BOLTON, R.

HEFELE, J.

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4 -- ..*Approvadtirpublic rdease;distribution is unlimited,TitleAuthor(s)Submitted toNon-Destructive Tracing of a Product Life Cycle ThroughGeometry Extraction from RadiographsJill Hefele, ESA-WERichard D. Bolton, NIS-6The 4th International Conference on Design of InformationInfrastructure Systems for Manufacturing 2000Melbourne, AustraliaNovember 5-17,2000Los AlamosNATIONAL LABORATORYLos Alamos National Laboratory, an affirmative actiordequal opportunity employer, is operated bythe-Unhrersity of Caliiomia for the U.S.Department of Energy under contracl W-7405-ENG-36. By acceptance of this aticle,”the publisher recognizes that the U.S. Governmentretains a nonexclusive, royalty-free license to publish or reproduce the published form of this contribution, or to allow others to do so, for U.S.Government purposes. Los Alemos National Laboratory requests that the publisher identify this article as work performed under theauspices of the U.S. Department of Energy. Los Alamos National Laboratory strongly supports academic freedom and a researcher’s right topublish; as an institution, however, the Laboratory does not endorse the viewpoint of a publication or guarantee its technical correctness.Form 836 (8/00)DISCLAIMERThis report was prepared as an account of work sponsoredby an agency of the United States Government. Neitherthe United States Government nor any agency thereof, norany of their employees, make any warranty, express orimplied, or assumes any legal liability or responsibility forthe accuracy, completeness, or usefulness of anyinformation, apparatus, product, or process disclosed, orrepresents that its use would not infringe privately ownedrights. Reference herein to any specific commercialproduct, process, or service by trade name, trademark,manufacturer, or otherwise does not necessarily constituteor imply its endorsement, recommendation, or favoring bythe United States Government or any agency thereof. Theviews and opinions of authors expressed herein do notnecessarily state or reflect those of the United StatesGovernment or any agency thereof.DISCLAIMERPortions of this document may be illegiblein electronic image products. Images areproduced from the best available originaldocument.. .NON-DESTRUCTIVE TRACING OF A PRODUCTLIFE CYCLE THROUGH GEOMETRYEXTRACTION FROM RADIOGRAPHSJ. Hefele and R. D. BoltonLos Alarnos National Laboratory, Los Alamos, NM, USAEm: jill @lanl.gov and rbolton @lanl.govKeyworda Photogrammetry, Geometry Rconstmction, Non-destructive TestingAbstract Tracing the internal changes seen by a product assembly during its useful lifecycle without disassembling or destructively testing the product providesmany challenges. When an assembly is disassembled for evaluation, theeffect of component interaction is 10SL particularly if operations such aspress-fitting have been used in the assembly process. It is undesirable todestructively evaluate a product when it is still in its useful life cycle. LosAlamos National Laboratory is developing a process in which radiographicinformation is used to characterise an entire assembly for life cycleevaluation and the geometric information is extracted for input into aComputer Aided Engineering (CAE) software package.Digitized radiographs have been reconstructed into solid models usingFotoGm geomeby extraction techniques and ProENGINEERm solidmodelling capabilities. Executed simultaneously, FotoGm translates theextracted geometry into a format useable by the ProENGINEERw software.Once tbe solid model is constructed, it is used for creation of finite elementanalysis inpu~ virtual environment model creation, and tooling design. Thecreation of the finite element model allows us to forestall future problemsusing predictive analyses. Virtual environment creation provides us with thecapability of creating a learning environment for technicians performingmaintenance or disassembly of problem units. And tooling design providesus the capability to safely transport severely darnaged assemblies in the eventof an accident scenario.1 INTRODUCTION.As a product matures through its useful life cycle, characterisation of theproduct’s current state becomes increasingly essential in order to forestallfunction and servicing problems. “As-Built” and “As-Is” characterisationmethodologies have been developed recently [1] [2] [3] using inspection dataas the raw input in modelling a product. This type of characterisation worlawell for portrayal of a component’s current state. However, oncecomponents are assembled into a final product, the geometry can easily bemodified due to the processes it has been subjected to during assembly orbecause of interactions with other