Theory and Application of the Parallel-Plate Plastimeter. Part 2

1935 ◽  
Vol 8 (4) ◽  
pp. 587-596 ◽  
Author(s):  
J. R. Scott
Keyword(s):  
Plastic Flow ◽  
Parallel Plate ◽  
Plastic Material ◽  
Compressive Load ◽  
Flow Equation ◽  
Simple Type ◽  
Plastic Properties ◽  
Further Development ◽  
Rubber Stock ◽  
Existing Data

Abstract In Part I (loc. cit.) the behavior of a plastic material in the parallel-plate (Williams) plastimeter was studied, and an expression was deduced showing how the rate of decrease in thickness of the sample during compression depends on the volume of the sample, its plastic properties, the compressive load, and the thickness itself. Subsequently, observations were published which showed that the basic principle adopted in this study was incorrect in certain particulars. Peek (loc. cit.), using these observations as a basis, deduced a new expression for the rate of decrease in thickness, though this is too complex for convenient practical use, except in an approximate simplified form. It has now been shown that the expression deduced in Part I, in spite of the inaccurate basis used, is sufficiently near to the truth to render substantially correct the conclusions there stated concerning the plastic properties of unvulcanized rubber stocks. By adopting the more accurate basis used by Peek, moreover, expressions for the rate of decrease in thickness can be deduced for materials showing more complex types of plastic flow than that considered in Part I or by Peek; this had proved impossible by the method previously used. The expression obtained by Peek for the simple type of plastic flow, as well as those now deduced for the more complex types, can be expressed in a form that furnishes a simple and rapid method of examining and analyzing experimental results. As a result of the work described in this paper, it is thus possible to determine, from results obtained with the parallel-plate plastimeter, whether or not a material such as unvulcanized rubber stock exhibits any of the types of plastic flow represented in the general form by Equation 1, and, if so, to find the values of the plastic constants of the material. The procedure is similar to that described in Part I, and consists simply in comparing, by superposition, a set of standard curves drawn on transparent paper with the curve plotted from experimental data. This further development of the method of studying plastic properties by means of the parallel-plate plastimeter should greatly increase its utility as an instrument of research. It has not yet been possible to apply the new method to a systematic study of rubber stocks, but from an examination of existing data it appears that these stocks, tested at 90° C., agree approximately with various forms of the generalized plastic flow equation already referred to.

Transformation of Energy by Rubber

1930 ◽  
Vol 3 (1) ◽  
pp. 74-86 ◽  
Author(s):  
Ira Williams
Keyword(s):  
Energy Loss ◽  
Plastic Flow ◽  
Elastic Strain ◽  
Physical State ◽  
Plastic Material ◽  
Frictional Resistance ◽  
Plastic Properties ◽  
Elastic Network ◽  
Time Required ◽  
Mechanical Change

Abstract The data which have been presented indicate that elasticity is a property of rubber which persists through vulcanization and is not created to any great extent. The physical state of the rubber after any period of cure depends on the balance between suppression of plastic properties either directly or indirectly through the influence of combination of sulfur, and the creation of plastic properties through the influence of heat. It is probable that sulfur also combines at a slower rate with the elastic portion of the rubber and finally results in a product of almost no mechanical strength. The transformation of energy by rubber depends upon the condition of the rubber as well as on the condition of the test. Heat liberated by elastic strain can be transformed almost quantitatively into mechanical work. Heat due to internal-frictional resistance which will be caused by both plastic and elastic flow is not reversible. Any reduction in time required for the transfer of energy reduces the amount lost through plastic flow. An increase in temperature increases the resistance of the elastic portion to strain, but also reduces the resistance to flow of the plastic portion. Sufficient increase in temperature causes a large energy loss due to a considerable but limited permanent flow of the rubber. This cannot be plastic flow of the elastic portion, since it is limited in extent, but can better be explained by some mechanical change such as a breaking of the anchorage between portions of the plastic material and elastic network.

Masonry: the brittle or plastic material?

