TABLE OF CONTENTS Mechanical testing is an essential part of quality control and certification of pipeline production. It is most often conducted at the pipe mill. A minimum amount of testing is required by design codes. Additional testing to match the needs of a specific project is often specified by the customer. This section outlines the four main categories of mechanical testing commonly performed: tension and compression tests for establishing the material stress-strain properties, Charpy and other impact tests for toughness, hardness tests for welds and heat-affected zones and the split-ring test for estimating bending-type residual stresses in the pipe.
The main mechanical properties of pipe materials are established by tensile testing. Because the properties along the axis and transverse to it can differ, distinction should be made between axial or longitudinal specimens and circumferential or transverse specimens. Full thickness, dog-bone shaped axial specimens are usually relatively easy to extract. ASTM A370-03a [A.1] (Figure 3) and API SP 5L [A.2] (Figure 4) provide guidelines as to preferred specimen dimensions. For smaller diameter and thinner wall pipes, a specimen width ( w) between 1.5 t and 2 t and a gage length ( L g) of at least 5w can be used as an alternate guideline for convenience (see Figure A.1). Saw cutting followed by machining to size should be the preferred method of extracting the specimens from the pipe. If flame cutting is used, then...
