The PICNIC TABLE

1
The PICNIC TABLE
by Jill Hood Sarah Young
2
Table Details

• Camping table designed to seat four
• Constructed of lightweight aluminium
• Folds away for easy travelling

3
Analysis Details

• Firstly analysing the difference in strength and
  stability of the join in the middle of the table,
  if it fixed or hinged or partially hinged.
• Secondly the stability of the table with the best
  outcome from the above analysis will be checked
  by placing different loading conditions on the
  seats.

4
Analysis Details

• For the analysis of the three different hinge
  mechanisms of the table, three different models
  were needed.
• For the Fixed table, half the design table was
  mirrored and connected.
• For the Partially hinged table the half design
  table was mirrored and the connecting line was
  fixed in the y direction.
• And for the Fully hinged table the half design
  table was mirrored and offset 5mm, and joined at
  the nodes by small solid beams.

5
Analysis Assumptions

• We visited the table and recorded all dimensions
  possible, to construct a model as real as
  possible to practicable.
• However some connections and beams were
  simplified to allow input into Strand 7.
• Hinge designs had to be simplified as they were
  difficult to input into Strand 7.

6
Design Procedure

• The table was started by modelling one of the
  seats, using beam and plate elements, then
  mirroring it.

7
Design Procedure

• Next half the table top and the connections were
  added. Beams were then offset to ensure they were
  connected to the plates.

8
Design Procedure

• The half table design was then mirrored to create
  the whole table, and loading conditions of an
  100kg person were placed on each seat, while an
  equivalent load of 100kg was also placed on the
  table.
• These loads were all entered as face pressures
  into Strand 7.

9
Final Table Design
10
Difficulties in Design

• One of the main difficulties in designing this
  table was the different cross sections of the
  beams, which meant beams and plates were not
  acting together. This was overcome by offsetting
  the beams, so their centroids were meeting at a
  joint.
• Beam cross sections
• Offset examples
• The hinges were also difficult to design, and had
  to be simplified greatly.

11
Beam Geometry

• The table consisted of many different sized beams
  with different cross sections

12
Hinges
Fixed Table Connection
Hinged Table Connection
13
(No Transcript)
14
Material Properties

• As the specifications on the box only stated that
  it was created of aluminium alloy, we needed to
  decide what type of alloy to use. The One Steel
  website contained tables with the general types
  of aluminium and what it was used for. It was
  decided to use 1200 H18 for the beam elements as
  this was for general purpose structural. For the
  table and chairs 6063 T6 and T5 were used
  respectively. This is also general purpose, but
  has a slightly higher yield strength, which was
  needed due to the load conditions.

15
What Did We Test?

• Different types of hingeshow did this effect the
  results?
• What happens if
• People are not sitting on all chairs
• A person is sitting on just the table
• The table thickness is changed
• How does the above affect beam plate stresses
  and node displacements.

16
Aluminium Alloy Property Chartby Onesteel
17
(No Transcript)
18
Chair Loading Effect
19
(No Transcript)