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Статті в журналах з теми "Aluminum alloys Fatigue Mathematical models"
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Bento, Rodrigo Teixeira, André Ferrus Filho, and Marco Antonio Fumagalli. "Structural Design and Stress Analysis of a High-Speed Turbogenerator Assembly Supported by Hydrodynamic Bearings." International Journal of Manufacturing, Materials, and Mechanical Engineering 10, no. 1 (January 2020): 54–67. http://dx.doi.org/10.4018/ijmmme.2020010104.
Повний текст джерелаАнотація:
Turbine and bushing bearing are the most critical components of high-speed machines. This article describes the design of a high-speed turbine supported by hydrodynamic bearings. The mathematical dimensioning and the FEM analysis are presented to validate the mechanical strength of the turbine and the bushing bearing models. Fatigue life and factor of safety were also determined. The simulations showed that the maximum Von Mises stress values obtained are associated to the centrifugal force generated by the system rotational movement. The results variation was mainly due to the properties of the materials proposed. For the turbine, 7075-T6 aluminum alloy and SAE 4340 steel obtained satisfactory behavior under a constant operating speed of 30,000 RPM. For the hydrodynamic bearing, the TM23 bronze alloy exhibited excellent results, without fracture, and low mechanical deformation. The models exhibited a great potential employment in several applications, such as biogas systems to generate electrical energy, and educational test bench for thermodynamic and tribological simulations.
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HARLOW, D. GARY. "PARTICLE STATISTICS IN ALUMINUM ALLOYS." International Journal of Reliability, Quality and Safety Engineering 13, no. 04 (August 2006): 379–95. http://dx.doi.org/10.1142/s021853930600232x.
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Pitting corrosion and fatigue crack growth are primary degradation mechanisms that affect the durability and integrity of structures made of aluminum alloys, and they are concerns for commercial transport and military aircraft. The heterogeneous nature of aluminum alloys is the reason that these are operative damage mechanisms. Typically, there are about 2,000 constituent particles per mm2on polished surfaces. Corrosion pits commence at the constituent particles and evolve into severe pits by sustained growth through clusters of particles. The severe pits are nucleation sites for subsequent fatigue crack growth. Even when the environment is not as deleterious, fatigue cracks nucleate from clusters of particles. Thus, the role of heterogeneous clusters of constituent particles is critical to the damage evolution of aluminum alloys. To formulate stochastic models that can serve as part of structural reliability analyses for the damage evolution in aluminum alloys, it is essential that quantitative descriptions of the spatial statistics of the particles and particle clusters, including their location, size, and density are developed. The primary purpose of this effort is to estimate statistically the distribution functions of the key geometrical properties of constituent particles in aluminum alloys and their role in damage evolution.
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Lee, Jungsub, Sang-Youn Park, and Byoung-Ho Choi. "Evaluation of Fatigue Characteristics of Aluminum Alloys and Mechanical Components Using Extreme Value Statistics and C-Specimens." Metals 11, no. 12 (November 27, 2021): 1915. http://dx.doi.org/10.3390/met11121915.
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In this study, the fatigue characteristics of aluminum alloys and mechanical components were investigated. To evaluate the effect of forging, fatigue specimens with the same chemical compositions were prepared from billets and forged mechanical components. To evaluate the cleanliness of the aluminum alloys, the cross-sectional area of specimens was observed, and the maximum inclusion sizes were obtained using extreme value statistics. Rotary bending fatigue tests were performed, and the fracture surfaces of the specimens were analyzed. The results show that the forging process not only elevated the fatigue strength but also reduced the scatter of the fatigue life of aluminum alloys. The fatigue characteristics of C-specimens were obtained to develop finite-element method (FEM) models. With the intrinsic fatigue properties and strain–life approach, the FEM analysis results agreed well with the test results.
