A Concept for a Material That Softens With Frequency

2008 ◽  
Vol 130 (9) ◽  
Author(s):  
J. Prasad ◽  
A. R. Diaz
Keyword(s):  
Composite Material ◽  
Elastic Modulus ◽  
Viscoelastic Properties ◽  
Dynamic Properties ◽  
Negative Stiffness ◽  
Numerical Homogenization ◽  
Two Phase ◽  
High Frequencies ◽  
Design Concepts ◽  
Inclusion Phase

This work presents design concepts to synthesize composite materials with special dynamic properties, namely, materials that soften at high frequencies. Such dynamic properties are achieved through the use of a two-phase material that has inclusions of a viscoelastic material of negative elastic modulus in a typical matrix phase that has a positive elastic modulus. A possible realization of the negative-stiffness inclusion phase is presented. A numerical homogenization technique is used to compute the average viscoelastic properties of the composite. The method and the properties of a composite material designed with it are demonstrated through an example.

A Concept for a Material That Softens With Frequency

2007 ◽  
Author(s):  
Jitendra Prasad ◽  
Alejandro R. Diaz
Keyword(s):  
Composite Material ◽  
Elastic Modulus ◽  
Viscoelastic Properties ◽  
Dynamic Properties ◽  
Negative Stiffness ◽  
Numerical Homogenization ◽  
Two Phase ◽  
High Frequencies ◽  
Design Concepts ◽  
Inclusion Phase

This work presents design concepts to synthesize composite materials with special dynamic properties, namely, materials that soften at high frequencies. Such dynamic properties are achieved through the use of a two-phase material that has inclusions of a viscoelastic material of negative elastic modulus in a typical matrix phase that has a positive elastic modulus. A possible realization of the negative stiffness inclusion phase is presented. A numerical homogenization technique is used to compute the average viscoelastic properties of the composite. The method and the properties of a composite material designed with it are demonstrated through an example.

scholarly journals RE-DESIGN OF A MOTORCYCLE HELMET FOR USE IN URBAN TRAFFIC: CONCEPTUAL DESIGN AND TESTING

2021 ◽  
Vol 1 ◽  
pp. 2531-2540
Author(s):  
Joanna Papadopoulou ◽  
Vassilis Papakostopoulos ◽  
Vassilis C. Moulianitis
Keyword(s):  
Urban Traffic ◽  
Von Mises Stress ◽  
Two Phase ◽  
Design Concepts ◽  
Motorcycle Helmet ◽  
Maximum Protection ◽  
Von Mises ◽  
Full Face ◽  
Phase Evaluation ◽  
Design And Testing

AbstractThis paper presents the re-design approach of an urban motorcycle helmet to prevent users bypassing the strap fastening system. Related studies show that although a full-face helmet provides the maximum protection to a rider, in practice, full-face helmeted riders in urban traffic tend to improperly fasten it. On that notion, the design goal was to conceive a helmet that combines the advantages of different helmet types while responding to urban driving needs. During design ideation possible solutions were examined focusing on different ways of accessing and fixating the helmet on a rider’s head, without using a strap fastening system. Preliminary concept development produced three design concepts, that were evaluated using two sets of prototypes: (a) the 3D printing method under a 1:2 scale was used to detect any design faults, while the 3D modeled concepts were evaluated in four different crash impacts regarding total deformation and von-Mises stress, and (b) 1:1 models of the three concepts were used by experienced riders to assess possible usability issues during helmet placement/removal. Results of the two-phase evaluation of the three concepts and design issues for further development of them are discussed.

scholarly journals Simulation of a two-phase composite material with a system of fibers disoriented in space

2020 ◽  
Author(s):  
E. M. Romanovskaia ◽  
E. A. Mityushov ◽  
S. A. Berestova ◽  
N. D. Romanovskaia
Keyword(s):  
Composite Material ◽  
Two Phase

Elastic modulus and viscoelastic properties of full thickness skin characterised at micro scales

Biomaterials ◽  
2013 ◽  
Vol 34 (8) ◽  
pp. 2087-2097 ◽  
Author(s):  
Michael L. Crichton ◽  
Xianfeng Chen ◽  
Han Huang ◽  
Mark A.F. Kendall
Keyword(s):  
Elastic Modulus ◽  
Viscoelastic Properties ◽  
Full Thickness ◽  
Full Thickness Skin ◽  
Thickness Skin

Study on the Dynamic Performance of Asphalt Concrete under Passive Confined Pressure

2012 ◽  
Vol 226-228 ◽  
pp. 1755-1759
Author(s):  
Hua Zhang ◽  
Fei Li ◽  
Yu Wei Gao
Keyword(s):  
Elastic Modulus ◽  
Asphalt Concrete ◽  
Poisson Ratio ◽  
Dynamic Properties ◽  
Dynamic Performance ◽  
Dynamic Strength ◽  
Confining Pressure ◽  
Mechanical Behaviors ◽  
One Dimensional ◽  
Stress States

