Blister Fracture Research Articles

Elucidation of Blister Fracture Phenomenon in High Temperature Water Contact Rubber

Elucidation of Blister Fracture Phenomenon in High Temperature Water Contact Rubber

Structural Changes in the Vanadium Sample Surface Induced by Pulsed High-Temperature Deuterium Plasma and Deuterium Ion Fluxes

The structural changes in the vanadium sample surface are studied as functions of the conditions of irradiation by pulsed high-temperature deuterium plasma and deuterium ion fluxes in the Plasma Focus installation. It is found that processes of partial evaporation, melting, and crystallization of the surface layer of vanadium samples take place in the plasma flux power density range q = 108–1010 W/cm2 and the ion flux density range q = 1010–1012 W/cm2. The surface relief is wavelike. There are microcracks, gas-filled bubbles (blisters), and traces of fracture on the surface. The blisters are failed in the solid state. The character of blister fracture is similar to that observed during usual ion irradiation in accelerators. The samples irradiated at relatively low power density (q = 107–108 W/cm2) demonstrate the ejection of microparticles (surface fragments) on the side facing plasma. This process is assumed to be due to the fact that the unloading wave formed in the sample–target volume reaches its irradiated surface. Under certain irradiation conditions (sample–anode distance, the number of plasma pulses), a block microstructure with block sizes of several tens of microns forms on the sample surfaces. This structure is likely to form via directional crack propagation upon cooling of a thin melted surface layer.

Failure behavior of rubber O-ring under cyclic exposure to high-pressure hydrogen gas

This paper presents the effects of hydrogen pressure, ambient temperature and pressure cycle pattern on fracture behavior of O-rings moulded from a peroxide-crosslinked EPDM rubber with white reinforcing filler under cyclic exposure to high-pressure hydrogen gas. By using a developed durability tester which enables the O-rings to expose cyclically high-pressure hydrogen gas, pressure cycle tests were performed at hydrogen pressures ranging from 10 to 70MPa and ambient temperatures ranging from 30 to 100°C under two pressure cycle patterns (test frequencies). The cyclic hydrogen exposure caused cracks in the O-rings, and their crack damage became more serious with an increase in the hydrogen pressure and the ambient temperature. The serious crack damage under high temperature is believed to be due to degradation of mechanical properties with increasing ambient temperature. At a hydrogen pressure of 10MPa, cracks (blisters) caused by bubbles formed from supersaturated hydrogen molecules after decompression were observed. At a hydrogen pressure of 35MPa or more, a large volume increase of the O-rings was observed by swelling; then, its volume increase induced extrusion fracture of the O-rings in addition to blister fracture. The crack damage also became more serious with a decrease in test frequency. The effect of the test frequency on the crack damage of the O-rings is presumed to be attributed to time-dependent crack growth behavior of the EPDM rubber.

A Visualizing Study of Blister Fracture in Rubber O-rings

A Visualizing Study of Blister Fracture in Rubber O-rings

On key parameters influencing cavitation damage upon fast decompression in a hydrogen saturated elastomer

A transparent silicone rubber (vinyltrimetoxysilane) has been exposed to pressurized hydrogen from 0.1 to 27 MPa, saturated and submitted to gas decompression over a wide range of controlled rates of pressure (between 0.2 and 90 MPa/min).A spatial and temporal follow up of the development of damage during and after decompression has been conducted. The pressure level and the decompression rate are both needed to predict if blister fracture will occur and, if it does, at what level of pressure in the chamber. Using these two parameters, it is possible in some cases to predict the onset of damage.

Influence of fillers on hydrogen penetration properties and blister fracture of rubber composites for O-ring exposed to high-pressure hydrogen gas

Ethylene–propylene rubber (EPDM) and nitrile–butadiene rubber (NBR) composites having carbon black, silica, and no fillers were exposed to hydrogen gas at a maximum pressure of 10 MPa; then, blister tests and the measurement of hydrogen content were conducted. The hydrogen contents of the composites were proportional to the hydrogen pressure, i.e., the behavior of their hydrogen contents follows Henry's law. This implies that hydrogen penetrates into the composite as a hydrogen molecule. The addition of carbon black raised the hydrogen content of the composite, while the addition of silica did not. Based on observations, the blister damages of composites with silica were less pronounced, irrespective of the hydrogen pressures. This may be attributed to their lower hydrogen content and relatively better tensile properties than the others.

Influence of Fillers on Hydrogen Penetration Properties and Blister Fracture of EPDM Comosites Exposed to 10MPa Hydrogen Gas

EPDM composites with carbon black (CB 50, CB 25), with silica (SC 60), and without fillers (NF) were exposed to 0.6 to 10 MPa hydrogen gases at 30°C, and the influence of fillers on hydrogen content and blister fracture of EPDM composites was investigated. The hydrogen contents of CB 50, CB 25, SC 60, and NF were proportional to hydrogen pressures up to 10 MPa. It is confirmed that the behavior of their hydrogen contents follows Henry's law. The addition of the carbon black raised the hydrogen content of EPDM composites, while the addition of the silica did not raise that of EPDM composites. With respect to diffusivity, the carbon black lowered the diffusivity of EPDM composites, while the silica hardly influences that of EPDM composites. According to the observation of blister damages of CB 50, CB 25, SC 60, and NF, the blister damage of SC 60 is the slightest. It is considered to be due to lower hydrogen content and relatively better tensile properties compared with the others.

Blister formation and erosion due to blister fracture of SiC or Si

For silicon wafer and silicon carbide, helium ion irradiation followed by annealing was repeated, and the weight loss was measured. The blister formation and its fracture processes were also examined. For Si, many blisters were observed at the surface after the first ion irradiation. After the annealing at 1173 K after the irradiation, small pores formed by helium desorption were observed. With the increase of the cycle number, surface roughness gradually increased. The weight loss due to annealing was about a half of that by ion sputtering. The sputtering yield due to the ion irradiation was approximately twice the reference value in the present experiment, perhaps due to the bubble fracture during the irradiation. For SiC, small blisters were observed on SiC crystals after the ion irradiation. The erosion amount due to only the process of annealing at 1323 K was several times larger than that of ion sputtering, although the sputtering yield due to the ion irradiation was roughly the same as the reference value. The present erosion was significantly large, so that this erosion has to be taken into account regarding the wall lifetime and impurity level of the core plasma.

Blister lid thickness measurements — A discussion in terms of the interbubble fracture model of blister formation

In measurements of blister lid thickness by such techniques as Rutherford back-scattering (RBS) and scanning electron microscopy (SEM) some discrepancies have been mentioned. The problem is briefly discussed and the suggestion that RBS could be measuring a stressed zone beyond the blister fracture plane is examined in terms of the gas pressure driven interbubble fracture model for bubble coalescence and blister nucleation. An extension of the model, where a microcracked region extends away from the original fracture plane, appears to provide a possible reason for local misalignment in this region and therefore supports the stressed zone proposal. The microcracked region suggested in the model both below and above the blister fracture plane also appears to fit the development of a permeable layer suggested from elastic recoil detection analysis studies of helium profiles in metals during and after blistering. A possible test of the model is proposed.