Publications

When measuring the structural dynamic response of test objects, the desired data is sometimes combined with some type of undesired periodic data. This can occur due to N-per-revolution excitation in systems with rotating components or when dither excitation is used. The response due to these (typically unmeasured) periodic excitations causes spikes in system frequency response functions (FRFs) and poor coherence. This paper describes a technique to remove these periodic components from the measured data. The data must be measured as a continuous time history which is initially processed as a single, long record. Given an initial guess for the periodic signal's fundamental frequency, an automated search will identify the actual fundamental frequency to very high accuracy. Then the fundamental and a user-specified number of harmonics are removed from the acquired data to create new time histories. These resulting time histories can then be processed using standard signal processing techniques. An example of this technique will be presented from a test where a vehicle is dithered with a fixed-frequency, sinusoidal force to linearize the behavior of the shock absorbers, while measuring the acceleration responses due to a random force applied elsewhere on the vehicle.

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This paper presents an analysis technique used to generate the structural response at locations not measured during the ejection of a captive-carried store. The ejection shock event is complicated by the fact that forces may be imparted to the store at eight distinct locations. The technique derives forcing functions by combining the initial field test data for a limited number of measurement locations with Frequency Response Functions (FRFs) measured using a traditional modal-type impact (tap) test at the same locations. The derived forcing functions were then used with tap test FRFs measured at additional locations of interest to produce the desired response data.

This report presents the results of an experimental program to determine the aging and loss-of-coolant accident (LOCA) behavior of electrical connections in order to obtain an initial scoping of their performance. Ten types of connections commonly used in nuclear power plants were tested. These included 3 types of conduit seals, 2 types of cable-to-device connectors, 3 types of cable-to-cable connectors, and 2 types of in-line splices. The connections were aged for 6 months under simultaneous thermal (99 C) and radiation (46 Gy/hr) conditions. A simulated LOCA consisting of sequential high dose-rate irradiation (3 kGy/hr) and high-temperature steam exposures followed the aging. Connection functionality was monitored using insulation resistance measurements during the aging and LOCA exposures. Because only 5 of the 10 connection types passed a post-LOCA, submerged dielectric withstand test, further detailed investigation of electrical connections and the effects of cable jacket integrity on the cable-connection system is warranted.