碳纤维复合材料铣削与磨削加工对比研究

使用单层钎焊金刚石磨头和金刚石涂层玉米铣刀对T800碳纤维增强环氧树脂复合材料层压板进行切边加工,研究铣削加工和磨削加工工艺对碳纤维增强复合材料(carbon fiber reinforced plastics,CFRP)表面质量的影响。通过对加工表面微观形貌的观察和表面粗糙度的测量对比,讨论2种加工方式下表面质量差异和缺陷形成的原因。结果表明:磨削加工的表面质量优于铣削加工的表面质量,铣削加工后CFRP表面会出现凹坑和树脂涂覆等缺陷,但磨削加工的表面纤维断口清晰可见,无明显缺陷。铣削工艺下的凹坑是纤维集束断裂而形成的,树脂涂覆是由刀具后刀面与工件材料的频繁挤压、摩擦而形成。在表面质量和加工缺陷要求严格的条件下,应优先选用磨削加工工艺。      

高速超高速磨削用CFRP砂轮功率消耗试验研究

针对钢基体砂轮质量大、在高速超高速磨削中功率消耗大的问题,从启动功率、空耗功率、磨削功率等几方面,测量并分析了碳纤维增强树脂基复合材料(carbon fiber reinforced polymer,CFRP)基体砂轮与钢基体砂轮功率消耗的情况。试验结果表明:与钢基体砂轮相比,CFRP砂轮的质量轻,能够有效减小砂轮在高速超高速磨削中的启动功率、空耗功率以及磨削功率;验证了CFRP砂轮在高速超高速磨削中减轻主轴负荷、减少能源消耗的优越性能。     

谈复合材料及其发展和关注的热点(下)

3.树脂基复合材料采用的增强材料 树脂基复合材料采用的增强材料主要有玻璃纤维、碳纤维、芳纶纤维、超高分子量聚乙烯纤维等.     

碳纤维增强Cu-Ti3SiC2复合材料的性能与烧结温度的关系

研究了在Cu-Ti3SiC2复合材料中添加2%体积含量碳纤维的致密度、电导率和硬度同烧结温度的关系。实验结果表明,加入碳纤维的Cu-Ti3SiC2复合材料较未加入碳纤维的Cu-Ti3SiC2复合材料的致密度和电导有少许下降,但布氏硬度有大幅度提高。随着烧结温度的上升,碳纤维增强Cu-Ti3SiC2复合材料的相对密度上升较快,在1000℃时达到99.21%。电阻率随烧结温度的上升而下降;布氏硬度随着烧结温度的上升而提高,但增幅较缓。     

C/SiC复合材料磨削的表面/亚表面损伤

采用树脂结合剂金刚石砂轮对二维正交编织结构C/SiC复合材料进行了平面磨削加工实验。通过对磨削加工表面形貌、磨削表面中碳纤维区域的粗糙度、磨削亚表面形貌的分析与测量,对C/SiC复合材料磨削表面/亚表面损伤进行了研究。结果表明:磨削表面中碳纤维损伤形式以阶梯状脆性断裂为主。对于编织方向平行于进给速度方向的纤维区域,脆性断裂尺寸、表面粗糙度受工艺参数影响较小;而对于编织方向垂直于进给速度方向的纤维区域,脆性断裂尺寸、表面粗糙度随进给速度增大无明显变化,但随磨削深度增大而明显增大。碳纤维区域亚表面损伤形式主要为阶梯状脆性断裂,而SiC区域亚表面损伤形式主要为脆性断裂及微裂纹,且损伤程度在实验参数范围内无明显差异。     

碳纤维复合材料环境适应性的研究进展

碳纤维增强复合材料由于具有密度小、比强度和比刚度高,抗疲劳性能优、阻尼性能好和耐腐蚀等优异的性能,已被广泛应用于水中兵器和水下运载器。碳纤维增强复合材料耐海水腐蚀、电偶腐蚀、耐老化性能及在海洋环境下的使用寿命评估已经成为舰艇及水中兵器复合材料应用研究的热点。本文总结和分析了国内外研究工作者对上述问题的研究成果,并提出了改善碳纤维增强复合材料环境适应性的措施,以期对我国海洋环境下复合材料的结构设计和应用提供参考。     

