CONFERENCE OF IRANIAN AEROSPACE SOCIETY | Year:2015 | دوره:14 |Papers Count:36

IN THIS PAPER, GENERALIZED DIFFERENTIAL QUADRATURE METHOD (GDQM) IS EMPLOYED TO ANALYZE VIBRATION OF A ROTATING DISKS BY CONSIDERING EFFECT OF RADIAL AND CIRCUMFERENTIAL IN-PLANE STRESSES. NATURAL FREQUENCIES AND VIBRATION MODES ARE DERIVED NUMERICALLY. FIRST, THE VERSATILITY AND ACCURACY OF THE PRESENTED SOLUTION ARE TESTED AGAINST PRESENTED EXACT RESULTS. THEN, EFFECTS OF THE RATIO OF RADII, ROTATION SPEED AND CIRCUMFERENTIAL MODE NUMBER ON THE NATURAL FREQUENCIES ARE INVESTIGATED.

IN THIS RESEARCH THE STUDY OF A NEW TYPE SANDWICH PANEL WITH GLASS/EPOXY SKINS AND CORRUGATED COMPOSITE-FOAM CORE UNDER TRANSVERSE LOADING ARE CONSIDERED. SANDWICH PANELS ARE A TYPE OF COMPOSITES THAT CONSIST OF TWO OUTER STRONG AND THIN SKINS AND A LIGHT AND THICK CORE LOCATED IN BETWEEN THE SKINS THAT PROVIDE GOOD ADVANTAGES LIKE HIGH STRENGTH/STIFFNESS TO WEIGHT OR MASS RATIO. CORRUGATED COMPOSITE LAMINATE WAS BUILT USING THE HAND LAYUP METHOD AND THE EXPERIMENTAL TECHNIQUE, VARTM (VACUUM ASSISTED RESIN TRANSFER MOLDING) WAS USED TO JOIN THE SKINS TO THE CORE WITH HIGHER QUALITY. SINGLE-POINT BENDING TEST LOAD WAS APPLIED TO THE SAMPLES ACCORDING TO ASTM STANDARD. FINITE ELEMENT ANALYSIS WAS APPLIED FOR DETERMINING MAXIMUM DEFLECTIONS OF SAMPLES, AS A SECOND METHOD. TWO TYPES OF CORE ARE CONSIDERED. FIRST IS A SIMPLE FOAM CORE BUT IN SECOND A CORRUGATED COMPOSITE LAMINATE WITH THREE DIFFERENT SHAPE CONSIST OF RECTANGULAR, TRIANGULAR AND TRAPEZOIDAL WITH ONE LAYER FOR THICKNESS AND 2 CENTIMETER FOR WAVELENGTH IS IMPROVISED. IT HAS BEEN SHOWN THAT THE FLEXURAL STIFFNESS OF SECOND TYPE SANDWICH PANEL WAS IMPROVED WITH CHANGING THE GEOMETRIC SHAPE OF CORRUGATED COMPOSITE IN FROM TRIANGULAR TO RECTANGULAR AND TRAPEZOIDAL. THE FLEXURAL STIFFNESS TO MASS RATIO WAS IMPROVED RESPECT TO SAMPLE WITH SIMPLE FOAM CORE BY ADDING ONE LAYER WOVEN GLASS-EPOXY CORRUGATED COMPOSITE WITH THREE GEOMETRIC SHAPE TO PVC FOAM CORE TOO. FINALLY THE EXPERIMENTAL AND FINITE ELEMENT RESULTS WERE COMPARED. ALSO THE NUMERICAL RESULTS SHOW A GOOD AGREEMENT WITH EXPERIMENTAL RESULTS.

THERE ARE DIFFERENT METHODS AND TECHNIQUES FOR CALCULATION OR MEASUREMENT OF THE AZIMUTH ANGLE. INDEPENDENT OF THE SELECTED ALGORITHM, THIS PAPER INVESTIGATES HOW ERROR IN DETERMINATION OF TRUE AZIMUTH INFLUENCES THE LABORATORY CALIBRATION, COARSE ALIGNMENT AND ALL-INERTIAL NAVIGATION OF A STRAPDOWN INS. THESE SURVEYS ARE PRESENTED IN BOTH ANALYTICAL AND PRACTICAL APPROACHES. THIS STUDY CLARIFY THAT HOW ACCURATE THE AZIMUTH MEASUREMENT IS REQUIRED FOR THE DESIRED APPLICATION. A NAVIGATION GRADE STRAPDOWN INS IS TESTED AND EVALUATED FOR PROOF OF CLAIMS.

IN THIS PAPER, STRUCTURE OF IDAS CANSAT THAT HAS BEEN DESIGNED, CONSTRUCTED AND TESTED IN IUST, IS PRESENTED. THIS PAPER INCLUDES A DESCRIPTION OF CANSAT MISSION, DESIGN OF MECHANICAL SUBSYSTEM, ELECTRONIC CIRCUITS, AND ALSO AN ANALYSIS OF PERFORMANCE ALGORITHMS. ONE OF THE SPECIAL FEATURES OF IDAS IS ITS VERY LIGHT WEIGHT IN COMPARISON WITH OTHER CONGENERS. THIS FEATURE LEADS TO A RELATIVELY COMPLEX DESIGN FOR MECHANICAL SUBSYSTEMS INCLUDING STRUCTURE, REACTION WHEEL AND PARACHUTE. A COMBINATION OF FREEWHEELING AND BALLS AND BOWL IDEAS HAS BEEN USED TO CONNECT THE PARACHUTE TO THE CANSAT STRUCTURE. THIS JOINT KEEPS THE CANSAT MOVEMENT PERPENDICULAR TO THE GROUND. THE PARACHUTE HAS BEEN DESIGNED FOR HIGH SAFETY MARGIN (IN WEIGHT AND SPEED), TO SATISFY THE EXPECTATIONS OF STABILITY ALONG WITH THE REACTION WHEEL. WITH THE STABILITY RESULTED, IMAGING WAS DONE WITHOUT ANY MECHANICAL DISTURBANCES AND WITH HIGH QUALITY. IN THE ELECTRONIC SUBSYSTEM, WE HAVE USED AN ARM MICROCONTROLLER TO CONTROL THE CAMERA. CAMERA’S DATA, DUE TO THEIR HIGH VOLUME, WERE STORED ON SD CARD AND SENT TO GROUND STATION IF NECESSARY. AS THE MICROCONTROLLER OPERATES IN HIGH CLOCK FREQUENCY, IT OFFERS CANSAT COMPLEX AND VARIED OPERATIONALLY SUCH AS RELEASE DETECTION AND DATA HANDLING. RELEASE DETECTION ALGORITHM IS SENSITIVE TO CANSAT ACCELERATION. THIS IS A NEW APPROACH AND REDUCES THE PROBABILITY OF FAULTY DETECTION. AFTER RELEASE, CANSAT TRIES TO ACHIEVE ITS GOAL AND TAKE PICTURES FROM GROUND WHILE READING, STORING AND SENDING THE SENSORS DATA TO THE GROUND STATION. TO VERIFY THESE FUNCTIONS, WE IMPLEMENTED SEVERAL TESTS AND EXPERIMENTS.

SELF-HEALING MATERIALS ARE A CLASS OF SMART MATERIALS THAT HAVE THE STRUCTURALLY INCORPORATED ABILITY TO REPAIR DAMAGE CAUSED DURING MECHANICAL USAGE. IN THE PRESENT STUDY, E-GLASS/EPOXY ANISOGRID COMPOSITE STRUCTURES FILLED WITH SELF-HEALING MATERIALS WERE FABRICATED. SELF-HEALING SYSTEM INCLUDES A NUMBER OF HOLLOW GLASS FIBERS CONTAINING ROOM TEMPERATURE CURING EPOXY RESIN AND RELATED HARDENER AS HEALING AGENTS. THE EFFECT OF SELF-HEALING MATERIALS VOLUME PERCENTAGE (5%, 8% AND 11%) ON THE HEALING EFFICIENCY OF MAXIMUM LOAD-BEARING CAPACITY OF RESULTANT SPECIMENS AFTER QUASI-STATIC DAMAGE, WAS EXPERIMENTALLY INVESTIGATED. THE RESULTS OF FLEXURAL TESTS SHOWED THAT INTRODUCTION OF SELF-HEALING MATERIALS AFFECTED THE MAXIMUM LOAD-BEARING CAPACITY OF THE SPECIMENS. THE MAXIMUM HEALING EFFICIENCY (84%) OF FLEXURAL LOAD-BEARING CAPACITY WAS OBSERVED IN THE SAMPLE CONTAINING 8VOL% SELF-HEALING MATERIALS. IN THE SAMPLES CONTAINING 5VOL% AND 11VOL% SELFHEALING MATERIALS, LOWER HEALING EFFICIENCY WAS OBSERVED THAN THE MAXIMUM VALUE, RESPECTIVELY DUE TO SHORTAGE OF HEALING AGENTS AND EXCESS OF STRUCTURAL DISCONTINUITIES CAUSED BY HOLLOW GLASS FIBERS.

