ULTRASONIC TESTING

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ULTRASONIC IS THE NAVY GIVEN TO?: SOUND FREQ ABOVE 20,000 HZ THE RANGE A HUMAN EAR CAN NOT HEAR.
WHAT ARE THE MOST COMMONLY USED FREQ IN U/T?: 2.25, 5, 10 MHZ
MHZ IS RESPRESNTED AS?: 1 MILLION CYLCES PER SECOND.
HOW IS TRANSMISSION OF U/T CHARACTERIZED?: BY PERIODIC VIBRATIONS REPRESENTED BY WAVE MOTION.
THE DISTANCE AN ULTRASONIC WAVE TRAVELS PER UNIT TIME IS?: VELOCITY
WAVELENGTH IS EQUAL TO TRAVEL DISTANCE FOR?: ONE CYCLE
THE TOTAL NUMBER OF CYCLES PASSING A GIVEN POINT IN 1 SEC?: FREQ
THE TOTAL DISTANCE TRAVELED PER UNIT TIME OR ACOUSTIC VELOCITY IS EQUAL TO?: WAVELENGHTH TIMES FREQ
HOW ARE VIBRATIONS GENERATED?: BY APPLING HIGH FREQ ELECTRICAL PULSES TO A TRANSDUCER ELEMENT CONTAINED IN A SEARCH UNIT.
WHAT IS PIEZOELECTRIC?: THE ABILITY OF A MATERIAL TO CONVERT ELECTRICAL ENERGT INTO MECHANICAL ENERGY AND VICE VERSA.
WHAT TRANSFORMS ELECTRICAL ENERGY INTO MECHANICAL ULTRASONIC ENERGY AND RECEIVE AND TRANSFORM U/T ENERGY BACK INTO ELECTRICAL ENERGY: TRANSDUCER ELEMENTS
HOW IS ULTRASONIC ENERGY TRANSMITTED FROM A SEARCH UNIT TO A TEST PART?: THRU COUPLING MEDIUM TO PREVENT AIR INTERFACE BETWEEN THEM.
IN WHAT TECHNIQUE ARE SHORT BURSTS OF ULTRASONIC ENERY ARE INTRODUCED INTO A PART AT REGULAR INTERVALS OF TIME?: PULSE ECHO
WHAT IS THRU TRANSMISSION?: WHEN A TRANSMITTING SEARCH UNIT PLACED ON ONE SRUFACE AND RECIVING UNIT PLACED ON THE OPPOSITE SURFACE.
HOW ARE DISCONTINUITIES DISCOVERD WITH THE THRU TRANSMISSION TECH?: THEY BLOC PASSAGE OF SOUND.
WHAT METHOD IS THE SEARCH UNIT PLACED DIRECTLY ON THE SURFACE?: CANTACT
HOW MANY MODES OF PROPAGATION ARE THERE?: LONGITUDINAL(COMPRESSED), SHEAR(TRANSVERSE), SURFACE( RAYLEIGH), AND LAMB(PLATES)WAVES.
What are characterized by particle movement parallel to direction of sound beam?: Longitudinal or compression waves
compression waves can propagate throught what materials?: solids, liquids or gases
characterized by particle movement perpendicular to the direction of the sound beam?: shear or transverse waves
What travels approximately 1/2 the speed of logitudinal waves?: shear
what consists of a transducer element mounted on a plastic wedge so waves ener the testpart at an angle?: shear
The most sensitive wave of the three types?: shear
a special type of shear wave in which the motion of the particles is confined to a thin layer of a solid?: Surface wave or rayleigh.
Surface waves can refelect around?: curves
Surface waves can detect defects how fare below the surface?: 1/2 wave length below surface
propagtion occurs when waves travel along a test part thinner than 4 wave lengths?: Lamb(plate) waves
sound beams have properties similar to?: Light beams
the angle at which sound is introduced into a part?: angle of incidence
the angle of incidence is equal to?: Angle of reflection
Sound reflects off an interface at the same angle at which it?: travels through the material
The change in direction of ultra sonic beam as it passes obliquely throug the interface between two materials with different acoustic velocities.: refraction
snells law applys to what?: incident and refracted angles
The characteristic of surfaces to change the mode of propagation of acoustic energy from one mode to another?: mode conversion
the incident angle of sound beam beyond which a specific refracted mode of vibration no longer exists?: critical angle
the critical angle at which longitudinal and shear waves no longer exist?: above the second critical angle
Sound beams are not straight sided projections they?: spread out and vary in intensity
in contact scanning there is an area beneath search units which cannot be inpected due to large initial pulse?: Dead zone
What is inherent to all UT equipment?: Dead zone
the shorter the post length the?: Shallower the dead zone
Area directly under a search unit to where the beam begins to spread?: Near field Fresnel zone
Near fields are not recommended for inspection due to?: amplitude variations
What is the far field and what else is it know as?: The zone beyond the near field. Fraunhofer zone
The intensity of the far field drops of exponentially as what?: distance from the face of the transducer increases.
What spreads in the far field?: beam spread
At a given freq the larger the transducer the?: Less the beam spread and vise versa
less beam spread means what?: you have a high freq in the part and vice versa
Why is beam spread important to calculate?: ceacuse in certain inspection applications the spreading sound beam can reflect off of walls or edges and casue confusing signals.
greater sensitivity is aquired by using?: Higher freq
Greater penetration is aquired by?: using lower frequencey
Defects need to be at least on dimension equal to or greater than what to dectect defects?: 1/2 the wave length side
coarse grain structures slatter and absorb what?: sound energy
depth of penetration in coarse materials are?: less
Surface conditions can cause what?: insufficant ultasonic energy reaching defects.

