Tensile testing

• Structural Properties– Load – Deformation– Stiffness– Ultimate load– Ultimate elongation

– These properties are dependent on cross-sectional area and length of specimen

• Mechanical Properties– Strain energy density– Modulus– Ultimate strain

– These properties are independent of CSA and length (i.e. same no matter what geometry is tested

Influences on testing

• Gripping (freeze clamps)

• Strain Rate

• Age

• Temperature

• Hydration

• Immobilization

Freeze clamps

• Also called cyrojaws.

• Use liquid N2 to freeze

• Must maintain freeze line

VDA

• Video extensometer• Local strains

Influences on testing

• Gripping (freeze clamps)

• Strain Rate

• Age

• Temperature

• Hydration

• Immobilization

Strain rates

• Avulsion versus mid-substance-– Some theorize that these effects are due to

strain rate, but REALLY depends on Age.

Influences on testing

• Gripping (freeze clamps)

• Strain Rate

• Age

• Temperature

• Hydration

• Immobilization

Mature versus immature, but then look at mature versus OLD

Age

• Puberty-adult see an increase in ult. Load

• Open epiphysis-avulsion

• Closed epiphysis (skeletally mature)-midsubstance

• Old-usually avulsion

• Stiffness decreases with age

• Ultimate load decreases with age– -see plot

Influences on testing

• Gripping (freeze clamps)

• Strain Rate

• Age

• Temperature

• Hydration

• Immobilization

Temperature

• Increase temp-decrease stiffness

• Race horses

• Tennis shoes

Influences on testing

• Gripping (freeze clamps)

• Strain Rate

• Age

• Temperature

• Hydration

• Immobilization

Waterbath

Influences on testing

• Gripping (freeze clamps)

• Strain Rate

• Age

• Temperature

• Hydration

• Immobilization

• How do we properly store a specimen for transplantation?– Freezing effects??– Irradiation?? Disease transmission

• Pre-tension on graft

Influences on testing

• Gripping (freeze clamps)

• Strain Rate

• Age

• Temperature

• Hydration

• Immobilization

• Exercise