Moment Diagrams Research Articles

ЗАДАЧА ПОТЕРИ УСТОЙЧИВОСТИ ТОНКОСТЕННЫХ КОНСТРУКЦИЙ ИЗ КОМПОЗИЦИОННЫХ МАТЕРИАЛОВ, СВОЙСТВА КОТОРЫХ ЗАВИСЯТ ОТ ТИПА НАГРУЖЕНИЯ

Experimental studies of deformation of laminated composite materials often show a complex dependence of stiffness and strength characteristics on the type of loading. The most obvious examples are the difference of elastic moduli in tension and compression, nonlinear shear diagrams. It is possible to take into account such effects in applications only with the use of nonlinear elasticity models. Such models should not contradict fundamental physical principles and, in addition, should not require too complex experiments for validation. In this paper, we consider and numerically implement a model of nonlinear elasticity based on the use of the triaxiality parameter to describe the type of the material stress state. For a numerical implementation, the finite element modelling software Abaqus with user-defined subroutines was used. As a demonstration example, the applied problem of compression of a thin-walled composite cylindrical shell supported by stiffeners is considered. During loading, the shell exhibits an unstable behavior and stress state in its various areas can change drastically. For example, a change from the prevailing tension to compression and vice versa. In this case, damage to the shell material is not observed until a complete structure failure due to the loss of stability of stiffeners, which allows considering only the elastic model for this problem. The use of linear elasticity theory to model such a critical behavior of the structure leads to inaccurate results even at the initial stage of loading, while the proposed model shows a good consistency of the loading diagram, as well as the shape and magnitude of the shell deflections with the experiment.

The experience of creating an asynchronous motor control system for the hydraulic drive of a crane-manipulator

The study introduces a mathematical model of an asynchronous motor control system for a hydraulic drive of a crane-manipulator, the model being implemented in the Matlab Simulink package. The choice of the frequency of the pulse-width modulation and the components of the controlled electric drive depends on the load diagram and the characteristics of a new electric motor. The paper emphasizes some features of this choice and also demonstrates the output characteristics of the motor powered by a sinusoidal voltage source and a frequency converter, which is a source of modulated pulse-width voltage

Demand aggregation for photovoltaic self-consumption

The mismatch between photovoltaic generation and residential load leads to relative modest rates of self-consumption of solar electricity unless expensive storage solutions are locally available. One alternative to batteries is the aggregation of demand of different prosumers, as the collective load diagram might be better adapted to the solar resource. This hypothesis is tested for empirical data from 18 dwellings and 3 small businesses in the city of Lisbon, Portugal. Results show that a relatively low number of dwellings and a local small shop with a PV system without any storage will reach 90% self-consumption rates at a much lower cost than an individually owned PV system with 1 kWh/kWp storage system. • Real demand data for residential dwellings and small business. • Prosumer aggregation more efficient than battery. • Aggregation of 10 households has significant impact on self-consumption rates. • Aggregation of different demand profiles is very effective.

Diagram based assessment strategy for first-order analysis of masonry arches

Efficiency in structural analysis is economically paramount. First-order assessment strategies play a vital role in establishing this efficiency. Structural masonry has the potential to be an advantageous structural system, but its analysis must be efficient. Utilizing the traditional assumptions of masonry, an equilibrium approach to the kinematic method of limit analyses, and an innovative visualization technique, collapse load diagrams (CLDs) are developed. First the limit analysis method is presented, and its ability to interact with AutoCAD® is discussed. The iterative algorithm for the CLD is developed and applied to a semi-circular arch subjected to an asymmetric point load and constant horizontal acceleration loading conditions. Lastly, a geometric data extraction technique is utilized to create CLDs for two double curvature AutoCAD® drawn arches and used to compare their first-order assessments and establish equivalent capacities.

Peculiarities of Determining the Physico-Mechanical Characteristics of Brittle Materials on Small-Sized Specimens

The paper presents methods for determining the elastic modulus, sound speed, logarithmic decrement of vibrations (internal friction), tensile, compressive and bending strength, crack resistance, specific work of fracture of small-sized specimens. The specimens of polycrystals of superhard materials, which are prepared in high-pressure apparatuses, or of other expensive sintered materials (boron carbide, silicon nitride, hard alloys), which have a high hardness and elastic modulus, have typically a small size. Most of such materials experience significant dynamic loads during operation in products (metal-cutting tools, armor protection elements). It has been shown that disk specimens of brittle materials 3–15 mm in size can be used to determine strength characteristics under dynamic loading. The use of such specimens makes it possible to avoid oscillations in the loading diagram and to reduce the measurement error of breaking load. Moreover, it is possible to determine on such specimens the specific work of fracture of brittle materials from energy balance in measuring bars. Methods for determining mechanical characteristics under dynamic loading using Hopkinson–Kolsky bars are described, and examples of using procedures for the investigation of hard alloys, polycrystals of superhard materials based on diamond and cubic boron nitride, boron carbide and silicon nitride, obtained by the Bakul Institute for Superhard Materials of the National Academy of Sciences of Ukraine, are given.

