Residual burst pressure prediction of COPVs after long-term seawater immersion subjected to internal pressure

Evaluation of strength degradation behavior and fatigue life prediction of plain-woven carbon-fiber-reinforced plastic laminates immersed in seawater

Laser Raman microspectroscopy was applied to quartz inclusions in coesite- and diamond-grade metapelites from the Kokchetav ultrahigh-pressure metamorphic (UHPM) complex, Northern Kazakhstan, and diamond-grade eclogite xenoliths from the Mir kimberlite pipe, Yakutiya, Russia to assess the quantitative correlation between the Raman frequency shift and metamorphic pressure. Quartz crystals sealed in garnets have a higher frequency shift than those in the matrix. Residual pressures retained by quartz inclusions depend on the metamorphic history of the garnet host. The Raman frequency shift of quartz inclusions in garnet from coesite-grade and diamond-grade metamorphic rocks shows no systematic change with increasing peak metamorphic pressures. The highest shifts of the main Raman bands of quartz were documented for monocrystalline quartz inclusions in garnets from a diamond-grade eclogite xenolith. Calibrations based on experimental work suggest that the measured Raman frequency shifts signify residual pressures of 0.1–0.6 GPa for quartz inclusions from coesite-grade metapelites from Kokchetav, 0.1–0.3 GPa for quartz inclusions from diamond-grade metapelites from Kokchetav, and 1.0–1.2 GPa for quartz inclusions from the diamond-grade eclogite xenoliths from the Mir kimberlite pipe. Normal stresses and internal (residual) pressures of quartz inclusions in garnet were numerically simulated with a 3-shell elastic model. Estimated values of residual pressures are inconsistent with the residual pressures estimated from the frequency shifts. Residual pressure slightly depends on P–T conditions at peak metamorphic stage. Laser Raman microspectroscopic analysis of quartz is a potentially powerful method for recovering an ultrahigh pressure metamorphic event. Monocrystalline quartz inclusions yielding a residual pressure greater than 2.5 GPa might indicate the presence of a former coesite.

Accurate prediction of the burst pressure is essential for structural integrity assessment of pipelines. Current design codes and models for residual burst pressure assessment of pipelines with surface corrosion defects are only applicable to axially orientated defects. Theoretical and empirical models for the prediction of burst pressure of thin-walled pipes with pre-existing localised and arbitrarily oriented surface corrosion defect are proposed. The theoretical model is based on power-law hardening and J2 flow theory while the empirical model is derived from nonlinear finite element analysis results of the burst pressure. Burst pressure experiments are used to validate the model predictions. The theoretical and empirical models are found to be reliable in predicting the effect of defect width, length, and orientation on the burst pressure.

Composite pressure vessels (i.e. types III and IV) are widely used for compressed natural gas (CNG) vehicles, as storage cylinders to reduce the weight while maintaining high mechanical properties. These vessels can achieve 70-80% of weight saving, as compared to steel vessels (type I). So, prediction of first ply failure and burst pressure of these vessels is of great concern. Thus, this paper involved a review of literature regarding the first ply failure and burst pressure of composite pressure vessels (types III and IV). The review included the researches related to the simulation, mathematical modeling, and experimental analysis. The study focused on simulation-related research more than others due to the complexities of mathematical modeling of such problems in addition to the high cost of experimental tests. The results indicated that the stacking sequence of layers, vessel thickness and the type of selected composites were the main factors that mainly affect the vessel burst pressure performance. Accordingly, the optimization in the vessel structure (composite fabric architecture) parameters plays an important role in the performance of burst pressure. This in turn will lead to a high vessel durability, longer life-time and better prediction of burst pressure. Furthermore, the study showed that the prediction of first ply failure is more important than burst pressure knowledge of pressure vessels because it gives an initial prediction of vessel failure before the final failure occurrence. This in turn, may prevent the catastrophic damage of vessel.

