Burst Pressure Research Articles

Evaluation of damage and failure analysis of CPVC pipes

In this paper, the work we have carried out has focused on the failure analysis of CPVC (chlorinated polyvinyl chloride) pipes. We stimulated the damage by notch effect and evaluated its properties using models available in the literature, specifically, the linear damage of Miner, the normalized damage and the unified theory. Burst tests allowed us to obtain ultimate pressure and time parameters for the virgin specimens and the residual parameters for the damaged ones. Then, we analyzed the effect of defect on the mechanical behavior of the studied structures; we found that the mechanical properties of the material were lost as defects increased. An observation and analysis of the pressure drop and thereafter the residual ultimate resistance brings out acceleration from it around the critical depth. Then, an evaluation of the static damage of the studied CPVC pipes was made according to model based on the experimental results of the burst tests and on the modification of the unified theory concepts and the static damage. Indeed, we evaluated the static damage of blank and notched tubes using mainly burst pressure parameters.

Capillarity Enabled Large-Array Liquid Metal Electrodes for Compact and High-Throughput Dielectrophoretic Microfluidics.

Dielectrophoresis (DEP) particle separation has label-free, well-controllable, and low-damage merits. Sidewall microelectrodes made of liquid metal alloy (LMA) inherits the additional advantage of thick electrodes to generate impactful DEP force. However, existing LMA electrode-based devices lack the ability to integrate large-array electrodes in a compact footprint, severely limiting flow rate and thus throughput. Herein, a facile and versatile method is proposed to integrate high-density thick LMA electrodes in microfluidic devices, taking advantage of the passive control ability of capillary burst valves (CBVs). CBVs with carefully designed burst pressures are co-designed in microfluidic channels, allowing self-assembly of LMA electrode array through simple hand-push injection. The arrayed electrode configuration brings the accumulative DEP deflection effect. Specifically, The fabricated 5000 pairs of sidewall electrodes in a compact chip are demonstrted to achieve ten times higher throughput in DEP deflection. The 5000-electrode-pair device is applied to successfully separate four mixed samples, including human peripheral blood mononuclear cells and A549 cellswith the flow rate of 70 µL min-1. It is envisioned that this work can greatly facilitate LMA electrode array fabrication and offer a robust and versatile platform for DEP separation applications.

A mussel inspired polyvinyl alcohol/collagen/tannic acid bioadhesive for wet adhesion and hemostasis

Bioadhesives are useful in surgery for hemostasis, tissue sealing and wound healing. However, most bioadhesives have limitations such as weak adhesion in wet conditions, insufficient sealing and poor clotting performance. Inspired by the adhesion mechanism of marine mussels, a novel bioadhesive (PCT) was developed by simply combining polyvinyl alcohol (PVA), collagen (COL) and tannic acid (TA) together. The results showed that the adhesion, sealing and blood coagulation properties boosted with the increase of tannic acid content in PCT. The wet shear adhesion strength of PCT-5 (the weight ratio of PVA:COL:TA=1:1:5) was 60.8 ± 0.6 kPa, the burst pressure was 213.7 ± 0.7 mmHg, and the blood clotting index was 39.3% ± 0.6%, respectively. In rat heart hemostasis tests, PCT-5 stopped bleeding in 23.7 ± 3.2 s and reduced bleeding loss to 83.0 ± 19.1 mg, which outperformed the benchmarks of commercial gauze (53.3 ± 8.7 s and 483.0 ± 15.0 mg) and 3 M adhesive (Type No.1469SB, 35.3 ± 5.0 s and 264.0 ± 14.2 mg). The as-prepared bioadhesive could provide significant benefits for tissue sealing and hemorrhage control along its low cost and facile preparation process.

