电弧增材制造螺栓连接剪切破坏模式与承载力研究

Experimental study on failure modes and load-bearing capacities of wire and arc additively manufactured steel bolted connections

电弧增材制造(WAAM)因具有合理的打印精度、较低的时间成本以及可生产大型复杂形状结构等优点,逐渐成为建筑行业一种有潜力的制造工艺。为了研究由于制造工艺和材料性能的差异引起的WAAM螺栓连接的基本力学性能差异和对WAAM钢的材料性能和螺栓连接的力学性能进行试验研究。共制作了24个不同打印方向的材性拉伸试件和72个不同尺寸、剪切面数与打印方向的WAAM螺栓连接试件。采用三维激光扫描技术测量试件尺寸,并进行静力拉伸试验和剪切试验。分析WAAM螺栓连接的破坏模式和承载力,研究打印方向对试验结果的影响。通过比较螺栓连接的破坏模式和承载力,进一步研究已有规范及文献计算方法对WAAM螺栓连接的适用性。结果表明:拉伸试件和螺栓连接试件在试验中均呈现各向异性现象,承载力的差异分别达到了10%和20%,材料各向异性对破坏模式产生了一定影响,导致有40%的具有相似尺寸但打印方向不同的成对试件呈现不同的破坏模式;由于WAAM钢材具有各向异性的特性及现有设计方法中未考虑倾斜承压破坏和端部撕裂两种破坏模式,使得现有规范无法准确预测WAAM螺栓连接的破坏模式和承载力。

The wire and arc additive manufacturing(WAAM),one of the methods of metal 3D printing,has shown significant potential in manufacturing large-scale steel structural elements with reasonable printing accuracy,time and cost in the construction industry.To investigate the mechanical performance differences of WAAM lap shear specimens caused by dfferences in the manufacturing process and material properties,experimental studies were conducted on the material properties of WAAM steel and the structural behaviours of WAAM lap shear specimens.In this paper,a total number of 24 WAAM lap shear specimens with three different print layer orientations and 72 WAAM lap shear connection specimens with different design configurations were fabricated,dimensionally measured with the 3D scanning technique,and subjected to tensile coupon tests and lap shear connection tests.The failure modes and load-bearing capacities of the bolted connections were analysed,focusing on the print layer orientations of the WAAM steel plates.The current code design provisions and design approaches proposed in the literature for steel structures were further evaluated by comparing the failure modes and load-bearing capacities of the bolted connection specimens.This research shows that both the material tensile specimen and the bolted connection specimen show anisotropy in the test,and the difference in bearing capacity reaches 10%and 20%respectively.The material anisotropy has a certain impact on the failure mode.The relatively accurate predictions of the capacity of the WAAM lap shear specimens following the current steel design standards are significantly compromised by not predicting failure modes correctly,which could be attributed to the influence of anisotropic material properties of the WAAM steel plates and the failure modes of tiltbearing and end-splitting which are not considered in current design provisions.