Optimal Energy Storage Sizing in Photovoltaic and Wind Hybrid Power System Meeting Demand-Side Management Program in Viet Nam

This paper proposes a new method to determine optimal energy storage sizing in photovoltaic and wind hybrid power generation systems. These generations are placed in a scheme of three blocks to forecast, measure, dispatch/control and distribute power flows in whole system to meet requirements of the demand-side management program in Viet Nam. Data about electric load power, power of solar irradiance, ambient temperature, wind speed and other weather conditions must be forecasted in a high accuracy. An algorithm to determine the optimal sizing is designed basing on forecasting data, constraints, the relation of quantities in whole system and the capability to charge/discharge energy of energy storage. The optimal sizing in this research helps to rearrange load diagrams that compensates deficient energy completely in stages having high and medium price levels. It can be applied at each bus to reduce cost for buying electricity from electric power system. The new proposal is illustrated by simulation results in a case study carried out by MATLAB 2017a.

АНАЛІЗ СПОСОБІВ РЕГУЛЮВАННЯ НАПРУГИ В ЕЛЕКТРИЧНИХ МЕРЕЖАХ СИСТЕМ ЕЛЕКТРОПОСТАЧАННЯ ВІЙСЬКОВИХ ОБ`ЄКТІВ

У статті розглядаються способи регулювання напруги в електричних мережах, засновані на зміні параметрів мережі, зміні реактивної потужності, використанні регулюємих силових трансформаторів, у яких можливо змінювати кількість витків їх обмоток та перерозподіляти магнітний потік й змінювати додаткові електрорушійні сили та кут їх вмикання. В електричній мережі можна здійснювати як централізоване (загальне), так і децентралізоване (місцеве) регулювання напруги. Загальне регулювання напруги здійснюється в центрах живлення і призводить до зміни напруги у всій електричної мережі і може бути використано для груп споживачів електричної енергії, що знаходяться в приблизно однакових умовах і мають збігаючись у часі графіки навантажень. Місцеве регулювання напруги використовується тоді, коли електрична мережа має багато ліній електропередачі, які мають значну довжину і істотно розрізняються графіками навантажень і режимів роботи споживачів електричної енергії. Як правило, місцеве регулювання напруги використовується у випадках забезпечення харчування електричною енергією споживачів першої категорії, до яких слід віднести споживачів військових об'єктів.

МЕТОД ПРОГНОЗА ДЕФОРМАЦИИ ЗЕМНОЙ ПОВЕРХНОСТИ ПРИ УСТРОЙСТВЕ КОТЛОВАНОВ В УСЛОВИЯХ ПЛОТНОЙ ГОРОДСКОЙ ЗАСТРОЙКИ С ПРИМЕНЕНИЕМ СПОСОБА «СТЕНА В ГРУНТЕ»

В статье предложен метод прогноза деформации земной поверхности при устройстве котлованов в условиях плотной городской застройки с применением способа «стена в грунте», основанный на моделировании методом конечных элементов.Приведены результаты численного моделирования строительства полузаглубленного сооружения под защитой «стены в грунте». Выявлены закономерности изменения напряженно-деформированного состояния в зависимости от параметров стены и физико-механических свойств грунтов. В работе приведены мульды оседаний поверхности при строительстве котлована способом «стена в грунте», эпюры изгибающих моментов, поперечных и продольных сил, возникающих в стене.Для оценки расхождения результатов моделирования в плоской и объемной постановке задачи выполнены численные эксперименты в Plaxis 2D и 3D.

Simulation of Loads on the Carrying Structure of an Articulated Flat Car in Combined Transportation

The article presents the findings of the research into loading on the carrying structure of an articulated flat car under combined transportation. The refined data of dynamic loads on the carrying structure of a flat car under train ferry transportation, as well as the main loading modes in rail track operation were determined by mathematical modeling. The adequacy of the models developed was checked with an F-test. The results of the calculation conducted made it possible to conclude that the hypothesis on adequacy of the models is not rejected. The peculiarities of the structural strength modeling for a flat car within operational loading diagrams are given. The graphics works were conducted in Solid Works. The capacity analysis was conducted by the finite element method in CosmosWorks. The 09G2S steel was used as a construction material. It is determined that the maximum equivalent loads in the flat car support structure do not exceed the admissible loads. Results of the research can be used in designing coupled flat cars to provide their capacity at mixed transportation.

