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162 Cards in this Set
- Front
- Back
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ULTRASONIC IS defined as what?
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SOUND FREQ ABOVE 20,000 HZ THE RANGE A HUMAN EAR CAN NOT HEAR.
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WHAT ARE THE MOST COMMONLY USED FREQ IN U/T?
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2.25, 5, 10 MHZ
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MHZ IS RESPRESNTED AS?
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1 MILLION CYLCES PER SECOND.
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HOW IS TRANSMISSION OF U/T CHARACTERIZED?
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BY PERIODIC VIBRATIONS REPRESENTED BY WAVE MOTION.
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THE DISTANCE AN ULTRASONIC WAVE TRAVELS PER UNIT TIME IS?
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VELOCITY
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WAVELENGTH IS EQUAL TO TRAVEL DISTANCE FOR?
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ONE CYCLE
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THE TOTAL NUMBER OF CYCLES PASSING A GIVEN POINT IN 1 SEC?
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FREQ
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THE TOTAL DISTANCE TRAVELED PER UNIT TIME OR ACOUSTIC VELOCITY IS EQUAL TO?
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WAVELENGHTH TIMES FREQ
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HOW ARE VIBRATIONS GENERATED?
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BY APPLYING HIGH FREQ ELECTRICAL PULSES TO A TRANSDUCER ELEMENT CONTAINED IN A SEARCH UNIT.
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WHAT IS PIEZOELECTRIC?
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THE ABILITY OF A MATERIAL TO CONVERT ELECTRICAL ENERGY INTO MECHANICAL ENERGY AND VICE VERSA.
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WHAT TRANSFORMS ELECTRICAL ENERGY INTO MECHANICAL ULTRASONIC ENERGY AND RECEIVE AND TRANSFORM U/T ENERGY BACK INTO ELECTRICAL ENERGY
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TRANSDUCER ELEMENTS
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HOW IS ULTRASONIC ENERGY TRANSMITTED FROM A SEARCH UNIT TO A TEST PART?
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THROUGH A COUPLING MEDIUM TO PREVENT AIR INTERFACE BETWEEN THEM.
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IN WHAT TECHNIQUE ARE SHORT BURSTS OF ULTRASONIC ENERGY INTRODUCED INTO A PART AT REGULAR INTERVALS OF TIME?
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PULSE ECHO
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WHAT IS THROUGH TRANSMISSION?
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WHEN A TRANSMITTING SEARCH UNIT PLACED ON ONE SURFACE AND RECEIVING UNIT PLACED ON THE OPPOSITE SURFACE.
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HOW ARE DISCONTINUITIES DISCOVERED WITH THE THROUGH TRANSMISSION TECHNIQUE?
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THEY BLOCK PASSAGE OF SOUND.
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WHAT METHOD IS THE SEARCH UNIT PLACED DIRECTLY ON THE SURFACE?
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CONTACT
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WHAT ARE THE MODES OF PROPAGATION ?
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LONGITUDINAL(COMPRESSED), SHEAR(TRANSVERSE), SURFACE( RAYLEIGH), AND LAMB(PLATES)WAVES.
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What are characterized by particle movement parallel to direction of sound beam?
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Longitudinal or compression waves
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Compression waves can propagate throught what materials?
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solids, liquids or gases
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What type of waves are characterized by particle movement perpendicular to the direction of the sound beam?
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shear or transverse waves
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What type of wave travels approximately 1/2 the speed of logitudinal waves?
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shear
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What consists of a transducer element mounted on a plastic wedge so waves enter the test part at an angle?
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shear
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The most sensitive wave of the three types?
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shear
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A special type of shear wave in which the motion of the particles is confined to a thin layer of a solid?
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Surface wave or rayleigh.
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Surface waves can refelect around?
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curves
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Surface waves can detect defects how far below the surface?
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1/2 wave length below surface
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Propagtion occurs when waves travel along a test part thinner than 4 wave lengths?
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Lamb(plate) waves
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Sound beams have properties similar to?
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Light beams
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The angle at which sound is introduced into a part?
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angle of incidence
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The angle of incidence is equal to?
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Angle of reflection
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Sound reflects off an interface at the same angle at which it?
