深松铲激光熔覆残余应力产生机理及其减阻特性研究

The traditional subsoiler encounters problems of high resistance and easy wearing in the subsoiling process. This project researches on how to improve the life of subsoiler. The laser cladding technology is introduced. The wear-resistant material is cladded on the subsoiler surface to improve its wear resistance. However, the residual stress is produced inevitably in the laser cladding process. The temperature field in the cladding process is numerically calculated using finite element method. The stress field is solved by means of thermal-stress indirect coupling. The Residual stress distribution characteristics are found by experiment. Furthermore, the residual stress generation mechanism is revealed by the method of combination of finite element numerical simulation and experimental means. Take soil as dispersed particles. The discrete element model of subsoiler-soil contact is established and numerically calculated aiming at obtaining the subsoiler actual stress state in the soil. According to the laser cladding actual situation, the method of controlling the residual stress segmented is proposed. The residual stress is used as prestress to improve subsoiler stress distribution, reduce the resistance effectively in the subsoiling process. Therefore, the life of subsoiler is improved by two approaches introduced above. The successful implementation of this project will not only provide key technology for wear-resistance and anti-resistance subsoiler development, but also provide a reference for laser cladding technology in soil-touching parts of other agricultural machinery.

本项目针对传统深松铲在深松整地过程中阻力大、易磨损的问题，围绕如何提高深松铲的使用寿命展开研究。引入激光熔覆技术，在深松铲表面熔覆耐磨材料，提高其抗磨损能力。激光熔覆中必然产生残余应力，利用有限元分析方法对熔覆过程的温度场进行数值计算，采取热-应力间接耦合法求解应力场，通过试验手段测试熔覆深松铲的残余应力分布特性，将试验测试与数值计算结果相结合，揭示熔覆残余应力的形成机理。将土壤看作散体颗粒，建立深松铲-土壤接触离散元模型并进行数值求解，探明深松铲在土壤中的受力情况。根据激光熔覆实际情况，提出一种残余应力分段控制方法，将残余应力作为预应力加以利用，改善深松铲作业过程的应力分布，有效减小深松作业阻力，达到双效提高深松铲使用寿命的效果。项目研究成果为高耐磨、抗阻力深松铲的研制提供关键技术，也为其他农机触土部件的激光熔覆提供借鉴。

深松整地是改善耕地质量，提高农业综合生产能力，促进农业可持续发展的重要举措。深松铲作为深松作业关键部件，在土壤中极易磨损。从而引起深松铲刃口变厚导致阻力增加，进而致使拖拉机油耗增加，作业质量变差。因此，深松铲耐磨方面的研究具有重要的意义。本项目把高能束熔覆技术应用于深松铲的表面耐磨处理，研究内容及其成果主要包含：（1）搭建了深松铲专用等离子熔覆平台，设计出一种深松铲等离子熔覆专用夹具和多功能工作台。（2）系统开展了等离子熔覆工艺方面的研究。1）探究了工作电流、送粉速度和扫描速度等主要工艺参数对单道等离子熔覆层形貌参数的显著特性及影响规律，建立了数学模型，优化了参数取值范围；2）利用灰关联分析法和极差分析法探究了工艺参数对多道搭接熔覆层表面平整度和显微硬度的综合影响，优化出最佳工艺参数组合；3）通过摩擦磨损试验，结合SEM、EDS、XRD等表征手段研究了熔覆层的摩擦磨损特性；4）实施了熔覆深松铲田间试验，结果表明熔覆处理后的深松铲尖耐磨性显著提高。（3）对等离子熔覆残余应力进行了深入的研究。1）设计了一种便携式钻孔法残余应力测试辅助钻孔装置，该装置能有效解决传统测量装置测量时存在的问题，并具有突出的优点；2）研究了工艺参数对单道等离子熔覆残余应力的影响，总结分析得到各种工艺参数对残余应力的影响规律，揭示残余应力产生机理；3）对多道搭接等离子熔覆残余应力进行了研究，探究了残余应力在熔覆层上的分布情况，优化出最优工艺参数组合；4）提出了一种残余应力分段调控方法，进行了去应力退火试验，退火温度对残余应力影响显著，620℃时残余应力降低效果最好。本项目所研究的基于高能束熔覆技术的农机具耐磨处理技术对于提升我国农机装备关键零部件的制造水平具有重要意义，研究成果也将为其他行业易磨损零部件的熔覆处理提供有益的借鉴。