15. 基于载荷谱的曲轴疲劳寿命计算研究—季炳伟
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Web stress calculation with dynamic load from PU simulation
Stress field with 12 unit loads
Stress combination and fatigue evaluation
Load history with different speed
fatigue evaluation
4
四、载荷谱曲线获取
曲轴强度单元力法
从PU动力学仿真结果中提取一个循环周期（720度）主轴颈和曲柄销RBE2独立点12个自由度 的动态变形量。 achieve the reference points’ dynamic deflection data of the main journal pin and crank pin from the PU dynamic simulation results, each point includes 6 degrees of freedom.
模型假设 Assumption
载荷类型 Load type
经典算法 Classical
截断简支梁 Truncated freely supported beam
爆压 PFP
考虑提前角 Байду номын сангаасdvance angle
载荷分布 Load distribution
评价方式 Evaluation method
否 No
8
七、结论
实例分析表明，基于载荷谱疲劳寿命的曲轴强度计算方法能够准确预测曲轴使用寿命。该算法具 有以下优点： a) 曲拐为连续梁模型，考虑相邻缸对当前曲拐的强度影响；The crankshaft model is
continues, the adjacent cylinder’s load was considered; b) 载荷来自多体动力学仿真，考虑爆压提前角，最接近实际工况；The applied load comes
余弦分布 Cosine 名义弯曲应力 Nominal bending stress
载荷法 Load
截断简支梁 Truncated freely supported beam 爆压+惯性力 PFP+ Inertia force 否No
余弦分布 Cosine 有限元应力 FEA stress
动力学法 Dynamic 连续梁 Continuous beam
弯矩+扭矩 Bending and torsion moments 是Yes
耦合点加载 Displacement 名义应力 Nominal stress
单元力法 Unit load 连续梁 Continuous beam
实际载荷曲线 Load spectrum
是Yes
耦合点加载 Displacement 有限元应力+疲劳软件 FEA stress in fatigue software
from multi-dynamic simulation, the advance angle is taken in count,which is closer to reality; c) 采用99.99%存活率的结构数据，失效率为0.01%； Survive factor of 99.99% is used; d) 单元力模型只需计算一次，在疲劳软件中加载各种转速工况和各个位置的曲拐载荷谱，计算 速度快；The unit load model only need to be calculated once, different load spectrum via critical speed and critical position can be applied on the model easily and quickly in the fatigue software; e) 采用子模型细化圆角位置，网格依赖性小。The fillet submodel was used to decrease the influence by mesh quality.
Results satisfied? SF evaluatio
Run the mode
3
三、单元力模型
Unit load method
Half web’s stress distribution with unit displacement load
Stress calculation
Transient dynamic method
5
五、疲劳分析
曲轴半拐单元力模型与载荷谱在疲劳分析软件中合成，分析单拐强度。 The load spectrum was applied on the half web model with unit stress fields.
6
五、疲劳分析
考虑以上疲劳影响因素。 The influence factors are considered in the fatigue calculation.
2
二、计算流程
曲轴强度单元力法
计算假定：Simulation assumption a) 对曲轴单拐进行单位载荷有限元计算分析， Analysis on the single web with unit load; a) 根据动力学曲轴强度计算结果决定计算的转速与评
估部位，The critical speed and critical position come from 1D dynamic simulation; b) 通过多体动力学仿真平台求得曲拐一个循环周期内 的载荷，The load spectrum for one engine cycle comes from multi-body dynamic simulation; c) 在圆角位置采用子模型细化,The fillet submodel is used to refine the mesh quality; d) 在疲劳分析软件中进行多自由度载荷谱叠加，完成 曲轴疲劳安全系数计算，采用Goodman或Smith图 等进行疲劳安全系数评价。The load spectrum is applies on the unit load model to complete the fatigue safety factor calculation, either Goodman or smith method can be selected.
7
六、实例计算
对该发动机从怠速600rpm到超转速2600rpm进行了计算，曲拐位置为12个曲拐。曲轴整体最小疲劳安 全系数如图5所示，最危险位置出现在1300rpm，web12处。 The speed range from idle speed 600rpm to overspeed 2600rpm were calculated with 12 half web positions.The most dangerous position occurred in the 12th web with speed of 1300rpm
Geometry modification
Geometry model
The End
FEM model
Unit load model with stress fields
Multi-body dynamic model
Fatigue Model
Load spectrum
计算流程图 Simulation flow
9
The End Thanks!
