The Experts below are selected from a list of 183 Experts worldwide ranked by ideXlab platform
Hossein Hosseini-toudeshky - One of the best experts on this subject based on the ideXlab platform.
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Investigation of effective parameters on composite patch debonding under static and cyclic loading using cohesive elements
Finite Elements in Analysis and Design, 2013Co-Authors: Hossein Hosseini-toudeshky, Ali Jasemzadeh, Bijan MohammadiAbstract:Abstract The major addressed issue in this paper is investigation of impressive parameters on initiation and propagation of debonding in the adhesive layer when it occurs concurrently with the growth of an initial crack in a single-side repaired Aluminum Panels by composite patches under cyclic loading. Using the softening behavior of thin layer solid like interface elements, debonding is modeled between the composite patch layer adjacent to the Aluminum Panel as a function of loading condition and stress field. A user element routine and two damage model routines were developed to include the interface element and to simulate the distribution of damage in adhesive layer under static and cyclic loading. Fatigue crack growth in Aluminum Panel was also modeled using a simple approach developed by the authors. It is shown that, it is possible to decrease the debonding propagation by implementing appropriate composite patch and adhesive dimensional and material properties.
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Effects of curing thermal residual stresses on fatigue crack propagation of Aluminum plates repaired by FML patches
Composite Structures, 2013Co-Authors: Hossein Hosseini-toudeshky, Mojtaba Sadighi, Ali VojdaniAbstract:Abstract One of the main disadvantages of using composite patches in repair of metallic Panels is development of thermal residual stresses due to the curing cycles of the bonded repairs. Fiber Metal Laminates (FMLs) have the overall larger thermal expansion coefficients when compared with the fully composite patches. In this study, the thermal residual stresses that occur due to the thermal expansion coefficient mismatch between the FML patch and underlying cracked Aluminum Panel are investigated using both numerical and experimental studies. The fatigue crack growth behaviors of centrally cracked Aluminum Panels in mode-І condition with single-side repairs of FML patches that are made by alternating layers of Aluminum and glass fiber-epoxy are carried out. Sensitivity of the curing temperature on fatigue crack-growth life extension and crack-front shape of the repaired Panels is also investigated. It is shown that implementing of various curing temperatures do not significantly affect the thermal residual stresses, crack-growth lives and crack-front shapes of the repaired Panels by FML patches.
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Composite Repair of Curved Stiffened Aluminum Panels under Combined Tension and Shear Cyclic Loadings
Applied Mechanics and Materials, 2012Co-Authors: Hossein Hosseini-toudeshky, Mir Ali Ghaffari, Bijan MohammadiAbstract:In this study, finite element method is used to investigate the fracture analyses, crack growth trajectory and fatigue life of curved stiffened Panels repaired with composite patches subjected to combined tension and shear cyclic loadings. For this purpose, 3-D finite element modeling are performed for consideration of real 3-D crack-front in general mixed-mode conditions. Contact elements are used between the crack surfaces on two crack sides to prevent interferences of crack surfaces and a complementary program was developed to handle the automatic fatigue crack growth modeling. The effects of various patch layups and shear-tension loading ratios on fracture parameters of the Aluminum Panel are investigated. It is shown that in low shear to tension ratios like 0.4, the patch layup of [90]4 (perpendicular to the initial crack) is more efficient than the patch with layups angle along the tension loading. As the shear to tension ratio increases, effect of patch layups with orientations of almost perpendicular to the crack trajectory on fatigue crack growth life is increased comparing with the patch layups parallel to the tension orientation like [90]4.
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Thermal residual stresses effects on fatigue crack growth of repaired Panels bounded with various composite materials
Composite Structures, 2009Co-Authors: Hossein Hosseini-toudeshky, Bijan MohammadiAbstract:Thermal residual stresses, due to the curing cycle of the bonded composite patch affects the stress/strain states and the crack patching efficiency of the single-side repaired Aluminum Panels. In this study the thermal residual stresses that occur as a result of the thermal expansion coefficient mismatch between the patch and the underlying cracked Aluminum Panel are investigated. The fatigue crack-growth life and the crack-front configuration of centrally cracked Aluminum Panels in mode-I condition with various single-side repairs of glass/epoxy, graphite/epoxy and boron/epoxy composite patches are curried out. Sensitivity of the obtained residual stresses to different curing temperatures of the repaired Panels with various composite patches is also investigated. It is shown that low curing temperatures (e.g., 60 °C) with long curing cycles have not a considerable effect on fatigue crack-growth life of the repaired Panels with glass/epoxy patch and have minor effects for repaired Panels with graphite/epoxy and boron/epoxy composite patches. It is also shown that considering the thermal residual stresses, the obtained FEM fatigue life and crack-front shapes of the repaired Panels using glass/epoxy patch are in good agreement with those obtained from the experiments.
