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"falling hammer impact tester instrument calibration specification" interpretation - Database & Sql Blog Articles
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**Interpretation of "Calibration Specification for Drop Hammer Impact Tester"**
The drop hammer impact tester comes in two main types: non-metallic and metallic. These devices are widely used across industries such as highways, railways, water conservancy, construction, building materials, chemicals, smelting, and steel production. They play a crucial role in evaluating the impact resistance of products.
Although several national standards existed before 2008, including JB/T9389-2008 for non-metallic drop hammer impact testers, GB/T5137.1-2002 for automobile safety glass testing, GB/T8363-2007 for ferritic steel testing, and GB/T11548-1989 for rigid plastic sheets, there was no specific technical standard for the performance of these instruments. This gap highlighted the need for a dedicated calibration specification.
In 2009, the Henan Provincial Institute of Metrology, Shanghai Institute of Metrology and Testing Technology, and Chengde Jinjian Testing Instrument Co., Ltd. formed a team to develop a calibration specification. The project was approved by the National Strength Hardness Measurement Committee in 2012 and officially released on January 23, 2014, becoming effective from April 23, 2014.
**Instrument Measurement Characteristics**
During the development of the calibration specification, it was essential to clearly define the requirements for each type of drop hammer impact tester based on existing national standards. A table outlining key metrological characteristics was created, helping technicians understand the parameters involved in calibration.
**Calibration Projects and Methods**
To ensure consistency during testing, various physical indicators were selected as calibration items. These included the workbench level, guide verticality, impact point deviation, drop hammer radius, surface roughness, hardness, and impact energy.
- **Workbench Level and Swing**: Ensuring the workbench is level and stable is critical. A frame level is used to measure the table’s level in two perpendicular directions. For non-fixed tables, the swing amount is also measured using dial gauges.
- **Guide Verticality**: Only applicable for interactive guides, this ensures the drop hammer moves vertically without lateral drift.
- **Impact Point Deviation**: Using carbon paper and white paper, repeated impacts are made to check the consistency of the impact location.
- **Drop Hammer Parameters**: The radius of curvature, surface roughness, and hardness of the hammer are measured using appropriate tools like a radius gauge, surface roughness samples, and a hardness tester.
- **Impact Energy**: Calculated using the formula $ E = \frac{1}{2}mv^2 $, where mass (m) and velocity (v) are measured. Energy loss is determined through speed measurements at different heights.
**Important Notes During Calibration**
- **Scope of Application**: The specification applies to non-metallic, metallic, falling ball, dart, and luggage impact testers. Other instruments may require different methods.
- **Workbench Stiffness**: While stiffness is important, it was excluded due to complexity and limited practical benefit.
- **Assembly Method**: Different assembly methods can affect results, but this was not included in the specification due to lack of standardized guidelines.
- **Sample Clamping**: Various clamping techniques are allowed, so they are not covered in the calibration process.
- **Carbon Paper Damage**: Care must be taken to avoid damaging the carbon paper and rubber board during high-energy tests.
- **Air Resistance**: At drop heights below 2 meters, air resistance has minimal effect, so it is often ignored.
- **Hardness Calibration**: Since hammer hardness remains stable over time, frequent recalibration is unnecessary to avoid damage to the hammer head.
- **Speed Measurement**: Special precautions are needed to protect the measuring equipment during calibration, such as using clay or rubber plates to absorb rebound.
This detailed approach ensures that all critical aspects of the drop hammer impact tester are properly calibrated, leading to more accurate and reliable testing results.