BENDING STRENGTH OF Si3N4 MONOLITHIC AND Si3N4/SiC COMPOSITE CERAMICS AND ELASTIC WAVE CHARACTERISTICS BY WAVELET ANALYSIS

2006 ◽  
Vol 20 (25n27) ◽  
pp. 4279-4284 ◽  
Author(s):  
KI WOO NAM ◽  
MI KYUNG KIM ◽  
HAE SOOK KIM ◽  
JIN WOOK KIM ◽  
SEOK HWAN AHN
Keyword(s):  
Elastic Wave ◽  
Structural Integrity ◽  
Bending Strength ◽  
Composite Ceramic ◽  
Bending Test ◽  
Composite Ceramics ◽  
Compression Load ◽  
Three Point Bending ◽  
Time Frequency ◽  
Signal Characteristics

This paper describes the investigation of bending strength and elastic wave signal characteristics of Si 3 N 4 monolithic and Si 3 N 4/ SiC composite ceramics with crack healing ability. The elastic wave signals, generated during the compression load by a Vickers indenter on the brittle materials, were recorded in real time, and the AE signals were analyzed by the time-frequency analysis method. The three-point bending test was performed on the Si 3 N 4 monolithic and Si 3 N 4/ SiC composite ceramic specimens with/without crack-healed. Consequently the bending strength of the crack-healed specimens at 1300°C was completely recovered up to that of the smooth specimens. And the frequency properties of crack-healed specimens tended to be similar to the distribution of the dominant smooth specimens frequency. This study suggests that the results of the signal information for the anisotropic ceramics show a feasible technique to guarantee structural integrity of a ceramic component.

Bending Strength of Al2O3 Ceramics for Textiles Machinery and Elastic Wave Characteristics by Wavelet Analysis

2007 ◽  
Vol 353-358 ◽  
pp. 345-348
Author(s):  
Ki Woo Nam ◽  
B.G. Ahn ◽  
M.K. Kim ◽  
C.S. Son ◽  
Jin Wook Kim ◽  
...  
Keyword(s):  
Elastic Wave ◽  
Bending Strength ◽  
Test Results ◽  
Composite Ceramics ◽  
Bending Tests ◽  
Three Point Bending ◽  
Wave Signal ◽  
Al2o3 Composite ◽  
Signal Characteristics ◽  
Optimized Conditions

The optimized conditions of pressureless sintering were investigated in order to obtain the bending strength and the elastic wave signal of Al2O3 composite ceramics for textiles machinery. As sintering conditions, a temperature range from 1400°C to 1700°C and time from 30 minutes to 150 minutes were applied. Three-point bending tests were conducted on the sintered materials to obtain the strength property. From the test results, the optimum sintering condition was 1600°C, 100 minutes. Al2O3 composite ceramics showed that the elastic wave signal characteristics had a regular correlativity between the optimum sintering temperature and time as well as the maximum bending strength.

Elastic Wave Signal Characteristics of SiC Ceramics with Crack Healing Ability by Wavelet Analysis

2005 ◽  
Vol 297-300 ◽  
pp. 2046-2051 ◽  
Author(s):  
Jin Wook Kim ◽  
B.W. Park ◽  
Seok Hwan Ahn ◽  
Ki Woo Nam
Keyword(s):  
Elastic Wave ◽  
Bending Strength ◽  
Spectral Characteristics ◽  
Compressive Load ◽  
Limited Range ◽  
Bending Test ◽  
Crack Healing ◽  
Sic Ceramics ◽  
Signal Characteristics ◽  
Ae Signals

This paper reports for signal characteristics of before-and-after healing treatment SiC ceramics with crack healing ability. The elastic wave signals generated during the compress load by a Vickers indenter on the brittle materials were recorded in real time, and the waveforms of the individual signals were examined and classified based on their spectral characteristics. The compress loads were applied with the range from 9.8N to 294N. In a bulk SiC specimen, the AE signals occurred only when the load was compressive loading and unloading. But, in the after crack healing specimen of 294N only, even though the external compressive load was stopped and kept on holding constant load states, the AE signals occurred irregularly and continuously. The results of the WT and frequency analysis showed that these existed as the property of frequency in the limited range between 100kHz and about 200kHz. Three-point bending test was performed for the cracked and healed SiC specimens. Consequently the bending strength of the crack healed specimens was recovered completely, but most of the samples with the crack healed showed that the properties of the dominant frequency were comparatively lower than that of the bulk SiC samples. The classification of the wave signals can be used to develop algorithms for autonomous health monitoring systems of brittle material structures.

