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Comparative Study on the Side-crack Electromagnetic Heating for Crack-enhanced and the Crack Propagation Experiment Method

Author: YangLiNa
Tutor: FuYuMing
School: Yanshan University
Course: Mechanical Design and Theory
Keywords: electromagnetic heat temperature field stress filed stress intensity factor DCpotential method
CLC: O346.1
Type: Master's thesis
Year: 2013
Downloads: 27
Quote: 0
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Abstract


With the development of heavy industry, metal materials were widely used. Inprocessing and using metal will be affected by high temperature, high pressure, tensile andshock, etc. Working under various kinds of loads, it is hard to avoid producing crack inmetal internal, the presence of cracks seriously influenced the safety and service life ofequipment, so avoid expanding of cracks is the most urgent problem to resolve in theproduction and application of heavy industry. Using the electromagnetic heat effect toprevent growing of metal internal and surface cracks is an novel and effective way.This paper theoretically launched the stress field near the tip of Ⅲ type crack, andused numerical simulation method to simulate the temperature and stress field near thecrack tip, and finally verified by experimental method proved that the temperature willexceed to the melting point with the formation of welded junction, passivation of thecrack tip to prevent crack growth.Used experimental method to compare and analysis the strengthening effect of pulsedischarge to prevent growing of cracks inⅠtype, Ⅱtype, Ⅲ type crack, will Ⅰ type, Ⅱtype, Ⅲ type crack separately carried on the tensile, impact and torsion of the mechanicalproperties experiments, and that after pulse discharge the percentage ofⅠ type crackspecimens tensile strength, Ⅱ type crack specimen impact toughness and Ⅲ type crackspecimen torsional strength increase. A numerical simulation method to simulate themoment of pulse discharge the thermal stress field in crack tip and the residual stress fieldafter cooling.This article analysised the effect of electromagnetic heat crack arrest for crackpropagation by numerical simulation. Using finite element software ANSYS simulated thechange of stress intensity factor before and after pulse discharge. The result show thatpulse discharge can inhibit crack extension.Finally, the testing and prediction method of fatigue crack length is explored in theexperiment aspect. In this paper, the direct-current-potential-drop (DCPD) technique isused to continuously monitor the crack propagation through detecting the voltage drop which is related to the crack length. Furthermore, the curve of crack length and voltage isfitted on cracking of AZ31B, which provides an experimental basis for measuring thefatigue crack propagation rate.

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CLC: > Mathematical sciences and chemical > Mechanics > Solid Mechanics > Strength theory > Fracture theory
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