Internal Stresses in Plasma Coatings with an Amorphous Structure

1998 ◽  
Author(s):  
Y. Borisov ◽  
V. Korzhyk
Keyword(s):  
Stress State ◽  
Boron Content ◽  
Amorphous Structure ◽  
Internal Stresses ◽  
Compressive Stresses ◽  
Stress Formation ◽  
Coating Layers ◽  
Plasma Sprayed ◽  
Amorphous Coatings ◽  
Material Temperature

Abstract The stress state of plasma sprayed amorphous coatings of the Fe-B based alloys with the boron content of 15-35 %, as well as of the above type alloys but with additions of Ni, Cr, Mo, was studied. Internal stresses depend on the type of a plasma gas, thickness and composition of the coatings, material, temperature and conditions of additional cooling of the substrate. Additional cooling of the substrate was found to be the most efficient method of decreasing the internal stress. Formation of compressive stresses in the coating layers adjoining the substrate is shown to lead to 25-30 % increase in its fatigue strength under alternating loads.

Theoretical study of the prestressing strand's stress by computer modeling methods

2020 ◽  
Vol 76 (11) ◽  
pp. 1139-1148
Author(s):  
A. G. Korchunov ◽  
E. M. Medvedeva ◽  
E. M. Golubchik
Keyword(s):  
Residual Stresses ◽  
High Strength ◽  
Pearlitic Steel ◽  
Internal Stresses ◽  
Steel Microstructure ◽  
Compressive Stresses ◽  
Wide Range ◽  
Prestressing Strands ◽  
Increasing Temperature ◽  
Wire Strand

The modern construction industry widely uses reinforced concrete structures, where high-strength prestressing strands are used. Key parameters determining strength and relaxation resistance are a steel microstructure and internal stresses. The aim of the work was a computer research of a stage-by-stage formation of internal stresses during production of prestressing strands of structure 1х7(1+6), 12.5 mm diameter, 1770 MPa strength grade, made of pearlitic steel, as well as study of various modes of mechanical and thermal treatment (MTT) influence on their distribution. To study the effect of every strand manufacturing operation on internal stresses of its wires, the authors developed three models: stranding and reducing a 7-wire strand; straightening of a laid strand, stranding and MTT of a 7-wire strand. It was shown that absolute values of residual stresses and their distribution in a wire used for strands of a specified structure significantly influence performance properties of strands. The use of MTT makes it possible to control in a wide range a redistribution of residual stresses in steel resulting from drawing and strand laying processes. It was established that during drawing of up to 80% degree, compressive stresses of 1100-1200 MPa degree are generated in the central layers of wire. The residual stresses on the wire surface accounted for 450-500 MPa and were tension in nature. The tension within a range of 70 kN to 82 kN combined with a temperature range of 360-380°С contributes to a two-fold decrease in residual stresses both in the central and surface layers of wire. When increasing temperature up to 400°С and maintaining the tension, it is possible to achieve maximum balance of residual stresses. Stranding stresses, whose high values entail failure of lay length and geometry of the studied strand may be fully eliminated only at tension of 82 kN and temperature of 400°С. Otherwise, stranding stresses result in opening of strands.

EFFECT OF AMMONIA SOLUTION ON COMPOSITION, STRUCTURE AND MAGNETIC PROPERTIES OF CHEMICALLY PREPARED Co-B NANO-PARTICLES

2012 ◽  
Vol 05 ◽  
pp. 134-141
Author(s):  
HOOMAN SABAROU ◽  
ABOLGHASEM ATAIE
Keyword(s):  
Magnetic Properties ◽  
Boron Content ◽  
Fine Particles ◽  
Chemical Reduction ◽  
Amorphous Structure ◽  
Ammonia Solution ◽  
Nano Particles ◽  
Reagent Solution ◽  
Sem Images ◽  
Composition Structure

