Inferring Viscoelastomer Dynamic Material Properties From Finite Element and Experimental Studies of Constrained Layer Damping Systems

Author(s):  
Stephen A. Hambric ◽  
Andrew W. Jarrett ◽  
Gilbert F. Lee ◽  
Jeffry J. Fedderly

Viscoelastic materials are often used to add damping to metal structures, usually via the constrained layer damping method. The added damping is strongly dependent on material temperature and frequency, as are the underlying material properties of the viscoelastomer. Several standardized test methods are available to characterize the dynamic material properties of viscoelastomers. However, they rely on limited test data which is extrapolated using the time-temperature superposition technique. The authors have found that the different testing methods typically produce significantly different material properties. A new approach to inferring viscoelastomer material properties is suggested here. Several metal bars are treated using constrained layer damping. Experimental modal analyses are conducted on the bars at different temperatures to produce sets of system resonance frequencies and loss factors. Corresponding finite element (FE) models of the treated bars are analyzed using assumed viscoelastomer material properties. The properties are adjusted by trial and error until the FE-simulated system loss factors match those of the measurements.

2006 ◽  
Vol 129 (2) ◽  
pp. 158-168 ◽  
Author(s):  
Stephen A. Hambric ◽  
Andrew W. Jarrett ◽  
Gilbert F. Lee ◽  
Jeffry J. Fedderly

Viscoelastic materials are often used to add damping to metal structures, usually via the constrained layer damping method. The added damping depends strongly on material temperature and frequency, as do the underlying material properties of the viscoelastomer. Several standardized test methods are available to characterize the dynamic material properties of viscoelastomers. However, they rely on limited test data which is extrapolated using the time—temperature superposition technique. The authors have found that the different testing methods typically produce significantly different dynamic material properties, or “master curves.” An approach for inferring viscoelastomer dynamic moduli with better accuracy is suggested here. Several metal bars are treated using constrained layer damping. Experimental modal analyses are conducted on the bars at different temperatures to produce sets of system resonance frequencies and loss factors. Corresponding finite element (FE) models of the treated bars are analyzed using assumed viscoelastomer material properties based on master curves generated using a standardized test technique. The parameters which define the master curves are adjusted by trial and error until the FE-simulated system loss factors match those of the measurements. The procedure is demonstrated on two viscoelastomers with soft and stiff moduli.


Materials ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2125 ◽  
Author(s):  
Paweł Dunaj ◽  
Stefan Berczyński ◽  
Karol Miądlicki ◽  
Izabela Irska ◽  
Beata Niesterowicz

The paper presents a new way to conduct passive elimination of vibrations consisting of covering elements of structures with low dynamic stiffness with polylactide (PLA). The PLA cover was created in 3D printing technology. The PLA cover was connected with the structure by means of a press connection. Appropriate arrangement of the PLA cover allows us to significantly increase the dissipation properties of the structure. The paper presents parametric analyses of the influence of the thickness of the cover and its distribution on the increase of the dissipation properties of the structure. Both analyses were carried out using finite element models (FEM). The effectiveness of the proposed method of increasing damping and the accuracy of the developed FEM models was verified by experimental studies. As a result, it has been proven that the developed FEM model of a free-free steel beam covered with polylactide enables the mapping of resonance frequencies at a level not exceeding 0.6% of relative error. Therefore, on its basis, it is possible to determine the parameters of the PLA cover. Comparing a free-free steel beam without cover with its PLA-covered counterpart, a reduction in the amplitude levels of the receptance function was achieved by up to 90%. The solution was validated for a steel frame for which a 37% decrease in the amplitude of the receptance function was obtained.


Author(s):  
Mark A. C. Neuert ◽  
Rebecca L. Austman ◽  
Cynthia E. Dunning

Compared to experimental studies using strain gauges, finite element (FE) models are not limited to strain measurements at discrete locations and can be used to examine the continuous strain and stress field throughout bone. As such, they can be a useful tool for biomechanical investigations interested in stress and strain changes as a result of multiple loading conditions, implant designs, etc. Critical to their development is the assignment of material properties.


1996 ◽  
Vol 18 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Wenkang Qi ◽  
Wenwu Cao

Finite element method (FEA) has been used to calculate the thickness resonance frequency and electromechanical coupling coefficient kt for 2–2 piezocomposite transducers. The results are compared with that of the effective medium theory and also verified by experiments. It is shown that the predicted resonance frequencies from the effective medium theory and the unit cell modeling using FEA deviate from the experimental observations for composite systems with a ceramic aspect ratio (width/length) more than 0.4. For such systems, full size FEA modeling is required which can provide accurate predictions of the resonance frequency and thickness coupling constant kt.


