Research On Design And Reliability Of Micromechanical Acceleration Lockout Switches

Aimed at the trend of miniaturization,integration and modularization about modern fuze power supply system,according to the characteristics of medium and large caliber non rotating projectile,a micro mechanical acceleration latch switch was proposed.The switch was designed by using a suspended mass with tooth-shaped structure and tooth shape fixed anchor,and the energy dissipation was realized by the mutual collision of the mass and fixed anchor during the moving process.The switch could implement the unlatch under the high amplitude and narrow pulse width acceleration and the latch under the low amplitude and long pulse width acceleration reliably,so the switch can distinguish the normal launch overload and drop impact.Firstly,the fuze environment force of the micro mechanical acceleration latch switch was analyzed,the working principle of the switch was studied,and the response characteristics of the switch under different conditions were obtained.Then,the structure of the switch was designed,the switch model was simplified by finite element analysis results,and the key parameters were analyzed.Then,the switch prototypes were fabricated by using UV-LIGA technology,and the function that the switch can distinguish the normal launch overload and drop impact was verified by the combination of the prototype test and the finite element analysis.Finite element simulation results show that the switch latches reliably under 3000g/3ms half sine acceleration pulse.The centrifugal test result shows that the static latching threshold of switch is from 2379g to 2485g.The dropping shock test and the finite element analysis results show that the switch do not latch under 15000g/0.3ms half sine acceleration.Simulation and test results demonstrate that the switch meets the design requirements.In order to enhance the practical application ability of the micro mechanical acceleration latch switch,reliability of the switch was studied.For the shock reliability,a flexible stop structure was proposed,based on the theory of continuous contact force,the model was established and simulated by Simulink to Study the collision dynamic process and effect of stop stiffness on collision force and collision rebounce.The prototypes were test by the drop hammer shock system,and test result shows that the cumulative failure distribution function(CDF)of the switch accords with Weibull distribution,Scale parameter(reference acceleration)p = 29600,shape parameter ? = 8.2.The fitting results show that the flexible stop can improves the shock resistance of the switch.For temperature reliability,the thermal stress distribution of the micro mechanical acceleration latch switch was studied by using Stoney expansion formula,and reliability enhancement test(RET)of switch was carried out.The RET results show that the failure modes are spring plastic deformation,dislocation of active component,delamination and fall off from package.According to the results of RET and thermal stress analysis,the reliability enhancement methods was proposed base on the structure design and manufacturing process.