STRENGTH OF MATERIALS II
Homework #3, Submission: May 5, 2021
PROBLEM 1. The state of strain at a point on an experimental aircraft wing has components, ɛx = 300 (10-
6), ɛy = -480 (10-6) and xy = -750 (10-6). Based on this information,
a) Determine the equivalent in-plane strains on an element oriented at an angle of 60o clockwise
from the original position and sketch the deformed element due to these strains within the x–y
plane.
b) Determine the in-plane principal strains and specify the orientation of the element and show how
the strains deform the element within the x–y plane.
c) Determine the maximum in-plane shear strain and average normal strain. Specify the orientation
of the element and show how the strains deform the element within the x–y plane.
PROBLEM 2. A bracket is loaded as shown in the figure. In order to determine the location and weight of
a particular hanging load P, a strain rosette is attached to the top of the bracket near the wall (assume
strain gages are at the wall). The rosette has three gauges, each are 120o apart as shown in the diagram.
The bracket material is steel, E = 210 GPa and = 0.3. When the weight, P, is placed at a distance, s, on
the rectangular bracket arm, the three gauges measure the following strains, εa=224.8 microstrain, εb=-
118.3 microstrain, εc=132.9 microstrain. From these three strains, determine the load, P, and the distance,
s.
