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ํด์๊ตฌ์กฐ๋ฌผ ์ฒด๊ฒฐ์ ์ํ Al6061 ํฉ๊ธ ๋ณผํธ์ ํตํฉ ์ ์กฐ๊ณต์ ์ค๊ณ
์ต๊ทผ ์์ก ๋ถ์ผ์์ ๊ฒฝ๋ํ์ ๋ํ ๊ด์ฌ์ด ์ฆ๊ฐํ๋ฉด์, ๊ฐ์ข
์์ก ๊ธฐ๊ณ ๋ถํ์ ๋น์ฒ ๊ธ์์ ์ ์ฉํ๋ ์ฌ๋ก๊ฐ ๋๊ณ ์๋ค. ํนํ, 6xxx ๊ณ์ด์ ์๋ฃจ๋ฏธ๋ ํฉ๊ธ์ ๋ฎ์ ๋น์ค๋, ์ฐ์ํ ๊ธฐ๊ณ์ ํน์ฑ ๋ฐ ๋์ ๋ด์์ฑ์ผ๋ก ์ธํด ์ํ ์ ๋ฐ์์๋ถํฐ ํด์ ๊ตฌ์กฐ๋ฌผ์ ์ด๋ฅด๊ธฐ๊น์ง ๋ค์ํ ํด์ ๋ถ์ผ์ ์ ์ฉ๋๊ณ ์๋ค. ํจ์ค๋๋ฅผ ์ฌ์ฉํ ๊ธฐ๊ณ์ ์ฒด๊ฒฐ์ ์ฌ์ฉ์ด ์ฝ๊ณ ์ ์ฉ์ด ์ฉ์ดํ์ฌ ์๋ฃจ๋ฏธ๋ ํฉ๊ธ๊ณผ ๊ฐ์ฌ์ ์ ํฉ์ ๋๋ฆฌ ์ฌ์ฉ๋์ด์๋ค. ํ์ฌ๊น์ง๋ ์ฐ์
ํ์ฅ์์๋ ์๋ฃจ๋ฏธ๋ ํฉ๊ธ๊ณผ ๊ฐ์ฌ์ ์ฒด๊ฒฐ์ ์ํด ์คํ
์ธ๋ฆฌ์ค๊ฐ ๋ณผํธ๊ฐ ์ฌ์ฉ๋๊ณ ์๋ค. ๊ทธ๋ฌ๋ ์๋ฃจ๋ฏธ๋ ํฉ๊ธ์ ๋ชจ์ฌ์ ๊ธฐ์กด์ ์คํ
์ธ๋ฆฌ์ค๊ฐ ๋ณผํธ๋ฅผ ์ฌ์ฉํ๊ฒ ๋๋ฉด ์ค๋์ ์ฆ๊ฐ๋ฟ๋ง ์๋๋ผ ์๋ฃจ๋ฏธ๋ ๋ชจ์ฌ์์ ๊ฐ๋ฐ๋ ๋ถ์์ด ๋ฐ์ํ๊ฒ ๋๊ณ ์ด๊ฒ์ ํนํ ํด์ ํ๊ฒฝ์์ ๋์ฑ ๊ฐ์ํ๋๋ค. ๋ฐ๋ผ์ ์คํ
์ธ๋ฆฌ์ค๊ฐ ๋ณผํธ๋ฅผ ์๋ฃจ๋ฏธ๋ ํฉ๊ธ ๋ณผํธ๋ก ๋์ฒดํ๋ ๊ฒ์ ์ถ๊ฐ์ ์ธ ๊ฒฝ๋ํ๋ฅผ ๋๋ชจํ ์ ์์ ๋ฟ๋ง ์๋๋ผ ํด์ ํ๊ฒฝ์์ ์ด๋ฌํ ๊ฐ๋ฐ๋ ๋ถ์์ ์์ฑ์ ๋ฏธ์ฐ์ ๋ฐฉ์งํ ์ ์๋ค.
