Study On The Design Theory And Key Technology For Large Dynamic Centrifuge

Depending on the equipment of centrifugal shakers, geotechnicalcentrifuges can be generally classified as static testing centrifuges anddynamic testing centrifuges (also known as centrifuge shaking tables), whilstthe name of latter classification is shortened as dynamic centrifuges herein.Presently dynamic centrifuges are internationally acknowledged as the mostadvanced and the most effective scientific experiment platforms ingeotechnical earthquake engineering and soil dynamics. Whereas only a fewmedium and small dynamic centrifuges established as an auxiliary functionexist in China, and moreover their major technical parameters lag far behindthe international levels. No large dynamic centrifuge has been constructed inChina, which situation hardly sorts with t the wide territory, complicatedengineering geotechnical conditions, rapid economy growth and seriousseismic risks in China. One large dynamic centrifuge is a quite complicatedand huge system involving multidisciplinary techniques and lackingsuccessful experience, furthremore its construction is characterized by manyproblems, great difficulties, long period, and huge cost. Currently only twolarge dynamic centrifuges have been constructed and have being improvedconstantly since their completion, while the one in USA has an accumulativeconstruction period of approximately16years. The manufacture technologyand test technology of dynamic centrifuges are both worldly undeveloped andstill in primary phase. Additionally the acquaintance of large dynamiccentrifuges is very limited and confined to the indexes and functions in China,so what lacks more is systematic study on the key technology and designtheory of large dynamic centrifuges.Based on the urgent need for large dynamic centrifuges in China and thelarge dynamic centrifuge (DCIEM-40-300) construction in Institute ofEngineering Mechanics taken as application background, this paper focuseson the design theory and key technology of large dynamic centrifuges to study,in which the key technology and design difficulties are firstly ascertained andthen the main difficulties and critical problems are analyzed referring tomodeling, formulation, calculation, validation and other process. The mainconclusive and creative works can be outlined, as follows：1．By detailed summaries on the developments both at home and abroad,the performance evaluation index differences and the grading standards fordynamic centrifuges and geotechnical centrifuges are put forward. Byreviewing the status of dynamic centrifuge manufacture technology and testtechnology, the principal development key and trend in China are proposed.Meanwhile, the design indexes of DCIEM-40-300dynamic centrifuge arepresented, and its scale and functions are also illustrated. 2． Following the newly development of correlation technology, theconstruction experience, structural composition and design methods of thetwo existing large dynamic centrifuges in UC Davis and PWRI respectivelyare deeply analyzed. Studying mechanical structures, dynamic restrictions andfunctional inherent conditions of each part of a large dynamic centrifugesystem fixes the key technology, design points and difficulties of foursubsystems, in which the centrifugal shaker is identified as the core of wholesystem.3．Based on the core of a large dynamic centrifuge, the new problems andmain difficulties of the centrifugal shaker with high shaking capacity and highshaking payload are studied in detail. Moreover, the new design method andbasic theory of the whole and the major components of large centrifugalshakers are proposed, in which the international latest technologies areemployed. Taking the design indexes of DCIEM-40-300dynamic centrifugeas a sample, the design procedures and basic methods are presented, includingthe main structure design, parameter definition and component selection,meanwhile the load characteristics and mechanical properties are also checked.An equivalent mass calculation model for buckets is established andformulated.4．Based on the overall design method of large centrifugal shakers, theanalytic models and transfer functions of centrifugal shaker dynamics areestablished and calculated on three levels respectively, by which the hydraulicmechanistic dynamic features of centrifugal shakers under three differentdesign conditions are showed. Also, taking the design indexes ofDCIEM-40-300dynamic centrifuge as a sample and utilizing the transferfunctions calculated ahead, the influence of main parameters of buckets oncentrifugal shaker dynamics is analyzed, and then the optimum designmethods for centrifugal shakers are proposed.5． The servo-control simulation model for centrifugal shakers andbuckets is built to study the three parameter feedback and feedforwardcontrollers of centrifugal shakers, meanwhile, the standards for calculating theoptimized parameters are given. Then, the best ability of current servo-controltheory to improve the frequency band and stability of hydraulic systems ispresented on the function request of dynamic centrifuge tests. Simultaneously,the optimum design methods for the servo-control system of large centrifugalshaker are discussed.6．By studying the operating environments, functional requirements andtransducer design problems of test data acquisition systems, a large scaledesign method for large dynamic centrifuges to gather multi-type signals andmulti-wire sensors is proposed and characterized with multiplexing functions.Under ideal conditions, the design requirements and structure types of testcontainers are analyzed, meantime the design method and fundamental theoryof new flexible shear beam containers are developed. In addition, the basic requirement and overall method for design of a new test image acquisitionsystem are also provided.7．The structural layout method of equipments and the critical problemsof civil construction are systematically researched. By investigating theloading condition of machine foundation and the generation mode of vibration,the foundation vibration models for large dynamic centrifuges are developedas well as calculation methods, and the foundation design of DCIEM-40-300dynamic centrifuge is presented. Otherwise, the mathematical model andcalculation method of wind resistance power are derived, and a simplifiedcalculation method is also presented to convenient for engineeringapplications. The intrinsic mechanism of air movement of operation halls isexplained.