The Bending Strength of Brittle Materials and the Characteristics of the Elastic Wave Signal by Vickers Indentation

2004 ◽  
Vol 261-263 ◽  
pp. 1635-1640 ◽  
Author(s):  
Seok Hwan Ahn ◽  
Ki Woo Nam ◽  
Kotoji Ando
Keyword(s):  
Elastic Wave ◽  
Room Temperature ◽  
Bending Strength ◽  
Brittle Materials ◽  
Bending Test ◽  
Vickers Indentation ◽  
Three Point Bending ◽  
Wave Signal ◽  
Wave Detector ◽  
Fracture Wave

Four kinds of brittle materials were used to evaluate the bending strength under three-point bending and the characteristics of the elastic wave signal by Vickers indentation. The bending test was carried out under room temperature and high temperature. A crack was made at the tension side of the specimen with a Vickers indenter to investigate fracture strength. Fracture wave detector was used to evaluate characteristics of waveform and frequency of the elastic wave signal.

Three-Point Bending Test Evaluation of Concrete Specimens by Non-Traditional Analysis of Acoustic Emission Method

2016 ◽  
Vol 837 ◽  
pp. 198-202
Author(s):  
Luboš Pazdera ◽  
Libor Topolář ◽  
Tomáš Vymazal ◽  
Petr Daněk ◽  
Jaroslav Smutny
Keyword(s):  
Acoustic Emission ◽  
Signal Analysis ◽  
Measurement Data ◽  
Bending Test ◽  
Test Evaluation ◽  
Acoustic Emission Method ◽  
Emission Method ◽  
Three Point Bending ◽  
Time Frequency ◽  
Emission Signal

The aim of the paper is focused on the analysis of the mechanical properties of the concrete specimens with plasticizer at three point bending test by the signal analysis of the acoustic emission signal. The evaluations were compared the measurement and the results obtained with theoretical presumptions. The Joint Time Frequency Analysis applied on measurement data and its evaluation is described. It is well known that the Acoustic Emission Method is a very sensitive method to determine active cracks into structure. However, evaluation of acoustic emission signals is very difficult. A non-traditional method was used to signal analysis of burst acoustic emission signals recorded during three point bending test.

Synthesis of Al2O3/AlB12/Al Composite Ceramic Powders by Pulsed Nd:YAG Laser Igniting Method and a Study of their Mechanical Properties

2010 ◽  
Vol 26-28 ◽  
pp. 919-924
Author(s):  
Kai Jin Huang
Keyword(s):  
Fracture Toughness ◽  
Reaction Mechanism ◽  
Nd:Yag Laser ◽  
Bending Strength ◽  
Composite Ceramic ◽  
Composite Ceramics ◽  
Ceramic Powders ◽  
Pulsed Nd:Yag Laser ◽  
Al Composite ◽  
Pure Al2o3

Based on the combined toughening principle, pure Al2O3/AlB12/Al composite ceramic powders have been synthesized using pulsed Nd:YAG laser igniting method. This method starts from Al and B2O3 powder mixtures, after which Al2O3/AlB12/AlN composite ceramics were fabricated by hot-press sintering at 1600°C for 2h under the protection of a N2 atmosphere. XRD and SEM techniques were used to characterize the phases and morphologies of the powders and the ceramics. The bending strength and the fracture toughness of the ceramics were measured by the three-point bending method and the indentation fracture method, respectively. The results show that the pure Al2O3/AlB12/Al composite ceramic powders can be successfully synthesized by pulsed Nd:YAG laser igniting method because the adiabatic temperature of Al-B2O3 system is more than 1800K. Al2O3 and AlB12 phases were formed by the liquid-liquid reaction mechanism and the liquid-solid reaction mechanism, respectively. The bending strength and the fracture toughness of the Al2O3/AlB12/AlN composite ceramics were 525.86MPa and 5.68MPa.m1/2, respectively. These values are 50.25% and 42% greater than those of the pure Al2O3 ceramic (350MPa and 4MPa.m1/2) due to the reinforcing and toughening in-situ formation of small AlN particles.

