Engineering topics

Sikora, Joseph G.

Publications and source records attributed to Sikora, Joseph G..

5 records

NASA NTRS2016

Optical Method for Detecting Displacements and Strains at Ultra-High Temperatures During Thermo-Mechanical Testing

An ultra-high temperature optical method incorporates speckle optics for sensing displacement and strain measurements well above conventional measurement techniques. High temperature pattern materials are used which can endure experimental high temperature environments while simultaneously having a minimum optical aberration. A purge medium is used to reduce or eliminate optical distortions and to reduce, and/or eliminate oxidation of the target specimen.

Smith, Russell W.↗

NASA NTRS2007

Portable Microleak-Detection System

The figure schematically depicts a portable microleak-detection system that has been built especially for use in testing hydrogen tanks made of polymer-matrix composite materials. (As used here, microleak signifies a leak that is too small to be detectable by the simple soap-bubble technique.) The system can also be used to test for microleaks in tanks that are made of other materials and that contain gases other than hydrogen. Results of calibration tests have shown that measurement errors are less than 10 percent for leak rates ranging from 0.3 to 200 cm3/min. Like some other microleak-detection systems, this system includes a vacuum pump and associated plumbing for sampling the leaking gas, and a mass spectrometer for analyzing the molecular constituents of the gas. The system includes a flexible vacuum chamber that can be attached to the outer surface of a tank or other object of interest that is to be tested for leakage (hereafter denoted, simply, the test object). The gas used in a test can be the gas or vapor (e.g., hydrogen in the original application) to be contained by the test object. Alternatively, following common practice in leak testing, helium can be used as a test gas. In either case, the mass spectrometer can be used to verify that the gas measured by the system is the test gas rather than a different gas and, hence, that the leak is indeed from the test object.

Rivers, H. Kevin↗

NASA NTRS2005

Test and Analysis of a Hyper-X Carbon-Carbon Leading Edge Chine

During parts production for the X43A Mach 10 hypersonic vehicle nondestructive evaluation (NDE) of a leading edge chine detected on imbedded delamination near the lower surface of the part. An ultimate proof test was conducted to verify the ultimate strength of this leading edge chine part. The ultimate proof test setup used a pressure bladder design to impose a uniform distributed pressure field over the bi-planar surface of the chine test article. A detailed description of the chine test article and experimental test setup is presented. Analysis results from a linear status model of the test article are also presented and discussed. Post-test inspection of the specimen revealed no visible failures or areas of delamination.

Smith, Russell W.↗

NASA NTRS2002

Thermal Vacuum Facility for Testing Thermal Protection Systems

A thermal vacuum facility for testing launch vehicle thermal protection systems by subjecting them to transient thermal conditions simulating re-entry aerodynamic heating is described. Re-entry heating is simulated by controlling the test specimen surface temperature and the environmental pressure in the chamber. Design requirements for simulating re-entry conditions are briefly described. A description of the thermal vacuum facility, the quartz lamp array and the control system is provided. The facility was evaluated by subjecting an 18 by 36 in. Inconel honeycomb panel to a typical re-entry pressure and surface temperature profile. For most of the test duration, the average difference between the measured and desired pressures was 1.6% of reading with a standard deviation of +/- 7.4%, while the average difference between measured and desired temperatures was 7.6% of reading with a standard deviation of +/- 6.5%. The temperature non-uniformity across the panel was 12% during the initial heating phase (t less than 500 sec.), and less than 2% during the remainder of the test.

Daryabeigi, Kamran↗

NASA NTRS1998

Evaluation of Heating Methods for Thermal Structural Testing of Large Structures

An experimental study was conducted to evaluate different heating methods for thermal structural testing of large scale structures at temperatures up to 350 F as part of the High Speed Research program. The heating techniques evaluated included: radiative/convective, forced convective, and conductive. The radiative/convective heaters included finned strip heaters, and clear and frosted quartz lamps. The forced convective heating was accomplished by closed loop circulation of heated air. The conductive heater consisted of heating blankets. The tests were conducted on an 1/8 inch thick stainless steel plate in a custom-built oven. The criteria used for comparing the different heating methods included test specimen temperature uniformity, heater response time, and consumed power. The parameters investigated included air circulation in the oven, reflectance of oven walls, and the orientation of the test specimen and heaters (vertical and horizontal). It was found that reflectance of oven walls was not an important parameter. Air circulation was necessary to obtain uniform temperatures only for the vertically oriented specimen. Heating blankets provided unacceptably high temperature non-uniformities. Quartz lamps with internal air circulation had the lowest power consumption levels. Using frosted quartz lamps with closed loop circulation of cool air, and closed loop circulation of heated air provided the fastest response time.

Daryabeigi, Kamran↗