ํ์ฌ๊น์ง ์๋ฃจ๋ฏธ๋ ํฉ๊ธ ๋ณผํธ ์ฑํ์ ๋ํด ์ผ๋ถ ์ฐ๊ตฌ๋ค์ด ์ํ๋์ด ์๋ค. ๊ทธ๋ฌ๋ ๋๋ถ๋ถ์ ์ฐ๊ตฌ๋ค์ ์ฌ๋ฃ์ ์ฑํ์ฑ ํ๊ฐ์ ๊ตญํ๋์ด ์์ผ๋ฏ๋ก ์ฑํ ๊ณต์ ์ ๋ํ ๋ช
ํํ๊ณ ์ฒด๊ณ์ ์ธ ์ค๊ณ ๊ธฐ์ค์ด ์๋ค. ๋ํ, ๋ณผํธ๋ฅผ ์ ์กฐํ๊ธฐ ์ํด ํ์์ ์ธ ํธ๋ฆฌ๋ฐ ๋ฐ ์ ์กฐ ๊ณต์ ์ ์ค๊ณ๊ฐ ๋๋ฝ๋์ด์๋ค.
๋ฐ๋ผ์ ๋ณธ ์ฐ๊ตฌ์์๋ ํด์๊ตฌ์กฐ๋ฌผ ์ฒด๊ฒฐ์ ์ํ Al6061 ํฉ๊ธ ๋ณผํธ์ ํตํฉ ์ ์กฐ๊ณต์ ์ค๊ณ๋ฅผ ์ํํ์๋ค. ์ด๋ฅผ ์ํด ์ด๋ก ์ค๊ณ ๋ฐ ์์น ํด์์ ์งํํ์๋ค. ์ด๋ก ์ค๊ณ์์๋, ์คํฌ๋ฅ ๊ท๊ฒฉ๊ณผ ๊ธฐํํ์ ๊ด๊ณ๋ฅผ ๊ณ ๋ คํ์ฌ ์ ์กฐ ๊ณต์ ์ ์ด๊ธฐ ์์ฌ๊ฒฝ๊ณผ ์์
๊น์ด๋ฅผ ๊ณ์ฐํ์๋ค. ํค๋ฉ ๊ณต์ ์ ์ํ ์ด๊ธฐ ์์ฌ ์น์๋ ์ฒด์ ์ผ์ ๋ฒ์น์ผ๋ก ๊ตฌํ์๋ค. ๊ฒฐํจ ์์ธก์ ์ฌ์ฉ๋๋ ๊ณต์ ํ๊ณ๋ฅผ ๊ณ ๋ คํ์ฌ, ๊ณต์ ๋จ์๋ฅผ ์ค์ ํ๊ณ , ํค๋ฉ ๊ณต์ ์ ์ค๊ณ ๊ท์น์ ์ํด ์๋น ํ์์ ๊ฒฐ์ ํ์๋ค. ๋ํ ์ค๊ณ๋ ํค๋ฉ ๊ณต์ ์ ๋ํด ์ฌ๋๋ธ๋ฒ์ ์ฌ์ฉํ์ฌ ์ฑํ ํ์ค์ ์์ธกํ์๋ค. ์ด๋ก ์ค๊ณ๋ฅผ ๋ฐํ์ผ๋ก ํค๋ฉ, ํธ๋ฆฌ๋ฐ ๋ฐ ์ ์กฐ ๊ณต์ ์ ๋ํ ์ ํ์์ํด์์ ์ํํ์๋ค. ํค๋ฉ ๋ฐ ํธ๋ฆฌ๋ฐ ๊ณต์ ์ค์ ๋ฐ์ํ๋ ๊ฒฐํจ์ ์์ธกํ๊ธฐ ์ํด ์ฐ์ฑํ๊ดด๊ธฐ์ค์ ์ ์ฉํ์๋ค. ๋ํ ์ ์กฐ ๊ณต์ ์์ ๊ธํ์ ์์
๋, ์ด์ก ์๋ ๋ฐ ๋ถ๋น ํ์ ์, ํธ๋ฆฌ๋ฐ ๊ณต์ ์์๋ ํ์น์ ๊ณก๋ฅ ๋ฐ๊ฒฝ, ํ๋ถ ๊ธํ์ ๋๋ ํญ ๋ฐ ํ์น์ ํ๋ถ ๊ธํ๊ฐ์ ์ ์ง ๊ฑฐ๋ฆฌ๋ฅผ ๊ฐ๊ฐ ์ค๊ณ ๋ณ์๋ก ์ ์ ํ๊ณ ๋ค๊ตฌ์ฐ๋ฒ์ ํตํด ๊ณต์ ์ ์ต์ ํํ์๋ค. ์ ์ ๋ ์ค๊ณ ๋ฐฉ๋ฒ์ ๊ฒ์ฆํ๊ธฐ ์ํด ์๋ฃจ๋ฏธ๋ ํฉ๊ธ ๋ณผํธ ์ฑํ ์คํ์ ์ํํ์๊ณ ๋์ ์น์ ์ ํ๋๋ฅผ ๊ฐ๋ ๊ฑด์ ํ ํ์์ Al6061 ํฉ๊ธ ๋ณผํธ๋ฅผ ์ป์ ์ ์์๋ค.|In recent years, with the increasing interest in weight reduction in the transportation sector, the application of non-ferrous metals to various transportation machinery parts has been increased. In particular, the 6xxx series of aluminum alloys are commonly used in marine applications from small vessels to offshore structures due to its low specific weight, high quality mechanical properties, and high resistance to corrosion. In order to join aluminum alloy and steel, mechanical joint by fasteners has been widely used because it is easy-and-practical for the application. Until now, stainless steels bolts have been used for fastening aluminum alloys and steels to industrial sites. However, when the stainless steel bolt is used for the base material of aluminum alloy, weight increases and galvanic corrosion occurs in aluminum, which is accelerated in marine environment particularly. Therefore, substituting aluminum alloy bolts for stainless steel ones can prevent such corrosion promotion in marine environment as well as extra weight increase.
To date, several studies have been conducted on aluminum alloy bolt forming. However, most studies are limited to the evaluation of formability of materials, so there is no clear and systematic design criterion for the forming process. Furthermore, the design of the trimming and thread-rolling
process, essential for manufacturing bolts, was not considered.
