Estimating method of fatigue life during cracking initiation of asphalt pavement based on modified Neuber equation
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摘要: 为预估沥青路面裂缝形成疲劳寿命, 根据局部应力-应变理论, 通过直接拉伸疲劳试验, 建立了沥青混合料的真实应力-应变循环曲线, 运用Neuber方程将名义应力、应变转换为局部应力、应变, 对循环曲线和Neuber方程进行修正, 以符合平面应变问题。通过等应变疲劳试验, 建立了沥青混合料的疲劳寿命方程, 提出了沥青路面裂缝形成寿命预估方法。根据应变疲劳寿命曲线可合理计算沥青混合料疲劳损伤, 由累积损伤可求得沥青路面裂缝形成疲劳寿命。
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关键词:
- 路面工程 /
- 局部应变 /
- 修正Neuber方程 /
- 裂缝形成 /
- 疲劳寿命
Abstract: To estimate the fatigue life of asphalt mixture during the cracking initiation of asphalt pavement, its true stress and strain loop curve was established by direct tension test based on partial stress and strain theory, its nominal stress and strain were converted into partial stress and strain through Neuber equation, and its loop curve and Neuber equation were modified in order to meet the question of plain stress.The fatigue equation of asphalt mixture was established by isostrain fatigue test, and an estimating method of fatigue life was put forward.It is pointed that the fatigue damage of asphalt mixture can be reasonably calculated by its strain fatigue life curve, and its fatigue life during the cracking initiation of asphalt pavement can be estimated by its cumulation damage.-
Key words:
- pavement engineering /
- partial strain /
- modified Neuber equation /
- cracking initiation /
- fatigue life
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表 1 矿料级配组成
Table 1. Aggregate gradation composition
筛孔尺寸/mm 26.500 19.000 16.000 13.200 9.500 4.750 2.360 1.180 0.600 0.300 0.150 0.075 通过率/% 100.0 99.9 96.1 84.7 75.0 45.9 34.1 23.3 18.6 12.7 8.9 6.3 
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表 2 马歇尔试验结果
Table 2. Result of Marshall test
指标 沥青油石比/% 空隙率/% 矿料间隙率/% 沥青饱和度/% 稳定度/kN 流值/0.1mm 结果 5.4 4.3 16.6 74.8 11.57 39.6
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表 3 真实应力幅和塑性应变幅
Table 3. True stress amplitude and plastic strain amplitude
应变水平 Δε Δσ/MPa Δεp 0.6 0.004 37 1.499 0.003 66 0.5 0.004 04 1.243 0.003 00 0.4 0.003 26 1.154 0.002 30 0.3 0.002 45 0.838 0.001 75
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表 5 循环应力-应变曲线修正参数
Table 5. Modified parameters of circular stress-strain curve
应变水平 ε'a/10-3 σ'a/MPa μ1 K" n" 0.6 1.979 0.865 0.464 693.828 1.012 0.5 1.830 0.717 0.463 0.4 1.488 0.665 0.457 0.3 1.116 0.483 0.458
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表 6 单调拉伸试验参数
Table 6. Parameters of monotony tensile test
试件编号 断裂应变 断裂应力/MPa 割线模量/MPa D1 0.006 66 0.198 45 200.945 D2 0.010 33 0.242 36 175.801 D3 0.007 14 0.206 36 165.510 D4 0.010 78 0.220 67 164.417 D5 0.010 60 0.226 52 187.162 平均值 0.009 10 0.218 87 178.767
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表 7 等应变疲劳试验中的εa与Nf
Table 7. εaand Nfof equal strain fatigue test
试件编号 S1 S2 S3 S4 S5 S6 S7 S8 εa/10-3 2.424 1.945 2.019 2.017 1.651 1.609 1.627 1.224 Nf 45 50 519 513 1 023 1 250 822 1 078
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表 8 不同算法下的b和c值
Table 8. b and c values of different methods
参数 麦夸特法+通用全局优化法 准牛顿法+通用全局优化法 改进差分进化算法 最大继承法 b 0.115 410 0.115 410 0.115 410 0.115 410 c -0.221 822 -0.221 822 -0.221 822 -0.221 822
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