Designation standards: ASTM D785-23 Publication date standards: 15.3.2023 SKU: NS-1140820 The number of pages: 6 Approximate weight : 18 g (0.04 lbs) Country: American technical standard Category:Technical standards ASTM
4.1?A
Rockwell hardness number is a number derived from the net increase
in depth impression as the load on an indenter is increased from a
fixed minor load to a major load and then returned to a minor load
(Procedure A). A Rockwell alpha (?) hardness number represents the
maximum possible remaining travel of a short-stroke machine from
the net depth of impression, as the load on the indenter is
increased from a fixed minor load to a major load (Procedure B).
Indenters are round steel balls of specific diameters. Rockwell
hardness numbers are always quoted with a scale symbol representing
the indenter size, load, and dial scale used. This test method is
based on Test Methods E18.
Procedure A (Section 11) yields the indentation of the specimen
remaining 15 s after a given major load is released to a standard
10-kg minor load. Procedure B (Section 12) yields the indentation
of the indenter into the specimen after a 15-s application of the
major load while the load is still applied. Each Rockwell scale
division represents 0.002-mm (0.00008-in.) vertical movement of the
indenter. In practice, the Rockwell hardness number is derived from
the following relationship:
4.2?A
Rockwell hardness number is directly related to the indentation
hardness of a plastic material, with the higher the reading the
harder the material. An ? hardness number is equal to 150 minus the
instrument reading. Due to a short overlap of Rockwell hardness
scales by Procedure A, two different dial readings on different
scales may be obtained on the same material, both of which may be
technically correct.
4.3?For
certain types of materials having creep and recovery, the time
factors involved in applications of major and minor loads have a
considerable effect on the results of the measurements.
4.4?The
results obtained by this test method are not generally considered a
measure of the abrasion or wear resistance of the plastic materials
in question.
4.5?Indentation hardness is used as an
indication of cure of some thermosetting materials at room
temperature. Generally, an uncured specimen has a hardness reading
below normal.
4.6?Each
Rockwell hardness scale in Table
1 is an extension of the proceeding less severe scale, and
while there is some overlap between adjacent scales, a correlation
table is not desirable. Readings on one material may be
satisfactory for such a table, but there is no guarantee that other
plastic materials will give corresponding readings because of
differences in elasticity, creep, and shear characteristics.
4.7?Before proceeding with this test method,
reference should be made to the specification of the material being
tested. Any test specimen preparation, conditioning, dimensions,
and/or testing parameters covered in the materials specification
shall take precedence over those mentioned in this test method. If
there are no material specifications, then the default conditions
apply.
1. Scope
1.1?This
test method covers two procedures for testing the indention
hardness of plastics and related plastic electrical insulating
materials by means of the Rockwell hardness tester.
1.2?The
values stated in SI units are to be regarded as standard. The
values given in parentheses are for information only.
1.3?This standard does not purport to
address all of the safety concerns, if any, associated with its
use. It is the responsibility of the user of this standard to
establish appropriate safety, health, and environmental practices
and determine the applicability of regulatory limitations prior to
use.
Note 1:?This test method and ISO 2039-2 are equivalent.
Procedure A of this test method is equivalent to the test method in
the main body of ISO 2039-2. Procedure B of this test method is
equivalent to the test method in the integral annex part of ISO
2039-2.
1.4?This international standard was
developed in accordance with internationally recognized principles
on standardization established in the Decision on Principles for
the Development of International Standards, Guides and
Recommendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
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