The purpose of the present paper is to give a comprehensive state of the art review of all electro-optical systems used to date for direct viewing of X-ray topographic images. Consideration is given to both direct conversion X-ray sensitive vidicon systems and to indirect conversion systems which use fluorescent screens to convert the X-ray image into a visible one. Included in this review is a discussion of the relative advantages and disadvantages of the various electro-optical systems, including cost, versatility, portability, simplicity of operation, sensitivity, and resolution capability.

The strain distribution associated with incipient microplasticity and its response to subsequent annealing were studied in smooth and notched silicon crystals. The characterization of plastic and elastic residual strains was carried out by X-ray topography based on PendellBsung Fringe (PF) patterns and was supplemented by X-ray doublecrystal diffractometry and specimen scanning with automatic Bragg angle control (ABAC). It was shown that the sites at or near the surface were preferred sites where, upon mechanical deformation, dislocation sources became activated. Microplastic zones thus formed constrained long-range, residual, elastic strains.

To study the relationship between crystal growth conditions and resultant crystalline perfection, large nickel single crystals more than 12 cm long and 2 to 3 cm in diameter have been grown from the melt by the Czochralski method. Unlike semiconducting materials, one cannot easily thin metal crystals, without straining them, for the purpose of applying ordinary Lang topography with μL∼l where kinematical scattering in imperfect crystals is a good approximation. This situation with metal crystals necessitates the use of dynamical diffraction effects in imperfect crystals to permit sample crystals to be thick enough to demonstrate their imperfections as in the bulk.

Some kinds of plastic deformation leave a residual pseudo-macrostress in the material. The existence of this stress in certain specimens introduces errors into the standard x-ray measurement of residual macrostress, namely, in specimens that have been stretched, compressed, bent, rolled, or drawn.

No error is involved in x-ray measurements on peened, ground, or machined surfaces, or in specimens where the source of the stress is remote from the surface examined.

The x-ray and magnetic evidence for pseudo-macrostress is reviewed.

The application of x-ray topographic techniques to the measurement of stress in thin, films is discussed. Quantitative measurements of stresses in thin films deposited on semiconductor substrates, such as silicon, are also discussed. Double crystal and single crystal techniques are used for such measurements. Both techniques are applied to the measurements of stress in silicon oxide, silicon nitride and polycrystalline silicon films on silicon. The doubly crystal technique is useful for measurements of stresses as low as 109 dynes/cm2 in films only 1000A thick. The single crystal technique is less sensitive by one order of magnitude. The advantage of the single crystal technique is its simplicity and speed. It is useful for large scale measurements as encountered in the manufacture of silicon integrated circuit.

The location of x-ray diffractometer line profiles is of fundamental importance in x-ray stress analysis. Objective estimates of the line profile position may be derived from diffractometer measurements at a number of equally-spaced points in the region of maximum intensity. These estimates are generally based upon the corresponding turning-point of a polynomial fitted to step-scanning data. Techniques are described which simplify the computation involved. A least-squares fitting of a quadratic is satisfactory for most routine applications provided that a reasonable number of points is involved. The three-point parabola method is less satisfactory. Expressions are presented, derived using the maximum-likelihood approach, for peak location and counting variance using both quadratic and cubic equations.

Software is described for complete computer control of residual stress measurements. One program (that incorporates either the two tilt method, the sins| procedure, or the Cohen-Marion technique) has been developed for use with either a normal detector or a position sensitive detector. The operator inputs the desired error in stress and various instrumental parameters that determine systematic errors. The counting strategy to obtain the total error is then determined by the software.

Employing this automated system, an investigation of a parabolic fit to the top of a diffraction profile indicates that a three point fit is satisfactory only for sharp profiles.

