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Meng, Junying, Faqiang Wang, Li Cui, and Jun Liu. "The lower bound of nonlocal gradient for non-convex and non-smooth image patches based regularization." Inverse Problems 38, no. 3 (February 11, 2022): 035010. http://dx.doi.org/10.1088/1361-6420/ac3c55.
Повний текст джерелаАнотація:
Abstract In the inverse problem of image processing, we have witnessed that the non-convex and non-smooth regularizers can produce clearer image edges than convex ones such as total variation (TV). This fact can be explained by the uniform lower bound theory of the local gradient in non-convex and non-smooth regularization. In recent years, although it has been numerically shown that the nonlocal regularizers of various image patches based nonlocal methods can recover image textures well, we still desire a theoretical interpretation. To this end, we propose a non-convex non-smooth and block nonlocal regularization model based on image patches. By integrating the advantages of the non-convex and non-smooth potential function in the regularization term, the uniform lower bound theory of the image patches based nonlocal gradient is given. This approach partially explains why the proposed method can produce clearer image textures and edges. Compared to some classical regularization methods, such as TV, non-convex and non-smooth regularization, nonlocal total variation and block nonlocal total variation, our experimental results show that the proposed method improves restoration quality.
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Chen, Hui, Yali Qin, Hongliang Ren, Liping Chang, Yingtian Hu, and Huan Zheng. "Adaptive Weighted High Frequency Iterative Algorithm for Fractional-Order Total Variation with Nonlocal Regularization for Image Reconstruction." Electronics 9, no. 7 (July 7, 2020): 1103. http://dx.doi.org/10.3390/electronics9071103.
Повний текст джерелаАнотація:
We propose an adaptive weighted high frequency iterative algorithm for a fractional-order total variation (FrTV) approach with nonlocal regularization to alleviate image deterioration and to eliminate staircase artifacts, which result from the total variation (TV) method. The high frequency gradients are reweighted in iterations adaptively when we decompose the image into high and low frequency components using the pre-processing technique. The nonlocal regularization is introduced into our method based on nonlocal means (NLM) filtering, which contains prior image structural information to suppress staircase artifacts. An alternating direction multiplier method (ADMM) is used to solve the problem combining reweighted FrTV and nonlocal regularization. Experimental results show that both the peak signal-to-noise ratios (PSNR) and structural similarity index (SSIM) of reconstructed images are higher than those achieved by the other four methods at various sampling ratios less than 25%. At 5% sampling ratios, the gains of PSNR and SSIM are up to 1.63 dB and 0.0114 from ten images compared with reweighted total variation with nuclear norm regularization (RTV-NNR). The improved approach preserves more texture details and has better visual effects, especially at low sampling ratios, at the cost of taking more time.
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Rawat, Angel, Raghu Piska, A. Rajagopal, and Mokarram Hossain. "Nonlocal plasticity-based damage modeling in quasi-brittle materials using an isogeometric approach." Engineering Computations 38, no. 6 (January 27, 2021): 2604–30. http://dx.doi.org/10.1108/ec-12-2019-0562.
