Section Modulus calculation and optimization

AIM: To find the Section Modulus of the hood and optimization to improve the overall Section Modulus.

SECTION MODULUS       

Section Modulus is a geometric property of a cross-section used in the design of flexural members that will experience deflection due to an applied bending moment. And the unit of the section modulus is `mm^3 or m^3`.

       " It is the ratio of area moment of inertia about the nuetral axis and the distance of the outermost fiber from the nuetral axis."

                     `Z = I/Y`   

                             Where `Z =` Section Modulus

                                        `I =` Area Moment of Inertia

                                        `Y =` Distance between outermost fibre from the nuetral axis.

Lets take Hood Assembly design to calculate area moment of inertia and thier distance from nuetral axis. But before going to calculate the inertia, first do inertia analysis of a HOOD.

INERTIA ANALYSIS OF A HOOD   

• If the cross-section is oriented like this which means impact is done by front side of hood and is always perpendicular to the cross-section axis.

         

• If the cross-section is oriented like this which means we are analysing side impact criteria, and is always perpendicular to the cross-section axis.

          

Hood Assembly Section Modulus analysis Process  

• Import Hood assembly in NX-CAD
• Activate the Hood Assembly
• Go to the part nevigator
• Create a datum plane exactly at the middle of the hood
• Create a intersection on Hood outer panel and hood inner panel
• If there is any gap inbetween the intersection so create a sketch and join those gap through studio spline command
• After that select the section inertia and take inertia from pop-up window 
• And then measure distance of the hood along the cross section and divide by 2 to get distance between outermost fiber
• Lastly use Section Modulus formula.

        Hood Assembly   

        

        Datum Plane and intersection about that plane

        

        

        Sketch 

        

        Section inertia (1st)

        

        Now for increase the strength, here we are going to offset the inner panel inetersection curve about 0.5mm and see the inertia again. Here we try to increase the inertia just becouse of inertia is directly proposional to the section modulus. 

        Section inertia 2nd

        

        Now measure the distance of the outermost fiber from the nuetral axis.

        For calcution of `Y` measure the distacne and divide by 2.

         

         Here, `Y = 438.50385 mm`

         Now Calculate the Section Modulus,

                                                    `Z = I/Y`

                Case-I,  [ `I = 2.952177750*e^5`]

                           `Z1 = I/Y`

                            `Z1 = (2.952177750*e^5) / 438.50385`

                            `Z1 = 0.99917 mm^3`

                Case-II, [`I = 2.981475838*e^5 mm^4`]

                              `Z2 = I/Y`

                               `Z2 = (2.981475838*e^5)/ 438.50385 mm^3`

                               `Z2 = 1.00909096 mm^3`

             Here we can clearly see that `Z2>Z1`

             It means when we offset the inner panel about 0.5mm, section modulus increase the strength of Hood Assembly.

CONCLUSION  

Hence Section modulus is succesfully calculated and also optimise to improve section modulus.