scholarly journals Wheeled Robot Dedicated to the Evaluation of the Technical Condition of Large-Dimension Engineering Structures

Robotics ◽  
2020 ◽  
Vol 9 (2) ◽  
pp. 28
Author(s):  
Jarosław Domin ◽  
Marcin Górski ◽  
Ryszard Białecki ◽  
Jakub Zając ◽  
Krzysztof Grzyb ◽  
...  

There are many reasons why engineering structures are at risk of losing their loading capacity during their long-term exploitation, which may lead to hazardous states. In such cases, structures must be strengthened. The most popular technique of strengthening is based on the use of composite materials—fiber-reinforced polymer (FRP) elements attached to the structure with the special resins. FRP elements are applied externally, often in hard to reach places, which makes it difficult to diagnose the durability and quality of such a connection. In this study, a combination of a modern thermographic method was proposed, which makes it possible to assess the degree of damage to the contact of the structure with the composite material along with the running platform (wheeled robot) equipped with a set of diagnostic sensors. The development potential of such a solution for subsequent projects was also indicated.

2020 ◽  
Vol 54 (26) ◽  
pp. 4067-4080 ◽  
Author(s):  
Wenhua Lin ◽  
Yeqing Wang ◽  
Youssef Aider ◽  
Mojtaba Rostaghi-Chalaki ◽  
Kamran Yousefpour ◽  
...  

Understanding the damage mechanisms of fiber-reinforced polymer matrix composite materials under high voltage conditions is of great significance for lightning strike protection and high voltage insulation applications of composite structures. In this paper, we investigated effects of the lightning impulse (LI) voltage and high voltage alternating current (HVAC) puncture on damage modes of the electrically nonconductive glass fiber-reinforced polymer (GFRP) matrix composite materials through experimental tests and numerical simulations. The LI and HVAC tests represent the lightning strike and high voltage insulation cable puncture conditions, respectively. Our experimental examinations showed that GFRP composite specimens subjected to the LI voltage test exhibited distinct damage modes compared with those in the HVAC puncture test. The GFRP composite material suffered more charring and fiber vaporization in the HVAC puncture test, whereas less matrix charring and fiber vaporization but severe fiber breakage and delamination in response to the LI voltage tests. The findings indicate that the thermal effect dominates the damage of GFRP composites inflicted by the HVAC puncture test, whereas the mechanical impact effect governs the GFRP composite damage in the LI voltage test. In addition, the electric arc plasma formation during the puncture of the GFRP composite material was modeled through solving Maxwell’s equations and the heat generation equations using finite element analysis. Simulation results provided insights on the effects of duration and intensity of the high voltage electric discharge on the composite damage.


2021 ◽  
Vol 11 (11) ◽  
pp. 4933
Author(s):  
Ji-Sang Yahng ◽  
Dae-Su Yee

Composite materials are increasingly being utilized in many products, such as aircrafts, wind blades, etc. Accordingly, the need for nondestructive inspection of composite materials is increasing and technologies that allow nondestructive inspection are being studied. Existing ultrasound methods are limited in their ability to detect defects due to high attenuation in composite materials, and radiographic examination methods could pose a danger to human health. Terahertz (THz) wave technology is an emerging approach that is useful for imaging of concealed objects or internal structures due to high transmittance in non-conductive materials, straightness, and safety to human health. Using high-speed THz tomography systems that we developed, we have obtained THz tomographic images of glass-fiber-reinforced polymer (GFRP) laminates with artificial internal defects such as delamination and inclusion. The defects have various thicknesses and sizes, and lie at different depths. We present THz tomographic images of GFRP samples to demonstrate the extent to which the defects can be detected with the THz tomography systems.


Author(s):  
Ю. Зубарев ◽  
Yu. Zubarev ◽  
А. Приемышев ◽  
A. Priyomyshev ◽  
А. Заостровский ◽  
...  

The peculiarities in polymeric composite material cutting are considered. The recommendations for use of different materials for cutters, their geometry and treatment modes are offered that allows obtaining the required quality of a product surface.


2018 ◽  
pp. 40-46
Author(s):  
N.I. Mykyievych

Introduction. Critical review of the available medical scientific sources demonstrates that despite the wide range of advantages, photopolymer composite materials have certain disadvantages. The main of those are contraction during polymerization and incomplete polymerization of the filling volume. These disadvantages cause the crevice between the direct restoration and the tooth wall, the possible discoloration can reduce tooth hardness. Some researchers recommend the application of inlays in order to prevent complications while restoring caries cavities in posterior teeth. Complete polymerization and reliable adjacency to dental tissues ensure sustainability of indirect photopolymer restoration and prevent secondary caries in restored areas. Objective. The study is aimed at raising the effectiveness of dental treatment by clinical evaluation of the quality of direct and indirect restorations made from composite materials. Methods and Materials. In order to conduct comparative clinical evaluation 90 patients with defects of coronal part of lateral teeth, aged 19-54 have been examined, who have orthognathic occlusion, don’t have dental and facial malformations or muscular and joint dysfunctions. They underwent 189 restorations of lateral teeth with cavities of O, MO, OD, MOD types due to medium or severe caries or because of dissatisfying condition of the previously inserted fillings. The patients were divided into two groups according to the method of treatment. The I (basic) group included 42 patients, who underwent 76 indirect restorations for reconstructing the defects of teeth crowns. The II (test) group included 54 patients, who underwent 113 direct restorations for reconstructing the defects of teeth crowns. Each group was subdivided into two subgroups. The patients who underwent 38 indirect restorations with photopolymer composite material Filtek Z 250 (3M ESPE) were placed in the subgroup I A, the patients who underwent 38 indirect restorations with material Charisma (Heraeus Kulzer) were placed in the subgroup I B. The patients who underwent 57 direct restorations with photopolymer composite material Filtek Z 250 (3M ESPE) were placed in the subgroup II A, the patients who underwent 56 direct restorations with material Charisma (Heraeus Kulzer) were placed in the subgroup II B. Clinical efficiency of both direct and indirect restorations was evaluated immediately after their application and then after 12 and 24 months with the help of visual and instrumental examination. When secondary caries was suspected, the target X-rays were taken with Heliodent Vario (Sirona). The evaluation was conducted according to the Ryge criteria (1998), approved by USPHS (United States Public Health Service). They include the following indicators: anatomic contour, marginal integrity and marginal coloration, secondary caries, surface texture, preservation of the restoration, restoration fracture, crevice at the edge of restoration, restoration abrasion, tooth fracture, no approximal adjacency, overhanging restoration, localized gingivitis. Results. The comparative analysis of the clinical efficiency of lateral teeth restorations made from photopolymer materials under study revealed significantly higher quality of indirect restorations (composite inlays), which demonstrated good clinical results even in long-term perspective. Only 5,3% of patients with indirect restorations (with both Filtek Z 250 and Charisma) underwent partial restoration in order to prevent further destruction. By contrast, the patients with direct restorations required the partial restoration in 7% with Filtek Z 250 and 8,9% with Charisma and needed immediate replacement of fillings in 10,5% and 17,8% correspondingly.


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