2010 ◽  
Vol 02 (02) ◽  
pp. 229-249 ◽  
Author(s):  
F. CHENG ◽  
G. U. UNNIKRISHNAN ◽  
J. N. REDDY

A viscoelastic analysis of the biological cell considering the microcellular material properties is carried out in this work. Three separate regions of the cell: the actin cortex, cytoplasm and nucleus are considered. The outer cortex and cytoplasm are modeled using standard linear viscoelastic model (SLS) and standard neo-Hookean viscoelastic solid, and a linear elastic material model is considered for the nucleus. The effect of the material properties of cytoplasm and actin cortex on the derivable parameters from three major experimental studies of magnetic twisting cytometry (MTC) and atomic force microscopy (AFM) and micropipette aspiration (MPA) are analyzed using the finite element method. The bead center displacement for the MTC, reaction force for AFM, and aspiration length ratio for the MPA are the major quantities derived from the finite element analysis. A number of parametric studies are also conducted and it is observed that SLS and SnHS models predict nearly identical results for the material constants.


Author(s):  
O. Marko ◽  
V. Livinskaya ◽  
E. Korbut

В материале статьи изложены результаты исследований влияния отечественной комплексной химической добавки ( УКД-1 ), содержащей структурированный углеродный наноматериал (УНМ) и характеризующейся совмещенным (ускоряющим твердение и пластифицирующим) эффектом, на изменения во времени формуемости бетонных смесей и на кинетику твердения бетона в беспрогревном варианте технологии монолитного бетонирования. Целью исследований являлось установление закономерностей изменения формуемости (осадки конуса) подвижных бетонных смесей с добавкой УКД-1 во времени в зависимости от изменяющихся факторов свойств цемента, температуры, условий транспортирования для разработки соответствующих рекомендаций по использованию этой новой добавки в монолитном бетоне. При выполнении экспериментальных исследований использовали стандартизированные методы испытаний. В результате установлено, что влияние добавки УКД-1 на сохранение формовочных свойств бетонных смесей подчиняется общим закономерностям, характерным для входящих в ее состав пластифицирующего и ускоряющих твердение бетона веществ, и определена допускаемая продолжительность транспортирования смесей с этой добавкой в диапазоне температуры от 05 оС до 2530 оС, что обеспечивает необходимые условия для ведения бетонных работ. С использованием стандартизированных и оригинальных методик экспериментально выявлены закономерности роста прочности тяжелого цементного бетона под влиянием отдельно взятого ускоряющего компонента добавки УКД-1 и этой добавки в зависимости от ее дозировки (в диапазоне 0,52,0 от массы цемента). Экспериментально оценены зависимости темпа роста бетона с добавкой УКД-1 от основных технологических факторов качества цемента, величины водоцементного отношения, состава бетона и консистенции бетонной смеси, температуры среды твердения и теплоизолирующих характеристик форм-опалубок. Это позволило обосновать рациональные режимы и параметры условий твердения бетона с добавкой УКД-1 для обеспечения прочности (на сжатие) в диапазоне 50100 от требуемой в проектном возрасте (28 сут.) без затрат энергии на ускорение его твердения.The results of researches of influence of domestic complex chemical additive ( UKD-1 ), containing the structured carbon nanomaterial (CNM) characterized by the combined (the accelerating curing and plasticizer) effect on the time variation of the formability of concrete mixtures and on kinetics of curing of concrete in technology of monolithic concreting technology without warming up are expounded in the article. The aim of this study was to establish patterns of change in formability (slump) of flowable concrete mixtures with the addition of UKD-1 in time depending on the varying factors: the properties of the cement, the temperature conditions of transportation, and to develop appropriate recommendations for the use of this new additive in monolith concrete. In carrying out experimental studies using standardized test methods. As a result, found that the influence of the additive UKD-1 for the preservation of the molding properties of concrete mixtures follows the general laws specific to its constituent plasticizing and accelerating the hardening of concrete materials, and defined the permissible duration of transportation with these additive mixtures in the temperature range from 0...5 C to 25...30 C, that provides the necessary conditions for year-round maintenance of concrete work. Standardized and original methods has reviled the regularities of growth of the strength of heavy cement concrete under the influence of the separately taken accelerating component of the additive UKD-1 and this additive, depending on the dosage (in the range (0,5...2,0) of the mass of cement)). The dependence of the growth rate of concrete with the additive of UKD-1 from the basic technological factors quality of cement, the values of water-cement ratio, concrete composition and consistency of the concrete mix, ambient temperature curing and heat-insulating characteristics form formwork experimentally evaluated. This proved the rational modes and parameters of the conditions of concrete hardening with the addition of UKD-1 for strength (compression) in the range of (50...100) of the required project in the aged (28 days), without cost of energy to accelerate its hardening.


