4材料在拉伸和压缩时的力学性能课件.ppt

1、Mechanics of Materials 钢压杆钢压杆 m m FFm m FFFNm m FFN FN ab m m FFm m FFN m Fm C A B D 600 300500400E40KN55KN25KN20KN R40KNFN2 C A B D E40KN55KN25KNR 2 0 40 R FN 2 = = - - - - ) ( 50 40 R + + + + = = + + = = FN2 20KNC A B D E40KN55KN25KN20KNR 4 ) ( 20KN + + = = FN4 FN3 F F F FNF k k F pFkkx n ApNF= =

2、= cosAA故有故有coscos =AFAFpNNAFN=F k k F S Fkkx n S maxmax=ANF maxAFNmaxNFAAFNmaxdh Fig.2 Tension Machine d l 标距标距 21 34 lFO EAFll =a) 弹性阶段弹性阶段 （elastic region)21 34 lFO 21 34 lFO 21 34 lFO C 21 34 lFO C lClS124 ll =AF =3A P P E=EAFll = Etg= bb C124 ll =3A P BD SGAF = %1001-=lll %AAA1001-=Fig.5 Yield S

3、trength and Ultimate Strength 0.20.2 0.2 割线斜率 ; tg=E脆性材料BrittleFig.4 Brittle vs. Ductile Behavior Fig.6 Necking Fig.10 Non-uniform Strain in Ductile Failure Fig.8 Ductile FailureFormation of Shear Lips nu= nS= nb= )F F b1h1b h LL1 LLL-=1 = = llEAlFlN= = = E=AFN = = ll(F1 F2 F3 1 1 11 11 111 111 l1 l

4、2 l3 A B C D F1 F2 F3 1 1 11 11 111 111 l1 l2 l3 A B C D R F1 （+）FN1F1 F2 F3 1 1 11 11 111 111 l1 l2 l3 A B C D R FN2 =-15KN （-）FN1 =20KN （+）FN3 =- 50KN （-）15 + - 20 50 F1 F2 F3 1 1 11 11 111 111 l1 l2 l3 A B C D R FN2 =-15KN （-）FN1 =20KN （+）FN3 =- 50KN （-）mEAlFlNBCBC1042. 1422-=mEAlFlNABAB1053.2411-=mEAlFlNCDCD1058. 1433-=F1 F2 F3 1 1 11 11 111 111 l1 l2 l3 A B C D )(.- -= =+ += =mmlluCDBCB30= =+ + += =llllCDBCABAD)(.缩短m104704 - - -l F m m Fx m m Ax (x)：+ F+ Al F A B C 12