"Hall-Petch equation" meaning in English

{
  "etymology_text": "Independently discovered by English scientists Eric O. Hall and Norman J. Petch, in 1951 and 1953 respectively.",
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  "lang_code": "en",
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      "glosses": [
        "A relationship between the yield point and grain size of a material given by the equation σ_y = σ₀ + k_y * d^(-0.5), where σ_y is the yield stress, d is the average grain diameter, and σ₀ and k_y are constants specific to a particular material."
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          "grain",
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      "raw_glosses": [
        "(materials science) A relationship between the yield point and grain size of a material given by the equation σ_y = σ₀ + k_y * d^(-0.5), where σ_y is the yield stress, d is the average grain diameter, and σ₀ and k_y are constants specific to a particular material."
      ],
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{
  "etymology_text": "Independently discovered by English scientists Eric O. Hall and Norman J. Petch, in 1951 and 1953 respectively.",
  "forms": [
    {
      "form": "the Hall-Petch equation",
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        "canonical"
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      "glosses": [
        "A relationship between the yield point and grain size of a material given by the equation σ_y = σ₀ + k_y * d^(-0.5), where σ_y is the yield stress, d is the average grain diameter, and σ₀ and k_y are constants specific to a particular material."
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        "(materials science) A relationship between the yield point and grain size of a material given by the equation σ_y = σ₀ + k_y * d^(-0.5), where σ_y is the yield stress, d is the average grain diameter, and σ₀ and k_y are constants specific to a particular material."
      ],
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}