What is Hardness: Definition and 49 Discussions

Hardness is a measure of the resistance to localized plastic deformation induced by either mechanical indentation or abrasion. In general, different materials differ in their hardness; for example hard metals such as titanium and beryllium are harder than soft metals such as sodium and metallic tin, or wood and common plastics. Macroscopic hardness is generally characterized by strong intermolecular bonds, but the behavior of solid materials under force is complex; therefore, there are different measurements of hardness: scratch hardness, indentation hardness, and rebound hardness.
Hardness is dependent on ductility, elastic stiffness, plasticity, strain, strength, toughness, viscoelasticity, and viscosity.
Common examples of hard matter are ceramics, concrete, certain metals, and superhard materials, which can be contrasted with soft matter.

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  1. S

    B Question about stress - strain graph and definition of hardness

    This is from my notes: Point D is called ultimate tensile strength and defined as highest possible within this material. So it means that point D should be at the highest point of the graph (more like absolute maximum in math)? Because it seems that from the graph point D is not at maximum...
  2. JAG-E

    Steel hardness vs yield or ultimate strength?

    I have found sources that state hardness can't be correlated to yield strength, but only to ultimate strength. Other sources state the opposite. Yet other sources claim you can do both with different equations. Can someone direct me to a source that addresses my question, or addresses the...
  3. dovidu

    Question regarding Hardness and Wear Resistance

    Hello, everyone i always had this question in mind, and also tried to look for answers on the web, but alas! i can't seem to find definite answer! i am currently making a fountainpen nib with a carbide point. the traditional material for fountainpen tipping is iridium + osmium alloy...
  4. L

    Vickers Hardness testing simulation on ANSYS

    I have tried to simulate the Vickers hardness on a substrate with a coating on it. I am really struggling to get it to work as the deformation is far too big. I have added the pictures of my model. Is there anyone that can help me with this?
  5. B

    Determination of Ca/Mg in orthophosphate-rich solutions

    I want to measure the Ca and Mg concentration in a solution that contains up to 250 mg/L of PO43-. Apparently, orthophosphates interfere with both flame photometric methods and complexometric methods with EDTA (or so I've read). Is there a standard method for measuring Ca and Mg in this type of...
  6. B

    Magnesium salt of EDTA is the same as EDTA-2NaMg?

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  7. H

    Making up for hardness and strength with size

    A skateboard axle is 8mm thick and typically 4140 steel. Can I make up for its hardness or other strength values with 1144 or even 1018 if I use a 20mm axle?
  8. E

    B Measuring Hardness of Substrates in Changed States

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  9. A

    Managing X-Ray Hardness and Low Frequency Use in Tissue Analysis

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  10. Dannalee Jayvia

    Water Hardness. Calculating Calcium.

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  11. C

    Solid solution hardening, concentration dependence

    When you add impurity atoms to a material, the yield strength often increases by a process known as solid solution hardening. This is because the impurity atoms create a barrier to dislocation motion. The literature describing this phenomenon dates back to the 1960s with some famous papers by...
  12. D

    What is the ideal hardness for a steel insert used in an impacting peening gun?

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  13. T

    Torsional Rigidity vs Hardness - Steel Shafts

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  14. N

    Why negative Rockwell Hardness value is considered as "no good"?

    I have read some pdf files and it says negative Rockwell hardness value is not used because of it would cause confusion. What I currently know is : HR(C/B) = N - h/s; for C scale, N = 130; while for B scale N = 100; s always = 0.002 and h is the permanent depth of the indentation...
  15. G

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  16. P

    Identifying the material with a particular hardness

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  17. Spinnor

    Heating an elastic solid by stressing it verses it's hardness.

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  18. M

    Math behind rockwell hardness measurement

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  19. N

    Understanding Water Hardness: Causes and Solutions | Homework Help

    Homework Statement I know what causes water hardness, how it can be resolved (or dissolved - hehe), but I'm not sure why certain parts of pipes would be harder than others. Specifically, why the water on the 1st and 2nd floor of a building would be harder than that on the 3rd and 4th floor. I...
  20. M

    Yield stress from tensile test and yield stress from hardness tests

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  21. L

    Difference beteween Strength, Hardness and Toughness

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  22. R

    Rubber O-Rings: Hardness, Strength & Compression Stress

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  23. E

    Question regarding Brinell/Vickers Hardness Test

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  24. C

    Stiffness and hardness , strength and toughness

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  25. S

    Aluminum alloys hardness measurement

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  26. M

    Heat treatment of steel and the effect on it's hardness

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  27. D

    Can I Accurately Test Hardness of Materials Without a Microscope?

