Tensile Tests of Vulcanized Rubber at High Speed

1931 ◽  
Vol 4 (2) ◽  
pp. 147-155 ◽  
Author(s):  
A. van Rossem ◽  
H. B. Beverdam
Keyword(s):  
Tensile Strength ◽  
High Speed ◽  
Strain Curve ◽  
Tensile Tests ◽  
Point Of View ◽  
General Tendency ◽  
Technical Literature ◽  
Rubber Ring ◽  
Vulcanized Rubber ◽  
Increase With Increase

Abstract The types of apparatus most frequently used for elongation tests of rubber have only a slow speed. Thus the maximum rate of elongation of the Schopper dynamometer is 120 cm. per minute and in ordinary practice 60 cm. per minute is the speed used. The normal rate ordinarily used in America with the Scott apparatus is 20 in. per minute. On the other hand, it has been found by experience that slightly vulcanized rubber which, on the Schopper machine, gives very good values of tensile strength and resilient energy at rupture, even excellent values, is on the contrary brittle when stretched very rapidly by hand and breaks with a very low elongation. Consequently it is of interest, chiefly from the point of view of a study of rubber, to carry out elongation tests at high speed. As is easily seen from the technical literature, this problem has been neglected. At the Bureau of Standards the influence of the rate of elongation on the results of tensile tests has already been studied, but the rate varied only between five and forty-five inches per minute. Briefly, the results of this study seem to indicate a general tendency for the elongation and resistance to extension to increase with increase in speed of elongation. Hauser and Rosbaud have also made tests on the influence of the speed of elongation, but their tests were on raw rubber and at extremely slow speeds. As for the brittleness which appears at high rates of elongation, only very casual references are to be found in the literature. By a study of gas black Park has proved that the maximum physical properties found by hand-testing do not agree with the maximum obtained with the Scott dynamometer. Recently Wright5 has also pointed out the “shortness” of vulcanized rubber and has emphasized the importance of tensile tests at high speed. Unfortunately, we did not have at our disposal any apparatus which permitted recording the stress-strain curve at high speed and reading the ultimate elongation and tensile strength. Accordingly, we used in our tests a Charpy ram pendulum, belonging to the section of metallography of the Polytechnical School of Delft. It is known that this apparatus as well as others similar to it are used in determining the energy necessary to rupture various materials. This apparatus was changed and on the two supporting surfaces were attached two pins in such a way that a rubber ring could be placed there without elongation as seen in Fig. 1. This ring was then broken with the ram pendulum. The greater the energy expended in breaking the ring, the less the pendulum rises. As is known, the energy expended in breaking the ring is calculated by the aid of a numerical table by comparison with an oscillation without rupture of the ring. For each type of vulcanizate, at least six rings were tested by this pendulum method. In addition some rings from the same vulcanizates were given the usual tensile test on the Schopper dynamometer. From the resulting curve the energy of rupture can be determined in kilograms in the usual manner by the aid of a planimeter.

Measurement of the Absorption of Oxygen by Vulcanized Rubber in Air

1939 ◽  
Vol 12 (2) ◽  
pp. 261-268
Author(s):  
A. G. Milligan ◽  
J. E. Shaw
Keyword(s):  
Tensile Strength ◽  
Physical Properties ◽  
Tensile Tests ◽  
Direct Measure ◽  
Mean Values ◽  
Reasonable Time ◽  
Aging Period ◽  
Vulcanized Rubber ◽  
Rubber Compounds ◽  
Made In

Abstract It is generally agreed that oxidation is the controlling factor in the decay of rubber compounds. Measurements of the decay of any physical properties—commonly tensile strength—can be made in a convenient time only if the decay is greatly accelerated, and there is always a grave doubt about the equality of the acceleration for different materials. There is also a difficulty in selecting a universally suitable aging period, since the decay of the physical properties is not linear. A direct measure of the rate of oxidation is, in our view, more fundamental and less equivocal. It can, moreover, be made in a reasonable time at a temperature not far removed from service temperatures. Again, whereas tensile tests require several samples of each point in the timecurve to give acceptable mean values, here a single sample suffices for the whole test, and this sample can be simply prepared from a specimen of any form by rasping. The merits and simplicity of the method should commend it to rubber technologists.

Have Mechanical Stresses Any Effect on the Oxidizability of Rubber?

