{"id":2796,"date":"2025-10-03T14:19:29","date_gmt":"2025-10-03T14:19:29","guid":{"rendered":"https:\/\/productionscrews.com\/"},"modified":"2025-10-03T14:19:29","modified_gmt":"2025-10-03T14:19:29","slug":"ultimate-guide-to-elastic-modulus-testing-from-bridge-safety-to-medical-implants","status":"publish","type":"post","link":"https:\/\/productionscrews.com\/vi\/ultimate-guide-to-elastic-modulus-testing-from-bridge-safety-to-medical-implants\/","title":{"rendered":"H\u01b0\u1edbng d\u1eabn t\u1ed1i \u01b0u v\u1ec1 ki\u1ec3m tra m\u00f4 \u0111\u00e0n h\u1ed3i: T\u1eeb an to\u00e0n c\u1ea7u \u0111\u1ebfn c\u1ea5y gh\u00e9p y t\u1ebf"},"content":{"rendered":"

H\u01b0\u1edbng d\u1eabn ki\u1ec3m tra \u0111\u1ed9 c\u1ee9ng c\u1ee7a c\u00e1c v\u1eadt li\u1ec7u<\/h2>\n

An to\u00e0n c\u1ee7a c\u1ea7u treo, \u0111\u1ed9 tin c\u1eady c\u1ee7a b\u1ed9 ph\u1eadn \u0111\u1ed9ng c\u01a1 ph\u1ea3n l\u1ef1c, v\u00e0 tu\u1ed5i th\u1ecd c\u1ee7a c\u1ea5y gh\u00e9p y t\u1ebf \u0111\u1ec1u ph\u1ee5 thu\u1ed9c v\u00e0o m\u1ed9t \u0111\u1eb7c t\u00ednh quan tr\u1ecdng: \u0111\u1ed9 c\u1ee9ng c\u1ee7a v\u1eadt li\u1ec7u. C\u00e1c k\u1ef9 s\u01b0 g\u1ecdi \u0111\u1eb7c t\u00ednh n\u00e0y l\u00e0 \u201cmodul \u0111\u00e0n h\u1ed3i\u201d. N\u1ebfu c\u00e1c k\u1ef9 s\u01b0 \u0111o\u00e1n sai gi\u00e1 tr\u1ecb n\u00e0y, c\u00e1c c\u1ea5u tr\u00fac c\u00f3 th\u1ec3 g\u1eb7p s\u1ef1 c\u1ed1 th\u1ea3m kh\u1ed1c. Nh\u01b0ng khi hi\u1ec3u \u0111\u00fang, h\u1ecd c\u00f3 th\u1ec3 thi\u1ebft k\u1ebf c\u00e1c b\u1ed9 ph\u1eadn nh\u1eb9 h\u01a1n, ch\u1eafc ch\u1eafn h\u01a1n v\u00e0 ho\u1ea1t \u0111\u1ed9ng t\u1ed1t h\u01a1n. Th\u1eed nghi\u1ec7m m\u00f4\u0111un \u0111\u00e0n h\u1ed3i l\u00e0 m\u1ed9t nh\u00f3m c\u00e1c th\u00ed nghi\u1ec7m d\u00f9ng \u0111\u1ec3 \u0111o \u0111\u1eb7c t\u00ednh quan tr\u1ecdng n\u00e0y. N\u00f3 li\u00ean quan \u0111\u1ebfn vi\u1ec7c \u00e1p d\u1ee5ng m\u1ed9t l\u1ef1c ki\u1ec3m so\u00e1t l\u00ean m\u1eabu v\u1eadt li\u1ec7u v\u00e0 \u0111o c\u1ea9n th\u1eadn m\u1ee9c \u0111\u1ed9 n\u00f3 u\u1ed1n cong ho\u1eb7c k\u00e9o d\u00e0i trong gi\u1edbi h\u1ea1n an to\u00e0n. \u0110i\u1ec1u n\u00e0y h\u01b0\u1edbng d\u1eabn s\u1ebd gi\u00fap b\u1ea1n hi\u1ec3u c\u00e1c nguy\u00ean t\u1eafc c\u01a1 b\u1ea3n<\/a> v\u1ec1 ki\u1ec3m tra m\u00f4 \u0111un \u0111\u00e0n h\u1ed3i, gi\u1ea3i th\u00edch c\u00e1c ph\u01b0\u01a1ng ph\u00e1p ki\u1ec3m tra kh\u00e1c nhau v\u00e0 h\u01b0\u1edbng d\u1eabn b\u1ea1n c\u00e1ch hi\u1ec3u k\u1ebft qu\u1ea3. Ch\u00fang ta s\u1ebd b\u1eaft \u0111\u1ea7u v\u1edbi v\u1eadt l\u00fd c\u01a1 b\u1ea3n c\u1ee7a \u1ee9ng su\u1ea5t v\u00e0 bi\u1ebfn d\u1ea1ng v\u00e0 ti\u1ebfn t\u1edbi gi\u1ea3i quy\u1ebft c\u00e1c v\u1ea5n \u0111\u1ec1 trong qu\u00e1 tr\u00ecnh ki\u1ec3m tra, cung c\u1ea5p cho b\u1ea1n ki\u1ebfn th\u1ee9c \u0111\u1ec3 th\u1ef1c hi\u1ec7n v\u00e0 hi\u1ec3u c\u00e1c ph\u00e9p \u0111o n\u00e0y m\u1ed9t c\u00e1ch t\u1ef1 tin.<\/p>\n

