SI units, unit symbols, and unit prefixes are used in the NIST Property Data Summaries.
Uncertainties:
No attempt has been made to assign uncertainties to the individual values obtained
from the literature. A survey of data in the NIST Structural Ceramics Database
indicates that relative combined standard uncertainties in the range of 5 % to 15 %
are not unusual for fracture toughness measurements. Exceptional cases having reported
uncertainties as low as 1 % or as high as 30 % can be found, but such cases are very
unusual. For a comprehensive discussion on estimates of uncertainty, see "Guidelies
for Evaluating and Expressing the Uncertainty of NIST Measurement Results,"
by B. N. Taylor and C. E. Kuyatt, NIST Technical Note 1297.
DISCLAIMERS:
A substantial effort has been made to select data for this database on the basis of sound scientific judgment. However, the National Institute of Standards and Technology (NIST) makes no warranties regarding its use, and NIST shall not be liable for any damage that may result from errors or omissions in the database.
Certain trade names and other commercial designations are used in this work for the purpose of clarity. In no case does such identification imply endorsement by the National Institute of Standards and Technology, nor does it imply that products or services so identified are necessarily the best available for the purpose.
DATA EVALUATION:
How are data evaluated?
Scientific and technical data may be examined from three viewpoints:
how well is the data generation described,
how do the data follow the known physical laws,
and how do the data compare to other measurements or calculations of the same phenomena.
The description of data generation is crucial. The identification and control of all relevant independent variables must be addressed and demonstrated. For mature areas such as thermodynamics and atomic physics, many measurement techniques are well characterized. In these cases, the adherence to physical laws and intercomparisons predominate. For areas in which behavior is not well understood, such as corrosion, data from different experiments are not usually comparable. Consequently, documentation of control of the experimental condition is most important.
Property Data Summaries are collections of property values derived from surveys of published data.
These collections typically focus on either one material or one particular property.
Studies of specific materials typically include thermal, mechanical, structural, and chemical properties,
while studies of particular properties survey one property across many materials. The property values may be typical,
evaluated, or validated. Values described as typical are derived from values for nominally similar materials.
CAUTION!
Typical values are only representative of trends of values commonlyfound for a general class
of materials and are not necessarily the best or most appropriate valuesfor any particular material.
Data Evaluation Levels
The data evaluation levels used throughout the NIST Ceramics WebBook are:
Certified (standard reference values)
Validated (confirmed via correlations and models)
Evaluated (basic acceptance criteria satisfied)
Commercial (manufacturer's data)
Typical (derived from surveys)
Research (preliminary values; work in progress)
Unevaluated (all other data)
Use of Commercial Names
Certain commercial equipment, instruments, or materials are identified in this document to specify adequately
the experimental procedures and conditions. Such identification does not imply recommendation or endorsement
by the National Institute of Standards and Technology, nor does it imply that the materials or equipment identified
are necessarily the best available for the purpose.
Fracture Toughness / Fracture Energy Data for Ceramics
Fracture Toughness Data for Brittle Materials
R.G. Munro, S.W. Freiman, and T.L. Baker
NISTIR 6153 (National Institute of Standards and Technology, 1998)