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Ma, Shuai, Zhibo Zhang, Zhuming Huang, Dongfu Song, Yiwang Jia, Nan Zhou, Kai Wang, Kaihong Zheng, and Huijing Du. "Prediction of Grain Size in Cast Aluminum Alloys." Crystals 12, no. 4 (March 29, 2022): 474. http://dx.doi.org/10.3390/cryst12040474.
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Grain refinement of cast alloys, especially aluminum–silicon and magnesium-based alloys, is an effective approach to improve the strength of alloys. Grain size is the most representative parameter used to characterize grain refinement in the industry, thereby attracting increasing attention for developing accurate grain size prediction models. In this paper, several important grain size prediction models under different adaptation conditions are reviewed. These models are obtained either by regression of experimental data or by physical/mathematical inference under certain assumptions of specified cases, focusing on the effects of alloy composition, solidification temperature gradient, grain growth rate, and fining agent composition, among others. The trends of grain size prediction models were also discussed. The results revealed machine learning as an effective tool to establish a data-driven prediction model of grain size in cast aluminum alloys.
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Golod, V. M., and L. Yu Dobosh. "DIAGNOSTICS OF DENDRITE STRUCTURE OF MULTICOMPONENT ALUMINUM ALLOYS." Litiyo i Metallurgiya (FOUNDRY PRODUCTION AND METALLURGY), no. 1 (April 6, 2018): 55–62. http://dx.doi.org/10.21122/1683-6065-2018-1-55-62.
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Stages of system analysis and mathematical models for predicting the dendritic structure of multicomponent aluminum alloys are considered. Computer diagnostics of nonequilibrium crystallization is realized by the joint use of the apparatus of computational thermodynamics and means of computational heat transfer for solving problems of computational materials science. The results of modeling the evolution of the dendritic structure are presented with a change in the diffusion intensity in the solid phase from equilibrium conditions to complete suppression.
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Kang, Hong-Tae, and Sai Boorgu. "Fatigue Life Prediction of Self-Piercing Rivet Joints Between Magnesium and Aluminum Alloys." MATEC Web of Conferences 165 (2018): 10004. http://dx.doi.org/10.1051/matecconf/201816510004.
Повний текст джерелаАнотація:
Various light materials including aluminum alloys and magnesium alloys are being used to reduce the weight of vehicle structures. Joining of dissimilar materials is always a challenging task to construct a solid structure. Self-piercing rivet (SPR) joint is one of various joining methods for dissimilar materials. Front shock tower structures were constructed with magnesium alloy (AM60) joined to aluminum alloy (Al6082) by SPR joints. To evaluate the durability performance of the SPR joints in the structures, fatigue tests of the front shock tower structures were conducted with constant amplitude loadings. Furthermore, this study investigated fatigue life prediction method of SPR joints and compared the fatigue life prediction results with that of experimental results. For fatigue life prediction of the SPR joints in the front shock tower structures, lap-shear and cross-tension specimens of SPR joint were constructed and tested to characterize the fatigue properties of the SPR joint. Then, the SPR joint was represented with area contact method (ACM) in finite element (FE) models. The load-life curves of the lap-shear and cross-tension specimens were converted to a structural stress-life (S-N) curve of the SPR joints. The S-N curve was used to predict fatigue life of SPR joints in the front shock tower structures. The test results and the prediction results were well correlated.
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Zakharchenko, Kirill, Vladimir Kapustin, Alexey Larichkin, and Yaroslav Lukyanov. "Influence of Technology of Hot Forming of Plates from Aluminum Alloys Al-Cu-Li-Zn and Al-Zn-Mg-Cu on Resistance to Fatigue Fracture." Metal Working and Material Science 22, no. 4 (December 8, 2020): 94–109. http://dx.doi.org/10.17212/1994-6309-2020-22.4-94-109.
