6
3.3 Notation of Leeb’s Hardness
•
When measuring the hardness of a sample material using the traditional static
hardness testing method, a change of applied pressure will result in a change in
the hardness reading. This will also happen during a Leeb’s Hardness test when
you change the impact device. In measuring the hardness of the same test
sample with different impact devices, the Leeb’s hardness values obtained will
vary.
For Example: 720 HLD
≠
720 HLC
•
Because different converting curves are obtained from different impact devices,
when converting hardness L into another hardness value the notation for the
converted hardness value should include the impact device used.
For example:
Hardness HV converted from hardness L using impact device D+15
Should be written as 22, 8 HV LD+15
Where:
22=hardness value HL
8=hardness value HV
L=Leeb’s
Method
LD+15-impact device
Hardness HRC converted from hardness L using impact device D should be
written as 35, 9 HRCLD
Where:
35=hardness value HL
9=hardness value HRC
L=Leeb’s
Method
D=Impact
device
4.
Pretreatment of Samples
4.1 Pretreatment of Sample Surface
To eliminate hardness errors resulting from the roughness of a sample’s surface when
using impact device D, DC or D+15, the test surface should be polished until its
roughness
Ra
is no more then 2
µ
m. PHASE II
SRG-1000
handheld surface roughness
tester or any other suitable instrument may be used to measure the surface roughness
of the sample material. The test surface should be clean and free from oil stains.
4.2 Curved
Surface
When testing a curved surface with a radius of curvature
R
less than 1.2 in (30mm), a
special small support ring washer should be used to compensate the curvature.
