弯幽应力( Stresses in beams 蒋应力表达式代入(1)式,得 F=E4=0∫,ud4=0中S:=1y0=0 今中性轴通过横截面形心 将应力表达式代入(2)式,得 E M= zE dA=0> OJ,JdA=0SIy-yyzd=0 →自然满足 将应力表达式代入(3)式,得 M=yE244∥Ep=M中E1=M M PEI(Stresses in Beams) 将应力表达式代入（1）式，得 将应力表达式代入（2）式，得 将应力表达式代入(3)式，得 中性轴通过横截面形心 z E I M =  1 自然满足 d 0 N = =  A y F E A  d = 0 A y A E  d = 0 A Sz = y A = d = 0  A y M zE A iy  d = 0 A yz A E  d = 0 A I yz = yz A A M y M yE A iz = =  d  I M E z =  y A M E A =  d 2 