EXPERIMENTAL STUDY ON MECHANICAL PROPERTIES OF STEEL TIE RODS
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摘要: 为了考察钢拉杆在不同受力条件下的力学性能,对10根GLG650钢拉杆试件分别进行单调受拉和低周往复拉压试验,得到钢拉杆的荷载-位移曲线、屈服承载力、最大承载力、极限承载力以及相应的变形和破坏形态。试验及分析结果表明:钢拉杆屈服强化阶段,荷载-位移曲线接近于直线;在往复拉压作用下,长细比较小的钢拉杆荷载-位移曲线出现循环软化现象。受拉屈服后,随着钢拉杆轴向变形加大,反向受压时其侧向挠曲变形随之增大,杆件中部在压弯作用下进入屈服。钢拉杆的断后伸长率约为3.4%~6.8%,远小于钢材试样的破断伸长率。钢拉杆破断多发生在加载端或固定端,受压弯累计塑性损伤的影响,长细比较小时杆件中部破断的情况增多。根据受力特征点确定的钢拉杆荷载-位移滞回规则,可供在往复荷载作用下弹塑性计算分析时应用。Abstract: In order to investigate the mechanical properties of steel tie rods under different loading conditions, the monotonic tension and low-cycle reciprocating tension and compression experiment was carried out on ten GLG650 steel tie rod specimens. The load-displacement curves, yield bearing capacity, maximum bearing capacity and ultimate bearing capacity of the steel tie rods and corresponding deformation and failure modes were obtained. The results of experiment and analysis show that the load-displacement curve of the steel tie rod is close to a straight line in the yield strengthening stage, and the load-displacement curves of the steel tie rods with smaller slenderness exhibit cyclic softening phenomenon under reciprocating tension and compression. After yielding in tension, as the axial deformation of the steel tie rod increases, its lateral deflection increases with the reverse compression, and the middle part of the rod enters into yield under compression and bending. The elongation after fracture of the steel tie rods is about 3.4% to 6.8%, which is much smaller than the elongation at breakage of the steel sample. Though the fracture mostly occurs at the loading end or fixed end, the fracture in the middle of the bar increases when the slenderness ratio is small, due to plastic damage accumulation under compression and bending. The load-displacement hysteresis rule of the steel tie rod determined according to the characteristic points can be used for elastic-plastic analysis under reciprocating load.
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表 1 钢拉杆试件规格
Table 1 Specifications of the steel tie rod specimens
直径d/mm 长度l/mm 长细比λ 材质 数量 25 2400 384.6 35CrMo 5 30 2400 320.4 35CrMo 5 注:钢拉杆长度l为两个销轴中心之间的间距。 表 2 钢材化学成分
Table 2 Chemical composition of the steel
拉杆直径
d/mmC/
(%)Si/
(%)Mn/
(%)P/
(%)S/
(%)Cr/
(%)Ni/
(%)Cu/
(%)Mo/
(%)Als/
(%)Al/
(%)25 0.37 0.22 0.58 0.021 0.007 0.93 0.014 0.013 0.018 0.017 0.019 30 0.38 0.23 0.59 0.010 0.002 0.92 0.035 0.040 0.086 0.017 0.019 表 3 钢材机械性能
Table 3 Mechanical properties of the steel
拉杆直径d/mm Rp0.2/MPa Rm/MPa A/(%) Z/(%) AkU/J 25 858 956 20.0 64.0 121.94 30 858 954 20.0 65.0 121.36 注:Rp0.2为0.2%残余变形相应的屈服强度;Rm为抗拉强度;A和Z分别破断伸长率和截面收缩率;AkU为−20 ℃的冲击功。 表 4 钢拉杆构件编号
