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.

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.

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.

CRACK-HEALING BEHAVIOR AND BENDING STRENGTH PROPERTIES OF SiC CERAMICS BASED ON THE TYPE OF ADDITIVE SiO2 EMPLOYED

2010 ◽  
Vol 24 (15n16) ◽  
pp. 2869-2874 ◽  
Author(s):  
KI WOO NAM ◽  
JONG SOON KIM ◽  
SEUNG WON PARK
Keyword(s):  
Fracture Toughness ◽  
Silicon Carbide ◽  
Surface Crack ◽  
Bending Strength ◽  
Crack Size ◽  
Strength Properties ◽  
Crack Healing ◽  
Sic Ceramics ◽  
Maximum Crack ◽  
Atmospheric Level

Silicon carbide ( SiC ) exhibits good strength at high temperatures and resistance to radioactivity. However, it has poor fracture toughness. The ability to heal cracks represents a very desirable means of overcoming this weakness. This study focuses on the crack-healing behavior and bending strength of SiC ceramics to which sintering additives have been added. Optimized crack-healing condition was found to be 1hr at an atmospheric level of 1100 °C. The maximum crack size that can be healed at the optimized condition was a semi-elliptical surface crack of 450 µm in diameter. Si oxide was revealed to be the principle material involved in crack-healing.

Development of the Green Composite Consists of Woodchips, Bamboo Fibers and Biodegradable

2008 ◽  
Vol 47-50 ◽  
pp. 322-325
Author(s):  
Hiroyuki Kinoshita ◽  
Koichi Kaizu ◽  
Miki Fukuda ◽  
Tokunaga Hitoo ◽  
Keisuke Koga ◽  
...  
Keyword(s):  
Particle Size ◽  
Bending Strength ◽  
Compressive Load ◽  
Charpy Impact ◽  
High Strength ◽  
Charpy Impact Test ◽  
High Energy ◽  
Bending Test ◽  
Green Composite ◽  
Bamboo Fibers

From the viewpoint of the effective utilization of natural resources, the green composite which is produced by solidifying woodchips has been developed[1][2][3]. However, since this composite was solidified by the compressive load without the binder, the composite was very brittle and had no water resistance [4]. In this study, to improve these defects, the biodegradable resin is used as an adhesive and bamboo fibers are used as reinforced fibers. By using woodchips with two kinds of the particle size, bamboo fibers with three kinds of the length and a biodegradable adhesive, several kinds of specimens changed those mixing ratio were produced. The composite consists of the ingredients which are friendly to the environment. By the four-point bending test and Charpy impact test, the bending strength and impact strength of the composites were examined. From the experimental results, it was found that the high bending strength and high energy absorption were obtained in case where woodchips with the small particle size and long bamboo fibers were used. The proposed composite has the high strength, and the practical application is also possible.

scholarly journals A Comparative Study on Crack-Healing Ability of Al2O3/SiC Structural Ceramic Composites Synthesized by Microwave Sintering and Conventional Electrical Sintering

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Madhan Mohankumar ◽  
A. N. Shankar ◽  
T. S. Karthik ◽  
R. Saravanakumar ◽  
Hemakesavulu Oruganti ◽  
...  
Keyword(s):  
Bending Strength ◽  
Microwave Sintering ◽  
Ceramic Composites ◽  
Bending Test ◽  
Crack Healing ◽  
Structural Ceramic ◽  
X Ray ◽  
Sem Micrographs ◽  
Before And After ◽  
Sio2 Phase

This study was conducted to assess and compare the crack-healing ability of conventional electrical sintered and microwave sintered Al2O3/x wt. % SiC (x = 5, 10, 15, and 20) structural ceramic composites. The crack-healing ability of both conventional electrical sintered and microwave sintered specimens was studied by introducing a crack of ∼100 µm length by Vickers’s indentation and conducting a heat treatment at 1200°C for dwell time of 1 h in air. The flexural or bending strength of sintered, cracked, and crack-healed specimens was determined by three-point bending test, and the phase variations by X-ray diffraction and SEM micrographs before and after crack-healing of both the sintering methods were studied and compared. The results show that almost all the specimens recovered their strength after crack-healing, but the strength of microwave sintered Al2O3/SiC structural ceramic composites has been shown to be better than that of conventional electrical sintered Al2O3/SiC structural ceramic composites. The microwave sintered crack-healed Al2O3/10 wt. % SiC specimen shows higher flexural strength of 794 MPa, which was 105% when compared with conventional electrical sintered Al2O3/10 wt. % SiC and crack-healed Al2O3/10 wt. % SiC specimen. It was found by X-ray diffractogram that before crack-healing, all the conventional electrical sintered samples have SiO2 phase which reduce the crack-healing ability and microwave sintered samples with 15 and 20 wt. % SiC show lesser SiO2 phase and 5 and 10 wt. % SiC samples have no SiO2 phase before crack-healing. However, after crack-healing treatment, all the samples have distinct SiO2 phase along with Al2O3 and SiC phases. Microwave sintered Al2O3/10 wt. % SiC specimen cracks were fully healed which was evident in SEM micrographs.

