ISO 178:2019 pdf free

ISO 178:2019 pdf free.Plastics一Determination of flexural properties
Flexural tests, according to the specific requirements on the data to be obtained, can be differentiated in several classes, comprising different complexity and requirements on accuracy. This starts with simple tests for obtaining flexural strength only on the one hand and on the other hand necessitates the use of a deflectometer to obtain the deflection accurately and free of compliance effects of the machine. The compliance of flexural testing machines has several possible sources (play and deformations in fixtures,deformations in the load train, and deformations of the load cell). Precise and true determination of deflection is especially important for the determination of the flexural modulus, for which the use of uncorrected crosshead displacement is not suitable. For a repeatable determination of flexural modulus results a compliance correction shall be applied or, preferably, a deflectometer shall be used.
Table 2 defines objectives of testing in increasing order of test complexity and appertaining need for accuracy. A good precision without absolute accuracy as indicated in type II-tests can be sufficient in many quality control environments when properties are to be supervised over periods of time only.
Accurate, meaning true and precise, results as indicated in type IV-tests are needed if the results are to be compared between laboratories. Different types of deflection measurement and different accuracy requirements for the deflection measurement are therefore defined, based on the needs on precision and trueness of the test results.
The machine shall be capable of continuously recording the crosshead displacement with an accuracy conforming to the class of ISO 9513 indicated in Table 2. This shall be valid over the whole range of deflections to be measured. Non-contact systems may be used provided they meet the accuracy requirements stated above. The measurement system shall not be influenced by machine compliance.
For the determination of the flexural modulus using the crosshead displacement as indicated in Type III,the latter shall be corrected for the compliance of the machine. If the machine is equipped with built in routines for compliance correction these shall preferably be applied. If such routines are not available,the procedure given in Annex C shall be used.ISO 178 pdf free download.