Distribution Of External Forces Research Articles

Experimental study on the stability of dike reinforced by steel sheet pile under storm surge

Over recent decades, upgrading dikes that defend against storm surges increasing in both intensity and frequency resulting from global warming, face challenges such as environmental impact and susceptibility to brittle failure. To address this issue, the steel sheet pile can be employed to improve the dike stability due to its resilience in withstanding substantial deformation. To investigate the reinforcement mechanism of the steel sheet pile, this study conducted three wave flume tests including the dike without configuration, the dike with single sheet pile, and the dike with double sheet pile. The dike stability and pile bending moment were analyzed based on the monitoring data. The experimental results showed that the single pile significantly improved the dike stability by reducing the seepage. The maximum bending moment for the single sheet pile occurred at approximately 1/3 of the pile depth, primarily due to its proximity to the wave impact area on the dike. The double pile further enhanced the dike stability primarily through the reduction of wave scour. The maximum bending moment for the double pile occurred at a lower position (2/3 of the pile depth) and was smaller due to the external force distribution and tie rod limitation.

SYSTEM FOR AUTOMATED CALCULATION OF PARAMETERS OF THE STAGE OF LAUNCHING AN UNMANNED AERIAL VEHICLE FROM A CATAPULT-TYPE LAUNCHER

This analysis focuses on the various stages involved in launching unmanned aerial vehicles (UAV) and highlights the key considerations that must be taken into account during these stages. When launching UAV in rugged terrain without a proper runway, alternative launch mechanisms, such as a catapult-type launcher, must be developed. The use of a catapult launcher offers several advantages, including the ability to launch in confined spaces and a quick preparation time. However, the development of a launcher is a complex process that requires a comprehensive approach, involving sophisticated engineering solutions to calculate launch parameters and the flight path of the UAV. Throughout the launch process, the UAV progresses through different stages, starting from the ignition of the starting engine until it reaches the desired height and speed. It is crucial to consider various parameters that influence the trajectory of the UAV during the launch phase. The authors determined the influence of the characteristics of the engines and launcher on the trajectory of the UAV and formulated a mathematical model for calculating the speed and coordinates of movement, which have a significant impact on the flight path. A system for automated calculation of the parameters of the first stage of launching a UAV from a catapult-type launcher is proposed, this system will reduce the time for product development, as well as reduce the influence of the human factor, which will lead to a decrease in the error in calculations. To analyze the starting characteristics of the product, a catapult model was chosen, which consists of a guide, a carriage and a UAV with a starting engine. The influence of the mass of the product, the launch angle and the distribution of external forces acting on the product are taken into account, which leads to the calculation of the initial values for further design. The result of the application of the system is to obtain the parameters of the speed of movement and the position of the flying object in tabular and graphical forms

Identification of the flexural stiffness parameters of an orthotropic plate from the local dynamic equilibrium without a priori knowledge of the principal directions

This paper proposes an inverse method to characterize orthotropic material properties from vibratory measurements on plate-like structures. The method is an adaptation of the Force Analysis Technique (FAT), which was originally developed to identify the external force distribution acting on a structure using its local discretized equation of motion. This method was recently adapted to the identification of elastic and damping properties of isotropic plates. In the present approach, the equation of motion of an orthotropic plate with respect to an arbitrary set of orthogonal axes is considered. The angle between the axes of the measurement mesh and the principal directions of orthotropy therefore explicitly appears in the equation and constitutes an unknown. A procedure to identify this angle together with the flexural stiffness parameters is proposed, as well as an automatic regularization procedure to overcome the high sensitivity of the inverse problem to measurement noise. The method is illustrated using simulated data. Experimental results shown on various structures demonstrate the ability of the method to simultaneously identify the principal orthotropy directions and the flexural stiffness parameters.

Crisis caused by an external force in a vortex source flowing to vacuum

A crisis caused by an external force (deceleration of the flow down to the radial Mach number equal to unity) is studied in the regime of vortex source flowing into vacuum. The dependences of the critical characteristics (critical radius, temperature, and velocity) on the gas circulation Γ is studied in two situations: at a constant external force distribution function and at a constant pressure in the zone of action of the force. It is shown that the adiabatic relation between the pressure, temperature, and density is valid. Explicit analytic solutions inside the zone for Γ = 0 and implicit solutions for Γ > 0 are obtained. In the case of a uniform distribution of the external force, it is found that the effect of the integral of force (work) on the critical characteristics dominates and is independent of the initial parameters (zone coordinate, temperature at the inlet, etc.). In the case of constant pressure, the regions of realization of the crisis in the space of the similarity numbers (force, circulation, and initial coordinate and temperature) are plotted.

