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CTOD test technology research several key issues

Author: ChenXiaoJuan
Tutor: MiaoZhangMu
School: Wuhan University of Technology
Course: Structural Engineering
Keywords: CTOD Ductile-brittle transition temperature Acceptance values Onrush point Local compression method
CLC: TB302
Type: Master's thesis
Year: 2011
Downloads: 154
Quote: 0
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Abstract

In materials and structural safety assessment, the toughness is extremely important mechanical index. In recent years, toughness test method, the crack tip opening displacement (CTOD) test has been more widely used, but there are a number of critical issues that need further study. In this paper, CTOD test the test temperature, the appropriate number of samples, the acceptance value is selected, the test of the \Material at different temperatures with different toughness. From the ductile-brittle transition temperature, this paper introduces and analyzes several ductile-brittle transition temperature of the test method. This study suggests that: CTOD test range where the resulting transition temperature Charpy impact than high, so the temperature does not have to CTOD test with the same impact test temperature can be raised. Test measured according to different ductile brittle transition temperature between, by the series of Charpy impact test transition temperature predicted transition temperature of CTOD test interval; if the CTOD test temperature transition in the temperature range of the material, the test results will be scattered In such cases, more samples should be prepared (less than 6); otherwise, can be prepared for three specimens. In this paper, EQ70 high strength steel were -10. ℃ and -60. ℃ The CTOD test results show that the value of CTOD at -10 ℃, the larger and smaller standard deviation; while at -60. C, CTOD value decreases, and a large dispersion. Description -60. ℃ in EQ70 transition temperature range of high strength steel, should take more (≥ 6 unit) samples to reduce dispersion of the results. Characterized characterized CTOD toughness of the material level. Evaluation of the toughness, the different number of samples should be used with the minimum of three levels of the same value as the characteristic value. More complex sample tissue fusion line, the test results are more discrete, comparison of the base material and weld sample tissue to be more uniform. Therefore, this study suggests that: base metal and weld machining three specimens can be tested; And when the fusion line specimen test temperature range in the transition temperature, the greater dispersion, according to conventional take three samples and characterized by the lowest value as the value is not able to characterize the toughness level, so be prepared for more sample (for example 6 above) to ensure its accuracy. When a sufficient number of samples, and the characteristic value is not very different than the acceptance value, the use of ECA (Engineering Criteria Evaluation) a combination of methods to ensure the structural safety. There are two factors that directly affect the results of the assessment materials, one acceptance value; Second CTOD measurement calculations. This study suggests that: For the acceptance of the value of the base material specimen test results should not be less than the API requirements; joint toughness specimens can be based on its existing structure and stress the importance of setting a reasonable acceptance status value, this paper the \CTOD measurement and calculation in a larger FV curve factor is not continuous, the pop-in. Trials will lead to the emergence of delamination crack FV curve in the \Based on delamination crack, this paper recommends strict accordance with specifications BS7448-1 for processing, in order to ensure their safety. This article take \The same batch EQ70 high strength steel weld specimens, two separate groups CTOD controlled trial. A group with \The results show that: Two specimens fatigue crack front flatness comparable level, indicating with \degrees, and can make the measured CTOD values closer to the true value; with only \CTOD test evaluation in actual use, if you use a \

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