| The echelle is widely used in the spectral analysis instruments in the fields of astronomy and medical treatment.It mainly uses periodic stepped groove to obtain high diffraction efficiency.For the master grating template used for mass reproduction,because of its large groove depth and severe groove type,it is usually prepared by mechanical rulling.In the process of fabricating the mechanical grating,the factors that affect the final groove results can be roughly divided into two aspects.On the one hand,it is related to the rulling equipment and knife,such as the equipment accuracy,the rulling knife quality,the process parameters and so on.On the other hand,it is related to the characteristics of aluminum film blank,such as characteristics of elastic-plastic deformation.At present,China has developed the world’s leading level of grating rulling machine and rulling tool,which can produce high-precision machine rulling grating.However,it is affected by the microstructure of the film itself,a small amount of rulling test is still needed to prepare the grating,and the experience value of tool placement is added to reduce the processing deviation caused by the unknown force grooving mechanism of aluminum film.It is very important to know the elastic-plastic deformation law of the aluminum film in the process of grooving for shortening the preparation period.In this paper,the aluminum film obtained by the latest step-by-step plating process is taken as the main research object.Firstly,the microstructure changes of aluminum film caused by step-by-step plating are analyzed.And use the scanning electron microscope equipment to observe the microstructure and compare with previous aluminum film,the differences between the two kinds of aluminum films were clarified.That is to say,the continuous and dense layered structure is produced by step plating,and then the layered interface was analyzed.Secondly,the mechanical properties of the single layer aluminum film and layered aluminum film were analyzed by nano indentation test and nano scratch test.The differences of hardness and elastic modulus were obtained,and the substrate effect included in the test results was analyzed.Meanwhile,the springback characteristics of aluminum films under different scratch depths were obtained.Then,a new model is established based on the mixing rate theory,the obtained microstructure and mechanical parameters of the film,the finite element method is used to simulate and analyze the rulling process of the echelle,the difference between the new model and the previous model of continuous homogeneous medium in simulation analysis is compared.The groove type of aluminum film with different film number,the transmission and distribution of velocity field and stress field in the process of layered aluminum film are obtained.In addition,the stress change of each element at the same position are obtained,and the influence of aluminum film layered interface on elastic-plastic deformation is explored.The results show that when the grain size is within the range of hall-petch effect,the more layered interface,the closer the position is to the depth,the smaller the springback of the film,and the closer it is to the ideal groove.Finally,the diffraction efficiency of different grating groove types is evaluated based on the rigorous coupled wave method,and the actual grating characterization experiment is carried out to verify the accuracy of the obtained rules.In this paper,the influence of the inner layer structure on the stress transfer and distribution and grooving process when rulling aluminum film of echelle is obtained,which can provide a theoretical basis for further reducing the number of trial rulling in the grating preparation process,and has a certain reference significance for improving the manufacturing process of the mechanical grating. |
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