Khoa H\u1ecdc C\u01a1 B\u1ea3n<\/h2>\n

Tr\u01b0\u1edbc khi \u00e1p d\u1ee5ng b\u1ea5t k\u1ef3 l\u1ef1c n\u00e0o trong ph\u00f2ng th\u00ed nghi\u1ec7m, b\u1ea1n c\u1ea7n hi\u1ec3u c\u00e1c nguy\u00ean l\u00fd v\u1eadt l\u00fd c\u01a1 b\u1ea3n. C\u00e1c kh\u00e1i ni\u1ec7m v\u1ec1 \u1ee9ng su\u1ea5t, bi\u1ebfn d\u1ea1ng v\u00e0 m\u1ed1i quan h\u1ec7 c\u1ee7a ch\u00fang, \u0111\u01b0\u1ee3c m\u00f4 t\u1ea3 b\u1edfi \u0110\u1ecbnh lu\u1eadt Hooke, t\u1ea1o n\u1ec1n t\u1ea3ng cho t\u1ea5t c\u1ea3 c\u00e1c ph\u00e9p \u0111o m\u00f4 \u0111un \u0111\u00e0n h\u1ed3i. Hi\u1ec3u r\u00f5 c\u00e1c nguy\u00ean l\u00fd n\u00e0y \u0111\u1ea3m b\u1ea3o d\u1eef li\u1ec7u t\u1eeb m\u1ed9t ki\u1ec3m tra c\u00f3 \u00fd ngh\u0129a v\u00e0 th\u1ec3 hi\u1ec7n c\u00e1ch m\u1ed9t v\u1eadt li\u1ec7u<\/a> th\u1ef1c s\u1ef1 c\u01b0 x\u1eed nh\u01b0 th\u1ebf n\u00e0o.<\/p>\n

Stress l\u00e0 g\u00ec?<\/h3>\n

\u00c1p l\u1ef1c \u0111o l\u01b0\u1eddng c\u00e1c l\u1ef1c n\u1ed9i t\u1ea1i m\u00e0 c\u00e1c h\u1ea1t trong m\u1ed9t v\u1eadt li\u1ec7u \u0111\u1ea9y l\u00ean nhau. \u0110\u00e2y l\u00e0 m\u1ed9t gi\u00e1 tr\u1ecb ti\u00eau chu\u1ea9n th\u1ec3 hi\u1ec7n l\u1ef1c ph\u00e2n b\u1ed1 tr\u00ean m\u1ed9t di\u1ec7n t\u00edch. Trong ki\u1ec3m tra v\u1eadt li\u1ec7u<\/a>Ch\u00fang t\u00f4i ch\u1ee7 y\u1ebfu xem x\u00e9t hai lo\u1ea1i:<\/p>\n

\u1ee8ng su\u1ea5t k\u1ef9 thu\u1eadt (\u03c3): \u0110\u00e2y l\u00e0 \u0111\u1ecbnh ngh\u0129a ph\u1ed5 bi\u1ebfn nh\u1ea5t \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng khi v\u1eadt li\u1ec7u k\u00e9o d\u00e3n \u0111\u00e0n h\u1ed3i. N\u00f3 \u0111\u01b0\u1ee3c t\u00ednh b\u1eb1ng c\u00e1ch chia l\u1ef1c t\u00e1c d\u1ee5ng b\u00ean ngo\u00e0i (F) cho di\u1ec7n t\u00edch m\u1eb7t c\u1eaft ngang ban \u0111\u1ea7u, kh\u00f4ng \u0111\u1ed5i (A\u2080) c\u1ee7a m\u1eabu th\u1eed.<\/p>\n

