The Forming Quality And Force Of Cu-Al Composite Sheet In Single Point Incremental Forming

Incremental sheet forming(ISF)is an advanced dieless sheet forming process,and it is ideal for design and trial-producing of sheet parts due to its low cost and short productive cycle.Cu-Al composite sheet as a composite material,combined the high heat conduction,high conductivity and corrosion resistance of copper and the light weight,cheap and abundant of aluminum,is widely applied to electric system,mechanical industry and lifestyle products.However,there is no intensive study of Cu-Al composite sheet in ISF.This paper focuses on the Cu-Al composite sheet.First,the characteristic of Cu-Al composite sheet in ISF is researched by experiment.Then,finite element model of Cu-Al composite sheet incremental forming is established in ABAQUS.Finally,forming force in single-pass and multi-pass incremental sheet forming is analyzed.Study results show as follow:(1)To study the formability,surface quality,interface and thickness distribution in ISF,Cu-Al composite sheet is formed by different process parameters.Results show that the formability increases slightly by increasing tool size,reducing step down and feed rate.The quality of contact surface is greatly affected by step down,forming angle and tool size,but non-contacted surface is only affected by forming angle.The interface between copper and aluminum has no obviously changes before and after ISF.The actual thickness of formed parts is always thinner than the value calculated by sine law.Compared to taking the aluminum layer as contact surface,the thickness of copper is thinner when the copper layer is contact surface.(2)To establish the finite element model of Cu-Al composite sheet incremental forming,sheet is defined by different ways(homogeneous and composite)in ABAQUS.Results show that both of two models are able to accurately simulate the forming process.When the sheet is defined as composite,the computation time is too long.(3)Forming force in single-pass incremental sheet forming is studied at different process parameters.Three predictive values of forming force are analyzed,and a new empirical equation is fitting.Results show that the axial and radial forming force increase as the step down,tool size and forming angle increase.The tangentialforming force is only obviously influenced by step down.There is a good agreement between experimental and finite element method,but theoretical formula(based on pure shear mechanism)and previous empirical equation are markedly different from actual measurement.The new empirical equation can accurately predicts the forming force.(4)The characteristic of forming force in multi-pass incremental sheet forming is analyzed,and ABAQUS is utilized to research the thickness distribution and forming force at different multi-pass tool path strategies.Results show that the stress condition in multi-pass incremental sheet forming is much more complex due to non-uniform thickness distribution and change of mechanical properties of formed parts.Suitable multi-pass tool path strategy can not only make the thickness distribution of formed parts more uniform,but also decreases the maximal value of forming force.