An improved passive confining pressure SHPB method was used to study the dynamic mechanical behaviors of asphalt concrete under quasi-one dimensional strain state. The effect of confining jacket material and its geometrical sizes on the confining pressure were discussed. The dynamic strength, dynamic modulus of elasticity and dynamic Poisson ratio of asphalt concrete were obtained. The influential rules of confining pressure on the dynamic properties were studied by comparing the stress-strain curves of asphalt concrete under different stress states. The study found that passive confining greater impact on the strength of asphalt concrete than elastic modulus and Poisson ratio, but the elastic modulus improved with the increase of confining pressure.

On the Measurement of Dynamic Properties of Lubricants under E. H. L. Conditions Using a Disc Machine

1974 ◽  
Vol 16 (5) ◽  
pp. 331-338 ◽  
Author(s):  
J. M. Davies ◽  
K. Walters
Keyword(s):  
Viscoelastic Properties ◽  
Dynamic Properties ◽  
Elastohydrodynamic Lubrication ◽  
Deborah Number ◽  
Theoretical Treatment

Johnson and Roberts (1)‡ have recently shown how a simple adaptation of the conventional disc machine can be used to measure the viscoelastic properties of lubricants under conditions of elastohydrodynamic lubrication. The present paper contains a theoretical treatment of the problem and derives operating formulae pertinent to conditions of low, finite and high Deborah number.

scholarly journals The Effect of Subsequent Stress-Induced Martensite Aging on the Viscoelastic Properties of Aged NiTiHf Polycrystals

Metals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1890
Author(s):  
Anton I. Tagiltsev ◽  
Elena Y. Panchenko ◽  
Ekaterina E. Timofeeva ◽  
Yuriy I. Chumlyakov ◽  
Ekaterina S. Marchenko ◽  
...  
Keyword(s):  
Elastic Modulus ◽  
Martensitic Transformation ◽  
Internal Friction ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Viscoelastic Properties ◽  
Oriented Growth ◽  
Compressive Stresses ◽  
Significant Change

This study investigated the effect of stress-induced martensite aging under tensile and compressive stresses on the functional and viscoelastic properties in Ni50.3Ti32.2Hf17.5 polycrystals containing dispersed H-phase particles up to 70 nm in size obtained by preliminary austenite aging at 873 K for 3 h. It was found that stress-induced martensite aging at 428 K for 12 h results in the appearance of a two-way shape memory effect of −0.5% in compression and +1.8% in tension. Moreover, a significant change in viscoelastic properties can be observed: an increase in internal friction (by 25%) and a change in elastic modulus in tensile samples. The increase in internal friction during martensitic transformation after stress-induced martensite aging is associated with the oriented growth of thermal-induced martensite. After stress-induced martensite aging, the elastic modulus of martensite (EM) increased by 8 GPa, and the elastic modulus of austenite (EA) decreased by 8 GPa. It was shown that stress-induced martensite aging strongly affects the functional and viscoelastic properties of material and can be used to control them.

scholarly journals Elastic Modulus Calculation Model of a Soil-Rock Mixture at Normal or Freezing Temperature Based on Micromechanics Approach

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Hao Yang ◽  
Zhong Zhou ◽  
Xiangcan Wang ◽  
Qifang Zhang
Keyword(s):  
Composite Material ◽  
Elastic Modulus ◽  
Freezing Temperature ◽  
Calculation Model ◽  
Frozen Soil ◽  
Experimental Comparison ◽  
Mesoscopic Structure ◽  
Embedded Model ◽  
Single Inclusion ◽  
Rock Interface

Considering rock wrapped by soil in the mesoscopic structure of soil-rock mixture at normal temperature, a two-layer embedded model of single inclusion composite material was established to obtain the elastic modulus of soil-rock mixture. Given an interface ice interlayer attached between the soil and rock interface in the mesoscopic structure of soil-rock mixture at freezing temperature, a three-layer embedded model of double inclusion composite material and multistep multiphase micromechanics model was established to obtain the elastic modulus of a frozen soil-rock mixture. With the effect of structure pore with soil-rock mixture at normal temperature taken into consideration, its elastic modulus was calculated with the three-layer embedded model. An experimental comparison found that the predicted effect of the three-layer embedded model on the soil-rock mixture was better than that of the two-layer embedded model. The elastic modulus of soil-rock mixture gradually increased with the increase in rock content regardless of temperature. The increase rate of the elastic modulus of the soil-rock mixture increased quickly especially when the rock content is between 50% and 70%. The elastic modulus of the frozen soil-rock mixture is close to four times higher than that of the soil-rock mixture at a normal temperature.

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