Effect of Porosity on Mechanical Properties of Rubber

1995 ◽  
Vol 68 (2) ◽  
pp. 219-229 ◽  
Author(s):  
A. I. Kasner ◽  
E. A. Meinecke
Keyword(s):  
Experimental Data ◽  
Mechanical Properties ◽  
Shape Factor ◽  
Compression Modulus ◽  
Stress Strain ◽  
Shape Factors ◽  
Porosity Level ◽  
Apparent Modulus ◽  
Analytical Expressions ◽  
Cylindrical Samples

Abstract Cylindrical samples, with different shape factors and levels of porosity, were prepared from a model EPDM compound and tested in compression. The modulus was reduced considerably with the introduction of porosity, especially when the shape factor was high. The stress-strain curves showed nonlinearity which depends on the shape factor and porosity level, and is related to bubble closure. The apparent modulus of bonded blocks was found to consist of two components: homogeneous compression modulus and a hydrostatic contribution. The first was obtained by compression of blocks between lubricated compression plates. It can be predicted from analytical expressions adapted from composite theories for high density foams in tension. The second arises from the pressure buildup inside the bonded blocks and depends on the shape factor and the porosity level. These moduli, after correcting for compressibility, were used to develop approximate relations describing the stress-strain curves of porous bonded blocks. The stress-strain curves of samples with different shape factors and levels of porosity could be predicted from experimental data or FEA estimates.

Application of Shape Factor to Mechanical Behavior of Thermal Interface Pads and Putties

2021 ◽  
Author(s):  
Karl F. Schoch ◽  
Philip Panackal ◽  
M. Garrett Bimstefer ◽  
Amanda Brocki ◽  
Daniel Urban
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Shape Factor ◽  
Compressive Strain ◽  
Peak Stress ◽  
Temperature Cycling ◽  
Strain Rates ◽  
Initial Shape ◽  
Thermal Interface ◽  
Shape Factors

Abstract Thermal interface materials (TIMs) are an essential part of managing thermal performance of electronic assemblies. Knowledge of the mechanical properties of these materials is required in order to have a robust design that will perform as required over the life of the product, including many thermal cycles, without causing damage to electrical components. In this paper, we report on mechanical properties of three putty TIMs and four pad TIMs, showing that the stiffness of the TIMs is proportional to the square of the initial shape factor over the range of shape factors from 1 to 18. Since the putties can flow more readily under pressure than the pads, the putties had a lower measured stiffness at a given shape factor compared to the pads. From these relationships, designers can predict loads with various geometries (i.e. shape factors) and loading rates (i.e. shock loading vs. temperature cycling) which can impact their design. While all of the materials were tested at compressive strain rates of 20 to 70% strain/minute, one putty was also tested at a 10x higher rate to determine the effect of a relatively high strain rate on the peak stress. In that case, the peak stress was approximately 3x higher than measured at the lower strain rates. However, the relaxed load at each strain rate tested was unaffected by strain rate, indicating that hardware assembly conditions can be adjusted to minimize stress on components and yet, still achieve an interface having low thermal resistance.

THE ANALYSIS OF STRESS DEFORMATION STATE PECULIARITIES OF MASONRY UNITS AND BED JOINTS

2011 ◽  
Vol 3 (3) ◽  
pp. 105-111 ◽  
Author(s):  
Robertas Zavalis ◽  
Bronius Jonaitis
Keyword(s):  
Experimental Data ◽  
Mechanical Properties ◽  
Elastic Modulus ◽  
Contact Zone ◽  
Strain Analysis ◽  
Stress Strain ◽  
Curing Conditions ◽  
Stiffness Properties ◽  
Deformation State ◽  
Masonry Units