真空浸渗C_(sf)/AZ91D复合材料的高温变形行为与机理

采用真空辅助压力浸渗法短切碳纤维增强镁基复合材料(Csf/AZ91D),在变形温度为400~490℃、应变速率为0.001~0.1s-1、最大变形量为50%的条件下,研究了Csf/AZ91D复合材料的高温压缩塑性变形行为,观察了复合材料变形前后的微观组织,通过与基体镁合金对比探讨了镁基复合材料高温塑性变形机理。结果表明,复合材料在高温压缩过程中碳纤维发生了显著的偏转和折断,致使复合材料的应变软化现象较镁合金更为明显;短碳纤维细化了基体组织并增加了界面数量,使得复合材料表现出较高的应变速率敏感性;短碳纤维和晶界对基体强化作用随变形温度升高而减弱,而复合材料应力水平随变形温度增加而显著降低,表现出比镁合金更高的表观变形激活能。     

连续Cf/Al复合材料板双辊铸轧制备及力学性能研究

本文利用电镀工艺制备了表面镀镍碳纤维,通过双辊铸轧短流程成型工艺成功制备了连续碳纤维增强铝基（Cf/Al）复合材料板,研究了浇注温度对铸轧复合材料板的微观组织、界面特征、断口形貌和力学性能的影响。结果表明,浇注温度为963～983K,轧制速度为2.7m/min,辊缝为2.0mm的条件下可制备出表面平整、无明显表面缺陷的Cf/Al铸轧复合材料板;其中,浇注温度为973K时,碳纤维与铝基体之间界面结合良好;纤维表面金属镍层明显改善了碳纤维与铝基体之间的浸润性,镍镀层还有效抑制了Al4C3脆性相的产生,使Cf/Al复合材料板力学性能大幅提升,其中浇注温度973K铸轧的Cf/Al复合材料板抗拉强度比初始的38.2MPa提高了87.4%。     

碳纤维复合材料在笔记本电脑外壳上的应用

介绍了短碳纤维增强复合塑料、热固性连续性碳纤维复合板材、热塑性连续性碳纤维复合板材、碳纤维复合薄膜等4种碳纤维复合材料在笔记本电脑外壳上的应用,并作出了展望。碳纤维与工程塑料、环氧树脂、PMMA等树脂复合后制备的笔记本电脑外壳,在同等强度条件下,相比传统工程塑料制备的笔记本电脑外壳,厚度可减薄50%~60%,重量减轻40%~50%,而且拥有良好的耐候性和耐腐蚀性。指出碳纤维复合材料研究的快速发展将会推动笔记本电脑市场的巨大变革,使笔记本电脑向着"更轻、更薄、更强"方向快速发展。     

钛合金/碳纤维布复合材料的界面与力学性能的研究

本文选用Ti-6Al-4V钛合金为基体,镀铜碳纤维布为增强相来制备钛合金/碳纤维布复合材料。通过放电等离子烧结法(SPS)对镀铜碳纤维布与钛合金薄片进行叠层烧结,制备钛合金/碳纤维布叠层复合材料,并对其界面形貌、微观组织与力学性能进行表征。结果表明：镀铜碳纤维均匀分布在钛合金/碳纤维布复合材料中,CuTi, Cu和少量的TiC沿着纤维和基体的界面分布。钛合金/碳纤维布复合材料具有比钛合金略高的塑性,同时屈服强度和抗压强度与钛合金相比有了明显的提高。碳纤维表面电镀铜对复合材料界面有着重要的影响：(1)显着降低钛合金/碳纤维布复合材料的烧结温度;(2)提高了碳纤维和钛基体之间的润湿性,改善了界面结合,从而提高了钛合金/碳纤维布复合材料的力学性能;(3)有效地抑制TiC脆性相的产生,与未镀铜的碳纤布增强钛复合复合材料相比,镀铜碳纤维布/钛合金复合材料具有更好的塑性。     