An Estimation of Joint Strength by Using Fe-Based Shape Memory Alloy Subjected to Bending Deformation at Various Deformation Rate

2014 ◽  
Vol 626 ◽  
pp. 228-233 ◽  
Author(s):  
Kazuki Fujita ◽  
Keizo Nishikori ◽  
Takeshi Iwamoto
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Deformation Rate ◽  
Bending Strength ◽  
Rate Sensitivity ◽  
Force Balance ◽  
Bending Test ◽  
Structural Members ◽  
Bending Deformation ◽  
Three Point Bending

In various kinds of shape memory alloy (SMA), Fe-based SMA (Fe-SMA) shows smaller shape memory effect compared with the other SMAs. However, Fe-SMA shows huge advantages on the excellent formability, machinability, etc. Moreover, its production cost is cheaper than other SMAs; therefore, the alloy is attempted to be applied to structural members such as joints and dampers. Since bending deformation at higher deformation rate is generated in the members, especially the joints, due to impact force such as earthquake or wind, a clarification on the bending strength of the joints at various deformation rate is strongly required. In this study, at first, it is attempted that the bending strength and its rate sensitivity of the joints which consist of Fe-based SMA are experimentally estimated by the three-point bending test at various deformation rate. Then, the force balance equation is challenged to be derived to predict the bending strength.

scholarly journals Evaluation of low-fusing ceramic systems combined with titanium grades II and V by bending test and scanning electron microscopy

2003 ◽  
Vol 11 (4) ◽  
pp. 354-360 ◽  
Author(s):  
Wilson José Garbelini ◽  
Guilherme Elias Pessanha Henriques ◽  
Manoel Troia Junior ◽  
Marcelo Ferraz Mesquita ◽  
Cássia Cilene Dezan
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Bond Strength ◽  
Bending Strength ◽  
Bending Test ◽  
Control Group ◽  
Three Point Bending ◽  
Grade Ii ◽  
Titanium Grade ◽  
Scanning Electron

The bond strength by three point bending strength of two metal substrates (commercially pure titanium or grade II, and Ti-6Al-4V alloy or grade V) combined to three distinct low-fusing ceramic systems (LFC) and the nature of porcelain-metal fracture by scanning electron microscopy (SEM) were evaluated. The results were compared to a combination of palladium-silver (Pd-Ag) alloy and conventional porcelain (Duceram VMK68). Sixty metal strips measuring 25x3x0.5mm were made - 30 of titanium grade II and 30 of titanium grade V, with application of the following types of porcelain: Vita Titankeramik, Triceram or Duceratin (10 specimens for each porcelain). The porcelains were bonded to the strips with dimensions limited to 8x3x1mm. The control group consisted of ten specimens Pd-Ag alloy/Duceram VMK68 porcelain. Statistical analyses were made by one-way analysis of variance (ANOVA) and Tukey test at 5% significance level. Results showed that the bond strength in control group (48.0MPa ± 4.0) was significantly higher than the Ti grade II (26.7MPa ± 4.1) and Ti grade V (25.2MPa ± 2.2) combinations. When Duceratin porcelain was applied in both substrates, Ti grade II and Ti grade V, the results were significantly lower than in Ti grade II/Vitatitankeramik. SEM analysis indicated a predominance of adhesive fractures for the groups Ti grade II and Ti grade V, and cohesive fracture for control group Pd-Ag/Duceram. Control group showed the best bond strength compared to the groups that employed LFC. Among LFC, the worst results were obtained when Duceratin porcelain was used in both substrates. SEM confirmed the results of three point bending strength.

