Abstract
IN THIS PAPER, AT FIRST THE ATTENUATION OF LAMB WAVES IN THREE-LAYER ADHESIVE JOINTS, INCLUDING TWO ELASTIC PLATES BONDED TOGETHER BY A VISCOELASTIC ADHESIVE LAYER, IS INVESTIGATED USING GLOBAL MATRIX METHOD AND THEN SUITABLE INCIDENCE ANGLE IS THEORETICALLY CALCULATED TO GENERATE LOW-ATTENUATION LAMB WAVES USING ANGLE BEAM TRANSDUCER. THEORETICAL BOUNDARY VALUE PROBLEM IN THREE-LAYER ADHESIVE JOINTS WITH PERFECT BOND AND TRACTION-FREE BOUNDARY CONDITIONS ON THEIR OUTER SURFACES IS SOLVED TO FIND A COMBINATION OF FREQUENCIES AND MODES WITH LOWEST ATTENUATION. CHARACTERISTIC EQUATION IS DERIVED BY APPLYING CONTINUITY AND BOUNDARY CONDITIONS IN THREE-LAYER JOINTS USING GLOBAL MATRIX METHOD. PHASE VELOCITY DISPERSION CURVES AND ATTENUATION INTENSITY PLOT IN HIGH AND LOW FREQUENCIES ARE OBTAINED WITH NUMERICAL SOLUTION OF THIS EQUATION BY A COMPUTER CODE FOR A THREE-LAYER JOINT, INCLUDING AN ALUMINUM REPAIR PATCH BONDED TO THE AIRCRAFT ALUMINUM SKIN BY A LAYER OF VISCOELASTIC EPOXY ADHESIVE. TO VALIDATE THE NUMERICAL SOLUTION RESULTS OF CHARACTERISTIC EQUATION, WAVE STRUCTURE CURVES ARE PLOTTED FOR A SPECIAL MODE IN TWO DIFFERENT FREQUENCIES IN THE ADHESIVE JOINT. ALSO, TRANSDUCER INCIDENCE ANGLE IS CALCULATED IN TERMS OF FREQUENCY FOR DIFFERENT MODES USING THEORETICAL METHOD TO GENERATE LAMB WAVE MODES WITH LOW ATTENUATION LEVEL BY ANGLE BEAM TRANSDUCER. THESE MODES ARE RECOGNIZABLE BY TRANSDUCERS IN INSPECTIONS WITH LAMB WAVES BECAUSE OF LOW ATTENUATION LEVEL.
Highlights
The applications of adhesive joints in plates and pipes to increase life, improve stiffness, protect against corrosion, and electrical insulation have been caused the widespread use of viscoelastic polymer material like epoxy with plates and pipes as adhesive and coating
Taghipour Birgani et al / Theoretical mod. of low-attenuation lamb wave modes generation in three-layer adhesive joints using angle beam transducer application is a three-layer adhesive joint including an aluminum patch bonded to a surface, like aircraft aluminum skin, by a viscoelastic epoxy adhesive layer
Taghipour Birgani et al / Theoretical mod. of low-attenuation lamb wave modes generation in three-layer adhesive joints using angle beam transducer horizontal (SH) waves in an elastic plate coated with viscoelastic material
Summary
The applications of adhesive joints in plates and pipes to increase life, improve stiffness, protect against corrosion, and electrical insulation have been caused the widespread use of viscoelastic polymer material like epoxy with plates and pipes as adhesive and coating. Of low-attenuation lamb wave modes generation in three-layer adhesive joints using angle beam transducer horizontal (SH) waves in an elastic plate coated with viscoelastic material. Puthillath and Rose (2010) inspected the titanium repair patches bonded to the aircraft aluminum skin using ultrasonic guided waves They plotted the wave structures using a theoretical method and selected the mode shape with maximum in-plane displacement for inspection, they didn’t take into consideration the effect of material damping. The propagation of Lamb waves in elastic-viscoelastic three-layer joints, including two elastic plates bonded together with a layer of viscoelastic adhesive, is investigated using Global matrix method and considering viscoelastic layer damping effect. Because these waves travel the maximum possible distance in joints and can detect the different defects namely interfacial defects
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