A set of six M8 bolts are used to provide a clamping force of 20 kN between two components in a machine. If the joint is subjected to an additional load of 18 kN after the initial preload of 8.5 kN per bolt has been applied, determine the stress in the bolts. The stiffness of the clamped

Question

A set of six M8 bolts are used to provide a clamping force of 20 kN between two components in a machine. If the joint is subjected to an additional load of 18 kN after the initial preload of 8.5 kN per bolt has been applied, determine the stress in the bolts. The stiffness of the clamped components can be assumed to be three times that of the bolt material. The proof stress of the low carbon steel bolt material is 310 MPa.

Accepted Answer

Taking [latex]k_c = 3k_b[/latex],

[latex]F_{b}=F_{i}+\frac{k_{b}}{k_{b}+k_{c}} F_{e}=F_{i}+\frac{k_{b}}{k_{b}+3 k_{b}} F_{e}=F_{i}+\frac{1}{4} F_{e}=8500+\frac{18,000 / 6}{4}=9250 N[/latex]

[latex]F_{c}=F_{i}-\frac{k_{c}}{k_{b}+k_{c}} F_{e}=F_{i}-\frac{3 k_{b}}{k_{b}+3 k_{b}} F_{e}=F_{i}-\frac{3}{4} F_{e}=8500-\frac{3(18,000 / 6)}{4}=6250 N[/latex]

As [latex]F_c[/latex] is greater than zero, the joint remains tight. The tensile stress area for the M8 bolt can be determined from

[latex]d_{p}=8-0.649519 imes 1.25=7.188 mm[/latex]

[latex]d_{r}=8-1.226869 imes 1.25=6.466 mm[/latex]

[latex]A_{t}=\frac{\pi}{16}(7.188+6.466)^{2}=36.61 mm ^{2}[/latex]

The stress in each bolt is given by

[latex]\sigma=\frac{F_{b}}{A_{t}}=\frac{9250}{36.61 imes 10^{-6}}=252.7 MPa[/latex]

This is 82% of the proof stress. The bolts are therefore safe.

Question 16.2: A set of six M8 bolts are used to provide a clamping force o...

Related Answered Questions

Verified Answer:

A self-locking power screw is required for a screw jack. An initial proposal is to use a single start 1.25-5 Acme power screw. The axial load is 4000 N and collar mean diameter is 1.75 in. Determine the lifting and lowering torques, the efficiency of the power screw, and whether the design ...

Verified Answer:

The Araldite for which data are given in Figure 16.24 is to be used for joining two sheets of metal. The joint should support loads of up to 180 N/mm width. If an overlap of 10 mm can be accommodated, determine the optimum sheet thickness. ...

Verified Answer:

Determine the optimum overlap for a simple lap joint for 1/16 in. sheet metal if the maximum load is 250 N/mm wide. Use the Araldite for which data are given in Figure 16.24. ...

Verified Answer:

Verified Answer:

An M10 bolt has been selected for a reusable application. The proof stress of the low carbon steel bolt material is 310 MPa. Determine the recommended preload on the bolt and the torque setting. ...

Verified Answer: