyword(s):  
Stress Distribution ◽  
Internal Pressure ◽  
Mechanical Characteristics ◽  
Leak Rate ◽  
Load Factor ◽  
Bolt Preload ◽  
Sealing Performance ◽  
Relationship Of ◽  
The Relationship ◽  
Good Agreement

The objective of the paper is to examine mechanical characteristics of bolted flanged connection with newly developed PTFE blended gaskets under internal pressure such as the contact gasket stress distribution, the sealing performance, the load factor, reduction in axial bolt load due to creep and the flange hub stress. The relationship between the leak rate and the contact gasket stress for newly developed PTFE blended gasket were measured according to JIS B 2490 as well as the stress - displacement relationship of the gaskets. Then, the leak rate for bolted flanged connection with the PTFE blended gaskets (2inch nominal flange) was measured under internal pressure while changing the bolt preloads. In addition, the load factor and the hub stress were measured experimentally. The changes in each axial bolt force were measured using the strain gauges taking into account gasket creep. Using FEM, the gasket stress distribution, the load factor and the hub stress are analyzed taking into account the creep phenomenon of the PTFE blended gasket. The optimal maximum bolt preload is determined and the FEM results of the load factor and hub stress are in a fairly good agreement with the measured results. The predicted leak rate is fairly coincided with the measured results.

scholarly journals Numerical simulation on the leakage and diffusion of the natural gas of the underground pipeline in the soil

2021 ◽  
Vol 2083 (3) ◽  
pp. 032082
Author(s):  
Meijuan Hu ◽  
He Li ◽  
Li Chen ◽  
Ping Xie ◽  
Zheju Zhang ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Natural Gas ◽  
Internal Pressure ◽  
Finite Model ◽  
Soil Environment ◽  
Leakage Model ◽  
Relationship Of ◽  
The Relationship ◽  
And Diffusion ◽  
Variation Trends

Abstract For the transportation pipeline with the diameter 1.219 m and the internal pressure 3-12 MPa, the leakage and diffusion of the natural gas of the pipeline in the soil was studied by numerical simulation. First, the finite model containing both pipeline and soil was established, and the porous media was used to simulate the real soil environment. And, the leakage amount of the natural gas was calculated at the cases with different porosities, the pressures inside the pipeline and the diameters of leakage port. Based on the classical theoretical leakage model of small hole in the air and simulation results analysis, the formula of the leakage amount was modified by the soil coefficient α to be suitable for soil environment. Then, the variation trends of the diffusion concentration of methane along different directions in the soil were analyzed by simulation, the influences of internal pressure of pipeline, the diameter of leakage and the porosity of soil were also discussed. Besides, the relationship of the safety distance with time was obtained.

scholarly journals The Relationship of Weight-adjusted Bone Mass Content Associated with COPD and Associated Factors

2020 ◽  
Vol 82 (s6) ◽  
Author(s):  
J. CHINDAPRASIRT ◽  
W. BOONSAWAT ◽  
P LIMPAWATTANA ◽  
D. THEERAKULPISUT ◽  
M MANJAVONG ◽  
...  
Keyword(s):  
Bone Mass ◽  
Associated Factors ◽  
Mass Content ◽  
Relationship Of ◽  
The Relationship

scholarly journals Creep of a heterogeneous polymer cylindrical shell

2021 ◽  
Vol 1030 (1) ◽  
pp. 012091
Author(s):  
Vladimir Andreev ◽  
Batyr Yazyev
Keyword(s):  
Cylindrical Shell ◽  
Composite Materials ◽  
Internal Pressure ◽  
Mechanical Characteristics ◽  
Structural Elements ◽  
Filled Polymer ◽  
Heterogeneous Polymer ◽  
Physical And Mechanical Characteristics

Abstract The article deals with the problem of calculating an heterogeneous cylindrical shell made of a filled polymer, which is in the process of creep under the action of constant internal pressure and temperature. The calculation is based on the Maxwell -Gurevich equation, which has been repeatedly tested in the calculations of structural elements made of polymer and composite materials. The dependence of the physical and mechanical characteristics of the material on temperature is taken into account.

Investigation of the Relationship of Muscle Mechanical Characteristics with Biosignal Energy

2006 ◽  
Vol 113 ◽  
pp. 151-156
Author(s):  
Mečislovas Mariūnas ◽  
Kristina Kojelyte
Keyword(s):  
Mechanical Characteristics ◽  
Extreme Points ◽  
Shift Function ◽  
Energy Equality ◽  
Second Derivatives ◽  
Digital Methods ◽  
Relationship Of ◽  
The Relationship ◽  
Analytical Expressions ◽  
Derivatives Of

Based on biosignal energy equality to the work performed by a muscle, in the estimation of energy dissipation within a biolotronic system, analytical expressions have been derived that have helped to calculate major mechanical characteristics of the muscle including elongation of the muscle, speed and acceleration of such elongation. The paper presents the analysis of relevant digital methods alongside with the formulae for the calculation of major mechanical characteristics when the relationship of a muscle biosignal that is presented in a graphical way. As shown, fatigue of the muscle is characterized by one of extreme points of the phase shift function. The values of the first and the second derivatives of the elongation function may be used for the evaluation of functional capacity of the muscle.

