The Thermal Expansion Coefficient Design And Tolerance Study Of Dual-material Planar Lattice

Not only the coefficients of thermal expansion(CTEs)of dual-material lattices can be designed,but also dual-material lattices have the characteristics of wide temperature application range,low cost,light,good mechanical properties and manufacturability.It is one of the most effective ways to reduce engineering thermal deformation and failure by using dual-material structure.However,the research time of dual-material lattice is not long.The topological structure of dual-material lattice is limited,and most of them focus on complex bending-dominated lattices and stretching-dominated lattice based on triangle and tetrahedron.The design and calculation of lattice materials with the point thermal expansion performance are complicated and the fabrication is difficult.In addition,the traditional tolerance theory cannot guarantee the accurate realization of the equivalent CTE of dual-material lattice.Therefore,it has significant engineering significance to propose a new type of dual-material lattice and study the tolerance distribution of dual-material lattice.The specific work is as follows:Firstly,the rectangular cell designs with CTEs of-7 ppm/?,0 ppm/? and 36.2 ppm/? were realized by using the matrix displacement method and the optimization algorithm of ANSYS tools respectively.In addition,the assembly method of interference fit and the heating method of non-contact heating were proposed,and the experimental verification of negative thermal expansion(NTE)cell was carried out,which proved the feasibility of the manufacturing process and the effectiveness of the large-scale thermal expansion design of dual-material rectangular lattice materials.Secondly,the bending degree and horizontal degree of the unit cell were introduced to study the overall thermal expansion performance of rectangular cell and the middle cell of lattice configuration with 3×3 cells.The thermal expansion effects and the sensitivity to the thermal expansion performance of different sizes variables of rectangular cell were analyzed,and the functional tolerance design was carried out by using this property.Finally,considering the effect of manufacturing error on the thermal expansion property of dual-material structure,the tolerance design of dual-material rectangular cell was carried out.Traditional tolerance theory can not guarantee the accurate realization of product performance,the size deviation optimization model and the size overall optimization model were put forward for the dual-material rectangular lattice.Based on optimization algorithm of ANSYS tools,the optimal tolerance design scheme of satisfying different thermal expansion properties of the unit cell was solved.For the size deviation optimization model,the design results were improved by two methods of gradually decreasing the tolerance level of sensitive size and decreasing the tolerance level of non-sensitive size first,which solved the problems of large difference in tolerance grade between different sizes of the unit cell and high tolerance grade of individual sizes,and further reduced the difficulty of the whole processing.Based on the requirement of thermal expansion in a certain direction,this paper proposes a new dual-material rectangular cell with overall thermal expansion property,and the experimental design and verification of NTE cell are carried out.At the same time,in order to ensure the accurate realization of the equivalent CTE of dual-material lattice,two kinds of functional tolerance design models are put forward,which are of great theoretical and practical significance to the fabrication and application of dual-material lattice.