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travels through the material
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The change in direction of ultrasonic beam as it passes obliquely throug the interface between two materials with different acoustic velocities.
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refraction
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Snells law applys to what?
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incident and refracted angles
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The characteristic of surfaces to change the mode of propagation of acoustic energy from one mode to another?
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mode conversion
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The incident angle of sound beam beyond which a specific refracted mode of vibration no longer exists?
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critical angle
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The critical angle at which longitudinal and shear waves no longer exist?
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above the second critical angle
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Sound beams are not straight sided projections they?
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spread out and vary in intensity
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In contact scanning there is an area beneath search units which cannot be inspected due to large initial pulse?
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Dead zone
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What is inherent to all UT equipment?
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Dead zone
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Area directly under a search unit to where the beam begins to spread?
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Near field Fresnel zone
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Near fields are not recommended for inspection due to?
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amplitude variations
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What is the far field and what else is it know as?
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The zone beyond the near field. Fraunhofer zone
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The intensity of the far field drops of exponentially as what?
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distance from the face of the transducer increases.
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What spreads in the far field?
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beam spread
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At a given freq the larger the transducer the?
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Less the beam spread and vice versa
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less beam spread means what?
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you have a high freq in the part and vice versa
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Why is beam spread important to calculate?
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Beacuse in certain inspection applications the spreading sound beam can reflect off of walls or edges and cause confusing signals.
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greater sensitivity is aquired by using?
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Higher freq
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Greater penetration is aquired by?
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using lower frequencey
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Defects need to be at least equal to or greater than what to dectect defects?
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1/2 the wave length side
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Coarse grain structures scatter and absorb what?
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sound energy
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depth of penetration in coarse materials are?
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less
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Surface conditions can cause what?
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insufficient ultrasonic energy reaching defects.
Beam divergence or widening of the sound beam |
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to minimize the effects of surface conditions the part shall be free of?
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loose heavy or uneven scales, machining or grinding particals or other loose foreign matter
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A back surface not parallel to the front surface can cause reflections at other than normal angles thus mode conversion in the part, this can cause?
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confusing indications or complete loss of back refection
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If the test specimen surface is curved beyond limits the what is required?
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a plastic shoe to match the search unit face to the curved surface
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When an ultrasonic beam strikes a boundry between two different materials part of the energy is transmitted to the second medium and aportion is reflected.
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acoustic impedance
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The greater the differences in acoustic impedance across the interface the greater?
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the reflection
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A thin film of liquid couplant material is required between the search unit and the part in order to ?
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displace air at the interface this allows transmission of ultrasonic energy into the test part.
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Any liquid which will tansmit ultrasonic energy and meets what standards may be used?
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Able to wet both face and test part.
Is not corrosive or toxic. Can be applied and removed easily. Is homogenous and free of air bubbles. is viscous |
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The ability of an inspection system to detect small discontinuities
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sensitivity
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Sensitivity is generally rated by?
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The ability to detect a specified size and depth flat bottom hole
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All equipment and transducers do not always produce identical indications for this reason what must be done?
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All inspections must be set up using a series of reference standards
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The ability of an inspection system to seperate signals from two interfaces close together in depth?
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resolution.
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Contains all the elemets of the basic search unit including a connection for the signal cable?
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Housing
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Quarts, lithium sulfaate, and polorized ceramics are all what?
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Crystal elements
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What is determined by thickness of elements material?
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FREQ
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What allows for attachment of signal connector and internal ground connector to crystal element
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Electrodes
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Serves to damp the ringing of the transducer element after it is excited?
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Backing material
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These faces improve coupling on rough surfaces and prevent wear of the search unit face. They also reduce the amount of power available from the search unit
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Wear face
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What is used to adapt search units for use in angle beams and surface wave inspection and or use on curves surfaces.
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Wedges and shoes
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How many types of search units are there
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3
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When a search unit is identified with angle only it indicates what?
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Incident angle only
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All immersion units use straight beam transducer why?
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Angle beams will not propagate through liquid
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Used to eliminate the near field?
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Delay line tip
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Uses two tranducer elements in one search unit
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Dual element
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Used to cover a range of refracted angles
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Variable angle
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What is the purpose of standards?
