Capabilities

Our capabilities webpage is currently under construction.

Eddy current testing plays a critical role in ensuring the safety of energy supply systems and transportation, especially in the inspection of power plant and aircraft. For example, it is used to detect cracks in steam generator tubes and welds in nuclear power plants. In aircraft structures, tests are carried out around fasteners, in fastener holes and on aircraft engines parts. For jet engine maintenance, it is used to detect fatigue cracks in rotors and blades. CNDE owns and maintains laboratory facilities and equipment to conduct experimental research.  Measurement systems are built around motion-controlled scanning systems, such as two XY-scanners and two multi-axis systems.  The maximum of 8 degrees of freedom can be assembled to form a scanner system of linear and rotation stages in various combinations.  The probe attached to the scanner can be connected to commercial eddy current instruments for data acquisition.  The instrument output can be recorded by the computer in control, for examining the standard EC inspection.  Or, for fundamental research, the probe is often driven and detected by laboratory-grade instruments such as impedance analyzer for high precision measurements.  To meet the wide spectrum of research needs, CNDE maintains an array of instruments and probes, including commercial EC instruments and impedance/gain-phase analyzers, as well as network analyzers and combinations of function generators and lock-in amplifiers.

PoC: N. Nakagawa

Ultrasonic testing (UT) forms a large part of the work produced by CNDE and includes modeling of propagating wave interactions with microstructural features and flaws, materials characterization measurements, transducer design and characterization methods and development and testing of novel inspection approaches for difficult materials and geometries.  Methods deployed at CNDE include standard contact and immersion measurements and inspections, as well as air-coupled and laser UT approaches.  Additional techniques include nonlinear acoustics (harmonic generation) and nonlinear resonance ultrasound spectroscopy (NRUS) for materials characterization.

Modeling efforts for strain waves includes interactions with various metal alloy grain morphologies, size distributions and texture/grain alignment conditions.  Materials characterization measurements allow prediction of microstructural conditions through attenuation and grain scattering measurements, and transducer design and characterization affords selection and application of the most appropriate material probing equipment and conditions.  Standard contact and immersion inspection constitute the bulk of materials characterizations and flaw detection work, where air-coupled and laser UT inspections are introduced when conditions require non-contact approaches.

Nonlinear methods have seen limited use outside the laboratory but offer significant sensitivities beyond standard linear approaches.  However, with the increased sensitivity comes increased complexity and a more limited application space.  Efforts at CNDE aim at simplification and standardization of nonlinear measurements so to allow inversion of results for the prediction of material properties.

The efforts at CNDE remain focused on increasing the utility, sensitivity, and economy of ultrasonic inspection approaches for the continued evolutions in engineering materials and their applications.

  • Ultrasonic measurements of acoustic velocities in engineered materials allow the determination of many of the material parameters used in design, including elastic moduli (Young’s, bulk, shear, etc.), Poisson’s ration and the higher order elastic constants.  With additional work, acoustoelastic constants can be measured that provide determination of ultrasonic velocity changes with stress/loading.With more careful and complex measurements of directionally and frequency dependent scattering, microstructural features such as grain sizes, shapes and orientations can be elucidated ultrasonically.  This capability was largely developed by Dr. Bruce Thompson and a cadre of modelers and experimentalists, both CNDE staff and graduate students, throughout the 1980’s and 1990’s.  The legacy of that work is an assortment of measurement models, procedures and processing codes that produce the so-called Figure-of-merit (FOM), a frequency dependent parameter relating the scattering potential of a given microstructure.   The key utility of FOM is that with a measure of the scattering potential combined with the flaw scattering models also developed, signal to noise ratios can be estimated for material inspections as well as inputs for probe designs for specific applications.   In turn, one could then estimate the smallest defect of a given flaw model type that could be reliably detected (above the background grain noise level).  These tools today are continuously being revised and tested, deployed and evaluated on current issues in the inspection community, such as micro-textural regions (MTRs) in Titanium alloy aero components.
    PoC: R. Roberts, L. Koester and D. Barnard
  • The key to providing insight into microstructure feature dimensions, such as grain size, is an understanding of the ultrasonic probe radiation field.  Whether an unfocused planar or focused probe, measurements of radiating field strength in 2 and 3 dimensions allow determination of the probe active diameters and geometric focal lengths.  Additional measurements of the pulse volume along with the grain noise modeling and flaw modeling allow optimizing probe designs to maximize sensitivity to small flaws in thick, noise, or highly attenuative materials.
    PoC: R. Roberts and D. Barnard
  • From the beginning, CNDE has been at the forefront of NDE measurement model development.  As NDE modeling software obtains widespread acceptance, CNDE continues to lead in the modeling of ultrasound measurement physics.  Computer simulation enables design of NDE inspections (probe optimization, scan configuration, data collection and processing) in complex geometries previously deemed uninspectable, within a fraction of the legacy time and cost.  The ability to design inspections in highly anisotropic materials (fiber reinforced composites, single crystal alloys) depends on the availability of computational models to reveal the complicated physics of energy transport in these materials.  More subtle definition of flawed material state implies sensing correspondingly subtle differences in material parameters (e.g. mean grain size or orientation).  Computational simulation of measurement response is essential for the quantification of measurement dependence on such parameters.  Beyond the design of NDE inspection, computational NDE simulation plays an important role in engineered lifecycle management by functioning in concert with material performance and degradation models to provide a physics-based high-confidence system deployment.
    instrumentation sequence

