STEREOLOGY DEFINITION MANUAL

The simple counting measurements, P P, P L, N L, P A and N A, are most important and are easily made. These measurements can be made manually with the aid of templates outlining a fixed field area, systems of straight or curved lines of known length, or a number of systematically spaced points. This table lists the most commonly used notations there are other, newly developed procedures where the notation has not been standardized. To facilitate communications, the International Society for Stereology (ISS) has proposed a standard system of notation, as shown in Table 1 (3). This is the body of measurements that describe the relationships between measurements made on the two-dimensional plane of polish and the characteristics of the three-dimensional microstructural features sampled. The second group of measurements belongs to the field referred to as stereology.

ISS Nomenclature for Stereological Measurements (Underwood, 3) Metrology methods are also used for individual feature analysis of particle size and shape measurement. Standard metrology methods are used and these can be automated. To obtain reproducible data, these surface conditions must be measured at a number of positions on a given specimen and on several specimens if the material being sampled is rather large. These measurements are made at a specific location (the surface) and may be subject to considerable variation. The first group includes measurements of depths ? i.e., depth of decarburization, depth of surface hardening, or thickness of coatings or platings.

Examples of the applications of stereological measurements have been reviewed by Underwood (2).Д«asically, two types of measurements of microstructures are made. At this time, true quantitative procedures are replacing chart methods for such purposes and they are gaining usage in quality control and research studies. Fortunately, there has been tremendous progress in the development of powerful, user-friendly image analyzers over the past two decades.Д¬hart methods for rating microstructures have been used for many years to evaluate microstructures, chiefly for conformance to specifications. What degree of counting accuracy can be expected when the subject is less familiar, such as microstructural features? Image analyzers, on the other hand, are quite good at counting but not as competent at recognizing features of interest. In this case the subject was one very familiar to the test subjects, yet only 3.8% obtained the correct count.

STEREOLOGY DEFINITION MANUAL

This experiment revealed a basic problem with manual ratings. Results were not Gaussian, however, as only 4.3% had higher values while 92% had lower values, some much lower. The correct answer was obtained by only 3.8% of the people. About 400 people were asked to count the number of times the letter вЂњeвЂќ appeared in a paragraph without striking out the letters as they counted. Many years ago, George Moore (1) and members of ASTM Committee E-4 on Metallography conducted a simple counting experiment.

Further, while humans are quite good with pattern recognition, as in the identification of complex structures, they are less satisfactory for repetitive counting. Although the fundamental relationships for stereology, the foundation of quantitative metallography, have been known for some time, implementation of these concepts has been restricted when performed manually due to the tremendous effort required.