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to establish inspection procedures.
to determain inspection sensitivity levels to check equipment performance to prevent repeatablity |
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What is used to check performace and calibration limits of equipment?
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Calibration standards
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ASTM CAL STANDARDS
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May be steel or aluminum
first 4 digits show material type. 5th digit shows DIA of flat bottom hole in 64th last four digits show metal travel distand to the top of the FBH |
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IAW blocks are used for?
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Angle beam calibration and some straight beam applications
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Miniture cal block is used for?
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Angle beam cal and some straight beam
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ASME plate is used for?
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surface wave CAL
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Reference standards
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manufactured to evaluate indications from parts under test.
simulate defect size, shape, and location made to part characteristics limited to specific applications employs EDM notches and drilled holes |
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Natural defect standards are?
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most accurate material and defect obtained but limited to specific inspections.
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Thickness measurement is used for?
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Checking part thickness when back side of part is not accessable.
checking large panels in interior areas where a micrometer can not reach. maintenance inspection for checking thickness loss due to wear or corrosion. |
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What is the test range of pulse echo method for thickness?
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.005-20 inches
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For thickness measurments using pulse echo of a material that is .25 or less what is required?
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Delay line tip or dual element transducer.
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What method of thickness meassurement applies continous electrical energy to the search unit?
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Resonance method
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By measuring the freq at which resonance occurs you can determine?
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Part thickness.
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As the test part thickness increases the fundamental and harmonics decrease and vice versa This is part of?
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Resonance method
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Thickness reference standards
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must be a known thickness
recommended to be of same velocity as material to be inspected smooth surface is required |
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Compression defects will appear where on the screen?
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Between the IP and Backwall
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shear mode 1st back reflection is from the?
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bottom corner of the part
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shear mode 2nd back reflection is from the?
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top corner of the part
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Shear mode 3rd back reflection is from?
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the bottom corner of the part same as the first
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When inspecting a weld you use a low freq L mode and?
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inspect 3-6 inches on either side of the weld
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Location of defect is noted on the screen and compared to?
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compared to a known reflection
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Estimated by measuring signal ampitude of a defect indication displayed on the CRT is directly related to the amount of reflected sound returning to the trasnducer?
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Size
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To gather orientation of defect you do what?
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If possible evaluate from several different directions using angle and straight beam
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Loss of and or multiple indications can be caused by what factors?
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Large grain size
porsity dispersion of precipitate particles in material lower fre will denerally reduce mulitple indications. |
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Delaminations can be detected by noting?
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A shift in the backwall
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Surface waves indications will move?
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Towards IP as search unit is moved toward the edge
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Surface waves can be generated when using?
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Straight beam search units
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Surface waves created from straight beam search units can be?
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Mistaken for discontinuities
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Straight beams used near a boundary causes reflection and mode conversion this is know as?
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Parallel boundaries
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Major variables to consider when developing and coducting ultasonic inspections on bonded structures?
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Top skin material type and thickness.
adhesive type and thickness underling structure |
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Things to consider for honeycomb material?
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Core material, cell size, thickness, and hieght
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Things to consider for laminates?
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Number of layers, layer thickness, and layer material
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Reference standards for composites must?
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Must be similar to test part with respect to material, geometry, and thickness.
Must contain bonds of good quality except for controlled areas of unbonds |
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In through transmission inspection method for composites, delamination or unbonds cause?
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Blocked transmission of sound to the receiving unit.
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When perfroming through transmission care must be taken to keep sending and receiving units in?
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Tangent with each other
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Employs an angle beam search unit because straight beam search units may produce multiple echo signals from the layers that would interfere with echo signals from the core?
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Pulse-Echo
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The back reflection can generally be established by?
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Damping the opposite side with your finger and noting a slight change in signal the backwall signal.
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An unbond below the first layer of adhesive will often not produce a ringing signal because?
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the adhesive bonded to the top sheet will dampen the signal
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Longitudinal waves are also called?
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Pressure or compressional waves
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Wavelength is directly proportional to what?
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To the velocity of the wave and inversely proportional to the frequency of the wave
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Sensitivity generally increases with?
