D a Standard Tes Designation: D — 94 Reapproved Standard Test Methods for Rubber O-Rings1 This standard is issued under the xed designation D ; the number immediately following the designation indicates the year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscript epsilon e indicates an editorial change since the last revision or reapproval. This standard has been approved for use by agencies of the Department of Defense.
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D a Standard Tes Designation: D — 94 Reapproved Standard Test Methods for Rubber O-Rings1 This standard is issued under the xed designation D ; the number immediately following the designation indicates the year of original adoption or, in the case of revision, the year of last revision.
A number in parentheses indicates the year of last reapproval. A superscript epsilon e indicates an editorial change since the last revision or reapproval. This standard has been approved for use by agencies of the Department of Defense. Scope 1. The values given in parentheses are for information only. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
Referenced Documents 2. Current edition approved Sept. Published November Originally published as D — Last previous edition D — Terminology 3. The O-ring is used as a dynamic or static seal usually installed in a machined groove. Signicance and Use 4. General Methods 5. Test Conditions 6. The specimens to be tested shall be kept in this room for a minimum of 30 min previous to the time of testing. For referee tests the minimum time for conditioning shall be 16 h. In cases where this temperature cannot be obtained, the actual temperature shall be reported.
Dimensional Measurements 7. In case of referee tests, both laboratories shall use the same spring force. An average reading shall be used for calculation. Tension Testing 8. Grips for testing rings shall consist of ball-bearing spools at least 9 mm 0. Stresses within the specimen shall be minimized by 1 rotating one spool one full revolution for each mm 6. Grips for testing straight specimens may be of any type provided breaks do not occur in a portion of the specimen that has been at any time in contact with the grips.
For specimens smaller than 25 mm 1 in. For these cases a specimen cut from a ring shall be employed. Set the machine for a speed of 6 50 mm 20 6 2 in. If a recorder is not used, note the spool center-to-center distance continually by means of a suitable scale. The stressed inside circumference, L, is equal to twice the distance between spools plus the circumference of one spool. Record the breaking force value, F, at the elongation specied for tensile stress and at the time of rupture.
Measure the center-to-center distance between the spools at rupture to the nearest 2. Follow the procedure described in 8. Discard results for any specimen that breaks at a point that has at any time contacted the grip, and test an additional specimen. A suitable extensiometer may be employed for elongation determination. Compression Set Test This can be done by employing shim stock of various thickness.
Amm 2-in. On smaller O-rings, a section of approximately 3 mm 18 in. NOTE 2—Testing a whole O-ring for compression set is always avoided because air trapped inside the O-ring results in a different set of conditions on the inside and outside surface of the specimen. Tension Set Test 9. At the end of this period release the specimen and allow it to recover for 10 min. At the end of this recovery period, measure the inside diameter with a step gage reference in 7. Close the plates, employing a sufficient number of bolts to prevent deection upon heating.
At the end of the heating period, release the plates as soon as possible and allow the specimens to cool to room temperature under the conditions described in Test Methods D Compression Set in Liquids The container needs to be large enough to hold the plates and withstand the vapor pressure of the liquid at test temperature. Measurement and reporting are the same except the type of liquid is listed in the report.
Low-Temperature Test If a greater or lesser stretch is used, report the actual stretch. Relative Density Test The minimum mass of the specimen shall be 0.
In the case of very small O-rings, two or more pieces may be used as the specimen to accomplish this total minimum mass. The surface tension on the suspending wire is critical; this wire should be of the smallest diameter corrosion-resistant wire that will support the specimen weight. This surface tension on the wire and the elimination of small air bubbles on the surface of the specimen can be reduced by the addition of a few drops of wetting agent to the water in the weighing beaker.
If the above procedure is used, operators should be aware that the test tube specied in Test Method D may not be adequate and alternative containers and heating system may be required. NOTE 5—A problem that can occur with large whole specimens is cracking at the point of maximum bend at the upper or lower portion, or both, of the specimen. When cracking is observed upon removal from the oil, or when breaks occur at these points during tension tests, a retest shall be made on segments cut from an O-ring.
