Matching Items (60)
Description
Aging-related damage and failure in structures, such as fatigue cracking, corrosion, and delamination, are critical for structural integrity. Most engineering structures have embedded defects such as voids, cracks, inclusions from manufacturing. The properties and locations of embedded defects are generally unknown and hard to detect in complex engineering structures. Therefore, early detection of damage is beneficial for prognosis and risk management of aging infrastructure system.
Non-destructive testing (NDT) and structural health monitoring (SHM) are widely used for this purpose. Different types of NDT techniques have been proposed for the damage detection, such as optical image, ultrasound wave, thermography, eddy current, and microwave. The focus in this study is on the wave-based detection method, which is grouped into two major categories: feature-based damage detection and model-assisted damage detection. Both damage detection approaches have their own pros and cons. Feature-based damage detection is usually very fast and doesn’t involve in the solution of the physical model. The key idea is the dimension reduction of signals to achieve efficient damage detection. The disadvantage is that the loss of information due to the feature extraction can induce significant uncertainties and reduces the resolution. The resolution of the feature-based approach highly depends on the sensing path density. Model-assisted damage detection is on the opposite side. Model-assisted damage detection has the ability for high resolution imaging with limited number of sensing paths since the entire signal histories are used for damage identification. Model-based methods are time-consuming due to the requirement for the inverse wave propagation solution, which is especially true for the large 3D structures.
The motivation of the proposed method is to develop efficient and accurate model-based damage imaging technique with limited data. The special focus is on the efficiency of the damage imaging algorithm as it is the major bottleneck of the model-assisted approach. The computational efficiency is achieved by two complimentary components. First, a fast forward wave propagation solver is developed, which is verified with the classical Finite Element(FEM) solution and the speed is 10-20 times faster. Next, efficient inverse wave propagation algorithms is proposed. Classical gradient-based optimization algorithms usually require finite difference method for gradient calculation, which is prohibitively expensive for large degree of freedoms. An adjoint method-based optimization algorithms is proposed, which avoids the repetitive finite difference calculations for every imaging variables. Thus, superior computational efficiency can be achieved by combining these two methods together for the damage imaging. A coupled Piezoelectric (PZT) damage imaging model is proposed to include the interaction between PZT and host structure. Following the formulation of the framework, experimental validation is performed on isotropic and anisotropic material with defects such as cracks, delamination, and voids. The results show that the proposed method can detect and reconstruct multiple damage simultaneously and efficiently, which is promising to be applied to complex large-scale engineering structures.
Non-destructive testing (NDT) and structural health monitoring (SHM) are widely used for this purpose. Different types of NDT techniques have been proposed for the damage detection, such as optical image, ultrasound wave, thermography, eddy current, and microwave. The focus in this study is on the wave-based detection method, which is grouped into two major categories: feature-based damage detection and model-assisted damage detection. Both damage detection approaches have their own pros and cons. Feature-based damage detection is usually very fast and doesn’t involve in the solution of the physical model. The key idea is the dimension reduction of signals to achieve efficient damage detection. The disadvantage is that the loss of information due to the feature extraction can induce significant uncertainties and reduces the resolution. The resolution of the feature-based approach highly depends on the sensing path density. Model-assisted damage detection is on the opposite side. Model-assisted damage detection has the ability for high resolution imaging with limited number of sensing paths since the entire signal histories are used for damage identification. Model-based methods are time-consuming due to the requirement for the inverse wave propagation solution, which is especially true for the large 3D structures.
