HRB500钢筋直螺纹机械连接失效研究与工艺优化

Failure study and process optimization on straight thread mechanical connection on HRB500 rebar

HRB400钢筋缩颈-滚压直螺纹机械连接工艺已在实际建筑工程中被广泛应用。国家大力推广的HRB500钢筋缩颈-滚压直螺纹机械连接的产品性能稳定性较差。通过计算机数值模拟的方法研究了HRB500钢筋在缩颈工序过程中的金属流动情况,从宏观表现和微观特征两个方面研究了HRB500钢筋直螺纹机械连接失效断口,明确了连接失效的原因。缩颈时钢筋横肋的金属流动速度不同,形成显微裂纹,造成应力集中,缩颈过程中塑性变形极其不均匀,降低了其拉伸塑性;提出了剥肋-缩颈-滚压直螺纹的钢筋机械连接优化工艺,给出了Ф32 mm以上钢筋剥肋后,为母材直径+2 mm的合理剥肋工艺参数。

The process of necking-rolling straight thread mechanical connection on HRB400 rebar has been widely used in practical construction projects,but the performance stability of the products connected by necking-rolling straight thread mechanical connection on HRB400 rebar promoted by China is poor. Therefore,the metal flow during the necking process of HRB500 rebar was studied by computer numerical simulation,and the failure fracture of the straight thread mechanical connection on HRB500 rebar was studied from the two aspects of macro performances and micro characteristics to confirm the cause of the connection failure. Furthermore,in the process of necking,the metal flow velocity of transverse rib was different,and the microcracks were formed to cause stress concentration. In addition,the plastic deformation during the necking process was extremely uneven,and the tensile plasticity was reduced. Thus,the optimization process of rebar mechanical connection with stripping-necking-rolling straight thread was proposed,and the reasonable stripping process parameters of base material diameter + 2 mm after stripping the ribs of rebar above Ф32 mm were given.