点接触乏油混合润滑的数值模拟研究

基于改进的统一Reynolds方程,对点接触乏油混合润滑进行数值模拟,研究供油量、载荷、卷吸速度等对混合润滑性能的影响。分析时将润滑区域分为两部分,在压力区润滑油完全充满间隙,在空穴区润滑油部分充满间隙,这两区域的润滑特性都采用离散化的Reynolds方程求解;采用快速傅立叶变换算法求解弹性变形,采用GaussSeidal低松弛迭代逐行扫描法求解压力。结果表明:随着初始供油量的变化,润滑油油膜压力、油膜厚度以及部分油膜比例都会受到影响;速度对点接触乏油混合润滑的影响主要表现在油膜厚度分布上,而载荷的影响主要表现在压力分布上;随着载荷的升高,油膜压力将增大,而油膜厚度有轻微的减小,随着速度的升高润滑油油膜厚度减小。     

织构长宽比对钻头轴承润滑减磨性能的影响

基于雷诺方程建立单一织构不可压缩牛顿流体润滑条件下的动压润滑理论模型,采用有限差分法和高斯-赛德尔迭代法求解雷诺方程,分析不同长宽比(平行速度方向为长度方向,垂直速度方向为宽度方向)织构表面对动压润滑性能的影响;并采用MMW-1型微机控制万能摩擦磨损试验机开展牙轮钻头滑动轴承模拟工况下的单元摩擦学实验,对比分析不同长宽比织构对销-盘摩擦副表面摩擦磨损性能的影响;综合数值仿真与单元摩擦学实验结果,分析织构长宽比对织构润滑减磨的影响机制。数值仿真结果表明,织构长宽比对织构动压润滑性能的影响与织构深度有较大的关系,织构深度小于最小油膜厚度时,织构长宽比越小,织构的动压润滑性能越好;织构深度大于最小油膜厚度时,织构长宽比越小,织构的动压润滑性能越差。单元摩擦学实验结果表明,不同长宽比织构均能有效提高表面的摩擦学性能,但表现为织构长宽比越小,织构表面抗摩擦磨损性能越好。数值仿真和实验结果的差异在于仿真分析为动压润滑状态,而单元实验研究则为混合润滑状态。     

高原机车悬挂方案对车辆振动特性的影响

针对青藏铁路冻土带路基下沉问题,为了实现高原机车转向架低动力作用,基于车辆多体系统动力学理论,建立了两种不同悬挂方案的高原机车动力学模型,研究了不同一、二系悬挂刚度比μ对车体、构架以及轮轨垂向振动的影响。发现一、二系悬挂刚度比在0.5~3范围内变化时,轮轨垂向力和构架垂向振动加速度增大了11.24%和12.2%,车体平稳性指标和垂向加速度分别减小了11.3%和15%,并分析了高原线路上两种悬挂方案机车动力学特性。计算结果表明,选择刚度较大的二系悬挂,虽然一定程度上恶化车体平稳性指标,但较小的一系刚度在中低速范围内,能够降低由轨道不平顺引起轮轨垂向冲击,显著抑制了对轨下部分损伤较大的低频振动,减小运行过程中机车对轨下部分的损害。     

超高效液相色谱-串联质谱法测定菠菜、苹果及大豆中二硝基苯胺类除草剂残留量

以菠菜、苹果和大豆为代表性分析物,建立了超高效液相色谱 串联质谱法（UPLC-MS/MS）检测蔬菜、水果及粮谷等植物源性食品中8种二硝基苯胺类除草剂（氟乐灵、二甲戊乐灵、仲丁灵、异乐灵、磺乐灵、氨基乙氟灵、氨磺乐灵和氨基丙氟灵）的残留量。采用电喷雾电离,正离子扫描,多反应监测（MRM）模式检测,并使用外标法定量。结果表明：8种二硝基苯胺类除草剂的测定低限均为10 μg/kg;在添加水平10~200 μg/kg范围内,加标回收率为70.0%～120%,相对标准偏差为0.56%～23.0%。该方法灵敏、有效,适用于蔬菜、水果和粮谷等植物源性食品中二硝基苯胺类除草剂多残留的测定。     

亲水性Obelisc R液相色谱-串联质谱法测定猪肉样品中氨基糖苷类药物残留

建立了高效液相色谱-串联质谱法测定猪肉中9种氨基糖苷类药物(壮观霉素、潮霉素B、双氢链霉素、链霉素、阿米卡星、卡那霉素、安普霉素、妥布霉素、庆大霉素)残留量。待测样品中的氨基糖苷类药物经磷酸盐缓冲溶液提取,调节pH值后,经SupelMIP~ SPE-Aminoglycosides分子印迹固相萃取柱净化、浓缩、定容,然后采用Obelisc R高效液相色谱柱分离,以串联质谱法正离子模式检测。该方法在20~1 000μg/L范围内线性关系良好。在线性范围内,分别进行高、中、低3个浓度的添加实验,样品的回收率在76.9%~89.4%之间,相对标准偏差在3.56%~11.4%之间。该方法简便、快速、准确,可以满足猪肉中氨基糖苷类药物残留的测定需求。     