The motivation of the proposed method is to develop efficient and accurate model-based damage imaging technique with limited data. The special focus is on the efficiency of the damage imaging algorithm as it is the major bottleneck of the model-assisted approach. The computational efficiency is achieved by two complimentary components. First, a fast forward wave propagation solver is developed, which is verified with the classical Finite Element(FEM) solution and the speed is 10-20 times faster. Next, efficient inverse wave propagation algorithms is proposed. Classical gradient-based optimization algorithms usually require finite difference method for gradient calculation, which is prohibitively expensive for large degree of freedoms. An adjoint method-based optimization algorithms is proposed, which avoids the repetitive finite difference calculations for every imaging variables. Thus, superior computational efficiency can be achieved by combining these two methods together for the damage imaging. A coupled Piezoelectric (PZT) damage imaging model is proposed to include the interaction between PZT and host structure. Following the formulation of the framework, experimental validation is performed on isotropic and anisotropic material with defects such as cracks, delamination, and voids. The results show that the proposed method can detect and reconstruct multiple damage simultaneously and efficiently, which is promising to be applied to complex large-scale engineering structures.
ContributorsChang, Qinan (Author) / Liu, Yongming (Thesis advisor) / Mignolet, Marc (Committee member) / Chattopadhyay, Aditi (Committee member) / Yan, Hao (Committee member) / Ren, Yi (Committee member) / Arizona State University (Publisher)
Created2019
Description
This thesis encompasses research performed in the focus area of structural health monitoring. More specifically, this research focuses on high velocity impact testing of carbon fiber reinforced structures, especially plates, and evaluating the damage post-impact. To this end, various non-destructive evaluation techniques such as ultrasonic C-scan testing and flash thermography were utilized for post-impact analysis. MATLAB algorithms were written and refined for the localization and quantification of damage in plates using data from sensors such as piezoelectric and fiber Bragg gratings sensors. Throughout the thesis, the general plate theory and laminate plate theory, the operations and optimization of the gas gun, and the theory used for the damage localization algorithms will be discussed. Additional quantifiable results are to come in future semesters of experimentation, but this thesis outlines the framework upon which all the research will continue to advance.
ContributorsMccrea, John Patrick (Author) / Chattopadhyay, Aditi (Thesis director) / Borkowski, Luke (Committee member) / Department of Military Science (Contributor) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
The goal of this research is to couple a physics-based model with adaptive algorithms to develop a more accurate and robust technique for structural health monitoring (SHM) in composite structures. The purpose of SHM is to localize and detect damage in structures, which has broad applications to improvements in aerospace technology. This technique employs PZT transducers to actuate and collect guided Lamb wave signals. Matching pursuit decomposition (MPD) is used to decompose the signal into a cross-term free time-frequency relation. This decoupling of time and frequency facilitates the calculation of a signal's time-of-flight along a path between an actuator and sensor. Using the time-of-flights, comparisons can be made between similar composite structures to find damaged regions by examining differences in the time of flight for each path between PZTs, with respect to direction. Relatively large differences in time-of-flight indicate the presence of new or more significant damage, which can be verified using a physics-based approach. Wave propagation modeling is used to implement a physics based approach to this method, which is coupled with adaptive algorithms that take into account currently existing damage to a composite structure. Previous SHM techniques for composite structures rely on the assumption that the composite is initially free of all damage on both a macro and micro-scale, which is never the case due to the inherent introduction of material defects in its fabrication. This method provides a novel technique for investigating the presence and nature of damage in composite structures. Further investigation into the technique can be done by testing structures with different sizes of damage and investigating the effects of different operating temperatures on this SHM system.
ContributorsBarnes, Zachary Stephen (Author) / Chattopadhyay, Aditi (Thesis director) / Neerukatti, Rajesh Kumar (Committee member) / Barrett, The Honors College (Contributor) / Department of English (Contributor) / Mechanical and Aerospace Engineering Program (Contributor)
Created2015-05
Description
This thesis encompasses research performed in the focus area of structural health monitoring. More specifically, this research focuses on high velocity impact testing of carbon fiber reinforced structures, especially plates, and evaluating the damage post-impact. To this end, various non-destructive evaluation techniques such as ultrasonic C-scan testing and flash thermography were utilized for post-impact analysis. MATLAB algorithms were written and refined for the localization and quantification of damage in plates using data from sensors such as piezoelectric and fiber Bragg gratings sensors. Throughout the thesis, the general plate theory and laminate plate theory, the operations and optimization of the gas gun, and the theory used for the damage localization algorithms will be discussed. Additional quantifiable results are to come in future semesters of experimentation, but this thesis outlines the framework upon which all the research will continue to advance.
