Results are presented from several studies where microfocus radiography has been applied to provide feedback necessary to improve reliability and performance of materials and components. Improving the reliability of advanced silicon nitride ceramics through the use of NDE was studied by exploring the relationship between process-related defects, radiography results, and fracture of test samples. Research in the areas of structural and electronic ceramic joining has been aided by monitoring the effects of process modifications with real-time microfocus radiography and computer- based image processing.Microfocus projection radiography was used to nondestructively examine a large quantity of silicon nitride modulus of rupture test bars for internal defects. Failure stress prediction was attempted using a fracture mechanics model and quantitative NDE data, and compared to actual failure stress.In-process NDE of silicon nitride ceramic to Incoloy 909 metal brazed test samples was performed. Correlation between NDE results, optical microscopy, and destructive mechanical strength levels of samples is discussed.Microfocus x-ray imaging was used to monitor the process of bonding microwave power transistors to metallized BeO ceramic substrates. Nonuniform distribution of the eutectic bond was readily detectable, thereby providing feedback for process improvement. Comparison is made between x-ray, optical, and infrared images.
A paint film is a dynamic entity. During its life it is in a slow but continuous state of change. Good weathering requires an unusual balance or compromise of physical and chemical forces within the paint film as it ages. There are perhaps some thirty types of physical and chemical actions within a paint film that cause it to change as it weathers. Many of these forces have been measured, and the rate of change of these forces in the aging film appears to dictate the useful life of the film. The importance of such factors as relative humidity, uniformity of film, film thickness, film shrinkage, moisture sorption, amount of film applied, and physical structure and a rating system for summarizing film properties are discussed in this paper. The field of weathering is so broad that only two general types of films weathered under atmospheric conditions will be considered in this paper: white type house paints and metal protective paints. House paints are primarily linseed oil base paints and metal protective paints are primarily oleoresinous base paints. The weathering of paints is big business. At our test fences and marinebasin at Sayville, L. L., there probably are 25,000 tests under way this year even though only 400 or 500 tests are added each year. There are two andone-half miles of test panels. ASTM Committee D-1 is considering weathering test sites because of the importance of having adequate weathering data.
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