The Fastress automatic residual stress measurement system was used to measure residual stress in unnotched shot peened 7075-T6 aluminum alloy specimens for a study of the effect of load and thermal exposure on residual stresses. Cyclic loads at zero and high mean stress conditions at stress levels in excess of those used in aircraft structures gave no apparent change in residual stress. Thermal exposure above 200°F resulted in significant changes in residual stress; at 225°F, 30 to 50 hours were required to cause the residual stress to reduce to onehalf the original value and less than 15 hours at 250°F was sufficient to cause a 50Z reduction. The data indicate that the cyclic load history that may be expected in aircraft structures is not sufficient to cause residual stress relaxation in areas remote from fasteners and other stress concentrations but that thermal exposure can cause significant relaxation.

Magnitude and distribution of residual stresses around cold-worked holes in 1045 steel were measured with the Fastress automatic stress X-ray analyzer. Permanent interferences between 0.8% and 6.2% at a hole with 0.5 in. diameter produced compressive hoop and radial stresses up to -60 ksi and -40 ksi respectively. The size of the zone with compressive stress is significantly wider than existing analysis predicts.

Stresses in polymeric materials can be measured by diffracting X-rays from embedded crystallites that yield suitable powder diffraction lines. An appropriate technique for this has been, reported by C. S. Barrett and Paul Predecki elsewhere and is reviewed here with additional details. It is based on a diffractometer modified so as to operate at very high 26 angles, with specimens prepared in various ways. Results show that adequate precision is reached by scanning Ka doublet in a few minutes and simply noting any displacement of peaks compared with peaks from an unstressed specimen; higher precision can be reached with slower scans or more detailed analysis of the peaks. Tests with embedded metallic particles were successful when the particles were (A) distributed throughout a moulded polymethyl methacrylate (Lucite) sheet of the order of a millimeter thick, alone or sandwiched between layers of particle-free material, or (B) embedded in polyester resin applied to a surface of Plexiglas bars, or (C) embedded in graphite-fiber epoxy composites in a layer at a chosen position within a specimen.

X-ray diffractometer studies of single-crystal quartz and orthoclase reveal the peak shock pressure experienced by the samples. This procedure may facilitate tapid, quantitative interpretation of the peak shock pressures experienced by materials occurring in lunar or terrestrial impact structures. Shocked specimens were obtained from the NASA 20 mm flat-plate accelerator at Johnson Space Center, Houston. Orthoclase single crystals were shocked normal to the (001) plane at pressure intervals between 0 and 297 kb. The amplitude of the 27.6° two-theta (002) maximum decreases as a function of increasing shock pressure. Quartz single crystals were shocked normal to the (0001) plane at pressure intervals between 0 and 310 kb. Examination of the peak amplitude/ half-width ratios for the 26.6° two-theta (101) and the 20.8° twotheta (100) reveals a general correlation of these ratios with shock pressure. This method seems appropriate for the calibration of shock pressures experienced by crystalline materials.

A technique and apparatus are described for obtaining the elastic constant E/(1 + v) in selected crystaliographic directions for the purpose of calibrating x-ray diffraction residual stress measurement methods. The preparation of a simple rectangular beam specimen with two active electrical resistance strain gages applied to the test surface is described. Samples are clamped in a diffractometer fixture designed to minimize displacement errors, and loaded in four-point bending to several stress levels below the proportional limit. A method is described for calculating E/(l + v) and an estimate of the experimental error.

Values of E/(l + v) obtained for several alloy-(hkl) combinations are presented. The results indicate that several alloys of current commercial interest exhibit significant elastic anisotropy.

In order to convert residual strains measured by x-ray diffraction techniques into residual stresses, appropriate x-ray elastic constants have to be measured. Since these x-ray elastic constants may depend on the metallurgical state, deformation, and entire specimen history, errors in stress values may result if the constants are not measured for representative material states. In the present work, it is shown that in same cases these errors may be large.

