The impact response of a force transducer in a falling weight deflectometer system is evaluated by an optical method. In
the method, a mass is made to collide with a force transducer and the impact force is measured highly accurately as the
inertial force acting on the mass. A pneumatic linear bearing is used to realize linear motion with a sufficiently small
friction acting on the mass, i.e., the moving part of the bearing. The method is an improved variation of the Levitation
Mass Method, which has been proposed and developed by the first author. The impact force, which has a maximum
value of approximately 1.66 kN and a full width at half maximum of approximately 5.0 ms, has been applied and
measured using the Levitation Mass Method with the standard uncertainty of approximately 3.3x10 N. This corresponds
to 2x10-2 (2%) of the maximum applied force in the experiments. The present status of the method and the points to be
considered for the future improvements are discussed.
In this paper, inertial force of an Actuator Arm of a Hard Disk Drive (HDD) in free oscillation after an impact load is accurately measured by means of a finite element analysis and by carrying out experiments using a modified Levitation Mass Method (LMM). A 3D finite element model of an actuator arm of a HDD is modeled in ANSYS/LS-DYNA using shell elements. An impact load, which is modeled as a half sine force pulse, is applied to a mass, which is attached with the Actuator Arm. The velocity and the inertial force of the mass in free oscillation are obtained from the simulation. In the LMM method, the arm is attached to a mass, i.e. the moving part of an aerostatic linear bearing, and the total force acting on the mass is measured as the inertial force of the mass using an optical interferometer. An impact is applied to the mass with the arm by colliding it to the metal base, and the inertial force of the arm is evaluated during the free oscillation. The velocity and the inertial force of the mass are calculated from the measured time-varying Doppler frequency shift. A good correlation between the experimental and numerical results is achieved. This numerical analysis can be further used to investigate the dynamic response of the actuator arm when it is subjected to different impact load, which is modeled with half sine force pulse with different pulse widths and amplitudes.
The authors proposed "Space Scale" concept for measuring astronaut body mass in spacecraft on orbit. For the development of the flight hardware, accuracy/precision/operability verification tests under simulated microgravity are mandatory. We tested our device on a business jet flying parabolas to simulate microgravity. In addition to design constraints from microgravity, human factor engineering aspects also had to be dealt with. Methods (1) Mass was calculated based on (Mass) = (Force) x (Acceleration). (2) For Flight Test Series #1, a metal dummy mass of 9.37kg was used on parabolic flight tests. (3)For Flight Test Series #2, human subject mass was measured. (4) To eliminate acceleration noise from cabin vibration and air turbulence, data were rigorously filtered post-flight. Results With Flight Test Series #1, mass of the dummy was successfully derived with the standard uncertainty of 2.1 % for single measurement, and 0.7 % for the mean value of 12 measurements. Each measurement duration was less than 3sec., with rubber cord length reduction of 1 m. Conclusion The parabolic flight environment was a noisy acceleration field. Future studies should look more into human factor engineering aspects.
The author has proposed a method, the Levitation Mass Method (LMM). In the LMM, the inertial force of a mass
levitated using a pneumatic linear bearing is used as the reference force applied to the objects under test, such as force
transducers, materials or structures. The inertial force of the levitated mass is measured using an optical interferometer.
In this paper, the previous achievement, the recent achievements, and the future prospects on the methods of generating
and measuring the static and dynamic micro-Newton level forces based on the LMM are discussed.
Mechanical response of an actuator arm of a 1-inch hard disk drive (HDD) against a small and steep impact load is accurately measured by means of modifying the Levitation Mass Method (LMM) whose basic concept was proposed by the first author. In the method, a mass that is levitated with an aerostatic linear bearing, and hence encounters negligible friction, is made to collide with a subject actuator arm and the dynamic bending test for the arm is realized. During the collision the Doppler frequency shift of the laser beam reflecting from the mass is accurately measured using an optical interferometer. The velocity, the position, the acceleration and the inertial force of the mass are calculated from the measured time-varying Doppler frequency shift. The importance and the problems concerning the present knowledge on the mechanical response of an actuator arm of a 1-inch hard disk drive (HDD) are also discussed.
The mechanical response of a palm of a human hand against impact force is accurately determined by means of a practical method, a variation of the Levitation Mass Method. In the method, a mass that is levitated with a pneumatic linear bearing, and hence encounters negligible friction, is made to collide with a material under test. During the collision the Doppler frequency shift of a laser beam reflecting from the mass is accurately measured using an optical interferometer. The velocity, position, acceleration and inertial force of the mass are calculated from the measured time-varying Doppler shift. The method is characterized by the fact that preparation of the test specimen is very easy, the testing time is very short and the measurement accuracy is very high. The possibility of using the method for biomedical engineering is discussed.
The impact response of an impact hammer is evaluated by means of an optical method. In the method, an object is first levitated using a pneumatic linear bearing, so that it encounters negligible friction, and is then made to collide with the impact hammer under test. The total force acting on the levitated mass (i.e., the product of the mass and acceleration) is measured highly accurately by measuring the Doppler frequency shift of a laser beam reflected from the colliding mass. The velocity, position, acceleration, and inertial force of the mass are then numerically calculated from the measured time-varying Doppler frequency shift. The output signal of a force transducer embedded in the hammer and the measured total force acting on the levitated mass are compared. The future prospects of the proposed method are discussed.
Impact response of an impact hammer is evaluated by means of an optical method. In the method, an object levitated with sufficiently small friction using a pneumatic linear bearing is collided with the impact hammer under test. The inertial force, that is the product of the mass and the acceleration, is measured highly accurately by means of measuring the Doppler frequency shift of the laser light beam reflected on the mass. The velocity, the position, the acceleration and the inertial force of the mass are then numerically calculated from the time-varying frequency. The output signal of a force transducer embedded in the hammer and the inertial force measured by the method are compared. The present status and the future prospects of the proposed method are discussed.
Attitude and position monitoring system of the cube corner prism used in a n optical interferometer, which is originally developed for our Levitated Superconductor Experiments, is discussed. In general, the point to be measured by an optical interferometer does not coincide with the measurement point such as the optical center of the cube corner prism used in the optical interferometer. If the attitude of the object, on which the cube corner prism and the point to be measured exist, changes during the measurements, this result in the measurement error. Using het developed system, the attitude an the position of the cube corner prism in an optical interferometer is monitored from a distant point. Further prospects in applying this developed method to a general interferometer are discussed.
A method for generating and measuring varying force by means of levitating a rigid object is discussed in this paper. The varying force is directly and accurately measured using an optical interferometer as the initial force acting on the inertial mass. The performance of the three-point bending tester based on the method is investigated by conducting several sets of three-point bending tests for aluminum bars. The future prospects of this method are discussed.
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