1949 ◽  
Vol 22 (3) ◽  
pp. 690-698
Author(s):  
Jean Le Bras ◽  
André Salvetti
Keyword(s):  
Tensile Strength ◽  
Infrared Absorption ◽  
Vibration Frequency ◽  
Molecular State ◽  
Mechanical Stresses ◽  
Point Of View ◽  
Negative Evidence ◽  
Linear Extensions ◽  
Vulcanized Rubber ◽  
Appreciable Increase

Abstract Subjection of rubber to mechanical stresses, whether static or dynamic, does not change its inherent oxidizability, at least within the limits of stress which were applied in the experiments described. Perhaps changes would have been observed if the range of stresses had been reached where crystallization phenomena became pronounced, for sufficient distortion or change in molecular state might have a certain influence on the oxidizability. For example, Williams and Dale, in a study of infrared absorption by rubber, pointed out that linear extensions greater than 400 per cent are necessary to bring about any appreciable increase in the vibration frequency of the C — C groups. However, the elongations employed in the present work cover, in general, the range of deformations to which vulcanized rubber products are normally subjected in service; hence there seemed to be no advantage in attempting to carry out the tests under more severe conditions. From another point of view, it would appear of interest to record the following observation. In all the oxidation tests under dynamic conditions, the test-specimens broke either by being cut through near the points where they were fastened, at random points where rupture began, or when the tensile strength was lowered too much by oxidation; but in no case was actual flexcracking observed. Although this is only negative evidence, the view of Eccher that ozone is indispensable to the formation of cracking would appear to be confirmed.

Subultimate Prestrain and Aging in Mild Steel

1965 ◽  
Vol 87 (2) ◽  
pp. 319-324 ◽  
Author(s):  
D. K. Felbeck ◽  
W. G. Gibbons ◽  
W. G. Ovens
Keyword(s):  
Mild Steel ◽  
High Speed ◽  
Strain Curve ◽  
Local Stress ◽  
Tensile Tests ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Limited Region ◽  
Small Increments ◽  
Necessary And Sufficient

Room-temperature tensile straining of mild steel followed by aging at 350 F causes return of the upper yield and a raising of the stress-strain curve. Tensile tests on a special rimmed steel of low Mn/C ratio show not only the expected raising of the stress-strain curve, but raising by an additional amount when several small increments of strain are each followed by aging at moderate temperatures. Longitudinal tensile prestrain by rolling gives substantially the same results. Tests of specimens prestrained in a limited region by impact or in slow tension and aged indicate that embrittlement of the whole specimen may result. The combined theories of Griffith and Orowan, plus an extension of the Ludwik triaxiality concept, can provide a consistent description of the local stress and average stress (energy) criteria that are necessary and sufficient for high-speed low-energy fracture to occur.

Ultra-Speed Tensile of Rubber and Synthetic Elastomers

1951 ◽  
Vol 24 (1) ◽  
pp. 144-160
Author(s):  
D. S. Villars
Keyword(s):  
Tensile Strength ◽  
High Speed ◽  
Relaxation Times ◽  
Strain Curve ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Elongation At Break ◽  
Different Types ◽  
Speed Up ◽  
Pass Through

Abstract A high speed stress-strain machine has been developed which is capable of recording the stress-strain curve of elastomers at elongation rates up to 270 per cent/msec. Data are reported on two series of gum and tread stocks of Hevea and of the synthetic elastomers, GR-S, Hycar-OR, Butyl, Perbunan, and Neoprene-GN. The second (elastomer) series was also run at 150° C. In general, stress-strain curves fall into two classes. Stocks of elastomers which are known to crystallize on stretching tend to show tensile strengths which decrease with increasing speed up to about 10 per cent/msec, pass through a minimum, and rise more or less drastically to values 100 per cent (or more) greater than the Scott tensile strength. Elastomers which do not crystallize on stretching tend to show a steady rise in tensile strength with increasing speed. Elongation at break curves show a maximum with crystallizing stocks and no maximum with noncrystallizing stocks. The shape of the modulus vs. speed curves is accounted for on the hypothesis of different types of slipping bonds with different characteristic relaxation times. The shift of curves for tread stocks with temperature allows the estimation of a heat of activation of slippage. This comes out to be of the order of 3 kg.-cal.

