SECTION A6.3 EXAMPLE2

Like in example A6.2 we find the strain in one of the materials if it were stressed to its limit, then find the corresponding maximum stress in the other material. Then do the same thing the other way around. The maximum torque that will allow both materials to remain in its elastic region will be the answer.

First, let the steel bolts reach thier maximum allowable stress, 10,000 psi. This will give a strain, at the steel bolt radius, of

Now find the strain at the aluminum bolt radius

From this, the stress on the aluminum bolts can be found

The stress is less than the allowable stress, both materials are within thier elastic limits.

This time let the aluminum bolts be stressed to thier limit. The strain will be

The strain and stress of the steel bolts are

The shearing stress is too high. Therefore, the stresses used in the torque equation will be from the previous answer

This give a maximum allowable torque of

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