Impact Testing

Impact Testing

Westmoreland Mechanical Testing & Research is most trusted name for testing metallic materials and their ability to resist often impact to help determine service life of a part. WMT&R has the capability of performing a variety of impact tests, including Charpy, IZOD, Instrumental, Drop-Weight and Dynamic Tear Testing.”

Expedited Impact Testing Services Are Available- Contact Us Today at 724-537-3131 or us.sales@wmtr.com


          • Nadcap Accredited since 1992
          • A2LA ISO 17025 621.01, 621.02 Accredited
          • Measuring ranging less than 1 foot-pound to 300 foot-pounds
          • Temperature ranges from -320°F to over 2000°F
          • Notch configurations include V-Notch, U-Notch, Key-Hole Notch, Un-Notched and ISO (DIN) V-Notch

Impact tests are used in studying the toughness of material. A material's toughness is a factor of its ability to absorb energy during plastic deformation. Brittle materials have low toughness as a result of the small amount of plastic deformation that they can endure. The impact value of a material can also change with temperature. Generally, at lower temperatures, the impact energy of a material is decreased. The size of the specimen may also affect the value of the Izod impact test because it may allow a different number of imperfections in the material, which can act as stress risers and lower the impact energy.

Impact testing most commonly consists of Charpy and IZOD Specimen configurations. The Charpy Impact Tests are conducted on instrumented machines capable of measuring less than 1 foot-pound to 300 foot-pounds at temperatures ranging from -320°F to over 2000°F. Impact test specimen types include notch configurations such as V-Notch, U-Notch, Key-Hole Notch, as well as Un-notched and ISO (DIN) V-Notch, with capabilities of impact testing sub size specimens down to ¼ size. IZOD Impact Testing can be done up to 240 foot-pounds on standard single notch and type-X3 specimens.


impact testing vnotch

impact testing unotchimpact testing keyhole

Charpy Impact Test

Instrumented Impact Testing


Also known as the Charpy V-notch test, is a standardized high strain-rate test which determines the amount of energy absorbed by a material during fracture. This absorbed energy is a measure of a given material's  notch toughness and acts as a tool to study temperature-dependent ductile-brittle transition.


Instrumented Impact Testing


IZOD Impact Strength Test

Izod impact testing is an ASTM standard method of determining the impact resistance of materials. A pivoting arm is raised to a specific height (constant potential energy) and then released. The arm swings down hitting a notched sample, breaking the specimen. The energy absorbed by the sample is calculated from the height the arm swings to after hitting the sample. A notched sample is generally used to determine impact energy and notch sensitivity.

The test is similar to the Charpy impact test but uses a different arrangement of the specimen under test. The Izod impact test differs from the Charpy impact test in that the sample is held in a cantilevered beam configuration as opposed to a three-point bending configuration.

Westmoreland Mechanical Testing & Research also offers a line of Instrumented Impact Testing designed to simulate real life rapid energy absorption conditions caused by: falling objects, blows, collisions, drops, etc.


Instrumented Impact Testing


Instrumented Impact Test

In standard testing, such as tensile and flexural testing, the material absorbs energy slowly.
In everyday life, materials often must absorb energies very rapidly from falling objects, blows, collisions, drops, etc. Instrumented Impact testing is designed to simulate these conditions. Westmoreland Mechanical Testing & Research offers a line of instrumented Impact Testing to meet these needs. Instrumented Impact Testing includes:

  • Penetration testing of thick panel specimens such as graphite-epoxy, fiberglass, polycarbonate and sheet steel.
  • Energy absorption and fracture resistance testing of large components including pipe, appliance housings, safety helmets, and automotive components.
  • Three-point bend testing to ASTM specification geometries such as ASTM E-604 dynamic tear test, ASTM E-436 drop weight tear test, and ASTM E-208 nil-ductility test.

 

Drop-Weight Test

Drop-Weight testing is preformed to ASTM E208. This test is conducted to determine the nil ductility transition temperature (NDT) of materials. Impact testing can also be conducted to your temperature requirements from elevated temperature down to -320°F.

Dynamic Tear Test

ASTM E604 is the standard test method for Dynamic Tear testing of metallic materials as defined by ASTM International. Dynamic Tear Testing has a wide range of Research and Development applications. Used to study the effects of metallurgical variables like heat treatment, composition, and processing methods on the dynamic tear fracture resistance of material. Manufacturing processes, such as welding, can be effectively evaluated for their effect on dynamic tear fracture resistance Additional uses for this impact test include evaluating the appropriateness of selecting a material for an application where a baseline correlation between Dynamic Tear energy and actual performance has been developed.

