SEARCH · Engineering Papers

Results for “Inspection”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 109 records · Page 6

All sources NASA NTRS DOE OSTI

NASA NTRS2012

Method to Enhance the Operation of an Optical Inspection Instrument Using Spatial Light Modulators

For many aspheric and freeform optical components, existing interferometric solutions require a custom computer-generated hologram (CGH) to characterize the part. The overall objective of this research is to develop hardware and a procedure to produce a combined, dynamic, Hartmann/ Digital Holographic interferometry inspection system for a wide range of advanced optical components, including aspheric and freeform optics. This new instrument would have greater versatility and dynamic range than currently available measurement systems. The method uses a spatial light modulator to pre-condition wavefronts for imaging, interferometry, and data processing to improve the resolution and versatility of an optical inspection instrument. Existing interferometers and Hartmann inspection systems have either too small a dynamic range or insufficient resolution to characterize conveniently unusual optical surfaces like aspherical and freeform optics. For interferometers, a specially produced, computer-generated holographic optical element is needed to transform the wavefront to within the range of the interferometer. A new hybrid wavefront sensor employs newly available spatial light modulators (SLMs) as programmable holographic optical elements (HOEs). The HOE is programmed to enable the same instrument to inspect an optical element in stages, first by a Hartmann measurement, which has a very large dynamic range but less resolution. The first measurement provides the information required to precondition a reference wave that avails the measurement process to the more precise phase shifting interferometry. The SLM preconditions a wavefront before it is used to inspect an optical component. This adds important features to an optical inspection system, enabling not just wavefront conditioning for null testing and dynamic range extension, but also the creation of hybrid measurement procedures. This, for example, allows the combination of dynamic digital holography and Hartmann sensing procedures to cover a virtually unlimited dynamic range with high resolution. Digital holography technology brings all of the power and benefits of digital holographic interferometry to the requirement, while Hartmann-type wavefront sensors bring deflectometry technologies to the solution. The SLM can be used to generate arbitrary wavefronts in one leg of the interferometer, thereby greatly simplifying its use and extending its range. The SLM can also be used to modify the system into a dynamic Shack-Hartmann system, which is useful for optical components with large amounts of slope. By integrating these capabilities into a single instrument, the system will have tremendous flexibility to measure a variety of optical shapes accurately.

Trolinger, James↗

NASA NTRS2019

Machine Learning Based AFP Inspection: A Tool for Characterization and Integration

Automated Fiber Placement (AFP) has become a standard manufacturing technique in the creation of large scale composite structures due to its high production rates. However, the associated rapid layup that accompanies AFP manufacturing has a tendency to induce defects. We forward an inspection system that utilizes machine learning (ML) algorithms to locate and characterize defects from profilometry scans coupled with a data storage system and a user interface (UI) that allows for informed manufacturing. A Keyence LJ-7080 blue light profilometer is used for fast 2D height profiling. After scans are collected, they are process by ML algorithms, displayed to an operator through the UI, and stored in a database. The overall goal of the inspection system is to add an additional tool for AFP manufacturing. Traditional AFP inspection is done manually adding to manufacturing time and being subject to inspector errors or fatigue. For large parts, the inspection process can be cumbersome. The proposed inspection system has the capability of accelerating this process while still keeping a human inspector integrated and in control. This allows for the rapid capability of the automated inspection software and the robustness of a human checking for defects that the system either missed or misclassified.

Sacco, Christopher↗

DOE OSTI2021

Inspection workcell

An inspection workcell includes an equipment rack for securing one or more part trays comprising inspection parts, one or more inspection stations for inspecting the inspection parts, and a robotic manipulator for transporting the one or more part trays from the equipment rack to the one or more inspection stations.

