October 1996 through September 1997 - Oak Ridge National ...

In addition to tlic nieasureinerit of temperature and thermal properties, the camera can also be
used for thermography applications for nondestructive evaluation of components. 7’1ie use of IR
traiisniitting fibers coupled to the camera was demonstrated and lias great potential for temperature
measurement within systems such a\ dies during liquid metal insertion.
TPlJC developed a portable canicra-control capability to allow off-site field work. The first
demonstration of this portability was in a reverse €1 IML fellowship with the Ford Scientific Research
p ?
Laboratory. 1 he purpox of this investigation is to siinultaneouslq image hot spots on tlie inboard
and outboard sides of a brake rotor during braking 011 a dynamometer. These hot spots result in
localizcd thcrmal expansion of the rotor that cause the torque variations we know as brake roughness
or brake judder. During the three visits to Ford, the ‘IPUC staff was able to record thousands of
images of this hot-spotting phenomenon as a function of initial rotor temperature and speed, brake
pad manufacturer aiid design. and braking behavior (i.e., dragging or stopping). In addition to the
qualitative images, which show tlie spatial and time evolution of the hot spots, a calibration was
performed that allowed tlie quantitative measurement of tcmpcrature as a fiinctioii of time and
location.
Tliese results Iiavc both sliort- and long-term benefits. In the short term, brake system
componcnts that are less likelq to cause hot spotting can be selected for cars about to be introduced
into the market. In the long term, tlie thermoelastic niodcls that describe hot spotting inaj be
refined and used to cvaluate future designs before they go into production. Visits to GM Delphi
Chassis Systems and the University of Southern I Ilinois are currently being planned for additional
work on brake systcnis and materials.
4.4 RESIDUAL STRESS USER CENTER
4.4.1 Background
llser projects and DOE programs are increasingly concerned with life prediction and failure
analysis of engineering structures. In many oi’ these cases. knowledge of residual stress gradients (sign
and magnitude) as a function of location at both tlic surface and throughout the volume of a
component is critical information for failure analysis and life prediction models. The Residual Stress
User Center (RSUC) Mas established to meet this need and to provide a facility for research into
controlling residual stresses. either through modifying the forming and finishing processes, by
chaiiges in the design, or through strewrelief procedures. KSlJC activities no\.c include both the X-ray
residual stress facility, tlie neutron residual stress facility (discussed in detail in Sect. 4.4.3), and the
developing use of synchrotron radiation and Rainan microprobe. The diffraction facilities can bc
utilized to measure macro (long-range) and micro (short-range) residual stresses in polycrystalline
materials. Ramaii microprobe is currently focused on alumina stress measurement in TBCs.
RS1JC‘ also characteriies the nonrandom grain distribution or texture in materials and relates tliiq
to directionally dependent materials properties. Texture is very common in materials sub-ject to
deformation and also in thin films. both areas of increasing importance.
4.4.2 Staff and Major Instruments
4.4.2.1 Staff
‘The Neutron Residual Stress Facility (NIXSF) is operated in a teain mode, with members of tlic
Metals and Ceramics (M&C). Solid-State (SSD). and Instrumentation and Controls (I&C) divisions
participating. Ihless otherwise noted, the following staff members are from the Diffraction and
Thennophysical Properties Group, Metals arid Ceramics Division. At the end of FY 1996 two group
members took positions in industry, and a new postdoc and {Jniversity of ‘Tennessee (UT)
subcontractor were added to the group during the year.
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