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Evaluation of nondestructive methods of testing brazed joints reveals that ultrasonic testing is effective in the detection of nonbonds in diffusion bonded samples. Radiography provides excellent resolutions of void or inclusion defects, and the neutron radiographic technique shows particular advantage for brazing materials containing cadmium.
Radiographic, ultrasonic, scanning laser acoustic microscopy (SLAM), and thermo-acoustic microscopy techniques were used to characterize silicon nitride and silicon carbide modulus-of-rupture test specimens in various stages of fabrication. Conventional and microfocus X-ray techniques were found capable of detecting minute high density inclusions in as-received powders, green compacts, and fully densified specimens. Significant density gradients in sintered bars were observed by radiography, ultrasonic velocity, and SLAM. Ultrasonic attenuation was found sensitive to microstructural variations due to grain and void morphology and distribution. SLAM was also capable of detecting voids, inclusions and cracks in finished test bars. Consideration is given to the potential for applying thermo-acoustic microscopy techniques to green and densified ceramics. The detection probability statistics and some limitations of radiography and SLAM also are discussed.
Radiographic, ultrasonic, scanning laser acoustic microscopy (SLAM), and thermo-acoustic microscopy techniques were used to characterize silicon nitride and silicon carbide modulus-of-rupture test specimens in various stages of fabrication. Conventional and microfocus X-ray techniques were found capable of detecting minute high density inclusions in as-received powders, green compacts, and fully densified specimens. Significant density gradients in sintered bars were observed by radiography, ultrasonic velocity, and SLAM. Ultrasonic attenuation was found sensitive to microstructural variations due to grain and void morphology and distribution. SLAM was also capable of detecting voids, inclusions and cracks in finished test bars. Consideration is given to the potential for applying thermo-acoustic microscopy techniques to green and densified ceramics. The detection probability statistics and some limitations of radiography and SLAM also are discussed.
Additive manufacturing of pressure-containing boundaries is of interest to numerous industries, so a project was initiated to develop several different methods to join and weld additively manufactured materials. The approach investigated in this study was a low energy, solid state spot weld. This general approach has been routinely used for conventionally prepared tubing and is now being expanded to additively manufactured components. Additively manufactured 304L stainless steel sheets, semi-tubes, and tubes were resistance spot welded and compared to comparable welds in conventionally manufactured tubing. Radiographic computed tomography and metallography were used to evaluate the suitability of the welds using three criteria: weld closure length, thickness, and width. All additively manufactured test welds closely matched the conventional tubing for these criteria
During component level thermal-vacuum deployment testing of eight rotary viscous dampers for the Tropical Rainfall Measuring Mission (TRMM) satellite, all the dampers failed to provide damping during a region of the deployment. Radiographic examination showed that air in the damping fluid caused the undamped motion when the dampers were operated in a vacuum environment. Improvements in the procedure used to fill the dampers with damping fluid, the installation of a Viton vacuum seal in the damper cover, and improved screening techniques eliminated the problem.
A timeline of pediatric bone healing using fracture healing characteristics that can be assessed solely using radiographs would be practical for forensic casework, where the fracture event may precede death by days, months, or years. However, the dating of fractures from radiographs is difficult, imprecise, and lacks consensus, as only a few aspects of the healing process are visible on radiographs. Multiple studies in both the clinical and forensic literature have attempted to develop a usable scale to assess pediatric bone healing on radiographs using various healing characteristics. In contrast to the orthopedic definition, a fracture in forensic casework is only considered to be healed when the area around the fracture has been remodeled to the point that the fracture is difficult to detect on a radiograph or on the surface of the bone itself, a process that can take several years. We subjectively assessed visible characteristics of healing in radiograms of fractures occurring in 942 living children and adolescents. By dividing these assessments into learning and test (validation) sets, the accuracy of a newly proposed fracture healing scale was compared to a previous study. Two machine learning models were used to test predictions of the new scale. All three models produced similar estimates with substantial imprecision. Results corroborate the Malone model with an independent dataset and support the efficacy of using less complex models to estimate fracture age in children.