Michaela De Giglio - One of the best experts on this subject based on the ideXlab platform.
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Strain wave acquisition by a fiber optic coherent sensor for impact monitoring
Materials, 2017Co-Authors: Claudio Sbarufatti, Alessio Beligni, Marco Mattarei, Matthieu Martinelli, Andrea Gilioli, Maurizio Ferrario, Mario Martinelli, Michaela De GiglioAbstract:A novel fiber optic sensing technology for high frequency dynamics detection is proposed in this paper, specifically tailored for structural health monitoring applications based on strain wave analysis, for both passive impact identification and active Lamb wave monitoring. The sensing solution relies on a fiber optic-based interferometric architecture associated to an innovative coherent detection scheme, which retrieves in a completely passive way the high-frequency phase information of the received optical signal. The sensing fiber can be arranged into different layouts, depending on the requirement of the specific application, in order to enhance the sensor sensitivity while still ensuring a limited gauge length if punctual measures are required. For active Lamb wave monitoring, this results in a sensing fiber arranged in multiple loops glued on an Aluminum thin Panel in order to increase the phase signal only in correspondence to the sensing points of interest. Instead, for passive impact identification, the required sensitivity is guaranteed by simply exploiting a longer gauge length glued to the structure. The fiber optic coherent (FOC) sensor is exploited to detect the strain waves emitted by a piezoelectric transducer placed on the Aluminum Panel or generated by an impulse hammer, respectively. The FOC sensor measurements have been compared with both a numerical model based on Finite Elements and traditional piezoelectric sensors, confirming a good agreement between experimental and simulated results for both active and passive impact monitoring scenarios.
Bijan Mohammadi - One of the best experts on this subject based on the ideXlab platform.
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Investigation of effective parameters on composite patch debonding under static and cyclic loading using cohesive elements
Finite Elements in Analysis and Design, 2013Co-Authors: Hossein Hosseini-toudeshky, Ali Jasemzadeh, Bijan MohammadiAbstract:Abstract The major addressed issue in this paper is investigation of impressive parameters on initiation and propagation of debonding in the adhesive layer when it occurs concurrently with the growth of an initial crack in a single-side repaired Aluminum Panels by composite patches under cyclic loading. Using the softening behavior of thin layer solid like interface elements, debonding is modeled between the composite patch layer adjacent to the Aluminum Panel as a function of loading condition and stress field. A user element routine and two damage model routines were developed to include the interface element and to simulate the distribution of damage in adhesive layer under static and cyclic loading. Fatigue crack growth in Aluminum Panel was also modeled using a simple approach developed by the authors. It is shown that, it is possible to decrease the debonding propagation by implementing appropriate composite patch and adhesive dimensional and material properties.
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Composite Repair of Curved Stiffened Aluminum Panels under Combined Tension and Shear Cyclic Loadings
Applied Mechanics and Materials, 2012Co-Authors: Hossein Hosseini-toudeshky, Mir Ali Ghaffari, Bijan MohammadiAbstract:In this study, finite element method is used to investigate the fracture analyses, crack growth trajectory and fatigue life of curved stiffened Panels repaired with composite patches subjected to combined tension and shear cyclic loadings. For this purpose, 3-D finite element modeling are performed for consideration of real 3-D crack-front in general mixed-mode conditions. Contact elements are used between the crack surfaces on two crack sides to prevent interferences of crack surfaces and a complementary program was developed to handle the automatic fatigue crack growth modeling. The effects of various patch layups and shear-tension loading ratios on fracture parameters of the Aluminum Panel are investigated. It is shown that in low shear to tension ratios like 0.4, the patch layup of [90]4 (perpendicular to the initial crack) is more efficient than the patch with layups angle along the tension loading. As the shear to tension ratio increases, effect of patch layups with orientations of almost perpendicular to the crack trajectory on fatigue crack growth life is increased comparing with the patch layups parallel to the tension orientation like [90]4.
