How to Determine Bolt Length and Stiffness for Aluminum Plates

What is the importance of determining bolt length and stiffness for two aluminum plates?

Why is it essential to consider bolt length and stiffness when designing a bolted joint for aluminum plates?

Answer:

When working with two identical aluminum plates that are compressed with one bolt and nut, determining the bolt length and stiffness is crucial for ensuring the stability and durability of the joint. The bolt length needs to be sufficient to prevent the joint from coming apart, while the bolt stiffness must be adequate to prevent the joint from buckling under stress.

In this scenario, the bolt length can be calculated using the equation: L = t1 + t2 + h + d + n, where t1 is the thickness of the first plate, t2 is the thickness of the second plate, h is the thickness of the washers, d is the thickness of the nut, and n is the number of threads per inch. Using the given data, the bolt length is calculated as 1.31 inches, which is rounded up to 1.33 inches as the nearest available preferred number.

Furthermore, the bolt stiffness can be determined using the equation: k = E*A / L, where E is the modulus of elasticity of the bolt material and A is the cross-sectional area of the bolt. The calculated bolt stiffness for this setup is 106,000 in-lb/psi, which indicates how resistant the bolt is to deformation.

Considering the bolt length and stiffness is essential during the design phase of a bolted joint, as it ensures the structural integrity and performance of the connection between the aluminum plates. By calculating these values accurately, engineers can ensure that the joint will withstand the expected loads and environmental conditions.