Study On Buckling And Contact Behaviours Of The Membrane Structure

A final proposition of the human society is that where do we come from and where are we going.The membrane structure is just the bridge of the starting and ending point.In the real world,the micron grade tissue cell and the 100-meter grade expansion structure are typical membrane structures.So it is important to carry out in-depth study of these structures.They are used widely in scientific research and engineering application because of their advantages including light weight,soft and deployable.However,wrinkles can appear on their surface easily due to their disadvantages such as thin walls and owe stiffness.As a result,they will be invalid quickly.In addition,the contact phenomenon occurs usually owing to the large deformation and rotation.And the complex boundaries multiply the difficulties in their application.Therefore,looking at the wrinkling and contact problems when applying the membrane structure,it is significant to make theoretical predictions,simulation analysis and experimental measurement.Firstly,based on the Euluer-Bernolli beam and thin wall assumptions,the three-point bending model of the inflated membrane beam under local uniform load is established.Then geometric parameters of the load are introduced to the equations,which are used to predict the wrinkling parameters.And the kink is introduced to describe the invalid state of the membrane structure.Through the simulation analysis and noncontact experiment,theories of wrinkle and kink are verified.Comparisons between the theoretical predictions and results from simulation and experiment are made,including some important parameters and relationships.Parameters are initial wrinkling and kink positions,critical wrinkling and kink loads,the wrinkling strain,the length of the wrink led region and the kink angle.Relationships include the load-displacement and the stress-wrinkling angle.The differences coming from these comparisons are no more than 10%,which means the predicted results are reliable.Therefore,the theories are applied to the airship envelope,which is the typical membrane structure,to predict its wrinkling and kink behaviors.Secondly,based on the stratospheric heat environment,the thermal structural coupled buckling analysis of the inflated membrane envelope is conducted.The longitudinal bending buckling process of the inflated envelope can be divided into three continuous stages,which are global buckling,interactive global-local buckling and kink.A variety of hoop ovalization buckling modes are observed under coupled mechanical-thermal load.Unlike the mechanical case,thermal load leads to a hoop negative ovalization buckling.Then,the interactive effects of these two loads on the buckling behaviors of the envelope are analyzed by adjusting the loading sequence.Although the wrinkling area,the mean amplitude of wrinkles and the whole bending deflection become larger after applying one type of load s to the wrinkled envelope caused by the other one,the two kinds of loads don’t satisfy the superposition principle.Thirdly,the inflated membrane ball-rigid substrate contact modal is established to study the membrane contact behavior.Based on the force balance method and Mooney–Rivlin hyper elastic modal,the equilibrium equations are simplified to four first order differential equations by parameters substitution.The different solution schemes are designed according to the different boundary conditions.There is a clear cut-off point when the friction appears on the interface.The circumferential stretch ratio and stress in the contact region increase with increasing the angle coordinate,which is in the opposite trend in the noncontact region.In the larger friction coefficient condition,the circumferential stretch in the contact region is relatively large and it is small in the noncontact region,so there will be a cross point with different friction coefficients.At this point,this parameter changes the fastest.Moreover,the most vulnerable position of the structure is in the middle along the meridian direction with the largest friction coefficient.Finally,the membrane contact-wrinkle modal is established to make the interaction between tissue cells and their extracellular organization visual.The tissue cell is equivalent to an elastic plane,which is loaded by the stress fibers.The extracellular organization is equivalent to a membrane substrate,which is wrinkled to make the interaction visible.And the biological bond is equivalent to the contact friction between the elastic plane and the membrane substrate.The simulation analysis method is used to solve the contact-wrinkle problem.With the increase of the displacement load,the membrane substrate is found wrinkling behaviors because of the interface friction.When increasing the membrane substrate module,the deflection of the substrate decreases and the elastic plane deflection increases due to the interface friction.As a result,the volume of the cavity decreases,which is formed by the substrate and the plane.The instability degree of the elastic plane become lower and the deflection of the membrane substrate reduces with increasing the modulus of the elastic plane,which results in the decrease of the cavity.