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S. Dixon - One of the best experts on this subject based on the ideXlab platform.
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the detectability of Kissing Bonds in adhesive joints using ultrasonic techniques
Ultrasonics, 2003Co-Authors: C. J. Brotherhood, Bruce W Drinkwater, S. DixonAbstract:This paper concerns a study of the detectability of dry contact Kissing Bonds in adhesive joints using three ultrasonic inspection techniques. Conventional normal incidence longitudinal and shear wave inspection were conducted on dry contact Kissing Bonds using a standard damped ultrasonic transducer and an electro-magnetic acoustic transducer (EMAT) respectively. The detectability of the dry contact Kissing Bonds was assessed by calculating the reflection coefficient of the imperfect interface at varying loads for a number of surface roughnesses. A high power ultrasonic method was also employed to determine the non-linear behavior of the adhesive interface. The non-linearity of the interface was determined by the ratio of the amplitudes of the first harmonic and fundamental frequencies of the transmitted waveform. It was found that the high power technique showed the greatest sensitivity to these Kissing Bonds at low contact pressures, however at high loads conventional longitudinal wave testing was more sensitive. It was also noted that a combination of two or more techniques could provide enhanced information about the Kissing Bond compared to a single technique alone.
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The detectability of Kissing Bonds in adhesive joints using ultrasonic techniques
Ultrasonics, 2003Co-Authors: C. J. Brotherhood, Bruce W Drinkwater, S. DixonAbstract:This paper concerns a study of the detectability of dry contact Kissing Bonds in adhesive joints using three ultrasonic inspection techniques. Conventional normal incidence longitudinal and shear wave inspection were conducted on dry contact Kissing Bonds using a standard damped ultrasonic transducer and an electro-magnetic acoustic transducer (EMAT) respectively. The detectability of the dry contact Kissing Bonds was assessed by calculating the reflection coefficient of the imperfect interface at varying loads for a number of surface roughnesses. A high power ultrasonic method was also employed to determine the non-linear behavior of the adhesive interface. The non-linearity of the interface was determined by the ratio of the amplitudes of the first harmonic and fundamental frequencies of the transmitted waveform. It was found that the high power technique showed the greatest sensitivity to these Kissing Bonds at low contact pressures, however at high loads conventional longitudinal wave testing was more sensitive. It was also noted that a combination of two or more techniques could provide enhanced information about the Kissing Bond compared to a single technique alone. © 2003 Elsevier B.V. All rights reserved.
Bruce W Drinkwater - One of the best experts on this subject based on the ideXlab platform.
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Modelling and measurement of the nonlinear behaviour of Kissing Bonds in adhesive joints
Ndt & E International, 2012Co-Authors: Simon A Neild, Bruce W DrinkwaterAbstract:Abstract The non-destructive evaluation of adhesively Bonded joints is a subject of significant industrial and academic interest. It is thought that areas of interfacial weakness develop firstly into Kissing Bonds before finally disBonding. Critically, there is a requirement to detect such defects at the earliest possible stage. Whilst a number of techniques such as high frequency ultrasonic C-scanning are able to robustly detect disBonding, the detection of interfacial weakness has proved elusive. In this paper we focus our attention on the Kissing Bond state, which we consider to be a Bond still in intimate contact, but with zero, or minimal, strength. Various researchers have shown that Kissing Bonds of this type behave nonlinearly when illuminated with ultrasound and have sought to make this the basis of a non-destructive evaluation procedure. In this paper we use a one-dimensional time domain model that includes an interfacial nonlinearity to predict the interaction of ultrasonic pulses with a Kissing Bond. With this model we show that the measured nonlinearity is highly dependent on the thickness of the adhesive layer to wavelength ratio. These effects are explained by the observation that the linear dynamics of the multi-layer Bonded system act as a series of bandpass filters on the nonlinear signals generated at the Kissing interface. It is suggested that, in order to make robust nonlinear measurements, these filtering characteristics should be known and compensated for.
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EXPERIMENTAL AND THEORETICAL CHARACTERIZATION OF Kissing BondS IN ADHESIVE JOINT USING NON‐LINEAR ULTRASONIC MEASUREMENT
2010Co-Authors: Bruce W Drinkwater, Simon A NeildAbstract:An approach to the detection and characterization of Kissing Bonds, assumed to be either compressively loaded fracture surfaces or contamination layers, is described. A through transmission set‐up is used to extract harmonics resulting from the interaction of a narrow‐band ultrasonic signal with a nonlinear Kissing Bond. A time‐domain model, based on a nonlinear interfacial stiffness, is used to predict the experimental results. Good quantitative agreement is demonstrated for the compressively loaded type of Kissing Bond.
