综合考虑疲劳强度影响因素的寿命预测方法

目的提出一种综合考虑疲劳强度影响因素的寿命预测方法。方法利用提出的综合疲劳强度因子Kz考虑应力集中、尺寸和表面状态等因素对疲劳强度的影响,结合S-N曲线方法,采用Goodman方程进行平均应力修正,采用Miner定理进行疲劳损伤累积,提出一种适用于机械结构的疲劳寿命预测方法。结果对一种复杂结构螺旋弹簧进行了位移控制的恒幅和变幅台架试验,并利用弹塑性有限元分析获得了关键危险点位置的应力响应历程。利用台架试验的寿命结果对提出的方法进行了验证,预测误差在2倍因子以内。结论提出的方法可以较好地预测机械结构的疲劳寿命。

A novel refined dynamic model of high-speed maglev train-bridge coupled system for random vibration and running safety assessment

Running safety assessment and tracking irregularity parametric sensitivity analysis of high-speed maglev train-bridge system are of great concern,especially need perfect refinement models in which all properties can be well characterized based on various stochastic excitations.A three-dimensional refined spatial random vibration analysis model of high-speed maglev train-bridge coupled system is established in this paper,in which multi-source uncertainty excitation can be considered simultaneously,and the probability density evolution method(PDEM)is adopted to reveal the system-specific uncertainty dynamic characteristic.The motion equation of the maglev vehicle model is composed of multi-rigid bodies with a total 210-degrees of freedom for each vehicle,and a refined electromagnetic force-air gap model is used to account for the interaction and coupling effect between the moving train and track beam bridges,which are directly established by using finite element method.The model is proven to be applicable by comparing with Monte Carlo simulation.By applying the proposed stochastic framework to the high maglev line,the random dynamic responses of maglev vehicles running on the bridges are studied for running safety and stability assessment.Moreover,the effects of track irregularity wavelength range under different amplitude and running speeds on the coupled system are investigated.The results show that the augmentation of train speed will move backward the sensitive wavelength interval,and track irregularity amplitude influences the response remarkably in the sensitive interval.

自控硬膜外镇痛对食管癌术后肺部感染干预效果及IL-10和TNF-α水平影响

目的分析自控硬膜外镇痛(PCEA)对食管癌术后肺部感染患者的干预效果及对白细胞介素-10(IL-10)、肿瘤坏死因子-α(TNF-α)水平的影响。方法选取2019年2月-2020年2月医院收治的行食管癌手术治疗的患者159例,按照随机数字表法分为自控硬膜外镇痛(PCEA)组91例、PCIA组68例。所有患者均行胸段硬膜外阻滞复合静脉全麻干预,PCIA组行自控静脉镇痛干预,PCEA组患者行自控硬膜外镇痛模式干预。对比两组患者麻醉前0.5 h(T1)、切皮后1 h(T2)、术后4 h(T3)、术后24 h(T4)、术后48 h(T5)时间点机体应激指标皮质醇(Cor)、应激激素生长激素(GH)、催乳素(PRL)水平、T淋巴细胞亚群指标CD3^(+)、CD4^(+)、CD8^(+)水平及CD4^(+)/CD8^(+)比值及IL-10、TNF-α水平变化及术后不同时间点疼痛情况,统计肺部感染发生情况。结果与T1时间点相比,两组患者T2时间点GH、Cor、PRL、IL-10、TNF-α水平均升高,T3、T4、T5时间点GH、Cor、PRL、IL-10、TNF-α水平逐渐降低,且PCEA组GH、Cor、PRL、IL-10、TNF-α水平低于PCIA组(P<0.05)。与T1时间点相比,两组患者T2时间点CD3^(+)、CD4^(+)水平、CD4^(+)/CD8^(+)值均降低,T3、T4、T5时间点CD3^(+)、CD4^(+)水平、CD4^(+)/CD8^(+)值逐渐升高,且PCEA组CD3^(+)、CD4^(+)水平、CD4^(+)/CD8^(+)值高于PCIA组(P<0.05)。与PCIA组相比,PCEA组术后不同时间点VAS评分均降低(P<0.05)。PCEA组肺部感染发生率3.30%低于PCIA组14.71%(P<0.05)。结论与PCIA相比,PCEA用于食管癌手术患者,可明显减轻患者机体应激反应、免疫功能抑制状态及IL-10、TNF-α异常变化,降低术后肺部感染的发生。