Roof challenge

Aim: For the given roof styling, develop the essesntial flanges and reinforcements, provide appropriate dimensions and check for draft analysis and to perform roof curvature study using NX-CAD.

Roof:- An automobile roof or car top is the portion of an automobile that sits above the passenger compartment, protecting the vehicle occupants from sun, wind, rain, and other external elements.

The roof is a styling surface part which is fixed with the BIW body through the rails and panels inside the upper roof to provide it strength and stiffness.

Ditch area plays an important role here to fix the reinforcement on the component.

The rails and reinforcements are joined to the ditch area with a spot weld where it's not the styling part.

The required tool opening angle is minimum 3 Degrees.

Factors which is considered before creating Ditch area,

• Headroom clearance
• Visibility criteria
• Back door assembly
• Windshield assembly

• Components of roof:

  • Front roof rail
  • Rear roof rail
  • Bow roof
  • Centre roof rail
  • Ditch area

  • Curvature study on the Roof:

    After getting the final body it has to be checked and justify that it passes the standards.

    Analysis:

    It is done to justify the position of the bow roofs.

    1.Roof crash test.

    2.Snow load test.

    3.Heat distortion criteria

    Heat distortion temperature is a temperature at which the metal softens and deform under a specific load.This study is done to check the ability of the roof to withstand high temperature with respect to the position of the reinforcement which contribute to the increase strength.To calculate the heat distortion criteria by the bow roof position formula,

    • 1 ) We need to create a sketch , draw a line on the center of the roof on OY axis (mid horizontal axis)
    • 2 ) Next draw a line from the center line by a 300mm distance

    • Snow Load criteria:

      Snow load criteria study is done to check the ability of the to withstand snowfall and bounce back to its orgin#al shape without any permenant deformation once the load is removed.

      • To calculate the snow load condition, we have a snow load formula
      • To measure the required values
      • Created a sketch and draw a line on OY axis from the center of the roof
      • From that line draw a parallel line distance of 100mm on both sides
      • Then make intersection points of these lines and draw a three point arc
      3) After that draw a line from 100mm distance on both sides of the 300mm line
    • 4) Then draw a line between the center of roof rails and draw the lines from the center line by the distance of 100mm on both sides.
    • 5) Atlast make an intersection on these lines from a coincident line to get points.

  • • Snow Load criteria:

      Snow load criteria study is done to check the ability of the to withstand snowfall and bounce back to its orginal shape without any permenant deformation once the load is removed.

      1 To calculate the snow load condition, we have a snow load formula
    • To measure the required values
    • 3Created a sketch and draw a line on OY axis from the center of the roof
      • 4From that line draw a parallel line distance of 100mm on both sideThen make intersection points of these lines and draw a three point arc .
      • #
    • #

      Snow load prediction formula :Q_r =[(I_y × t²)/(α × s×(R_X+R_Y/2)² × 10^-8)]

      Where

      α = M_y× L_x²× 10^-12 ,M_y=Y(L_y -Y)

      Judgement Condition:Q_r≥3.1

      t=Roof plate thicness in mm

      L_Y =Distance between Front and rear roof rail on vehicle O-Y in mm i.e length of the roof panel with the centre point between roof rail FR/RR as the referance point of the front and rear

      Y=Distance from front roof rail centre to bow roof in mm

      S - Distance for which BOW bears divided load in mm

      S= L₁/2+L₂/2

      I_y=Geometrical moment of inertia of roof BOW (Cross-section)mm⁴

      R_x=Lateral direction curvature radius of roof panel Y cross section on Roof ROW in mm

      R_y =Longitudinal direction of the curvature radius of roof panel X cross section

    • RESULT:_

      • Essential roof components such as bow and center rails required with flanges and reinforcements are designed.
      • Curvature study on roof was analysied with heat distortion and snow load standards
      • Draft analysis was done to check toolablilty.