Mobile QR Code QR CODE : Journal of the Korean Society of Civil Engineers

  1. ์—ฐ์„ธ๋Œ€ํ•™๊ต ํ† ๋ชฉํ™˜๊ฒฝ๊ณตํ•™๊ณผ ์„๋ฐ•์‚ฌํ†ตํ•ฉ๊ณผ์ • (Yonsei University)
  2. ์—ฐ์„ธ๋Œ€ํ•™๊ต ํ† ๋ชฉํ™˜๊ฒฝ๊ณตํ•™๊ณผ ๊ต์ˆ˜ (Yonsei University)


์œ ๋ณ€ํ•™์  ๋ชจ๋ธ, ์†๋„์˜์กด์„ฑ, ์ง์ ‘์ธ์žฅ์‹œํ—˜, ๋ณ€ํ˜•๋ฅ ์†๋„
Rheological model, Rate dependency, Direct tension test, Strain rate

  • 1. ์„œ ๋ก 

  • 2. ์œ ๋ณ€ํ•™์  ๋ชจ๋ธ(Rheological Model)

  •   2.1 ์ ํƒ„์„ฑ ์†์ƒ(Visco-Elastic Damage; VED) ๋ชจ๋ธ

  •   2.2 ์ ์†Œ์„ฑ ์†์ƒ(Visco-Plastic Damage; VPD) ๋ชจ๋ธ (Kim, 2011)

  •   2.3 ์ ํƒ„์†Œ์„ฑ ์†์ƒ(Visco-Elasto-Plastic Damage; VEPD) ๋ชจ๋ธ

  • 3. ๋ชจ๋ธ ๊ฒ€์ฆ

  •   3.1 ์‹คํ—˜๊ฒฐ๊ณผ์™€์˜ ๋น„๊ต

  •   3.2 ๋ณ€์ˆ˜ ์—ฐ๊ตฌ(Parameter Study)

  • 4. ๊ฒฐ ๋ก 

1. ์„œ ๋ก 

์ฝ˜ํฌ๋ฆฌํŠธ๋Š” ์†๋„์˜์กด์„ฑ์„ ๊ฐ€์ง„ ์žฌ๋ฃŒ๋กœ์„œ, ์™ธ๋ถ€์—์„œ ๊ฐ€ํ•ด์ง€๋Š” ํ•˜์ค‘ ์†๋„์— ๋”ฐ๋ผ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๊ฐ•๋„, ํƒ„์„ฑ๊ณ„์ˆ˜, ํŒŒ๊ดด์—๋„ˆ์ง€ ๋“ฑ์˜ ๋ฌผ์„ฑ์€ ๋‹ค๋ฅด๊ฒŒ ๋‚˜ํƒ€๋‚˜๋ฉฐ, ํ•˜์ค‘ ์†๋„๊ฐ€ ์ฆ๊ฐ€ํ• ์ˆ˜๋ก ๋ฌผ์„ฑ์˜ ์†๋„์˜์กด์„ฑ์€ ๋” ํฌ๊ฒŒ ์ฆ๊ฐ€ํ•œ๋‹ค(Bischoff and Perry, 1991; Malvar and Ross, 1998). ์ด๋Ÿฌํ•œ ์žฌ๋ฃŒ ๋ฌผ์„ฑ์˜ ์†๋„์˜์กด์„ฑ์€ DIF(Dynamic Intensity Factor)๋ผ ๋ถˆ๋ฆฌ๋Š” ๊ณก์„ ์œผ๋กœ ํ‘œํ˜„๋  ์ˆ˜ ์žˆ๋Š”๋ฐ, ์ด๋Š” ๋ณ€ํ˜•๋ฅ  ์†๋„์— ๋”ฐ๋ฅธ ์žฌ๋ฃŒ์˜ ๋™์  ๋ฌผ์„ฑ๊ณผ ์ •์  ๋ฌผ์„ฑ์˜ ๋น„์œจ์„ ๋„์‹œํ•œ ๊ณก์„ ์ด๋‹ค.

์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๊ฐ•๋„๋Š” ๋‹ค๋ฅธ ๋ฌผ์„ฑ์— ๋น„ํ•˜์—ฌ ๋” ํฐ ์†๋„ ์˜์กด์„ฑ์„ ๋‚˜ํƒ€๋‚ด๋ฉฐ(Bischoff and Perry, 1995; Hentz et al., 2004; Toutlemonde, 1995), ๊ฐ•๋„์— ๋Œ€ํ•œ DIF๋ฅผ ๊ตฌํ•˜๊ธฐ ์œ„ํ•œ ๋งŽ์€ ์—ฐ๊ตฌ๊ฐ€ ์ง„ํ–‰๋˜์–ด ์™”๋‹ค(Groute et al., 2001; Hughes and Gregory, 1972; Ross et al., 1989). Fig. 1์€ ์‹คํ—˜ ๊ฒฐ๊ณผ๋กœ ์–ป์€ DIF ๊ณก์„ (Malvar and Ross, 1998)์ด๋‹ค. ๊ทธ๋ฆผ์—์„œ ์‚ดํŽด๋ณผ ์ˆ˜ ์žˆ๋“ฏ์ด ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๋™์  ๊ฐ•๋„ ์ƒ์Šน๋น„๊ฐ€ ๋ณ€ํ˜•๋ฅ  ์†๋„์— ๋”ฐ๋ผ ํฌ๊ฒŒ ๋‘ ๊ตฌ๊ฐ„์œผ๋กœ ๋‚˜ํƒ€๋‚˜๋ฉฐ, ๋‚ฎ์€ ๋‹จ๊ณ„์—์„œ ์ค‘๊ฐ„ ๋‹จ๊ณ„์˜ ๋ณ€ํ˜•๋ฅ  ์†๋„(์•ฝ 101PIC9A95.gif)๊นŒ์ง€๋Š” ์™„๋งŒํžˆ ์ฆ๊ฐ€ํ•˜๋‹ค๊ฐ€ ์ดํ›„ ๊ธ‰๊ฒฉํžˆ ์ฆ๊ฐ€ํ•˜๋Š” ์–‘์ƒ์„ ๋‚˜ํƒ€๋‚ธ๋‹ค. ์ด๋Ÿฌํ•œ ์ฝ˜ํฌ๋ฆฌํŠธ ์†๋„์˜์กด์„ฑ์˜ ์ •ํ™•ํ•œ ๋ฉ”์ปค๋‹ˆ์ฆ˜์€ ๊ทœ๋ช…๋˜์ง€ ์•Š์•˜์ง€๋งŒ, ์ด๋Š” Stefan effect๋ผ ๋ถˆ๋ฆฌ๋Š” ํ˜„์ƒ์œผ๋กœ ์„ค๋ช…๋  ์ˆ˜ ์žˆ์œผ๋ฉฐ, ์ด ํ˜„์ƒ์„ ๊ฐ„๋žตํžˆ ๊ธฐ์ˆ ํ•˜๋ฉด ๋‹ค์Œ๊ณผ ๊ฐ™๋‹ค(Rossi, 1991). ์–‡์€ ํŒ ์‚ฌ์ด์— ์ ์„ฑ์œ ์ฒด๊ฐ€ ์กด์žฌํ•˜๊ณ  ์™ธ๋ถ€์˜ ํž˜์„ ๊ฐ€ํ•ด ๋‘ ํŒ์„ ๋ถ„๋ฆฌ์‹œํ‚ฌ ๋•Œ, ์™ธ๋ถ€ ํ•˜์ค‘์˜ ์†๋„๊ฐ€ ์ฆ๊ฐ€ํ• ์ˆ˜๋ก ์œ ์ฒด๊ฐ€ ํŒ์„ ์žก์•„๋‹น๊ธฐ๋Š” ์ ์„ฑ๋ ฅ์€ ํฌ๊ฒŒ ๋‚˜ํƒ€๋‚œ๋‹ค. ์ฝ˜ํฌ๋ฆฌํŠธ ์•ˆ์—๋Š” ์ˆ˜๋งŽ์€ ๋ฏธ์„ธ๊ณต๊ทน์ด ์กด์žฌํ•˜๋ฉฐ, ๊ณต๊ทน ์†์—๋Š” ์ ์„ฑ์„ ๊ฐ€์ง„ ์ž์œ ์ˆ˜(free water)๊ฐ€ ์กด์žฌํ•œ๋‹ค. ๋•Œ๋ฌธ์—, ์ด๋Ÿฌํ•œ ์ฝ˜ํฌ๋ฆฌํŠธ์— ๊ฐ€ํ•ด์ง€๋Š” ํ•˜์ค‘ ์†๋„์— ๋”ฐ๋ผ์„œ ์ฝ˜ํฌ๋ฆฌํŠธ๋Š” Stefan Effect์™€ ๊ฐ™์€ ์†๋„์˜์กด์ ์ธ ์ €ํ•ญ์„ ๋‚˜ํƒ€๋‚ด์–ด ๋น ๋ฅธ ํ•˜์ค‘์†๋„์— ๋Œ€ํ•˜์—ฌ ๋” ํฐ ์ €ํ•ญ๋ ฅ์„ ๊ฐ–๊ฒŒ ๋œ๋‹ค. ๋†’์€ ๋‹จ๊ณ„์˜ ๋ณ€ํ˜•๋ฅ  ์†๋„์—์„œ๋Š” ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ํŒŒ๊ดด์˜์—ญ(Fracture process zone)์—์„œ์˜ micro-/meso-inertia์— ์˜ํ•œ ํšจ๊ณผ๊ฐ€ ์žฌ๋ฃŒ์˜ ํŒŒ๊ดด๋ฅผ ์ง€๋ฐฐํ•˜๊ฒŒ ๋œ๋‹ค(Pedersen et al., 2008; Vegt et al., 2006).

