铸造用CO2硬化酚醛树脂粘结剂系统的优化

铸造用CO2硬化碱性酚醛树脂粘结剂是一种新型的粘结剂系统,由一种特殊合成的碱性酚醛树脂、碱、硼砂和硅烷等组分组成。基于此,以抗压强度为主要考察指标,通过对粘结剂中酚醛树脂、碱、硼砂和硅烷加入量进行正交试验,得出优化的配比为酚醛树脂∶KOH∶硼砂∶硅烷=100∶45∶16∶1,组成了稳定的粘结剂系统,吹入CO2气体硬化后系统得到了较高强度。KOH、硼砂对强度的影响比较显著。在粘结剂中按一定比例分别加入乙醇、丙酮、甘油等物质,并进行粘结剂强度试验,这些材料对粘结剂强度能有一定促进作用,其中两种有机活性助剂,可以明显改善粘结强度,加入量分别为粘结剂量的5%、15%。通过优化,粘结剂初强度可达1.5MPa以上,终强度值可达3.7 MPa以上。最后通过扫描电镜对砂样粘结桥断口形貌分析,证明有机活性助剂在粘结剂系统中主要起络合、交联作用。     

用尿-酚醛树脂作型砂粘结剂的探讨

一、前言粘结剂是造型材料的重要组成部分之一。在有机粘结剂中,合成树脂用量越来越大。因为合成树脂粘结剂具有粘结力强,性能良好,原料广泛,质量容易控制,适合大量生产等特点。在型砂粘结剂的应用方面,生产成本和生产率的问题已广泛引起重视。目前国内铸造生产上使用的合成树脂粘结剂以酚醛树脂和糠醇改性树脂为多。酚醛树脂的粘结力强,耐热性好,发气量和发气速度     

玻纤增强改性酚醛树脂复合材料在水润滑轴承上的应用研究

以腰果壳油、聚砜为改性剂对酚醛树脂进行增强改性,将改性后的酚醛树脂通过湿缠绕方法和玻璃纤维粘合,制成了水润滑轴承外壳,并研究了玻璃纤维含量对水润滑轴承外壳压缩强度的影响。结果表明,玻璃纤维含量为45%时,制成的水润滑轴承外壳具有良好的拉伸强度、压缩强度和冲击强度,吸水膨胀极小,可用于水润滑轴承,是优良的水润滑轴承黄铜外壳替代材料。     

偶联剂改性人造石墨对摩擦材料摩擦磨损性能的影响

采用硅烷偶联剂KH-550、KH-560和钛酸酯偶联剂NDZ-401对人造石墨进行改性,并采用XD-MSM定速式摩擦试验机和MPX-2000磨损试验机分别考察3种不同偶联剂改性人造石墨对酚醛树脂基摩擦材料摩擦磨损性和速度/压力敏感性的影响,利用扫描电镜分析摩擦表面的形貌。结果表明:与未改性人造石墨相比,偶联剂改性人造石墨可提高摩擦材料的摩擦磨损性能和抗速度/压力敏感性。其中钛酸酯偶联剂NDZ-401改性人造石墨利于提高摩擦材料的摩擦因数稳定性和抗速度/压力敏感性;而硅烷偶联剂KH-560改性人造石墨可以提高摩擦材料抗磨损性能。     

用改质沥青制备碳－石墨材料的研究

采用交联催化法使普通的中温煤沥青成为碳－石墨材料的优质粘结剂，在探讨改质原理的基础上分析了改进的低压浸渍工艺对浸渍增密效果的影响，提出了新的浸渍增密规律──２／３法则．并研究了改质沥青的残碳律及由它制成的碳－石墨材料的强度等性能的变化情况，结果表明，用此法改质的沥青不仅具有良好的综合性能．而且易与工业生产配套，是一种很有实用价值的碳－石墨材料用粘结剂。     

