ASM Metals HandBook Vol. 8 - Mechanical Testing and Evaluation
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36. R. Charles and S. Prochazka, “Stress Rupture Testing of Silicon Carbide at Very High Temperatures,”
Technical Report 77CRD035, General Electric Co., March 1977
37. T.P. Dabbs, C.J. Fairbanks, and B.R. Lawn, Subthreshold Indentation Flaws in the Study of Fatigue
Properties of Ultrahigh-Strength Glass, Methods for Assessing the Structural Reliability of Brittle
Materials, STP 844, S.W. Freiman and C.M. Hudson, Ed., ASTM, 1984, p 142–153
38. S.R. Choi, J.E. Ritter, and K. Jakus, Failure of Glass with Subthreshold Flaws, J. Am. Ceram. Soc., Vol
72 (No. 2), 1990, p 268–274
39. M. Adams and G. Sines, A Statistical, Micromechanical Theory of the Compressive Strength of Brittle
Materials, J. Am. Ceram. Soc., Vol 61 (No. 3–4), 1978, p 126–131
40. M. Adams and G. Sines, Crack Extension from Flaws in a Brittle Material Subjected to Compression,
Technophysics, Vol 49, 1978, p 97–118
41. C.A. Tracy, A Compression Test for High Strength Ceramics, J. Test. Eval., Vol 15 (No. 1), 1987, p 14–
19
42. C.A. Tracy, M. Slavin, and D. Viechnicki, Ceramic Fracture during Ballistic Impact, Advances in
Ceramics, Vol 22, Fractography of Glasses and Ceramics, 1988, p 319–333
43. J. Lankford, Compressive Strength and Microplasticity in Polycrystalline Alumina, J. Mater. Sci., Vol
12, 1977, p 791–796
44. J. Lankford, Uniaxial Compressive Damage in α-SiC at Low Homologous Temperatures, J. Am. Ceram.
Soc., Vol 62 (No. 5–6), 1979, p 310–312
45. M. Adams and G. Sines, Methods for Determining the Strength of Brittle Materials in Compressive
Stress States, J. Test. Eval., Vol 4 (No. 6), 1976, p 383–396
Mechanical Testing of Polymers and Ceramics
High-Temperature Strength Tests
Fast Fracture. The overwhelming majority of high-temperature strength tests of isotropic ceramics have been
done in four-point loading. Standards are being developed that are extensions of the low-temperature
procedures. A variety of furnaces and environments can be used, with temperatures typically up to 1600 °C
(2910 °F) in air and with some vacuum and inert gas systems at temperatures up to 2000 °C (3630 °F). The test
fixtures themselves must be dense ceramics, usually fairly pure forms of silicon carbide, although occasionally
alumina fixtures are used at lower temperatures, and graphite fixtures are used in inert atmospheres.
The upsurge in tensile testing has been driven in large part by new programs to use ceramics at high
temperatures in heat engines. As a result, most tensile test systems have been designed with high temperatures
in mind (Ref 23, 24, 25, 26). The gripping schemes must be not only elaborate enough to avoid stress
concentrators and to align very precisely, but also capable of being used in conjunction with furnaces. Most
tension systems use cold grips with relatively long (for ceramics) specimens of 150 mm (6 in.). Such systems
are commercially available, and extensive testing is underway in the United States, Japan, and Germany.
Multiaxial strength tests are extremely rare at high temperatures and usually based on ring-on-ring loaded disks.
The limited results for these experiments suggest that the high-temperature equibiaxial strength is 15 to 30%
less than uniaxial strengths (Ref 46, 47).
Creep and Stress Rupture. Direct tension tests of long duration are becoming more common, but most test
systems are complicated and expensive. They typically are derivatives of the fast-fracture systems, using cold
grips and long specimens (Ref 24, 25, 26, 27). Most experiments are limited to a 1000 h duration. An
economical alternative test system with hot grips and a “flat dog bone” specimen configuration has been
developed and is optimized for long-duration, low-stress creep experiments (Ref 23). A short tapered specimen
for similar experiments has been successfully used (Ref 26).
Strains must be measured with specialized extensometers, because ceramic strains are extremely small and
resolutions of 1 μm (0.04 mil) must be recorded over the course of hours. The extensometers in use today are
either delicate mechanical units (Ref 26) or lasers that monitor distance between flags (Ref 23) or diffract when
passed through a narrow slit between two flags (Ref 27).