Повний текст джерелаАнотація:
Purpose This paper aims to present a nonlocal gradient plasticity damage model to demonstrate the crack pattern of a body, in an elastic and plastic state, in terms of damage law. The main objective of this paper is to reconsider the nonlocal theory by including the material in-homogeneity caused by damage and plasticity. The nonlocal nature of the strain field provides a regularization to overcome the analytical and computational problems induced by softening constitutive laws. Such an approach requires C1 continuous approximation. This is achieved by using an isogeometric approximation (IGA). Numerical examples in one and two dimensions are presented. Design/methodology/approach In this work, the authors propose a nonlocal elastic plastic damage model. The nonlocal nature of the strain field provides a regularization to overcome the analytical and computational problems induced by softening constitutive laws. An additive decomposition of strains in to elastic and inelastic or plastic part is considered. To obtain stable damage, a higher gradient order is considered for an integral equation, which is obtained by the Taylor series expansion of the local inelastic strain around the point under consideration. The higher-order continuity of nonuniform rational B-splines (NURBS) functions used in isogeometric analysis are adopted here to implement in a numerical scheme. To demonstrate the validity of the proposed model, numerical examples in one and two dimensions are presented. Findings The proposed nonlocal elastic plastic damage model is able to predict the damage in an accurate manner. The numerical results are mesh independent. The nonlocal terms add a regularization to the model especially for strain softening type of materials. The consideration of nonlocality in inelastic strains is more meaningful to the physics of damage. The use of IGA framework and NURBS basis functions add to the nonlocal nature in approximations of the field variables. Research limitations/implications The method can be extended to 3D. The model does not consider the effect of temperature and the dissipation of energy due to temperature. The method needs to be implemented for more real practical problems and compare with experimental work. This is an ongoing work. Practical implications The nonlocal models are suitable for predicting damage in quasi brittle materials. The use of elastic plastic theories allows to capture the inelastic deformations more accurately. Social implications The nonlocal models are suitable for predicting damage in quasi brittle materials. The use of elastic plastic theories allows to capture the inelastic deformations more accurately. Originality/value The present work includes the formulation and implementation of a nonlocal damage plasticity model using an isogeometric discretization, which is the novel contribution of this paper. An implicit gradient enhancement is considered to the inelastic strain. During inelastic deformations, the proposed strain tensor partitioning allows the use of a distinct potential surface and distinct failure criterion for both damage and plasticity models. The use of NURBS basis functions adds to more nonlocality in the approximation.
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Zhang, Yi, Weihua Zhang, and Jiliu Zhou. "Accurate Sparse-Projection Image Reconstruction via Nonlocal TV Regularization." Scientific World Journal 2014 (2014): 1–7. http://dx.doi.org/10.1155/2014/458496.
Повний текст джерелаАнотація:
Sparse-projection image reconstruction is a useful approach to lower the radiation dose; however, the incompleteness of projection data will cause degeneration of imaging quality. As a typical compressive sensing method, total variation has obtained great attention on this problem. Suffering from the theoretical imperfection, total variation will produce blocky effect on smooth regions and blur edges. To overcome this problem, in this paper, we introduce the nonlocal total variation into sparse-projection image reconstruction and formulate the minimization problem with new nonlocal total variation norm. The qualitative and quantitative analyses of numerical as well as clinical results demonstrate the validity of the proposed method. Comparing to other existing methods, our method more efficiently suppresses artifacts caused by low-rank reconstruction and reserves structure information better.
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Xue, Jize, Yongqiang Zhao, Wenzhi Liao, and Jonathan Chan. "Nonlocal Tensor Sparse Representation and Low-Rank Regularization for Hyperspectral Image Compressive Sensing Reconstruction." Remote Sensing 11, no. 2 (January 19, 2019): 193. http://dx.doi.org/10.3390/rs11020193.
Повний текст джерелаАнотація:
Hyperspectral image compressive sensing reconstruction (HSI-CSR) is an important issue in remote sensing, and has recently been investigated increasingly by the sparsity prior based approaches. However, most of the available HSI-CSR methods consider the sparsity prior in spatial and spectral vector domains via vectorizing hyperspectral cubes along a certain dimension. Besides, in most previous works, little attention has been paid to exploiting the underlying nonlocal structure in spatial domain of the HSI. In this paper, we propose a nonlocal tensor sparse and low-rank regularization (NTSRLR) approach, which can encode essential structured sparsity of an HSI and explore its advantages for HSI-CSR task. Specifically, we study how to utilize reasonably the l 1 -based sparsity of core tensor and tensor nuclear norm function as tensor sparse and low-rank regularization, respectively, to describe the nonlocal spatial-spectral correlation hidden in an HSI. To study the minimization problem of the proposed algorithm, we design a fast implementation strategy based on the alternative direction multiplier method (ADMM) technique. Experimental results on various HSI datasets verify that the proposed HSI-CSR algorithm can significantly outperform existing state-of-the-art CSR techniques for HSI recovery.
