阅读说明：本技术 一种复杂双曲度蒙皮零件成形方法 (Forming method of complex double-curvature skin part ) 是由 李奎 刘波 鲁帆 刘杰民 陈明 于 2021-07-27 设计创作，主要内容包括：本发明公开了一种复杂双曲度蒙皮零件成形方法,通过预成形模具采用主动式充液成形方式首先成形出零件底部1/5－1/3范围内的双曲度部分,通过终成形模具采用被动式充液成形方式成形出双曲度零件侧壁及侧壁上的局部特征。本发明第一步采用主动式充液成形的方式,改变了蒙皮零件在采用蒙皮拉型成形过程中的受力状态,消除了拉型过程中受力不均匀、截面尺寸变化大产生的顶部破裂、悬空区起皱问题,第二步采用被动式充液成形的方式,成形过程中形成“软拉延筋”有利于抑制起皱,同时可以成形出双曲度蒙皮零件侧壁凹坑、凸起等局部复杂特征。(The invention discloses a forming method of a complex double-curvature skin part, which comprises the steps of firstly forming a double-curvature part at the bottom of the part within the range of 1/5-1/3 by adopting an active liquid-filling forming mode through a pre-forming die, and forming the side wall of the double-curvature part and local characteristics on the side wall of the double-curvature part by adopting a passive liquid-filling forming mode through a final forming die. The method adopts an active liquid-filling forming mode in the first step, changes the stress state of the skin part in the skin drawing forming process, eliminates the problems of top fracture and suspended area wrinkling caused by uneven stress and large section size change in the drawing forming process, adopts a passive liquid-filling forming mode in the second step, forms 'soft-drawing extending ribs' in the forming process, is favorable for inhibiting wrinkling, and can form local complex characteristics of pits, bulges and the like on the side wall of the double-curvature skin part.)

1. A complex double-curvature skin part forming method is characterized in that a double-curvature part in the range of a part bottom 1/5-1/3 is firstly formed through a pre-forming die in an active liquid-filling forming mode, and a double-curvature part side wall and local features on the side wall are formed through a final forming die in a passive liquid-filling forming mode, and the method comprises the following specific steps:

step 1, constructing a reference profile;

step 2, constructing a molded surface of a pre-formed female die;

step 3, manufacturing a preformed die: the device comprises a pre-forming female die, a pre-forming blank holder and a pre-forming liquid filling interface;

step 4, constructing a final forming male die molded surface: extracting the reference molded surface except the flange surface and the die fillet, and constructing a final-structure forming male die molded surface;

step 5, constructing a molded surface of a final forming female die: extracting a flange surface, a stretching surface and a die fillet of the reference molded surface, and then carrying out normal amplification offset to construct a final forming die molded surface;

step 6, manufacturing a final forming die, which comprises a final forming female die, a final forming blank holder, a final forming male die, a male die adapter block, a final forming guide plate, a male die base and a final forming liquid filling interface;

step 7, placing the plate on a pre-forming female die, positioning the plate, and combining the pre-forming female die and a pre-forming blank holder to set an initial blank holder force;

step 8, supplementing a liquid medium to the pre-forming female die through the pre-forming liquid filling interface, and increasing the edge pressing force along with the increase of the liquid pressure to enable the plate to be gradually attached to the pre-forming female die, wherein the edge pressing force F is P1 & S1+ P2 & S2, P1 is the liquid pressure, S1 is the area within the fillet of the pre-forming female die, S2 is the flange area of the plate, P2 is a general experience value, and the liquid medium is selected according to the formed part material and the thickness;

step 9, placing the preformed working piece as a final-forming initial plate on a final-forming female die, supplementing a liquid medium to a final-forming liquid chamber through a final-forming liquid filling interface, positioning the plate in a mode of profile matching through a preformed bottom profile and a final-forming male die bottom profile, and stopping the final-forming male die from moving downwards when a flange of the plate is in contact with the upper surface of the final-forming female die and liquid overflows from the upper surface of the final-forming female die;

step 10, after the positioning of the part is finished, carrying out die assembly on the final-forming blank holder and a final-forming female die, and setting blank holder force;

and 11, the final forming male die starts to move downwards according to the set displacement curve, meanwhile, a liquid medium is supplemented into the liquid chamber through the final forming liquid filling interface, and the final forming male die continuously moves downwards to the final position of the part.