Resilient Energy

1943 ◽  
Vol 16 (3) ◽  
pp. 591-608
Author(s):  
E. C. B. Bott
Keyword(s):  
Tensile Strength ◽  
Finite Differences ◽  
Practical Method ◽  
Cross Sectional Area ◽  
Point Of View ◽  
Sectional Area ◽  
Cross Sectional ◽  
Vulcanized Rubber ◽  
Reinforcing Agent ◽  
Strength Based

Abstract 1. The tensile strength of vulcanized rubber may be expressed in terms of its elongation by means of the calculus of finite differences. 2. This expression for tensile strength, based on the theoretical cross-sectional area, gives an expression for the tensile strength based on the original cross-sectional area when the former quantity is divided by the factor (E + 1), E being the elongation. 3. The expression for tensile strength based on the original cross-sectional area is integrated with respect to the elongation to give the resilient energy. 4. The trapezoidal rule has proved itself to be superior to the calculus of finite differences as a practical method of obtaining the resilient energy. 5. The total resilient energies are plotted on graphs against the percentage by volume of reinforcing agent or filler. Tangents drawn at any desired point corresponding to a certain percentage of filler give values for the partial resilient energies of base mix and of filler by the method of tangent intercepts. 6. The expressions for tensile strength are composed of one, two or three functions ; the number of functions is, in general, inversely proportional to the percentage of the filler in the vulcanizate. 7. The expressions for tensile strength and for resilient energies have no significance regarding the structure of vulcanized rubber; they have been evolved from the point of view of usefulness for evaluating compounds. 8. The values of the partial resilient energies of base mix and of filler obtained by the method of tangent intercepts have no physical meaning; they are a means of calculating the total resilient energy of a sample of vulcanized rubber.

X-Ray Investigation of the Crystallization of Vulcanized Rubber on Stretching

1948 ◽  
Vol 21 (3) ◽  
pp. 621-626 ◽  
Author(s):  
B. V. Lukin ◽  
V. I. Kasatochkin
Keyword(s):  
Tensile Strength ◽  
Crystalline Phase ◽  
Oxidative Degradation ◽  
Point Of View ◽  
Crystal Formation ◽  
Stress Strain ◽  
X Ray ◽  
Vulcanized Rubber ◽  
Cross Links ◽  
Ray Methods

Abstract 1. x-Ray methods have been used to investigate the amount of crystalline phase in stretched samples as a function of the vulcanization time. 2. Curves relating the percentage of crystalline phase to the vulcanization time have sharply defined maxima. 3. A comparison of the curves relating tensile strength to vulcanization time with the curves of crystal formation shows their analogous character, the position of the maxima approximately corresponding to one and the same vulcanization time. 4. The position of the maxima on the curves of crystal formation is not related to the degree of stretching. 5. The effect of accelerators is to shift the maximum on the curve of crystal formation to the region of short vulcanization times and to increase the percentage of crystalline phase. 6. The curves of crystal formation and of tensile strength, and thus the behavior of the stress-strain curves for various vulcanization times, is interpreted from the point of view of the existence of two processes—the process of forming a network of cross-links by the interaction of rubber with sulfur, and the process of oxidative degradation of the rubber.

The Effect of Solvents on the Stress-Strain Curve of Vulcanized Rubber

1930 ◽  
Vol 3 (1) ◽  
pp. 19-21 ◽  
Author(s):  
H. A. Tiltman ◽  
B. D. Porritt
Keyword(s):  
Tensile Strength ◽  
Marked Effect ◽  
Strain Curve ◽  
Theoretical Interest ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Cohesive Forces ◽  
Effect Of Solvents ◽  
Vulcanized Rubber ◽  
Permanent Effect

Abstract (1) The results indicate that the rigidity of a piece of vulcanized rubber is considerably reduced by the absorption of small amounts of a solvent; thus, at a strain of 6 ( = 600 per cent elongation) the absorption of 5 per cent by weight ( = 8 per cent by volume) of benzene lowers the rigidity by 21 per cent. (2) The greatest effect is produced by the first 20 or 30 per cent (by weight) of absorbed benzene, further absorption having a less marked effect on the stress-strain curve. (3) The absorption of solvent seems to have very little effect on the breaking elongation, although the tensile strength is considerably lowered. This conclusion, however, is probably no longer true in the case of rubber swollen by immersion in liquid, where the absorption is very much greater than in the present tests. (4) Absorption of solvent followed by complete drying appears to produce a slight, but technically negligible, permanent effect on the stress-strain curve. It is evident from these results that when it is necessary to use solvents, either in the process of manufacture or the after-treatment of rubber products, these should be selected as free as possible from high-boiling constituents liable to be permanently retained by the rubber with consequent detriment to its strength. A conclusion of some theoretical interest is that since all the stresses in the present investigation were calculated on the dimensions of the original dry rubber, the low rigidity of swollen rubber cannot be ascribed simply to the “dilution” of the rubber by the absorbed liquid, but must be due to a loosening of the cohesive forces between the ultimate particles of the material.

