Specimen dumbbell

Strictly the terms brittle and tough fracture can only be applied to failure under carefiilly specified test conditions. That is to say that the statement that a glassy polymer, such as poly(methyl methacrylate), undergoes brittle fracture at ambient temperatures needs qualifying test conditions must be stated. These are usually that the material has been formed into a dumbbell shaped specimen. 

Tensile and Elongation. Samples of the belt wedge mbber, located between belts 1 and 2, were removed from both shoulders (serial side and opposite serial side) and buffed to a uniform thickness of 0.5-1.0 mm. Care was taken so that no signihcant heat was introduced to the samples by the buffing. Specimens were die-cut using an ASTM D 638 Type V dumbbell die and tested per ASTM D 412. Results obtained included modulus values at 100%, ultimate elongation, and tensile strength. Samples were tested at 20"/min (50.8 cm/min). 

The two network precursors and solvent (if present) were combined with 20 ppm catalyst and reacted under argon at 75°C to produce the desired networks. The sol fractions, ws, and equilibrium swelling ratio In benzene, V2m, of these networks were determined according to established procedures ( 1, 4. Equilibrium tensile stress-strain Isotherms were obtained at 25 C on dumbbell shaped specimens according to procedures described elsewhere (1, 4). The data were well correlated by linear regression to the empirical Mooney-Rivlin (6 ) relationship. The tensile behavior of the networks formed In solution was measured both on networks with the solvent present and on networks from which the oligomeric PEMS had been extracted. 

Tensile strength, which is a measure of the ability of a polymer to withstand pulling stresses, is usually measured using a dumbbell-shaped specimen (ASTM D-638-72 Figures 14.11 and 14.12). These test specimens are conditioned under standard conditions of humidity and temperature before testing. 

The tensile strength can be measured in two ways (1) direct tensile strength from dumbbell specimens (2) splitting tensile strength from cylinders. Alternatively... 

There are two simple ways to prepare samples (a) with a very sharp razor blade or an Exacto knife, cut in one continuous motion and (b) using a sharp paper punch, cut two holes close together and cut two parallel fines to make dumbbell-shaped specimens. 

A special split tensile specimen mold was made to measure tensile properties of propellant during cure. A miniature casting is made in a dumbbell-shaped mold. The gage section of the mold is split axially so that it can be removed to expose the partially cured propellant. The mold is placed in a tensile tester, and the specimen is pulled with the end parts in place. Figure 17 shows that during the early stages of cure... 

Figure 16. Effect of moisture on uniaxial tensile properties. Dumbbell specimen exposed 14 days to 95% relative humidity, during which time the propellant absorbed 0.31% water. T = 25°C. 1 = 0.74 minr1...

Dumbbell-shaped specimens having a minor diameter of 0.5 were used for this test, and the cross head speed of the Tinius Olsen Universal Test Apparatus was set at 0.5, /sec. The data is presented on the following pages in Tables 1 2... 

When a metal specimen is subjected to the tensile test, the micropores around the centre of the dumbbell start to grow and combine. As soon as the metal wall which is initially still intact is no longer able to withstand the stress, the object tears. Apart from the above-mentioned growth of the pores, sliding processes in the crystal lattice also play a part in the formation of the fracture. 

Vulcanized rubber was ozonized as follows. Natural rubber was compounded with the ingredients shown in Table III and cured at 141 °C. for 13 minutes. The vulcanizates were cut off from the sheets with JIS No. 1 dumbbell cutter to obtain the specimens for the ozone crack test. The test pieces were exposed to an oxygen atmosphere containing 0.01% ozone under an elongation of 50%, and a time, t0, required for the initial crack formation was measured. 

Tensile properties of PVC filled with precipitated calcium carbonate particles having two different mean sizes were studied. The particles were porous agglomerates of spherical primary particles. 10-50 parts of the particles were mixed with 100 parts PVC and 3 parts lead stearate using a mixing roll. Tensile tests were carried out using dumbbell test specimens. 20 refs. 

Tensile properties are one of the most important single indications of the strength of a material. Mechanical properties of polymeric materials are often measured using standard test sample configurations. In these studies, a tensile dumbbell-shaped test specimen which conforms to ASTM D638 was used for all measurements. 

The EWF tests were named with a eode indicating material, erosshead rate and orientation, in that order. In this way, PC20-10T (or P) results correspond to tests carried out on PC20 blends tested at 10 mm/min in 90° (or 0°) crack propagation with respect to the melt flow direction. It is important to mention that even the fact that tensile parameters were determined on thicker (4 mm) dumbbell specimens could invalidate their use in EWF validations due to some morphological and crystallinity differences, some SEM observations and DSC measurements on plaques and dumbbell test specimens verified that these microstructural features are quite similar on both specimen geometries (Table 1). 

The copolymers were injection molded into miniature dumbbell specimens at the temperature above LCTT with a Custom Scientific Instruments (CSI) Mini-Max injection molding machine. The specimens for thermal treatment were annealed at 200CC for 4 hr and then at a few tens degree below LCTT for 40 hr under vacuum to develop crystalline order. 

The second polymer (sample E) was an ethylene-hexene copolymer which Is slightly branched, and had an My of 211,000 and a nominal density of 0.955 g/cm. Specimens approximately one millimeter thick were prepared from both polymers by molding flat sheets from which dumbbell-shaped bars were cut with a die. The sheets were molded by heating the polymer for ten minutes at 440K In a press at which time the heat was turned off and pressure applied. The polymer was then cooled In the press over... 

Moduli, tensile strengths and elongations at break are performed on a mechanical tensile tester (Instron 4204-GB) according to French standard NFT 51-034, with injected dumbbell specimens (length x thickness 150 x 4 mm2) conditioned at 54% RH and 23°C. Strain-stress curves are obtained with a velocity of 50 mm/min. Each mechanical parameter is determined from ten tested specimens. 

The ASTM procedure describes procedures for determining tensile properties of materials in the form of standard dumbbell-shaped test specimens, with thickness between 1.0 mm (0.04 in.) and 14 mm (0.55 in.). The ASTM emphasizes, where directly comparable results are desired, that all samples should be of equal thickness. 

NR was added mixing continued for 4 min when DCP was added, and the system was mixed for additional 2 min. The blends were sheeted using a laboratory mill at 1.25-mm nip setting. The sheets were cut into small pieces and re-mixed at 150°C for 1 min and sheeted out again in the laboratory mill. The blended sheets were compression-molded into the dumbbell specimens (2 0.2 mm) in an electrically heated hydraulic press at 150°C for 3 min. The specimens under compression were quenched in cold water (which should keep the crystallinity at a low level). The irradiations were done at T = 25°C, in the y-chamber-900 at BARC, Mumbai. 

Tensile tests on different polymer blends employ specimens of different sizes. To conduct a tensile test, a specimen capable of being gripped at both ends is required. The basic types of dumbbell configurations and dimensions recommended by ISO are illustrated in Eigure... 

German Standards DIN 53442 Constant amplitude of deformation Dumbbell shaped (tensile dumbbell) test specimens Variable frequency... 

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