Development of machine learning based classifier for the pressure test result prediction of type IV composite overwrapped pressure vessels

The stringent safety regulations of type IV composite overwrapped pressure vessels (COPVs) for commercial vehicles mandate a certification process involving pressurization up to 1050 bar, with the critical requirement of withstanding burst pressures of 1570 bar. Analyzing proof test data is crucial to enhance and ensure tank safety regarding burst pressure. In this study, we developed various machine learning classifiers for structure health monitoring and damage prediction of COPVs. The classifiers were trained using a substantial amount of acoustic emission data collected during burst and pressure cycling tests. The test results were employed as label inputs during the training process. Statistical features were extracted per time unit and trained using Naive Bayes, Logistic Regression, Decision Tree, XGBoost, and TabNet models. Upon training the data collected from the burst pressure test, TabNet, Decision Tree, and XGBoost achieved classification accuracies above 0.94. Notably, TabNet demonstrated also the best performance for the pressure cycling test with an accuracy of 0.98. Furthermore, TabNet provided visualizations of feature sensitivity in relation to classification results. This study marks the first development of a machine learning classifier for predicting the damage state of COPV tanks in commercial applications pertaining to required safety tests.

Investigation of Burst Pressure of Flat-Scored Metal Diaphragms in Hypersonic Impulse Facilities

Flat-scored metal diaphragms are essentially used in various hypersonic impulse facilities as quick-opening valves. Their burst pressure is a key parameter to optimize the performance of shock wave experimental devices and ensure the activation of overpressure safety devices. However, the conventional method to predict the burst pressure relies on time-consuming experiments that pose significant challenges for ultrahigh driving conditions. In this study, the finite element method (FEM) based on the Johnson–Cook model is adopted to predict the burst pressure of diaphragms used in a shock tube. The influences of the diaphragm thickness and groove depth on the burst pressure are analyzed. A simplified approximation based on the simulation results is obtained to estimate the burst pressure under a static load rapidly. This method is more generalizable than the existing equation and produces results in good agreement with experimental results. Furthermore, the burst pressure is investigated under different dynamic loads using the proposed FEM method. The results show that the dynamic load results in larger burst pressures than the static load, indicating that the burst pressure depends on the load type, the loading rate, and the magnitude of the applied forces.

Multifunctional Polymer Nanocomposite Coated Antibacterial Filters for Air-Purification

Air and environmental pollution require products used and produced in industrial areas to have natural ingredients and low energy consumption. It is impossible for standard used filters to clean bacteria in homes, workplaces and areas working with biological creatures. Therefore, the production of multifunctional composite and hybrid filter papers is necessary. In the study, filter papers coated with nanocomposite solutions prepared from green synthesized nanosilver (AgNPs) with plant extracts and Polyvinyl Alcohol (PVA). Scanning Electron Microscope (SEM) analyses showed that silver nanoparticles and PVA homogeneously coat the filter paper fibers, thereby reducing the average pore diameters by only 3% compared to commercial standards of filter paper. Using nanosilver, plant extracts, and PVA, a filter with 36% higher burst pressure resistance was produced. The antibacterial effect is provided to the filters with a high effect of up to 100,000 times, by coating them with nanosilver and plant extracts. This study enabled the production of antibacterial and high mechanical strength filter paper with natural ingredients, low energy and raw material consumption, and low cost. In this way, bacteria and pollutants in the air environment will be cleaned without harming the environment and also human health.

A novel discrete linkage-type electrode for radiofrequency-induced intestinal anastomosis

Introduction For decades, radiofrequency (RF)-induced tissue fusion has garnered great attention due to its potential to replace sutures and staples for anastomosis of tissue reconstruction. However, the complexities of achieving high bonding strength and reducing excessive thermal damage present substantial limitations of existing fusion devices. Materials and methods This study proposed a discrete linkage-type electrode to carry out ex vivo RF-induced intestinal anastomosis experiments. The anastomotic strength was examined by burst pressure and shear strength test. The degree of thermal damage was monitored through an infrared thermal imager. And the anastomotic stoma fused by the electrode was further investigated through histopathological and ultrastructural observation. Results The burst pressure and shear strength of anastomotic tissue can reach 62.2 ± 3.08 mmHg and 8.73 ± 1.11N, respectively, when the pressure, power and duration are 995 kPa, 160 W and 13 s, and the thermal damage can be controlled within limits. Histopathological and ultrastructural observation indicate that an intact and fully fused stomas with collagenic crosslink can be formed. Conclusion The discrete linkage-type electrode presents favorable efficiency and security in RF-induced tissue fusion, and these results are informative to the design of electrosurgical medical devices with controllable pressure and energy delivery.