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Introduction. One of the primary objectives in the development of promising aircraft products is to reduce the weight of the aircraft structure. This problem can be solved by applying new low density materials such as aluminum alloys alloyed with lithium (for example, Al-Cu-Li-Zn) in the design of parts. The use of these materials in aircraft construction is limited by the processing technology, which must be such as not to damage the material and not reduce its strength properties. Such technologies include processing by pressure with heating, when creep processes are activated and the material passes into a state close to superplasticity. The purpose of the work: assessment of the effect of pressure shaping of aluminum alloys Al-Cu-Li-Zn and Al-Zn-Mg-Cu in creep mode on strength. The paper investigates the influence of the technology of pressure shaping of aluminum alloys Al-Cu-Li-Zn and Al-Zn-Mg-Cu on the resistance to fatigue failure. The work uses a method that allows to determine the ultimate stresses using diagrams of the accumulation of irreversible deformations; method of forming thick plates (40 mm) in the creep mode. The previously selected optimum temperatures for forming the plates are used. A non-contact coordinate measuring system is used to perform surface inspection after shaping. Fractography of the fracture of samples of alloy Al-Cu-Li-Zn and Al-Zn-Mg-Cu after fatigue failure is performed. Mathematical modeling of the deformation process of plates in creep mode is carried out in the MSC.Marc package. As a result, a conservative evaluation of the endurance limit for aluminum alloys Al-Cu-Li-Zn and Al-Zn-Mg-Cu is obtained. The shaping of thick plates in the creep mode is carried out. More than 80% of the board surface is formed with a deviation of less than 1 mm from the target size. Fatigue tests of samples made of molded panels of alloys Al-Cu-Li-Zn and Al-Zn-Mg-Cu are carried out, fatigue curves are plotted. The fractography of the surface of the fatigue fracture showed the presence of oxides in the samples of alloy Al-Cu-Li-Zn, in contrast to alloy Al-Zn-Mg-Cu. The results of fatigue tests are discussed, showing that the characteristics of the technological process of shaping and heat treatment do not deteriorate the fatigue properties of the investigated alloys. Comparative tests show that alloy Al-Cu-Li-Zn has higher fatigue characteristics. Mathematical modeling show that the use of the Boyle-Norton steady-state creep law is not enough to describe the process of plate forming. The necessity of setting the inverse problem of creep age forming is noted, where the coordinates of the punches of the loading device should act as boundary conditions.
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Zahran, B. "Using Neural Networks to Predict the Hardness of Aluminum Alloys." Engineering, Technology & Applied Science Research 5, no. 1 (February 8, 2015): 757–59. http://dx.doi.org/10.48084/etasr.529.
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Aluminum alloys have gained significant industrial importance being involved in many of the light and heavy industries and especially in aerospace engineering. The mechanical properties of aluminum alloys are defined by a number of principal microstructural features. Conventional mathematical models of these properties are sometimes very complex to be analytically calculated. In this paper, a neural network model is used to predict the correlations between the hardness of aluminum alloys in relation to certain alloying elements. A backpropagation neural network is trained using a thorough dataset. The impact of certain elements is documented and an optimum structure is proposed
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Chausov, Mykola, Andrii Pylypenko, Pavlo Maruschak, and Abdellah Menou. "Phenomenological Models and Peculiarities of Evaluating Fatigue Life of Aluminum Alloys Subjected to Dynamic Non-Equilibrium Processes." Metals 11, no. 10 (October 13, 2021): 1625. http://dx.doi.org/10.3390/met11101625.
Повний текст джерелаАнотація:
Physical-mechanical models for predicting the fatigue life of aluminum alloys D16ChATW and 2024-T351 are proposed and tested. Damage accumulation patterns are established for these alloys in the initial state and after dynamic non-equilibrium processes (DNP) of different intensity that occur at maximum cycle stresses σmax from 340 to 440 MPa, cycle asymmetry coefficients R = 0.1 and load frequency f = 110 Hz. The main model parameters are the initial alloy hardness HV and the limiting parameters of scatter of hardness values m. These parameters are evaluated in the process of cyclic loading with fixed maximum stresses of the cycles. Relative values me are also considered. For the alloys in the initial state, the proposed models are shown to be in good agreement with the experimental results. Conversely, structural changes taking place in alloys after DNP complicate the prediction of their fatigue life.
