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Fatigue crack propagation in a helicopter component subjected to impact damage

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Defence Technology（防务技术） 2021年第2期17卷 416-428页

作者： M.Fossati M.Pagani M.Giglio a.manes Politecnico di Milano Dipartimento di Meccanicavia la Masa 1MilanoItaly

Damage tolerant methodology is increasingly used in aeronautical components,especially due the fact that the Aviation Regulation requires such an assessment in case an accidental damage occurs.At present,there is a strong and actual interest in applying such procedures to helicopter components that are subjected to high frequency cyclic loads.In this paper,an investigation on a damaged transmission shaft for a tail rotor transmission of an actual helicopter has been carried out focusing on the fatigue crack propagation.A complete sequence of experimental tests was performed in order to create an actual ballistic damage and to subsequently check the damage tolerant behaviour.The shaft was damaged by oblique ballistic impact and was subsequently subjected to torsional fatigue loading.During the fatigue cycles several cracks propagated from the ballistic damages.Both of these steps(impact and fatigue loading)were also simulated by a complex modelling approach based on Finite Element Models and fracture mechanics theory.The comparison between the experimental and numerical results shows a good agreement but it underlines the need for a very refined modelling technique capable to replicate all the features associated with the damage in order to reliably simulate the subsequent propagation phase.

关键词： Ballistic impact Damage Fatigue Crack propagation

Jorge manes Rubio:万物有灵

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青年视觉 2024年第1期 156-163页

作者：马宁 Jorge manes Rubio(图) Rademakers Gallery(图) 不详

试着想象一种瓦解现有知识体系的世界——时间不再线性地向前无限绵延,“过去”“现在”与“未来”与其所依存的时间概念解绑,从天然附带的历时性意义中抽身,从而得以构建-个共时性的瞬间,它们之间的联系将完全基于物体、族群或空间。... 详细信息

试着想象一种瓦解现有知识体系的世界——时间不再线性地向前无限绵延,“过去”“现在”与“未来”与其所依存的时间概念解绑,从天然附带的历时性意义中抽身,从而得以构建-个共时性的瞬间,它们之间的联系将完全基于物体、族群或空间。时间像是一个循环相连的莫比乌斯环,连同其严酷的单向度属性-并消融的,是极端的二元关系。

关键词：二元关系万物有灵单向度历时性共时性莫比乌斯环现有知识

Testing and numerical simulation of a medium strength rock material under unconfined compression loading

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Journal of Rock Mechanics and Geotechnical Engineering 2018年第2期10卷 197-211页

作者： Aria Mardalizad Riccardo Scazzosi Andrea.manes Marco Giglio Politecnico di Milano Department of Mechanical Engineering

This study aims to numerically and experimentally investigate the response of a medium strength rock material under unconfined compression loading up to failure. The unconfined compressive strength(UCS) is one of the most important parameters in characterising rock material behaviour. Hence the UCS is crucial in understanding the failure mechanism of fractured rocks. An effective approach to determine the UCS and to investigate the behaviours of rock materials under unconfined compression is essential in the majority of research fields of rock mechanics. The experimental configuration for the unconfined compression test, suggested by the protocols of the ASTM standard, has some limitations which affect the accuracy in determination of the real UCS. Among several alternative configurations proposed, the Mogi’s configuration seems to be the most appropriate one. Therefore, the ASTM and Mogi’s configurations were used to perform the tests on a medium strength rock material, i.e. Pietra Serena sandstone. The results using two configurations were discussed in terms of the differences. The tests were also replicated in LSDYNA using a finite element method(FEM) coupled smooth particle hydrodynamics(SPH) technique.This technique is employed in this study due to its capabilities to cope with large deformation issues related to the rocks. An advanced material model, called the Karagozian and Case Concrete(KCC) model,is implemented in the numerical simulations. The KCC model consists of three independent fixed failure surfaces and it can consider the damage accumulation based on the current state of stress among these failure surfaces. An equation-of-state(EOS) is used in conjunction with KCC material model for decoupling the volumetric and deviatoric responses. The numerical and experimental results were finally compared with the focus on the stress-strain diagram and the failure patterns. The comparison shows that the numerical results are in good agreement with the experimental results.

关键词： Pietra Serena sandstone Unconfined compression Mogi's configuration Karagozian and Case Concrete(KCC) model Finite element method(FEM) Smooth particle hydrodynamics(SPH)

Measuring the geometry of a developing scour hole in clear-water conditions using underwater sonar scanning

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International Journal of Sediment Research 2020年第1期35卷 105-114页

作者： Ashley Rogers Costantino manes Toru Tsuzaki Faculty of Engineering and the Environment University of Southampton Department of Environmental Land and Infrastructure Engineering