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Thermal residual stresses effects on fatigue crack growth of repaired Panels bounded with various composite materials
Composite Structures, 2009Co-Authors: Hossein Hosseini-toudeshky, Bijan MohammadiAbstract:Thermal residual stresses, due to the curing cycle of the bonded composite patch affects the stress/strain states and the crack patching efficiency of the single-side repaired Aluminum Panels. In this study the thermal residual stresses that occur as a result of the thermal expansion coefficient mismatch between the patch and the underlying cracked Aluminum Panel are investigated. The fatigue crack-growth life and the crack-front configuration of centrally cracked Aluminum Panels in mode-I condition with various single-side repairs of glass/epoxy, graphite/epoxy and boron/epoxy composite patches are curried out. Sensitivity of the obtained residual stresses to different curing temperatures of the repaired Panels with various composite patches is also investigated. It is shown that low curing temperatures (e.g., 60 °C) with long curing cycles have not a considerable effect on fatigue crack-growth life of the repaired Panels with glass/epoxy patch and have minor effects for repaired Panels with graphite/epoxy and boron/epoxy composite patches. It is also shown that considering the thermal residual stresses, the obtained FEM fatigue life and crack-front shapes of the repaired Panels using glass/epoxy patch are in good agreement with those obtained from the experiments.
Stephen C Conlon - One of the best experts on this subject based on the ideXlab platform.
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nonlinear structural surface intensity an application of contact acoustic nonlinearity to power flow based damage detection
Applied Physics Letters, 2010Co-Authors: Fabio Semperlotti, Stephen C ConlonAbstract:The concept of structural surface intensity is extended to the nonlinear domain introducing a physical quantity denominated nonlinear structural surface intensity (NSSI). This quantity is formulated for mechanical systems whose dynamic response is governed by nonlinear harmonic frequencies due to contact nonlinearities. A specific experiment simulating a “loose joint” type of damage in a stiffened bolted Aluminum Panel was designed to validate the NSSI formulation. Damage was introduced in the form of loose bolts characterized by a contact nonlinear response. The nonlinear response resulted from separation and impact at closure of the joined structures due to active interrogation by an external dynamic force. The results prove that NSSI is a monotonic function of the damage size.
Claudio Sbarufatti - One of the best experts on this subject based on the ideXlab platform.
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Strain wave acquisition by a fiber optic coherent sensor for impact monitoring
Materials, 2017Co-Authors: Claudio Sbarufatti, Alessio Beligni, Marco Mattarei, Matthieu Martinelli, Andrea Gilioli, Maurizio Ferrario, Mario Martinelli, Michaela De GiglioAbstract:A novel fiber optic sensing technology for high frequency dynamics detection is proposed in this paper, specifically tailored for structural health monitoring applications based on strain wave analysis, for both passive impact identification and active Lamb wave monitoring. The sensing solution relies on a fiber optic-based interferometric architecture associated to an innovative coherent detection scheme, which retrieves in a completely passive way the high-frequency phase information of the received optical signal. The sensing fiber can be arranged into different layouts, depending on the requirement of the specific application, in order to enhance the sensor sensitivity while still ensuring a limited gauge length if punctual measures are required. For active Lamb wave monitoring, this results in a sensing fiber arranged in multiple loops glued on an Aluminum thin Panel in order to increase the phase signal only in correspondence to the sensing points of interest. Instead, for passive impact identification, the required sensitivity is guaranteed by simply exploiting a longer gauge length glued to the structure. The fiber optic coherent (FOC) sensor is exploited to detect the strain waves emitted by a piezoelectric transducer placed on the Aluminum Panel or generated by an impulse hammer, respectively. The FOC sensor measurements have been compared with both a numerical model based on Finite Elements and traditional piezoelectric sensors, confirming a good agreement between experimental and simulated results for both active and passive impact monitoring scenarios.