Most investigators have at some time resorted to using flexure testing, which is much less expensive and allows
strains to be readily measured from the curvature in the specimen. In a sense, the bend specimen acts as a
deflection magnifier, because the deflection associated with the integrated curvature is larger and easier to
measure than the extension of a tension specimen. The drawback of the method is that a stress gradient in the
specimen changes dramatically as the material creeps. Flexural creep testing is not a constant stress test. The
strain is measured from the curvature, but this too must be adjusted for the proper constitutive equation.
In recent years, it has become painfully evident that flexural creep data can be misleading or even erroneous, a
consequence of the stress gradient, the relaxation of such gradient, and the complicated constitutive equations
that apply to ceramics. Analytical attempts to deconvolute the tensile and compressive creep behavior are
usually tainted or compromised by the assumptions that have to be made about the constitutive equations. It is
far more rational to conduct direct tension or compression experiments for careful creep work. Flexure tests can
be used for qualitative assessments of conditions for the onset of creep.
Stress-rupture data require extremely long-duration experiments. Some static-fatigue phenomena occur in the
absence of bulk creep deformation, and flexure testing may be eminently suitable in these cases.
References cited in this section
23. D.F. Carroll, S.M. Wiederhorn, and D.E. Roberts, Technique for Tensile Creep Testing of Ceramics, J.
Am. Ceram. Soc., Vol 72 (No. 9), 1989, p 1610–1614
24. T. Soma, M. Matsui, and I. Oda, Tensile Strength of a Sintered Silicon Nitride, Nonoxide Technical and
Engineering Ceramics, Proc. of the International Conf., (Limerick, Ireland), S. Hampshire, Ed., 1985, p
361–374
25. T. Ohji, Towards Routine Tensile Testing, Int. J. High Technol. Ceram., Vol 4, 1988, p 211–225
26. G. Grathwohl, Current Testing Methods—A Critical Assessment, Int. J. High Technol. Ceram., Vol 4,
1988, p 123–142
27. K.C. Liu, H. Pih, and D.W. Voorhes, Uniaxial Tensile Strain Measurement for Ceramic Testing at
Elevated Temperatures: Requirements, Problems, and Solutions, Int. J. High Technol. Ceram., Vol 4,
1988, p 69–87
46. M.N. Giovan and G. Sines, Strength of a Ceramic at High Temperatures under Biaxial and Uniaxial
Tension, J. Am. Ceram. Soc., Vol 64 (No. 2), 1981, p 68–73
47. G.D. Quinn and G. Wirth, Multiaxial Strength and Stress Rupture of Hot Pressed Silicon Nitride, J. Eur.
Ceram. Soc., Vol 6 (No. 3), 1990, p 169–178
Mechanical Testing of Polymers and Ceramics
Proof Testing
Ceramic users ultimately must have confidence that components will have a reliable minimum strength or
performance level. The object of using nondestructive evaluation methods is to be able to discern defects to
permit the culling of unacceptable components, but the state of the art is inadequate at the moment. Proof
testing is a viable means of weeding out unacceptable parts in monolithic, brittle ceramics (Ref 48, 49, 50).
Proof testing entails stressing all components to a proof stress, σ
p
, in order to cause fracture in the parts that are
weaker than σ
p
.
There are, however, severe restrictions on the utility of this method. Proof testing is only effective if the test
precisely simulates the actual service conditions. Any deviation incurs risk. A further problem occurs if the
material is susceptible to slow crack growth during the proof test. For a proof test to be effective in narrowing a
strength distribution, it can be shown that the slow-crack-growth exponent n must meet the criterion (n - 2)/m >
1.0 (Ref 50). Ideally, n should be high under the conditions of the proof test. In the worst case, if unloading
rates are low, it is even possible for some specimens to be weaker than σ
p
after the test.
Proof tests are typically done to stress levels commensurate with or somewhat higher than the stresses expected
in service. If slow crack growth is anticipated in the service conditions, it may be necessary to apply proof
stresses much higher than the service levels. Analytical procedures exist that permit integration of the slow
crack growth and statistical analyses, which allow the estimation of minimum lifetimes (Ref 48, 51), usually in
the form of strength-probability-time diagrams (Ref 51).
The proof test only culls out specimens with defects at the time of the proof test. If new flaws subsequently
develop (e.g., during high-temperature exposure or service loadings), the proof test may be negated.
