Transcript Structural Requirements

SMC 4133 AUTOMOTIVE STRUCTURES
BODY STRUCTURAL ELEMENT
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Consists of frames and panels
Made of thin-walled structural elements
Non-symmetrical section
Forms of several pieces using spot weld
All materials in this slide are taken from Donald E Malen. 2011. Fundamentals of Automobile Body Structure Design, SAE International.
SMC 4133 AUTOMOTIVE STRUCTURES
CLASSICAL BEAM BEHAVIOURStructural Requirements
All materials in this slide are taken from Donald E Malen. 2011. Fundamentals of Automobile Body Structure Design, SAE International.
SMC 4133 AUTOMOTIVE STRUCTURES
BEAM STIFFNESS
Structural Requirements
INSPIRING CREATIVE AND INNOVATIVE MINDS
All materials in this slide are taken from Donald E Malen. 2011. Fundamentals of Automobile Body Structure Design, SAE International.
SMC 4133 AUTOMOTIVE STRUCTURES
EXAMPLE 1
Structural Requirements
Does the given section size meets both requirements?
Answer: Stress = 208N/mm^2, Deflection = 5.6 mm
INSPIRING CREATIVE AND INNOVATIVE MINDS
All materials in this slide are taken from Donald E Malen. 2011. Fundamentals of Automobile Body Structure Design, SAE International.
SMC 4133 AUTOMOTIVE STRUCTURES
AUTOMOTIVE BEAM SECTIONS
• Beam sections in a body structure are
commonly
non-symmetrical
Structural
Requirements
• Deflection of the beam generally will not be collinear with the applied load
• Use principle axis to find deflection that collinear with the load
Deflection
- Resolve the load
- Solve for the resulting deflection
- Calculate the resultant deflection
Stress
- Resolve the moment
- Solve for the resulting stress
- Find the resultant stress
All materials in this slide are taken from Donald E Malen. 2011. Fundamentals of Automobile Body Structure Design, SAE International.
SMC 4133 AUTOMOTIVE STRUCTURES
EXAMPLE 2
Structural Requirements
Determine the tip deflection and the stress at point A.
y
x
INSPIRING CREATIVE AND INNOVATIVE MINDS
All materials in this slide are taken from Donald E Malen. 2011. Fundamentals of Automobile Body Structure Design, SAE International.
SMC 4133 AUTOMOTIVE STRUCTURES
• Point loading of thin-walled sections
Structural Requirements
All materials in this slide are taken from Donald E Malen. 2011. Fundamentals of Automobile Body Structure Design, SAE International.
SMC 4133 AUTOMOTIVE STRUCTURES
EXAMPLE 3
Structural Requirements
Determine latch structure stiffness.
Answer: K system = 33.2 N/mm
INSPIRING CREATIVE AND INNOVATIVE MINDS
All materials in this slide are taken from Donald E Malen. 2011. Fundamentals of Automobile Body Structure Design, SAE International.
SMC 4133 AUTOMOTIVE STRUCTURES
TORSION OF THIN-WALLED MEMBERS
Closed section
Structural Requirements
INSPIRING CREATIVE AND INNOVATIVE MINDS
All materials in this slide are taken from Donald E Malen. 2011. Fundamentals of Automobile Body Structure Design, SAE International.
SMC 4133 AUTOMOTIVE STRUCTURES
Structural Requirements
Non-uniform thickness
Uniform thickness
INSPIRING CREATIVE AND INNOVATIVE MINDS
All materials in this slide are taken from Donald E Malen. 2011. Fundamentals of Automobile Body Structure Design, SAE International.
SMC 4133 AUTOMOTIVE STRUCTURES
EXAMPLE 4
Structural Requirements
Determine the angle of rotation and the shear stress under the pure torque
of T =250 kNmm. Take shear modulus G = 78 Gpa.
Answer: Angle = 0.312 degree, Shear stress = 25 N/mm^2
INSPIRING CREATIVE AND INNOVATIVE MINDS
All materials in this slide are taken from Donald E Malen. 2011. Fundamentals of Automobile Body Structure Design, SAE International.
SMC 4133 AUTOMOTIVE STRUCTURES
Open section
Structural Requirements
EXAMPLE 5
Recalculate EXAMPLE 4 but now using open section as shown below
and comment on the result.
Answer: Angle = 803 degree, Shear stress = 2197 N/mm^2
All materials in this slide are taken from Donald E Malen. 2011. Fundamentals of Automobile Body Structure Design, SAE International.
SMC 4133 AUTOMOTIVE STRUCTURES
BUCKLING OF THIN-WALLED MEMBERS
Structural Requirements
• Most of the failure modes are caused by plate buckling of section elements
• Buckling stress of the rocker:
INSPIRING CREATIVE AND INNOVATIVE MINDS
All materials in this slide are taken from Donald E Malen. 2011. Fundamentals of Automobile Body Structure Design, SAE International.
SMC 4133 AUTOMOTIVE STRUCTURES
Critical compressive plate bucklingStructural
stress (simply
supported):
Requirements
a/b > 1
a/b < 1
Plate flexural rigidity
INSPIRING CREATIVE AND INNOVATIVE MINDS
All materials in this slide are taken from Donald E Malen. 2011. Fundamentals of Automobile Body Structure Design, SAE International.
SMC 4133 AUTOMOTIVE STRUCTURES
Buckling Stress
Structural Requirements
k = buckling constant
All materials in this slide are taken from Donald E Malen. 2011. Fundamentals of Automobile Body Structure Design, SAE International.
SMC 4133 AUTOMOTIVE STRUCTURES
Techniques to prevent buckling
Structural Requirements
Reducing width by adding a bead
Reducing width by chamfering corners
Reducing width by adding corners
INSPIRING
CREATIVE
AND INNOVATIVE
All materials in this slide are taken from
Donald E Malen.
2011. Fundamentals
of AutomobileMINDS
Body Structure Design, SAE International.