双疏纳米涂层改善轴承密封性能技术研究

为了提升滚动轴承密封性能,提出了采用双疏纳米涂层改善滚动轴承密封的方案并进行了系统的试验研究。首次独立研发了可实时光学监测润滑剂端泄的密封试验机。采用水和不同粘度的甘油水溶液作为润滑剂,对比研究了不同转速下双疏纳米涂层对密封性能的改善效果。试验结果表明,在一定的转速范围内,这种双疏纳米涂层都具有一定的防侧泄性能;在速度较低时纳米涂层可以显著提升密封性能,随着速度提高,密封性能下降。     

An approach to measure infill matric suction of irregular infilled rock joints under constant normal stiffness shearing

Rock joints infilled with sediments can strongly influence the strength of rock mass. As infilled joints often exist under unsaturated condition, this study investigated the influence of matric suction of infill on the overall joint shear strength. A novel technique that allows direct measurement of matric suction of infill using high capacity tensiometers (HCTs) during direct shear of infilled joints under constant normal stiffness (CNS) is described. The CNS apparatus was modified to accommodate the HCT and the procedure is explained in detail. Joint specimens were simulated by gypsum plaster using three-dimensional (3D) printed surface moulds, and filled with kaolin and sand mixture prepared at different water contents. Shear behaviours of both planar infilled joints and rough joints having joint roughness coefficients (JRCs) of 8–10 and 18–20 with the ratios of infill thickness to asperity height (t/a) equal to 0.5 were investigated. Matric suction shows predominantly unimodal behaviour during shearing of both planar and rough joints, which is closely associated with the variation of unloading rate and volumetric changes of the infill material. As expected, two-peak behaviour was observed for the rough joints and both peaks increased with the increase of infill matric suction. The results suggest that the contribution of matric suction of infill on the joint peak normalised shear stress is relatively independent of the joint roughness.     

控锻控冷工艺对GCr15轴承钢力学性能的影响

探究不同控锻控冷热处理工艺对GCr15钢力学性能的影响,测试了它的回火稳定性、冲击性能、滚动接触疲劳寿命。结果表明,采用控锻控冷工艺可提高试样的抗回火稳定性,冲击性能提高50%以上,接触疲劳寿命提高40%以上。     

精密磨床转台静压轴承的强健化设计

针对精密磨床转台静压轴承性能仿真数据与其回转精度实测数据不一致的问题，为提高转台静压轴承的设计水平，提出了静压轴承的强健化设计方法。该方法考虑了轴承结构参数在轴承全生命周期内的变化，分析了半径间隙、油腔尺寸、节流比及润滑油黏度在设计、加工、装配和服役4个阶段的变化规律，重点研究了半径间隙在各阶段对轴承性能造成的影响，给出了转台静压轴承的强健化设计流程。通过一个径向轴承的设计实例对该强健化设计方法进行了说明，并将设计结果与传统设计进行了对比。对比的指标是轴承在4个阶段的刚度、承载力和温升，这3个指标对轴承回转精度有直接影响。研究表明：进行强健化设计后，在生命周期内静压轴承的刚度和承载力的变化量为10%~27%，温度的变化量为0.5%~1.6%，较传统设计更能保证转台回转精度的稳定。     

Modeling and analysis of multiple access channel capacity based on hybrid energy storage and energy harvesting

Energy harvesting (EH) has been considered as a promising technology to solve the constrained energy problem in the devices of IoT with its advantages of flexible deployment and sustainable energy supply.For multiple access channel with energy harvesting,a hybrid energy storage structure model composed by super capacitor and battery was proposed for the devices of IoT.According to the peculiarities of medium access channel and energy harvesting system,an optimized energy allocation strategy with exponential-type decline (ETD) was presented,the upper and lower bounds of the average throughput were deduced,in particular,the gap of two bounds was derived to be a constant.The channel capacity was further obtained by utilizing the relationship between the average throughput and the channel capacity.In the simulations,the effect of harvested energy,storage capacity and the number of nodes on the channel capacity were analyzed respectively.Experiment results show that compared with the conventional wireless node with single battery storage,the proposed hybrid energy storage structure can improve the harvested energy value and increase the multiple access channel capacity by using adaptive modulation scheme when transmitting the signals.     

