APPLICATION OF THE COLLISION-IMPARTED VELOCITY METHOD FOR .
NASA CR-1 34494ASRL TR 154-8APPLICATION OF THE COLLISION-IMPARTEDVELOCITY METHOD FOR ANALYZING THERESPONSES OF CONTAINMENT ANDDEFLECTOR STRUCTURES TO ENGINEROTOR FRAGMENT IMPACTnoztDELE RThomas P. Collins,dEmmett A. WitmerAeroelastic and Structures Research LDepartment of Aeronautics and AstrMassachusetts Institute of Tech nra'AutiCambridge, Massachusetts 0213ao wAugust 1973K43Prepared forAEROSPACE SAFETY RESEARCH AND DATA INSTITUTELEWIS RESEARCH CENTERNATIONAL AERONAUTICS AND SPACE ADMINISTRATIONCLEVELAND, OHIO 44135NASA Grant NGR 22-009-339unko
1. Report NoNASA CR -1344942. Government Accesson No.4 Title and SubtitleApplication of the Collision-Imparted Velocity Method for Analyzingthe Responses of Containment and Deflector Structures to Engine RotorFragment Impact7. Author(s)Thomas P. Collins and Emmett A.3. Recipient's Catalog No.5 Report DateAugust 19736 Perorming Organization Code8 Performing Organization Report NoASRL TR 154-8Witmer10 Work Unit No9. Performing Organization Name and AddressMassachusetts Institute of TechnologyAeroelastic and Structures Research LaboratoryCambridge, Massachusetts 0213911. Contract or Gant NoNGR 22-009-33913. Type of Report and Period CoveredContractor Report12 Sponsoring Agency Name and AddressNational Aeronautics and Space AdministrationWashington, DC. 2054615 Supplementary NotesTechnical Monitors:Technical Advisor:14 Sponsoring Agency CodePatrick T. Chiarito and Solomon Weiss, Aerospace Safety Research and DataInstituteRichard t. Kemp, Materials and Structures DivisionNASA Lewis Research Center, Cleveland, Ohio16 AbstractAn approximate analysis termed the collision imparted velocity method (CIVM) has been employedfor predicting the transient structural responses of containment rings or deflector rings which aresubjected to impact from turbojet-engine rotor burst fragments.These 2-d structural rings may heinitiallycircular or arbitrarily curved and may have either uniform or variable thickness;elastic, strain hardening, and atrain rate material properties are accossodated.Also these ringsmay be free or supported in various ways. The fragments have been idealized, for convenience, asbeing circular and non-deformable with appropriate mass and pre-impact velocity properties foreach of the one to n fragments considered. The effects of friction between each fragment and theimpacted ring are taken into account.This approximate analysis utilizes kinetic energy and momentum conservation relations in orderto predict the after-impact velocities of the fragment and the impacted ring segment. This informa tion is then used in conjunction with a finite element structural response computation code to pre dict the transient, large deflection responses of the ring.Similarly, the equations of motion foreach fragment are solved in small steps in time.The effects of varying certain geometric and mechanical property parameters upon the struc tural ring responses and upon the fragment motions have been explored briefly for both free com plete containment rings and for partial-ring fragment deflectors which are supported in each ofseveral ways. Also, some comparisons of predictions with experimental data for fragment-impactedfree containment rings are presented.17. Key Words (Suggested by Author(s))Turbo3et Rotor ContainmentAircraft HazardsAircraft SafetyStructural MechanicsFinite Element MethodTransient Structural Response19. Security Classif (of this report)UnclassifiedLarge DeflectionsElastic-PlasticBehaviorStrain AnalysisComputer Program18. Distribution StatementUnclassified, Unlimited20. Security Classf (of this page)Unclassified21 No of Pages249For sale by the National Technical Information Service, Springfield, Virginia 22151NASA-C-168 (R1-6-71)/ 22 Price
