ASTM F1801-97
(Test Method)Standard Practice for Corrosion Fatigue Testing of Metallic Implant Materials
Standard Practice for Corrosion Fatigue Testing of Metallic Implant Materials
SCOPE
1.1 This practice covers the procedure for performing corrosion fatigue tests to obtain S-N fatigue curves or statistically derived fatigue strength values, or both, for metallic implant materials.
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Designation: F 1801 – 97
Standard Practice for
Corrosion Fatigue Testing of Metallic Implant Materials
This standard is issued under the fixed designation F 1801; 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 F 601 Practice for Fluorescent Penetrant Inspection of Me-
tallic Surgical Implants
1.1 This practice covers the procedure for performing cor-
G 15 Terminology Relating to Corrosion and Corrosion
rosion fatigue tests to obtain S-N fatigue curves or statistically
Testing
derived fatigue strength values, or both, for metallic implant
2.2 ANSI Standard:
materials. This practice describes the testing of axially loaded
ANSI B46.1 Surface Texture
fatigue specimens subjected to a constant amplitude, periodic
forcing function in saline solution at 37°C and in air at room
3. Terminology
temperature. The environmental test method for implant mate-
3.1 Definitions:
rials may be adapted to other modes of fatigue loading such as
3.1.1 The terminology used in conjunction with this practice
bending or torsion. While this practice is not intended to apply
complies to Terminology E 1150 and Terminology G 15.
to fatigue tests on implantable components or devices, it does
3.2 Definitions of Terms Specific to This Standard:
provide guidelines for fatigue tests with standard specimens in
3.2.1 S-N curves—S-N curves (also known as Wöhler-
an environment related to physiological conditions.
curves) show the correlation between the applied stress (S) and
1.2 The values stated in SI units are to be regarded as the
the counted number (N) of cycles to failure.
standard.
1.3 This standard does not purport to address all of the
4. Significance and Use
safety concerns, if any, associated with its use. It is the
4.1 Implants, particularly orthopedic devices, are usually
responsibility of the user of this standard to establish appro-
exposed to dynamic forces. Thus, implant materials must have
priate safety and health practices and determine the applica-
high fatigue resistance in the physiological environment.
bility of regulatory limitations prior to use.
4.1.1 This practice provides a procedure for fatigue testing
in a simulated physiological environment. Axial tension-
2. Referenced Documents
tension fatigue tests in an environmental test chamber are
2.1 ASTM Standards:
2 recommended as a standard procedure. The axial fatigue
E 4 Practices for Force Verification of Testing Machines
loading shall comply with Practice E 466 and Practice E 467.
E 466 Practice for Conducting Force Controlled Constant
2 4.1.1.1 Bending and rotating bending beam fatigue tests or
Amplitude Axial Fatigue Tests of Metallic Materials
torsion tests may be performed in a similar environmental cell.
E 467 Practice for Verification of Constant Amplitude Dy-
4.1.2 This practice is intended to assess the fatigue and
namic Loads on Displacements in an Axial Load Fatigue
2 corrosion fatigue properties of materials that are employed or
Testing Machine
projected to be employed for implants. This practice is suitable
E 468 Practice for Presentation of Constant Amplitude Fa-
2 for studying the effects of different material treatments and
tigue Test Results for Metallic Materials
surface conditions on the fatigue behavior of implant materials.
E 739 Practice for Statistical Analysis of Linear or Linear-
2 The loading mode of the actual implants may be different from
ized Stress-Life ( S-N) or Strain-Life (e-N) Fatigue Data
that of this practice. Determining the fatigue behavior of
E 1012 Practice for Verification of Specimen Alignment
2 implants and implant components may require separate tests
Under Tensile Loading
that consider the specific design and loading mode.
E 1150 Definitions of Terms Relating to Fatigue
4.1.3 As a substitute for body fluid, 0.9 % saline solution is
F 86 Practice for Surface Preparation and Marking of Me-
recommended as a standard environment. One of the various
tallic Surgical Implants
Ringer’s solutions or another substitute for body fluid may also
be suitable for particular tests. However, these various solu-
tions may not give equal fatigue endurance results. The
This practice is under the jurisdiction of ASTM Committee F-4 on Medical and
Surgical Materials and Devices and is the direct responsibility of Subcommittee
F04.15 on Material Test Methods.
Current edition approved April 10, 1997. Published April 1998. Annual Book of ASTM Standards, Vol 03.02.
