Question

2. Figure (b) shows a bolt under tension (M20x2.5). The property class of the bolt is ISO 8.8. The design factor is na=3.0 for the bolt. Answer the following questions. (a) Determine the whole bolt length (L) of the bolt (consider 3 threads after the nut). What are the thread (Lt) and the shank (La) lengths of the bolt? (8 points). (b) Estimate the stiffness of the bolt in the grip (7 points). (c) The stiffness of the member is estimated as 5,500x106 N/m. When P=50 kN is applied without preload (F;=0 N), estimate the displacement of the bolt from the initial setting (10 points). (d) The stiffness of the member is estimated as 5,500x100 N/m. When P=50 KN is applied with preload (F=120 kN), estimate the displacement of the bolt from the initial setting i.e. before the preload) (10 points).

STEEL

Answer 1

Sdution : - Given data: - The property clouss of the belt is = 150 8,8 . The desigen factor iq=ha = 3:0 Pla . . 60mm I LEO /2 012 Sthreadą. M20x2.5 bolle (a). Length d put of thickness of mit = 14.spomene . [standar net Thund longehicle) = 34,95 + length of +2295 7.65+7;5 +14.99.7in The = 29.900m) size]

Length of shack (25) = 80-(3x2,5) : 123 = 80-715 Thength of shank (ks) = 72.5mm Length of bolt = length of shauk + length of - thread = 72.50 +29.9.0. | Cength of bot = 102.4 mm :: E = 19 Goal., (b) Shiffres et boilt. : - . ko - A ...here, A Aren of cross section E => Young's modulni . de length of bolt in grup 37 de --) x 20%x193x103 80X10-3 : =) 757.90922 xlo NIM.

(C) Given: - stiffness of the member ią Esticealed . .. => 5; 50 x10$ when p-50 KN trember Witwa = p It if given that stifforss of member :- K4 =51700 X10%N/M. bolt

Ce stiffriss factor = kb (4) korken C = 757.90922X 106NIM (157.90922x106)+ ( 5900x108) - Le = 0,12112 of pretension load = fpretension = 0 nel-bolt - Fofre twic =>p.c

=) 50kry $0.127112 Writ bot =) 6.0556KN stiffress. = kb.-) writ bot ...Y=> Whet bot .. kb. =6.0556x10°N : ..757.90922x10 N: ya 0.007989 mm TY= 71989*103 mm) id) if fpsreland. = 120KN Whet bolt = Fpielcond twice = 120kN + (0.12001950)... je 126.0556KN Sedeflection - Whet bolt 196.0556X16% 757.90922 XI0 = 0.16632 mm 1S deflection = 0.16632 mm