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An improved shear-lag model is adopted in this paper to study the fiber pull-out by considering interface properties in a representative volume element (RVE). The surface roughness, represented by grooves distributed around the fiber, is introduced to analyze the influence of roughness on fiber pull-out comparing it with a round fiber. The influence of groove shapes is also discussed. The interfacial stiffness is introduced in the improved shear-lag model by the cohesive zone modeling to simulate a practical interface connection. To represent the residual stress in composites, a pressure load is added on the surface of the RVE to analyze its influence on the fiber pull-out. The results show that the proposed theory can accurately predict the stress distribution in the RVE. Furthermore, the maximum reaction force increases with an improvement in roughness and interfacial stiffness, while the pressure can improve the reaction force in the third stage of fiber pull-out process. The proposed theory can predict the stress field and fiber pull-out process accurately. It can improve the efficiency and effectivity of micro-experiment with the reference of theoretical results. The results obtained using the proposed theory in this research can also be useful for the design and analysis of composite materials. [ABSTRACT FROM AUTHOR]

Cardiovascular diseases have been a leading cause of death for the past several decades. A comparison of blood flow patterns through diseased and treated arteries can be beneficial in diagnosis and treatment. The computational fluid dynamic (CFD) analysis was utilized to numerically simulate the blood flow dynamics of stenosed and stented carotid artery bifurcation. Two lumen models were generated: first with the stenosis and then a stent was introduced to remove the abnormality. The control volume method was implemented to discretize the blood domain, and then the steady-state velocity inlet was used based on the measured blood flow rate. The transitional flow was observed in the post-stenotic region due to the high Reynold's number near peak systole; however, the flow exhibited laminar characteristics at the peak diastole. Four distinct locations downstream of the stenosis were used to compare the results. The internal carotid artery (ICA) stenosis resulted in high wall shear stresses, irregular flow patterns, and low-pressure areas. The velocity and pressure profiles oscillated in the immediate vicinity downstream of the stenosis. The stented model showed minimal pressure and velocity fluctuations, as well as minimal wall shear stresses. Additionally, for the stented model, the flow could not enter the transitional regime under both conditions. The proposed simulation methodology can be utilized until the abnormalities in the carotid artery geometry are removed and normal blood flow characteristics are achieved, which then become the basis for an optimal design of a carotid artery stent. [ABSTRACT FROM AUTHOR]

A multistage damage detection method is introduced in this work that uses piezoelectric lead zirconate titanate (PZT) transducers to excite/sense the Lamb wave signals. A continuous wavelet transformation (CWT), based on the Gabor wavelet, is applied to accurately process the complicated wave signals caused by the damage. For a network of transducers, the damage can be detected in one detection cell based on the signals scattered by the damage, and then it can be quantitatively estimated by three detection stages using the outer tangent circle and least-squares methods. First, a single-stage damage detection method is carried out by exciting a transducer at the center of the detection cell to locate the damaged subcell. Then, the corner transducers are excited in the second and third stages of detection to improve the damage detection, especially the size estimation. The method does not require any baseline signal, and it only utilizes the same arrangement of transducers and the same data processing technique in all stages. The results from previous detection stages contribute to the improvement of damage detection in the subsequent stages. Both numerical simulation and experimental evaluation were used to verify that the method can accurately quantify the damage location and size. It was also found that the size of the detection cell plays a vital role in the accuracy of the results in this Lamb-wave-based multistage damage detection method. [ABSTRACT FROM AUTHOR]