热处理对石墨填充高岭土基矿物聚合物复合材料摩擦学性能的影响

对20%石墨填充高岭土基矿物聚合物复合材料在不同温度下进行热处理,利用扫描电镜、X射线衍射和红外光谱等表征手段及显微硬度实验、三点弯曲实验,研究了材料的微观结构、机械性能及摩擦学性能与热处理温度之间的关系。结果表明,随热处理温度的提高,材料的微观结构发生较大变化,材料的显微硬度和弯曲强度均呈现先下降后又缓慢上升的趋势;材料经300℃和600℃的高温处理后仍具有较好的摩擦学性能,处理温度较低时,材料的磨损形式以磨粒磨损和粘着磨损为主;处理温度较高时,磨损形式以磨粒磨损和疲劳磨损为主。     

摩阻材料用亚麻油改性酚醛树脂的试验

为得到高性能的摩阻材料,将苯酚和亚麻油在酸性条件下反应,然后在碱性条件下与甲醛反应合成亚麻油改性酚醛树脂。利用红外光谱分析、热分析、力学性能测试等手段研究亚麻油对酚醛树脂的改性作用,并对亚麻油改性酚醛树脂作基体的摩阻材料的摩擦磨损性能和力学性能进行测试。结果显示,改性树脂的耐热性、粘结性和韧性较未改性的树脂得到了提高。改性树脂的切应力为18.5 MPa,冲击强度为120.2 kJ•m–2,洛氏硬度为111.2 HRR;摩阻材料摩擦性能稳定,从热衰退敏感的250～350 ℃温度变化范围内,摩擦因数仅下降了0.03,仍保持在0.39的水平;温度为200 ℃时,磨损率仅为0.30 cm3•N–1•m–1,冲击强度达780 kJ•m–2,洛氏硬度为113.2 HRR。研究表明亚麻油改性酚醛树脂有望成为高性能摩阻材料的树脂基体。     

不同改性矾土添加量下树脂基复合摩擦材料的性能

通过添加质量分数为4%~12%的改性矾土,并减少酚醛树脂的添加量制备了树脂基复合摩擦材料,研究了树脂基复合摩擦材料的力学性能、抗热衰退性能及摩擦磨损性能。结果表明:添加质量分数为8%的改性矾土时,摩擦材料的硬度、弯曲强度、冲击韧性略有降低,但仍处于较高的水平,但材料的摩擦因数增幅较大,高温抗热衰退系数较未添加改性矾土试样的提高近12%,表现出良好的抗热衰退性能。     

变型运输机制动器的修理和保养

一、注意制动器上摩擦衬片的摩擦系数 目前拖拉机变型运输机上广泛应用的摩擦衬片材料是压模材料,它是将石棉纤维(为主体)与树脂粘结剂、调整摩擦系数的填充剂以及石墨等混合后在高温下模压成型.     

酚醛树脂/石墨模压成型复合材料双极板的制备与性能

以石墨与酚醛树脂粉料为原料通过低温热模压成形工艺制备低成本酚醛树脂／石墨复合材料双极板，对材料的力学性能与导电性能进行了研究。结果表明：酚醛树脂含量是影响复合材料导电性能与力学性能的主要因素，酚醛树脂含量低于20％时，材料具有较高的导电性能；提高固化温度与固化压力，可以提高材料的抗弯强度，但材料的导电性能明显降低；适中的固化压力与固化温度有利于材料具有较好的力学性能与导电性能。     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

Quantum Cooperative Robotics and Autonomy

The intersection of Quantum Technologies and Robotics Autonomy is explored in the present paper.The two areas are brought together in establishing an interdisci...     

考虑进油孔有限长滑动轴承油膜力的近似解析解

针对具有进油孔的有限长滑动轴承油膜力求解问题,采用变分原理和分离变量法,求得了有限长滑动轴承油膜压力分布的近似解析表达式。将油膜压力分布的近似解析表达式在油膜存在区域上进行积分,即得到了油膜力。将提出的计算有限长滑动轴承油膜力方法与无限长轴承模型、有限元方法的计算结果进行了比较,发现了提出的方法与有限元方法的计算结果很接近。最后,研究了进油孔位置和进油压力对油膜存在区域、油膜力等的影响,研究结果表明进油孔位置和进油压力对油膜存在区域和油膜力有较大的影响。     