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HABARA, YOSHINOBU, YUKINORI NAGATANI, HOLGER B. NIELSEN, and MASAO NINOMIYA. "DIRAC SEA AND HOLE THEORY FOR BOSONS II: RENORMALIZATION APPROACH." International Journal of Modern Physics A 23, no. 18 (July 20, 2008): 2771–81. http://dx.doi.org/10.1142/s0217751x08040354.
Повний текст джерелаАнотація:
In bosonic formulation of the negative energy sea, so-called Dirac sea presented in the preceding paper [arXiv:hep-th/0603242], one of the crucial points is how to construct a positive definite inner product in the negative energy states, since naive attempts would lead to nonpositive definite ones. In the preceding paper, the nonlocal method is used to define the positive definite inner product. In the present paper we, make use of a kind of ∊-regularization and renormalization method which may clarify transparently the analytical properties of our formulation.
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LECHTENFELD, OLAF. "SEMICLASSICAL APPROACH TO FINITE-N MATRIX MODELS." International Journal of Modern Physics A 07, no. 28 (November 10, 1992): 7097–118. http://dx.doi.org/10.1142/s0217751x92003264.
Повний текст джерелаАнотація:
We reformulate the zero-dimensional Hermitian one-matrix model as a (nonlocal) collective field theory, for finite N. The Jacobian arising as a result of changing variables from matrix eigenvalues to their density distribution is treated exactly. The semiclassical loop expansion turns out not to coincide with the (topological) [Formula: see text] expansion, because the classical background has a nontrivial N dependence. We derive a simple integral equation for the classical eigenvalue density, which displays strong nonperturbative behavior around N=∞. This leads to IR singularities in the large-N expansion, but UV divergencies appear as well, despite remarkable cancelations among the Feynman diagrams. We evaluate the free energy at the two-loop level and discuss its regularization. A simple example serves to illustrate the problems and admits explicit comparison with orthogonal-polynomial results.
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Kong, Xiangyang, Yongqiang Zhao, Jize Xue, Jonathan Cheung-Wai Chan, Zhigang Ren, HaiXia Huang, and Jiyuan Zang. "Hyperspectral Image Denoising Based on Nonlocal Low-Rank and TV Regularization." Remote Sensing 12, no. 12 (June 17, 2020): 1956. http://dx.doi.org/10.3390/rs12121956.
Повний текст джерелаАнотація:
Hyperspectral image (HSI) acquisitions are degraded by various noises, among which additive Gaussian noise may be the worst-case, as suggested by information theory. In this paper, we present a novel tensor-based HSI denoising approach by fully identifying the intrinsic structures of the clean HSI and the noise. Specifically, the HSI is first divided into local overlapping full-band patches (FBPs), then the nonlocal similar patches in each group are unfolded and stacked into a new third order tensor. As this tensor shows a stronger low-rank property than the original degraded HSI, the tensor weighted nuclear norm minimization (TWNNM) on the constructed tensor can effectively separate the low-rank clean HSI patches. In addition, a regularization strategy with spatial–spectral total variation (SSTV) is utilized to ensure the global spatial–spectral smoothness in both spatial and spectral domains. Our method is designed to model the spatial–spectral non-local self-similarity and global spatial–spectral smoothness simultaneously. Experiments conducted on simulated and real datasets show the superiority of the proposed method.
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Zhang, Hao, Jianhua Ma, Jing Wang, Yan Liu, Hao Han, Hongbing Lu, William Moore, and Zhengrong Liang. "Statistical image reconstruction for low-dose CT using nonlocal means-based regularization. Part II: An adaptive approach." Computerized Medical Imaging and Graphics 43 (July 2015): 26–35. http://dx.doi.org/10.1016/j.compmedimag.2015.02.008.
