【作者】 赵慧慧；

【导师】 吴林；

【作者基本信息】 哈尔滨工业大学 ， 材料加工工程， 2012， 博士

【摘要】 GMAW(Gas Metal Arc Welding)多重堆积再制造是修复较大金属构件破损的重要手段，其热过程复杂、影响因素多，是目前再制造领域研究的热点之一。本文以实现GMAW再制造多重堆积路径优化为目标，以单热源多重加热模式下的热过程为重点，对成形过程多次加热温度场理论解析进行了探索，采用有限元模拟和实验方法对其多重加热模式下的复杂应力、变形、路径影响规律进行了系统研究，并建立了多重堆积路径模糊综合评价系统，实现了多指标路径优化。为大型构件高效率、高质量再制造的实际应用建立了理论基础，并为再制造堆积路径优化提供一种可行的技术手段。首先，对GMAW多道堆积多次加热温度场理论解析进行探索研究，采用集中点热源、三维分布双椭球热源，在静止、运动坐标系下推导出电弧热源多次加热、道间冷却及最终冷却过程动态温度场解析公式。在Matlab环境下编程实现了多道堆积加热目标区域温度场、热循环、道间等待时间范围等特征参数的计算。进而研究了多道堆积过程前道热积累对后道的预热，以及后道对前道的后热作用，对比分析了不同堆积方向、不同规范下的热循环特点。同向比交错式堆积散热好，规范过大会导致热积累严重，工件过热。分析了道间等待时间对热循环的影响规律，可利用道间等待时间有效控制多重堆积的热量积累。上述研究为预估再制造工艺参数范围提供了依据。根据基体对熔覆层的外部约束形式将所研究的GMAW再制造修复工件划分为：一维、二维约束两种情况。采用数值模拟研究方法，建立了一维约束的平板堆积和二维约束的块状基体堆积修复有限元模型，并分析其温度场、应力场、变形的规律。研究表明，层内前道、后道之间存在预热、后热交互作用，后道对前道有应力释放作用；层间前层对后层预热，后层对前层后热并具有应力释放作用。多重堆积过程经历单热源多次加热，热积累严重，容易导致整体过热、成形变差，可通过设置合理道间等待时间避免工件过热。在确定的规范参数下，随着道数增加，一维约束平板堆积过程横向道间应力逐渐降低，而二维约束块状基体修复过程横向约束大，横向道间应力逐渐升高。在三个方向变形中高度方向翘曲变形最大，对修复表面平整度影响也最大。进一步研究了过程参数对多重堆积过程的影响规律。堆积长度越长，拉压应力过渡越陡。道间等待时间越长，道间应力、层间应力升高，残余应力降低。在成形效率允许范围内，尽量选择较长道间等待时间，避免工件过热，有利于成形均匀，降低残余应力。针对两种约束情况，研究了层内、不同层间堆积顺序和方向对温度场、应力场、翘曲变形的影响。散热状况方面同向堆积优于交错式堆积，残余应力方面交错式堆积优于同向堆积。其它参数不变，可通过调整堆积路径而改善温度场、应力、翘曲变形状况。再制造多重堆积路径组合多、评价指标多，导致最优路径选择困难。本文以堆积路径影响规律为数据支撑，模拟人的思维决策模式，开发了再制造多重堆积路径模糊综合评价方法，实现了多指标下的路径优化。多指标包括：散热状况、成形状况、残余应力、翘曲变形、成形效率。通过评价指标因素集、评价结果向量、模糊词集、论域的确立，以及精确量模糊化、模糊推理及模糊量非模糊化，建立了模糊综合评价模型。并在Visual C++编程环境下开发了友好的系统交互界面。专家级用户根据知识和经验直接输入权重；非专家级用户根据产品质量要求采用层次分析法计算权重。最后，选取火车钩舌磨损件进行了实例验证。结合前述得出的路径影响规律，分析了钩舌S面从外到里同向、交错式方向，以及从里到外同向、交错式方向四种堆积路径，在各指标下对堆积路径进行了排序，并采用数值模拟和实验方法进行了验证。根据火车钩舌修复质量要求，对指标重要性排序为：残余应力、成形状况、散热状况、效率、翘曲变形。采用所开发的路径模糊综合评价系统，确定了最优路径为由外到内交错式堆积。进而采用钩舌再制造修复专机对磨损件进行修复，测试了成型件力学性能，结果满足使用要求。更多还原

