Guided Wave Energy Distribution Analysis in Inhomogeneous Plates

An analysis of guided wave energy propagation in a inhomogeneous multi-layered composite structure is presented. It has earlier been reported that ultrasonic guided wave energy within an inhomogeneous composite materials tend to follow the orientation of the fibers, even when the plane of the incident wave is not along the fiber direction [1–3]. In this paper, an exact analysis of a plane wave incident onto a generally anisotropic, visco-elastic, multi-layered composite structure is use here to study the energy flow behavior of guided ultrasonic waves in inhomogeneous composite plates [4] is used to predict this behavior. The reflected and refracted coefficients are obtained by using the well know Thomson-Haskell transfer matrix method [5] which transfer boundary conditions from one side of a solid medium to the other. Then, the power flow vector is used to study the energy distributions within the plates as well as the generation mechanism of guided waves

Guided Wave Energy Distribution Analysis in Inhomogeneous Plates

An analysis of guided wave energy propagation in a inhomogeneous multi-layered composite structure is presented. It has earlier been reported that ultrasonic guided wave energy within an inhomogeneous composite materials tend to follow the orientation of the fibers, even when the plane of the incident wave is not along the fiber direction [1–3]. In this paper, an exact analysis of a plane wave incident onto a generally anisotropic, visco-elastic, multi-layered composite structure is use here to study the energy flow behavior of guided ultrasonic waves in inhomogeneous composite plates [4] is used to predict this behavior. The reflected and refracted coefficients are obtained by using the well know Thomson-Haskell transfer matrix method [5] which transfer boundary conditions from one side of a solid medium to the other. Then, the power flow vector is used to study the energy distributions within the plates as well as the generation mechanism of guided waves.</p

Genetic Algorithms for Inversion of Ultrasonic Data for the Elastic Constants Measurement in Orthotropic Material Systems

Fiber reinforced composite materials have been used in many structural applications varying from swimming pool diving boards to advanced aerospace components. The primary advantage of composites includes a high stiffness to weight ratio which in the past has come at an increased cost. Continued improvements in the development of cost effective manufacturing methods and development of low cost fibers and resin materials have increased the use of composites in infra-structural applications such as buildings, and bridges. As fiber reinforced composites become more widely used, the need for a reliable method to nondestructively characterize the material stiffness properties and identify material defects is becoming critical for ensuring a reliable level of performance.</p

Guided Wave Behavior Analysis in Multi-Layered Inhomogeneous Anisotropic Plates

Guided waves behave much differently in inhomogeneous anisotropic plates than in homogeneous anisotropic plates. It has been reported before that guided waves in inhomogeneous plates tend to follow preferred directions based on the location of ply-groups as well as the orientation of the fibers [1]. The pattern obtained by imaging the leaked energy into the surrounding fluid (earlier called as Plate Wave Flow Patterns) has been shown to indicate fiber orientations [2]. In this paper, a model based on the Thomson-Haskell transfer matrix is employed to obtain the internal distributions of the energy vector within the inhomogeneous plate. Based on the theoretical results, the plate wave flow patterns can be predicted and compared with the experimental results. The results provide insight into the understanding of the generation mechanism of guided wave mode patterns in inhomogeneous plates.</p

Validity of the Elastic Constant Approximations for the Ultrasonic Evaluation of Multi-Layered Inhomogeneous Composites

Several ultrasonic wave mechanics models which are based on the effective elastic properties of the overall fiber reinforced composites are currently being used in the industry and academia. Due to the repetition of the ply orientation and the lay-up sequence traditionally used in the industry, these models which often “smear” the individual ply elastic properties to obtain effective elastic properties of the entire composite. [1,2] This is an acceptable approximation for long wave length waves propagation in homogeneous or quasi-homogeneous ply lay-ups media and has provided useful results in the non-destructive evaluation process.</p

Protocol for MRI-guided virus injection in macaque deep brain regions

Summary: Effective delivery of viruses into required brain regions is critical to the success of optogenetic or chemogenetic experiments. However, in monkeys, due to the large size and heterogeneity of their brain, precise injections in deep brain regions have been challenging. Here, we present a protocol for virus injection in monkey deep brain regions under the guidance of MRI. We describe the steps for installing the guiding grid, MRI scanning, MRI-based localization, and virus injection.For complete details on the use and execution of this protocol, please refer to Chen et al. (2023).1 : Publisher’s note: Undertaking any experimental protocol requires adherence to local institutional guidelines for laboratory safety and ethics

Acousto-Ultrasonic Evaluation of Hybrid Composites Using Oblique Incidence Waves

Multi-layered composite structures are becoming widely used in industry. The quantitative evaluation of the quality of bonded interfaces is critical. With the introduction of composite materials as a substitute for metal, the potential for reducing the overall weight of structure is being realized. The composite structure must be designed layer by layer in order to meet the same functional specifications that were met by the previous metal design. The resulting laminate is a sophisticated product with a complex structure and anisotropic material properties. Because of its complexity and anisotropy it is very difficult to inspect. Conventional inspection methods cannot be used and new methods must be developed.</p

An Adaptive Classifier for Detecting Helicopter Drivetrain Damage Using Acoustic Emission

This paper describes recent developments in a program to detect damage to helicopter drivetrains using acoustic emission (AE)1,2. Data obtained from an SH-60 drivetrain on an NAWC test stand was correlated with seeded fault damage in order to identify acoustic emission characteristics unique to the various sources. The objective is to extend prior work in applications of pattern recognition techniques and advanced machine intelligence to AE3,4,5 by designing and implementing an autonomous adaptive procedure to recognize and classify drivetrain damage from AE data.</p

Intersection of Nanotechnology and Healthcare

Multi-layered composite structures are becoming widely used in industry. The quantitative evaluation of the quality of bonded interfaces is critical. With the introduction of composite materials as a substitute for metal, the potential for reducing the overall weight of structure is being realized. The composite structure must be designed layer by layer in order to meet the same functional specifications that were met by the previous metal design. The resulting laminate is a sophisticated product with a complex structure and anisotropic material properties. Because of its complexity and anisotropy it is very difficult to inspect. Conventional inspection methods cannot be used and new methods must be developed