Optimization of Electrospun Bilayer Vascular Grafts through Assessment of the Mechanical Properties of Monolayers.

Small-diameter vascular grafts must be obtained with the most appropriate materials and design selection to harmoniously display a variety of features, including adequate tensile strength, compliance, burst strength, biocompatibility, and biodegradability against challenging physiological and hemodynamic conditions. In this study, monolayer vascular grafts with randomly distributed or radially oriented fibers are produced using neat, blended, and copolymer forms of polycaprolactone (PCL) and poly(lactic acid) (PLA) via the electrospinning technique. The blending ratio is varied by increasing 10 in the range of 50-100%. Bilayer graft designs are realized by determining the layers with a random fiber distribution for the inner layer and radial fiber orientation for the outer layer. SEM analysis, wall thickness and fiber diameter measurements, tensile strength, elongation, burst strength, and compliance tests are done for both mono- and bilayer scaffolds. The findings revealed that the scaffolds made of neat PCL show more flexibility than the neat PLA samples, which possess higher tensile strength values than neat PCL scaffolds. Also, in blended samples, the tensile strength values do not show a significant improvement, whereas the elongation values are enhanced in tubular samples, depending on the blending ratio. Also, neat poly(l-lactide-co-caprolactone) (PLCL) samples have both higher elongation and strength values than neat and blended scaffolds, with some exceptions. The blended specimens comprising a combination of PCL and PLA, with blending ratios of 80/20 and 70/30, exhibited the most elevated burst pressures. Conversely, the PLCL scaffolds demonstrated superior compliance levels. These findings suggest that the blending approach and fiber orientation offer enhanced burst strength, while copolymer utilization in PLCL scaffolds without fiber alignment enhances their compliance properties. Thus, it is evident that using a copolymer instead of blending PCL and PLA and combining the PLCL layer with PCL and PLA monolayers in bilayer vascular graft design is promising in terms of mechanical and biological properties.

Experimental and computational failure analysis of hydrogen embrittled steel cords in a reinforced thermoplastic composite pipe

Reinforced thermoplastic pipes (RTPs) have attracted considerable attention lately in the oil and gas sector as potential alternative to carbon steel pipes. However, some RTP systems have been experiencing failures as a result of deficient design and inadequate operation practices. This study presents a comprehensive assessment of the failure of a steel-reinforced flexible thermoplastic composite layered pipe in a sour environment characterized by hydrogen sulfide (H2S) exposure. Utilizing scanning electron microscopy (SEM) and electron dispersive spectroscopy (EDS), the investigation conclusively attributes the failure of the RTP to hydrogen embrittlement of the carbon steel cords and wires in the reinforcement layer. Finite element models at both meso-scale and full RTP scale were developed, incorporating a novel damage initiation and propagation criterion for failure prediction of embrittled and non-embrittled (e.g. ductile) reinforcement steel cords. The numerical models consistently predicted a reduced burst pressures of the hydrogen embrittled case of the RTP, with a close match with field observations. They also predicted failure modes that closely matched the SEM findings, hence highlighting the unsuitability of the existing steel cords in RTPs for use in sour service environments. Additionally, the presence of moisture in the annular space was identified as an exacerbating factor. This investigation provides important insights for the future design and operation of RTPs susceptible to hydrogen embrittlement, paving the way for improved structural integrity and safety measures. Further research avenues may involve modeling hydrogen diffusion in the thermoplastic layers, simulating the movement of moisture in the annulus through the capillary effect, and incorporating fracture toughness degradation for a more thorough understanding of the interplay between mechanical and environmental factors in the hydrogen embrittlement of steel-reinforced RTP composite pipes.