IN THIS PAPER, NUMERICAL INVESTIGATIONS OF TURBULENT REACTING AND NON-REACTING LOW SWIRL FLOWS HAVE BEEN CARRIED OUT. LARGE EDDY SIMULATION (LES) AND DYNAMICALLY THICKENED FLAME MODELS ARE APPLIED TO PREDICT LOW SWIRL FLOW FIELD AND FLAME STRUCTURE. SIMULATION OF THE LEAN PREMIXED LOW SWIRL METHANEAIR FLAME SHOWS THAT THE FLAME IS LIFTED AND STABILIZED AT ABOUT X/D»0.6 ABOVE THE BURNER EXIT. THE LES RESULTS REVEAL THAT COHERENT STRUCTURES ARE DIFFERENT IN REACTING AND NON-REACTING SWIRL FLOWS.

THIS CASE INVOLVES THE FLOW OVER THE ONERA M6 WING. IT WAS TESTED IN A WIND TUNNEL AT TRANSONIC MACH NUMBERS 0.8395 AND ANGLES-OF-ATTACK 3.06 DEGREE. THE REYNOLDS NUMBERS WERE ABOUT 12 MILLION BASED ON THE MEAN AERODYNAMIC CHORD. THE ONERA M6 WING IS A CLASSIC CFD VALIDATION CASE FOR EXTERNAL FLOWS BECAUSE OF ITS SIMPLE GEOMETRY COMBINED WITH COMPLEXITIES OF TRANSONIC FLOW (I.E. LOCAL SUPERSONIC FLOW, SHOCKS, AND TURBULENT BOUNDARY LAYERS SEPARATION). THE ONERA M6 WING IS A WELL-KNOWN REFERENCE USED TO VALIDATE CFD METHODS IN THE TRANSONIC DOMAIN, ONE OF THE AREAS THAT THE FLUID DYNAMICS HAD A LARGE IMPACT IN ONERA M6.THE ONERA-M6 WING IS A WIDELY USED THREE-DIMENSIONAL TEST CASE FOR THE VALIDATION OF NUMERICAL METHODS AND TURBULENT MODELS, THE PERFORMANCE OF ANY AIRBORNE VEHICLE LARGELY DEPENDS ON ITS WING DESIGN.

SATELLITE FOR EARTHQUAKE PREDICTION INCLUDES ELECTRICAL POWER, ATTITUDE DETERMINATION AND CONTROL, TELEMETRY, TRACKING AND COMMAND, COMMAND AND DATA HANDLING, THERMAL AND STRUCTURES AND MECHANISM SUBSYSTEMS. THE SATELLITE WILL BE RELIABLE IF THE RELIABILITY OF ITS SUBSYSTEMS IS ENOUGH. IN OTHER WORDS, THE RELIABILITY OF EACH SUBSYSTEM SHOULD BE DETERMINED, IN ORDER TO ELIMINATE OR LIMIT FAILURES TO ACCEPTABLE LEVELS. IN THIS PAPER, DIFFERENT SUBSYSTEMS OF A SATELLITE FOR EARTHQUAKE PREDICTION HAVE BEEN REVIEWED. THEN, RELIABILITY OF SATELLITE SUBSYSTEMS HAS BEEN DETERMINED BY USING FMECA ANALYSIS. FINALLY, WITH RELIABILITY COMPARISON BETWEEN CENTRALIZED AND RING ARCHITECTURE, MOST RELIABLE CONFIGURATION HAS BEEN PROPOSED. ACCORDING TO THE CALCULATIONS WITH FMECA METHOD, THE CENTRALIZED ARCHITECTURE IS MORE RELIABLE THAN RING ARCHITECTURE.

IN THIS PAPER A CIVIL AIRCRAFT FUEL SYSTEM DESIGN WITH SPECIAL FOCUS ON REFUEL AND DEFUEL SYSTEM IS CONSIDERED AND FUNCTIONAL PROTOCOL DESIGN OF THE BOTH REFUEL AND DEFUEL SYSTEMS WITH LAYOUT DESIGN IS PRESENTED. REFUEL SYSTEM OF A COMMERCIAL AIRCRAFT WITH ABOUT 150 PASSENGERS IS DESIGNED BYSPECIFYING INTERFACES WITH RELEVANT SYSTEMS INCLUDING FUEL MEASUREMENT, FUEL MANAGEMENT AND TANK VENTING AS WELL AS FUEL TRANSFER.DEFUEL SUBSYSTEM FUNCTIONAL PROTOCOL IS DESIGNED AS WELL. SOME OF THE REFUEL PIPELINES AND BOOST PUMPS WERE EMPLOYED FOR DEFUEL APPLICATION. SEQUENCE OF TANK REFUELING AND DEFUELING WITH THEIR LIMITS WERE DISCUSSED AND ALSO SOME RELEVANT REGULATIONS (SPECIALLY FROM IRANIAN CIVIL AVIATION DERIVATIVES) WERE USED AND THEIR COMPLIANCE WERE CHECKED TO MAKE THE DESIGN ACCURATE.IN A BRIEF MANNER, TANK REFUELING STARTS FIRSTLY FROM THE WING TANK. FUEL IS DELIVERED TO THE OUTER WING TANK AND WHEN IT REACHES THE FULL CAPACITY, A SPILL PIPE PLACED AT THE TOP OF THE OUTER WING TANK TRANSFER THE FUEL TO THE INNER WING TANK AUTOMATICALLY. INNER WING TANK IS FILLED UP WHEN HIGH LEVEL SENSORS BECOMES WET AND FUEL MEASUREMENT AND MANAGEMENT SYSTEMS INVOLVED. THE DESIGN LAYOUT AND PROTOCOLS COMPLY ALL OF THE REFUEL AND DEFUEL REQUIREMENTS LIKE SOME OTHER COMMERCIAL AIRCRAFT DESIGN. FUNCTIONAL PROTOCOLS ALGORITHMS WHICH ARE REQUIRED FOR MANAGEMENT SYSTEM DESIGN WERE COMPLETELY DETERMINED FOR REFUEL AND DEFUEL SYSTEMS.

SQUARE AND CIRCULAR SECTIONED TUBES ARE ONE OF THE MOST COMMONLY USED STRUCTURAL ELEMENTS DUE TO THEIR PREVALENT OCCURRENCE AND EASY MANUFACTURABILITY. FOR EXAMPLE, SQUARE TUBES CAN DISSIPATE ELASTIC AND INELASTIC ENERGY THROUGH DIFFERENT MODES OF DEFORMATION. SUCH METHODS OF DEFORMATION INCLUDE LATERAL COMPRESSION, LATERAL INDENTATION, AXIAL CRUSHING, SPLITTING AND TUBE INVERSION. IN THIS PAPER, A COMPARATIVE EXPERIMENTAL STUDY ON THE LATERAL COMPRESSION OF SQUARE ALUMINUM AND COMPOSITE COLUMNS IS PRESENTED. THE ALUMINUM SPECIMENS WERE MADE OF AVAILABLE COMMERCIAL COLUMNS AND COMPOSITE SPECIMENS WERE FABRICATED FROM E-GLASS FIBERS AND EPOXY RESIN. THE ANGLES BETWEEN FIBERS AND TUBE AXIS WERE 30˚/-30˚. THE ENDS OF FABRICATED COLUMNS WERE CUT OUT TO ENSURE THAT THE COLUMNS ARE FREE FROM BURRS OR UNEVEN ENDS. THE FABRICATED COLUMNS WERE CUT OUT TO THE DESIRED LENGTH. THREE ALUMINUM SPECIMENS HAD 35 MM SIDE LENGTH AND THE OTHER ALUMINUM SPECIMENS HAD 45 MM SIDE LENGTH. ALSO, ALL OF THE COMPOSITE SPECIMENS HAD THE SAME SIDE LENGTH OF 60 MM. THE DEFORMATION MODES OF ALUMINUM AND COMPOSITE SPECIMENS AND THE EFFECTS OF DEFORMATION MODES ON THEIR ENERGY ABSORPTION CAPACITIES ARE INVESTIGATED AND COMPARED. ALSO, THE LOAD-DISPLACEMENT DIAGRAMS OF ALUMINUM AND COMPOSITE SPECIMENS ARE SKETCHED AND THE INFLUENCES OF DEFORMATION MODES ON THE CORRESPONDING LOAD-DISPLACEMENT DIAGRAMS ARE INVESTIGATED. MEANWHILE, LATERAL COMPRESSION TESTS WERE CARRIED ON SOME ALUMINUM AND COMPOSITE SQUARE COLUMNS WITH DIFFERENT GEOMETRIES. SIX ALUMINUM SPECIMENS AND FIVE COMPOSITE SPECIMENS WERE PREPARED AND COMPRESSED LATERALLY BETWEEN TWO RIGID PLATES IN A DMG MACHINE MODEL 7166 AND THE EXPERIMENTAL APPEARANCES OF THE TESTS ARE DISCUSSED.

