课程名称︰材料力学 课程性质︰系定必修 课程教师︰周元昉 开课学院：工学院 开课系所︰机械系 考试日期（年月日）︰2009六月二十二 考试时限（分钟）：180MIN 是否需发放奖励金：是 （如未明确表示，则不予发放） 试题 : PART 1 Choose the correct answer for each problem and give explanations or calculations.Each problem has a score of 8%.No score will be granted without explanationa or calculations. 1.Five thin-walles tubes of same material and smae wall thickness encircle the same amount of area.If they are subjected to the same twisting moment, which one has smallest angle of twist per unit length? (A) ___ (B) ___ (C) __ (D) (E) / \ / \ | | /\ | | \___/ |__| /__\ 圆形 \___/ (正八角形) (正六角形) (正方形) (正三角形) 2.A positive twisting moment Mt of a circular shaft is defined as shownin fig.2.The distributed external torque t(x) is positive when points in the positive x direction.If a shaft is fixed at its right end and the twisting moment is Mt(x)=toL[cos(2(pi)x/L)-1]+T<x-a>^0,to=const then the corresponding reaction at right end x=L is (A)-2toL+T (B)2toL-T (C)2toL-T (D)-T (E) T ___________ ______________ / | | \ \ | ---->-> +Mt <-<----| / / | | \ \___________| |______________/ 3.If postive shearing force V,bending moment M,and distributed load q of a slender member are defined as shown in Fig.3,which relation is correct? ___________ ______________ / | ^ +M ^ | \ \ | ) ( | / / | | \ \___________| |______________/ ___________ ______________ / | | +V ^ | \ \ | | | | / / | | | | \ \___________| V | |______________/ -------------------------- | | | | | | | | | +q | | | | | | | | | _v_v__v__v__v__v__v__v__v__ / \ ^ y \ / | / \ | \_________________________/ |__________>x (A) b (B) (C) (D) (E) ∫ qdx=V(b)-V(a) d^2M dV b dM a ------=q ----=q ∫ Vdx=M(b)-M(a) -----=-V dx^2 dx a dx 4."Planes remain planes after bending"is assumption in deriving the flexural theory of beams.If E is Young's modulus,Iis the second moment of area,M is the bending moment ,q is the distributed load,v is the lateral deflection ,σis the normal stress,εis the normal strain,ρis the distance measured from the neutral axis,which item has nothing to do with the assumption? (A)The neutral axis passes through the centroid..(B) M d^2ν (C) -y ----=---- ε=---- EI d^2x ρ (D) d^2M (E) My -----=q σ=- --- dx^2 I 5. If a load pointing to the positive y direction is considered as positive, then the load of the beam shown in Gig.5 can be expressed as /\ / ^\ |P -- /^ | \ | | / | | ^\| M(逆时针MOMENT) Wo| /^ | | | | | | |/_|_|_|_|_V\V________________________________ | |-->X \ | | | -- \V | | |----a--|--a--| \ | | |-----b------| \V | |---c----------| \ | | \V (A) wo wo q(x)=---x－ ---<x-a>^1－wo<x-a>^0－P<x-b>^-1－M<x-c>^-2 a a (B) wo 2wo q(x)=---x－ ---<x-a>^1－P<x-b>^-1－M<x-c>^-2 a a (C) wo wo q(x)=---x－ ---<x-a>^1－wo<x-a>^0＋P<x-b>^-1＋M<x-c>^-2 a a (D) wo wo q(x)=---x－ ---<x-a>^1－wo<x-a>^0＋P<x-b>^-1－M<x-c>^-2 a a (E) wo 2wo q(x)=---x－ ---<x-a>^1－P<x-b>^-1+M<x-c>^-2 a a 6.Beams with different supports are loaded at their center with a concentrated force P.Which one has a nonzero curvature at the right end? (A) |\ P |/| | | | |_______________v___________________ △ △ |-------L/2-----| |----------------L-------------------| (B) P | | _______________v___________________ △ △ |-------L/2-----| |----------------L-------------------| (C) P | | | | | |______________v_________________ | | △ |￣------L/2-----| |----------------L-------------------| (D) P | | | | | | | |______________v________________| | | | | | |￣------L/2-----| ￣ |----------------L-------------------| (E) P | | | | | |______________v_________________ | | | | | ------L/2-----| |----------------L-------------------| 先PO选择题好了 我快累死了..... --

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