Study on the Burst Failure Mechanism and Residual Strength of Casing With Compound Wear Based on Extended Finite Element Method

Abstract Based on the data of wear casing for ShunNan 501 well in Northwest oilfield and the stress–strain intrinsic relationship of P110 tubing, a two-dimensional mechanical model of casing with compound wear is established by using the nonlinear extended finite element method (XFEM) and the burst failure criterion of damage evolution with due consideration of wear type, angle between crescents, overlap depth of crescents, and wear depth caused by drill pipe body and tool joint. The accuracy and reliability of model are verified by the full-scale burst test data. The effects of wear types, angle between crescents, overlap depth of crescents, and wear depth on the internal pressure yield strength (IPYS), burst strength and failure behavior for casing with compound wear are analyzed, by which it is found that casing with compound wear exist stress interference and complex interaction between stress interference and stress concentration, and the burst failure mechanism of casing with compound wear is revealed. Based on the gray correlation analysis result of wear parameters, a prediction model of the residual strength for P110 casing with compound wear is established by 1stOpt software and universal global optimization (UGO) algorithm.

Effect of Hydride Morphology on Fracture behavior of Zr-2.5%Nb Pressure Tube Material

Hydrogen generated due to corrosion reaction is partly absorbed by Zr-2.5%Nb pressure tube (PT) material during service in the Pressurized Heavy Water Reactors (PHWRs). Hydrogen present in excess of the solubility limit get precipitated and embrittles the host PT material. The degree of embrittlement of the host PT matrix is governed by the morphology of the hydride precipitates. An experimental setup was designed, fabricated and used to form hydrides of different morphologies using internal pressurization. The internal pressure during the treatment was sufficient to induce hoop stresses more than the threshold for stress for re-orientation of hydrides in the PT spool. The design of the setup ensured constant pressure inside the PT spool while cooling from hydrogen solutionizing temperature. Metallographic examination of the hydrogen charged PT spool after the reorientation treatment revealed formation of stress reoriented hydrides. Series of burst tests were carried out on the PT spools with varying hydride morphology. The burst pressure as well as the final crack extension were found to be function of hydride morphology. This paper summarizes multiple full scale burst tests performed on as received Zr-2.5%Nb PT spools as well as on PT spools with varying hydride content and morphology.

Pipette-operable microfluidic devices with hydrophobic valves in sequential dispensing with various liquid samples: multiplex disease assay by RT-LAMP.

Microfluidic dispensing technologies often require additional equipment, posing challenges for their integration into point-of-care testing (POCT) applications. In response to this challenge, we have developed a pipette-operable microfluidic device fabricated using 3D printing technology for precise liquid dispensing. This device features three reaction chambers and three distinct hydrophobic valves to control the flow direction of liquids. Through these valves, the pipette-operable microfluidic device can sequentially dispense and isolate the liquid into the three reaction chambers, allowing for the individual conduction of three distinct reactions. These hydrophobic valves, with optimized flow resistance and burst pressure, can sustain a volumetric flow rate of up to 25 μL s-1, making them compatible with a standard pipette, a syringe, or a dropper operation. Furthermore, the device is successfully used to operate with various liquids, including BSA, DMEM, FBS, plasma, and blood, representing that the device has the potential to be used for various applications. Additionally, distinct RT-LAMP primer sets have been incorporated for diagnosing SARS-CoV-2, influenza A, and influenza B within each chamber through lyophilization. This pipette-operable microfluidic device serves as a versatile tool for diagnosing these three diseases using a single loading process, with results readable by the naked eye or image assay within 30 minutes of incubation. Finally, the design concepts are extended to engineer a microfluidic device with 20 reaction chambers, offering significant potential for multi-disease diagnostics.

High magnetization composite magnetic fluid: structure, magnetorheology and new sealing mechanism in rotating seals.

