An Efficient Damage Quantification Method for Cylindrical Structures Enhanced by a Dry-Point-Contact Torsional-Wave Transducer

Quantification of damage sizes in cylindrical structures such as pipes and rods is of paramount importance in various industries. This work proposes an efficient damage quantification method by using a dry-point-contact (DPC) transducer based on the non-dispersive torsional waves in the low-frequency range. Theoretical analyses are first carried out to investigate the torsional wave interaction with different sizes of defects in cylindrical structures. A damage quantification algorithm is designed based on the wave reflections from the defect and end. Capitalizing on multiple excitations at different frequencies, the proposed algorithm constructs a damage image that identifies the geometric parameters of the defects. Numerical simulations are conducted to validate the characteristics of the theoretically-predicted wave-damage interaction analyses as well as the feasibility of the designed damage quantification method. Using the DPC transducer, experiments are efficiently carried out with a simple physical system. The captured responses are first assessed to confirm the capability of the DPC transducer for generating and sensing torsional waves. The sizes of the defects in two representative steel rods are then quantified with the proposed method. Both numerical and experimental results demonstrate the efficacy of the proposed damage quantification method. The understandings of the wave-damage interaction and the concept of the damage quantification algorithm lay out the foundation for engineering applications.

Structure and microstructure behavior of iron doped potassium sodium niobate powders

In this paper, the synthesis and characterization of the potassium sodium niobate doped with iron powders have been studied. Solid-state oxide reaction sintering was used. The powders produced in this work exhibit no homogeneous microstructure, which introduced the growth of random cylindrical structures and will can contribute to the increased porosity ceramics. It was observed average particle size of 3μm, besides, also it was observed the formation of agglomerations and an increase in the size of these clusters with the increase in the amount of iron. The calcination temperature was 950 °C. This is slightly higher than other potassium sodium niobate powders systems. In addition to the physical and microstructural properties, structural properties are presented and analyzed for the first-time using Mössbauer spectroscopy as complementary technique in Fe 3+doped potassium sodium niobate powders. This work is important to state solid physics because establishes the influence of iron in the potassium sodium niobate system, and so the future obtaining of multifunctional materials that have piezoelectric and magnetic properties.

Numerical analysis of the elastic-plastic behavior of a tubular structure in FGM under pressure and defect presence

Given the field of application and the many advantages, the use of FGM (Functionally Graded Materials) materials has recently been extended in several components and more particularly in cylindrical structures, which have been the subject of several recent studies. Our work aims to use the finite element method to analyze a cylindrical structure in FGM with properties gradated in the direction of the radius (Thickness) solicited purely in internal pressure by the implementation of a UMAT subroutine in the calculation code ABAQUS. The elasto-plastic behavior of the FGM is described by the flow theory represented by the equivalent stress of Von Mises and an incremental hardening variable. The TTO model (Tamura-Tomota-Ozawa) was used only to determine the elastic-plastic properties of the FGM material. The radial, tangential and axial stresses according to the thickness were evaluated in the first part of our work. In the second part, these stresses are evaluated under the same conditions but with the presence of a micro-cavity. The results obtained show clearly that these stresses are in direct relation not only with the thickness and properties of the FGM tube but also with the presence of the cavity.

Causes of Failures in Circular Concrete Silo Walls, Particularly Under Environmental Influences

The paper reports the results of a case study for achieving longer service life and increasing the environmental sustainability of concrete silos. Damage mechanisms in concrete silo walls, and respectively in cylindrical structures (e.g., chimneys, cooling towers, and tanks), are widely diverse. The common causes of failures include those due to poor design considerations, construction deficiencies, non-compliance with operational rules and regulations, lack of maintenance, and insufficient and/or corroded reinforcements, together with the environmental conditions affecting the walls. In addition to the ultimate limit state design, temperature-induced cracking may often be underestimated in the design of reinforced concrete silos, leading to premature deterioration and losses in serviceability. Cracks from environmental or service conditions facilitate the ingress of moisture and corrosive agents. Therefore, there is an increased interest in reducing the appearance of cracks and limiting their width. The aim of this paper is to highlight the synergistic effects in the design, construction, and operation of silo walls, particularly under varying environmental influences. The research undertaken indicates that systematic errors can be identified and corrected.

3D Printing of Temporary Prostheses for Controlled-Release of Drugs: Design, Physical Characterization and Preliminary Studies

In recent years, the use of 3D printing technologies in orthopedic surgery has markedly increased, as they offer the possibility of printing personalized prostheses. The work presented in this article is a preliminary study of a research project which aims to manufacture customized spacers containing antibiotics for use in joint replacement surgery. The objective of this work was to design and print different 3D constructs to evaluate the use of different materials, their properties after the process of 3D printing, such as resistance, and the release kinetics of drugs from the constructs. Different designs and different materials were analyzed to obtain a 3D construct with suitable properties. Our design takes advantage of the micropores created between the layers of the 3D printed filaments to release the contained drug. Using polylactic acid (PLA) we were able to print cylindrical structures with interconnected micropores and a hollow chamber capable of releasing methylene blue, which was selected as a model drug. The final PLA 3D construct was printed with a 10% infill. The physical and technological characteristics, morphological changes at body temperature and interaction with water were considered to be acceptable. The PLA 3D printed constructs were found to have sufficient strength to withstand a force of 500 kg. The results obtained allow to continue research in this project, with the aim of manufacturing prostheses containing a reservoir of antibiotics or other drugs in their interior for their subsequent controlled release.

Morphing of soft tubes by anisotropic growth

We present a study of smart growth in layered cylindrical structures. We start from the characterization of a compatible growth field in an anisotropic growing tube with the aim to show a small perturbation in the compatible growth field that may produce a controlled deprivation of compatibility and localization of elastic energy storage in a composite structure made up of anisotropic growing tubes.

Vibrations of Slender Structures Caused by Vortices

Slender cylindrical structures such as overhead transmission lines, skyscrapers, chimneys, risers, and pipelines can experience flow induced vibration (FIV). The vortex vibrations are a type of FIV; they arise because of oscillating forces caused by flow separation and the detachment of vortices. The paper presents a brief overview of experimental research on vortex induced vibration - VIV of short, rigid cylinders elastically supported (with a small aspect ratio). This overview summarizes the basic results of the vortex vibration (VIV) which have been performed in the last five decades. These studies were mainly related to determining the influence of selected parameters - mass, damping and Reynolds number on the cylinder response, either in one direction only or simultaneously in the flow direction and transverse to the flow direction, and with the search for a map of vortex images in the trace (vortex wake pattern map).