Issue 41

Z. Li et alii, Frattura ed Integrità Strutturale, 41 (2017) 378-387; DOI: 10.3221/IGF-ESIS.41.49 379 under the influence of residual stress, pointing out that the effect of residual stress on structural mode is too big to be ignored. Taking the Chunyi Bridge on Haihe River as an example, Ding Daiwei et al. [7] expounded the test principle of blind hole method, examined the impact of welding residual stress on the steel box girder bridge, and obtained the distribution and features of the welding residual stress. Mo Mingchao [8] contoured the internal residual stress in welds by cutting open the vertical welding seam, and conducted contour precision testing and fitting. In the principle of blind hole drilling, this paper aims to measure residual stress, draw residual stress distribution maps, and analyze the influencing factors of welding residual stress, thereby providing a basis for the design of similar components. T EST OVERVIEW Test materials here are 8 specimens in this research, numbered from CH-1 to CH-8. Specimens CH-1~CH-5 are made of the material Q235B, while specimens CH-6~CH-8 are made of the material Q345B. See Tabs. 1 and 2 below for the chemical compositions and mechanical properties of the two types of materials. Material Chemical composition (%) C Si Mn P S Alt Q345B 0.069 0.472 0.86 0.014 0.002 0.021 Q235B 0.18 0.029 0.42 0.018 0.003 0.025 Table 1: The chemical compositions of test materials Material Mechanical properties σ y /MPa σ s /MPa δ/% Impact properties /J Q345B 460 530 29.5 104 Q235B 335 450 33 115 Table 2: The mechanical properties of test materials Test equipment The HK21B type residual stress detector (Fig. 1) and 3-element rosette strain gauge BX120-3CA are adopted for the test. Figure 1: HK21B residual stress detector Specimen design Eight welded I-shaped members (CH-1 ~ CH-8) are prepared for the test. The thickness of the specimens varies: CH-1 ~ CH-3 and CH-6 ~ CH-8 are 6mm thick; CH-4 and CH-5 are 10mm thick. Fig. 2 illustrates the specimen sizes and Fig. 3 displays the sizes and width-thickness ratios of the specimens. T