scholarly journals Elastic Modulus, Strength and Fracture Toughness of Alumina Ceramics Containing Pores.

2002 ◽  
Vol 110 (1282) ◽  
pp. 554-559 ◽  
Author(s):  
Masahiro ASHIZUKA ◽  
Eiichi ISHIDA ◽  
Taishi MATSUSHITA ◽  
Masahiro HISANAGA
Keyword(s):  
Fracture Toughness ◽  
Elastic Modulus ◽  
Alumina Ceramics

Finite Element Modeling of Microcrack Growth in Cortical Bone

2011 ◽  
Vol 78 (4) ◽  
Author(s):  
Susan Mischinski ◽  
Ani Ural
Keyword(s):  
Fracture Toughness ◽  
Finite Element ◽  
Elastic Modulus ◽  
Crack Growth ◽  
Line Strength ◽  
Crack Deflection ◽  
Cement Line ◽  
Fracture Properties ◽  
Cement Lines ◽  
Microcrack Growth

Bone is similar to fiber-reinforced composite materials made up of distinct phases such as osteons (fiber), interstitial bone (matrix), and cement lines (matrix-fiber interface). Microstructural features including osteons and cement lines are considered to play an important role in determining the crack growth behavior in cortical bone. The aim of this study is to elucidate possible mechanisms that affect crack penetration into osteons or deflection into cement lines using fracture mechanics-based finite element modeling. Cohesive finite element simulations were performed on two-dimensional models of a single osteon surrounded by a cement line interface and interstitial bone to determine whether the crack propagated into osteons or deflected into cement lines. The simulations investigated the effect of (i) crack orientation with respect to the loading, (ii) fracture toughness and strength of the cement line, (iii) crack length, and (iv) elastic modulus and fracture properties of the osteon with respect to the interstitial bone. The results of the finite element simulations showed that low cement line strength facilitated crack deflection irrespective of the fracture toughness of the cement line. However, low cement line fracture toughness did not guarantee crack deflection if the cement line had high strength. Long cracks required lower cement line strength and fracture toughness to be deflected into cement lines compared with short cracks. The orientation of the crack affected the crack growth trajectory. Changing the fracture properties of the osteon influenced the crack propagation path whereas varying the elastic modulus of the osteon had almost no effect on crack trajectory. The findings of this study present a computational mechanics approach for evaluating microscale fracture mechanisms in bone and provide additional insight into the role of bone microstructure in controlling the microcrack growth trajectory.

scholarly journals Sintering of alumina ceramics reinforced with a bioactive glass of 3CaO.P2O5-SiO2-MgO system

Cerâmica ◽  
2015 ◽  
Vol 61 (358) ◽  
pp. 160-167 ◽  
Author(s):  
A. W. Huang ◽  
C. Santos ◽  
R. O. Magnago ◽  
R. F. F. Silva ◽  
K. Strecker ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Relative Density ◽  
Transient Liquid Phase ◽  
Xrd Analysis ◽  
Alumina Ceramics ◽  
Crystalline Phases ◽  
Powder Mixtures ◽  
Solid State Sintering ◽  
Sintering Condition

<p>Alumina-based ceramics, Al<sub>2</sub>O<sub>3</sub>, exhibit a combination of properties which favor its use as biomaterial, specifically as structural dental prosthesis. Its most important properties as biomaterial are its elevated hardness, chemical stability and biocompatibility. Usually, Al<sub>2</sub>O<sub>3</sub> is processed by solid-state sintering at a temperature of about 1600 <sup>o</sup>C, but it is very difficult to eliminate the porosity due to its diffusional characteristics. The objective of this work was the development and characterization of sintered Al<sub>2</sub>O<sub>3</sub> ceramics, densified with a transient liquid phase formed by a bioactive 3CaO.P<sub>2</sub>O<sub>5</sub>-SiO<sub>2</sub>-MgO glass. Powder mixtures of 90 wt.% Al<sub>2</sub>O<sub>3</sub> and 10 wt.% bioglass were milled, compacted and sintered at 1200 <sup>o</sup>C to 1450 <sup>o</sup>C. Comparatively, monolithic Al<sub>2</sub>O<sub>3</sub> samples were sintered at 1600 <sup>o</sup>C/120 min. The sintered specimens were characterized by relative density, crystalline phases, microstructure and mechanical properties. The results indicate that the specimen sintered at 1450 <sup>o</sup>C/120 min present the best properties. Under this sintering condition, a relative density of 95% was reached, besides hardness higher than 9 GPa and fracture toughness of 6.2 MPa.m<sup>1/2</sup>. XRD analysis indicate alumina (αAl<sub>2</sub>O<sub>3</sub>), whitlockite (3CaO.P<sub>2</sub>O<sub>5</sub>) and diopsite [3(Ca,Mg)O.P<sub>2</sub>O<sub>5</sub>], as crystalline phases. Comparatively, monolithic sintered Al<sub>2</sub>O<sub>3</sub> samples presented 92% of relative density with 17.4 GPa and 3.8 MPa.m<sup>1/2</sup> of hardness and fracture toughness respectively.</p>

Fabrication of Carbon Nanotube Reinforced Boron Carbide Composite by Hot-Pressing Following Extrusion Molding

2014 ◽  
Vol 616 ◽  
pp. 27-31 ◽  
Author(s):  
Tomohiro Kobayashi ◽  
Katsumi Yoshida ◽  
Toyohiko Yano
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Elastic Modulus ◽  
Carbon Nanotube ◽  
Boron Carbide ◽  
Vickers Hardness ◽  
Hot Pressing ◽  
Bending Strength ◽  
Extrusion Direction ◽  
Sem Observation

The CNT/B4C composite with Al2O3 additive was fabricated by hot-pressing following extrusion molding of a CNT/B4C paste, and mechanical properties of the obtained composite were investigated. Many CNTs in the composite aligned along the extrusion direction from SEM observation. 3-points bending strength of the composite was slightly lower than that of the monolithic B4C. Elastic modulus and Vickers hardness of the composite drastically decreased with CNT addition. Fracture toughness of the composite was higher than that of the monolithic B4C.

