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(xún)來(lái)源： 中國(guó)學(xué)術(shù)期刊全文數(shù)據(jù)庫(kù)
查詢(xún)網(wǎng)址：http://59.69.171.7/kns50/scdbsearch/scdetail.aspx?QueryID=14&CurRec=1
熱擠壓模具的優(yōu)化設(shè)計(jì)
摘要：熱擠壓模具立體模型開(kāi)發(fā)利用ANSYS軟件及其二次開(kāi)發(fā)語(yǔ)言ANSYS的參數(shù)設(shè)計(jì)，進(jìn)行有限元分析和優(yōu)化設(shè)計(jì)。熱擠壓模具的三維應(yīng)力分布很不均勻,懸臂梁有嚴(yán)重的應(yīng)力集中。獲得最佳層面，數(shù)據(jù)結(jié)果表明最佳的高度是89.59630.1+5.6。擠壓模分流孔是最佳半徑 80.06565.048毫米和毫米，應(yīng)力集中減少了27%。
關(guān)鍵詞：三位一體方式，造型，熱擠壓模具，優(yōu)化設(shè)計(jì)
引言
隨著生活水平的不斷提高,由于鋁合金型材的導(dǎo)熱性能較好，鋁零件廣泛應(yīng)用于生活中的每一環(huán)節(jié)。因此，在鋁合金的擠壓型材中，各種類(lèi)型的散熱器型材已被廣泛地應(yīng)用在電器、機(jī)械等行業(yè)中。產(chǎn)品變的日趨多樣化、復(fù)雜化和高精密度化，擠壓模具是基礎(chǔ)的擠壓工藝。它不僅決定著產(chǎn)品形態(tài)、大小、精度和表面狀態(tài),而且影響到產(chǎn)品的性能。所以擠壓模具是擠壓技術(shù)的關(guān)鍵。
擠壓模具研究改進(jìn)質(zhì)量和延長(zhǎng)其壽命通常試圖將三維有限元模型簡(jiǎn)化為二維,但只不過(guò)是構(gòu)造簡(jiǎn)單的結(jié)構(gòu)形狀。沒(méi)有三維有限元分析,其結(jié)果不能給制造業(yè)提供實(shí)際幫助和提供有用的資訊。本文主要介紹鋁型材擠壓模具優(yōu)化設(shè)計(jì)模型。
1實(shí)體造型
圖1主要顯示一種平面組合的熱擠壓模具。其外部直徑為227.000毫米,其高度為80.000毫米。其他參數(shù)見(jiàn)圖1，建模方法如下：
1.1坐標(biāo)P1和P5
直線(xiàn)L(y = kx + b)和圓弧(x2 + y2 =R2)之間的相交點(diǎn)坐標(biāo)是
1.2坐標(biāo)P2和P6
直線(xiàn)L1(y = kx + b)和直線(xiàn)L2(y =S1)之間的相交點(diǎn)坐標(biāo)P2是
直線(xiàn)L3(y = kx + b)和直線(xiàn)L4(y =S1)之間的相交點(diǎn)坐標(biāo)P6是
1.3 坐標(biāo)P3, P4, P7, 和 P8
P3和P1是關(guān)于Y軸對(duì)稱(chēng)。P4和P2也是關(guān)于Y軸對(duì)稱(chēng)。P7和P5是關(guān)于X軸對(duì)稱(chēng)。P8和P6也是關(guān)于X軸對(duì)稱(chēng)。
1.4 變量方程
由公式(1)-(6)，得點(diǎn)P1和P2，和R = R1.得點(diǎn)P5和P6，和R = R2。
R1,R2,T1,T2,S1和S2是沿著高度(h)的變化規(guī)律來(lái)表達(dá)模具的功能R1=f1(z),R2=f2(z),T1=f3(z),T2=f4(z),S1=f5 (z),和S2=f6(z),z €[0, H]。
1.5 在一些高度的部分形狀
用直線(xiàn)連接P1-P4, P5-P8,蘗與圓弧相交于點(diǎn)(P1-P8),在一些高度獲得了部分形狀。
1.6 在每一高度的部分形狀
高度劃分為若干界面(微粒)等部分(微粒決定著精密，如果微粒較高的,精度更佳)。在每節(jié)高度形狀如圖2所示。
1.7 光滑曲面