KSCE_35_4_03_F1.jpg

Fig. 1. Comparison of Various Theories and Experimental Data (Malvar and Ross, 1998)

KSCE_35_4_03_F2.jpg

Fig. 2. Spring set of RBSN (Rigid Body Spring Network) Element (Bolander and Berton et al, 2004)

์ด๋Ÿฌํ•œ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์†๋„์˜์กด์„ฑ์€ ์œ ๋ณ€ํ•™์ (rheological) ๋ชจ๋ธ์„ ํ†ตํ•œ ๊ฑฐ์‹œ์ ์ธ(macroscopic) ๋ฐฉ๋ฒ•์œผ๋กœ ๋ชจ์‚ฌ๋  ์ˆ˜ ์žˆ๋‹ค. ์„ ํ–‰ ์—ฐ๊ตฌ์—์„œ๋Š” ์†์ƒ์„ ๊ณ ๋ คํ•œ ์ ์†Œ์„ฑ ๋ชจ๋ธ์ด ๊ฐœ๋ฐœ๋˜์–ด ๋™ํ•ด์„ ๋ฐ ๋™ํ•˜์ค‘์„ ๋ฐ›๋Š” ์ฝ˜ํฌ๋ฆฌํŠธ ๊ท ์—ด์„ ํ•ด์„ํ•˜๋Š”๋ฐ ์‚ฌ์šฉ๋˜์—ˆ๋‹ค(Barpi, 2004; Gatuing and Pijaudier-Cabot, 2002; Kim et al., 2013; Kim, 2011; Kim and Lim, 2011; Kim et al., 2011). ๋ณธ ์—ฐ๊ตฌ์—์„œ๋Š” ๊ธฐ์กด ๊ฐœ๋ฐœ๋œ ์ ์†Œ์„ฑ ์†์ƒ ๋ชจ๋ธ์„ ์ ํƒ„์„ฑ ์š”์†Œ์™€ ๊ฒฐํ•ฉํ•˜์—ฌ, ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์†๋„์˜์กด์ ์ธ ๋‘ ๊ฐ€์ง€ ํ˜„์ƒ(Stefan effect, Inertia effect)์„ ํšจ๊ณผ์ ์œผ๋กœ ๋ชจ์‚ฌํ•  ์ˆ˜ ์žˆ๋Š” ๋ชจ๋ธ์„ ํ‰๊ฐ€ํ•˜์˜€๋‹ค.

๋ณธ ๋…ผ๋ฌธ์—์„œ ํ‰๊ฐ€๋œ ์žฌ๋ฃŒ ๋ชจ๋ธ์€ ๋ฌด์ž‘์œ„ ๊ฒฉ์ž ๋ชจ๋ธ์˜ ์ผ์ข…์ธ RBSN(Rigid-Body-Spring- Network) ๋ชจ๋ธ์„ ๊ธฐ๋ฐ˜์œผ๋กœ ๊ฐœ๋ฐœ๋˜์—ˆ๋‹ค. RBSN์€ ์žฌ๋ฃŒ๋ฅผ ๊ฐ•์ฒด๋“ค์˜ ์กฐํ•ฉ์œผ๋กœ ๋‚˜ํƒ€๋‚ด๊ณ , ๊ฐ•์ฒด์™€ ๊ฐ•์ฒด ์‚ฌ์ด์—๋Š” ์Šคํ”„๋ง ์กฐํ•ฉ์ด ์กด์žฌํ•˜์—ฌ ์žฌ๋ฃŒ์˜ ๊ฑฐ๋™์„ ๋‚˜ํƒ€๋‚ธ๋‹ค(Bolander and Saito, 1998). Fig. 2๋Š” 2์ฐจ์›์—์„œ์˜ RBSN ์š”์†Œ๋ฅผ ๋‚˜ํƒ€๋‚ด๋ฉฐ, ์…€๊ณผ ์…€ ์‚ฌ์ด์˜ ๊ฒฝ๊ณ„๋ฉด์—๋Š” ํฌ๊ธฐ๊ฐ€ ์—†๋Š” ์„ธ ๋ฐฉํ–ฅ(์ˆ˜์ง, ์ „๋‹จ, ํšŒ์ „) ์Šคํ”„๋ง์ด ์กด์žฌํ•œ๋‹ค. ์†๋„ ์˜์กด์„ฑ์„ ๋ชจ์‚ฌํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ๊ธฐ์กด ์Šคํ”„๋ง ์„ธํŠธ์— ์ ํƒ„์„ฑ, ์ ์†Œ์„ฑ ์š”์†Œ๋ฅผ ๊ฒฐํ•ฉํ•˜์˜€๊ณ , ์Šคํ”„๋ง์˜ ์†์ƒ(Damage)์ด ๊ณ ๋ ค๋œ ์„ธ ๊ฐ€์ง€ ๋ชจ๋ธ(์ ํƒ„์„ฑ ์†์ƒ(VED), ์ ์†Œ์„ฑ ์†์ƒ(VPD), ์ ํƒ„์†Œ์„ฑ ์†์ƒ(VEPD))์ด ๊ณ ๋ ค๋˜์—ˆ์œผ๋ฉฐ(Fig. 3), ๊ฐ ๋ชจ๋ธ์— ๋Œ€ํ•œ ๊ตฌ์„ฑ๋ฐฉ์ •์‹์„ ์œ ๋„ํ•˜๊ณ  ์ด์— ๋Œ€ํ•œ ๊ฒ€์ฆ์„ ์ˆ˜ํ–‰ํ•˜์˜€๋‹ค.

๊ฒ€์ฆ์˜ ๊ณผ์ •์œผ๋กœ ๋ณ€ํ˜•๋ฅ  ์†๋„์— ๋”ฐ๋ฅธ ์ง์ ‘์ธ์žฅ์‹œํ—˜์ด ๋ชจ์‚ฌ ๋˜์—ˆ์œผ๋ฉฐ, ํ•ด์„๊ฒฐ๊ณผ๋Š” ๋ชจ๋ธ์˜ ๋ณ€์ˆ˜ ์—ฐ๊ตฌ(Parameter study)๋ฅผ ํ†ตํ•˜์—ฌ ์‹คํ—˜๊ฒฐ๊ณผ์˜ ์‘๋ ฅ ๋ณ€ํ˜•๋ฅ  ๊ณก์„ ๊ณผ ๋น„๊ต ๊ฒ€์ฆ๋˜์—ˆ๋‹ค. ์ •ํ•ด์ง„ ๋ณ€์ˆ˜๋ฅผ ํ†ตํ•˜์—ฌ ๋‹ค์–‘ํ•œ ๋ณ€ํ˜•๋ฅ  ์†๋„์—์„œ์˜ ์‘๋ ฅ ๋ณ€ํ˜•๋ฅ  ๊ด€๊ณ„๋ฅผ ๊ตฌํ•˜์˜€๊ณ , ์ด๋ฅผ ํ†ตํ•ด ๋ณ€ํ˜•๋ฅ  ์†๋„์— ๋”ฐ๋ฅธ ์ฝ˜ํฌ๋ฆฌํŠธ ๋ฌผ์„ฑ์˜ ๋ณ€ํ™” ์ถ”์ด๋ฅผ ํ™•์ธํ•˜์˜€๋‹ค.

๋ชจ๋ธ์— ์ ์šฉ๋œ ๋ณ€์ˆ˜๊ฐ€ ํ•ด์„ ๊ฒฐ๊ณผ์— ๋ฏธ์น˜๋Š” ์˜ํ–ฅ์„ ์‚ดํŽด๋ณด๊ธฐ ์œ„ํ•˜์—ฌ, ๋‘ ๊ฐ€์ง€ ๋ณ€ํ˜•๋ฅ  ์†๋„(1PIC9C1C.gif, 10PIC9C9A.gif)์—์„œ ๋ณ€์ˆ˜ ๊ฐ’์˜ ๋ณ€ํ™”๊ฐ€ ์‘๋ ฅ ๋ณ€ํ˜•๋ฅ  ๊ณก์„ ์— ๋ฏธ์น˜๋Š” ์˜ํ–ฅ์„ ์‚ดํŽด๋ณด์•˜๋‹ค.

KSCE_35_4_03_F3.jpg

Fig. 3. Rheological Models for Rate Dependency

2. ์œ ๋ณ€ํ•™์  ๋ชจ๋ธ(Rheological Model)

2.1 ์ ํƒ„์„ฑ ์†์ƒ(Visco-Elastic Damage; VED) ๋ชจ๋ธ

์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๋™์  ๋ฌผ์„ฑ์„ ํ‘œํ˜„ํ•˜๊ธฐ ์œ„ํ•˜์—ฌ, Maxwell unit์ด ๊ธฐ์กด ์Šคํ”„๋ง์— ๋ณ‘๋ ฌ๋กœ ์—ฐ๊ฒฐ๋œ, Standard Linear Solid(SLS) ๋ชจ๋ธ์„ ๋„์ž…ํ•˜์˜€๋‹ค(Fig. 3(a)). SLS ๋ชจ๋ธ์—์„œ ๋ฐœ์ƒํ•˜๋Š” ์‘๋ ฅ์€ ๋‹ค์Œ๊ณผ ๊ฐ™์ด ๋‚˜ํƒ€๋‚ผ ์ˆ˜ ์žˆ๋‹ค.

PICA25B.gif              (1)

์—ฌ๊ธฐ์„œ PICA47F.gif์€ Maxwell unit์—์„œ ๋ฐœ์ƒํ•˜๋Š” ์‘๋ ฅ์ด๋‹ค. PICA50D.gif๋Š” ์Šคํ”„๋ง unit์— ๋ฐœ์ƒํ•˜๋Š” ์‘๋ ฅ์œผ๋กœ ๋‹ค์Œ๊ณผ ๊ฐ™์ด ๋‚˜ํƒ€๋‚ผ ์ˆ˜ ์žˆ๋‹ค.

PICA55C.gif (2)

์—ฌ๊ธฐ์„œ PICA57C.gif๋Š” ํŒŒ๊ดด ๊ณผ์ •๋™์•ˆ ์†์ƒ๋œ ์Šคํ”„๋ง์˜ ๊ฐ•์„ฑ์„ ๋‚˜ํƒ€๋‚ด๋ฉฐ ๋‹ค์Œ๊ณผ ๊ฐ™์ด ํ‘œํ˜„๋œ๋‹ค.

PICA5EA.gif   (3)

PICA61A.gif๋Š” ์†์ƒ๊ณ„์ˆ˜(Damage Factor)๋กœ PICA65A.gif์˜ ๋ฒ”์œ„๋ฅผ ๊ฐ–๊ณ , ๊ท ์—ด์ด ์ง„์ „๋˜์–ด ์Šคํ”„๋ง์— ๋ฐœ์ƒํ•˜๋Š” ์†์ƒ์ด ์ฆ๊ฐ€ํ•จ์— ๋”ฐ๋ผ ๊ฐ’์ด ์ฆ๊ฐ€ํ•œ๋‹ค.

Eq. (1)์—์„œ Maxwell unit์— ๋ฐœ์ƒํ•˜๋Š” ์‘๋ ฅ(PICA699.gif)๊ณผ ๋ณ€ํ˜•๋ฅ (PICA708.gif)์˜ ๊ด€๊ณ„๋Š” ๋‹ค์Œ๊ณผ ๊ฐ™์ด ๊ธฐ์ˆ ๋œ๋‹ค.