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Higher frequency (shorter wavelengths).
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Resolution also generally increases as?
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The frequency increases.
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When sound travels through a medium it?
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Its intensity diminishes with distance
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The combined effect of scattering and absorption is called?
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Attenuation
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The greater the impedance mismatch?
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The greater the percentage of energy that will be reflected at the interface or boundary between one medium and another
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Refraction is defined how?
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A change in direction of a wave due to a change in its speed.
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When an ultrasonic wave passes through an interface between two materials at an oblique angle, and the materials have different indices of refraction what occurs?
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Both reflected and refracted waves are produced
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Refraction takes place at an interface due to?
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The different velocities of the acoustic waves within the two materials.
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Snell's Law describes ?
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The relationship between the angles and the velocities of the waves
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The first critical angle is known as?
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When a longitudinal wave moves from a slower to a faster material, there is an incident angle that makes the angle of refraction for the wave 90 degrees
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Mode conversion occurs when ?
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A wave encounters an interface between materials of different acoustic impedances and the incident angle is not normal to the interface
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Mode conversion occurs every time a wave ?
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Encounters an interface at an angle
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When sound waves pass through an interface between materials having different acoustic velocities, refraction takes place where?
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At the interface
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The larger the difference in acoustic velocities between the two materials?
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The more the sounds is REFRACTED.
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Shear waves travel slower or faster than longitudinal waves?
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Slower
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The signal-to-noise ratio is a measure of how ?
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The signal of the defect compares to other background reflections
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The shorter the pulse (often higher frequency)?
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The better the detection of the defect
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The near field is also known as what?
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The Fresnel zone
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The active element of most acoustic transducers used today is ?
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A piezoelectric ceramic
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Lower frequencies (0.5MHz-2.25MHz) provide ?
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Greater energy and penetration in a material
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High frequency (15.0MHz-25.0MHz) provide ?
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Reduced penetration but greater sensitivity
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The sound that emanates from a piezoelectric transducer does not originate from a point, but ?
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Originates from most of the surface of the piezoelectric element
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The phenomenon in which a beam spreads out as it propagates through a material is known as?
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Beam Divergance of Beam Spread
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In the far field, or Fraunhofer zone where is the sound pressure the greatest?
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Along the centerline of the beam.
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Beam spread is greater when?
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Using a low frequency transducer
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As the diameter of the transducer increases?
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The beam spread will be reduced.
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A focused transducer can improve what?
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The sensitivity and axial resolution
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Angle beam transducers and wedges are typically used to introduce what kind of wave into the test material?
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refracted shear wave
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Pulse Length is:
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The amount of time the pulse is applied to the transducer
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Pulse energy is?
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The voltage applied to the transducer. Typical pulser circuits will apply from 100 volts to 800 volts to a transducer.
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In the A-scan presentation reflector depth can be determined by:
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Postion of the reflector signal on the horizontal sweep.
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The B-Scan presentation is:
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A cross-sectional view of the test specimen
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A thin crystal element in a transducer will have a higher or lower frequency?
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Higher frequency
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The velocity of sound depends on?
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Density and elasticity of the material the sound is moving through.
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Acoustic impedance is defined by:
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The product of material density and acoustic velocity
Z=pV |
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As bandwidth decreases what happens?
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Sensitivity increases
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How is bandwidth decreased?
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By decreasing transducer damping
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As bandwidth increases resolution does what?
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Increases
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What type of transducer should be used when the defect is expected to be at an orientation other than parallel to the surface?
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Angle Beam
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What is the gain control used for?
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Adjusting the height of the signals.
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The term period refers to what?
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The amount of time it takes to complete one cycle
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The incident angle that yields a 90° longitudinal wave is defined as?
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The First Critical Angle
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Metallurgical discontinuities in the structure affect higher or lower frequencies?
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Higher Frequencies
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The range of frequencies and transducer and and ultrasonic instrument produce are known as what?
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Bandwidth
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Intended to establish the correlation between the signal
amplitude with the area of a flat bottom hole reflector. These sets of blocks contain flat-bottom holes of differing diameters all at the same distance from the sound entry surface. |
Area amplitude blocks
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