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DebRoy, T., A. De, H. K. D. H. Bhadeshia, V. D. Manvatkar, and A. Arora. "Tool durability maps for friction stir welding of an aluminium alloy." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 468, no. 2147 (July 25, 2012): 3552–70. http://dx.doi.org/10.1098/rspa.2012.0270.
Повний текст джерелаАнотація:
Friction stir welding is not used for hard alloys because of premature tool failure. A scheme is created that exploits the physical three-dimensional heat and mass flow models, and implements them into a fast calculation algorithm, which, when combined with damage accumulation models, enables the plotting of tool durability maps that define the domains of satisfactory tool life. It is shown that fatigue is an unlikely mechanism for tool failure, particularly for the welding of thin plates. Plate thickness, welding speed, tool rotational speed, shoulder, and pin diameters and pin length all affect the stresses and temperatures experienced by the tool. The large number of these variables makes the experimental determination of their effects on stresses and temperatures intractable and the use of a well-tested, efficient friction stir welding model a realistic undertaking. An artificial neural network that is trained and tested with results from a phenomenological model is used to generate tool durability maps that show the ratio of the shear strength of the tool material to the maximum shear stress on the tool pin for various combinations of welding variables. These maps show how the thicker plates and faster welding speeds adversely affect tool durability and how that can be optimized.
Дисертації з теми "Aluminum alloys Fatigue Mathematical models"
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Morrissey, Ryan J. "Strain accumulation and shakedown in fatigue of Ti-6A1-4V by Ryan J Morrissey." Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/17144.
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Warke, Virendra S. "Removal of Hydrogen and Solid Particles from Molten Aluminum Alloys in the Rotating Impeller Degasser: Mathematical Models and Computer Simulations." Link to electronic thesis, 2003. http://www.wpi.edu/Pubs/ETD/Available/etd-0626103-111317.
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Przybyla, Craig Paul. "Microstructure-sensitive extreme value probabilities of fatigue in advanced engineering alloys." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/34780.
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A novel microstructure-sensitive extreme value probabilistic framework is introduced to evaluate material performance/variability for damage evolution processes (e.g., fatigue, fracture, creep). This framework employs newly developed extreme value marked correlation functions (EVMCF) to identify the coupled microstructure attributes (e.g., phase/grain size, grain orientation, grain misorientation) that have the greatest statistical relevance to the extreme value response variables (e.g., stress, elastic/plastic strain) that describe the damage evolution processes of interest. This is an improvement on previous approaches that account for distributed extreme value response variables that describe the damage evolution process of interest based only on the extreme value distributions of a single microstructure attribute; previous approaches have given no consideration of how coupled microstructure attributes affect the distributions of extreme value response. This framework also utilizes computational modeling techniques to identify correlations between microstructure attributes that significantly raise or lower the magnitudes of the damage response variables of interest through the simulation of multiple statistical volume elements (SVE). Each SVE for a given response is constructed to be a statistical sample of the entire microstructure ensemble (i.e., bulk material); therefore, the response of interest in each SVE is not expected to be the same. This is in contrast to computational simulation of a single representative volume element (RVE), which often is untenably large for response variables dependent on the extreme value microstructure attributes.
