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ISO 148-3-2016 pdf free download
ISO 148-3-2016 pdf free download.Metallic materials — Charpy pendulum impact test — Part 3:
Preparation and characterization of Charpy V-notch test pieces for indirect verification of pendulum impact machines
Matériaux métalliques — Essai deflexion par choc sur éprouvet.te Charpy— Partie 3: Preparation et caractérisation des éprouvettes Charpy a entaille en V pour Ia verification indirecte des machines d’essai mouton -pendule.
A.4.3 Intercomparison among p pendulum impact testing machines (p < 6)
When the number of instruments participating to the comparison is limited, the value Sp IS not a reliable estimate of the standard deviation of the mean values between instruments. To assess Uchar, other methods should be used. These methods combine the systematic differences observed between the instruments participating in the intercomparison (between-instrument uncertainty) and the measurement uncertainty assessed for the individual instruments (within-instrument uncertainty). An example is the so-called BOB or Type-B-on-bias-approach (see Reference 191).
To have better control over the quality of the impact pendulums participating in the certification exercise, sonic CRM producers prefer to limit the number of impact pendulums to those in their own laboratory (intralaboratory). This approach offers the benefit of better defining the range for acceptable machine performance. However, it can be argued that it affects the independence of the averaged values. This is why the interlaboratory comparison is generally preferred in ISO Guide 35.
AS Uncertainty due to material instability
The stability of the certified value of a CRM is typically threatened by two possible effects: degradation of the material during transport from producer to user (short-term stability), and degradation of the material during storage between the moment of production and the distribution to the CRM user (long- term stability). In the case of the steels currently used for the production of Charpy CRMs, neither short- nor long-term stability has presented problems (see References IIDI. (UI and 1121). However, this should remain a subject of investigation, especially when selecting new types of steel for the production of Charpy CR Ms. Until then, the values for UIts and are considered negligibly small.
A.6 Uncertainty due to sample-to-sample variation — Homogeneity of the batch
Due to the heterogeneity of the steel microstructure, and the nature of the impact fracture process. samples from the same batch often have measurably different KVvalues. This implies that the average value of the set of verification test pieces tested by the CRM user is not exactly the same as the average of the RM batch from which the set was drawn.
For a single sample, the standard uncertainty, Uhom, associated with this homogeneity issue equals the standard deviation of the batch, SRM. To assess this standard deviation, tests are performed on a representative number of samples hoin selected from the batch, The tests are performed in repeatability conditions, excluding or at least minimizing the contributions to the standard deviation coming from machine, operator or other factors.
NOTE The value of SRM can also be deduced from the results of the interlahoratory comparison (see A.4). In this case, the within-laboratory and the between-laboratory variance of the results are separated using ANOVA (analysis of variance). The within-laboratory variance is related to SRM.ISO 148-3-2016 pdf free download.
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