Investigation on short-term burst pressure of plastic pipes reinforced by cross helically wound steel wires

Plastic pipes reinforced by cross helically wound steel wires (PSP), which have exhibited excellent mechanical performance, consist of inner polyethylene (PE) layer, winding layer and outer PE layer. The winding layer is composed of two monolayers where steel wires are cross helically wound. An analytical procedure is developed to predict the short-term burst pressure of PSP as the monolayer is assumed to be elastic and orthotropic. The 3D anisotropic elasticity and Maximum Stress Failure Criterion are employed in the formulation of the elasticity problem. Good agreement between the theoretical results and the experimental data shows that the proposed approach can well predict the short-term burst pressure of PSP.

Strength differential effect and influence of strength criterion on burst pressure of thin-walled pipelines

In the framework of the finite deformation theory, the plastic collapse analysis of thin-walled pipes subjected to the internal pressure is conducted on the basis of the unified strength criterion （USC）. An analytical solution of the burst pressure for pipes with capped ends is derived, which includes the strength differential effect and takes the influence of strength criterion on the burst pressure into account. In addition, a USC- based analytical solution of the burst pressure for end-opened pipes under the internal pressure is obtained. By discussion, it is found that for the end-capped pipes, the influence of different yield criteria and the strength differential effect on the burst pressure are significant, while for the end-opened pipes, the burst pressure is independent of the specific form of the strength criterion and strength difference in tension and compression.

Prediction of Burst Pressure of a Radial Truck Tire Using Finite Element Analysis

This paper is concerned with the numerical prediction of the burst pressure of a radial truck tire. Even though relatively rare, the tire fracture or failure brings up a big accident. Especially, the tire burst or rupture is a rapid loss of inflation pressure of a truck and bus tire leading to an explosion. The tire burst pressure, under this extreme loading condition, can be predicted by identifying the pressure at which the cord breaking force of the composite materials is attained. Recently, the use of finite element analysis in tire optimal design has become widely popular. In order to determine the burst pressure of a radial truck tire, an axisymmetric finite element model has been developed using a commercial finite element code with rebar element. The numerical result shows that the bead wire among the various layers modeled the rebar element breaks off first in the radial truck tire. The finite element modeling with the rebar element on the bead wire of a radial truck tire is able to well predict the tire burst pressure identifying the pressure at which the breaking force of steel bead wires is reached. The model predictions of tire burst pressure should be correlated with test data, in which case the tire is hydro-tested to destruction. The effect of the design change with the different bead structure on the tire burst pressure is discussed.

ESTIMATE OF BURSTING PRESSURE OF MILD STEEL PRESSURE VESSEL AND PRESENTATION OF BURSTING FORMULA

In order to get more precise bursting pressure formula of mild steel, hundreds of bursting experiments of mild steel pressure vessels such as Q235（Gr.D） and 20R（1020） are done. Based on statistical data of bursting pressure and modification of Faupel formula, a more precise modified formula is given out according to the experimental data. It is proved to be more accurate after examining other bursting pressure value presented in many references. This bursting formula is very accurate in these experiments using pressure vessels with different diameter and shell thickness. Obviously, this modified bursting formula can be used in mild steel pressure vessels with different diameter and thickness of shell.

Effect of growth hormone on colonic anastomosis after intraperitoneal administration of 5-fluorouracil, bleomycin and cisplatin: An experimental study