Multicomponent lattice Boltzmann equation method with a discontinuous hydrodynamic interface

In the multicomponent lattice Boltzmann equation simulation method (MCLB), applied to the continuum regime of fluid flow, the finite width of the fluid-fluid interface introduces unphysical scales. We present a practical, robust, computationally efficient, and easy to implement solution to this problem which needs only low order interpolation to be stable and accurate and is applicable to any MCLB variant which uses a continuous phase field to distinguish between immiscible fluids with arrested coalescence. Our method extends the ideas of Kim and Pitsch, [Phys. Fluids 19, 108101 (2007)] and uses no external force distribution whatsoever to generate continuum interfacial physics, i.e., the Laplace law and no traction conditions on interfacial stresses. As such, it is amenable to the simplest form of Chapman-Enskog analysis used for lattice Boltzmann models. We assess our method and proceed to compare key results obtained with it against other equivalent data, obtained using the established continuum regime MCLB technique based upon the work of Lishchuk, Care, and Halliday, [Phys. Rev. E 67, 036701 (2003)] and Halliday, Hollis, and Care, [Phys. Rev. E 76, 026708 (2007)], quantifying performance in terms of the minimum feasible capillary available to simulation using that technique.

3D atomistic simulation of fatigue behaviour of cracked single crystal of bcc iron loaded in mode III

We present new results of 3D molecular dynamic (MD) simulations of a mechanical behaviour of an edge crack ( 1 ¯ 1 0 ) [1 1 0] (crack plane/crack front) in a single crystal of bcc iron cyclically loaded in mode III at room temperature. Our previous 3D molecular dynamic simulations showed that this crack under monotonic uniaxial tension loading in mode I emitted blunting dislocations in the inclined 〈 1 1 ¯ 1 〉 { 1 ¯ 1 2 } slip systems and it was stable up to very high loads, in qualitative agreement with experiments and continuum predictions. Our question is how the cyclic loading in mode III changes the crack behaviour and its stability. The paper also brings information on how the distribution of external forces in mode III influences the fatigue crack behaviour and how the defects generated by the crack can produce experimentally observed advances of the crack front in local modes I, II, I + II and II + III.

Surface activated bonding of copper through silicon vias and gold stud bumps at room temperature

A comprehensive investigation of the surfaces of copper through silicon vias (Cu-TSVs) and gold stud bumps is presented. These vias and stud bumps were bonded at room temperature using a nanobonding and interconnection equipment. The influence of heating on the bonded interface was also studied. In order to achieve an intimate contact between the Au-stud bumps and Cu-TSVs, the stud bumps were flattened under an external force of 20 N before bonding. The surface roughness of the flattened area was improved due to deformation of the bumps. Specimens with high deformation provided better alignment accuracy than those with low deformation. The Cu-TSV surface showed inhomogeneous behavior due to the influence of electroplating and chemical mechanical polishing. Tensile pulling test of the bonded interfaces showed three fractures modes in the bulk of the Au bump and the Au pad. The electrical resistance of the bonded interface was dependent on the surface morphology of the bumps and TSVs, the distance between the bumps and TSVs, the locations of the bumps and TSV with respect to the argon fast atom beams, and the distribution of external force during bonding. Heating at 200 °C for 60 h in air increased the electrical resistance of the bonded interface. This investigation shows that the vertical integration of Au/Cu at room temperature and low bonding force can be applied to three-dimensional interconnections for low cost miniaturized systems.

Interactive Analysis of Closed Loop Electro-hydraulic Control Systems

Without exhaustive system simulation, using full featured software, predicting electro-hydraulic control system performance represents a challenge for many system designers. In this paper, an introductory study has been presented as a preliminary stage for an ultimate goal, which is developing cost effective Interactive Electro-hydraulic Closed Loop System Analyzer (IEHCLSA). IEHCLSA is software aiming ultimately, through several modules in further developments, to solve for the static and dynamic characteristics of a controlled hydraulic actuator in a feedback loop fashion. This study shows in a systematic calculation approach how to properly calculate the pressure, flow and power required to achieve certain acceleration/deceleration rate while a cylinder is moving. The study will be associated with the first version of the software, which will be used to solve this part of the problem interactively. The following set of design parameters will be used as inputs to the stream of the calculations, the hydraulic cylinder dimensions, equivalent moving mass, volumes of the hydraulic lines, hydraulic fluid bulk modulus, required deceleration/acceleration rate and the external force distribution over the cylinder stroke. The calculation outcome will be hydraulic cylinder stiffness, natural frequency, flow and pressurerequirements. Using such software may reduce the effort, time and cost of hydraulic system prototyping.

