散熱器型材分流組合模的設(shè)計(jì)
散熱器型材分流組合模的設(shè)計(jì),散熱器,分流,組合,設(shè)計(jì)
Stress Analysis and Optimum Design of Hot Extrusion Dies
Abstract: A three-dimensional model of a hot extrusion die was developed by using ANSYS software and its second development language—ANSYS parametric design language. A finite element analysis and optimum design were carried out. The three-dimensional stress diagram shows that the stress concentration is rather severe in the bridge of the hot extrusion die, and that the stress distribution is very uneven. The optimum dimensions are obtained. The results show that the optimum height of the extrusion die is 89.596 mm.The optimum radii of diffluence holes are 65.048 mm and 80.065 mm. The stress concentration is reduced by 27%.
Key words: three-dimensional method; modeling; hot extrusion die; optimum design
Introduction
With the continuous improvement of living standards, better thermal conductivity of aluminum alloy profiles. Aluminum components widely used in every aspect of life. Therefore, the aluminum alloy extrusion profiles, profiles of various types of radiators have been widely used in electrical appliances, machinery, and other industries. Variable products and the growing diversity and complexity of high-precision, the extrusion process is the basis for extrusion die. It not only determines the shape, size, accuracy and surface state, but also affect the performance of the product. So extrusion die extrusion technology is the key.
Studies to improve extrusion die quality and prolong its life span usually attempt to simplify 3-D finite element model to 2-D, but it is only right for simple structural shapes. Without a 3-D finite element analysis, the results cannot give practical manufacturing help and offer useful information[3-5]. In this paper, aluminium profile extrusion die was modeled to get in optimum design[6-8].
1 Solid Modeling
Figure 1 shows the male die of a hot extrusion planar combined die. Its external diameter is 227.000 mm, its height is 80.000 mm. Other parameters are shown in Fig. 1. The modeling method is as follows.
1.1 Coordinates of P1 and P5
The coordinates of the point of intersection between the beeline L (y = kx + b) and the circular arc (x2 + y2 =R2) are
1.2 Coordinates of P2 and P6
The coordinates of the intersection point (P2) between beeline L1 (y = kx+b) and beeline L2 (y =S1) are
The coordinates of the intersection point (P6) between beeline L3 (y = kx+b) and beeline L4 (y =S1) are
1.3 Coordinates of P3, P4, P7, and P8
P3 and P1 are symmetric about the y-axis. P4 and P2 are also symmetric about the y-axis. P7 and P5 are symmetric about the x-axis. P8 and P6 are also symmetric
about the x-axis.
1.4 Variables in the equations
In Eqs. (1)-(6), for points P1 and P2, and R = R1. For points P5 and P6, and R = R2.
R1, R2, T1, T2, S1, and S2 are the change rule along the height (H) of the die expressed as the functions R1=f1 (z), R2=f2 (z), T1=f3 (z), T2=f4 (z), S1=f5 (z), andS2=f6 (z), z €[0, H].
1.5 Section shape at some height
With lines linking P1-P4, P5-P8, with circular arc filleting at the point of intersection (P1-P8), the section shape at some height is obtained.
1.6 Section shape at every height
H is divided to interfacial number (INUM) equal parts (INUM is decided by the precision, if the INUM is higher, the precision is better). The section shape is drawn at every height as shown in Fig. 2.
1.7 Smooth curved surface
Using SKIN command in ANSYS, smooth curved surfaces were built along the lines. They are the surfaces of the influence hole. Using the VA (it generates a volume bounded by existing area) command, a solid was created from those surfaces.
1.8 Symmetry of the die
The main body and kernel of the die were drawn using the Boolean operations of add, subtract, etc. (Fig. 3).The symmetry of the die was used to accelerate the computations using a 1/4-solid model for the finite element analysis (Fig. 4).
2 Computing Model
A planar die that extrudes the aluminium alloy (6063Al-Mg-Si) was used as an example. The liquidoid of Al is 657℃[9], and the melt temperature of Al+Mg2Si is 558℃. Taking the extrusion pressure and the products quality into account, the working temperature was determined to be 450℃.
The die material is 4Cr5MoSiV1(H13). Below the 450℃, its Young modulus and Possion ratio are 210 GPa and 0.25, respectively. Its yield strength is 1200MPa.The friction coefficient is 0.3. The Solid92 3-D solid element was used to carry through the free mesh. In order to load the frictional force while extruding, the surface effect element Surf154 was used to produce the regular quadrangles (Fig. 5). For the 1600 t extruder, the extrusion intensity was computed using Eq. (7)[10]. The values are shown in Table 1.
The bridge collapse often takes place in the die. And its strength is determined by the height and the distribution of the diffluence holes. In this paper, the height (H) and the radii (R1 and R2) of the diffluence holes were used as design variables and the maximum equivalent pressure (smax) was used as the goal function.The design variable ranges are listed in Table 2.
3 Computed Results
Figure 6 is the equivalent stress diagram. From Fig. 6 we can see that the stress is largest at the bridge, as expected 24 maximum equivalent stress values are listed in Table 3 from large to small. The data shows that the nodal maximum equivalent stress is 1066.5 MPa, which is 14.5% higher than the second one (912.0 MPa), and that the stress convergence is very severe in the bridge, this part is apt to produce crack.
The initial value of the design variables R1, R2, H, q1, and q2 were 75.000 mm, 88.000 mm, 80.000 mm, 30.000 , and 30.000 , respectively, and the maximum equivalent stress smax= 1066.5 MPa. In the 21 iterations, the optimum iteration was the eighteenth. The design variable values were R1=65.048 mm, R2=80.065 mm, H = 89.596 mm, q1=30.642 , q2=20.045 . The maximum equivalent stress smax= 723.1 MPa, which is 27% less. The optimum results are shown in Table 4.
4 Conclusions
1) Based on ANSYS software, its second development language APDL was used to develop a 3-D model of the hot extrusion die that extrudes aluminium profile has been obtained.
2) The 3-D stress distribution was very uneven, with severe stress concentrations in the bridge of the hot extrusion die. The optimal geometric design had 27% lower maximum stress, A better die will not only reduce die number but also reduce time lost changing dies, which will greatly heighten productivity.
3）Die cantilever design of large-scale streaming into false structure Not only is effective to reduce the pressure on the mold to take greater positive die as a result of dangerous sections of the fracture. greatly extend the life of the die, but this can not bring streaming bridge structure also more effective to reduce the thickness of the bottom die velocity, the velocity Extruded ensure a balanced, stable. Meanwhile, the structural design of the extrusion die for the wide disparity in thickness solid Profile Die Design, opened up a new way of thinking and approach.
References
[1] Karacs G. Computer aided methods for die design. Proceedings of the Conference on Mechanical Engineering, 1998, 2: 463-466.
[2]Mueller G. Design optimization with the finite element program ANSYS. International Journal of Computer Applications in Technology, 1994, 7: 271-277.
作者： 帥詞俊; 肖剛; 倪正順;
英文作者： SHUAI Cijun **; XIAO Gang; NI Zhengshun College of Mechanical and Electronic Engineering; Central South University; Changsha; China;
[刊名]：Tsinghua Science and Technology , 清華大學(xué)學(xué)報(bào)(英文版), 編輯部郵箱 2004年 03期??
查詢來源： 中國(guó)學(xué)術(shù)期刊全文數(shù)據(jù)庫
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