HIV infection changes glomerular podocyte cytoskeletal composition and results in distinct cellular mechanical properties

2007 ◽  
Vol 292 (2) ◽  
pp. F701-F710 ◽  
Author(s):  
R. Tandon ◽  
I. Levental ◽  
C. Huang ◽  
F. J. Byfield ◽  
J. Ziembicki ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Mechanical Characteristics ◽  
Stress Fibers ◽  
Wild Type ◽  
Force Microscopy ◽  
Hemodynamic Forces ◽  
Filtration Barrier ◽  
Atomic Force ◽  
Relationship Of ◽  
The Relationship

In addition to forming the selective filtration barrier for the renal glomerulus, podocytes maintain glomerular capillary architecture by opposing distending hemodynamic forces. To understand the relationship of cytoskeletal properties and the mechanical characteristics of podocytes, we studied filamin expression and distribution and measured cell membrane deformability in conditionally immortalized wild-type (WT) mouse podocytes, and in podocytes derived from a mouse model of HIV-associated nephropathy (HIVAN). In the WT cells, filamin and F-actin were localized at the periphery and in prominent stress fibers. In the HIVAN cells, filamin expression was reduced, and stress fibers were sparse. In a microaspiration assay, HIVAN cells ruptured under minimal negative pressure. Atomic force microscopy demonstrated that the WT cells had a stiffness of 17 kPa, whereas the value for the HIVAN cells was 4 kPa. These results demonstrate that the mechanical properties of WT and HIVAN podocytes are markedly different in a manner that is consistent with differences in the composition and arrangement of their cytoskeletons. The mechanical properties of the WT podocytes suggest that these cells can better maintain capillary integrity than the HIVAN podocytes and implicate pathological assembly of the cytoskeleton as a mechanism of HIVAN.

FEM Stress Analysis and the Sealing Performance Evaluation of Bolted Pipe Flange Connections With Large Nominal Diameter Subjected to Internal Pressure

2016 ◽  
Author(s):  
Akira Muramatsu ◽  
Koji Sato ◽  
Maksud Uddin Khan ◽  
Toshiyuki Sawa
Keyword(s):  
Internal Pressure ◽  
Mechanical Characteristics ◽  
Measured Data ◽  
Leak Rate ◽  
Load Factor ◽  
Stress Distributions ◽  
Nominal Diameter ◽  
Sealing Performance ◽  
The Relationship ◽  
Good Agreement

The gasket fundamental characteristics such as the stress-strain curves of compressed sheet gaskets (CSG) and the spiral wound gaskets (SWG) and the relationship between the average gasket stress and the leak rate using rigid platens were measured. Then, using the measured data of the gasket properties, the mechanical characteristics of bolted pipe flange connections under internal pressure are examined such as the contact gasket stress distribution, hub stress and changes in axial bolt forces (the load factor) using FEM. FEM code employed is ABAQUS. Using the obtained gasket stress distributions and the fundamental gasket relationship between the gasket stress and the leak rate, the leak rates of bolted pipe flange connections are predicted. In addition, the effect of nominal diameters (from 2” to 24”) on the mechanical characteristics is examined. For verification of the FEM calculations, experiments to measure the load factor, the hub stress and the leak rates were performed using 2” and 24” bolted pipe flange connections. The FEM results of the load factor, the hub stress and the leak rate are in a fairly good agreement with the measured results. The value of the load factor is found to be positive for 2” pipe flanged joints, while it is negative for 24” pipe flanged connection due to the flange rotation. It is noticed that the values of the load factor decreases with an increase of the nominal diameter of pipe flanges. The hub stress is kept constant when the gasket stress is held constant for each connection with each nominal diameter while it increases as the nominal diameter increases according to ASME codes. In addition, the leak rate increases as the nominal diameter increases.

TECHNOLOGICAL SUPPORT OF CONTACT RIGIDITY OF MACHINE PARTS

2021 ◽  
pp. 1-28
Author(s):  
V. F. Bezyazychnyj ◽  
M. N. Dmitrieva
Keyword(s):  
Mechanical Characteristics ◽  
Contact Stiffness ◽  
Turbine Engine ◽  
Technological Support ◽  
Contact Rigidity ◽  
Machine Parts ◽  
Engine Components ◽  
Relationship Of ◽  
The Relationship ◽  
Physical And Mechanical Characteristics

The theoretical provisions on establishing the relationship between the geometric characteristics of the surfaces of contacting parts, as well as the physical and mechanical characteristics of the material of these surfaces on their contact stiffness, including the contact stiffness of the surfaces of parts of high-load gas turbine engine components, are presented. The analysis of dependencies on the relationship of contact stiffness and pliability of surfaces with the technological conditions of their processing by various types of cutting process (turning, milling, grinding) is given.

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