Efficiency of a diamond-riveted joint For a plate of width b joined by diamond riveting with rivet-hole diameter d, the (simplified) efficiency based on the net-width criterion across the weakest critical section is:

Introduction / Context:
Joint efficiency compares the strength of a riveted (or bolted) joint to that of the unperforated plate. For diamond riveting (a staggered, centrally concentrated pattern), the weakest net section often passes through a single rivet hole on the line of the plate center.

Given Data / Assumptions:

• Plate width b; rivet-hole diameter d (finished hole).
• Critical section governed by net area across the least net width (simplified classical approach).
• Shear/tear or bearing checks are assumed non-governing for this idealized question.

Concept / Approach:
Efficiency η (by net-width) = (net tensile strength) / (gross tensile strength) = (b - total hole deduction across the weakest section) / b. In single-line diamond patterns, the weakest section typically cuts only one hole on the central line, so deduction = d.

Step-by-Step Solution:

Verification / Alternative check:
For multiple-hole sections (e.g., chain riveting), deductions increase and efficiency reduces accordingly; diamond staggering aims to maximize net width and thus efficiency.

Why Other Options Are Wrong:

• (b - 2d)/b, (b - 3d)/b, (b - 4d)/b correspond to sections cutting more than one hole, not the critical diamond section here.
• 1 - (π d^2) / (4 b^2) is unrelated to net-width criterion (area ratio of a circle to a square band) and not the standard expression.

Common Pitfalls:
Using pitch/edge distance rules to adjust the deduction; this simplified question isolates the net-width effect only.

Final Answer:
(b - d) / b