A high-speed impact testing method for evaluating mechanical properties of materials is proposed using an inertial mass and a dual beat-frequencies laser Doppler interferometer (DB-LDI). In this method, an inertial mass levitated using an aerostatic linear bearing is made to collide with the material being tested at a high initial velocity. During the collision, the velocity of the mass, which is even higher than the critical velocity (±0.56 m/s) defined by the frequency difference of the Zeeman laser, is accurately measured using the DB-LDI. The position, acceleration, and impact force of the mass are calculated from the measured velocity. Using the proposed method, the mechanical properties of a visco-elastic material under a high-speed impact loading condition can be accurately evaluated.
A method to calibrate a force transducer under dynamic conditions has been developed. Calibration is achieved by a drop ball test based on the levitation mass method using an optical interferometer. From the conducted experiments, the output of the force transducer could be corrected, in line with the previous paper written by the authors. Moreover, the dynamic correction coefficient could be obtained by this method, even without an expensive air slider, which was used in our previous method. The calibration performed by the developed method proved to be very significant in correcting the dynamic force measurement error by the force transducer with a very small root mean square (RMS) error compared to the results of measurement in the absence of calibration and dynamic correction. The RMS error of measurement result by the force transducer with dynamic calibration and dynamic correction using the developed method is about 1.6 N. This error is equivalent to 1% of the maximum force applied to the force transducer, which is approximately 160 N.
This paper deals with mechanical response of material against small impact force using levitation mass method (LMM). Material properties observed by evaluate deformation of material and force acting on the material. In LMM, the force acting on the material is generated by collision of a levitated mass which has very small friction. The impact Force and deformation of material which cause of the collision is accurately measured by optical interferometer. A dynamic impact force, less than 10 N are applied to the three types of material. The mechanical response of material is indicated by time of collision, Whv and ratio of loss energy. It shows stiffness properties and elasticity level of material, respectively.
Copper beryllium (CuBe)is materials that are widely used for mechanical applications. In this paper,the use of copper beryllium for cantilever spring of a vibration sensor will beinformed. Cantilever spring plays important role in a vibration sensor, becauseit transfers vibration energy of the measured system into the sensor.Therefore, it is important to know the dynamic characteristics of thecantilever spring. An optical method, called Levitation Mass Method (LMM), isproposed to measure the dynamic characteristic of the cantilever. In themethod, the force of cantilever spring is measured as the inertial force workedon a mass. A pneumatic linear bearing is used to realize a linear motion withsufficiently small friction acting on the mass, i.e., the moving part of thelinear bearing. The inertial force acting on the mass is calculated from thevelocity of the mass, and the velocity is determined highly accurately by meansof measuring the Doppler shift frequency of the laser light beam reflecting onthe mass using an optical interferometer. It is shown that the proposed methodshows the dynamic characteristic of the vibration sensor well.
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