PICA795.gif          (4)

์—ฌ๊ธฐ์„œ PICA7F4.gif๊ณผ PICA882.gif์€ ๊ฐ๊ฐ Maxwell unit์˜ ์Šคํ”„๋ง ๋ณ€ํ˜•๋ฅ ๊ณผ ๋Œ€์‰ฌํฌํŠธ(Dashpot) ๋ณ€ํ˜•๋ฅ ์„ ๋‚˜ํƒ€๋‚ธ๋‹ค. PICA8F0.gif์€ ํŒŒ๊ดด ๊ณผ์ •๋™์•ˆ ์†์ƒ๋œ Maxwell unit์˜ ์Šคํ”„๋ง ๊ฐ•์„ฑ์„ ๋‚˜ํƒ€๋‚ด๋ฉฐ Eq. (3)๊ณผ ๊ฐ™์ด ํ‘œํ˜„๋œ๋‹ค. PICA93F.gif์€ ๋Œ€์‰ฌํฌํŠธ์˜ ์ ์„ฑ๊ณ„์ˆ˜์ด๋ฉฐ ๋‹ค์Œ๊ณผ ๊ฐ™์ด ๊ธฐ์ˆ ๋œ๋‹ค.

PICA9CD.gif    (5)

PICAA2C.gif๋Š” ๋Œ€์‰ฌํฌํŠธ์˜ ์ดˆ๊ธฐ ์ ์„ฑ๊ณ„์ˆ˜๋ฅผ ๋‚˜ํƒ€๋‚ธ๋‹ค. ์ „์ฒด ๋ณ€ํ˜•๋ฅ  PICAA9A.gif์€ Maxwell unit์— ๋ฐœ์ƒํ•˜๋Š” ์Šคํ”„๋ง๊ณผ ๋Œ€์‰ฌํฌํŠธ ๋ณ€ํ˜•๋ฅ ์˜ ํ•ฉ์œผ๋กœ ๋‹ค์Œ๊ณผ ๊ฐ™์ด ๋‚˜ํƒ€๋‚ผ ์ˆ˜ ์žˆ๋‹ค.

PICAAF9.gif             (6)

Eq. (6)์„ ์‹œ๊ฐ„ t์— ๋Œ€ํ•˜์—ฌ ๋ฏธ๋ถ„ํ•˜๊ณ , Eq. (4)๋ฅผ ์ด์šฉํ•˜๋ฉด ๋‹ค์Œ๊ณผ ๊ฐ™์€ Maxwell unit์˜ ๊ตฌ์„ฑ๋ฐฉ์ •์‹์„ ์–ป์„ ์ˆ˜ ์žˆ๋‹ค.

PICAB57.gif             (7)

์œ ๋„๋œ ์‹์„ ํ•ด์„ ์•Œ๊ณ ๋ฆฌ์ฆ˜์— ์ ์šฉํ•˜๊ธฐ ์œ„ํ•˜์—ฌ ๋‹ค์Œ๊ณผ ๊ฐ™์ด ๊ฐ ๋ณ€์ˆ˜๋ฅผ ์‹œ๊ฐ„๊ฐ„๊ฒฉ์— ๋Œ€ํ•˜์—ฌ ์ด์‚ฐํ™” ํ•˜์˜€๋‹ค.

PICABC6.gif             (8)

PICAC05.gif    (9)

PICAC83.gif   (10)

Eqs. (8)~(10)์„ Eq. (7)์— ๋Œ€์ž…ํ•˜์—ฌ ์ •๋ฆฌํ•˜๋ฉด ๋‹ค์Œ๊ณผ ๊ฐ™๋‹ค.

PICAD40.gif          (11)

์—ฌ๊ธฐ์„œ PICADCD.gif ์ด๊ณ , PICAE7A.gif ์ด๋‹ค. ์ด๋Ÿฌํ•œ ํ˜•ํƒœ์˜

์œ ๋„๋Š” DEM(Discrete Element Method) ์ฝ”๋“œ ๊ธฐ๋ฐ˜์˜ Burgerโ€™s model์˜ ์œ ๋„๊ณผ์ •๊ณผ ์œ ์‚ฌํ•˜๋‹ค(Chen, 2011).

ํ•ด์„๊ณผ์ •์˜ ์ดˆ๊ธฐ ๋‹จ๊ณ„์—์„œ ๊ฒฐ์ •๋œ ์ดˆ๊ธฐ ๋ณ€ํ˜•๋ฅ  PICAEE9.gif์€ Maxwell unit์˜ ์ดˆ๊ธฐ์‘๋ ฅ PICAFA5.gif์„ ๊ตฌํ•˜๋Š”๋ฐ ์‚ฌ์šฉ๋˜๋Š”๋ฐ, ์ด๋Š” ์ดˆ๊ธฐ ์‹œ๊ฐ„๊ฐ„๊ฒฉ์—์„œ๋Š” ๋Œ€์‰ฌํฌํŠธ๊ฐ€ ํ™œ์„ฑํ™” ๋˜์ง€ ์•Š์•„, ์ „์ฒด ๋ณ€ํ˜•๋ฅ  PICB023.gif์ด Maxwell unit์˜ ์Šคํ”„๋ง ๋ณ€ํ˜•๋ฅ ๊ณผ ๋™์ผํ•˜๊ธฐ ๋•Œ๋ฌธ์ด๋‹ค. ์ดˆ๊ธฐ ๋‹จ๊ณ„์—์„œ ๊ตฌํ•˜์—ฌ์ง„ ์ดˆ๊ธฐ ๋ณ€ํ˜•๋ฅ ๊ณผ ์ดˆ๊ธฐ ์‘๋ ฅ(PICB0A1.gif,PICB0E1.gif)์€ ๋‹ค์Œ ์‹œ๊ฐ„๊ฐ„๊ฒฉ์—์„œ ๊ฒฐ์ •๋œ ๋ณ€ํ˜•๋ฅ  PICB120.gif๊ณผ ํ•จ๊ป˜ Eq. (11)์„ ์ด์šฉํ•˜์—ฌ ์ƒˆ๋กœ์šด ์‘๋ ฅ PICB16F.gif์„ ๊ตฌํ•˜๋Š”๋ฐ ์ด์šฉ๋œ๋‹ค.

๋ชจ๋ธ์˜ ์ „์ฒด ์‘๋ ฅ์€ Eq. (11), Eq. (2)์™€ ํ•จ๊ป˜ Eq. (1)์„ ํ†ตํ•˜์—ฌ ๊ตฌํ•  ์ˆ˜ ์žˆ๋‹ค.

2.2 ์ ์†Œ์„ฑ ์†์ƒ(Visco-Plastic Damage; VPD) ๋ชจ๋ธ (Kim, 2011)

๋„์ž…๋œ ์ ์†Œ์„ฑ ์†์ƒ ๋ชจ๋ธ์€ Fig. 3(b)์™€ ๊ฐ™์ด ๋‚˜ํƒ€๋‚œ๋‹ค. ์Šคํ”„๋ง์— ์ ์†Œ์„ฑ ์žฅ์น˜๊ฐ€ ์ง๋ ฌ๋กœ ์—ฐ๊ฒฐ๋˜์–ด์žˆ๋‹ค. ๋ชจ๋ธ์— ํฌํ•จ๋œ ๋ณ€์ˆ˜์ธ PICB1AF.gif๊ณผ PICB1EE.gif๋Š” 2.1์˜ ์ ํƒ„์„ฑ ์†์ƒ ๋ชจ๋ธ์—์„œ ๋„์ž…ํ•œ Eq. (3), (5)์™€ ๊ฐ™์€ ์†์ƒ๊ณ„์ˆ˜๋กœ ํ‘œํ˜„๋œ๋‹ค. ์ „์ฒด ๋ณ€ํ˜•๋ฅ (PICB24D.gif)์€ ๋‹ค์Œ๊ณผ ๊ฐ™์ด ๋‚˜ํƒ€๋‚œ๋‹ค.

PICB319.gif              (12)

์—ฌ๊ธฐ์„œ PICB388.gif๋Š” ํƒ„์„ฑ ๋ณ€ํ˜•๋ฅ ์ด๊ณ , PICB463.gif๋Š” ์ ์†Œ์„ฑ ๋ณ€ํ˜•๋ฅ ์ด๋‹ค. ๋ชจ๋ธ์— ์ž‘์šฉํ•˜๋Š” ์‘๋ ฅ์€ ๋‹ค์Œ๊ณผ ๊ฐ™์ด ๋‚˜ํƒ€๋‚ผ ์ˆ˜ ์žˆ๋‹ค.

PICB4D2.gif               (13)

๋ชจ๋ธ์˜ ์ ์†Œ์„ฑ ์˜์—ญ(PICB521.gif)์€ ๋‹ค์Œ๊ณผ ๊ฐ™์€ Perzyna type ์‹์œผ๋กœ ํ‘œํ˜„๋  ์ˆ˜ ์žˆ๋‹ค.

PICB5FD.gif           (14)

์—ฌ๊ธฐ์„œ PICB66B.gif๋Š” Macaulay function ์ด๋ฉฐ, N(PICB6F9.gif)์€ ๋ชจ๋ธ์˜ ๋ณ€์ˆ˜์ด๋‹ค. Eq. (14)๋Š” Eq.(13)๊ณผ ํ•จ๊ป˜, ๋‹ค์Œ๊ณผ ๊ฐ™์ด ์‹œ๊ฐ„๊ฐ„๊ฒฉ์— ๋Œ€ํ•˜์—ฌ ์ด์‚ฐํ™”๋œ ํ˜•ํƒœ๋กœ ๋‚˜ํƒ€๋‚œ๋‹ค.