References cited in this section
48. S.M. Wiederhorn, Reliability, Life Prediction and Proof Testing of Ceramics, Ceramics for High
Performance Applications, J. Burke, A. Gorum, and R. Katz, Ed., Brook Hill Publishing, 1974, p 635–
664
49. D.W. Richerson, Modern Ceramic Engineering, Marcel Dekker, 1982
50. J.E. Ritter, Jr., P.B. Oates, E.R. Fuller, and S.M. Wiederhorn, Proof Testing of Ceramics, Part I:
Experiment, J. Mater. Sci., Vol 15, 1980, p 2275–2281
51. R.W. Davidge, Mechanical Behavior of Ceramics, Cambridge University Press, 1979
Mechanical Testing of Polymers and Ceramics
Fracture Toughness
Fracture toughness values are used extensively to characterize the fracture resistance of ceramics and other
brittle materials. Numerous techniques are available, and the choice of technique is determined by the type of
information needed and type of flaws.
Fracture toughness values obtained through different techniques cannot be directly compared. Although much
effort has been focused on this subject, it appears that a complementary number of techniques may have to be
used to generate K
Ic
values under different testing conditions.
To successfully standardize test measurements, careful attention and consideration must be given to testing
details (both operators and machine), sample preparation, and prehistory in terms of microstructure,
thermomechanical processing, and composition.
Both indentation crack length (fracture) and indentation strength methods can be successfully used to measure
K
Ic
only at ambient temperature in ceramic materials where neither significant slow crack growth nor R-curve
behavior is observed. Simple sample preparation and small sample size are needed for such techniques.
Double torsion is applicable at high temperatures when enough material is available and under conditions
where notch/crack geometry is established to allow for nearly uniform K
I
value at the crack front.
Various double-cantilever techniques are advantageous because they use a small amount of material. Analytical
solutions are available for accurately computing K
I
values from double-cantilever configurations. However,
loading fixtures and details are difficult and cumbersome, especially for high-temperature use. In ceramic
multilayer electronic capacitors, miniaturization of the double-cantilever beam has proven to be useful.
The Japanese Industrial Standards (JIS) Association committee on the standardization of fine ceramics adopted
the use of both indentation crack length/fracture and single-edge precracked beam techniques as standards in
JIS R 1607 in 1989. However, these and other techniques still need to resolve the meaning of average resistance
to crack growth and the undesirably high cost of machining, sample preparation, and fixturing.
The following sections briefly describe some common methods of fracture toughness testing. More information
is also provided in the article “Fracture Resistance Testing of Brittle Solids” in this Volume.
Double Torsion Technique. This type of specimen test is popular and allows the use of a variety of specimen
geometries. Basically, the specimen is a thin plate of about 75 mm by 25 mm by 2 mm (3 in. by 1 in. by 0.08
in.). A variety of specimen width-to-length ratios can be used. The specimen sometimes has a side groove,
which is usually cut along its length to guide the crack. Best results are obtained without a groove, provided
that there is good alignment. The specimen is best loaded and supported by ball bearings. It can be studied in
terms of crack-growth behavior as well as fast fracture toughness measurements.
The double torsion technique requires a large amount (volume) of material, which may not always be available.
The technique also suffers from the fact that the crack front is curved, which means that it is not under a
uniform stress intensity. However, the technique is useful at high temperatures and severe environments and
requires no particular fixtures (simple loading conditions).
A rigid machine is essential to conduct either precracking work or experiments where crack velocity is related
to specimen compliance (during constant deflection or deflection rate trials). Some strain energy is stored in the
test machine because of its finite compliance.
Indentation Fracture. Interest in this technique stems from its simplicity and the small volume of material
required to conduct K
Ic
measurements. A Vickers indentation is implanted onto a flat ceramic surface, and
cracks develop around the indentation in inverse proportion to the toughness of the material. By measuring
crack lengths, it is possible to estimate K
Ic
. The crack morphology formed during the elastic-plastic contact
between a sharp indenter and a brittle medium consists of both median and lateral vent cracks. It must be noted
that under small indentation loads, only small, shallow cracks form. The median vent cracks are used for
fracture toughness computations.