Beam divergants or widing of the sound beam
to minimize the effects of surface conditions the part shall be free of?: loose heavy or uneven scales machining or grinding particals or other loose foreign matter
The position of the sides and walls of the part can affect the test what part of variables affecting transmission is this?: geometry of the part
A back surface not parallel to the front surface can casue reflections at other than normal angles thus mode conversion in the part this can cause?: confusing indications or complete loss of back refection
if the test specimen surface is curved byond limits the what is required?: a plastic shoe to match the search unit face to the curved surface
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.: acoustic impedance
the greater the differences in acoustic imedance across the interface the greater?: the refection
a thin film of liquid couplant material is required between the search unit and the part in or to ?: displace air at the interface this allows transmission of ultrasonic enery into the test part.
any liquid which will tansmit ultrasonic enery and meets what standards may be used?: 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
the ability of an inspection system to detect small discontinuities: sensitivity
sensitivity is generlly rated how>: the ability to detect a specified size and depth flat bottom hole
all equipment and trasducers do not always produce identical indications for this reason what must be done?: all inspections must be set up using a series of reference standards
the ability of an inspection syste to separate signals from two interfaces colse togather in depth?: resoulution.
contains all the elemets of the basic search unit including a connection for the signal cable?: housing
quarts, lithium sulfaate, and polorized ceramics are all what?: crystal elements
what is determined vy thickness of elements material?: FREQ
allow for attachment of signal connector and internal ground connector to crystal element: electrodes
serves to damp the ringing of the transducer element after it is excited?: backing material
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: wear face
What is used to adapt search units for use in angle beams and surface wave inspection and or use on curves surfaces.: wedges and shoes
how many types of search units are there: 3
when a search unit is identified with angle only it idicates what?: incedient angle only
when transducer is identified with angle and material it indicates?: refracted angle
all immersion units use straight beam transducer why?: angle beams will not propagate through liquid
used to eliminate the near field?: delay line tip
uses two tranducer elements in one search unit: dual element
used to cover an range of refracted angles: variable angle
Freq range for USN-52?: low .3-4 MHZ
BB- .4-10
din- 2.0-8
high- 3-10
the usn-52 has an inspection range of?: .2-200 inches in steel
What type of screen does the usn-52 have and what are the power requirements?: electroluminescent display

110-220 vac 50-60hz or 6 D-size Nicad lead acid or alkaline batt
The MXU-715/E has a freq range of?: 1-15 mhz
the MXU-715/E has a inspection range of?: .1-150 inches in steel
How much does the MXU-715/e weight and what are the power requirements?: 45 lbs

115/120 vac 60hz or 24 DC battery
The usn-52 weight how much?: 5.98lbs with batt and 3.1 without
what is the purpose of standards?: to establish inspection procedures.

to determain inspection sensitivity levels

to check equipment performance

to prevent repeatablity
used to chec performace and caliration limits of equipment: calibration standards
ASTM CAL STANDARDS: 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
IAW blocks: used for angle beam calibration and some straight beam applications
miniture cal block: used for angle beam cal and some straight beam
ASME plate: used for surface wave CAL
Reference standards: manufactured to evaluate indications from parts under test.

