自适应大流量安全阀的流固耦合分析与保压实验

为提高自适应大流量安全阀关键零件的可靠性及寿命,利用UG软件建立自适应大流量安全阀关键零件的三维模型,并借助ANSYS Fluent软件对其进行了网格划分,通过单向流固耦合分析得到了一级锥阀、二级差动阀芯等关键零件的应力、应变云图;为进一步研究自适应大流量安全阀的低压密封性,利用ZF-2WG液压支架阀综合实验台对其进行了6、14 MPa 2种不同压力的打压实验。仿真及实验结果表明：一级锥阀的锥面附近区域为应力集中区域,锥尖附近区域为应变集中区域;二级阀芯4个阻尼孔靠差动腔侧的出口处为应力集中区域,二级阀芯外环形差动腔接触流体区域为应变集中区域;通过操作控制P口压力为6、14 MPa,保压时间为120 s,压力值基本保持在设定值,保压效果非常理想。     

Ausbau des Stichkanals nach Salzgitter von SKS‐km 3,550 bis 14,918

Expansion of the branch channel to Salzgitter from SKS‐km 3,550 to 14,918 The branch channel to Salzgitter will be extended to the waterway category Vb in the next years. This will enable inland waterway vessels with a width of 11,45 m and a loaded draft of 2,80 m to run it without limitations. The reaches Wedtlenstedt and Üfingen will be extended in most areas to a trapezoidal cross section with a width at water level of 36,90 m and a water depth of 4,00 m. The exit basins of the locks will be extended on one side. Overall about 1 000 000 m² of soil will be moved. About 300 000 m² of clay sealing and 460 000 m² of rip‐rap will be installed. Three culverts have to be replaced by new constructions to adapt to the new cross section of the channel. In addition two bridges will be modified to allow for a clearance of 5,25 m. At present the plan approval procedure is carried out. It is expected to achieve the plan approval order in 2017. The construction is planned to start in 2018. Completion is scheduled for 2024.     

电晕处理对聚乙烯薄膜热封性能的影响

聚乙烯薄膜经过电晕处理后,热封温度提高,热封强度降低。这可通过降低电晕处理强度,适当延长热封时间和添加一定比例的mLLDPE树脂,以减小电晕处理对聚乙烯薄膜热封性能的影响。     

蒸馏淡化用密封圈材料寿命预测

低温多效蒸馏中,传热管与管板密封圈长期处于高温、高盐度海水侵蚀环境,密封圈材料寿命对设备稳定运行有重要意义。采用统计方法预测研发的专用三元乙丙材料的使用寿命。根据寿命预测方法和使用环境,选定了加速老化的试验条件和性能参数,开展了相应的加速老化试验。寿命预测结果显示当压缩永久变形指标的临界值在0.10~0.50范围内时,预测EPDM材料的使用寿命是13.2~3.6 a。     

我国航空用橡胶密封型材的现状与发展

从产品结构、结构设计、成型加工、主体材料选择和适航要求方面总结我国航空用橡胶密封型材的技术概况,指出我国航空用橡胶密封型材技术在材料研发、结构设计和成品性能检测方面的不足,建议我国航空用橡胶密封型材行业贯彻适航理念,以产品配套促进基础研究。     

基于变形控制标准的高土石坝地震可靠度分析

基于可靠度分析的设计方法是科学定量地研究和保证岩土工程安全性的重要手段之一。通过定量考察土石坝工程中的不确定性因素,综合评估地震失效概率,可为高土石坝抗震设计和风险评估提供参考。以坝顶震陷率作为地震安全控制指标,提出了同时考虑地震和筑坝料参数不确定性的高土石坝地震可靠度分析方法。首先,采用地震烈度作为地震危险性的宏观衡量尺度,通过引入地震烈度概率模型,将基于概率烈度的地震动峰值作为地震强度因子,调整规范谱人工地震波的幅值进行动力有限元计算。然后,采用适用于处理小样本和非线性问题的高斯过程响应面法,建立筑坝料参数与坝顶震陷率之间的非线性映射关系,结合蒙特卡罗法计算高土石坝地震失效概率。最后,以紫坪铺面板堆石坝为例,应用该方法考察了设计基准期内的地震失效概率。     

