scholarly journals A Gaussian Beam Based Recursive Stiffness Matrix Model to Simulate Ultrasonic Array Signals from Multi-Layered Media

Sensors ◽  
2020 ◽  
Vol 20 (16) ◽  
pp. 4371
Author(s):  
Chirag Anand ◽  
Roger Groves ◽  
Rinze Benedictus
Keyword(s):  
Gaussian Beam ◽  
Stiffness Matrix ◽  
Composite Structures ◽  
Finite Size ◽  
Modeling Technique ◽  
Beam Model ◽  
Inherent Anisotropy ◽  
Reinforced Plastic ◽  
Fdtd Methods ◽  
Difference Time

Ultrasonic testing using arrays is becoming widely used to test composite structures in the Aerospace industry. In recent years, the Full Matrix Capture (FMC) technique has been implemented to extract the signals for post-processing to form an image. The inherent anisotropy and the layering of the structure pose challenges for the interpretation of this FMC data. To overcome this challenge, modeling techniques are required that take into account the diffraction caused by finite-size transducers and the response of the structure to these bounded beams. Existing models either homogenize the entire structure, use computationally expensive finite difference time domain (FDTD) methods, or do not consider the shape of the bounded beam, which is used to test such structures. This paper proposes a modeling technique based on combining the Multi-Gaussian beam model with the recursive stiffness matrix method to simulate the FMC signals for layered anisotropic media. The paper provides the steps required for the modeling technique, the extraction of the system efficiency factor, and validation of the model with experimentally determined signals for aluminum as an isotropic material such as aluminum and Carbon Fiber Reinforced Plastic (CFRP) laminate as a layered material. The proposed method is computationally inexpensive, shows good agreement with the experimentally determined FMC data, and enables us to understand the effects of various transducer and material parameters on the extracted FMC signals.

Equivalent Finite Element Modeling of Thick Composite Structures for Analysis of Composite Hingeless Hub System

2004 ◽  
Vol 261-263 ◽  
pp. 585-590
Author(s):  
Hoon Cheol Park ◽  
Yanti Rachmadini ◽  
Sang Min Lim ◽  
Sang Ki Lee ◽  
Kwang Joon Yoon ◽  
...  
Keyword(s):  
Finite Element ◽  
Composite Structures ◽  
Complex Geometry ◽  
Three Dimensional ◽  
Modeling Technique ◽  
Beam Model ◽  
Plane Stress Condition ◽  
Element Analysis ◽  
Three Dimensional Modeling ◽  
Dimensional Modeling

Finite element analysis for thick composite structures is rather complicated. Two-dimensional modeling, which is relatively easy to make, can cause inaccurate result since the plane stress condition cannot be applied, while three-dimensional modeling is hard to make. In the three- dimensional modeling, it is difficult to model all the layers with different material properties and ply orientation in the structure. In this paper, an equivalent modeling is proposed and numerically tested for analysis of thick composite structures. The method has been verified for the modeling of composite plate and circular composite tube in order to find their bending deflection and natural frequency. MSC/NASTRAN and PATRAN are used for the calculation. It has been confirmed that three-dimensional analysis must be conducted for thick structures and the equivalent modeling is proven to be accurate when layers with same characteristics are properly grouped. The proposed modeling technique has been applied to analyze hingeless composite rotor hub system designed by Korea Aerospace Research Institute (KARI). Detailed three-dimensional modeling for this structure is almost impossible to make due to its complex geometry of thick composite structures. Using the proposed equivalent modeling technique, failure analysis was performed based on stress/strain criterion and the safety of each part was checked. Deflection of the hub system was validated comparing with the result from the simple analytical beam model, and the numerical result will be used for the next design cycle of the composite hub system.

scholarly journals Modeling and Imaging of Ultrasonic Array Inspection of Side Drilled Holes in Layered Anisotropic Media

Sensors ◽  
2021 ◽  
Vol 21 (14) ◽  
pp. 4640
Author(s):  
Chirag Anand ◽  
Roger M. Groves ◽  
Rinze Benedictus
Keyword(s):  
Anisotropic Medium ◽  
Stiffness Matrix ◽  
Composite Structures ◽  
Layered Medium ◽  
Plane Waves ◽  
Anisotropic Media ◽  
Full Matrix ◽  
Inherent Anisotropy ◽  
Transmission And Reflection Coefficients ◽  
Modeling Techniques

There has been an increase in the use of ultrasonic arrays for the detection of defects in composite structures used in the aerospace industry. The response of a defect embedded in such a medium is influenced by the inherent anisotropy of the bounding medium and the layering of the bounding medium and hence poses challenges for the interpretation of the full matrix capture (FMC) results. Modeling techniques can be used to understand and simulate the effect of the structure and the defect on the received signals. Existing modeling techniques, such as finite element methods (FEM), finite difference time domain (FDTD), and analytical solutions, are computationally inefficient or are singularly used for structures with complex geometries. In this paper, we develop a novel model based on the Gaussian-based recursive stiffness matrix approach to model the scattering from a side-drilled hole embedded in an anisotropic layered medium. The paper provides a novel method to calculate the transmission and reflection coefficients of plane waves traveling from a layered anisotropic medium into a semi-infinite anisotropic medium by combining the transfer matrix and stiffness matrix methods. The novelty of the paper is the developed model using Gaussian beams to simulate the scattering from a Side Drilled Hole (SDH) embedded in a multilayered composite laminate, which can be used in both immersion and contact setups. We describe a method to combine the scattering from defects with the model to simulate the response of a layered structure and to simulate the full matrix capture (FMC) signals that are received from an SDH embedded in a layered medium. The model-assisted correction total focusing method (MAC-TFM) imaging is used to image both the simulated and experimental results. The proposed method has been validated for both isotropic and anisotropic media by a qualitative and quantitative comparison with experimentally determined signals. The method proposed in this paper is modular, computationally inexpensive, and is in good agreement with experimentally determined signals, and it enables us to understand the effects of various parameters on the scattering of a defect embedded in a layered anisotropic medium.