Effect of Zr Content on Properties of Mg-Zr PM Damping Alloys

2011 ◽  
Vol 84-85 ◽  
pp. 58-63
Author(s):  
Zi Li Liu ◽  
Fei Fei ◽  
Ping Shen ◽  
Gui Bin Zhou ◽  
Xi Qin Liu
Keyword(s):  
Mechanical Properties ◽  
Bending Strength ◽  
Bending Test ◽  
Damping Capacity ◽  
Micro Hardness ◽  
Three Point Bending ◽  
Zr Addition ◽  
Maximum Value ◽  
Damping Peak ◽  
Zr Alloy

Mg-xZr damping alloys (x=0.6, 1.5, 2.5, 5, mass %) were prepared by PM (powder metallurgy ) technology, and effects of Zr contents on microstructure, mechanical properties and damping capacities of Mg-xZr damping alloys were researched by three-point bending test and DMA, etc. The results show that the microstructure become into strip-shaped morphology, more granular particles appear in the grain boundaries or inside grains, and the grains are more refined with the increase of Zr additions. Micro-hardness and bending strength of the Mg-xZr damping alloys increase with increasing addition of Zr, and reach the maximum value with Zr addition of 2.5%. The damping capacities of Mg-xZr alloys increase slowly with the temperature from 27°C to 100°C, and increase rapidly above 100°C. The damping peaks appear at temperature of 160°C. Mg-5％Zr alloy exhibits the highest damping capacity, and its tanf value reaches to 0.084. The temperature of the damping peak increases with increasing frequencies, showing the characteristic of relaxation damping.

CRACK-HEALING BEHAVIOR AND BENDING STRENGTH OF Al2O3/SiC COMPOSITE CERAMICS ACCORDING TO THE AMOUNT OF ADDITIVE Y2O3

2010 ◽  
Vol 24 (15n16) ◽  
pp. 2910-2915 ◽  
Author(s):  
KI WOO NAM
Keyword(s):  
High Temperature ◽  
Vickers Hardness ◽  
Bending Strength ◽  
Composite Ceramic ◽  
Crack Healing ◽  
Composite Ceramics ◽  
Strength Recovery ◽  
In Situ Observations ◽  
Healing Temperature

Three Al 2 O 3/ SiC composite ceramics were prepared, which included 1, 3 or 5 wt. % Y 2 O 3, and their high-temperature bending strengths and in-situ crack-healing behaviors examined. A surface elliptical-crack of about 100 µm in diameter was introduces on the specimens using a Vickers hardness indenter. From in-situ observations, the Al 2 O 3/ SiC composite ceramic with 3 wt.% Y 2 O 3 showed superior crack-healing ability than the 1 and 5 wt.% Y 2 O 3 ceramics. The as-cracked specimen with 3 wt.% Y 2 O 3 showed strength recovery on healing for 1 hr at 1473 K in air, which may have been due to the lower crack-healing temperature on the addition of 3 wt.% Y 2 O 3. The heat-resistance limit temperatures of the crack-healed Al 2 O 3/ SiC composite ceramics were 1073, 1373 and 873 K for 1, 3 and 5 wt.% Y 2 O 3, respectively.

Evaluation of Acoustic Emission Events Generated at Three Point Bending of Different Concrete Specimens by Spectral Analysis

2016 ◽  
Vol 258 ◽  
pp. 485-488
Author(s):  
Lubos Pazdera ◽  
Libor Topolář ◽  
Petr Daněk ◽  
Jaroslav Smutny ◽  
Karel Mikulasek
Keyword(s):  
Acoustic Emission ◽  
Bending Test ◽  
Acoustic Emission Method ◽  
Emission Method ◽  
Direct Evaluation ◽  
Cement Ratio ◽  
Three Point Bending ◽  
Time Frequency ◽  
Frequency Domains ◽  
The Individual

The paper aims to the determine of the mechanical properties of the concrete specimens at three-point bending test by application of the Acoustic Emission Method. Recorded acoustic emission events generated during three-point loading have been chosen. Some frequency and joint time-frequency methods are applied to these records. Time series as acoustic emission events may be analyzed in the time, frequency, and/or time-frequency domains. The selection is based on the type of the signal in question, on the type of analysis to be used or the result achieved. In many applications, direct evaluation of the time-amplitude representation is neither easy nor advantageous. The individual mixtures were different in cement dosage and water-cement ratio based on how much the amount of cement was increased while maintaining consistency S2 according to EN 206.

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