Therefore, the integrated manufacturing process design of Al6061 alloy bolts for fastening offshore platforms was performed in this study. To do this, we carried out theoretical design and numerical analysis. At theoretical design, the initial rod diameter and the penetration depth in thread-rolling process were calculated according to the screw standards and geometric relation. Thereafter, the dimensions of the initial workpiece for the heading process were obtained by volume constancy law. Considering process limitations to predict the defects, the number of the stage was set, and preform was determined by the design rule in the heading process. In addition, the forming load for the designed heading process was predicted by using the slab method. Based on theoretical design, FE-analysis for the heading, trimming and thread-rolling process was conducted. The ductile fracture criterion was applied to predict the defects during the heading and trimming process. In addition, the Taguchi method is used to optimize the trimming and thread-rolling process with the set of design parameters, such as the penetration depth, transfer velocity, and revolutions per minute of rolling dies in the thread-rolling process, and the blade radius of the punch, land width of the bottom die, and stop distance between the punch and bottom die in the trimming process, respectively. To verify the proposed design, the aluminum alloy bolt forming experiment was carried out and sound Al6061 alloy bolt with high dimensional accuracy was obtained.1. Introduction 1
1.1 Research background 1
1.2 Precedent research 4
1.3 Objective and scope of study 8
2. Theoretical design of Al6061 alloy bolts manufacturing process 9
2.1 Procedures for theoretical design 9
2.2 Process design for thread-rolling 12
2.2.1 Calculation of initial diameter in thread-rolling process 12
2.2.2 Determination of penetration depth 13
2.3 Process design for heading 16
2.3.1 Determination of initial height of head section 16
2.3.2 Theoretical prediction of defects and setting of the number of process stages 17
2.3.3 Preform design for heading process 20
2.3.4 Forming load prediction by slab method 23
3. FE-analysis of cold-former forging process 29
3.1 Conditions of FE-analysis in heading process 29
3.2 Results of FE-analysis in heading process 31
3.3 Design of experiment for trimming process 34
3.3.1 Taguchi method 34
3.3.2 Parameter design for the Taguchi method 36
3.4 Conditions of FE-analysis in trimming process 43
3.5 Results of FE-analysis in trimming process 45
4. FE-analysis of thread-rolling process 55
4.1 Design of experiment for thread-rolling process 55
4.2 Conditions of FE-analysis in thread-rolling process 58
4.3 Results of FE-analysis in thread-rolling process 60
5. Experiment for manufacturing Al6061 alloy bolts 71
5.1 Experimental procedure 71
5.2 Experimental results 72
6. Conclusions 75
References 77
๊ฐ์ฌ์ ๊ธ 82Maste
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