超声振动辅助缓进给磨削温度场仿真与试验分析

目的通过对比研究磨削过程中超声振动辅助缓进给磨削工件表面的温度变化,验证超声振动对磨削热的影响,为进一步研究磨削机理提供依据。方法基于磨削温度场解析模型,建立了磨削热源平均强度。运用ANSYS软件热分析模块分别对普通缓进给磨削和超声辅助缓进给磨削进行了工件表面温度场仿真,得到了不同载荷步的温度场分布以及工件表面的温度时间变化曲线,较准确地反映了磨削工件时工件表面的温度变化。结果试验和模拟表明,缓进给磨削工件时,工件表面温度较高,对工件施加超声振动后,能够有效降低磨削力,减少磨削过程中产生的热量,降低工件表面温度20%左右。结论超声振动辅助磨削工件时,由于工件高频振动导致磨粒与工件间断性接触,使磨削过程变为有规律的脉冲状断续磨削,有利于工件散热,降低了磨削温度,为避免缓进给磨削时容易出现的磨削烧伤现象提供了技术支持。     

钢轨打磨用复合砂轮磨削温度场的研究

为研究钢轨打磨用钎焊金刚石插片复合砂轮磨削时的温度场,用复合砂轮和树脂锆刚玉砂轮在不同压力下磨削65Mn钢工件,并对比其磨削温度。基于试验数据,用有限元法分析复合砂轮磨削钢轨时的温度场。结果表明:随着磨削压力的增大,砂轮产热增大,但复合砂轮磨削产热相对较小。相对于相同条件下用树脂砂轮打磨时,用复合砂轮打磨钢轨时的磨削表面最高温度降低近10%。      

基于温度匹配法的平面磨削3D有限元仿真及试验

为了准确预测工件表面及亚表面不同深度的温度场变化,基于反热源原理,以实际测量的磨削温度为基础,采用温度匹配法建立适应真实磨削加工时接触区的热源模型。运用有限元法,仿真计算工件磨削温度场的变化,并与瑞利分布热源模型预测结果对比,对工件表面及亚表面不同深度磨削弧区的磨削温度场进行测量。结果表明:基于温度匹配法建立的热源模型模拟的表面及亚表面不同深度温度场与实测值具有很好的一致性,相对误差在3.0%～7.5%,比瑞利热源模型预测的温度场分布精度提高了近2倍。      

An investigation of workpiece temperature variation of helical milling for carbon fiber reinforced plastics (CFRP)

Better prediction about the temperature distribution of workpiece has a great significance for improving performance of cutting process, especially relating to the workpiece of carbon fiber reinforced plastics (CFRP). In this paper, a heat transfer model is developed to investigate the temperature distribution of CFRP workpiece in helical milling process. Depending on characteristics of helical milling, two kinds of heat sources have been presented, the geometrical shapes of which are modeled as semicircle arc and line. The complex trajectory of each heat source relative to the stable workpiece has been studied. Based on the analysis, unsteady state three-dimensional governing equation of heat transfer in CFRP workpiece with adiabatic boundary condition is proposed. The solution procedure of this nonhomogeneous heat transfer equation consists of two steps: it is transformed into homogeneous equation according to the heat transfer theory firstly; and then the homogeneous equation is solved using the separation of variables. Basing on the solution of the homogeneous equation, the temperature distribution resulting from the moving semicircle arc heat source and the line heat source has been studied detailedly. In order to calculate the heat generation in the helical milling process, a cutting force model is presented and the heat partition transferring into the CFRP workpiece is solved using the Conjugate Gradient Method. A series of tests of helical milling for CFRP are conducted, and the experiment results agree well with the results calculated by the predicted model. This model can be extended to optimize the cutting condition and restrain the thermal damage of the CFRP workpiece.     

Application of alumina fiber reinforced plastics as a grinding material

This work deals with the evaluation of ceramic fiber reinforced plastics as a grinding or polishing material. The plastics were manufactured by mixing continuous alumina fiber of definite diameters and thermosetting resin as a bond material. Composites containing fibers of three different diameters ranging from 10 to 22 μm were used in the study. The performance of these composites was evaluated for surface finishing of hardened steel. Bars of the composite were pressed against the rotating workpiece material S55C on a lathe. Wear of the work and the composite and the surface finish of the work materials were investigated. The self-sharpening characteristic was confirmed and the chip removal process is explained. The most important factor affecting the rate of metal removal to tool wear loss is the average pressure. The fine surface is obtained with the fine fiber. The advantages of the alumina fiber reinforced plastics as a grinding tool are their toughness and flexural strength. They assure a practically fracture-free grinding operation. Resin matrix composites reinforced with ceramic fibers are proposed as efficient tool materials for small stock removal. Paper presented at the First International Conference of New Manufacturing Technology, Chiba, Japan, March 1990.     

