Comparative study between 2D and 3D FEM techniques in single bolt, single lap, composite bolted joints for space structures

Two-dimensional and three-dimensional finite element models have been developed to study the effects of bolt-hole clearance on the mechanical behavior of bolted composites (graphite/epoxy) joints in space structures. The type of the studied joint was single bolt, single lap, and the geometry is a standard type for these kind of composite joints space structures. In this study, two approaches, 2D (linear analysis) and 3D (nonlinear analysis) were developed and the results were compared to numerical and experiment results from literature. The contact between the parts affecting the accuracy and efficiency of the models is detailed. The model’s capability to predict the three-dimensional effects such as secondary bending and through-thickness variations of the stress and stain tensor fields is presented

Numerical analysis for the influence of the geometrical and mechanical parameters on the stiffness and strength of the composite bolted joints

The paper deals with the influence of the geometric (joint clearance) and mechanical parameters (bolt preload, axial force applied to the joint) on the stiffness and strength of the single-bolt, single-shear laminated composite joints using epoxy resin and carbon fibers reinforcement. In the first part of the paper, the finite element model is presented, using three-dimensional elements for studding the influence of the geometric and mechanical parameters on the stiffness of the joint. In the second part, the microscopic failure of the constituent layers using the Hashin failure criterion for composite materials is presented, as well as the influence of the studied parameters on the occurrence of the first lamina failure and the progressive failure phenomenon from the microscopic to the macroscopic level of the joint

Thermal Effects on Single - Lap, Single - Bolt, Hybrid Metal – Composite Joint Stiffness

three-dimensional finite element model has been developed to study the temperature effects on stiffness in linear-elastic range of the bolted metal-composite joints. In this study a quasi - symmetric lay - up for CFRP / vinyl ester epoxy laminate is used in conjunction with aluminum alloy (AA 7075 T6), having different thermal expansion coefficients. This generates an uneven load - deformation characteristics and three - dimensional stress field around the hole in single - lap single - bolt joints. The finite element model (FEM) was developed in commercial software PATRAN and the analysis including geometric and full nonlinearity frictional based contact has been performed using NASTRAN SOL 400 solver. The numerical model was calibrated using comparisons of the experimental measurements for surface strains and axial stiffness. The ability of the model to capture the three - dimensional effects such as secondary bending and through - thickness variation of stresses and strains in the presence of temperature variations is highlighted. The numerical and experimental results concluded that the thermal expansion material properties have a strong effect on the stiffness and linear behavior of the single - lap, single - bolt hybrid metal - composite joints

Machine learning based assessment of preclinical health questionnaires

Background: Within modern health systems, the possibility of accessing a large amount and a variety of data related to patients' health has increased significantly over the years. The source of this data could be mobile and wearable electronic systems used in everyday life, and specialized medical devices. In this study we aim to investigate the use of modern Machine Learning (ML) techniques for preclinical health assessment based on data collected from questionnaires filled out by patients. Method: To identify the health conditions of pregnant women, we developed a questionnaire that was distributed in three maternity hospitals in the Mureș County, Romania. In this work we proposed and developed an ML model for pattern detection in common risk assessment based on data extracted from questionnaires. Results: Out of the 1278 women who answered the questionnaire, 381 smoked before pregnancy and only 216 quit smoking during the period in which they became pregnant. The performance of the model indicates the feasibility of the solution, with an accuracy of 98 % confirmed for the considered case study. Conclusion: The proposed solution offers a simple and efficient way to digitize questionnaire data and to analyze the data through a reduced computational effort, both in terms of memory and computing power used.acceptedVersio