Compact and ultrafast all optical 1-bit comparator based on wave interference and threshold switching methods

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Asghar Askarian
Keyword(s):  
Finite Difference Time Domain ◽  
Contrast Ratio ◽  
Logical Structure ◽  
Ring Resonators ◽  
Plane Wave Expansion ◽  
Threshold Switching ◽  
Wave Interference ◽  
All Optical ◽  
Fdtd Methods ◽  
Difference Time

Abstract In this study, we are going to design all optical 1-bit comparator by combining wave interference and threshold switching methods. The final structure composed of two nonlinear ring resonators and seven waveguides. The functionality of the suggested logical structure is analyzed and simulated by using plane wave expansion (PWE) and finite difference time domain (FDTD) methods. According to results, the proposed all optical 1-bit comparator has faster response and smaller footprint than all previous works. The maximum ON-OFF contrast ratio, delay time and area of the suggested optical comparator are about 16.67 dB, 1.8 ps, and 513 µm2, respectively.

scholarly journals From Time-Collocated to Leapfrog Fundamental Schemes for ADI and CDI FDTD Methods

Axioms ◽  
2022 ◽  
Vol 11 (1) ◽  
pp. 23
Author(s):  
Eng Leong Tan
Keyword(s):  
Finite Difference ◽  
Time Domain ◽  
Finite Difference Time Domain ◽  
Fdtd Method ◽  
Unconditionally Stable ◽  
Alternating Direction Implicit ◽  
One Dimensional ◽  
Alternating Direction ◽  
Fdtd Methods ◽  
Difference Time

The leapfrog schemes have been developed for unconditionally stable alternating-direction implicit (ADI) finite-difference time-domain (FDTD) method, and recently the complying-divergence implicit (CDI) FDTD method. In this paper, the formulations from time-collocated to leapfrog fundamental schemes are presented for ADI and CDI FDTD methods. For the ADI FDTD method, the time-collocated fundamental schemes are implemented using implicit E-E and E-H update procedures, which comprise simple and concise right-hand sides (RHS) in their update equations. From the fundamental implicit E-H scheme, the leapfrog ADI FDTD method is formulated in conventional form, whose RHS are simplified into the leapfrog fundamental scheme with reduced operations and improved efficiency. For the CDI FDTD method, the time-collocated fundamental scheme is presented based on locally one-dimensional (LOD) FDTD method with complying divergence. The formulations from time-collocated to leapfrog schemes are provided, which result in the leapfrog fundamental scheme for CDI FDTD method. Based on their fundamental forms, further insights are given into the relations of leapfrog fundamental schemes for ADI and CDI FDTD methods. The time-collocated fundamental schemes require considerably fewer operations than all conventional ADI, LOD and leapfrog ADI FDTD methods, while the leapfrog fundamental schemes for ADI and CDI FDTD methods constitute the most efficient implicit FDTD schemes to date.

Systematic Process Chain Creation for CFRP Structures in Early Product Development Stages

2016 ◽  
Vol 1140 ◽  
pp. 328-334
Author(s):  
Matthias Behr ◽  
Carsten Schmidt
Keyword(s):  
Composite Structures ◽  
Production Costs ◽  
Preliminary Design ◽  
Process Chain ◽  
Whole Process ◽  
Reinforced Plastic ◽  
Building Process ◽  
Process Chains ◽  
Carbon Fibre Reinforced Plastic ◽  
Specific Sequences

A planning method is presented which allows to systematically building process chains based on a preliminary design of composite structures. The method utilises the specific sequences of procedural steps that occur in the production of carbon fibre reinforced plastic (CFRP) structures, to build sub process chains for each component of the structure. Process restrictions are considered to evaluate the suitability of different production processes. To obtain the whole process chain of the structure, different joining methods are applied in addition to combine the components and its sub process chains. The results of the presented method are used in an overarching development procedure to investigate resulting impacts on the solution. Possible impacts could be the production costs or the material characteristics.

scholarly journals Influence of machining damage generated during trimming of CFRP composite on the compressive strength

2019 ◽  
Vol 54 (11) ◽  
pp. 1413-1430 ◽  
Author(s):  
N Nguyen-Dinh ◽  
C Bouvet ◽  
R Zitoune
Keyword(s):  
Surface Roughness ◽  
Mechanical Behavior ◽  
Composite Structures ◽  
Compressive Loading ◽  
Machined Surface ◽  
Reinforced Plastic ◽  
Cfrp Composite ◽  
Optical Topography ◽  
Induced Defects ◽  
Machining Damage

Machining of composite materials is a challenging task due to the heterogeneity and anisotropy of composite structures. The induced defects reduce integrity of the machined surface as well as the loading capacity of the composite structure in service. Therefore, it is necessary to quantify the damage induced during trimming and correlate the quality of the machined surface to mechanical properties. The correlation of the surface roughness criteria, widely used in literature, to the mechanical behavior raise several contradictions. For this reason, new parameters for the characterization of the machined surface are proposed and correlated to the mechanical behavior under compressive loading. In this context, carbon fiber-reinforced plastic laminates are conventionally trimmed, and the machining damage is characterized using scanning electron microscope observations, X-ray tomography, and 3D optical topography. The results reveal that crater volume and maximum depth of damage quantify the machining damage more realistic compared to the classical surface roughness criteria.

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