    CNDE’s strength in NDE simulation lies in its ability to generate computational models from first principles, custom designed to address unique inspection challenges that fall outside the capabilities of commercially available software.  Ongoing CNDE research is developing models for complex heterogeneous materials (aerospace alloys, composites, additive manufacturing) which quantify the dependence of measured response to material properties and defect parameters.  Capabilities to simulate and optimize inspection instrumentation (phased arrays, complex scanning) enable effective inspection of increasingly complex geometries and materials.  Importantly, reflecting its roots as an industry laboratory, CNDE is experienced in industrial collaboration to bring these capabilities to bear on current industry-critical inspection problems.     
    element radiation profilesPoC: R. Roberts

  • Nonlinear acoustics at CNDE primarily focuses on two measurement approaches; generation of second harmonic content in pulse-echo and through-transmission scenarios and nonlinear resonance ultrasound spectroscopy (NRUS).  Second harmonic generation (SHG) has the potential to be a highly sensitive modality for evaluating subtle changes in metal microstructures as a result of thermal degradation and early fatigue damage.  However, the technique is not easily applied in the field, and absolute measurements of the nonlinear effect are the best option for inversion of the resulting response to provide insight into specific microstructural changes or conditions.At CNDE, efforts in SHG have concentrated on the procedures involved in the measurements, including the probe calibrations necessary for absolute measurements.  To this end, significant simplifications have been made to the calibration for planar contact probes coupled to samples of interest, and the calibration has been extended to immersion probes.  This extension is a necessity if simplified scanning is ever to be a useful approach in inspections.  With calibrated immersion probes, the nonlinearity of the immersing fluid can be measured and accounted for, and in this way, allow nonlinear through transmission immersion scanning.  This approach is in the process of development, testing and evaluation.NRUS will not, in general, ever be a true fieldable nondestructive evaluation modality.  However, it has proven useful in elucidating the nonlinear response of various materials (metals, ceramics, composites) in various conditions (aging heat treated, quenched, fatigued, local plastic deformation, etc.).  CNDE has assembled a relatively low cost accelerometer-based NRUS measurement (compared to the laser interferometer approaches) that has demonstrated significant utility, ease of use and sensitivity for evaluating the nonlinear response of materials.  Continued development is underway.
    PoC: D. Barnard

Air-coupled ultrasound is an outgrowth of the need for non-contact (and non-immersion) ultrasonic inspection, and is particularly useful in polymer composite materials.  In general the frequencies used are limited to the rage of 50kHz to 1MHz, because the attenuation in even short paths in air is quite high.  With the lower frequency comes longer wavelengths and hence a decrease in spatial resolution.  However, the high attenuations typically seen in polymer composite materials is easier to overcome at the lower frequencies used in air coupled approaches.