Plastic hinge relocation in reinforced concrete beams using Cu-Al-Mn SMA bars

Self-centering earthquake resistant systems have attracted the attention of researchers because of their promising potential in controlling seismic residual drifts, and, therefore, reducing the associated repair costs. The use of Ni-Ti superelastic shape memory alloy (SMA) constitutes a considerable portion of this research. Cu-Al-Mn superelastic SMA has been recently developed to eliminate the high cost of Ni-Ti SMA, as well as, to have better machining characteristics. This paper explores the use of Cu-Al-Mn SMA bars to relocate the plastic hinge of concrete beams through an experimental–numerical study. The cyclic performance of four beams was examined. The first was reinforced with steel bars and the remaining three were reinforced with combination of SMA and steel bars. The location of the SMA bars was different for each of the examined beams. The beams were loaded such that the moment diagram is zero at midspan and maximum at the ends to simulate the expected seismic moments. Results of the experimental–numerical investigation confirmed the recentering capability of SMA RC beams. Relocating the plastic hinge, by placing Cu-Al-Mn SMA bars away from the beam ends, improved the strength, rigidity, and energy dissipation.

An Abrasive Wear Forecasting Method in the Design of Soil-Cutting Tools

This study presents an abrasive wear forecasting method for soil-cutting tools at the stage of tool engineering. The essence of the proposed method consists in constructing expected loading diagrams and revealing pressure values in different parts of a soil-cutting component and then selecting material for its manufacturing or hardening. It is shown that based on synthesis of load diagrams, the regions of highest abrasive wear on a soil-cutting tool are found.

DYNAMIC STRESS IN AUTOMOBILE BRIDGEWORKS

The article considers and solves the problem of determining dynamic characteristics of automobile steel bridges. In the laboratory conditions, possible loads are simulated and stress diagrams are constructed. By measuring stresses in a real bridge, experimental loading diagrams are constructed for all possible loads. By comparison with the model diagrams, the stress effect in permanent joints is shown. The stress evolution is shown depending on the traffic flow.

Mechanical Fracture Parameters of Extruded Polystyrene

Extruded polystyrene (XPS) is a material with applications in the building industry, where it is typically used as thermal insulation. Fracture experiments in the three-point bending configuration were conducted on XPS beam specimens with an initial stress concentrator made before testing. The nominal dimensions of the beams were 40 × 40 × 160 mm. The depth of the initial edge notch on the bottom side of the specimen was approximately 1/3 of specimen height. The span length was 120 mm. Load vs. displacement diagrams were recorded during fracture tests, and subsequently the modulus of elasticity (E), effective fracture toughness (KIce) and specific fracture energy (GF) of the XPS were determined. The mean values obtained for the mechanical fracture parameters and coefficients of variation (number of specimens) were the following: E = 10.7 MPa, 9.2 % (7); KIce = 0.0547 MPa∙m1/2, 16.7 % (3); GF = 183.2 J∙m–2, 34.3 % (3).

Phase diagram of dipolar-coupled XY moments on disordered square lattices

The effects of dilution disorder and random-displacement disorder are analyzed for dipolar-coupled magnetic moments confined in a plane, which were originally placed on the square lattice. In order to distinguish the different phases, new order parameters are derived and parallel tempering Monte Carlo simulations are performed for a truncated dipolar Hamiltonian to obtain the phase diagrams for both types of disorder. We find that both dilution disorder and random-displacement disorder give similar phase diagrams, namely disorder at small enough temperatures favors a so-called microvortex phase. This can be understood in terms of the flux closure present in dipolar-coupled systems.

Enhanced moment and shear recovery for classic beams and frames

From the early days of finite element analysis the numerical static condensation method has been applied to elements with internal nodes to reduce their memory requirements and to simplify their assembly. The static condensation method was first used by Wilson (1965) to eliminate the internal degrees of freedom in a quadrilateral finite element constructed from four triangles. This study applies modern symbolic analysis software to static condensation to reveal additional observations about its benefits and efficiency. It is shown that the stiffness matrix and force vector transformation matrices can be written in closed form for a given element type and used for more efficient post-processing. In addition, it is shown that the classic cubic beam and linear bar element matrices are the symbolic static condensation versions of the three node quintic beam and quadratic bar, respectively. That allows the cubic beam element to be easily post-processed to give cubic moment and quadratic moment and shear diagrams, respectively.