钢轨打磨用新型复合砂轮及其磨削试验

利用钎焊技术和传统热压技术研发出一款钢轨打磨用新型复合砂轮,复合砂轮除含传统树脂砂轮的成分外还含金属结合剂金刚石插片,用其在钢轨打磨试验机上与传统树脂砂轮进行工件打磨对比试验,分析工件打磨后的打磨温度和表面粗糙度变化,并对钢轨打磨后的磨屑进行电镜、能谱分析。试验结果表明:与纯树脂砂轮相比,采用新型复合砂轮打磨工件,其打磨温度峰值下降10%左右,砂轮中插片数越多下降比例越大;工件表面粗糙度下降比例在9%以上,且随着砂轮中插片数量的增加而增大;同时,磨屑中球状磨屑比例更低,球状磨屑中O元素质量分数更小。      

Temperatures in deep grinding of finite workpieces

This paper investigates the diverse thermal effects generated in high efficiency deep grinding (HEDG). Using a new thermal model of circular arc contact with transient analysis, the transient behaviour of the maximum contact temperature has been analysed for various grinding conditions. It is found that steady state conditions can be achieved for the conditions of sufficient workpiece length and high workspeeds. The effect is important for the understanding of the deep grinding process and for the prediction of satisfactory grinding conditions. HEDG conditions also have very apparent effects on the depth of heat penetration to the workpiece. The parameters investigated include mean contact angle, Peclet number and the heat source distribution. Experimental results are presented for specific energy, energy partition and mean temperature for high efficiency deep grinding.     

Temperature distribution in a workpiece during cylindrical plunge grinding

In cylindrical plunge grinding, a large amount of heat flows into the workpiece continuously, accumulates and remains even after the process, which causes dimensional error. Therefore it is necessary to investigate the temperature distribution in the workpiece during grinding and analyze the influence of grinding heat on the dimension. Such an investigation has not been done enough, because the technology to measure the temperature distribution in the rotating workpiece has not matured. Considering such background, an in-process measuring system has been developed, which makes it possible to detect the temperature distribution in a wide range from the outer surface to the inside of the rotating workpiece. The system consists of small temperature sensors which are embedded into the workpiece, a micro computer attached on the workpiece which acquires the data from the sensors and transmits to a personal computer by a wireless communication device. Furthermore the contact type thermocouple which enables to measure the rotating surface temperature is added to the system. Measurement experiments revealed that the grinding heat conducts from the workpiece surface toward the center, accumulates, and remains in the workpiece even after the process. Heat conduction simulation was also performed. Good agreement was achieved between the simulated temperatures and experimental measurements.     

Experimental and finite element analysis of temperature and energy partition to the workpiece while grinding with a flexible robot

Grinding processes performed with flexible robotic tool holders are very unlike conventional types of grinding because of low stiffness of the robot's structure. A special flexible robotic grinding process is used for in situ maintenance of large hydroelectric equipment for bulk material removal over large areas rather than as a finishing step, as is the case for most conventional grindings. Due to the low structural stiffness of tool holder, cutting is interrupted at each revolution of wheel during the grinding process. In this study, an investigation is carried out to determine the temperatures and energy partition to the workpiece for the above-mentioned flexible robotic grinding process by a three-dimensional finite element thermal model. Experiments were undertaken using embedded thermocouples to obtain the subsurface temperature at several points in the workpiece during the process. Then, energy partition to the workpiece was evaluated using a temperature-matching method between the experimental and numerical results. This ratio is used for predicting the temperature field at the wheel–workpiece interface with a relevant heat source function. Kinematics of cut and the flexible robot's dynamic behavior are considered in applying the heat input to the model. The energy partition to the workpiece in this specific flexible grinding process is found to be lower than for analogous conventional precision grinding processes. Two models, one from the literature and one from the power model of the process, are modified and proposed for determining the energy partition. The results showed that the energy partition ratio decreases by increasing the process power. Also, this ratio slightly decreases at higher feed speeds. In addition, lower temperatures were seen at higher powers due to the lower intensity of heat input over a larger contact area. Experimental observations show close agreement between simulated contact temperatures and measured results.