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DOE OSTI2019

Using an Artificial Neural Network for Nondestructive Evaluation of the Heat Treating Processes for D2 Tool Steels

In nondestructive evaluation (NDE) of heat-treated steels, different variables of the heat treating process have complex effects on outputs of NDE methods, and hence, the effect of one desired variable on NDE outputs should be evaluated to help interpreting the changes. In the present paper, the potential of the magnetic hysteresis method was evaluated for simultaneous detection of the austenitizing and tempering temperatures of AISI D2 samples parts subjected to different heat treatment conditions. To produce the microstructural changes, five groups of the samples were austenitized at 1025-1130 °C, quenched in oil and finally each group was tempered in the range 200-650 °C. SEM and x-ray diffractometry techniques were used to characterize different produced microstructures. For accurate and simultaneous prediction of tempering and austenitizing temperatures, an artificial neural network (ANN) was implemented for magnetic hysteresis outputs including magnetic saturation, coercivity and maximum differential permeability. The study revealed that the magnetic NDE system coupled to ANN has the ability to be adopted as an effective expert NDE tool to predict heat treatment effects on D2 tool steels.

36 MATERIALS SCIENCE↗

DOE OSTI2014

Metrology, applications and methods with high energy CT systems

The increase of Computed Tomography (CT) as an applicable metrology and Non Destructive Testing (NDT) method raises interest on developing the application fields to larger objects, which were rarely used in the past due to their requirements on the imaging system. Especially the classical X-ray generation techniques based on standard equipment restricted the applications of CT to typical material penetration lengths of only a few cm of steel. Even with accelerator technology that offers a suitable way to overcome these restrictions just the 2D radioscopy technique found a widespread application. Beside the production and detection of photons in the MeV range itself, the achievable image quality is limited using standard detectors due to the dominating absorption effect of Compton Scattering at high energies. Especially for CT reconstruction purposes these effects have to be considered on the development path from 2D to 3D imaging. Most High Energy CT applications are therefore based on line detectors shielding scattered radiation to a maximum with an increase in imaging quality but with time consuming large volume scan capabilities. In this contribution we present the High-Energy X-ray Imaging project at the Fraunhofer Development Centre for X-ray Technology with the characterization and the potential of the CT-system according to metrological and other application capabilities.

43 PARTICLE ACCELERATORS↗

NASA NTRS1996

Detection of Delamination in Composite Beams Using Broadband Acoustic Emission Signatures

Delamination in composite structure may be caused by imperfections introduced during the manufacturing process or by impact loads by foreign objects during the operational life. There are some nondestructive evaluation methods to detect delamination in composite structures such as x-radiography, ultrasonic testing, and thermal/infrared inspection. These methods are expensive and hard to use for on line detection. Acoustic emission testing can monitor the material under test even under the presence of noise generated under load. It has been used extensively in proof-testing of fiberglass pressure vessels and beams. In the present work, experimental studies are conducted to investigate the use of broadband acoustic emission signatures to detect delaminations in composite beams. Glass/epoxy beam specimens with full width, prescribed delamination sizes of 2 inches and 4 inches are investigated. The prescribed delamination is produced by inserting Teflon film between laminae during the fabrication of composite laminate. The objectives of this research is to develop a method for predicting delamination size and location in laminated composite beams by combining smart materials concept and broadband AE analysis techniques. More specifically, a piezoceramic (PZT) patch is bonded on the surface of composite beams and used as a pulser. The piezoceramic patch simulates the AE wave source as a 3 cycles, 50KHz, burst sine wave. One broadband AE sensor is fixed near the PZT patch to measure the AE wave near the AE source. A second broadband AE sensor, which is used as a receiver, is scanned along the composite beams at 0.25 inch step to measure propagation of AE wave along the composite beams. The acquired AE waveform is digitized and processed. Signal strength, signal energy, cross-correlation of AE waveforms, and tracking of specific cycle of AE waveforms are used to detect delamination size and location.