THIS PAPER PRESENTS A NEW APPROACH TO IMPROVE THE PERFORMANCE OF MEMS CAPACITIVE ACCELEROMETER USING A METAL BLOCK IN THE PROOF MASS STRUCTURE. IN ADDITION, FOR THE DESIGN OF THE CAPACITIVE ACCELEROMETER IS FOCUSED ON THE SPRING GEOMETRY AND IS SHOWN THAT THE LENGTH OF LONG BEAM AND THICKNESS OF THE SERPENTINE SPRING ARE CRITICAL PARAMETERS WHICH SHOULD BE OPTIMIZED TO DECREASE THE SPRING CONSTANT IN THE SENSE DIRECTION AND INCREASE IT IN OTHER DIRECTIONS. THE FINITE ELEMENT METHOD SIMULATOR, ANSYS, IS USED TO FIND OPTIMUM DIMENSIONS AND TO PREDICT SPECIFICATIONS OF THE ACCELEROMETER. SENSITIVITY IS INCREASED FROM 42.853 TO 17.7 PF/G AND THE NOISE FLOOR IS DECREASED FROM 52.1 TO 21.9 MM/Ö`HZ BY ADDING THE CUPPER BLOCK IN THE PROOF MASS. THE RESONANCE FREQUENCY IS DROPPED FROM 36955 TO 23769 HZ, TOO.

IN THIS PAPER, THE EFFECTS OF VARIOUS PARAMETERS ON THE LIMIT DRAWING RATIO (LDR) IN DEEP DRAWING OF TWOLAYER (ALUMINUM-ST12) METALLIC SHEETS AND CHANGES ON PROCESS CONDITIONS WERE INVESTIGATED THROUGH A NUMERICAL SIMULATIONS AND EXPERIMENTS. THE PURPOSE OF THIS RESEARCH WAS TO OBTAIN MORE FORMABILITY IN DEEP DRAWING PROCESS. THE LDR HAS BEEN OBTAINED IN DEEP DRAWING OF TWO-LAYER METALLIC SHEETS, WITH ALUMINUM INNER LAYER WHICH WAS IN CONTACT WITH THE PUNCH AND STEEL OUTER LAYER WHICH WAS IN CONTACT WITH THE DIE, AND SIMULATION RESULTS DEMONSTRATED A GOOD AGREEMENT WITH EXPERIMENTAL TEST RESULTS. THE EFFECTS OF PARAMETERS SUCH AS THE THICKNESS OF EACH LAYER, VALUE OF DIE ARC RADIUS, FRICTION COEFFICIENT BETWEEN BLANK AND PUNCH AND FRICTION COEFFICIENT BETWEEN BLANK AND DIE ON THE LDR WERE INVESTIGATED. THE RESULTS INDICATED THAT THE LDR IS DEPENDENT ON MENTIONED PARAMETERS, SO THE LDR AND AS A RESULT THE TWO-LAYER METALLIC SHEET FORMABILITY CAN BE INCREASED BY IMPROVEMENT OF THESE FACTORS IN DEEP DRAWING PROCESS.

FUNCTIONALLY GRADED MATERIALS (FGMS) ARE MADE OF ADVANCED COMPOSITES IN WHICH THE MATERIAL PROPERTIES VARY CONTINUOUSLY AND SMOOTHLY IN A STRUCTURE. LASER BENDING IS AN ADVANCED PROCESS IN SHEET FORMING IN WHICH A LASER HEAT SOURCE IS USED TO SHAPE FGM PLATE. LASER FORMING OF FUNCTIONALLY GRADED METAL –METAL PLATES OFFERS THE ADVANTAGES OF REQUIRING NO EXTERNAL FORCES AND THUS REDUCES COST AND INCREASES FLEXIBILITY. FGM PLATE FORMING BY USING A MODERN LASER TECHNIQUE IS TAKEN INTO CONSIDERATION IN THIS PAPER. IT IS ASSUMED THAT THE MATERIAL PROPERTY OF EACH PLATE VARIES EXPONENTIALLY THROUGH THE THICKNESS. THIS PAPER PRESENTS A NUMERICAL MODEL TO ESTIMATE THE ANGLE BENT DURING THE LASER FORMING OF A FGM PLATE. FINITE ELEMENT (FE) SIMULATION IS PERFORMED WITH THE ABAQUS/CAE STANDARD SOFTWARE PACKAGE. THREE DIMENSIONAL NONLINEAR COUPLED THERMO-MECHANICAL SOLID ELEMENTS WITH EIGHT NODES C3D8T ARE USED FOR THERMAL AND STRUCTURE ANALYSIS. FOR THE ANALYSIS, THE SAME MESH MODEL IS USED. ACCORDING TO THE LAW OF THE CHANGE IN THE PROPERTIES OF FGM MATERIAL IN LINE WITH THE SHEET THICKNESS, THE SUBROUTINE FOR THE APPLICATION OF MATTER SPECIFICATIONS (VUMAT) IS USED TO DEFINE MATTER. BY USING FINITE ELEMENT SIMULATION, THE EFFECTS OF MOVEMENT SPEED, LASER DIAMETER AND LASER POWER ON THE VALUE OF THE FGM PLATE TRANSVERSE BENDING ANGLE ARE INVESTIGATED. BY COMPARING THE SIMULATION WITH ANALYTICAL FORMULAS, IT IS OBSERVED THAT THE FE RESULTS ARE IN GOOD AGREEMENT WITH THE ANALYTICAL RESULTS. PLASTIC DEFORMATION IS CONSIDERED DURING BOTH HEATING AND COOLING AND IS CALCULATED BASED ON A HISTORYDEPENDENT INCREMENTAL STRESS–STRAIN RELATIONSHIP. ON THE BASIS OF THE PROPOSED MODEL WITH KNOWN TEMPERATURE DISTRIBUTIONS, THE BENDING ANGLE INDUCED BY LASER CAN BE CALCULATED. COMPARISON OF THE PRESENT MODEL WITH ANALYTICAL DATA IS PROVIDED TO DEMONSTRATE THE ACCURACY OF THE PRESENT MODEL UNDER TGM.

THE STUDY OF VIBRATION OF CYLINDRICAL SHELLS IS VERY IMPORTANT. IN THIS PAPER, A STUDY ON THE VIBRATION CHARACTERISTICS OF THIN TO MODERATELY THICK CYLINDRICAL SHELLS IS PRESENTED AND THE EFFECTS OF DIFFERENT KINEMATIC RELATIONS AND INERTIA TERMS ARE INVESTIGATED. THEOBJECTIVE IS TO STUDY THE NATURAL FREQUENCIES OF THE CYLINDRICAL SHELLS. THE GOVERNING EQUATIONS ARE OBTAINED USING ENERGY APPROACH BASED ON THE FIRST ORDER SHEAR DEFORMATION THEORY (FSDT) OF SANDERS- KOITER. THESE EQUATIONS ARE SOLVED, FOR A SIMPLY SUPPORTED CYLINDRICAL SHELL, BY EMPLOYING GALERKIN' S PROCEDURE. RESULTS ARE PRESENTED ON THE FREQUENCY CHARACTERISTICS AND INFLUENCEOF DIFFERENT SHELL THEORIES. THE PRESENT ANALYSIS IS VALIDATED BYCOMPARING RESULTS WITH THOSE AVAILABLE IN THE LITERATURE.

HOVER PERFORMANCE OF A TWIN-ROTOR TEST MODEL IN TERMS OF ROTOR OVERLAP SWEEP, BLADE COLLECTIVE PITCH ANGLE, AND ROTOR ROTATIONAL SPEED WAS ESTIMATED. THE TEST MODEL CONSISTED TWO THREE-BLADED ROTORS WITH A DIAMETER OF 1220MM AND CONSTANT CHORD OF MM, GIVING A BLADE ASPECT RATIO OF 16.05. THE BLADES WERE RECTANGULAR PLANFORM WITH CROSS NACA0012 SECTIONS MADE OF COMPOSITE CARBON FIBER AND HAD NO TWIST OR TAPER. IN THIS MODEL, THE REAR ROTOR WAS FIXED ON THE FUSELAGE AND THE FRONT ROTOR COULD MOVE LONGITUDINALLY FOR TESTS UP TO 40% ROTOR OVERLAP SWEEP. THE TEST PLAN WAS PREPARED BASED ON CENTRAL COMPOSITE DESIGN (CCD) THAT WAS FOUND AS A LOW COST EXPERIMENTAL DESIGN METHOD. THE MATHEMATICAL EXPRESSIONS OF THRUST AND POWER REQUIRED SHOWED THAT OPTIMAL PERFORMANCE (I.E., MINIMUM POWER REQUIRED AT MAXIMUM THRUST) CAN BE OBTAINED FOR NON-OVERLAP ROTORS AT 11.5 COLLECTIVE PITCH AND RPM.