2019 ◽  
pp. 22-28
Keyword(s):  
Plastic Material ◽  
Experimental Studies ◽  
Point Of View ◽  
Plastic Properties ◽  
Plastic Deformations ◽  
Base Materials ◽  
Stress States ◽  
Creep Deformations ◽  
Structural Point

The results of experimental studies of masonry on the action of dynamic and static (short-term and long-term) loads are presented. The possibility of plastic deformations in the masonry is analyzed for different types of force effects. The falsity of the proposed approach to the estimation of the coefficient of plasticity of masonry, taking into account the ratio of elastic and total deformations of the masonry is noted. The study of the works of Soviet scientists revealed that the masonry under the action of seismic loads refers to brittle materials in the complete absence of plastic properties in it in the process of instantaneous application of forces. For the cases of uniaxial and plane stress states of the masonry, data on the coefficient of plasticity obtained from the experiment are presented. On the basis of experimental studies the influence of the strength of the so-called base materials (brick, mortar) on the bearing capacity of the masonry, regardless of the nature of the application of forces and the type of its stress state, is noted. The analysis of works of prof. S. V. Polyakov makes it possible to draw a conclusion that at the long application of the load, characteristic for the masonry are not plastic deformations, but creep deformations. It is shown that the proposals of some authors on the need to reduce the level of adhesion of the mortar to the brick for the masonry erected in earthquake-prone regions in order to improve its plastic properties are erroneous both from the structural point of view and from the point of view of ensuring the seismic resistance of structures. It is noted that the proposal to assess the plasticity of the masonry of ceramic brick walls and large-format ceramic stone with a voidness of more than 20% is incorrect, and does not meet the work of the masonry of hollow material. On the basis of the analysis of a large number of research works it is concluded about the fragile work of masonry.

Rubber Plastometer with Uniform Rate of Shear—Shearing-Cone Plastometer

1946 ◽  
Vol 19 (3) ◽  
pp. 822-831 ◽  
Author(s):  
G. H. Piper ◽  
J. R. Scott
Keyword(s):  
Plastic Flow ◽  
Mechanical Design ◽  
Plastic Material ◽  
Edge Zone ◽  
Uniform Rate ◽  
Wide Range

Abstract A new shearing-cone plastometer, suitable for investigating the plastic-flow relations of highly viscous materials over a wide range of stress, is described. A mushroom-shaped rotor, having upper and lower surfaces of conical type, is rotated in the plastic material contained in a cylindrical mould. With this type of shearing surface the rate of shear is uniform throughout the material, except for a small edge zone, thus overcoming some disadvantages of previous plastometers. The mechanical design is based on the Mooney shearing-disk plastometer except that provision is made for a wide range of speeds of rotation.

scholarly journals Autowave Physics of Material Plasticity

Crystals ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 458 ◽  
Author(s):  
Lev B. Zuev ◽  
Svetlana A. Barannikova
Keyword(s):  
Plastic Flow ◽  
Flow Localization ◽  
Plastic Properties ◽  
Plastic Flow Localization ◽  
Flow Development ◽  
Strain Invariant ◽  
Deformation Hardening ◽  
Set Up ◽  
Structure Collapse ◽  
Flow Stage

The notions of plastic flow localization are outlined in the paper. It is shown that each type of localized plasticity pattern corresponds to a definite stage of deformation hardening. In the course of plastic flow development, a changeover in the types of localization patterns occurs. The types of localization patterns are limited in number: four pattern types are all that can be expected. A correspondence was set up between the emergent localization pattern and the respective flow stage. It is found that the localization patterns are manifestations of the autowave nature of plastic flow localization process, with each pattern type corresponding to a definite mode of autowave. In the course of plastic flow development, the following modes of autowaves will form in the following sequence: switching autowave → phase autowave → stationary dissipative structure → collapse of the autowave. Of particular interest are the phase autowave and the respective pattern observed. Propagation velocity, dispersion, and grain size dependence of wavelength were determined experimentally for the phase autowave. An elastic-plastic strain invariant was also introduced to relate the elastic and plastic properties of the deforming medium. It is found that the autowave characteristics follow directly from this invariant.