This framework has been demonstrated in the context of characterizing microstructure-sensitive high cycle fatigue (HCF) variability due to the processes of fatigue crack formation (nucleation and microstructurally small crack growth) in polycrystalline metallic alloys. Specifically, the framework is exercised to estimate the local driving forces for fatigue crack formation, to validate these with limited existing experiments, and to explore how the extreme value probabilities of certain fatigue indicator parameters (FIPs) affect overall variability in fatigue life in the HCF regime. Various FIPs have been introduced and used previously as a means to quantify the potential for fatigue crack formation based on experimentally observed mechanisms. Distributions of the extreme value FIPs are calculated for multiple SVEs simulated via the FEM with crystal plasticity constitutive relations. By using crystal plasticity relations, the FIPs can be computed based on the cyclic plastic strain on the scale of the individual grains. These simulated SVEs are instantiated such that they are statistically similar to real microstructures in terms of the crystallographic microstructure attributes that are hypothesized to have the most influence on the extreme value HCF response. The polycrystalline alloys considered here include the Ni-base superalloy IN100 and the Ti alloy Ti-6Al-4V. In applying this framework to study the microstructure dependent variability of HCF in these alloys, the extreme value distributions of the FIPs and associated extreme value marked correlations of crystallographic microstructure attributes are characterized. This information can then be used to rank order multiple variants of the microstructure for a specific material system for relative HCF performance or to design new microstructures hypothesized to exhibit improved performance. This framework enables limiting the (presently) large number of experiments required to characterize scatter in HCF and lends quantitative support to designing improved, fatigue-resistant materials and accelerating insertion of modified and new materials into service.
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Chiu, LiRen, and 邱立仁. "Mathematical Models of Stress-Strain of Aluminum Alloys under High Strain Rates." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/50416777519515833946.
Повний текст джерелаАнотація:
碩士國立臺灣大學
機械工程學研究所
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The three kinds of aluminum alloys in common use, namely, Al2024-T351, Al6061-T6 and Al7075-T6, are adopted as the specimen materials. By computer curve-fitting, we want to find constitutive equations. The equations describe the relationships between flow stress, strain, strain-rate and temperature. We could use the equations to predict the flow stress under deformation process in any part of the specimens. In the condition of 0≦strain≦0.6, 18℃≦temperature≦500℃, and 100 per sec≦strain-rate≦500 per sec, the flow stress-strain behaviors of the three aluminum alloys can be represented by mathematical models developed in this research. High strain-rate and short deformation-time result in that a great quantity of heat generated from plastic work is unable to radiate, and conduct immediately, then temperature increases in the specimen. We should consider the temperature-rise when we find the equations.
Книги з теми "Aluminum alloys Fatigue Mathematical models"
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Rybakov, A. S. Fiziko-matematicheskai︠a︡ modelʹ impulʹsno-dugovoĭ svarki ali︠u︡minievykh splavov. Tula: Tulʹskiĭ gos. universitet, 2002.
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ZnO bao mo zhi bei ji qi guang, dian xing neng yan jiu. Shanghai Shi: Shanghai da xue chu ban she, 2010.
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Vermolen, Fred. Mathematical Models for Particle Dissolution in Extrudable Aluminum Alloys. Delft Univ Pr, 1998.
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M, Stefanescu Doru, and United States. National Aeronautics and Space Administration., eds. Micro and macro segregation in alloys solidifying with equiaxed morphology: NCC8-57, final report. [Washington, DC: National Aeronautics and Space Administration, 1996.
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Ren, Binyan. Mechanical and microstructural characteristics of an Al-Li-Cu-Zr alloy during superplastic deformation. 1991.
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Isothermal fatigue behavior of a [90] □Sic/Ti-15-3 composite at 426 C□. [Washington, D.C.]: NASA, 1991.
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United States. National Aeronautics and Space Administration., ed. Isothermal fatigue behavior of a [90] Sic/Ti-15-3 composite at 426 C. [Washington, D.C.]: NASA, 1991.
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Center, Langley Research, ed. Empirical modeling of environment-enhanced fatigue crack propagation in structural alloys for component life prediction. Hampton, Va: National Aeronautics and Space Administration, Langley Research Center, 1995.
Знайти повний текст джерелаЧастини книг з теми "Aluminum alloys Fatigue Mathematical models"
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Tiryakioğlu, Murat, and Hüseyin Özdeş. "Ductility–Fatigue Life Relationships in Aluminum Alloy Castings: Role of Structural Quality." In Encyclopedia of Aluminum and Its Alloys. Boca Raton: CRC Press, 2019. http://dx.doi.org/10.1201/9781351045636-140000323.