Computational models of myocardial endomysial collagen arrangement

Collagen extracellular matrix is one of the factors related to high passive stiffness of cardiac muscle. However, the architecture and the mechanical aspects of the cardiac collagen matrix are not completely known. In particular, endomysial collagen contribution to the passive mechanics of cardiac muscle as well as its micro anatomical arrangement is still a matter of debate. In order to investigate mechanical and structural properties of endomysial collagen, we consider two alternative computational models of some specific aspects of the cardiac muscle. These two models represent two different views of endomysial collagen distribution: (1) the traditional view and (2) a new view suggested by the data obtained from scanning electron microscopy (SEM) in NaOH macerated samples (a method for isolating collagen from the other tissue). We model the myocardial tissue as a net of spring elements representing the cardiomyocytes together with the endomysial collagen distribution. Each element is a viscous elastic spring, characterized by an elastic and a viscous constant. We connect these springs to imitate the interconnections between collagen fibers. Then we apply to the net of springs some external forces of suitable magnitude and direction, obtaining an extension of the net itself. In our setting, the ratio forces magnitude / net extension is intended to model the stress / strain ratio of a microscopical portion of the myocardial tissue. To solve the problem of the correct identification of the values of the different parameters involved, we use an artificial neural network approach. In particular, we use this technique to learn, given a distribution of external forces, the elastic constants of the springs needed to obtain a desired extension as an equilibrium position. Our experimental findings show that, in the model of collagen distribution structured according to the new view, a given stress / strain ratio (of the net of springs, in the sense specified above) is obtained with much smaller (w.r.t. the other model, corresponding to the traditional view) elasticity constants of the springs. This seems to indicate that by an appropriate structure, a given stiffness of the myocardial tissue can be obtained with endomysial collagen fibers of much smaller size.

A self-adjusting active compliance controller for multiple robots handling an object

Abstract This paper presents the concept and experimental validation of a self-adjusting active compliance controller for n robots handling its compliant behaviour concerning partly unknown flexible object. The control strategy is based on the decomposition of the 6 n -dimensional position/force space and includes a feedforward and feedback level. The feedforward level contains motion coordination, force distribution of external forces, creation of internal forces, and an additional loop adding the elastic displacements due to the applied forces to the planned robot positions. The feedback level is organized in the form of an active compliance control law. For adjusting the controller to the, in general, unknown flexible behaviour, which in practice is the main problem of the controller design, a quasi-static model of the system is derived for different contact cases of the object and a procedure is presented, which by use of this model is capable of determining the compliance of the considered system and therefore of adjusting the controller. Experiments with two puma-type robots have been conducted to show the applicability of the self-adjusting control strategy. The task has been to grasp and move an unconstrained object. It is shown, that the system can adjust the control parameters to the unknown system compliance and that the control performance is improved considerably.

An application of psychophysical ratings to external force estimation

An estimation of external force applied during hand-intensive work at actual work site has practical restrictions since direct measurement requires much equipment and time. This paper proposes a method that can estimate external forces applied at actual working environment on the basis of results of lab experiment. The psychophysical rating, specifically CR-10 scale developed by G. Borg, is adopted as the major tool to estimate external forces. This study also shows the general shape of the external force distribution for the most oommon and potentially risky hand postures of hand-intensive jobs.

Properties of an excitable dynein model for bend propagation in cilia and flagella

Murase & Shimizu (1986, J. theor. Biol. 119, 409) introduced an excitable dynein-microtubule system based on a three-state mechanochemical cycle of dynein to demonstrate bend propagation in the absence of a curvature control mechanism. To examine the essential behavior of this class of models in a viscous fluid, we have represented the force generated by the complex dynein mechanochemistry by a formal model consisting of "force" and "activation" functions vs. sliding distance. Since the model has excitable properties with threshold phenomena and hysteresis switching between two opposed subsystems, it closely resembles the more realistic dynein kinetic scheme in its overall properties but is specified by fewer parameters. This model displays both bend initiation and bend propagation when the filaments at the basal end are either fixed or free to slide. A passive region is necessary at one end of the axoneme in order to obtain stable wave propagation; bends propagate towards the end with the passive region. Stable bend propagation is highly sensitive to small perturbations in external force distribution.

Some Consideration on Fatigue Design Diagram for Ship Hull Structure

Fatigue tests on ship hull structures have been conducted by R. Weck and J. J. W. Nibbering and also in Japan by Mitsubishi Heavy Industries, Ltd. and other shipbuilders. On the basis of the results of these tests, this paper deals with a tentative plan of a fatigue design diagram centering on consideration of fatigue crack initiation life.Structural members under consideration are transverse strength members with joints, longitudinal strength members with openings and longitudinals with scallops.In calculating damage (D), the hot spot stress is used which is obtained by multiplying nominal stress by given stress concentration ratio Kt in cracked part of each structural member and stress increase ratio Ke due to decrease in effective width of face bars.The diagram shows the lower limit of the relation between the hot spot stress and crack initiation life Nc. By using the diagram, frequency distribution of external force, and Miner's law, the possibility of fatigue failure of each structural member can be examined by whether damage (D) is greater than 1.0 or not.The author has verified the appropriateness of the design diagram by comparing it with analysis results of fatigue failures in actual ship and the diagram has been compared with the fatigue test results of basic welded joints of simple shapes and the fatigue test results of smooth, simple shape specimens by constant strain amplitude.