Generation of all manner of lamb and surface waves are possible with air coupled ultrasound without the need for wedges, and these modes as well as longitudinal and shear modes have been deployed to detect interlayer delaminations, skin-to-core disbonds and impact damaged crushed cores (in honeycomb sandwich constructions), fiber waviness (marcels) and dry-fiber/resin starved regions in resin transfer molded parts as small as fairings and as large as wind turbine blades.

PoC: D. Barnard

The research into Laser-based ultrasound at CNDE is largely focused on adapting the technology to production environments.  Thus far, our primary focus has been on optimizing it for the detection of defects during 3D printing of metal parts.  Since the feature size of these parts is less than a hundred microns, we have focused on reducing the inspection dimensions from standard approaches requiring ~1 mm to only needing 20 to 50 um. CNDE has numerous tools to optimize laser-based ultrasound for additive manufacturing and other emerging machining technologies.

CNDE utilizes COMSOL finite-element simulations that capture the coupled physics between the laser induced thermodynamics and the resulting acoustic vibrations. Complete 3D models can be simulated for modest sized geometries. In addition to our modelling resources, CNDE also has an inventory of laser ultrasound generation sources and detectors that cover a range of power levels, spot sizes and sensitivities, with the ability to couple these components to multi-axis scanning stages.

PoC: T. Bigelow

There are four X-ray inspection laboratories at CNDE equipped with three microfocus tubes and three standard X-ray tubes. Six X-ray tubes have versatile capabilities and cover voltage range 20KV-320KV, and power 1-3000W. A high-resolution computed tomography (CT) facility with a microfocus X-ray tube (225 kV, 2-micron focal spot), 4-axis microstep positioner and a CMOS flat panel detector allows both high resolution (2 micron) digital radiography and 3D CT to be performed. The twin-head 225kV microfocus has both transmission target and reflection target, and allows high resolution mode and high-power mode can be flexibly chosen based on application. High-speed CT reconstruction algorithms are developed in the lab and provide flexibility of raw data acquisition. Open source image analysis software is available for visualizing 2D and 3D data sets. Real-time radiography can be accomplished using X-ray systems based on both image intensifier and flat panel digital detector. A standard x-ray tube (320kV, 1.5 /3 mm spot) with a multi-axis positioner coupled to a germanium/MCA photon counting detector allows for energy-sensitive materials characterization.  Several germanium, CdZnTe and NaI detectors enable spectral analysis of x-ray transmission and scattering. X-ray detector testing and fabrication can be carried out in the inspection labs with versatile X-ray source. The suite of X-ray inspection techniques is complimented by an X-ray simulation capability, which provides unique analysis tools for evaluating the effect of various parameters on image quality. Through collaborations with the Department of Mechanical Engineering, we also have access to a real-time stereographic imaging system composed of two 200 kV X-ray tubes and two 16-inch diameter image intensifiers. A State-of-the-art SAXS (Small-angle X-ray scattering) system is also available through collaboration with the Department of Chemical and Biological Engineering. Our laboratory resources include:

  • MicroCT Lab
    • Three microfocus X-ray sources for high resolution X-ray imaging
    • 3D high resolution Computed Tomography up to 2-10 μm spatial resolution
  • Image Analysis Lab
    • Computed Tomography reconstruction and 3D volumetric data integration and visualization
    • X-ray radiography simulation software XRSIM
  • High energy X-ray diffraction (HEXRD) Lab
    • Residual stress and strain depth profiling with high energy X-ray diffraction
    • 5mm depth for Aluminum with Tungsten Kα1 line (Energy 59.318 keV)

Research Interests and Capabilities:

  • X-ray Radiography
    • Quality control for PCB and IC chips in harsh environment
    • Field inspection with digital radiography of plastic and metal pipelines
    • Automatic Defect Recognition (ADR)
  • High Resolution Computed Tomography
    • Iterative reconstruction algorithms for limited angle scan and reduce artifacts
    • Digital metrology and defect characterization for industrial applications
    • Data fusion using multi-modal NDE technologies with THz and UT
  • Materials Characterization for Additive Manufacturing
    • High energy X-ray diffraction (HEXRD) analysis for residual stress
    • Diffraction contrast tomography (DCT) microstructure characterization
  • New Modality of X-ray Imaging
    • X-ray phase contrast imaging and tomography
    • Dual-energy and spectral computed tomography

