灰色系统理论在桥梁劣化预测模型中的应用

根据辽宁地区桥梁承载力下降检测资料,应用灰色系统理论对在役桥梁劣化趋势进行分析,提出以时间与状态得分为等间隔初始序列,推导出桥梁劣化预测模型按指数分布表达式,并对检测序列进行分析验证,为桥梁劣化预测提供参考。     

H型钢接触网支柱在风荷载作用下的疲劳性能分析

H型钢接触网支柱在高速铁路中得到广泛使用,直接影响铁路接触网系统安全。长期处于风荷载作用下,H型钢接触网支柱存在疲劳问题。通过建立数值计算模型,应用热点应力的表面外推法,对H型钢接触网支柱柱脚焊缝在风荷载作用下的疲劳性能进行分析。以兰新高铁H型钢接触网支柱为例,依据热点应力-寿命曲线,计算支柱焊缝的疲劳寿命。分析结果表明:其他条件不变的情况下,改变型钢规格和柱高,热点位置不发生变化;随着支柱高度增加,疲劳寿命降低21%左右;随着型钢截面的增大,疲劳寿命增加23%左右。     

汽车车轮加速疲劳试验的研究

以累积损伤理论为基础，对汽车车轮加速疲劳试验进行了研究，以缩短试验时间，降低试验成本。     

U71 Mn 50 kg·m-1普通碳素钢钢轨疲劳裂纹扩展速率试验研究

根据室内对U71Mn50kg·m-1普通碳素钢钢轨按三点弯曲标准进行的试验,测定该钢轨的疲劳裂纹扩展速率,即裂纹扩展深度a及其对应的循环次数N值。利用中值法求得裂纹扩展深度对循环次数的微分值。根据断裂理论求得相应的裂纹前沿应力强度因子幅度ΔK。根据Paris公式,对以上两值取自然对数进行线性回归分析,确定该公式中U71Mn50kg·m-1普通碳素钢钢轨疲劳裂纹扩展速率的两个材料常数C为3 8771×10-12,m为3 6343。     

A probabilistic damage tolerance concept for welded joints Part 2: a supplement to the rule based S–N approach

The first part of this paper presented the required statistics and stochastic models for reliability analysis of the fatigue fracture of welded plate joints. This present Part 2 suggests a probabilistic damage tolerance supplement to the design S–N curves for welded joints. The goal is to provide the practising engineer with simple tools that predict the reliability against fatigue fracture during service life. The impact of the chosen fatigue design factors (FDF) and the uncertainty in the applied stresses is revealed. The effect of an in-service inspection programme is also predicted. The results are presented as dimensionless matrices and suggested for use in support of decision-making at the design stage, without any advanced fracture mechanics modelling and stochastic simulation. One important advantage of this format is that the probability levels are presented regardless of actual weld class and target service life (TSL). This is obtained by introducing the FDF as a key parameter to the results. This parameter is defined as the ratio of predicted fatigue life over TSL. FDF is always calculated in the S–N approach which is mandatory in fatigue life prediction. Various welded details (classes) will have the same reliability level for the same FDF. This is true at the end of TSL and at earlier stages, i.e. fractions of TSL. The absolute value of TSL is immaterial for a given FDF. In the case of in-service inspection, the inspection interval is also given without dimensions as a fraction of TSL.

Only the influence of future scheduled inspections is treated. Updating based on actual inspection results is not included as the scope of work is inspection planning at the design stage. Results for some frequent cases occurring in practice are readily derived and presented.     

运用二阶摄动方法预测焊接点疲劳微弯裂纹的路径发展

利用二阶摄动方法分析研究了轻微弯曲疲劳裂纹尖端应力强度因子的变化幅度,进一步得到了在循环载荷下直线裂纹微弯延伸尖端应力强度因子变化幅值的近似表达式.以匹配渐进扩张的形式考虑了远区域边界条件的效果,研究了裂尖附近的渐进应力场.利用Irwin公式计算出了由于裂纹发展而引起的应变能释放率变化幅值.预测了在具有非均匀断裂韧度的物质中裂纹的延伸.考虑了循环载荷、残余应力,以及由于焊接而引起的物质衰变等因素,利用了二阶摄动方法预测了沿着焊接点传播的弹脆性裂纹路径.     

Fatigue design for plug/ring type gas welded joints of sts301l including welding residual stresses

This paper presents a fatigue design method for plug and ring type gas welded joints, which incorporates welding residual stress effects. A non-linear finite element analysis (FEA) was first performed to simulate the gas welding process. The numerically predicted residual stresses of the gas welds were then compared to experimental results measured using a hole drilling method. In order to evaluate the fatigue strength of the plug and ring type gas welded joints, a stress amplitude (σ _a ) _R taling the welding residual stress of the gas weld into account was introduced and is based on a modified Goodman equation incorporating the effect of the residual stress. Using the stress amplitude (σ _a ) _R , the ΔP-N _f relations obtained from fatigue tests for plug and ring type gas welded joints having various dimensions and shapes were systematically rearranged into (σ _a ) _R -N _f relations. It was found that the proposed stress amplitude (σ _a ) _R could provide a systematic and reasonable fatigue design criterion for the plug and ring type gas welded joints.     

Prediction of fatigue life and estimation of its reliability on the parts of an air suspension system

Air suspension systems have been implemented in various commercial vehicles, such as buses and special purpose trucks, because of the comfortable ride and easy height control. An evaluation of the durability of vehicle parts has been required for service life and safety starting in the early stages of design. The cyclic load applied to the vehicle can cause fatigue failure of parts, such as the suspension frame. This paper presents a method to predict the fatigue life of the suspension frame at the design stage of the air suspension system used in a heavy-duty vehicle. To estimate the fatigue life using the SN method, the Dynamic Stress Time History (DSTH) is necessary for the part of interest. DSTH can be obtained from the results of the flexible body dynamic analysis using the Belgian road simulation and the Modal Stress Recovery (MSR) method. Furthermore, the reliability of the predicted fatigue life can be evaluated by considering the variations in material properties. The probability and distribution of the expected life cycle can be obtained using experimental design with a minimum number of simulations. The advantage of using statistical methods to evaluate the life cycle is the ability to predict replacement time and the probability of failure of mass-produced parts. This paper proposes a rapid and simple method that can be effectively applied to the design of vehicle parts.     

高速公路桥面病因分析及防治措施

从设计和施工两方面分析影响高速公路桥面破坏的主要原因，提出了相应阶段应采取的措施。     

40 Cr钢和50车轴钢超高周疲劳性能研究及疲劳断裂机理探讨

在对称拉压超声疲劳试验装置基础上,开发研制非对称拉压超声疲劳试验装置和三点弯曲超声疲劳试验装置。采用超声疲劳试验方法,结合扫描电镜断口微观分析,对40 Cr钢和50车轴钢光滑试样和缺口试样,在超高周疲劳范围内的疲劳性能和疲劳断裂机制进行研究,主要研究成果如下。对40 Cr