Cell Wall Fracture Mechanism in Ultrasonic Assisted Cutting of Honeycomb Materials

Revealing the ultrasonic cutting mechanism of honeycomb composite is important for determining the acoustic parameters of the ultrasonic system and selecting the parameters of the cutting process. Understanding more details of the stress on the cell wall from ultrasonic vibrating tool and the conditions for cell wall breakage is essential to study the machining mechanism. According to the evolution of contact state between the straight edge cutter and the honeycomb cell wall in a cycle, the cutting force acting on the cell wall is divided into three stages: transverse cutting load action, longitudinal cutting load action, and no cutting load action. The cell wall deflection and stress equations under transverse cutting load were established by applying elastic thin plate small deflection theory. The deformation and fracture characteristics of the honeycomb cell wall were analyzed by combining the analytical and the finite element model. The results showed that the ultrasonic vibration of the cutter greatly improved the stiffening effect of the cell wall and its fracture was caused by the deflection under the transverse cutting load, which exceeded the maximum allowable deformation after local stiffening. In addition, with only longitudinal cutting load, it was difficult to break the critical buckling state that leads to cell wall fracture.

Analysis of the Frequency of Acoustic Emission Events in Terms of the Assessment of the Reduction of Mechanical Parameters of Cellulose–Cement Composites

The article proposes the application of the acoustic emission method as a technique for the evaluation of mechanical parameters of cellulose–cement composites. The analysis focused on frequency values in a time series analysis of elements subject to three-point flexural stress. In the course of a statistic analysis, it has been demonstrated that a significant reduction of the recorded frequency values is associated with a considerable reduction in strength. This allowed the authors to determine the range of frequencies related to the depreciation in the strength of an element. The tests were carried out on elements cut from a full-size cellulose–cement board. Samples exposed to potential operational factors (environmental and exceptional) were analysed. It was shown that the frequencies recorded before reaching the maximum load during bending of samples exposed to environmental factors (water and low temperature) were significantly different (were much lower) from the sounds emitted by elements subjected to exceptional factors (fire and high temperature). Considering the fact that the analysed frequencies of acoustic emission events occur before the maximum stresses in the material are reached and the elements are destroyed, this provides the basis for the use of the acoustic emission method to assess the condition of cellulose–cement composites in terms of lowering mechanical parameters by observing the frequency of events generated by the material during load action. It was found that generating by material frequencies above 300 kHz during bending does not result in a significant decrease in mechanical parameters. The emission of signals with frequencies ranging from 200 to 300 kHz indicate that there was a decline in strength exceeding 25% but less than 50%. The registration of signals with frequencies below 200 kHz indicates that the reduction in mechanical parameters was greater than 50%.

INFLUENCE OF CREEP CONCRETE ON SPACE STABILITY THIN-WALLED DOME COVERINGS

The task was set, due to the capabilities of modern software systems, to assess the effect of the increase in inelastic deformations under prolonged load action on the loss of stability of thin-walled dome coverings. The study of the dependences of the forms of the loss of stability of dome covering from creep concrete that will help further with optimization calculations when determining of the most influencing parameters of designs. Calculation results of thin-walled concrete dome roof of circular outline under the influence of operational loadings with use of two modern program complexes are given in article. It is investigated intense and deformation condition of dome coverings as a part of construction from position of forecasting of possible forms of loss of stability, with use of opportunities of the final and element «MidasCivil» computer system. In work provisions of the theory of elasticity, mechanics of deformation of solid body, construction mechanics and also methods of mathematical modeling based on application of finite element method are used. The received results give the chance to rationally select geometrical parameters and material of design and also to set structural strength safety factors at the solution of problems of stability of different covers taking into account possible creep of material.

The Staple-Shape Plate Springs Engineering Calculation Method

The new types of elastic devices – staple-shape plate spring and leaf spring - have been developed at the Kyiv National University of Construction and Architecture. The staple-shape plate spring is an elastic plate where the ends are deflected from its middle part in the same direction and are made in the form of consoles equipped with hinge attachments. The middle part of the plate as a parallel to the line of the load action is designed with variable length section. In each section, the axis, relative to which the moment of the section inertia is a maximum, is perpendicular to the spring bending plane, designed as the equal resistance beam. This article substantiates the feasibility of using a staple-shape plate spring to improve the elastic suspension of truck cabs. The recommendations for choosing the most promising mass production directions, as well as the engineering calculation methods of such springs, have been developed. Objects of the study are devices intended for machines and their components dynamic loads shock absorption, differing in having a bracket shape and being a subject to bending in the plane of the highest rigidity of their cross sections, as well as shock absorbers using these springs, in particular KamAZ cabs suspension. This research implementation allows significantly reducing the metal consumption and elastic devices manufacture complexity, as well as can be useful in the design and operation of elastic car suspensions.Keywords: elastic device, staple-shaped plate spring, leaf spring, elastic suspension

