Zhenying Xu

Non-Destructive Testing of Polycrystalline Silicon Solar Panel by Scan Acoustic Microscopy

The inner structure and defects of the silicon panel will influence the transfer efficiency and the stability of the polycrystalline solar cells, thus the non-destructive testing of the silicon panel is very important. In this paper, a Scan Acoustic Microscopy is applied to test the inner structure of polycrystalline silicon solar panel. From the grey image of C-Scan by the microscopy, the amplitude distribution of the bottom wave generated by the interaction between the inner grains of the polycrystalline silicon and the acoustic beam can be seen clearly. Furthermore, the defects as well as their size and position can also be tested by A-Scan, B-Scan and C-Scan with high resolution and high accuracy. The experiment results show that it is a good non-destructive method to test and evaluate the quality of the inner structure of polycrystalline silicon solar panel.

A piezoelectric transducer for weld defect detection based on first-order shear horizontal (SH1) mode

Ultrasonic guided wave is a new non-destructive evaluation (NDE) method since it offers the potential to quickly inspect defects along long length of welds. During the mode study, a shear horizontal (SH) mode has been discovered, which is particularly attractive for NDT as it is non-leaky and almost non-dispersive. However, rare weld guided transducers have been developed so far, let alone used for wide commercialization. This paper develops a new piezoelectric transducer based on the SH1 mode at high frequency. Experiments have been carried out to validate its performance, including mode verification, energy attenuation calculation and defect detection. The results show that the transducer can work effectively and detect defects with localization errors under 3.5%, which shows great value for further theoretical study as well as engineering applications.

Shrinkage Optimization of Flat Receptacle Using the Finite Element Method

Flat receptacle, which is used in extruding the large aluminum profiles, is in harsh work conditions. Due to the irregularity of inner hole of flat receptacle, inconsistent resistance of shrinking fitting affects the inner hole within which nonuniform deformation occurs. If the nonuniformity exceeds the specified dimension accuracy, tiresome work including mould repairing and structure optimization has to be done. ANSYS is used to simulate the flat receptacle. It is shown that the maximum stress appears in the arc area of inner hole. Therefore, we present one new method using the preloaded layer with changeable shrinkage to replace the preloaded layer with uniform shrinkage. Considering the processing and assembling factors, we adopt the elliptical outer layer and circular inner layer as the new structure. Then the optimizations of flat receptacle with uniform and changeable shrinkage are implemented using the optimizing module, receptively. The optimized results show the maximum equivalent stress in the corner of inner-hole decreases about 5.47% if adopting the changeable shrinkage. The numerical simulation results show that the feasibility of changeable shrinkage and elliptical preloaded layer.

The effect of joint geometry parameters on ultrasonic weld-guided modes in thick steel plates

Ultrasonic guided waves are widely applied in non-destructive testing (NDT) due to its high efficiency, however, the inspection of large areas of complex structures can be challenging. Weld can be taken as a wave-guide because it can concentrate and guide energy of ultrasonic waves to travel along the direction of weld, which shows a potential for rapid NDE of long welds. In this paper, the effect of joint geometry parameters on two ultrasonic weld-guided modes, named the SHw0 and the Sw0 mode, in 10 mm thick steel-AISI-4340 plates has been analyzed through semi-analytical finite element simulations. Results show that the propagation properties of the SHw0 mode is almost stable with different geometry parameters. However, the phase velocity and attenuation of Sw0 will change with the increase of weld width and reinforcing height, which can be taken into consideration when we are choosing a mode as well as frequency in application of weld-guided waves.

Design of Acoustic Emission Monitoring System for Defects of Hull Plate

An acoustic emission (AE) monitoring system has been developed for micro cracks of hull plate, which has a human-machine interface (HMI) designed by Labview, with functions of signal acquisition, storage and replay, key parameters extraction. With the powerful signal processing capabilities of MATLAB, defects can be rapidly and accurately located.

Numerical investigation on micro-bending and springback with improved surface layer model

Surface layer model can explain the first order size effect, but it is difficult to solve the micro-bending and springback due to the size effect. So the improved surface layer model was proposed based on the constitutive model considering the first order size effect. It consists of upper surface layer, upper transition layer, inner layer, bottom transition layer and bottom surface layer. And the micro V-bending geometry model was developed using analysis method. Combined with the dynamic explicit and static implicit codes, the corresponding finite element model was established in ABAQUS to simulate the micro V-bending and springback of H62 ultra-thin sheet. The comparison between the improved model and traditional model showed that it is more accurate for the forming force, stress changes and residual stress with improved model. The improved surface model can be better used into the micro-forming investigation.

Study on Micro-Bulk Forming of Sheet Metal by Laser Shock

The μLSF is a micro-plastic forming method with the laser-induced shock load generated by the plasma in confined medium. It is characterized in the high-pressure and ultra-high strain ratio. This paper developed the model of metal micro-bulk forming by laser shock, simulated the process of forming and compared the influence law of forming depth under the conditions of different laser energy ranging from 3J to 10.6J and sheet thickness ranging from 0.13mm to 0.30mm on. It showed that there exists a threshold for magnitude of the laser energy. The forming depth increased with the increase of magnitude when the magnitude was smaller than the threshold. However, it decreased with the increase of magnitude when the magnitude was larger than the threshold. When the magnitude of the laser energy was chosen, the forming depth presented non-linear reduction with the increase of sheet thickness.

The Analysis of Wave Form for 3-D Wave Tank

The 3-D numerical model of wave tank is developed considering the effects of wave generating and absorbing based on viscous fluid motion differential equations (N-S equation) and the volume of fluid (VOF) method by the use of FLUENT solver. The simulation is also made by the analysis of the existing methods of wave simulation. The wave form of the 3-D wave tank is analyzed with the result of diverse diversification at different wave location and their relationship. The flow path of each particle of the wave during the propagation is also been analyzed, which provides guidance for the wave form analysis.

The Investigation of the First Order Size Effect in Micro-Plastic Forming

With the rapid development of MEMS and electronic industry, the demands for micro-parts are increasing gradually. However, size effects make the traditional forming theories and deformation mechanism not suitable in micro forming field. In this paper, we introduced the classification of the size effects. It pointed out that the size effects can be divided into the first order and the second order size effects in the micro-forming. For the first order size effects, the theory model was established based on the surface layer model. It also clarified the phenomenon that flow stress of the blank reduced with the increase of the ratio of grain size and thickness (t decreases or d increases). Finally, the model was verified with the experimental results of the first order size effects in the references, confirming the effectiveness of the theoretical model. It provides a method to theoretically and experimentally study the micro-plastic forming.

Experimental Study of Micro Deep Drawing for H62 Brass

In this paper, the influence of grain size and blank hold force on micro deep drawing stress and displacement are studied by self-made device. The results show that drawing stress decreases and elongation rate increases with the increase of grain size, the concentrated force area of cylinder-shaped part is transferred from the area punch fillet to die fillet area. Twin grain ratio and twinning degree near the punch fillet are increasing. Twin grain distribution becomes uneven with the increase of grain size. In micro deep drawing, the displacement increases with the increase of blank hold force, meanwhile, forming stress almost remains constant. The flange wrinkling can be inhibited.