Okafor, A. C.↗

NASA NTRS2012

Elements of Nondestructive Examination for the Visual Inspection of Composite Structures

Visual inspection (VI) of composite structures provides an effective, wide field survey to ensure design and material compliance is maintained for the entire service life of the manufactured component. Visual inspection is one of the most commonly used nondestructive inspection methods to assess surface defects on composites. By applying visual inspection elements, mechanical damage that could affect component residual strength can be identified and a disposition reached before a potentially catastrophic event occurs. This technique is non-contact and applied at all stages of the composite structure s processing and use. Additionally, VI is required to be performed in all service environments until decommission. By following Level I and Level II damage accept/reject criteria set forth in this document, the material review (MR) process can be initiated. This nondestructive evaluation (NDE) method should be complemented with additional NDE methods to best understand the nature of the observed indications. When VI identification is followed by interrogation using effective complimentary NDE methods, the final Material Review Board (MRB) disposition of the component can be effectively achieved. Although elements of the visual inspection method are discussed and expressly required by the various range standards (KNPR 8715.3 and AFSPCMAN 91-710), emphasis should be placed on supporting the interpretation of recorded visual observations. Sound engineering practices and procedures should be applied with the interpretation of nondestructive testing (NDT) results when the residual strength data specific to a vessel design is incomplete or absent.

Tommy B. Yoder↗

DOE OSTI2014

Imaging and quantitative data acquisition of biological cell walls with Atomic Force Microscopy and Scanning Acoustic Microscopy

This chapter demonstrates the feasibility of Atomic Force Microscopy (AFM) and High Frequency Scanning Acoustic Microscopy (HF-SAM) as tools to characterize biological tissues. Both the AFM and the SAM have shown to provide imaging (with different resolution) and quantitative elasticity measuring abilities. Plant cell walls with minimal disturbance and under conditions of their native state have been examined with these two kinds of microscopy. After descriptions of both the SAM and AFM, their special features and the typical sample preparation is discussed. The sample preparation is focused here on epidermal peels of onion scales and celery epidermis cells which were sectioned for the AFM to visualize the inner surface (closest to the plasma membrane) of the outer epidermal wall. The nm-wide cellulose microfibrils orientation and multilayer structure were clearly observed. The microfibril orientation and alignment tend to be more organized in older scales compared with younger scales. The onion epidermis cell wall was also used as a test analog to study cell wall elasticity by the AFM nanoindentation and the SAM V(z) feature. The novelty in this work was to demonstrate the capability of these two techniques to analyze isolated, single layered plant cell walls in their natural state. AFM nanoindentation was also used to probe the effects of Ethylenediaminetetraacetic acid (EDTA), and calcium ion treatment to modify pectin networks in cell walls. The results suggest a significant modulus increase in the calcium ion treatment and a slight decrease in EDTA treatment. To complement the AFM measurements, the HF-SAM was used to obtain the V(z) signatures of the onion epidermis. These measurements were focused on documenting the effect of pectinase enzyme treatment. The results indicate a significant change in the V(z) signature curves with time into the enzyme treatment. Thus AFM and HF-SAM open the door to a systematic nondestructive structure and mechanical property study of complex biological cell walls. A unique feature of this approach is that both microscopes allow the biological samples to be examined in their natural fluid (water) environment.

nanoindentation↗

DOE OSTI2016

Effect of electrode manufacturing defects on electrochemical performance of lithium-ion batteries: Cognizance of the battery failure sources