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The relationships between tensile properties and fatigue life in cast aluminum alloys have been reviewed. Strong relationships were found between fatigue life and the quality factor, QT, that uses tensile ductility to characterize structural quality for a number of cast aluminum alloys. The model developed by the authors to estimate the Basquin parameters as a function of QT is introduced along with a step-by-step guide on how to apply it to cast aluminum alloys. This model provides much more reliable estimates for cast aluminum alloys than other models available in the literature.
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Banabic, Dorel, Dan Sorin Comsa, and Tudor Balan. "Anisotropic Yield Criteria for Aluminum Alloy Sheets." In Encyclopedia of Aluminum and Its Alloys. Boca Raton: CRC Press, 2019. http://dx.doi.org/10.1201/9781351045636-140000156.
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Anisotropy is a key feature of the plastic behavior of aluminum alloy sheets. Significant research efforts have been dedicated during the past few decades to characterize and model this behavior. Advanced anisotropic yield criteria are available today in the scientific literature. This article reviews the most important yield criteria, in historical order, with an emphasis on the models particularly adapted to aluminum alloys. Along with the mathematical description, illustrations of their performance are provided together with the parameter identification procedure and the required input data. The mechanical parameters that describe plastic anisotropy are also summarized. The relevance of the available models for practical applications is analyzed, and guidance is provided for the selection and aware use of these yield criteria in engineering.
Тези доповідей конференцій з теми "Aluminum alloys Fatigue Mathematical models"
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Kurata, Masahiro, Jun-Hee Kim, Jerome P. Lynch, Kincho H. Law, and Liming W. Salvino. "A Probabilistic Model Updating Algorithm for Fatigue Damage Detection in Aluminum Hull Structures." In ASME 2010 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. ASMEDC, 2010. http://dx.doi.org/10.1115/smasis2010-3838.
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The use of aluminum alloys in the design of naval structures offers the benefit of light-weight ships that can travel at high-speed. However, the use of aluminum poses a number of challenges for the naval engineering community including higher incidence of fatigue-related cracks. Early detection of fatigue induced cracks enhances maintenance of the ships and is critical for preventing the catastrophic failure of the hull. Furthermore, monitoring the integrity of the aluminum hull can provide valuable information for estimating the residual life of hull components. This paper presents a model-based damage detection methodology for fatigue assessment of hulls that are instrumented with a long-term hull monitoring system. At the core of the data driven damage detection approach is a Bayesian model updating algorithm enhanced with systematic enumeration and pruning of candidate solutions. The Bayesian model updating approach significantly reduce the computational effort by systematically narrowing the search space using errors functions constructed using the estimated modal properties associated with the condition of the structure. This study proposes the use of the Bayesian model updating technique to detect damage in an aluminum panel modeled using high-fidelity finite element models. The performance of the proposed damage detection method is tested through simulation of a progressively growing fatigue crack introduced in the vicinity of a welded stiffener element. An experimental study verifies the accuracy of the proposed damage detection method using an aluminum plate excited with a controlled excitation in the laboratory.
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Zedan, Y., S. A. Niknam, A. Djebara, and V. Songmene. "Burr Size Minimization When Drilling 6061-T6 Aluminum Alloy." In ASME 2012 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/imece2012-86412.
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The burr formation mechanisms strongly depend on the machining methods as well as cutting conditions. Cutting fluids play significant roles in machining, including reduction of friction and temperature. Using a cutting fluid, however, degrades the quality of the environment and increases machining costs. In the present work, initially the effects of cutting fluid application (dry, mist and flood) and their interaction with cutting parameters on the burr size during drilling of 6061-T6 aluminum alloys were investigated using multi-level full factorial design. Second-order non-linear mathematical models were developed to predict burr height for various lubrication modes. The accuracy of the regression equations formulated to predict burr height when using different lubrication modes has been verified through carrying out random experiments in the range of variation of these variables. A procedure was developed to minimize burr size for drilling holes by presenting the optimal levels of process parameters. Taguchi optimization method based on L9 orthogonal array design of experiment was then used which has shown very accurate process parameters selection that leads to minimum burr height. According to experimental study, it was observed that dry and mist drilling can produce parts with quality comparable with those obtained in wet drilling when using the optimal cutting conditions. In addition, increase in cutting speed and feed rate exhibits a decrease in burr size.
