機械設(shè)計5第56章連接(編輯修改稿)
2025-02-04 15:12 本頁面
【文章內(nèi)容簡介】 tiffness should be as small as possible, the remendation is ： metal gasket (or no gasket) ～ ， leather gasket (皮革墊片 )， copper asbestos gasket(銅皮石棉墊片 ) ， rubber gasket(橡膠墊片 )。 mbbCCC?—— Relative stiffness of the bolt （ 1） Static strength formula： F is a constant ? ?? ??????212124FddF????※ ： 1） to reduceF2， you must reduce relative stiffness of the bolt， ., ↑Cm ↓Cb 2） to keep tightness of the bolt conn., F1 must be larger than 0 FCC CFFFFmbb?????? 002（ 2） Formula of fatigue strength： F=0~F SKKSdFCCCacambba????????????)2)(()(222m i nm i n121m i nm a x??????????????F=0~F→F2=F0~ F2, variable stresses are between σmin ~ σmax 210m in212m a x44dFdF??????σa J G σm A C M N N3‘ σminN 3 Tight bolt conn. under shear stresses Reamed hole bolt: the lateral force F is equilibrated by shear and pretighting loadings ? ?ppLdF ?? ??m i n0 Crushing strength between the bolt and the hole： Notice： 1） d0 is the diameter of a shear plane 2） Lmin is minimum height of the pressive plane 3） 〔 σp〕 is the smaller of the materials ? ???? ??204dFShear strength of the bolt： Notice： 1） d0 is the diameter of a shear plane 2） Lmin is minimum height of the pressive plane 3） 〔 σp〕 is the smaller of the materials Homework ? Problem 59 on page 102 (8th Edition) Performance rate (性能等級 ) of Bolts, the screws and doublescrew bolts—— including ten levels(Table 58) the digits before the decimal point indicate ?B/100, and after the decimal point ?s/?B ., indicates σB=400Mpa and σs=320Mpa Performance rate of the nuts—— including 7 levels (Table 59) The digits indicate roughly ?min/100 I Materials of conn. pieces 167。 57 Materials and allowable stresses of Conn. Pieces II Allowable stresses of conn. pieces S、 Sτ、 Sp —— Safety factor (Table 510) ※ ： To search safety factors for Tight bolt conns., pilot calculation (試算 ) is necessary. ? ? ? ?pp ( S te e l sss BppSSSS?????? ?????? ? ? ???? ? ? ?） （ Cast iron ）Aim： Shapes of adjoining plane—— symmetrical, convenient for manufacture, same centroid(形心 ) Bolt arrangement—— enough space and edge distance for a wrench (扳手 ), see Table 55 I Structural design of the bolt groups 167。 5— 6 Design of bolt groups Processing and installation—— Diameter and length of the bolts is the same Amount of bolts on the circumference should be 4, 6 and 8 Adjoining plane and bolt—— uniform stress distribution, avoid additional bending moment. Lateral loads Axial loads II Mechanical analysis on bolt groups Loading types Aim： Find out the bolt subjected to the largest force and solve the force Torque Bending moment Equilibrium condition： f F0 z i≥Ks F∑→F0 ≥Ks F∑ ／ z i f Ks— Antiskid coefficient, Ks=~ i— Number of adjoining planes f— friction coefficient (Table 56)
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