Experimental Study On Mechanical Response Of Cantilever Isomerized Rectangular Plate Under Bending Load

With the continuous progress and development of science and technology,the service conditions of materials become more and more complex,they often work under various loads and various physical fields.As a common component in engineering,plate structure is easily damaged by the existence of cracks and complex loading conditions;the current research is mostly theoretical and less involved in experimental aspects.Therefore,testing the mechanical properties of plate structures under different conditions is of great significance for the design and analysis in engineering.Based on the principle of deformation coordination,the formula for calculating the relative sliding displacement of the indenter and the specimen was derived;the shape and size of the sample are designed and analyzed based on the bearing characteristics of the platform.And the torsional loading unit was designed as the function expansion of the self-made instrument;besides,the Statics and Dynamics Simulation Analysis of the instrument was carried out by ANSYS Workbench and the results showed that the strength met the design requirements.Three dimensional strain measurement system was used to test the accuracy of the origin,the positioning accuracy,the repeatability of the positioning accuracy and the speed characteristics of the 6-DOF parallel motion system,the result was that the error of the original point was not "accumulated",the positioning accuracy was within 0.05 mm,but the speed characteristic along the X axis was better.The trajectory planning of the platform was carried out by MATLAB,and the platform recurrence capability was ideal.And the accuracy of the torsion and bending units were tested,the error were 1.47% and 2.38%.On the basis of the above research,the mechanical properties of 7075 aluminum alloy under the cantilever bending load were tested based on the Kirchhoff thin plate bending theory,the main results were as follows:(a)For the change of prefabricated defects,the increase of the size led to the carrying capacity decrease and strain value of the hole edge and bending angle increase;Due to the different shape,smaller radius of curvature caused stress concentration due to the "tip effect",which made the bearing capacity decrease and the bending angle increases.The increase of the location of the defect relative to the bending section led to the bearing capacity increase and the bending angle decrease,however,the influence showed a nonlinear influence trend,there was the best distance to maximize the carrying capacity.The increase of the angle between the defect and the bending section made the bearing capacity increase and the bending angle decreases.From the analysis of multiple defects superposition,the specimen cracks along the curved section,then expands to the axial direction.Under the premise of meeting the strength requirements,the anti-crack holes can be properly set to delay the crack propagation.(b)With the change of loading conditions,the bearing capacity was enhanced as the loading point deviates from the center of the specimen.The increase of the loading speed enhanced the bearing capacity,but the bending angle remained basically unchanged;the increase of the overlapping distance of the two plates increased the bearing capacity,and the bending angle decreased significantly.(c)For multi-field coupling conditions,the increase of temperature led to the decrease of the bearing capacity,the increase of the residual deformation and the decrease of the bending angle;the increase of the pre torsion angle reduced the bearing capacity,and the bending angle changed with the different laws under other conditions,showing a downward trend.(d)With the increase of the angle between the rolling direction and sampling direction,the bearing capacity was enhanced and the bending angle was reduced.