地铁健康监测PCBN模型的参数相关性分析

对城市盾构地铁结构的健康服役和安全可靠性进行评价时,多局限于静态推理,通过构建PCBN(Pair-Copula Bayes Network)网络结构得到评判指标的多元联合概率分布,实现参数相依性的准确识别和高精度重构。基于3种失效模式对盾构地铁结构节点相关性分析及安全状态评价,充分挖掘监测数据的隐藏信息,表征盾构地铁结构的风险状态。以武汉地铁三号线某空推段为工程背景进行PCBN模型建模。结果表明:PCBN模型得出的地铁安全状态与地铁工程中的实际风险信息非常吻合,体现了构建PCBN网络模型的准确性和实用性。     

Slope reliability and back analysis of failure with geotechnical parameters estimated using Bayesian inference

A Bayesian approach is proposed for the inference of the geotechnical parameters used in slope design. The methodology involves the construction of posterior probability distributions that combine prior information on the parameter values with typical data from laboratory tests and site investigations used in design. The posterior distributions are often complex, multidimensional functions whose analysis requires the use of Markov chain Monte Carlo (MCMC) methods. These procedures are used to draw representative samples of the parameters investigated, providing information on their best estimate values, variability and correlations. The paper describes the methodology to define the posterior distributions of the input parameters for slope design and the use of these results for evaluation of the reliability of a slope with the first order reliability method (FORM). The reliability analysis corresponds to a forward stability analysis of the slope where the factor of safety (FS) is calculated with a surrogate model from the more likely values of the input parameters. The Bayesian model is also used to update the estimation of the input parameters based on the back analysis of slope failure. In this case, the condition FS = 1 is treated as a data point that is compared with the model prediction of FS. The analysis requires a sufficient number of observations of failure to outbalance the effect of the initial input parameters. The parameters are updated according to their uncertainty, which is determined by the amount of data supporting them. The methodology is illustrated with an example of a rock slope characterised with a Hoek-Brown rock mass strength. The example is used to highlight the advantages of using Bayesian methods for the slope reliability analysis and to show the effects of data support on the results of the updating process from back analysis of failure.     

Performance-based seismic fragility analysis of retaining walls based on the probability density evolution method

Seismic fragility analysis is an efficient way to study the seismic behaviour and performance of structures under the excitation of earthquakes of varying intensity, and an essential part of the seismic risk assessment of structures. A recently developed dynamic reliability methodology, the probability density evolution method (PDEM), is proposed for the dynamic reliability and seismic fragility analysis of a retaining wall. The PDEM can obtain an instantaneous probability density function of the seismic responses and easily acquire the seismic reliability of the structural system. An important advantage of the PDEM is its high efficiency relative to that of the Monte Carlo simulation method, which is often used in the reliability and fragility analysis of structures. The present study uses a typical gravity retaining wall to illustrate stochastic seismic responses and fragility curves that can be obtained by the PDEM. The combined uncertainties of the seismic force and soil properties are explicitly and systematically modelled by stochastic ground motions and random variables respectively. The performance of the retaining wall is analysed for different acceptable levels of backfill settlement. Additionally, seismic fragility curves are constructed without assuming the distribution of the seismic response.     

Monte-Carlo抽样法在边坡可靠性分析中的应用研究

针对复杂边坡可靠性分析时,功能函数具有高度非线性和隐式表达的特性,为克服传统边坡可靠性分析解决此类问题的不足,将Monte-Carlo重要抽样与响应面法相结合,利用响应面法实现边坡极限状态函数的显式表达,并确定设计验算点,以该点为新的抽样中心应用Monte-Carlo重要抽样计算边坡的失效概率。通过两个算例进行了分析,结果表明:该方法在保证精度的同时提高计算效率,适于解决含有大量随机变量的复杂边坡工程可靠性分析。