Building 01-103, the Drill Bit Repair Building was originally recorded as SHPO Resource No. B18848 in 2020 during an architectural survey of the Area 1 Subdock (Collins et al. 2022). It was recommended individually eligible for listing in the NRHP under Criteria A and C and contributing to the significance of the Area 1 Subdock Historic District. The SHPO concurred with these determinations in a letter dated April 29, 2022 (Reed 2022). The Drill Bit Repair Building retains all seven aspects of integrity. The location, materials, workmanship, feeling, and association have not changed since its original construction. The design was modified slightly in 1996 with the addition of a removable and non-destructive chain-link fence. Nearby buildings 01-101 and 01-102 were removed (Collins and Menocal 2020) but the other buildings and storage yards remain. Therefore, the integrity of setting has been changed, but not to the degree that the building no longer conveys its significance (see Figures 4 and 5 for comparison). Building 01-103 was constructed in 1985 to coincide with the relocation of the Area 3 Subdock to Area 1. The design for the new Subdock provided a centralized cluster of buildings surrounded by two large storage yards. The buildings included administrative and engineering office space, warehouses, a radiograph building, and Building 01-103 as the drill bit maintenance and repair building, among others. The Drill Bit Repair Building was critical to the success of underground nuclear testing and is eligible under Criterion A for its contribution to broad patterns of history by maintaining specially designed equipment for underground nuclear testing at the NNSS. It is also eligible under Criterion C as it is the only recorded example of a facility built specifically for the maintenance of big-hole drill bits on the NNSS. As it retains both significance and integrity, it remains individually eligible under Criteria A and C. In addition to its individual significance, the Drill Bit Repair Building also contributes to the significance of the Area 1 Subdock Historic District as a representative of a big-hole drilling support facility necessary for underground nuclear testing. The building and the equipment therein were designed specifically for testing at the NNSS, where much of the early technology and methods for big-hole drilling were developed. Its removal will result in not only the demolition of a contributing element but also a change in the physical features of the district’s setting that contribute to its historic significance. The change in setting will diminish the district’s integrity. However, the district still contains numerous examples of other buildings constructed for the purpose of supporting big-hole drilling and remains eligible under Criteria A and C.
Boron/aluminum specimens were made with crack-like slits in the center and with various proportions of 0 and + or - 45 deg plies. They were fatigue loaded and then fractured to determine their residual strengths. The fatigue loads were generally in the range of 60 to 80 percent of the static tensile strength of the specimen as determined from a previous study, and the stress ratio was .05. For virtually all of the specimens the fatigue loading was continued for 100,000 cycles. The specimens were radiographed after the fatigue loading to determine the nature of the fatigue damage. A few specimens were sectioned and examined in a scanning electron microscope after being radiographed in order to verify the interpretation of the radiographs and also to get a better insight into the nature of the fatigue damage. The results indicate that the fatiguing does not significantly affect the strength of the specimens tested. The results of the radiography and of the scanning electron microscopy indicate that the 45 deg plies suffer extensive damage in the form of split and broken fibers and matrix cracking in the vicinity of the ends of the split. By contrast, the only significant damage to the 0 deg plies was a single 0 deg matric crack growing from the ends of the slit and between the 0 deg fibers.
Boron/aluminum specimens were made with crack-like slits in the center and with various proportions of 0 and + or - 45 deg plies. They were fatigue loaded and then fractured to determine their residual strengths. The fatigue loads were generally in the range of 60 to 80 percent of the static tensile strength of the specimen as determined from a previous study, and the stress ratio was .05. For virtually all of the specimens the fatigue loading was continued for 100,000 cycles. The specimens were radiographed after the fatigue loading to determine the nature of the fatigue damage. A few specimens were sectioned and examined in a scanning electron microscope after being radiographed in order to verify the interpretation of the radiographs and also to get a better insight into the nature of the fatigue damage. The results indicate that the fatiguing does not significantly affect the strength of the specimens tested. The results of the radiography and of the scanning electron microscopy indicate that the 45 deg plies suffer extensive damage in the form of split and broken fibers and matrix cracking in the vicinity of the ends of the split. By contrast, the only significant damage to the 0 deg plies was a single 0 deg matric crack growing from the ends of the slit and between the 0 deg fibers.
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Pressed high explosives have small density variations associated with the pressing process, from a few to sub percent depending on the material. Variations at these levels are known to have an impact on HE performance. Currently, a destructive testing method based on physical sectioning followed by immersion density measurements (slice and dice) is utilized. However, this method has poor spatial resolution limited by the the sectioning size, 1-2 cm. If possible, radiographic methods including Computed Tomography (CT) would be preferred, as they are non-destructive and have higher (less than .1 mm) spatial resolution. However, beam hardening, scattered radiation, and detector effects make density reconstructions at this level extremely challenging.
The Multi-Probe 22A experiments took place on the Omega EP laser in March 2022. The goal was to discover issues with simultaneous x-ray and proton radiography of static and dynamic test objects. The x-ray and proton probes were generated by short-pulse laser-matter interactions. Significant crosstalk between the proton beam and x-ray detector was observed. Several static radiographs were made, including a set of proton images made with different laser energies. No dynamic objects were radiographed.
The capabilities were investigated of projection microfocus X-radiography, ultrasonic velocity and attenuation, and reflection scanning acoustic microscopy for characterizing silicon carbide specimens. Silicon carbide batches covered a range of densities and different microstructural characteristics. Room temperature, four point flexural strength tests were conducted. Fractography was used to identify types, sizes, and locations of fracture origins. Fracture toughness values were calculated from fracture strength and flaw characterization data. Detection capabilities of radiography and acoustic microscopy for fracture-causing flaws were evaluated. Applicability of ultrasonics for verifying material strength and toughness was examined.