在ANSYS使用表面指揮,順利沿直線(xiàn)建立曲面，他們是影響面孔。利用VA(它利用現(xiàn)有的面積產(chǎn)生一定容量)指揮,從創(chuàng)立了堅(jiān)實(shí)的表面。
1.8 對(duì)稱(chēng)性模具
主體和核心的模具畫(huà)圖時(shí)用布爾操作增加,減掉等(圖3)。對(duì)稱(chēng)性模具用于加速計(jì)算時(shí)使用的有限元分析模型為1/4-實(shí)體模型(圖4)。
2 計(jì)算模型
用擠壓鋁合金(6063Al-Mg-Si)的一個(gè)平面模具來(lái)作為例子。鋁的液相是657℃[9],Al+Mg2Si的熔體溫度是558℃?？紤]到產(chǎn)品質(zhì)量和擠壓壓力,工作溫度定為450℃。
模具材料是4Cr5MoSiV1(H13)。下面是450℃,它的華模和泊松比分別是210GPa和0.25。其屈服強(qiáng)度是1200mpa，摩擦系數(shù)是0.3。固92通過(guò)免費(fèi)網(wǎng)用來(lái)傳送三維實(shí)體元素。為了負(fù)荷的摩擦力而擠壓，表面效應(yīng)單元154經(jīng)常被用來(lái)生產(chǎn)組合體(圖5)。用擠壓機(jī)為1600噸,擠壓強(qiáng)度計(jì)算公式為(7)[10]。其值見(jiàn)列表1。
橋梁倒塌經(jīng)常是由于擠壓，其高度和力量是分布在分流洞。本文中,高度(H)和半徑(R1 and R2) 是分流孔的設(shè)計(jì)變量,作為最高壓力(smax) 相當(dāng)于作為目標(biāo)的功能。設(shè)計(jì)可變幅度如下列表2.
3 計(jì)算結(jié)果
圖6相當(dāng)于應(yīng)力圖。從圖6中我們能看見(jiàn)最大的壓力是在橋臂上，預(yù)計(jì)最大應(yīng)力值等于24 從大至小見(jiàn)列表3。數(shù)據(jù)顯示,最高相當(dāng)于節(jié)點(diǎn)應(yīng)力1066.5 MPa，這是14.5%,高于二之一(912.0 MPa)，這是非常嚴(yán)重的收斂壓力,在懸臂上這部分是容易產(chǎn)生裂縫的。
初步設(shè)計(jì)變量值R1, R2, H, q1, and q2 分別是75.000 mm,88.000 mm, 80.000 mm, 30.000 , and 30.000 ,最大當(dāng)量應(yīng)力 smax= 1066.5 MPa。在迭代21時(shí) ,最佳迭代是第十八。設(shè)計(jì)變量值R1=65.048 mm, R2=80.065 mm, H = 89.596 mm, q1=30.642 , q2=20.045 。最高壓力相當(dāng)于 smax= 723.1 MPa, 即減少27%。 最佳結(jié)果見(jiàn)如下列表4。
4 結(jié)論
1) 基于ANSYS軟件，三維模型用于研制二次開(kāi)發(fā)語(yǔ)言APDL，它是根據(jù)鋁熱擠壓模具概況取得。
2) 熱擠壓模具的三維應(yīng)力分布很不均勻,懸臂梁有嚴(yán)重的應(yīng)力集中。 最優(yōu)幾何設(shè)計(jì)最大應(yīng)力降低了27%, 一個(gè)好的模具不但可減少模具加工人數(shù)也減少改變模具損失的時(shí)間，這將大大提高生產(chǎn)率。
3）將大懸臂的鋁型材模具設(shè)計(jì)成假分流模的結(jié)構(gòu)，不僅有效地減小了由于模具承受較大的正面壓力所導(dǎo)致的?？孜ｋU(xiǎn)斷面的斷裂，極大地延長(zhǎng)了模具的使用壽命，而且，這種帶不分流橋的結(jié)構(gòu)，還有效地減小了模孔底部較大壁厚處的流速，確保了擠壓型材流速的均衡、平穩(wěn)。同時(shí)，這種結(jié)構(gòu)的擠壓模具設(shè)計(jì)方案，為壁厚相差懸殊的實(shí)心型材模具的設(shè)計(jì)，開(kāi)辟了新的思路和途徑。
參考文獻(xiàn)
[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
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