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Study on Nonlinear Behaviour of Ultrasonic Interface Signals in Diffusion Bonding of 304 Stainless Steel

Author: YeJiaLong
Tutor: GangTie
School: Harbin Institute of Technology
Course: Materials Processing Engineering
Keywords: Diffusion welding Ultrasonic testing Nonlinear imaging Signal Analysis
CLC: TG453.9
Type: Master's thesis
Year: 2011
Downloads: 82
Quote: 0
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Abstract


Base metal diffusion bonding technology because no melting of the unique advantages have become aviation , aerospace and other fields essential technology. Diffusion bonding interface defects seriously affect the existence of welded structures in service service performance , therefore , it is necessary to carry out non-destructive testing . Defects due to diffusion welding head mostly micron level, and there is weak binding defects , the use of radiography and conventional ultrasonic flaw detection quite difficult . With the constant improvement of ultrasonic nonlinear theory , nonlinear ultrasonic nondestructive testing technology has been in the detection of small defects in solid media are widely used . In this paper, signal processing techniques for diffusion bonding interface ultrasonic nonlinear behavior were studied. First, by controlling the surface treatment before welding and welding , was prepared having the typical defects diffusion welding head , and its testing, to obtain a reflected ultrasonic signal data interface state . Acoustic nonlinearity in the contact on the basis of theoretical analysis , namely the use of smooth and rough interface model interface model for solid state interface connectors different nonlinear effects were compared. There are two different algorithms for diffusion welding interface nonlinear ultrasound imaging, and obtained by comparing the ideal algorithm. The nonlinear diffusion bonding interface ultrasound images and ultrasonic C- scan images were compared for differences between the two . Combined with devastating results of the experiment , analyze different interface states ultrasonic echo signals in time domain and frequency domain characteristics . And characteristics of ultrasonic signals from the interface ultrasonic nonlinear effects , microscopic characteristics of the interface shear strength and joint perspective of the defects are not welded together , the weak bonding interface defects and good welding characteristics . The results show that nonlinear ultrasonic detection diffusion welding defects at the interface more sensitive to weak binding .

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Welding, metal cutting and metal bonding > Welding process > Pressure welding > Other pressure welding
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