PICB796.gif  (15)

    PICB814.gif                  

์—ฌ๊ธฐ์„œ PICB873.gifPICB8C2.gif๋Š” ์œ ํšจ์ด์™„์‹œ๊ฐ„(effective relaxation time)์„ ๋‚˜ํƒ€๋‚ด๊ณ , PICB911.gif์€ ์ž„๊ณ„ ์‘๋ ฅ(critical stress)๋กœ์„œ ํŒŒ๊ดด ๊ธฐ์ค€(fracture criteria)๋กœ๋ถ€ํ„ฐ ๊ฒฐ์ •๋˜๋Š” ๊ฐ’์ด๋‹ค. PICB950.gif์€ ์‹œํ—˜ ์‘๋ ฅ์œผ๋กœ์„œ ์‹œ๊ฐ„ ๊ฐ„๊ฒฉ n์—์„œ ๊ฒฐ์ •๋œ PICB9DE.gif๋กœ๋ถ€ํ„ฐ ๊ตฌํ•ด์ง„๋‹ค. ์ฃผ์–ด์ง„ Eq. (15)์—๋Š” ์ขŒํ•ญ๊ณผ ์šฐํ•ญ์— PICBA1D.gif ํ•ญ์ด ์žˆ๋Š”๋ฐ, ์ด ์‹์„ ์ˆ˜์น˜ํ•ด์„์ ์œผ๋กœ ํ’€๊ธฐ ์œ„ํ•˜์—ฌ Golden section search ์•Œ๊ณ ๋ฆฌ์ฆ˜์„ ์‚ฌ์šฉํ•˜์˜€๋‹ค. ํ•ด์„๊ณผ์ •์—์„œ PICBA4D.gif๊ณผ PICBA7D.gif ์‚ฌ์ด์˜ ์ตœ์ ์˜ PICBADC.gif ๊ฐ’์„ ๊ตฌํ•  ์ˆ˜ ์žˆ์œผ๋ฉฐ, ํ•ด์„์€ ์ตœ์†Œ์˜ ์˜ค์ฐจ PICBB4A.gif๋ฅผ ์–ป์„ ๋•Œ๊นŒ์ง€ ๋ฐ˜๋ณต๋œ๋‹ค. ๊ตฌํ•œ PICBBD8.gif ๊ฐ’๊ณผ ํ•ด๋‹น ์‹œ๊ฐ„๊ฐ„๊ฒฉ์—์„œ ๊ณ„์‚ฐ๋œ PICBC46.gif๋Š” Eq. (13)๊ณผ ํ•จ๊ป˜ ์ ์†Œ์„ฑ ๋ณ€ํ˜•๋ฅ ์„ ๊ตฌํ•˜๋Š”๋ฐ ์‚ฌ์šฉ๋œ๋‹ค.

PICBD03.gif       (16)

      

2.3 ์ ํƒ„์†Œ์„ฑ ์†์ƒ(Visco-Elasto-Plastic Damage; VEPD) ๋ชจ๋ธ

๋ณธ ์—ฐ๊ตฌ์—์„œ ์ œ์•ˆ๋œ ์ ํƒ„์†Œ์„ฑ ์†์ƒ๋ชจ๋ธ์€ Fig. 3(c)์™€ ๊ฐ™์ด ๋‚˜ํƒ€๋‚œ๋‹ค. ์ ํƒ„์„ฑ์„ ๋‚˜ํƒ€๋‚ด๋Š” Maxwell unit์ด ์ ์†Œ์„ฑ ๋ชจ๋ธ๊ณผ ๋ณ‘๋ ฌ๋กœ ๊ฒฐํ•ฉ๋˜์–ด ์žˆ์œผ๋ฉฐ, ๋ชจ๋ธ์— ์ž‘์šฉํ•˜๋Š” ์‘๋ ฅ์€ ๋‹ค์Œ๊ณผ ๊ฐ™๋‹ค.

PICBD62.gif (17)

์—ฌ๊ธฐ์„œ PICBDE0.gif์€ Maxwell unit์˜ ์‘๋ ฅ์„ ๋‚˜ํƒ€๋‚ด๊ณ  Eq. (11)๋กœ๋ถ€ํ„ฐ ์œ ๋„๋œ๋‹ค. PICBE3E.gif๋Š” ์ ์†Œ์„ฑ unit์˜ ์‘๋ ฅ์„ ๋‚˜ํƒ€๋‚ด๊ณ , Eq. (15)๋กœ๋ถ€ํ„ฐ ์œ ๋„๋œ๋‹ค.

3. ๋ชจ๋ธ ๊ฒ€์ฆ

3.1 ์‹คํ—˜๊ฒฐ๊ณผ์™€์˜ ๋น„๊ต

๋ณธ ๋…ผ๋ฌธ์—์„œ๋Š” ์ง์ ‘์ธ์žฅ์‹œํ—˜์— ๋Œ€ํ•œ ์‹คํ—˜ ๊ฒฐ๊ณผ(Cadoni et al., 2013)๋ฅผ ํ† ๋Œ€๋กœ ๊ฐœ๋ฐœ๋œ ๋ชจ๋ธ์˜ ํ•ด์„๊ฒฐ๊ณผ๋ฅผ ๋น„๊ต ๊ฒ€์ฆํ•˜์˜€๋‹ค. ์‹คํ—˜์—์„œ๋Š” ํ•œ ๋ณ€์ด 60mm์ธ ์ •์œก๋ฉด์ฒด ์ฝ˜ํฌ๋ฆฌํŠธ ์‹œํŽธ(PICBEDC.gif3.6MPa, PICBF3A.gif41,600MPa, PICBF99.gif2,420kg/m3)์„ ์‚ฌ์šฉํ•˜์˜€๊ณ , ์‹คํ—˜ ๊ฒฐ๊ณผ๋กœ์„œ ์„ธ ๊ฐ€์ง€ ๋ณ€ํ˜•๋ฅ  ์†๋„(10-6PICBFD9.gif(quasi-static), 1PICC018.gif, 10PICC077.gif)์— ๋Œ€ํ•œ ์‘๋ ฅ ๋ณ€ํ˜•๋ฅ  ๊ด€๊ณ„๋ฅผ ๋„์‹œํ•˜์˜€๋‹ค(Fig. 4). ์‹คํ—˜์„ ํ†ตํ•œ ์‘๋ ฅ ๋ณ€ํ˜•๋ฅ  ๊ณก์„ ์„ ํ†ตํ•˜์—ฌ ๋ณ€ํ˜•๋ฅ  ์†๋„๊ฐ€ ์ฆ๊ฐ€ํ• ์ˆ˜๋ก ๊ทธ๋ž˜ํ”„์˜ ์ฒจ๋‘(peak)๊ฐ’, ์ดˆ๊ธฐ ๊ธฐ์šธ๊ธฐ, ๊ทธ๋ž˜ํ”„๊ฐ€ ์ฐจ์ง€ํ•˜๋Š” ๋ฉด์ ์ด ์ฆ๊ฐ€ํ•จ์„ ํ™•์ธํ•  ์ˆ˜ ์žˆ์œผ๋ฉฐ, ๊ฐ๊ฐ ์ธ์žฅ ๊ฐ•๋„, ํƒ„์„ฑ๊ณ„์ˆ˜, ํŒŒ๊ดด ์—๋„ˆ์ง€์˜ ์ฆ๊ฐ€๋ฅผ ๋‚˜ํƒ€๋‚ธ๋‹ค.

ํ•ด์„์— ์‚ฌ์šฉ๋œ ๋ฉ”์‰ฌ ํ˜•์ƒ์€ Fig. 5์™€ ๊ฐ™์œผ๋ฉฐ, ์—ฌ๊ธฐ์„œ L๊ณผ h๋Š” ๊ฐ๊ฐ 60mm์ด๋ฉฐ, ์‹œํŽธ์˜ ๋‘๊ป˜ ์—ญ์‹œ 60mm์ด๋‹ค. ์‹œํŽธ์˜ ์ขŒ์ธก๋ฉด์€ ๊ณ ์ •๋‹จ์ด๋ฉฐ, ์šฐ์ธก๋ฉด์—๋Š” ์ธ์žฅ๋ฐฉํ–ฅ์˜ ๋ณ€์œ„๊ฐ€ ํ•˜์ค‘์œผ๋กœ ๊ฐ€ํ•ด์ง„๋‹ค. ์ด๋•Œ ๊ฐ€ํ•ด์ง€๋Š” ๋ณ€์œ„๋Š” ๋งค ์‹œ๊ฐ„๊ฐ„๊ฒฉ์—์„œ ์ผ์ •๋Ÿ‰์˜ ์ฆ๋ถ„๋งŒํผ ์ฆ๊ฐ€ํ•˜์—ฌ ์ผ์ •ํ•œ ๋ณ€ํ˜•๋ฅ  ์†๋„๋ฅผ ๋‚˜ํƒ€๋‚ด๋Š”๋ฐ, ์ด๋ฅผ ํ†ตํ•ด ์ฃผ์–ด์ง„ ๋ณ€ํ˜•๋ฅ  ์†๋„(1PICC0C6.gif, 10PICC115.gif)์— ๋”ฐ๋ฅธ ์‘๋ ฅ ๋ณ€ํ˜•๋ฅ ์˜ ์‹คํ—˜๊ฒฐ๊ณผ๋ฅผ ๋ชจ์˜ํ•  ์ˆ˜ ์žˆ์—ˆ๋‹ค. ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์ธ์žฅ์—ฐํ™”๊ฑฐ๋™์€ Fig. 6์™€ ๊ฐ™์€ ์ด์ค‘์„ ํ˜•(bilinear) ์—ฐํ™” ๊ฑฐ๋™์„ ๊ฐ€์ •ํ•˜์˜€๊ณ , ์š”์†Œ์˜ ๊ฐ•์„ฑ ๊ฐ์†Œ๋Š” ์ด๋Ÿฌํ•œ ์—ฐํ™” ๊ณก์„ ์„ ๋”ฐ๋ผ ๋ฐœ์ƒํ•œ๋‹ค.