Arterial Pressure and Neurologic Morbidity During Carotid Surgery Under Peridural Anesthesia

Accurate prediction of burst pressure in line pipes is critical for their safety design and operation. Different equations for predicting burst pressure of line pipes have been proposed over the years, but broad agreements between the prediction equations did not exist. To this end, the present authors recently developed a new multi-axial plastic yield theory that is referred to as Average Shear Stress Yield (ASSY) theory [6]. Based on this theory, a theoretical closed-form solution for predicting burst pressure was proposed as a function of the pipe diameter, thickness, ultimate tensile stress and strain hardening exponent. The results showed that the ASSY-based burst pressure solution predicts generally the average of experimental data, and gives the best prediction among different models in a comparison of over 100 full-size burst tests for different line pipe geometries and grades. This conclusion is consistent with the observation by Zimmerman et al. [7]. On the other hand, Law at al. [1–3] recently proposed a so-called CIS (cylindrical instability stress) model that can implicitly predict the burst pressure of line pipes, and claimed that the CIS model is the best one for predicting burst pressure. To clarify the argument and to determine a truly accurate prediction equation, this paper will reevaluate the available models of burst pressure using various experimental data used by Law et al. and others. Detailed comparisons and discussions on the predictions of burst pressure with the experimental results are performed.

Two pups with SCC colonies were removed from service. The most dominant cracks in the colonies are short and deep. One of the pups had a bulge in the area of the SCC colony. The two pups were subjected to hydrostatic burst tests and detailed post-test metallurgical examination. A companion paper covers the formation, dormancy, and growth of these SCC colonies using forensic analysis. This paper covers two main elements aimed at understanding the behavior of pipes with SCC colonies and supporting the work covered in the companion paper: (1) Burst pressure prediction, and (2) Analysis of the bulge. Burst pressure predictions were made with available material properties and flaw dimensions measured by MPI, UT, and PAUT prior to the actual burst tests. After the burst tests, the predictions were updated with more relevant material property data and the flaw dimensions obtained from fracture surfaces exposed. The modified Ln-Sec, CorLAS™, MAT-8, and Level 2 of API 579 burst pressure models and the associated Charpy to fracture toughness correlations were used. Two flaw interaction rules, CEPA and PRCI-CRES, were used to determine the single equivalent crack dimensions for input into the burst pressure models. The burst pressure predictions were compared with the experimentally measured burst pressures. Of the multiple factors affecting the burst pressure prediction, the selection of flaw interaction rules has the most prominent impact on the accuracy of the burst pressure prediction. The selection of burst pressure models has a secondary impact with the exception of API 579, which tends to give lower burst pressure predictions than other models. The formation of the bulge was simulated under different longitudinal/axial loading conditions and two levels of internal pressure. It is shown that the level of the residual bulge has a strong dependence on the severity of SCC (length, depth, and spatial distribution), the level of maximum internal pressure before depressurization, and the longitudinal stress state. Compressive longitudinal stress reduces the level of internal pressure needed to produce a bulge of the same magnitude when the severity of SCC remains constant. Multiple possible conditions could have existed to produce the observed bulge.

Recto-anal inhibitory reflex (RAIR) is an integral part of normal defecation. The physiologic characteristics of RAIR along anal length and anterior-posterior axis are unknown. The aim of this study was to perform topographic and vector-graphic evaluation of RAIR along anal canal using high definition manometry (HDM), and examine the role of various muscle components. Anorectal topography was assessed in 10 healthy volunteers using HDM probe with 256 sensors. Recto-anal inhibitory reflex data were analyzed every mm along the length of anal canal for topographic, baseline, residual, and plateau pressures during five mean volumes of balloon inflation (15 cc, 40 cc, 71 cc, 101 cc, 177 cc), and in 3D by dividing anal canal into 4 × 2.1 mm grids. Relaxation pressure progressively increases along anal canal with increasing balloon volume up to 71 cc and thereafter plateaus. In 3D, RAIR is maximally seen at the middle and upper portions of anal canal (levels 1.2-3.2 cm) and posteriorly. Peak residual pressure was seen at proximal anal canal. Recto-anal inhibitory reflex is characterized by differential anal relaxation along anterior-posterior axis, longitudinally along the length of anal canal, and it depends on the rectal distention volume. It is maximally seen at internal anal sphincter pressure zone. Multidimensional analyses indicate that external anal sphincter provides bulk of anal residual pressure. Our findings emphasize importance of sensor location and orientation; as anterior and more distal location may miss RAIR.