POC: Z. Zhang

The thermography research group at Iowa State University Center for NDE has parallel programs in flash- and vibro-thermography. Our goal is to advance the state-of-the-art in thermographic nondestructive testing through basic scientific research. Our primary current efforts are focused around vibrothermographic nondestructive testing. Vibrothermography, also known as “thermosonic”, “sonic infrared”, and “Sonic IR”, involves exciting a specimen with vibration and looking for heat generated at cracks. A piezoelectric stack generates the high amplitude vibration and the specimen is imaged with an infrared camera to see vibration-induced heating of cracks and flaws in the material. Current theory suggests that the heat is generated by frictional rubbing between crack faces. Our research group is working simultaneously to better understand the crack heating and vibration, and to develop improved measurement apparatus and experimental procedure.

Flash thermography finds delaminations in composite materials from how they block heat flowing from an initial pulse. Vibrothermography (Sonic IR) finds cracks in metals and delaminations in composite materials by detecting frictional heating of rubbing flaw surfaces. For both modalities we have unique capabilities derived from our custom reconfigurable instrumentation. We can use innovative heat/vibration sources and integrate innovative analysis. In flash thermography we have introduced the use of model-based inversion to interpret hidden subsurface structures. Our focus on vibrothermography (Sonic IR) has been in studying the underlying physics of the crack heating process and in developing a model (VibroSim) to predict the capability and reliability of vibrothermography crack detection.

Vibrothermography image of a turbine blade, analyzed with ISU-developed image sequence processing.

PoC: Dr. S. Holland

Vibrothermography image of a turbine blade, analyzed with ISU-developed image sequence processing.
Vibrothermography image of a turbine blade, analyzed with ISU-developed image sequence processing.

Microwave and millimeter waves occupy the frequency spectrum covering ~300 MHz-30 GHz and 30 GHz-300 GHz, corresponding to wavelengths (in air) of 1000-1 mm, respectively. Materials interact with these waves in ways that lends itself extremely useful for certain nondestructive testing and evaluation (NDT&E) applications. Although initially considered under the category of “emerging technologies”, much has taken place in advancing microwave and millimeter wave NDT&E techniques over the past three decades. As such, microwave nondestructive testing was recently recognized and designated by the American Society for Nondestructive Testing (ASNT) as a “Method” on its own. The unique features and capabilities offered by these techniques, and the sustained R&D efforts in this area over several decades, have brought these techniques to forefront of NDT&E science, engineering and applications. These features include:

  • ability to penetrate dielectric (electrically nonconductive) materials,
  • high sensitivity to detecting small flaws, as a result of relatively small wavelengths and large available signal bandwidth,
  • coherent properties of the waves allowing for the use of signal amplitude and phase, in addition to wave polarization,
  • one-sided and non-contact measurement capabilities (i.e., no need for couplants),
  • sensitivity to surface properties of metals and carbon composites,
  • non-ionizing nature of the waves, and
  • relative ease-of-use.

Examples of recent successful investigations and developments using microwave and millimeter wave techniques include:

  • Comprehensive materials characterization (e.g., porosity, mixture content, etc.) and chemical reactions such as cure-state monitoring in various chemically-produced materials (i.e., resin binder, rubber, etc.).
  • resin cure-state.
  • Inspection of complex dielectric composites and layered structures made of polymers, ceramics, thermal barrier coatings, radomes, etc.
  • Porosity estimation in composites and ceramics such as thermal barrier coatings and composite skin subjected to loading (i.e., aircraft radome skin),
  • Fatigue crack detection and characterization on metal surfaces, using several novel methods.
  • Detection and evaluation of surface anomalies (e.g., scratches, impact damage) in metals and carbon composites.
  • Comprehensive materials characterization of cementitious materials chemical and physical properties including chloride permeation and alkali-silica gel reaction (ASR) detection and evaluation.
  • Development of hybrid measurement technique using embedded modulated scattering PIN diode-loaded dipole antenna for material characterization and microwave imaging,
  • Near-field high-resolution imaging.
  • Real-time, 3D, portable, battery-operated and high-resolution imaging.
  • Frequency-modulated continuous-wave (FM-CW) radar for short-range applications such as detection and evaluation of flaws in composite structures (e.g., walls).
  • Microwave and millimeter wave noninvasive diagnosis of human skin for cancer and burns.