In this study, the effect of ammonia solution addition as a pH adjusting component on the thermal behavior, phase composition, morphology, and magnetic properties of reduced Co - B nano-particles fabricated by chemical reduction route have been studied using DSC, XRD, SEM, and VSM techniques, respectively. Chemical composition of the samples was measured by ICP. The ICP results showed that basic pH of reagent solution, derived from utilizing ammonia solution, caused the boron content to decrease. XRD results indicated an amorphous structure for both samples synthesized with and without ammonia solution. Analysis of the DSC results showed that crystallization behavior has dramatically altered, owing to utilize ammonia solution. While the sample synthesized without ammonia solution showed three distinctive exothermic peaks at 216,470, and 540°C, the sample synthesized in the presence of ammonia solution exhibited only two exothermic peaks at 235 and 470°C and one endothermic peak at 370°C. SEM images reveal that the samples have a net- like morphology and the net is formed by many interconnected spherical fine particles with sizes less than 100 nm. Saturation magnetization of the sample synthesized in the presence of ammonia solution has improved significantly, probably due to the less amount of boron.

Structure and Electrochemical Behavior of Plasma-Sprayed LSGM Electrolyte Films

2002 ◽  
Vol 756 ◽  
Author(s):  
H. Zhang ◽  
X. Ma ◽  
J. Dai ◽  
S. Hui ◽  
J. Roth ◽  
...  
Keyword(s):  
Electrochemical Behavior ◽  
Electrochemical Impedance ◽  
Amorphous Structure ◽  
Solid Oxide ◽  
X Ray Diffraction ◽  
X Ray ◽  
Spray Process ◽  
Plasma Spray Process ◽  
Electrolyte Film ◽  
Plasma Sprayed

ABSTRACTAn intermediate temperature solid oxide fuel cell (SOFC) electrolyte film of La0.8Sr 0.2Ga0.8Mg0.2O2.8 (LSGM) was fabricated using a plasma spray process. The microstructure and phase were investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical behavior of the thermal sprayed LSGM film was investigated using electrochemical impedance spectroscopy (EIS). The study indicates that thermal spray can deposit a dense LSGM layer. It was found that the rapid cooling in the thermal process led to an amorphous or poor crystalline LSGM deposited layer. This amorphous structure has a significant effect on the performance of the cell. Crystallization of the deposited LSGM layer was observed during annealing between 500–600 °C. After annealing at 800 °C, the ionic conductivity of the sprayed LSGM layer can reach the same level as that of the sintered LSGM.

Invariant stress state parameters for forging upsetting of magnesium in the shell

2021 ◽  
Vol 23 (1) ◽  
pp. 79-88
Author(s):  
Yuriy Loginov ◽  
◽  
Yuliya Zamaraeva ◽  
◽  
◽  
...  
Keyword(s):  
Stress State ◽  
Deformable Body ◽  
Great Influence ◽  
Precipitation Process ◽  
Software Module ◽  
Plastic Properties ◽  
Compressive Stresses ◽  
Element Simulation ◽  
Processed Material ◽  
Mathematical Evaluation

Introduction. For pressure treatment of low-plastic metals, it is necessary to develop special techniques for increasing plasticity. In the cold state, an increase in plastic properties is possible due to an increase in the level of compressive stresses during deformation. In the processes of forging precipitation, this is achieved by using shells or clips of various types. At the same time, the configuration of the precipitation tool also matters. To create additional compressive stresses and increase the ductility of the metal, the working surface of the tool can be configured differently than with a normal free draft, where it is obviously larger than the contact surface area of the workpiece, so that metal broadening can occur. The stress state has a great influence on the plasticity of the processed material. This state is described by methods of tensor representation, but to assess the situation, it is customary to use invariants of tensors in one form or another, which eliminates the influence of coordinates on the results of the analysis. In the sections of deformable body mechanics dealing with the influence of the stress state on plasticity, the first, but sometimes other invariants of the stress tensor are used, the invariants themselves are transformed into the stress state indicator and the lode coefficient. The aim of the work: mathematical evaluation of invariant parameters of the stress state of the magnesium precipitation process at room temperature, according to the results of which it is possible to obtain a positive result in real experiments. Research methods: finite element simulation using the DEFORM software module. Results and discussion. The theoretical justification of increasing the plasticity of the magnesium billet in the process of precipitation in the cage without its compression is carried out. An increase in the stress state index modulo 2...5 times is revealed, which contributes to an increase in the plasticity of the metal. At the same time, a zone with a lode coefficient close to zero is identified. It is adjacent to the middle of the height of the workpiece at the point of contact with the cage and can be a dangerous cross-section from the position of crack formation.