Table 4 Steel tie rod member number
构件编号 直径d/mm 加载方式 MON-D25-1、2 25 单向受拉 CYC-D25-1~3 25 往复拉压 MON-D30-1、2 30 单向受拉 CYC-D30-1~3 30 往复拉压 表 5 钢拉杆单调受拉试验结果
Table 5 Experimental results of steel tie rods under monotonic tension
试件编号 Fy/kN Δy/mm Fm/kN Δm/mm Fu/kN Δu/mm Fc/kN Δc/mm μ δ/(%) MON-D25-1 423.40 12.33 463.78 74.25 463.78 74.25 309.24 82.26 6.02 4.18 MON-D25-2 421.36 14.96 467.61 75.00 467.61 75.00 303.85 85.26 5.01 3.41 MON-D30-1 621.33 12.71 700.27 102.82 700.27 102.82 444.03 113.04 8.09 5.05 MON-D30-2 597.59 14.01 673.22 125.60 673.22 125.60 443.14 134.04 8.97 6.03 注:Fy、Fm、Fu和Fc分别为屈服承载力、最大承载力、极限承载力和断裂承载力;Δy、Δm、Δu和Δc分别为与屈服承载力、最大承载力、极限承载力和断裂承载力相对应的位移;μ为延性系数,μ=Δu/Δy;δ为断后伸长率,δ=(lc−l0)/l0×100%,其中l0和lc分别为杆体的初始长度与破断后的长度。 表 6 钢拉杆单调受拉破坏情况
Table 6 Failure of steel tie rods under monotonic tension
试件编号 照片 颈缩部位 破断位置 MON-D25-1 加载端 距加载端U型接头463 mm MON-D25-2 固定端 距固定端U型接头456 mm MON-D30-1 加载端 距加载端U型接头315 mm MON-D30-2 中间段 距加载端U型接头1015 mm 注:左侧(S侧)为加载端,右侧(N侧)为固定端;钢拉杆试件破断位置均为颈缩部位。 表 7 钢拉杆往复拉压试验结果
Table 7 Experimental results of steel tie rods under cyclic tension and compression
试件编号 Fy/kN Δy/mm Fm/kN Δm/mm Fu/kN Δu/mm Fc/kN Δc/mm μ δ/(%) CYC-D25-1 404.01 10.88 462.37 80.76 462.26 89.59 303.29 96.97 7.42 4.54 CYC-D25-2 418.60 12.42 464.85 73.10 464.84 88.20 317.49 94.84 5.89 4.34 CYC-D25-3 403.13 10.91 460.89 65.04 427.50 89.93 297.51 94.30 5.96 4.03 CYC-D30-1 584.22 14.49 664.57 77.75 642.25 141.83 442.67 150.37 5.37 6.64 CYC-D30-2 568.01 11.64 662.24 90.00 654.79 128.33 431.08 138.74 7.73 6.23 CYC-D30-3 571.16 11.45 656.47 89.06 639.47 145.16 433.10 154.82 7.78 6.75 注:Fy、Fm、Fu和Fc分别为屈服承载力、最大承载力、极限承载力和断裂承载力;Δy、Δm、Δu和Δc分别为与屈服承载力、最大承载力、极限承载力和断裂承载力相对应的位移;μ为延性系数,μ=Δu/Δy;δ为断后伸长率,δ=(lc−l0)/l0×100%。 表 8 钢拉杆往复拉压破坏情况
Table 8 Failure of steel tie rods under cyclic tension and compression
试件编号 照片 颈缩部位 起始时点 破断时点 破断位置 CYC-D25-1 加载端 9Δy1+ 10Δy1+ 距加载端U型接头468 mm CYC-D25-2 加载端 9Δy1+ 11Δy1+ 距加载端U型接头473 mm CYC-D25-3 固定端 9Δy1+ 11Δy1+ 距固定端U型接头448 mm CYC-D30-1 中间段 13Δy1+ 15Δy1+ 距加载端U型接头1248 mm CYC-D30-2 加载端 13Δy1+ 15Δy1+ 距加载端U型接头295 mm CYC-D30-3 中间段 13Δy1+ 15Δy1+ 距固定端U型接头1258 mm 注:左侧(S侧)为加载端,右侧(N侧)为固定端;钢拉杆试件破断位置均为颈缩部位。 表 9 钢拉杆屈曲临界荷载
Table 9 Critical buckling loads of the steel tie rods
直径 Ncr/kN(总长) Ncr1/kN(杆长) Nexp/kN D25 6.75 10.35 17.66 D30 14.00 21.38 26.99 注:E=2.06×105 MPa;l=2400 mm,ld25=1937.6 mm,ld30=1941.8 mm。 表 10 试件钢材的硬化系数
Table 10 Steel hardening coefficients of the specimens
试件编号 硬化系数k 试件编号 硬化系数k MON-D25-1 0.0132 MON-D30-1 0.0146 MON-D25-2 0.0129 MON-D30-2 0.0149 CYC-D25-1 0.0165 CYC-D30-1 0.0145 CYC-D25-2 0.0192 CYC-D30-2 0.0157 CYC-D25-3 0.0139 CYC-D30-3 0.0152 平均值 0.0151 平均值 0.0150 -
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