ContributorsMccrea, John Patrick (Author) / Chattopadhyay, Aditi (Thesis director) / Borkowski, Luke (Committee member) / Barrett, The Honors College (Contributor) / Mechanical and Aerospace Engineering Program (Contributor) / Department of Military Science (Contributor)
Created2015-05
Description
Composite structures, particularly carbon-fiber reinforced polymers (CFRPs) have been subject to significant development in recent years. They have become increasingly reliable, durable, and versatile, finding a role in a wide variety of applications. When compared to conventional materials, CFRPs have several advantages, including extremely high strength, high in-plane and flexural stiffness, and very low weight. However, the application of CFRPs and other fiber-matrix composites is complicated due to the manner in which damage propagates throughout the structure, and the associated difficulty in identifying and repairing such damages prior to structural failure. In this paper, a methods of detecting and localizing delaminations withint a complex foam-core composite structure using non-destructive evaluation (NDE) and structural health montoring (SHM) is investigated. The two NDE techniques utilized are flash thermography and low frequency ultrasonic C-Scan, which were used to confirm the location of seeded damages within the specimens and to quantify the size of the damages. Macro fiber composite sensors (MFCs) and piezoelectric sensors (PZTs) were used as actuators and sensors in pitch-catch and pulse-echo configurations in order to study mode conversions and wave reflections of the propagated Lamb waves when interacting with interply delaminations and foam-core separations. The final results indicated that the investigated NDE and SHM techniques are capable of detecting and quantifying damages within complex X-COR composites, with the SHM techniques having the potential to be used \textit{in situ} with a high degree of accuracy. It was also observed that the presence of the X-COR significantly alters the behavior of the wave when compared to a standard CFRP composite plate, making it necessary to account for any variations if wave-base techniques are to be used for damage detection and quantification. Lastly, a time-space model was created to model the wave interactions with damages located within X-COR complex sandwich composites.
ContributorsRajadas, Abhishek Chattopadhyay (Author) / Chattopadhyay, Aditi (Thesis director) / Neerukatti, Rajesh Kumar (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Materials Science and Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05
Description
Carbon nanotube (CNT) membranes (buckypaper) are manufactured with multiple procedures, vacuum filtration, surfactant-free, and 3D printing. A post-manufacturing process for resin impregnation is subjected to the membranes. The effects of manufacturing processes on the microstructure and material properties are investigated for both pristine and resin saturated samples manufactured using all procedures. Microstructural characteristics that are studied include specific surface area, porosity, pore size distribution, density, and permeability. Scanning electron microscopy is used to characterize the morphology of the membrane. Brunauer-Emmett-Teller analysis is conducted on membrane samples to determine the specific surface area. Barrett-Joyner-Halenda analysis is conducted on membrane samples to determine pore characteristics. Once the microstructure is characterized for each manufacturing process for both pristine and resin saturated samples, material properties of the membrane and nanocomposite structures are explored and compared on a manufacturing basis as well as a microstructural basis. Membranes samples are interleaved in the overlap of carbon fiber polymer matrix composite tubes, which are subjected to fracture testing. The effects of carbon nanotube membrane manufacturing technology on the fracture properties of nanocomposite structures with tubular geometries are explored. In parallel, the influences of manufacturing technology on the electromechanical properties of the membrane that effect a piezoresistive response are investigated for both pristine and resin saturated membranes manufactured using both methods. The result of this study is a better understanding of the relationships between manufacturing technology and the effected microstructure, and the resulting influences on material properties for both CNT membranes and derivative nanocomposite structures. Developing an understanding of these multiscale relationships leads to an increased capacity in designing manufacturing processes specific to optimizing the expression of desired characteristics for any given application.
