GB/T 15970.5-1998 Corrosion of metals and alloy - Stress corrosion testing - Part 5: Preparation and use of C-ring specimens
1 Scope
1.1 This standard covers procedures for designing, preparing, stressing, exposing and inspecting C-ring test specimens for investigating the susceptibility of a metal to stress corrosion. Analysis of the state and distribution of stress in the C-ring is presented. The term "metal" as used in this standard includes alloys.
1.2 The C-ring is a versatile, economical specimen for determining the susceptibility to stress corrosion cracking of all types of metals in a wide variety of product forms including parts joined by welding. It is particularly suitable for tests of tube, rod and plate (see Figure 1). Notched specimens may also be used (see 5.3.8).
1.3 C-ring specimens may be stressed to predetermined levels, using simple equipment for application of either constant load or constant strain.
2 Normative references
The following standards contain provisions which, through reference in this standard, constitute provisions of this standard. At the time of publication, all editions listed were valid. All normative references are subject to revision, and parties to agreements based on this standard are encouraged to investigate the possibility of applying the latest editions of the normative standards indicated below.
GB/T 15970.1-1995 Corrosion of metals and alloys - Stress corrosion testing - Part 1: General guidance on testing procedures.
GB/T 15970.6-1998 Corrosion of metals and alloys - Stress corrosion testing - Part 6: Preparation and use of pre-cracked specimens.
3 Definition
For the purpose of this standard, the definitions are given in GB/T 15970.1.
4 Principle
4.1 The test consists of subjecting a specimen to constant load or to constant strain with a view to determining stress corrosion susceptibility by reference to one or more of the parameters enumerated in clause 7.
4.2 Corrosive environments may cause a deterioration of the properties of stressed materials beyond those observed with the same combination of environment and material when the latter is not subjected to stress. This enhanced deterioration may be expressed in a number of different ways for the purpose of assessing stress corrosion susceptibility.
4.3 The commonest form of deterioration due to stress corrosion involves the initiation and growth of cracks, one or more of which may eventually lead to total failure of a specimen if the test is conducted for an appropriate time.
4.4 Wide variations in test results may be obtained for a given metal and environment even when testing nominally identical specimens and the replication of tests is frequently necessary. If specimens are prepared to different sizes or orientations or are subjected to different stressing procedures, test results may be even more variable.
4.5 The time required for cracks to appear after exposure of stressed specimens to the test environment or the threshold stress below which cracks do not appear may be used as a measure of the stress corrosion resistance of the material in the test environment at the stress level employed.
Foreword i
ISO Foreword ii
Introduction iii
1 Scope
2 Normative references
3 Definition
4 Principle
5 Specimens
6 Procedure
7 Assessment of results
8 Test report
Annex A (Normative) Formula for calculating stressing of C-ring specimens
