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A three-dimensional statistical damage constitutive model for geomaterials
Hangzhou Li,Hongjian Liao,Guangdong Xiong,Bo Han,Guiping Zhao 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.1
We present a constitutive model for geomaterials. The unified strength theory, which is modified to be more suitable for the geotechnicalengineering, is introduced to reflect the effect of the intermediate principal stress. The polyaxial test data of several rock types verifiesthat the unified strength theory is versatile. The failure of the micro-elements of material is supposed to be distributed randomly and followsWeibull distribution, and the strengths of elements obey the unified strength theory. A statistical damage variable is proposed. Based on the continuum damage mechanics, a statistical damage constitutive model under the complex stress state is proposed. The proposedmodel is verified by the tests of soft rock. The result shows that the model can well predict the stress-strain relationship of soft rock,especially the strain softening behavior. The influences of the parameters of the model are investigated.
Dong Luo,Yuanyuan Li,Hangzhou Yang,Hao Sun,Hongbin Chen 국제구조공학회 2020 Smart Structures and Systems, An International Jou Vol.26 No.4
In order to achieve effective corrosion monitoring of buried metal pipelines, a Novel nondestructive Testing (NDT) methodology using ultra-long (250 mm) Polymer Optical Fiber (POF) sensors coated with the Fe-C alloy film is proposed in this study. The theoretical principle is investigated to clarify the monitoring mechanism of this method, and the detailed fabrication process of this novel POF sensor is presented. To validate the feasibility of this novel POF sensor, exploratory research of the proposed method was performed using simulated corrosion tests. For simplicity, the geometric shape of the buried pipeline was simulated as a round hot-rolled plain steel bar. A thin nickel layer was applied as the inner plated layer, and the Fe-C alloy film was coated using an electroless plating technique to precisely control the thickness of the alloy film. In the end, systematic sensitivity analysis on corrosion severity was further performed with experimental studies on three sensors fabricated with different metal layer thicknesses of 25 μm, 30 μm and 35 μm. The experimental observation demonstrated that the sensor coated with 25 μm Fe-C alloy film presented the highest effectiveness with the corrosion sensitivity of 0.3364 mV/g at Δm = 9.32 × 10<sup>-4</sup> g in Stage I and 0.0121 mV/g in Stage III. The research findings indicate that the detection accuracy of the novel POF sensor proposed in this study is satisfying. Moreover, the simple fabrication of the high-sensitivity sensor makes it cost-effective and suitable for the on-site corrosion monitoring of buried metal pipelines.