Research On Technological Law And Key Technology Of Bionic Coupling Laser Manufacturing For Iron Based Alloy Functional Surface

As an interdisciplinary regarding traditional manufacture, life (biological) science,information science and materials science, bionic manufacturing is an importancemanufacturing method and technique necessary to develop in machine manufacturing.Processize, automation and intelligentialize in the production and manufacture is thedeveloping direction to produce bionic products in the future. At present, a lot of bionicproducts, such as the bionic brake hub (dish), the bionic machine tool guide way, the bionicmould and the bionic gear etc., have achieved great breakthrough in the research of energyconservation, synergia and durable technology, it is in the urgent need to integrate with themodern advanced manufacturing technology, sequentially speed up the process ofindustrialization of the bionic products.As a means of bionic manufacturing technology, laser processing could primely meetthe forming and modifying requirements for bionic functional unit. Through the interactionbetween laser and material, the process of fusion, gasification and phase transformation isconducted, and then a unit, hereinafter referred to as the coupling unit, with couplingcharacteristics of morphology, structure and mechanics is produced in the treated zone. Dueto the variety of processing parameters set, accordingly, the characteristics of coupling unitpresent diversity, which increase the difficulty of quality control in the manufacturingprocess. Conducting selective manufacturing among the characteristics of geometricalmorphology, physical structure and mechanical performance, can form a set of practicaltechnology in typical mechanical parts to build bionic coupling surface, which not onlywiden the bionic manufacturing method, but also expand the application scope of lasertechnology. Besides, it provides new foundation for the manufacturing levels and efficiency. Selection of processing parameters is the key skill of bionic manufacturing using lasertechnology. Conducting experiments of basic, optimization and testing frequently is usual inthe manufacture using laser, which not only increase the manufacturing costs, but also delaythe progress in the development for new product. Therefore, it is of great researchsignificance and comprehensive social and economic benefits to develop regression modelsregrading laser parameters and characteristics of bionic coupling unit and database systemwith functions of parameter selection, results prediction and multi-objective optimization.In this paper, medium steel, die steel and gray cast iron, derive from die, brake disc andmachine tool slide guide separately, were selected as base materials. Digital descriptionabout the morphological, structural and mechanical characteristics of bionic functionalsurface was conducted. The significant parameters affecting the above characteristics wereconcluded and extracted. Using experimental design and statistical analysis, regressionmodels regarding morphological, structural, hardness characteristics of peg-shaped anddam-shaped bionic coupling unit and processing parameters, tensile properties of bioniccoupling surface and parameters of laser and unit distribution were developed. Then, thedependability of above models was tested with mathematical and experimental methods.Combined the developed models and data analysis, the effects of the process parameters andtheir interaction on the characteristics of coupling unit (functional surface) were discussed.Researchs show that the average peak power, pulse duration and defocusing amounthave significant effects on the structural characteristics of bionic coupling unit. The spreadvelocity of isothermal surface can be accelerated by increasing the average peak powerand/or reducing the defocusing amount, while the spread time of isothermal surface can beextended by increase pulse duration, which is beneficial to fabricate the bionic coupling unitwith larger structural depth.The morphology of peg-shaped bionic coupling unit is the synergy results of processingparameters, surface tension from molten pool, phase change and vaporizing pressure. Activeelement, such as sulfur, in matrix can change the sign of temperature coefficient of surfacetension when the temperature is in a certain range, which makes the profile present diversitycharacteristics. When power density is smaller, the profile of coupling unit presents a sombrero profile. However, with the increase of power density and pulse duration, theprofile may become waviness along the diameter direction.The average peak power, pulse duration and defocusing amount all have significanteffects on the average hardness of coupling unit, and it is variational with the range ofprocessing parameters changing. For peg-shaped bionic coupling unit, the average hardnessincrease with the increase of power density, while the dam-shaped ones have the contraryresults. Due to the existence of the overlap, remelting and tempering in treated area isgenerated, which make the average hardness lower than peg-shaped bionic coupling unit.The influence of process parameters to the tensile properties is closely related to theprocessing quality of coupling unit. When pulse energy, pulse duration and space is in acertain range, the tensile strength of bionic specimen increase with the augment of energy,pulse duration and the decrease of the space between the units. However, the tensile strengthdecreases due to the accumulation of fabricating defects when the above parametersexceeding a certain range.Take partial parameter selection and quality control for example, this research providesa synergetic method for controlling the partial parameters to manufacture bionic couplingsurface. That is, by constructing morphological overlapping coefficient and middle function,we can not only match frequency and speed according to overlapping rate, but also conductaccuracy control for the morphological characteristics of bionic coupling surface under thefixed parameter set of average peak power, pulse duration and defocusing amount.In addition, this research conduct database modelling based on the overall considerationon laser manufacturing for bionic coupling surface and/or unit. To avoid omitting parametersor characteristics regarding the whole process, the entity relationship diagram was applied inthe conceptual design. The constraints were set according to the relationships amongmaterial, processing parameters and fabricating results, so as to assure the rationality andstandardability of the models.Based on the database system, application program for parameter query under certainprecision was developed combining with the actual problems of parameter selection in themanufacture of bionic coupling unit/surface, which can not only avoid the no data phenomenon in precise query, but also ensure the data in the database be effective. Inaddition, the application programs regarding prediction of manufacturing results andparameter optimization were also developed based on the mathematical models. It is ofgreat significance in economizing cost and shortening cycle in the development of newbionic products. Meanwhile, it can also lay the foundation for realizing processize andintelligentialize in bionic manufacturing.The full dissertation is divided into eight chapters. The first chapter expounds theresearch background and status quo of preparation for bionic function surface using lasertechnology, and the common modeling methods in advanced manufacture. The secondchapter introduces the evaluation methods for the characteristic parameters of bioniccoupling unit and functional surface based on the digital description for the characteristicsafter laser process. The third chapter conducts mathematical model for the characteristics ofpeg-shaped bionic coupling unit, and discusses the effects of processing parameters on thestructural and morphological characteristics of unit. The fourth chapter conductsmathematical model for the characteristics of dam-shaped bionic coupling unit, anddiscusses the effects of processing parameters on the structural and morphologicalcharacteristics of unit. The fifth chapter develops mathematical models for average hardnessof coupling unit and tensile strength of bionic surface, and analysis their influence underprocessing parameters and distribution characteristics of units. The sixth chapter provides acooperative method for controlling the partial parameters to manufacture bionic couplingsurface based on the problem of parameter selection and quality control. The seventh chapterdesigns database models for material, bionic coupling surface, coupling unit and processingparameters etc., and develops application programs for parameter selection, qualityprediction and parameter optimization based on the mathematical models and database. Theeighth chapter is the conclusions of this dissertation.