NASA Scientific and Technical Aerospace Reports

37
MECHANICAL ENGINEERING
Includes mechanical devices and equipment; machine elements and processes. For cases where the application of a device or the host
vehicle is emphasized see also the specific category where the application or vehicle is treated. For robotics see 63 Cybernetics,
Artificial Intelligence, and Robotics; and 54 Man/System Technology and Life Support.
20040068130 NASA Langley Research Center, Hampton, VA, USA
Recent Developments and Status of the Langley Single Vector Balance Calibration System (SVS)
Jones, Shirley M.; Rhew, Ray D.; 2004; 6 pp.; In English; Fourth International Symposium on Strain Gauge Balances, 10-13
May 2004, San Diego, CA, USA; No Copyright; Avail: CASI; A02, Hardcopy
The Langley Research Center (LaRC) Single Vector Balance Calibration System (SVS) was first introduced in 2000 by
Peter Parker. The SVS combines the Design of Experiments (DOE) methodology with a novel load application system. Since
that time three systems have been designed and developed with different load range capabilities (ranging from 2 pounds to
3,000 pounds). Approximately fifteen balances have been calibrated and their data compared to conventional techniques. This
paper will present results of these comparisons, based on the mathematical models and accuracies, and discuss differences that
were observed. In addition, changes in the implementation of the initial load schedules developed using DOE will be
highlighted. One of the principles behind DOE is randomization. The initial loading schedules used to date have been
randomized in the traditional DOE sense but not for repeat calibrations or experiments. Implementation of this randomization
within blocks and its impact on data quality will be reviewed. Areas of potential future development will be presented which
include changes in the centers to include loads with the force position system in the pure error estimates.
Author
Calibrating; Error Analysis; Mathematical Models
20040070764 Louisiana Tech Univ., Ruston, LA, USA
Elastic-Plastic Thermal Stress Analysis of a High-Pressure Cryogenic Storage Tank
Barker, J. Mark; Field, Robert E., Technical Monitor; August 15, 2003; 5 pp.; In English
Report No.(s): EB-2003-08-00005-SSC; No Copyright; Avail: Other Sources
The thermal stresses on a cryogenic storage tank contribute strongly to the state of stress of the tank material and its ability
to withstand operational stresses. These thermal stresses also affect the growth of any surface damage that might occur in the
tank walls. These stresses are particularly of concern during the initial cooldown period for a new tank placed into service,
and during any subsequent thermal cycles. A previous preliminary elastic analysis showed that the thermal stress on the inner
wall would reach approximately 1,000MPa (145,000 psi). This stress far exceeds the ASTM specified room temperature values
for both yield (170MPa) and ultimate (485 MPa) strength for 304L stainless steel. The present analysis determines the thermal
stresses using an elastic-plastic model. The commercial software application ANSYS was used to determine the transient
spatial temperature profile and the associated spatial thermal stress profiles in a segment of a thick-walled vessel during a
typical cooldown process. A strictly elastic analysis using standard material properties for 304L stainless steel showed that the
maximum thermal stress on the inner and outer walls was approximately 960 MPa (tensile) and - 270 MPa (compressive)
respectively. These values occurred early in the cooldown process, but at different times, An elastic-plastic analysis showed
significantly reducing stress, as expected due to the plastic deformation of the material. The maximum stress for the inner wall
was approximately 225 MPa (tensile), while the maximum stress for the outer wall was approximately - 130 MPa
(compressive).
Author
Elastic Properties; Stress Distribution; Thermal Stresses; High Pressure; Storage Tanks; Plastic Properties; Cryogenic
Equipment
20040070814 Texas-Pan American Univ., Edinburg, TX, USA
Improved Temperature Dynamic Model of Turbine Subcomponents for Facilitation of Generalized Tip Clearance
Control
Kypuros, Javier A.; Colson, Rodrigo; Munoz, Afredo; January 2004; 13 pp.; In English
Contract(s)/Grant(s): NAG3-2857; No Copyright; Avail: CASI; A03, Hardcopy
This paper describes efforts conducted to improve dynamic temperature estimations of a turbine tip clearance system to
facilitate design of a generalized tip clearance controller. This work builds upon research previously conducted and presented
in and focuses primarily on improving dynamic temperature estimations of the primary components affecting tip clearance (i.e.
the rotor, blades, and casing/shroud). The temperature profiles estimated by the previous model iteration, specifically for the
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