Повний текст джерела
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Liu, Pengfei, Liang Xiao, and Liancun Xiu. "Mixed Higher Order Variational Model for Image Recovery." Mathematical Problems in Engineering 2014 (2014): 1–15. http://dx.doi.org/10.1155/2014/924686.
Повний текст джерелаАнотація:
A novel mixed higher order regularizer involving the first and second degree image derivatives is proposed in this paper. Using spectral decomposition, we reformulate the new regularizer as a weightedL1-L2mixed norm of image derivatives. Due to the equivalent formulation of the proposed regularizer, an efficient fast projected gradient algorithm combined with monotone fast iterative shrinkage thresholding, called, FPG-MFISTA, is designed to solve the resulting variational image recovery problems under majorization-minimization framework. Finally, we demonstrate the effectiveness of the proposed regularization scheme by the experimental comparisons with total variation (TV) scheme, nonlocal TV scheme, and current second degree methods. Specifically, the proposed approach achieves better results than related state-of-the-art methods in terms of peak signal to ratio (PSNR) and restoration quality.
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Nguyen, Giang Dinh, Alexander M. Korsunsky, and Jonathan Belnoue. "Coupled Damage-Plasticity Modelling of Ductile Failure in an Aluminium Alloy." Applied Mechanics and Materials 784 (August 2015): 266–73. http://dx.doi.org/10.4028/www.scientific.net/amm.784.266.
Повний текст джерелаАнотація:
The ductile failure of metallic alloys is characterized by the long plateau of the stress-strain response during plastic deformation. In aluminium alloys this complex process is principally mediated by crystal slip associated with dislocation nucleation, motion, interaction, and locking. This results in hardening, i.e. the increase in the flow stress and progressive exhaustion of ductility, eventually leading to damage. Therefore, in the advanced stages of deformation the strength increase at the material level competes with overall stiffness and strength decrease due to effective cross-section reduction by decohesion and voiding. Capturing the complex hierarchical failure of these materials requires developing sophisticated concurrent constitutive descriptions of both plastic deformation and damage at different stages of failure. In the present study the modelling of aluminium alloy failure is accomplished using a plasticity-based model with nonlinear hardening coupled with isotropic damage in a thermodynamically consistent framework. The model developed in this way is enhanced with nonlocal regularization to deal with material instabilities issues due to softening. Emphasis is placed on the correspondence between experimental measurements of the essential work of fracture and the non-essential work of fracture, and both local and spatial sets of model parameters. This approach is the key to assuring a constitutive response consistent with experimental observations, an issue usually overlooked in nonlocal constitutive modelling. Numerical examples are used to demonstrate the features of the new approach.
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de la Cruz Rodríguez, J., J. Leenaarts, S. Danilovic, and H. Uitenbroek. "STiC: A multiatom non-LTE PRD inversion code for full-Stokes solar observations." Astronomy & Astrophysics 623 (March 2019): A74. http://dx.doi.org/10.1051/0004-6361/201834464.
Повний текст джерелаАнотація:
The inference of the underlying state of the plasma in the solar chromosphere remains extremely challenging because of the nonlocal character of the observed radiation and plasma conditions in this layer. Inversion methods allow us to derive a model atmosphere that can reproduce the observed spectra by undertaking several physical assumptions. The most advanced approaches involve a depth-stratified model atmosphere described by temperature, line-of-sight velocity, turbulent velocity, the three components of the magntic field vector, and gas and electron pressure. The parameters of the radiative transfer equation are computed from a solid ground of physical principles. In order to apply these techniques to spectral lines that sample the chromosphere, nonlocal thermodynamical equilibrium effects must be included in the calculations. We developed a new inversion code STiC (STockholm inversion Code) to study spectral lines that sample the upper chromosphere. The code is based on the RH forward synthesis code, which we modified to make the inversions faster and more stable. For the first time, STiC facilitates the processing of lines from multiple atoms in non-LTE, also including partial redistribution effects (PRD) in angle and frequency of scattered photons. Furthermore, we include a regularization strategy that allows for model atmospheres with a complex depth stratification, without introducing artifacts in the reconstructed physical parameters, which are usually manifested in the form of oscillatory behavior. This approach takes steps toward a node-less inversion, in which the value of the physical parameters at each grid point can be considered a free parameter. In this paper we discuss the implementation of the aforementioned techniques, the description of the model atmosphere, and the optimizations that we applied to the code. We carry out some numerical experiments to show the performance of the code and the regularization techniques that we implemented. We made STiC publicly available to the community.
