High hydrostatic pressure tests

In addition to developing solid RP structures, work has been conducted on sandwich structures such as filament-wound plastic skins with low-density foamed core or a plastic honeycomb core to develop more efficient strength-to-weight structures. Sandwich structures using a syntactic core have been successfully tested so that failures occurred at prescribed high-hydrostatic pressures of 28 MPa (4,000 psi). 

High hydrostatic pressure (HHP) and pulsed electric fields (PEFs) are rather novel technologies where relatively little research has been carried out. These methods have mostly been tested in combination with other decontamination methods and also mostly on either microorganisms in vitro or on foods of animal origin (e.g. milk, eggs and meat) (Raso and Barbosa-Canovas, 2003 Ross et al., 2003). More research is needed in order to find out if such methods are applicable to the fresh produce industry. 

In industry, hydrostatic pressure testing of pipes is still widely used to assess their resistance to this type of failure. Typical results are shown in Fig. 6 [57, 58], where failure times of HDPE pipes are given as a function of the circumferential (or hoop) stress. At relatively high stresses, ductile failure is observed (stage I) although deformation is initially homogeneous, small local variations (arising from variations in the specimen thickness, for exam-... 

Results of the KC Blood Strike Through Test, the Impact Penetration Test, the Hydrostatic Pressure Test, the Biological Fluid Resistance Test (2 psi) were highly correlated (i.e., they differentiated between different types of gowns in a similar manner). 

In Ref [62], the studied object was an epoxy polymer on the basis of resin UP5-181, cured by iso-methyltetrahydrophthalic anhydride in the ratio by mass 1 0.56. Testing specimens were obtained by the hydrostatic extrusion method. The indicated method choice is due to the fact, that high hydrostatic pressure imposition in deformation process prevents the defects formation and growth, resulting to the material failure [64]. The extrusion strain was calculated according to the Eqs. (14.10) and (4.39) and makes up 0.14, 0.25, 0.36, 0.43 and 0.52. The obtained by hydrostatic extrusion specimens were annealed at maximum temperature 353 K during 15 min. 

In the case, the experiments of in situ Raman were planned to understand the mechanism of exfoliation of the nanoparticles in the contact. They were performed in collaboration with the Laboratoire des Sciences de la Terre of Ecole Normale Sup6rieure de Lyon. The tribometer using a fiat made of sapphire was placed directly under the microscope of a Raman spectrometer. The originality of the experimental device used involved the presence of a diamond anvil cell to carry ont tests with very high hydrostatic pressures (35 GPa) (Figure 2.71). 

The two types of pressure testing are hydrostatic and pneumatic. Hydrostatic pressure testing with clean water is the preferred method. The test section should be completely filled with the test medium, taking care to bleed off any trapped air. Venting at high points may be required to purge air pockets while the test section is filling. 

Other stressing treatments employed to improve the microbial stability of some meat products merit consideration. This is the case for high hydrostatic pressure (HHP) treatment in use in several countries for the preservation of various sausage or dry-cured ham. By a proteomic investigation, it was notably shown that Lact. sakei can react differently from other bacterial species after an HHP treatment (Jofre et al. 2007). In addition, flow cytometry was successfully used to test the ability of Lact. sakei cells to survive different stresses like acidic or high temperature stresses (Bonomo et al. 2013) illustrating one of the numerous tools available for starter culture selection. 

Mechanical properties of hydrogenated titanium alloys are strongly dependent on the applied stress tensor, especially on its hydrostatic component. This was illustrated by the high-pressure tensile and extrusion tests on the Ti-6Al-2.5Mo-2Cr alloy and the same alloy hydrogenated to a = 0.15 wt.%H. Tests were carried out using the apparatus at the Institute of Metal Physics UD RAS operating at hydrostatic pressures of machine oil to 15 kbax and temperatures to 250°C. 

All evidence indicated that the cylinder ruptured due to the hydrostatic pressure of expanding liquid ammonia due to excessive heat on the cylinder. Fragments of the cylinder were sent to a testing laboratory for failure analysis. The ruptured cylinder was a full cylinder just put in service. According to the company s literature search, a full cylinder would become hydrostatically full of liquid ammonia at about 130° F (54.4° C). If the liquid was further heated, tremendous pressures would be developed. An alternate possibility was that the cylinder was heated to 250° F (121° C) (the steam supply temperature). Raising the temperature that high is unlikely with the crude heating methods and the expected heat losses, but if they were, the internal cylinder pressure could reach... 

The hydraulic crush point of a foam is also important in determining to what maximum hydrostatic pressure it can be subjected without rapid failure via high water absorption. Water absorption is another important factor. A high-quality syntactic foam displayed less than 3% water absorption after six weeks of exposure to its ultimate hydrostatic strength for 1-in-diameter by 2-in-long test specimens. The test pressure employed should be not greater than 75 to 80% of the crush point. 

The effect of temperature is complex. It has been shown that the higher the test environment temperature, the faster the ESC onset. The transition to brittle behavior is accelerated to shorter times by increasing temperature, cyclic loading, dilational stress, and stress concentrations. Localized concentration of the stress due to local geometrical features as notches, voids, and inclusions will increase the stress and modify the nature of the stress field. Craze initiation is accelerated by stress fields with high dilational stress and retarded under hydrostatic pressure (Wright 1996). 

The inlet and outlet portions of the valves are hydrostatically tested with water at the appropriate pressures required by the applicable section of the ASME code. Set pressure and seat leakage tests are performed with steam using a pro-rated spring. Final set pressure tests are conducted using the final design springs with either high pressure steam or low pressure steam and an assist device. 

The simplest deformations are isotropic compression under hydrostatic pressure, uniaxial extension (or compression), and simple shear. They are used to determine the bulk modulus K, Young s modulus E, and shear modulus G, respectively (37-44). Elastomer testing for commercial applications is highly dependent on the method, the conditions (eg, strain rate, temperature), and the shape of the samples. Therefore, mechanical tests have been standardized for imiformity and simplicity by the American Society for Testing and Materials (ASTM) (45). 

GghI (1970). Gent (124) proposed a model in which the hydrostatic tensile stress at an inclusion or local heterogeneity increases the free volume and therefore effectively reduces the Tg of the material. At a sufficiently high stress concentration, the reduction in Tg is sufficient to reduce the local Tg to the test temperature. The reduced yield stress of the material in this mbber-like phase and the hydrostatic tensile stress then leads to cavitation and craze initiation. Implicit in this free-volume approach is that an imposed hydrostatic pressure will tend to prevent the formation of crazes in accordance with experimental observation. The criterion is summarized in the equation for the critical applied stress for initiation,... 

Finally, a a band on the itinerant-electron side of the Mott-Hubbard transition in the presence of localized t spins S = 3/2 signals covalent-mixing parameters X and therefore a cubic-field splitting (Eq. 5 of Goodenough, this volume) that approaches Aex- To test this deduction, hydrostatic pressure was used to induce a transition from the high-spin to the low-spin states in CaFeOs the transition was observed to occur at a pressure Pc 30 GPa [50]. 

For special applications, such as deep-sea submersible cables, tests for breakdown resistance and performed at hydrostatic pressure, at high and low temperatures between 0 and 100. 

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