The reflected percentage of ultrasound energy, R1, travels from time location ta
to arrive back at the PZT
transducer at time location t1 where it can be measured as amplitude V1 from the electrodes. The TDOA between the
initial pulse and first received echo is ¨t
1
=t1-t0, which is used to measure the steel thickness T1, as described in
equation (4). The remaining percentage of energy, R2
=86.15%, travels through the tungsten layer until it reaches the
second boundary, air, at time location tb, which has very low acoustic impedance of 0.0004 MRayls. Due to the very
large difference in acoustic impedance between air and tungsten, the signal energy is completely reflected back into
the tungsten material travelling towards the steel layer. When the signal reaches the tungsten-steel boundary at time
location tc
, another percentage energy R1 is reflected back, however, this time it is reflected back into the tungsten
layer. The remaining percentage of energy R2, makes its way through the steel layer to arrive back at the transducer
at time t2 with voltage magnitude V2. The TDOA ¨t
2
= t2-t1 is used in equation (4) to measure the thickness of the
tungsten layer T2. Note that the ultrasound signal at time location t2 will be reflected again into the steel, such that
the whole cycle is repeated until all signals are attenuated according to equation (7), where V is the exponential
decrease in voltage amplitude of the sound signal at distance d, and V0 is the initial voltage amplitude produced by
the PZT at t0. The attenuation coefficient Į, expressed in dB/cm, is dependent on the PZT resonant frequency and
varies with manufacturer processing technology. Therefore, Į is experimentally calculated by measuring the initial
voltage sample Vi
and a final voltage sample Vf
separated by distance d according to equation (8)
The reflected percentage of ultrasound energy, R1, travels from time location ta
to arrive back at the PZT
transducer at time location t1 where it can be measured as amplitude V1 from the electrodes. The TDOA between the
initial pulse and first received echo is ¨t
1
=t1-t0, which is used to measure the steel thickness T1, as described in
equation (4). The remaining percentage of energy, R2
= 86.15 % , เดินทางผ่านทังสเตนชั้นจนกว่าจะถึง
ขอบที่สองอากาศที่ TB ที่ตั้งเวลาที่มีอิมพีแดนซ์ของเสียน้อยไปนาน mrayls . เพราะมาก
ความแตกต่างขนาดใหญ่ในอิมพีแดนซ์ของเสียระหว่างอากาศและทังสเตน สัญญาณพลังงานอย่างสมบูรณ์สะท้อนกลับไป
วัสดุทังสเตนเดินทางต่อเหล็กชั้น When the signal reaches the tungsten-steel boundary at time
location tc
, another percentage energy R1 is reflected back, however, this time it is reflected back into the tungsten
layer. The remaining percentage of energy R2, makes its way through the steel layer to arrive back at the transducer
at time t2 with voltage magnitude V2. The TDOA ¨t
2
= t2-t1 ใช้ในสมการ ( 4 ) เพื่อวัดความหนาของชั้น
Tungsten T2 ทราบว่าสัญญาณอัลตราซาวนด์ที่ T2 ที่ตั้งเวลาจะปรากฏอีกครั้งในเหล็ก เช่น
ทั้งวงจรซ้ำจนกว่าสัญญาณทั้งหมดจะเป็นตามสมการ ( 7 ) เมื่อ V คือแรงดันไฟฟ้าลดลงชี้แจง
ในแอมพลิจูดของสัญญาณเสียงที่ระยะห่าง D and V0 is the initial voltage amplitude produced by
the PZT at t0. The attenuation coefficient Į, expressed in dB/cm, is dependent on the PZT resonant frequency and
varies with manufacturer processing technology. Therefore, Į is experimentally calculated by measuring the initial
voltage sample Vi
and a final voltage sample Vf
separated by distance d according to equation (8)
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