Laser Direct-Write Microfabrication and Patterning.

The ability to generate small structures is central to modern science and technology. In this work, four laser direct-write microfabrication and micropatterning techniques were studied: (a)Laser micromachining of channels in PMMA using a CO2 laser was investigated experimentally and theoretically. Heat transfer models for the channel depth, channel profile, laser power and scanning speed were developed and applied in this work. These models, are in excellent agreement with experimental results, with a maximum deviation of approximately 5% for the range of experimental parameters (laser power, scanning speed) tested. (b)A sub-micrometer resolution laser direct-write polymerization system for creating two-dimensional and three-dimensional structures was developed using a frequency-doubled Nd:YAG laser. Experimental studies and Monte Carlo simulations were conducted to understand the detailed microscale optical scattering, chemical reaction, polymerization, and their influence on critical fabrication parameters. The experimental data are in good agreement with the theoretical model. (c)Direct laser interference was developed for rapid and large area fabrication of two-dimensional and three dimensional periodic structures on photopolymerizable materials with 10ns pulses from a frequency-tripled Nd:YAG laser emitting at 355 nm. Three different photopolymerizable materials were investigated: pentaerythritol triacrylate (PETIA) with photoinitiator N-methyldiethanolamine (N-MDEA); SU-8 with absorber TINUVIN 384-2; and Shipley 1813. (d)A new approach to fabricating nanometer sized cavity arrays on Poly(3,4-ethylene dioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) thin films using laser-assisted near-field pattering was investigated. Periodic nano-cavity arrays were patterned by combining direct laser interference technology and laser induced near-field technology. An analytical model based on Mie theory was developed, the predicted intensity distributions on the substrate indicate a strong near-field enhancement confined to a very small area (nanometer scale).Ph.D.Mechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/60759/1/yuandj_1.pd

Application of electro-hydraulic proportional control in cathode rod pulling out system of lead electrolysis

In the process of lead electrolysis, due to its production characteristics, it is necessary to extract and collect the cathode conductive rod on the cathode plate after electrolysis, so as to make it reusable. At present, most of the lead electrolytic manufacturers in China still rely on manual extraction in this process. In this study, a rapid, stable and effective cathode rod extraction equipment for lead electrolysis is designed by means of electro-hydraulic proportional technology. AMESim simulation and experimental research on the equipment are also carried out

An Ensemble Learning Aided Computer Vision Method with Advanced Color Enhancement for Corroded Bolt Detection in Tunnels

Bolts, as the basic units of tunnel linings, are crucial to safe tunnel service. Caused by the moist and complex environment in the tunnel, corrosion becomes a significant defect of bolts. Computer vision technology is adopted because manual patrol inspection is inefficient and often misses the corroded bolts. However, most current studies are conducted in a laboratory with good lighting conditions, while their effects in actual practice have yet to be considered, and the accuracy also needs to be improved. In this paper, we put forward an Ensemble Learning approach combining our Improved MultiScale Retinex with Color Restoration (IMSRCR) and You Only Look Once (YOLO) based on truly acquired tunnel image data to detect corroded bolts in the lining. The IMSRCR sharpens and strengthens the features of the lining pictures, weakening the bad effect of a dim environment compared with the existing MSRCR. Furthermore, we combine models with different parameters that show different performance using the ensemble learning method, greatly improving the accuracy. Sufficient comparisons and ablation experiments based on a dataset collected from the tunnel in service are conducted to prove the superiority of our proposed algorithm

Kinematic Analysis and Virtual Prototype Simulation of the Thrust Mechanism for Shield Machine

The hydraulic thrust system of the shield machine is used for driving forward and pose adjustment. It is of great significance to figure out the thrust mechanism and motion characteristics of the shield machine to ensure the safety of tunnel excavation. This study aims to develop a model to explore the influence of thrust cylinder advancement on the motions of the shield machine. Firstly, the study carried out mechanism analysis of the thrust mechanism for the shield machine and established a method to describe the position and attitude of the shield machine during the tunneling process by the homogeneous transformation matrix. Then, a new inverse kinematic model was proposed to quantify the relationship between the telescoping movements of cylinders and shield machine motions, and the Jacobian matrix was derived to solve the instantaneous kinematics analysis. Furthermore, a virtual prototype model was developed to simulate the kinematic behavior of the shield machine and validate the accuracy of the kinematic model. The model provides the basic constraint relations for the practical position control system and lays a strong foundation for the dynamic model and automatic trajectory tracking control of shield machines for future studies. Based on the proposed model, the displacement, velocity, and acceleration of cylinders that drive the shield machine to the target motions can be solved exactly. It can provide a reference for the pose control of the shield machine during the practical shield tunneling

