CHAPTER 2

THERMAL STRESSES AND COMPOSITE BAR

Unit 4

Example :A series composite bar from the same material have a force P1 = 70kN , P2 = 120kN , P4 = 300kN, as figure 4.1 below calculate :

a. P3

b. total elogation if E = 210GPa

20cm

P4

10cm15cm

A

B

CP3P2

P1

2m 1m1.5mFigure 4.1

4.2 Paralell Composite Bar

BAR 1

BAR 2

Base on figure 4.2 above the parallel composite bar will bring out the same elongation and compression. Each bar consist the same Total Force

Figure 4.2

example :

A typical composite bar might be a cylinder made of steel and diameter of 50mm is put into a hollow bar that made of copper and outside diameter of 70mm. Consider the whole bar have the same length of 200mm being compress by a force 250kN at each end

Given : Esteel = 207GN/m2 , Ecopper = 107GN/m2 calculate:a. Stress in steelb. Stress in copperc. Change on length

Practice:A steel cylinder is 0.5m outer diameter and 0.4m inner diameter and 1.5m long. It is filled with concrete and used as a vertical column to support a weight of 30kN. Determine the compression and the stresses in both steel and concrete.

Given :Esteel =205GPa

Econcrete = 10GPa

Unit 5

example :

Two cylinder bar as figure 5.1 below have the change of temperature of 70C. Calculate the stresses. Given:

Esteel = 200GN/m2 ⍺steel = 12 x 10-6/C

Ecopper = 112GN/m2 ⍺copper = 17 x 10-6/C

copper steel

100mm 100mm30mm

figure 5.1

example :

A parallel composite bar of length 1m made of glasses and magnesium as figure 5.2. each bar have 30mm wide and 15mm thick, calculate:

i. stress in glasses and magnesium when the

tempurature rise from 18C to 30C ii. stress in glasses and magnesium consider the whole bar being compress by a force of 12kN Given : Eglass = 75GN/m2 ⍺glass = 8 x 10-6/C

Emagnesium = 41GN/m2 ⍺magnesium = 25.2 x 10-

6/C

15mm

30mm

1m

figure 5.2

glass

magnesium