THE RELIABILITY OF SENSORS FUSION FOR EARTHQUAKE SATELLITE PREDICTION IS THE SUBJECT, WHICH WILL ESTIMATE IN THIS PAPER. USING DIFFERENT SENSORS IN THE SATELLITE AND FUSION OF THEIR INFORMATION WILL BE MORE HELPFUL FOR EARTHQUAKE PREDICTION. IN THIS PAPER DIFFERENT TYPES OF PASSIVE AND ACTIVE SENSORS WILL REVIEW AND THEN WITH USE OF FMECA ANALYSIS, RELIABILITY OF EACH SENSOR TYPE WILL CALCULATE AND FINALLY RELIABILITY OF SENSORS FUSION WILL ESTIMATE. DEPEND ON THE TYPE OF SATELLITE AND ITS MISSION; DIFFERENT SENSORS FUSION WILL BE USED. WITH THE RESULTS OF THIS PAPER, ONE CAN CHOOSE RELIABLE SENSORS FUSION ACCORDING TO ITS PROCEDURE FOR EARTHQUAKE PREDICTION WITH SATELLITE. THE RESULTS HAS SHOWN THAT USING PASSIVE MICROWAVE SENSORS WITH ACTIVE SYNTHETIC APERTURE RADAR IN EARTHQUAKE PREDICTION SATELLITE WILL GIVE THE BEST RELIABILITY AMONG OTHER SENSORS FUSION WITH RESPECT TO SATELLITE MISSION.

THE AUTHOR GIVES A REVIEW OF CRITERIA FOR THE ESTABLISHMENT OF ACTIVE ORBITAL SPACECRAFT, TAKING INTO ACCOUNT THE ANALYSIS OF ASPECTS OF THE APPLICATION OF THE PROPULSION SYSTEM RUNNING ON HYDROGEN PEROXIDE AND THE POSSIBILITY OF HIS RETURN TO THE EARTH SURFACE.AS A RESULT, PROPOSED THE CONCEPT OF CREATING A MODERN TYPE OF SPACECRAFT - MANEUVERING IN ORBIT RETURNING UNMANNED ORBITER IN THE EMBODIMENT OF THE SATELLITE REMOTE SENSING (SRS). IN A PAPER REFLECTS THE RESULTS OF OPTIMIZING THE DESIGN OF THE LAUNCH VEHICLE (LV). ARTICLE EXAMINES THE PRECEDING SCHEMATIC DESIGN ELEMENTS OF SPACE ROCKET COMPLEX. IN PARTICULAR, THE ELEMENTS OF LV, ORBITER, AND THEIR PROPULSION SYSTEMS.CARRIED INITIAL CALCULATIONS AERODYNAMIC PARAMETERS OF ORBITER ON THE DESCENT AND MANEUVERING IN LOW ORBIT.

IN THIS PAPER, ANALYTICAL SOLUTIONS OF A CLASS OF OPTIMAL LINE-OF-SIGHT (LOS) GUIDANCE LAWS ARE DERIVED FOR MOVING TARGETS USING LINEARIZED MODEL. THE PURSUER CONTROL DYNAMICS IS ASSUMED TO BE PERFECT AND THE MANEUVERING ACCELERATION IS APPLIED NORMAL TO LOS. THE CLOSED-LOOP OPTIMAL SOLUTIONS ARE OBTAINED FOR FOUR DIFFERENT FINAL CONDITIONS, I.E., FIXED OR FREE FINAL POSITION AND NORMAL VELOCITY. THE FINAL ANGLE CONSTRAINT MAY BE APPLIED BY THE FINAL NORMAL VELOCITY.

THIS ARTICLE DISCUSSES THE DETAILS AND CONSTRUCTIONS OF NOVEL BIO-PAYLOAD AND PHOTO CAPTURING CANSAT STRUCTURESWHICH HAVE BETTER EFFICIENCY INTHEIR SUBSYSTEMS SPECIALLYIN ELECTRICAL AND COMMUNICATIONAL SUBSYSTEMS. FOR IMPLEMENTING THIS SYSTEM DESIGNING, THESE CANSATS HAVE LIMITATIONS ON SIZE AND WEIGHT WHICH BIO-PAYLOAD CANSAT AND PHOTO CAPTURING CANSAT MUST BE UNDER 1.08 KG AND 0.35 KG IN WEIGHT, UNDER 66 AND 100 MM IN DIAGONALAND ALSO UNDER 115 AND 340 MM IN HEIGHT RESPECTIVELY. THUS THE SYSTEM IS SO SMALL AND NEEDS TO BEDESIGNED WELL TO PROVIDE SUBSYSTEMS CONDITIONS. IN THIS PAPER OPTIMUM CONSTRUCTION, CANCELLING AND PREVENTING FROM OCCURRING NOISES, COMMUNICATIONAL SUBSYSTEM AND ITS COMPONENTS, NOVEL BATTERY PLACEMENT AND NOVEL GRAPHICAL USER INTERFACE (GUI) WHICH IS THE HEART OF EARTH CONTROL STATION DESIGNED FOR BIO-PAYLOAD CANSAT, WILL BE DISCUSSED IN DETAILS. FIRST OF ALL WE DESCRIBE THE STRUCTURE WHICH HAS INNOVATIVE MODEL ON PREVENTING NOISES IN ELECTRICAL AND COMMUNICATIONAL SYSTEMSBY GIVING THEM THE APPROPRIATE PLACEMENT AND ALSO USING SHIELDING IN ELECTRICAL CIRCUITS SPECIALLY TO PREVENT FROM FLICKER AND THERMAL NOISES WHICH HAVE PROFOUND EFFECTS ON PCBS TRACKS, THEN IT IS DESCRIBED THE DIFFERENT COMMUNICATION SUBSYSTEMSECTIONS SUCH ASTRANSCEIVER MODULES, DATA ACQUISITION BOARD ANDEARTH STATIONWHICH ONE OF THE MOST IMPORTANT OF ITS DUTY IS ANALYZING AND CATEGORIZING EACH RECEIVING DATA FRAME.THESE NOVEL METHODS ANDFUNCTIONALITIESWERE USED TO MAKE DATA TRANSMITTING MORE ACCURATE AND SAFETY TO BE A SUCCESSFUL MODELTHAT CAN BE USED FOR CONSTRUCTING NEW AND DIFFERENT AEROSPACE SYSTEMS. ALSO THESE CANSATSSHOWS THEIRFABULOUS FUNCTIONALITY IN ACHIEVING FIRST AND THIRD RANKS IN THE FOURTH IRANIAN CANSATCOMPETITION.

THIS ARTICLE AIMS TO SHED LIGHT ON, FIRST, WHAT IS THE MISSILE TECHNOLOGY CONTROL REGIME (MTCR) AND THEN IT EXPLAINS HOW ITS GUIDELINES WORK AND IMPACT THE TARGETED COUNTRIES. THE PAPER CONTINUES THEN TO DISCUSS THE EXPECTED IMPACT OF EXPORT CONTROLS, PARTICULARLY THE MTCR, ON TARGET COUNTRIES, AND THEN IT ANALYZES THE INDIA’S SPACE TECHNOLOGY DEVELOPMENT PROCESS TO DETERMINE THE EXTENT TO WHICH THE EXPORT CONTROLS HAD INFLUENCED TECHNOLOGY DEVELOPMENT POLICIES IN THIS COUNTRY SPACE PROGRAM. IT CONCLUDES THAT INSTEAD OF SLOWING DOWN OR STOPPING TECHNOLOGY ACCUMULATION, THE CONTROLS ACTUALLY INCREASED ITS PACE OF THE SPACE PROGRAM SINCE IT BECAME MORE EXPLICITLY PLANNED AND ACCELERATED UNDER THE PRESSURES OF EXPORT CONTROLS.

