《工程力学》课后习题解答

FAFA日1-1试画出以下各题中圆柱或圆盘的受力图。与其它物体接触处的摩擦力均略去。OAWABBOWABOBFBWFBAWAFAFOAWABOBWAFOAWBFAFABFAFBFBFFBAOBWAAOWFOAOW1-2试画出以下各题中AB杆的受力图。AAAECWWDBWWDBBACWBAFCBACWBAEFECEFWFDDBFBAFFACBFBFBAFAFAAFDDWDBFBAFACFBAWBACWBFBqABACDAWFBABCWDFACBDWA’D’B’qqABFFAACWqFFFBABDBABFDFFDCAWCBFBFCBFACBDFFBWFFBAFDFqFABFAFFAFBxFBWADAAFCDBFBWADAFAxFFDFBADAADWBCFBFAFAAAFD’BDABWC(f)AFDFDBFBFCAFCBFBDAFABWBFBCBFABFBC(f)BW2-2杆AC、BC在C处铰接，另一端均与墙面铰接，如图所示，F和F作用在销钉C上，12F=445N，F=535N，不计杆重，试求两杆所受的力。12AF14B3BCF2yyFACFBCF2FxF=0yF=0x15AC2315BCACNACBCAC与BC两杆均受拉。BCaADFFABCD封闭的力三角形：FBCBADAFAFDFDFFFAFFFFFF=D=A==D=ABCABAC21515F=FF=F=1.12FD2A2的自重不计，试求两支座的约束力。oBAFFDEAαFBFBAFdAeFFBcBFF=B=ACDCEED25522+ED=CDCE=CE5522+244 CE1F=F=20=10kNBCD2F=EDF=520=10.4kNACD22-6如图所示结构由两弯杆ABC和DE构成。构件重量不计，图中的长度单位为cm。已知4F4BC68D6EAEF=FDEF=FDEFFDDEFE(2)取ABC为研究对象，受力分析并画受力图；画封闭的力三角形：FBFAFF’DDF’33D3AFAF=F'=F=F=166.7NADE23=lBl=l=lBl=lMl/2AlBMl/3ABlMl/2ABθlMl/2BABlFBFAlFBM=0：F=FABBMMF=Ml/3ABFAFAFBM=0：F=FABBMMF=BlMFl/2FABABθlFBlM=0BF=FBMM：F=F=ABlcos93-3齿轮箱的两个轴上作用的力偶如题图所示，它们的力偶矩的大小分别为M=500Nm，1M=125Nm。求两螺栓处的铅垂约束力。图中长度单位为cm。2MM2AF50MFBABM=0Fl一M+MM=0B12MM500125F=1一2=MM500125Bl50：F=F=750NAB3-5四连杆机构在图示位置平衡。已知OA=60cm，BC=40cm，作用BC上的力偶的力偶矩大小为M=1N.m，试求作用在OA上力偶的力偶矩大小M和AB所受的力F。各杆重21ABBABM2M1OFCCBM2FBM=0FBCsin30oM=0B2M1F=2==5NBBCsin30o0.4sin30oF’AABF’BF'=F'=F=5NABBAFAM1FOM=0FOA+MM=0A1A2BABM=3A1CqqC2M=8A.80.8BBDy2BABxFAxFxFAxFFBAyBxAxF=0.4kNAAxBBF=0:y约束力的方向如图所示。AyBF=1.24kNAyyq=22BM=3BAxFdxxxFdxxAAy12BBAy0F=0:FyAyFBBx约束力的方向如图所示。AyB0AxBF2.12kNAxyyM=FAxAFAxAxFAyCCBDFB0.80.80.80.8F=0:F=0xAxAy约束力的方向如图所示。