Characterization of Shrinkage and Stresses in Large Area Maskless Photopolymerization

Large Area Maskless Photopolymerization (LAMP) is a high throughput direct digital manufacturing technology being developed for producing ceramic investment casting molds. Polymerization shrinkage and accompanying stresses developed during photopolymerization of ceramic particle-loaded resins in LAMP can cause deviations from the desired geometry. The extent of deviations depends on photoinitiator concentration, filler loading, degree of monomer conversion and operating parameters such as energy dose. An understanding of shrinkage and stresses built up in the part can assist in developing source geometry compensation algorithms and exposure strategies to alleviate these effects. Real-time Fourier Transform Infrared Spectroscopy (RTFTIR) operated in Attenuated Total Reflectance (ATR) mode is used to characterize the three-dimensional shrinkage stresses. This work is sponsored by DARPA Grant HR0011-08-1-0075.Mechanical Engineerin

A New Calculation Method of Cutterhead Torque Considering Shield Rolling Angle

The existing cutterhead torque calculation method usually simplifies the characteristics of the shield, which ignores the rolling angle. In this paper, the cross-river shield project of Wuhan Metro Line 8 is taken as the research focus. Firstly, the measured data of the cutterhead torque (CT), the rolling angle and rotation direction were analyzed. Then on this basis, the penetrability, tunneling thrust, and rolling angle were taken as the influential factors to analyze CT sensitivity. Finally, based on the theoretical calculation model, a modified solution of CT was obtained considering the rolling angle. The results show that the rolling angle can be reduced to zero by changing the direction of the cutterhead rotation; the rolling angle has a greater impact on CT than the other two factors as shown through the analysis of the range difference and Statistical Product and Service Solutions (SPSS) method. As the absolute value of the rolling angle increases, CT also increases, and the relationship between them is linear. To a certain extent, the rolling angle of the shield can reflect the difficulty of tunneling and the running status. By monitoring the rolling angle of the shield, the prediction of CT can be more in line with the actual construction conditions

Kinematic Analysis and Virtual Prototype Simulation of the Thrust Mechanism for Shield Machine

The hydraulic thrust system of the shield machine is used for driving forward and pose adjustment. It is of great significance to figure out the thrust mechanism and motion characteristics of the shield machine to ensure the safety of tunnel excavation. This study aims to develop a model to explore the influence of thrust cylinder advancement on the motions of the shield machine. Firstly, the study carried out mechanism analysis of the thrust mechanism for the shield machine and established a method to describe the position and attitude of the shield machine during the tunneling process by the homogeneous transformation matrix. Then, a new inverse kinematic model was proposed to quantify the relationship between the telescoping movements of cylinders and shield machine motions, and the Jacobian matrix was derived to solve the instantaneous kinematics analysis. Furthermore, a virtual prototype model was developed to simulate the kinematic behavior of the shield machine and validate the accuracy of the kinematic model. The model provides the basic constraint relations for the practical position control system and lays a strong foundation for the dynamic model and automatic trajectory tracking control of shield machines for future studies. Based on the proposed model, the displacement, velocity, and acceleration of cylinders that drive the shield machine to the target motions can be solved exactly. It can provide a reference for the pose control of the shield machine during the practical shield tunneling

A New Calculation Method of Cutterhead Torque Considering Shield Rolling Angle

The existing cutterhead torque calculation method usually simplifies the characteristics of the shield, which ignores the rolling angle. In this paper, the cross-river shield project of Wuhan Metro Line 8 is taken as the research focus. Firstly, the measured data of the cutterhead torque (CT), the rolling angle and rotation direction were analyzed. Then on this basis, the penetrability, tunneling thrust, and rolling angle were taken as the influential factors to analyze CT sensitivity. Finally, based on the theoretical calculation model, a modified solution of CT was obtained considering the rolling angle. The results show that the rolling angle can be reduced to zero by changing the direction of the cutterhead rotation; the rolling angle has a greater impact on CT than the other two factors as shown through the analysis of the range difference and Statistical Product and Service Solutions (SPSS) method. As the absolute value of the rolling angle increases, CT also increases, and the relationship between them is linear. To a certain extent, the rolling angle of the shield can reflect the difficulty of tunneling and the running status. By monitoring the rolling angle of the shield, the prediction of CT can be more in line with the actual construction conditions