Burchard, Ross L.↗

DOE OSTI2017

IAEA Domestic Inspections in the US

The Voluntary Offer Agreement between the United States and the IAEA for the implementation of IAEA safeguards in the United States, INFCIRC/288, entered into force in 1980. Under this Agreement, the United States provides to the IAEA an Eligible Facilities List, which lists facilities eligible for IAEA inspection and verification of compliance through either a reporting-only process or for full-scope safeguards (to include inspections). Approximately 300 facilities are currently listed on the Eligible Facilities List. Since 1981, the IAEA has conducted over 700 inspections on ~20 of these facilities. Currently, four NRC-licensed facilities have been selected under the Initial (Reporting) Protocol, and one DOE facility, KAMS at the SRS, has been selected for full-scope safeguards. These IAEA inspections are documented in the ID/288 database managed by staff at ORNL and the Y-12 National Security Complex for the NNSA Office of Nonproliferation and Arms Control. This database also maintains records of US designated inspectors, the status of indices checks, and inspection schedules. The database was most recently updated in FY 2014 to include information related to the IAEA visit to URENCO-USA in New Mexico and will be upgraded again via proposal in FY 2017 to include the Small Quantities Protocol (SQP) inspections in the US Caribbean territories, associated with INFCIRC/366. During the FY 2017 upgrade, the system will also be overhauled to allow for quicker updates and to improve performance using a modern software package.

White-Horton, Jessica↗

DOE OSTI2017

NXIS - Well integrity inspection in unconventional gas wells

The objective of this project is to advance the state-of-the-art and to develop an integrity inspection system capable of detecting physical flaws in the wellbore structure of conventional and unconventional hydrocarbon producing wells. Measuring the integrity of multiple wellbore casings and cement annuli for onshore and offshore wells remains a challenging task. We propose a multi-modality inspection system composed of neutron and X(gamma)-ray imaging modalities (nXis) to address the above challenge. The functional principle of this wellbore integrity inspection system is the combination of high-energy modalities, such as X(gamma)-ray and neutron backscatter imaging, with conventional low-energy modalities, such as electromagnetic or ultrasound imaging techniques. By combining multiple sensing modalities into one sensing system and by fusing data between modalities, one can gather more information about the integrity of the wellbore structure compared to simply using multiple sensors individually. Imaging prototypes for gamma, neutron, and electromagnetics were designed, manufactured, and tested at GE Global Research and Starfire Industries. Wellbore phantoms with engineered defects were manufactured and the performance of the developed wellbore integrity inspection tool prototypes was evaluated in a test pit test at an industrial GE Oil & Gas facility. Data analysis and fusion between various inspection techniques show enhanced defect detectability. These exciting results were presented at various technical conferences and discussed with operators in the oil & gas industry. Great interest from oil operators lead to discussions about joint industrial partnerships to move the developed technology from the prototype phase to the product phase.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2017

PF-WFS Shell Inspection Update December 2016

Since the last project update in FY16:Q2, PF-WFS personnel have advanced in understanding of shell inspection on Coordinate Measuring Machines {CMM} and refined the PF-WFS process to the point it was decided to convert shell inspection from the Sheffield #1 gage to Lietz CM Ms. As a part of introspection on the quality of this process many sets of data have been reviewed and analyzed. This analysis included Sheffield to CMM comparisons, CMM inspection repeatability, fixturing differences, quality check development, probing approach changes. This update report will touch on these improvements that have built the confidence in this process to mainstream it inspecting shells. In addition to the CMM programming advancements, the continuation in refinement of input and outputs for the CMM program has created an archiving scheme, input spline files, an output metafile, and inspection report package. This project will continue to mature. Part designs may require program modifications to accommodate "new to this process" part designs. Technology limitations tied to security and performance are requiring possible changes to computer configurations to support an automated process.

42 ENGINEERING↗

DOE OSTI2019

Y-12 Groundwater Protection Program CY 2018 Triennial Report of the Monitoring Well Inspection and Maintenance Program Y-12 National Security Complex Oak Ridge, Tennessee

This document is the Triennial Report for the Well Inspection and Maintenance Program of the Y-12 National Security Complex (Y-12) Groundwater Protection Program (GWPP) at U.S. Department of Energy (DOE) Y-12 and includes monitoring well inspections and well maintenance activities performed at Y-12 during calendar years (CYs) 2016 through 2018. This report formally documents well inspections completed by GWPP on active and inactive groundwater monitoring wells that are part of the Y-12 monitoring network and includes well inspections performed by URS|CH2M Oak Ridge, L.L.C. (UCOR), which administers the DOE Office of Environmental Management Y-12 Water Resources Restoration Program (WRRP). The WRRP includes wells that are utilized for the regulatory monitoring of Resource Conservation and Recovery Act (RCRA) post-closure permits and Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) Remedial Effectiveness and Records of Decision and Solid Waste Disposal Facility (Landfill) permits and includes monitoring wells located at the CERCLA Environmental Management Waste Management Facility. Beginning in 2018, UCOR terminated three of their RCRA post-closure permits and is monitoring the former RCRA-permitted facilities under CERCLA. Consequently, the number of monitoring wells in the Y-12 network that receive UCOR-performed inspections has decreased significantly.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2018

