Research On The Effect Of The Magnetorheological Elastomer Flexible Die On The Sheet Metal Forming Process

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.