Crack dependence on sample preparation is well known for shallow cracks. The preparation of the sample
surface, using effective polishing to achieve a stress state representative of the bulk, is recommended in order to
achieve maximum crack length. Annealing also can be used. Ratios of crack length to indent radius of about 23
or more are recommended in order to achieve consistent results. In addition, the crack length must be measured
immediately after the indentation to minimize possible post-indentation slow crack growth, especially in
glasses, glass-ceramics, and ceramics that have a glassy grain boundary.
Chevron Notch Method. This method is gaining popularity because it uses a relatively small amount of
material. The fracture toughness calculations are dependent on the maximum load and on both specimen and
loading geometries. No material constants are needed for the calculations. The technique is also suitable for
high-temperature testing, because flaw healing is not a concern. However, it requires a complex specimen shape
that has an extra machining cost. A sawed notch is induced in a test bar that is usually 3 mm by 4 mm by 50
mm (0.12 in. by 0.16 in. by 2 in.). The notch angle varies from 30 to 50°. On subsequent testing of the
specimen, a crack will develop at the chevron tip and extend stably as the load is increased, and later there is
catastrophic fracture.
Double-Cantilever Beam Method. In this method, one of three different loading configurations can be applied
(wedge load, applied load, or applied moment). A tapered double-cantilever double beam has also been
suggested. Fracture toughness is derived from the notch length, specimen dimensions, and normal tensile load.
This technique has a number of advantages over other fracture toughness tests. Stress intensity is independent
of the crack length, in the case of the constant applied moment loading, and sample preparation and the testing
procedure are both relatively simple. The specimen must be precracked (sharp cracks emanating from a blunt
notch) to ensure that failure initiates from a sharp flaw of the correct geometry. Most of the time, a number of
very small cracks emanate from a blunt notch with a tip radius of about 15 nm (0.6 μin.) or more. This usually
results in crack growth away from the notch tip (uncontrolled geometry) and produces anomalously higher
fracture toughness values than those obtained from specimens that have sharp cracks with the appropriate
geometry.
Single-Edge Notched Beam. This method has been commonly used because of its simplicity (Fig. 30). The
sharp crack requirement is replaced by a narrow notch, which is easier to introduce and can be measured more
accurately. Fracture-toughness measurements are usually conducted using four-point bending apparatus.
Unfortunately, it has been reported that the results of this test are very sensitive to the notch width and depth,
and either a precracked single-edge notched beam or a single-edge precracked beam is preferred.
Fig. 30 Single-edge notched beam specimen
Single-Edge Precracked Beam. The main feature of the method is the loading fixture for precracking (Fig. 31),
in which a beam-shaped specimen (flexure bend bar was also suggested) is compressively loaded against a
centrally located groove in an anvil (Fig. 32). This generates a local tensile field of a Vickers indentation (or a
straight notch), which is placed in the center of the tensile surface of the specimen. Then, on gradual loading,
pop-in sound is detected, and a median crack is induced from the indent, extending both inward and sideways.
Eventually, the crack front is arrested as a straight line through the thickness of the specimen.
Fig. 31 Loading fixture for precracking of the single-edge precracked beam specimen
Fig. 32 Loading anvil technique for generating a precrack in the single-edge precracked beam method
This technique is a refinement of the single-edge notched beam technique for introducing a precrack. It is
necessary to carefully prepare (grind/polish) the beam surfaces and edges 0.08 nm (3 mils) or better to help
eliminate undesirable crack starters. Careful parallelism and squareness of sample surfaces is essential for the
success of precracking. The specimen is then loaded to failure in bend fixtures in the same fashion as a single-
edge notched beam.
Compression Precracking. Suresh et al. (Ref 52) developed this procedure for measuring fracture toughness in
either bending or tension after precracking notched specimens in uniaxial cyclic compression to produce a
controlled and through-thickness fatigue flaw. After precracking, the specimen can be loaded in flexure in the
single-edge notched beam configuration.
Reference cited in this section
52. S. Suresh, L. Ewart, M. Maden, W.S. Slaughter, and M. Nguyen, Fracture Toughness Measurements in
Ceramics: Precracking in Cyclic Compression, J. Mater. Sci., Vol 22, 1987, p 1271
Mechanical Testing of Polymers and Ceramics
Hardness Testing
Hardness is defined in the conventional sense as a means of specifying the resistance of a material to
deformation, scratching, and erosion. It is an important property for engineering applications that require good
tribological resistance, such as seals, slurry pumps, rollers, and guides. Hardness tests are based on indenting
the sample with a hard indenter, which may be spherical, conical, or pyramidal. There is a lack of experimental
evidence to support the use of hardness for ceramics evaluation, because a combination of plastic flow,
fragmentation, and cross-cracking leads to considerable scatter between indentations and to differences between
observers.
