Hydrostatic compression tests, capillary rheometry tests, and extrusion tests performed on unvulcanized rubber confirm importance of compressibility for die swell — Arguments from dimensional analysis

It is known that liquid crystalline polymer (LCP) melts have a high elasticity which can be measured from its effect on the rheology on the cessation of shear. On the other hand, LCPs show very limited die swell after extrusion. In this paper, the results of experimental measurements of the die swell for a liquid crystalline material and polypropylene (PP), an amorphous polymer, are presented. The extrudate thickness 5 cm below the die lip is optically measured and the results are analyzed using ImageJ software. A numerical simulation of the die swell based on the capillary rheometry data and oscillatory rheometry is performed for LCP materials using ANSYS ® POLYFLOW ®. Different viscoelastic properties are used to model the LCP and optimum properties to model the die swell for the base volume flow rate are determined. Results show similarity between die swell modeling for the LCP at the base volume flow rate but increasing the die swell results in some deviation from the experimental results.

Download Full-text

A New Constitutive Model for the Compressibility of Elastomers at Finite Deformations

Rubber Chemistry and Technology ◽

10.5254/1.3544956 ◽

2001 ◽

Vol 74 (4) ◽

pp. 541-559 ◽

Cited By ~ 69

Author(s):

Jeffrey E. Bischoff ◽

Ellen M. Arruda ◽

Karl Grosh

Keyword(s):

Uniaxial Tension ◽

Volume Change ◽

Constitutive Models ◽

Hydrostatic Compression ◽

Constitutive Law ◽

Elastic Behavior ◽

Compression Tests ◽

Volume Response ◽

Using Data ◽

Nonlinear Elastic

Abstract Although traditional constitutive models for rubbery elastic materials are incompressible, many materials that demonstrate nonlinear elastic behavior are somewhat compressible. Clearly important in hydrostatic deformations, compressibility can also significantly affect the response of elastomers in applications for which several boundaries are rigidly fixed, such as bushings, or triaxial states of stress are realized. Compressibility is also important for convergence of finite element simulations in which a rubbery elastic constitutive law is in use. Volume changes that reflect compressibility have been observed historically in both uniaxial tension and hydrostatic compression tests; however, there appear to be no data obtained from both types of tests on the same material by which to validate a compressible hyperelastic law. In this paper, we propose a new compressible hyperelastic constitutive law for elastomers and other rubbery materials in which entropy and internal energy changes contribute to the volume change. Using data from the literature, we show that this law is capable of reproducing both the pressure—volume response of elastomers in hydrostatic compression, as well as the stress—stretch and volume change—stretch data of elastomers in uniaxial tension.

Download Full-text

Laboratory velocities and attenuation of P‐waves in limestones during freeze‐thaw cycles

Geophysics ◽

10.1190/1.1443586 ◽

1994 ◽

Vol 59 (2) ◽

pp. 245-251 ◽

Cited By ~ 20

Author(s):

Jean‐Michel Remy ◽

Michel Bellanger ◽

Françoise Homand‐Etienne

Keyword(s):

Hydrostatic Compression ◽

P Wave ◽

Compression Tests ◽

Freezing And Thawing ◽

P Waves ◽

Freeze Thaw ◽

Rock Samples ◽

Wave Velocities ◽

P Wave Velocities ◽

Freezing And Thawing Cycles

The velocity and the attenuation of compressional P‐waves, measured in the laboratory at ultrasonic frequencies during a series of freezing and thawing cycles, are used as a method for predicting frost damage in a bedded limestone. Pulse transmission and spectral ratio techniques are used to determine the P‐wave velocities and the attenuation values relative to an aluminum reference sample with very low attenuation. Limestone samples were water saturated under vacuum conditions, jacketed with rubber sleeves, and immersed in an antifreeze bath (50 percent methanol solution). They were submitted to repeated 24-hour freezing and thawing cycles simulating natural environment conditions. During the freeze/thaw cycles, P‐wave velocities and quality factor Q diminished rapidly in thawed rock samples, indicating modification of the pore space. Measurements of crack porosity were conducted by hydrostatic compression tests on cubic rock samples that had been submitted to these freeze/thaw cycles. These measurements are used as an index of crack formation. The hydrostatic compression tests confirmed the phases of rock damage that were shown by changes in the value of Q. Furthermore, comparisons between Q values and crack porosity demonstrated that the variations of P‐wave attenuation are caused by the creation of new cracks and not by the enlargement of pre‐existing cracks.

Download Full-text

Electron Microscopy of Shock Loaded Polycrystalline Beryllium

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100052547 ◽

1974 ◽

Vol 32 ◽

pp. 506-507 ◽

Cited By ~ 1

Author(s):

J. M. Galbraith ◽

L. E. Murr ◽

A. L. Stevens

Keyword(s):

Electron Microscopy ◽

Wave Propagation ◽

Structural Change ◽

Single Crystal ◽

Diffraction Pattern ◽

Shock Loading ◽

Slip Systems ◽

Compression Tests ◽

X Ray Diffraction ◽

X Ray

Uniaxial compression tests and hydrostatic tests at pressures up to 27 kbars have been performed to determine operating slip systems in single crystal and polycrystal1ine beryllium. A recent study has been made of wave propagation in single crystal beryllium by shock loading to selectively activate various slip systems, and this has been followed by a study of wave propagation and spallation in textured, polycrystal1ine beryllium. An alteration in the X-ray diffraction pattern has been noted after shock loading, but this alteration has not yet been correlated with any structural change occurring during shock loading of polycrystal1ine beryllium.This study is being conducted in an effort to characterize the effects of shock loading on textured, polycrystal1ine beryllium. Samples were fabricated from a billet of Kawecki-Berylco hot pressed HP-10 beryllium.

