U型板带连续挤压扩展成形力学模型

Mechanical model of continuous extrusion expansion forming for U-shaped strips

以TLJ630连续挤压机生产的U型板带为模型,将腔体和模具区的金属切分为6个切块,利用上限法建立每个切块的动可容速度场,求得每个切块塑性变形所消耗的功率、速度间断面产生的剪切功率和沿边界面的摩擦造成的功率,将6个切块的功率求和得到U型板带连续挤压扩展成形中的总功率,最终得到腔体入口的挤压应力。结果表明,随着腔体扩展角α_(1)和模具挤压角α_(3)的增大,腔体入口挤压应力先减小后增大,α_(1)的最佳区间为33°~39°;腔体入口挤压应力与腔体扩展通道长度H_(2)成反比而与模具挤压通道长度H_(3)成正比,模具挤压通道的极限长度H_(3)为57 mm;腔体入口挤压应力随着U型板带外径尺寸R_(2)和直边段长度L 10的增加而增加;U型铜排的极限尺寸为外径R_(2)=132 mm,直边段长度L_(10)=160 mm,U型板带总长为712 mm,厚度14 mm时,对应腔体入口的挤压应力达到极限p^(k)=1050 MPa。最后通过工程试验对理论计算结果进行了验证。

Taking the U-shaped strips produced by TLJ630 continuous extruder as model,the metal in chamber and die areas was divided into 6 sections.The kinematically admissible velocity field of each section was established by upper limit method,and the power consumed by plastic deformation of each section,shear power generated by velocity discontinuous surface and power caused by friction along edge interface were obtained.The total power in continuous extrusion expansion molding of U-shaped strips was obtained by adding up all the powers of 6 sections.Finally,the extrusion stress at the entrance of chamber was obtained.The results show that the extrusion stress at the entrance of chamber decreases firstly and then increases with the increase of chamber extension angleα_(1) and die extrusion angleα_(3),and the optimal range ofα_(1) is 33°-39°.The extrusion stress at the entrance of chamber is inversely proportional to the extension channel length of chamber H_(2) but directly proportional to the squeezing channel length of die H_(3).The limit of squeezing channel length of die H_(3) is 57 mm.The extrusion stress at the entrance of chamber increases with the increase of outer diameter R_(2) and straight length=L_(10) of U-shaped strips.As the outer diameter of the limit size of U-shaped strips R_(2)=132 mm,the straight length L 10=160 mm and the thickness is 14 mm,the overall size of U-shaped strips is 712 mm,the extrusion stress at the entrance of chamber correspondingly reaches its limit p^(k)=1050 MPa.Finally,the theoretical calculation results were verified by engineering tests.