【作者】 卢文博；

【导师】 王成国；

【作者基本信息】 山东大学 ， 材料学， 2012， 博士

【摘要】 受电弓滑板是电力机车获取动力能源的主要集电元件,它的质量对电力机车的受流状况及接触导线的寿命具有重要影响,目前常用的滑板按照其材质的不同可分为碳系滑板、金属系滑板和复合材料滑板三种类型。随着列车运营速度的不断提高,传统的滑板译不能满足高速列车的要求。本文针对现有滑板存在的缺点,研制出一种新型结构的受电弓滑板材料。该滑板以层状铺设的铜网做骨架以实现优良的导电性,铜网间的复合材料层提供了良好的减磨耐磨特性。本文围绕层状结构受电弓滑板的研制,开展了对滑板的结构设计、配方和工艺优化等方面的研究,通过对比滑板的导电、抗冲击和耐磨性能,确定滑板的最优配方和工艺,并对滑板的导电和磨损机理进行了分析。在受电弓滑板的结构设计中,综合考虑复合材料组分和铜网对滑板电阻率、冲击强度和摩擦性能的影响,确定了滑板的结构为层状结构,铜网的最佳尺寸为孔径3.16mm×6.3mm,厚度0.48mm。对层状结构树脂基滑板中复合材料的组成进行设计,分析了树脂含量和纤维类型对滑板性能的影响。实验发现酚醛树脂含量的变化对滑板电阻率的影响较小；冲击强度随酚醛树脂含量的增加而降低,在酚醛树脂含量较低时,冲击断面与冲击载荷的方向有一定的角度,说明纤维增强体起到了改变裂纹方向和延缓裂纹扩展的作用,冲击强度较高；而酚醛树脂含量较高时,滑板的冲击断口平整,与载荷加载方向在一个平面,呈脆性断裂,冲击强度较低；磨损量随酚醛树脂含量的增加先减小后增大,在树脂含量为26.4%时,磨损量最低,从而确定26.4%为树脂基滑板的最佳树脂含量。通过对纤维增强复合材料滑板的载流磨损现象和性能的研究发现：碳纤维的加入有利于提高滑板的导电性和耐磨性；铜纤维的加入有利于提高滑板的导电性,改善电弧烧蚀现象；硅灰石纤维的加入改善了滑板的摩擦特性。确定采用碳纤维、铜纤维和硅灰石纤维作为滑板的混杂增强纤维。采用均匀设计和回归分析的方法对滑板的配方组成进行优化,对碳纤维、石墨、硅灰石纤维、铜粉和铜纤维五个因素的混料问题进行均匀设计,并对滑板的性能进行回归分析,分析各因素对材料性能的影响程度,确定滑板的最佳配方。结果发现：电阻率与铜纤维的含量大致呈线性关系,随铜纤维含量的增加而降低；冲击强度与碳纤维的含量有关,随着碳纤维含量的增加而增大；摩擦系数主要受碳纤维、石墨和硅灰石纤维含量的影响；影响滑板磨损量的因素较多,碳纤维、石墨、硅灰石纤维和铜纤维的含量对该性能均有一定程度的影响,其中碳纤维、石墨和硅灰石纤维的交互作用明显。根据均匀设计和回归分析的实验结果,对实验配方进行优化,确定层状结构树脂基受电弓滑板的最优配方为：酚醛树脂26.4%,丁腈橡胶2.4%,碳纤维15.2%,石墨14.2%,硅灰石4.8%,铜纤维8%,铜粉5%,铜网24%。通过正交试验优化滑板的模压制备工艺,根据实验结果和极差大小,确定模压工艺参数对滑板综合性能的影响顺序为：加压时机>模压温度>保压时间>模压压力；最佳模压工艺为：模压温度170℃,模压压力60MPa,单位厚度保压时间5min·mm-1,加压时机3mmin。应用XRD、Raman、SEM和FTIR实验技术,对浓硝酸氧化处理前后碳纤维结构和形貌进行表征,从而选择最佳的氧化处理时间；将硝酸处理后的纤维进行硅烷偶联处理,分析表面处理对滑板性能的影响。结果表明硝酸处理并未改变碳纤维的本体结构,随着液相氧化时间的延长,碳纤维表面的晶粒尺寸略有减小,表面结构趋于紊乱,无序结构与石墨结构的比值R随处理时间的延长而增大；氧化处理使碳纤维的表面沟槽增多并加深,当氧化时间达到12h时,纤维表面有凹坑和孔洞出现,对纤维的损伤较大；经过9h硝酸处理后,FTIR可观察到-COOH,-OH等官能团的吸收峰,因此选择最佳液相氧化时间为9h；将硝酸处理9h后的碳纤维进行硅烷偶联处理,处理后纤维表面的轴向沟槽变浅,偶联剂起到了覆盖微裂纹和沟槽的作用。采用两种表面处理后的碳纤维制备受电弓滑板,表面处理对滑板电阻率的影响不大,硅烷偶联复合处理使滑板的电阻率略有升高；硝酸氧化处理后,滑板的冲击强度略有升高,硅烷偶联复合处理的滑板冲击强度比未处理的提高了37%,从冲击断面的SEM图分析,硅烷处理提高了树脂与纤维的界面结合强度,拔出的碳纤维表面上粘附一层厚薄不均匀的树脂,硅烷偶联剂中的柔性基团的存在有利于冲击能的吸收；碳纤维的两种表面处理均提高了滑板的耐磨性,硅烷偶联复合处理使滑板的磨损量比未处理的滑板降低了32%。因此硅烷偶联复合处理是提高滑板性能的有效表面改性方式。为提高树脂基滑板的耐温性能,对滑板进行焙烧处理,分析焙烧温度对滑板性能的影响,从而确定最佳焙烧温度为600℃。为提高焙烧后滑板的性能,对滑板进行致密化处理。结果表明随焙烧-浸渍次数的增加,滑板的密度、导电性、冲击强度和耐磨性与一次焙烧处理后的滑板试样相比均得到提高,除导电性能外,经过致密化处理后的试样性能仍低于未焙烧处理的滑板试样,纤维与树脂之间仍有孔隙存在,制约着滑板性能的提高；随浸渍次数的增加,试样的可增重比例减小,当浸渍3次之后,滑板的性能变化较小,确定滑板的最佳致密化工艺为焙烧4次、浸渍3次。通过对焙烧型滑板中酚醛树脂含量对滑板性能影响的研究,最终确定焙烧型滑板的配比为：酚醛树脂25.8%,碳纤维15.2%,硅灰石4.8%,石墨14.2%,铜纤维8%,铜网24%,铜粉8%。通过SEM和EDS技术对不同类型滑板的磨损表面形貌进行分析,讨论滑板的机械磨损机理,结果表明添加铜纤维和铜网后,滑板的磨损形式由涂抹型的粘着磨损转变为擦伤型的粘着磨损,对碳纤维进行硅烷偶联改性可增加纤维与基体的粘结力,耐磨性提高；树脂基滑板的磨损机理为擦伤型的粘着磨损；随焙烧处理温度的提高,滑板的磨损形式由粘着磨损逐渐转化为粘着磨损和磨粒磨损共同作用的结果。更多还原

【Abstract】 Pantograph contact strip is the main collecting electricity component of electric locomotive. It can help electric locomotive power supply system to obtain electric energy. The quality of contact strip has important impact on current carrying condition of electric locomotives and service life of contact wire. According to its material, strip can be classified into three types:carbon series strip, metal series strip and composites strip. As operation speed of electric locomotive continuous improvements, traditional contact strip can not meet the demand of the high speed train. In this paper, we designed a new structure contact strip to overcome the shortcomings of traditional contact strip. The contact strips obtained excellent conductivity by laminar laying copper mesh being framework, and had good wear resistance due to composite laminated structures. Focus on development of layer structure pantograph contact strip, the structure design, formula and process optimization were investigated in this paper. We could get the optimal formula and process condition by comparing resistivity, impact strength and wear resistance of different formula and process samples. The conductive and wear mechanism of contact strip were also analyzed.In the structure design of pantograph contact strip, layer structure was determined by balancing against the influence