ASTM C730-98(2003)

Standard Test Method for Knoop Indentation Hardness of Glass

SIGNIFICANCE AND USE
The Knoop indentation hardness is one of many properties that is used to characterize glasses. Attempts have been made to relate Knoop indentation hardness to tensile strength, grinding speeds, and other hardness scales, but no generally accepted methods are available. Such conversions are limited in scope and should be used with caution, except for special cases where a reliable basis for the conversion has been obtained by comparison tests.
SCOPE
1.1 This test method covers the determination of the Knoop indentation hardness of glass and the verification of Knoop indentation hardness testing machines using standard glasses.
1.2 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 and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 09-Oct-1998
• ICS: 81.040.10 - Raw materials and raw glass
• Technical Committee: C14 - Glass and Glass Products
• Drafting Committee: C14.04 - Physical and Mechanical Properties

Relations

• Replaces: ASTM C730-98 - Standard Test Method for Knoop Indentation Hardness of Glass
• Effective Date: 10-Oct-1998
• Replaced By: ASTM C730-98(2008) - Standard Test Method for Knoop Indentation Hardness of Glass
• Effective Date: 01-Apr-2008
• Referred By: ASTM F1538-03(2017) - Standard Specification for Glass and Glass Ceramic Biomaterials for Implantation
• Effective Date: 10-Oct-1998
• Referred By: ASTM D116-86(2020) - Standard Test Methods for Vitrified Ceramic Materials for Electrical Applications
• Effective Date: 10-Oct-1998
• Referred By: ASTM C1326-13(2023) - Standard Test Method for Knoop Indentation Hardness of Advanced Ceramics
• Effective Date: 10-Oct-1998
• Referred By: ASTM F561-19 - Standard Practice for Retrieval and Analysis of Medical Devices, and Associated Tissues and Fluids
• Effective Date: 10-Oct-1998

