Experimental Study On Disfigurements Inspection Of Structures With ESPI Method

Disfigurements of structures include inner disfigurements and surface disfigurements.Disfigurements on the surface of structures are visible and easy to be detected,but inner ones are covered and hard to be found.Some detecting methods are widely used and have solved many problems,such as Infrared Imaging Method, Ultrasonic Method,X-Ray method,etc.But there is few reported literature about quantified researches on inner disfigurement,especially when the disfigurement is small.The existence of small disfiguration in structures is a big hidden trouble for the safety,so a method that can be used to detect inner disfigurements is concerned by many companies.In the view of Photo-Optic Mechanics,Elastic Mechanics,and FEM method,the deformation of inner disfigurements in structures was studied with ESPI and Phase-Shift in this dissertation and some valuable results and conclusions were obtained.With ESPI and Phase-Shift method,referring many relative literatures,we did some research on inner disfigurements,designed some specimen used in the study, and compared the strongpoint and weak point of each loading method.We found the temperature load was not stable and was hard to be controlled.Gas pressure is a better load so we advanced the gas pressure method and got lots of data.The research settled the base of further studies,and raised some suggestion to improve the experiment.It studied an experimental technology which can be used to detect inner disfigurements in structures.The cover layer of disfigurement is simulated with elastic sheet and its deformation under load is obtained.The study can be used to detect inner disfigurement whose proportion is 1/80 <α< 1/5,where the proportion is location depth is divided by the diameter.We used the mechanical mode,numerical simulation and experiment study in this dissertation,which made the study more effective.Mechanical model provide instruction for the theoretic analysis,while the results from numerical simulation can be used to design the specimen.The loads set in the simulation can guide the experimental loads,and that avoided the some accidents.ESPI method and phase-shift technique are used in the dissertation successfully, and the deformation of the cover layer which is made of Aluminium alloy is detected. It proves that there is feasibility and advantage of ESPI when it is used in inner disfigurement detection.This study provides a new method that can detect inner disfigurement and widens the application of ESPI.