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Harlow, D. Gary, and Robert P. Wei. "Life Prediction: The Need for a Mechanistically Based Probability Approach." In ASME 2000 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2000. http://dx.doi.org/10.1115/imece2000-2651.
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Abstract Concerns with life assessment and management for existing engineered systems and aging infrastructure worldwide have increased the emphasis on the development of methods for reliability and durability predictions. Increasingly it is being recognized that the traditional statistically and empirically based methods are inadequate. These methods are appropriate for interpolations, but their usefulness for extrapolation is limited. Effective predictors, i.e., those that provide precise estimates beyond the range of conditions employed in the development of supporting data and assessments of risk, must be based upon mechanistic models that capture the functional dependence on all the key external and internal variables. This type of modeling, to reflect typical industrial applications, requires multidisciplinary research that addresses the chemical and micromechanical processes that control damage evolution in materials and quantifies the stochastic aspects of these processes. The purpose of this paper is to demonstrate the use and applicability of the mechanistically based probability methodology and to provide a framework from which other applications can be addressed. The approach is illustrated through mechanistically based probability modeling of corrosion and corrosion fatigue of aluminum alloys and creep crack growth in high strength steels.
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Karve, Girish S., and Hongyan Zhang. "Dependence of Impact Performance on Process Parameters and Weld Attributes for Spot Welded Advanced High Strength Steels." In ASME 2004 International Mechanical Engineering Congress and Exposition. ASMEDC, 2004. http://dx.doi.org/10.1115/imece2004-59130.
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In order to improve fuel economy and safety of vehicles, many advanced materials such as aluminum alloys and advanced high strength steels have been introduced in automobile body construction in recent years. A key to the adoption of such materials is their manufacturability, such as forming and welding. Resistance welding, as the major enabling technique, has been widely applied in joining these materials. Although there has been a large amount of research in characterizing static and fatigue strengths of Al or AHSS welds, their impact performance is largely unknown, even though it is extremely important for safety. In this paper, the impact strength of AHSS spot welded specimens is analyzed, as a function of welding process parameters and weldment geometry. Both energy and peak load during impacting, as well as failure mode were recorded. The geometric attributes of spot welds, such as indentation width, nugget width, indentation depth, etc. were measured before the specimens were destructively tested. Then these quantities were linked to the impact strength of the welds. Besides several advanced high strength steels, high strength, low alloy (HSLA) steels were also tested in the study for comparison. Models were developed to correlate impact strength with individual factors, both welding parameters and spot weld geometry variables. The effects of interactions between the factors were also investigated. The results showed that these parameters should be examined together in determining a weld’s impact performance.
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Zhou, Jun, Mohammad S. Davoud, and Hai-Lung Tsai. "Investigation of Transport Phenomena in Three-Dimensional Gas Metal Arc Welding of Thick Metals." In ASME/JSME 2007 Thermal Engineering Heat Transfer Summer Conference collocated with the ASME 2007 InterPACK Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/ht2007-32686.
