Entangled Polymers: Constraint Release, Mean Paths, and Tube Bending Energy

2008 ◽  
Vol 41 (18) ◽  
pp. 6843-6853 ◽  
Author(s):  
D. J. Read ◽  
K. Jagannathan ◽  
A. E. Likhtman
Keyword(s):  
Tube Bending ◽  
Bending Energy ◽  
Entangled Polymers ◽  
Constraint Release

scholarly journals Contraction of Entangled Polymers After Large Step Shear Deformations in Slip-Link Simulations

Polymers ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 370 ◽  
Author(s):  
Yuichi Masubuchi
Keyword(s):  
Dynamics Simulation ◽  
Uniaxial Deformation ◽  
Single Chain ◽  
Orientational Relaxation ◽  
Entangled Polymers ◽  
Constraint Release ◽  
Large Step ◽  
Entangled Polymer ◽  
Convective Constraint Release ◽  
Chain Contraction

Although the tube framework has achieved remarkable success to describe entangled polymer dynamics, the chain motion assumed in tube theories is still a matter of discussion. Recently, Xu et al. [ACS Macro Lett. 2018, 7, 190–195] performed a molecular dynamics simulation for entangled bead-spring chains under a step uniaxial deformation and reported that the relaxation of gyration radii cannot be reproduced by the elaborated single-chain tube model called GLaMM. On the basis of this result, they criticized the tube framework, in which it is assumed that the chain contraction occurs after the deformation before the orientational relaxation. In the present study, as a test of their argument, two different slip-link simulations developed by Doi and Takimoto and by Masubuchi et al. were performed and compared to the results of Xu et al. In spite of the modeling being based on the tube framework, the slip-link simulations excellently reproduced the bead-spring simulation result. Besides, the chain contraction was observed in the simulations as with the tube picture. The obtained results imply that the bead-spring results are within the scope of the tube framework whereas the failure of the GLaMM model is possibly due to the homogeneous assumption along the chain for the fluctuations induced by convective constraint release.

scholarly journals Comparative Analysis of Different Tube Models for Linear Rheology of Monodisperse Linear Entangled Polymers

Polymers ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 754 ◽  
Author(s):  
Volha Shchetnikava ◽  
Johan Slot ◽  
Evelyne van Ruymbeke
Keyword(s):  
Experimental Data ◽  
Comparative Analysis ◽  
Hierarchical Model ◽  
Linear Viscoelasticity ◽  
Star Polymers ◽  
Contour Length ◽  
Large Set ◽  
Linear Polymers ◽  
Entangled Polymers ◽  
Constraint Release

The aim of the present paper is to analyse the differences between tube-based models which are widely used for predicting the linear viscoelasticity of monodisperse linear polymers, in comparison to a large set of experimental data. The following models are examined: Milner–McLeish, Likhtman–McLeish, the Hierarchical model proposed by the group of Larson, the BoB model of Das and Read, and the TMA model proposed by the group of van Ruymbeke. This comparison allows us to highlight and discuss important questions related to the relaxation of entangled polymers, such as the importance of the contour-length fluctuations (CLF) process and how it affects the reptation mechanism, or the contribution of the constraint release (CR) process on the motion of the chains. In particular, it allows us to point out important approximations, inherent in some models, which result in an overestimation of the effect of CLF on the reptation time. On the contrary, by validating the TMA model against experimental data, we show that this effect is underestimated in TMA. Therefore, in order to obtain accurate predictions, a novel modification to the TMA model is proposed. Our current work is a continuation of earlier research (Shchetnikava et al., 2014), where a similar analysis is performed on well-defined star polymers.

CERROTRU Alloy

Alloy Digest ◽  
1979 ◽  
Vol 28 (12) ◽  
Keyword(s):  
Melting Point ◽  
Liquid Metal ◽  
Physical Properties ◽  
Tensile Properties ◽  
Eutectic Alloy ◽  
Heat Treating ◽  
Tube Bending ◽  
Metal Products

Abstract CERROTRU Alloy is a bismuth-base eutectic alloy that melts at 281 F (138 C). It has the highest melting point of the bismuth-base alloys commonly used in industry. It provides production engineers with an easily castable material that is ready for use soon after it freezes. The alloy can be recovered easily and recycled into new uses any number of times. Cerrotru alloy has many uses including anchoring, molds for plastics, filler for tube bending and liquid metal in heat treating. This datasheet provides information on composition, physical properties, hardness, and tensile properties. It also includes information on casting, heat treating, and machining. Filing Code: Bi-15. Producer or source: Cerro Metal Products.