The sealing capacity of magnetofluidic (MF) rotating seals is limited by the highest magnetization of the sealing ferrofluids (FFs) of about 1000 G (80 kA m-1). A sharp, almost an order of magnitude, increase in the supported pressure drop is possible by using a magnetorheological (MR) suspension as sealing fluid, owing to the much higher saturation magnetization of MR fluids compared to FFs. However, rotating seals with MR fluids have several shortcomings, such as a significant increase of the friction torque due to the growth of shear stress in the strong magnetic field specific to MF seals and leakage of the non-magnetic carrier liquid. At least partly, these issues can be avoided by using ferrofluid based extremely bidisperse MR suspensions of micrometer-sized iron (Fe) particles dispersed in a ferrofluid, as sealing fluid. The composite Fe3O4-Fe magnetic fluid used in this study consisted of hundreds of nanometers up to few microns size structures of interconnected (welded) Fe nanoparticles (FeMNPs) dispersed in a high colloidal stability ferrofluid with 500 G (40 kA m-1) saturation magnetization. The volume fraction of iron NPs varies from 0.5 to 15% in the ferrofluid carrier which significantly increases the magnetization and simultaneously produces important changes of flow properties in magnetic field of the resulting composite fluid, from Newtonian to strongly non-Newtonian behavior. The evaluation of the magnetic and magnetorheological behavior includes the dependence of magnetization, effective viscosity, magnetoviscous effect and dynamic yield stress on the volume fraction of Fe nanoparticles dispersed in the ferrofluid carrier. The seal gap filled with interconnected Fe nanospheres consists in randomly distributed microregions with a high intensity and high gradient magnetic field that captures the ferrofluid and provides a new sealing mechanism. Already a small amount of interconnected Fe nanospheres additive (2.5-5.0% volume fraction) produces four times increase of the rotating seal burst pressure, a much higher increase than what can be obtained from using a conventional magnetic fluid with the same magnetization. The nano-composite sealing magnetic fluid proved to be a cost-effective solution to significantly increase the performance of multi-stage rotating MF seals.

Highly transparent and strong nanohesive hydrogel patch for tissue adhesion

This research aimed to design and fabricate a biocompatible dual-layer chitosan hydrogel adhesive patch with exceptional mechanical properties by employing a nanoadhesive strategy to assess its tissue adhesion performance. The design involves physical cross-linking to construct a robust chitosan hydrogel as a backing membrane, followed by in situ photocuring to create the adhesive hydrogel layer, resulting in an integrated chitosan hydrogel adhesive patch. To facilitate adhesion between the hydrogel patch and biological tissue, surface-activated silica nanoparticles serve as interfacial connectors, analogous to nanoglue, promoting binding of the hydrogel to the substrate. Characterization of the patch reveals an adhesive energy of 282 J/m<sup>2</sup> to biological tissues in vitro and a burst pressure of 450 mmHg (1 mmHg=0.133 kPa). The patch exhibits outstanding mechanical properties, with a tensile strength of 4.3 MPa, an elongation rate of 65%, and a fracture toughness of 3.82 kJ/m<sup>2</sup>. Additionally, the nanohesion-based chitosan hydrogel adhesive patch is highly transparent and demonstrates excellent biocompatibility. It holds promise for applications in various biomedical fields, including tissue repair and drug delivery, thereby providing a robust material foundation for advancements in clinical surgery.

Automatic microdispenser-integrated multiplex enzyme-linked immunosorbent assay device with autonomously driven centrifugal microfluidic system.

In this study, we established the control and design theory of an autonomously driven dispenser at a steady rotation speed and proposed a dispenser-integrated multiplex enzyme-linked immunosorbent assay (ELISA) device. In establishing the theory of the dispenser, we estimated the flow rate in the dispenser and the applied pressure onto the passive valves, so that the suitable burst pressure of the valves and flow rate could be designed. The dispenser-integrated multiplex ELISA device has the potential to perform flow control for executing an ELISA of 6 samples/standards per chip or 18 samples/standards per compact disk by just steadily rotating a chip. In the immunoassay evaluation of the device using mouse IgG detection, it was confirmed that the device could assay 5 μL of several standards in just 30 min without nonspecific reactions, and although this system has a high limit of detection (LOD, 63.4-164 pg mL-1) it is equal to that of manual assay with a titer plate. The device can be fabricated by transferring the microchannel pattern from a mold without complex assembly or alignment, and it can control the liquid operation by just steadily rotating. Thus, the device system developed will contribute to reducing the cost of fabricating chips and control equipment for ELISA systems. Consequently, a compact, portable, and low-cost ELISA system for point-of-care testing is expected to be realized.

