Viscoelasticity - Orthopaedic Biomaterials in Research and Practice - page 98

ANSWER:
HDPE—Because body temperature is well above the T g of HDPE, this
material will be characterized by more rubbery behavior and is thus
more susceptible to creep under constant loading.
PROBLEM 4.16
Characterize the following viscoelastic phenomena as more indicative of
creep or stress relaxation:
1. A polymeric component showing little signs of wear after explan-
tation has been significantly deformed from its original state
2. A decrease in tension in the rotator cuff ligaments as a result of
overuse
3. Skin wrinkles during the aging process
4. Straightening of teeth using orthodontic bracing
5. Stretching of the rotator cuff ligaments as a result of aging
ANSWER:
Creep, stress relaxation, stress relaxation, creep, creep.
annotated bibliography
1. Burstein AH, Frankel VH: The viscoelastic properties of some
biological materials. Ann NY Acad Sci 146:158-165, 1968.
An early but useful introduction to the viscoelastic properties of hard
and soft musculoskeletal tissue. Easy to read.
2. Coletti JM, Akeson WH, Woo SL-Y: A comparison of the physi-
cal behavior of normal articular cartilage and the arthroplasty surface.
J Bone Joint Surg 54A:147-160, 1972.
Illustrates the indentation test and discusses the behavior of normal and
abnormal cartilage. An appendix shows how the viscoelastic behavior of
these tissues may be represented by a model.
3. Dumbleton JH: Tribology of Natural and Artificial Joints . Elsevier,
Amsterdam, 1981.
Tribology is the combined science of friction, lubrication, and wear.
This is a good source on the orthopaedic aspects of these topics. Chapters 2
and 3 discuss viscosity.
4. Flugge V: Viscoelasticity . Blaisdell, Waltham, UK, 1967.
An intermediate level topic on viscosity. Chapter 1 covers the standard
test (this is the apparent source of this approach) and may be followed with
an elementary knowledge of differential equations.
5. Frankel VH, Burstein AH: Orthopaedic Biomechanics . Lea &
Febiger, Philadelphia, 1970.
Chapter 4 discusses viscoelasticity, using the body and model approach,
without mathematics.
6. Frisen M, Magi M, Sonnerup L, Viidik A: Rheological analy-
sis of soft collageneous tissue. Part 1: Theoretical considerations. Part 2:
Experimental evaluations and verifications. J Biomech 2:12-20, 21-28,
1969.