In this paper, the analysis of various effects that have influence to the mechanical properties of masonry is made. Masonry is nonhomogeneous and anisotropic material composed of two materials with different stiffness properties. In order to analyze masonry deformations it is necessary to evaluate all effects that have influence to masonry mechanical properties (Table 1). The analysis of stress-strain state of masonry is presented in this paper. During the analysis of stressstrain state, the mechanical properties of masonry units and mortar were defined from experimental investigation of samples of unit and mortar materials. The following conclusions were reached based on the analysis of experimental data: 1) The deformations and stresses along the height of masonry unit distributes unevenly. The stresses and deformations near the bed joint are higher than in the middle of the unit (4 pav). 2) From experimental data it was determined that the deformation of bed joints mostly depend on contact zone between units and mortar. The contact zone deformation contains about 80…90% of all bed joint deformation. 3) The elastic modulus of mortar inside the composite is different from modulus of mortar specimens cast separately due to different laying and curing conditions. The elastic modulus values performed from composite were 15…25 times less than the values from standard mortar prisms (EN 1015-11). It is advisable to use real (defined from experiments) masonry units and mortar properties when detailed, numerical stress-strain analysis is performed. 4) Experimental analysis showed that bed joints have big influence to vertical deformation of masonry in axial compression. Masonry units have influence to mechanical properties of mortar joints. The experiment was carried out, during which dry and wet masonry units were used. Units were wet out to eliminate there absorption characteristics. Extra wet out units had an effect to the stiffness of bed joints (12 pav).

Microbial aggregates in wastewater treatment

1994 ◽  
Vol 30 (8) ◽  
pp. 87-95 ◽  
Author(s):  
Jerzy J. Ganczarczyk
Keyword(s):  
Experimental Data ◽  
Wastewater Treatment ◽  
Shape Factor ◽  
Regression Models ◽  
Settling Velocity ◽  
Shape Factors ◽  
Sludge Flocs ◽  
Stable Conditions ◽  
Factor Function

Basic forms of microbial aggregates generated in wastewater treatment and techniques used to study them, are described and discussed. The role of the free-setting velocity in evaluation of some physical properties of activated sludge flocs is emphasized. Several regression models were applied to correlate the flocs' settling velocity with flocs' size values. For the studied samples a simple linear model proved to be superior to a multiplicative one, and an introduction to this model of a settling shape factor function instead of constant intercepts, provided a very good correlation of the experimental data. It is expected that a difference between shape factors for the most stable conditions of the flocs and those for the flocs under the settling conditions will make it possible to determine softness or stiffness of these microbial aggregates.

Compressive strength and creep behavior of hydrate-consolidated sand

1990 ◽  
Vol 27 (2) ◽  
pp. 255-258 ◽  
Author(s):  
I. Cameron ◽  
Y. P. Handa ◽  
T. H. W. Baker
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Strain Rate ◽  
Creep Behavior ◽  
Gas Hydrates ◽  
Peak Stress ◽  
Strain Rates ◽  
Stress Strain ◽  
Frozen Sand ◽  
Cylindrical Samples

Cylindrical samples of sand consolidated with tetrahydrofuran hydrate were tested for their compressive strength and creep behavior under uniaxial compression. The samples were 15 cm in length and 7.5 cm in diameter and were tested at −10 °C. The results, when combined with our previous measurements on similar samples at −6 °C, show that the material becomes stronger by about 10% with decrease in temperature; otherwise, the slopes of the peak stress – strain rate curves are the same. These results are similar to those of sand consolidated with ice, except that in the latter case the increase in strength over the same temperature range is about 30%. Furthermore, the slope of the peak stress – strain rate curve for the hydrate-consolidated sand is almost zero, whereas for the ice-consolidated sand it is quite steep. Consequently, at strain rates below 10−5 s−1 the hydrate-consolidated sand is stronger, whereas at strain rates above 10−5 s−1 the ice-consolidated sand is the stronger material. Noticeable differences were also observed in the creep behavior of the hydrate- and ice-consolidated sands. At −10 °C, ice-consolidated sand failed in about 15 h under a stress of about 7 MPa, whereas hydrate-consolidated sand failed after 52.3 h under a stress of 12.2 MPa and some samples did not fail even after 540 h when subjected to a stress of 9.3 MPa. Key words: gas hydrates, ice, frozen sand, mechanical properties, compressive strength, creep behavior.

The study on the mechanical properties of magnetorheological elastomers under triaxial compression

2020 ◽  
pp. 1045389X2097827
Author(s):  
Yong Xu ◽  
Ming Li ◽  
Hao Li ◽  
Shihong Zhang ◽  
Hui Wang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Magnetic Flux ◽  
Magnetic Particles ◽  
Poisson Ratio ◽  
Triaxial Compression ◽  
Compression Modulus ◽  
Magnetic Flux Density ◽  
Stress Strain ◽  
Magnetorheological Elastomers ◽  
Volume Compression