A novel scanning technique using a rotating-head sonar profiler attached to a slider mechanism is presented as a means to directly measure the complex erosion and deposition features of local scour holes developing in clear-water conditions around vertical cylinders mimicking bridge piers.Extensive validation shows that the method produces high-density elevation surfaces to within≌1.5±2 mm accuracy in a quasi-non-invasive manner.This equates to 0.5±0.7% relative to the flow depth which sonar resolution is well known to scale with.Experimental data from three trials using different cylinder diameters indicate that monitoring of the entire scour hole over time(instead of only the maximum depth as is commonly done in laboratory experiments) can reveal important information about local scour evolution.In particular,results show that the scour-hole volume scales with the maximum scour depth cubed(V-y~3) through three linear regimes.The transition to the third linear regime was found to represent a step change in the scour evolution process.Following the recent theoretical framework proposed by manes and Brocchini(2015),this change,termed the crossover point,was interpreted as the point where the production of turbulent kinetic energy plateaus which corresponds to a stabilization in the erosive power of the horseshoe vortex.Scour development beyond the crossover point is characterised by a significant reduction in the rate of volumetric scour,relative to the steadily-increasing maximum scour depth.This overall reduction in volume-development is attributed to a balance between erosion from in-front of the pier and deposition around the sides using topography analysis.It is speculated that the existence of the crossover point may help to identify the characteristic length and time scales describing the evolution of local scour,which may be used for modeling purposes.

关键词： Local scour Scour volume Clear water Sonar Scour hole geometry Similarity

Radical resection of pancreatic cancer

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Hepatobiliary & Pancreatic Diseases International 2008年第1期7卷 11-18页

作者： Alexander Koliopanos C Avgerinos Athanasios Farfaras C manes Christos Dervenis Department of Surgery G. Gennimatas Hospital Department of Surgery Agia Olga Hospital Athens 14233 Greece

BACKGROUND: Pancreatic adenocarcinoma (PCa) is a disease with dismal prognosis, and the only possibility of cure, albeit small, is based on the combination of complete resection with negative histopathological margins (R0 resection) with adjuvant treatment. Therefore, a lot of effort has been made during the last decade to assess the role of extensive surgery in both local recurrence and survival of patients with PCa. DATA SOURCES: Medline search and manual cross- referencing were utilized to identify published evidence- based data for PCa surgery between 1973 and 2006, with emphasis to feasibility, efficacy, long-term survival, disease free survival, recurrence rates, pain relief and quality of life. RESULTS: Extended surgery is safe and feasible in high volume surgical centers with comparable short-term results. Organ preserving surgery is a main goal because of quality of life reasons and is performed whenever possible from the tumor extent. Concerning long-term survival major vein resection does not adversely affect outcome. To date, there are no changes in long-term survival attributed to the extended lymph node dissection. However, there is a benefit in locoregional control with fewer local recurrences and extended lymphadenectomy allows better staging for the disease. CONCLUSIONS: Extended PCa surgery is safe and feasible despite the inconclusive results in patient’s survival benefit. In the future, appropriately powered randomized trials of standard vs. extended resections may show improved outcomes for PCa patients.

关键词： pancreatic adenocarcinoma extended lymphadenectomy vascular resection survival benefit short-term outcome long-term outcome morbidity mortality

Investigation of mechanical behaviour of a quasi-brittle material using Karagozian and Case concrete (KCC) model

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Journal of Rock Mechanics and Geotechnical Engineering 2019年第6期11卷 1119-1137页

作者： Aria Mardalizad Marco Caruso Andrea.manes Marco Giglio Politecnico di Milano Department of Mechanical EngineeringMilanItaly Politecnico di Milano Material Testing LaboratoryMilanItaly

The mechanical behaviour of a quasi-brittle material,i.e.Pietra Serena sandstone,was investigated both numerically and experimentally in order to build a reliable numerical modelling system applicable to more complex cases.The Karagozian and Case concrete(KCC)model was exploited as the material constitutive law and a new method to utilise this model for efficient and accurate simulation of quasibrittle materials is discussed.The capability of this model is evaluated by comparing the results of the numerical simulations with the corresponding experimental results,and the method itself is critically assessed.

关键词： Finite element method (FEM) Triaxial compression test Brazilian disc test Quasi-brittle behaviour Karagozian and Case concrete (KCC) model

Outcome of nonerosive gastro-esophageal reflux disease patients with pathological acid exposure

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World Journal of Gastroenterology 2009年第45期15卷 5700-5705页

作者： Fabio Pace Stefano Pallotta Gianpiero manes Annalisa de Leone Patrizia Zentilin Luigi Russo Vincenzo Savarino Matteo Neri Enzo Grossi Rosario Cuomo Division of Gastroenterology Department of Clinical Sciences "L. Sacco" University HospitalVia G. B. Grassi 74-20157 MilanoItaly Gastroenterology Unit D.I.M.I University of GenovaViale Benedetto XV 6 16132 Genova Italy Gastroenterology Unit Dip. Med. Clin e Sper. AOU Federico ⅡVia S. Pansini 5 80131 Napoli Italy Department of Medicine and Aging Sciences and Ce.S.I "G. D'Annunzio" University & FoundationVia dei Vestini 31 66013 Chieti Italy Department of Medical Bracco Imaging SpAVia XXV Aprile 4 20097 San Donato Milanese Milano Italy

