Flexoelectric control of beams with atomic force microscope probe excitation

Based on the converse flexoelectric effect, flexoelectric actuator is designed and used to control the dynamic displacement of cantilever beams. First, shell-type stress expression based on double-curvature shell induced by the converse flexoelectric effect is developed, which can be simplified to a flexoelectric-laminated cantilever beam by applying two Lamé parameters and beam radius of curvature. Then, the flexoelectric actuator is designed with a conductive atomic force microscope probe and a flexoelectric layer. An inhomogeneous electric field is generated when the external voltage is applied on the atomic force microscope probe and the flexoelectric layer, which leads to stress in the longitudinal direction of beam and control moment. With the flexoelectric-induced bending moment, displacement induced by the external force and flexoelectric actuator is derived. The displacement is related to many parameters, such as actuation voltage, atomic force microscope probe radius and flexoelectric layer thickness. Cases are studied to optimize the control effect with different parameters. Results show that vibration control effect is enhanced with a higher actuation voltage and a smaller atomic force microscope probe radius for each mode. Besides, the thicker flexoelectric layer enhances the control effect with a larger bending moment arm for each mode. Dynamic vibration is controlled effectively by converse flexoelectric effect.

SIMULATOR FOR ROUGHNESS MEASUREMENT WITH SPHERICAL PROBE

A measurement of surface roughness is commonly carried out with the aid of profilometers, but when measuring the roughness of a curved surface arise difficulties. A technical problem consists in a probe feed along the normal to a nominal surface and filtration followed to exclude a low-frequency constituent of a profile. That is why it is purposeful to use coordinate measuring machines which have a probe with a spherical tip. For the first time there is presented a simulator of a spherical probe flat contact and surface roughness. A contact model developed is based on the regulations of analytical geometry. With the use of a numerical algorithm one finds a contact point and the center of a probe circle. On the basis of the simulator there is carried out an investigation of the impact of a probe radius upon roughness parameters Ra, Rmax, Rq. As initial data were used measurement results of the profilometer and profiles modeled with the aid of Monte-Carlo statistical method. It is defined that with the increase of the radius of the spherical probe its penetrating capacity decreases. That is why height parameters of roughness are distorted. The application of the spherical probe with the radius of 5-50 mkm ensures satisfactory results.

Systematic Analysis of Porosities in Metal-Organic Frameworks

Porosities of several metal-organic frameworks (MOFs) are computationally analyzed and discussed regarding their sensitivity to numerical parameters. Further, we investigate and discuss the influence of the probe radius on the calculated porosities. A clear differentiation between void and accessible porosity is carried out. This is essential as it impacts the comparison to experimental and theoretical results. We present two different approaches to calculate porosities, and discuss their advantages and drawbacks. All results are compared to well established methods. It will be highlighted that the calculated properties are numerically sensitive to the choice of the used approach and numerical parameters. <br>

A New Method of Distribution of Measurement Points on Curvilinear Surfaces of Products

The article presents the method of selecting scanning lines along which coordinate measurements, performed by using, e.g., a coordinate measuring machine working in the single point probing mode, of free-form surfaces of measured workpieces may be conducted. Additionally, the proposed method supports the user of a coordinate measuring system during defining the number of measurement points distributed along selected scanning lines, thus deciding on the final distribution of measurement points on a measured surface of a product. The proposed method enables distributing measurement points in the parts of a measured product characterized by the worst quality of manufacturing. Moreover, the new method is very automated, therefore it affects the increase in the efficiency of coordinate measurements. The effect of using the new method is the non-uniform distribution of measurement points located on free-form surfaces. The presented algorithm takes into account the lengths of selected cross-sections of a measured curvilinear surface of an object, its geometrical complexity and the accuracy of the probe radius correction process. The decision regarding the number of measurement points is made on the basis of the accuracy analysis of the calculations of the corrected measurement points obtained during the probe radius correction process and the accuracy of the substitute model representing a measured curvilinear surface. Two methods of the correction process were used. The accuracy of the applied methods of the probe radius compensation process was estimated on the basis of the deviations calculated between corrected measurement points and scanning lines. The selection of scanning lines and the number of measurement points was realized by using the expert system based on the fuzzy logic. The paper presents the results of both simulation and experimental investigations. The numerical calculations were performed for two selected free-form surfaces. The verification of the developed algorithm was carried out during experimental investigations based on a measurement of a selected free-form surface. The conducted research was aimed at verifying the correctness of the distribution of measurement points generated using the proposed method. In the case of real measurements, measurement points should be located in the places of surfaces of products characterized by the largest deviations of manufacturing. The results of the conducted investigations confirm the usefulness of the developed algorithm for defining the distribution of measurement points on curvilinear surfaces in the coordinate measuring technique. Moreover, the way of implementation of the developed method of the distribution of measurement points in selected commercial measurement software is presented, thus enabling the use of the new method in the industry.

A methodology for measuring and evaluating geometric errors of aero-engine blades based on genetic algorithm

Measuring and evaluating geometric errors of an aero-engine blade are a complex research topic. At present, there is not a uniform evaluation criterion and completed strategy in the blade manufacturing industry. This article proposes an effective strategy for measuring and evaluating geometric errors of an aero-engine blade: first, measuring six feature curves and calculating the coordinate transformation value with singular value decomposition to improve the accuracy of blade localization; then, an improved measurement method based on the model offset is introduced to eliminate probe radius compensation errors. Finally, the geometric errors of blade are evaluated using the collected measurement data based on genetic algorithm, and a practical evaluation criterion is provided. The proposed strategy for two aero-engine blades has been performed to demonstrate the effectiveness of the proposed methodology and show that it can prevent false feedback for the underlying manufacturing process for aero-engine blades.

Checking the accuracy of selected methods of probe radius correction

Artykuł prezentuje analizę dokładności dwóch metod korekcji promieniowej, które bazują na krzywych Béziera. Metody te mogą być stosowane do pomiaru powierzchni swobodnych. Analiza dokładności wybranych metod została przeprowadzona w odniesieniu do wzorcowych skorygowanych punktów pomiarowych.