components owing to use.Characterisation of a product in its assembled state provides it’s ownchallenges. Capturing the “As-Is” state of components in the assembledconfiguration requires non-destructive methods of evaluation. Radiographyand Computed Tomography [4] can provide the raw data necessary for thistype of characterisation. We have concentrated our initial developmentefforts on the use of radiographic data because much of our historical dataexists in this state. Changes can occur to component geometry as a productmoves through its useful life cycle and these variations from the “As-Built”state can also be captured using non-destructive evaluation techniques, thusMowing life-cycle data points to be collected as an assembly ages.This paper will examine the data collection and manipulation processesfor characterisation of a product as it moves through its useful life cycleusing photogrammetric, radiographic, and computer-aided engineeringmodelling techniques. We will also inspect issues related to data collectionmethods employed to obtain the best possible data for use in product modelreconstruction.2 DATA COLLECTION PROCESSThe data collection process for model reconstruction of a productconsists of three steps; initial survey of data collection environment,documentation of environment through digital photographs, and radiographyof the product being examined.2.1 Initial SurveyThe initial survey of the data collection environment establishes anetwork of control points to be used as reference between the digitalphotographs taken in the next step and the real world. A theodolite is usedto measure the location and orientation of the control points placed in the. *data collection environment prior to photography. A minimum of fourcontrol points is required. Stick-on targets are also set and located using thetheodolite or by measuring the distance between control pointshrgets aridestablishing an arbitrary but correctly scaled co-ordinate system during thisphase. The targets are used as references in the documentary photographs.Theodolite measurements can be made at this point to locate the radiographicfilm holder and the x-ray source.2.2 Environment Documentation Using Digital PhotographsOnce the control points and targets have been established, theenvironment can be documented using digital photography. The assembly tobe evaluated must be visible in at least two of the photographs taken withdifferent perspectives. It is essential that the carnerdlens combination usedto take the photographs in this step have been calibrated using testphotographs of a specially designed calibration field. Analysis of the digitalphotographs is benefited through inclusion of a fair amount of overlap in thephotographs taken. Section 4 discusses this in more detail.2.3 RadiographyRadiographic data provides the true basis for reconstruction of theassembly of interest. The same principles apply to radiographicdocumentation for assembly reconstruction as do to environmentdocumentation for site reconstruction; i.e. more overlap in radiographicimages, the better.3 DATA MANIPULATIONonce the raw data is collected in the form of survey daa digitalphotographs, and digital (or digitised) radiographs, the reconstruction canbegin. Analysis begins with identification of the camerdlens combinationused to collect the digital photographs. This provides the FotoGw softwarewith the necessary information for resection of the images. Images aremathematically resected as a set with ties to control points. The analyticalprocess is well-documented on Vexcel’s web site [5]. Radiographic imagescan be over-laid into the digital photograph site reconstruction data or can bereconstructed as a separate data set if survey data has been collecteddocumenting the location of the x-ray source and radiographic film frame.4 DATA COLLECTION ISSUES,,,Data collection techniques effect the results obtained during thereconstruction process. The type of targets used, for example, determine theease with which points are identified in the digital photographs whileprocessing the data. Additionally, the precision of the transit system used,completeness of the survey techniques, choice of camera locations, numberof control points identified, number of images used in data processing, andtype of image geometry used all effect the final results obtained in the dataset analysis..4.1 TargetsFigure 1 illustrates examples of types of targets used. Of the three typesof targets shown, we have found the easiest to work with in thephotogrammetry environment is on the extreme right.