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measurement of the ultrasonic nonlinearity of Kissing Bonds in adhesive joints
Ndt & E International, 2009Co-Authors: Bruce W Drinkwater, Simon A NeildAbstract:Abstract This paper presents a study of the detectability of Kissing Bonds in adhesive joints using an ultrasonic inspection technique to measure nonlinearity. Kissing Bonds are defined as adhesive Bonding defects in which the adhesive and the substrate are not fully Bonded together but are in some way connected, for example, through contact between disBonded surfaces or through coupling via a very thin layer of contaminant. The result is a region that exhibits reduced normal or shear stiffness and is difficult to detect using conventional non-destructive testing techniques. It is hypothesised that when an ultrasonic wave of large magnitude propagates through the Kissing Bond area, the system will behave nonlinearly. This hypothesis is the starting point for this paper, and it is tested by measuring the degree of nonlinearity exhibited by perfectly and imperfectly Bonded specimens. Perfectly disBonded adhesive joints are tested over a range of compressive loads from an initial zero-load ‘open’ condition to a final highly loaded ‘closed’ condition and the degree of nonlinear behaviour measured. It is shown that adhesive joints exhibit significant nonlinearity under light compressive loads and that the level of nonlinearity decreases rapidly with compressive load. Good agreement is also observed between experimental results and a nonlinear spring model of the adhesive joint, based on its quasi-static interfacial stiffness.
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the detectability of Kissing Bonds in adhesive joints using ultrasonic techniques
Ultrasonics, 2003Co-Authors: C. J. Brotherhood, Bruce W Drinkwater, S. DixonAbstract:This paper concerns a study of the detectability of dry contact Kissing Bonds in adhesive joints using three ultrasonic inspection techniques. Conventional normal incidence longitudinal and shear wave inspection were conducted on dry contact Kissing Bonds using a standard damped ultrasonic transducer and an electro-magnetic acoustic transducer (EMAT) respectively. The detectability of the dry contact Kissing Bonds was assessed by calculating the reflection coefficient of the imperfect interface at varying loads for a number of surface roughnesses. A high power ultrasonic method was also employed to determine the non-linear behavior of the adhesive interface. The non-linearity of the interface was determined by the ratio of the amplitudes of the first harmonic and fundamental frequencies of the transmitted waveform. It was found that the high power technique showed the greatest sensitivity to these Kissing Bonds at low contact pressures, however at high loads conventional longitudinal wave testing was more sensitive. It was also noted that a combination of two or more techniques could provide enhanced information about the Kissing Bond compared to a single technique alone.
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The Interaction of Lamb Waves with Solid‐Solid Interfaces
AIP Conference Proceedings, 2003Co-Authors: Bruce W Drinkwater, Michel Castaings, Bernard HostenAbstract:This paper deals with the topic of the interaction of Lamb waves, more specifically the A0 and S0 modes, with a solid‐solid interface. This solid‐solid interface is the contact between two dry, rough surfaces and could represent a Kissing Bond in an adhesive joint or the contacting surfaces of a bolted joint. In this paper, a very thick elastomer with high internal damping is loaded against one surface of a glass plate to create a solid‐solid interface. The principal effect is shown to be increased attenuation of the guided waves propagating along the glass plate. This attenuation is caused by leakage of energy from the plate into the elastomer, where it is dissipated due to high viscoelastic damping. It is shown that the increase in attenuation is strongly dependent on the compressive load applied across the solid‐solid interface. This interface is represented as a spring layer in a continuum model of the multi‐layered system. Both normal and shear stiffnesses of the interface are quantified from the att...
Anne-françoise Gourgues-lorenzon - One of the best experts on this subject based on the ideXlab platform.