2. The method for forming the complex double-curvature skin part according to claim 1, wherein the step 1 is used for constructing a reference profile by the following specific process: the drawing direction is adjusted according to a double-curvature skin part model, so that the final drawing height of a part is minimized, a normal plane of the drawing direction is constructed, the normal plane is within the range of 15 mm-25 mm above the part model, a drawing contour line and a flange face are constructed on the normal plane, two ends of the drawing contour line are in transition by adopting large arcs, the drawing contour line is larger than the part model contour, the drawing contour line is constructed into a drawing face along the drawing direction, an external insertion extension face of the part model is intersected with the drawing face, the flange face is intersected with the drawing face, the two intersections are trimmed and rounded to obtain a female die fillet and a male die fillet, the edge line distance radius of the part model is larger than 15mm, and a reference profile is constructed.

3. The method for forming the complex double-curvature skin part according to claim 1, wherein the step 2 is to construct a pre-forming female die profile by the specific process of: and constructing a flange surface of a preformed female die according to the translation of the flange surface of the reference molded surface, wherein the height from the flange surface of the preformed female die to the bottom of the part model is 1/5-1/3 of the height of the part model, and trimming and rounding the flange surface of the preformed female die and the reference molded surface to construct the flange surface of the preformed female die.

4. The method for forming the complex double-curvature skin part as claimed in claim 1, wherein in the step 8, the P2 is selected to be 0.8-2.5 MPa according to the material and thickness of the formed part.

Technical Field

The invention relates to the field of sheet plastic forming, in particular to a forming method suitable for complex double-curvature skin parts.

Background

The aircraft skin is a part which surrounds the outside of the aircraft framework structure and is fixed on the framework by bonding or riveting to form the aerodynamic appearance of the aircraft, and the part plays a role in bearing and transmitting starting load. The aluminum alloy skin part is widely applied to the field of aviation manufacturing, and is divided into a single-curvature skin part and a double-curvature skin part according to the appearance of the part, the traditional large-scale skin part is usually manufactured by skin drawing, but for the double-curvature skin part with pits, bulges and large part section size change, especially for the part with the end of the skin part having the curvature change in different directions, the phenomenon of no film sticking can occur at the transition part of the pits, the bulges and the like and the skin molded surface by adopting the drawing process. Generally, the change of the section size of a skin part is controlled within the range of 6% by adopting a skin drawing process, the change of the section size exceeds 6%, the wrinkling phenomenon of a plate material in a suspension area is easy to cause due to the non-uniform deformation of the plate material in the drawing process, and in areas with large change of the section size, the risks of orange peel and breakage are easy to occur at large deformation positions due to large difference of deformation amounts at different section positions, so that the qualified part is difficult to form. At present, split forming or a drop forming process is mostly adopted for the skin part of the type, and when drop forming is adopted, wrinkling phenomenon is generated in the forming process of each stage, and manual repair is needed, so that the surface quality of the formed part is poor, and the thickness distribution is uneven. When split forming is adopted, the assembly difficulty is increased, and the pneumatic layout of skin parts is influenced.

Disclosure of Invention

In order to overcome the defects of no film sticking, wrinkling, cracking and the like of a complex double-curvature skin part in the drawing process, the invention provides a forming method and a die structure of the complex double-curvature skin part, and solves the forming problem of a large complex double-curvature skin part.

The technical scheme adopted by the invention for solving the technical problems is as follows: a complex double-curvature skin part forming method is characterized in that a double-curvature part in the range of a part bottom 1/5-1/3 is firstly formed through a pre-forming die in an active liquid-filling forming mode, and a double-curvature part side wall and local features on the side wall are formed through a final forming die in a passive liquid-filling forming mode, and the method comprises the following specific steps:

1 constructing a reference profile: adjusting the drawing direction according to a double-curvature skin part model to enable the final drawing height of the part to be minimum, constructing a normal plane of the drawing direction, wherein the normal plane is within the range of 15-25 mm above the part model, constructing a drawing contour line and a flange surface on the normal plane, two ends of the drawing contour line are transited by adopting large arcs, the drawing contour line is larger than the part model contour, constructing a drawing surface on the drawing contour line along the drawing direction, intersecting an external insertion extension surface and the drawing surface of the part model, intersecting the flange surface and the drawing surface, trimming and rounding the two intersection parts to obtain a female die fillet and a male die fillet, and constructing a reference profile, wherein the edge line distance rounding of the part model is larger than 15mm, as shown in figure 2.