Digital Modeling Phenomenon Of Surface Ground Movement

With the development of specialized software applications it was possible to approach and resolve complex problems concerning automating and process optimization for which are being used field data. Computerized representation of the shape and dimensions of the Earth requires a detailed mathematical modeling, known as "digital terrain model". The paper aims to present the digital terrain model of Vulcan mining, Hunedoara County, Romania. Modeling consists of a set of mathematical equations that define in detail the surface of Earth and has an approximate surface rigorously and mathematical, that calculated the land area. Therefore, the digital terrain model means a digital representation of the earth's surface through a mathematical model that approximates the land surface modeling, which can be used in various civil and industrial applications in. To achieve the digital terrain model of data recorded using linear and nonlinear interpolation method based on point survey which highlights the natural surface studied. Given the complexity of this work it is absolutely necessary to know in detail of all topographic elements of work area, without the actions to be undertaken to project and manipulate would not be possible. To achieve digital terrain model, within a specialized software were set appropriate parameters required to achieve this case study. After performing all steps we obtained digital terrain model of Vulcan Mine. Digital terrain model is the complex product, which has characteristics that are equivalent to the specialists that use satellite images and information stored in a digital model, this is easier to use

Temperature Effects on Damage Mechanisms of Hybrid Metal – Composite Bolted Joints Using SHM Testing Method

This paper presents the quasi-static thermo-mechanical loading effects on the progressive damage mechanisms and failure modes of the single-bolt, single-shear, hybrid metal-composite, bolted joints in aerospace applications. A three-dimensional finite element method (FEM) technique was used to model the countersunk head bolted joint in details, including geometric and frictional based contact full nonlinearities and using commercial software PATRAN as pre/post-processor. The progressive damage analysis (PDA) in laminated (CFRP/ vinyl ester epoxy) composite material including nonlinear shear behavior, Hashin-type failure criteria and strain-based continuous degradation rules for different values of temperatures was made using SOL 400 NASTRAN solver. In order to validate the numerical results and close investigation of the fracture mechanisms for metal-composite bolted joints by determining ultimate failure loads, experiments were conducted in temperature controlled chamber using SHM (Structural Health Monitoring) technique. The results show that the thermal effects are not negligible on failure mechanism in hybrid aluminum-CFRP bolted joints having strong different thermal expansion coefficients. The complex 3D FEM model using advanced linear continuum solid-shell elements proved computational efficiency and ability to accurately predict the various failure modes as bearing and shear-shear out, including the temperature effects on the failure propagation and damage mechanism of hybrid metal-composite bolted joints

Emergency Treatment of Transverse Colon Cancer

This chapter deals with the emergency treatment of transverse colon cancer. The main complications that classify transverse colon cancer in an emergency setting are obstruction, perforation accompanied by localized or generalized peritonitis, and hemorrhage which may be occult or cataclysmic with hemorrhagic shock. We present the technical principles of radical surgical resection using embryological, anatomical, and oncological concepts. In this chapter we also discuss the principles of lymphadenectomy associated with complete excision of the mesocolon with high vascular ligation, in particular with T3 or T4 cancers requiring D2/D3 lymphadenectomy. The use of infrapyloric, gastro-epiploic, and prepancreatic lymphadenectomy is recommended due to the frequent metastases in these regional lymph nodes

Host-Detrimental Role of Esx-1-Mediated Inflammasome Activation in Mycobacterial Infection

The Esx-1 (type VII) secretion system is a major virulence determinant of pathogenic mycobacteria, including Mycobacterium marinum. However, the molecular events and host-pathogen interactions underlying Esx-1-mediated virulence in vivo remain unclear. Here we address this problem in a non-lethal mouse model of M. marinum infection that allows detailed quantitative analysis of disease progression. M. marinum established local infection in mouse tails, with Esx-1-dependent formation of caseating granulomas similar to those formed in human tuberculosis, and bone deterioration reminiscent of skeletal tuberculosis. Analysis of tails infected with wild type or Esx-1-deficient bacteria showed that Esx-1 enhanced generation of proinflammatory cytokines, including the secreted form of IL-1β, suggesting that Esx-1 promotes inflammasome activation in vivo. In vitro experiments indicated that Esx-1-dependent inflammasome activation required the host NLRP3 and ASC proteins. Infection of wild type and ASC-deficient mice demonstrated that Esx-1-dependent inflammasome activation exacerbated disease without restricting bacterial growth, indicating a host-detrimental role of this inflammatory pathway in mycobacterial infection. These findings define an immunoregulatory role for Esx-1 in a specific host-pathogen interaction in vivo, and indicate that the Esx-1 secretion system promotes disease and inflammation through its ability to activate the inflammasome