Common techniques for measuring hardness in ceramics are Vickers (HV), Knoop (HK), and Rockwell
superficial (HR). More detailed information is given in the article “Indentation Hardness Testing of Ceramics”
in this Volume. The following guidelines should also be considered when conducting hardness measurements:
• Hardness tests can be used for engineering ceramics if it is recognized that errors (as high as 15%) and
biases lead to high levels of uncertainty and increase with increasing hardness level.
• The indentation must be larger than the microstructural features. An adequate number of indentations
must be used, preferably ten or more of good geometry.
• Badly damaged indentations must be ignored. Cracking from corners has to be accepted, but the
impression of the corners must be undamaged.
• The machine-observer combination must have a means of calibration, preferably a high hardness test
block.
• The geometry of the diamond indenter must be checked at intervals, especially in high-load tests.
• Hardness can vary with indentation load for small loads. Indentation loads greater than or equal to 9.8 N
(2.2 lbf) are recommended for Knoop and Vickers indentations.
Mechanical Testing of Polymers and Ceramics
Acknowledgments
The information in this article is largely taken from:
• K.E. Amin, Toughness, Hardness, and Wear, Ceramics and Glasses, Vol 4, Engineered Materials
Handbook, ASM International, 1991, p 599–609
• R.J. Del Vecchio, Tensile Testing of Elastomers, Tensile Testing, P. Han, Ed., ASM International, 1992,
p 135–146
• J.-C. Huang, Mechanical Properties, Engineering Plastics, Vol 2, Engineered Materials Handbook,
ASM International, 1988, p 433–438
• J.A. Nairn and R.J. Farris, Important Properties Divergences, Engineering Plastics, Vol 2, Engineered
Materials Handbook, ASM International, 1988, p 655–658
• R. Nimmer, Impact Loading, Engineering Plastics, Vol 2, Engineered Materials Handbook, ASM
International, 1988, p 679–700
• G.D. Quinn, Strength and Proof Testing, Ceramics and Glasses, Vol 4, Engineered Materials
Handbook, ASM International, 1991, p 599–609
• R.B. Seymour, Polymers for Engineering Applications, ASM International, 1987, p 17–31, 151–157
• R.B. Seymour, Overview of Polymer Chemistry, Engineering Plastics, Vol 2, Engineered Materials
Handbook, ASM International, 1988, p 63–67
• J.L. Throne and R.C. Progelhof, Creep and Stress Relaxation, Engineering Plastics, Vol 2, Engineered
Materials Handbook, ASM International, 1988, p 659–678
Mechanical Testing of Polymers and Ceramics
References
1. R. Seymour, Overview of Polymer Chemistry, Engineering Plastics, Vol 2, Engineered Materials
Handbook, ASM International, 1988, p 64
2. A. Kumar and R. Gupta, Fundamentals of Polymers, McGraw-Hill, 1998, p 30, 337, 383
3. L.E. Nielson, Mechanical Properties of Polymers, Van Nostrand Reinhold, 1962
4. F.N. Kelly and F. Bueche, J. Polym. Sci., Vol 50, 1961, p 549
5. V. Shah, Handbook of Plastics Testing Technology, 2nd ed., John Wiley & Sons, 1998
6. ISO/IEC Selected Standards for Testing Plastics, 2nd ed., ASTM, 1999
7. J. Nairn and R. Farris, Important Properties Divergences, Engineering Plastics, Vol 2, Engineered
Materials Handbook, ASM International, 1988, p 655–658
8. T. Osswald, Polymer Processing Fundamentals, Hanser/Gardner Publications Inc., 1998, p 19–43