三绕组变压器的双绕组等效建模及在Matpower中的应用

针对实际电网存在着大量的三绕组变压器,但国际上一些著名商业软件,如BPA仿真软件、Matpower这一权威潮流计算开源软件,均只提供双绕组变压器模型,限制了其在具有三绕组变压器的电力系统中的应用的问题,潮流计算是自主开发的电力系统各种应用软件的核心模块,因此依托国际权威开源程序进行二次开发,是一种较好的选择。对Matpower要求的数据格式进行了归纳,对变压器的一般的等值电路及带理想变压器的等值电路和带标幺值的等值电路进行了分析研究,提出了三绕组变压器转换为双绕组等效模型的建模方法,使得原先只适应双绕组变压器的潮流计算软件可以适用于三绕组变压器电网的潮流计算;最后以Matpower软件为例进行了案例计算,并用PSASP仿真软件进行对比验证。研究结果证明,所提出的建模方法是有效的。     

On the Relation of Load to Average Gap in the Contact Between Surfaces with Longitudinal Roughness

A computer simulation model for the contact between longitudinally-oriented rough surfaces has been formulated. This model closely duplicates the actual surf ace contact deformation behavior by taking into account the elastic interactions between the asperities. There were no assumptions made about the shapes, or any deformation behavior of the asperities, except for their obeying the laws of elasticity. The plastic deformations on the high asperity peaks were taken into account by setting a ceiling on their contact pressures at the material hardness value. The simulations used real surface profiles which were digitized from unworn circumferentially ground steel surfaces. Each pair of these profiles was mathematically combined to form an equivalent rough profile pressing against an infinitely rigid flat and having the appropriately adjusted elastic modulus. A total of 28 different pairs of profiles were used in the simulations. Each contacting pair was subjected to 30 different load levels and the local contact pressures and deformations were calculated. The contact simulations yielded some important mathematical relationships between parameters, such as the real area of contact, average gap, and average asperity load through statistical curve fitting. Two analytical functions were generated to relate the average load to average gap and the real area of contact to load.     

Fifth International Summer School on Screw-Theory Based Methods in Robotics

正3-11 September,2014University of Bologna,Bologna,Italy www.summerscrews.org summerscrews2014.ing.unibo.it SUMMER 20SCREWS 14In 2014,our screw-theory school comes to the world's oldest university.In early September,Summer Screws'14 will gather six experts in the application of screw theory in robotics and up to 40 participants at the University of Bologna,Bologna,Italy.The school will teach attendees how to apply existing methods and empower them to develop new ones in their own research.The basic theoretical notions will be introduced in a rigorous manner,emphasizing examples,applications,and exercises.Scholarships are available.     

电站锅炉模糊风险评价方法研究与应用

针对电站锅炉风险等级评价问题,将模糊综合评价技术应用到电站锅炉风险等级评价中。开展了电站锅炉失效影响因素及模糊评价因素的重要程度分析,建立了一套科学合理适于在线评价的电站锅炉风险评价体系,提出了模糊综合评价技术与改进的模糊层次分析法相结合的模糊风险评价方法,利用改进的模糊层次分析法计算了指标体系中各层指标权重。对某一台电站锅炉的实际运行工况影响子因素进行了模糊风险评价,采用模糊合成算子进行模糊综合运算得到电了站锅炉运行工况影响子因素的评价向量。研究结果表明:电站锅炉的运行工况影响子因素的风险评价等级为第6级,失效可能性等级为小,该电站锅炉运行工况良好。     

INDUSTRIAL ENGINEERING AND VISUALISATION-A PRODUCT DEVELOPMENT PERSPECTIVE

Taking the actual project of teaching and researching process for example, the relationship between the industrial engineering and product development is discussed. And use the novel visualization technology to support the industrial engineering and product development. How to use the new computer modeling and simulating technologies to support the product development and industrial engineering, is introduced especially. The support includes both domestic products and industrial systems. The visualization and computer technologies take a very important role in some system or multi-direction modeling, those technologies mentioned above can help the industrial engineers study the effect of design on the whole life circle, including the producing steps. So the engineers can avoid making the wrong decision which may cause bad effects on the whole industrial engineering.     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...