Research On Testing Mechanical Properties Of The Film Automatically Based On Laser Interference

Film is a kind of semiconducting material with excellent characteristic of light,heat,electricity,magnetism,etc.It's an important achievement in the development of new material technology.The mechanical properties of thin film have direct relation with usability like stability,reliability and service life,so the accurate test of mechanical properties is an important trend in the field of thin film materials.Bulge test has special advantages among many test methods.One test can bring multiple mechanical properties parameters like elastic modulus,interfacial binding energy,etc.Relevant theoretical models are also mature.Firstly,it investigates the development status of bulge test in recent years at home and abroad and introduces the relevant theoretical models of bulge test,and then it puts forward a automation bulge test device based on laser interference.According to need of simultaneous pressure loading and detection and micro-displacement detection for the bulge test,the pressure chamber and film clamping device are designed.The pressure chamber is composed of three interconnected holes in the cube,and the three holes are each connected to the pressurized pipe,pressure sensor and the clamped device of the test piece,and the film is clamped by the flange.Stepping motor drives the ball screw sliding table what drive the cylinder push rod to realize pressure loading,and the pressure.sensor is used to detect pressure.It uses the laser interference for micro-displacement detection.In view of the importance of the extraction of interference fringe displacement information,two methods are proposed which are each based on image processing and silicon photocell.The first method makes use of the image processing technique based on the theory of interference imaging and its displacement resolution can reach 158.2nm,but it has higher requirement for the imaging quality of interference fringe.The second method makes use of the photoelectric characteristic of silicon photocell and it can realize the displacement resolution of 316.4nm.The method has good applicability.Because several operation and detection are performed in bulge test,the measurement and control system is designed based on FPGA and Lab VIEW.The design content of Verilog program and Lab VIEW program is introduced in detail.FPGA realizes the stepping motor control,voltage acquisition and transmission of pressure sensor and silicon photocell.LabVIEW realizes test data reception and display.The elastic modulus of the pure aluminum film is tested by the bulge test device presented in this paper for three times.The elastic modulus of the aluminum film is 71.954GPa,72.275GPa and 73.127GPa based on the relationship of change between the pressure and the center displacement and theoretical models.The relative error is 4.28%,4.75%and 5.98%compared with the reference value of 69GPa.The test results are verified and the theory model of the bulge test is analyzed by the finite element tool of ANSYS,and the error of the theory model is 0.21%.The test device is highly automated and the test results are more accurate,and the synchronization of displacement value of the thin film center and the pressure value is high.It has great significance to test mechanical properties of the film.