\u03c3 = F \/ A\u2080<\/p>\n

\u1ee8ng su\u1ea5t th\u1ef1c (\u03c3_t): \u0110\u1ecbnh ngh\u0129a n\u00e0y ph\u1ea3n \u00e1nh th\u1ef1c t\u1ebf r\u1eb1ng di\u1ec7n t\u00edch m\u1eb7t c\u1eaft ngang c\u1ee7a m\u1eabu thay \u0111\u1ed5i khi n\u00f3 b\u1ecb bi\u1ebfn d\u1ea1ng. N\u00f3 \u0111\u01b0\u1ee3c t\u00ednh b\u1eb1ng c\u00e1ch chia l\u1ef1c t\u00e1c d\u1ee5ng (F) cho di\u1ec7n t\u00edch m\u1eb7t c\u1eaft ngang hi\u1ec7n t\u1ea1i (A).<\/p>\n

\u03c3_t = F \/ A<\/p>\n

\u0110\u1ec3 x\u00e1c \u0111\u1ecbnh m\u00f4 \u0111un \u0111\u00e0n h\u1ed3i, \u0111i\u1ec1u n\u00e0y x\u1ea3y ra khi bi\u1ebfn d\u1ea1ng r\u1ea5t nh\u1ecf, s\u1ef1 thay \u0111\u1ed5i v\u1ec1 di\u1ec7n t\u00edch l\u00e0 nh\u1ecf b\u00e9. Do \u0111\u00f3, s\u1ef1 kh\u00e1c bi\u1ec7t gi\u1eefa \u1ee9ng su\u1ea5t k\u1ef9 thu\u1eadt v\u00e0 \u1ee9ng su\u1ea5t th\u1ef1c kh\u00f4ng qu\u00e1 quan tr\u1ecdng, v\u00e0 \u1ee9ng su\u1ea5t k\u1ef9 thu\u1eadt l\u00e0 ti\u00eau chu\u1ea9n cho ph\u00e9p t\u00ednh n\u00e0y. S\u1ef1 ph\u00e2n bi\u1ec7t ch\u1ec9 tr\u1edf n\u00ean quan tr\u1ecdng sau khi v\u1eadt li\u1ec7u b\u1eaft \u0111\u1ea7u bi\u1ebfn d\u1ea1ng v\u0129nh vi\u1ec5n v\u00e0 x\u1ea3y ra hi\u1ec7n t\u01b0\u1ee3ng \u201ch\u1eb9p c\u1ed5\u201d.<\/p>\n

X\u00e1c \u0111\u1ecbnh ch\u1ee7ng lo\u1ea1i<\/h3>\n

\u0110\u1ed9 bi\u1ebfn d\u1ea1ng \u0111o l\u01b0\u1eddng s\u1ef1 bi\u1ebfn d\u1ea1ng, th\u1ec3 hi\u1ec7n m\u1ee9c \u0111\u1ed9 c\u00e1c h\u1ea1t trong v\u1eadt li\u1ec7u di chuy\u1ec3n so v\u1edbi nhau. Gi\u1ed1ng nh\u01b0 \u1ee9ng su\u1ea5t, n\u00f3 l\u00e0 m\u1ed9t \u0111\u1ea1i l\u01b0\u1ee3ng chu\u1ea9n h\u00f3a, l\u00e0m cho n\u00f3 kh\u00f4ng c\u00f3 \u0111\u01a1n v\u1ecb (kh\u00f4ng c\u00f3 \u0111\u01a1n v\u1ecb \u0111o l\u01b0\u1eddng).<\/p>\n

Bi\u1ebfn d\u1ea1ng k\u1ef9 thu\u1eadt (\u03b5): \u0110\u00e2y l\u00e0 s\u1ef1 thay \u0111\u1ed5i chi\u1ec1u d\u00e0i (\u0394L) c\u1ee7a m\u1eabu chia cho chi\u1ec1u d\u00e0i ban \u0111\u1ea7u (L\u2080). Th\u01b0\u1eddng \u0111\u01b0\u1ee3c bi\u1ec3u th\u1ecb d\u01b0\u1edbi d\u1ea1ng s\u1ed1 th\u1eadp ph\u00e2n, ph\u1ea7n tr\u0103m ho\u1eb7c trong \u0111\u01a1n v\u1ecb vi bi\u1ebfn d\u1ea1ng (\u03bc\u025b).<\/p>\n