During LIB electrode manufacturing, it is difficult to avoid the certain defects that diminish LIB performance and shorten the life span of the batteries. This study provides a systematic investigation correlating the different plausible defects (agglomeration/blisters, pinholes/divots, metal particle contamination, and non-uniform coating) in a LiNi 0.5 Mn 0.3 Co 0.2 O 2 positive electrode with its electrochemical performance. Additionally, an infrared thermography technique was demonstrated as a nondestructive tool to detect these defects. The findings show that cathode agglomerates aggravated cycle efficiency, and resulted in faster capacity fading at high current density. Electrode pinholes showed substantially lower discharge capacities at higher current densities than baseline NMC 532 electrodes. Metal particle contaminants have an extremely negative effect on performance, at higher C-rates. The electrodes with more coated and uncoated interfaces (non-uniform coatings) showed poor cycle life compared with electrodes with fewer coated and uncoated interfaces. Further, microstructural investigation provided evidence of presence of carbon-rich region in the agglomerated region and uneven electrode coating thickness in the coated and uncoated interfacial regions that may lead to the inferior electrochemical performance. In conclusion, this study provides the importance of monitoring and early detection of the electrode defects during LIB manufacturing processes to minimize the cell rejection rate after fabrication and testing.

25 ENERGY STORAGE↗

DOE OSTI2019

Baseline Evaluation of Eddy Current Testing for PWSCC Susceptible Materials

This technical letter report (TLR) summarizes technical efforts focused on assessments of eddy current testing (ET) examinations using various mockups for obtaining baseline surface and subsurface conditions on materials susceptible to primary water stress corrosion cracking (PWSCC). The scope of this work included nondestructive evaluation characterization of weld surfaces on mockups that were identified for application of various surface peening approaches. All of the work reported here was conducted prior to planned peening of these surfaces to evaluate pre-peening conditions, and subsequently compare the baseline ET results with post-peening conditions. The overall objective of this work was to demonstrate the effectiveness of employing ET for detecting near/sub-surface defects on mockups in support of peening assessments for surface stress improvement and mitigation of PWSCC in these materials. The U.S. Nuclear Regulatory Commission has communicated their expectations to industry for eddy current inspections of peened, inlayed, and onlayed dissimilar metal welds and is interested in better understanding detection performance and sensitivity of ET techniques to support the development of a technical foundation for detection and sizing limits, effective ET qualification requirements, alternate inspections or programs for evaluating PWSCC mitigation processes, and development of ET acceptance standards that can be referenced in the appropriate American Society of Mechanical Engineers Section XI Code Case (N-770-X). This TLR provides a technical discussion focused on the ET data obtained, the analysis, and conclusions drawn from surface examinations of various plate standards and actual components extracted from cancelled nuclear power plants.

36 MATERIALS SCIENCE↗

DOE OSTI2014

An Unattended Verification Station for UF6 Cylinders: Implementation Concepts and Development Status

In recent years, the International Atomic Energy Agency (IAEA) has pursued innovative techniques and an integrated suite of safeguards measures to address the verification challenges posed by advanced centrifuge technologies and the growth in separative work unit capacity at modern centrifuge enrichment plants. These measures would include permanently installed, unattended instruments capable of performing the routine and repetitive measurements previously performed by inspectors. Among the unattended instruments currently being explored by the IAEA is an Unattended Cylinder Verification Stations (UCVS) that could provide independent verification of the declared relative enrichment, 235U mass and total uranium mass of 100% of the declared cylinders moving through the plant, as well as the application and verification of an ‘Non-destructive Assay Fingerprint’ to preserve verification knowledge on the contents of each cylinder throughout its life in the facility. As the IAEA’s vision for a UCVS has evolved, Pacific Northwest National Laboratory (PNNL) and Los Alamos National Laboratory (LANL) have been developing and testing candidate nondestructive assay (NDA) methods for inclusion in a UCVS. Modeling and multiple field campaigns have indicated that these methods are capable of assaying relative cylinder enrichment with a precision comparable to or perhaps better than today’s high-resolution handheld devices, without the need for manual wall-thickness corrections. In addition, the methods interrogate the full volume of the cylinder, thereby offering the IAEA a new capability to assay the absolute 235U mass in the cylinder and much-improved sensitivity to substituted or removed material. Building on this prior work a UCVS field prototype is being developed and tested. This paper describes potential implementation concepts, a preliminary UCVS prototype design and functional description, and preparations for upcoming field trials.

