Loading devices
Cormet provides various kinds of loading devices for stress corrosion cracking (SCC), sulphide stress cracking (SSCC), hydrogen induced cracking (HIC), fracture mechanical and fatigue studies.
Proof Ring is the most simple and affordable loading device. We offer 10-20 kN and 20-38 kN capacity proof rings. The most common specimen type is the round tensile specimen that goes through the test cell lids. Flat tensile specimen holders are available and we also make custom specimen holders for your need. A load cell can be added to proof ring to monitor test load during longer tests and when creep can be an issue.
Proof ring is quite versatile and can be used to tackle different kinds of constant load needs. We also offer loadcells to proof rings that enable you to monitor the load during the test. Loadcell allows for easy load level adjustment and can also tell if sample extends during the test as that results in load drop.
We also have proof ring for elevated temperature and pressure applications. Tiny autoclave is placed in the middle of the proof ring. This is practical solution for H2S testing as the whole system can be placed in regular draft cabinet at H2S lab. As seen on the right side it can be equipped with gas in/out lines. Sample is isolated from the small autoclave enabling electrochemistry measurements.
Cormet’s workhorse for stress corrosion cracking tests is a PC operated electromechanical loading device. It can perform Slow Strain Rate Tests (SSRT), Constant Load (CL) tests and Low Frequency Cyclic Fatigue (LFCF) tests. The loading device can be used in ambient temperature, autoclave and high temperature gas environments. There are several models available of which the 25 kN and 50 kN instruments are the most popular. The operational principle of the versatile and flexible controlling software is based on sequenced load patterns that can be combined and connected in series.
The highest cyclic loading frequency of Cormet’s electromechanical instrument is about 0.1 Hz depending on the amplitude, loading mode and loading pattern. Servohydraulic or electrically operated loading instruments are needed for the higher cyclic frequencies. Cormet can integrate an autoclave into such a loading device or integrate the servohydraulic actuator with a Cormet autoclave.
The core of the HIC instrument is a glass container in which the specimens are assembled. However, the accessories including gas volume flow meters, water traps, a draft cabinet, ventilation and gas neutralization tools make the instrument more complicated. The HIC testing procedures are described in NACE TM0284-2016.
Operation of four point bending (FPB) instruments is described in NACE TM0177-2016 Method B, ASTM G 39-2011 and ISO 7539-2 (1989). The FPB tests are often performed in HIC testing containers.
Constant-load instruments are used for evaluation of critical stress in a given environment using the Time-to-Failure (TTF) value as a testing result. Standards NACE TM0177-2016 Method A and ASTM G 47 – 98 (2004) describe how to perform the constant load tests. In addition to the simple proof rings, Cormet offers spring loaded and motor controlled constant load instruments.
The effect of high pressure hydrogen on material properties is an interesting topic. Tensile tests and fatigue tests can be performed using regular loading devices and specimens in pressure chambers. It is also possible to use hollow tensile and fatigue specimens that are pressurised internally with hydrogen. The crack growth and fracture mechanical tests must be performed using regular precracked notched specimens.