BACKGROUND Growth hormone(GH)plays a crucial role in wound healing and tissue repair in postoperative patients.In particular,colonic anastomosis healing following colorectal surgery is impaired by numerous chemotherapy agents.AIM To investigate whether GH can improve the healing of a colonic anastomosis following the adverse effects of intraperitoneal administration of 5-fluorouracil(5-FU),bleomycin and cisplatin.METHODS Eighty Wistar rats underwent laparotomy and a 1 cm-resection of the transverse colon,followed by an end-to-end anastomosis under general anesthesia.The rats were blindly allocated into four equal groups and administered a different daily intraperitoneal therapeutic regimen for 6 days.The control group(A)received normal saline.Group B received chemotherapy with 5-FU(20 mg/kg),bleomycin(4 mg/kg)and cisplatin(0.7 mg/kg).Group C received GH(2 mg/kg),and group D received the aforementioned combination chemotherapy and GH,as described.The rats were sacrificed on the 7th postoperative day and the anastomoses were macroscopically and microscop-ically examined.Body weight,bursting pressure,hydroxyproline levels and inflammation markers were measured.RESULTS All rats survived until the day of sacrifice,with no infections or other complications.A decrease in the body weight of group D rats was observed,not statistically significant compared to group A(P=1),but significantly different to groups C(P=0.001)and B(P<0.01).Anastomotic dehiscence rate was not statistically different between the groups.Bursting pressure was not significantly different between groups A and D(P=1.0),whereas group B had a significantly lower bursting pressure compared to group D(P<0.001).All groups had significantly more adhesions than group A.Hydroxyproline,as a measurement of collagen deposition,was significantly higher in group D compared to group B(P<0.05),and higher,but not statistically significant,compared to group A.Significant changes in group D were recorded,compared to group A regarding inflammation(3.450 vs 2.900,P=0.016)and fibroblast activity(2.75 vs 3.25,P=0.021).Neoangiogenesis and collagen deposition were not signifi-cantly different between groups A and D.Collagen deposition was significantly increased in group D compared to group B(P<0.001).CONCLUSION Intraperitoneal administration of chemotherapy has an adverse effect on the healing process of colonic anastomosis.However,GH can inhibit the deleterious effect of administered chemotherapy agents and induce colonic healing in rats.

Experimental models of high-risk bowel anastomosis in rats:A systematic review

BACKGROUND Anastomotic leaks remain one of the most dreaded complications in gastrointestinal surgery causing significant morbidity,that negatively affect the patients’quality of life.Experimental studies play an important role in understanding the pathophysiological background of anastomotic healing and there are still many fields that require further investigation.Knowledge drawn from these studies can lead to interventions or techniques that can reduce the risk of anastomotic leak in patients with high-risk features.Despite the advances in experimental protocols and techniques,designing a high-quality study is still challenging for the investigators as there is a plethora of different models used.AIM To review current state of the art for experimental protocols in high-risk anastomosis in rats.METHODS This systematic review was performed according to The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.To identify eligible studies,a comprehensive literature search was performed in the electronic databases PubMed(MEDLINE)and Scopus,covering the period from conception until 18 October 2023.RESULTS From our search strategy 102 studies were included and were categorized based on the mechanism used to create a high-risk anastomosis.Methods of assessing anastomotic healing were extracted and were individually appraised.CONCLUSION Anastomotic healing studies have evolved over the last decades,but the findings are yet to be translated into human studies.There is a need for high-quality,well-designed studies that will help to the better understanding of the pathophysiology of anastomotic healing and the effects of various interventions.

Theoretical Assessment of Burst Failure of Internally Pressurized Defect-Free Pipelines with Plastic Anisotropy

In the framework of finite deformation theory, the burst failure analysis of end-opened defect-free pipes with plastic anisotropy under internal pressure is carried out. The analytical solutions of burst pressure and the corresponding equivalent stress and strain are obtained for thin-walled pipes, which can take into account the effects of material plastic anisotropy and strain hardening exponent. The influences of plastic anisotropy on the burst pressure and the corresponding equivalent stress and strain are discussed. It is shown that the burst pressure and the corresponding equivalent stress and strain are dependent upon the plastic anisotropy of material, and the degree of dependence is related to the strain hardening exponent of material. In addition, the effects of the strain hardening exponent on burst failure are investigated.

Evaluation of remaining useful life for corroded pipeline with finite element simulation and reliability theory

An integrated approach was proposed to evaluate the remaining useful life(RUL)of corroded petroleum pipelines.Two types of failure modes(i.e.,leakage and burst failure)were considered,and the corresponding limit state functions(LSFs)were established with the structural reliability theory.A power-law function was applied to model the growth of corrosion defects,and the effect of external environmental factors on the growth of the pipeline s defect was considered.Moreover,the result was compared with the commonly used linear growth model.After that,a finite element simulation model was established to calculate the burst pressure of the pipeline with corrosion defects,and its accuracy was verified through hydraulic burst test and by comparison with international criteria.On that basis,the probability that the pipeline may fail was calculated with Monte Carlo simulation(MCS)and by considering the LSFs,and the pipeline s RUL was obtained accordingly.Furthermore,sensitivity analysis was conducted to determine the sensitivity parameters for the corrosion and RUL of the pipeline.The results indicate that the radial corrosion rate,wall thickness and working pressure have a great influence on the failure probability of the pipeline.Thus,corresponding measures should be adopted during the operation process of the pipeline to reduce the corrosion rate and increase the wall thickness,so as to prolong the pipeline s RUL.

