国家速滑馆弯折高钒密封索疲劳性能试验研究

Study on fatigue performance of Galfan fully locked coil cable in bending state for National Speed Skating Oval

国产高钒密封索因其供货期短、性价比高的优势在国家速滑馆工程中获得应用。为了解该材料的疲劳耐久性能,以国家速滑馆工程为背景,结合密封索实际工作状态,对弯折状态工作密封索开展试验研究。基于100年重现期风荷载下索网结构应力和变形情况,制定疲劳试验的拉力范围和弯折角度要求,测量了不同疲劳周次下密封索弹性模量变化情况。试验结果表明:国家速滑馆正常使用条件下弯折拉索疲劳周次达到200万次,可以满足本工程100年使用年限需求;当密封索弯折角度超过正常弯折角度并达到4°时,疲劳周次可以达到200万次,但会出现跳丝情况;超载并达到拉索抗拉力设计值时,密封索最外层钢丝出现断丝和跳丝损伤情况,但损伤位置距离锚具和索夹较远,循环加载可达到40万次以上;观察钢丝断口SEM微观形貌发现,疲劳裂纹由外层钢丝内侧转角部位最先出现,与有限元分析最大主拉应力位置相同;密封索初始弹性模量为170~180 GPa,随着疲劳周次增加,密封索等效弹性模量呈上升趋势,当存在少量断丝时该趋势不变。

Domestic-produced Galfan fully locked coil cables are used for the National Speed Skating Oval(NSSO) due to their advantages in procurement duration and cost efficiency. In order to obtain the fatigue durability of the cable, an experimental study for this fully locked coil cable series was carried out under a simulated loading state equivalent to the cable service state in NSSO. The cable loading ranges and bending angles in experiment were finalized to be consistent with the structural response(loading and deformation) of the cable net structure of NSSO calculated under 100-year return period wind load. The deviation of elastic modulus of fully locked coil cable under different fatigue cycles were measured. The test results demonstrate that under normal service condition, the fatigue cycles of the cable of NSSO can reach 2 million times under bending status, which can satisfy the 100-year design life requirements of the project. When the bending angle exceeds its maximum angle under design service condition and reaches 4°, the fatigue cycle can still reach 2 million times as well, but wire fracture is observed on the cable body. When the cable is further loaded to its design strength, wire fractures at the outermost layer can also be observed, the fracture location is far away from the anchor point and the cable clamp, and the fatigue cycle under this condition can reach 0.4 million times. The SEM micrograph of the fractured wire shows that the fatigue crack initially appears at the inner corner of the outer layer wire, which matches the location of the maximum principal tensile stress obtained through finite element analysis.The initial elastic modulus of the tested fully locked coil cable is around 170-180 GPa. An increasing trend of elastic modulus is observed with the increasing fatigue cycles, regardless of small amount of wire fractures.