Structural Designing With Ceramic Materials

1978 ◽  
Vol 100 (2) ◽  
pp. 260-266 ◽  
Author(s):  
W. Duckworth ◽  
G. Bansal
Keyword(s):  
Stress Distribution ◽  
Ceramic Materials ◽  
Failure Stress ◽  
Central Problem ◽  
Structural Members ◽  
Basic Framework ◽  
Griffith’S Criterion ◽  
Structural Applications

A central problem in attempting to use ceramic materials in demanding structural applications is uncertainty about the stresses to which they can be safely subjected. A ceramic rarely, if ever, exhibits a characteristic failure stress. This stress depends on the nature and distribution of microscopic flaws that intensify stress locally, and fracture initiates at a single “worst” flaw when Griffith’s criterion for crack instability is met. Within the basic framework, theories are available for treating effects of time, size, and stress distribution on failure stress. This paper reviews these theories, and discusses their use in specifying limiting stresses in designing structural members.

Analytical and High-Resolution EM Study of Crystalline Phases formed at Metal-Ceramic Interface

1990 ◽  
Vol 48 (2) ◽  
pp. 426-427
Author(s):  
N. Merk ◽  
A. P. Tomsia ◽  
G. Thomas
Keyword(s):  
Cross Section ◽  
Dissimilar Materials ◽  
Ceramic Materials ◽  
Electron Micrograph ◽  
Scanning Electron Micrograph ◽  
Structural Applications ◽  
Metal Ceramic ◽  
The Subject ◽  
Ceramic Compounds ◽  
Scanning Electron

A recent development of new ceramic materials for structural applications involves the joining of ceramic compounds to metals. Due to the wetting problem, an interlayer material (brazing alloy) is generally used to achieve the bonding. The nature of the interfaces between such dissimilar materials is the subject of intensive studies and is of utmost importance to obtain a controlled microstructure at the discontinuities to satisfy the demanding properties for engineering applications . The brazing alloy is generally ductile and hence, does not readily fracture. It must also wett the ceramic with similar thermal expansion coefficient to avoid large stresses at joints. In the present work we study mullite-molybdenum composites using a brazing alloy for the weldment.A scanning electron micrograph from the cross section of the joining sequence studied here is presented in Fig. 1.

Characterization and Production of Structurat Ceramics in the Systems Fe(1-X)O-Fe3O4 and MgO-MgFe2O4.

1999 ◽  
Vol 5 (S2) ◽  
pp. 810-811
Author(s):  
A. Huerta ◽  
R. Ordoñez ◽  
H.A. Calderon ◽  
M. Umemoto ◽  
K. Tsuchiya ◽  
...  
Keyword(s):  
Ceramic Materials ◽  
Grain Structure ◽  
Second Phase ◽  
Magnetic Recording Media ◽  
Mechanically Alloyed ◽  
Ceramic Oxides ◽  
Plasma Sintering ◽  
Structural Applications ◽  
Spark Plasma ◽  
Second Phases

Ceramic materials are widely studied for their high temperature structural applications. In many crystalline ceramics the range of solid solution decreases with temperature and thus precipitation of a second phase occurs. Thus, ceramics can be hardened by precipitation of second phases. However little is known regarding the effect of precipitation and nanocrystalline grain structure in the ductility of ceramic materials. On the other hand, oxide ceramics are under intense-investigation for their technological advantages in magnetization, dielectric response and chemical stability in such diverse uses as magnetic recording media, induction cores and microwave resonant circuits. This investigation has been undertaken to produce, characterize and measure the properties of ceramics that can be hardened by precipitation. The selected systems include Fe(1-x)O-Fe3 and MgO MgFe2O4. Mechanical milling is used to produce nanocrystalline ceramic oxides in the systems Fe(1-x)O-Fe3 and MgO-MgFe2O4 The mechanically alloyed powders are consolidated by means of spark plasma sintering (SPS) at temperatures ranging from 673 K to 1273 K and a pressure varying from 500 to 50 MPa in vacuum.