An Industrial Steerable Needle for Inspecting Extremely Confined Spaces in Nuclear Facilities - 18316

We present a novel, compliant mechanism inspired by steerable needles for endoscopic surgery that provides the capability to navigate extremely confined spaces for the purpose of infrastructure inspection. Extremely confined spaces are commonly encountered during infrastructure inspection of nuclear facilities. These spaces can include pipes and ventilation ducts. Often these infrastructure features go uninspected simply because there is no viable way to access their interior. In addition, it is not uncommon for extremely confined spaces to be laid-out in a spider-web fashion that must be selectively navigated in order to execute an inspection. Recently, millimeter-scale imagers have become commercially available. These imagers are small enough to fit inside an extremely confined space, but there is currently no means to bring the imager to the portion of the structure that must be inspected. In this work this problem is addressed by taking inspiration from the field of steerable needles used in endoscopic surgery. Steerable needles are long flexible shafts that are capable of being directed through the human body using control forces applied external to the body. Unfortunately, steerable needles cannot be directly applied to the problem of navigating maze-like arrangements of extremely confined spaces. Traditional steerable needles must operate within a solid medium that can be penetrated in order to be steered so they are not directly applicable to navigating extremely confined spaces. However surgical steerable needles do suggest an approach to the problem. Steerable needles are typically made from super-elastic nitinol. This material has the property that it can experience high strain without yielding. Furthermore, superelastic nitinol is stiff enough that it is possible to push the tube down a long, maze-like arrangement of a confined space without buckling. The stiffness properties of nitinol combined with its high yield strain makes it an attractive material for navigating a tube through a maze-like arrangement of extremely confined spaces. The ability to selectively navigate extremely confined spaces opens up new possibilities to use emerging miniature imaging technology for infrastructure inspection. (authors)

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

DOE OSTI2018

Systems and Tools to Facilitate Aging Management Inspections of Used Nuclear Fuel Dry Storage Systems - 18382

The Used Nuclear Fuel (UNF) dry storage systems (DSSs) are currently used at almost all the nuclear plants in the USA for the storage of their UNF as the spent fuel pools are running out of capacity to store any additional discharged fuel. Even though these DSSs are supposed to be at the reactor site for a short amount of time, they are expected to be at the reactor sites for an extended duration due to the unavailability of Interim Storage Facilities (ISF) or a permanent disposal sites like Yucca Mountain. Maintaining the integrity of the DSS canisters and storage overpacks so they can safely protect the fuel and maintain the integrity of UNF is of utmost importance during storage at reactor site ISFSI or at the ISF. Comprehensive and robust Aging Management Program (AMP) is an important aspect for DSSs to satisfy these requirements. In order to address this industry need, TN Americas have developed an enhanced NUHOMS{sup R} DSS licensed by NRC under 10 CFR Part 72 regulations and a comprehensive AMP development which includes prevention, inspection, monitoring and mitigation of any corrosion or degradation of DSS components. For DSC and HSM inspection, two remotely operating delivery systems have been developed using non-destructive examination (NDE) methods including robotic crawler and inspection ring system. This paper describes details of these developments and status of their deployment for implementation at various utility ISFSI sites. TN Americas completed the detailed design of the DSC inspection system and conducted functional tests of the inspection system on a DSC mockup and the system is ready for deployment at any NUHOMS{sup R} ISFSI site. TN Americas is committed to offer the most robust and comprehensive AMP systems, tools and services to the industry to assure the safety of the deployed DSS at the utility sites. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2018

Hanford Double Shell Tank Integrity Inspection - Integration of Customized Robotics - 18400