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Fatigue lifetime and tearing resistance of AA2198 Al-Cu-Li alloy friction stir welds: Effect of defects
International Journal of Fatigue, 2015Co-Authors: Thilo F Morgeneyer, A. Denquin, Anne-françoise Gourgues-lorenzonAbstract:The fatigue strength and failure mechanisms of defect-free ("sound") and flaw bearing friction stir butt-welds of 3.1 mm-thick AA2198-T8 Al-Li-Cu alloy have been investigated via S-N curves at R = 0.1 using cross weld specimens. The fatigue strength of sound welds is only reduced by 10-15% at the aimed lifetime of 105 cycles compared to the base material. Joint Line Remnant (JLR) bearing welds have a similar fatigue strength as sound welds and the JLR is not the crack initiation site. Kissing Bond (KB) bearing welds that have undergone a weld root polishing show a reduction in fatigue strength by 17% compared to sound welds. For specimens loaded at or above yield strength of the weld nugget the crack systematically initiates from the KB during the first cycle, which is interpreted further using fracture mechanics. The strongest reduction, about 28% in fatigue strength, is found for welds with an initial gap between the parent sheets (GAP welds) along with initiation at intergranular surface microcracks. Kahn tear tests show a reduction in tearing resistance for the flaw bearing welds with a similar ranking as for the fatigue strength.
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Microstructural Characterization of Internal Welding Defects and Their Effect on the Tensile Behavior of FSW Joints of AA2198 Al-Cu-Li Alloy
Metallurgical and Materials Transactions A, 2014Co-Authors: Thomas Le Jolu, A. Denquin, Thilo F Morgeneyer, Mohamed Sennour, Anne Laurent, Jacques Besson, Anne-françoise Gourgues-lorenzonAbstract:Internal features and defects such as joint line remnant, Kissing Bond, and those induced by an initial gap between the two parent sheets were investigated in AA2198-T851 friction stir welded joints. They were compared with the parent material and to defect-free welds obtained using a seamless sheet. The cross-weld tensile strength was reduced by the defects by less than 6 pct. The fracture elongation was not significantly affected in view of experimental scatter. Fracture location, however, changed from the thermomechanically affected zone (retreating side) to the defect in the weld nugget for the welds bearing a Kissing Bond and for some of the gap welds. The Kissing Bond was shown by EBSD to be an intergranular feature; it fractured under a normal engineering stress close to 260 MPa during an in situ SEM tensile test. Synchrotron tomography after interrupted tensile testing confirmed opening of the Kissing Bond. For an initial gap of 23 pct of the sheet thickness, intergranular fracture of copper-enriched or oxide-bearing grain boundaries close to the nugget root was evidenced. The stress and strain state of cross-weld specimens loaded under uniaxial tension was assessed using a 3D finite element, multi-material model, determined on the basis of experimental data obtained on the same specimens using digital image correlation.
Thilo F Morgeneyer - One of the best experts on this subject based on the ideXlab platform.
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Fatigue lifetime and tearing resistance of AA2198 Al-Cu-Li alloy friction stir welds: Effect of defects
International Journal of Fatigue, 2015Co-Authors: Thilo F Morgeneyer, A. Denquin, Anne-françoise Gourgues-lorenzonAbstract:The fatigue strength and failure mechanisms of defect-free ("sound") and flaw bearing friction stir butt-welds of 3.1 mm-thick AA2198-T8 Al-Li-Cu alloy have been investigated via S-N curves at R = 0.1 using cross weld specimens. The fatigue strength of sound welds is only reduced by 10-15% at the aimed lifetime of 105 cycles compared to the base material. Joint Line Remnant (JLR) bearing welds have a similar fatigue strength as sound welds and the JLR is not the crack initiation site. Kissing Bond (KB) bearing welds that have undergone a weld root polishing show a reduction in fatigue strength by 17% compared to sound welds. For specimens loaded at or above yield strength of the weld nugget the crack systematically initiates from the KB during the first cycle, which is interpreted further using fracture mechanics. The strongest reduction, about 28% in fatigue strength, is found for welds with an initial gap between the parent sheets (GAP welds) along with initiation at intergranular surface microcracks. Kahn tear tests show a reduction in tearing resistance for the flaw bearing welds with a similar ranking as for the fatigue strength.