\u03b5 = \u0394L \/ L\u2080<\/p>\n

Bi\u1ebfn d\u1ea1ng th\u1ef1c (\u03b5_t): C\u00f2n g\u1ecdi l\u00e0 bi\u1ebfn d\u1ea1ng logarit, \u0111\u01b0\u1ee3c t\u00ednh b\u1eb1ng c\u00e1ch c\u1ed9ng t\u1ea5t c\u1ea3 c\u00e1c thay \u0111\u1ed5i nh\u1ecf v\u1ec1 chi\u1ec1u d\u00e0i tr\u00ean chi\u1ec1u d\u00e0i hi\u1ec7n t\u1ea1i. Ch\u1ee7 y\u1ebfu \u0111\u01b0\u1ee3c s\u1eed d\u1ee5ng trong ph\u00e2n t\u00edch bi\u1ebfn d\u1ea1ng d\u1ebbo cao c\u1ea5p.<\/p>\n

\u0110\u1ed1i v\u1edbi th\u1eed nghi\u1ec7m m\u00f4 \u0111un \u0111\u00e0n h\u1ed3i, c\u00e1c bi\u1ebfn d\u1ea1ng nh\u1ecf li\u00ean quan c\u00f3 ngh\u0129a l\u00e0 bi\u1ebfn d\u1ea1ng k\u1ef9 thu\u1eadt cung c\u1ea5p m\u1ed9t ph\u00e9p \u0111o ch\u00ednh x\u00e1c cao v\u00e0 \u0111\u1ee7 \u0111\u1ec3 ph\u1ea3n \u00e1nh ph\u1ea3n \u1ee9ng c\u1ee7a v\u1eadt li\u1ec7u. N\u00f3 tr\u1ef1c ti\u1ebfp ph\u00f9 h\u1ee3p v\u1edbi c\u00e1c ph\u00e9p \u0111o \u0111\u01b0\u1ee3c th\u1ef1c hi\u1ec7n b\u1edfi c\u00e1c thi\u1ebft b\u1ecb g\u1ecdi l\u00e0 extensometer.<\/p>\n

\"m\u00e1y<\/a><\/p>\n

\u0110\u1ecbnh lu\u1eadt Hooke v\u00e0 \u0110\u1ed9 \u0111\u00e0n h\u1ed3i<\/h3>\n

Nguy\u00ean t\u1eafc c\u1ed1t l\u00f5i c\u1ee7a th\u1eed nghi\u1ec7m m\u00f4 \u0111un \u0111\u00e0n h\u1ed3i l\u00e0 \u0110\u1ecbnh lu\u1eadt Hooke. N\u00f3 ph\u00e1t bi\u1ec3u r\u1eb1ng \u0111\u1ed1i v\u1edbi m\u1ed9t v\u1eadt li\u1ec7u ph\u1ea3n \u1ee9ng \u0111\u00e0n h\u1ed3i, \u1ee9ng su\u1ea5t t\u1ef7 l\u1ec7 thu\u1eadn tr\u1ef1c ti\u1ebfp v\u1edbi bi\u1ebfn d\u1ea1ng. M\u1ed1i quan h\u1ec7 \u0111\u01b0\u1eddng th\u1eb3ng n\u00e0y \u0111\u00fang khi v\u1eadt li\u1ec7u kh\u00f4ng b\u1ecb bi\u1ebfn d\u1ea1ng v\u0129nh vi\u1ec5n.<\/p>\n

\u03c3 = E\u03b5<\/p>\n

H\u1eb1ng s\u1ed1 trong ph\u01b0\u01a1ng tr\u00ecnh n\u00e0y l\u00e0 M\u00f4 \u0111un \u0111\u00e0n h\u1ed3i (E), c\u00f2n \u0111\u01b0\u1ee3c bi\u1ebft r\u1ed9ng r\u00e3i l\u00e0 M\u00f4 \u0111un Young. N\u00f3 th\u1ec3 hi\u1ec7n \u0111\u1ed9 c\u1ee9ng t\u1ef1 nhi\u00ean c\u1ee7a v\u1eadt li\u1ec7u. M\u1ed9t v\u1eadt li\u1ec7u c\u00f3 m\u00f4 \u0111un \u0111\u00e0n h\u1ed3i cao, nh\u01b0 th\u00e9p, s\u1ebd bi\u1ebfn d\u1ea1ng r\u1ea5t \u00edt d\u01b0\u1edbi m\u1ed9t t\u1ea3i tr\u1ecdng nh\u1ea5t \u0111\u1ecbnh. M\u1ed9t v\u1eadt li\u1ec7u c\u00f3 m\u00f4 \u0111un \u0111\u00e0n h\u1ed3i th\u1ea5p, nh\u01b0 nh\u1ef1a m\u1ec1m, s\u1ebd bi\u1ebfn d\u1ea1ng nhi\u1ec1u h\u01a1n.<\/p>\n