28 steel, double-shell, million gallon waste storage tanks located at the Hanford site in Washington State store both radioactive and hazardous waste. To monitor their condition and ensure continued viability, these tanks are inspected periodically through a comprehensive integrity program. In 2012, the first leak in a double-shell tank at Hanford was discovered in the 241-AY tank farm (Tank AY-102) and the failure was observed to be from the primary tank bottom. However, the exact failure location and damage mechanism have not been determined. A decision was made to pursue the capability to inspect the primary tank bottom region in order to provide additional tank integrity information. This work is particularly challenging due to the confined space in the double-shell tank annulus region (i.e. the 30 inch space between the primary and secondary tank shells), the limited dimensions of the tank risers that provide access to the annulus space (risers as small as 10 inches in diameter), and also the very small dimensions of the air channels in the concrete refractory pad that the primary waste storage tank rests on (channels are approximately two inches in diameter). Veolia Nuclear Solutions, along with Key Subcontractor Inuktun, were contracted to provide the capability to conduct these tank inspections in support of Hanford's double-shell tank integrity program. The Veolia Nuclear Solutions /Inuktun team designed, built, tested and delivered a tethered miniature robotic crawler system that utilizes the marsupial approach - a larger deployment crawler positions a smaller inspection crawler. The deployment crawler is installed via the tank riser, is magnetically coupled to the side of the tank shell, and drives to the selected deployment location at the end of one of the refractory channels where the small inspection robot is subsequently deployed. Operation of the equipment is controlled from a trailer outside the tank farm (a distance of several hundred feet). The system design includes a custom mechanism that provides for positioning and cable handling as well as the controls interface (laptop connected via control cables). The solution leveraged the Veolia Nuclear Solutions/Inuktun team's experience with delivering similar modular systems for other US and international sites. This simple but innovative solution delivered on an accelerated project schedule underlines the ability to provide effective robotic solutions to the nuclear industry. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2020

Savannah River Site H-Canyon Process Exhaust Tunnel Inspection Crawler Development - 20036

This paper covers development of a remote crawler used to inspect a subterranean radiochemical process ventilation tunnel located at the Savannah River Site near Aiken, SC. The purpose of the inspection was to ascertain the apparent structural condition of the tunnel with video footage. Manned entry is prohibited due to the hazardous environment requiring a fully-remote approach. The inspection system used high-definition cameras to archive over 1000 linear feet in the tunnel. While previous inspections had been undertaken, this crawler was developed to overcome obstacles that had put tunnel regions out of reach of prior inspection platforms. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2023

Cost‐benefit assessment framework for robotics‐driven inspection of floating offshore wind farms

Abstract Operations and maintenance (O&M) of floating offshore wind farms (FOWFs) poses various challenges in terms of greater distances from the shore, harsher weather conditions, and restricted mobility options. Robotic systems have the potential to automate some parts of the O&M leading to continuous feature‐rich data acquisition, operational efficiency, along with health and safety improvements. There remains a gap in assessing the techno‐economic feasibility of robotics in the FOWF sector. This paper investigates the costs and benefits of incorporating robotics into the O&M of a FOWF. A bottom‐up cost model is used to estimate the costs for a proposed multi‐robot platform (MRP). The MRP houses unmanned aerial vehicle (UAV) and remotely operated vehicle (ROV) to conduct the inspection of specific FOWF components. Emphasis is laid on the most conducive O&M activities for robotization and the associated technical and cost aspects. The simulation is conducted in Windfarm Operations and Maintenance cost‐Benefit Analysis Tool (WOMBAT), where the metrics of incurred operational expenditure (OPEX) and the inspection time are calculated and compared with those of a baseline case consisting of crew transfer vessels, rope‐access technicians, and divers. Results show that the MRP can reduce the inspection time incurred, but this reduction has dependency on the efficacy of the robotic system and the associated parameterization e.g., cost elements and the inspection rates. Conversely, the increased MRP day rate results in a higher annualized OPEX. Residual risk is calculated to assess the net benefit of incorporating the MRP. Furthermore, sensitivity analysis is conducted to find the key parameters influencing the OPEX and the inspection time variation. A key output of this work is a robust and realistic framework which can be used for the cost‐benefit assessment of future MRP systems for specific FOWF activities.