9. K.M. Ralls, T.H. Courtney, and J. Wulff, Introduction to Materials Science and Engineering, John
Wiley & Sons, 1976
10. S. Turner, Mechanical Testing, Engineering Plastics, Vol 2, Engineered Materials Handbook, ASM
International, 1988, p 547
11. R.B. Seymour, Polymers for Engineering Applications, ASM International, 1987, p 155
12. V. Shah, Handbook of Plastics Testing Technology, 2nd ed., John Wiley & Sons, 1998
13. Recognized Components Directories, Underwriters Laboratories
14. R.D. Deanin, Polymer Structure, Properties and Applications, Cahners, 1982
15. R.P. Nimmer, Analysis of the Puncture of a Polycarbonate Disc, Polym. Eng. Sci., Vol 23, 1983, p 155
16. R.P. Nimmer, An Analytical Study of Tensile and Puncture Test Behavior as a Function of Large-Strain
Properties, Polym. Eng. Sci., Vol 27, 1987, p 263
17. L.M. Carapelucci, A.F. Yee, and R.P. Nimmer, Some Problems Associated with the Puncture Testing of
Plastics, J. Polym. Eng., June 1987
18. J.G. Williams, Fracture Mechanics of Polymers, Ellis Horwood, 1984
19. D.D. Huang and J.G. Williams, J. Mater. Sci., Vol 22, 1987, p 2503
20. M.K.V. Chan and J.G. Williams, Int. J. Fract., Vol 19, 1983, p 145
21. Y.W. Mai and B. Cotterell, Int. J. Fract., Vol 32, 1986, p 105
22. C.R. Brinkman and G.D. Quinn, Standardization of Mechanical Properties Tests for Advanced
Ceramics, Mechanical Testing Methodology for Ceramic Design and Reliability, Marcel Dekker, 1998,
p 353–386
23. D.F. Carroll, S.M. Wiederhorn, and D.E. Roberts, Technique for Tensile Creep Testing of Ceramics, J.
Am. Ceram. Soc., Vol 72 (No. 9), 1989, p 1610–1614
24. T. Soma, M. Matsui, and I. Oda, Tensile Strength of a Sintered Silicon Nitride, Nonoxide Technical and
Engineering Ceramics, Proc. of the International Conf., (Limerick, Ireland), S. Hampshire, Ed., 1985, p
361–374
25. T. Ohji, Towards Routine Tensile Testing, Int. J. High Technol. Ceram., Vol 4, 1988, p 211–225
26. G. Grathwohl, Current Testing Methods—A Critical Assessment, Int. J. High Technol. Ceram., Vol 4,
1988, p 123–142
27. K.C. Liu, H. Pih, and D.W. Voorhes, Uniaxial Tensile Strain Measurement for Ceramic Testing at
Elevated Temperatures: Requirements, Problems, and Solutions, Int. J. High Technol. Ceram., Vol 4,
1988, p 69–87
28. J. Nilsson and B. Mattsson, A New Tensile Test Method for Ceramic Materials, Ceramic Materials and
Components for Engines, W. Bunk and H. Hausner, Ed., German Ceramic Society, Berlin, 1986, p 651–
656
29. A. Rudnick, C.W. Marschall, W.H. Duckworth, and B.R. Emrich, “The Evaluation and Interpretation of
Mechanical Properties of Brittle Materials,” U.S. Air Force Technical Report TR 67-316, Air Force
Materials Laboratory, April 1968
30. J.E.O. Ovri and T.J. Davies, Diametral Compression of Silicon Nitride, Mater. Sci. Eng., Vol 96, 1987,
p 109–116
31. R. Morrell, Mechanical Properties of Engineering Ceramics: Test Bars versus Components, Mater. Sci.
Eng., Vol A109, 1989, p 131–137
32. G.D. Quinn and R. Morrell, Flexure Testing for Design of Engineering Ceramics: A Review, J. Am.
Ceram. Soc., Vol 74 (No. 9), 1991, p 2037–2066
33. S. Thrasher, Ceramic Applications in Turbine Engines (CATE) Program Summary, Proc. of the 21st
Contractors Coordination Meeting, Report P138, Society of Automotive Engineers, March 1984, p