Injectable, shear-thinning, photocrosslinkable, and tissue-adhesive hydrogels composed of diazirine-modified hyaluronan and dendritic polyethyleneimine.

In the present study, we report the first synthesis of diazirine-modified hyaluronic acid (HA-DAZ). In addition, we also produced a precursor polymer solution composed of HA-DAZ and dendritic polyethyleneimine (DPI) that showed strong shear-thinning properties. Furthermore, its viscosity was strongly reduced (i.e., from 5 × 105 mPa s at 10-3 s-1 to 6 × 101 mPa s at 103 s-1), substantially, which enhanced solution injectability using a 21 G needle. After ultraviolet irradiation at 365 nm and 6 mW cm-2, the HA-DAZ/DPI solution achieved rapid gelation, as measured using the stirring method, and its gelation time decreased from 200 s to 9 s as the total concentrations of HA-DAZ and DPI increased. Following UV irradiation, the storage modulus increased from 40 to 200 Pa. In addition, reversible sol-gel transition and self-healing properties were observed even after UV irradiation. This suggests that the HA-DAZ/DPI hydrogel was crosslinked in multiple ways, i.e., via covalent bonding between the diazirine and amine groups and via intermolecular interactions, including hydrogen bonding, electrostatic interactions, and hydrophobic interactions. A lap shear test showed that the HA-DAZ/DPI hydrogel exhibited strong adhesiveness as a fibrin glue following UV irradiation. Finally, the HA-DAZ/DPI hydrogel showed higher tissue reinforcement than fibrin glue in an ex vivo burst pressure test of the porcine esophageal mucosa.

Effect of pre-incisional and peritoneal local anesthetics administration on colon anastomosis and wound healing.

Previous research has shown that levobupivacaine is as effective as bupivacaine but carries a lower risk of cardiac and central nervous system toxicity. This study explores whether levobupivacaine and bupivacaine are preferable for all patients, includ-ing those with comorbidities, particularly focusing on their effects on colonic anastomosis. The primary objective is to examine the influence of levobupivacaine and bupivacaine on colonic anastomosis. Additionally, the study will assess their impact on wound healing and their anti-adhesive properties. Conducted between July 28, 2022, to August 4, 2022, at the Hamidiye Animal Experiments Laboratory, this study was approved by the University Science Health, Hamidiye Animal Experiments Local Ethics Committee. This study was conducted using 21 male Sprague rats aged 16-20 weeks. The rats were allocated into three equal groups of seven each: Group C: pre-incisional isotonic; Group B: pre-incisional bupivacaine; and Group L: pre-incisional levobupivacaine. Macroscopic adhesion scores (MAS) were recorded during laparotomy and tissue samples were taken for histopathological examination and hydroxyproline levels measurement. Wound tensile strength along the middle incision line and anastomotic burst pressure were also assessed. MAS was statistically significantly lower in Groups B and L compared to Group C (p<0.001). The wound histopathology score (WHS) was significantly higher in Group L than in Group B (p=0.021). Colon histopathology scores (CHSs) were also signifi-cantly higher in Group L compared to Group C (p=0.011). TThe study found that bupivacaine and levobupivacaine did not significantly enhance wound healing, although le-vobupivacaine significantly improved WHS relative to bupivacaine. According to the findings of this study, levobupivacaine can enhance clinical practice by being used in patients undergoing colon anastomosis. It contributes significantly to the durability of colon anasto-mosis, has a more positive effect on wound healing compared to bupivacaine, and exhibits anti-adhesive properties. Additional clinical trials are necessary to validate these results further.

Results of the use of human platelet-rich fibrin membrane applied on colorrhaphy in nourished and malnourished rats.

