Experimental Study On Mechanical Response Of Annular Lattice Structure Under Tension Torsion Load

With the continuous development of ships,high-speed railwa ys,large aircraft and satellites,the trend of large-scale and high-speed engineering equipment poses new requirements for the innovation of structures and materials.In the case of satisf ying the strength,reducing the qualit y is equivalent to reducing energy consumption and increasing production econom y.With the continuous development of pol ymerization and reinforcement technology of n ylon materials,the mechanical properties of nylon materials have been comparable to metal materials.In the environment of poor lubrication or eas y corrosion,it can replace metals to manufacture components with low service load,such as gears and bearings.The experimental research on the mechanical response of th e lattice structure made of nylon material can pla y a reference role in the optimization design and application of the lattice structure.In this paper,the research progress of the lattice structure 's mechanical properties both here and abroad has been s y ntheticall y anal yz ed,and three kinds of circular lattice structure of cell element along the circular arra y have been proposed.The three kinds of cell elements are trigonometric,quadrangular and round.The tubular structure of the same sectional area ha s been compared,and the shape and size of the specimen were introduced.With the help of the finite element software ANSYS Workbench,the strain response of each structure under the stress and shear stress has been anal yzed,and the same sampling points w ere selected for comparison.Then the quadrangle lattice structure was taken as an example.The effect of cell dimension change on variable response of cell dimension can be obtained b y optimization of minimum strain as the optimization target.The sensiti vity of var ying parameters to variable response has been anal yz ed.Based on the principle of the fitting method used in the software,the relation between the relative densit y of the lattice structure and the response of the strain has been derived.After optimization,the tensil e strain of the model is reduced b y 3.59%,and the torsional strain is reduced by 1.39%.By comparing the research progress of material testing t echnology and instrument both here and abroad,it was found that most of the existing mechanical performance testing instrument needs to sample the tested objects,and few tests have been carried out for the mechanical properties of the structure.In this paper,it has been introduced that the functions,the la yout methods of each module,th e main indexes of loading and the realization method of tension torsion composite loading of the multi load and multi ph ysical field coupling material mechanics performance test device.The fixture of the test device has been improved,and the test range of the device has been expanded to facilitate the realization of the in-situ observation.After the fixture was replaced,the assembl y proper alignment has been adjusted,and the linearit y and accurac y of the sensor have been verified.The relationship betw een the numerical value of the grating ruler of the displacement measurement and the actual deformation of the specimen has been anal yz ed,and the tensile curve measured b y the device has been corrected.It was pointed out that the in-situ observation of t he tensile test mode with one side fixed and one side motion needs the function of automatic tracking and distance compensation,and the gra y gradient algorithm was used to judge whether the image is clear and control the motor to make adjustment.After th e completion of the previous work,independent research and development of multi load and multi physical field coupling material mechanical performance testing device has been used to test the repeated tensile test of the rectangular section specimens and t ubular specimen s made b y the material increasing method in this paper.The statistics of Young's modulus,tensile strength and elongation can be found that the repeatabilit y of the test is good after the statistical test.The fracture morphology shows tha t the specimen has no whole fracture,so the specimen has stable mechanical properties.Then the tensile,torsion and pre tensile torsion loading tests of the annul ar lattice structure specimens made b y increasing material manufacturing technique have been carried out.The equivalent elastic modulus of the quadrilateral lattice structure is 40.736 MP a,and the abilit y to resist deformation is better than the other three structures.The tensile strength of the circular lattice structure is 14.225 MP a,which is the best in the four structures.The average shear strain of quadrilateral lattice structure is 1.66%,and the ability to resist shear stress and deformation is better than the other two lattice structures.The size of the torsional strain of four structu res has been anal yz ed and the corresponding variation distribution has been compared by three dimensional digital speckle.Finall y,the torsion curves of each structure under different pretension force have been compared.It is found that with the increase of pretension,the average shear strain of the three lattice structures has a tendenc y to decrease,while the average shear strain of the original tubular structure increases first and then decreases.