Smith, Leon E.↗

DOE OSTI2013

Passive Neutron Non-Destructive Assay for Remediation of Radiological Waste at Hanford Burial Grounds- 13189

The Hanford burial grounds contains a broad spectrum of low activity radioactive wastes, transuranic (TRU) wastes, and hazardous wastes including fission products, byproduct material (thorium and uranium), plutonium and laboratory chemicals. A passive neutron non-destructive assay technique has been developed for characterization of shielded concreted drums exhumed from the burial grounds. This method facilitates the separation of low activity radiological waste containers from TRU waste containers exhumed from the burial grounds. Two identical total neutron counting systems have been deployed, each consisting of He-3 detectors surrounded by a polyethylene moderator. The counts are processed through a statistical filter that removes outliers in order to suppress cosmic spallation events and electronic noise. Upon completion of processing, a 'GO / NO GO' signal is provided to the operator based on a threshold level equivalent to 0.5 grams of weapons grade plutonium in the container being evaluated. This approach allows instantaneous decisions to be made on how to proceed with the waste. The counting systems have been set up using initial on-site measurements (neutron emitting standards loaded into surrogate waste containers) combined with Monte Carlo modeling techniques. The benefit of this approach is to allow the systems to extend their measurement ranges, in terms of applicable matrix types and container sizes, with minimal interruption to the operations at the burial grounds. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2018

Forensic Analysis of Faulted NSTX-U Inner Poloidal Field Coil

The failure of the NSTX-U PF1A upper coil suspended plasma operations during the project's first operational campaign after commissioning. Initial nondestructive testing and examination of the failed coil was followed by extensive nondestructive radiography. Destructive testing facilitated visual borescope/videoscope inspection through the cooling path, vacuum testing, and electrical testing of every conductor segment. One conductor cooling path visually evidenced a void through the sidewall of the cooling path in a layer-to-layer region. The identified void in the conductor cooling path was not proximal to a braze or joggle. Electrical testing indicated that the voided conductor segment was a member of a group of 14 conductor segments that evidenced low-resistance connectivity. Four braze joints and two lead segments were subjected to 400-lbf/in 2 hydrostatic pressure testing followed by helium leak testing and evidenced that there were no detectable leaks in the tested cooling path segments. The faulted region was proximal to the center of the coil pack and evidenced historical electrical pitting and molten conductor debris. Samples of the epoxy resin insulation system were extracted and analyzed with dynamic mechanical analysis and differential scanning calorimetry techniques. Epoxy resin insulation samples were subjected to immersion testing per ASTM D570. Metallurgical samples were extracted from the coil pack conductors and subjected to hardness testing and grain structure analysis. The base material testing results indicated no abnormalities. In conclusion, the coil incipient failure was determined to most likely have resulted from conductive material located between conductor and insulation layers.

25 ENERGY STORAGE↗

NASA NTRS1999

The Effect of Penetration Depth on Thermal Contrast of NDT by Thermography

Nondestructive evaluation by Thermography (TNDE) is generally classified into two categories, the passive approach and the active approach. The passive approach is usually performed by measuring the natural temperature difference between the ambient and the material or structure to be tested. The active approach, on the other hand, requires the application of an external energy source to stimulate the material for inspection. A laser, a heater, a hot air blower, a high power thermal pulse, mechanical, or electromagnetic energy may provide the energy sources. For the external heating method to inspect materials for defects and imperfection at ambient temperature, a very short burst of heat can be introduced to one of the surfaces or slow heating of the side opposite to the side being observed. Due to the interruption of the heat flow through the defects, the thermal images will reveal the defective area by contrasting against the surrounding good materials. This technique is called transient Thermography, pulse video Thermography, or thermal wave imaging. As an empirical rule, the radius of the smallest defect should be at least one to two times larger than its depth under the surface. Thermography is being used to inspect void, debond, impact damage, and porosity in composite materials. It has been shown that most of the defects and imperfection can be detected. However, the current method of inspection using thermographic technique is more of an art than a practical scientific and engineering approach. The success rate of determining the defect location and defect type is largely depend on the experience of the person who operates thermography system and performs the inspection. The operator has to try different type of heat source, different duration of its application time, as well as experimenting with the thermal image acquisition time and interval during the inspection process. Further-more, the complexity of the lay-up and structure of composites makes it more difficult to determine the optimal operating condition for revealing the defects. In order to develop an optimal thermography inspection procedure, we must understand the thermal behavior inside the material subjected to transient heat in order to interpret the thermal images correctly. Fabrication of finite element models of characteristic defects in composite materials subjected to transient heat will enable the development of appropriate procedure for thermography inspection. Design of phantom defects could be modeled and behavior characterized prior to physically building these test parts. Since production of phantom test parts can be very time consuming and laborious, it is important to design good representative defects.