THIS PAPER EXAMINES THE PROBLEM OF ROCKET TRAJECTORY UNCERTAINTY DUE TO UNCERTAIN THRUST OF THE ROCKET IN THE SIMPLE FORM. SO FAR, BEEN LESS ATTENTION TO THIS ISSUE.THE GOAL IS TO FIND A WAY TO CORRECT THE ROCKET TRAJECTORY IN THE PRESENCE OF THRUST UNCERTAINTY IN THE LAUNCH PHASE. FIRST, THE SIMULATION OF ROCKET MOTION IN TWO DIMENSIONS IS PERFORMED. THEN THE EFFECTS OF THRUST CHANGES ARE EXAMINED. IT ASSUMED THAT THE ONLY CONTROLLING FACTOR, IS THE PITCH ANGLE OF THE ROCKET. TO COMPUTE THE CORRECT PITCH ANGLES FOR VARIOUS UNCERTAINTIES AT THE START OF MIDCOURSE PHASE, RANGE ERROR FUNCTION IS DEFINED. THE ROOTS OF THIS FUNCTION IS CALCULATED BY USING BISECTION METHOD. AFTER OBTAINING THE CORRECT PITCH ANGLES, A TWO-LAYER FEED FORWARD NEURAL NETWORK IS DESIGNED. THE INPUTS OF THIS NETWORK ARE RANGE, HEIGHT, VELOCITY AND INCORRECT PITCH ANGLE OF THE ROCKET IN THE BEGINNING OF MIDCOURSE PHASE, AND THE OUTPUT IS THE CORRECT PITCH ANGLE. FINALLY, MATHEMATICAL FUNCTION OF DESIGNING NETWORK BE EXTRACTED. SIMULATION RESULTS SHOW THE EFFECTIVENESS OF THE PROPOSED METHOD.

FORMING LIMIT CURVE (FLC) IS A SUITABLE METHOD TO DETERMINE THE FORMABILITY OF METALLIC SHEETS IN SHEET METAL FORMING OPERATIONS. THE AIM OF THIS RESEARCH IS TO PRESENT A SIMULATION-BASED APPROACH FOR PREDICTION OF THE FORMING LIMIT CURVE IN TWO-LAYER METALLIC SHEETS. IN THIS PAPER, THE FORMABILITY OF TWO-LAYER (AL3004- ST12) METALLIC SHEETS, WITH ALUMINUM INNER LAYER WHICH WAS IN CONTACT WITH THE PUNCH AND STEEL OUTER LAYER WHICH WAS IN CONTACT WITH THE DIE WERE NUMERICALLY INVESTIGATED. TWO DIFFERENT CRITERIA, INCLUDING THE ACCELERATION (I.E. THE SECOND TIME DERIVATIVES) OF THICKNESS AND MAJOR STRAIN EXTRACTED FROM THE STRAIN HISTORY INFORMATION OF FE SOFTWARE, WERE APPLIED TO ACCURATELY DETERMINE THE START OF LOCALIZED NECKING IN FORMING LIMIT CURVES. THIS IS TO SAY THAT THE LOCALIZED NECKING WILL BE STARTED WHEN THE ACCELERATION OF THE THICKNESS OR MAJOR STRAIN GETS ITS MAXIMUM VALUE. THE PUBLISHED EXPERIMENTAL INFORMATION FOR AL/ST TWO-LAYER METALLIC SHEETS HAD BEEN USED TO EVALUATE THE SIMULATION RESULTS. IT WAS SHOWN THAT THE PRESENTED METHODS WERE IN GOOD AGREEMENT WITH THE EXPERIMENTALLY OBSERVED DATA. USING THE PRESENTED METHODS, THE INFLUENCES OF SOME PROCESS PARAMETERS ON THE FLC WERE INVESTIGATED. IT WAS SHOWN THAT PROCESS PARAMETERS SUCH AS, THICKNESS OF EACH LAYER, FRICTION COEFFICIENT BETWEEN BLANK AND PUNCH, FRICTION COEFFICIENT BETWEEN BLANK AND DIE/BLANK HOLDER AND LAY-UP HAD SIGNIFICANT INFLUENCE ON THE FLC OF TWO-LAYER METALLIC SHEETS. THE RESULTS ILLUSTRATED THAT THE FLC IS DEPENDENT ON MENTIONED PARAMETERS, SO THE TWO-LAYER METALLIC SHEET FORMABILITY CAN BE INCREASED BY IMPROVEMENT OF THESE FACTORS IN FORMING LIMIT TESTS.

THE METALLIC FOAMS HAVE FOUND WIDE APPLICATIONS IN INDUSTRY DUE TO THEIR USEFUL PROPERTIES SUCH AS LOW DENSITY, HIGH HARDNESS, THERMAL AND ACOUSTIC INSULATION AND HIGH PERMEABILITY TO GAS. THESE MATERIALS ARE USED FOR THE PRODUCTION OF LIGHT WEIGHT STRUCTURES BECAUSE OF THE LOW DENSITY. DUE TO THEIR HIGH ENERGY ABSORPTION PROPERTIES OF POROUS MATERIALS IN COMPRESSION STRESS, METALIC FOAMS CAN BE SUBSTITUTE WITH PREVIOUS STRUCTURE HAVE BEEN USED BEFORE. THE MAJOR APPLICATIONS OF POROUS MATERIALS ARE IN AEROSPACE AND AUTOMOTIVE INDUSTRIES. FOAMS ARE WIDELY USED IN INDUSTRY SO PREDICTION OF THEIR BEHAVIOUR IS VERY IMPORTANT. IN RECENT YEARS, EXTENSIVE RESEARCHES HAVE BEEN DONE ON THE BEHAVIOUR OF THESE MATERIALS AND SO FAR SEVERAL CONSTITUTIVE EQUATIONS ARE PRESENTED FOR FOAMS. THERE ARE TWO TYPES OF WORK HARDENING: ISOTROPIC HARDENING AND KINEMATIC HARDENING. A NEW CONSTITUTIVE EQUATION FOR ISOTROPIC HARDENING FOAM IS PROVIDED IN THIS STUDY WHICH INCLUDES 3 PARAMETERS.THESE EQUATIONS ARE INTEGRATED USING RETURN MAPPING ALGORITHM AND DEVELOPED IN MATLAB. THEN COEFFICIENTS OF THIS EQUATION ARE OPTIMIZED USING GENETIC ALGORITHM AND THE EXPERIMENTAL AND NUMERICAL RESULTS HAVE BEEN COMPARED. FOUR TYPES OF ALUMINUM FOAMS HAVE BEEN STUDIED IN THIS INVESTIGATION INCLUDING ALPORAS, FOAMINAL, ALULIGHT AND CYMAT THAT ARE COMMERCIALLY AVAILABLE. COMPARISON BETWEEN NUMERICAL RESULTS AND EXPERIMENTAL DATA SHOWS THAT THIS NEW EQUATION IS ABLE TO PREDICT THE BEHAVIOUR OF FOAMS WITH ACCEPTABLE ACCURACY AND THERE IS GOOD AGREEMENT BETWEEN NUMERICAL AND EXPERIMENTAL CURVES.

THE RAREFIED GAS FLOW THROUGH DIVERGENT MICRO/NANO CHANNELS IS NUMERICALLY STUDIED USING A PARTICLE-BASED METHOD, DIRECT SIMULATION MONTE-CARLO (DSMC). SIMPLIFIED BERNOULLI-TRIALS (SBT) COLLISION SCHEME IS EMPLOYED AS COLLISION PARTNER SELECTION METHOD. THE SIMULATIONS ARE PERFORMED FOR NITROGEN GAS FLOWING THROUGH DIVERGENT NANOCHANNELS WITH VARIOUS DIVERGENCE ANGLES (0O, 4O, 8O, 12O AND 16O). THE KNUDSEN NUMBER FALLS IN THE SLIP AND EARLY-TRANSITION REGIMES (0.03£KNI £0.2) AND INLET-TO-OUTLET PRESSURE RATIO IS SET TO THREE. THE CENTERLINE PRESSURE AND MACH NUMBER DISTRIBUTIONS ARE PROVIDED FOR VARIOUS KNUDSEN NUMBERS AND DIVERGENCE ANGLES. ADDITIONALLY, THE CONTOURS OF PRESSURE AND MACH NUMBER ARE PRESENTED FOR DIFFERENT DIVERGENCE ANGLES. THE RESULTS INDICATE THAT THE RAREFICATION EFFECTS AND CENTERLINE AND SLIP VELOCITY INCREASE BY INCREASING THE DIVERGENT ANGLE; WHILE, THE CENTERLINE PRESSURE DECREASES BY AN INCREASE IN DIVERGENCE ANGLE. IT IS FOUND THAT THERE IS NO REVERSAL FLOW FOR RAREFIED GAS FLOW THROUGH DIVERGENT MICRO/NANOCHANNELS. THESE RESULTS ON RAREFIED GASEOUS FLOW THROUGH DIVERGENT NANOCHANNELS ARE CONSIDERABLY DIFFERENT THAN THEIR CONTINUUM COUNTERPARTS.