17 WIND ENERGY↗

DOE OSTI2025

Non-destructive evaluation and machine learning methods for inspection of spent nuclear fuel canisters: A state-of-the-art review

Nuclear energy is among the cleanest and most efficient energy sources currently available. The operation of nuclear power plants (NPPs) produces large amounts of high-level radioactive waste known as spent nuclear fuel (SNF). Currently, large amounts of SNF is stored in dry cask storage systems (DCSSs) for extended interim storage until a permanent disposal solution becomes available. During the extended interim storage, the DCSS, particularly the SNF canisters, may degrade and abnormal conditions may occur. Therefore, non-destructive evaluation (NDE) and machine learning (ML) approaches are necessary for inspection of SNF canisters. This paper presents a state-of-the-art review of literature by summarizing recent progress made on the applications of NDE and ML for inspection of SNF canisters. Sixteen NDE methods are examined and compared: visual inspection, ultrasonic guided waves (UGWs), laser-based approaches, acoustic emission (AE), eddy current testing (ECT), non-invasive acoustic sensing, dynamic modal testing, cosmic ray muons tomography, neutron imaging, gamma rays detection, fiber optical sensors, through-wall communications, X-ray computed tomography (CT), vibrothermography, monoenergetic photon sources, and surface acoustic wave (SAW) sensors. The technology readiness level (TRL) for each method is assessed and compared. Recent publications on ML-enhanced visual inspection, AE, non-invasive acoustic sensing, dynamic modal testing, and neutron imaging for SNF canisters are summarized and future research needs are identified. In conclusion, this review article provides a convenient reference on the state-of-the-art applications of NDE and ML methods for inspection of SNF canisters.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗

DOE OSTI2017

A compliant mechanism for inspecting extremely confined spaces

We present here a novel, compliant mechanism that provides the capability to navigate extremely confined spaces for the purpose of infrastructure inspection. Extremely confined spaces are commonly encountered during infrastructure inspection. Examples of such spaces can include pipes, conduits, and ventilation ducts. Often these infrastructure features go uninspected simply because there is no viable way to access their interior. In addition, it is not uncommon for extremely confined spaces to possess a maze-like architecture that must be selectively navigated in order to properly perform an inspection. Efforts by the imaging sensor community have resulted in the development of imaging sensors on the millimeter length scale. Due to their compact size, they are able to inspect many extremely confined spaces of interest, however, the means to deliver these sensors to the proper location to obtain the desired images are lacking. To address this problem, we draw inspiration from the field of endoscopic surgery. Specifically we consider the work that has already been done to create long flexible needles that are capable of being steered through the human body. These devices are typically referred to as 'steerable needles.' Steerable needle technology is not directly applicable to the problem of navigating maze-like arrangements of extremely confined spaces, but it does provide guidance on how this problem should be approached. Specifically, the super-elastic nitinol tubing material that allows steerable needles to operate is also appropriate for the problem of navigating maze-like arrangements of extremely confined spaces. Furthermore, the portion of the mechanism that enters the extremely confined space is completely mechanical in nature. The mechanical nature of the device is an advantage when the extremely confined space features environmental hazards such as radiation that could degrade an electromechanically operated mechanism. Here, we present a compliant mechanism developed to navigate maze-like arrangements of extremely confined spaces. The mechanism is shown to be able to selectively navigate past three 90° bends. The ability to selectively navigate extremely confined spaces opens up new possibilities to use emerging miniature imaging technology for infrastructure inspection.

47 OTHER INSTRUMENTATION↗

DOE OSTI2020

Y-12 Groundwater Protection Program Monitoring Well Inspection and Maintenance Plan

This plan describes the systematic approach for: inspecting the physical condition of monitoring wells at Y-12, determining maintenance needs that extend the life of a well, and identifying those wells that no longer meet acceptable monitoring well design or well construction standards and require plugging and abandonment. The inspection and maintenance of groundwater monitoring wells is one of the primary management strategies of the Y-12 Groundwater Protection Program (GWPP) Management Plan, that is, the “proactive stewardship of the extensive monitoring well network at Y-12" (Consolidated Nuclear Security, L.L.C. [CNS], 2018). Effective stewardship, and a program of routine inspections of the physical condition of each monitoring well, ensures that representative water-quality samples and hydrologic data are obtained from the well network and protects the subsurface environment. In accordance with the Y-12 GWPP Monitoring Optimization Plan (MOP) for Groundwater Monitoring Wells at the Y-12 National Security Complex, Oak Ridge, Tennessee (CNS, 2017), the status designation (active or inactive) for each well determines the scope and extent of well inspections and maintenance activities. This plan, in conjunction with the above document, formalizes the GWPP approach to focus available resources on monitoring wells which provide the most useful data, and for that reason the GWPP inspects and performs maintenance on the wells sampled by the GWPP. This plan applies to groundwater monitoring wells installed at Y-12 and the related waste management facilities located within the three hydrogeologic regimes: (1) the Bear Creek Hydrogeologic Regime (Bear Creek Regime), (2) the Upper East Fork Poplar Creek Hydrogeologic Regime (East Fork Regime), and (3) the Chestnut Ridge Hydrogeologic Regime (Chestnut Ridge Regime). The Bear Creek Regime encompasses the section of Bear Creek Valley (BCV) immediately west of Y-12. The East Fork Regime encompasses most of the Y-12 process, operations, and support facilities in BCV west of Scarboro Road. The Chestnut Ridge Regime is directly south of Y-12 and encompasses a section of Chestnut Ridge that is bounded to the west by a surface drainage feature (Dunaway Branch, located immediately west of Industrial Landfill II) and by Scarboro Road to the east. The GWPP maintains an extensive database of geographic and construction details and related information for the monitoring wells in each hydrogeologic regime in the Updated Subsurface Database for Bear Creek Valley, Chestnut Ridge, and Parts of Bethel Valley on the U.S. DOE Oak Ridge Reservation (CNS, 2019). A detailed description of the hydrogeologic framework at Y-12 can be found in the GWPP Management Plan (CNS, 2018).