Chu, Tsuchin Philip↗

NASA NTRS2008

Characterization of Fatigue Damage for Bonded Composite Skin/Stringer Configurations

The fatigue damage was characterized in specimens which consisted of a tapered composite flange bonded onto a composite skin. Quasi-static tension tests were performed first to determine the failure load. Subsequently, tension fatigue tests were performed at 40%, 50%, 60% and 70% of the failure load to evaluate the debonding mechanisms. For four specimens, the cycling loading was stopped at intervals. Photographs of the polished specimen edges were taken under a light microscope to document the damage. At two diagonally opposite corners of the flange, a delamination appeared to initiate at the flange tip from a matrix crack in the top 45deg skin ply and propagated at the top 45deg/-45deg skin ply interface. At the other two diagonally opposite corners, a delamination running in the bondline initiated from a matrix crack in the adhesive pocket. In addition, two specimens were cut longitudinally into several sections. Micrographs revealed a more complex pattern inside the specimen where the two delamination patterns observed at the edges are present simultaneously across most of the width of the specimen. The observations suggest that a more sophisticated nondestructive evaluation technique is required to capture the complex damage pattern of matrix cracking and multi-level delaminations.

Paris, Isabelle↗

DOE OSTI2013

High-energy x-ray diffractometer for nondestructive strain depth profile measurement

We describe a lab-based high-energy x-ray diffraction system and a new approach to nondestructively measuring strain profiles in polycrystalline samples. This technique utilizes the tungsten K{sub α1} characteristic radiation from a standard industrial x-ray tube. We introduce a simulation model that is used to determine strain values from data collected with this system. Examples of depth profiling are shown for shot peened aluminum and titanium samples. Profiles to 1 mm depth in aluminum and 300 μm depth in titanium with a depth resolution of 20 μm are presented.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2023

The ARENA Test Bed – A Versatile Resource for I&C Development and Validation

The Accelerated and Real-time Experimental Nodal Assessment (ARENA) Test Bed at the Pacific Northwest National Laboratory (PNNL) is a versatile resource for development and validation of instrumentation and control (I&C) technologies. This capability was created to facilitate in-situ testing of nuclear electrical cables in various simulated operational environments. Using cable trays, a control box, and selected test components, low voltage cables can be staged to experience local adverse environments such as elevated temperature and water immersion. Cable condition can be continuously monitored over time to track the effect of local stresses using nondestructive assessment tools. A heads-up display (ARENA TV) plots key data in real-time for users. The ARENA Test Bed has recently been used to evaluate the potential for spread spectrum time domain reflectometry (SSTDR) to monitor thermal aging of a portion of live cable powering a three-phase motor. The arrangement provided the opportunity to directly compare the performance of the novel online SSTDR method with offline results from the more standard frequency domain reflectometry (FDR) method. The ability of SSTDR and FDR to identify the presence of water in immersed shielded and unshielded cables and to detect ground faults was also assessed. A digital twin is being developed to track and predict FDR signals from a thermally aging conceptual cable region to compare with measured signals from the ARENA physical counterpart. The test bed concept addresses an important need in nuclear I&C monitoring tool development. New tools and techniques can be developed in the test bed and validated versus known methods and physical measurements. Digital twins and machine learning engines can be populated with measured data in a controlled environment that would not be readily available in the actual nuclear power plant. Proposed monitoring strategies can be confirmed for effectiveness through objective evaluation. It is anticipated that the PNNL ARENA Test Bed will be a valuable resource in advancing nuclear plant instrumentation.