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Zhang, Jiachao, Ying Tong та Liangbao Jiao. "Simultaneous Patch-Group Sparse Coding with Dual-Weighted ℓp Minimization for Image Restoration". Micromachines 12, № 10 (1 жовтня 2021): 1205. http://dx.doi.org/10.3390/mi12101205.
Повний текст джерелаАнотація:
Sparse coding (SC) models have been proven as powerful tools applied in image restoration tasks, such as patch sparse coding (PSC) and group sparse coding (GSC). However, these two kinds of SC models have their respective drawbacks. PSC tends to generate visually annoying blocking artifacts, while GSC models usually produce over-smooth effects. Moreover, conventional ℓ1 minimization-based convex regularization was usually employed as a standard scheme for estimating sparse signals, but it cannot achieve an accurate sparse solution under many realistic situations. In this paper, we propose a novel approach for image restoration via simultaneous patch-group sparse coding (SPG-SC) with dual-weighted ℓp minimization. Specifically, in contrast to existing SC-based methods, the proposed SPG-SC conducts the local sparsity and nonlocal sparse representation simultaneously. A dual-weighted ℓp minimization-based non-convex regularization is proposed to improve the sparse representation capability of the proposed SPG-SC. To make the optimization tractable, a non-convex generalized iteration shrinkage algorithm based on the alternating direction method of multipliers (ADMM) framework is developed to solve the proposed SPG-SC model. Extensive experimental results on two image restoration tasks, including image inpainting and image deblurring, demonstrate that the proposed SPG-SC outperforms many state-of-the-art algorithms in terms of both objective and perceptual quality.
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Rabczuk, Timon. "Computational Methods for Fracture in Brittle and Quasi-Brittle Solids: State-of-the-Art Review and Future Perspectives." ISRN Applied Mathematics 2013 (March 20, 2013): 1–38. http://dx.doi.org/10.1155/2013/849231.
Повний текст джерелаАнотація:
An overview of computational methods to model fracture in brittle and quasi-brittle materials is given. The overview focuses on continuum models for fracture. First, numerical difficulties related to modelling fracture for quasi-brittle materials will be discussed. Different techniques to eliminate or circumvent those difficulties will be described subsequently. In that context, regularization techniques such as nonlocal models, gradient enhanced models, viscous models, cohesive zone models, and smeared crack models will be discussed. The main focus of this paper will be on computational methods for discrete fracture (discrete cracks). Element erosion technques, inter-element separation methods, the embedded finite element method (EFEM), the extended finite element method (XFEM), meshfree methods (MMs), boundary elements (BEMs), isogeometric analysis, and the variational approach to fracture will be reviewed elucidating advantages and drawbacks of each approach. As tracking the crack path is of major concern in computational methods that preserve crack path continuity, one section will discuss different crack tracking techniques. Finally, cracking criteria will be reviewed before the paper ends with future research perspectives.
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Mifdal, Jamila, Bartomeu Coll, Jacques Froment, and Joan Duran. "Variational Fusion of Hyperspectral Data by Non-Local Filtering." Mathematics 9, no. 11 (May 31, 2021): 1265. http://dx.doi.org/10.3390/math9111265.
