求助帖

List[l1, l2, lp, ks, pin, h, l1v, udy, ks1, ks2, pis2] =
List[25.4, 12.7, 76.2, 1.4, 16.5, 124.5, 67.3, 1.65, 4.9, 0.3, 8.1];
ls = Sqrt[(lp + l1 - l1*(1 - (u/l2)^2)^0.5)^2 + u^2*(1 + l1/l2)^2];
fnsd = -((pin + ks*lp)/ls - ks)*(l1/
l2)*(2 + (lp + l1)/(l2^2 - u^2)^0.5 + (l2/
l1)*((h + lp + l1 - (l1 - l2)*(l2^2 - u^2)^0.5)/h))*u;
fg[u_] :=
Which[-udy <= u <= udy, ks1*u, u > udy,
ks1*udy + (ks2*ks1)/(ks2 + ks1)*(u - udy),
u < -udy, -(ks1*udy + (ks2*ks1)/(ks2 + ks1)*(-u - udy))]
fd3 = D[fg[u] + fnsd, u];
fd1 = D[fg[u], u];
fd2 = D[fnsd, u];
Plot[{fd1, fd2, fd3}, {u, 0, 8},
PlotStyle -> {{Red}, {Black, Dashed}, {Blue, Dashed}}, Frame -> True,
FrameLabel -> {"位移 cm", "有效刚度 kN/cm"},
FrameTicks -> {{All, False}, {All, None}},
PlotLegends -> Placed[{"NSDwithGAS", "GAS", "NSD"}, Right]]


我想让两个间断的曲线中间连接起来就像第二张图的示意，请问这个怎么实现，谢谢了