Exploring The Laws Of Thermal Deformation Nonsimilarity Using Microscopic Theoretical

The thermal deformation of the structure is the main factor to affect the accuracy of the instrument.It is difficult to solve the error caused by the non-similar thermal deformation by controlling the ambient temperature and using low expansion materials.It is necessary to exploring the non-similarity law of thermal deformation and improve structure to solve these problems.A method based on molecular dynamics theory was proposed to study the non-similarity law in this paper.The non-similarity law was verified by the thermal deformation experiment,and the structure of the laser collimation system was designed.The main tasks are as follows:(1)The principles of thermal deformation and non-similar thermal deformation were expounded,and the causes of non-similar thermal deformation were explained from thermal stress principle.The mechanism of thermal deformation was explained by the Frankel diatomic model at the micro level,and the mechanism of non-similar thermal deformation was explained by force analysis of atoms.The method was proposed to explore the law of non-similar thermal deformation by using molecular dynamics.(2)The principle of molecular dynamics simulation was introduced.The square aluminum models were established using Lammps simulation software.The appropriate model parameters were selected.The simulation process and matters needing attention were introduced.The simulation results were visualized to observe the deformation of the models in real time by Ovito visualization software.(3)The relationship between the thermal deformation and the length,height or heating range of different cubes was analyzed by the scatter matrix.The surface atomic coordinates of different cubes with different length and height under different heating ranges were calculated based on the regression analysis.The mathematical model between deformation and temperature increment of each part of the upper surface was established.(4)The experimental system was built.The temperature of standard parts was controlled by high-precision temperature control box.The fixed frame and alignment structure were designed.The measurement system of thermal deformation was selected and improved.And the efficient acquisition program was compiled.The parameters of inductance probe,temperature sensor and deformation of heating plate were calibrated.The standard parts with different shapes were tested to verify and improve the law of non-similar thermal deformation.(5)According to the law of non-similar thermal deformation,the laser collimating system was improved.The measurement parameters of the laser collimating system were calibrated,and the comparative experiment was designed to verify the improvement effect of the laser collimating system.The experimental results show that the laser beam stability was improved more than 40% by improving laser collimating system.