Viscoelasticity
Students are introduced to the concept of viscoelasticity and some of the material behaviors of viscoelastic materials, including strain rate dependence, stress relaxation, creep, hysteresis and preconditioning. Viscoelastic material behavior is compared to elastic solids and viscous fluids. Students learn about materials that have viscoelastic behavior along with the importance of engineers understanding viscoelasticity. To best engage the students, conduct the first half of the associated Creepy Silly Putty activity before conducting this lesson.
Silly putty is a great example of a viscoelastic material.Copyright Glitch010101, Wikipedia {PD} http://en.wikipedia.org/wiki/File:Silly_putty_dripping.jpg
When designing devices, engineers must understand how the materials that they select will react to the forces that the devices encounter. Since some materials are viscoelastic, engineers must know which materials these are and understand their behaviors. Bioengineers also study biological materials and how they function in healthy and diseased states. Biological materials are viscoelastic so bioengineers must understand viscoelastic behavior to fully characterize the behavior of these materials. As part of the process, engineers must also understand the environments in which their devices will operate to ensure effective and successful performance. For example, if designing a device to operate on viscoelastic materials in the human body, an engineer must understand and take into consideration how that environment will react to the forces imposed by the device.
After this lesson, students should be able to:
- Demonstrate an understanding of viscoelastic material behavior including strain rate dependence, stress relaxation, creep, hysteresis and preconditioning.
- Communicate scientific information about why the molecular-level structure of viscoelastic materials is important in the functioning of designed materials.
- List the types of materials that are viscoelastic.