AIM: To assess the management and outcome of nonerosive gastro-esophageal reflux disease (NERD) patients who were identified retrospectively, after a 5-year follow-up.METHODS: We included patients with gastro-esophageal reflux disease (GERD) symptoms who had a negative endoscopy result and pathological 24-h esophageal pH-monitoring while off therapy. We interviewed them after an average period of 5 years (range 3.5-7 years) by means of a structured questionnaire to assess presence of GERD symptoms, related therapy, updated en-doscopic data and other features. We assessed predictors of esophagitis development by means of univariate and multivariate statistical analysis.RESULTS: 260 patients (137 women) were included. Predominant GERD symptoms were heartburn andregurgitation in 103/260 (40%). 70% received a maintenance treatment, which was proton pump inhibitor (PPI) in 55% of cases. An average number of 1.5 symptomatic relapses per patient/year of follow-up were observed. A progression to erosive gastro-esophageal reflux disease (ERD) was found in 58/193 (30.0%) of patients undergoing repeat endoscopy; 72% of these were Los Angeles grade A-B. CONCLUSION: This study shows that progression to ERD occurs in about 5% of NERD cases per year, despite therapy. Only two factors consistently and independently influence progression: smoking and absence of PPI therapy.

关键词：病理性食管胃病反流患者疾病质子泵抑制剂 pH监测

Role of symptoms in diagnosis and outcome of gastric cancer

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World Journal of Gastroenterology 2008年第8期14卷 1149-1155页

作者： Giovanni Maconi Gianpiero manes Gabriele Bianchi Porro Department of Clinical Sciences Chair of Gastroenterology L. Sacco University Hospital Via G.B. Grassi 74 Milan 20157 Italy

Gastric cancer is one of the most common cancers and the second most common cause of cancer deaths worldwide. Apart from Japan, where screening programmes have resulted in early diagnosis in asymptomatic patients, in most countries the diagnosis of gastric cancers is invariably made on account on dyspeptic and alarm symptoms, which may also be of prognostic significance when reported by the patient at diagnosis. However, their use as selection criteria for endoscopy seems to be inconsistent since alarm symptoms are not sufficiently sensitive to detect malignancies. In fact, the overall prevalence of these symptoms in dyspeptic patients is high, while the prevalence of gastro-intestinal cancer is very low. Moreover, symptoms of early stage cancer may be indistinguishable from those of benign dyspepsia, while the presence of alarm symptoms may imply an advanced and often inoperable disease. The features of dyspeptic and alarm symptoms may reflect the pathology of the tumour and be of prognostic value in suggesting site, stage and aggressiveness of cancer. Alarm symptoms in gastric cancer are independently related to survival and an increased number, as well as specific alarm symptoms, are closely correlated to the risk of death.Dysphagia, weight loss and a palpable abdominal mass appear to be major independent prognostic factors in gastric cancer, while gastro-intestinal bleeding, vomiting and also duration of symptoms, do not seem to have a relevant prognostic impact on survival in gastric cancer.

关键词：胃癌症状诊断癌症阶段消化不良

Delayed gastric emptying is associated with pylorus-preserving but not classical Whipple pancreaticoduodenectomy:A review of the literature and critical reappraisal of the implicated pathomechanism

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World Journal of Gastroenterology 2006年第37期12卷 5951-5958页

作者： Kosmas I Paraskevas Costas Avgerinos Costas manes Dimitris Lytras Christos Dervenis 2~(nd) Departments of Surgery Agia Olga General Hospital Athens Greece 1~(st) Departments of Surgery Agia Olga General Hospital Athens Greece

Pylorus-preserving pancreaticoduodenectomy (PPPD) is nowadays considered the treatment of choice for periampullary tumors, namely carcinoma of the head, neck, or uncinate process of the pancreas, the ampulla of Vater, distal common bile duct or carcinoma of the peri-Vaterian duodenum. Delayed gastric emptying (DGE) comprises one of the most troublesome complications of this procedure. A search of the literature using Pubmed/Medline was performed to identify clinical trials examining the incidence rate of DGE following standard Whipple pancreaticoduodenectomy (PD) vs PPPD. Additionally we performed a thorough in-depth analysis of the implicated pathomechanism underlying the occurrence of DGE after PPPD. In contrast to early studies, the majority of recently performed clinical trials demonstrated no significant association between the occurrence of DGE with either PD or PPPD. PD and PPPD procedures are equally effective operations regarding the postoperative occurrence of DGE. Further randomized trials are required to investigate the effi cacy of a recently reported (but not yet tested in large- scale studies) modifi cation, that is, PPPD with antecolic duodenojejunostomy.

关键词：胃疾病幽门螺杆菌胰十二指肠切除术病理机制