An analytical and experimental investigation was carried out on G40-800/R6376 graphite epoxy laminates to evaluate the Edge Crack Torsion (ECT) test as a candidate for a standard Mode 3 interlaminar fracture toughness test for laminated composites. The ECT test consists of a (90/(+/- 45)(sub 3)/(+/- 45)(sub 3)/90))(sub s) laminate with a delamination introduced by a non-adhesive film at the mid-plane along one edge and loaded in a special fixture to create torsion along the length of the laminate. Dye penetrate enhanced X-radiograph of failed specimens revealed that the delamination initiated at the middle of the specimen length and propagated in a self similar manner along the laminate mid-plane. A three-dimensional finite element analysis was performed that indicated that a pure Mode 3 delamination exists at the middle of specimen length away from both ends. At the ends near the loading point a small Mode 2 component exists. However, the magnitude of this Mode 2 strain energy release rate at the loading point is small compared to the magnitude of Mode 3 component in the mid-section of the specimen. Hence, the ECT test yielded the desired Mode 3 delamination. The Mode 3 fracture toughness was obtained from a compliance calibration method and was in good agreement with the finite element results. Mode 2 End-Notched Flexure (ENF) tests and Mode 1 Double Cantilever Beam (DCB) tests were also performed for the same composite material. The Mode 1 fracture toughness was much smaller than both the Mode 2 and Mode 3 fracture toughness. The Mode 2 fracture toughness was found to be 75% of the Mode 3 fracture toughness.
Ultrasound is of prO)len accuracy in abdominal and thoracic trauma and may be useful to diagnose extremity injury in situations where radiography is not available such as military and space applications. We prospectively evaluated the utility of extremity , ultrasound performed by trained, non-physician personnel in patients with extremity trauma, to simulate remote aerospace or military applications . Methods: Patients with extremity trauma were identified by history, physical examination, and radiographic studies. Ultrasound examination was performed bilaterally by nonphysician personnel with a portable ultrasound device using a 10-5 MHz linear probe, Images were video-recorded for later analysis against radiography by Fisher's exact test. The average time of examination was 4 minutes. Ultrasound accurately diagnosed extremity, injury in 94% of patients with no false positive exams; accuracy was greater in mid-shaft locations and least in the metacarpa/metatarsals. Soft tissue/tendon injury was readily visualized . Extremity ultrasound can be performed quickly and accurately by nonphysician personnel with excellent accuracy. Blinded verification of the utility of ultrasound in patients with extremity injury should be done to determine if Extremity and Respiratory evaluation should be added to the FAST examination (the FASTER exam) and verify the technique in remote locations such as military and aerospace applications.
A field-portable tagged neutron interrogation system is being developed for detection of explosives and chemical warfare agents by prompt γ-ray neutron activation analysis. The system combines an associated particle imaging deuterium-tritium neutron generator with a high-purity germanium γ-ray detector. Fine spatial resolution neutron and α detectors enable precise mapping of characteristic γ-ray emission distributions onto high-clarity neutron radiographic images. A narrow coincidence gate associated with each tagged neutron ensures a large signal-to-background ratio, thus significantly improving sensitivity to the chemical compositions of the items being assessed. Recent experimental results recorded from test objects involving mock explosives and other chemicals are presented.
Roentgen signs, subperiosteal, endosteal, and trabecular bone growth are evaluated in turkeys fed phosphorus at the 0.5, 0.56, 0.68, 0.90, and 2.70 percent levels. Calcium levels of 0.30, 0.40, 0.60, 1.2, and 3.60 percent were also tested. Vitamin D levels of 0, 100, 300, 900 and 27,000 I.U. per day were likewise evaluated. Roentgen signs, bone mineral as measured by T-125 gamma ray absorption, and bone mineral growth patterns as shown by radiograph area projection are correlated with calcium, phosphorus, and vitamin D feeding levels. Differences in bone growth at the various feeding levels were observed which were not reflected by differences in other studied parameters.
A fi eld-portable tagged neutron interrogation system is being developed for detection of explosives and chemical warfare agents by prompt gamma-ray neutron activation analysis. The system combines an associated particle imaging deuterium-tritium neutron generator with a high-purity germanium gamma-ray detector. Fine spatial resolution neutron and alpha detectors enable precise mapping of characteristic gamma-ray emission distributions onto high-clarity neutron radiographic images. A narrow coincidence gate associated with each tagged neutron ensures a large signal-to-background ratio, thus signifi cantly improving sensitivity to the chemical compositions of the items being assessed. Recent experimental results recorded from test objects involving mock explosives and other chemicals are presented.