Which of the following relation is correct for Ernst-Merchant Theory? [where ϕ = Shear angle, α = Rake angle, β = Friction angle]

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  1. \(\phi = \frac{\pi}{2} - \frac{1}{2}(\alpha - \beta)\)
  2. \(\phi = \frac{\pi}{4} + \frac{1}{2}(\alpha - \beta)\)
  3. \(\phi = \frac{\pi}{2} + \frac{1}{2}(\alpha - \beta)\)
  4. \(\phi = \frac{\pi}{4} - \frac{1}{2}(\alpha - \beta)\)

Answer (Detailed Solution Below)

Option 2 : \(\phi = \frac{\pi}{4} + \frac{1}{2}(\alpha - \beta)\)
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Concept:

From the merchant first analysis

\(2\phi + \beta - \alpha = \frac{\pi }{2}\)

Where, ϕ = shear angle, β = friction angle, α = cutting rake angle

26 June 1

There are several theories for the relationship between α (rake angle), β (friction angle), and ϕ (shear angle).

Ernst – Merchant theory:

\(\phi = \frac{\pi }{4} - \frac{\beta }{2} + \frac{\alpha }{2}\)

Stabler theory (Modified Ernst – Merchant theory):

\(\phi = \frac{\pi }{4} - \beta + \frac{\alpha }{2}\)

Lee and Shaffer theory:

\(\phi = \frac{\pi }{4} - \beta + \alpha \)
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