This may be accomplished by using two or more pieces for the specimen in the case of very small O-rings see Note 2. Heat Aging Test The report shall state which method was employed.
Hardness Test With certain precautions and proper technique the following test methods may be employed. It is recommended that for O-rings of crosssectional thickness less than 6 mm 0. Use caution 1 to center the specimen so the point of the indentor reads on the center or thickest portion, and 2 to apply just enough pressure to bring the base of the instrument in close contact with the specimen without compressing the specimen.
A holding xture may be employed which will provide 1 limitation of travel of the durometer head and 2 a selfcentering feature to eliminate alignment difficulties. A xture that accomplishes these requirements is shown in Fig. Any xture or design principle that will accomplish the stipulations of 1 and 2 above may be employed. If hardness measurements are made with this instrument on O-rings of smaller cross section, the values obtained may be different from those obtained on a standard specimen.
Fixtures as shown in For O-rings of less than 3-mm 0. This is to increase the total thickness to greater than the length of the indentor point.
The total depth of the groove must be adjusted to a depth that will reduce within 62 the hardness of a standard specimen of the same material. Immersion Test The detailed procedure for O-rings, outlined in this section however, shall take precedence in case of conict.
For sizes too large in circumference to insert as described, the O-ring shall be cut into segments. The specimen shall be a segment 90 6 2 mm 3. All tests for hardness, tension, elongation, and volume change shall be made in triplicate. The same three specimens may be used for all tests with hardness and volume determinations made prior to stress-strain tests.
In the case of liquids that are volatile at room temperature, the specimen must be quickly placed back into the test liquid after hardness and volume test and prior to tension testing. For whole O-rings 6 mm 0. For cross-section sizes less than 4 mm 0. Add enough liquid to cover the specimens to a depth of 25 mm 1.
NOTE 4—For liquid mixtures, where the volume percent of the most minor constituent is known, the liquid volume of that constituent shall be This test method is recommended for determining the hardness of O-rings with a cross-sectional thickness of 6 mm 0. NOTE 7—Values obtained with the micro hardness tester may differ from durometer values due to the difference in methods.
The surface effect from aging or curing is more pronounced with the micro tester. O-Ring Mold Shrinkage Test The specimens are then measured for inside diameter and cross-sectional thickness within 0. Great care must be taken in both the manufacture and maintenance of this mold. Care must be taken not to dent, scratch, or otherwise damage the cavity.
The mold cavities must be kept clean. The surface nish must be the best commercial practice. This gives the width of the cross section. Check each half for depth. The total of the two halves gives the total depth of the cavity.
ASTM D1414 Rubber O-Ring Tensile Strength Testing
ASTM D describes several procedures and tests for determining physical and mechanical properties of o-rings; both when they are new and based on aging. O-rings are typically used as seals. They are usually assembled with some tension around a shaft or within an o-ring groove to facilitate manufacturing by precluding bulging or bunching during assembly. TestResources universal test machines and special o-ring fixturing can be used to perform the tests to determine the tensile strength aspects of o-rings, in strict accordance with the details of ASTM D ASTM D calls for tensile tests of o-rings as loops. The o-ring specimen is to be looped around two cylinders that are sized appropriately for the diameter of the o-ring.
ASTM D1414 TESTING FIXTURE
This simple circular elastomer design is interesting since O-rings are used in so many sealing applications. The versatility of an O-ring allows it to function in multiple modalities. Static rubber rings are used for gas sealing and specialized applications including vacuums. Rubber bands are also commonly tested under this standard to test their tensile strength and elongation characteristics. Rings under tension in high temperature environments can experience something called the Gough-Joule effect where they tend to contract in this scenario. Alongside Gough-Joule, quality managers may age their rubber specimens inside an environmental conditioning chamber to test other parameters. Cracking, flaking, general brittleness, and other characteristics can appear in the rubber O-rings when they are exposed to temperature cycles and solar radiation.
ASTM D1414 Tension Testing and Tension Set of Rubber O-Rings
Standard Test Methods for Rubber O-Rings