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Arc welding is generally used to join thick metals in many engineering applications. However, poor penetration often occurs due to arc heat diffusion into the base metal. Hence, arc welding of thick metals normally requires grooving and/or preheating of the base metal and sometimes requires multiple passes for very thick metals or metals with high conductivity, such as aluminum alloys. In gas metal arc welding of thick metals with grooves and preheating, complicated melt flow and heat transfer are caused by the combined effect of droplet impingement, gravity, electromagnetic force, surface tension, and plasma arc pressure. Understanding these complicated transport phenomena involved in the welding process is critical in improving the penetration depth and weld quality. In this study, mathematical models and associated numerical techniques have been developed to study the effects of grooves and preheating on melt flow, diffusion of species, and weld penetration in gas metal arc welding of thick metals. Complex melt flow, transient weld pool shape and distributions of temperature and species in the weld pool are calculated. The continuum formation is adopted to handle liquid region, mushy zone and solid region. VOF technique is used to handle transient deformed shape of weld pool surface. The preliminary results show both grooves and preheating have important effects on the melt flow in weld pool and the weld penetration. Computer animations showing the evolutions of temperature; melt flow; and the interaction between droplets and weld pool will be presented.
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Motalab, Mohammad, Muhannad Mustafa, Jeffrey C. Suhling, Jiawei Zhang, John Evans, Michael J. Bozack, and Pradeep Lall. "Thermal Cycling Reliability Predictions for PBGA Assemblies That Include Aging Effects." In ASME 2013 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/ipack2013-73230.
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The microstructure, mechanical response, and failure behavior of lead free solder joints in electronic assemblies are constantly evolving when exposed to isothermal aging and/or thermal cycling environments. Traditional finite element based predictions for solder joint reliability during thermal cycling accelerated life testing are based on solder constitutive equations (e.g. Anand viscoplastic model) and failure models (e.g. energy dissipation per cycle model) that do not evolve with material aging. Thus, there will be significant errors in the calculations with lead free SAC alloys that illustrate dramatic aging phenomena. In this research, we have developed a new reliability prediction procedure that utilizes constitutive relations and failure criteria that incorporate aging effects, and then validated the new approach through correlation with thermal cycling accelerated life testing experimental data. As a part of this work, a revised set off Anand viscoplastic stress-strain relations for solder have been developed that included material parameters that evolve with the thermal history of the solder material. The effects of aging on the nine Anand model parameters have been determined as a function of aging temperature and aging time, and the revised Anand constitutive equations with evolving material parameters have been implemented in commercial finite element codes. In addition, new aging aware failure criteria have been developed based on fatigue data for lead free solder uniaxial specimens that were aged at elevated temperature for various durations prior to mechanical cycling. Using the measured fatigue data, mathematical expressions have been developed for the evolution of the solder fatigue failure criterion constants with aging, both for Coffin-Manson (strain-based) and Morrow-Darveaux (dissipated energy based) type fatigue criteria. Similar to the findings for mechanical/constitutive behavior, our results show that the failure data and associated fatigue models for solder joints are affected significantly by isothermal aging prior to cycling. After development of the tools needed to include aging effects in solder joint reliability models, we have then applied these approaches to predict reliability of PBGA components attached to FR-4 printed circuit boards that were subjected to thermal cycling. Finite element modeling was performed to predict the stress-strain histories during thermal cycling of both non-aged and aged PBGA assemblies, where the aging at constant temperature occurred before the assemblies were subjected to thermal cycling. The results from the finite element calculations were then combined with the aging aware fatigue models to estimate the reliability (cycles to failure) for the aged and non-aged assemblies. As expected, the predictions show significant degradations in the solder joint life for assemblies that had been pre-aged before thermal cycling. To validate our new reliability models, an extensive test matrix of thermal cycling reliability testing has been performed using a test vehicle incorporating several sizes of fine pitch PBGA daisy chain components. Before thermal cycling began, the assembled test boards were divided up into test groups that were subjected to several sets of aging conditions (preconditioning) including different aging temperatures (T = 25, 55, 85 and 125 C) and different aging times (no aging, and 6 and 12 months). After aging, the assemblies were subjected to thermal cycling (−40 to +125 C) until failure occurred. As with the finite element predictions, the Weibull data failure plots have demonstrated that the thermal cycling reliabilities of pre-aged assemblies were significantly less than those of non-aged assemblies. Good correlation was obtained between our new reliability modeling procedure that includes aging and the measured solder joint reliability data.