Approximation of relaxation curves in the nonlinear region of mechanical behavior by means of new relaxation kernels

Аскадский, А.А.; Valetskii, M. P.

doi:10.1007/bf00613108

Cited by 5 publications

(6 citation statements)

References 4 publications

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“…17 If entanglements are present, then they will function as topological knots and enhance mechanical properties at large strain. The coupling model of Ngai et al…”

Section: Stress Relaxationmentioning

confidence: 99%

“…McKenna and Zapas 25 impose a large deformation initially and then apply incremental strains at selected time intervals. Askadskii et al 17,26 use a nonlinear integral expansion representation of time-dependent stress to model nonlinear stress relaxation based on the rate of entropy generation. Yoshioka 27 employs a nonlinear model with one relaxation time to predict yielding in glassy polymers at large deformation.…”

Section: Stress Relaxationmentioning

confidence: 99%

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Nonlinear stress relaxation in palladium(II) complexes with triblock copolymers of styrene and butadiene

Das

Belfiore

2004

J of Applied Polymer Sci

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Above 200% strain, the mechanical response of triblock copolymers which contain styrene and butadiene is modified significantly by complexation with dichlorobis(acetonitrile)palladium(II). This pseudosquare-planar transition metal salt forms -complexes with, and catalyzes the dimerization of, alkene groups in the main chain and the side group of Kraton's butadiene midblock. Between 10 and 100% strain, the plastic flow regime is similar for undiluted Kraton™ and its Pd 2ϩ complexes, but the level of engineering stress is approximately twofold larger for the complex that contains 4 mol % palladium(II) [Pd(II)]. Nonlinear stress relaxation measurements in the plastic flow regime (i.e., beyond the yield point but before the large upturn in stress) are analyzed at several different levels of strain. Transient relaxation moduli were modeled by a three-parameter biexponential decay with two viscoelastic time constants. The longer relaxation time for Kraton™ increases at higher strain, and in the presence of 4 mol % palladium chloride. A phenomenological model is proposed to describe the effect of strain on relaxation times. This model is consistent with the fact that greater length scales are required for cooperative segmental reorganization at larger strain. The resistance ⍀ to conformational reorganization during stress relaxation is estimated via integration of the normalized relaxation modulus versus time data. This resistance increases at higher initial jump strain because conformational rearrangements are influenced strongly by knots and entanglements at larger strain. The effect of strain on ⍀ is analyzed in terms of time-strain separability of the relaxation modulus. Linear behavior is observed for ⍀ versus inverse strain (i.e., 1/), and the magnitude of the slope [i.e., Ϫd⍀/d(1/)] is threefold larger in the absence of PdCl 2 (CH 3 CN) 2 .

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“…17 If entanglements are present, then they will function as topological knots and enhance mechanical properties at large strain. The coupling model of Ngai et al…”

Section: Stress Relaxationmentioning

confidence: 99%

Section: Stress Relaxationmentioning

confidence: 99%

Nonlinear stress relaxation in palladium(II) complexes with triblock copolymers of styrene and butadiene

Das

Belfiore

2004

J of Applied Polymer Sci

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“…In general, stress relaxation can be viewed as the reorientation of chain segments via rotation about single bonds in the backbone that increases the conformational entropy of network strands 17. If entanglements are present, then they will function as topological knots and enhance mechanical properties at large strain.…”

Section: Stress Relaxationmentioning

confidence: 99%

“…McKenna and Zapas25 impose a large deformation initially and then apply incremental strains at selected time intervals. Askadskii et al17, 26 use a nonlinear integral expansion representation of time‐dependent stress to model nonlinear stress relaxation based on the rate of entropy generation. Yoshioka27 employs a nonlinear model with one relaxation time to predict yielding in glassy polymers at large deformation.…”

Section: Stress Relaxationmentioning

confidence: 99%

Hedgehog signaling controls Soma‐Germen interactions during Drosophila ovarian morphogenesis

Besse

Busson

Pret

2005

Developmental Dynamics

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The genetic analysis of Drosophila adult oogenesis has provided insights into the molecular mechanisms that control cell proliferation, differentiation, migration, and intercellular signaling. However, little is known about the larval and pupal cellular events leading to the formation of the highly organized adult ovary, which is composed of ovarioles each containing germline cells enveloped by specialized somatic cells. We describe here the presence of ovarioles devoid of any germ cells in adult females mutant for fused, which encodes a Hedgehog signal transducing serine/threonine kinase. We show that this phenotype corresponds to a requirement for fused function for the organization of germ cells with respect to ovarian somatic cells during ovariole formation specifically during pupal stages and provide some evidence by means of clonal analysis suggesting that fused function may be necessary in the germline. hedgehog is expressed specifically in somatic terminal filament cells in pupal ovaries, and females bearing hedgehog

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“…Hence, the well-known expression for the temperature dependence of the stress relaxation time [4] arises. Thus, we will rewrite equation (5) in the form…”

mentioning

confidence: 99%

Comparative Analysis of the Relaxation Properties of Virgin and Recycled Polypropylene

Голованов¹,

Попова

Марков

et al. 2010

International Polymer Science and Technology

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Approximation of relaxation curves in the nonlinear region of mechanical behavior by means of new relaxation kernels

Cited by 5 publications

References 4 publications

Nonlinear stress relaxation in palladium(II) complexes with triblock copolymers of styrene and butadiene

Nonlinear stress relaxation in palladium(II) complexes with triblock copolymers of styrene and butadiene

Hedgehog signaling controls Soma‐Germen interactions during Drosophila ovarian morphogenesis

Comparative Analysis of the Relaxation Properties of Virgin and Recycled Polypropylene

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