Повний текст джерелаАнотація:
The fusion of multisensor data has attracted a lot of attention in computer vision, particularly among the remote sensing community. Hyperspectral image fusion consists in merging the spectral information of a hyperspectral image with the geometry of a multispectral one in order to infer an image with high spatial and spectral resolutions. In this paper, we propose a variational fusion model with a nonlocal regularization term that encodes patch-based filtering conditioned to the geometry of the multispectral data. We further incorporate a radiometric constraint that injects the high frequencies of the scene into the fused product with a band per band modulation according to the energy levels of the multispectral and hyperspectral images. The proposed approach proved robust to noise and aliasing. The experimental results demonstrate the performance of our method with respect to the state-of-the-art techniques on data acquired by commercial hyperspectral cameras and Earth observation satellites.
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Volokh, K. Y. "REVIEW OF THE ENERGY LIMITERS APPROACH TO MODELING FAILURE OF RUBBER." Rubber Chemistry and Technology 86, no. 3 (September 1, 2013): 470–87. http://dx.doi.org/10.5254/rct.13.87948.
Повний текст джерелаАнотація:
ABSTRACT Nonlinear theories of elasticity describe rubber deformation but not failure; however, in reality, rubbers do fail. In the present work, we review a new approach of energy limiters that allows for unifying hyperelasticity theories with failure descriptions, and we discuss results of this unification. First, we introduce the energy limiter concept, which allows the enforcement of failure descriptions in elasticity theories. The limiter provides the saturation value for the strain energy, hence indicating the maximal energy that may be stored and dissipated by an infinitesimal material volume. The limiter is a material constant that can be calibrated via macroscopic experiments. Second, we illustrate the new approach with examples in which failure initiation is predicted but its propagation is not tracked. Examples include the problems of crack initiation, cavity instability, and rupture of inflating membranes. In addition, the traditional strength-of-materials criteria are reassessed. Third, the theory is used for three-dimensional explicit finite element simulations of a high-velocity penetration of a stiff elastic body into a rubber plate. These simulations show that a high-velocity penetration of a flat projectile leads to a diffused nonlocal failure, which does not trigger the mesh sensitivity. To the contrary, a low-velocity penetration of a sharp projectile leads to a highly localized cracklike failure, which does trigger the mesh sensitivity. Calculation of the characteristic length of failure localization allows for setting the mesh size that provides regularization of the simulations. The fact that the calculation is based on results of solely macroscopic experiments is noteworthy.
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Huang, Jianping, Lihui Wang, and Yuemin Zhu. "Compressed Sensing MRI Reconstruction with Multiple Sparsity Constraints on Radial Sampling." Mathematical Problems in Engineering 2019 (February 10, 2019): 1–14. http://dx.doi.org/10.1155/2019/3694604.
Повний текст джерелаАнотація:
Compressed Sensing Magnetic Resonance Imaging (CS-MRI) is a promising technique for accelerating MRI acquisitions by using fewer k-space data. Exploiting more sparsity is an important approach to improving the CS-MRI reconstruction quality. We propose a novel CS-MRI framework based on multiple sparse priors to increase reconstruction accuracy. The wavelet sparsity, wavelet tree structured sparsity, and nonlocal total variation (NLTV) regularizations were integrated in the CS-MRI framework, and the optimization problem was solved using a fast composite splitting algorithm (FCSA). The proposed method was evaluated on different types of MR images with different radial sampling schemes and different sampling ratios and compared with the state-of-the-art CS-MRI reconstruction methods in terms of peak signal-to-noise ratio (PSNR), feature similarity (FSIM), relative l2 norm error (RLNE), and mean structural similarity (MSSIM). The results demonstrated that the proposed method outperforms the traditional CS-MRI algorithms in both visual and quantitative comparisons.
