m(x f(x)= F(x) F(x) 1 dm F(x)=」fxdh F( fx p(x) 积分分布函数(a)和微分分布函数(b) F(x)-故障概率 ∫(x)-故障概率密度dx dm n f x 1 ( ) = n m x F x ( ) ( ) = ( ) ( ) 1 f x dx dm dx n dF x = = − = x F(x) f (x)dx