UNIVERSITY OF NEWCASTLE UPON TYNE
SCHOOL OF MECHANICAL AND SYSTEMS ENGINEERING
MECHANICS OF SOLIDS
Strengths & Testing Laboratory
DOWNHILL SKI PROJECT
Skis are designed with a number
of criteria in mind. One of these is stiffness
skiers want skis that are
neither too stiff nor too flexible. Looked at from this point of view, a ski is a beam with a somewhat
more complex shape that is treated in standard textbooks on the strength of ma
terials. In this mini
project you are asked to investigate the stiffness of a ski of a construction that was regarded as a high
tech in 1998. Find out all you can about it in the three weeks you have available.
Things you need to know:
A good start
ing point for background detail is the case study described by Gibson and
Ashby (L.J. Gibson and M.F. Ashby,
, Pergamon Press 1988, Chapter 9.5:
Library reference 620.11
GIB, in the Undergraduate Reference Collection).
You can test th
e ski stiffness using very simple equipment. Do not load it with more than
about 10 kg mass. It is advisable to load the beam symmetrically, e.g. loading point half
way between the supports in three
The thickness of the aluminium skin is 1
.8 mm (for black ski) and 1 mm (for purple ski).
The thickness of the polyethylene coating on the bottom surface is 1.2 mm. Young’s
modulus for aluminium and polyurethane foam are 70 and 0.4 GPa respectively; the shear
modulus of polyurethane is 0.2 GPa.
Useful expressions for sandwich beams are provided on an information sheet.
Determine what dimensions to measure and set out a method for calculating the stiffness.
Decide what features of the beam construction can be ignored in t
Discuss any interesting aspects of ski design that may have emerged in your investigation.
Report a figure for ski stiffness under clearly specified conditions.
Say why you think it is useful to be able to calculate the stif
fness rather than to rely only
on the experimental measurements?
Revise Date: 2.3.2007.
Lecturer: G.R. Johnson
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