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Laghrib, Amine, Fatimzehrae Aitbella, and Abdelilah Hakim. "A second-order nonlocal regularized variational model for multiframe image super-resolution." International Journal of Nonlinear Sciences and Numerical Simulation, August 16, 2021. http://dx.doi.org/10.1515/ijnsns-2019-0109.
Повний текст джерелаАнотація:
Abstract In this paper, we propose a new nonlocal super-resolution (SR) model which is a combination of the nonlocal total variation (TV) regularization and the nonlocal p-Laplacian term (with p = 2). This choice is motivated by the success of the nonlocal TV term in preserving image edges and the efficiency of the nonlocal p-Laplacian term in preserving the image texture. To ensure the convergence of the proposed optimization SR problem, we prove the existence and uniqueness of a solution in a well-posed framework. In addition, to resolve the encountered minimization problem, we proposed a modified primal-dual algorithm and numerical results are also given to show the performance of the proposed approach.
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Forghani, Alireza, and Reza Vaziri. "Computational Modeling of Damage Development in Composite Laminates Subjected to Transverse Dynamic Loading." Journal of Applied Mechanics 76, no. 5 (June 15, 2009). http://dx.doi.org/10.1115/1.3129705.
Повний текст джерелаАнотація:
This paper presents a robust computational model for the response of composite laminates to high intensity transverse dynamic loading emanating from local impact by a projectile and distributed pressure pulse due to a blast. Delaminations are modeled using a cohesive type tie-break interface introduced between sublaminates while intralaminar damage mechanisms within the sublaminates are captured in a smeared manner using a strain-softening plastic-damage model. In the latter case, a nonlocal regularization scheme is used to address the spurious mesh dependency and mesh-orientation problems that occur with all local strain-softening type constitutive models. The results for the predicted damage patterns using the nonlocal approach are encouraging and qualitatively agree with the experimental observations. The predictive performance of the proposed numerical model is assessed through comparisons with available instrumented impact test results on a class of carbon-fiber reinforced polymer (CFRP) composite laminates. Force-time histories and other derived cross-plots such as the force versus projectile displacement and progression of projectile energy loss as a function of time are compared with available experimental results to demonstrate the efficacy of the model in capturing the details of the dynamic response. Another case study involving the blast loading of CFRP composite laminates is used to further highlight the capability of the proposed model in simulating the global structural response of composite laminates subjected to distributed pressure pulses.
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Faupel, Alex, Ido Meshi, and Caglar Oskay. "Reduced order multiscale model for compression kink-band failure in composites." Journal of Composite Materials, July 13, 2022, 002199832211140. http://dx.doi.org/10.1177/00219983221114012.
Повний текст джерелаАнотація:
A multiscale model for compression kink band failure in fibrous composites is presented. The computational model predicts the progression of damage associated with the formation of kink bands, which experiments demonstrate to involve excessive shear straining of the matrix material and fiber fracture. The uniqueness of the study is establishing the concurrent treatment of nonlinear deformation and failure of the composite constituents at the scale of the material microstructure, and the formation of kink bands at the mesoscopic scale. The model incorporates computational homogenization of the material response, a nonlocal gradient regularization scheme, and a curvature-based criterion for macroscopic fiber break to predict kink band formation. The multiscale approach resolves mesoscale mechanisms associated with kink banding while offering computational benefits compared to direct mesomechanical approaches. An accessible implementation within finite element analysis software is presented and the model is verified with analysis of a mesoscale domain incorporating initial fiber waviness. In quasi-static simulations, the kink band initiates due to matrix softening that results in the onset of buckling and is completely formed when fibers break as a result of localized curvature. Results from parametric studies confirm that compression strength is not directly related to measures of the kink band morphology, but it is strongly correlated with the shear strength and initial fiber misalignment angle. The predicted effects of material properties representing various carbon fiber reinforced polymers and a range of fiber misalignment angles on kink band width and failure strength corroborate analytical and experimental results presented in the literature.