KSCE_35_4_03_F4.jpg

Fig. 4. Experimental Stress-Strain Curves(Cadoni et al., 2013)

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Fig. 5. Mesh Configuration and Boundary Conditions of Specimen for Simulation

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Fig. 6. Bilinear Stress-Crack Opening Relation(Kim, 2011)

์‹คํ—˜์„ ํ†ตํ•œ ์‘๋ ฅ ๋ณ€ํ˜•๋ฅ  ๊ณก์„ ๊ณผ ๋น„๊ตํ•˜๊ธฐ ์œ„ํ•˜์—ฌ, ํ•ด์„์„ ํ†ตํ•œ ์‘๋ ฅ๊ณผ ๋ณ€ํ˜•๋ฅ ์„ ๋‹ค์Œ๊ณผ ๊ฐ™์ด ๊ตฌํ•˜์˜€๋‹ค. ํ•ด์„ ๊ณผ์ •๋™์•ˆ ์ขŒ์ธก ๊ณ ์ •๋‹จ๊ณผ ์šฐ์ธก ํ•˜์ค‘ ์žฌํ•˜์ง€์ ์˜ ๋ชจ๋“  ๋…ธ๋“œ์— ๋ฐœ์ƒํ•˜๋Š” ํž˜์˜ ์ดํ•ฉ์„ ๊ฐ๊ฐ ๊ตฌํ•˜๊ณ , ์‹œํŽธ์˜ ๋‹จ๋ฉด์ ์œผ๋กœ ๋‚˜๋ˆ„์–ด ์ขŒ์ธก๊ณผ ์šฐ์ธก์˜ ์‘๋ ฅ์„ ๊ตฌํ•˜์˜€๋‹ค. ์ดํ›„ ์ขŒ์ธก๊ณผ ์šฐ์ธก์—์„œ ๊ณ„์‚ฐ๋œ ์‘๋ ฅ์˜ ํ‰๊ท ์„ ๊ตฌํ•˜์—ฌ ์‹œํŽธ์˜ ์‘๋ ฅ์„ ๊ตฌํ•˜์˜€๋‹ค. ๋ณ€ํ˜•๋ฅ ์€ ์šฐ์ธก๋ฉด์˜ ๋ชจ๋“  ๋…ธ๋“œ์—์„œ ๋ฐœ์ƒํ•˜๋Š” ๋ณ€์œ„์˜ ํ‰๊ท ์„ ๊ตฌํ•˜๊ณ  ์ด๋ฅผ ์‹œํŽธ์˜ ์ „์ฒด ๊ธธ์ด๋กœ ๋‚˜๋ˆ„์–ด ๊ตฌํ•˜์˜€๋‹ค.

ํ•ด์„๊ฒฐ๊ณผ๋Š” ๋ชจ๋ธ์— ๋“ค์–ด๊ฐ„ ๋ณ€์ˆ˜ ๊ฐ’์„ ๋ณ€ํ™˜์‹œํ‚ค๋Š” ๊ณผ์ •์„ ํ†ตํ•˜์—ฌ ์‹คํ—˜๊ฒฐ๊ณผ์— ๊ทผ์‚ฌ์‹œ์ผฐ์œผ๋ฉฐ, ๊ฐ ๋ชจ๋ธ๋ณ„๋กœ ๋ณ€ํ˜•๋ฅ  ์†๋„ 1PICC1F1.gif์„ ๊ธฐ์ค€์œผ๋กœ ๋ณ€์ˆ˜๋ฅผ ์‹คํ—˜๊ฒฐ๊ณผ์— ๋งž๊ฒŒ ์กฐ์ ˆํ•˜์˜€๋‹ค. ์ดํ›„ ๋ณ€์ˆ˜ ๊ฐ’์„ ๋ณ€ํ™”์‹œํ‚ค์ง€ ์•Š๊ณ  ๋‹ค๋ฅธ ๋ณ€ํ˜•๋ฅ  ์†๋„์—์„œ์˜ ์‘๋ ฅ ๋ณ€ํ˜•๋ฅ  ๊ด€๊ณ„๋ฅผ ๋ชจ์˜ํ•˜์˜€๋‹ค.

๊ฐ ๋ชจ๋ธ์— ์‚ฌ์šฉ๋œ ๋ณ€์ˆ˜๋Š” ๋‹ค์Œ๊ณผ ๊ฐ™๋‹ค.

์ ํƒ„์„ฑ ์†์ƒ(VED) ๋ชจ๋ธ์— ๋“ค์–ด๊ฐ„ ๋ณ€์ˆ˜๋Š” PICC230.gif, PICC270.gif, PICC2DE.gif 2.8MPaโ€งs์ด๋‹ค. ์—ฌ๊ธฐ์„œ PICC34D.gif์€ ์ ํƒ„์„ฑ ๋ชจ๋ธ์ด ์ฆ๊ฐ€์‹œํ‚ฌ ์ˆ˜ ์žˆ๋Š” ์ตœ๋Œ€ ๊ฐ•์„ฑ๊ณผ ๊ด€๋ จ์ด ์žˆ์œผ๋ฉฐ, PICC3AB.gif๋Š” ์Šคํ”„๋ง ์š”์†Œ์˜ ๊ฐ•์„ฑ์œผ๋กœ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ํƒ„์„ฑ๊ณ„์ˆ˜ PICC3FA.gif์™€ ๊ฐ™๋‹ค. ํ•ด์„์—์„œ๋Š” PICC498.gif์™€ PICC535.gif๋ฅผ ๋ณ€ํ™”์‹œํ‚ค์ง€ ์•Š์•„, ์‹ค์งˆ์ ์œผ๋กœ PICC594.gif ๋งŒ์ด ๋ณ€์ˆ˜๋กœ ์‚ฌ์šฉ๋˜์—ˆ๋‹ค.

์ ์†Œ์„ฑ ์†์ƒ(VPD) ๋ชจ๋ธ์— ๋“ค์–ด๊ฐ„ ๋ณ€์ˆ˜๋Š” PICC5F2.gif, PICC670.gif, PICC6FE.gif =1.8 ์ด๋‹ค. ์—ฌ๊ธฐ์„œ PICC72E.gif๋Š” ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ํƒ„์„ฑ๊ณ„์ˆ˜๋ฅผ ๋‚˜ํƒ€๋‚ธ๋‹ค. ํ•ด์„์—์„œ๋Š” PICC75E.gif์™€ PICC78E.gif, ๋‘ ๋ณ€์ˆ˜๊ฐ€ ์กฐ์ ˆ๋˜์—ˆ๋‹ค.

์ ํƒ„์†Œ์„ฑ ์†์ƒ(VEPD) ๋ชจ๋ธ์— ๋“ค์–ด๊ฐ„ ๋ณ€์ˆ˜๋Š” PICC7CD.gif, PICC87A.gif, PICC8E8.gif 2.9MPaโ€งs, PICC966.gif 0.042MPaโ€งs๋กœ์„œ, ๋‘ ๊ฐ€์ง€ ๋ณ€์ˆ˜(PICC9A6.gif๊ณผ PICCA05.gif)๊ฐ€

์กฐ์ ˆ๋˜์—ˆ๋‹ค. ์ ์†Œ์„ฑ ์†์ƒ ๋ชจ๋ธ์—์„œ ๊ณ ๋ ค๋˜์—ˆ๋˜, PICCA44.gif์™€ PICCA93.gif ๋‘ ๊ฐ€์ง€

๋ณ€์ˆ˜ ์ค‘ N์„ 1๋กœ ๊ณ ์ •์‹œํ‚ค๊ณ  PICCB31.gif ๊ด€๊ณ„์‹์„ ํ†ตํ•˜์—ฌ PICCB80.gif๋กœ

๋ณ€์ˆ˜๋ฅผ ํ•˜๋‚˜ ์ค„์—ฌ ๋ชจ๋ธ์„ ๋‹จ์ˆœํ™” ์‹œ์ผฐ๋‹ค.

ํ•ด์„ ๊ฒฐ๊ณผ๋Š” ์‹คํ—˜์—์„œ ์ง„ํ–‰ํ•œ ๋ณ€ํ˜•๋ฅ  ์†๋„(1PICCBFE.gif, 10PICCC3D.gif)์—์„œ์˜ ์‘๋ ฅ ๋ณ€ํ˜•๋ฅ  ๊ด€๊ณ„์™€ ๋น„๊ต๋˜์—ˆ์œผ๋ฉฐ, ๊ฒฐ๊ณผ๋Š” Fig. 7(a)~(c)์— ๋‚˜ํƒ€๋‚ด์—ˆ๋‹ค. ๊ทธ๋ฆผ ์ „๋ฐ˜์—์„œ ํ™•์ธํ•  ์ˆ˜ ์žˆ๋Š” ๋ฐ”์™€ ๊ฐ™์ด, ๊ทธ๋ž˜ํ”„์˜ ํƒ„์„ฑ ๊ตฌ๊ฐ„์—์„œ์˜ ์‘๋ ฅ์˜ ๊ฐ’์ด ์ƒ์Šนํ•˜๊ณ  ์ถœ๋ ์ด๋Š” ํ˜„์ƒ์ด ๋ฐ˜๋ณต๋จ์„ ํ™•์ธํ•  ์ˆ˜ ์žˆ๋Š”๋ฐ, ์ด๋Š” ํ•ด์„์—์„œ ์ •์˜ํ•œ ๊ฒฝ๊ณ„์กฐ๊ฑด์„ ๋”ฐ๋ผ ๋ฐœ์ƒํ•˜๋Š” ์ž…์‚ฌํŒŒ์™€ ๋ฐ˜์‚ฌํŒŒ์˜ ์˜ํ–ฅ์œผ๋กœ ๋‚˜ํƒ€๋‚˜๋Š” ํ˜„์ƒ์ด๋‹ค. ํ•ด์„๊ณผ์ •๋™์•ˆ ์šฐ์ธก๋ฉด์˜ ๋…ธ๋“œ์—์„œ ๋ฐœ์ƒํ•˜๋Š” ์‘๋ ฅ์„ ์ธก์ •ํ•˜๊ณ , ์ด ์‘๋ ฅ์˜ ํƒ„์„ฑ์˜์—ญ์—์„œ ์ƒ์Šนํ•˜๊ณ  ์ถœ๋ ์ด๋Š” ํ•œ ๊ตฌ๊ฐ„๋™์•ˆ์˜ ์‹œ๊ฐ„์„ ์ธก์ •ํ•˜๋ฉด 2.84 ร— 10-5s๋กœ, ํ•ด์„์— ์‚ฌ์šฉ๋œ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์ด๋ก ์  ํŒŒ์˜ ์ „๋‹ฌ์†๋„ PICCC9C.gif๊ฐ€ ์‹œํŽธ์˜ ๊ธธ์ด L์„ ์™•๋ณตํ•˜๋Š” ์‹œ๊ฐ„ 2.85 ร— 10-5s๊ณผ ๊ฑฐ์˜ ์ผ์น˜ํ•จ์„ ํ™•์ธํ•˜์˜€๋‹ค. ์‹คํ—˜์€ SHPB(Split Hopkinson Pressure Bar)๋ฅผ ์ด์šฉํ•˜์—ฌ ์‘๋ ฅ ๋ณ€ํ˜•๋ฅ ์„ ์ธก์ •ํ•œ ๊ฒƒ์œผ๋กœ, ์‹œํŽธ์˜ ์–‘์ชฝ์— ๊ธˆ์†์œผ๋กœ ๊ตฌ์„ฑ๋œ ์‚ฌ๊ฐ ๋‹จ๋ฉด์˜ bar๊ฐ€ ์—ฐ๊ฒฐ๋˜์–ด ์žˆ์–ด ํ•œ์ชฝ bar๋ฅผ ํ†ตํ•˜์—ฌ ์ „๋‹ฌ๋œ ์ธ์žฅ ํŒŒ(Tensile wave)๊ฐ€ ์‹œํŽธ์„ ํ†ต๊ณผํ•˜์—ฌ ๋‹ค์Œ ํŽธ bar๋กœ ์ „๋‹ฌ๋˜๋Š” ๊ฒฝ๊ณ„์กฐ๊ฑด์„ ๊ฐ€์ง€๊ณ  ์žˆ๋‹ค(Cadoni et al., 2013). ๋•Œ๋ฌธ์—, ๋ณธ ํ•ด์„์˜ ์‹œํŽธ๋งŒ ๋Œ€์ƒ์œผ๋กœ ํ•˜์—ฌ ์–‘์ชฝ์˜ ๊ฒฝ๊ณ„์กฐ๊ฑด์„ ์„ค์ •ํ•œ ๊ฒƒ๊ณผ๋Š” ๊ทธ ๊ฒฝ๊ณ„์กฐ๊ฑด์ด ๋‹ฌ๋ผ ํ•ด์„๊ฒฐ๊ณผ์™€ ๊ฐ™์€ ํƒ„์„ฑ๊ตฌ๊ฐ„์—์„œ์˜ ์ฃผ๊ธฐ์  ๋–จ๋ฆผ ํ˜„์ƒ์ด ๋‚˜ํƒ€๋‚˜์ง€ ์•Š์•˜๋‹ค. ๋˜ํ•œ ์‹คํ—˜์—์„œ ์‚ฌ์šฉํ•œ ์ธก์ • ์‹œ๊ฐ„๊ฐ„๊ฒฉ์€ ์ตœ๋Œ€ 10-6s๋กœ์„œ, ํ•ด์„์—์„œ ์ด์šฉํ•œ ์‹œ๊ฐ„๊ฐ„๊ฒฉ 4.0 ร— 10-7s๋ณด๋‹ค 2.5๋ฐฐ๋งŒํผ ํฌ๋‹ค. ๋•Œ๋ฌธ์—, ํ•ด์„์—์„œ ์ฃผ์–ด์ง„ ์‹œ๊ฐ„ ์•ˆ์— ๋” ๋งŽ์€ ๋ฐ์ดํ„ฐ๋“ค์ด ๋“ค์–ด์™€ ์ƒ๊ธฐ ๋–จ๋ฆผ ํ˜„์ƒ์ด ๋” ํฐ ๋นˆ๋„๋กœ ๋‚˜ํƒ€๋‚ฌ์Œ์„ ์ถ”์ธกํ•  ์ˆ˜ ์žˆ๋‹ค.

