Unformatted text preview: 2.15. [2.2] A horizontal shaft transmits a torque T of 50 N7
m to a tube, as shown in Fig. P.2.15, thmugh a rubber canĀ»
hector glued to both members What is the shear stress on
elements of cylindrical surfaces in the rubber connector cone
centric with the shaft as a function of r, the radius of the
aforementioned cylindrical surface? 2.11. [2.2] Shown in Fig. P.2.l7 are two plates fastened
together by three rivets in what is called a lap joint, What is
the average shear stress river the sections of the rivets in the
plane of the Interface between the two plates assuming that
each rivet transmits the same load? In rivet calculations it is
American practice to discount frictional forces between the
plates (this gives an added measure of safety in deSign). If
across all cross sections of the plates (i.e., along cuts across
the width of the plates including those like 14ā11) the normal
stress is assumed unitonn for each such section, What section
has the largest stress. and what is the value of this stress?
Again, do not consider friction. 17:125mn Figure thus 12.5 mm \
12.5mm \
7 Will/āIII,ā
hāā\ā\\ā\ V l 40033 N Figure ā.17. Shear Stress "3:25 i = 40,000 3(13) ā
is = 1,086 x 103 Pa Section with largest tensile stress is '
along centerliue of rivets. Thus (t")(.0125)[.15D(3)(.0125)] = 40.090 Tn = 2.844 X 107 Pa 2.39. What is the maximum torque T transmitted by the
flange connection in Fig. P239? There are eight bolts each
having a diameter of 5 mm The maximum allowable stress
per bolt is 300 MPa. FBD Fball F 501! = TA
7z'(0.005)2 =(300x10ā)
=5890N
2T = 0 ' T = ngBult
= (8)(O.200)(5890) 2.49. In Fig. 132.49 we show a section of a shaft A rotating
concentrically with speed to inside a journal bearing B and
separated from B by a film of oil of thickness e and viscosity
u. Newtonās viscosity law r = Mall/er) gives the shear stress
on interfaces normal to radius r in the oil. If there is a linear
profile of the oil and if it āsticks" to the metal surfaces (i.e., it
has the same speed as the surface at the surface), what is the torque T needed to rotate the shaft? Take the length of the
hearing to be L. Velocity
proļ¬le < The velocity profile is determined as fol
lows: _ (rr)
V=mt"  0 0 (or 0) Note profile is linear and V = 0 at r = r0 + e as required. Simplifying:
rr
. _ _ o
. . V ā wroU e ] Use Newton's viscosity law: d
it indāl = ulmroltā 1,)
The shear stress is thus the same for all interfaces having a radial direction.
Hence, to get torque T noting diagram we can say dT It dA To our ( EĀ°)(rD de L)rĀ° il ...
View
Full Document
 Spring '08
 PITTERESSI

Click to edit the document details