scholarly journals Effect of Small Addition of Cobalt on Magnetic Properties and Internal Stresses Sources in the Form of Free Volumes and Pseudo-Dislocation Dipoles in Fe78CoXSi11-XB11 (x = 0 Or 2) Alloys / Wpływ Nieznacznego Dodatku Kobaltu Na Właściwości Magnetyczne Oraz Źródła Naprężeń Wewnętrznych W Postaci Wolnych Objętości Oraz Pseudodyslokacyjnych Dipoli W Stopach Fe78CoXSi11-XB11 (x = 0 Or 2)

2015 ◽  
Vol 60 (4) ◽  
pp. 3095-3100 ◽  
Author(s):  
M. Szota
Keyword(s):  
Magnetic Properties ◽  
Amorphous Materials ◽  
Amorphous Structure ◽  
Small Addition ◽  
Structural Defects ◽  
Internal Stresses ◽  
Structure Defects ◽  
Alloy Addition ◽  
Application Potential ◽  
Technical Industry

Amorphous materials in the form of tapes, despite being discovered more than half a century ago, are still the object of interest for materials engineers and electro-technical industry. They possess a great application potential, and are constantly studied for new variations. Due to the different structure from the commonly manufactured textured FeSi sheets, FeCoB based amorphous alloys demonstrate very good, so called soft magnetic properties. This paper presents the results of studying the structure and magnetic properties of tapes of Fe78CoxSi11-xB11(X = 0 or 2) alloys of amorphous structure. In addition, the effect of Co alloy addition on the type of structural defects in the area of ferromagnetic saturation approach was examined. It was found that a small addition of Co affects the increase of saturation magnetization value, as well as the distribution of magnetization vectors within the stresses sources in form of structure defects.

Characterization of Plasma-Sprayed Ceramic Coating Layers for Melting Crucible of Metal Fuels

2017 ◽  
Vol 17 (11) ◽  
pp. 8598-8602
Author(s):  
Ki-Hwan Kim ◽  
Song Hoon ◽  
Jong-Hwan Kim ◽  
Ki-Won Hong ◽  
Jeong-Yong Park
Keyword(s):  
Ceramic Coating ◽  
Melting Crucible ◽  
Coating Layers ◽  
Plasma Sprayed

Buckling of Thin Cylindrical Shells Under Locally Elevated Compressive Stresses

2010 ◽  
Vol 133 (1) ◽  
Author(s):  
J. Michael Rotter ◽  
Minjie Cai ◽  
J. Mark F. G. Holst
Keyword(s):  
Stress State ◽  
Cylindrical Shells ◽  
Peak Stress ◽  
Theoretical Research ◽  
Design Rule ◽  
Uniform Stress ◽  
Geometric Imperfection ◽  
Buckling Strength ◽  
Shell Buckling ◽  
Compressive Stresses

Thin cylindrical shells used in engineering applications are often susceptible to failure by elastic buckling. Most experimental and theoretical research on shell buckling relates only to simple and relatively uniform stress states, but many practical load cases involve stresses that vary significantly throughout the structure. The buckling strength of an imperfect shell under relatively uniform compressive stresses is often much lower than that under locally high stresses, so the lack of information and the need for conservatism have led standards and guides to indicate that the designer should use the buckling stress for a uniform stress state even when the peak stress is rather local. However, this concept leads to the use of much thicker walls than is necessary to resist buckling, so many knowledgeable designers use very simple ideas to produce safe but unverified designs. Unfortunately, very few scientific studies of shell buckling under locally elevated compressive stresses have ever been undertaken. The most critical case is that of the cylinder in which locally high axial compressive stresses develop extending over an area that may be comparable with the characteristic size of a buckle. This paper explores the buckling strength of an elastic cylinder in which a locally high axial membrane stress state is produced far from the boundaries (which can elevate the buckling strength further) and adjacent to a serious geometric imperfection. Care is taken to ensure that the stress state is as simple as possible, with local bending and the effects of internal pressurization eliminated. The study includes explorations of different geometries, different localizations of the loading, and different imperfection amplitudes. The results show an interesting distinction between narrower and wider zones of elevated stresses. The study is a necessary precursor to the development of a complete design rule for shell buckling strength under conditions of locally varying axial compressive stress.