FOREWORDThis report has been prepared by the Aeroelastic and Structures ResearchLaboratory (ASRL), Department of Aeronautics and Astronautics, MassachusettsInstitute of Technology, Cambridge, Massachusetts under NASA Grant No.NGR 22-009-339 from the Lewis Research Center, National Aeronautics and SpaceAdministration, Cleveland, Ohio 44135. Mr. Patrick T. Chiarito and Mr. SolomonWeiss of the Lewis Research Center served as technical monitors and Mr. RichardH. Kemp served as technical advisor. The valuable cooperation and advice re ceived from these individuals is acknowledged gratefully.We are indebted to Messrs. G.J. Mangano and R. DeLucia of the NavalAir Propulsion Test Center, Phila., Pa. for,,supplying pertinent rotor fragmentdata and 4130 cast steel uniaxial static sttess-strain data.The authors especially wish to acknowledge the careful reviewing ofthis report and the many constructive suggestions from their colleaguesDr. R. W-H. Wu and Dr. John W. Leech. Mr. R.P. Yeghiayan of the'MIT-ASRLalso provided valuable advice and discussion during the conduct of thesestudies.The use of SI units (NASA Policy Directive NPD 2220.4, September 14,1970) was waived for the present document in accordance with' provisions ofparagrph 5d of that Directive by the authority of the Director of the LewisResearch Center.ii
CONTENTSPageSection1IINTRODUCTIONof the Engine Rotor Fragment Problem1.1Outline1.2Review of Some Analysis options1.3Current Status of the Fragment RingCollision-Interaction and Response Analyses1.3.1TEJ-JET Status1.3.2CFM-JET StatusCIVM-JET Status1.3.3251214 151-4. Purposes and Scope of the Present Study16COLLISION-IMPARTED VELOCITY METHOD182.1Outline of the Method182.2Fragment-Idealization Considerations192.3Collision-Interaction Analysis, Including2.4451327Friction31Prediction of Containment/Deflector RingMotion and Position322.5Prediction of Fragment Motion and Position352.&Collision Inspection and Solution Procedure362.6.1One-Fragment Attack362.6.2N-Fragment Attack40CONTAINMENT RING RESPONSE PREDICTIONS413.1Single-Fragment Examples423.2Three-Fragment Examples4648DEFLECTOR RING RESPONSE PREDICTIONS4.1Hinged-Fixed/Free Deflector Deflector Examples50535658SUMMARY AND COMMENTS61REFERENCES64-112ILLUSTRATIONSiii
CONTENTS ContinuedPageSectionAppendix A:USER'S GUIDE'TO THE CIVM-JET-4A PROGRAM113General Description of the /Deflector Ring Geometry,Supports, Elastic Restraints, andMaterial PropertiesA. 1.3Fragment Geometry and Initial Con A.1.4A. 2A. 3ditions115Solution Procedure116Description of Program and Subroutines118A.2.1Program Contents118A.2.2Partial List of Variable Names121Input Information and Procedure131A.3.1Energy Accounting Option142A.3.2Input for Special Cases of the GeneralStress-Strain RelationsA.4Description of the OutputA. 5Complete FORTRAN IV Listing of the CIVM-JET-4AA.6114142143Program146Illustrative Examples199A. 6.1A.6.2Free Circular Uniform-Thickness ContainmentRing Subjected to Single-Fragment Attack199A.6.1.1Input Data200A.6.1.2Solution Output Data205Elastic Foundation-Supported Variable-ThicknessPartial Ring (Deflector) Subjected to SingleFragment Attack216A.6.2.1Input Data217A.6.2.2Solution Output Data221APPENDIX B: SUMMARY OF THE CAPABILITIES OF THE COMPUTER CODESJET 1, JET 2, AND JET 3 FOR PREDICTING THE TWODIMENSIONAL TRANSIENT RESPONSES OF RING STRUCTURESiv237
CONTENTS ContinuedLIST OF ILLUSTRATIONSPageFigure641Rotor Burst Containment Schematic2Schematics of the Rotor Burst Fragment-Deflection65Concept3Schematics of Various Types of Rotor-Burst Frag 66ments and Failures4Schematics of-Two-Dimensional and Three-DimensionalEngine Casing Structural Response to Engine Rotor67Fragment Impact5Summary of Choice of Transient Structural ResponseAnalysis Method and Plan of Action for the EngineRotor Fragment Containment/Deflection Problem686Contanmant-Structure Schematics697Deflector Structure Schematics708Schematic of a 2D Containment Ring Subjected toFragment Impact971Information Flow Schematic for Predicting Ringand Fragment Motions in the Collision-ImpartedVelocity Method7210Schematics of Actual and Idealized Fragments7311Idealization of Ring Contour for Collision Analysis7612Exploded Schematic of the Lumped Mass Collision1378"Model at the Instant of ImpactThe Trajectory of the Image Point T in the pN-TPlane to Describe the Statg at each Contact Instant79for Various Impact Processes-14Coordinates, Generalized Displacements, and Nomen clature for a 2D Arbitrarily-Curved-Ring Finite Element15Inspection82for Determining a Collision of the Fragment83with the Ringv