SOME THIN-WALLED STRUCTURES SUCH AS FRUSTA, DOME, EGGBOX AND CONES ARE WIDELY USED IN THE AEROSPACE APPLICATIONS. THIS ARTICLE REPRESENTS A NOVEL ENERGY ABSORBER WITH QUASI-CUP GEOMETRY UNDER THE QUASISTATIC AXIAL COMPRESSION LOADING BETWEEN TWO RIGID PLATENS BY THE EXPERIMENTAL METHOD. FOR THIS PROPOSE, SOME QUASI-CUP SPECIMENS, THAT HAVE BEEN PRODUCED BY SHAPING THE CIRCULAR BLANKS WITH TEFLON-PAD FORMING, WERE USED IN THE IN THE AXIAL COMPRESSION TESTS. THE QUASI-CUP SPECIMENS WERE PREPARED WITH DIFFERENT APEX ANGLES, THICKNESS AND MATERIAL PROPERTIES TO INVESTIGATE INFLUENCES OF THE MENTIONED PARAMETERS ON THE ENERGY ABSORPTION PROCESS. DIAGRAMS OF AXIAL LOAD-DISPLACEMENT AND ABSORBED ENERGY-DISPLACEMENT OF EACH SAMPLE ARE SKETCHED AND ITS SPECIFIC ABSORBED ENERGY IS OBTAINED BY CALCULATING THE RATIO OF TOTAL ABSORBED ENERGY PER MASS OF THE STRUCTURE. THE EXPERIMENTAL RESULTS SHOW THAT WHEN A QUASI-CUP SPECIMEN IS FILLED BY THE POLYURETHANE FOAM WITH DENSITY OF 50 KG/M3 AND PLATEAU STRESS OF 0.26 MPA, SPECIFIC ABSORBED ENERGY BY THE SPECIMENS INCREASES. ALSO, THE TESTS DEMONSTRATE THAT BY ENHANCING THE APEX ANGLE OF THE QUASI-CUP SPECIMENS, ULTIMATE DISPLACEMENT REDUCES AND AXIAL LOAD ENHANCES. EXPERIMENTS INDICATE THAT THERE IS AN OPTIMUM VALUE FOR APEX ANGLE AND A QUASI-CUP SPECIMEN WITH THE OPTIMUM APEX ANGLE HAS THE HIGHEST SPECIFIC ABSORBED ENERGY, IN COMPARISON WITH THE OTHER ONES. FURTHERMORE, EXPERIMENTAL MEASUREMENTS SHOW THAT WHEN THICKNESS OF THE QUASI-CUP SPECIMENS INCREASES, SPECIFIC ABSORBED ENERGY BY THE SAMPLES INCREASES, TOO. TOTALLY, THE CURRENT RESEARCH WORK INTRODUCES A QUASI-CUP SPECIMEN WITH APEX ANGLE OF 90O IN THICK-WALLED CONDITION AND WITH THE POLYURETHANE FOAM-FILLER AS A SUITABLE ENERGY ABSORBER STRUCTURE.

THE PRESENT STUDY IS BASED ON A RECENT VARIATIONAL MECHANICS ANALYSIS OF MICROCRACKING DAMAGE, IN ANGLE-PLY LAMINATES OF THE TYPE [Q(2) M /Q(1)N] S. IN THIS RESEARCH, THE EFFECTS OF DELAMINATIONS COMING FROM THE TIPS OF MICROCRACKS IN THE MIDDLE SUBLAMINATES ARE CONSIDERED FOR PREDICTING THE CRITICAL DENSITIES TO UNDERSTAND WHICH MODE OF DAMAGES IS MORE POSSIBLE IN VARIOUS LAY-UPS FOR TRANSVERSELY CRACKS. NORMAL BOUNDARY AND TRACTION CONTINUITY CONDITIONS HAVE BEEN USED IN CALCULATING THE STRESS ENERGY DENSITY. AFTER DERIVING A VERY GOOD APPROXIMATION FOR THE PRINCIPLE OF MINIMUM COMPLEMENTARY ENERGY WITH CONSIDERING COMPLEX EQUATIONS, THE STRESS FIELDS ARE PROVIDED. IT WILL BE SHOWN THAT PERTURBATION STRESSES HAVE A SIGNIFICANT EFFECT ON THE ENERGY RELEASE RATE FOR FORMATION OF MICROCRACKING AND INDUCE DELAMINATION.IN THIS ANALYSIS, A UNIT CELL IN THE PLY LEVEL OF COMPOSITE LAMINATE CONTAINING BOTH TRANSVERSE CRACKING AND DELAMINATION IS CONSIDERED. THEN THE VALUES OF THE ADMISSIBLE STRESSES AND COMPLIANCE OF CRACKED LAMINATE ARE USED FOR EVALUATING THE ENERGY RELEASE RATE OF MICROCRACKING AND INDUCED DELAMINATION. EVENTUALLY THE GRAPHS FOR DIFFERENT LAYUPS IN SUCH SYMMETRIC LAMINATE HAS BEEN DRAWN WHICH SHOW TOO MUCH IMPORTANT POINTS FOR DESIGNERS IN PRACTICAL APPLICATIONS. THE OBTAINED RESULTS HAVE BEEN COMPARED WITH FINITE ELEMENT METHOD IN ABAQUS SOFTWARE. IT CAN BE EMPHASIZED THAT THE CURRENT APPROACH OPENS A NEW PROSPECT FOR PERCEIVING OF THE COMPOSITES’ STRUCTURAL BEHAVIOR IN A VULNERABLE POSITION...

THIS WORK IS CONCERNED WITH THE COMPUTATION OF TWOSIDED LID-DRIVEN SQUARE CAVITY FLOWS BY THE LATTICE BOLTZMANN METHOD (LBM) TO OBTAIN MULTIPLE STABLE SOLUTIONS. THE VELOCITY FIELD IS SOLVED BY AN INCOMPRESSIBLE GENERALIZED LATTICE BOLTZMANN METHOD. IN THE TWO-SIDED SQUARE CAVITY TWO OF THE WALLS MOVE WITH EQUAL VELOCITY MOVE IN SUCH A WAY THAT PARALLEL WALLS MOVE IN OPPOSITE DIRECTIONS WITH THE SAME VELOCITY. CONVENTIONAL NUMERICAL SOLUTIONS SHOW THAT THE SYMMETRIC SOLUTIONS EXIST FOR ALL REYNOLDS NUMBERS FOR ALL THE GEOMETRIES, WHEREAS MULTIPLICITY OF STABLE STATES EXIST ONLY ABOVE CERTAIN CRITICAL REYNOLDS NUMBERS. HERE WE DEMONSTRATE THAT LATTICE BOLTZMANN METHOD CAN BE EFFECTIVELY USED TO CAPTURE MULTIPLE STEADY SOLUTIONS FOR ALL THE AFORESAID GEOMETRIES. THE STRATEGY EMPLOYED TO OBTAIN THESE SOLUTIONS IS ALSO DESCRIBED. AT LOW REYNOLDS NUMBERS, THE RESULTING FLOW FIELD IS SYMMETRIC WITH RESPECT TO ONE OF THE CAVITY DIAGONALS FOR THE TWO-SIDED DRIVEN CAVITY, WHILE IT IS SYMMETRIC WITH RESPECT TO BOTH CAVITY DIAGONALS FOR THE FOUR-SIDED DRIVEN CAVITY. IT IS FOUND THAT FOR PARALLEL MOTION OF THE WALLS, THERE APPEARS A PAIR OF COUNTER-ROTATING SECONDARY VORTICES OF EQUAL SIZE NEAR THE CENTER OF A WALL. BECAUSE OF SYMMETRY, THIS PAIR OF COUNTER-ROTATING VORTICES HAS SIMILAR SHAPES AND THEIR DETAILED STUDY AS TO HOW THEY GROW WITH INCREASING REYNOLDS NUMBER HAS NOT YET BEEN MADE BY LATTICE BOLTZMANN METHOD.

SIMULATION OF VORTEX STRUCTURES AND STUDYING THEIR EFFECTS ON THE PERFORMANCE FACTORS, IS ONE OF THE MOST DEMANDING STAGES IN THE AERODYNAMIC DESIGN OF FLIGHT VEHICLES. THESE CHAOTIC FLOW PATTERNS ARE MORE IMPORTANT FOR HIGH MANEUVER DELTA WING AIRCRAFTS WHERE THE HIGH ATTACK ANGLES ARE UNAVOIDABLE. IN SUCH CONDITIONS A LONGITUDINAL VORTEX IS ALWAYS OBSERVED ON TOP OF THE LEADING EDGE AND PLAYS A VERY IMPORTANT ROLE IN AERODYNAMIC PERFORMANCE SHIFTS AND STABILITY OF FLIGHT VEHICLE. IN THIS PAPER, THE RESULTS OF HIGHLY ACCURATE THREE DIMENSIONAL NUMERICAL SIMULATION OF CROPPED DELTA WING FOR INVESTIGATING THE VORTEX BEHAVIOR, HAS BEEN PRESENTED. FOR THIS STUDY THE NAVIER-STOCKS EQUATIONS HAVE BEEN SOLVED BY 24 COMPUTATIONAL NODES OF CLUSTER COMPUTER, IN A 3D STRUCTURAL GRID DOMAINS.

