Structure and Properties Characterization of Ceramic Coatings Produced on Steel Using a Combined Technique

STEEL is the most widely used material in engineering,but unfortunately,steel exhibits poor wear resistanceand obvious contact corrosion.For decades,researchersprepared coatings on steel to improve its properties;ceramic is one of these coatings.To obtain ceramiccoatings on steel,many researchers use techniques suchas plasma spraying,laser cladding,etc.,but some ofthem are too expensive,some of them have a deep heataffected zone in the substrate,and some of them cannot bond well with the subs…     

EFFECT OF AGING ON HYDROGEN EMBRITTLEMENT SUSCEPTIBILITY OF STEEL Cr21Ni6Mn9N

Effects of 650℃ aging for 1—1000 h on structure and hydrogen embrittlement susceptibility(HES)of steel Cr21Ni6Mn9N have been investigated.The results show that M_(23)C_6 typecarbide precipitates at grain boundaries and Cr-depletive region appears beside them duringaging.The precipitates grow and connect each other as the aging time prolongs.Meanwhile,the degree of Cr-depletion aggravates first and then recovers gradually while the aging time isvery long,i.e.,1000 h.The HES of the steel increases with increasing aging time but does notreduce with the recovery of Cr content at the Cr-depletive region.That implies that the ex-isting of carbides at grain boundaries might be the main reason which promotes the HES ofsteel during aging.     

置换DCT域中频系数的盲水印嵌入算法研究*

介绍了一种基于离散余弦变换域(DCT)中频系数置换的盲水印算法,用该算法对数字水印进行了自适应嵌入方法研究.该算法突破了数字水印的加性算法、乘性算法等传统的水印嵌入方法;解决了被提取水印中含有原始图像DCT系数从而影响水印检测准确性的问题.该算法使用人类视觉模型对水印图像进行自适应嵌入,使嵌入的数字水印从根本上不可逆.实验证明该算法对数字水印的滤波、剪切、噪声等攻击有很强的鲁棒性.     

液态模锻2A50特种车辆轮盘冷隔缺陷的成因与防治

对液态模锻2A50铝合金负重轮轮盘的冷隔产生进行了分析,表明其起源于轮缘周表面晶界处,并且向内部扩展.冷隔产生的主要原因是铝液紊乱,波动至下模外套直壁上,下压过程中,铝液难以冲破这层表面层,于是形成冷隔.通过缓冲滤渣漏斗工装、适当调节导流槽铝液流速、增加捞渣工序等措施,减少了铝液表面氧化膜的数量,使铝液平稳填充,杜绝铝液波动,从而消除冷隔的产生.     

铝合金液态模锻流变充型能力预报模型

基于一维流动换热原理,通过谐波法求解一维耦合热传导——热对流方程,得到温度的沿程衰减规律,进而求出流变阻力的沿程增大规律;同时求解压力的沿程衰减规律,结合合金熔体停止流变机理和条件,建立铝合金液态模锻流变充型能力预报模型.该模型包含液态模锻工艺参数、材料性能参数及模具结构参数,适用于液相线温度以下的广义半固态合金熔体.采用6066铝合金通过间接液态模锻的阿基米德螺旋线试样长度验证模型的有效性,结果表明:理论结果与实验结果的最大相对偏差为8.2％.与现有的充型能力模型相比,本文的流变充型距离模型在预报精度及适用范围方面有一定的进步性.     

安徽省城市化水平与水资源利用效率关系研究

以安徽省各地级市为研究对象构建城市化综合评价体系,并以熵值法对该区域综合城市化水平进行评价,同时基于生态足迹理论对水资源利用效率进行量化,创新性地验证了城市化水平与水资源利用之间的相互关系.研究发现:安徽省城市化水平可分为4个阶段,其中合肥市城市化水平最高;2018年安徽省水资源生态足迹总量为4724亿hm2,农业用水生态足迹占比最高,其次为工业用水生态足迹;水资源生态足迹总量随着城市化发展呈现急剧增长,然后缓慢下降,最后缓慢增长的变化趋势;随着城市化的不断发展,水资源利用效率不断提高,水资源生态压力先增加后缓慢降低.研究结论为安徽省城市水资源可持续发展提供决策支持.     