Author(s):  
Н.С. Гуриненко ◽  
Э.И. Батяновский

В материале статьи приведены результаты исследований влияния новой комплексной полифункциональной добавки, содержащей пластификатор, ультрадисперсный микрокремнезем (УДМК) и ускоряюще-уплотняющий компонент, на кинетику твердения (темп роста) и уровень прочности на сжатие тяжелого конструкционного бетона. С применением методов математической статистики оценено влияние на процесс твердения (рост прочности) цементного камня и цементного бетона, составляющих полифункциональную добавку компонентов (при разном их соотношении в комплексе в целом). На этом основании (включая результаты экспериментальной оценки прочности образцов цементного камня и бетона) разработаны и запатентованы составы полифункциональной добавки в бетон, характеризующиеся оптимальным диапазоном содержания в ее составе компонентов: суперпластификатора на основе поликарбоксилатных смол ‒ 0,25 %...0,5 % от массы цемента, ультрадисперсного микрокремнезема (SiO2) ‒ 0,25 %...1,0 % от МЦ, ускорителя твердения ‒ сульфата натрия (Na2SO4) ‒ 0,35 %...0,5 % от МЦ и уплотняющей структуру добавки ‒ сульфата алюминия (Al2(SO4)3) ‒ 0,15 %...0,25 % от МЦ, при меньших значениях для тяжелого конструкционного бетона класса ≤ С50/60 и бόльших значениях для высокопрочного, особо плотного бетона класса ≥ С70/85 (прочностью fcm.28 ≥ 100 МПа). В исследованиях прочностных характеристик и эксплуатационных свойств бетона применены стандартизованные методики испытаний. Результаты экспериментальных исследований подтверждены производственными испытаниями разработки, их данные заактированы и подтверждают возможность экономии цемента на 10 %…15 % без снижения прочностных и эксплуатационных свойств бетона, при снижении затрат тепловой энергии на обогрев изделий из бетона с добавкой в 1,5…2,0 раза (за счет сокращения времени подачи теплоносителя до 1,5…2,0 ч (с последующим твердением по методу термоса) и снижения температуры разогрева бетона до 45 °С…50 °С). The article presents the results of studies of the effect of a new complex multifunctional additive containing a plasticizer, ultradispersed microsilica (UDMS) and an accelerating-sealing component on the hardening kinetics (growth rate) and the level of compressive strength of heavy structural concrete. Using the methods of mathematical statistics, the influence on the hardening process (growth of strength) of cement stone and cement concrete of the components constituting a multifunctional additive (with their different ratios in the complex as a whole) was evaluated. On this basis (including the results of an experimental assessment of the strength of cement stone and concrete samples), compositions of a polyfunctional additive to concrete have been developed and patented, characterized by the optimal range of content in its composition of components: superplasticizer based on polycarboxylate resins – 0.25 %...0.5 % of the mass of cement, ultradispersed microsilica (SiO2) – 0.25 %...1.0 % of WC, hardening accelerator – sodium sulfate (Na2SO4) – 0.35 %...0.5 % from WC and the additives that seal the structure - aluminum sulfate (Al2(SO4)3) – 0.15 %...0.25 % of WC, at lower values for heavy structural concrete of class ≤ С50/60 and higher values for high-strength , especially dense concrete of class ≥ С70/85 (strength fcm.28 ≥ 100 MPa). In studies of the strength characteristics and operational properties of concrete, standardized test methods were used. The results of experimental studies are confirmed by production tests of the development, their data are recorded and confirm the possibility of saving cement by 10 %...15 % without reducing the strength and operational properties of concrete, while reducing the cost of heat energy for heating concrete products with an additive of 1.5...2.0 times (by reducing the time of supplying the coolant to 1.5...2.0 h (with subsequent hardening by the thermos method) and reducing the temperature of concrete heating to 45 °C...50 °C).


2020 ◽  
Vol 27 (1) ◽  
pp. 89-96
Author(s):  
Klaus Heller ◽  
Moritz Hallmannseder ◽  
David Colin ◽  
Kalle Kind ◽  
Klaus Drechsler

AbstractTo achieve cost-efficient manufacturing and a high part quality in Thermoset Automated Fiber Placement (TS-AFP), knowledge about the interaction between material and process parameters is of special interest. Material properties of prepregs are well known at the cured state of the resin. However, there are no standardized test procedures for the mechanical behavior of the uncured prepreg tapes. To investigate the intra-ply shear deformation behavior of uncured unidirectional prepreg tapes, we compared several measurement procedures and conducted experiments for rheometer based tests using 8552/AS4 material. We identified a rotational parallel platens rheometer test method and a torsion bar rheometer test method to be suitable. Experiments using both methods revealed that the Torsion Bar Test has a higher repeatability and the analysis is less complex. Furthermore, first results show that changes in material properties caused by aging can be analyzed using this method. In the future,we will use the Torsion Bar Test to characterize changes in deformation behavior due to material aging as well as material modifications. By this, we will be able to provide data for the material modeling thus enabling the prediction of lay-up defects such as buckling due to steering.


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