Section Modulus calculation and optimization

Title –To evaluate section modulus for the hood assembly and suggest improved section modulus area.

Objectives-

1. To get section modulus for designed hood inner outer assembly
2. To suggest better section modulus for better performance

Introduction-

Section modulus is the defined as the ratio of total moment resisted by the section to the stress at the extreme fibres.

By knowing section modulus, we understand how much load will be carried by the structure without failure.

Load carrying capacity is directly proportional to the section modulus. Bigger the section modulus bigger the load carrying capacity for that structure.

The section modulus of the cross-sectional shape is of significant importance in designing structures. It is a direct measure of the strength of the structure. A structure that has a larger section modulus than another will be stronger and capable of supporting greater loads.

It includes the idea that most of the work in bending is being done by the extreme fibres of the structure, ie the top and bottom fibres of the section. The distance of the fibres from top to bottom is therefore built into the calculation.

The elastic modulus is denoted by Z. To calculate Z, the distance (y) to the extreme fibres from the centroid (or neutral axis) must be found as that is where the maximum stress could cause failure.

Calculation for section modulus-

Section modulus of section can be calculated by using formula given as

S=I/y

Where,

S= Section modulus

I= Moment inertia value from the inertia analysis

y= Distance from neutral axis to the outermost fibre

Section modulus study for the Hood Assembly

For the section modulus study, we are having Hood assembly. This assembly contains following parts

1. Hood outer panel
2. Hood inner panel
3. Hood hinge assembly LH+RH
4. Latch

Section modulus for the hood assembly is evaluated by considering hood inner and outer panels in assembled condition as shown in above figure.

By finding section modulus we need to try finding better section which will results in better section modulus than the existing one if possible, to increase the strength of the section.

Section Modulus for the existing hood design

Using NX cad software we able to find the

I_max=4.173004768e+08(mm⁴)

I_min=1.195216398e+06(mm⁴)

For the section modulus we always use minimum MOI as it is the value where section having more chances to be failed

Now we are going to calculate section modulus as,

S= I_min/y

S=1.195216398e+06/440…………………….(y=440 mm)

S=2,716.40 mm³

Section Modulus for the improved hood design

As section modulus for the existing design is less we having scope to improve it by changing current section to new one with better MOI.

We have found there are many embosses in current design, we try to eliminate some of the embosses and prepare new section as shown in below figure.

From above figure

I_max=7.549951422e+08(mm⁴)

I_min=1.798111639e+06(mm⁴)

Now we are going to calculate section modulus as,

S= I_min/y

S=1.798111639e+06/440…………………….(y=440 mm)

S=4,086.61 mm³

Comparison between old section with new one

1. As we have calculated section modulus for both sections, we come to know that from this analysis, later one is having more section modulus.
2. Since new section will have more section modulus, this section will have more strength than existing section.

Conclusion-

1. As the section area increased section modulus also increased
2. New section strength is more than existing section
3. More strengthen section will be more safer towards failure