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Prototyping of automated systems
Published in Fuewen Frank Liou, Rapid Prototyping and Engineering Applications, 2019
There are other types of actuators. For example, a piezoelectric actuator makes use of the phenomenon in which forces applied to a segment of material lead to the appearance of an electrical charge on the surface of the segment. Therefore, a piezoelectric actuator can be very simple in shape and can be used in micromachines as shown in Figure 8.7. A piezoelectric element is placed in between an electromagnetic positioning element and a weight. Initially, the electromagnetic positioning element is fixed to the ground with electromagnetic force. When the voltage is applied to the piezoelectric element in the middle, the piezoelectric element will expand and thus the weight will move to the right side. When the weight travels to the right, the electromagnetic force will then be released so that the entire object will move to the right due to inertia. This process can repeat quickly, and thus, the entire object can continue to move to the right side. Therefore, the piezoelectric element can act as an actuator. Many micro/nanosystems use this type of principle to make a micro/nanoactuator. Some devices used as actuators are complete automated systems in themselves. Robots are a prime example. Off-the-shelf X–Y tables are used as components in many systems where a reprogrammable position control is desired. The X–Y table is just two servo-controlled linear actuators (often servomotors and ball screws) with their linear axes perpendicular to each other. The X–Y table may move the table under a stationary tool such as a glue dispenser, or may move a tool over a stationary worktable. Programmable X–Y tables are used to control water-jet cutters that are used to cut shoe leather, plastics, and floor mats for cars. Clothing manufacturers are improving efficiency by using powerful X–Y tables to move knives or lasers used to cut materials. Numerical control (NC) equipment can cut metal under the control of a built-in digital controller instead of being controlled by a human operator.
A simple repair method of fatigue cracks using stop-holes reinforced with wedge members: applicability to reinitiated cracks and effects of an anti-fatigue smart paste
Published in Welding International, 2020
All fatigue tests were conducted under axial tensile load control with a load ratio R = 0 (the load waveform was a 4.1 Hz frequency sine wave). During the fatigue test the strain at the ‘Side’ position described in section 2.3.3 was measured continuously and was recorded with the load data at proper intervals. A CCD microscope lens was mounted on a servomotor X-Y table operating at a pitch of 0.01 mm and in situ observations of the fatigue crack were made when a specific number of cycles were reached. A fixed focus lens with a magnification of 400-fold was used for detailed observations such as measurements of crack length and crack opening and closing and a zoom lens with a magnification of 25–40-fold was used for macro-observation of the crack region including changes in the smart paste.
Automatic restraint and visual detection of fatigue crack growth when applying an anti-fatigue smart paste to bolt holes
Published in Welding International, 2018
Ichihiko Takahashi, Yoshihisa Tanaka
The bolt hole periphery was at times visually inspected during the tests and, when necessary, loading was temporarily halted and a photograph was taken or the length measured. For length measurement, the distance from the left and right notch end tips, the crack origins, to the crack tip or black area tip was measured, using a CCD microscope lens mounted on a servo-motor-type X-Y table operated under PC control at a pitch of 0.01 mm. Since, however, the notch ends were covered by the plain washer and invisible from the exterior, their location was decided on the basis of the distance the table had moved from the side edge of the specimen.