X-ray stress measurement process of aluminum alloy by analysis of the full width at half maxima
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摘要: 文中采用X射线法测试6061-T6铝合金焊接接头残余应力,为探究合理的应力测试工艺方案,对预置应力的等强梁进行X射线应力测试,测试过程中先后增加准直器直径和摇摆角,以衍射曲线半高宽表征衍射晶粒群微观应变,研究在准直器直径和摇摆角增加时衍射晶粒群微观应变均匀性的变化,对材料进行取向成像分析,并对比在晶粒择优取向强弱不同的两个区间内应力测试的结果. 结果表明,应力测试精度与晶粒择优取向的强弱相关,在晶粒择优取向较强的空间范围内,采用大于1°的摇摆角时,小角度晶界附近的相邻亚晶都能够参与衍射,从而使衍射晶粒群微观应变趋于均匀,因此X射线应力测试精度较高,在d = 2 ~ 4 mm范围内,增加准直器直径d可增加衍射晶粒数目,但对衍射晶粒群微观应变均匀性及应力测试精度的影响不大.Abstract: In this paper, X-ray method is used to test the residual stress of 6061-T6 aluminum alloy welded joints. In order to explore a reasonable stress measurement process, X-ray stress test is performed on the pre-stressed equal-strength beam. The diameter of the aperture and the oscillation angle are successively increased during the test. The full width at half maximum of the diffraction profile is used to characterize the microscopic strain of the diffracted grain group. The change in the uniformity of the microscopic strain of the diffracted grain group is analyzed when the aperture diameter and oscillation angle increase, as wll as performing orientation imaging analysis to compare the grain selection between two stress test scheme in different intervals of preferred orientation of the grains. The results show that the stress test accuracy is related to the strength of the preferred orientation of the grains. In the spatial range where the preferred orientation of the grains is strong, when oscillation angle greater than 1° is used, the adjacent sub-crystals near the small-angle grain boundary can participate in the diffraction, so that the microscopic strain of the diffracted crystal grain group tends to be uniform, so the X-ray stress measurement accuracy is higher, and when the aperture is added in the range of d = 2 ~ 4 mm, the increase of diameter d can increase the number of diffracted grains, but has little effect on the microscopic strain uniformity of the diffracted grain group and the accuracy of stress testing.
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Keywords:
- stress measurement /
- X-ray /
- microstrain /
- measurement process
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表 1 对比试验方案
Table 1 Comparative test plan
组号 准直器直径d/mm 摇摆角 $\;\beta$ /(°)A-1 2 0 A-2 3 0 A-3 4 0 B-1 4 0 B-2 4 1 B-3 4 2 -
[1] 方洪渊. 焊接结构学[M]. 北京: 机械工业出版社, 2017. Fang Hongyuan. Welding structure[M]. Beijing: China Machine Press, 2017.
[2] Liu Z C, Jiang C, Li B C, et al. A residual stress dependent multiaxial fatigue life model of welded structures[J]. Fatigue & Fracture of Engineering Materials & Structures, 2018, 41(2): 300 − 313.
[3] Kessal B A, Fares C, Meliani M H, et al. Effect of gas tungsten arc welding parameters on the corrosion resistance and the residual stress of heat affected zone[J]. Engineering Failure Analysis, 2020, 107: 104200. doi: 10.1016/j.engfailanal.2019.104200
[4] Song S, Dong P. Residual stresses at weld repairs and effects of repair geometry[J]. Science and Technology of Welding and Joining, 2017, 22(4): 265 − 277. doi: 10.1080/13621718.2016.1224544
[5] Božić Ž, Schmauder S, Wolf H. The effect of residual stresses on fatigue crack propagation in welded stiffened panels[J]. Engineering Failure Analysis, 2018, 84: 346 − 357. doi: 10.1016/j.engfailanal.2017.09.001
[6] Lin J, Ma N, Lei Y, et al. Measurement of residual stress in arc welded lap joints by cosα X-ray diffraction method[J]. Journal of Materials Processing Technology, 2017, 243: 387 − 394. doi: 10.1016/j.jmatprotec.2016.12.021
[7] 孙建通, 李晓延, 张亮, 等. 轧制铝合金的X-射线法残余应力测试[J]. 焊接学报, 2017, 38(1): 61 − 64. Sun Jiantong, Li Xiaoyan, Zhang Liang, et al. X-ray residual stress measurement for rolled aluminum alloy[J]. Transactions of the China Welding Institution, 2017, 38(1): 61 − 64.
[8] 邓云华, 李晓延, 李庆庆, 等. 钛及钛合金X射线应力测试参数的选择[J]. 焊接学报, 2013, 34(2): 31 − 34. Deng Yunhua, Li Xiaoyan, Li Qingqing, et al. Parameters selection of X-ray diffraction stress measurment for titanium alloy[J]. Transactions of the China Welding Institution, 2013, 34(2): 31 − 34.
[9] Tsuji A, Okano S, Mochizuki M. Method of X-ray residual stress measurement for phase transformed welds[J]. Welding in the World, 2015, 59(4): 577 − 583. doi: 10.1007/s40194-015-0232-5
[10] 王小鹏, 李晓延, 吴奇, 等. 织构对6061-T6铝合金X射线应力测试精度的影响机理[J]. 材料导报, 2020, 34(20): 20081 − 20085. doi: 10.11896/cldb.19110034 Wang Xiaopeng, Li Xiaoyan, Wu Qi, et al. Influence mechanism of texture on the accuracy of X-ray stress measurement for 6061-T6 aluminum alloy[J]. Materials Reports, 2020, 34(20): 20081 − 20085. doi: 10.11896/cldb.19110034
[11] Hauk V. Structural and residual stress analysis by nondestructive method[M]. Amsterdam: Elsevier Science B V, 1997.
[12] Schäfer N, Chahine G A, Wilkinson A J, et al. Microstrain distributions in polycrystalline thin films measured by X-ray microdiffraction[J]. Journal of Applied Crystallography, 2016, 49(2): 632 − 635. doi: 10.1107/S1600576716003204
[13] Withers P J, Bhadeshia H K D H. Residual stress. Part 2 - Nature and origins[J]. Materials Science and Technology, 2001, 17(4): 366 − 375. doi: 10.1179/026708301101510087
[14] Stukowski A, Markmann J, Weissmüller J, et al. Atomistic origin of microstrain broadening in diffraction data of nanocrystalline solids[J]. Acta Materialia, 2009, 57(5): 1648 − 1654. doi: 10.1016/j.actamat.2008.12.011
[15] Wilkens M. X-ray diffraction line broadening of crystals containing small-angle boundaries[J]. Journal of Applied Crystallography, 1979, 12(2): 119 − 125.
[16] Naga Krishna N, Tejas R, Sivaprasad K, et al. Study on cryorolled Al–Cu alloy using X-ray diffraction line profile analysis and evaluation of strengthening mechanisms[J]. Materials & Design, 2013, 52: 785 − 790.
[17] Ortiz A L, Shaw L. X-ray diffraction analysis of a severely plastically deformed aluminum alloy[J]. Acta Materialia, 2004, 52(8): 2185 − 2197. doi: 10.1016/j.actamat.2004.01.012
[18] 张定铨, 何家文. 材料中残余应力的X射线衍射分析和作用[M]. 西安: 西安交通大学出版社, 1999. Zhang Dingquan, He Jiawen. Residual stress analysis by X-ray diffraction and its functions [M]. Xi’an: Xi’an Jiaotong University Press, 1999.