The Temperature Dependence of Yield Stress and Fracture Toughness in Unstabilized Zirconia Crystals

1986 ◽  
Vol 78 ◽  
Author(s):  
T. W. Coyle ◽  
R. P. Ingel ◽  
P. A. Willging
Keyword(s):  
Fracture Toughness ◽  
Flexural Strength ◽  
Temperature Dependence ◽  
Yield Stress ◽  
Test Temperature ◽  
Room Temperature ◽  
Single Edge ◽  
Melting Technique ◽  
Strength Tests ◽  
Edge Notch

ABSTRACTThe flexural strength and the single edge notch beam fracture toughness of undoped ZrO2 crystals, grown by the skull melting technique, were examined from room temperature to 1400°C. On heating the toughness increased with test temperature to a maximum of 4.0 MPajm at 1225°C then gradually decreased to 2.6 MPa/m. Upon cooling after a 20 minute hold at 1250°C an increase in toughness to 5 MPa/m was observed at 1200°C; upon cooling to lower temperatures Kic gradually diminished. The loaddeflection curves for the flexural strength tests showed marked nonlinearity before failure for samples tested on cooling. The temperature dependence of the apparent yield stress suggests that initial yielding occurs by slip above 1200°C but that from 1200°C to 1050°C the observed yielding is due to stress induced tetragonal to monoclinic transformation.

Comparative Analysis of Fracture Toughness Obtained by Different Techniques in Alumina Matrix - Dispersed TZP Zirconia Composites

2016 ◽  
Vol 869 ◽  
pp. 46-51
Author(s):  
Daniel Alessander Nono ◽  
Eron Fernandes da Silva ◽  
Maria do Carmo de Andrade Nono ◽  
Francisco Piorino Neto ◽  
Sergio Luiz Mineiro
Keyword(s):  
Fracture Toughness ◽  
Tetragonal Zirconia ◽  
Ceramic Composites ◽  
Alumina Matrix ◽  
Single Edge ◽  
Chemical Inertness ◽  
Edge Notch ◽  
Properties Of Materials ◽  
Experimental Values ◽  
Benefit Cost

The fracture toughness is one of the requirements for mechanical properties of materials for use in satellites. The ceramic TZP zirconia (tetragonal zirconia polycrystals) have been investigated for applications in ballistic armor. Due to the chemical inertness and fracture toughness, this material has the potential to act as a screen against impacts of micrometeorites and space debris. The ceramic composites of alumina-zirconia 3Y-TZP (tetragonal zirconia polycrystals doped with 3 mol% ytria ) are the materials with the best benefit / cost for this application. This paper presents and discusses the results obtained from the use of two techniques for determining fracture toughness. The composite alumina - 18.5% of 3Y-TZP zirconia nanoparticles obtained from deflocculated powders have been tested for Vickers and the SEVNB penetration method (Single-Edge-Notch Beam V) to obtain the fracture toughness values (KIC). The KIC values obtained were analyzed due to the lower dispersion of experimental values. The SEVNB method showed better reliability in determining the toughness values in the studied ceramics.

scholarly journals Effect of microwave disinfection on physical and mechanical properties of acrylic resins

2008 ◽  
Vol 19 (4) ◽  
pp. 348-353 ◽  
Author(s):  
Rafael Leonardo Xediek Consant ◽  
Erica Brenoe Vieira ◽  
Marcelo Ferraz Mesquita ◽  
Wilson Batista Mendes ◽  
João Neudenir Arioli-Filho
Keyword(s):  
Flexural Strength ◽  
Room Temperature ◽  
Physical And Mechanical Properties ◽  
Hardness Test ◽  
Knoop Hardness ◽  
Microwave Energy ◽  
Bending Test ◽  
Acrylic Resins ◽  
Strength Tests ◽  
The Impact

This study evaluated the effect of microwave energy on the hardness, impact strength and flexural strength of the Clássico, Onda-Cryl and QC-20 acrylic resins. Aluminum die were embedded in metallic or plastic flasks with type III dental stone, in accordance with the traditional packing technique. A mixing powder/liquid ratio was used according to the manufacturer's instructions. After polymerization in water batch at 74ºC for 9 h, boiling water for 20 min or microwave energy at 900 W for 10 min, the specimens were deflasked after flask cooling at room temperature, and submitted to finishing. Specimens non-disinfected and disinfected by microwave irradiation were submitted to hardness, impact and flexural strength tests. Each specimen was immersed in distilled water and disinfected in a microwave oven calibrated to 650 W for 3 min. Knoop hardness test was performed with 25 g load for 10 s, impact test was carried out using the Charpy system with 40 kpcm, and 3-point bending test with a crosshead speed of 0.5 mm/min until fracture. Data were submitted to statistical analysis by ANOVA and Tukey's test (?=0.05). Disinfection by microwave energy decreased the hardness of Clássico and Onda-Cryl acrylic resins, but no effect was observed on the impact and flexural strength of all tested resins.