Tr\u00ean \u0111\u1ed3 th\u1ecb \u1ee9ng su\u1ea5t - bi\u1ebfn d\u1ea1ng, m\u1ed1i quan h\u1ec7 n\u00e0y xu\u1ea5t hi\u1ec7n d\u01b0\u1edbi d\u1ea1ng m\u1ed9t \u0111\u01b0\u1eddng th\u1eb3ng b\u1eaft \u0111\u1ea7u t\u1eeb zero. \u0110\u1ed9 d\u1ed1c c\u1ee7a \u0111\u01b0\u1eddng n\u00e0y l\u00e0 m\u00f4 \u0111un \u0111\u00e0n h\u1ed3i. V\u00f9ng m\u00e0 m\u1ed1i quan h\u1ec7 tuy\u1ebfn t\u00ednh n\u00e0y gi\u1eef nguy\u00ean g\u1ecdi l\u00e0 \u201cv\u00f9ng \u0111\u00e0n h\u1ed3i.\u201d N\u1ebfu t\u1ea3i tr\u1ecdng \u0111\u01b0\u1ee3c lo\u1ea1i b\u1ecf trong v\u00f9ng n\u00e0y, v\u1eadt li\u1ec7u s\u1ebd tr\u1edf v\u1ec1 k\u00edch th\u01b0\u1edbc ban \u0111\u1ea7u. Khi \u1ee9ng su\u1ea5t v\u01b0\u1ee3t qu\u00e1 \u0111i\u1ec3m d\u1eebng ch\u1ea3y c\u1ee7a v\u1eadt li\u1ec7u, \u0111\u01b0\u1eddng cong l\u1ec7ch kh\u1ecfi \u0111\u01b0\u1eddng th\u1eb3ng, v\u00e0 v\u1eadt li\u1ec7u b\u01b0\u1edbc v\u00e0o \u201cv\u00f9ng d\u1ebbo,\u201d n\u01a1i x\u1ea3y ra bi\u1ebfn d\u1ea1ng v\u0129nh vi\u1ec5n. To\u00e0n b\u1ed9 m\u1ee5c \u0111\u00edch c\u1ee7a th\u1eed nghi\u1ec7m m\u00f4 \u0111un \u0111\u00e0n h\u1ed3i l\u00e0 \u0111o ch\u00ednh x\u00e1c \u0111\u1ed9 d\u1ed1c c\u1ee7a ph\u1ea7n ban \u0111\u1ea7u, th\u1eb3ng, \u0111\u00e0n h\u1ed3i c\u1ee7a \u0111\u01b0\u1eddng cong.<\/p>\n

Ph\u01b0\u01a1ng ph\u00e1p th\u1eed t\u0129nh<\/h2>\n

C\u00e1c th\u1eed nghi\u1ec7m t\u0129nh l\u00e0 nh\u1eefng ph\u01b0\u01a1ng ph\u00e1p ch\u00ednh trong \u0111\u1eb7c t\u00ednh v\u1eadt li\u1ec7u. Ch\u00fang li\u00ean quan \u0111\u1ebfn vi\u1ec7c \u00e1p d\u1ee5ng t\u1ea3i tr\u1ecdng ch\u1eadm r\u00e3i v\u1edbi t\u1ed1c \u0111\u1ed9 kh\u00f4ng \u0111\u1ed5i v\u00e0 \u0111o l\u01b0\u1eddng bi\u1ebfn d\u1ea1ng ph\u00e1t sinh. C\u00e1c ph\u01b0\u01a1ng ph\u00e1p n\u00e0y \u0111\u00e3 \u0111\u01b0\u1ee3c ti\u00eau chu\u1ea9n h\u00f3a t\u1ed1t, hi\u1ec3u r\u00f5 r\u1ed9ng r\u00e3i, v\u00e0 l\u00e0 n\u1ec1n t\u1ea3ng cho h\u1ea7u h\u1ebft c\u00e1c b\u1ea3ng d\u1eef li\u1ec7u v\u1eadt li\u1ec7u. L\u1ef1a ch\u1ecdn gi\u1eefa ch\u00fang ph\u1ee5 thu\u1ed9c v\u00e0o lo\u1ea1i v\u1eadt li\u1ec7u, c\u00e1ch s\u1eed d\u1ee5ng, v\u00e0 h\u00ecnh d\u1ea1ng m\u1eabu th\u1eed c\u00f3 s\u1eb5n.<\/p>\n