【Abstract】 GMAW (Gas Metal Arc Welding) remanufacturing is an important approach torepair damages on large metal components and has become one of the researchfocuses in the remanufacturing field, which has complicated thermal process andnumerous influence factors. In this paper, in order to realize the multiple depositingpath optimization of GMAW remanufaturing, the thermal process with the multipleheating pattern was systematically investigated. Theoretical derivation of multipleheating temperature field was explored. The stress, deformation and effect ofdepositing paths under the special heating pattern were researched by adoptingnumerical simulation and experimental methods, and a fuzzy comprehensiveevaluation system of multiple depositing paths was developed to realize the pathoptimization with multiple indicators. The achievements of this research could lay astrong theoretical foundation for the application of efficient and high-qualityremanufacture of large components and provide a feasible technological approachfor remanufacturing path optimization.Firstly, the theoretical derivation of temperature field in GMAW multiple planedepositing was conducted. The dynamic temperature field equations of single-passdepositing, multi-pass depositing, inter-pass cooling and last cooling wereanalytically derived by using both the point heat source and double ellipsoid heatsource under the static and moving coordinate systems respectively. In Matlabenvironment, the temperature field, thermal cycles, the inter-pass idle time rangeand the cooling time were calculated. Furthermore, the pre-heating effects of forepasses on rear passes and the post-heating effects of rear passes on fore passes in themultiple depositions were researched. The thermal cycles in the depositions ofdifferent directions and different powers were compared and analyzed. It was shownthat the heat diffusion condition of the same direction deposition was better than thatof the alternating direction deposition. When the power was too large, heataccumulation made the component over-heating. The effect of inter-pass idle timeon thermal cycles was analyzed. The heat accumulation could be controlledeffectively by setting inter-pass waiting times. The research could provide guidancefor the preliminary estimation of process parameter range.According to the character of external constraint, the remanufacturingcomponents researched in the paper were approximately classified into twosituations of one-dimensional and two-dimensional constraints. The finite elementmodels of deposition on plate substrate with one-dimensional constraint and repairprocess on block substrate with two-dimensional constraint were developed respectively. The temperature field, stress field and deformation of depositions wereanalyzed. Research results show that in one layer there are pre-heating andpost-heating effects between fore and rear passes, and the stress release effects ofrear passes on fore passes. There also are pre-heating and post-heating effectsbetween fore and rear layers, and the stress release effect of rear layers on forelayers. The component experienced multiple heating processes with single heatingsource in the deposition, and the heat accumulation was serious, resulting in thegeneration of excess heat and the bad forming. And the generation of excess heatcould be avoided by altering inter-pass idle times. Under the process parametersadopted, the transversal inter-pass stress decreased in the deposition on platesubstrate with one-dimensional constraint, and increased in the repair process onblock substrate with two-dimensional constraint. The deformation on altitudinaldirection was the largest, and had the largest effect on the planeness of repairsurface.Furthermore, the effects of process parameters on multiple depositions wereresearched. Results show that the transition of residual stresses varies steeper withthe increase of depositing length. The inter-pass and inter-layer stresses increase andthe residual stress decreases with the increase of inter-pass idle time. It is seen that alonger inter-pass idle time would avoid the overheating of component, decrease theresidual stress, and acquire a better forming result. Moreover, in the two differentconstraint situations, the effects of depositing sequences and directions ontemperature field, stress and deformation were researched. The heat diffusioncondition in the deposition of the same direction is better than that in the depositionof alternating direction, and the residual stress of component deposited in thealternating direction are smaller than that of component deposited in the samedirection. The temperature field, stress and deformation could be improved byoptimizing depositing paths, as keeping other parameters constant.There are numerous depositing path possibility and evaluating indicators inmultiple depositions of remanufacture, and it is difficult to choose the optimaldepositing path. In this paper, the path optimization under multiple indicators wascarried out by simulating the thinking and reasoning pattern of human and adoptingthe fuzzy comprehensive evaluation, which was developed based on the effects ofdepositing path. The multiple indicators included heat conduction, formingcondition, residual stress, buckling deformation and efficiency. The fuzzycomprehensive evaluation model was developed, which included the evaluationindicator set, evaluation result vectors, fuzzy language set, universe of fuzzy sets,fuzzification process, fuzzy deduction and non-fuzzification process. Meanwhile, aninteractive interface of fuzzy comprehensive evaluation of multiple depositing pathswas developed in Visual C++environment. For the professional users, weights could be input directly according to the knowledge and experience, and for the commonusers, the analytic hierarchy process was adopted.Finally, the verification was conducted via coupler knuckle instance. Accordingthe obtained effects of depositing paths, four depositing paths were researched,including the paths from the outside to the inside in the same and alternatingdirections and the paths from the inside to the outside in the same and alternatingdirections. The depositing paths were sequenced under each indicator, and verifiedby numerical simulation and experiments of coupler knuckle repair. According tothe repair quality requirements of coupler knuckle, the orders of indicators wereresidual stress, forming condition, heat conduction, efficiency and bucklingdeformation. The optimal path was obtained through the fuzzy comprehensiveevaluation system developed, which was from outside to inside in alternatingdirection. Moreover, the worn coupler knuckle was repaired by adopting theremanufacturing repair equipment of coupler knuckle. And the mechanicalperformances of component were tested, satisfying the operating requirements.更多还原