Design And Manufacturing Of Porous Structure Based On Additive Manufacturing

Porous material has terrifically good physical and mechanical properties which is widely used in lightweight design of many fields.Traditional methods of pore processing could not effectively control the opening and closing of pores so that the performance is mostly random and ambiguous.The advent of additive manufacturing has been recognized as a disruptive technology for preparation of porous structure.Building up parts layer by layer increases design freedom,manufacturing simplicity and performance controllability.Coated sand-based additive manufacturing has already changed the casting patterns,which means that foundry of metal part is no longer restricted by difficulties of tooling processing especially in the case of intricately shaped castings.Despite this,the double consumption of time and cost caused by the heavy sand mold itself is also recognized as one of the challenges that we have to overcome as manufacturing industry is proceeding at an astounding rate.If we can take advantages of the structural characteristics of porous material and make use of the technical advantages of additive manufacturing to reduce unnecessary molding materials at the same time meet the strength requirements,the rapid casting of large parts will open a new situation.The overall effort of the present article is to versatilely descript the porous structure in terms of design,simulation and manufacturing.In design,the honeycomb structure and lattice structure are optimized with the changes of shape and size by Solidworks while the three period minimal surface structures are modeled by Rhino.Five kinds of connective porous structures with variable of types,sizes,porosity,pore distribution are constructed.Then the relationship between characteristic length and porosity of varied porous structures are summarized so that reverse solution of structural parameter can come true.Finite Element Analysis is used to simulate the stress distribution of the porous structures.The cross section with relatively high stress showed by Ansys are focused on to provide a theoretical basis for the subsequent analysis of mechanical properties.All types of porous structures are manufactured by SLS Printer with coated ceramsite.The appearance and weight of porous structures are observed and measured respectively.The actual porosity calculated by the weight is highly close to designed value and relative error is less than 8%.Then uniaxial compression testing is carried out with universal material testing machine.The mechanical properties of porous structures with various porosity and shapes were evaluated from compression strength,compression modulus,specific strength and specific stiffness.The results show that as the porosity increases,the compressive strength naturally decreases.However,from the compressive data available of different porous structures,the reduction would vary from structure to structure.The optimized honeycomb porous structure which is anisotropic has admirable compression properties while the Gyroid minimal surface porous structure also has a relatively good compression performance for the reasonable pore distribution and large area under stress.