nuclear electrical cables, ARENA Test Bed, conditi↗

NASA NTRS1971

The fabrication, testing and delivery of boron/epoxy and graphite/epoxy nondestructive test standards

A description is given of the boron/epoxy and graphite/epoxy nondestructive test standards which were fabricated, tested and delivered to the National Aeronautics and Space Administration. Detailed design drawings of the standards are included to show the general structures and the types and location of simulated defects built into the panels. The panels were laminates with plies laid up in the 0 deg, + or - 45 deg, and 90 deg orientations and containing either titanium substrates or interlayered titanium perforated shims. Panel thickness was incrementally stepped from 2.36 mm (0.093 in.) to 12.7 mm (0.500 in.) for the graphite/epoxy standards, and from 2.36 mm (0.093 in.) to 6.35 mm (0.25 in.) for the boron/epoxy standards except for the panels with interlayered shims which were 2.9 mm (0.113 in.) maximum thickness. The panel internal conditions included defect free regions, resin variations, density/porosity variations, cure variations, delaminations/disbonds at substrate bondlines and between layers, inclusions, and interlayered shims. Ultrasonic pulse echo C-scan and low-kilovoltage X-ray techniques were used to evaluate and verify the internal conditions of the panels.

Pless, W. M.↗

NASA NTRS1991

NDE of ceramics and ceramic composites

Although nondestructive evaluation (NDE) techniques for ceramics are fairly well developed, they are difficult to apply in many cases for high probability detection of the minute flaws that can cause failure in monolithic ceramics. Conventional NDE techniques are available for monolithic and fiber reinforced ceramic matrix composites, but more exact quantitative techniques needed are still being investigated and developed. Needs range from flaw detection to below 100 micron levels in monolithic ceramics to global imaging of fiber architecture and matrix densification anomalies in ceramic composites. NDE techniques that will ultimately be applicable to production and quality control of ceramic structures are still emerging from the lab. Needs are different depending on the processing stage, fabrication method, and nature of the finished product. NDE techniques are being developed in concert with materials processing research where they can provide feedback information to processing development and quality improvement. NDE techniques also serve as research tools for materials characterization and for understanding failure processes, e.g., during thermomechanical testing.

Vary, Alex↗

NASA NTRS1993

NDE of ceramics and ceramic composites

Vary, Alex A.↗

DOE OSTI2023

High spatial resolution direct conversion amorphous selenium X-ray detectors with monolithically integrated CMOS readout

Recent progress in the field of micron-scale spatial resolution direct conversion X-ray detectors for high-energy synchrotron light sources serve applications ranging from nondestructive and noninvasive microscopy techniques which provide insight into the structure and morphology of crystals, to medical diagnostic measurement devices. Amorphous selenium ( a -Se) as a wide-bandgap thermally evaporated photoconductor exhibits ultra-low thermal generation rates for dark carriers and has been extensively used in X-ray medical imaging. Being an amorphous material, it can further be deposited over large areas at room temperatures and at substantially lower costs as compared to crystalline semiconductors. Here, to address the demands for a high-energy and high spatial resolution X-ray detector for synchrotron light source applications, we have thermally evaporated a -Se on a Mixed-Mode Pixel Array Detector (MM-PAD) Application Specific Integrated Circuit (ASIC). The ASIC format consists of 128 × 128 square pixels each 150 μm on a side. A 200 μm a -Se layer was directly deposited on the ASIC followed by a metal top electrode. The completed detector assembly was tested with 45 kV Ag and 23 kV Cu X-ray tube sources. The detector fabrication, performances, Modulation Transfer Function (MTF) measurements, and simulations are reported.

36 MATERIALS SCIENCE↗