CONTENTS ContinuedPageFigure16Fragment Idealizations used in the Present Study17Ring-Fragment Modeling and Response Data for Con tainment Rings subjected to Single-Fragment Attack188586Effect of Friction on the Predicted Maximum Circum ferential Strain Produced on 4130 Cast Steel Con 90tainment Rings by Single Fragment Impact19Predicted Maximum Circumferential Strain for SingleFragment Attack as a Function of Ring Thickness For91Fixed Ring Axial Lengths20Predicted Maximum Circumferential Strain for SingleFragment Attack as a Function of Ring Weight for92Fixed Ring Axial Lengths21Predicted Ring Weight for Single Fragment Attack asa Function of Ring Axial Length for Fixed Values of93Maximum Circumferential Strain22Comparison of Predicted Ring Profiles Obtained withand without Strain Rate Effects with NAPTC Photo 94graphic Test Data23Comparison of Ring Outer Surface Strains at a "Lobe"of the Ring Deformed by 3-Fragment Attack for theEL-SH and EL-SH-SR Cases as a Function of Time after98Initial Impact24Schematics and Nomenclature for an Idealized99Integral-Type Fragment Deflector25Influence of the Initial-Impact Locatione!upon thePath of the Fragment which Impacts the Idealized101Hinged-Fixed/Free Deflector26Predicted Maximum Circumferential Strain as a Functionof Deflector Ring Thickness (h/R Ratio) for various Axial103Lengthsvi
CONTENTS ConcludedFigure27PagePredicted Variation in Maximum Circumferential Strainas a Function of Deflector Ring Weight (wr/(KE)0 Ratio) forVarious Axial Lengths28104Predicted Deflector Ring Weight for Single Fragment Attack asa Function of Ring Axial Length for Fixed Values of Maximum105Circumferential Strain29Fragment Path Data at TAIl 650 Microseconds for 0 16 Degrees as a Function of Deflector Ring Thicknessfor Fixed Values of L (Idealized H-F/F Deflector)30106Predicted Maximum Circumferential Strain of theFoundation-SupportedDeflector as a Function ofDeflector Thickness for Two Different Sets of108Support-Structure Rigidities31Predicted Fragment-Path Diversion as a Function of TimeAfter Initial Impact for Two Different Sets of Support109Structure Rigidities32Predicted Fragment Path Diversion Data at 650 Microsecondsafter Initial Impact as a Function of Deflector Thickness,hd for Two Different Sets of Support-Structure RigiditiesA.1Geometrical Shapes of Structural Rings Analyzed by .theCIVM-JET-4A ProgramA.21ll230Nomenclature for Geometry, Coordinates, and Displacements ofArbitrarily-Curved Variable-Thickness Ring Elements231A.3Schematics for the Support Conditions of the Structure232A.4Schematicof Possible Piecewise Linear Representation ofUniaxial Static Stress-Strain Material Behavior234A.5Example Problem: Uniform Thickness Containment Ring235A.6Example Problem: Variable-Thickness 90-Deg Partial Ring(Deflector) with Uniform Elastic Foundation Applied toa Portion of the Ring236vii
SUMMARYArguments are presented supporting the proposition that the development andthe selective utilization of prediction methods which are restricted to two-dimen sional (2-d) transient large-deflection elastic-plastic responses of engine rotorburst fragment containment/deflector structures are useful and advisable for para metric and trendg-sfuaies. In conjunction with properly-selected experimentalstudies of rotor-burst fragment interaction with actual containment and/or deflectorstructure -- wherein three-dimensional effects occur -- one may be able to developconvenient rules-of-thumb to estimate certain actual 3-d containment/deflectionstructural response results from the use of the very convenient and more efficientbut simplified 2-d response prediction methods.Accordingly, the collision-imparted velocity method (CIVM) for predicting thecollision-interaction behavior of a fragment which impacts containment/deflectorstructures