BS EN ISO 148-2:2008 Metallic materials. Charpy pendulum impact test. Verification of testing machines
BS EN ISO 148 consists of the following parts, under the general title Metallic materials. Charpy pendulum impact test:
BS EN ISO 148-2 covers the verification of the constructional elements of pendulum-type impact testing machines. It is applicable to machines with 2 mm or 8 mm strikers used for pendulum impact tests carried out, for instance, in accordance with ISO 148-1.
It could also be applied to pendulum impact testing machines of various capacities and of different design.
Impact machines used for industrial, general or research laboratory testing of metallic materials in accordance with this part of ISO 148 are referred to as industrial machines. Those with more stringent requirements are referred to as reference machines. Specifications for the verification of reference machines are found in BS EN ISO 148-3.
This part of ISO 148 describes two methods of verification.
- The direct method, which is static in nature, involves measurement of the critical parts of the machine to ensure that it meets the requirements of this part of ISO 148. Instruments used for the verification and calibration are traceable to national standards. Direct methods are used when a machine is being installed or repaired, or if the indirect method gives a non-conforming result.
- The indirect method, which is dynamic in nature, uses reference test pieces to verify points on the measuring scale.
A pendulum impact testing machine is not in compliance with this part of BS EN ISO 148 until it has been verified by both the direct and indirect methods and meets the requirements. The requirements for the reference test pieces are found in ISO 148-3.
This part of ISO 148 takes into account the total energy absorbed in fracturing the test piece using an indirect method. This total absorbed energy consists of
- The energy needed to break the test piece itself
- The internal energy losses of the pendulum impact testing machine performing the first half-cycle swing from the initial position.
Internal energy losses are due to
- Air resistance, friction of the bearings of the rotation axis and of the indicating pointer of the pendulum which can be determined by the direct method
- Shock of the foundation, vibration of the frame and pendulum for which no suitable measuring methods and apparatus have been developed.
Contents of BS EN ISO 148-2 inlcude:
- Normative references
- Terms and definitions
- Definitions pertaining to the machine
- Definitions pertaining to energy
- Definitions pertaining to test pieces
- Symbols and abbreviated terms
- Testing machine
- Direct verification
- Machine framework
- Anvil and supports
- Indicating equipment
- Indirect verification by use of reference test pieces
- Reference test pieces used
- Absorbed energy levels
- Requirements for reference test pieces
- Limited direct verification
- Bias and repeatability
- Frequency of verification
- Verification report
- Direct verification
- Indirect verification
- Measurement uncertainty of the result of the indirect verification of a Charpy pendulum impact machine
- Measurement uncertainty of the results of the direct verification of a Charpy pendulum impact testing machine
- Direct method of verifying the geometric properties of pendulum impact
testing machines using a jig
The suitability of a pendulum impact testing machine for acceptance testing of metallic materials has usually been based on a calibration of its scale and verification of compliance with specified dimensions, such as the shape and spacing of the anvils supporting the specimen.
The scale calibration is commonly verified by measuring the mass of the pendulum and its elevation at various scale readings. This procedure for evaluation of machines had the distinct advantage of requiring only measurements of quantities that could be traced to national standards. The objective nature of these traceable measurements minimized the necessity for arbitration regarding the suitability of the machines for material acceptance tests.
However, sometimes two machines that had been evaluated by the direct-verification procedures described above, and which met all dimensional requirements, were found to give significantly different impact values when testing test pieces of the same material.
This difference was commercially important when values obtained using one machine met the material specification, while the values obtained using the other machine did not. To avoid such disagreements, some purchasers of materials added the requirement that all pendulum impact testing machines used for acceptance testing of material sold to them must be indirectly verified by testing reference test pieces supplied by them. A machine was considered acceptable only if the values obtained using the machine agreed, within specified limits, with the value furnished with the reference test pieces.
Watch a video of the charpy pendulum test on YouTube.