PoC: R. Zoughi and M.T. Al Qaseer

Several examples of various applications and results are provided below.

Calculated (extracted) volume fractions of inclusions in: a) non-reactive samples, and b) reactive samples.
Calculated (extracted) volume fractions of inclusions in: a) non-reactive samples, and b) reactive samples.
Measured and modeled dielectric constants: a) permittivity of ASR-reactive and non-reactive samples, and b) loss factor of ASR-reactive and non-reactive samples.
Measured and modeled dielectric constants: a) permittivity of ASR-reactive and non-reactive samples, and b) loss factor of ASR-reactive and non-reactive samples.

Section of fiberglass pipe joint (left), X-ray image showing lack of adhesive at the joint (center) and millimeter wave (Ka-band, 26.5-40 GHz) SAR image (right). Sample Courtesy of Fiberglass Structural Engineering, Inc.


Millimeter Wave (26.5-40 GHz) 3D SAR image of a thick HDPE sample with porosity. Sample Courtesy of NDT Innovations, Inc.


Aircraft radome mimic, map of interior flaws, near-field image (using open -ended waveguide) at 33 GHz and near-field image (using open -ended waveguide) at 73 GHz.


Portable real-time SAR imaging system for inspecting cylindrical pipes (left), PVC pipe with internal damage (center), and microwave SAR image of the damage (right).


Portable, real-time, high-resolution 3D Microwave Camera, with a size of ~260 mm x 210 mm x 180 mm and a weight of 4.8 Kg (left) and most recent handheld real-time Microwave Camera based on Chaotic Excitation Synthetic-Aperture Radar (CESAR), with a size of ~140 mm x 89 mm x 55 mm (right).

Electromagnetic radiation in the terahertz frequency range, best known as Terahertz radiation (hereafter abbreviated as THz), has emerged as a promising measurement technique for a variety of applications in science and engineering.  Commonly referred to THz frequency range ~0.1-10 THz, is one of the last frontiers in the electromagnetic spectrum to be used for inspection purposes. Unlike X-ray, THz radiating similar to microwave and millimeter wave is non-ionizing and hence causes no known harm to the human body and the materials being examined. THz can penetrate many common gases, non-polar liquids, and non-metallic solids including air, plastics, gasoline, paper, plant material, clothing, fatty tissue, and composites. Because they lie in a frequency region in which molecular resonances dominate, the absorption spectra of THz exhibit distinct signatures for substances such as water vapor, polar plastics, certain gases, DNA, crystalline solids, biofuel, and explosives. As such, THz radiation has significant potential for materials characterization (i.e., spectroscopy).  These advantages make THz a particularly attractive characterization tool in the areas of automotive, aviation, food, energy, materials, pharmaceuticals, medical diagnosis, forensics, defense, and homeland security.

In recent past, under the support of NASA, the Air Force, and the Army, CNDE has expanded its state-of-the-art modeling and processing capabilities further into THz technology. For example, significant progress was made in addressing the inspection problem of the space shuttle’s external tank foam insulation as well as in providing assistance to Air Force Research Laboratory’s THz development. Elsewhere at ISU, faculty and researchers from various science and engineering disciplines have also quickly recognized the potential of THz technology. Driven by these needs, the acquisition of THz systems for imaging and spectroscopy was realized in 2008 via a major funding boost from the National Science Foundation’s Major Research Instrumentation program, and a new $0.5M THz research facility was established. With this new THz facility, a number of applications in physics, chemistry and engineering have been extensively studied, including the detection of chemical contamination in drinking water pipe systems, solvation of ionic liquids, fundamental studies of multiphase combustion and flow processes, and nondestructive evaluation of composite materials. The growing potential of THz has been further explored in inspecting many other advanced materials such as ceramic tiles and high-molecular weight fiber polymers used in military personal protection applications.

