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31.
32.
川西平原属沉积平原,不到2m厚的表土下面全是沙卵石,沙卯石厚度达二、三十米。地面覆盖农田,沟垄纵横,限制了车载钻机的进入。以往地震勘探多采取浅井组合方式激发,所获得的地震资料能量差、面波强,对农田破坏面积大。若使用SH30—2A型轻便工程钻机,配上自制的冲击管,采取冲击钻进,从管中下药柱的方式,可实现沙卵石地区的深井激发,提高资料采集质量,且效率高、成本低。 相似文献
33.
Y. L. Hao R. Yang M. Niinomi D. Kuroda Y. L. Zhou K. Fukunaga A. Suzuki 《Metallurgical and Materials Transactions A》2003,34(4):1007-1012
Alloys for implant devices require improved strength but a reduced Young’s modulus, in order to become mechanically more compatible
with adjacent bone tissues. In this study, a new metastable β-type titanium alloy, Ti-29Nb-13Ta-4.6Zr (wt pct), was subjected to aging treatment to produce different microstructures,
and the resulting mechanical properties, including the Young’s modulus, were measured. The Young’s modulus of this alloy is
found to be sensitive to microstructures generated by various heat treatments. For microstructures varying from (α + β) to (α + β + ω) and (β + ω), the Young’s modulus increases with an accompanying increase in tensile strength and hardness, but decreases in ductility.
The (β + ω) microstructure has a low strength, high modulus, and poor ductility and cannot be used for biomedical applications. For
an (α + β) microstructure, the volume fraction of the phases is shown to be the main factor that determines the mechanical properties. 相似文献
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35.
LaNiO3 was synthesized by sol-gel method in which lanthanum nitrate and nickel nitrate were used as start materials and citric acid was used as complex for gel formation.The precursor was dried and subsequently heated at elevated temperature to form the desired product.XRD analysis shows that pure LaNiO3 was synthesized.Electrical conductivity and electrochemical performance of the material were tested.The electrical conductivity decreases from 34.5that there are current peaks in the curve, which is the evidence of the electrochemical activity of LaNiO3. 相似文献
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39.
Longjie Zhou A. Zimmermann Yu-Ping Zeng F. Aldinger 《Journal of Materials Science》2004,39(8):2675-2681
The bipolar electric fatigue behaviour of antiferroelectric ceramics with the composition of Pb0.88Ba0.10La0.02(Zr0.55Sn0.35Ti0.10)O3 was investigated under various cycling fields. The material exhibits a degradation in the maximum field induced strain, a diffuse AFE-FE phase transition and an enhancement in the diffusion character of the FE-AFE phase transition due to electric cycling. Those variations increase with cycle number, indicating a logarithmic fatigue up to 108 cycles. There is no indication for the variations to be recovered, and the symmetry of the negative and positive parts of the strain hysteresis loops still remains. Higher cycling field results in a stronger deterioration of the maximum field induced strain and a larger extent of diffusion in AFE-FE and FE-AFE phase transitions. The normalized maximum strain shows nearly the same scale of degradation when the materials are cycled at various electric fields. After a heat treatment at 500°C for 1 h, the variations in the AFE-FE and FE-AFE phase transition due to cycling disappear, whereas the maximum strain resumes almost to its original value. Electrochemical variations are considered to contribute to the main fatigue mechanism for the material under investigation. 相似文献
40.
A. Carpinteri S. Valente F. P. Zhou G. Ferrara G. Melchiorri 《Materials and Structures》1997,30(5):269-276
Three series of novel tensile and flexural creep tests on partially-damaged concrete specimens were carried out in order to gain some insight into creep crack growth and failure of strain-softening materials. In the tests, each specimen was initially loaded to a given point in the descending branch and thus had a lower load-carrying capacity than that at the peak-point. Then, the specimen was unloaded and reloaded to sustain a load which was from 70% to 95% of its current load-carrying capacity. Experimental creep curves display a three-stage process, consisting of primary, secondary and tertiary stages, with a decreasing, constant and increasing creep rate, respectively. The secondary stage dominates the whole failure lifetime, whereas both the secondary and tertiary stages are important in terms of creep deformation. Failure life-time seems to be more sensitive to the change of load level in flexural tests rather than in tensile tests. The decrease in load-carrying capacity due to damage tends to result in a shorter failure lifetime and a lower critical load level for creep rupture. The descending branch of the static load-deflection or load-CMOD curve may be used as an envelope criterion for creep fracture. 相似文献