|
Products
Charpy/Impact
Testing
Drop
Tower
Pendulum Machines
Automatic Charpy
Machines
Instrumented
Impact Testing
Quality Control
Specimens
Double Pendulum
Dynamic Tear
In-Situ Heating &
Cooling
Automatic
Pendulum Return
Automatic
Specimen Transfer
Percent Shear,
Lateral Expansion, Notch Verification
Digital Optical Comparator
Hardness
Testing
Charpy Data
Fitting
Circuit
Board Testing
Beverage Can Tester
Tongs
Shock Testing
Refurbished Equipment
MultiPurpose
Corrosion Cell
High Temperature
Reference
Electrode
Pressure Vessel
Manufacture
Pre-Owned
Equipment
Buy and
Sell
Analytical
Services
Finite
Element/Fracture
Mechanics
Neutron Transport
Analysis
P-T Curve
Analysis
Experimental
Services
Mechanical
Property Testing
Surveillance
Capsule Testing
Failure
Analysis
Services
Failure Analysis
News &
Information
MPM
Product
News
Directions to MPM
Nuclear News
| |
 
Introduction
The current ASTM E 23
methods for measuring percent shear fracture area are tedious and inaccurate.
While the use of a lateral expansion gage is adequate for standard specimens,
miniature and subsize specimens often require an alternative procedure. MPM
has developed a new technology for accurate shear and lateral expansion
measurement. In addition, the system can be used for Charpy notch and other
important dimensional verification. MPM has designed three optics and imaging
systems to meet the needs of industry for accurate measurements on Charpy test
specimens before and after impact testing. These systems can also be
used as a digital
optical comparator.
Detailed information is available in our journal article
System Features
Figure 1 and 2 (below) shows
the hardware used for acquiring fracture surface and notch
images. The system consists of a camera, optics, lighting, and data acquisition
software. The hardware in Figure 1 includes a telecentric lens
for accurate and precise quantitative measurements such as the notch radius,
notch depth, and included angle. The hardware in Figure 2 is used in cases
where only percent shear measurements are needed.
Figure 1 - MPM Model 7200 - Complete
Hardware for Percent Shear, Lateral Expansion,
and Notch Verification |
Figure 2 - MPM Model 7100 - Basic Hardware for Percent Shear
Measurement |
Percent Shear Measurement
Figure 3 - Percent Shear Measurement
Using Manual
Outline Method |
An
accurate digitized image of the fracture surface is used for the percent shear
measurement. Figure 3 shows the versatility of the system as the percent
shear of an atypical specimen is calculated. Certain features of this
specimen shown do not follow the typical fracture trends found in classical
Charpy bar fractures. The specimen in Figure 3 exhibited a fracture
normal to the main crack plane, and this area should not be included in the
brittle fracture area definition. With the digital imaging system, the
percent shear of any fracture surface is measurable. In
addition to outlining the surface as shown, the software package includes five equations which use the instrumented
striker characteristic load data to calculate percent shear. This latter method is
very effective for materials where the brittle region is difficult to resolve.
The instrumented striker results can also be used to check optical
measurements, and this approach is very effective for quality assurance
verification.
Lateral Expansion Measurement
Lateral Expansion (LE) measurements require calibration to real
world coordinates. A high-accuracy reticle as shown in Figure 4 can be
used for this purpose. Additionally, MPM has developed two-dimensional
calibration software that re-maps the pixels to account for second-order effects
(e.g. minor lens distortion and optical axis non-perpendicularity). The LE
measurement is made in accordance with ASTM E23 directly on the fracture surface
as shown in Figure 5. The final result is calculated based on the
measurements made on the two specimen halves (Figure 6).
Figure 4 - Real World Coordinate Calibration Screen |
Figure 5 - Lateral Expansion Display |
Figure 6 - Final Results Screen |
|
Charpy Notch And Specimen Dimension Verification
The system can also be used to measure the Charpy notch
radius (Figure 6), the notch included angle (Figure 7), and the notch depth
(Figure 8). Measurement of Charpy
specimen dimensions, such as the notch radius and included angle, requires a
telecentric lens and backlighting to achieve high accuracy (Figure 9). In
most cases, the notch radius is measured using magnifications ~200X. Lower
magnifications are used for the measurement of the notch depth, notch angle,
and cross section. The system can be provided with fully automatic
measurement and acquisition of key Charpy specimen parameters including notch
radius, depth, and angle.
Figure 6 - Notch Radius Tool |
Figure 7 - Automatic Included Angle Measurement |
Figure 8 - Notch Depth Tool |
Figure 9 - Telecentric Lens with
Stepper
Motor and Computer Control
for Automatic Measurement
of Key
Charpy Test Specimen
Data Such as
Notch Radius, Angle, and Depth. |
Back to Top
|
| Search |
Contact Us