The Experts below are selected from a list of 297 Experts worldwide ranked by ideXlab platform
Junyang Wang - One of the best experts on this subject based on the ideXlab platform.
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Damage Tolerance Analysis of Cracked Stiffened Composite Panels
Journal of Composite Materials, 2001Co-Authors: Puhui Chen, Zhen Shen, Junyang WangAbstract:An approach based on a displacement compatibility model is developed for stiffened composite panels with a crack. Some important improvements on the Damage Tolerance Analysis of the stiffened composite panels have been made in comparison with previous work. Some new results are obtained regarding the effects of adhesive nonlinearity, stringer stiffness and bending, and stringer spacing on strengths and crack growth behaviours of bonded skin/stringer panels. The study indicates that the adhesive nonlinearity benefits the load bearing capacity of the panels. When the stringer is quite thick in comparison to the skin thickness, its out-of-plane bending will lower panel failure strains. Increasing stringer stiffness can not often guarantee the high failure strains of bonded skin/stringer composite panels. As the stringer stiffness exceeds some value, its increase has a negative effect on the load bearing capacity of the panels. For a given ratio of stringer stiffness to panel stiffness, the failure strains of...
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Impact Damage Tolerance Analysis of Stiffened Composite Panels
Journal of Composite Materials, 2001Co-Authors: Puhui Chen, Zhen Shen, Junyang WangAbstract:An approach based on a displacement compatibility model is presented for both riveted and bonded stiffened composite panels containing impact Damage. This represents the first application of the displacement compatibility model to the failure Analysis of impacted stiffened composite panels, and some newresults are obtained for the impact Damage Tolerance properties of stiffened composite panels. In the present Analysis, the previous displacement compatibility model for a stringer/orthotropic skin panel is improved for a stringer/unbalanced skin panel. The impact Damage is simplified as an elliptic hole based on the compressive failure mechanisms of impacted composite laminates and stiffened panels. Predictions for failure loads and Damage arrest capability agree well with experimental results for several composite panel configurations. The important results obtained in this study are: (1) Damage arrest capability is dominated by the strength of the skin/stringer attachment; (2) distinct two-stage failure ...
Harry R. Millwater - One of the best experts on this subject based on the ideXlab platform.
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Probabilistic Damage Tolerance Analysis for General Aviation
Advanced Materials Research, 2014Co-Authors: Harry R. Millwater, Juan D. Ocampo, Anthony M. CastaldoAbstract:The General Aviation (GA) fleet includes about 150,000 airplanes that were certificated with no fatigue evaluation requirements. The average age of these airplanes is about 40 years, and many are high-time. To mitigate the aging effects on the GA fleet, a probabilistic Damage Tolerance Analysis (PDTA) program has been developed. A PDTA approach also provides a mechanism whereby inspection and maintenance operations can be included into the simulation, thus providing engineers the opportunity to assess the benefits of maintenance actions. This paper describes the probabilistic methodology to be utilized in a computer software program (SMART|DT) that performs risk assessment of small airplanes employing NASGRO® or a user selected code as the crack growth engine. The methodology can assess a range of random variables, calculate the extreme value distribution (EVD) of maximum stress per flight from a general aviation (GA) spectrum, and generate a surrogate model for accurate and fast calculations of crack grow. The main objective is to develop a comprehensive probabilistic methodology such that engineers can conduct a risk assessment of GA structural issues in support of policy decisions.
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probabilistic Damage Tolerance for small airplanes using a linear elastic crack growth fracture mechanics surrogate model
54th AIAA ASME ASCE AHS ASC Structures Structural Dynamics and Materials Conference, 2013Co-Authors: Juan Ocampo, Harry R. MillwaterAbstract:Most general aviation (GA) aircraft are designed for safe-life based upon a crack initiation type failure mechanism, e.g., Miner’s rule. However, newer GA aircraft have fatigue crack growth as a design option. In addition, it may be necessary to evaluate a field event such as a cracked structure to ascertain the remaining life. Therefore, a risk based probabilistic Damage Tolerance Analysis (PDTA) program is needed in several aerospace situations. A comprehensive probabilistic Damage Tolerance method requires a combination of deterministic crack growth, inspection methods, probabilistic methods, and random variable modeling to provide a single probability-of-failure, cumulative probability-of-failure, and hazard rate with and without inspection. In this work, a general methodology to conduct probabilistic crack growth based Damage Tolerance methodology for small airplanes will be developed and incorporated in a computer software. Random variables can be included in the model using Monte Carlo Sampling (MCS) and efficient numerical integration algorithms. Probabilistic Damage Tolerance Analysis involves mathematically complex models and computational expensive simulations, which makes these analyses very inefficient. In this work the computational weight will be reduced using an error based adaptive surrogate model; the surrogate model will include the most influential random variables. The surrogate model will be used as a temporary substitution for the original crack growth model. An example problem will be presented to demonstrate the methodology.
