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The Exploration on the Application of Acoustic Emission Technique in Testing Jointed Members of Soli

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Tutor: ZhaoXiaoMao
School: Beijing Forestry University
Course: Wood Science and Technology
Keywords: Acoustic emission,NDT,jonted members,bending moment test
CLC: TS664.1
Type: Master's thesis
Year:  2013
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Abstract:
Acoustic emission(AE),the phenomenon of acoustic propagation,is a transient elastic wave generated by a raid release of strain energy,when deformation or fracture is resulted due to the external or internal stress in a material or structure.AE technique is a non-destructive technique which has been applied to the assessment on performance of material or construction member.Over the past decade,AE technique has been applied in the field of wood science,e.g.,in evaluating the mechanical properties of wood and wood composites,and in-process timber drying control,as well as blade wear monitoring in the process of cutting etc.However, the studies of the relationship between the jointed members of solid wood furniture and the occurrence of AE characteristics was rare in the literature.The objectives of this paper were to investigate the relationships between the jointed members performances of furniture and occurrences of AE characteristics.The results of this research were expected to improve the method of non-destructive assessments of the furniture structures, and were provided to academic institutions and industry as reference for research purposes.Summary of the major findings of this research were listed as follows:(1) First,static bending test was performed with Manchurian walnut,which was often used in the furniture industry,to discuss the occurrence of AE related responses.These were devoted to investigate the AE characteristics of wood subjected to bending:The results show that AE signals were found mostly concentrating in the range beyond the point of proportional limited stress,and the number of AE characteristics showed the tendency of drastic increase and reaches the extremum at the maximum load;and the location of sensors were supposed to near to the sources of AE signal as possible.(2) Then.the jointed members were prepared according to the factors of joints type,adhesive and the assembling approaches.bending moment test was performed to discuss the AE related responses of various jointed members of furniture:The results show that due to the different failure mode of various jointed members comes with different AE signals,and there was distinct difference between the amplitude of jointed members with or without adhesive with analysis of distribution of amplitude and energy.,and the critical AE parameters and critical load of when cracks began to expand can be determined with real-time AE monitoring method.(3) At last, bending moment test was performed to discuss the AE related responses of L-type square-end mortise and tenon joints with adhesive members for various precracked specimens:The results show that the precrack specimens have higher and more intensive ringdown counts AE signals generated earlier, and the number of ringdown count of precrack specimens were less intensive and lower than specimens with no crack at maximum load.By analyzing, it is known that for each crack length’s test specimen,the maximum ringdown count at the first compact district, the relative energy value released at this point, the cumulative ringdown counts to this point, and the cumulative energy to this point are strongly correlated with the crack length.
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