AIRCRAFT FUEL SYSTEMS ARE COMPLEX SYSTEMS ANDTHE FUEL AS AN IMPORTANT PART OF THE SYSTEM NEEDS SOME SAFE SUBSYSTEMS IN ORDER TO MAINTAIN THE FUEL PRESSURE AND OXYGEN PERCENTAGE IN THE SAFE RANGE. THE PRESSURE AND FLAMMABILITY OF FUEL MAY CAUSE DANGEROUS SITUATION FOR AN AIRCRAFT. THE STRUCTURAL LIMITS OF THE FUEL TANKS MAKES THE DESIGNER TO PREPARE SOME FACILITIES TO LEVEL VAPOR FUEL PRESSURE IN THE TANKS, THIS IS DONE BY VENTING SYSTEM. FURTHERMORE THE FUEL FLAMMABILITYOBLIGATES THE DESIGNER TO LEVEL OXYGEN PERCENTAGE VIA VENTING AND INERTING. IN ORDER TO DESIGN A SAFE AND RELIABLE FUEL SYSTEM, THERE SHOULD BE FACILITIES PREVENTING ANY DIFFERENTIAL PRESSURE AND IGNITION IN THE FUEL SYSTEM AND TANKS. THE PRESSURE BETWEEN THE TANKS AND EACH TANK WITH ATMOSPHERE IS ADJUSTED VIA VENTING SYSTEM. THE VENTING IS DONE BY TRANSFERRING FUEL VAPOR TO THE SURGE TANKS WHICH ARE RELATED TO ATMOSPHERE THROUGH NACA DUCT. IN SOME PHASES SUCH AS CRUISE, AN OPEN VENTING SYSTEM CAN MAINTAIN OXYGEN PERCENTAGE IN THE FUEL VAPOR IN A SAFE MARGIN IN ORDER TO PREVENT IGNITION IN THE TANKS, YET IT IS NOT SATISFIED IN ALL PHASES OF FLIGHT. A NOBLE SYSTEM PRESENTED FOR THIS AIM IS INERTING SYSTEM IN WHICH BY REDUCING AND CONTROLLING OXYGEN PERCENTAGE IN A TANK, ANY FLAME POSSIBILITY IS PROHIBITED. THE INERTING SYSTEM CONTROLS THE FUEL VAPOR OXYGEN PERCENTAGE. THIS IS DONE BY DISCHARGING NITROGEN ENRICHED AIR IN THE FUEL TANKS. IN THIS PAPER IT IS TRIED TO DESCRIBE THE ROLE AND IMPORTANCE OF THESE SYSTEM AND STANDARDS LEAD TO UTILIZING THESE SYSTEMS IN A CIVIL AIRCRAFT FUEL SYSTEM. ALSO IT IS TRIED TO PRESENT THE FUEL SYSTEM DESIGNED BY THE WRITERS USING VENTING AND INERTING IN THE TANKS.

IN THIS PAPER, FREE VIBRATION ANALYSIS OF A STEPPED TIMOSHENKO SHAFT WITH NEGLIGIBLE DAMPING IS INVESTIGATED BY MEANS OF THE FINITE ELEMENT METHOD IN BOTH UNIFORM AND NON-UNIFORM STATUS. NON-UNIFORMITY IS ASSUMED TO BE IN CROSS SECTIONAL AREA OF THE SHAFT WHERE THE MIDDLE PART OF THE STEPPED SHAFT IS IN CONICAL FORM. THE TIMOSHENKO BEAM ELEMENT WITH LINEAR SHAPE FUNCTIONS WAS USED FOR THE FINITE ELEMENT MODELING OF THE SHAFT. ASSEMBLING OF MASS AND STIFFNESS MATRICES, EQUATION OF MOTION DERIVATION AND EIGENVALUE SOLUTION WERE PERFORMED BY USE OF MATLAB SOFTWARE. NATURAL FREQUENCIES OF THE SHAFT WERE CALCULATED AND THEIR CORRESPONDING MODE SHAPES WERE PLOTTED FOR TWO BOUNDARY CONDITIONS NAMELY CLAMPED AND SIMPLY SUPPORTED. THE DIFFERENCE BETWEEN NATURAL FREQUENCIES OBTAINED FROM THE TIMOSHENKO MODEL WERE COMPARED WITH THOSE FROM CLASSICAL BERNOULLI-EULER THEORY AND THE EFFECTS OF ROTARY INERTIA AND SHEAR DEFORMATION ON THE MAGNITUDES OF CALCULATED NATURAL FREQUENCIES WERE STUDIED. IT HAS BEEN OBSERVED THAT UNIFORM STEPPED SHAFTS ARE STIFFER THAN NON-UNIFORM STEPPED ONES FOR EQUAL AMOUNT OF MASS, SINCE THEIR FREQUENCY PARAMETER IS HIGHER. ADDITIONALLY, IT BECAME EVIDENT THAT THE EFFECTS OF TRANSVERSE SHEAR AND ROTARY INERTIA WILL BE MUCH MORE PRONOUNCED AS THE MODE NUMBER INCREASES.

THE PRESENT STUDY REPRESENTS THE INFLUENCE OF MULTIWALLED CARBON NANOTUBES FUNCTIONALIZED WITH CARBOXYL GROUPS (MWCNT-COOH) ON FLEXURAL BEHAVIOR OF CARBON FIBER REINFORCED POLYMER (CFRP) GRID COMPOSITE STRUCTURES WITH ANISOGRID LATTICE PATTERNED REINFORCEMENT FORMED BY HELICAL AND LONGITUDINAL RIBS. THREE-POINT BENDING TEST HAS BEEN CARRIED OUT USING HOUNSFIELD TESTING MACHINE. THE EPOXY/MWCNT NANOCOMPOSITES WITH DIFFERENT CARBON NANOTUBES CONTENT (0, 0.1 AND 0.4 WT.% OF MWCNT) WERE USED AS THE MATRIX OF GRID COMPOSITE STRUCTURES. THE RESULTS OF FLEXURAL TEST DEMONSTRATE THAT THE MAXIMUM FLEXURAL LOAD AND ENERGY ABSORPTION OF GRID SAMPLES INCREASE FROM 0% TO 0.4% WITH INCREASING THE NANOTUBE CONTENT. MAXIMUM VALUE OF IMPROVEMENT IN MAXIMUM FLEXURAL LOAD AND ENERGY ABSORPTION ARE 20% AND 35% FOR THE SAMPLES WITH 0.4 WT.% OF MWCNTS.

THIS PAPER PROPOSES A METHOD TO GENERATE A UNIFORM FLIGHT PATH FOR SURVEILLANCE OF A REGION, USING THE LIMIT CYCLE CONCEPT. THE PROPOSED METHOD IS BASED ON THE LIMIT CYCLE CHARACTERISTIC OF SECOND ORDER NONLINEAR SYSTEMS FOR REAL-TIME FLIGHT PATH PLANNING FOR UAVS. THE GENERATED FLIGHT PATH COVERS WHOLE AREA OF A CIRCLE WITH ARBITRARY RADIUS AND DENSITY OF THE TRAJECTORIES. UAVS BY TRACKING SUCH TRAJECTORIES ARE ABLE TO GET THE PRECISE AERIAL PHOTOS OR MOVIES (OR ANOTHER TASK WHICH NEEDS SUCH A TRAJECTORY). THE PROPOSED REAL-TIME FLIGHT PATH IS DIVIDED TO THREE MAIN PHASES; IN THE FIRST PHASE, THE UAV TAKES OFF FROM THE LAUNCH STATION AND MOVES TO THE NEAR OF THE CENTER OF THE CONSIDERED CIRCULAR SIGHTLY AREA FOR GETTING THE AERIAL PHOTOS OR MOVIES. THIS PHASE IS ALSO DONE BASED ON THE LIMIT CYCLE NAVIGATION METHOD TO GENERATE THE SAFE TRAJECTORY AGAINST THE OBSTACLES (OBSTACLE AVOIDANCE USING LIMIT CYCLE NAVIGATION). IN THE SECOND PHASE, THE FLYING OBJECT TRACKS A UNIFORM HELICOIDAL TRAJECTORY TO REACH THE CIRCULAR LIMIT CYCLE, TO SCAN A CIRCULAR SIGHTLY AREA, COMPLETELY. IN THE LAST PHASE, WHEN THE SCANNING OF THE SIGHTLY AREA HAS BEEN ACCOMPLISHED, THE UAV COMES BACK TO THE LAUNCH STATION ON THE TRAJECTORY THAT PRODUCED BY A SIMILAR PROCEDURE OF THE FIRST PHASE. FINALLY, SOME SIMULATIONS ARE CARRIED OUT TO SHOW THE FLIGHT PATH GENERATED BY THIS IDEA.

