Pendulum for precision force measurement

A pendulum and a method for correcting the restoring force of the pendulum are proposed for realizing an instrument based on the levitation mass method without the use of pneumatic linear bearings. As an example a material tester using the pendulum, which evaluates the mechanical response of general objects against impact forces, is developed. The characteristics of the restoring force are accurately determined using the same instrument under the free-swing condition without the object under test. To demonstrate the high performance of the developed instrument, the impact response of a gel block is accurately determined. The possible applications of the developed method are discussed

Measurement of the electrical and mechanical responses of a force transducer against impact forces

A method for measuring the electrical and mechanical responses of force transducers to impact loads is proposed. The levitation mass method (LMM) is used to generate and measure the reference impact force used. In the LMM, a mass that is levitated using an aerostatic linear bearing (and hence encounters negligible friction) is made to collide with the force transducer under test, and the force acting on the mass is measured using an optical interferometer. The electrical response is evaluated by comparing the output signal of the force transducer with the inertial force of the mass as measured using the optical interferometer. Simultaneously, the mechanical response is evaluated by comparing the displacement of the sensing point of the transducer, which is measured using another optical interferometer, with the inertial force of the mass. To demonstrate the efficiency of the proposed method, the impact responses of a force transducer are accurately determined.This article was originally published online and in print with an incorrect version of Fig. 1. AIP apologizes for this error. All online versions of the article have been corrected. There correct version of Fig. 1 appears below

Method of generating and measuring static small force using down-slope component of gravity

A method of generating and measuring static small forces at the micro-Newton level is proposed. In the method, the down-slope component of gravity acting on a mass on an inclined plane is used as a static force. To realize a linear motion of the mass with a small friction, an aerostatic linear bearing is used. The forces acting on the mass, such as the down-slope component of gravity and the dynamic frictional force, are determined by the levitation mass method. In an experiment, a static small force of approximately 183 muN is generated and measured with a standard uncertainty ofapproximately 2 muN

Microforce materials tester

A material tester for evaluating the mechanical response of general objects against micro-Newton level impact forces has been proposed. In the tester, an inertial mass is made to collide with the material under test. The impact force acting on the material is measured as the inertial force of the mass. A pneumatic linear bearing is used to realize linear motion with small friction acting on the mass that is the moving part of the bearing. The velocity of the mass is measured highly accurately by means of an optical interferometer. The acceleration, the inertial force, and the position of the mass is numerically calculated from the velocity after the collision measurement. The other force, which is mainly consisted of the friction acting inside the bearing, is determined using the same instrumentations. Using the estimated friction inside the bearing, the measured force is corrected. The force acting on the mass from the material under test of approximately 0.1 mN is measured with the standard uncertainty of approximately 1.4 µN

Measurement of force acting on a moving part of a pneumatic linear bearing

A method for evaluating the components of the force acting on a moving part of a pneumatic linear bearing is proposed. The total force acting on the moving part is accurately measured as the inertial force using an optical interferometer. Then, the components of the force, such as the force component depending on position, the force component depending on velocity, and the force component depending on tilt angle, are evaluated using the least-squares method. In the experiment, the total force acting on the moving part is measured with the standard uncertainty of approximately 0.001 N, which corresponds to approximately 0.003% (30 ppm) of the gravitational force acting on it (M = 4.119 kg) of approximately 40 N (40 N). The experimentally evaluated values of these force components well coincide with the theoretically expected values

Method for evaluating material viscoelasticity

A method for evaluating the viscoelasticity of materials under oscillation load is proposed. In the method, a material under test is connected to a mass, which generates an oscillating inertial force after the mass is manually struck using a hammer. A pneumatic linear bearing is used to realize linear motion with sufficiently small friction acting on the mass that is the moving part of the bearing. The inertial force acting on the mass is determined highly accurately by means of measuring the velocity of the mass using an optical interferometer