Y type tee needed feeding strain method, forming manipulation of the most difficult because wall thin, its primary forming difficulty lies in along the axial feeding, under the effect of axial force, if the lack of internal pressure head instability wrinkling is easy to attack, especially the y-shaped tee as fill material than the big, unilateral mending shoes than T tee tube internal high pressure forming, so the wrinkling control more difficult. Progressive forming inner pressure, however, branch item of easy cracking attacks caused excessive thinning, and, if the internal pressure booster has shaken or it is no good opportunity, again after corrugate pipe will attack craze, namely two shortcomings exist together, as shown in figure 3 b. This article through the manipulation of the inductive skills measures such as loading path, and to prevent wrinkling and cracking defects, the end of the ultra-thin y-shaped tee forming. For aerospace tee pipe fittings need all the thin-walled aluminum alloy, choose 5 kneading a03 aluminum alloy pipe, the internal high pressure forming aluminum alloy tee for discussion. Its head diameter D – 40 t, branch pipe axis and head Angle, branch pipe diameter D = 36 t. Its diameter-thick ratio reaches 40, director of wrinkling and branch pipe, high pressure forming crack is still need some processing of key problem. In the 1960 s of hydraulic bulge forming tee skills, forming pressure is less than 30 mpa, forming precision; In the 1990 s, because of the ultrahigh pressure and computer manipulation skills break, the rapid development of internal high pressure forming ability, for the thin-walled tube all the multipass fine supply for more than a new skill path through seminars and use first touch the T tube high pressure forming t-pipe, Y type tee and cross cross pipe, etc., meantime y-shaped tee because of the asymmetry, forming the most difficult.
T type tee in thin-walled tube high pressure forming, the German experts put forward T tee tube high pressure forming mould clamping force, axial feed force, backstepping punch, plastic pressure formula for technology parameters, such as budget, axial instability criterion was deduced. Experts in the United States, when the pressure is not high, friction is satisfied with the coulomb’s law; In contact pressure near the pipe metal at the stress of the event, need to introduce the pure shear stress model, gives the branch pipe pushing force calculation formula of the punch, a beneficial effect to prevent the top of the branch pipe cracking. Japanese expert seminar elongation, hardening exponent and the filling rate of the data on the effects of aluminum alloy T tee branch pipe height. Primary discussion of the wall thickness is larger domestic experts T hydraulic extrusion forming t-pipe, choose low pressure, three-way pipe diameter and thickness ratio (hereinafter referred to as diameter-thick ratio) is less than 3518 ~ 1 ¨, less, high pressure forming aspects for discussion.
American experts on the internal high pressure forming technology parameters of Y type tees budget to choose stainless steel tube billet diameter thick than 34, developed the branch Angle for 600 Y type tee. Shanghai jiaotong university, this paper introduces a y-shaped tee hydraulic extrusion mold equipment, can make the biggest diameter tee thickness ratio.
The article first introduces Harbin industrial university in Y type tee tube high pressure forming over the years has made some research achievements, especially in diameter-thick ratio of 183 stainless steel Y type tee and diameter of 40 ratio of thick aluminum alloy y-shaped three-way tube internal high pressure forming research results. Pressure forming, because branch and director of the Angle, the branch of obtuse Angle side and acute side, information activity, difficult for shoes also is different. To grasp the tee both sides decided to fill capacity is remind mending shoes in Y type tee forming, the influence of the obtuse Angle to fill recycle ratio and acute side filling capacity is define as the loading ratio, the stainless steel thin wall tee practice feeding ratio 5.0.
Because of lower aluminium alloy material plastic, after adding preform has the tee pipe fittings of internal high pressure forming process, the preform and the end tee pipe fittings as shown in figure 4. Branch pipe maximum height of 0.71 D. The obtuse Angle side filling capacity is a practice of 1.22 D, and acute side filling rate of only 0.06 D, the loading ratio has reached 20, can all the loading along the obtuse Angle lateral side.
Because with thin wall and aluminum alloy pipe and steel mould friction coefficient between data to a district activity comparison difficult, in the process of axial feeding easy corrugate faults, as shown in figure 5 a. Together, because of the aluminum alloy material hardening exponent only 0.23, far below the stainless steel material, the forming process is used for the top branch crack faults, usually along with the wrinkling and cracking, and this shortcoming is similar to that of a thin-walled stainless steel tee forming, as shown in figure 5 b. As long as after forming difficulty preform differentiation, and reasonable control loading paths, the ability to prevent faults, shape and dimension satisfied with the requirements of the parts. For all components in aerospace lightweight piping system to supply a new path.
Internal high pressure forming has a forcing all the forming characteristics of single section components, can use hollow pipe material to make all the variable cross-section components, so in aviation, aerospace and car parts to improve the internal flow field, such as cutting seam, progressive components reliability, progressive fatigue strength, etc.
Source: Zhejiang Yaang Pipe Industry Co., Limited (www.yaang.com)