simulate defect size, shape, and location

made to part characheristics

limited to specific applications

employs EDM notches and drilled holes
natural defect standards: most accurate material and defect obtained but limited to specific inspections.
Thickness measurement is for?: 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 corr.
What is the most common method for thinkness measurement?: Pulse-echo
For pulse echo thickness messurent what unit should you use?: any
What is the test range of pulse echo method for thickness?: .005-20 inches
For thickness measurments using pulse echo of a material that is .25 or less what is required?: Delay line tip or dual element trasducer.
what method of thickness meassurement applies continous electrical energy to the search unit?: Resonance method
By measuring the freq at which resonance occurs you can determain?: Part thickness.
As the test part thickness increases the fundamental and harmonics decrease and vice versa This is part of?: resonance method
A basic ultrasonic instrument that can also be used for thinkness measurments or?: A instrument specifically designed for thickness being measured.
thickness reference standards: must be a known thickness

recommended to be of same velocity as material to be inspected

smooth surface is required
Compression defects will appear where on the screen?: Between the IP and BR
shear mode 1st BR is from the?: bottom corner of the part
shear mode 2nd BR is from the?: top corner of the part
shear mode 3rd BR is from?: the bottom corner of the part same as the first/
when inspecting a wel you use a low freq L mode and?: inspect 3-6 inches on either side of the weld
Location of defect is noted on the screen and?: compared to a known reflection
Estimated by measuring signal ampitude of a defect inication displayed on the CRT is directly related to the amount of reflected sound returning to the trasnducer?: size
To gather orientation of defect you do what?: if possible evaluate from several different directions using angle and straight beam
Several different types of indications will be encountered and can?: cause confusion and false conclusions.
Loss of and or multiple indications can be cause by what factors?: Large grain size

porsity

dispersion of precipitate particles in material

lower fre will denerally reduce mulitple indications.
Delamination can be detected by noting?: a reduction in distance between BR mulitples
Surface waves indications will move?: towards IP as search unit is moved toward the edge
surface waves can be generated when using?: straight beam search units
Surface waves created from straight beam search units can be?: mistaken for discontinuities
straight beams used near a boundry causes reflection and mode conersion this is know as?: parallel boundaries
major variables to consider when developing and coducting ultasonic inspections on bonded structures?: Top skin material type and thickness.

adhesive type and thickness

underling structure
things to consider for honeycomb material?: core material, cell size, thickness, and hieght
things to consider for laminates?: number of layers, layer thickness, and layer material
unbonds or voids in an outer skin-to-adhesive interface?: class I
unbonds or voids at the adhesive to core interface?: class II
voids between layers of laminates?: class III
voids in foam adhesive or unbonds between the adhesive and closure member at core closure member joints?: class IV
water in core?: class V
Reference standards for composites?: 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
Composite ref standards must be bonded using?: the adhesive cure cylces prescribed for the test part
thru transmission inspection method for composites, Delamination or unbonds cause?: blocked transmission of sound to the receiving unit.
the minimum size unbond that can be detected is proportional to the?: Receiving search unit.
When perfroming thru transmission care must be taken to keep sending and receiving units in?: tangent with each other
This method is only applicable to honeycomb structures and is best applied to structures with single layer skin.: Pulse-echo
employs an angle beam search unit because straight bean surch units may produce multiple echo signals from the layers that would interfere with echo signals fro the core?: pulse-echo
for pulse echo inspection of B/C/L what angle transducer should you use?: 30-90 degrees
The back refelction can generally be established by damping the opposite skin with your finger and noting a slight change in signal the back side of the core signal will be where?: immediately in front of the damped signal
what method is used when the best sensitivity is needed for detecting unbonds between the top sheet and the adhesive?: ringing
An unbond below the first layer of adhesive will often not produce a rignhing signal because>: the adhesive bonded to the top sheet will dampen the signal
This inspection method of B/C/L is effective for laminates doublers and shin to closure member bonds when acesses to the back side is avalible?: damping
What is the special ultrasonic test equipment?: The TTU-527/E compsite laminate tester
the TTU-527/E test what?: carbon graphite epozy composite laminates and indicates the presence of delamination by and aduble and visual alarm

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