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At least 109 records · Page 6

All sources NASA NTRS DOE OSTI

NASA NTRS2017

Simulation of Guided-Wave Ultrasound Propagation in Composite Laminates: Benchmark Comparisons of Numerical Codes and Experiment

Ultrasonic wave methods constitute the leading physical mechanism for nondestructive evaluation (NDE) and structural health monitoring (SHM) of solid composite materials, such as carbon fiber reinforced polymer (CFRP) laminates. Computational models of ultrasonic wave excitation, propagation, and scattering in CFRP composites can be extremely valuable in designing practicable NDE and SHM hardware, software, and methodologies that accomplish the desired accuracy, reliability, efficiency, and coverage. The development and application of ultrasonic simulation approaches for composite materials is an active area of research in the field of NDE. This paper presents comparisons of guided wave simulations for CFRP composites implemented using four different simulation codes: the commercial finite element modeling (FEM) packages ABAQUS, ANSYS, and COMSOL, and a custom code executing the Elastodynamic Finite Integration Technique (EFIT). Benchmark comparisons are made between the simulation tools and both experimental laser Doppler vibrometry data and theoretical dispersion curves. A pristine and a delamination type case (Teflon insert in the experimental specimen) is studied. A summary is given of the accuracy of simulation results and the respective computational performance of the four different simulation tools.

Composite↗

NASA NTRS1986

Ultrasonic stress wave characterization of composite materials

The work reported covers three simultaneous projects. The first project was concerned with: (1) establishing the sensitivity of the acousto-ultrasonic method for evaluating subtle forms of damage development in cyclically loaded composite materials, (2) establishing the ability of the acousto-ultrasonic method for detecting initial material imperfections that lead to localized damage growth and final specimen failure, and (3) characteristics of the NBS/Proctor sensor/receiver for acousto-ultrasonic evaluation of laminated composite materials. The second project was concerned with examining the nature of the wave propagation that occurs during acoustic-ultrasonic evaluation of composite laminates and demonstrating the role of Lamb or plate wave modes and their utilization for characterizing composite laminates. The third project was concerned with the replacement of contact-type receiving piezotransducers with noncontacting laser-optical sensors for acousto-ultrasonic signal acquisition.

Duke, J. C., Jr.↗

DOE OSTI2021

Shear wave generation by mode conversion in picosecond ultrasonics: Impact of grain orientation and material properties

Abstract Picosecond ultrasonics has seen wide application in the investigation of interfaces in semiconductors and 3D imaging in biological systems. Shear ultrasonic waves are important for elastic constant and grain orientation measurement in ceramic materials. In this study, we investigate the impact of grain orientation and material's elastic properties on the generation efficiency of shear waves by mode conversion at a transducer thin film/substrate interface. The solution of acoustic wave equations suggests that crystal grain orientation has a strong impact on the generated shear wave amplitude. This dependence is found to be closely related to the magnitude of longitudinal component of wave displacements. The applicability of analytical model is validated by the experimental results from time‐domain Brillouin scattering. Moreover, material properties determine acoustic wave amplitudes based on the acoustic mismatch model and, particularly, large elastic anisotropy defined by Zener ratio favors strong shear waves. In the light of this analysis, several recommendations on suitable grain orientations and film materials are made to facilitate shear wave detection.

Wang, Yuzhou↗

NASA NTRS1974

A transmission oscillator ultrasonic spectrometer

A continuous wave ultrasonic instrument capable of measuring very small changes in acoustic attenuation and phase velocity is described. This transmission oscillator ultrasonic spectrometer (TOUS) exhibits high sensitivity because it oscillates marginally. In spite of this high sensitivity, the TOUS system is relatively simple, compact, and inexpensive. These features suggest that the TOUS is suitable not only for precise laboratory measurements of the physical properties of materials, but also for field applications in nondestructive testing.

Conradi, M. S.↗

NASA NTRS2014

Process for Nondestructive Evaluation of the Quality of a Crimped Wire Connector

A process and apparatus for collecting data for nondestructive evaluation of the quality of a crimped wire connector are provided. The process involves providing a crimping tool having an anvil and opposing jaw for crimping a terminal onto a stranded wire, moving the jaw relative to the anvil to close the distance between the jaw and the anvil and thereby compress the terminal against the wire, while transmitting ultrasonic waves that are propagated through the terminal-wire combination and received at a receiving ultrasonic transducer as the jaw is moved relative to the anvil, and detecting and recording the position of the jaw relative to the anvil as a function of time and detecting and recording the amplitude of the ultrasonic wave that is received at the receiving ultrasonic transducer as a function of time as the jaw is moved relative to the anvil.