has been combined with a modified version of the JET 3C two-dimensionalstructural response code to predict the transient large-deflection, elastic-plasticresponses and motions of containment/deflector structures subjected to impact byone or more idealized fragments. Included are the effects of friction between eachfragment and the attacked structure. A single type of fragment geometry has beenselected for efficiency and convenience in these fragment/structure interaction andresponse calculations, but the most important fragment parameters, it is believed,have been retained; n fragments each with its own mf, If, Vf, 0)f, rf, and rc maygbe employed.Calculations have been carried out and reported illustrating the applicationof the present CIVM-JET analysis and program for predicting 2-d containment ringlarge-deflection elastic-plastic transient responses to (a) single-fragment impactand (b) to impacts by three equal-size fragments.The influence of containment ringthickness, axial length, and strain-rate dependence, as well as friction between thefragment and the impacted structure have been explored.Similar illustrative calculations have been performed and reported for the-re sponses of (a) ideal hinged-fixed/free and (b) elastic-foundation-supported fragment deflector rings of uniform thickness to impact by a single idealized fragment. Withrespect to the latter more-realistic and yet-idealized model, it was found thatplausible increases in the values for the stiffnesses of the "elastic foundation"was a more effective means for changing the path of the attacking fragment than byplausible increases in the thickness of the deflector ring itself.Although calculations were of very limited scope, some interesting responsetrends were noted. More extensive calculations in which-more of the problem variable!accommodated in the CIVM-JET-4A analysis and program are included and in which eachof certain quantities are varied over plausible ranges would provide a more illumi nating picture of the roles and effectiveness of these parameters with respect tofragment-containment and/or fragment-deflection protection.It is believed that the present analysis method and program (CIVM-JTET-4A) pro vides a convenient, versatile, and efficient means for estimating the effects ofnumerous problem variables upon the severe nonlinear 2-d responses of variable thickness containment/deflector structures to engine-rotor-fragment impact. Althougha limited number of comparisons of predictions with appropriate experimental data shoNencouraging agreement, more extensive comparisons are required to establish a firmerassessment and confidence level in the accuracy and the adequacy of the present pre diction method, consistent with its inherent 2-d limitations.Vill
SECTION 1INTRODUCTION1.1Outline of the Engine Rotor Fragment ProblemAs pointed out in Refs. 1 through 6, for example, there has been a not insignificant number of failures of rotor blades and/or disks of turbines andcompressors of aircraft turbojet engines of both commercial and military air craft each year, with essentially no improvement in the past 10 years in thenumber of uncontained failures.The resultinW uncontained fragments, if suffi ciently energetic, might injure personnel occupying the aircraft or mightcause damage to fuel lines and tanks, control systems, and/or other vital com ponents, with the consequent possibility of a serious crash and loss of life.It is necessary, therefore, that feasible means be devised for protecting (a)on-board personnel and (b) vital components from such fragments.