To evaluate the effects of platelet-rich fibrin (PRF) on the healing of intestinal sutures in rats. Forty rats were distributed into four groups. Two groups were treated with a standard diet and considered nourished (I and II). Two other groups were treated with cornmeal and considered malnourished (III and IV). All animals underwent cecotomy and cecorrhaphy. Groups II and IV had sutures overlapped with human PRF membrane. The following parameters were evaluated: animal weight, death, rupture site, rupture pressure, collagen, and reticulin dosage in the suture line. The use of PRF did not influence deaths, rupture pressure or rupture location. For malnourished animals, a significant difference was observed in relation to the rupture site, corresponding to the suture line (p = 0.038) and reticulin dosage (p = 0.040), when PRF was used. There was no difference in relation to burst pressures. The use of PRF did not influence intestinal healing in nourished rats. In the group of malnourished animals, its use favored healing.

Assessment of Bridging Stents in In Situ Laser Fenestrations of Aortic Endografts With Intravascular Ultrasound

ObjectiveTreatment of complex aortic aneurysms with the in situ laser fenestration (ISLF) technique involves implantation of a balloon expandable stent graft (bSG) in the created fenestration. Adequate expansion of this bSG is of importance both to achieve seal and to ensure target vessel stability. This experimental study assessed the expansion rate of different bSGs in the ISLF setting using intravascular ultrasound (IVUS). MethodsA commercially available aortic endograft was used to test the laser fenestration technique (Zenith Alpha, Cook Medical LLC, Bloomington, IN, USA). The ISLF was stented with the following bSGs: two Gore Viabahn VBX balloon expandable endoprostheses (WL Gore & Associates, Bloomington, IL, USA), three BeGraft Peripheral and three BeGraft Plus (Bentley InnoMed GmbH; Hechingen, Germany), and three Advanta V12 (Atrium, Hudson, NH, USA). The bSGs were expanded in three steps: (1) nominal, (2) rated burst pressure, and (3) dilatation with a non-compliant balloon at 15 atmospheres. After each step, an IVUS assessment of the bSG minimal diameter and the area at the fenestration (FA) and in a fully expanded segment distal to the fenestration (SA) was performed. A mean of the three IVUS measurements was used as the value for comparison. An insufficient bSG expansion was defined as a mean of FA/SA of < 0.8 (i.e., < 80% expansion). ResultsThe VBX was the only bSG that could be expanded to its intended diameter (i.e., at least 80%) at nominal pressure. The BeGraft Peripheral and BeGraft Plus showed the lowest expansion degrees after nominal and rated burst pressure. All bSGs that were tested reached a sufficient expansion degree after the use of a higher pressure balloon. ConclusionIn this ex vivo experiment, a dilatation up to nominal pressure showed satisfactory expansion only for the VBX. The consistency of the results when applied to the different types of stent grafts that were analysed reflects structural stent graft specific issues to consider when choosing the right device in cases of ISLF.

Determination of critical material damage parameter for Indian clad tube burst behavior under severe accident scenario

During loss of coolant accident scenario in PHWRs, heat removal from clad tubes containing the uranium oxides fuel may get severely impaired. This results in increase in temperature of the fuel clad and subsequent increase in the clad tube internal pressure. This causes the clad tube to deform and balloon leading to the increase in diameter of the fuel clad. After a critical value of deformation is reached, the clad tube gets burst. The burst process is due to initiation of crack in the clad due to creep deformation process in the presence of internal pressure and high temperature environment. In this work, experimental data of fuel clad bursts from literature have been used to evaluate a critical damage parameter that can be used to predict the onset of burst phenomenon of clad tubes. Finite element modelling of the fuel clad has been carried out to simulate the ballooning deformation of the fuel clad tubes due to creep. Norton’s creep model has been used in the simulation. The critical damage parameter evaluated, using analysis and experimental data, has been used subsequently to predict burst time of Zircaloy-4 fuel clad when subjected to different types of loading environments. An exponential decay type correlation has been obtained from the finite element analysis results which can be used by safety analysts to predict burst pressure of Zircaloy-4 fuel clad of Indian PHWR as a function of burst temperature or vice-versa.