scholarly journals Experimental Investigation on the Influence of Fiber Path Curvature on the Mechanical Properties of Composites

Materials ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2602
Author(s):  
Huaqiao Wang ◽  
Jihong Chen ◽  
Zhichao Fan ◽  
Jun Xiao ◽  
Xianfeng Wang
Keyword(s):  
Tensile Strength ◽  
Path Planning ◽  
Composite Laminates ◽  
Bending Strength ◽  
High Strength ◽  
Bending Test ◽  
Fiber Placement ◽  
Automated Fiber Placement ◽  
Fiber Path ◽  
Path Curvature

Automated fiber placement (AFP) has been widely used as an advanced manufacturing technology for large and complex composite parts and the trajectory planning of the laying path is the primary task of AFP technology. Proposed in this paper is an experimental study on the effect of several different path planning placements on the mechanical behavior of laminated materials. The prepreg selected for the experiment was high-strength toughened epoxy resin T300 carbon fiber prepreg UH3033-150. The composite laminates with variable angles were prepared by an eight-tow seven-axis linkage laying machine. After the curing process, the composite laminates were conducted by tensile and bending test separately. The test results show that there exists an optimal planning path among these for which the tensile strength of the laminated specimens decreases slightly by only 3.889%, while the bending strength increases greatly by 16.68%. It can be found that for the specific planning path placement, the bending strength of the composite laminates is significantly improved regardless of the little difference in tensile strength, which shows the importance of path planning and this may be used as a guideline for future AFP process.

Bending and flexural-buckling strength of steel members considering strain-rate-effects at elevated temperatures

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Fuminobu Ozaki ◽  
Takumi Umemura
Keyword(s):  
Strain Rate ◽  
Elevated Temperatures ◽  
Bending Strength ◽  
Transient State ◽  
Bending Test ◽  
Content Type ◽  
Buckling Strength ◽  
Flexural Buckling ◽  
Steel Members ◽  
Collapse Temperature

PurposeIn this study, the bending strength, flexural buckling strength and collapse temperature of small steel specimens with rectangular cross-sections were examined by steady and transient state tests with various heating and deformation rates.Design/methodology/approachThe engineering stress and strain relationships for Japan industrial standard (JIS) SN400 B mild steels at elevated temperatures were obtained by coupon tests under three strain rates. A bending test using a simple supported small beam specimen was conducted to examine the effects of the deformation rates on the centre deflection under steady-state conditions and the heating rates under transient state conditions. Flexural buckling tests using the same cross-section specimen as that used in the bending test were conducted under steady-state and transient-state conditions.FindingsIt was clarified that the bending strength and collapse temperature are evaluated by the full plastic moment using the effective strength when the strain is equal to 0.01 or 0.02 under fast strain rates (0.03 and 0.07 min–1). In contrast, the flexural buckling strength and collapse temperature are approximately evaluated by the buckling strength using the 0.002 offset yield strength under a slow strain rate (0.003 min–1).Originality/valueRegarding both bending and flexural buckling strengths and collapse temperatures of steel members subjected to fire, the relationships among effects of steel strain rate for coupon test results, heating and deformation rates for the heated steel members were minutely investigated by the steady and transient-state tests at elevated temperatures.

Research on Damage and Bending Properties of AZ31 Magnesium Alloy

2012 ◽  
Vol 184-185 ◽  
pp. 1163-1166
Author(s):  
Xi An Xie ◽  
Gao Feng Quan
Keyword(s):  
Magnesium Alloy ◽  
Applied Load ◽  
Bending Strength ◽  
Az31 Magnesium Alloy ◽  
Bending Test ◽  
Bending Properties ◽  
Four Point Bending ◽  
Heat Treated ◽  
Four Point Bending Test ◽  
Initial Cracks

Through the four-point bending test of lath-shaped heat treated AZ31 magnesium alloy, the bending properties and damage characteristics were explored. The results show that the optimal bending strength of the magnesium alloy were 355.1MPa and 259.2MPa for extruded and cast samples, respectively, after corresponding heat treatment with 350°C, 90min and 400°C, 30min. The initial cracks both occurred at the loading point after applied load exceeded the yield limit of AZ31 magnesium alloy. Surface bump, cracks and other damage morphology accompanied by a large number of twinning organizations were found on the surface of the samples.

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