Crack propagation and burst pressure of longitudinally cracked pipelines using extended finite element method

Selective seam weld corrosion (SSWC) is a form of corrosion attack that preferentially occurs along the weld bond line/fusion zone of linepipes. SSWC is an integrity threat mainly for vintage pipes, particularly those manufactured before 1970 using ERW (DC-ERW and LF-ERW) and flash welding. SSWC has resulted in multiple pipeline failures. Assessing the significance of SSWC, e.g., producing a reasonably accurate prediction of burst pressure of a pipeline segment containing SSWC, remains a challenge for the pipeline industry. This project consists of four major parts: - Review prior work on burst pressure prediction, - Evaluate the performance of current burst pressure models against the 12 SSWC failures described in a previously published report, - Use a first-principles approach to examine the relative impact of factors affecting the burst pressure prediction of SSWC, and - Develop directions for improving burst pressure predictions for pipeline segments containing SSWC. The evaluation of the current burst pressure models enables the understanding of their limitations and the potentials for improvements. The examination of various factors affecting burst pressure prediction allows the identification of major factors that must be incorporated into future burst pressure models for accurate burst pressure prediction. The outcomes of this work provide clear directions for future model improvements.

The microorganisms living on plastics called “plastisphere” have been classically described as very abundant, highly diverse, and very specific when compared to the surrounding environments, but their potential ability to biodegrade various plastic types in natural conditions have been poorly investigated. Here, we follow the successive phases of biofilm development and maturation after long-term immersion in seawater (7 months) on conventional [fossil-based polyethylene (PE) and polystyrene (PS)] and biodegradable plastics [biobased polylactic acid (PLA) and polyhydroxybutyrate-co-hydroxyvalerate (PHBV), or fossil-based polycaprolactone (PCL)], as well as on artificially aged or non-aged PE without or with prooxidant additives [oxobiodegradable (OXO)]. First, we confirmed that the classical primo-colonization and growth phases of the biofilms that occurred during the first 10 days of immersion in seawater were more or less independent of the plastic type. After only 1 month, we found congruent signs of biodegradation for some bio-based and also fossil-based materials. A continuous growth of the biofilm during the 7 months of observation (measured by epifluorescence microscopy and flow cytometry) was found on PHBV, PCL, and artificially aged OXO, together with a continuous increase in intracellular (3H-leucine incorporation) and extracellular activities (lipase, aminopeptidase, and β-glucosidase) as well as subsequent changes in biofilm diversity that became specific to each polymer type (16S rRNA metabarcoding). No sign of biodegradation was visible for PE, PS, and PLA under our experimental conditions. We also provide a list of operational taxonomic units (OTUs) potentially involved in the biodegradation of these polymers under natural seawater conditions, such as Pseudohongiella sp. and Marinobacter sp. on PCL, Marinicella litoralis and Celeribacter sp. on PHBV, or Myxococcales on artificially aged OXO. This study opens new routes for a deeper understanding of the polymers’ biodegradability in seawaters, especially when considering an alternative to conventional fossil-based plastics.

Comparison of numerical modelling approaches for the residual burst pressure of thick type IV composite overwrapped pressure vessels related to low-velocity impact

Burst pressure prediction of corroded pipes in Finite Element Analysis (FEA) has commonly adopted various forms of stress-based criteria by comparing the von Mises stress in the corroded ligament with a reference stress associated with the material’s true Ultimate Tensile Strength (UTS). However, many variations and inconsistencies exist in terms of how the von Mises stress is selected and what is the appropriate reference stress. These inconsistencies not only cause confusion in selecting the appropriate failure criterion, but also lead to challenges in accurate prediction of burst pressure for corroded pipes. In light of physical burst test evidence, a plastic instability-based failure criterion was recently proposed for FEA prediction of burst pressure of corroded pipes. This new failure criterion is fundamentally identical to that used for predicting the burst pressure of uncorroded pipes. Based on the physical burst test results from a recent research program, this study critically examined the prediction performance of the plastic instability-based criterion and various stress-based criteria by statistical methods. The plastic instability-based criterion clearly demonstrated a more consistent prediction performance than the stress-based criteria. As an important implication of this study, the new failure criterion significantly improved the confidence of FEA prediction of burst pressure for corroded pipes in the absence of physical burst tests. The findings of this study also confirmed the ductile failure mechanism of corroded pipes and therefore demonstrated the importance of incorporating the strain hardening property in pipe corrosion assessment models.

Burst pressure prediction in graphite/epoxy pressure vessels using neural networks and acoustic emission amplitude data : Hill, E.K.; Walker, J.L.; Rowell, G.H. Materials Evaluation, Vol. 54, No. 6, pp. 744–748. (Jun. 1996)

A new methodology for the prediction of burst pressure for API 5L X grade flawless pipelines