Section Modulus calculation and optimization

Hood Section Modulus Calculation and Optimization

Section Modulus

• The ratio of total movement restricted by the section to the stress in the extreme fiber
• If the section modulus increases the movement of resistance increases and hence its load-bearing capacity.

Formula:

S = i/y

Where,

S = Section Modulus (mm³)

i = Moment of Inertia (mm⁴⁾

y = distance between the neutral axis and the extreme end of the object (mm)

Case 1: Calculating Section Modulus for Existing Hood

Creating External Boundry for Section Inertia Calculations

• Take the Clip section of the current Hood Inner Panel and Hood Outer Panel
• Specify the plane on which section needs to be made (In this case XY plane)
• Scroll down to Section Curve Setting > Select Save Copy of Section Curve to get the selected section.

• Now to edit the section we need to project the Section on the New Sketch on a parallel plane by selecting the external boundaries of the Hood Outer Panel and Hood Inner Panel.

• Now join both projected curves as shown in the image below, to calculate Section Inertia.

• Further, search for Section Inertia Analysis and select the current curve.
• Detailed information about Center of Gravity, Max Moment of Inertia, Min Moment of Inertia, Section length, and Section Aera will be displayed.

Calculations:

Inputs

Max Moment Of Inertia (i_max)= 8.240963433x10⁵ mm⁴

Mim Moment Of Inertia (i_min) = 6.251384949x10³ mm⁴

Distance between two extreme ends = 478mm

i.e: Distance between the neutral axis and the extreme end of the object (y) = 478/2 mm

y = 239 mm

Section Modulus for Existing Hood (S₁) = Moment of Inertia (i)

Distance between the neutral axis and the extreme end of the object (y)

Therefore,

by considering min moment of inertia (i_min)

S₁ = 6.251384949x10³ mm⁴ / 239 mm

S₁ = 26.15642 mm³

Case 2: Calculating Section Modulus for Optimized Hood

• To improve section modulus, the area of the section needs to be increased,
• Offsetting the Projected curve of the Hood Inner Panel by 0.5mm.

Section Inertia Analysis

Calculations:

Inputs

Max Moment Of Inertia (i_max)= 8.215689200x10⁵ mm⁴

Mim Moment Of Inertia (i_min) = 6.453749426x10³ mm⁴

Distance between two extreme ends = 478mm

i.e: Distance between the neutral axis and the extreme end of the object (y) = 478/2 mm

y = 239 mm

Section Modulus for Optimized Hood (S₂) = Moment of Inertia (i)

Distance between the neutral axis and the extreme end of the object (y)

Therefore,

by considering min moment of inertia (i_min)

S₂ = 6.453749426x10³ mm⁴ / 239 mm

S₂ = 27.00313 mm³

Conclusion:

1. Section Modulus of Case 2 is greater than Section Modulus of Case 1

2. Section Modulus is directly proportional to Moment of inertia and Section Area

i.e: As section area increases valve of Section Modulus increases.

3. Case 2 will have greater strength than Case 1 and will have increased load carrying capacity.