Converting HV to MPa 1

[yaston4]

I am trying to find the reference and validity of converting the hardness value into MPa by multiplying the HV value by 9.807 as stated from the surface engineering forum, does anyone know of any references or experiences with this.

http://www.gordonengland.co.uk/hardness/hvconv.htm

Many Thanks

 

[ione]

1 kg(force) = 9.81 N

Does what above tell you anything?

 

[SJones]

ISO/TR 10108

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[TVP]

yaston4,

There are two different things to consider here. The first is what exactly is HV? The following is the definition from ASTM E 384 Standard Test Method for Knoop and Vickers Hardness of Materials

Vickers hardness number, HV, n — an expression of
hardness obtained by dividing the force applied to a Vickers
indenter by the surface area of the permanent impression made
by the indenter.

So, this means that the value of HV can be a "pressure" with units of MPa or GPa.

The second issue is how does this relate to the strength of a material. The answer is that increasing HV corresponds to increasing tensile strength. It does not have a meaningful correlation to yield strength. However, you cannot divide HV by 9.907 or any other number and obtain a tensile strength. This can only be approximated, with values given in either ISO/TR 10108 or ISO 18265.

 

[rb1957]

i wonder if the OP is trying to model an impact test, and so is asking about how to load his FEM, rather than correlate hardness to UTS ?

if you are trying to model it remember it is an "impact" test. applyinf a pressure to an area (ie using a static representation of the impact) is pretty much doomed to failure.

you need to use NL FEA to model the impact.

 

[drawoh]

yaston4,

The article discusses converting results in kgf/mm² into N/m²[ ](Pa). This is straightforward units conversion. It should be dead easy.

JHG

 

[Cockroach]

There are conversion hardness charts that correlate strength of material to differing hardnesses. This is very theoretical and known to have errors. You can find them online with search engines.

Regards,
Cockroach