Download Full-text

In situ investigation of the primary recrystallization of alpha titanium in HVEM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100110313 ◽

1978 ◽

Vol 36 (1) ◽

pp. 634-635

Author(s):

S. Naka ◽

R. Penelle ◽

R. Valle

Keyword(s):

Dimensional Analysis ◽

Texture Evolution ◽

Cold Work ◽

Three Dimensional ◽

Primary Recrystallization ◽

Thin Foils ◽

In Situ Investigation ◽

Grain Growth Model ◽

Alpha Titanium

The in situ experimentation technique in HVEM seems to be particularly suitable to clarify the processes involved in recrystallization. The material under investigation was unidirectionally cold-rolled titanium of commercial purity. The problem was approached in two different ways. The three-dimensional analysis of textures was used to describe the texture evolution during the primary recrystallization. Observations of bulk-annealed specimens or thin foils annealed in the microscope were also made in order to provide information concerning the mechanisms involved in the formation of new grains. In contrast to the already published work on titanium, this investigation takes into consideration different values of the cold-work ratio, the temperature and the annealing time.Two different models are commonly used to explain the recrystallization textures i.e. the selective grain growth model (Beck) or the oriented nucleation model (Burgers). The three-dimensional analysis of both the rolling and recrystallization textures was performed to identify the mechanismsl involved in the recrystallization of titanium.

Download Full-text

Dislocations in alumina deformed by prismatic slip

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100110179 ◽

1978 ◽

Vol 36 (1) ◽

pp. 606-607

Author(s):

J. Cadoz ◽

J. Castaing ◽

J. Philibert

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Basal Slip ◽

Prismatic Slip ◽

Compression Tests ◽

Thin Sections ◽

Burgers Vector ◽

Maximum Deformation ◽

Transmission Electron ◽

Mechanical Thinning

Plastic deformation of alumina has been much studied; basal slip occurs and dislocation structures have been investigated by transmission electron microscopy (T.E.M.) (1). Non basal slip has been observed (2); the prismatic glide system <1010> {1210} has been obtained by compression tests between 1400°C and 1800°C (3). Dislocations with <0110> burgers vector were identified using a 100 kV microscope(4).We describe the dislocation structures after prismatic slip, using high voltage T.E.M. which gives much information.Compression tests were performed at constant strainrate (∿10-4s-1); the maximum deformation reached was 0.03. Thin sections were cut from specimens deformed at 1450°C, either parallel to the glide plane or perpendicular to the glide direction. After mechanical thinning, foils were produced by ion bombardment. Details on experimental techniques can be obtained through reference (3).

Download Full-text

Dimensional Analysis of Protective Factors and Suicidality Among Combat Vietnam Veterans

PsycEXTRA Dataset ◽

10.1037/e517292011-677 ◽

2009 ◽

Author(s):

Rumi Price ◽

Gregory Widner ◽

William True ◽

Monica Matthieu

Keyword(s):

Protective Factors ◽

Dimensional Analysis ◽

Vietnam Veterans

Download Full-text

Infinite Dimensional Analysis

10.1007/978-3-662-03004-2 ◽

1994 ◽

Cited By ~ 111

Author(s):

Charalambos D. Aliprantis ◽

Kim C. Border

Keyword(s):

Dimensional Analysis ◽

Infinite Dimensional ◽

Infinite Dimensional Analysis

Download Full-text

Effect Of Elevated Temperatures On Complete Concrete Deformation Diagrams

Promyshlennoe i Grazhdanskoe Stroitel stvo ◽

10.33622/0869-7019.2019.11.09-14 ◽

2019 ◽

pp. 9-14

Keyword(s):

Experimental Data ◽

Elastic Modulus ◽

Elevated Temperatures ◽

Peak Load ◽

Relative Deformation ◽

Deformation Characteristics ◽

Compression Tests ◽

Strain Behavior ◽

Different Temperatures ◽

Deformation Diagrams

The analysis of the previous results of the study on concrete stress-strain behavior at elevated temperatures has been carried out. Based on the analysis, the main reasons for strength retrogression and elastic modulus reduction of concrete have been identified. Despite a significant amount of research in this area, there is a large spread in experimental data received, both as a result of compression and tension. In addition, the deformation characteristics of concrete are insufficiently studied: the coefficient of transverse deformation, the limiting relative compression deformation corresponding to the peak load and the almost complete absence of studies of complete deformation diagrams at elevated temperatures. The two testing chambers provided creating the necessary temperature conditions for conducting studies under bending compression and tension have been developed. On the basis of the obtained experimental data of physical and mechanical characteristics of concrete at different temperatures under conditions of axial compression and tensile bending, conclusions about the nature of changes in strength and deformation characteristics have been drawn. Compression tests conducted following the method of concrete deformation complete curves provided obtaining diagrams not only at normal temperature, but also at elevated temperature. Based on the experimental results, dependences of changes in prism strength and elastic modulus as well as an equation for determining the relative deformation and stresses at elevated temperatures at all stages of concrete deterioration have been suggested.

Download Full-text