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:C 730–98 (Reapproved 2003)
Standard Test Method for
Knoop Indentation Hardness of Glass
This standard is issued under the fixed designation C 730; 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.
1. Scope
B = included transverse edge angle (see Fig. 1).
1.1 This test method covers the determination of the Knoop 3.1.1.2 Knoop indentation hardness tests in glass are made
indentation hardness of glass and the verification of Knoop at a test load of 100 gf (0.1 kgf).
indentation hardness testing machines using standard glasses. 3.1.1.3 The rate of indenter motion prior to contact with the
1.2 This standard does not purport to address all of the specimen shall be 0.20 6 0.05 mm/min. This low rate of load
safety concerns, if any, associated with its use. It is the application tends to alleviate the effect of the magnitude of the
responsibility of the user of this standard to establish appro- load on Knoop hardness number.
priate safety and health practices and determine the applica- 3.1.1.4 The indenter should remain in contact with the
bility of regulatory limitations prior to use. specimen between 20 and 30 s. Most of the calibrated
machines that are used for making Knoop hardness tests are
2. Referenced Documents
dash-pot controlled and this dwell time is consistent with the
2.1 ASTM Standards: adjustment of the dash-pot to meet the loading rate standard.
E4 Practices for Force Verification of Testing Machines 3.1.1.5 Table 1 gives the Knoop hardness of several glasses
E 384 Test Method for Microindentation Hardness of Ma- as a function of load when the loading rate and dwell time are
terials held at the values recommended above.
3.1.2 Knoop indentation hardness test—an indentation
3. Terminology
hardness test using a calibrated machine to force a pointed,
3.1 Descriptions of Terms Specific to This Standard:
rhombic-base, pyramidal diamond indenter having specified
3.1.1 Knoop hardness number (KHN)—a number obtained face angles, under a predetermined load, into the surface of the
by dividing the applied load in kilograms-force by the pro-
material under test and to measure the long diagonal of the
jected area of the indentation in square millimetres, computed resulting impression after removal of the load.
from the measured long diagonal of the indentation and the
NOTE 1—A general description of the Knoop indentation hardness test
included edge angles of the diamond. It is assumed that the
is given in Test Method E 384. The present method differs from this
indentation is an imprint of the undeformed indenter.
description only in areas required by the special nature of glasses.
3.1.1.1 The Knoop hardness number (KHN) is computed as
4. Significance and Use
follows:
4.1 The Knoop indentation hardness is one of many prop-
KHN 5 ~P/A !5~P/d C ! (1)
p p
erties that is used to characterize glasses. Attempts have been
made to relate Knoop indentation hardness to tensile strength,
P = load, kgf,
grinding speeds, and other hardness scales, but no generally
A = projected area of the indentation, mm ,
p accepted methods are available. Such conversions are limited
d = length of the long diagonal of the indentation, mm,
in scope and should be used with caution, except for special
C = ⁄2 (cot A/2 3 tan B/2),
p
cases where a reliable basis for the conversion has been
A = included longitudinal edge angle (see Fig. 1), and
obtained by comparison tests.
5. Apparatus
This test method is under the jurisdiction of ASTM Committee C14 on Glass
5.1 Testing Machines:
and Glass Products and is the direct responsibility of Subcommittee C14.04 on
5.1.1 There are two general types of machines available for
Physical and Mechanical Properties.
Current edition approved Oct. 10, 1998. Published January 1999 . Originally making this test. One type is a self-contained unit built for this
e1
approved in 1972. Last previous edition approved in 1995 as C 730 – 85 (1995) .
purpose,andtheothertypeisanaccessoryavailabletoexisting
Annual Book of ASTM Standards, Vol 03.01.
Copyright ©ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA19428-2959, United States.
C 730–98 (2003)
FIG. 1 Knoop Indenter Showing Maximum Usable Dimension
A,B
TABLE 1 Knoop Hardness of NIST Standard and Other Glasses
GE
Laboratory NIST 710 NIST 711 NIST 715 Fused NIST 710 NIST 711 NIST 715 GE Fused Quartz
Quartz
25-gf Load 50-gf Load
A 486 411 589 614 497 394 575 559
C 594 450 537 415
D 479 426 505 541 478 380 538 501
E 521 415 608 620 497 392 574 586
F 498 414 568 643 484 403 567 577
G
Avg 516 423 567.5 609.5 499 397 563.5 556
Departure, max, 15 6 11 11 8 5 5 10
%
Range, max, % 22 9 18 17 12 9 7 15
100-gf Load 200-gf Load
A 475 387 558 554 468 380 550 523
C 478 387 554 593 468 371 544 530
D 452 368 521 473 433 360 529 474
E 490 396 544 530 488 372 546 510
F 467 381 538 524 457 367 524 502
G 481 388 550 558
Avg 474 384.5 544 539 463 370 539 508
Departure, max, 544 12 6337
%
Range, max, % 8 7 7 22 12 5 5 11
A
NIST 710—NIST standard soda-lime-silica glass (no longer available; NIST 710a may be substituted), NIST 711—NIST standard lead-silica glass. NIST 715—NIST
standard alkali-free aluminosilicate glass.
B
These data were obtained fromASTM round-robin testing.
microscopes. Usually, this second type is fitted on an inverted- 5.1.2 Design of the machine should be such that the loading
stage microscope. Good descriptions of the various machines rate, dwell time, and applied load can be standardized within
3,4
are available. the limits set forth in 3.1.1.2-3.1.1.4. It is an advantage to
eliminate the human element whenever possible by appropriate
Specifications for Knoop indenters can be found in the book Small, L.,
Hardness Theory and Practice (Part I: Practice), Service Diamond Tool Co., Ann Mott, B. W., Micro-Indentation Hardness Testing, Butterworth’s Scientific
Arbor, MI, 1960, pp. 241–243. Publications, London, 1956.
C 730–98 (2003)
machine design. The machine should be designed so that 0.1 gf. Other methods of verifying the load application are
vibrationsinducedatthebeginningofatestwillbedampedout given in PracticesE4.
by the time the indenter touches the sample. 7.2 Verification by Standard Glasses—Table 1 gives the
5.1.3 Thecalibrationofthebalancebeamshouldbechecked Knoop hardness of several standard glasses. Knoop hardness
monthly or as needed. Indentations in standard glasses are also measurement on a piece of one of these glasses that has been
used to check calibration when needed. ground and polished within the last 24 h should agree with the
5.2 Indenter: value in the table 65 %. Tests should be made using 100 gf.
5.2.1 The indenter shall meet the specifications for Knoop
8. Procedure
indenters. See Test Method E 384.
8.1 Specimen Placement—Place the specimen on the stage
5.2.2 Fig. 1 shows the indenter and its maximum usable
dimensions. The diagonals have an approximate ratio of 7:1, of the machine in such a way so that the specimen will not be
able to rock or shift during the measurement.
and the depth of the indentation is about ⁄30 the length of the
long diagonal. A perfect Knoop indenter has the following 8.2 Specimen Leveling:
8.2.1 The surface of the specimen being tested must lie in a
angles:
plane normal to the axis of the indenter. Fig. 2 shows an
5.2.2.1 Included longitudinal angle 172° 308 009.
5.2.2.2 Included transverse angle 130° 008 009. indentation as it will appear through the microscope with five
points labeled. To level the specimen, make a test indentation
5.2.3 The constant C for a perfect indenter is 0.07028 and
p
the specifications require a variation of not more than 1 percent using a 100-gf load.
8.2.2 The following minimum specifications must be met:
from this value.
5.3 Measuring Microscope—Themeasurementsystemshall
OA5OB65%
be so constructed that the length of the diagonals can be
OC5OD65%
determined with errors not exceed
...