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Knoop hardness Formula

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Knoop hardness test comprises of pressing the pyramid-shaped rhombic indenter (longitudinal edge angle 172.5°, transverse edge angle 130°) into a specimen with a defined test load (between 1 gf and 2 kgf). Check FAQs

HK = 14.2 \cdot \frac{P}{d^{2}}

HK - Knoop hardness?P - Indentation Load?d - Diagonal length?

Knoop hardness Example

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With units

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Here is how the Knoop hardness equation looks like with Values.

Here is how the Knoop hardness equation looks like with Units.

Here is how the Knoop hardness equation looks like.

0.4913 = 14.2 \cdot \frac{0.1}{{1.7}^{2}}

0.4913kgf/mm² = 14.2 \cdot \frac{0.1kgf}{{1.7mm}^{2}}

0.4913 = 14.2 \cdot \frac{0.1}{{1.7}^{2}}

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Knoop hardness Solution

Follow our step by step solution on how to calculate Knoop hardness?

FIRST Step Consider the formula

HK = 14.2 \cdot \frac{P}{d^{2}}

Next Step Substitute values of Variables

∴

HK = 14.2 \cdot \frac{0.1kgf}{{1.7mm}^{2}}

Next Step Convert Units

∴

HK = 14.2 \cdot \frac{0.9807N}{{0.0017m}^{2}}

Next Step Prepare to Evaluate

∴

HK = 14.2 \cdot \frac{0.9807}{{0.0017}^{2}}

Next Step Evaluate

∴

HK = 4818492.38754291Pa

Next Step Convert to Output's Unit

∴

HK = 0.491349480968858kgf/mm²

LAST Step Rounding Answer

∴

HK = 0.4913kgf/mm²

Knoop hardness Formula Elements

Variables

Knoop hardness

Symbol: HK

Measurement: PressureUnit: kgf/mm²

Note: Value should be greater than 0.

Formulas to find Knoop hardness

Indentation Load

Indentation load in microhardness test. Loads will be in the range of 1-1000 grams.

Symbol: P

Measurement: ForceUnit: kgf

Note: Value can be positive or negative.

Formulas to find Indentation Load

Diagonal length

Diagonal length in microhardness test. The diagonal length is in millimetre.

Symbol: d

Measurement: LengthUnit: mm

Note: Value should be greater than 0.

Formulas to find Diagonal length

Other formulas in Hardness category

Go Brinell hardness

HB = 2 \cdot \frac{P load}{π \cdot D \cdot (D - \sqrt{D^{2} - d^{2}})}

Go Tensile strength from Brinell hardness

TS = (\frac{3.45}{9.8067}) \cdot HB

Go Vickers hardness

HV = 1.854 \cdot \frac{P}{d^{2}}

How to Evaluate Knoop hardness?

Knoop hardness evaluator uses Knoop hardness = 14.2*Indentation Load/(Diagonal length^2) to evaluate the Knoop hardness, Knoop hardness test involves pressing the pyramid-shaped rhombic indenter (longitudinal edge angle 172.5°, transverse edge angle 130°) into a specimen with a defined test load (between 1 gf and 2 kgf). Knoop hardness is denoted by HK symbol.

How to evaluate Knoop hardness using this online evaluator? To use this online evaluator for Knoop hardness, enter Indentation Load (P) & Diagonal length (d) and hit the calculate button.

FAQs on Knoop hardness

What is the formula to find Knoop hardness?

The formula of Knoop hardness is expressed as Knoop hardness = 14.2*Indentation Load/(Diagonal length^2). Here is an example- 5E-8 = 14.2*0.980664999999931/(0.0017^2).

How to calculate Knoop hardness?

With Indentation Load (P) & Diagonal length (d) we can find Knoop hardness using the formula - Knoop hardness = 14.2*Indentation Load/(Diagonal length^2).

Can the Knoop hardness be negative?

No, the Knoop hardness, measured in Pressure cannot be negative.

Which unit is used to measure Knoop hardness?

Knoop hardness is usually measured using the Kilogram-Force per Square Millimeter[kgf/mm²] for Pressure. Pascal[kgf/mm²], Kilopascal[kgf/mm²], Bar[kgf/mm²] are the few other units in which Knoop hardness can be measured.

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