【作者】 张睿；

【导师】 王忠金；

【作者基本信息】 哈尔滨工业大学 ， 材料加工工程， 2022， 博士

【摘要】 板材薄壁零件在航空航天、汽车、高铁等运载装备领域中应用极其广泛。随着运载装备性能的不断提高,板材薄壁零件结构也日趋复杂。对于这类复杂板材薄壁零件的成形通常采用板材软模成形方法。传统软模成形方法中软模材料性能是恒定的,如果软模材料性能可以随着板材零件变形过程应力状态的变化而改变,那么会有利于成形件的变形,提高其成形性。磁流变弹性体软模板材成形方法就是在此背景下而提出的。磁流变弹性体在外加磁场作用下其力学性能发生瞬态变化,能实现性能的可控与可调,将这一性能应用在板材成形中,既可以满足板材成形过程中不同阶段对力的需求,又适应了板材的变形过程。实现了板材零件成形过程中对所需成形力实时控制的目的,为提高板材零件的成形性提供了可能。然而,板材磁流变弹性体软模成形作为新近提出的方法,诸多关于磁流变弹性体性能和外加磁场控制如何影响板材成形规律等问题还缺少深入的研究。在此背景下,本文选择磁流变弹性体软模对板材成形过程的影响进行研究,旨在分析磁流变弹性体在外加磁场控制下对板材成形极限、回弹、构型的影响规律,为板材磁流变弹性体软模成形技术的应用提供理论基础。首先,研究了不同磁场条件下磁流变弹性体软模对Al6061铝合金板材胀形过程构形和应变分布的影响。通过外加磁场对磁流变弹性体性能的调控,可以实现Al6061铝合金板材磁流变弹性体软模胀形过程构形的控制。并进一步通过有限元分析了磁流变弹性体不同磁场对胀形过程构形的影响,获得了磁流变弹性体对板材流动、厚向应变分布和受力状态的影响规律。其次,对Al1060铝合金板材磁流变弹性体软模成形极限进行了研究,发现对于通过外加磁场调控磁流变弹性体性能可以改变板材的成形极限。恒定磁场条件下,磁场强度从0T增加到0.13T,Al1060铝合金板材的成形极限随之增大。可调磁场条件下,磁场强度为0.2-0T路径相比于可调磁场强度0.07-0T和0.13-0T路径,其成形极限分别提高了5%和8%。再次,选择具有回弹特征明显的6k21-T4铝合金双曲率板材零件进行有限元分析研究,获得了不同弹性体剪切模量对双曲率板材零件回弹的影响规律。得到了双曲率件回弹量随着弹性体剪切模量变化的趋势。通过优化弹性体剪切模量,得到在弹性体剪切模量为70MPa条件下成形的双曲率件的回弹量最小。最后,对薄壁圆锥筒形零件进行了有限元分析与磁流变弹性体整形实验。通过有限元分析对比了磁流变弹性体恒定剪切模量与变剪切模量条件下的零件回弹精度,得出了磁流变弹性变剪切模量对薄壁圆锥筒形零件回弹影响的规律。在有限元分析基础上进行了薄壁圆锥筒形零件磁流变弹性体可调磁场条件下的整形实验,分析并得到了可调磁场、磁性粒子质量分数以及磁流变弹性体基体剪切模量对薄壁圆锥筒形零件回弹影响的规律。更多还原

【Abstract】 Sheet metal thin-walled parts are widely used in aerospace,automobile,high-speed rail and other transport fields.Sheet metal parts are becoming more and more complex with the continuous development of technology and the improvement of performance.For this kind of complex thin-walled sheet metal parts,the sheet metal flexible die forming method is usually used.Generally,different flexible die mediums are selected to form different t ypes of sheet metel parts.However,the influence of property of the flexible die on the stress state of the sheet metal is different.Once the flexible die is determined,it cannot be changed in the forming process.The sheet metal forming needs to change the flexible die performance in different forming stages to meet the requirements of forming force.If the properties of flexible die can adapt to stress changing in sheet metal forming process,it will help to improve the formability of sheet metal.Therefore,it is necessary to develop new sheet metal forming methods.The magnetorheological elastomer flexible die sheet metal forming is proposed under this background.Magnetorheological elastomer has the magnetorheological effect under the action of exte rnal magnetic field.When the magnetic field is applied,its mechanical properties will change transiently,which can realize the controllability and adjustability of the properties of magnetorheological elastomer.When this property is applied to sheet me tal forming,it can not only meet the force requirements of different positions in the sheet metal forming process,but also adapt to the sheet metal deformation process.The real-time control of forming force in the time and space is realized,which makes it possible to improve the formability of sheet metal parts.On the basis of the existing flexible die forming technology,the selection range of flexible die materials is widened.However,the magnetorheological elastomer flexible die sheet metal forming as a newly proposed method has not been thoroughly studied on many issues.For example,how the properties of MRE,the control of applied magnetic field affect the forming law of sheet metal.Under this background,this paper chooses the magnetorheological elastomer flexible die to study the sheet metal formability.The aim is to analyze the influence of magnetorheological elastomer on sheet metal forming limit,springback and configuration under the external magnetic fields.It provides a theoretical basi s for the application of the magnetorheological elastomer flexible die sheet metal forming technology.Firstly,the influence of magnetorheological elastomer on the configuration and strain distribution of the bulging process of Al6061 aluminum alloy sheet under different magnetic field conditions is studied.The control of the bulging configuration for Al6061 aluminum alloy sheet can be realized by controlling the properties of the magnetorheological elastomer under the external magnetic fields.Furthermore,the influence of different magnetic fields of magnetorheological elastomers on the bulging process configuration is analyzed through numerical simulation,and the influence rules of magnetorheological elastomers on the blank flowing,thickness strain di stribution and stress state are obtained.Secondly,the Al1060 aluminum alloy forming limit for magnetorheological elastomer flexible die sheet forming was studied.It is found that the forming limit of Al1060 sheet can be changed by adjusting the properti es of magnetorheological elastomers through external magnetic fields.The forming limit of Al1060 sheet increases with the magnetic field strength increases from0 T to 0.13 T under the condition of constant magnetic fields.When the magnetic field is adjustd,the forming limit in the condition of 0.2-0T of the adjustable magnetic field path is increased by 5% and 8% respectively compared with adjustable magnetic field strength of 0.07-0T and 0.13-0T.Thirdly,double curved sheet metal parts of the 6k21-T4 aluminum alloy with typical characteristic shapes are investigated.Effects of different elastomer shear modulus on the forming quality and springback of double curved sheet metal parts are studied by finite element analysis.By optimizing the shear modulus of elastomer,it is found that elastomer can promote the material flow in the difficult deformation area.When the shear modulus of elastomer is70 MPa,the springback value is the minimum.Finally,finite element numerical simulation and magnetorheological elastomer shaping experiment were carried out for thin-walled conical drawing.Firstly,the springback accuracy of parts under the condition of constant shear modulus and variable shear modulus of magnetorheological elastomer is compared through finite element numerical simulation,and the rule on the springback of thin-walled conical drawing is obtained.On the basis of finite element numerical simulation,the reshaping experiment of thin-walled conical drawing was carried out under the condition of adjust able magnetic field of magnetorheological elastomers,and the rules of the influence of different variable magnetic fields,magnetic particle mass fractions and shear modulus of magnetorheological elastomers on the springback of thin-walled conical cylindrical parts were analyzed and obtained.更多还原