Influence of yield-to-tensile strength ratio(Y/T) on failure assessment of defect-free and corroded X70 steel pipeline

The effect of yield-to-tensile strength ratio(Y/T) on failure pressure of X70 pipeline without and with corrosion defects was investigated.The stress-strain response of materials was characterized by a power-law hardening curve.Two formulas to estimate the strain hardening exponent n for a special Y/T were obtained by least squared regression method and the influence of Y/T on n was analyzed.As an application of n-Y/T expression,the analytical solutions of burst pressure for X70 pipeline without and with corrosion defects were also obtained.The results indicate that the burst pressure of defect-free X70 pipe without corrosion defects is a function of the Y/T,pipe geometry t0/D0 and engineering tensile strength,and increases as Y/T or t0/D0 increases; whilst the burst pressure of corroded X70 pipe decreases with the increase of defect depths,d/t.Comparisons indicate that the present analytical solutions closely match available experimental and numerical data.

Pharmacological interventions for improved colonic anastomotic healing:A meta-analysis

AIM: To identify pharmaceuticals for the prophylaxis of anastomotic leakage (AL), we systematically reviewed studies on anastomosis repair after colorectal surgery.

Impact of remote ischemic preconditioning on wound healing in small bowel anastomoses

AIM： To investigate the influence of remote ischemic preconditioning （RIPC） on anastomotic integrity. METHODS： Sixty male Wistar rats were randomized to six groups. The control group （n = 10） had an end- to-end ileal anastomosis without RIPC. The preconditioned groups （n = 34） varied in time of ischemia and time of reperfusion. One group received the amino acid L-arginine before constructing the anastomosis （n = 9）. On postoperative day 4, the rats were re-laparotomized, and bursting pressure, hydroxyproline concentration, intra-abdominal adhesions, and a histological score concerning the mucosat ischemic injury were collected. The data are given as median （range）.RESULTS： On postoperative day 4, median bursting pressure was 124 mmHg （60-146 mmHg） in the control group. The experimental groups did not show a statistically significant difference （P 〉 0.05）. Regarding the hydroxyproline concentration, we did not find any significant variation in the experimental groups. We detected significantly less mucosal injury in the RIPC groups. Furthermore, we assessed more extensive intra-abdominal adhesions in the preconditioned groups than in the control group. CONCLUSION： RIPC directly before performing small bowel anastomosis does not affect anastomotic stability in the early period, as seen in ischemic preconditioning.

Effects of albumin/glutaraldehyde glue on healing of colonic anastomosis in rats

To evaluate the effect of local surgical adhesive glue (albumin/glutaraldehyde-Bioglue) on the healing of colonic anastomoses in rats. METHODSForty Albino-Wistar male rats were randomly divided into two groups, with two subgroups of ten animals each. In the control group, an end-to-end colonic anastomosis was performed after segmental resection. In the Bioglue group, the anastomosis was protected with extraluminar application of adhesive glue containing albumin and glutaraldehyde. Half of the rats were sacrificed on the fourth and the rest on the eighth postoperative day. Anastomoses were resected and macroscopically examined. Bursting pressures were calculated and histological features were graded. Other parameters of healing, such as hydroxyproline and collagenase concentrations, were evaluated. The experimental data were summarized and computed from the results of a one-way ANOVA. Fisher’s exact test was applied to compare percentages. RESULTSBursting pressures, adhesion formation, inflammatory cell infiltration, and collagen deposition were significantly higher on the fourth postoperative day in the albumin/glutaraldehyde group than in the control group. Furthermore, albumin/glutaraldehyde significantly increased adhesion formation, inflammatory cell infiltration, neoangiogenesis, and collagen deposition on the eighth postoperative day. There was no difference in fibroblast activity or hydroxyproline and collagenase concentrations. CONCLUSIONAlbumin/glutaraldehyde, when applied on colonic anastomoses, promotes their healing in rats. Therefore, the application of protective local agents in colonic anastomoses leads to better outcomes.