POC: C. Chiou

(Left) THz pulsed system coupled with the motorized scan gantry; (Right) continuous-wave system connected to a separate measurement station in through-transmission mode.


THz imaging of a floss box again demonstrates THz’s time-resolved ability to “peel” through the interior of a structure: top skin, below top skin and middle floss core.


(Left) Fresh autumn leaves taken outside the THz facility (shown with a 15-cm ruler) and (right) their corresponding images under THz. A piece of plastic tape is also revealed in the right image.

Ground penetrating radar (GPR) is used in subsurface inspection of structures, to include earthen structures such as dams and levees, or concrete structures such as bridges, damns and other concrete structures.  At CNDE there is the capability of inspection of very deep earthen structures utilizing the low frequency 200 MHz antenna, all the way up to the shallower materials utilizing the 2.6 GHz antenna.  CNDE has built a test levee to develop a capability assessment tool to better understand and characterize the potential of ground penetrating radar to develop an inspection for earthen levees and dams.  The test levee is co-located with CNDE at the Applied Sciences Complex. The size of the test levee is approximately 10 feet in height and width at the crest of the structure with an appropriate corresponding slope on the sides of the structure.  The length of the test levee is approximately 21 feet, not including the access ramp at one end of the test levee to allow access with the GPR equipment.

PoC: D. Eisenmann

Fluorescent penetrant inspection (FPI) is a heavily utilized NDE method when detection of surface breaking cracks in nonporous materials is needed. The method includes multiple steps which should be optimized for the material, surface condition, anticipated crack morphology/location/size, and inspection environment. While FPI is used by many industries, it is a major contributor to the inspection requirements of the aerospace industry. Over 90% of aviation components are inspected with FPI at least once during their lifetime. CNDE has the capability to perform FPI at all four levels of sensitivity, from level 1 water washable to level 4 postemulsifyable hydrophilic.

PoC: D. Eisenmann

Magnetic particle inspection (MPI) is used for surface and near surface crack detection on ferromagnetic materials. There are two basic types of MPI inspection available at CNDE, wet inspection utilizing a bench system, and dry powder utilizing a yoke. For wet applications, a magnetic field is generated thru the specimen and the oil or water-based fluid containing magnetic particles is flowed over the areas of interest.  For dry powder applications, a magnetic field is induced into a part, and dry iron filing are sprinkled onto the surface of the part.  For either type of applications, cracks and other discontinuities will result in a localized change in magnetic flux density (flux leakage), which attracts the magnetic particles which can be detected either by ultraviolet or visible light.

PoC: D. Eisenmann

Structural health monitoring (SHM) is the automation of the condition assessment task performed using collected field measurements. This automation is typically enabled by sensing systems, which include transducers, data acquisition systems, and signal processing techniques. These sensing systems provide continuous condition-based data about the monitored structure. In the context of NDE, SHM can be used to combine NDE data for accelerating or improving the accuracy of evaluations, or simply to guide the inspector during the NDE process. Successful research in SHM requires a strong multi-disciplinary approach, combining expertise in structural, mechanical, chemical, electrical, computer, and aerospace engineering. Iowa State University is particularly well positioned to conduct such research projects given the rich diversity of expertise of its different faculty members and the renowned capabilities of CNDE in the field of NDE. Example of SHM research at ISU aimed at augmenting NDE performance includes:

Multi-Functional Materials – Our research program on multi-functional materials studies novel methods to augment conventional structural materials with additional functionalities, in particular self-sensing. For instance, we are studying how we can alter the electrical properties of self-sensing materials through the use of nano- and micro-fillers, including carbon nanotubes and carbon black. We have explored the use of self-sensing cementitious materials to create smart pavements, and to accelerate NDE through eddy current techniques. Other examples of self-sensing materials that we have studied include smart carbon-fiber reinforced polymers capable of self-diagnosis. Our group has produced a tutorial publication on multi-functional materials.

Left: Block of conductive cement paste being tested in compression [S1]; Right: Electrical signal from five smart carbon fiber-reinforced polymer being pulled until failure (capacitance versus strain).