Pressure profile definition over the metal orthotropic deck surface of the decking superstructure ballast pocket from the local load action

The article discusses the interaction issue between the track and the rolling stock to determine the forces working on the track during the passage of a rolling load, and their further distribution through the ballast bed. The study aims to determine the vertical pressure profile working on the orthotropic metal ballast bed slab of the railway superstructure. To determine the load share from the rolling stock transferred from the rails to the cross-sleepers, the rail is represented as a beam of infinite length with one or several concentrated forces. To determine the cross-sleeper stress-strain state, it is considered as a short beam on a cushion course. The article presents the substantiation of the flow mechanics formulas application possibility to the ballast bed. Based on the Boussinesq problem solution, calculation formulas are obtained for determining the pressure along with the ballast bed plate. The results obtained by the proposed method were compared with other authors’ experimental data and the finite element modeling results in the Midas FEA software package. The analysis took into account the design features of the ballast bed plates and the track superstructure on the existing superstructures. A theoretical study of the influence of the sheet of the covering bending stiffness on the pressure profile northing is carried out. The proposed method is applicable for various superstructure and the ballast bed slab, and also takes into account the uneven pressure distribution on the inner and outer rails from the trainload, changes in eccentricity along the length of the structure, different thickness of the ballast bed under the cross-sleepers ends, as well as the effect of centrifugal force.

A Balanced Strategy for the FFBS Operator Integrating Dispatch Area, Route, and Depot Based on Multimodel Technologies

Bicycle scheduling is the essential strategy for balancing the demand for the public bicycle system (PBS). Existing literature pays more attention to bike scheduling models and their solutions, but seldom discusses the dispatch area and depot center. Reasonable dockless public bicycle dispatch area and optimal dockless bike dispatch depot location in the service area were discussed from the existing shared bicycle operation data in this paper. We proposed a feasible framework including bike trip network segmentation, mean-shift clustering based on the point position, VRP model, genetic algorithm, and TOPSIS evaluation method. The effectiveness and superiority of the division of the dispatch area are verified. The main evidence for this article is (1) although the cycling networks of bicycles are different at different times of the day, the results of community division are relatively stable and have great similarities. (2) The plan of the dispatch area has impacted on the operation efficiency of the PBS. For a scheduling area, the target value of the optimal scheduling strategy corresponding to different dispatch centers is obviously different. Therefore, the location of the dispatch center has a great impact on the quality of the scheduling strategy. The dispatch area determined by bike trip OD community detection has stable characteristics of scheduling costs. (3) This work is an attempt to combine big data and model technology to assist city management. We build a feasible framework to serve a balanced strategy for FFBS which can provide reasonable dispatch area, optimal dispatch depot location, dispatch truck’s route length, load action, and time window. Our proposed framework provides new ideas for regional traffic dispatching for the traffic management department and FFBS operator, which has certain practical reference significance.

Application of Structural Deformation Monitoring Based on Close-Range Photogrammetry Technology

The problem of structural deformation monitoring has always been a research hotspot in engineering architecture. Research on structural deformation monitoring is the main way to solve the risk of engineering construction. Based on using close-range photogrammetry technology to monitor structural deformation, combining with image recognition technology to collect and process image data, and using the conditions of direct linear transformation and collinear equation to calculate based on the extracted coordinates of the measuring point, finally, according to the coordinates of the measuring point and the deflection value of the bridge structure, the study is carried out. Experiment: first, five sets of data are used to calibrate the close-range photogrammetry equipment of measurement point accuracy are analyzed, then the bridge piers and the measurement point coordinates, the lasso, under different load on the accuracy of close-range photogrammetry technology is analyzed, according to the relevant data of the error of the close-range photogrammetry technology are analyzed, and through the calculation of different measurement methods to analyze the direct linear transformation manifested in the article. The final results show that the X-axis coordinate range of the measured points in the auxiliary spatial coordinate system is 25∼40, Y-axis coordinate range is 8∼36, and Z-axis coordinate range is 10∼35. The coordinates of measuring points of bridge cables are distributed in the fourth quadrant of the spatial coordinate system. The accuracy values of all coordinates of the measuring points under the close-range photogrammetry equipment are less than 0.1 mm, indicating that the close-range photogrammetry equipment has a good effect on the calibration of measuring points, and the error generated when the load action of each measuring point of the bridge cable is 10 N is greater than that generated when the load action is 20 N. In different calculation and measurement methods, the results obtained by total station measurement and calculation method are reduced by about 0.04∼0.07 m compared with the actual value; the results obtained by direct linear transformation method are increased by about 0.02∼0.04 m compared with the actual value; and the results obtained by other measurement and calculation methods are increased by about 0.04∼0.06 m compared with the actual value.