【作者】 孟海波；

【导师】 韩鲁佳；

【作者基本信息】 中国农业大学 ， 农产品加工及贮藏工程， 2005， 博士

【摘要】 农作物秸秆资源的开发利用于国于民、乃至对农业生态系统的可持续发展都具有重要意义。秸秆的机械破碎加工是秸秆饲用和实现秸秆饲料商品化生产的首要环节。秸秆破碎加工直接影响着加工机具的能量消耗,也是造成机具工作刀片材料损耗的重要原因,还会对秸秆加工质量产生影响。秸秆物料的力学性质与工程材料相比存在很大差异,是设计、改进加工机具与加工工艺的重要依据。为此,首先研制了可模拟秸秆切割破碎加工工况的秸秆力学特性研究试验台,为解决秸秆加工机具参数优化设计提供理论依据。同时,从加工刀片的材料和材料处理工艺入手,对不同材料、不同结构和不同工艺刀片的耐磨性和可靠性进行了研究,完善了设计制造工艺。 1.利用扫描电镜(SEM)观察分析了玉米秸秆的组织结构特征。采用三点弯曲法研究了玉米秸秆在弯曲载荷下的力学特性。在材料实验仪上进行了玉米秸秆弯曲断裂实验。结果表明,秸秆的力学性能与其组织结构密切相关,秸秆组织结构的差异是造成秸秆力学性能变化的内在原因。玉米秸秆弯曲断裂过程分为线性和非线性阶段;断裂过程中,玉米秸秆所需折断力最大达到215.44N,变形范围超过15mm。秸秆所需折断力的变化受到截面积、节位和存放时间的影响。 2.模拟秸秆切割破碎加工工况,研制了秸秆破碎加工试验台。试验台主要包括加速系统、力学参数采集系统、高速摄影及图像运动分析系统和总体控制系统四部分。能够实现高速切割和切割速度连续可调,自动采集力学参数、实时记录切割运动图像等功能,便于操作,安全可靠,是研究秸秆力学特性的有效工具和手段。 3.利用高速摄像机在线拍摄了秸秆切割破碎加工运动过程,采用图像运动分析系统分析了切割过程中秸秆的运动规律。切割速度、支撑方式和定刀等因素对秸秆切割破碎加工运动过程均有重要的影响。 4.利用自制的秸秆破碎加工试验台,全面研究了各项因素对玉米秸秆切割破碎加工力学特性的影响规律。对于麦秸、稻秸这类细长柔韧性高的秸秆,切割速度、动定刀间隙是切割阻力和切断率的重要影响因素,刃口的锋利程度对切断率和切割阻力也有重要影响。 5.选取影响秸秆破碎加工过程的四个主要因素,包括切割速度、动定刀间隙、切割根数和含水率,安排了四因素二次回归正交组合试验,利用SPSS计算分析,建立了切割阻力的回归模型和切断率的回归模型。采用线性加权和法对两个回归模型进行了优化。利用Matlab计算得到优化方案,确定了比较理想的秸秆破碎加工工艺条件。 6.利用9RZ-60型秸秆揉切机对加工刀片进行了磨损试验;采用扫描电镜(SEM)对刀片进行了磨损微观形貌分析和断裂刀片的成分分析与失效分析。结果表明,刀片的装机位置、刀片材料以及秸秆物料对刀片的耐磨性均有显著影响。原有刀片刃口局部材料的硬度不够,材质脆性过大,有过热现象。制造刀片的65Mn材料组织很不均匀,表明锻造后未经用以消除锻造组织不均的专门的正火处理。最后确定选用65Mn材料,采用新的热处理工艺方案,对揉切机刀片在工作室的配置方式进行了改进。结果表明,结构改进显著提高了刀片的耐用性能,降低了单位生产量的刀片材料损耗,提高了揉切机的生产率,加工质量也得到相应改善。更多还原

【Abstract】 It is significant for the Country and people, even for sustainable agricultural ecosystem to utilize and develop crop straw resources. Cutting process of straw is the first important tache for feeding and commercial production of straw during the utilization of straw feed. Cutting process of straw affects the energy consumption of the machine, causes wastage of cutters on the machine, and have an impact on the straw process quality. The physical properties of straw are important basis for designing and improving the machine and processing technics, and it varies greatly from the engineering materials. Therefore, the test-bed of physical properties which could simulate the cutting process of straw was designed to provide the academic basis for optimizing the parameters of the machine. The abrasion resistance and strength toughness of cutters with cutters of different materials, different structures and different processing were studied. Results have been showed as below.Firstly, mechanics properties of corn straws have been discussed by experiment on three-point bending corn straws on the materials testing instrument in the paper. The microstructure of corn straws has been observed by SEM. Results show that there were two phases during the rupture of corn straw. Maximum of broken force reached 215.44N, and that of displacement reached 15mm. The mechanics of corn straws is relative to its microstructure. Broken force was affected by cross area of straws, storage time and position of nodes.Secondly, based on analysis of the structural theory of the machine processing straw, a new test-bed cutting straws has been developed. It contains four systems, includes accelerating system, acquisition system of strain parameter, high-speed photographs system and main controlling system. And it is convenient to arrange testing apparatus on the test-bed. And it is easy to operate.Thirdly, The cutting process of straws has been recorded by high-speed photograpy camera. Motion law for the process of straw cutting was analyzed with MAS (motion analysis system).Fourthly, based on the experimental study and theoretic analysis, key factors affecting the process of cutting of corn straws have been researched on the new test-bed for cutting straw. Cutting speed and clearance between moving and fixed cutter are both the key parameters affecting the cutting resistance and rate of cutting straw for wheat and paddy straw which are acerose and flexile, influence of tartness of the cutters on the cutting resistance and rate of straws cutting was very important as well.Fifthly, the paper investigates the relationships between the cut resistance, cutting rate and key factors, such as cutting speed, clearance between moving and fixed cutters, count of cutting straws, and straws water content by means of regression orthogonal analysis method. Regression models about the relationships were established. A target function from cut resistance model and rate of straws cutting model has been constructed by weighted linear summation method. A bi-index optimization of straws cutting has been carried out by Matlab , and a group of optimized parameters were obtained.Finally, cutters abrasion experiment has been conducted on the 9RZ-60 model straw rubbing and cutting machine in the paper. Macro-analyses and micro-analyses, and analyses of chemical compositions of the cutter made of 65Mn and metallographic examinations are observed by SEM. It indicated that bladematerials and cutters position in the workroom on the machine and properties of straws were the main factors to the blade wear respectively. Because of over-heated, hardness of part blade on the cutter is inadequate. The cutter made of 65Mn was not heated specially after forging. A new heat treatment scheme was conducted, and collocation of cutters in the workroom was changed, and three kinds of feeding form were designed. Results show that the life of cutters was extended, and blade materials wastage was reduced, and productivity of the rubbing and cutting machine was increased, process quality was improve更多还原