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Extreme Value Modeling of Gust and Maneuver Loads for General Aviation
52nd AIAA ASME ASCE AHS ASC Structures Structural Dynamics and Materials Conference, 2011Co-Authors: Gulshan Singh, Harry R. Millwater, Laura C. DomyancicAbstract:Gust and maneuver exceedance curves for loads in terms of number of occurrences per nautical mile were developed for general aviation aircraft in the 1960’s and are commonly used for modeling aircraft loads. A number of usages exist for different flying conditions and aircraft such as: single engine instructional usage, twin-engine normal usage, aerobatic usage, etc. However, structural integrity based on Damage Tolerance Analysis is dependent upon the maximum load seen by the structure during a specified number of flights. As such, generalized extreme value modeling was used to query the gust and maneuver exceedance curves and generate extreme value distributions for the maximum load per flight for the different usage categories (considering both gust and maneuver loading). The results indicate that the typical assumption that the maximum load can best be represented by the Type I (Gumbel) distribution is not always accurate and the use of generalized extreme value theory is a better solution. The resulting extreme value loads are available to be used for Damage Tolerance Analysis.
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A Bayesian-Updating Computational Method for Probabilistic Damage Tolerance Analysis
51st AIAA ASME ASCE AHS ASC Structures Structural Dynamics and Materials Conference<BR> 18th AIAA ASME AHS Adaptive Structures Conference<BR&, 2010Co-Authors: Michael Shiao, William J. Hughes, Harry R. MillwaterAbstract:The Damage Tolerance approach, widely used in the aircraft industry, recognizes the existence of initial flaws and incorporates inspection and repair/replacement as a potentially effective strategy to sustain structural reliability and safety. However, in applications, due to lack of data, it has been a major hurdle to build reliable probabilistic distributions including the initial flaw size distribution, probability of detection, and fracture mechanics-related parameters. This paper discusses the computational challenges and proposes an efficient computational strategy for updating probabilistic Damage Tolerance modeling assumptions using detection results from multiple inspection times. The proposed strategy combines an efficient probabilistic Damage Tolerance methodology with MCMC to generate a posterior a PDF for subsequent reliability and maintenance update. A fracture mechanics example is presented that demonstrates the feasibility and the potential of the approach.
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Probabilistic Sensitivity-Based Ranking of Damage Tolerance Analysis Elements
Journal of Aircraft, 2010Co-Authors: Harry R. Millwater, David H. WielandAbstract:A Damage Tolerance Analysis contains a number of elements such as expected usage, structural and fatigue-related material properties, crack size, geometry, stress intensity factor, retardation model and constants, and others. Understanding of the relative significance of these elements is integral to performing a successful Damage Tolerance Analysis and determining future research efforts to improve the accuracy of Damage Tolerance Analysis. These elements have associated with them inherent uncertainty (as in material properties) or statistical uncertainty (as in loads, initial crack sizes, and geometry). Also, the assumptions contained in the Analysis methods may result in modeling errors, that is, the use of simplified models to represent complex behavior. In this research, the relative significance of the elements of a Damage Tolerance Analysis were calculated and ranked from a probabilistic sensitivity standpoint. The expected variation of Damage Tolerance Analysis inputs, for example, initial crack size, fracture toughness, hole size, etc., were modeled with probability distributions determined from experimental tests and aircraft or component teardowns. Discrete parameters such as the retardation model were varied through discrete changes to the model and reAnalysis. The probabilistic sensitivities, the derivative of the probability of failure with respect to statistical moments (mean, standard deviation), were determined using Monte Carlo sampling and used as the metric to rank the importance of the Damage Tolerance Analysis elements. The methodology was applied through a numerical Analysis to a fatigue critical location of a T-38 wing considering three different usages ranging from severe to mild.
Puhui Chen - One of the best experts on this subject based on the ideXlab platform.