ContributorsWoodward, John Michael (Author) / Chattopadhyay, Aditi (Thesis director) / Yekani Fard, Masoud (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05
Description
Epoxy resins and composite materials are well characterized in their mechanical properties. However these properties change as the materials age under different conditions, as their microstructure undergoes changes from the absorption or desorption of water. Many of these microstructural changes occur at the interfacial region between where the matrix of the composite meets the reinforcement fiber, but still result in significant effects in the material properties. These effects have been studied and characterized under a variety of conditions by artificially aging samples. The artificial aging process focuses on exposing samples to environmental conditions such as high temperature, UV light, and humidity. While conditions like this are important to study, in real world applications the materials will not be simply resting in a laboratory created environment. In most circumstances, they are subjected to some kind of stress or impact. This report will focus on designing an experiment to analyze aged samples under tensile loading and creating a fixture that will sustain loading while the samples are aged. . The conditions that will be tested are control conditions at standard temperature and humidity in the laboratory, submerged, thermal heating, submerged and heated, and hygrothermal.
ContributorsNothern, Bradley James (Author) / Yekani Fard, Masoud (Thesis director) / Chattopadhyay, Aditi (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
Shape Memory Polymers (SMPs) are smart polyurethane thermoplastics that can recover their original shape after undergoing deformation. This shape recovery can be actuated by raising the SMP above its glass transition temperature, Tg. This report outlines a process for repeatedly recycling SMPs using 3D printing. Cubes are printed, broken down into pellets mechanically, and re-extruded into filament. This simulates a recycling iteration that the material would undergo in industry. The samples are recycled 0, 1, 3, and 5 times, then printed into rectangular and dog-bone shapes. These shapes are used to perform dynamic mechanical analysis (DMA) and 3-point bending for shape recovery testing. Samples will also be used for scanning electron microscopy (SEM) to characterize their microstructure.
ContributorsSweeney, Andrew Joseph (Author) / Yekani Fard, Masoud (Thesis director) / Chattopadhyay, Aditi (Committee member) / W.P. Carey School of Business (Contributor) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
Seamless carbon fiber reinforced polymer matrix (CFRP) composites are being investigated in many structural applications with the purpose of withstanding the extreme pressures and maintaining stiffness in mechanical systems. This report focuses on: fabrication of CFRP tubes and end caps, the production of a pressurization system to test standards set by Fiber Reinforced Composite (FRC) Pipe and Fittings for Underground Fire Protection Service [1], developing a library for different damage types for seamless composite pipes, and evaluating pre-existing flaws with flash thermography, carrying out hydrostatic testing, and performing nondestructive testing (NDT) to characterize damage induced on the pipes such as cracking, crazing, and fiber breakage. The tasks outlined will be used to develop design guidelines for different combinations of loading systems.
ContributorsFoster, Collin William (Author) / Yekani Fard, Masoud (Thesis director) / Chattopadhyay, Aditi (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
Filament used in 3D printers can vary by size, color, and material. Most commonly thermoplastics are used for rapid prototyping by industry. Recycled filament has the potential to reduce cost and provide a more sustainable and energy efficient approach to 3D printing. This can be a viable option if recycled parts show comparable mechanical characteristics to non-recycled material. This report focuses on the development of a methodology to efficiently characterize recycled filament for application in industry. A crush sample in the shape of a hollow cube and a dog-bone shaped specimen will be created using a filament extruder and 3D printer. The crush sample will be broken and extruded to produce a recycled filament. The crush sample will undergo a varying number of recycles (i.e. breakings) per sample group to simulate mechanical degradation; 0, 1, 2, and 5 recycling loops. The samples will undergo micro mechanical (microscopy analysis) and macro mechanical (tensile) characterization.
ContributorsPalermo, Marissa Nicole (Author) / Chattopadhyay, Aditi (Thesis director) / Yekani Fard, Masoud (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-12