Deformation and its Structure in Llo Ti-Al-Nb Compound Alloys

1988 ◽  
Vol 133 ◽  
Author(s):  
Yoo-Dong Hahn ◽  
Sung H. Whang
Keyword(s):  
Temperature Dependence ◽  
Yield Stress ◽  
Uniaxial Compression ◽  
High Temperatures ◽  
Room Temperature ◽  
Fracture Strain ◽  
Positive Temperature ◽  
Deformation Structures ◽  
Miniature Specimens ◽  
Deformation Tests

ABSTRACTThe ternary TiAl-Nb (Llo) alloys stabilized at 1000°C for a week were prepared into miniature specimens for compressive deformation tests. The specimens were deformed in uniaxial compression at room temperature as well as various high temperatures. The yield stress and fracture strain were determined with respect to Nb concentration, and as a function of temperature to investigate positive temperature dependence.Dislocation structures and other deformation structures of the deformed alloys were studied by TEM.

Microstructure and Mechanical Properties of SiC Whisker-Reinforced ZrB2 Ultra-High Temperature Ceramic

2008 ◽  
Vol 368-372 ◽  
pp. 1730-1732 ◽  
Author(s):  
Ping Hu ◽  
Xing Hong Zhang ◽  
Jie Cai Han ◽  
Song He Meng ◽  
Bao Lin Wang
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
High Temperature ◽  
Flexural Strength ◽  
Hot Pressing ◽  
Room Temperature ◽  
Pressing Temperature ◽  
Sintering Time ◽  
Microstructure And Mechanical Properties ◽  
Ultra High Temperature

SiC whisker-reinforced ZrB2 matrix ultra-high temperature ceramic were prepared at 2000°C for 1 h under 30MPa by hot pressing and the effects of whisker on flexural strength and fracture toughness of the composites was examined. The flexural strength and fracture toughness are 510±25MPa and 4.05±0.20MPa⋅m1/2 at room temperature, respectively. Comparing with the SiC particles-reinforced ZrB2 ceramic, no significant increase in both strength and toughness was observed. The microstructure of the composite showed that the SiC whisker was destroyed because the SiC whisker degraded due to rapid atom diffusivity at high temperature. The results suggested that some related parameters such as the lower hot-pressing temperature, a short sintering time should be controlled in order to obtain SiC whiskerreinforced ZrB2 composite with high properties.

Fracture toughness of Si3N4 fibers: A combined methodology based on single-edge notch tension and micropillar splitting

2018 ◽  
Vol 44 (17) ◽  
pp. 22036-22040
Author(s):  
Xun Sun ◽  
Haitao Liu ◽  
Lingwei Yang ◽  
Ru Jiang ◽  
Haifeng Cheng
Keyword(s):  
Fracture Toughness ◽  
Single Edge ◽  
Single Edge Notch ◽  
Edge Notch

Fracture Mechanism and Fracture Toughness at the Interface Between Cortical and Cancellous Bone

2019 ◽  
Vol 141 (11) ◽  
Author(s):  
Pankaj Shitole ◽  
Arpan Gupta ◽  
Rajesh Ghosh
Keyword(s):  
Fracture Toughness ◽  
Cortical Bone ◽  
Cancellous Bone ◽  
Fracture Mechanism ◽  
Fracture Mechanisms ◽  
J Integral ◽  
Single Edge ◽  
Plastic Part ◽  
Edge Notch ◽  
Sample Width

