【作者】 周宁；

【导师】 彭颖红； 李大永；

【作者基本信息】 上海交通大学 ， 机械工程， 2016， 硕士

【摘要】 微通道扁管平行流换热器凭借其制冷剂充注量少、换热效率高等特点正逐渐替代传统管翅式换热器在车用空调中获得了广泛应用,在商用及家用空调领域也拥有广阔的应用前景。微通道扁管是平行流换热器的核心部件,按成形方式不同可分为挤压管与折叠管两类。折叠管采用辊弯工艺成形,相比挤压管有耐腐蚀性强、生产效率高等优势,由于其截面形状复杂,给折叠管辊弯成形工艺设计带来了很大挑战。本文针对十孔折叠微通道扁管,围绕其辊弯成形工艺及承压性能,开展了以下研究工作:(1)对折叠管原材料(层叠铝带箔)进行了力学性能试验,测量了厚向异性系数等基本材料参数,并基于Hill’48屈服准则建立了层叠铝带箔的弹塑性本构模型,为折叠管辊弯成形有限元仿真提供了材料模型;(2)基于ABAQUS建立了十孔折叠管的辊弯成形有限元仿真模型,并采用显式动力算法进行求解。运用建立的有限元模型对设计的辊轮形状进行改进与验证,解决了折叠管辊弯成形中小内径弯角及两侧半圆形弯角成形的难题,从而保证了成形后折叠管的精度要求。进一步通过截取试验生产中间道次板材断面与仿真进行对比,结果验证了有限元仿真的正确性;(3)通过有限元仿真对折叠管梯形孔的弯角减薄进行了分析,并进一步分析了润滑条件、板料厚向异性及梯形孔几何参数对弯角减薄的影响。分别采用宽幅板成形法中的顺序成形与全波成形对梯形孔成形方案进行了设计,并通过仿真对比分析了两种成形方式下的辊弯角减薄,结果表明采用全波成形能够有效降低梯形孔弯角的减薄量;(4)对折叠管进行了极限承压有限元仿真,并使用GTN渐进损伤模型描述钎焊后折叠管材料的断裂,通过压爆试验验证了有限元仿真的正确性,从而提供了一种有效的方法能够在设计阶段对折叠管承压性能进行评估。在此基础上,进一步分析了孔数、弯角的减薄及梯形孔参数变化对折叠管极限承压值的影响。更多还原

【Abstract】 With the advantages of less requirements of refrigerant and higher heat exchange efficiency,the micro-channel parallel flow heat exchanger,which is taking the place of traditional finned tube heat exchanger widely used in field of automotive air conditioners,has a bright future in field of commercial and household air conditioners.Micro-channel tube is key component of heat exhchanger,which can be classified as extruded tube and folded tube according to the difference of forming techinique.Comparing with extruded micro-channel tube,the folded tube produced by roll forming has an advantage of higher corrosion resistant property and higher producing efficiency.At the same time the complex section profile makes it a challenge to design the flower patterns and rollers.This thesis focuses on the roll forming technology and pressure bearing property of folded tube with ten holes,the details of which are listed as below:(1)The mechanical properties and coefficient of normal anisotropy of composite aluminum sheet are measured by uniaxial tension tests.The elastic-plastic constitutive model is built based on Hill’48 yield criterion,which prepares the sheet model for simulation of folded tube’s roll forming.(2)The FEA model of folded tube’s roll forming process is built in ABAQUS,which is solved by explicit algorithm.The shape of the rollers are modified and verified by means of FEA,which makes it possible to forming the bending angle with smaller outer radius and half round bending angle on the sides of folded tube.The modified rollers guarantee that the folded tube’s forming quality meets the accuracy requirement.Good agreements of cross section profiles between FEA and testing results are obtained,which verifies the accuracy of the simulation.(3)The thickness reductions at bending angles are analyzed via FEA.Furthermore,the lubrication conditions,the coefficient of normal anisotropy value and geometry parameters of trapezoidal holes’ effects on thickness condition are analyzed.New forming schemes based on sequential forming and full-wave forming are employed to design the forming rollers.The forming qualites of new schemes are estimated,the simulation results of which show that the full-wave forming scheme can reduce the thickness reduction at bending angle remarkablely.(4)The GTN damage model is employed to simulate the pressure bearing process of the brazing welded folded tube.The bursting test results verify the accuracy of pressure-bearing FEA model,which provides an effective way to estimate the pressure-bearing property in design phase.Moreover,the total number of the holes,the thickness reductions at bending angle and geometry parameters of trapezoidal holes’ effects on ultimate pressure-bearing value are debated in this thesis.更多还原