Effect of high-pressure rheology of lubricating oils on boundary lubrication

High-pressure rheology of lubricating oil was determined using different experiments, and the phase diagram was drawn. The four-ball wear tests were used to evaluate anti-wear characteristics of oils in boundary lubrication condition. The bridged ring compound oils showed the minimum wear scar in the four-ball wear tests. The diameter of wear scar decreases with increasing the elastohydrodynamic film-forming capability. Next, we considered the molecular packing parameter T_VE−T at the four-ball wear test. The T_VE−T values of bridged ring compound oils were in the range 250-360 and oils were elastic-plastic solid. It is concluded that the solidified oil film under boundary lubrication conditions has the anti-wear action.     

Micro-stereolithography photopolymer solidification patterns for various laser beam exposure conditions

Micro-stereolithography is a novel micro-manufacturing process that fabricates 3D microstructures by solidifying the photopolymer using a UV laser in a layer-by-layer fashion. In this paper, variation in the photopolymer solidification pattern due to the scanning pattern and pitch of a focused laser beam was investigated experimentally. Also, experiments were conducted to determine the effects of the layer thickness on the solidification width and depth in multi-layer solidification. The experimental results were compared to numerical simulations. The results showed that a zigzag-shaped scanning pattern was faster and more stable than a crank-shaped pattern. It was also determined that the scanning pitch should be selected according to solidification depth and width for a given scanning pattern, and that the layer thickness has little effect on the solidification depth. Based on the results, several microstructures were successfully fabricated, such as a micro-tube with a helical separation wall and a microlink.Nomenclature P_L The power of the laser beam - The wavelength of the laser beam - f The focal length of the focusing lens - z The depth from the surface of photopolymer - V_S The scanning feed of the laser beam - W₀(z) The Gaussian half-width of the focused laser beam at a given depth z - E_C The critical exposure of the photopolymer - D_P The penetration depth of the photopolymer - W_{0 min} The Gaussian half-width at the focal point - R The Gaussian half-width of the laser beam that passes into the focusing lens - w The scanning width of the laser beam - L The solidified width of the photopolymer - h The solidified depth of the photopolymer - D₁ The layer thickness - D₂ The total solidified depth in a multi-layer solidification     

SOLIDIFICATION MICROSTRUCTURE AND FRACTURE MORPHOLOGY OF SiCp/ZA27 COMPOSITE

ＩＮＴＲＯＤＵＣＴＩＯＮＺｉｎｃ ａｌｕｍｉｎｕｍａｌｌｏｙｓｗｅｒｅｄｅｖｅｌｏｐｅｄａｓｗｅａｒ ｒｅｓｉｓｔｉｎｇｍａｔｅｒｉａｌｓｉｎ 196 0’ｓ .Ｔｈｅｓｅａｌｌｏｙｓｐｒｅｓｅｎｔｓｏｍｅａｄｖａｎｔａｇｅｓａｓｌｉｇｈｔｗｅｉｇｈｔ ,ｇｏｏｄｍｅｃｈａｎｉｃａｌｐｒｏｐｅｒｙｔ,ｅｓｘｃｅｌｌｅｎｔｗｅａｒ ｒｅｓｉｓｔｉｎｇ ,ｌｏｗｃｏｓｔａｎｄｓｏｏｎｉｎｃｏｍｐａｒｉｓｏｎｗｉｔｈｃｏｐｐｅｒａｌｌｏｙｓ .ＴｈｕｓＺｎ Ａｌａｌｌｏｙｓｈａｖｅｂｅｅｎｎｏｔｉｃｅｄｗｉｄｅｌｙｂ…     

水泥固化锌污染高岭土的淋滤试验研究

采用水泥作为固化剂对锌污染高岭土进行固化/稳定处理,采用TCLP淋滤试验对固化后养护7和28天的人工锌污染土的化学淋滤特性进行了研究。结果表明,当初始Zn2+浓度达到某一临界值之前,浸出液pH保持在10-12之间,超过临界浓度后,浸出液pH迅速下降至8以下;EC值随初始Zn2+浓度变化同样存在临界值,超过这一临界值后,浸出液的EC值迅速上升至7.8mS/cm以上;浸出液pH值随初始Zn2+浓度不同分布在6.7-11.6的范围内;在这一范围内,Ca2+和Zn2+浓度随pH值升高而降低;浸出液中,由水泥固化土中淋滤出的Ca2+与Zn2+为淋滤液中的主要离子成分。     