Westmoreland Mechanical Testing & Research can provide the following standard tests:

ASTM E23
ASTM E208
ASTM E604
ASTM E436

ASTM E23M


Standard Test Methods for Notched Bar Impact Testing of Metallic Materials

The essential features of an impact test are: a suitable specimen (specimens of several different types are recognized), a set of anvils, and specimen supports on which the test specimen is placed to receive the blow of the moving mass, a moving mass that has sufficient energy to break the specimen placed in its path, and a device for measuring the energy absorbed by the broken specimen.

These test methods of impact testing relate specifically to the behavior of metal when subjected to a single application of a force resulting in multi-axial stresses associated with a notch, coupled with high rates of loading and in some cases with high or low temperatures. For some materials and temperatures the results of impact tests on notched specimens, when correlated with service experience, have been found to predict the likelihood of brittle fracture accurately.

The type of specimen chosen depends largely upon the characteristics of the material to be tested. A given specimen may not be equally satisfactory for soft nonferrous metals and hardened steels; therefore, many types of specimens are recognized. In general, sharper and deeper notches are required to distinguish differences in very ductile materials or when using low testing velocities. For complete information on ASTM E23M, go to www.astm.org

 

ASTM E208


Standard Test Method for Conducting Drop-Weight Test to Determine Nil-Ductility Transition Temperature of Ferritic Steels

The drop-weight test employs simple beam specimens specially prepared to create a material crack in their tensile surfaces at an early time interval of the test. The test is conducted by subjecting each of a series (generally four to eight) of specimens of a given material to a single impact load at a sequence of selected temperatures to determine the maximum temperature at which a specimen breaks. The impact load is provided by a guided, free-falling weight with an energy of 250 to 1400 ft·lbf (340 to 1900 J) depending on the yield strength of the steel to be tested. The specimens are prevented by a stop from deflecting more than a few tenths of an inch.

The usual test sequence is as follows: After the preparation and temperature conditioning of the specimen, the initial drop-weight test is conducted at a test temperature estimated to be near the NDT temperature. Depending upon the results of the first test, tests of the other specimens are conducted at suitable temperature intervals to establish the limits within 10°F (5°C) for break and no-break performance. A duplicate test at the lowest no-break temperature of the series is conducted to confirm no-break performance at this temperature.

In 1984, the method of applying the crack-starter weld bead was changed from a two-pass technique to the current single-pass procedure, and the practice of repair-welding of the crack-starter weld bead was prohibited. For steels whose properties are influenced by tempering or are susceptible to temper embrittlement, the nil-ductility transition (NDT) temperature obtained using the single-pass crack-starter weld bead may not agree with that obtained using the previous two-pass crack-starter weld bead, or when the crack-starter bead was repaired.

The fracture-strength transitions of ferritic steels used in the notched condition are markedly affected by temperature. For a given "low" temperature, the size and acuity of the flaw (notch) determines the stress level required for initiation of brittle fracture. The significance of this test method is related to establishing that temperature, defined herein as the NDT temperature, at which the "small flaw" initiation curve falls to nominal yield strength stress levels with decreasing temperature.

Interpretations to other conditions required for fracture initiation may be made by the use of the generalized flaw-size, stress-temperature. The diagram was derived from a wide variety of tests, both fracture-initiation and fracture-arrest tests, as correlated with the NDT temperature established by the drop-weight test. Validation of the NDT concept has been documented by correlations with numerous service failures encountered in ship, pressure vessel, machinery component, forged, and cast steel applications. For complete information on ASTM E208, go to www.astm.org

 

ASTM E604


ASTM E604 - 15 Standard Test Method for Dynamic Tear Testing of Metallic Materials

The DT energy value is a measure of resistance to rapid progressive fracturing. In a number of applications, the enhanced resistance that may develop during about one plate thickness of crack extension from a sharp notch is of major interest. In the test method, a sufficiently long fracture path is provided so that the results serve as a measure of this property.

