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

I was reading through the standard complexiometric method of determining hardness in water, and the procedure mentioned the use of the magnesium salt of EDTA. I looked up online to purchase this reagent but all I could find was disodium magnesium salt of EDTA. Are they one and the same? Thanks!
7. ### 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. ### B Measuring Hardness of Substrates in Changed States

Just wondering, if an experiment had ever been conducted to measure hardness of a substrate when it was in a changed state. MOHs law measure products when they were at room temperature (although I guess temperature was never really a consideration). So what would be the MOH's hardness of ice...
9. ### Managing X-Ray Hardness and Low Frequency Use in Tissue Analysis

I got question in exam, 1) How to control hardness of X-ray? 2) why low frequency of x-ray is used for investigating tissue?? so in 1) what does controlling hardness means?? and in 2) can't we use high frequency of X-ray ?so that it will penetrate more as tissue are poor absorber...
10. ### Water Hardness. Calculating Calcium.

Homework Statement I have been asked to determine the concentration of calcium ions, in a 100 mL sample of water. Eriochrome black T Indicator was used. Magnesium was removed through a precipitate. The water sample changes colour to red. pH 10 buffer solution was also used. the 3 test amounts...
11. ### 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. ### What is the ideal hardness for a steel insert used in an impacting peening gun?

I'm designing a tool that will be driven by an impacting peening gun. The peening gun will be act like a jack hammer with a flat tipped cylindrical anvil. The tool being hit will have a steel insert that will act to transfer the energy from the impacting peening anvil to the tool. I've done...
13. ### Torsional Rigidity vs Hardness - Steel Shafts

Hi, I'm a mechanic and I need to settle a point with a fellow mechanic. I was describing how a 3/8"s extension twisted during use, and I said maybe I need one that has been hardened properly. As in *through hardened*. He said I am confusing hardness with rigidity. And to look into...
14. ### 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. ### Fusion of human brain and nanobots, what can be its hardness level?

I'm aware my following thoughts are highly speculative at best, i just wish to be explained, are they total magic, do they have anything common with reality, what can be their Mohs scale level? I thought about a story, where people fused their brain with nanobots, while they still think like...
16. ### Identifying the material with a particular hardness

Hello , Pursuant to a relentless mugging into material data sheets,I am still unable to identify the material of a component corresponding to the hardness of which i measured using an ultrasonic equipment. its 240-260 HV(vickers).I need to know the material for procuring the component to the...
17. ### Heating an elastic solid by stressing it verses it's hardness.

I bought a cheaper set of roller blade wheels (you get what you pay for). With new wheels installed I had to work much harder to take longer on my usuall route. The new wheels had a hardness of 82a. The original wheels had a hardness of 80a and the last set had a hardness of 85a. The new wheels...
18. ### Math behind rockwell hardness measurement

I need to calculate the force of a pin impacting a solid metal. I know the shape of the indenter, the precise shape and depth of the indentation and the mechanical properties of the solid metal including modulus, yield and ultimate strength. The pin is being driven by ultrasonic wave guide so it...
19. ### 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. ### Yield stress from tensile test and yield stress from hardness tests

Why can there sometimes be a difference observed between them?
21. ### Difference beteween Strength, Hardness and Toughness

Hi, am I right to say that: Hardness is a material's resistance to plastic deformation. E.g. if a spoon is hard, it's difficult to bend it. Toughness is how much deformation a material can undergo before fracture. E.g. how much energy a spoon can absorb while deforming before it breaks...
22. ### Rubber O-Rings: Hardness, Strength & Compression Stress

Hi guys I have a general query regarding Rubber O-rings. For an application , say seal between 2 mating flanges of pipes ,with water pressure say about 10bars, How exactly does the hardness of rubber effect the the sealing? Is there a direct relation between hardness & strength ? Can some...
23. ### Question regarding Brinell/Vickers Hardness Test

Vickers Hardness Test Question : For Vickers Hardness Test to test the material hardness we uses different force [kfg], Why do we need to use different force like 1kgf and 5kgf? Brinell Hardness Test Question : Pure Copper : Require force is 62.5 Steel : Require force is...
24. ### Stiffness and hardness , strength and toughness

