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21.
Shou-ren Wang Hao-ran Geng Lin-hai Hui Ying-zi Wang 《Journal of Materials Engineering and Performance》2007,16(1):113-118
A multiphase reticulated porous ceramic (RPC) as Si3N4–Al2O3–SiO2 was fabricated by replication techniques. Proper volumes of additives and twice sinter- twice immerse process endow the RPC
an excellent crack healing and submerging property. The compressive strength and fracture toughness improved owing to the
crack bridging behavior. The existence of pores in struts in RPC blunt the crack tip and increased the external force needed
to propagate the crack. The mechanisms play a beneficial role in enhancing the compressive strength and fracture strength.
Si3N4 RPC with additives of 5%Al and 5% Al2O3 yielded the compressive strength of 9.8 MPa and fracture toughness of 0.3 MPa m1/2. 相似文献
22.
S. Abiraman H. K. Varma T. V. Kumari P. R. Umashankar Annie John 《Bulletin of Materials Science》2002,25(5):419-429
This study investigates quantitatively and qualitatively the sol-gel derived bioactive glass-ceramic system (BGS)—apatite-wollastonite
(AW) type granules in the size range of 0.5–1 mm, as an effective graft material for bone augmentation and restoration. Scanning
electron micrographs (SEM) of the sintered granules revealed the rough material surface with micropores in the range 10–30
μm. X-ray diffraction (XRD) pattern of the granules revealed the presence of crystalline phases of the hydroxyapatite and
wollastonite, and the functional groups of the silicate and phosphates were identified by Fourier transform infrared spectroscopy
(FT-IR). Thein vitro cell culture studies with L929 mouse fibroblast cell line showed very few cells adhered on the BGS disc after 24 h. This
could be due to the highly reactive surface of the disc concomitant with the crystallization but not due to the cytotoxicity
of the material, since the cellular viability (MTT assay) with the material was 80‰ Cytotoxicity and cytocompatibility studies
proved that the material was non-toxic and biocompatible. After 12 weeks of implantation of the BGS granules in the tibia
bone of New Zealand white rabbits, the granules were found to be well osteointegrated, as observed in the radiographs. Angiogram
with barium sulphate and Indian ink after 12 weeks showed the presence of microcapillaries in the vicinity of the implant
site implicating high vascularity. Gross observation of the implant site did not show any inflammation or necrosis. SEM of
the implanted site after 24 weeks revealed good osteointegration of the material with the newly formed bone and host bone.
New bone was also observed within the material, which was degrading. Histological evaluation of the bone healing with the
BGS granules in the tibial defect at all time intervals was without inflammation or fibrous tissue encapsulation. After 2
weeks the new bone was observed as a trabeculae network around the granules, and by 6 weeks the defect was completely closed
with immature woven bone. By 12 weeks mature woven bone was observed, and new immature woven bone was seen within the cracks
of the granules. After 24 weeks the defect was completely healed with lamellar bone and the size of the granules decreased.
Histomorphometrically the area percentage of new bone formed was 67.77% after 12 weeks and 63.37% after 24 weeks. Less bone
formation after 24 weeks was due to an increased implant surface area contributed by the material degradation and active bone
remodeling. The osteostimulative and osteoconductive potential of the BGS granules was established by tetracycline labelling
of the mineralizing areas by 2 and 6 weeks. This sol-gel derived BGS granules proved to be bioactive and resorbable which
in turn encouraged active bone formation. 相似文献
23.
24.
利用测井资料预测塔河油田地层破裂压力 总被引:7,自引:1,他引:6
针对塔河油田奥陶系碳酸盐岩油藏 ,介绍了地层破裂压力预测和地层裂缝高度预测的基本原理 ,选择了塔河油田 4口井的资料进行了破裂压力和裂缝高度预测的成果处理。为塔河油田奥陶系碳酸盐岩储层改造提供了较为可靠的施工参数 相似文献
25.
通过高炉鼓风机扩压叶片断裂事故,从化学分析、物理检验,结合使用情况对扩压叶片断裂原因进行了详细分析,并提出了改进措施。 相似文献
26.
In this work we present the discrete models for dynamic fracture of structures built of brittle materials. The models construction is based on Voronoi cell representation of the heterogeneous structure, with the beam lattice network used to model the cohesive and compressive forces between the neighboring cells. Each lattice component is a geometrically exact shear deformable beam which can describe large rigid body motion and the most salient fracture mechanisms. The latter can be represented through the corresponding form of the beam constitutive equations, which are derived either at microscale with random distribution of material properties or at a mesoscale with average deterministic values. The proposed models are also placed within the framework of dynamics, where special attention is paid to constructing the lattice network mass matrix as well as the corresponding time-stepping schemes. Numerical simulations of compression and bending tests is given to illustrate the models performance. 相似文献
27.
The apparent tensile strength of technical flax fibers was determined in single‐fiber tests at various clamping lengths (20, 40, and 80 mm) and the outcome was compared with literature data. It was demonstrated that the strength of flax at each clamping length obeyed the two‐parameter Weibull model. The failure mode and sequence were studied in situ (i.e., during loading) by SEM and acoustic emission (AE). The failure sequence (axial splitting of the technical fiber along its elementary constituents, radial cracking of the elementary fibers, multiple fracture of the elementary fibers) concluded reflected the hierarchical build‐up of the flax bast fibers. To the above failure events AE amplitude ranges were assigned. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3638–3645, 2003 相似文献
28.
G. Lange 《Materialwissenschaft und Werkstofftechnik》2003,34(1):80-85
Failures by notch induced fatigue fractures Notches produce local stress concentrations and promote the formation of fatigue cracks. Characteristic types of notches as a result of design, manufacturing and operation are presented and remedial measures are discussed. Examples demonstrate the effect of different kinds of notches on various components. 相似文献
29.
一种可切削玻璃陶瓷的压痕断裂特性 总被引:4,自引:2,他引:2
将断裂韧性测试的压痕方法与压痕弯曲方法相结合,独立地分离出了压痕残余应力因子x,使其成为可测参量,并建立了压痕一压痕弯曲的断裂韧性测试方法.将这种方法应用于一种可切削玻璃陶瓷的测试,获得的K1c值为K1c=2.03MPa·m1/2,与单边切口法(SENB)获得的K1c值有较好的一致性.测得的残余应力因子X=0.093,符合Anstis经验公式的预测. 相似文献
30.
介绍了锦化化工(集团)有限责任公司出现的VCM压缩机曲轴断裂事故,并从断口的部位、形貌特征,断轴的几何状态、受力状态及树料性能等方面分析了曲轴断裂的根本原因。 相似文献