2 5
Annual Book of ASTM Standards, Vol 03.01. Available from American National Standards Institute, 11 W. 42nd St., 13th
Annual Book of ASTM Standards, Vol 13.01. Floor, New York, NY 10036.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
F 1801
chloride ions are the most critical constituent in these solutions 5.4.1 For corrosion fatigue testing, the machine shall be
in initiating corrosion fatigue. fitted with an environmental test cell surrounding the specimen
gauge section as shown in Fig. 1. A heated solution reservoir,
4.1.4 Because implants are manufactured from highly cor-
rosion resistant materials, no visible corrosion may be detect- a solution pump, and connecting lines for circulating the test
solution to the specimen surface are required. The solution
able by optical or electron-optical (SEM) means. Only a
decrease of fatigue strength in the high cyclic life range may be should be pumped from the reservoir through the system at a
rate that will maintain the temperature at 37 6 1°C in the test
noticeable. Therefore, S-N curves covering a broad fatigue
loading range should be generated in 0.9 % saline solution cell, but with flow rates low enough to avoid flow-dependent
phenomena like erosion-corrosion. The reservoir should have a
(Ringer’s solutions) and air. Comparison of fatigue curves
generated in air and saline solution may be the only way to minimum capacity of 1000 mL per square centimeter of
assess the effect of the saline environment. specimen surface exposed to the electrolyte. The reservoir shall
4.1.5 Where the fatigue behavior of a material system is be vented to the atmosphere. If the solution volume decreases,
the reservoir shall be replenished with distilled water to
already established, it may suffice to test modifications of the
material properties or surface condition in only a selected stress maintain the saline concentration, or the solution should be
exchanged. During long testing periods exchange of the
range.
solution is recommended. A typical environmental test cell for
4.1.6 The recommended loading frequency of one Hertz
axial fatigue testing is shown in Fig. 1.
corresponds to the frequency of weight-bearing during walk-
5.4.2 The test equipment should be manufactured of mate-
ing. For screening tests, higher test frequencies may be used;
rials or should be protected in a manner that corrosion is
but it must be realized that higher frequencies may affect the
avoided. In particular galvanic corrosion in conjunction with
results.
the test specimen and loosening of the specimen grips due to
4.1.7 Summary of Standard Conditions—For inter-
corrosion must be excluded.
laboratory comparisons the following conditions are consid-
ered as the standard test. Axial tension-tension tests with
6. Test Solution
cylindrical specimens in 37°C 0.9 % saline solution and air
6.1 To prepare the saline solution, dissolve9gof reagent-
under a loading frequency of 1Hz.
grade sodium chloride in distilled water and make up to 1000
mL. If other typical Ringer’s solutions are used, note the
5. Testing Equipment
solution in the report.
5.1 The mechanics of the testing machine should be ana-
lyzed to ensure that the machine is capable of maintaining the
7. Test Specimen
desired form and magnitude of loading for the duration of the
7.1 Specimen Design:
test (compare Practice E 4).
7.1.1 Axial Fatigue Testing:
5.2 Axial Fatigue Testing:
7.1.1.1 The design of the axial load fatigue test specimens
5.2.1 Tension-tension fatigue tests may be performed on one
should comply to Practice E 466 (see Fig. 2, Fig. 3, Fig. 4 and
of the following types of axial fatigue testing machines:
Fig. 5). For the dimensional proportions of flat specimens refer
5.2.1.1 Mechanical,
to the drawing in Practice E 468. The ratio of the test section
5.2.1.2 Electromechanical or magnetically driven, and
area to end section area will depend on the specimen geometry
5.2.1.3 Hydraulic or electrohydraulic.
and should comply to those standards. The test specimens
5.2.2 The machine shall have a load-monitoring system,
specified in Practice E 466 and Practice E 468 are designed so
such as a transducer mounted in series with the specimen. The
that fatigue failure should occur in the section with reduced
test loads shall be monitored continuously in the early stage of
diameter and not at the grip section.
the test and periodically thereafter, to ensure that the desired
7.1.1.2 For bending tests one may refer to the specimen
load is maintained. The magnitude of the varying loads,
configuration suggested in Practice E 466.
measured dynamically as described in Practice E 467 shall be
7.1.1.3 To calculate the load necessary to obtain the re-
maintained within an accuracy of less than or equal to 2 % of
quired stress, the cross-sectional area of the specimen test-
the extreme loads applied during testing.