BELMONT ALLOY 2505

Alloy Digest ◽  
1978 ◽  
Vol 27 (11) ◽  
Keyword(s):  
Low Temperature ◽  
Physical Properties ◽  
Tensile Properties ◽  
Heat Treating ◽  
Tube Bending

Abstract BELMONT ALLOY 2505 is a bismuth-base, eutectic, low-melting alloy. It melts at 158 F and provides engineers and technicians with an easily castable material that is ready for use as soon as it freezes. Alloy 2505 can be recovered easily and recycled into new uses any number of times. Its many uses include shuttle blocks, tube bending, chucks for lens buffing and grinding, anchoring, dies, and low-temperature solder. This datasheet provides information on composition, physical properties, hardness, and tensile properties. It also includes information on forming, heat treating, and machining. Filing Code: Bi-9. Producer or source: Belmont Metals Inc..

scholarly journals Universally bistable shells with nonzero Gaussian curvature for two-way transition waves

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Nikolaos Vasios ◽  
Bolei Deng ◽  
Benjamin Gorissen ◽  
Katia Bertoldi
Keyword(s):  
Gaussian Curvature ◽  
Energy Landscape ◽  
Propagation Distance ◽  
Energy Landscapes ◽  
Bending Energy ◽  
Nonlinear Dynamic Response ◽  
One Dimensional ◽  
Doubly Curved Shells ◽  
Doubly Curved ◽  
The Waves

AbstractMulti-welled energy landscapes arising in shells with nonzero Gaussian curvature typically fade away as their thickness becomes larger because of the increased bending energy required for inversion. Motivated by this limitation, we propose a strategy to realize doubly curved shells that are bistable for any thickness. We then study the nonlinear dynamic response of one-dimensional (1D) arrays of our universally bistable shells when coupled by compressible fluid cavities. We find that the system supports the propagation of bidirectional transition waves whose characteristics can be tuned by varying both geometric parameters as well as the amount of energy supplied to initiate the waves. However, since our bistable shells have equal energy minima, the distance traveled by such waves is limited by dissipation. To overcome this limitation, we identify a strategy to realize thick bistable shells with tunable energy landscape and show that their strategic placement within the 1D array can extend the propagation distance of the supported bidirectional transition waves.

scholarly journals Experimental Investigation of the Effects of Irradiating Schemes in Laser Tube Bending Process

Metals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1123
Author(s):  
Mehdi Safari ◽  
Ricardo J. Alves de Sousa ◽  
Jalal Joudaki
Keyword(s):  
Laser Beam ◽  
Contact Process ◽  
Steel Tube ◽  
Thickness Variation ◽  
Tube Bending ◽  
Lateral Bending ◽  
Bending Angle ◽  
Laser Tube ◽  
Bending Process ◽  
Thickness Variations

The laser tube bending process (LTBP) process is a thermal non-contact process for bending tubes with less springback and less thinning of the tube. In this paper, the laser tube bending process will be studied experimentally. The length of irradiation and irradiation scheme are two main affecting process parameters in the LTBP process. For this purpose, different samples according to two main irradiation schemes (Circular irradiating scheme (CIS) and axial irradiating scheme (AIS)) and different lengths of laser beam irradiation (from 4.7 to 28.2 mm) are fabricated. The main bending angle of laser-bent tube, lateral bending angle, ovality, and thickness variations is measured experimentally, and the effects of the irradiating scheme and the length of irradiation are investigated. An 18 mm diameter, 1 mm thick mild steel tube was bent with 1100 Watts laser beam. The results show that for both irradiating schemes, by increasing the irradiating length of the main and lateral bending angle, the ovality and thickness variation ratio of the bent tube are increased. In addition, for a similar irradiating length, the main bending angle with AIS is considerably higher than CIS. The lateral bending angle by AIS is much less than the lateral bending angle with CIS. The results demonstrate that the ovality percentage and the thickness variation ratio for the laser-bent tube obtained by CIS are much more than the values associated with by AIS laser-bent tube.

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