(!30Figure 1 Exsmples of Target Gwmetry.4.2 Transit System Measurement PrecisionThe precision inherent in the theodolite used to take measurementsduring the initial survey stage will effect the precision in measurementstaken digitally in the reconstructed data set. It is, therefore, essential tochose a transit system with as high a precision as possible. Figure 2compares the same measurements taken in two different data sets by thesame theodolite. The error, 2-3 mm, is within the stated precision of statedby the manufacturer.0-.1 .1..3 .2..3 .3-.4 .4..s .5-.6 .6-,7 .7-.0 =-.8TlM91~l . m-s-Trandl_2 (cm) IFigure 2 Comparison of Transit Measurements.4.3 Photogrammetry Measurement PrecisionThe precision of the photogrammetric software reconstruction is also animportant issue when choosing tools to be usd” for reconstruction efforts.Figure 3 compares the differences observed in measurements reconstructedfrom digital images using the FotoG W software withmeasurements made with the theodolite.the same123456Transit vs. FotoG (-)Figure 3 Comparison of Transit Measurements w“tb FotoG Software.4.4 Number of Control Points vs. PrecisionThe system of control points established in the initial survey during areconstruction effort establishes the reference between the digitallydocumented environment and the “As-Is” condition that exists in the realworld. The number of control points used has an effect on the precisionattained during reconstruction. A minimum of four control points isrequired. Figure 4 shows the effeet of increasing the number of controlpoints used during a reconstruction from four to eight to sixteen to thirty-two. In general, the more control points used, the better. However, there isa break even point where increasing the number of control points has only asmall benefit to increasing precision.40g:J*26!,20I “10so0-.< .1.2 .2-3 .%4 4-5 d-d S-.7 .7-1 >B-m-, .Ws m,-) I.0-.1 .1.2 ”3.3 3-4 4-5 B-s S-.7 .7-1 ●BTmMkl-m. nbo(”l I,.., .,.., ,,.., .,..4 .4.., .,.., ,6.,, ,..’ ,4,.... II. I .ro .,.,.. ,,.,Figure 4 Eff=t of Number of Control Points on Precision.4.5 Number of Images vs. PrecisionThe data collection process can be the most time-consuming element ofa reconstruction effort. Documentation of the site and assemblyenvironments in a complete manner is extremely important to the resultinganalysis. The number of images, however, is not nearly as important as thequality of the images taken. A few images with good overlap,, say greaterthan 60% coverage, and strong geometry, approximately 90% convergenceangles, will give the best results in a reconstruction. The upper two graphsin Figure 5 illustrate the increase in precision from using three images withgood geometry as compared to two. However, as illustrated by the lower leftgraph, adding a fourth image with not quite as strong geometry had anegative effect on the precision. The analyses pictured in the two lowergraphs in Figure 5 both employed the use of four images, but the analysispictured on the left used images with stronger geometry than that on theright.1 I1n!!!w-II. ...I ,“.., ., ..,’ .,’.., .,.” .“.., .,.x ... . .. >.‘1..”,., - “, .,> **I.m B..l .1..!3 .1>2 >.5 .U.1 Ja .X.4 til*UU.1 .“, . ?.4 (dc-m *., .’.’, .,$4 ,.s Is-, ,-s .s. , ,.4TM”.., .“, .,., I.* I]:~’~’!..,, .,,.., .!.., ! .,!.., .,.,, .,,.., .,..,, .,,. , ,,1...,,.1 -.., -1.1-4(C*Figure 5 Effectof Number of Images on Precision.5 CONCLUSIONPhotogrammetry, radiography, and reverse engineering reconstructiontechniques are effective tools in the non-destructive evaluation of the productlife cycle of an assembly. ‘llese techniques can be used to forestallproblems before they become catastrophic. Research and developmentcontinue to improve processes and software development in this area.6[1][2][3][4][5]REFERENCESDolin R. M., Hefele J. (1997). As-Built Engineering: A Philosophy for RepresentingProduct Definition, LA-VR-97-3631 Proceedings Nuclear Explosives Design PhysicsConference, Livermore, CA.Hefele, et. al., (1997). Product Characterisation Using Inspection Data in an As-BuiltEngineering Environmen& fbmedings Second Bienm”al Tti-Laboratory Engin=ringConference on Modeling and Simulation, Los Alamos, NM.Hefele, J. Dolin R. M. (1998). Density Effect of Inspection Data in As-Built Modelingof Parts, J30ceedings ~ International Conference on Engineering Design andAutomation, Maui, HLKelley T. A., et. al. (1998). Reverse Engineering Using Computed Tomography,Proceedings fl Annual Review of Progress in Quantitative NondestructiveEvaluation, Snowbird, UTClose Range Photogrammetry – Learn About Photogrammetry,http:/hvww.vexcel.comLfotog/learn.h tml

NON-DESTRUCTIVE TRACING OF A PRODUCT LIFE CYCLE THROUGH GEOMETRY EXTRACTION FROM RADIOGRAPHS

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NON-DESTRUCTIVE TRACING OF A PRODUCT LIFE CYCLE THROUGH GEOMETRY EXTRACTION FROM RADIOGRAPHS

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