-Two commonly recognized concepts for providing this-protection are evi dent.First, the structure surrounding the "failure-prone" rotor region couldbe designed to contain (that is, prevent the escape of) rotor burst fragmentscompletely.Second, the structure surrounding this rotor could be designed soas to prevent fragment penetration in and to deflect fragments away from cer tain critical regions or directions, but to permit fragment escape readily inThese two concepts are illustratedother "harmless" regions or directions.schematically in Figs. 1 and 2.In certain situations, the first scheme(complete containment) may be required, while in other cases either scheme mightbe acceptable.For the latter situation, one seeks the required protection forthe least weight and/or cost penalty.A definitive comparative weight/costassessment of these two schemes is not available at this time because of (a)inadequate knowledge of the fragment/structure interaction phenomena and (b)incomplete analysis/design tools, although much progress has been made in thesetwo areas in the past several years; however, this question is explored in alimited preliminary fashion in the present report.Studies reported in Refs. 1 through 3 of rotor burst incidents in com merical aviation from the Federal Aviation Administration (FAA), the NationalTransportation Safety Board (NTSB), and other sources, indicate that uncontained 1
fragment incidences occur at the rate of about 1 for every 106 engine flighthours.In 1971,for example,124 fragment-producing rotor failures were re ported in U.S. commercial aviation (Ref. 2); in 35 of these incidents, uncon The total number of failures and thetained rotor fragments were reported.number of uncontained failures are classified as to fragment type in threebroad categories as follows (Ref. 2):Fragment TypeTotal No. ofFailuresNo. of UncontainedFailures13136410518Disk SegmentRim SegmentRotor BladesThe sizes and the kinetic energies of the attacking fragments, however, arenot reported.From a detailed study of NTSB and industrial records, Clarke (Ref. 3)was able to find 32 case histories with descriptive and photographic informa tion sufficient to permit a reasonable determination of the type and size ofthe largest fragment and the associated kinetic energy.His assessment is thatthese data are sufficient to define trends for disk bursts.According toClarke, the disk breakup modes for the 11,000 to 19,000-lb thrust range of enginesstudied are classified into four categories:(1) rim segment failures, (2) rim/web failures, (3) hub or sector failures, and (4) shaft-type failures; these andother types of engine rotor fragments are illustrated in Fig. 3.Rim failuresRim/web failures include rim and webcontain only rim sections or serrations.sections but do not include hub structure.Hub or sector fragments result whenthe rotor fails from the rim to the hub, thus nullifying the disk hoop strengthand allowing the disk to separate into several large sections.The shaft-typefailure mode usually occurs as a result of a bearing failure or a disk unbalancethat fails the disk shaft or the attaching tie rods; this mode can release morethan one engine stage from the nacelle.Accordingly, the 32 cases of failure aredivided into these four categories as follows; with the number of failures andpercent of total failures shown in parentheses (number/percent): rim (15/47),rim/web (3/9), sector (10/31), and shaft (4/13).Thus the rim and the sectorfailures comprise the lion's share of the failure modes for these 32 cases.Although in one case there were 10 major fragments,2inabout 80 percent of the
cases there were 4 or fewer fragments, with an overall mean of 3 major fragments.A major fragment is defined as one which contains a section of the rotor diskwhose largest dimension isgreater than 20 per cent of the disk diameter and alsocontains more kinetic energy than a single blade from the same stage.report, blade failures are not included as major fragments.In thatFailed blades (ex cluding fan blades) tend to be contained in accordance with Federal Aviation Regu lations (FAR) Part 33.In
ASRL TR 154-8 . APPLICATION OF THE COLLISION-IMPARTED . VELOCITY METHOD FOR ANALYZING THE RESPONSES OF CONTAINMENT AND noz . DEFLECTOR . STRUCTURES TO ENGINE . t . ROTOR FRAGMENT IMPACT . DELE R , Thomas P.Collins d . Emmett A. Witmer . Aeroelastic and Structures Research L ra 'A Department of Aeronautics and Astr . uti
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