Angle gage for torsion testing

Processing of metals by pressure suggests using of various measuring devices. We developed and manufactured a device for measuring angular deformations upon elastic and plastic torsion of circular specimens. The design is based on the operation principle of the planetary mechanism without a movable solar central wheel. Design of the device is based on the Boyarshinov concept added with a round protractor with a graduated scale from 0 to 360° and rotating needle placed on the axis to indicate the angular displacement. The use of the planetary gear significantly improves the accuracy of measuring the angles of rotation of the cross sections of the sample relative to each other at a distance of the calculated length. To low the weight of the device, the main parts were made of aluminum alloy D16Т. Rated diameters of the central wheel and satellite are D1 = 220 mm, D3 = 20 mm, respectively; the linkage module m = 1 mm; the number of teeth on the wheel and satellite is 220 and 20, respectively. Laboratory tests of the device were carried out on a KM-50 torsional machine using a cylindrical sample with a diameter of 15 mm and a working length of 120 mm made of steel 40Kh. The results provided determination of the elastic shear modulus with a deviation of ~2.5% of the reference value. Experimental data were used to plot the torsion diagram and then to get shear diagram τ = τ(γ) according to P. Ludwik’s formula. This diagram was transformed into the hardening curve σ = σ(e) using von Mises theory of the plasticity. The obtained mechanical characteristics allowed us to draw a conclusion on the essential accuracy of measuring angular displacements using the developed device. Thus, the developed and easy to use device can be recommended as testing equipment for determination of the mechanical characteristics of materials under conditions of shear deformations.

Comparison of Fracture Tests Numerical Models Created with Real Material Properties

This contribution discusses numerical models of three different fracture tests – three-point bending (3PB), modified compact tension (modCT) and wedge-splitting test (WST). The aim is to compare loading diagrams (loading force vs. crack mouth opening displacement) obtained from these numerical models, created with real material properties. These properties were acquired from experimental data measurement. To assemble the numerical models, ATENA Science FEM software was used. In this software, damaging of the structure/specimen occurred by cracks can be modelled, their initiation and progressive propagation can be seen throughout the loading process.

Interaction diagram based method for fire resistance design of eccentrically loaded concrete-filled steel tubular columns

Previous investigations have highlighted that the current design method in Annex H of EN 1994-1-2 for the calculation of fire resistance of slender concrete-filled steel tubular (CFST) columns was unsafe, which led to the appointment of a Project Team (SC4.T4) by the European Committee for Standardization (CEN) to develop a new Annex H in EN1994-1-2 to replace the existing one. This paper presents the outcome of the Project Team, a new simplified fire design method for CFST columns, focusing in particular on eccentrically loaded columns for which there had been no systematic research. An extensive parametric study consisting of 5046 analysis cases has been carried out, covering all the practical ranges of application of CFST columns. The method accounts for minor and major axis eccentricities with large eccentricities up to e/D = 1. Different bending moment diagrams, ranging from single curvature to double curve bending, were considered. The proposed new design method is in line with the cold design method in EN1994-1-1 and achieves the criteria of acceptance for safe and accurate design of structures in fire which were set by the CEN/TC250 Horizontal Group Fire.

Generating MMM diagram for defining the safety margin of self driving cars

Autonomous driving, is considered as the future of mobility, and research on this topics growing exponentially. On the one hand, these vehicles must be controllable, making rapid maneuvers possible, in case of a sudden accident situation, while on the other hand their motion must be stable, to maintain directional stability under disturbances. It is important to specify the so called “safety margin”, the range of possible motions that the vehicle can produce with keeping its stability. The limits of the possible movement of a vehicle depend on its parameters. The aim of our study is to determine which parameters affect the controllability and stability of a vehicle. To find this, we used the “MRA moment method” to create the “Yaw Moment Diagram” in our simulation environment. This method is usually used to map the possible range of motion and judge the stability and controllability of a possible motion state. Here we will use a two track vehicle model, with nonlinear tire characteristics, and complete model of suspension linkage to create the MMM diagram of a vehicle with given parameters.

Vibration behavior of thin-walled steel members subjected to uniform bending

Abstract This article reports the results of an investigation on the effects of internal moments on the vibration behavior of thin-walled steel members. The analyses are based on the Generalized Beam Theory (GBT), a thin-walled bar theory accounting for cross-section in-plane deformations - its main distinctive feature is the representation of the member deformed configuration by means of a linear combination of cross-section deformation modes, multiplied by their longitudinal amplitude functions. The study concerns a simply supported T-section (with unequal flanges) members exhibiting a wide range of lengths and subjected to uniform internal moment diagrams - their magnitudes are specified as percentages of the corresponding critical buckling values. After providing a brief overview of the main concepts and procedures involved in performing a GBT-based structural analysis, the vibration behavior of load-free and loaded T-section members is addressed - the influence of the applied loadings is assessed in terms of (i) the fundamental frequency difference and (ii) the change in the corresponding vibration mode shape. For validation purposes, some GBT results are compared with values yielded by shell finite element analysis performed in the code ABAQUS (Simulia, 2008).