MODELING AND STRENGTH ANALYSYS OF A VESSEL FOR TRANSPORTING EXPLOSIVE MATERIALS

2016 ◽  
pp. 93-106
Author(s):  
Marcin SZCZEPANIAK ◽  
Piotr KRYSIAK ◽  
Janusz Śliwiński ◽  
Andrzej WOJCIECHOWSKI ◽  
Patrycja WOJCIESZYŃSKA
Keyword(s):  
Stress Distribution ◽  
Wave Front ◽  
Blast Wave ◽  
Experimental Tests ◽  
Measured Data ◽  
Strain Gauges ◽  
Structural Members ◽  
Distribution Versus ◽  
Explosive Materials ◽  
Real Model

The paper presents calculations and a real model for a vessel transporting goods with explosive materials. Two options of the vessel were fabricated. An extreme value of pressure at the blast wave-front generated by the explosion of 1 kg TNT inside the vessel was determined at the beginning. Then analytical calculations of stress values for vessel frame were conducted. In order to verify the stress level, strain gauges have been attached to the surface of structural members. In the next stage experimental tests were conducted on the proving ground by ex-plosion of 1 kg of TNT inside the vessel. Deformations were measured at the tests. An analysis of measured data is illustrated in diagrams of stress distribution versus time.

scholarly journals Damage-tolerant 3D-printed ceramics via conformal coating

2021 ◽  
Vol 7 (28) ◽  
pp. eabc5028
Author(s):  
Seyed Mohammad Sajadi ◽  
Lívia Vásárhelyi ◽  
Reza Mousavi ◽  
Amir Hossein Rahmati ◽  
Zoltán Kónya ◽  
...  
Keyword(s):  
High Strength ◽  
Ceramic Materials ◽  
Soft Phase ◽  
Conformal Coating ◽  
Hierarchical Assembly ◽  
Damage Propagation ◽  
Simple Strategy ◽  
Structural Applications ◽  
Soft Polymer ◽  
Damage Tolerant

Ceramic materials, despite their high strength and modulus, are limited in many structural applications due to inherent brittleness and low toughness. Nevertheless, ceramic-based structures, in nature, overcome this limitation using bottom-up complex hierarchical assembly of hard ceramic and soft polymer, where ceramics are packaged with tiny fraction of polymers in an internalized fashion. Here, we propose a far simpler approach of entirely externalizing the soft phase via conformal polymer coating over architected ceramic structures, leading to damage tolerance. Architected structures are printed using silica-filled preceramic polymer, pyrolyzed to stabilize the ceramic scaffolds, and then dip-coated conformally with a thin, flexible epoxy polymer. The polymer-coated architected structures show multifold improvement in compressive strength and toughness while resisting catastrophic failure through a considerable delay of the damage propagation. This surface modification approach allows a simple strategy to build complex ceramic parts that are far more damage-tolerant than their traditional counterparts.

scholarly journals Nanoscale stacking fault–assisted room temperature plasticity in flash-sintered TiO2

2019 ◽  
Vol 5 (9) ◽  
pp. eaaw5519 ◽  
Author(s):  
Jin Li ◽  
Jaehun Cho ◽  
Jie Ding ◽  
Harry Charalambous ◽  
Sichuang Xue ◽  
...  
Keyword(s):  
Room Temperature ◽  
Oxygen Vacancies ◽  
Crack Formation ◽  
High Stress ◽  
Ceramic Materials ◽  
Sintering Process ◽  
Flash Sintering ◽  
Structural Applications ◽  
Deformation Behaviors

Ceramic materials have been widely used for structural applications. However, most ceramics have rather limited plasticity at low temperatures and fracture well before the onset of plastic yielding. The brittle nature of ceramics arises from the lack of dislocation activity and the need for high stress to nucleate dislocations. Here, we have investigated the deformability of TiO2 prepared by a flash-sintering technique. Our in situ studies show that the flash-sintered TiO2 can be compressed to ~10% strain under room temperature without noticeable crack formation. The room temperature plasticity in flash-sintered TiO2 is attributed to the formation of nanoscale stacking faults and nanotwins, which may be assisted by the high-density preexisting defects and oxygen vacancies introduced by the flash-sintering process. Distinct deformation behaviors have been observed in flash-sintered TiO2 deformed at different testing temperatures, ranging from room temperature to 600°C. Potential mechanisms that may render ductile ceramic materials are discussed.