Damage tolerance of fractured rails on continuous welded rail track for high-speed railways

Broken gap is an extremely dangerous state in the service of high-speed rails, and the violent wheel–rail impact forces will be intensified when a vehicle passes the gap at high speeds, which may cause a secondary fracture to rail and threaten the running safety of the vehicle. To recognize the damage tolerance of rail fracture length, the implicit–explicit sequential approach is adopted to simulate the wheel–rail high-frequency impact, which considers the factors such as the coupling effect between frictional contact and structural vibration, nonlinear material and real geometric profile. The results demonstrate that the plastic deformation and stress are distributed in crescent shape during the impact at the back rail end, increasing with the rail fracture length. The axle box acceleration in the frequency domain displays two characteristic modes with frequencies around 1,637 and 404 Hz. The limit of the rail fracture length is 60 mm for high-speed railway at a speed of 250 km/h.

     

锂离子电池内隔膜褶皱的原因及消除

在锂离子电池制造过程中,电芯注入电解液时,隔膜局部区域出现褶皱并在隔膜和极片间残留有气泡是一个常见的现象.隔膜上的褶皱和隔膜/极片间界面的缺陷会造成电池内阻分布不均匀,内阻低的地方电池循环过程中可能会局部过充或过放,进而影响电池的一致性及循环性能.针对这一现象,对不同种类的隔膜进行了研究,发现溶剂碳酸二甲酯(DMC)在流动浸润隔膜过程中,各种隔膜均会产生褶皱,且褶皱间距随隔膜厚度的增加略有增大.通过对DMC流动浸润隔膜的前端进行分析,发现隔膜产生褶皱主要有两个原因:DMC局部浸润隔膜过程中,毛细作用导致隔膜在液体流动前端出现隆起,在隔膜和极片间出现间隙.同时,DMC扩散到隔膜和极片的内部孔隙所排出的气体在极片/隔膜界面处积累形成气泡,导致隔膜出现局部的变形和皱褶.为解决上述问题,本文提出在电池加工过程中把涂布有聚偏氟乙烯(PVDF)的复合隔膜与正负极片热压黏合,粘合力抵消DMC浸润隔膜时所产生的毛细作用,能够减少或完全消除隔膜的褶皱.实验表明,当隔膜和正极极片热压后的剥离强度小于10 mN/cm时,黏结力尚不足以完全平衡毛细作用,隔膜仍会出现局部的皱缩,但褶皱数量明显减少.当剥离强度大于15 mN/cm时,隔膜的褶皱现象才被完全消除,说明提高隔膜与极片间的黏结强度,是一个解决隔膜/极片界面处缺陷的有效方法,隔膜褶皱等宏观缺陷的消除也有利于提高锂离子电池的一致性及循环稳定性,具有明确的实际应用价值.     

螺噁嗪类光致变色材料的制备

以吲哚啉螺噁嗪类光致变色染料、水性聚氨酯为主要成分制备了一种光致变色组合物,并测试了其耐光稳定性。结果表明:制得的光致变色材料经氙灯照射50h后仍然具有良好的光致变色性能,该方法显著提高了吲哚啉螺噁嗪类光致变色材料的耐光稳定性。     

低电阻率耐候性导电碳浆的制备

研究石墨和炭黑的形貌、粒径以及配比对导电碳浆电阻率的影响,分析聚酯和有机硅改性聚酯制备导电碳浆耐候性的差异及原因.试验表明:D90为12.8μm的不等轴鳞片状石墨SFG-10和高度链状团聚炭黑350 G的质量比为7:3时制备的导电碳浆电阻率低,为4×10-2Ω·cm,且硬度H>4;在高低温、高湿和紫外光照射试验条件下,聚酯和有机硅改性聚酯制备导电碳浆电阻值最大变化率分别为36.7％和9.5％,有机硅改性聚酯能显著提高导电碳浆的耐候性.