ํ•œํŽธ, ํ•ด์„ ๊ฒฐ๊ณผ ๊ทธ๋ž˜ํ”„(Fig. 7(d))๋ฅผ ํ†ตํ•ด ๋ณ€ํ˜•๋ฅ  ์†๋„๊ฐ€ ๋นจ๋ผ์งˆ์ˆ˜๋ก ์‘๋ ฅ ๋ณ€ํ˜•๋ฅ  ๊ทธ๋ž˜ํ”„์—์„œ ์‘๋ ฅ์ด ํ•œ๋ฒˆ ์ถœ๋ ์ด๋Š” ๊ฐ„๊ฒฉ์ด ๋” ํฌ๊ฒŒ ๋‚˜ํƒ€๋‚จ์„ ํ™•์ธํ•  ์ˆ˜ ์žˆ๋Š”๋ฐ, ์ด๋Š” ์‘๋ ฅ์ด ํ•œ๋ฒˆ ์ถœ๋ ์ด๋Š” ์‹œ๊ฐ„๊ฐ„๊ฒฉ์€ ์•ž์„œ ๊ธฐ์ˆ ํ•œ ํŒŒ๊ฐ€ ์‹œํŽธ์˜ ๊ธธ์ด๋ฅผ ์™•๋ณตํ•˜๋Š” ์‹œ๊ฐ„์œผ๋กœ ๋™์ผํ•˜์ง€๋งŒ, ๋™์ผํ•œ ์‹œ๊ฐ„๊ฐ„๊ฒฉ์—์„œ ๋ฐœ์ƒํ•˜๋Š” ๋ณ€ํ˜•์ด ๋†’์€ ๋ณ€ํ˜•๋ฅ  ์†๋„์—์„œ ๋” ํฌ๊ฒŒ ๋ฐœ์ƒํ•˜๊ธฐ ๋•Œ๋ฌธ์ด๋‹ค.

KSCE_35_4_03_F7.jpg

Fig. 7. Simulated Stress-Strain Curves with Experiment

Fig. 7(a)~(c)์˜ ํ•ด์„ ๊ฒฐ๊ณผ๋Š” ๊ฐ๊ฐ์˜ ๋ชจ๋ธ์ด ๋ชจ๋‘ ๋ณ€ํ˜•๋ฅ  ์†๋„์— ๋”ฐ๋ฅธ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๋ฌผ์„ฑ ๋ณ€ํ™”๋ฅผ ๋ฐ˜์˜ํ•˜๊ณ  ์žˆ์Œ์„ ๋ณด์—ฌ์ค€๋‹ค. ์ ํƒ„์„ฑ ์†์ƒ(VED) ๋ชจ๋ธ์˜ ๊ฒฝ์šฐ(Fig. 7(a)) ๋ณ€ํ˜•๋ฅ  ์†๋„๊ฐ€ 1PICD03B.gif์ธ ๊ฒฝ์šฐ ์‹คํ—˜๊ฒฐ๊ณผ์™€ ์‘๋ ฅ ๋ณ€ํ˜•๋ฅ  ๊ด€๊ณ„๊ฐ€ ๊ฑฐ์˜ ์œ ์‚ฌํ•จ์„ ํ™•์ธํ•  ์ˆ˜ ์žˆ์ง€๋งŒ, 10PICD09A.gif์ธ ๊ฒฝ์šฐ, ์ธ์žฅ ๊ฐ•๋„๊ฐ€ ์‹คํ—˜๊ฐ’์— ๋น„ํ•˜์—ฌ ๋” ๋‚ฎ๊ฒŒ ๋‚˜ํƒ€๋‚จ์„ ํ™•์ธํ•˜์˜€๋‹ค. Fig. 7(b)๋Š” ์ ์†Œ์„ฑ ์†์ƒ(VPD) ๋ชจ๋ธ์˜ ์‘๋ ฅ ๋ณ€ํ˜•๋ฅ  ๊ด€๊ณ„๋ฅผ ๋‚˜ํƒ€๋‚ธ๋‹ค. ๋ณ€ํ˜•๋ฅ  ์†๋„๊ฐ€ 1PICD0E9.gif์ธ ๊ฒฝ์šฐ ๊ฐ•๋„์˜ ๋ณ€ํ™”๋Š” ์ž˜ ๋‚˜ํƒ€๋‚ด์ง€๋งŒ, ํƒ„์„ฑ๊ณ„์ˆ˜์˜ ๋ณ€ํ™”(์ดˆ๊ธฐ ๊ธฐ์šธ๊ธฐ์˜ ์ƒ์Šน)๋Š” ๋‚˜ํƒ€๋‚ด์ง€ ๋ชปํ•˜์—ฌ ์ •์ ํ•˜์ค‘ ์ƒํƒœ์˜ ์ดˆ๊ธฐ ๊ธฐ์šธ๊ธฐ์™€ ๋™์ผํ•จ์„ ํ™•์ธํ•  ์ˆ˜ ์žˆ๋‹ค. ๋ณ€ํ˜•๋ฅ  ์†๋„๊ฐ€ 10PICD128.gif์ธ ๊ฒฝ์šฐ ์ ํƒ„์„ฑ ์†์ƒ ๋ชจ๋ธ์— ๋น„ํ•˜์—ฌ ํƒ„์„ฑ๊ตฌ๊ฐ„์—์„œ์˜ ๋–จ๋ฆผ ํ˜„์ƒ์ด ํฌ๊ฒŒ ๋‚˜ํƒ€๋‚ฌ๊ณ  ๊ทธ ์ „์ฒด์ ์ธ ๊ฒฝํ–ฅ์€ ์‹คํ—˜๊ฒฐ๊ณผ์™€ ๋น„๊ตํ–ˆ์„ ๋•Œ, ํƒ„์„ฑ๊ณ„์ˆ˜์˜ ๋ณ€ํ™”(์ดˆ๊ธฐ ๊ธฐ์šธ๊ธฐ์˜ ์ƒ์Šน)๋ฅผ ๋‚˜ํƒ€๋‚ด์ง€ ์•Š๋Š” ๊ฒƒ์„ ํ™•์ธํ•˜์˜€๋‹ค. ์ด๋Š” ๊ฐœ๋ฐœ๋œ ์ ์†Œ์„ฑ ์†์ƒ๋ชจ๋ธ์ด ์ •์  ์ธ์žฅ๊ฐ•๋„๋ฅผ ๋„˜๋Š” ์‘๋ ฅ์ด ๋ฐœ์ƒํ•  ๋•Œ ํ™œ์„ฑํ™”๋˜๋Š” ํŠน์„ฑ ๋•Œ๋ฌธ์ด๋‹ค. Fig. 7(c)๋Š” ์ ํƒ„์†Œ์„ฑ ์†์ƒ(VEPD) ๋ชจ๋ธ์˜ ๊ฒฐ๊ณผ๋ฅผ ๋‚˜ํƒ€๋‚ด๋ฉฐ, ๋‘ ๊ฐ€์ง€ ๋ณ€ํ˜•๋ฅ  ์†๋„(1PICD168.gif, 10PICD1F5.gif)์—์„œ ์‹คํ—˜์„ ํ†ตํ•œ ์‘๋ ฅ ๋ณ€ํ˜•๋ฅ  ๊ด€๊ณ„๋ฅผ ์ž˜ ๋ชจ์‚ฌํ•จ์„ ํ™•์ธํ•˜์˜€๋‹ค.