B0F21kNB0AyBAy4-13活动梯子置于光滑水平面上，并在铅垂面内，梯子两部分AC和AB各重为Q，重心在AAhllaDEPBCAyllPQPQQDExBCBBB22CyBCB2lFFAyFAxhQFDBFBDAlxM(F)=0:AB2D均布载荷集度q=10kN/m，力偶M均布载荷集度q=10kN/m，力偶M=40kNqMADABCaaaaaMyqdxMqDCFCFCFDaxdxFDaaCD0F=5kNDDyC0DF=25kNCyqdxqABCxABF’CFFABaCFFABaBy约束力的方向如图所示。AC0AABC0B图所示，载荷如图，试求刚架的支座约束力(尺寸单位为m，力的单位为kN，载荷集度单位为kN/m)。3C3BADBA4A3BDB6CDCDyyxxdxC3BABDFxDFAx4FFAy4FBF=0:F+100=0xAxAxAy约束力的方向如图所示。B1BAy1BAyCFCFFCxxdxD3FDCD0DyF=50xdx3ABxDABxFAxFAyF3FAyFBBxAxF=50kNAxAy0DFAyAyy约束力的方向如图所示。Ay0BDBxzybBFDAACMa5-5作用于半径为120mm的齿轮上的啮合力F推动皮带绕水平轴AB作匀速转动。已知皮FFFByFB20oBDyDFAyFFAyAFAxxxFNFxFNFxxFFN1kN(+)x-)2kNFNxx2用，试校核桁架的强度。BBCAFyFFABAC4AxAFFFFFF=0FF=0yFsin300+Fsin450=0ABACFcos300+Fcos450F=0ABACFFAC222F=F=58.6kN=FAB=82.9MPa[]ABA1=FAC=131.8MPa[]ACA2所以桁架的强度足够。SWllBA2CyFABAF=F=2F=70.7kNFCFFABFACF=F=50kNABll12Fll12FFAB50103160MPad20.0mmABA11d2S4ACAb2WACAb2W2所以可以确定钢杆的直径为20mm，木杆的边宽为84mm。FAC22F2FFAB312FFAB31160MPaF154.5kN412FFAC31160MPaF97.1kNACA1d2428-18图示阶梯形杆AC，F=10kN，l=l=400mm，A=2A=100mm2，E=200GPa，试计算杆1212FFABCFFFFNN2lllFlN11FlN2212EAEA12AC杆缩短。8-26图示两端固定等截面直杆，横截面的面积为截面上的最大拉应力与最大压应力。ABFl/3l/3A，承受轴向载荷F作用，试计算杆内横DFFl/3=N=N2==N1=ABCDFFAFFBF=0FF+FF=0xABxF=FF=F+FF=FN1AN2AN3Bl+l+l=0ABBCCDl=FlN1ABl=FlN2BCl=FlN3CDABEABCEACDEAF=F=F/3ABF2Fl,maxA3AFFy,maxA3AlalaaDBCDFFN1FN1FN2FBxBDFByFlFFlFlBN1N221 EAEAN2N14F=FF=FN15N25 A的强度足够。MPa，许用挤压应力[σ]=340MPa。板件与铆钉的材料相等。bsbFFF66FdFd141F (=Fb=4=125MPa共[(]=340MPabsAd6bsb对板件受力分析，画板件的轴力图；2F/4F/4F/4F/4bF=FN1=4=125MPa[]=160MPa1A(b2d)61=FN1=F=125MPa[]=160MPa1A(bd)61所以，接头的强度足够。l/l/l/l/qFBBAABBAl xF2FxB1BARARRACR=FARR=FACF=F(0xF=F(l/2xF=F(0xF=F(l/2xS111l)M=F(lx)(l/2xl)221FFFS x(-)FMx(-)Fl/2qBABx(0xl)F=qlqx=q(l(0xl)S44M=qlxqx2(0xl)142FSqlMMxx10-5图示各梁，试利用剪力、弯矩与载荷集度的关系画剪力与弯矩图。FFlFBABl/2ll/2Aql/2qlll/2qlBqql2qqql2BBqBBAAAl/2l/l/2l/2l/l/2qqqBBAABBAl/3