My question is why does sigma x = a number and sigma y = o? And why do they use
ID: 1730300 • Letter: M
Question
My question is why does sigma x = a number and sigma y = o? And why do they use negative N/A minus My/I?
Determine the principal stress in the beam at point A. 60 kN 50 mm 150 kN 150 mm 0.5 m 0.25 m Using the method of sections and consider the FBD of the beam's left cut segment Fig. a 150 N- N 150 kN V-60 () 60(0.5) M 0 A = 0.06(0.15) = 0.0()9 m V60 kN (006)0.15) 16.8750-m Referring to Fig. b, A 005 (005)(0.06 0.1510-3 m The normal stress developed is the combination of axial and bending stress. Thus N M For point A, y 0.075 0.050.025 m. Then 150 30100.025) 16.875(10) ?= 0.009 =-61.11(10°) Pa = 61.11 MPa (c)Explanation / Answer
The load 60KN causes the beam to bend along x-axis and the load 150KN is also acting along x-axis. So stresses will be along x-axis.
the 150 KN creates the compressive stress at A as its action is direct and the load 60KN causes bending of beam, since it is a cantilever beam the fibres below the nuetral axis will be in compression and point A also lies below NA. So -ve sign in both terms is due to compressive stress.
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