Research On Modal Strain Energy Method For Damage Detection Of Elastic Structures

With the in-depth research of the structural damage identification technology,vibration-based structural damage detection theory has been greatly developed. Thedamage identification technology which based on the modal strain energy has madeconsiderable progress in recently years. Through the structural dynamics theory, thetypical engineering structures (eg. beams and plates) is employed to explore the modalstrain energy method of damage identification for elastic structures further more in thispaper. The main work and academic contributions are listed as follows:(1) Starting from the basic vibration theory of the elastic beam and the elasticplate, different kinds of vibration based structural damage detection theories andmethods is discussed, and the pros or cons of them are studied via the numericalexample.(2) A novel method is proposed for structural damage detection via changing ofthe unit modal strain energy. A principle is employed that the modal properties will bechanging as structure is damaged. An indicator is built through comparing the modalstrain energy before and after an elastic beam is injured. Firstly, an elastic beam’sstiffness is regarded that it is built by unit stiffness, and a formula is defined for unitstiffness sensitivity. Thereafter, the contact between elastic beams before and afterdamaged is built by modal strain energy. Results are given after simulation, the accurateand efficiency of this method is verified in the end.(3) Developing from simple one-dimensional elastic beam to two-dimensionalelastic thin elastic, one modal strain energy method of damage identification for anelastic thin plate is proposed. This method achieves the extension from line to face. Thenumerical modelling and case studies are carried out for a simple elastic beam. It can beseen from the results that the method’s identification accuracy is accurate and thedetection results is obvious.(4) Based on the experimental method, several kinds of damage beams aredesigned to test the modal strain energy method of damage detection for an elasticstructure. Results indicate, this method has enough ability to damage detectionexcluding the effects of noise and measurement of experimental error.Compared with other ways of structural damage identification, this method onlyneed the first four order modes, and it has good recognition for a single injury, multi-trauma injuries, and the injuries to varying degrees and of the boundary conditions. Besides it has good applicability and high sensitivity releative to other methods.