The microstructure at the interface of cortical and cancellous bone is quite complicated. The fracture mechanisms at this location are necessary for understanding the comprehensive fracture of the whole bone. The goal of this study is to identify fracture toughness in terms of J integral and fracture mechanism at the interface between cortical and cancellous bone. For this purpose, single edge notch bend (SENB) specimens were prepared from bovine proximal femur according to ASTM-E399 standard. Bone samples were prepared such that half of the sample width consists of cortical bone and other half of the width was cancellous bone; this interfacial bone is referred as a corticellous bone. Elastic–plastic fracture mechanics was used to measure fracture toughness. The J integral (both elastic and plastic) was used to quantify the fracture toughness. The plastic part of J integral value (Jpl) of corticellous specimen was 9310 J m−2, and shown to be 27 times of the J integral of the elastic part (Jel), 341 J m−2. The total J integral of the corticellous bone was found to be 9651 J m−2, which is close to two times of the cortical bone, 4731 J m−2. This study observed that J integral of corticellous bone is higher than the cortical bone since more energy is required for plastic deformation of corticellous bone due to crack branches and slowdown at the interface between cortical and cancellous bone.

Strain Rate Dependence of the Flow Stress and Work-Hardening of Single Crystals of NI3(Al,Hf)B

1994 ◽  
Vol 364 ◽  
Author(s):  
S. S. Ezz ◽  
Y. Q. Sun ◽  
P. B. Hirsch
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Temperature Dependence ◽  
Single Crystals ◽  
Yield Stress ◽  
Strain Rate Sensitivity ◽  
Work Hardening ◽  
Room Temperature ◽  
Rate Sensitivity ◽  
Controlling Mechanism

AbstractThe strain rate sensitivity ß of the flow stress τ is associated with workhardening and β=(δτ/δln ε) is proportional to the workhardening increment τh = τ - τy, where τy is the strain rate independent yield stress. The temperature dependence of β/τh reflects changes in the rate controlling mechanism. At intermediate and high temperatures, the hardening correlates with the density of [101] dislocations on (010). The nature of the local obstacles at room temperature is not established.

Fracture Toughness Estimation for Pipeline Girth Welds

2002 ◽  
Author(s):  
Henryk G. Pisarski ◽  
Colin M. Wignall
Keyword(s):  
Fracture Toughness ◽  
Weld Metal ◽  
Specimen Geometry ◽  
Single Edge ◽  
Single Edge Notch ◽  
Edge Notch ◽  
Loading Modes ◽  
Girth Welds ◽  
The Relationship ◽  
Single Edge Notch Bend

The relationship between fracture toughness estimated using standard single edge notch bend (SENB), single edge notch tension (SENT) test specimens and fracture toughness associated with a circumferential flaw in a pipe girth weld is explored in terms of constraint using the Q parameter. It is shown that in the elastic-plastic regime, use of standard deeply notched SENB specimens provides a conservative assessment of fracture toughness, for both weld metal and HAZ, because of the high constraint associated with this specimen geometry. Use of specimen geometries and loading modes associated with lower constraint (e.g. SENT and shallowed notched SENB specimens), allow for improved estimates of fracture toughness to be made that are appropriate for the assessment of circumferential flaws in pipe girth welds. Recommendations are given on the specimen designs and notch orientations to be employed when evaluating weld metal and HAZ fracture toughness.

Constraint Based Fracture Assessment of Seam-Welded Pipes Containing Axial Flaws

2006 ◽  
Author(s):  
Yuri Tkach ◽  
Anthony Horn ◽  
Adam Bannister ◽  
Edmund Bolton
Keyword(s):  
Fracture Toughness ◽  
Crack Depth ◽  
High Stress ◽  
Stress Triaxiality ◽  
Single Edge ◽  
Fracture Toughness Testing ◽  
Single Edge Notch ◽  
Seam Weld ◽  
Edge Notch ◽  
Toughness Testing

An Engineering Critical Assessment (ECA) of a pipeline containing an axial defect is usually conservative if standard fracture test pieces are used for the fracture toughness testing. Conventional fracture toughness testing standards employ specimens containing deep cracks in order to guarantee conditions leading to high stress triaxiality and crack-tip constraint. In the current work, single edge notch bend (SENB) and single edge notch tension (SENT) test specimens of two different a/W (crack depth/specimen width) ratios (0.15 and 0.6) were used to obtain HAZ fracture toughness of a seam weld. The influence of specimen geometry and a/W ratio on fracture toughness was investigated. The Master Curve methodology was employed to characterise HAZ fracture toughness of the seam weld in the ductile-to-brittle transition region. The reference temperature T0 was estimated using the test results obtained on specimens of different geometries and constraint levels. A series of ECAs of the pipe containing a surface axial flaw was performed and the benefits of a constraint based fracture mechanics analysis were demonstrated.

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