Elastic Deformation and Molecular Weight in Polyisobutylene

1946 ◽  
Vol 19 (4) ◽  
pp. 1047-1050
Author(s):  
John Rehner
Keyword(s):  
Molecular Weight ◽  
Parallel Plate ◽  
Compressive Load ◽  
Published Data ◽  
Fractional Powers ◽  
Rapid Procedure ◽  
Molecular Weights ◽  
High Elasticity ◽  
Polymer Dissolution ◽  
Straight Lines

Abstract Although various properties of high polymers are known to depend on molecular weight, there appear to be no published data which show explicitly how the molecular weight of a rubber-like substance influences the modulus of high elasticity, even though a psychological perception of some such relationship has long existed. Also, the various expressions that have been derived by statistical methods contain molecular weight as a factor ranging from an inverse first power up to inverse higher fractional powers. Some time ago a need arose in this laboratory for estimating the average molecular weights of samples of polyisobutylene by a rapid procedure. Because of the slowness of polymer dissolution, methods based on measurements of the polymer in the dissolved state had to be ruled out and an investigation was, therefore, made of the rate of compression of a variety of samples in a Williams parallel-plate plastometer. It was found possible to render negligible the viscous component of deformation by using a sufficiently high compressive load and by limiting readings to an interval of about one minute. When the observed deformation values were plotted against the logarithm of time, straight lines were obtained. The slopes of the lines could be correlated, at least approximately, linearly with the reciprocal average molecular weights of the samples.

scholarly journals Determination of plastic properties of metals by instrumented indentation using a stochastic optimization algorithm

2009 ◽  
Vol 24 (3) ◽  
pp. 936-947 ◽  
Author(s):  
I. Peyrot ◽  
P-O. Bouchard ◽  
R. Ghisleni ◽  
J. Michler
Keyword(s):  
Mechanical Properties ◽  
Optimization Algorithm ◽  
Plastic Material ◽  
Element Model ◽  
Optimization Approach ◽  
Plastic Properties ◽  
Acta Mater ◽  
Multiple Data Sets ◽  
Load Displacement ◽  
Commercial Solver

A novel optimization approach, capable of extracting the mechanical properties of an elasto-plastic material from indentation data, is proposed. Theoretical verification is performed on two simulated configurations. The first is based on the analysis of the load–displacement data and the topography of the residual imprint of a single conical indenter. The second is based on the load–displacement data obtained from two conical indenters with different semi-angles. In both cases, a semi-analytical approach [e.g., Dao et al., Acta Mater.49, 3899 (2001) and Bucaille et al., Acta Mater.51, 1663 (2003)] is used to estimate Young’s modulus, yield stress, and strain hardening coefficient from the load–displacement data. An inverse finite element model, based on a commercial solver and a newly developed optimization algorithm based on a robust stochastic methodology, uses these approximate values as starting values to identify parameters with high accuracy. Both configurations use multiple data sets to extract the elastic-plastic material properties; this allows the mechanical properties of materials to be determined in a robust way.

Local Mechanical Characterization of Metal Foams by Nanoindentation

2015 ◽  
Vol 662 ◽  
pp. 59-62 ◽  
Author(s):  
Jiří Němeček ◽  
Vlastimil Kralik
Keyword(s):  
Cell Walls ◽  
Plastic Material ◽  
Spherical Indentation ◽  
Isotropic Hardening ◽  
Plastic Properties ◽  
Macro Scale ◽  
Static Indentation ◽  
Indentation Tests ◽  
Constitutive Parameters

This paper deals with microstructure and micromechanical properties of two commercially available aluminium foams (Alporas and Aluhab). Since none of the materials is available in a bulk and standard mechanical testing at macro-scale is not possible the materials need to be tested at micro-scale. To obtain both elastic and plastic properties quasi-static indentation was performed with two different indenter geometries (Berkovich and spherical tips). The material phase properties were analyzed with statistical grid indentation method and micromechanical homogenization was applied to obtain effective elastic wall properties. In addition, effective inelastic properties of cell walls were identified with spherical indentation. Constitutive parameters related to elasto-plastic material with linear isotropic hardening (the yield point and tangent modulus) were directly deduced from the load–depth curves of spherical indentation tests using formulations of the representative strain and stress introduced by Tabor.