Sensing Skin for Structural Health Monitoring – Our research program on sensing skin for SHM studies soft sensing technologies that emulate biological skin to enable local sensing over global areas. The soft sensing technology is centered around a soft elastomeric capacitor (SEC) behaving as a strain gauge and capable of covering large areas at low costs. Recent research developments have demonstrated the SEC technology in a network configuration to detect and localize fatigue cracks on steel bridges.

Picture of soft elastomeric capacitor.
Picture of soft elastomeric capacitor.

High-Rate Structural Health Monitoring – Our research program on high-rate structural health monitoring (HR-SHM) investigates how fast we can estimate the health of a system. The research is applicable to high-rate systems, which are defined as engineering systems experiencing high-rate (<100 ms) and high-amplitude (acceleration > 100 gn) events such as a blast or impact. Examples of such systems include hypersonic vehicles, advanced weaponry, and blast mitigation systems. We have written an introductory paper on the field of HR-SHM.

PoC: S. Laflamme

The Ultrasonic Composites laboratory at the Center is a full-fledged research lab using various wave propagation methods for the NDE of composite and mixed materials. We have worked on layered materials, fibrous as well as particulate composites. We have experience in the bulk material testing as well as guided waves such as Lamb waves and Rayleigh waves. We can test composite parts a few mm thin to a few inches thick. The frequency range for the testing is 0.5 MHz to 10 MHz. ‘Tap testing” is a very basic test for testing composites. We have developed an instrumented tap tester and we can measure the stiffness changes in composites. Starting with defect size of porosity we have experience of detecting and characterizing various kinds of defects such as micro-cracks, delaminations, fiber waviness, impact damage, fiber breakage etc. Testing with a single transducer or with a phased array is possible. Acoustic emission is normally caused in composites due propagating defect and we have experience of testing composites with Acoustic Emission (AE) systems. We have an 8 channel AE system for such testing.

Apart from testing composites we have in-house experience and capability of manufacturing samples with engineered defects. We can make autoclave as well as press cured samples. These samples can have defects such as: contamination, inserts, delaminations, horizontal and vertical fiber waviness, various energy level impact damage, and fatigue damage. Inserts such as thin metallic film, Teflon layers, micro-balloon layer, and true delamination are possible. Characterization of the defects in these samples is also possible.

Coda wave method is an upcoming defect characterization method. We have capability and experience in the Coda wave detection of incipient damage in composites.

PoC: V. Dayal

Coda wave detection of incipient damage in composites.
Coda wave detection of incipient damage in composites.

CNDE has available on-site mechanical testing capabilities useful for either sample preparation/generation or validation after nondestructive testing.  Included are servo-hydraulic load frame systems and an instrumented drop tower.  The servo-hydraulic units are available for application of compression, tension and torsion loadings.  The units can be configured for either uniaxial loading or cyclic fatigue in either constant load or constant displacement conditions, with software for collecting load data.  Fixtures are available for axial loading, 3 or 4-point bending, Iosipescu (shear), compression after impact (for fiber laminate testing) and additional fixturing can be custom made.   The instrumented drop tower features a useful impact energy range of 4 – 102 Joules and fixturing can be custom made to hold non-planar parts securely during impact.  Data outputs include impact force, impact energy and impactor velocity throughout the test.

PoC: Mr. D. Barnard

Technical Assistance Program

The Center for NDE is a partner with the Center for Industrial Research and Service (CIRAS).  One of the programs within CIRAS is the Manufacturing Extension Partnership; the Technical Assistance Program (TAP) of the effort assists Iowa manufacturers with a variety of issues, including inspection and quality control and assurance. CNDE/CIRAS/TAP brings expertise in the field of nondestructive evaluation to Iowa industry.

Through this interaction, we assist companies by:

  • Explaining & demonstrating the principles of various inspection methods
  • Perform feasibility studies to determine if NDE methods will work for a given application
  • Develop/Evaluate inspection procedures for old or new designs, recommend new techniques
  • Provide unbiased information on sources of equipment, NDT testing laboratories, and NDE advances

In short, our intent is to help manufacturers become educated consumers of NDE products and services.

The point of contact is:

Dave Utrata (515-294-6095, heydave@iastate.edu)