of composites component and copper mesh on resistivity, impact strength and wear property. The optimal pore diameter size of copper mesh was3.16mm×6.3mm and the thickness was0.48mm.In the materials composition design of layer structure resin matrix pantograph contact strip, influence of the resin content and fiber type on performance of contact strip was analyzed. The results showed that phenolic resin content had small impact on the resistivity of contact strip. The impact strength decreases with the increase of phenolic resin content. When phenolic resin content was lower, there was a certain angle between impact fracture section and impact load direction, which suggested that fiber reinforced played an important role in changing directions of crack as well as slowing crack propagation, showing higher impact strength. Impact fracture section of pantograph slide plate was not only smooth but also on the same with load direction when phenolic resin content was higher, appearing brittle fracture with lower impact strength. With the increase of phenolic resin content, the wear loss increased first and then decreased. The wear loss was lowest when resin content was26.4%. Thus, the optimal content of phenolic resin was26.4%. The study of electrical sliding wear phenomena and behavior of composite contact strip revealed that adding carbon fiber could facilitat conductivity and wear resistance. The existence of copper fiber obviously enhanced the conductivity and improved the arc ablation phenomenon. The wear resistance was greatly improved due to extinguishing of the wollastonite fiber. So we choose carbon fiber, copper fiber and wollastonite fiber as hybrid fiber to reinforce contact strip.The uniform design and regression analysis method were used in formula design of contact strip. The influence of carbon fiber, graphite, wollastonite fiber, copper powder and copper fiber content on properties of pantograph contact strip was investigated. The appropriate formula was determined by mean of regression analysis. The results showed that electrical conductivity was linear to copper fiber content and decreased with the increase of copper fiber content. Impact strength of pantograph contact strip was in direct proportion to CF content. The friction coefficient of pantograph contact strip was mainly influenced by carbon fiber, graphite and wollastonite content. Many factors including CF, graphite, wollastonite and copper content influenced wear loss, and significant interaction was found in CF, graphite and wollastonite fiber. Copper powder had smaller effect to performance of pantograph contact strip. According to the results of uniform design and regression analysis experiment, the formula of contact strip was optimized and the optimum of layered structure resin matrix pantograph contact strip as follows:phenolic resin at26.4%, nitride rubber at2.4%, carbon fiber at15.2%, graphite at14.2%, wollastonite fiber at4.8%, copper fiber at8%, copper powder at5%, and copper mesh at24%.By the orthogonal experiment, the mold pressing process was optimized. Based on test results and range value, the sequence of affecting contact strip behavior was ranked as pressure applying time>molding temperature>holdup time> pressure. The optimum process parameters were molding temperature at170℃, holdup time at5min·mm-1, pressure at60MPa, and pressure applying time at3min.Raman spectroscopy (Raman), X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were used to investigate the evolution of surface structure and morphology before and after oxidation treated. Thereby the best oxidation time was determined. Carbon fibers oxidated by nitric acid was treated by silane coupling agents and investigated the effect of different surface treatment on performance of contact strip. The results indicated