167_Mechanics SolutionInstructors_Sol.Manual-Mechanics_Materials_7e.book_Gere_light.1

167_Mechanics SolutionInstructors_Sol.Manual-Mechanics_Materials_7e.book_Gere_light.1

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Sec_2.5.qxd 9/25/08 3:00 PM Page 161 161 SECTION 2.5 Thermal Effects Misfits and Prestrains Problem 2.5-12 A steel wire AB is stretched between rigid supports (see figure). The initial prestress in the wire is 42 MPa when the temperature is 20°C. (a) What is the stress in the wire when the temperature drops to 0°C? (b) At what temperature T will the stress in the wire become zero? 14 10 6/°C and E 200 GPa.) (Assume Solution 2.5-12 Steel wire with initial prestress From Eq. (2-18): 1 Initial prestress: 1 Initial temperature: T1 E 42 MPa (200 GPa)(14 20°C 42 MPa 56 MPa 1 T2 0°C 10 6/°C)(20°C) ; 98 MPa (b) TEMPERATURE WHEN STRESS EQUALS ZERO 10 6/°C (a) STRESS E ( T) 1 42 MPa 200 GPa 14 2 E ( T) 2 WHEN TEMPERATURE DROPS TO T 0°C 20°C 2 0 1 E ( T) 0 s1 Ea ¢T NOTE: Positive T means a decrease in temperature and an increase in the stress in the wire. (Negative means increase in temp.) Negative T means an increase in temperature and a decrease in the stress. ¢T Stress stress equals the initial stress 1 plus the additional 2 due to the temperature drop. T 42 MPa 15°C (200 GPa)(14 * 10 6/°C 20°C 15°C 35°C ; 0.008 in. Problem 2.5-13 A copper bar AB of length 25 in. and diameter 2 in. is placed in position at A room temperature with a gap of 0.008 in. between end A and a rigid restraint (see figure). The bar is supported at end B by an elastic spring with spring constant k 1.2 106 lb/in. (a) Calculate the axial compressive stress c in the bar if the temperature 9.6 10 6/°F and E 16 106 psi.) rises 50°F. (For copper, use (b) What is the force in the spring? (Neglect gravity effects.) (C) Repeat (a) if k : 25 in. d = 2 in. B k C ...
View Full Document

This note was uploaded on 12/22/2011 for the course MEEG 310 taught by Professor Staff during the Fall '11 term at University of Delaware.

Ask a homework question - tutors are online