Th\u1eed nghi\u1ec7m k\u00e9o<\/h3>\n

Th\u1eed nghi\u1ec7m k\u00e9o l\u00e0 ti\u00eau chu\u1ea9n v\u00e0ng \u0111\u1ec3 x\u00e1c \u0111\u1ecbnh m\u00f4 \u0111un \u0111\u00e0n h\u1ed3i c\u1ee7a c\u00e1c v\u1eadt li\u1ec7u c\u00f3 th\u1ec3 k\u00e9o d\u00e0i, nh\u01b0 kim lo\u1ea1i v\u00e0 nh\u1ef1a. N\u00f3 cung c\u1ea5p nhi\u1ec1u th\u00f4ng tin ngo\u00e0i ch\u1ec9 m\u00f4 \u0111un, bao g\u1ed3m \u0111\u1ed9 b\u1ec1n k\u00e9o, gi\u1edbi h\u1ea1n ch\u1ea3y, v\u00e0 kh\u1ea3 n\u0103ng k\u00e9o d\u00e0i c\u1ee7a v\u1eadt li\u1ec7u tr\u01b0\u1edbc khi g\u00e3y.<\/p>\n

Nguy\u00ean t\u1eafc li\u00ean quan \u0111\u1ebfn vi\u1ec7c k\u00e9o m\u1eabu th\u1eed b\u1eb1ng l\u1ef1c theo m\u1ed9t h\u01b0\u1edbng v\u00e0 \u0111o l\u01b0\u1ee3ng n\u00f3 k\u00e9o d\u00e0i. Thi\u1ebft b\u1ecb ch\u00ednh l\u00e0 M\u00e1y th\u1eed nghi\u1ec7m \u0111a n\u0103ng (UTM), \u00e1p d\u1ee5ng t\u1ea3i tr\u1ecdng ho\u1eb7c chuy\u1ec3n \u0111\u1ed9ng c\u00f3 ki\u1ec3m so\u00e1t. M\u1ed9t th\u00e0nh ph\u1ea7n quan tr\u1ecdng l\u00e0 extensometer, thi\u1ebft b\u1ecb \u0111o bi\u1ebfn d\u1ea1ng ch\u00ednh x\u00e1c cao, \u0111o tr\u1ef1c ti\u1ebfp tr\u00ean b\u1ec1 m\u1eb7t m\u1eabu th\u1eed. Ch\u00fang c\u00f3 th\u1ec3 l\u00e0 thi\u1ebft b\u1ecb k\u1eb9p v\u00e0o m\u1eabu ho\u1eb7c h\u1ec7 th\u1ed1ng kh\u00f4ng ti\u1ebfp x\u00fac nh\u01b0 video extensometers.<\/p>\n

Quy tr\u00ecnh r\u1ea5t ti\u00eau chu\u1ea9n h\u00f3a (v\u00ed d\u1ee5, theo ASTM E8 cho kim lo\u1ea1i):<\/p>\n