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Microstructural Characterization of Internal Welding Defects and Their Effect on the Tensile Behavior of FSW Joints of AA2198 Al-Cu-Li Alloy
Metallurgical and Materials Transactions A, 2014Co-Authors: Thomas Le Jolu, A. Denquin, Thilo F Morgeneyer, Mohamed Sennour, Anne Laurent, Jacques Besson, Anne-françoise Gourgues-lorenzonAbstract:Internal features and defects such as joint line remnant, Kissing Bond, and those induced by an initial gap between the two parent sheets were investigated in AA2198-T851 friction stir welded joints. They were compared with the parent material and to defect-free welds obtained using a seamless sheet. The cross-weld tensile strength was reduced by the defects by less than 6 pct. The fracture elongation was not significantly affected in view of experimental scatter. Fracture location, however, changed from the thermomechanically affected zone (retreating side) to the defect in the weld nugget for the welds bearing a Kissing Bond and for some of the gap welds. The Kissing Bond was shown by EBSD to be an intergranular feature; it fractured under a normal engineering stress close to 260 MPa during an in situ SEM tensile test. Synchrotron tomography after interrupted tensile testing confirmed opening of the Kissing Bond. For an initial gap of 23 pct of the sheet thickness, intergranular fracture of copper-enriched or oxide-bearing grain boundaries close to the nugget root was evidenced. The stress and strain state of cross-weld specimens loaded under uniaxial tension was assessed using a 3D finite element, multi-material model, determined on the basis of experimental data obtained on the same specimens using digital image correlation.
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Effect of welding defects on plastic behaviour and fatigue lifetime of friction stir welded Al-Cu-Li alloy
International Conference on Fracture, 2013Co-Authors: Thomas Le Jolu, Thilo F MorgeneyerAbstract:The effects of joint line remnant (JLR), Kissing Bond (KB), and clearance between the sheets (Gap) on tensile and fatigue properties of 2198-T851 friction stir welds have been quantitatively evaluated with respect to a reference weld made using one single sheet. The JLR has no significant influence in the investigated conditions. KB and Gap-induced defects do not significantly influence plastic yield but may induce premature crack initiation by ductile tearing and intergranular decohesions respectively. A critical value for KB opening (280 MPa), a threshold value for fatigue crack propagation from the KB (1 MPa√m) and crack growth rates consistent with literature data have been determined.
Xinqi Yang - One of the best experts on this subject based on the ideXlab platform.
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Influences of joint geometry on defects and mechanical properties of friction stir welded AA6061-T4 T-joints
Materials & Design, 2020Co-Authors: Xinqi Yang, Guang ZhouAbstract:Abstract In this paper, AA6061-T4 T-joints with three different joint geometries of T-lap/T-butt-lap/T-butt were fabricated successfully by friction stir welding. The distributions and formation mechanisms of defects in friction stir welded (FSWed) T-joints were discussed through macro and micro-observations, respectively. Hardness profiles of the as-welded samples were also measured to evaluate the softening effect during the process. What’s more, influences of joint geometry and the traverse speed on the tensile properties of FSWed T-joints were investigated. All the experimental results indicate that tunnel defects and Kissing Bond are easily formed and vary significantly in T-joints of the three joint geometries. Defects are moderated to a large extent with decreasing the traverse speed, but the specific relationship to tensile properties is complicated. T-lap joints present the superior tensile properties along the skin direction among the three geometries, the same as T-butt joints along the stringer direction. All the as-welded samples almost fractured in the locations of softening zones and Bonding surfaces.
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Characteristics of defects and tensile behaviors on friction stir welded AA6061-T4 T-joints
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2012Co-Authors: Xinqi Yang, Guang Zhou, Xiaodong Xu, Z. ShenAbstract:Abstract In the present study, AA6061-T4 T-joints were successfully fabricated by friction stir welding (FSW) in three different combination ways of skins and stringers. Distributions and formation mechanisms of tunnel defects, Kissing Bond defects, original joint line with severe plastic deformation (OJLwSPD) defects, and zigzag line defects in T-joints were investigated by macro- and micro-observations. Influences of defects distributions and welding parameters on the tensile behaviors of T-joints were examined. To a better understanding of failure behaviors of T-joints, fracture locations and fracture surfaces of tensile samples were also investigated.
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effect of Kissing Bond on fatigue behavior of friction stir welds on al 5083 alloy
Journal of Materials Science, 2006Co-Authors: Caizhi Zhou, Xinqi Yang, Guohong LuanAbstract:Fatigue properties of FS welds with a Kissing Bond (Bonded welds) were studied by comparing the test results of Bonded welds with those of sound welds. The fatigue life of Bonded welds is 21∼43 times shorter than that of sound welds under the stress ratio R = 0.1, and the fatigue characteristic values of each welds have decreased from 100.24 MPa for sound welds to 65.57 MPa for Bonded welds at 2 × 106 cycles. At the macroscopic level there is no evidence of failure by shear. The fatigue fracture revealed cracks initiated from the root tip of Kissing Bond.