Hello can someone please tell me the difference between stiffness and hardness and between strength and toughness? thanks
25. ### Aluminum alloys hardness measurement

Hello Rockwell B or Rockwell E - which one is better to measure the hardness of aluminum alloys? Thank you!
26. ### Heat treatment of steel and the effect on it's hardness

Newbie to the forum, so forgive me if I post this in the wrong place! If I heat steel (a bearing outer race to be exact) from room temperature to approx 200C, the hardness of the steel will reduce. If the temperature is then allowed to reduce back to room temperature, what will happen to the...
27. ### Can I Accurately Test Hardness of Materials Without a Microscope?

Hi I'm not a physicist but I'm looking for a simple way to test the hardness of different materials. I need to do a demonstration and collect results with a science class, the task sheet that accompanies the lesson says to place a cloth over the materials and hit them with a hammer. I would...
28. ### Calculating Water Hardness: Ca2+ & Mg2+

Homework Statement A sample of water is known to have 190 g/m^3 Ca2+ and 84 g/m^3 Mg2+. What is the hardness of the water in mg CaCO3/L? Homework Equations Hardness = (Ca2+) + (Mg2+) The Attempt at a Solution I need to convert my units into mg CaCO3/L or Normality before summing...
29. ### Rockwell hardness of valve lifters

Hey guys, I have a set of rocker arms that I converted from a hydraulic to a mechanical adjuster and I am having problems with the adjuster screw I am currently using. Whats happening is that when the adjuster screw hits the valve lifter, its digging away at the top of the lifter causing a...
30. ### Hardness vs. density (for Elements)

I heard someone suggest a correlation between the two, my guess is NO direct correlation exists. Pick an Element on the periodic table, hardness and density do not always correlate. I'm sure atomic lattace structure plays a larger role here. Diamond is the hardest, but by no means high in...
31. ### Dynamic hardness measurements

hello. can anyone help me find information about "dynamic hardness measurements" ? a direction to books or websites will be very helpful... thanks
32. ### Discover Hardness Values for PCBN, Molybdenum, Tungsten Carbide, Diamond & More

Is there a website or book that lists hardness values for the following: Polycrystalline Boron Nitride Molybdenum Tungsten Carbide Diamond h13 B4C SiC Al2O3 I've tried www.matweb.com, but they only have hardness values for some of these materials. I can't locate PCBN in their...
33. ### 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. ### 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. ### Discover the Surprising Truth About the Hardness of Teeth and Bones

Hi all, My 9 year old just asked me what is harder.. teeth or bones? Any suggestions?
36. ### Hardness vs Weight: Highest Hardness-to-Weight Ratio Element

What element has the highest hardness to weight ratio.
37. ### 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. ### 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. ### 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. ### 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. ### 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. ### Hardness vs Brittleness Aluminum

I'm wondering if anyone is willing to share some comparison numbers between any aluminum's hardness value and its impact resistance value. A friend and I are disagreeing on something, I think the harder the treatment is, the more brittle it becomes. He doesn't think so.
43. ### 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. ### 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. ### Relation between vickers and rockwell hardness

I am doing my university project about the relation between vickers and rockwell hardness. I know that there is not a mathematical relation but I need to find a good approximation. I have practice both tests in more than 50 specimens (HV70-HV950) and I have more than 300 (HV1,HR1),(HV2,HR2)...
46. ### The relationship between crystal and hardness

Hello all, Who can tell me the ralationship between crystal and hardness of the coatings. I do XRD and measure hardness but the some coatings with high intensity of XRD peak show the low hardness. The questions are: what direction of planes is useful for hadrness? what elements affect on...
47. ### Metal hardness value table? (Rockwell)

I'm looking for the hardness value for Steel 4130, Steel 1018, Al 6061-T6, and Brass 360. (Rockwell-B). Is there a website where I can find these value? Thank you!
48. ### 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. ### 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...