| The bulging-pressure forming process refers to selecting seamless steel tube of a certain specification according to the dimension parameters of automobile axle housing products,forming the preformed tube blank by necking the end portion of initial tube and bulging the middle part of initial tube,and then carrying out overall hydraulic filling and pressing to obtain the part of axle housing.The tube blank used in the hydraulic bulging of forming small-scale automobile axle housing by bulging and pressing is thin-walled slender tube,with the characteristics of long length and small outer diameter of the middle bulging area,which easily appear the problem of instability and crack of the bulging area during bulging.In this paper,through analyzing the influence law of ratio of length to outer diameter on bulging forming,the reasonable value range of the ratio of length and outer diameter parameters of the bulging area is obtained,so as to improve the finished product rate of bulging tube blank.Aiming at the hydraulic bulging process of small-scale hydraulic bulging automobile axle housing,the mechanical model of tube blank hydraulic bulging is established,the stress-strain analysis of tube blank hydraulic bulging process is carried out,and the deformation mode of"three drum shape"is analyzed easily when tube blank is bulging under the axial force;The twice technological schemes of hydraulic bulging of tube blank with large the ratio of length to outer diameter parameter is given,which makes the tube blank stable in the first bulging and correct in forming with small the ratio of length to outer diameter parameter before the second bulging;Taking the hydraulic bulging of small off-road vehicle B40L as an example,the twice hydraulic bulging processes with the length to outer diameter parameter of n1 and n2 are given.Under the combined process scheme of the ratio of length to outer diameter parameter for initial tube blank of（?）133×4mm,the numerical model of twice hydraulic bulging of tube blank is established to carry out numerical simulation,which obtains the optimal loading path of twice bulging and analyses the forming process and quality of twice bulging of tube blank under the optimal loading path,and the correctness of theoretical analysis in Chapter2 is verifiedAiming at the twice bulging process of thin-walled slender tube used in small off-road vehicle B40L,the numerical simulation was carried out with several different combinations of the ratio of length to outer diameter parameter n1 and n2,and the effect of the combinations of the ratio of length to outer diameter parameter[n1 n2]in different bulging areas on tube blank forming;By comparing the forming results,deformation state,equivalent stress-strain distribution,wall thickness and wall thickness reduction rate of tube blank,the reasonable value range of the ratio of length to outer diameter parameter n1 and n2is given.Taking the hydraulic bulging process of thin-walled slender tube used in small off-road vehicle B40L as the research object,the test scheme is designed and two kinds of tube blanks with the specifications of（?）133×4mm and（?）140×4mm are selected to carry out twice 1:1production tests on the special hydraulic press for hydraulic bulging,the wall thickness distribution of the test sample is measured and compared with the simulation results to verify the reliability of the combined range of the ratio of length to outer diameter parameter,and further improves the hydraulic bulging technology of the small automobile axle housing. |