基于载荷谱的曲轴疲劳寿命计算研究 Research on Fatigue Life Calculation for
Crankshaft based on Load Spectrum
潍柴动力技术中心 季炳伟
2013年3月25日
一、方案比较
方法对比Comparison conclusion
Method type
Stress field with 12 unit loads
Stress combination and fatigue evaluation
Load history with different speed
fatigue evaluation
4
四、载荷谱曲线获取
曲轴强度单元力法
从PU动力学仿真结果中提取一个循环周期（720度）主轴颈和曲柄销RBE2独立点12个自由度 的动态变形量。 achieve the reference points’ dynamic deflection data of the main journal pin and crank pin from the PU dynamic simulation results, each point includes 6 degrees of freedom.
模型假设 Assumption
载荷类型 Load type
经典算法 Classical
截断简支梁 Truncated freely supported beam
爆压 PFP
考虑提前角 Байду номын сангаасdvance angle
载荷分布 Load distribution
评价方式 Evaluation method
否 No
8
七、结论
实例分析表明，基于载荷谱疲劳寿命的曲轴强度计算方法能够准确预测曲轴使用寿命。该算法具 有以下优点： a) 曲拐为连续梁模型，考虑相邻缸对当前曲拐的强度影响；The crankshaft model is
continues, the adjacent cylinder’s load was considered; b) 载荷来自多体动力学仿真，考虑爆压提前角，最接近实际工况；The applied load comes
余弦分布 Cosine 名义弯曲应力 Nominal bending stress
载荷法 Load
截断简支梁 Truncated freely supported beam 爆压+惯性力 PFP+ Inertia force 否No
余弦分布 Cosine 有限元应力 FEA stress
动力学法 Dynamic 连续梁 Continuous beam
弯矩+扭矩 Bending and torsion moments 是Yes
耦合点加载 Displacement 名义应力 Nominal stress
单元力法 Unit load 连续梁 Continuous beam
实际载荷曲线 Load spectrum
是Yes
耦合点加载 Displacement 有限元应力+疲劳软件 FEA stress in fatigue software
from multi-dynamic simulation, the advance angle is taken in count,which is closer to reality; c) 采用99.99%存活率的结构数据，失效率为0.01%； Survive factor of 99.99% is used; d) 单元力模型只需计算一次，在疲劳软件中加载各种转速工况和各个位置的曲拐载荷谱，计算 速度快；The unit load model only need to be calculated once, different load spectrum via critical speed and critical position can be applied on the model easily and quickly in the fatigue software; e) 采用子模型细化圆角位置，网格依赖性小。The fillet submodel was used to decrease the influence by mesh quality.
Results satisfied? SF evaluatio
Run the mode
3
三、单元力模型
Unit load method
Half web’s stress distribution with unit displacement load
Stress calculation
Transient dynamic method
5
五、疲劳分析
曲轴半拐单元力模型与载荷谱在疲劳分析软件中合成，分析单拐强度。 The load spectrum was applied on the half web model with unit stress fields.
6
五、疲劳分析
考虑以上疲劳影响因素。 The influence factors are considered in the fatigue calculation.
2
二、计算流程
曲轴强度单元力法
计算假定：Simulation assumption a) 对曲轴单拐进行单位载荷有限元计算分析， Analysis on the single web with unit load; a) 根据动力学曲轴强度计算结果决定计算的转速与评
估部位，The critical speed and critical position come from 1D dynamic simulation; b) 通过多体动力学仿真平台求得曲拐一个循环周期内 的载荷，The load spectrum for one engine cycle comes from multi-body dynamic simulation; c) 在圆角位置采用子模型细化,The fillet submodel is used to refine the mesh quality; d) 在疲劳分析软件中进行多自由度载荷谱叠加，完成 曲轴疲劳安全系数计算，采用Goodman或Smith图 等进行疲劳安全系数评价。The load spectrum is applies on the unit load model to complete the fatigue safety factor calculation, either Goodman or smith method can be selected.
7
六、实例计算
对该发动机从怠速600rpm到超转速2600rpm进行了计算，曲拐位置为12个曲拐。曲轴整体最小疲劳安 全系数如图5所示，最危险位置出现在1300rpm，web12处。 The speed range from idle speed 600rpm to overspeed 2600rpm were calculated with 12 half web positions.The most dangerous position occurred in the 12th web with speed of 1300rpm
Geometry modification
Geometry model
The End
FEM model
Unit load model with stress fields
Multi-body dynamic model
Fatigue Model
Load spectrum
计算流程图 Simulation flow
9
The End Thanks!
基于载荷谱的曲轴疲劳寿命计算研究 Research on Fatigue Life Calculation for
Crankshaft based on Load Spectrum
潍柴动力技术中心 季炳伟
2013年3月25日
一、方案比较
方法对比Comparison conclusion
Method type