In order to design magnetorheological elastomers (MREs) based craftsmanship for metal forming, a comprehensive study on the mechanical properties of MREs under triaxial compression is required. An experimental setup integrating free compression and triaxial compression is designed to characterize isotropic MREs specimens under compression mode. The results showed that the MREs specimen in mold had successively experienced free compression stage, transition stage and triaxial compression stage during the experiment. The stress-strain curves of the MREs specimen changed when the concentration of magnetic particles increased from 0 to 44.7%, and the strain required to reach the transition stage was reduced. The effect of magnetic flux density on the stress-strain curves of the MREs specimen depended on the concentration of magnetic particles. The measured data obtained at different strain rates revealed maximum changes of 15.7% and 0.096% in volume compression modulus and Poisson ratio, respectively, which occurred under the magnetic flux density of 200 mT and CIP concentrations of [Formula: see text]. In this study, through a set of experiments, the stress-strain curves of the MREs specimen under different concentrations was elucidated, and their effects on the volume compression modulus and Poisson ratio were discussed.

Mechanical Properties and Stress/Strain Characteristics of Critical Currents in Reinforced Bronze-processed Nb3Sn Wires

2004 ◽  
Vol 39 (9) ◽  
pp. 433-438 ◽  
Author(s):  
Kazumune KATAGIRI ◽  
Kazuo WATANABE ◽  
Koshichi NOTO ◽  
Koichi KASABA ◽  
Yoshitaka SHOJI
Keyword(s):  
Mechanical Properties ◽  
Critical Currents ◽  
Stress Strain

scholarly journals An Additive Model to Predict the Rheological and Mechanical Properties of Polypropylene Blends Made by Virgin and Reprocessed Components

Recycling ◽  
2021 ◽  
Vol 6 (1) ◽  
pp. 2
Author(s):  
Francesco Paolo La Mantia ◽  
Maria Chiara Mistretta ◽  
Vincenzo Titone
Keyword(s):  
Experimental Data ◽  
Mechanical Properties ◽  
Additive Model ◽  
Industrial Process ◽  
Theoretical Predictions ◽  
Experimental Values ◽  
Polypropylene Blends ◽  
Polypropylene Sample

In this work, an additive model for the prediction of the rheological and mechanical properties of monopolymer blends made by virgin and reprocessed components is proposed. A polypropylene sample has been reprocessed more times in an extruder and monopolymer blends have been prepared by simulating an industrial process. The scraps are exposed to regrinding and are melt reprocessed before mixing with the virgin polymer. The reprocessed polymer is, then, subjected to some thermomechanical degradation. Rheological and mechanical experimental data have been compared with the theoretical predictions. The results obtained showed that the values of this simple additive model are a very good fit for the experimental values of both rheological and mechanical properties.

scholarly journals Ability of Constitutive Models to Characterize the Temperature Dependence of Rubber Hyperelasticity and to Predict the Stress-Strain Behavior of Filled Rubber under Different Defor Mation States

Polymers ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 369
Author(s):  
Xintao Fu ◽  
Zepeng Wang ◽  
Lianxiang Ma
Keyword(s):  
Experimental Data ◽  
Temperature Dependence ◽  
Mechanical Response ◽  
Constitutive Models ◽  
Uniaxial Tensile ◽  
Uniaxial Tensile Test ◽  
Chain Model ◽  
Stress Strain ◽  
Filled Rubber ◽  
Yeoh Model

In this paper, some representative hyperelastic constitutive models of rubber materials were reviewed from the perspectives of molecular chain network statistical mechanics and continuum mechanics. Based on the advantages of existing models, an improved constitutive model was developed, and the stress–strain relationship was derived. Uniaxial tensile tests were performed on two types of filled tire compounds at different temperatures. The physical phenomena related to rubber deformation were analyzed, and the temperature dependence of the mechanical behavior of filled rubber in a larger deformation range (150% strain) was revealed from multiple angles. Based on the experimental data, the ability of several models to describe the stress–strain mechanical response of carbon black filled compound was studied, and the application limitations of some constitutive models were revealed. Combined with the experimental data, the ability of Yeoh model, Ogden model (n = 3), and improved eight-chain model to characterize the temperature dependence was studied, and the laws of temperature dependence of their parameters were revealed. By fitting the uniaxial tensile test data and comparing it with the Yeoh model, the improved eight-chain model was proved to have a better ability to predict the hyperelastic behavior of rubber materials under different deformation states. Finally, the improved eight-chain model was successfully applied to finite element analysis (FEA) and compared with the experimental data. It was found that the improved eight-chain model can accurately describe the stress–strain characteristics of filled rubber.

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