Fig. 7(d)๋Š” ์ ํƒ„์†Œ์„ฑ ์†์ƒ ๋ชจ๋ธ์„ ์ด์šฉํ•œ ๋‹ค์–‘ํ•œ ๋ณ€ํ˜•๋ฅ  ์†๋„(0.1PICD438.gif, 0.5PICD747.gif, 1PICD8BF.gif, 5PICD94C.gif, 10PICD97C.gif)์—์„œ์˜ ์‘๋ ฅ ๋ณ€ํ˜•๋ฅ  ๊ด€๊ณ„๋ฅผ ๋ณด์—ฌ์ค€๋‹ค. ๊ทธ๋ฆผ์—์„œ ํ™•์ธํ•  ์ˆ˜ ์žˆ๋Š” ๋ฐ”์™€ ๊ฐ™์ด, ๋ณ€ํ˜•๋ฅ  ์†๋„๊ฐ€ ์ฆ๊ฐ€ํ• ์ˆ˜๋ก ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๋ฌผ์„ฑ(์ธ์žฅ๊ฐ•๋„, ํƒ„์„ฑ๊ณ„์ˆ˜, ํŒŒ๊ดด์—๋„ˆ์ง€)์ด ์ฆ๊ฐ€ํ•˜๊ณ , ๋ณ€ํ˜•๋ฅ  ์†๋„๊ฐ€ ๊ฐ์†Œํ• ์ˆ˜๋ก ์‹คํ—˜์„ ํ†ตํ•œ ์ •์  ํ•˜์ค‘ ํ•˜์—์„œ์˜ ์‘๋ ฅ ๋ณ€ํ˜•๋ฅ  ๊ด€๊ณ„๋กœ ํ•ด์„ ๊ฒฐ๊ณผ๊ฐ€ ์ˆ˜๋ ดํ•ด ๋‚˜๊ฐ์„ ํ™•์ธํ•˜์˜€๋‹ค.

3.2 ๋ณ€์ˆ˜ ์—ฐ๊ตฌ(Parameter Study)

๊ฐœ๋ฐœ๋œ ์ ํƒ„์†Œ์„ฑ ์†์ƒ(VEPD) ๋ชจ๋ธ์— ์ ์šฉ๋œ ๋‘ ๋ณ€์ˆ˜(PICD9CB.gif, PICD9FB.gif)๊ฐ€ ํ•ด์„ ๊ฒฐ๊ณผ์— ๋ฏธ์น˜๋Š” ์˜ํ–ฅ์„ ํŒŒ์•…ํ•˜๊ธฐ ์œ„ํ•ด, ๋‘ ๊ฐ€์ง€ ๋ณ€ํ˜•๋ฅ  ์†๋„(1PICDA3B.gif, 10PICDA7A.gif)์—์„œ ๊ฐ๊ฐ PICDAC9.gif, PICDB09.gif์˜ ๊ฐ’์„ ๋ณ€ํ™”์‹œ์ผœ๊ฐ€๋ฉด์„œ ํ•ด์„ ๊ฒฐ๊ณผ๋ฅผ ๋น„๊ตํ•˜์˜€๋‹ค(Fig. 8(a)~(d)).

KSCE_35_4_03_F8.jpg

Fig. 8. Parameter Study on VEPD Model

Fig. 8(a), (b)๋Š” ๋ณ€ํ˜•๋ฅ  ์†๋„ 1PICDBC5.gif์—์„œ ๋‘ ๋ณ€์ˆ˜์˜ ์˜ํ–ฅ์„ ์‚ดํŽด๋ณธ ๊ฒƒ์œผ๋กœ, Fig. 8(a)๋Š” PICDC14.gif์„ ํ•ด์„์—์„œ ์ •ํ•ด๋†“์€ ๊ฐ’(2.9MPaโ€งs)์œผ๋กœ ๊ณ ์ •์‹œ์ผœ ๋†“๊ณ , PICDC64.gif๋ฅผ 0.0208, 0.0416, 0.0832MPaโ€งs๋กœ ๋‘ ๋ฐฐ์”ฉ ๋ณ€ํ™”์‹œ์ผœ๊ฐ€๋ฉด์„œ ์‘๋ ฅ ๋ณ€ํ˜•๋ฅ  ๊ด€๊ณ„๋ฅผ ๋„์‹œํ•œ ๊ฒƒ์ด๋‹ค. Fig. 8(b)๋Š” PICDCC2.gif๋ฅผ ํ•ด์„์—์„œ ์ •ํ•œ 0.042MPaโ€งs์œผ๋กœ ๊ณ ์ •์‹œ์ผœ ๋†“๊ณ , PICDD11.gif๋ฅผ 1.45, 2.9, 5.8MPaโ€งs ๋กœ ๋‘ ๋ฐฐ์”ฉ ๋ณ€ํ™”์‹œ์ผœ๊ฐ€๋ฉด์„œ ์‘๋ ฅ ๋ณ€ํ˜•๋ฅ  ๊ด€๊ณ„๋ฅผ ๋„์‹œํ•œ ๊ฒƒ์ด๋‹ค. Fig. 8(c), (d)๋Š” ๋ณ€ํ˜•๋ฅ  ์†๋„ 10PICDD70.gif์ธ ๊ฒฝ์šฐ์— ๋Œ€ํ•˜์—ฌ ๊ฐ™์€ ๋ฐฉ๋ฒ•์œผ๋กœ ๋„์‹œํ•œ ๊ทธ๋ž˜ํ”„์ด๋‹ค. ๊ฒฐ๊ณผ๋ฅผ ํ†ตํ•ด์„œ, ๋‚ฎ์€ ๋ณ€ํ˜•๋ฅ  ์†๋„(1PICDE1D.gif)์— ๋น„ํ•˜์—ฌ ๋†’์€ ๋ณ€ํ˜•๋ฅ  ์†๋„(10PICDE8B.gif)์ธ ๊ฒฝ์šฐ ๋‘ ๋ณ€์ˆ˜(PICDEDB.gif, PICDF39.gif)๊ฐ€ ํ•ด์„ ๊ฒฐ๊ณผ(์ธ์žฅ ๊ฐ•๋„ ๋ฐ ์—ฐํ™”๊ตฌ๊ฐ„)์— ๋ฏธ์น˜๋Š” ์˜ํ–ฅ์ด ์ƒ๋Œ€์ ์œผ๋กœ ํผ์„ ํ™•์ธํ•˜์˜€๊ณ , PICDFA8.gif์ด PICDFF7.gif์— ๋น„ํ•˜์—ฌ ํ•ด์„๊ฒฐ๊ณผ์— ๋ฏธ์น˜๋Š” ์˜ํ–ฅ์ด ๋” ํผ์„ ํ™•์ธํ•˜์˜€๋‹ค. ์ด๋ฅผ ํ†ตํ•ด ์†๋„ ์˜์กด์„ฑ์„ ๋‚˜ํƒ€๋‚ด๋Š” ๋Œ€์‰ฌํฌํŠธ์˜ ์ ์„ฑ๊ณ„์ˆ˜์ธ ๋‘ ๋ณ€์ˆ˜(PICE027.gif, PICE095.gif)๊ฐ€ ํฐ ๋ณ€ํ˜•๋ฅ  ์†๋„์— ๋” ๋ฏผ๊ฐํ•˜๊ฒŒ ๋ฐ˜์‘ํ•˜๋Š” ๊ฒƒ๊ณผ, ๊ฐœ๋ฐœ๋œ ๋ชจ๋ธ์˜ ์ ํƒ„์„ฑ์˜์—ญ์˜ ๋ณ€์ˆ˜(PICE0B5.gif)๊ฐ€ ์ ์†Œ์„ฑ ์˜์—ญ์˜ ๋ณ€์ˆ˜(PICE0E5.gif)์— ๋น„ํ•˜์—ฌ ๊ฐ•๋„ ์ƒ์Šน ๋ฐ ์—ฐํ™”๊ตฌ๊ฐ„์— ๋” ํฐ ์˜ํ–ฅ์„ ๋ฏธ์นจ์„ ํ™•์ธํ•˜์˜€๋‹ค.

4. ๊ฒฐ ๋ก 

๋ณธ ์—ฐ๊ตฌ์—์„œ๋Š” ๋™ํ•˜์ค‘์„ ๋ฐ›๋Š” ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๋™์  ๋ฌผ์„ฑ ๋ณ€ํ™”๋ฅผ ๋ชจ์‚ฌํ•˜๊ธฐ ์œ„ํ•˜์—ฌ, ๊ธฐ์กด RBSN ๋ชจ๋ธ์˜ ๊ฑฐ๋™์„ ๋‚˜ํƒ€๋‚ด๋Š” ์Šคํ”„๋ง ์„ธํŠธ์— ์†๋„์˜์กด์  ๊ฑฐ๋™์„ ๋ชจ์‚ฌํ•  ์ˆ˜ ์žˆ๋Š” ์œ ๋ณ€ํ•™์ (Rheological) ์š”์†Œ๋ฅผ ๋„์ž…ํ•˜์˜€๋‹ค. ๊ฐœ๋ฐœ๋œ ๋ชจ๋ธ์€ ์ ํƒ„์„ฑ ์†์ƒ(VED), ์ ์†Œ์„ฑ ์†์ƒ(VPD), ์ ํƒ„์†Œ์„ฑ ์†์ƒ(VEPD)์˜ ์„ธ ๊ฐ€์ง€ ๋ชจ๋ธ๋กœ์„œ, ๊ฐ ๋ชจ๋ธ์˜ ๊ตฌ์„ฑ๊ด€๊ณ„๋ฅผ ์œ ๋„ํ•˜๊ณ  ์ด๋ฅผ ์„ ํ–‰ ์‹คํ—˜๊ฒฐ๊ณผ์™€ ๋น„๊ต ๋ฐ ํ‰๊ฐ€ํ•˜์˜€๋‹ค. ๋‹ค์Œ์€ ๋ณธ ์—ฐ๊ตฌ์˜ ๊ฒฐ๋ก ์ด๋‹ค.

(1)๊ฐœ๋ฐœ๋œ ์ ํƒ„์„ฑ ์†์ƒ(VED) ๋ชจ๋ธ์€ ๋ณ€ํ˜•๋ฅ  ์†๋„์— ๋”ฐ๋ฅธ ๋ฌผ์„ฑ(์ธ์žฅ๊ฐ•๋„, ํƒ„์„ฑ๊ณ„์ˆ˜, ํŒŒ๊ดด์—๋„ˆ์ง€)๋ณ€ํ™”๋ฅผ ๋‚˜ํƒ€๋‚ธ๋‹ค. ํ•˜์ง€๋งŒ, ์‹คํ—˜์„ ํ†ตํ•œ ์ธ์žฅ๊ฐ•๋„์˜ ๋ณ€ํ™” ์ถ”์ด๋Š” ์ž˜ ๋ชจ์‚ฌํ•˜์ง€ ๋ชปํ•จ์„ ํ™•์ธํ•˜์˜€๋‹ค.

