Engineering topics
Publications and source records attributed to Rummel, W. D..
Reusable test panels available to assess reliability of techniques that use fluorescent penetrant to detect fatigue cracks. Ultrasonic cleaning method developed for removing penetrant from panels prior to reuse.
Specimens suitable for investigating the reliability of production nondestructive evaluation (NDE) to detect tightly closed fatigue cracks in high strength alloys representative of those materials used in spacecraft engine/booster construction were produced. Inconel 718 was selected as representative of nickel base alloys and Haynes 188 was selected as representative of cobalt base alloys used in this application. Cleaning procedures were developed to insure the reusability of the test specimens and a flaw detection reliability assessment of the fluorescent penetrant inspection method was performed using the test specimens produced to characterize their use for future reliability assessments and to provide additional NDE flaw detection reliability data for high strength alloys. The statistical analysis of the fluorescent penetrant inspection data was performed to determine the detection reliabilities for each inspection at a 90% probability/95% confidence level.
X-radiographic, liquid penetrant, ultrasonic, eddy current and magnetic particle testing techniques were optimized and applied to the evaluation of 4340 steel (180 KSI-UTS) and 6Al-4V titanium (STA) alloy specimens. Sixty steel specimens containing a total of 176 fatigue cracks and 60 titanium specimens containing a total of 135 fatigue cracks were evaluated. The cracks ranged in length from .043 cm (0.017 inch) to 1.02 cm (.400 inch) and in depth from .005 cm (.002 inch) to .239 cm (.094 inch) for steel specimens. Lengths ranged from .048 cm (0.019 inch) to 1.03 cm (.407 inch) and depths from 0.010 cm (.004 inch) to .261 cm (0.103 inch) for titanium specimens. Specimen thicknesses were nominally .152 cm (0.060 inch) and 0.635 cm (0.250 inch) and surface finishes were nominally 125 rms. Specimens were evaluated in the "as machined" surface condition, after etch surface and after proof loading in a randomized inspection sequence.
Liquid penetrant, ultrasonic, eddy current and X-radiographic techniques were optimized and applied to the evaluation of 2219-T87 aluminum alloy test specimens in integrally stiffened panel, and weld panel configurations. Fatigue cracks in integrally stiffened panels, lack-of-fusion in weld panels, and fatigue cracks in weld panels were the flaw types used for evaluation. A 2319 aluminum alloy weld filler rod was used for all welding to produce the test specimens. Forty seven integrally stiffened panels containing a total of 146 fatigue cracks, ninety three lack-of-penetration (LOP) specimens containing a total of 239 LOP flaws, and one-hundred seventeen welded specimens containing a total of 293 fatigue cracks were evaluated. Nondestructive test detection reliability enhancement was evaluated during separate inspection sequences in the specimens in the 'as-machined or as-welded', post etched and post proof loaded conditions. Results of the nondestructive test evaluations were compared to the actual flaw size obtained by measurement of the fracture specimens after completing all inspection sequences. Inspection data were then analyzed to provide a statistical basis for determining the flaw detection reliability.
X-radiographic, penetrant, ultrasonic, and eddy current techniques were optimized and applied to the evaluation of 2219-T87 aluminum alloy test specimens. One hundred eighteen specimens containing a total of 328 fatigue cracks were evaluated. The cracks ranged in length from 1.27 to 0.018 cm and in depth from 0.451 to 0.003 cm. Specimen thicknesses were nominally 0.152 and 0.532 cm. Specimens were evaluated in the 'as-milled' surface condition, in the etched surface condition, and, after proof loading, in a randomized inspection sequence. Results of the nondestructive test evaluations were compared with actual crack size obtained by analysis of the fractured specimens. Inspection data were then analyzed to provide a statistical basis for determining the threshold crack detection sensitivity for each of the inspection techniques at a 95% probability and 95% confidence level.
Holographic interferometry compares unknown field of optical waves with known one. Differences are displayed as interference bands or fringes. Technique was evaluated on fatigue-cracked 2219-T87 aluminum-alloy panels. Small cracks were detected when specimen was incrementally unloaded.
X-radiographic penetrant, ultrasonic, eddy current, holographic, and acoustic emission techniques were optimized and applied to the evaluation of 2219-T87 aluminum alloy test specimens. One hundred eighteen specimens containing a total of 328 fatigue cracks were evaluated. The cracks ranged in length from 0.500 inch (1.27 cm) to 0.007 inch (0.018 cm) and in depth from 0.178 inch (0.451 cm) and 0.001 inch (0.003 cm). Specimen thicknesses were nominally 0.060 inch (0.152 cm) and 0.210 inch (0.532 cm) and surface finishes were nominally 32 and 125 rms and 64 and 200 rms respectively. Specimens were evaluated in the as-milled surface condition, in the chemically milled surface condition and, after proof loading, in a randomized inspection sequence. Results of the nondestructive test (NDT) evaluations were compared with actual crack size obtained by measurement of the fractured specimens. Inspection data was then analyzed to provide a statistical basis for determinating the threshold crack detection sensitivity (the largest crack size that would be missed) for each of the inspection techniques at a 95% probability and 95% confidence level.
Experimental results are presented for a program conducted to determine the effects of fabrication-induced defects on the performance of an ablative heat shield material. Exposures representing a variety of space shuttle orbiter mission environments-humidity acoustics, hot vacuum and cold vacuum-culuminating in entry heating and transonic acoustics, were simulated on large panels containing intentional defects. Nondestructive methods for detecting the defects, were investigated. The baseline materials were two honeycomb-reinforced low density, silicone ablators, MG-36 and SS-41. Principal manufacturing-induced defects displaying a critical potential included: off-curing of the ablator, extreme low density, undercut (or crushed) honeycomb reinforcements, and poor wet-coating of honeycomb.
Results are presented from an investigation to determine the effects of fabrication-induced defects on the performance of an ablative heat shield material in a simulated space shuttle reentry environment. Nondestructive methods for detecting the defects were investigated. The material considered is a fiber-filled, honeycomb-reinforced, low-density elastomer. Results were obtained for density variations, voids, fiber bundles, crushed honeycomb, undercut honeycomb, unbonded areas, face sheet delaminations, and cure variations. The data indicate that, within reasonable tolerances, the fabrication defects investigated are not critical in terms of reentry performance of the heat shield.
Martin Marietta fabricated a hat-section-stiffened compression panel of graphite/epoxy composite that was analyzed to optimize the structural configuration and material distribution. The fabrication processes developed were modified following the appearance of several problems associated with the unique physical properties of the material. Quality control processes were developed, with emphasis in the areas of ultrasonics and X-ray.