1298378162

BOOK REVIEWS

OPTtMIZED VIBRATION TESTING AND ANALYSIS

E. Szymkowiak

Institute of Environmental Sciences. Mt. Prospect. IL 1983. 107 pages. $25.00

Vibration tests are wideły used to assure the suit* ability of a test object for its Intended use In a po-tentlally damaging vlbratlon envlronment. These tests are essentlal to prove in advance that an Item has a high probability of survival under soch vibra-tlon. Should the item fali the test. design or construc-tlon weaknesses are uncovered and can bef|xed prlor to usage. Costly f|xes in the field can thus be mini-mlzed and. In the case of crltlcal mllltary hardware, lives can be saved because rellable performance of the equipment is assured on the field of battle. Items subjected to vibration tests can vary wideły In slze. weight complexity. and cost; the test environment can be simple or complex. Yet the procedures for conducting the tests must be safe and comform with the requirements.

This document Is the text for a tutorlal course on vibration testing and analysis sponsored by the Chesapeake Chapter of the IES. The author points out in the Introduction that the same basie operating procedures are used for test setup, performance, and post test data analysis regardless of the level of complexity of the test item or the naturę of the environmental slmulation. The objectives of the publication are clearly stated:

1.    To acquaint the reader with a basie procedurę to set up and perform vibration tests.

2.    To provide detali on constraints which must be observed in order that tests may be performed safetly and accurately.

3.    To provide some Insight Into the major prob-lems that can occur during vibration testing, and into the probable Solutions.

There is clearly a need for tralnlng and guldance In the area of vibration testing. This publication was reyiewed with two questlons in mind. Does the document satisfy its stated objectives and does it stand alone as a useful guldance document?

Section II discusses the necessity for a Standard Operating Procedurę (SOP) to be used by vlbration test operators to set up and perform all vibration tests. An excełlent flow chart for such a proceduro is included in the document. The author did not include specific details on all steps in the SOP, but he did discuss a nu mb er of key steps that might invołve actlon by an environmental slmulation engineer. For example. the necessity for a complete wrltten descrip-tion of the test requlrements was stressed. Alignment, survey, and checkout of the test fixture are dlscussed with a view to avoidlng potentlal problems. Instru-mentation and test control procedures are deseribed, as are the necessity and means for over-test protec-tion. Finally. procedures for test performance are glven and requirements for post-test data analysis are dlscussed. including the advantage of quick tooks at data between test phases.

Section III provides considerabie detali on the constraints involved in measuring. analyzing. and inter-preting data. Resolution consideratlons as they are affected by the selection of filter bandwidth are dlscussed as they relate to both response meesure-ments and vibratłon test control. Record length constraints on accuracy are described, and problems of measuring relat!ve motion or differentlal dlsplace-ment between two parts of a structure are discussed. Interpretation of time history data is addressed, and the use of transfer functions in interpreting time synchronized data sampłes Is discussed.

Section IV addresses problems related to the evalua-tion and control of the environment. The flxture survey to sełect control accelerometer locations, including the over-test protection accelerometer. is described in some detali; the fixture checkout to verify the test setup is briefly discussed. Averaging. particularly spatial averaging and ensemble averaging.