连续定向凝固技术研究

在自行设计的竖直热型连铸机上,进行了连续定向凝固实验和温度测定,对其中传热和凝固过程进行了数值模拟,考察了主要工艺参数对锡铸锭表面质量和内部组织的影响,以及固液界面形状的变化规律。结果表明:型温、拉速、冷却水量等工艺参数主要是通过影响固液界面的位置、形状来影响铸锭表面和内部质量的,在本实验条件下,型温在244~248℃、拉速在1.25~2.20×10-4m/s、冷却水量在252~377L/m2.s之间时,才能获得表面光亮,内部为完整定向凝固组织的铸坯;当铸型温度高于242℃,拉速在1.25×10-4~3.4×10-4m/s之间时,形成较平的固液界面,得到定向凝固的铸锭组织;获得了固液界面形状与主要工艺参数间的关系式。     

金属-气体共晶定向凝固制备藕状多孔金属的研究

金属-气体共晶定向凝固(Gasar)是一种制备规则多孔金属的新工艺.利用自行开发的Gasar装置,成功制备了具有规则气孔分布的藕状多孔金属Mg,并研究了铸型预热温度和气体压力等工艺参数对气孔率、气孔大小和分布的影响.结果表明:提高铸型预热温度可以完全消除无气孔金属壳;随着氢气压力的增大,铸锭的平均直径都在减小;在整个Gasar凝固中约有8%左右的氢气溢出.     

金属熔体凝固微观组织模拟的相场方法研究

全面阐述了现有的金属熔体凝固微观组织模拟的相场模型:纯物质、二元合金理想溶液或正规溶液和稀溶液相场模型,指出构造适合于具有复杂溶液模型的金属熔体凝固微观组织模拟相场模型的必要性.提出采用相图计算热力学模型构造相场模型中的体系自由能,并对相场参数做出相应修正,建立了能对具有复杂溶液模型的金属熔体凝固微观组织进行准确模拟的相场模型.利用该相场模型对Ti-Al金属熔体中晶体的自由生长和定向生长进行了模拟,得到许多与试验观察和理论分析相一致的结果.     

不同冷却速率下Zn-2Ni合金包晶凝固研究

采用SEM、EDS及XRD研究了Zn-2Ni合金从750 ℃以不同冷却速率冷却的包晶凝固组织特点.结果表明,冷却速率为0.04 ℃/s时Zn-2Ni合金凝固组织中的包晶γ相仅局部依附于初生γ相上生长;冷却速率为1 ℃/s和36 ℃/s时合金凝固组织中均未能观察到包晶δ相;表明Zn-2Ni合金发生包晶凝固时有别于常规包晶凝固特点,包晶δ相在初生γ相上形核困难且生长速率缓慢.     

矩形电磁冷坩埚连续铸造钛合金的成形性研究

在自行研制的多功能冷坩埚电磁约束定向凝固装置上进行了钛合金扁形锭的冷坩埚连续成形试验,考察了工艺参数变化对所成形钛合金锭成形性的影响.结果表明增大感应线圈匝数和增加加热功率可提高铸锭表面质量,但是提高抽拉速度和降低底料与线圈之间的相对位置会降低表面质量.在所研究的参数中,对铸锭表面质量影响的主次因素依次为感应线圈的匝数、加热功率、抽拉速度、底料相对线圈位置.在讨论这些参数的作用原理基础上,提出了可获得良好表面质量的工艺参数,获得了截面为矩形、表面光滑、无裂纹缺陷的钛合金矩形锭.     

高密度脉冲电流作用下LY12铝合金的凝固组织

研究了高密度脉冲电流作用下ＬＹ１２铝合金的凝固组织,试验结果表明嵩密度的脉冲电流可明显地改善该合金凝固组织。和未经电流处理的样品相比,其组织明显细化和等轴化,且脉冲电流愈强,且脉冲电流愈强,这种效果愈显著。