Usually, the classical Bragg-Brentano diffractometer arrangement is used for X-ray strain measurements. For measurements in different ψ-directions, the specimen is rotated clockwise or counter-clockwise around the diffractometer axis using a separate driving system (ω-diffractometer).During the measurements, primary and reflected X-ray beams are placed in the same plane as the normal of the specimen and the normals of the measured ﹛h,k,l﹜ -planes. However, the Bragg- Brentano principle also can he applied to strain measurements in different ψ-directions with a number of advantages if the specimen is rotated around an axis lying parallel to the diffractometer plane (ψ- diffractometer) (1). The principle, construction and characteristics of the ψ-diffractometer are described and compared with those of the ω-diffractometer.

The diffractometer employs dual fixed detectors and a moving, vertically mounted X-ray tube. Lattice strain is measured in two specimen directions simultaneously. The drive has three concentric shafts; the outer driven by a cone drive worm and gear; a middle fixed shaft supporting the detectors and an inner shaft geared in a 1:2 ratio carrying the specimen mount. Scanning angles are measured to an accuracy of ±0.001°. A large range of specimen sizes can be accommodated.

X-ray residual stress measurements have been made with a commercial portable X-ray diffraction apparatus that uses parallel beam optics and that was specifically designed for residual stress measurements. This machine differs from X-ray diffraction units using the usual parafocusing geometry in several respects, most notably reduced sample placement errors and larger sample sizes that can be accommodated. Two special modes of operation are available and will be discussed. These are the ability to use the side inclining method for stress analysis and the ability to use an oscillating ψ motion, the latter mode being useful for examining large grain size materials.

The 3.8 MeV proton beam from the University of Florida Van de Graaff accelerator has been used to perform trace element analysis of approximately 1200 samples (mostly from autopsies) of human tissues by proton-induced X-ray emission analysis (PIXE). Fifteen different organs and a variety of diseases have been studied. Preliminary data are presented indicating the variations of various elements in human kidney as a function of age. Analysis of samples from infants also indicate essential and non-essential elements in human kidney. On the average twelve trace elements (with atomic number equal to or larger than nineteen) are observed in each organ. Quantitative measurements have been made on several elements including K, Ca, Mn, Fe, Cu, Zn, Pb, Br, Rb, Sr, Cd, and Ba.

A new type of calibration standard has been developed for X-ray fluorescence analysis of thin samples. Each standard consists of a polymer film containing a single calibration element. The film is cast from a homogeneous solution containing known amounts of an organometallic compound and a polymer. Polymers of cellulose acetate-propionate and polystyrene are used because of their low moisture affinity. The films have a low (2-4 mg/cm2) mass per unit area for minimal X-ray attenuation. Standards of V, Co, Hi, and Pb have been successfully made. Typical concentrations of 20 μg/cm2 yield excellent spectra with a low background. The method shows promise for making standards of additional elements.

Chemical analysis of geological materials such as nickel ores has been accomplished by atomic absorption (1,3) x-ray fluorescence (11,14) and conventional wet methods (10). Procedures utilizing these techniques are capable of producing excellent results but are often difficult and time consuming.

Minerals often present serious problems in chemical analysis by wet methods. X-ray analysis can therefore offer the analyst considerable savings in time providing the obstacles which exist are understood and minimized or eliminated. The most serious problems to solve are absorption and enhancement effects, mineralogical differences among samples, sample preparation, and particle size effects which often influence the intensities of the analytical lines. In addition, the element of interest may be of low concentration in a variable and unknown matrix.

A procedure using tube excited energy dispersive x-ray fluorescence analysis with interelement corrections has been developed for multielement analysis of major and trace elements and ash content of coal, coke, and fly ash. The procedure uses pressed pellets and an exponential correction for interelement effects. The average deviations ranged from about 0.0003% for V at an average concentration of about .003% to 0.1% for S at an average concentration of 4%. About 25 elements were measured and 100 second minimum detectable concentrations ranged from about one part per million for elements near arsenic to about one tenth of one percent for sodium.