    \n
  1. M\u1eabu th\u1eed h\u00ecnh d\u1ea1ng \u201cch\u00f3-b\u00f2\u201d \u0111\u01b0\u1ee3c gia c\u00f4ng ch\u00ednh x\u00e1c. H\u00ecnh d\u1ea1ng n\u00e0y \u0111\u1ea3m b\u1ea3o r\u1eb1ng s\u1ef1 g\u00e3y x\u1ea3y ra \u1edf ph\u1ea7n trung t\u00e2m, \u0111\u1ed3ng \u0111\u1ec1u.<\/li>\n
  2. M\u1eabu th\u1eed \u0111\u01b0\u1ee3c c\u1ed1 \u0111\u1ecbnh trong k\u1eb9p c\u1ee7a UTM. Extensometer \u0111\u01b0\u1ee3c g\u1eafn c\u1ea9n th\u1eadn v\u00e0o ph\u1ea7n th\u1eed nghi\u1ec7m.<\/li>\n
  3. L\u1ef1c k\u00e9o \u0111\u01b0\u1ee3c \u00e1p d\u1ee5ng v\u1edbi t\u1ed1c \u0111\u1ed9 bi\u1ebfn d\u1ea1ng ho\u1eb7c chuy\u1ec3n \u0111\u1ed9ng kh\u00f4ng \u0111\u1ed5i, theo ti\u00eau chu\u1ea9n quy \u0111\u1ecbnh.<\/li>\n
  4. Ph\u1ea7n m\u1ec1m c\u1ee7a UTM ghi l\u1ea1i l\u1ef1c t\u1eeb c\u1ea3m bi\u1ebfn l\u1ef1c v\u00e0 d\u1ecbch chuy\u1ec3n t\u1eeb extensometer c\u00f9ng l\u00fac, t\u1ea1o ra \u0111\u1ed3 th\u1ecb l\u1ef1c - d\u1ecbch chuy\u1ec3n.<\/li>\n
  5. D\u1eef li\u1ec7u n\u00e0y sau \u0111\u00f3 \u0111\u01b0\u1ee3c chuy\u1ec3n \u0111\u1ed5i th\u00e0nh \u0111\u1ed3 th\u1ecb \u1ee9ng su\u1ea5t - bi\u1ebfn d\u1ea1ng, t\u1eeb \u0111\u00f3 t\u00ednh m\u00f4 \u0111un l\u00e0 \u0111\u1ed9 d\u1ed1c c\u1ee7a ph\u1ea7n ban \u0111\u1ea7u, th\u1eb3ng c\u1ee7a \u0111\u01b0\u1eddng cong.<\/li>\n<\/ol>\n

    Theo kinh nghi\u1ec7m, c\u00e1c v\u1ea5n \u0111\u1ec1 ph\u1ed5 bi\u1ebfn c\u00f3 th\u1ec3 l\u00e0m h\u1ecfng k\u1ebft qu\u1ea3. Tr\u01b0\u1ee3t m\u1eabu th\u1eed trong k\u1eb9p c\u00f3 th\u1ec3 t\u1ea1o ra v\u00f9ng \u201c\u0111\u1ea7u ch\u00e2n\u201d cong trong \u0111\u01b0\u1eddng cong, c\u1ea7n ch\u1ec9nh s\u1eeda d\u1eef li\u1ec7u. V\u1ecb tr\u00ed ho\u1eb7c \u00e1p l\u1ef1c kh\u00f4ng \u0111\u00fang c\u1ee7a extensometer c\u00f3 th\u1ec3 t\u1ea1o ra t\u1eadp trung \u1ee9ng su\u1ea5t. H\u01a1n n\u1eefa, t\u1ed1c \u0111\u1ed9 t\u1ea3i l\u00e0 r\u1ea5t quan tr\u1ecdng; th\u1eed nghi\u1ec7m nh\u1ef1a qu\u00e1 nhanh c\u00f3 th\u1ec3 g\u00e2y ra c\u1ee9ng h\u00f3a theo t\u1ed1c \u0111\u1ed9 bi\u1ebfn d\u1ea1ng, l\u00e0m t\u0103ng gi\u1ea3 t\u1ea1o m\u00f4 \u0111un \u0111o \u0111\u01b0\u1ee3c.<\/p>\n

    Th\u1eed nghi\u1ec7m n\u00e9n<\/h3>\n

    \u0110\u1ed1i v\u1edbi c\u00e1c v\u1eadt li\u1ec7u \u0111\u01b0\u1ee3c thi\u1ebft k\u1ebf \u0111\u1ec3 ch\u1ecbu n\u00e9n, ch\u1eb3ng h\u1ea1n nh\u01b0 b\u00ea t\u00f4ng, g\u1ed1m s\u1ee9 ho\u1eb7c foam c\u1ea5u tr\u00fac, ph\u01b0\u01a1ng ph\u00e1p th\u1eed n\u00e9n l\u00e0 ph\u00f9 h\u1ee3p. Nguy\u00ean t\u1eafc c\u1ee7a n\u00f3 tr\u00e1i ng\u01b0\u1ee3c v\u1edbi th\u1eed k\u00e9o: m\u1ed9t l\u1ef1c \u0111\u1ea9y \u0111\u01b0\u1ee3c t\u00e1c d\u1ee5ng l\u00ean m\u1eabu th\u1eed, v\u00e0 \u0111\u1ed9 gi\u1ea3m chi\u1ec1u cao c\u1ee7a n\u00f3 \u0111\u01b0\u1ee3c \u0111o.<\/p>\n

