Section Modulus calculation and optimization

                                                                                                            IMPROVING SECTION MODULUS 

Sectional Modulus is an important mechanical property for any part, because it tells us about the Load resisting ability of the part. This property becomes even more important when it comes to Automotive parts because, safety becomes paramount while designing Automotive parts. Even more so when designing parts that get impacted directly in case of a crash. So, we need to make sure that our design provides the part with the best possible Sectional Modulus. 

Sectional Modulus - 

Sectional Modulus is defined as the ratio of Moment of Inertia of the part to the distance between neutral axis and extreme point of the part. 

                                                                                                  S = I / y

                                                               where, S - Sectional Modulus;

                                                                        I - Moment of Inertia;

                                                                        y - Distance of the Neutral axis to the extreme point of the part.

As mentioned earlier, Sectional Modulus tells us about the Load bearing capacity of the said part. So, higher the Sectional Modulus, better it is in terms of the ability to abosrb loads. 

As it can be seen from the formula, the factors affecting the Sectional Modulus are Moment of Inertia and the distance of neutral axis to extreme point. So, technically, in order to improve the Sectional Modulus, we either increase the Area Moment of Inertia or we decrease the distance between the neutral axis and the extreme point of the part. But, in our case, we have a limitation in terms of the length of the hood we design based on the master sections. So, the only property we can change in order to improve the Sectional Modulus is the Moment of Inertia.

So, we need to increase the Area Moment of Inertia of the Hood in order to increase the Sectional Modulus of the Hood. 

Distance of Neutral axis from the extreme point of the part - (Constant throughout) 

                                                           

                                                                           The distance "y" is 477.5 / 2 = 238.75 mm. 

Initial Moment of Inertia of the Hood -

                                                                       

                                                           Minimum Moment of Inertia is considered. It is 7145.287594 mm^4. 

                                                                                  =  7145.287594 / 238.75

                                                                                                 =  29.9279

Updated Moment of Inertia of the Hood -

                                     

                                                            Minimum Moment of Inertia is considered again. It is 7345.171146 mm^4.

                                                                    Using these in the Sectional Modulus equation, we get -

                                                                                    =  7345.171146 / 238.75 

                                                                                                 =  30.9121

As we can see there is an increase of around 1 mm^3 in the Sectional Modulus upon increasing the Moment of Inertia of the Hood. 

This was acheived by offsetting the Inner panel by 0.6 mm away from the Outer panel. Increasing it any further would affect the Hemming tolerances of the Assembly.