Spring 2005 W.Wang
ME 557 Homework #2
1. Two moiré fringe patterns obtained using a tensile specimen (at two different levels of deformation) are attached. Grating frequencies of 150 lines/in were used in both cases. Treat these patterns as “uniform” strain fields. Define the fringe “nearest” the 6-in scale position as n=0, where fringe order increases towards the 10-in scale position.
Infer the axial strain induced along the centerline of the specimen, as follow;
a) Calculate axial strain in accordance with: = np/(lg -np). Use the fringes which appear between the 6-in and 10-in scale locations… that is, define the gage length, lg, as lg ~10 in- 6 in = 4in
b) Calculate axial strain using the “calculus” approach as discussed in class, the fringe locations must be corrected for displacements in this case
2. A circular plate of radius R and thickness h with a transverse load P applied at the center undergoes a displacement
where is the flexural rigidity of the plate. Sketch the moiré fringe pattern observed if the optical arrange of shadow moiré as shown in class is used in the displacement analysis