Standards and methods for dent assessment and failure prediction of pipelines:A critical review

Dent,a common mechanical damage on pipelines,is associated with a significant local plastic deformation.Dents can cause pipeline failures,especially when they are combined with other types of defects such as gouges,fatigue,corrosion,and cracks.In this work,a systematic review of various assessment methods and standards for pipeline dents,including the combination of a dent with other defects,is conducted.Generally,the methods available today are not sufficiently accurate and reliable to assess pipeline dents,especially the dent-defect combinations.For plain dents on pipelines,both the depthbased criterion and the strain-based criterion are commonly used in engineering.Their main problems include inaccuracy and conservatism.For a dent combined with other defects,the existing assessment techniques are not mature enough to give reliable results.Both experimental testing and numerical modeling through finite element(FE)analysis are capable of investigating the influence of dents and dent-defect combinations on burst failure pressure of the pipelines,although an approximation to the reality is still the main difficulty existing in the experimental testing and FE analysis.Nowadays,relevant studies on assessment techniques for plain dents,a dent with fatigue and a dent with a single gouge have been common in literature.The combinations of a dent with corrosion or cracks have been rarely assessed due to complicated mechanisms involving a multi-physics coupling effect.Development of novel assessment methods by integrating mechanical stress and strain,electrochemical reactions and steel metallurgy will be a key topic to accurately assess the dent-defect combinations for improved pipeline integrity.

A biodegradable magnesium surgical staple for colonic anastomosis: In vitro and in vivo evaluation

Staplers have been widely used in the clinical treatment of gastrointestinal reconstruction.However,the current titanium(Ti)staple will remain in the human body permanently,resulting in some adverse effects.In this study,we developed a type of biodegradable staple for colonic anastomosis using 0.3 mm diameter magnesium(Mg)alloy wires.The wire surface was modified by micro-arc oxidation treatment(MAO)and then coated with poly-L-lactic acid(PLLA)to achieve a moderate degradation rate matching the tissue healing process.The results of tensile tests on isolated porcine colon tissue anastomosed by Mg and Ti staples showed that the anastomotic property of Mg staples was almost equal to that of Ti staples.The in vitro degradation tests indicated the dual-layer coating effectively enhanced the corrosion resistance and maintained the tensile force of the coated staple stable after 14-day immersion in the simulated colonic fluid(SCF).Furthermore,24 beagle dogs were employed to conduct a comparison experiment using Mg-based and clinical Ti staples for 90-day implantation by ent-to-side anastomosis of the colon.The integrated structure of Mg-based staples was observed after 7 days and completely degraded after 90 days.All animals did not have anastomotic leakage and stenosis,and 12 dogs with Mg-based staples fully recovered after 90 days without differences in visceral ion levels and other side effects.The favorable performance makes this Mg-based anastomotic staple an ideal candidate for colon reconstruction.

Experimental research of stent anastomosis of gastrojejunostomy in a porcine model

Background Gastrojejunostomy is one of the most frequently used procedures for general surgeons. The creation of anastomosis between various parts of the gastrointestinal tract is a basic technical component and major task in the daily practice of almost all gastrointestinal procedures. This research evaluated a new procedure of making gastrointestinal anastomosis with stent.Methods Twenty experimental mini-pigs were randomized into two groups. In stent anastomosis group （SA）, the anastomoses were constructed with a poly-levolactic acid stent. In hand-sewn group （HA）, the anastomoses were performed with a single-layer continuous suture. Abdominal X-ray with intraluminal contrast was performed on the 10th postoperative day. Five pigs of each group were sacrificed on the postoperative days 3 and 14 to determine anastomotic bursting pressure in situ, hydroxyproline concentration, and histopathological evaluation of the anastomotic sites.Results There was no intraoperative morbidity or mortality. The median time needed for the sutured anastomosis was （21.7±2.3） minutes and for the stent anastomosis was （11.9±1.9） minutes （P 〈0.001）. Abdominal X-ray with intraluminal contrast demonstrated normal gas distribution and showed no evidence of leakage or obstruction. Macroscopic appearance at the longitudinal opening of anastomosis was always good in both groups. The median anastomotic bursting pressure was （18.2±1.6） kPa in SA group on postoperative day 3, compared with （11.7±3.2） kPa in HA group （P=0.003）. The anastomotic bursting pressure on day 14 was not significantly different between SA group （（27.1±2.6）kPa） and HA group （（28.3±1.7） kPa） （P=0.388）. The hydroxyproline concentrations were not significantly different.Conclusions The stent anastomosis was not considered to be more difficult than a sutured anastomosis. This method is proved to be safe and feasible compared with the traditional hand-sewn method in the porcine model. The method increases early anastomotic strength in this study.