| Laser transmission connection has been widely used in medicine because of its advantages of good connection quality,small deformation,high efficiency,easy operation,non-contact,automation and so on.It has become a connection(packaging)technology with biocompatible metal and polymers.However,polystyrene is a non-polar polymer with low surface energy.The direct connection between polystyrene and titanium can't be achieved by means of laser transmission connection.In this dissertation,the connection between polystyrene and titanium is realized by two methods: oxygen plasma modification and laser surface treatment.The experiment and mechanism research,process research and temperature field numerical simulation study on laser transmission connection polystyrene and titanium are carried out.In the field of experiment,two technologies are studied for the surface modification of polystyrene by oxygen plasma and the treatment of titanium by laser scanning oxidation.The polystyrene and titanium,the polystyrene and laser scanning oxidized titanium,oxygen plasma modified polyphenylene and titanium,oxygen plasma modified polyphenylene and laser scanning oxidized titanium are studied by laser transmission connection experiment and tensile test.The bonding strength of these four different combinations curves was plotted.It was found that the strength of the modified polystyrene with the laser treated titanium was the highest;The failure form of the titanium welded parts is the interface failure.In the field of the joint mechanism,first of all,the microstructure of the weld was observed by Kean microscope.It was found that the bubbles were formed at the weld.The results show that the joint strength with the small and uniform bubbles is the highest,and the formation of the bubble can produce mechanical riveting between the two connectors,so the formation of the bubble is a reason for the high connection strength.Secondly,the contact angle of the Ti,PS,PS with oxygen plasma treated and Ti with laser scanned was carried out respectively.The surface energy changes before and after the material treatment are studied.It is found that the surface energy of the titanium with laser scanning oxidation and PS treated by oxygen plasma has been greatly improved.The improvement of the surface energy improves the compatibility at the connection interface.It is another reason to improve the connection strength.Finally,the interface of the joint is studied by the method of X ray photoelectron spectroscopy,and the photoelectron spectra of different elements are compared.The results show that the Ti-C and Ti-O chemical bonds formed when the polystyrene treated by oxygen plasma and the titanium treated by the laser are joined,and the formation of the chemical bond is one of the causes of the high bonding strength.In the process research,the process parameters are screened by Isight software and the sensitivity analysis is carried out.According to the results of sensitivity analysis,five process parameters which have the greatest impact on the strength of the connection are selected.They are laser connection power,laser connection speed,surface treatment power,surface scanning rate and oxygen plasma treatment time.The test design is carried out by the response surface method,and a mathematical model is established between the connection strength and the process parameters.The response surface of the process parameters and the contour map of the connection strength are studied,and the interactive influence between the parameters of the process is studied and analyzed.By using different optimization criteria,the optimal combination of process parameters is obtained.In the field of numerical simulation of temperature field,ANSYS analysis software is used to process and load the connector,study the variation of temperature field,explore the effect of laser power and connection rate on the temperature field,compare the simulation results of the connection width to the experimental results for verifying the accuracy of the model.The method of oxygen plasma treatment and laser oxidation can effectively solve the difficult problem of the connection between polystyrene and titanium.By optimizing the process parameters,the optimum combination of process parameters is obtained.This study lays a foundation for the industrial application of the process. |
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