Muaj ntau qhov laj thawj rau kev khoov ntawm cov yeeb nkab steel, xws li cov teebmeem kub ntawm vuam seams thaum vuam, eccentricity ntawm kev tsim, nrog rau compression, qhov tsis txaus ntawm lub zog khoov, thiab lwm yam. Tab sis hauv paus, khoov yog lub luag haujlwm ntawm kev ntxhov siab hauv cov yeeb nkab steel. Yooj yim muab, khoov yog qhov tsis sib xws. Yog li, puas tsis muaj kev ntxhov siab sab hauv ntawm cov kav hlau ncaj ncaj? tsis muaj. Cov yeeb nkab steel ncaj kuj muaj kev ntxhov siab sab hauv, tab sis qhov kev ntxhov siab sab hauv ntawm lub raj ncaj qha yog tsawg dua.
Internal stress yog dab tsi? Kub thiab sab nraud quab yuam cuam tshuam rau kev sib cuam tshuam ntawm cov molecule thaum deformation. Thaum cov yeeb nkab steel yog tsim thiab welded, qhov vuam kub kuj tseem cuam tshuam los ntawm kev cuam tshuam ntawm sab nraud tsim khoov. Qhov hla ntawm cov yeeb nkab steel yog lub nplhaib-zoo li tus, uas yuav ua rau muaj ob qho kev nyuaj siab ntawm lub nplhaib no: mus rau lub nplhaib-shaped quab yuam thiab perpendicularity ntawm lub nplhaib-zoo li tus duab. Cov kev ntxhov siab thaum uas tig mus yuav ua rau lub raj tsis puag ncig; ntsug txoj kev nyuaj siab yuav ua rau lub raj khoov. Yog li ntawd, muaj cov txheej txheem txias txias thaum lub sij hawm tsim cov kav hlau ncaj, lub hom phiaj yog kom tshem tawm cov kev ntxhov siab sab hauv ntawm cov yeeb nkab steel thiab ua kom muaj kev siv cov kav hlau ncaj.