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  28. S

    Calculating Water Hardness: Ca2+ & Mg2+

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  29. U

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  30. J

    Hardness vs. density (for Elements)

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  31. K

    Dynamic hardness measurements

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  32. E

    Discover Hardness Values for PCBN, Molybdenum, Tungsten Carbide, Diamond & More

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  33. R

    Limit to the strength, the hardness, and the density of a material?

    Is there a limit to how strong a material we can create? Does yield strength have an upper bound, and how high is that upper bound above materials created today? What about hardness? Is Diamond the limit? Could we ever make a machine that could survive the pressures and temperature found in...
  34. N

    General Chemistry (Hardness)

    Homework Statement Which of the following is expected to have the greatest hardness? NaF NaI MgF2 MgI2 CaI2 The Attempt at a Solution I can not seem to find what affects the hardness of them, only how to calculate it after you have the data from experiments via google. I know the...
  35. R

    Discover the Surprising Truth About the Hardness of Teeth and Bones

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  36. C

    Hardness vs Weight: Highest Hardness-to-Weight Ratio Element

    What element has the highest hardness to weight ratio.
  37. J

    Hardness of Neutronium: Estimating Magnitude

    on Mohs' scale what is the hardness of neutronium in its native environment? we record the mass of a teaspoon full, so compared to the ratio of EM to gravity, what is the next level to fermi gas of degenerate matter? just how hard is it? an order of magnitude estimate will be fine. seems...
  38. M

    Problem with brinell hardness tester

    Hello my friends, I have a problem with very old brinell hardness tester system called "kingscan II" by kingtester.com this system contain a Pulnix TM-7CN ccd cam - the cam hacked by adding light source (8 leds), data cable (connect to the serical and parallel port - and viga card with video...
  39. K

    Calculate Total Water Hardness (ppm of Equiv. CaCO3)

    I'm having trouble figuring out the total water hardness in ppm of equivalent CaCO3. In the lab manual it shows the example equation as (150 mg/1L H2O) x (1 L H2O/1000 mL H2O) x (1.00 mL H2O/1.00 g H2O) x (1 g/1000 mg) = 150 ppm of equivalent CaCO3. The professor stated the equation is...
  40. C

    Testing Iron Hardness & Cheap Magnetic Alternatives

    If I were to go to a random hardware store and look at some iron, how would I be able to tell how soft or hard the iron was? Also, is there any other cheap magnetic material that would work better then iron to make an electromagnet with? Thank you for your time.
  41. F

    Is it possible to find uncertainty for water hardness?

    Homework Statement I am told to find the uncertainty for the titration part of determining the water hardness in my chemistry lab. I only have the following data: By titrating 281.75 mL of titrant, it was determined that 532.08 ppm is the hardness of the water.Also, for water remediation, my...
  42. S

    Hardness vs Brittleness Aluminum

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  43. S

    Quenching and Hardness Testings

    Lets say I quenched two bars of steel, both 1040 steel, one was quenched in water, other in oil. How will that affect the hardness testing on the Rockwell scale, as well as impact tests? And the higher the hardness of the steel the less it'll perform on the impact test right? Because it'll...
  44. H

    Hardness & Torsion Testing: Notes, Articles & Theories

    Hi there, can anyone just help me in finding articles, notes, theories about Hardness tests(Brinnel, Vickers, Rockwell) and Torsion test...please
  45. B

    Relation between vickers and rockwell hardness

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  46. V

    The relationship between crystal and hardness

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  47. L

    Metal hardness value table? (Rockwell)

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  48. R

    Factors Affecting Glass Hardness: Exploring Atomic Scale Properties

    I am currently working on a research project aimed at explaining hardness variation of glasses with applied load (indentation size effect) and loading time (hardness creep). I am using the Vickers Hardness scale. My question (that hopefully someone here can answer) is what factors and...
  49. T

    Is there an optimum hardness for bone?

    Obviously, anyone with osteoporosis can tell you that bones can be too soft. But can bones be too hard? I thought that this may be possible because part of cushioning we get when we do everything from walking to jumping, comes from the flexing/compressing of bones (however small). The rest...
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