255–267
34. R. Sedlacek and F.A. Halden, Method for Tensile Testing Brittle Materials, Rev. Sci. Instr., Vol 33 (No.
3), 1962, p 298–300
35. R. Jones and D.J. Rowcliffe, Tensile-Strength Distributions for Silicon Nitride and Silicon Carbide
Ceramics, J. Am. Ceram. Soc., Vol 58 (No. 9), 1979, p 836–844
36. R. Charles and S. Prochazka, “Stress Rupture Testing of Silicon Carbide at Very High Temperatures,”
Technical Report 77CRD035, General Electric Co., March 1977
37. T.P. Dabbs, C.J. Fairbanks, and B.R. Lawn, Subthreshold Indentation Flaws in the Study of Fatigue
Properties of Ultrahigh-Strength Glass, Methods for Assessing the Structural Reliability of Brittle
Materials, STP 844, S.W. Freiman and C.M. Hudson, Ed., ASTM, 1984, p 142–153
38. S.R. Choi, J.E. Ritter, and K. Jakus, Failure of Glass with Subthreshold Flaws, J. Am. Ceram. Soc., Vol
72 (No. 2), 1990, p 268–274
39. M. Adams and G. Sines, A Statistical, Micromechanical Theory of the Compressive Strength of Brittle
Materials, J. Am. Ceram. Soc., Vol 61 (No. 3–4), 1978, p 126–131
40. M. Adams and G. Sines, Crack Extension from Flaws in a Brittle Material Subjected to Compression,
Technophysics, Vol 49, 1978, p 97–118
41. C.A. Tracy, A Compression Test for High Strength Ceramics, J. Test. Eval., Vol 15 (No. 1), 1987, p 14–
19
42. C.A. Tracy, M. Slavin, and D. Viechnicki, Ceramic Fracture during Ballistic Impact, Advances in
Ceramics, Vol 22, Fractography of Glasses and Ceramics, 1988, p 319–333
43. J. Lankford, Compressive Strength and Microplasticity in Polycrystalline Alumina, J. Mater. Sci., Vol
12, 1977, p 791–796
44. J. Lankford, Uniaxial Compressive Damage in α-SiC at Low Homologous Temperatures, J. Am. Ceram.
Soc., Vol 62 (No. 5–6), 1979, p 310–312
45. M. Adams and G. Sines, Methods for Determining the Strength of Brittle Materials in Compressive
Stress States, J. Test. Eval., Vol 4 (No. 6), 1976, p 383–396
46. M.N. Giovan and G. Sines, Strength of a Ceramic at High Temperatures under Biaxial and Uniaxial
Tension, J. Am. Ceram. Soc., Vol 64 (No. 2), 1981, p 68–73
47. G.D. Quinn and G. Wirth, Multiaxial Strength and Stress Rupture of Hot Pressed Silicon Nitride, J. Eur.
Ceram. Soc., Vol 6 (No. 3), 1990, p 169–178
48. S.M. Wiederhorn, Reliability, Life Prediction and Proof Testing of Ceramics, Ceramics for High
Performance Applications, J. Burke, A. Gorum, and R. Katz, Ed., Brook Hill Publishing, 1974, p 635–
664
49. D.W. Richerson, Modern Ceramic Engineering, Marcel Dekker, 1982
50. J.E. Ritter, Jr., P.B. Oates, E.R. Fuller, and S.M. Wiederhorn, Proof Testing of Ceramics, Part I:
Experiment, J. Mater. Sci., Vol 15, 1980, p 2275–2281
51. R.W. Davidge, Mechanical Behavior of Ceramics, Cambridge University Press, 1979
52. S. Suresh, L. Ewart, M. Maden, W.S. Slaughter, and M. Nguyen, Fracture Toughness Measurements in
Ceramics: Precracking in Cyclic Compression, J. Mater. Sci., Vol 22, 1987, p 1271
Overview of Mechanical Properties and Testing for
Design
Howard A. Kuhn, Concurrent Technologies Corporation
Introduction
DESIGN is the ultimate function of engineering in the development of products and processes, and an integral
aspect of design is the use of mechanical properties derived from mechanical testing. The basic objective of
product design is to specify the materials and geometric details of a part, component, and assembly so that a
system meets its performance requirements. For example, minimum performance of a mechanical system
involves transmission of the required loads without failure for the prescribed product lifetime under anticipated
environmental (thermal, chemical, electromagnetic, radiation, etc.) conditions. Optimum performance
requirements may also include additional criteria such as minimum weight, minimum life cycle cost,
environmental responsibility, human factors, and product safety and reliability.
This article introduces the basic concepts of mechanical design and its general relation with the properties
derived from mechanical testing. Product design and the selection of materials are key applications of
mechanical property data derived from testing. Although existing and feasible product shapes are of infinite
variety and these shapes may be subjected to an endless array of complex load configurations, a few basic stress
conditions describe the essential mechanical behavior features of each segment or component of the product.
These stress conditions include the following: