Testing methods specimen design

Our goals in designing the immersion testing system were (i) to emulate or improve upon operations as specified in the manual immersion test method, (ii) to increase sample throughput, (iii) to improve the precision and accuracy of measurements, (iv) to establish procedures for testing materials in hazardous liquids, and (v) to provide sufficient flexibility to handle different types of specimens and enable future expansion of operations. 

ISO 1872-1 1993 Plastics - Polyethylene (PE) moulding and extrusion materials - Part 1 Designation system and basis for specifications ISO 1872-2 1997 Plastics - Polyethylene (PE) moulding and extrusion materials - Part 2 Preparation of test specimens and determination of properties ISO 1969 2004 Fibre ropes - Polyethylene - 3- and 4-strand ropes ISO 3458 1976 Assembled joints between fittings and polyethylene (PE) pressure pipes -Test of leakproofness under internal pressure ISO 3459 1976 Polyethylene (PE) pressure pipes - Joints assembled with mechanical fittings - Internal under-pressure test method and requirement ISO 3501 1976 Assembled joints between fittings and polyethylene (PE) pressure pipes -Test of resistance to pull out... 

The design of thickwalled components for pulsating pressure is based on the stress calculation with analytical or numerical methods and the determination of the maximum equivalent stress in relation to the admissible stresses at uniaxial conditions. The latter have to be extracted from Woehler-tests with specimen. If the stresses yield too large at load conditions including a safety factor, the design must be optimized by avoiding the major stress concentrations at bore intersections. The avoidance of T-intersections is reducing stresses by factor 2-3 (Fig. Id). 

Heat distortion temperatures (HDTs) are widely used as design criteria for polymeric articles. These are temperatures at which specimens with particular dimensions distort a given amount under specified loads loads and deformations. Various test methods, such as ASTM D648, are described in standards compilations. Because of the stress applied during the test, the HDT of a polymer is invariably higher than its Tg. 

The different combinations of components and formats lead to a wide variety of behavior and properties. Consequently, the test methods used must allow for these differences. The scope of multipart or multispecimen standards provides guidance as required on the appropriate test method or specimen design, so that, for example, a range of specimen designs are available in the tensile test discussed below. 

It is very desirable to fabricate a standard test specimen in the dame cycle as the part being bonded. This specimen should be designed for a test method that is indicative of the prime structural loading requirement. For example, if the critical item is normally loaded in tensile shear, the specimen should be of the lap-shear type. 

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