THE REDUCTION OF WEIGHT IS AN IMPORTANT ISSUE THAT ALL OF DESIGNERS HAVE A NOTICEABLE FOCUS ON THAT.IN THIS PAPER WE HAVE DETERMINED THE EFFECT OF OTHER ALLOYS IN AIRPLANES STRUCTURE AS ONE OF THE MOST EFFECTIVE WAYS OF REDUCING THE AIRPLANES WEIGHT.THE MOST FOCUSED THING IN HERE IS THAT, WITCH PART OF AIRPLANE IS GOING TO BE MADE BY OTHER ALLOYS.FOR EXAMPLE IF WE USE COMPOSITE IN WING OF A80.66 TON TRANSPORT JET INSTEAD OF AL, THE REDUCTION OF WEIGHT WOULD MAKE ITS WEIGHT ABOUT 75.9 TON. OTHER SYNTAXES ARE CALCULATE AS THE RESULT. BUT WE CAN NOT CALCULATE THESE NUMBERS FOR ALL AIRPLANES. SO ALL OF THE RESULTS OF WEIGHT REDUCTIONS ARE CALCULATED FOR A 80.66 TON TRANSPORT JET THAT IS DESIGNED FOR BRINGING ABOUT 186 PASSENGERS TO THE RANGE OF 4000 KM. SINCE THIS KIND OF AIRPLANE IS ONE OF THE MOST PRODUCED NUMBER IN TRANSPORT JETS (FOR EXAMPLE A320), IT CAN GIVE A GOOD PREVIEW TO THE DESIGNERS OF THESE KIND OF AIRPLANE, TO SELECT THE TYPE OF ALLOY AND THE TYPE OF SYNTAX THAT THIS ALLOY WOULD BE USED. BUT THE SPEED OF CALCULATIONS IN THE FIRST STEP OF AIRPLANE DESIGN IS IMPORTANT, TOO.SO WE OUR METHOD OF CALCULATING IS AS SHORT AS IT CAN BE.

IN THIS PAPER, THE FINITE ELEMENT METHOD (FEM) IS USED TO STUDY THE DELAMINATION GROWTH AND POST BUCKLING OF COMPOSITE LAMINATES CONTAINING EMBEDDED DELAMINATION UNDER THE COMPRESSIVE LOADING. DELAMINATION DECREASES AN ELASTIC BUCKLING LOAD OF THE COMPOSITE STRUCTURES AND LEADS UNEXPECTED STRUCTURAL FAILURE AT LOADS BELOW THE DESIGN LEVEL. THE INVESTIGATED COMPOSITE LAMINATES WHICH ARE MADE OF CARBON FIBER/EPOXY HAVE THE STACKING SEQUENCE OF [90/ (0/90) 3// (0/90) 14] CONTAINING A CIRCULAR AS WELL AS SQUARE DELAMINATION. THE SYMBOL // ILLUSTRATES THE POSITION OF DELAMINATION IN THE LAMINATE. FOR MODELING AND ANALYSIS THE LAMINATE, THE THREE-DIMENSIONAL CONTINUUM SHELL ELEMENTS HAVE BEEN USED VIA THE ABAQUS 6.12 SOFTWARE. FURTHERMORE, THE SURFACEBASED COHESIVE BEHAVIOR IS UTILIZED TO SIMULATE COHESIVE ZONE MODEL (CZM) WHICH IS APPLIED FOR DAMAGE PROPAGATION. IN ADDITION, THE SURFACE TO SURFACE CONTACT HAS BEEN APPLIED IN THE DELAMINATION ZONE TO PREVENT OVERLAPS BETWEEN ELEMENTS THROUGH SIMULATION. TWO DIFFERENT APPROACHES HAVE BEEN ADOPTED TO SOLVE BUCKLING PROBLEM: LINEAR, BASED ON THE SOLUTION OF EIGENVALUES PROBLEM, AND NONLINEAR. THE RIKS METHOD WAS USED TO SOLVE THE NONLINEAR SYSTEM. THE LOAD/DISPLACEMENT BEHAVIOR OF EMBEDDED DELAMINATION GROWTH FOR COMPOSITE LAMINATES IS PRESENTED. RESULTS REPORTED IN THIS STUDY ARE FOCUSED ON THE EFFECTS OF THE SHAPES AND GEOMETRY IMPERFECTIONS ON POST BUCKLING RESPONSE AS WELL AS. VALIDATION OF THE CIRCULAR DELAMINATION SPECIMEN HAS BEEN PERFORMED WITH EXPERIMENTAL AND PREVIOUS NUMERICAL DATA.

FATIGUE LIFE PREDICTION OF NOTCHED COMPONENTS UNDER FULLY REVERSED CYCLIC LOADING IS THE ESSENTIAL PART OF THE DESIGN AND ASSESSMENT OF THE STRUCTURES SUBJECTED TO CYCLIC LOADS. IN THE NUMERICAL FATIGUE LIFE PREDICTION, THERE ARE NORMALLY TWO APPROACHES: IN THE FIRST APPROACH AN ELASTIC FINITE ELEMENT (FE) ANALYSIS IS PERFORMED AND THEN A LOCAL PLASTIC CORRECTION USING NEUBER'S RULE IS ADDED TO CONSIDER LOCAL PLASTICITY. IN THE SECOND APPROACH, LOCAL STRESS AND LOCAL STRAINS ARE OBTAINED FROM A DIRECT CYCLIC ELASTIC-PLASTIC (CEP) FE ANALYSIS. IN THIS PAPER, THESE TWO APPROACHES APPLIED TO A SIMPLE BUT WIDELY USED ENGINEERING CASE AND THE OBTAINED RESULTS COMPARED WITH THE EXPERIMENTS. THE RESULTS DEMONSTRATED THAT USING CYCLIC ELASTIC-PLASTIC ANALYSIS, MORE ACCURATE FATIGUE LIFE PREDICTION CAN BE OBTAINED.

THERMOFORMING, AS A COMMON AND SIMPLE METHOD OF FORMING POLYMERIC PARTS, IS A DEFORMATION PROCESS OF A POLYMER IN THE RUBBERY STATE ABOVE ITS GLASS TRANSITION TEMPERATURE. HOWEVER THE CONTACT OF THE SOFTENED POLYMERIC SHEETS WITH THE DIE SURFACE AT DIFFERENT STAGES OF THERMOFORMING CAN AFFECT THE FINAL GEOMETRY OF THE COMPONENT.POLY METAL METHACRYLATE (PMMA) IS A TYPE OF POLYMER WITH MANY INDUSTRIAL APPLICATIONS SUCH AS MANUFACTURING AIRPLANE CANOPY BUBBLE WHICH IS CARRIED OUT AT HIGH TEMPERATURE (130OC). IT IS IDEALLY PROCESSED SLIGHTLY ABOVE ITS GLASS TRANSITION TEMPERATURE AND AT LOW STRAIN RATES TO LIMIT OPTICAL DISTORTIONS. AN ACCURATE MODEL IS NEEDED TO DESCRIBE THE POLYMER BEHAVIOR IN NUMERICAL SIMULATIONS TO RELIABLY PREDICT THE RESULTING SHAPE AND PROVIDE INDUSTRY WITH INEXPENSIVE AND FAST TOOL DESIGN.THE BEHAVIOR OF PMMA IS HIGHLY NONLINEAR AND DEPENDS ON THE TEMPERATURE, SO SIMULATION OF ITS FORMING PROCESS IS A USEFUL SOLUTION TO VERIFY THE EFFECT OF RELEVANT PARAMETERS USING FEM. PROCESS SIMULATION REQUIRES AN APPROPRIATE MECHANICAL BEHAVIOR FOR PMMA. IN THIS PAPER, DIFFERENT MECHANICAL BEHAVIORS OF PMMA ARE USED TO SIMULATE THE CANOPY BUBBLE FORMING PROCESS. FIRST, FOUR SIMULATIONS WITH ELASTIC-PLASTIC MODEL, MOONEY-RIVLIN, OGDEN AND POLYNOMIAL ARE DONE BY ABAQUS/IMPLICIT. THEN, TWO CROSS SECTIONS ARE DEMONSTRATED IN TWO PERPENDICULAR PATH SAMPLES THROUGH FINAL SHAPES. FINALLY SECTION PROFILES ARE COMPARED WITH EXPERIMENTAL PROFILE AND AN APPROPRIATE MECHANICAL BEHAVIOR FOR PMMA IN HIGH TEMPERATURE FORMING PROCESSES IS SUGGESTED.