Residual Stress Measurement of Plasma Sprayed Coating Layers in ZrO2

2007 ◽  
Vol 544-545 ◽  
pp. 451-454
Author(s):  
Soo Wohn Lee ◽  
Jia Zhang ◽  
Huang Chen ◽  
J. S. Song ◽  
Jae Kyo Seo ◽  
...  
Keyword(s):  
Residual Stress ◽  
Stress Measurement ◽  
Diffraction Method ◽  
Spray Coating ◽  
X Ray Diffraction ◽  
Plasma Sprayed Coatings ◽  
Coating Layers ◽  
Sprayed Coating ◽  
Plasma Sprayed ◽  
Sprayed Coatings

Plasma sprayed coatings have been widely applied in modifying surface properties of metal components. It is also useful to prevent various types of wear, corrosion, erosion and thermal. But the residual stress is still an important problem which can effect the properties of sprayed coating. So it’s necessary to find out the reason of residual stress and the relationship between plasma sprayed condition and residual stress. Plasma spray coating layers with conventional ZrO2 powder was examined to calculate residual stress by X-ray diffraction method with various coating thickness.

New Challenge of Plasma Spray Coatings in Nano Oxide Ceramics

2006 ◽  
Vol 317-318 ◽  
pp. 533-538
Author(s):  
Soo Wohn Lee ◽  
Huang Chen ◽  
Yi Zeng ◽  
Chuan Xian Ding
Keyword(s):  
Electron Microscopy ◽  
Deposition Efficiency ◽  
Metallic Substrate ◽  
Atmospheric Plasma ◽  
Ceramic Powders ◽  
Plasma Sprayed Coatings ◽  
Coating Layers ◽  
Sprayed Coating ◽  
Plasma Sprayed ◽  
Sprayed Coatings

Nanostructured and conventional Al2O3, ZrO2, and TiO2 were deposited using an atmospheric plasma spraying (APS). The size of commercial nano-ceramic powders was varied from 5nm up to 150nm. The microstructure and phase composition of the plasma sprayed coatings on metallic substrate were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). It was found that nano-sized ceramic powders enhanced the deposition efficiency on the metallic substrate rather than the micro-sized conventional commercial powders. Density and mechanical property such as microhardness were better in the case of the nano-sized ceramic powders than that of the conventional micro-sized ceramic powders, which are associated with the fine surface roughness and less size in pores of the coating layers. The wear rate of the nanostructured coating was lower than that of the conventional coating. The results were explained in terms of their microstructure of the coatings layers. Also, photocatalytic characterization of the plasma sprayed coatings, using nanocrystalline size TiO2 as feedstock with various powder sizes and shapes as well as adding with different photocatalytic oxides, was performed. The photocatalytic reactivity using plasma sprayed coating layers can be utilized into various applications.

Novel Nanostructural Biomaterial Composites

2002 ◽  
Author(s):  
R. J. Narayan
Keyword(s):  
Heart Valves ◽  
Antimicrobial Properties ◽  
Internal Stresses ◽  
Dlc Coatings ◽  
Compressive Stresses ◽  
Diamondlike Carbon ◽  
Nanotube Composites ◽  
Novel Processing ◽  
Hardness Values ◽  
Poor Adhesion

Hydrogen-free diamondlike carbon (DLC), with hardness values close to that of diamond, possess many desirable biocompatible properties for a variety of biomedical applications. The DLC coatings can be applied to joints prostheses, heart valves, and other medical devices. Unfortunately, hydrogen-free DLC coatings have a large compressive stresses which result in poor adhesion and wear characteristics. In this paper, we present results on silver doping of DLC to alleviate internal stresses as well as create DLC-Ag nanocomposites where Ag is in the form of nanoparticles. The Ag nanoparticles are expected to impart antimicrobial properties by providing sources of electrons. In the second part of the paper, we have created DLC and nanotube composites where nanotubes grow normal to the surface. This novel architecture not only alleviates internal stresses, but DLC + Nanotube composites have enhanced hardness and unique antimicrobial properties. Finally, we discuss novel multilayer DLC and hydroxyapatite (HA) composite where HA and DLC films are deposited sequentially at room temperature. The HA films with composites close to that of bone is considered very desirable for biocompatibility and integration with base structures. We discuss novel processing, characterization, hardness and bioeompatible properties of all these composites in detail.

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