that nitric acid oxidation treatment did not change the entity structure of carbon fibers. With the increase of the oxidation time, interplanar spacing of carbon fiber surface increased and crystalline size decreased slightly. The entire structure disordered and R values of carbon fiber increased with the increase of oxidation time. The grooves of surface became wider and deeper with the increase of the oxidation time. Some big holes and grooves could be observed when the oxidation time reached to12h, which would severely damage the fiber. After oxidation treatment to9h,-COOH,-OH could be found by FTIR. So the best oxidation time was9h. After silane coupling agents treated, the grooves of the surface were covered with thin films and the surface grooves became shallower compared with the fiber treated by nitric acid. The results showed that silane coupling agents were effective for overlaying the micro cracks and grooves. The performance of contact strip which reinforced by different trcated carbon fiber was investigated. Surface treatment had little effect on resistivity of contact strip. The resistivity of contact strip increased slightly after silane coupling agent treatment. Impact strength increased after surface treatment by nitric acid and the impact strength increase by37%after silane coupling agent treatment. From scanning electron microscopy images, it could be seen that the surface of fiber coated with resin in uneven thickness. The existence of flexible groups came from silane coupling agent facilitated absorption of impact energy, which indicated that silane treatment improved interface bonding strength between resin and fiber. The wear resistance was enhanced by surface treatment of carbon fibers, and the wear loss decreased by32%after silane coupling agent treatment. The technology of silane coupling agent compound treatment was an effective method to improve performance of contact strip.In order to improve heat resistance, we adopted calcinations to treat contact strip. The influence of calcinations temperature on properties of contact strip was analyzed to confirm the optimum temperature at600℃. The densification process was used to improve the properties of contact strip treated with calcinations. The results showed that the density, conductivity, impact strength and wear resistance were improved with increase of calcinations-impregnation times compared with contact strip treated by one-shot calcinations. The performance of contact strip after densification process was still lower than untreated contact strip. The existence of pore between fiber and resin restricted improvement of contact strip performance. The weight increase rate was decreased when increasing of impregnation time. The properties changed very slight when impregnation time was three, thus we confirmed the best densification process as four times of calcinations and three times of impregnation. The impact of resin content on performance of calcinations type pantograph contact strip was analyzed to determine optimal formula as follows:phenolic resin at25.8%, carbon fiber at15.2%, graphite at14.2%, wollastonite fiber at4.8%, copper fiber at8%, copper powder at8%, and copper mesh at24%.The morphologies of the worn surfaces were observed with SEM and EDS, and the wear mechanics were discussed. The results showed that the adhesive wear behavior changed from smearing type to scratches type after adding copper fiber and mesh. Silane compound treatment of carbon fiber would enhance adhesive strength between fiber and matrix to improve wear resistance. The wear mechanism of resin matrix contact strip was smearing type adhesive wear. Raising calcinations temperature made the major wear mechanism of contact strip changed from adhesive wear to adhesive wear together with abrasive wear.更多还原