section must be measured accurately. The dimensions should
5.3 Non Axial Fatigue Testing—Corrosion fatigue tests be measured to the nearest 0.03 mm (0.001 in.) for specimens
under loading conditions different from axial tension-tension
less than 5.00 mm thick (0.197 in.), and to the nearest 0.05 mm
may be requested. In such cases established experimental (0.002 in.) for specimens more than 5.00 mm thick (0.197 in.).
arrangements for bending, rotating bending beam, or torsional
Surfaces intended to be parallel and straight should be carefully
testing may replace the axial tension-tension mode. An envi- aligned.
ronmental test chamber is attached to the equipment and the
7.2 Specimen Dimensions—Consult Practice E 466 and
environmental tests are carried out under conditions as de- Practice E 468 for the dimensions of fatigue specimens for
scribed in this standard. Except for the mechanical testing
axial tension-tension loading (Fig. 2, Fig. 3, Fig. 4, and Fig. 5).
arrangements the conditions of this standard practice apply If bending specimens corresponding to the example of Practice
where possible. Reporting should follow Section 9 and should
F 466 are used, observe the suggested dimensions.
include all details where the testing deviates from the standard 7.3 Specimen Preparation:
procedure.
7.3.1 The method of surface preparation and the resulting
5.4 Environmental Chamber: surface condition of the test specimens are of great importance
F 1801
FIG. 1 Example for Environmental Chamber for Axial Corrosion Fatigue Testing
FIG. 2 Specimens With Tangentially Blending Fillets Between the Test Section and the Ends
FIG. 3 Specimens With a Continuous Radius Between Ends
because they influence the test results strongly. Standard compared should be prepared the same way. Mechanically
preparation shall consist of machining, grinding, or polishing, finished specimens must then be degreased in acetone, flushed
or all of these. A final mechanical polish is suggested to give a first with ethyl alcohol, then with distilled water, and finally
finish of 16 Min RA or less in accordance with ANSI B46.1. blown dry with warm air.
Alternatively a finish with 600 grit paper in the longitudinal 7.3.1.1 Surface passivation may be carried out where ap-
direction may be used. However, specimens that are to be propriate (compare Practice F 86).
F 1801
FIG. 4 Specimens With Tangentially Blending Fillets Between the Uniform Test Section and the Ends
FIG. 5 Specimens With Continuous Radius Between Ends
7.3.1.2 The surface preparation may be also exactly such as results due to the growth of a passive film. The elapsed time
used or intended to be used for surgical implants. A full account should thus be reported.
of the surface preparation should be given in the test protocol.
8. Procedure
7.3.2 All specimens used in any given series of experiments,
including comparison between air and liquid environment,
8.1 Test Set-Up:
should be prepared with the same geometry and by the same 8.1.1 Specimen grips must be designed so that alignment is
method to ensure comparable and reproducible results. Regard-
consistently good from one specimen to the next. Every effort
less of the machining, grinding or polishing method used, the should be made to prevent misalignment, due either to twist
final mechanical working direction should be approximately (rotation of the grips) or to a displacement in their axes of
parallel to the long axis of the specimen to avoid notch effects symmetry.
of surface grooves. 8.1.2 For axial fatigue testing, alignment should be verified
7.3.3 Fillet undercutting and the introduction of residual according to Practice E 4, Practice E 467, and Practice E 1012.
stresses into the specimen must be avoided. Both effects can be 8.2 Test Conditions:
caused by poor machining practice. Fillet undercutting can be 8.2.1 The environment shall be air at room temperature or
identified by visual inspection. The introduction of unwanted 0.9 weight % NaCl solution at 37 6 1°C. The pH should be
residual stresses can be avoided by careful control of the measured before and after the test is begun and should be
machining process. monitored in 24 h intervals, and at the end of the test.
7.3.4 Specimens that are subject to surface alterations under 8.2.1.1 The specimens should be exposed to the liquid
ambient conditions shall be protected appropriately, - prefer- environment 2 h prior to the start of the cyclic loading.
ably in an inert medium or exsiccator- to prevent surface 8.2.2 Mechanical test conditions for tension-tension, con-
change until beginning of the test. stant amplitude loading are shown in Fig. 6, with an “A” ratio
7.3.5 Visual inspections at a magnification of approximately equal to 0.9 or an “ R” value equal to 0.053. Other values for
203 shall be performed on all specimens. When such inspec- S and the A and R ratios may be used, but must be reported.
max
tions reveal potential defects, nondestructive dye penetrant, 8.2.2.1 The fatigue test should be carried out at a frequency
ultrasonic methods, or other sui
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