1232 Databases

Data bases can either stand separately or can be integrated into design codes. Separate databases for materials have existed for some time in book form and are often compilations of test results reported in the literature (e.g., qualified databases must be incorporated into design codes if materials are included in the requirements of the code (e.g. ASME Boiler and Pressure Vessel Code and Mil-Hdbk-17).

Conventional databases are often organized according to material system (e.g., ceramics, composites, nickel-based superalloy, etc.). The data is then often organized according to type of property such as thermal, mechanical, or physical. Finally, information is often summarized as a mean or range of values. Less frequently the standard deviation and number of tests is provided. Even less frequently the individual data points are provided. Usually a reference is provided for the original source of the information. Unless the information is being used to "qualify" a material, the information is seldom screened to determine if the tests were conducted in accordance with accepted test methods and practices.

Three predominant formats for databases have emerged in recent years: hard copy (usually book form); electronic-local access (compact disk, floppy disk, or magnetic tape) and electronic-remote access (Internet-based). Each of these formats has its advantages and disadvantages as discussed in the following sections.

An example of hard-copy database is The Materials Selector, which covers many advanced materials and is available in a multivolume set [17]. Hard-copy databases provide a permanent record of data, especially if it is qualified (e.g., recognized test methods were used to generate statistically significant data). Unfortunately, the time required to collect, organize, and publish the information makes the some of the data obsolete even before the information is published. In addition hard-copy databases are difficult to search, and any relational aspects must be manually implemented.

There are several examples of electronic-local access databases [18-20], which are increasingly available on stand-alone, searchable compact or floppy disk formats [19, 20]. Some electronic databases [18] can be accessed by engineering analysis software such as finite-element analysis (FEA) or computer-aided design (CAD) software packages to add even more usability to the database. Flexibility, searchability, and relational aspects are all advantages of the electronic-local access database. Unfortunately, unless some provision is added to provide periodic updates to the information, these databases suffer the same obsolescence drawback as the hard-copy database.

Several examples of electronic-remote access data bases [21, 22] reveal an exciting tread in information management. Web-based electronic databases can be accessed and searched using a variety of criteria. With the proper interface, even engineering analysis software such as FEA or CAD software packages can access these online databases. Flexibility, searchability, and relational aspects are all advantages of the electronic-remote access database. The final advantage is that the information contained in online databases can be constantly update as required. A possible drawback is that Internet access is required, but this requirement is usually easily met.

Several key aspects must be present in a successful database. Among these are completeness (recently over 130 separate items were identified for producing a qualified database for a ceramic composite in the Mil-Hdbk-17 effort), usability (the interface must be user-friendly and "intuitive" including the relational search capabilities), and up-to-date (data entry must be simple and self-guided). It is interesting to note that ASTM considers electronic databases so critical that a committee has been created (Committee E49 Computerized Systems and Chemical and Material Information) to aid not only in establishing standards for electronic databases, but also to assist other ASTM committees in reporting results in ways amenable to (and consistent with) the efforts of Committee E49. An example of a complete data set for an electronic database is shown in Fig. 12.9 where both quantified and graphical information are contained in the data sets. An example of an electronic-local access database interface is shown in Fig. 12.10.

FIGURE 12.9 Complete electronic database containing both quantified and graphical information [19] (www.macsch.com/products/mvision).
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FIGURE 12.10 User interface for material database system (DBS) [20] www.trl. com/mds.
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