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"This text is a guide how to solve problems in which viscoelasticity is present using existing commercial computational codes. The book gives information on codes' structure and use, data preparation and output interpretation and verification. The first part of the book introduces the reader to the subject, and to provide the models, equations and notation to be used in the computational applications. The second part shows the most important computational techniques : finite elements formulation, boundary elements formulation, and presents the solutions of viscoelastic problems with Abaqus."

"Describes general mathematical modeling of viscoelastic materials as systems with fading memory. Discusses the interrelation between topics such as existence, uniqueness, and stability of initial boundary value problems, variational and extremum principles, and wave propagation. Demonstrates the deep connection between the properties of the solution to initial boundary value problems and the requirements of the general physical principles. Discusses special techniques and new methods, including Fourier and Laplace transforms, extremum principles via weight functions, and singular surfaces and discontinuity waves."

"The flow behavior of fluids such as molten plastics, biological fluids, and paints is much more varied and complex than that of traditional Newtonian fluids. The role of numerical simulation in the study of such flows has increased tremendously over the past fifteen years, and the phenomena and numerical difficulties in complex flows have led to new and challenging mathematical questions. Studying such flows presents a host of problems, as well as opportunities for mathematical analysis, including questions of asymptotics, qualitative dynamics, and adequacy of numerical methods. Mathematical Analysis of Viscoelastic Flows presents an overview of mathematical problems, methods, and results relating to research on viscoelastic flows. This monograph is based on a series of lectures presented at the 1999 NSF-CBMS Regional Research Conference on Mathematical Analysis of Viscoelastic Flows. It begins with an introduction to phenomena observed in viscoelastic flows, the formulation of mathematical equations to model such flows, and the behavior of various models in simple flows. It also discusses the asymptotics of the high Weissenberg limit, the analysis of flow instabilities, the equations of viscoelastic flows, jets and filaments and their breakup, as well as several other topics."

"ABSTRAKTelah dilakukan pengujian sifat-sifat viskoelastik dari Polyethylene Densitas Tinggi (High Density Polyethylene atau HDPE) dengan menggunakan uji creep dan uji relaksasi tegangan. Besarnya beban yang diberikan dalam uji creep adalah dari 100 N sampai 350 N dengan interval 50 N. Untuk mencapai beban konstan digunakan kecepatan regangan 50 mm/min dan 5 mm/min. Regangan konstan yang digunakan dalam uji relaksasi tegangan adalah 1,25%, 2,5%, 3,75%, 5%, 6,25% dan 7,5%. Regangan konstan ini dicapai dengan menggunakan kecepatan regangan 50 mm/min dan 5 mm/min. Pengujian dilakukan selama 30 menit untuk setiap uji creep dan uji relaksasi tegangan. Uji creep juga dilakukan dengan uji makroindentasi. Pengujian ini memakai bola baja dengan diameter 7,93, 11,08, 25,4 dan 44,43 mm, dan beban yang diberikan adalah 4,434, 6,434, 8,434, 10,434 dan 12,434 kg. Setiap pengujian dilakukan selama 2 jam. Data setiap pengujian dianalisa menggunakan model yang merupakan kombinasi dari pegas (spring) dan peredam (dashpot). Uji creep menggunakan model empat elemen yang menghasilkan empat konstanta yaitu konstanta elastik El dan E2 dan konstanta viskos n1 dan n2 . Relaksasi tegangan memakai model tiga elemen yang menghasilkan tiga konstanta yaitu konstanta elastik El dan E2 dan konstanta viskos n1. Pada uji creep, seluruh konstanta mempunyai nilai yang meningkat dengan kecepatan regangan yang meningkat, kecuali konstan viskos n2 . Pengaruh dari pemberian beban konstan adalah dengan pertambahan beban konstan maka semua konstanta mempunyai nilai yang meningkat. Sedang uji relaksasi tegangan memiliki nilai konstanta yang berbanding terbalik dengan uji creep. Pengujian dengan makroindentasi menghasilkan efek dari diameter bola yaitu dengan makin besar diameter diperoleh makin besar nilai konstanta elastik. Sedang efek dari pemberian beban yaitu dengan makin besar beban diperoleh makin besar nilai konstanta viskos.

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The tests of the viscoelastic properties of High Density Polyethylene (HDPE) has been done which was using creep and stress relaxation tests. The constant loads that are applied for creep test are 100N to 350N steps 50N. In order to get the constant loads, it was used different of strain rate; 50mm/min and 5mm/min. The stress relaxation test was done in different constant strains and the constant strains are from 1.25% to 7.5% step 1.25%. Similar to creep test, the constants strain are reached using strain rate 50mm/min and 5mm/min. Every sample of creep and stress relaxation was tested and hold for 30 minutes. The other creep test is macroindentation test which used ball indenter with 7.93, 11.08, 25.4, and 44.43mm in diameters and 4.434, 6.434, 8.434, 10.434, and 12.434 kg in constant loads.

The data were analyzed using standard linear viscoelastic solid model. The creep test was using four elements model which have two elastic constants El, E2, and two viscous constants n1, n2. While stress relaxation test was using three elements model, which have two elastic constants and one viscous constant.

The result of the tests are, the strain rate affect both of elastics and viscous constants. All the constants in the creep test increase as the strain rate increase except the viscous constant n2. The effect of constant loads is as the load increase, the constant elastics and viscous decrease. On the other hand, in the stress relaxation test has contrary effect with the creep test. In the macroindentation test, as the diameter increase, the elastic constants increase. More over, as the load increase, the viscous constants increase.

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