2??1?W?i??2??(?i)??(?i)v(?il)??
?2?????W?i??21??(i)??(?i)v(?il)? 4????4?(?i)??(?i)?W（i）??4? ??W?(i)??(i)（i）??D??W(i)/W(i)4??? ?v?asin(wt)
d2v??aw2sin(wt) 2dt?
?l?(i)?l???F(?i)2l??dF(?i)?sign??dt??????signv(?il)??????? ??
图4 单一弹簧模型的运动
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例1 施加重力和边界速度的弹性体FLAC3D计算