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Damage Tolerance Analysis of Cracked Stiffened Composite Panels
Journal of Composite Materials, 2001Co-Authors: Puhui Chen, Zhen Shen, Junyang WangAbstract:An approach based on a displacement compatibility model is developed for stiffened composite panels with a crack. Some important improvements on the Damage Tolerance Analysis of the stiffened composite panels have been made in comparison with previous work. Some new results are obtained regarding the effects of adhesive nonlinearity, stringer stiffness and bending, and stringer spacing on strengths and crack growth behaviours of bonded skin/stringer panels. The study indicates that the adhesive nonlinearity benefits the load bearing capacity of the panels. When the stringer is quite thick in comparison to the skin thickness, its out-of-plane bending will lower panel failure strains. Increasing stringer stiffness can not often guarantee the high failure strains of bonded skin/stringer composite panels. As the stringer stiffness exceeds some value, its increase has a negative effect on the load bearing capacity of the panels. For a given ratio of stringer stiffness to panel stiffness, the failure strains of...
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Impact Damage Tolerance Analysis of Stiffened Composite Panels
Journal of Composite Materials, 2001Co-Authors: Puhui Chen, Zhen Shen, Junyang WangAbstract:An approach based on a displacement compatibility model is presented for both riveted and bonded stiffened composite panels containing impact Damage. This represents the first application of the displacement compatibility model to the failure Analysis of impacted stiffened composite panels, and some newresults are obtained for the impact Damage Tolerance properties of stiffened composite panels. In the present Analysis, the previous displacement compatibility model for a stringer/orthotropic skin panel is improved for a stringer/unbalanced skin panel. The impact Damage is simplified as an elliptic hole based on the compressive failure mechanisms of impacted composite laminates and stiffened panels. Predictions for failure loads and Damage arrest capability agree well with experimental results for several composite panel configurations. The important results obtained in this study are: (1) Damage arrest capability is dominated by the strength of the skin/stringer attachment; (2) distinct two-stage failure ...
H. Ishiduka - One of the best experts on this subject based on the ideXlab platform.
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Comparison of crack growth behaviour between full-scale railway axle and scaled specimen
International Journal of Fatigue, 2016Co-Authors: M. Yamamoto, K. Makino, H. IshidukaAbstract:Abstract There is an increasing demand for railway-axle Damage Tolerance Analysis. However, few studies have focused on the correspondence between the theoretical crack growth behaviour and the observed results for railway axles under constant stress amplitude. This paper presents the results of crack propagation tests using full-scale axles conducted in accordance with the ASTM E 647 standard. The threshold stress intensity factor range is also evaluated using a full-scale axle. Moreover, the crack growth behaviour of the full-scale axles is compared to that exhibited by compact tension specimens, which is obtained in the same manner.
Zhen Shen - One of the best experts on this subject based on the ideXlab platform.
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Damage Tolerance Analysis of Cracked Stiffened Composite Panels
Journal of Composite Materials, 2001Co-Authors: Puhui Chen, Zhen Shen, Junyang WangAbstract:An approach based on a displacement compatibility model is developed for stiffened composite panels with a crack. Some important improvements on the Damage Tolerance Analysis of the stiffened composite panels have been made in comparison with previous work. Some new results are obtained regarding the effects of adhesive nonlinearity, stringer stiffness and bending, and stringer spacing on strengths and crack growth behaviours of bonded skin/stringer panels. The study indicates that the adhesive nonlinearity benefits the load bearing capacity of the panels. When the stringer is quite thick in comparison to the skin thickness, its out-of-plane bending will lower panel failure strains. Increasing stringer stiffness can not often guarantee the high failure strains of bonded skin/stringer composite panels. As the stringer stiffness exceeds some value, its increase has a negative effect on the load bearing capacity of the panels. For a given ratio of stringer stiffness to panel stiffness, the failure strains of...
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Impact Damage Tolerance Analysis of Stiffened Composite Panels
Journal of Composite Materials, 2001Co-Authors: Puhui Chen, Zhen Shen, Junyang WangAbstract:An approach based on a displacement compatibility model is presented for both riveted and bonded stiffened composite panels containing impact Damage. This represents the first application of the displacement compatibility model to the failure Analysis of impacted stiffened composite panels, and some newresults are obtained for the impact Damage Tolerance properties of stiffened composite panels. In the present Analysis, the previous displacement compatibility model for a stringer/orthotropic skin panel is improved for a stringer/unbalanced skin panel. The impact Damage is simplified as an elliptic hole based on the compressive failure mechanisms of impacted composite laminates and stiffened panels. Predictions for failure loads and Damage arrest capability agree well with experimental results for several composite panel configurations. The important results obtained in this study are: (1) Damage arrest capability is dominated by the strength of the skin/stringer attachment; (2) distinct two-stage failure ...