    Nh\u1eefng \u0111i\u1ec3m kh\u00e1c bi\u1ec7t ch\u00ednh so v\u1edbi th\u1eed k\u00e9o l\u00e0 \u0111\u00e1ng k\u1ec3. C\u00e1c m\u1eabu th\u1eed th\u01b0\u1eddng l\u00e0 c\u00e1c h\u00ecnh tr\u1ee5 ho\u1eb7c kh\u1ed1i d\u00e0y ng\u1eafn \u0111\u1ec3 tr\u00e1nh b\u1ecb bi\u1ebfn d\u1ea1ng u\u1ed1n cong d\u01b0\u1edbi t\u1ea3i tr\u1ecdng, \u0111i\u1ec1u n\u00e0y s\u1ebd l\u00e0m k\u1ebft qu\u1ea3 kh\u00f4ng h\u1ee3p l\u1ec7. M\u1ed9t v\u1ea5n \u0111\u1ec1 ph\u1ed5 bi\u1ebfn l\u00e0 'b\u00f3ng tr\u00f2n', n\u01a1i ma s\u00e1t gi\u1eefa c\u00e1c \u0111\u1ea7u m\u1eabu th\u1eed v\u00e0 c\u00e1c t\u1ea5m c\u1ee7a m\u00e1y ng\u0103n c\u1ea3n s\u1ef1 m\u1edf r\u1ed9ng, khi\u1ebfn m\u1eabu th\u1eed ph\u00ecnh ra \u1edf gi\u1eefa. \u0110i\u1ec1u n\u00e0y d\u1eabn \u0111\u1ebfn \u1ee9ng su\u1ea5t kh\u00f4ng \u0111\u1ec1u.<\/p>\n

    C\u00e1c \u1ee9ng d\u1ee5ng \u0111\u1eb7c th\u00f9 cho c\u00e1c v\u1eadt li\u1ec7u c\u00f3 \u0111\u1ed9 ch\u1ecbu n\u00e9n cao nh\u01b0ng c\u00f3 th\u1ec3 d\u1ec5 v\u1ee1 trong k\u00e9o. C\u00e1c ti\u00eau chu\u1ea9n nh\u01b0 ASTM E9 (cho kim lo\u1ea1i) v\u00e0 ASTM C39 (cho tr\u1ee5 b\u00ea t\u00f4ng) quy \u0111\u1ecbnh quy tr\u00ecnh, \u0111\u1ea3m b\u1ea3o t\u00ednh nh\u1ea5t qu\u00e1n v\u00e0 kh\u1ea3 n\u0103ng so s\u00e1nh d\u1eef li\u1ec7u.<\/p>\n

    Th\u1eed u\u1ed1n cong<\/h3>\n

    Th\u1eed u\u1ed1n, hay th\u1eed b\u1ebb, r\u1ea5t h\u1eefu \u00edch cho c\u00e1c v\u1eadt li\u1ec7u d\u1ec5 v\u1ee1 nh\u01b0 g\u1ed1m s\u1ee9 v\u00e0 m\u1ed9t s\u1ed1 nh\u1ef1a c\u1ee9ng, n\u01a1i vi\u1ec7c t\u1ea1o ra m\u1eabu th\u1eed k\u00e9o h\u1ee3p l\u1ec7 g\u1eb7p kh\u00f3 kh\u0103n v\u00e0 nguy c\u01a1 g\u00e3y s\u1edbm g\u1ea7n c\u00e1c k\u1eb9p.<\/p>\n

    Nguy\u00ean t\u1eafc li\u00ean quan \u0111\u1ebfn vi\u1ec7c h\u1ed7 tr\u1ee3 m\u1ed9t m\u1eabu th\u1eed d\u1ea1ng d\u1ea7m v\u00e0 t\u00e1c d\u1ee5ng t\u1ea3i tr\u1ecdng v\u00e0o trung t\u00e2m c\u1ee7a n\u00f3 \u0111\u1ec3 l\u00e0m cho n\u00f3 u\u1ed1n cong. \u0110\u1ed9 m\u00f4 \u0111un \u0111\u01b0\u1ee3c t\u00ednh t\u1eeb \u0111\u01b0\u1eddng cong t\u1ea3i tr\u1ecdng - \u0111\u1ed9 l\u1ec7ch. C\u00f3 hai thi\u1ebft l\u1eadp ch\u00ednh:<\/p>\n