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Difficulty: MediumFasteners and Joints

A technician is evaluating a mechanical linkage where a solid cylindrical pin passes vertically through a single mounting tab on a bracket and a single tab on a control arm, forming a simple lap joint. During operation, the control arm exerts a strong horizontal pull away from the bracket. What is the primary type of stress acting on the pin in this configuration?

  1. Single shear stress, as the lateral forces attempt to cut the pin along the single interface between the two overlapping tabs.Answer
  2. B
    Double shear stress, since the lateral load is distributed across multiple points along the length of the fastener.
  3. C
    Tensile stress, because the horizontal pulling action forces the pin to stretch along its vertical axis.
  4. D
    Compressive stress, as the horizontal pull causes the mounting tabs to squeeze the pin from top to bottom.

Answer

The primary stress acting on the pin is single shear stress.
In a simple lap joint with one tab overlapping another, there is exactly one contact plane where the two parts meet. When horizontal forces pull these parts in opposite directions, they create a scissor-like action across that single plane, subjecting the pin to single shear stress.

Step-by-Step Solution

1
Analyze the orientation of the applied force relative to the pin.
The control arm pulls horizontally, while the pin is mounted vertically.
Determining the angle of force helps rule out tension, which requires force parallel to the pin's axis.
2
Determine the number of shear planes in the joint.
The joint consists of a single mounting tab on the bracket and a single tab on the arm, creating exactly one plane of intersection.
The number of mating surfaces determines whether the joint experiences single or double shear.
3
Identify the primary stress based on the force and planes.
Since a perpendicular force acts across one intersection plane, the pin experiences single shear stress.
Forces attempting to slide overlapping materials in opposite directions cause shear along their contact interface.

Key Concept

Identifying load distribution and shear stress in lap joints.
Estimated Time:1m 0s
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Topics

Fasteners and Joints

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