scholarly journals Mechanical Study of Some Polystyrene composites modified with adding inorganic fillers

2022 ◽  
Vol 9 (12) ◽  
pp. 711-714
Author(s):  
HM Shaker
Keyword(s):  
Tensile Strength ◽  
Zinc Oxide ◽  
Strain Curve ◽  
Weight Percent ◽  
Elongation At Break ◽  
Micro Particles ◽  
Increase With Increase ◽  
Mechanical Study ◽  
Measured Stress ◽  
Solution Casting Method

Polystyrene-Zinc oxide microcomposites have been prepared for Mechanical study. The Zinc oxide micro particles were added to polystyrene by different concentrations that are (3, 5, and 7) by weight percent of the pure polymeric matrix. Solution casting method is used for preparing such composites. Different Mechanical properties of (PS-ZnO) microcomposites have been measured. Stress strain Curve is investigated for both pure Polystyrene and its composites with zinc oxide. The results showed that the Tensile Strength varies with the increase of ZnO in a specific way. Elongation at break of (PS-ZnO) micro composites increase with increase the content of (ZnO). An explanation of such behavior in tensile strength as well as Elongation at break has been discussed.

Aging of Rubber in the Oxygen Bomb at Room Temperature

1943 ◽  
Vol 16 (4) ◽  
pp. 924-925
Author(s):  
J. R. Scott
Keyword(s):  
Tensile Strength ◽  
Oxygen Concentration ◽  
Room Temperature ◽  
Accelerated Aging ◽  
Natural Aging ◽  
Tensile Tests ◽  
Oxygen Bomb ◽  
Vulcanized Rubber ◽  
Accelerated Aging Test ◽  
Aging Test

Abstract The work described below was carried out as a first step in determining whether an oxygen-bomb test at room temperature could be used as an accelerated aging test for unvulcanized rubber compositions, e.g., as used on surgical and adhesive plasters and for combining shoe fabrics, because a high-temperature test is unsatisfactory in such cases, owing to the melting of the compositions. The only infallible way of assessing the value of an accelerated test for such compositions is by comparison with natural aging, but as this is a very lengthy process and as the deterioration is difficult to measure quantitatively, it was decided to make preliminary tests on the effect of high oxygen concentration at room temperature by using vulcanized rubber. Although the results proved to be negative so far as the original purpose of the work was concerned, it is considered of interest to place them on record in view of the prominence given in some papers on aging to the relationship between oxygen concentration and rate of oxidation and deterioration of rubber. A mix composed of rubber 100, sulfur 3, zinc oxide 5, stearic acid 1, and diphenylguanidine 0.75, was vulcanized for 30 minutes at 153° C. Tensile tests, using standard ring-specimens and the Schopper machine, were made on unaged specimens and on specimens that had been aged (1) in an oxygen bomb at 300 lb. per sq. in. oxygen pressure and at room temperature (about 10° C), (2) in a Geer oven at 70° C. Four rings were used for each test, the tensile strength and breaking elongation figures quoted being the average for the two rings giving the highest tensile strength, and the figures for the elongations at constant loads the average of all four rings.

scholarly journals Influence of Hydrostatic Extrusion on the Mechanical Properties of the Model Al-Mg Alloys

2021 ◽  
Author(s):  
Aleksandra Towarek ◽  
Wojciech Jurczak ◽  
Joanna Zdunek ◽  
Mariusz Kulczyk ◽  
Jarosław Mizera
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Tensile Strength ◽  
Microstructural Analysis ◽  
Tensile Tests ◽  
Hydrostatic Extrusion ◽  
Microstructure Formation ◽  
Initial State ◽  
Degree Of Deformation ◽  
Al Mg Alloys

AbstractTwo model aluminium-magnesium alloys, containing 3 and 7.5 wt.% of Mg, were subjected to plastic deformation by means of hydrostatic extrusion (HE). Two degrees of deformation were imposed by two subsequent reductions of the diameter. Microstructural analysis and tensile tests of the materials in the initial state and after deformation were performed. For both materials, HE extrusion resulted in the deformation of the microstructure—formation of the un-equilibrium grain boundaries and partition of the grains. What is more, HE resulted in a significant increase of tensile strength and decrease of the elongation, mostly after the first degree of deformation.

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