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2018

Fast Ultrasonic Imaging with Total Focusing Method (TFM) for Inspection of Additively Manufactured Polymer Composite Component

Ultrasonic adaptive imaging based on the phased-array technology and the synthetic focusing algorithm Total Focusing Method (TFM) is proposed for fast ultrasonic nondestructive evaluation of additively manufactured composite materials. Nondestructive evaluation and inspection of additively manufactured parts and components are necessary for quality assurance of the materials. Effective detection of defects and anomalies in manufactured parts prevents extra cost and production time. However, there are several limitations encountered when using conventional methods of nondestructive inspection for as built additively manufactured parts due to surface conditions and geometrical complexity. Post-processing operations, such as machining, are usually needed to detect possible defects such as layer disband, micro-cracks, and voids in the composite parts. The capability of aperture focusing in phased array ultrasonic methods provides the opportunity for the adjustment of the delay laws in ultrasonic beams and reduces the noise and beam distortion for better imaging. An additively manufactured carbon fiber reinforced Acrylonitrile Butadiene Styrene (ABS) composite sample with artificial side and bottom-drilled holes of different sizes, used to represent defects, was successfully inspected using the Total Focusing Method (TFM). Unlike conventional ultrasonic techniques, results show a promising way to provide inspection of as built additively manufactured composite parts with rough surface finishes. The proposed method helps to decrease inspection time and eliminate extra machining and preparation costs.

Taheri, Hossein↗

NASA NTRS1975

Reliability-based optimum inspection and maintenance procedures

The development of reliability-based optimum inspection and maintenance schedules for engines needs an understanding of the fatigue behavior of the engines. Critical areas of the engine structure prone to fatigue damage are usually identified beforehand or after the fleet has been put into operation. In these areas, fatigue cracks initiate after several flight hours, and these cracks grow in length until failure takes place when these cracks attain the critical lengths. Crack initiation time and its growth rate are considered to be random variables. Usually, the inspection (fatigue) or test data from similar engines are used as prior distributions. The existing state-of-the-art is to ignore the different lengths of cracks obserbed at various inspections and to consider only the fact that a crack existed (or did not exist) at the time of inspection. In this paper, a procedure has been developed to obtain the probability of finding a crack of a given size at a certain time if the probability distributions for crack initiation and rates of growth are known. Application of the developed stochastic models to devise optimum procedures for inspection and maintenance are also discussed.

Nanagud, S.↗

NASA NTRS1985

Ultrasonic inspection of carbon fiber reinforced plastic by means of sample-recognition methods

In the case of carbon fiber reinforced plastic (CFRP), it has not yet been possible to detect nonlocal defects and material degradation related to aging with the aid of nondestructive inspection method. An approach for overcoming difficulties regarding such an inspection involves an extension of the ultrasonic inspection procedure on the basis of a use of signal processing and sample recognition methods. The basic concept involved in this approach is related to the realization that the ultrasonic signal contains information regarding the medium which is not utilized in conventional ultrasonic inspection. However, the analytical study of the phyiscal processes involved is very complex. For this reason, an empirical approach is employed to make use of the information which has not been utilized before. This approach uses reference signals which can be obtained with material specimens of different quality. The implementation of these concepts for the supersonic inspection of CFRP laminates is discussed.

Bilgram, R.↗