Modelling of TBC system failure: Stress distribution as a function of TGO thickness and thermal expansion mismatch

2006 ◽  
Vol 13 (3) ◽  
pp. 409-426 ◽  
Author(s):  
M. Martena ◽  
D. Botto ◽  
P. Fino ◽  
S. Sabbadini ◽  
M.M. Gola ◽  
...  
Keyword(s):  
Thermal Expansion ◽  
Stress Distribution ◽  
Failure Stress ◽  
System Failure ◽  
Thermal Expansion Mismatch

Continuum Isotropic Elastic Model for Sintering of Ceramic Materials

2012 ◽  
Vol 727-728 ◽  
pp. 1069-1074
Author(s):  
Vergel C. Serrano ◽  
Jairo Arturo Escobar ◽  
G.O. Porras
Keyword(s):  
Stress Distribution ◽  
Shear Viscosity ◽  
Fem Simulation ◽  
Continuum Theory ◽  
Dimensional Change ◽  
Ceramic Materials ◽  
Linear Displacement ◽  
Elastic Model ◽  
Simulation Results ◽  
The Continuum

In this work a sintering model that assumes infinitesimal displacements rates has been structured using the continuum theory of sintering develop by Olevsky and Skorokhod [1, 2] and the sintering model develop by Sasan Kiani et al. [3, 4]. The model was used to estimate dimensional change and the density distribution using linear displacement rates (LRDs) as the only input. Furthermore, if the sintering potential and dense material shear viscosity are known, the stress distribution can be approximated. The magnitude of two stress norms (i.e. Von Misses stress and the stress tensor first invariant) determined using experimental and calculated LDRs are compared using three different geometries. From FEM simulation results it was inferred that densification can occur in presence of tension stresses if their magnitude is lower than the calculated sintering potential.

scholarly journals Stress distribution in column-plate foundations of Monument of Christ The King erected in Świebodzin

2020 ◽  
pp. 37-47
Author(s):  
Jakub Marcinowski ◽  
Volodymyr Sakharov
Keyword(s):  
Stress Distribution ◽  
Numerical Simulations ◽  
Side Surface ◽  
Wind Load ◽  
Vertical Load ◽  
Structural Members ◽  
Dead Load ◽  
Initial State ◽  
The Dead ◽  
Resultant Forces

The paper presents results of numerical simulations of the stress distribution and deformations within of foundations of huge monument of Christ The King erected in Świebodzin (Poland) in 2010. It is 3 meters taller than the better known statue of Christ the Redeemer in Rio de Janeiro, standing at 30.1 meters tall without its pedestal. Foundations were built as a system of reinforced concrete columns and slabs which can be classified as a spatial column-slab system. Actual mechanical parameters of the substrate and of the artificial mound made of field stones, sand, gravel and clay were adopted in calculations. The numerical simulations of structural members of foundation and determination of the stress distribution are presented in the article. Monument itself was not included into the model. Instead of it the rigid cantilever was introduced to which resultant forces were applied. Three different stages were distinguished: the initial state after foundation and mound accomplishment, the initial state plus the dead load and the initial state plus the dead load and the wind load. It was assumed that the wind load was taken into account in a quasi-static formulation by applying the equivalent horizontal force and the torque. Stresses and displacements for these three stages were determined by Finite Element Method using Simulia ABAQUS system. It was disclosed what was a contribution of particular parts of foundations in sustaining loads in considered load cases. The state of exertion of structural members of foundations and the soil itself was assessed. It was showed that the column-slab foundations and soils of the mound play important role in taking loads of the statue, spreading them and safe transferring to the undisturbed level of natural soils. According to the numerical simulations results the columns of foundation take as much as 64% of the vertical load (in the most unfavourable load conditions). At the same time soils of the mound take through the side surface of piles about 20 % of the vertical load.

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