Fracture surfaces of non-austenitic steels tested in their temperature transition region have areas that appear bright and areas that appear dull. The bright, faceted appearing areas are termed "cleavage" fracture, and the dull appearing areas are termed "shear" fracture after their respective mode of fracture on a micro scale.
This test method can serve the following purposes:

  • In research and development, to evaluate the effects of metallurgical variables such as composition, processing, or heat treatment, or of fabricating operations such as forming and welding on the dynamic tear fracture resistance of new or existing materials.
  • In service evaluation, to establish the suitability of a material for a specific application only where a correlation between DT energy and service performance has been established.
  • For information, specifications of acceptance, and manufacturing quality control when a minimum DT energy is requested. Detailed discussion of the basis for determining such minimum values in a particular case is beyond the scope of this test method. For complete information on ASTM E604, go to www.astm.org

 

ASTM E436


Standard Test Method for Drop-Weight Tear Tests of Ferritic Steels

This test method can be used to determine the appearance of propagating fractures in plain carbon or low-alloy pipe steels (yield strengths less than 825 MPa) over the temperature range where the fracture mode changes from brittle (cleavage or flat) to ductile (shear or oblique).

This test method can serve the following purposes:
For research and development, to study the effect of metallurgical variables such as composition or heat treatment, or of fabricating operations such as welding or forming on the mode of fracture propagation.
For evaluation of materials for service to indicate the suitability of a material for specific applications by indicating fracture propagation behavior at the service temperature(s).
For information or specification purposes, to provide a manufacturing quality control only when suitable correlations have been established with service behavior. For complete information on ASTM E436, go to www.astm.org

 

Heat Treatment Capabilities

Westmoreland Mechanical Testing & Research maintains capabilities to heat treat material to various conditions onsite. Our facilities can handle a wide variety of thermo-mechanical processing.

For ferrous alloys:

    • Radiant Furnaces and Environmental Chambers
      • Homogenizing, Annealing, Spheroidizing, Process/Recrystallization Annealing, Stress Relieving
      • Normalizing, Quenching, and Tempering up to +2750°F
      • Cryogenic treatments down to -320°F

For non-ferrous alloys:

  • Forced Convection Furnaces
  • Solution Treating, Annealing, and Artificial Aging up to +1200°F


 


Manufacturing Technologies

On-Site Mechanical Engineering

The on-site Mechanical Engineering laboratory is staffed by specialists and engineers in product evaluation of actual prototype components and subassemblies. From custom design and fabrication of fixtures, to conducting the test, our mechanical engineers have the expertise and resources to assist our various testing departments in delivering data to customers in an efficient and timely manner.


On-Site Machine Shop

The on-site high-technology, full-service Machine Shop at Westmoreland Mechanical Testing & Research encompasses a clean, temperature-controlled environment and state-of-the-art equipment, with the ability to machine all test specimens onsite. In addition to machining standard specimens, our Machine Shop has the ability and resource to custom-design and machine fixtures for testing finished parts, odd shapes, and difficult or exotic materials.

Our reputation for quality machining and superior turnaround times brings us production work from other laboratories and mills. With our advanced in-house capabilities, and substantial engineering experience, we are known as specialists in low-stress grinding and machining sub size specimens to very close tolerances.

 

FAQ’s

Why impact testing is important?
Impact test determines the amount of energy absorbed by a material during fracture. This absorbed energy is a measure of a given material's toughness and acts as a tool to study temperature-dependent brittle-ductile transition. It is to determine whether the material is brittle or ductile in nature.

Why impact test is done?
Purpose of the test. Impact testing is used to determine material behavior at higher deformation speeds. Classical pendulum impact testers determine the impact energy absorbed by a standardized specimen up to break by measuring the height of rise of the pendulum hammer after impact.

What are the types of impact tests?
Test Types. There are basically two types of impact tests: pendulum and drop weight. Izod, Charpy, and tensile impact are the most common of the pendulum type tests.

What is impact testing machine?
Impact testing machines evaluate an object's capacity to withstand high-rate loading and it is commonly used to determine the service life of a part or material. Impact resistance can be among the most challenging qualities to measure. ... There are two standard kinds of impact test: Charpy and IZOD.

Why do we use notch in impact test?
Impact energy is a measure of the work done to fracture a test specimen. When the striker impacts the specimen, the specimen will absorb energy until it yields. The test specimen continues to absorb energy and work hardens at the plastic zone at the notch. When the specimen can absorb no more energy, fracture occurs.

 

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