Ua rau: Instability nyob rau hauv txhua yam khoom ntawm steel strips, defects nto, los yog tseem ceeb deviations nyob rau hauv geometric qhov ntev.
Kev daws: Xaiv cov khoom siv raw khoom tsim nyog, ntxiv dag zog rau kev tshuaj xyuas thiab lees txais cov khoom siv raw; thiab xa rov qab los yog hloov cov khoom tsis tsim nyog.