(2)์ ์†Œ์„ฑ ์†์ƒ(VPD) ๋ชจ๋ธ์€ ๋ณ€ํ˜•๋ฅ  ์†๋„์— ๋”ฐ๋ฅธ ๋ฌผ์„ฑ(์ธ์žฅ๊ฐ•๋„, ํŒŒ๊ดด์—๋„ˆ์ง€) ๋ณ€ํ™”๋ฅผ ๋‚˜ํƒ€๋‚ธ๋‹ค. ๋น ๋ฅธ ๋ณ€ํ˜•๋ฅ  ์†๋„(10PICE125.gif)์—์„œ ์‘๋ ฅ ๋ณ€ํ˜•๋ฅ  ๊ด€๊ณ„์˜ ๋ณ€ํ™” ์ถ”์ด๋ฅผ ์‚ดํŽด๋ณด์•˜์„ ๋•Œ, ์ ํƒ„์„ฑ ์†์ƒ ๋ชจ๋ธ์— ๋น„ํ•˜์—ฌ ์‹คํ—˜์„ ํ†ตํ•œ ์ธ์žฅ๊ฐ•๋„ ๋ณ€ํ™” ์ถ”์ด๋ฅผ ๋” ์ž˜ ๋‚˜ํƒ€๋‚ด๋Š” ๊ฒƒ์œผ๋กœ ๋ณด์ด๋‚˜, ์ •์  ์ธ์žฅ๊ฐ•๋„ ์ดํ›„์— ํ™œ์„ฑํ™”๋˜๋Š” ๋ชจ๋ธ์˜ ํŠน์„ฑ์œผ๋กœ ์ธํ•ด ํƒ„์„ฑ๊ณ„์ˆ˜ ๋ณ€ํ™”๋Š” ๋‚˜ํƒ€๋‚ด์ง€ ๋ชปํ•จ์„ ํ™•์ธํ•˜์˜€๋‹ค.

(3)์ ํƒ„์†Œ์„ฑ ์†์ƒ(VEPD) ๋ชจ๋ธ์€ ์ ํƒ„์„ฑ ์†์ƒ ๋ชจ๋ธ๊ณผ ์ ์†Œ์„ฑ ์†์ƒ ๋ชจ๋ธ์„ ๊ฒฐํ•ฉํ•œ ๊ฒƒ์œผ๋กœ์„œ, ๋ณ€ํ˜•๋ฅ  ์†๋„์— ๋”ฐ๋ฅธ ๋ฌผ์„ฑ(์ธ์žฅ๊ฐ•๋„, ํƒ„์„ฑ๊ณ„์ˆ˜, ํŒŒ๊ดด์—๋„ˆ์ง€) ๋ณ€ํ™”๋ฅผ ๋‚˜ํƒ€๋‚ธ๋‹ค. ๋˜ํ•œ ์‹คํ—˜์„ ํ†ตํ•œ ์ธ์žฅ๊ฐ•๋„์˜ ๋ณ€ํ™” ์ถ”์ด๋ฅผ ์ž˜ ๋ชจ์‚ฌํ•˜๋ฉฐ, ํƒ„์„ฑ๊ณ„์ˆ˜ ๋ฐ ํŒŒ๊ดด์—๋„ˆ์ง€ ๋ณ€ํ™”๋„ ์ž˜ ๋ชจ์‚ฌํ•  ์ˆ˜ ์žˆ๋Š” ๊ฒƒ์œผ๋กœ ํŒ๋‹จ๋œ๋‹ค. ์ ํƒ„์„ฑ ์†์ƒ ๋ชจ๋ธ์— ๊ฐ€ํ•ด์ง€๋Š” ๋ณ€ํ˜•๋ฅ  ์†๋„๊ฐ€ ๋Š๋ ค์งˆ์ˆ˜๋ก, ์‹คํ—˜์„ ํ†ตํ•œ ์ •์  ํ•˜์ค‘ ์ƒํƒœ์˜ ์‘๋ ฅ ๋ณ€ํ˜•๋ฅ  ๊ด€๊ณ„๋กœ ์ˆ˜๋ ดํ•จ์„ ํ™•์ธํ•˜์˜€๊ณ , ๋ชจ๋ธ์˜ ๋‘ ๋ณ€์ˆ˜(PICE155.gif, PICE194.gif)๊ฐ€ ๋น ๋ฅธ ํ•˜์ค‘ ์†๋„์—์„œ ํ•ด์„ ๊ฒฐ๊ณผ์— ๋” ํฐ ์˜ํ–ฅ์„ ๋ฏธ์น˜๊ณ , PICE1E3.gif์— ๋น„ํ•˜์—ฌ PICE232.gif์ด ํ•ด์„ ๊ฒฐ๊ณผ์— ๋” ํฐ ์˜ํ–ฅ์„ ๋ฏธ์น˜๋Š” ๊ฒƒ์„ ํ™•์ธํ•˜์˜€๋‹ค.

(4)ํ•ด์„ ๊ฒฐ๊ณผ๋กœ๋ถ€ํ„ฐ ๋‚˜ํƒ€๋‚œ ์‘๋ ฅ-๋ณ€ํ˜•๋ฅ  ๊ด€๊ณ„์˜ ํƒ„์„ฑ๊ตฌ๊ฐ„์—์„œ Bump ํ˜„์ƒ(์‘๋ ฅ์˜ ์ƒ์Šน๊ณผ ์ถœ๋ ์ž„์ด ๋ฐ˜๋ณต๋˜๋Š” ํ˜„์ƒ)์ด ๋ฐœ์ƒํ•จ์„ ํ™•์ธํ•  ์ˆ˜ ์žˆ๋Š”๋ฐ, ์ด๋Š” ํ•ด์„ ๋ชจ๋ธ์˜ ๊ฒฝ๊ณ„์กฐ๊ฑด์— ๋”ฐ๋ฅธ ์ž…์‚ฌํŒŒ์™€ ๋ฐ˜์‚ฌํŒŒ์˜ ์˜ํ–ฅ์— ์˜ํ•˜์—ฌ ๋ฐœ์ƒํ•˜๋Š” ํ˜„์ƒ์ด๋‹ค. ์‘๋ ฅํŒŒ๊ฐ€ ์ƒ์Šนํ•˜์—ฌ ํ•œ๋ฒˆ ์ถœ๋ ์ด๋Š”๋ฐ ๊ฑธ๋ฆฌ๋Š” ์‹œ๊ฐ„์€ ํŒŒ๊ฐ€ ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ๋งค์งˆ์„ ์™•๋ณตํ•˜๋Š” ์‹œ๊ฐ„๊ณผ ๋™์ผํ•จ์„ ํ™•์ธํ•˜์˜€๊ณ , ์ด๋Ÿฌํ•œ ํŒŒ๊ฐ€ ํƒ„์„ฑ ์˜์—ญ์—์„œ ์ฃผ๊ธฐ์ ์œผ๋กœ ๋‚˜ํƒ€๋‚˜๋Š” ๊ฒƒ์„ ํ™•์ธํ•˜์˜€๋‹ค.

์ด๋Ÿฌํ•œ ๋ชจ์˜ ๊ฒฐ๊ณผ๋Š” ์‹คํ—˜ ๊ฒฐ๊ณผ์™€ ์ „์ฒด์ ์ธ ๊ฒฝํ–ฅ์ด ์œ ์‚ฌํ•˜๋‚˜ ๋‹ค์†Œ์˜ ์ฐจ์ด๋ฅผ ๋‚˜ํƒ€๋‚ด๋Š”๋ฐ ์ด๋Š” ๋‘ ๊ฐ€์ง€ ์›์ธ(์‹คํ—˜๊ณผ ๋‹ค๋ฅธ ๊ฒฝ๊ณ„์กฐ๊ฑด, ํ•ด์„๊ณผ ์‹คํ—˜ ๊ฐ„์˜ ์ธก์ •์‹œ๊ฐ„ ๊ฐ„๊ฒฉ ์ฐจ์ด)์—์„œ ๋‚˜ํƒ€๋‚œ๋‹ค๊ณ  ํ•  ์ˆ˜ ์žˆ๋‹ค.

๋ณธ ์—ฐ๊ตฌ๊ฒฐ๊ณผ๋ฅผ ํ†ตํ•ด, ์ ํƒ„์†Œ์„ฑ ์†์ƒ(VEPD) ๋ชจ๋ธ์ด ์ง์ ‘์ธ์žฅ์„ ๋ฐ›๋Š” ์ฝ˜ํฌ๋ฆฌํŠธ์˜ ์†๋„์˜์กด์„ฑ์„ ์ž˜ ๋ชจ์‚ฌํ•  ์ˆ˜ ์žˆ์Œ์„ ํ™•์ธํ•˜์˜€๋‹ค. ํ–ฅํ›„ ์—ฐ๊ตฌ์—์„œ๋Š”, ๊ฐœ๋ฐœ๋œ ์ ํƒ„์†Œ์„ฑ ์†์ƒ ๋ชจ๋ธ์— ์ ์šฉ๋œ ๋‘ ๊ฐœ์˜ ๋ณ€์ˆ˜๋ฅผ ์ ์ ˆํžˆ ์กฐ์ ˆํ•˜์—ฌ ๋ณด๋‹ค ๋‹ค์–‘ํ•œ ์ฝ˜ํฌ๋ฆฌํŠธ ์žฌ๋ฃŒ์˜ ์†๋„์˜์กด์„ฑ์— ๋Œ€ํ•œ ์‹คํ—˜ ๊ฒฐ๊ณผ๋ฅผ ๋ชจ์‚ฌํ•˜๊ณ ์ž ํ•œ๋‹ค. ๋˜ํ•œ ์‹คํ—˜์„ ํ†ตํ•œ ์žฌ๋ฃŒ์˜ ์†๋„์˜์กด์ ์ธ ํŒŒ๊ดดํ˜•์ƒ์„ ๊ฐœ๋ฐœ๋œ ๋ชจ๋ธ์„ ํ†ตํ•˜์—ฌ ๋น„๊ต ๊ฒ€์ฆํ•ด๋ณด๊ณ ์ž ํ•œ๋‹ค.

Acknowledgements

์ด ๋…ผ๋ฌธ์€ 2014๋…„๋„ ์ •๋ถ€(๋ฏธ๋ž˜์ฐฝ์กฐ๊ณผํ•™๋ถ€)์˜ ์žฌ์›์œผ๋กœ ํ•œ๊ตญ์—ฐ๊ตฌ์žฌ๋‹จ์˜ ์ง€์›์„ ๋ฐ›์•„ ์ˆ˜ํ–‰๋œ ์—ฐ๊ตฌ์ž„(No.2014R1A2A2A010 04421).

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