UHPLC-LTQ-Orbitrap HRMS法结合特征裂解途径分析鉴定薄荷水提物中4种类群化学成分

采用超高效液相色谱-线性离子阱-串联静电轨道阱高分辨质谱(UHPLC-LTQ-Orbitrap HRMS)法对薄荷水提物中4种类群化学成分进行分析鉴定。选取Acquity UPLC~BEH C18色谱柱(2.1mm×100mm×1.7μm),以乙腈-0.1%甲酸水溶液为流动相,流速0.30mL/min,梯度洗脱分析。根据高分辨质谱提供的准分子离子峰和碎片离子信息,获取目标化合物的相对分子质量和结构信息,并结合保留时间、对照品分析、参考文献数据和ClogP值等相关信息,鉴定了85种化学成分,包括38种黄酮、16种酚酸、7种苯丙素和24种萜类。结果表明,采用UHPLC-LTQ-Orbitrap HRMS技术能够提高中药化学成分的分析效率,该方法可为合理开发薄荷的药用和食用价值奠定化学基础。     

超高效合相色谱-串联质谱法测定口含烟中对羟基苯甲酸酯

建立了QuEChERS-超高效合相色谱-串联质谱法（UPC²-MS/MS）测定口含烟中对羟基苯甲酸酯类防腐剂。采用乙腈提取,基质分散固相萃取净化,UPC^{2 TM} HSS C18 SB色谱柱（3.0 mm×100 mm×1.8 μm）分离,内标法定量。优化后的对羟基苯甲酸酯的合相色谱分离条件为：主要流动相为CO₂,改性剂为甲醇-异丙醇混合溶液（V/V,1∶1）,系统流速1.5 mL/min,离子化辅助溶剂（补偿溶剂）为0.1%甲酸-甲醇溶液,动态备压1.03×10⁷ Pa,柱温55 ℃,可在3 min内完成单个样品分析。4种成分的线性范围均为0.5~5.0 mg/kg;在低、中、高加标水平下,方法的平均回收率为94.6%~105.6%,相对标准偏差小于5%。实际样品测定结果表明,单个成分的含量和多种成分的总含量均小于10 mg/kg,低于GB 2760-2014对于此类防腐剂在食品中添加限量的要求。该方法环境友好、高效、准确,适用于口含烟中对羟基苯甲酸酯类物质的测定。     

新型无油涡旋压缩机性能

基于热力学第一定律、质量守恒定律和气体状态方程,综合考虑工作腔的两种内泄漏以及工作腔壁面与介质气体之间的传热,构建了无油涡旋压缩机的热力学模型。运用欧拉法求解所建立的热力学模型,得到了气体在吸气-压缩-排气全过程中容积、温度、压力和质量随主轴转角的变化情况,并对比分析了不同传热和泄漏的影响规律。对研制开发的无油涡旋压缩机进行了变转速性能测试,分别测试了不同排气压力下的温度、排气量、功率。结果表明：传热对压力和温度的影响最大,而泄漏对工作腔质量的影响最大。随着转速的增大,温度、排气量、功率都呈明显的增大趋势。该热力学模型对无油涡旋压缩机的研发和性能分析具有一定的指导和借鉴作用。     

Effect of Spot Continual Induction Hardening on the Tribological Performance of Grey Cast Iron with Curved Surface

In order to investigate the effect of a spot continual induction hardening (SCIH) process on the tribological performance of grey cast iron with a curved surface, dry sliding wear tests were performed under different loads. The curved surface structure of the workpiece and feed velocity of the inductor were considered important influence factors. X-ray diffractometry (XRD), energy-dispersive spectroscopy (EDS), and scanning electron microscopy (SEM) were used to investigate the phases, compositions, and morphologies of grey cast iron after the SCIH process and tribological tests. The results showed that the wear mechanism of grey cast iron was always adhesive and abrasive wear at different loads when the workpiece was not strengthened. In the case of partial strengthening, the wear mechanism changed from adhesive and abrasive wear to fatigue–exfoliative wear with increasing load. Oxidative wear always appeared as the dominant wear mechanism when the workpiece was completely strengthened. The wear resistance of the concave surface was always larger than that of the convex surface under the same feed velocity of the inductor. Relatively low feed velocity of the inductor in the SCIH process can optimize the wear resistance of grey cast iron with a curved surface.     

Effect of heat treatment on the microstructure and properties of Ni based soft magnetic alloy

A Ni‐based alloy was heat treated by changing the temperature and ambient atmosphere of the heat treatment. Morphology, crystal structure, and physical performance of the Ni‐based alloy were characterized via SEM, XRD, TEM, and PPMS. Results show that due to the heat treatment process, the grain growth of the Ni‐based alloy and the removal of impurities and defects are promoted. Both the orientation and stress caused by rolling are reduced. The permeability and saturation magnetization of the alloy are improved. The hysteresis loss and coercivity are decreased. Higher heat treatment temperature leads to increased improvement of permeability and saturation magnetization. Heat treatment in hydrogen is more conducive to the removal of impurities. At the same temperature, the magnetic performance of the heat‐treated alloy in hydrogen is better than that of an alloy with heat treatment in vacuum. The Ni‐based alloy shows an excellent magnetic performance on 1,373 K heat treatment in hydrogen atmosphere. In this process, the µ_m, B_s, P_u, and H_c of the obtained alloy are 427 mHm^?1, 509 mT, 0.866 Jm^?3, and 0.514 Am^?1, respectively. At the same time, the resistivity of alloy decreases and its thermal conductivity increases in response to heat treatment.