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This paper is focused on the approximation of absorbed Charpy impact energy-temperature curves (KV-T) and the management of sub-size test piece results in Charpy pendulum impact tests. Both subjects are frequently underestimated but may have a strong impact on the assessment of product quality and structural integrity. The status of related test standards, product standards, structural integrity assessment procedures and corresponding research is reviewed.
It is concluded that the state of regulation is partly insufficient and wrong. There is a wide gap between the state of knowledge in the field of materials testing and the requirements of product standards and structural integrity assessment procedures. The present paper aims at boosting and supporting the necessary discussion among the parties involved to raise the level of technical safety. Correspondingly, a large experimental database was created by Charpy impact testing of popular modern structural Steels with nominal yield strength from 235 MPa to 960 MPa. KV-T data were generated using test pieces with thicknesses between 2.5 mm and 10 mm. Different strategies for KV-T curve fitting, definition of transition temperatures, as well as upper and lower shelf energy levels were followed, and different scaling procedures were applied to the sub-size test piece results. The results show that proportional scaling of sub-size to full-size test piece results in terms of KV should be disallowed because it is a wrong approach.
Regulations still incorporating such procedures should be revised as soon as possible. Existing nonproportional scaling and conversion procedures were applied. The results obtained illustrate that neither an overall nor consistent conservatism nor an adequate conservatism level can be achieved. In summary, the standardizing bodies should enforce the discussion to revise relevant test standards considering more precise specifications on Charpy data fitting. Furthermore, proposals are made for an improved management of sub-size test piece results.
Strategic aspects for the development of measurement uncertainty annexes for ISO testing standards
(2017)
The presentation shows an overview over the current situation of the development of measurement uncertainty annexes for ISO mechanical testing standards. The comparability of measurement uncertainty statements is not ensured. The utilization of ready calculated measurement uncertainty values remains unclear. Partly the measurement uncertainty values clash with existing product standards where minimum values e.g. for the materials strength are determined. A route forward is shown to solve the current problems.