Yost, William T.↗

DOE OSTI2024

Utah FORGE: Direct Shear Test Data for Investigating Seismic Precursors to Shear Failure of Fractures

This dataset includes results of direct shear tests to investigate the mechanical and geophysical response of dry and saturated fractures in Indiana limestone and Sierra White granite. Direct shear tests were performed on tensile-induced fractures in Indiana limestone and Sierra White granite in a custom water-pressurized chamber. The provided Excel files include the representative seismic wave signals and the normalized wave amplitudes of ultrasonic wave transducers. A link to the published journal article presenting the data and describing the experiment in detail is provided as well.

15 GEOTHERMAL ENERGY↗

NASA NTRS1993

Extra-corporeal blood access, sensing, and radiation methods and apparatuses

The described invention is related to extra-corporeal blood access and radiation methods and apparatuses and, in particular, to subjecting flowing blood to energy in variety of forms, including radiation, electromagnetic force fields or atomic particles. It is directed to methods and apparatuses for accessing flowing blood and for subjecting the blood to electrical conductive, electrostatic or electromagnetic fields or for radiating the blood with some type of radiation, e.g., radio waves, ultrasonic or audio waves, microwaves, IR rays, visible light, UV radiation, x-rays, alpha, beta or gamma rays. An apparatus is employed which includes one or more access ports or windows for radiating blood and/or for sensing/analyzing blood. This invention is useful for killing viruses and bacteria in blood, monitoring blood for medical purposes, genetic modification of blood, and analyzing and/or treating blood components.

Castle, Kent D.↗

NASA NTRS2010

TPSAS-NF1676L-10178-DND

The objective is to investigate the capability of carbon nanotube (CNT) strain sensors for reception of ultrasonic waves. The goal is to measure and simulate the response of CNT sensors to ultrasonic waves and to examine their frequency response and directionality. These measurements will be used to validated simulations to establish guidelines for future CNT acoustic sensor research and development.

Eric Madaras↗

NASA NTRS1999

Rotary Motors Actuated by Traveling Ultrasonic Flexural Waves

Efficient miniature actuators that are compact and consume low power are needed to drive space and planetary mechanisms in future NASA missions. Ultrasonic rotary motors have the potential to meet this NASA need and they are developed as actuators for miniature telerobotic applications. These motors have emerged in commercial products but they need to be adapted for operation at the harsh space environments that include cryogenic temperatures and vacuum and also require effective analytical tools for the design of efficient motors. A finite element analytical model was developed to examine the excitation of flexural plate wave traveling in a piezoelectrically actuated rotary motor. The model uses 3D finite element and equivalent circuit models that are applied to predict the excitation frequency and modal response of the stator. This model incorporates the details of the stator including the teeth, piezoelectric ceramic, geometry, bonding layer, etc. The theoretical predictions were corroborated experimentally for the stator. In parallel, efforts have been made to determine the thermal and vacuum performance of these motors. Experiments have shown that the motor can sustain at least 230 temperature cycles from 0 C to -90 C at 7 Torr pressure significant performance change. Also, in an earlier study the motor lasted over 334 hours at -150 C and vacuum. To explore telerobotic applications for USMs a robotic arm was constructed with such motors.

Bar-Cohen, Yoseph↗

NASA NTRS1999

Rotary Motors Actuated by Traveling Ultrasonic Flexural Waves

Efficient miniature actuators that the compact and consume low power are needed to drive space and planetary mechanisms in future NASA missions. Ultrasonic rotary motors have the potential to meet this NASA need and they are developed as actuators for miniature telerobotic applications.

piezoelectric↗

NASA NTRS1979

Broadband electrostatic acoustic transducer for ultrasonic measurements in liquids

A broadband capacitive electrostatic acoustic transducer (ESAT) has been developed for use in a liquid environment at megahertz frequencies. The ESAT basically consists of a thin conductive membrane stretched over a metallic housing. The membrane functions as the ground plate of a parallel plate capacitor, the other plate being a dc biased electrode recessed approximately 10 microns from the electrically grounded membrane. An ultrasonic wave incident on the membrane varies the membrane-electrode gap spacing and generates an electrical signal proportional to the wave amplitude. The entire assembly is sealed for immersion in a liquid environment. Calibration of the ESAT with incident ultrasonic waves of constant displacement amplitude from 1 to 15 MHz reveals a decrease in signal response with increasing frequency independent of membrane tension. The use of the ESAT as a broadband ultrasonic transducer in liquids with a predictable frequency response is promising.