The Pendulum as a Source of Energy for Plasticity Measurements

1936 ◽  
Vol 9 (4) ◽  
pp. 626-632
Author(s):  
Ira Williams
Keyword(s):  
Plastic Flow ◽  
Parallel Plate ◽  
Elastic Recovery ◽  
Time Factor ◽  
Mathematical Treatment ◽  
Parallel Plates ◽  
Simple Apparatus ◽  
Constant Area ◽  
Rapid Control ◽  
Control Work

Abstract ADVANCEMENT in methods for studying the consistency of rubber during the last 10 years has been confined largely to various modifications of previous tests and to better interpretation of the data obtained. The extrusion plastometer introduced by Marzetti (11) has been modified by Behre (1) to provide a battery of instruments, by Dillon and Johnston (5) to provide more simple apparatus capable of operating at increased rates of shear, and by Dillon (4) to provide an instrument for rapid control work. The parallel-plate plastometer (16) has received numerous modifications of form. DeVries (2) modified the plates to provide a constant area of contact with the rubber. This modification was used by van Rossem and van der Meyden (14) who stressed the necessity of following the elastic recovery as well as the rate of compression. Karrer (8) pointed out the need for controlling the time factor during compression and recovery and has described an instrument (9) with which each measurement requires about 30 seconds. The balance plastometer, which employs parallel plates, was described by Hoekstra (7) and is well adapted to following the elastic recovery after the rubber has been compressed under any conditions of thickness and time. A parallel-plate instrument with interchangeable parts to provide various methods of applying pressure and following recovery was described by Lefeaditis (10). The relation between compression and the extent of recovery has been considered by Dillon (3), who concluded that the measurement of either the compression or the elastic recovery as obtained with the usual parallel-plate plastometer was sufficient if the comparison was confined to a number of batches of a given stock or type of rubber. He also pointed out that elastic recovery depends on the speed of the previous deformation. Hoekstra (6), after considering some of the factors involved in plastic flow, concluded that elastic recovery should be measured only after compression of a rubber to the fixed thickness. The general usefulness of the parallel-plate plastometer has been greatly increased by the mathematical treatment of Peek (13) and Scott (15). A third type of plastometer, consisting of a disk which rotates in compressed rubber while the resistance to shear is measured, has been described by Mooney (12).

Corrosion Assessment Method Validation for High-Grade Line Pipe

2010 ◽  
Author(s):  
Michael Besel ◽  
Steffen Zimmermann ◽  
Christoph Kalwa ◽  
Theo Ko¨ppe ◽  
Andreas Liessem
Keyword(s):  
Plastic Flow ◽  
Predictive Accuracy ◽  
Plastic Material ◽  
Assessment Method ◽  
Burst Pressure ◽  
High Grade ◽  
Line Pipe ◽  
Corrosion Defect ◽  
Von Mises Plasticity ◽  
Grade Steel

The present paper deals with the pressure containment and deformation capacity of corroded high-grade steel line pipe. Firstly, some well established models are investigated concerning their predictive accuracy if applied to high-grade line pipe steel. In particular, it will be shown that all models under consideration tend to overestimate the remaining strength in the case of high-grade steel pipes. Afterwards, FE-analyses are performed in order to study the local evolution of plastic flow in the area of the corrosion defect; at the same time, the burst pressure is predicted applying von Mises plasticity and a simple failure criterion. Although different defect geometries are associated with well pronounced differences in the evolution of the plastic flow around the corrosion defect no significant effect on the burst pressure is found. Finally, the main results of a hydrostatic burst test performed on a pristine X100 line pipe joint are presented. It appears that the material under consideration seems to have anisotropic plastic material properties which may have effect on burst pressure.

Investigation of Relationship between Structural and Crystallographic Condition of some Constructional Materials and their Mechanical Properties

2016 ◽  
Vol 870 ◽  
pp. 207-213
Author(s):  
V.V. Novokreschenov ◽  
R.V. Rodyakina ◽  
M.A. Karimbekov
Keyword(s):  
Mechanical Properties ◽  
Crystal Lattice ◽  
Linear Relationship ◽  
Plastic Flow ◽  
Analytical Study ◽  
Relative Strength ◽  
Plastic Properties ◽  
Face Centered ◽  
The Relationship ◽  
Stretching Process

This paper presents the results of an analytical study into the relationship between the strength and plastic properties of a series of structural materials. For this purpose the behavior of different materials during the stretching process of flat tensile samples with a circular hub was studied. It was found that the criterion of relative strength A depends on the structure and type of the crystal: materials, having a body-centered crystal lattice A < 1, and materials, having face-centered crystal lattice, A > 1. Astable linear relationship, depending on the structure and the type of crystal lattice of the material, between the criterion of relative strength A, geometric parameters of the sample (R and b) with the hub, length of the zone of material’s plastic flow lp and tension δ was found to exist.

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