2, constructing a pre-forming concave die molded surface: and constructing a flange surface of a pre-forming female die according to the translation of the flange surface of the reference profile, wherein the height from the flange surface of the pre-forming female die to the bottom of the part model is 1/5-1/3 of the height of the part model, and trimming and rounding the flange surface of the male pre-forming female die and the reference profile to construct the flange surface of the pre-forming female die.

3, manufacturing a preformed die: the device comprises a pre-forming female die, a pre-forming blank holder, a pre-forming liquid filling interface and the like.

4 construct the final forming punch profile: and extracting the reference molded surface except the flange surface and the die fillet to construct a final-structure forming male die molded surface.

5, constructing a molded surface of a final forming female die: and extracting a flange surface, a stretching surface and a die fillet of the reference molded surface, and then carrying out normal amplification offset to construct a final forming die molded surface.

And 6, manufacturing a final forming die, wherein the final forming die comprises a final forming female die, a final forming blank holder, a final forming male die, a male die adapter block, a final forming guide plate, a male die base, a final forming liquid filling interface and the like.

7, placing the plate material on a pre-forming female die, positioning the plate material, closing the pre-forming female die 9 and the pre-forming blank holder 10, and setting initial blank holder force.

And 8, supplementing a liquid medium to the pre-forming female die through the pre-forming liquid filling port, and increasing the edge pressing force along with the increase of the liquid pressure to enable the plate to be gradually attached to the pre-forming female die, wherein the edge pressing force F is P1S 1+ P2S 2, P1 is the liquid pressure, S1 is the area within the fillet of the pre-forming female die, S2 is the flange area of the plate, P2 is a general experience value, and the selection range is (0.8-2.5 MPa) according to the formed part material and the thickness.

9, placing the preformed working procedure piece as a final-forming initial plate on a final-forming female die, and supplementing a liquid medium to a final-forming liquid chamber through a final-forming liquid filling interface. The preformed bottom molded surface and the final forming male die bottom molded surface are positioned in a molded surface matching mode, and when the flange of the plate material is in contact with the upper surface of the final forming female die and liquid overflows from the upper surface of the final forming female die, the final forming male die stops moving downwards.

And 10, after the positioning of the part is finished, assembling the final-forming blank holder and the final-forming female die, and setting blank holder force.

And 11, the final forming male die starts to move downwards according to the set displacement curve, meanwhile, a liquid medium is supplemented into the liquid chamber through the final forming liquid filling interface, and the final forming male die continuously moves downwards to the final position of the part.

The invention has the advantages that the area of the suspension area can be reduced by adopting an active liquid-filling forming mode in the first step, the plate is uniformly restrained in the thickness direction under the action of liquid pressure, the bottom double-curvature part of the complex double-curvature part can be formed, the stress state of the skin part in the drawing process is changed, the problems of top fracture and suspension area wrinkling caused by uneven stress and large change of section size in the drawing process are eliminated, the greatest difficulty in the forming process of the large-size double-curvature skin part is solved, and better part surface quality can be obtained by adopting the active liquid-filling forming mode. And the second step adopts a passive liquid-filling forming mode, the plate is gradually attached to the male die under the action of liquid pressure in the drawing process, a soft tensile extending rib is formed in the forming process, wrinkling is favorably inhibited, and local complex characteristics such as pits and bulges on the side wall of the double-curvature skin part can be formed.

The invention will be described in further detail with reference to the following drawings and specific embodiments.

Drawings

FIG. 1 is a schematic view of a double curvature skin part;

FIG. 2 is a schematic view of a build datum profile;

FIG. 3 is a schematic view of the profile of the preform female mold;

FIG. 4 is a schematic view of a preform mold configuration;

fig. 5 is a schematic view of the final forming die structure.