Cantrell, J. H., Jr.↗

NASA NTRS2002

Scanning Ultrasonic Spectroscopy System Developed for the Inspection of Composite Flywheels

Composite flywheels are being considered as replacements for chemical batteries aboard the International Space Station. A flywheel stores energy in a spinning mass that can turn a generator to meet power demands. Because of the high rotational speeds of the spinning mass, extensive testing of the flywheel system must be performed prior to flight certification. With this goal in mind, a new scanning system has been developed at the NASA Glenn Research Center for the nondestructive inspection of composite flywheels and flywheel subcomponents. The system uses ultrasonic waves to excite a material and examines the response to detect and locate flaws and material variations. The ultrasonic spectroscopy system uses a transducer to send swept-frequency ultrasonic waves into a test material and then receives the returning signal with a second transducer. The received signal is then analyzed in the frequency domain using a fast Fourier transform. A second fast Fourier transform is performed to examine the spacing of the peaks in the frequency domain. The spacing of the peaks is related to the standing wave resonances that are present in the material because of the constructive and destructive interferences of the waves in the full material thickness as well as in individual layers within the material. Material variations and flaws are then identified by changes in the amplitudes and positions of the peaks in both the frequency and resonance spacing domains. This work, conducted under a grant through the Cleveland State University, extends the capabilities of an existing point-by-point ultrasonic spectroscopy system, thus allowing full-field automated inspection. Results of an ultrasonic spectroscopy scan of a plastic cylinder with intentionally seeded flaws. The result of an ultrasonic spectroscopy scan of a plastic cylinder used as a proof-of-concept specimen is shown. The cylinder contains a number of flat bottomed holes of various sizes and shapes. The scanning system was able to successfully detect all the defects in the material. Ultrasonic spectroscopy results for a second specimen are shown along with a conventional ultrasonic C-scan. The second specimen is a section of a flywheel subcomponent that has a series of drilled holes and notches. This specimen is employed as a defect detection standard to evaluate the various nondestructive evaluation methods under consideration. Scanning results demonstrate the ability of the system to detect flaws on the order of 10 mils in the radial direction and 5 mils in the circumferential direction. Work conducted to date has shown that scanning ultrasonic spectroscopy is a viable tool for the inspection of composite flywheel systems. Ongoing development work is focused on refining the system and scanning parameters for improved resolution and defect detection.

Martin, Richard E.↗

NASA NTRS1994

Method of determining load in anisotropic non-crystalline materials using energy flux deviation

An ultrasonic wave is applied to an anisotropic sample material in an initial direction and the intensity of the ultrasonic wave is measured on an opposite surface of the sample material by two adjacent receiving points located in an array of receiving points. A ratio is determined between the measured intensities of two adjacent receiving points, the ratio being indicative of an angle of flux deviation from the initial direction caused by an unknown applied load. This determined ratio is then compared to a plurality of ratios of a similarly tested, similar anisotropic reference material under a plurality of respective, known load conditions, whereby the load applied to the particular anisotropic sample material is determined. A related method is disclosed for determining the fiber orientation from known loads and a determined flux shift.

Prosser, William H.↗

NASA NTRS1981

Quantitative broadband ultrasonic backscatter - An approach to nondestructive evaluation in acoustically inhomogeneous materials

The use of a broadband backscatter technique to obtain the frequency dependence of the longitudinal-wave ultrasonic backscatter coefficient from a collection of scatterers in a solid is investigated. Measurements of the backscatter coefficient were obtained over the range of ultrasonic wave vector magnitude-glass sphere radius product between 0.1 and 3.0 from model systems consisting of dilute suspensions of randomly distributed crown glass spheres in hardened polyester resin. The results of these measurements were in good agreement with theoretical prediction. Consequently, broadband measurements of the ultrasonic backscatter coefficient may represent a useful approach toward characterizing the physical properties of scatterers in intrinsically inhomogeneous materials such as composites, metals, and ceramics, and may represent an approach toward nondestructive evaluation of these materials.

Odonnell, M.↗

NASA NTRS1999

Ultrasonic Nondestructive Characterization of Adhesive Bonds

Adhesives and adhesive joints are widely used in various industrial applications to reduce weight and costs, and to increase reliability. For example, advances in aerospace technology have been made possible, in part, through the use of lightweight materials and weight-saving structural designs. Joints, in particular, have been and continue to be areas in which weight can be trimmed from an airframe through the use of novel attachment techniques. In order to save weight over traditional riveted designs, to avoid the introduction of stress concentrations associated with rivet holes, and to take full advantage of advanced composite materials, engineers and designers have been specifying an ever-increasing number of adhesively bonded joints for use on airframes. Nondestructive characterization for quality control and remaining life prediction has been a key enabling technology for the effective use of adhesive joints. Conventional linear ultrasonic techniques generally can only detect flaws (delamination, cracks, voids, etc) in the joint assembly. However, more important to structural reliability is the bond strength. Although strength, in principle, cannot be measured nondestructively, a slight change in material nonlinearity may indicate the onset of failure. Furthermore, microstructural variations due to aging or under-curing may also cause changes in the third order elastic constants, which are related to the ultrasonic nonlinear parameter of the polymer adhesive. It is therefore reasonable to anticipate a correlation between changes in the ultrasonic nonlinear acoustic parameter and the remaining bond strength. It has been observed that higher harmonics of the fundamental frequency are generated when an ultrasonic wave passes through a nonlinear material. It seems that such nonlinearity can be effectively used to characterize bond strength. Several theories have been developed to model this nonlinear effect. Based on a microscopic description of the nonlinear interface binding force, a quantitative method was presented. Recently, a comparison between the experimental and simulated results based on a similar theoretical model was presented. A through-transmission setup for water immersion mode-converted shear waves was used to analyze the ultrasonic nonlinear parameter of an adhesive bond. In addition, ultrasonic guided waves have been used to analyze adhesive or diffusion bonded joints. In this paper, the ultrasonic nonlinear parameter is used to characterize the curing state of a polymer/aluminum adhesive joint. Ultrasonic through-transmission tests were conducted on samples cured under various conditions. The magnitude of the second order harmonic was measured and the corresponding ultrasonic nonlinear parameter was evaluated. A fairly good correlation between the curing condition and the nonlinear parameter is observed. The results show that the nonlinear parameter might be used as a good indicator of the cure state for adhesive joints.

