The use of polymeric pipes such as polyethylene (PE) and polyvinyl chloride (PVC) has recently increased in water distribution networks. This necessitates the understanding of the viscoelastic beha...

Simulation of transient flow in viscoelastic pipe networks

Rotational and oscillatory shear rheometry were used to quantify the flow behavior under minimal and significant solvent evaporation conditions for polymer solutions used to fabricate isoporous asymmetric membranes by the self-assembly and non-solvent induced phase separation (SNIPS) method. Three different A-B-C triblock terpolymer chemistries of similar molar mass were evaluated: polyisoprene-^-polystyrene-6-poly(4-vinylpyridine) (ISV); polyisoprene-6polystyrene-6-poly(V,A-dimethylacrylamide) (ISD); and polyisoprene-Z>-polystyrene-h-poly(fer/butyl methacrylate) (ISB). Solvent evaporation resulted in the formation of a viscoelastic film typical of asymmetric membranes. Solution viscosity and film viscoelasticity were strongly dependent on the chemical structure of the triblock terpolymer molecules. A hierarchical magnitude (ISV>ISB>ISD) was observed for both properties, with ISV solutions displaying the greatest solution viscosity, fastest film strength development, and greatest strength magnitude.

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A rheometry method to assess the evaporation‐induced mechanical strength development of polymer solutions used for membrane applications

This paper shows a piezoelectric response from an innovative sensor obtained by casting epoxy-SbSI (antimony sulfoiodide) nanowires nanocomposite to a grid structure printed using a fuse deposition modeling (FDM) method. The grid is shown to be a support structure for the nanocomposite. The applied design approach prospectively enables the formation of sensors with a wide spectrum of shapes and a wide applicability. The voltage signal obtained as a result of the piezoelectric effect reached 1.5V and 0.5V under a maximum static stress of 8.5 MPa and under a maximum dynamic stress of 22.3 kPa, respectively. These values are sufficient for potential application in sensor systems. The effect of a systematic increase in the voltage signal with subsequent cycles was also observed, which similarly allows the use of these sensors in monitoring systems for structures exposed to unfavorable cyclical loads. The obtained results also show that the piezoelectric signal improves with increase in strain rate.

https://www.mdpi.com/1996-1944/13/22/5281/pdf

Assessment of the Piezoelectric Response of an Epoxy Resin/SbSINanowires Composite Filling FDM Printed Grid.

Sandwich beam structures have many applications in various fields of engineering including especially in aerospace and transportation industries. Using the viscoelastic material as the core layer in these structures, one could include significant amount of damping with minimum impact on the total mass of the structure. In the current study, vibration damping analyses of the sandwich beam structure using the finite element formulations are presented. These formulations are developed based on the linear and non-linear displacement fields in the viscoelastic core layer. Results obtained from the present study were compared with those reported in literature and it is shown that the non linear displacement field exhibits more accurate damping response than the linear model. Parametric sensitivity analysis has been carried out to show the damping behavior of partially treated sandwich beam under different configuration. Genetic algorithm is utilized in finding the optimum configuration to achieve the highest damping. Results show that for damping behavior of beam with the clamped-clamped boundary condition, the partially treated beam structure is more effective than the fully treated one. Also the effect of the heat dissipation in the damping layer of the beam on the damping performance of the viscoelastic material is investigated under the steady-state harmonic excitation. The generated heat has been taken into the consideration by implementing the finite difference formulation based on the irregular grids. Results obtained clearly indicate that the temperature gradient developed in the structure and hence the amplitude of the response increases after every cycle.

/pdf/vibration-and-thermal-analysis-and-optimum-design-of-25stybj0vz.pdf

Vibration and thermal analysis and optimum design of viscoelastic sandwich beam

Abstract. This paper reports and discusses the results of some experimental investigations carried out with the aim to identify the best conditions for a safe exposure of the 3D printed large-scale replica of Michelangelo’s David during its exhibition in the Italian Pavilion of the Expo 2020 Dubai.The whole project posed numerous challenges due to the dimension of the Michelangelo’s David (which is over seven metres high and weighs more than five ton). As a matter of fact, on the one hand, no standardized procedures have been still established to define accuracy and quality of 3D printing. On the other hand, the large-scale printing opens up new issues concerning the mechanical properties requested of the printing material and the printing set-up that is necessary to ensure the stability and durability of the printed replica.After a general picture of the whole project, thermal characterization of the material used to print the replica and mechanical tests of samples obtained form the replica are reported and discussed. Thermal characterisation showed that the stiffness of the material was strongly influenced by temperature and that it decreased continuously as this parameter increased. Mechanical tests showed a brittle behaviour, with a collapse load approximately 10 times higher than the internal loads resulting from the self-weight alone.The analyses here presented constitute some of the groundwork carried out for the realisation and installation of the 3D printed replica of Michelangelo’s David. This conceptualisation, considering both the extreme environmental conditions and the large-size of the replica, has been particularly challenging and the adopted procedure was useful to verify the different phases of the realisation of the replica.


https://doi.org/10.5194/isprs-archives-xlviii-m-2-2023-1573-2023

Lessons learnt on 3d printing michelangelo’s david replica

Simply stated, viscoelasticity is the response of a polymer when subjected to forces of various kinds. Polymers respond to external forces that are between elastic solid and a viscous liquid. The authors use a molecular, rather than a mechanical, approach in describing polymer behavior, providing a good understanding of the fundamental concepts. The book will provide the reader with a very good understanding of viscoelastic behavior on a molecular scale and details the latest testing methods, some of which include dielectric and nuclear magnetic resonance (NMR) methods, impedance spectroscopy, and thermally simulated currents. The authors provide an excellent background for not only learning about these techniques but also explaining the similarities and differences that each technique provides. Other topics cover the theory of viscoelastic behavior using models, timetemperature relationships, transitions, and relaxations. Also, there is information of the effects of fillers, crosslinking, swelling, and crystallization on viscoelastic behavior and on interfacial polarization. There are some examples using real polymers and problems that involve numerical modeling and analysis, some of which are included in a CD-ROM. Each chapter has an extensive set of questions; the answers are included in the back of the book. This book would appeal to those wishing to learn about viscoelastic behavior and testing methods and would make a good book for graduate studies in polymer chemistry because the book assumes familiarity with polymers and basic chemistry.

J. Shea

Papers

Introduction to Polymer Viscoelasticity, 3rd Edition - [Book Review]