Fracture Toughness and Adhesion Energy of Sol-gel Coatings on Glass

2002 ◽  
Vol 17 (1) ◽  
pp. 224-233 ◽  
Author(s):  
Jaap Den Toonder ◽  
Jürgen Malzbender ◽  
Gijsbertus De With ◽  
Ruud Balkenende
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Elastic Modulus ◽  
Sol Gel ◽  
Industrial Applications ◽  
Adhesion Energy ◽  
Scratch Testing ◽  
New Methods ◽  
Quantitative Results ◽  
Coating Fracture

The reliability of coatings that are used in industrial applications critically depends on their mechanical properties. Nanoindentation and scratch testing are well-established techniques to measure some of these properties, namely the elastic modulus and hardness of coatings. In this paper, we investigate the possibility of also assessing the coating fracture toughness and the energy of adhesion between the coating and the substrate using indentation and scratch testing. Various existing and new methods are discussed, and they are illustrated by measurements on particle-filled sol-gel coatings on glass. All methods are based on the occurrence of cracking, and they are therefore only applicable to coating systems that act like brittle materials and exhibit cracking during indentation and scratching. The methods for determining the fracture toughness give comparable results, but the values still differ to within about 50%. The values of the adhesion energy obtained from different measurements are consistent, but it remains uncertain to which extent the obtained values are quantitatively correct. The results show that the methods used are promising, but more research is needed to obtain reliable quantitative results.

Interfacial Fracture Toughness of a Plasma Sprayed Hydroxyapatite Coating Used for Orthopedic Implants

1998 ◽  
Vol 550 ◽  
Author(s):  
Y. Sugimura ◽  
M. Spector
Keyword(s):  
Fracture Toughness ◽  
Elastic Modulus ◽  
Adhesion Strength ◽  
Unit Area ◽  
Interfacial Fracture ◽  
Orthopedic Implants ◽  
New Method ◽  
Aqueous Environment ◽  
Interfacial Fracture Toughness ◽  
Plasma Sprayed

AbstractThis study introduces a new method for evaluating the adhesion strength of a coating on a substrate. The interfacial fracture toughness, Γi is used to assess the work per unit area required to separate an interface. Γi is measured for the as-received specimens of hydroxyapatite plasma sprayed on Ti-6A1-4V substrate. Calculation of the interfacial fracture toughness requires that the elastic modulus of the coating to be known. The Young's modulus of the plasma sprayed hydroxyapatite is assessed using a bend test. The effect of aqueous environment on the interfacial fracture toughness is also investigated.

A Method to Determine Fracture Toughness Using Berkovich Indenter for Bulk Materials

2013 ◽  
Vol 331 ◽  
pp. 456-460
Author(s):  
Min He ◽  
Duan Hu Shi ◽  
Feng Yang ◽  
Ning Zhang ◽  
Hua Feng Guo
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Elastic Modulus ◽  
Penetration Depth ◽  
Effective Elastic Modulus ◽  
Berkovich Indenter ◽  
Bulk Materials ◽  
Ductile Materials ◽  
Penetration Depths ◽  
Determine Fracture Toughness

An indentation approach with Berkovich indenter is proposed to determine fracture toughness for ductile materials. With decrease of effective elastic modulus, an approximate linear relationship between logarithmic plastic penetration depth and logarithmic effective elastic modulus, and a quadratic polynomial relationship between the plastic penetration depths and penetration loads are exhibited by indentation investigation with Berkovich indenter. The damage constructive equation of effective elastic modulus is proposed to determine the critical effective elastic modulus at the fracture point, which is the key problem to calculate the indentation energy to fracture. The critical plastic penetration depth is identified after the critical effective elastic modulus can be predicted by conventional mechanical properties. The fracture toughness is calculated according to the equation of penetration load, plastic penetration depth and the critical plastic penetration depth.

Literature Review: Properties of Silica Fume Concrete

2014 ◽  
Vol 1004-1005 ◽  
pp. 1516-1522
Author(s):  
Xi Xi He ◽  
Qing Wang
Keyword(s):  
Fracture Toughness ◽  
Tensile Strength ◽  
Compressive Strength ◽  
Elastic Modulus ◽  
Silica Fume ◽  
Water Demand ◽  
Interfacial Transition Zone ◽  
Normal Concrete ◽  
Plastic Shrinkage ◽  
Micro Level

Silica fume (SF) modifies interfacial transition zone between cement paste and aggregate at the micro level. Properties of both fresh and hardened silica fume concrete are affected significantly compared to normal concrete. Experiments indicate that concretes become more cohesive and less prone to segregation in the presence of silica fume, moreover, performance of water demand, setting of time, plastic shrinkage varies respectively from concretes without silica fume. Obvious mechanical enhancement of concrete is observed in the aspects of compressive strength tensile strength, elastic modulus as well as fracture toughness.

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