Qu, Jianmin↗

DOE OSTI2022

Development of a Laser Ultrasonics-based Approach for Rapid Screening of High Entropy Alloys

This project utilized a laser ultrasonic technique to systematically study temperature-induced evolution of material properties in a set of interrelated binary alloys and a high entropy alloy (HEA) fabricated using arc-melting and spark plasma sintering processes. This technique involved the use of a nanosecond duration, high-intensity pulsed laser to thermo-elastically generate ultrasonic waves that propagate in the bulk of the metal alloy. Sub-nanometer-scale displacements associated with the propagating bulk ultrasonic waves were detected along the epicenter on the opposite surface of the sample using a 1 GHz bandwidth photorefractive interferometer. Phase transformations and microstructural changes were inferred from the temperature-dependent trends in the bulk acoustic velocities and features in the ultrasonic epicentral waveforms measured in the binary alloys. These inferences were then correlated with electron/optical microscopy observations and predictions using calculations of phase diagrams (CALPHAD). The results showed that the laser-generated ultrasonic pulses were strongly influenced by changes in material microstructure and could accurately track thermally driven phase transformations and detect the presence of microscale heterogeneities (grain boundaries, dendritic structures, etc.) in the set of binary alloy samples. The measurement approach was then applied to a quinary HEA sample for estimating phase transition temperature and determining microstructural heterogeneity. The rapid, non-contact and non-destructive ultrasonic testing approach demonstrated here is amenable to high throughput combinatorial investigations that can be applied to graded composition HEAs produced using advanced manufacturing methods. When paired with atomistic simulations and CALPHAD modeling, this approach can overcome the bottlenecks faced by current material characterization methods in efficiently screening the vast discovery space of HEAs that spans over a hundred million unique quinary alloy compositions.

36 MATERIALS SCIENCE↗

NASA NTRS1990

Tensile stress acoustic constants of unidirectional graphite/epoxy composites

Previously, the stress acoustic constants (SACs) of unidirectional graphite/epoxy composites were measured to determine the nonlinear moduli of this material. These measurements were made under compressive loading in order to obtain the sufficient number of values needed to calculate these moduli. However, because their strength in tension along fiber directions can be several times greater, most composites are used under tensile loading. Thus, it is important to characterize the nonlinear properties of these materials in tension as well. The SACs which are defined as the slope of the normalized change in ultrasonic 'natural' velocity as a function of stress were measured in a unidirectional laminate of T300/5208 graphite/epoxy. Tensile load was applied along the fiber axis with the ultrasonic waves propagating perpendicular to the fiber direction. Changes in velocity were measured using a pulsed phase locked loop ultrasonic interferometer with the nominal frequency of the ultrasonic waves being 2.25 MHz.

Prosser, W. H.↗

NASA NTRS1990

Tensile Stress Acoustic Constants of Unidirectional Graphite/Epoxy Composites

Previously, the stress acoustic constants (SAC's) of unidirectional graphite/epoxy composites were measured to determine the nonlinear moduli of this material. These measurements were made under compressive loading in order to obtain the sufficient number of values needed to calculate these moduli. However, because their strength in tension along fiber directions can be several times greater, most composites are used under tensile loading. Thus, it is important to characterize the nonlinear properties of these materials in tension as well. The SAC's which are defined as the slope of the normalized change in ultrasonic "natural" velocity as a function of stress were measured in a unidirectional laminate of T300/5208 graphite/epoxy. Tensile load was applied along the fiber axis with the ultrasonic waves propagating perpendicular to the fiber direction. Changes in velocity were measured using a pulsed phase locked loop ultrasonic interferometer with the nominal frequency of the ultrasonic waves being 2.25 MHz.

Prosser, W. H.↗