Tuesday, October 3, 2000
"When you manufacture a part, the final shape of the part isn't
always the same shape as the mold from which it was formed," says Philippe
Geubelle, a professor of aeronautical and astronautical engineering at the
University of Illinois (Urbana, IL). He says the difference is caused by
residual stresses that build up in materials. "We need to understand the
residual stresses to predict the final shape of a product," he says.
Residual stress build-up occurs because each of the materials
included has its own thermal expansion properties. For example, as materials are
heated and cooled, the differing materials expand and contract according to
their expansion properties, creating stresses in the part that deform it after
it comes out of the mold.
"If you make a part that is supposed to have a 90-degree bend,
residual stresses might make it 91 or 92 degrees," says Geubelle. "Those few
degrees might make a big difference if the part spans a long distance, such as
an airplane's fuselage," he says.
Geubelle and his colleagues Charles Tucker and Scott White are
developing a software program that will help engineers compensate for warpage
and deformation due to residual stress build up. For more information, contact
Geubelle at the University of Illinois, 306 Talbot Lab, 104 S. Wright St.,
Urbana, IL 61801 or e-mail firstname.lastname@example.org.