Li Jun Liu

Composition heterogeneity of tetrafluoroethylene-hexafluoropropylene random copolymers characterized by successive self-nucleation and annealing

In the present work, successive self-nucleation and annealing (SSA) was applied to a series of tetrafluoroethylene-hexafluoropropylene random copolymers (FEPs). Multiple melting peaks were observed for all FEP samples after SSA thermal treatment. The lamellar crystal thicknesses were calculated from the melting temperatures, and the mass percentages of the crystals of specific thickness were obtained from the areas of the melting peaks. As a result, distributions of the lamellar thickness, which can be correlated to the composition distribution, were determined. It was found that the composition distribution of the FEP samples tended to become more heterogeneous as the content of hexafluoropropylene (HFP) comonomer increases. Samples with the same HFP content might also have different composition distributions.

Die-Casting Die Design Based on the Application of CAE Simulation

High pressure die casting is a high volume component manufacturing process which is used extensively in many aspects. There are many factors affecting the quality of die-casting die. In this paper, the CAE simulations of filling and solidification processes for die-casting are studied. Numerical analyses are presented for two practical die-casting parts using HZ CAE software. The temperature distributions and filling states in solidification and filling process are presented. Then the deficiencies of the part are predicted. Based on the analyzing results, the structures of the two dies are optimized and longer die service life and high-quality castings are obtained. It is proved that CAE simulation results can offer a helpful reference for die-casting die design.

Local Laser Bionic Blocking Experimental Study of Hot Work Mould Surface Cracks

For the short life of hot work die in enterprise directly caused problems the waste of resources and the rising cost of production. Based on studying the biological prototype of crack-resistance of plant lamina and found that surface thermal fatigue crack is one of the main factors affecting the service life of hot work mould, it is put forward thoughts about the local bionic laser melting on mould surface to block cracks. Different from the traditional mould surface integral laser transformation hardening (LTH) technology, using laser melting simulating plant lamina to block cracks on the partial surface of mold, life of bionic strengthened die is improved within 1~1.5 times. Experiment results show that a new method is provided to improve the service life of casting mould and promoting this technology will bring significant economic benefits for the mould industry.

Forward and Reverse Driving Noise Analysis of HDM Based on Sound Signal

As there are the errors during the manufacturing and assembling of horizontal driving machine (HDM). The exceptional knocking noise is generated during some products running. The failure rate of product quality is rising as well. The forward and reverse driving noise of HDM was tested and analyzed. The pictures was collected by universal tool microscope. The results show that hot runner is not smooth enough to reduce transferring pressure and increase the shrinkage of worm pouring gate, which lead to slight conical degree of product and pitch deviation at worm pouring gate. As the pitch makes worm inset slightly worm gear when clockwise rotating, the noise and vibration was produced consequently in this direction. The proposals were given, such as strengthening the maintenance of hot runners, controlling and inspecting product conical degree, and optimizing HDM mould and increasing its accuracy, and so on.

Study and Application of CAE Simulation in Die-Casting Die Design

The CAE simulations of filling and solidification processes for die-casting are studied. Numerical analysis is presented for a practical die-casting part using HZ CAE software. The temperature distributions and filling states in solidification and filling process are presented. Then the deficiencies of the part are predicted. Based on the analyzing results, the two die halves are modified and the die-casting parameters are adjusted. The service life of the revised die is increased from 12,000 shots to 20,000shots. It is proved that CAE simulation results can offer a helpful reference for die-casting die design.

Laser Local Stripe Bionic Strengthening of Mould Surface

In order to solve the problems of the waste of resources, and reduce the cost directly caused by the short life of the hot die in enterprises, this paper analyzes the wear of hot die which is one of the main factors affecting service life, and a thought that enhanced mold through laser surface local stripe grid bionic process is pointed out. Different from traditional laser hardening technology, the service life of mold processed by bionic laser melting enhancement simulating butterfly wings is nearly doubled. Experimental results provide a new way to improve die life, and the application of laser local stripe grid bionic process will bring enterprises significant economic benefits for its extension in mould industry.

Detection of Laser Melting Bionic Stripe Quality on Mould Surface Based on Acoustic Signal

In order to rescue the problems of controlling laser bionic strengthening local stripe of mould surface quality, it is put forward thoughts about the laser bionic local melting stripe of mould surface quality detection based on acoustic signal. Analyzed with the relationship between defocusing distance and acoustic signal characteristic, laser bionic strengthening local stripe quality, the results show that acoustic signal is weakened with the increased absolute value of defocusing distance. As the defocusing distance is 0mm, the role of the laser is primarily ablation and the stripe quality is the worst; the function of laser on the surface materials is too weak to strengthen when the defocusing distance is -4mm; laser on target surface plays its role of strengthening, mainly owing to melting, with defocusing distance of +4mm. Overall tests show that, based on the quantitative detection of acoustic signal characteristic, it could inspect and control the quality of strengthening stripe, and it will realize the overall control of laser bionic strengthening mould surface quality with guiding significance.

Laser Bionic Strengthening Local Grid of Mould Surface

For the short life of enterprise hot work die directly caused to problems in the waste of resources and the rising cost of production. Based on studying the biological prototype of crack-resistance of dragonfly wings and finding surface thermal fatigue crack is one of the main factors affecting life of the hot work mould, it is put forward thoughts about the local laser bionic strengthening the grid mould surface. Different from the traditional mould surface integral laser transformation hardening (LTH) technology, by using laser melting simulating dragonfly wings to block localized crack in the partial surface of mold, bionic strengthened die life is improved within 1~1.5 times. Experiment results on die steel shows that it is provided a new method to improve the service life of die casting mold and promoting this technology will bring significant economic benefits for the mold industry.

Determination of Optimal Temperature for Defect-Free Casting of Aluminium in the LP-LFC Process

Fluidity of ZL101 aluminium alloys in the low-pressure lost foam casting (LP-LFC) process has been investigated by altering various temperature variables. The experimental results indicate that the LP-LFC process had fine fluidity, and the pouring temperature was lower than conventional lost foam casting. The effect of the metal temperature on the fluidity is marginal in the LP-LFC process. Excessive pouring temperature not only aggrandizes energy consumption but also deteriorates porosity defect. The success of casting cooling fin demonstrates the advantages of LP-EPC process in producing high-complicated castings.

Product Design Strategies and Methods for Automatic Conveying

Conveying is the important part of product processes, which is significantly affected by product structures. Based on the point of conveying, appropriate design will be result in significant improving conveying performance and reducing the degree of automatic conveying difficulty, then equipment would be simplified, and investment reduced. The design strategies for allover include: reducing the parts quantity and variants, corresponding the part geometry with the conveying manner, and parts geometry convenient for checking and identifying. The methods include two situations: design for conveying in the machining process and design for conveying in the assembly process. Applications of parts design for automatic conveying are illustrated.