Railway ground vibrations induced by wheel and rail singular defects

Railway local irregularities are a growing source of ground-borne vibration and can cause negative environmental impacts, particularly in urban areas. Therefore, this paper analyses the effect of railway track singular defects (discontinuities) on ground vibration generation and propagation. A vehicle/track/soil numerical railway model is presented, capable of accurately predicting vibration levels. The prediction model is composed of a multibody vehicle model, a flexible track model and a finite/infinite element soil model. Firstly, analysis is undertaken to assess the ability of wheel/rail contact models to accurately simulate the force generation at the wheel/rail contact, in the presence of a singular defect. It is found that, although linear contact models are sufficient for modelling ground vibration on smooth tracks, when singular defects are present higher accuracy wheel/rail models are required. Furthermore, it is found that the variation in wheel/rail force during the singular defect contact depends on the track flexibility, and thus requires a fully coupled vehicle/track/foundation model. Next, a parametric study of ground vibrations generated by singular rail and wheel defects is undertaken. Six shapes of discontinuity are modelled, representing various defect types such as transition zones, switches, crossings, rail joints and wheel flats. The vehicle is modelled as an AM96 train set and it is found that ground vibration levels are highly sensitive to defect height, length and shape.     

竖向钢筋电渣压力焊缺陷产生及防治

分析了竖向钢筋电渣压力焊在房屋建筑与桥梁施工中产生缺陷的原因,并提出了防治措施。     

PD3余热淬火钢轨接触焊焊后热处理研究

淬火钢轨接触焊后存在接头晶粒粗化,塑性、韧性大幅度下降,硬度不均匀等现象,使用中钢轨焊接接头的脆性增大,产生接头低塌并导致马鞍形磨耗和波浪磨耗。为解决上述问题,PD3余热淬火钢轨接触焊后必须对焊接接头进行焊后热处理。焊后热处理采用中频感应加热,加热温度为845℃～920℃,然后喷风冷却接头全断面,喷风压力0 25MPa～0 30MPa,喷风冷却时间120s。结果表明,接头经热处理后的硬度、韧塑性能接近或超过原淬火轨水平,落锤、静弯、实物疲劳性能有较大的提高,满足了无缝线路钢轨的使用要求。     

新型立式铝-钢复合接头焊后性能实验研究

本文通过对新型立式铝—钢复合接头焊接后的抗拉强度、疲劳性能、抗冲击性能等实验研究，得出了新型立式铝—钢复合接头焊接后在力学性能上满足工程应用要求的结论。     

船舶结构用铝—钛—钢复合过渡接头疲劳性能研究

铝－钛－钢爆炸复合板作为新型舰船结构铝合金，钢之间连接过渡接头取代传统的铆接连接具有优越的连接性能和施工工艺。本研究模拟实际应用条件，测定了其焊接前后在固定应力水平下的弯曲疲劳寿命和弯曲疲劳Ｓ－Ｎ曲线，并运用计算机得到Ｓ－Ｎ曲线的回归方程，为复合过渡接头疲劳寿命的预测和最大应力的控制等提供了依据。     

港珠澳跨海集群工程海底沉管隧道防火设计

港珠澳跨海集群工程海底隧道是目前世界上最长的公路沉管隧道,运营期设置有主动与被动的双重防火系统。结合港珠澳海底沉管隧道的主要技术特点,提出防火设计中热释放率、火灾次数、耐火等级以及采取防护措施后构件的主要耐火指标。依据工程防火的具体实施条件,通过综合比较,沉管结构防火设计采用防火板直接覆面方式,沉管接头防火采用由刚性防火板与柔性防火隔断共同组成的具有自主知识产权的双层防护系统。     

铝热焊用一次性坩埚的研制

分析一次性坩埚所选的原沙、树脂砂和粘结剂等原料的参数。研究树脂砂的强度、发气量、表面稳定性、耐热性等性能,保证树脂砂的适用性。使用成型的树脂自硬砂一次性坩埚进行焊接,焊接接头的硬度平均为288HB,力学性能主要参数Rm为790MPa,静弯平均为1500kN。根据TB/T1632 91要求对焊接接头的硬度、力学性能、静弯强度进行试验。分析焊接接头夹杂物情况和焊缝金相组织形貌,并与使用镁质坩埚的情况进行对比。试验结果显示,研制的一次性坩埚可以满足铝热焊接使用。     

全叠片电机定子焊接工艺研究

从焊接方法,焊接材料,焊接规范,消除焊接应力等方面,进行试验分析,确定焊接应力小、变形量小的焊接工艺,使得全叠片电机定子的焊接质量完全达到了设计要求。     

电力机车辅助系统地面联调试验系统的开发

介绍了电力机车(动力车)辅助系统地面联调试验的设计要求、系统构成及工作原理,并对SS9型机车采用辅助变流器供电的辅助机组进行了地面联调部分试验,获取了许多重要数据,为今后的研究、设计提供了依据。