新型装配式冰场受力性能试验与模拟分析

为在2022年冬奥会期间将国家游泳中心泳池场地改造为冰壶场地,结合临时场地的新型制冰方式,提出了一种全装配式的冰壶场地及支承结构体系的构造作法.对此装配式冰场进行了现场试验测试和有限元受力性能分析,研究了装配式冰场的自振频率和振型特点,分析了冰场在使用荷载作用下的整体变形和各组件的应力水平,探讨了极端荷载作用下冰面受力、变形及开裂等关键问题.研究表明,所提装配式冰场方案具有较大刚度和承载力,能够满足冬奥会冰壶比赛对冰面的要求；此类冰场宜使用轻型浇冰车作业,大型浇冰车轮压引起的弯矩和剪力作用下冰面存在开裂的可能.     

GCr15轴承钢成品套圈热处理后点线状缺陷原因分析

在热处理后的GCr15成品轴承套圈表面发现疑似裂纹的点线状缺陷。通过无损检测、光学显微镜、扫描电镜、能谱分析等手段对缺陷进行分析,发现缺陷处存在较大尺寸的氧化铝和硅酸盐复合夹杂物。通过采取“高拉碳”、“白渣操作”、“软吹”“保护浇铸”等措施后,钢水纯净度得到进一步提高,避免了点线状缺陷的再次发生。     

改进ILoG算子的故障检测方法

针对强背景噪声干扰下轮对轴承故障特征微弱、难以准确检测的问题,提出了一种自适应改进高斯拉普拉斯(improved Laplacian of Gaussian,简称ILoG)算子的微弱故障检测方法。ILoG算子滤波器具有优良的信号突变特征检测能力,将其用于轮对轴承故障信号的冲击特征检测,同时利用水循环算法(water cycle algorithm,简称WCA)的寻优特性,并行搜寻筛选最佳的ILoG算子影响参数,通过对参数优化后ILoG算子滤波后信号做进一步包络解调分析,提取出轮对轴承微弱的故障特征信息。对实际轮对轴承外圈和内圈故障信号分析的结果表明,该方法可以有效检测出轴承微弱故障特征频率,故障检测效果优于小波阈值和多尺度形态学差值滤波方法。     

Effect of functionally graded structure design on durability and thermal insulation capacity of plasma-sprayed thick thermal barrier coating

This paper aimed to design and optimize the structure of a thick thermal barrier coating by adding graded layers to achieve a balance between high thermal insulation capacity and durability. To this end, conventional TBC, conventional TTBC, and functionally graded TTBCs were deposited on the superalloy substrate by air plasma spraying. To determine the quality of the bond strength of the coatings, the bonding strength was measured. The durability of coatings was evaluated by isothermal oxidation and thermal shock tests. Then, at a temperature of 1000 °C, the thermal insulation capacity of the coatings was carried out. The microstructure of the coatings was characterized by a scanning electron microscope. The results showed that the thickness of the TGO layer formed on the bond coat in the conventional TBC and TTBC under the oxidation test at 1000 °C after 150 h was 2.79 and 2.11 μm, respectively, whereas, in the functionally graded TTBC samples, no continuous TGO layer was observed as a result of internal oxidation. The functionally graded TTBC presented higher durability than conventional TTBC due to improved bonding strength, thermal shock resistance, and the lack of a TGO layer at the bond/top coat interface. Also, the thermal insulation capacity of the functionally graded TTBC (with 1000 μm thickness of YSZ coating) was better than TTBC.     

The Marine Polysaccharide Ulvan Confers Potent Osteoinductive Capacity to PCL-Based Scaffolds for Bone Tissue Engineering Applications

Hybrid composites of synthetic and natural polymers represent materials of choice for bone tissue engineering. Ulvan, a biologically active marine sulfated polysaccharide, is attracting great interest in the development of novel biomedical scaffolds due to recent reports on its osteoinductive properties. Herein, a series of hybrid polycaprolactone scaffolds containing ulvan either alone or in blends with κ-carrageenan and chondroitin sulfate was prepared and characterized. The impact of the preparation methodology and the polysaccharide composition on their morphology, as well as on their mechanical, thermal, water uptake and porosity properties was determined, while their osteoinductive potential was investigated through the evaluation of cell adhesion, viability, and osteogenic differentiation of seeded human adipose-derived mesenchymal stem cells. The results verified the osteoinductive ability of ulvan, showing that its incorporation into the polycaprolactone matrix efficiently promoted cell attachment and viability, thus confirming its potential in the development of biomedical scaffolds for bone tissue regeneration applications.