The numbering in the figures illustrates: 1. the method comprises the following steps of flange face, 2 drawing contour lines, 3 female die fillet, 4 drawing face, 5 male die fillet, 6 part model, 7 external plug-in extension face, 8 preformed female die flange face, 9 preformed female die, 10 preformed blank holder, 11 preformed liquid filling interface, 12 process part, 13 exhaust hole, 14 final forming liquid filling interface, 15 final forming liquid chamber, 16 final forming female die, 17 final forming guide plate, 18 male die base, 19 male die adapter plate, 20 final forming blank holder and 21 final forming male die.

Detailed Description

Fig. 1-5 are schematic diagrams of a hydroforming process of a large complex double-curvature skin part according to the present invention, wherein the forming process mainly comprises the following steps:

1 constructing a reference profile: adjusting the drawing direction according to a double-curvature skin part model 6 to enable the final drawing height of the part to be minimum, constructing a normal plane of the drawing direction, wherein the normal plane is within the range of 15-25 mm above the part model, constructing a drawing contour line 2 and a flange face 1 on the normal plane, two ends of the drawing contour line 2 are transited by adopting large arcs, the drawing contour line 2 is larger than the contour of the part model 6, constructing a stretching face 4 on the drawing contour line 2 along the drawing direction, intersecting an external insertion extension face 7 and the stretching face 4 of the part model 6, intersecting the flange face 2 and the stretching face 4, trimming and rounding two intersecting parts to obtain a female die fillet 3 and a male die fillet 5, rounding the edge line distance of the part model 6 to be larger than 15mm, and constructing a reference profile as shown in figure 2.

2, constructing a pre-forming concave die molded surface: and (3) constructing a pre-forming female die flange face 8 according to the translation of the flange face 1 of the reference profile, wherein the height from the pre-forming female die flange face 8 to the bottom of the part model 6 is 1/5-1/3 of the height of the part model 6, and trimming and rounding the convex pre-forming female die flange face 8 and the reference profile to construct the pre-forming female die flange face 8.

3, manufacturing a preformed die: comprises a pre-forming female die 9, a pre-forming blank holder 10, a pre-forming liquid filling interface 14 and the like.

4 construct the final forming punch profile: and extracting the reference molded surface except the flange surface 1 and the die fillet 3 to construct a structural final forming male die molded surface.

5, constructing a molded surface of a final forming female die: and extracting the flange surface 1, the stretching surface 4 and the die fillet 3 of the reference molded surface, and then carrying out normal amplification offset to construct a final forming die molded surface.

The 6-manufacture final forming die comprises a final forming female die 16, a final forming blank holder 20, a final forming male die 21, a male die adapter block 19, a final forming guide plate 17, a male die base 18, a final forming liquid filling interface 14 and the like.

7, placing the plate material on a pre-forming female die 9, positioning the plate material, and closing the pre-forming female die 9 and a pre-forming blank holder 10 to set an initial blank holder force.

And 8, supplementing a liquid medium to the pre-forming female die 9 through the pre-forming liquid filling port 11, increasing the edge pressing force along with the increase of the liquid pressure, enabling the plate to be gradually attached to the pre-forming female die 9, wherein the edge pressing force F is P1 & S1+ P2 & S2, P1 is the liquid pressure, S1 is the area within the fillet of the pre-forming female die, S2 is the flange area of the plate, P2 is a general empirical value, and the selection range is (0.8-2.5 MPa) according to the formed part material and the thickness.

9, placing the preformed working piece 12 as a final-forming initial plate on a final-forming female die 16, and supplementing a liquid medium to a final-forming liquid chamber 15 through a final-forming liquid filling interface 14. The preformed bottom molded surface and the final forming male die 21 bottom molded surface are positioned in a molded surface matching mode, and when the flange of the plate material is in contact with the upper surface of the final forming female die 16 and liquid overflows from the upper surface of the final forming female die 16, the final forming male die 21 stops moving downwards.

10 after the positioning of the part is completed, the final forming binder 20 is matched with the final forming female die 16, and meanwhile, the binder force is set.

The final forming male die 21 starts to move downwards according to the set displacement curve, meanwhile, liquid media are supplemented into the liquid chamber 15 through the final forming liquid filling port 14, and the final forming male die 21 continuously moves downwards to the final position of the part.