Rope Elements Research Articles

Modeling critical interaction for metastasis between circulating tumor cells (CTCs) and platelets adhered to the capillary wall

Background and objectiveWe used a 2D fluid-solid interaction (FSI) model to investigate the critical conditions for the arrest of the CTCs traveling through the narrowed capillary with a platelet attached to the capillary wall. This computational model allows us to determine the deformations and the progression of the passage of the CTC through different types of microvessels with platelet included. MethodsThe modeling process is obtained using the strong coupling approach following the remeshing procedure. Also, the 1D FE rope element for simulating active ligand-receptor bonds is implemented in our computational tool (described below). ResultsA relationship between the CTCs properties (size and stiffness), the platelet size and stiffness, and the ligand-receptor interaction intensity, on one side, and the time in contact between the CTCs and platelet and conditions for the cell arrest, on the other side, are determined. The model is further validated in vitro by using a microfluidic device with metastatic breast tumor cells. ConclusionsThe computational framework that is presented, with accompanying results, can be used as a powerful tool to study biomechanical conditions for CTCs arrest in interaction with platelets, giving a prognosis of disease progression.

EXPERIENCE IN MEASURING EFFORT IN ROPE ELEMENTS OF CABLE BRIDGES

The work is devoted to the issue of carrying out technical diagnostics of determining the forces in the cables of the cable-stayed bridge across the harbor of the Dnipro River in the city of Kyiv on the object: "Construction of the Podilsk bridge crossing over the Dnipro River in the city of Kyiv" at the final stages of jacking up the span structure of the bridge. As is known, the general methodology of technical diagnostics is based on conducting static or dynamic tests. Tests are conducted to determine the nature and magnitude of loads on the bridge structure, to determine the actual stress level in the elements. Moreover, sometimes some types of tests are carried out not only on bridges whose construction is finished, but also on structures during their construction. One of these types of tests is the tests performed to determine the amount of load in cable elements of cable-stayed bridges. Currently, one of these types of tests is the tests performed to determine the amount of load in cable elements of cable-stayed bridges. At present, the acceptable methods for determining the forces in the rope elements of cable-stayed bridges are: installation of electronic dynamometers in the places of anchoring of the ropes to measure the load, geodetic measurements of the sagging of the cable-stayed ropes, determination of the frequency of self-oscillations of the cable-stayed ropes, etc. The paper presents the results of the tests of measuring the forces in the cables of the span structure due to their own weight by exciting mechanical oscillations in them and determining the frequencies of the natural oscillations, and measuring the slack of the cables (arrows of the slack) by laser 3-D scanning of the cables.

On calculation of stress-strain state of steel closed ropes in extension and twisting. Part 2. Influence of torsion on the stress-strain state of closed rope

Comparative analysis of the results of determination of stress-strain state in a closed lifting rope during extension and twisting was conducted via analytical calculation according to the linear static equations and computer-aided finite element modeling. Computer modeling allows to establish the features of variation of internal axial forces and torques in the layers that are laid with different directions. It makes possible to predict workability of a closed lifting rope during operation. The most intensive redistribution of internal forces and torques in the internal and subsurface layers during rope turns under the effect of external torque was found out in comparison with extension. Decrease of the torque and axial force values to zero in the deposited external layer during its untwisting testifies about switching this layer off the operation and possibility of rope lamination in the case of external pressure absence. Internal compression of subsurface layer from the side of external rope layer, in its turn, decreases possibility of stability loss (opening) of this layer during its twisting. Deviation from the common rule for variation features of relative elongation ε during joint extension and twisting was shown during modeling. So, external untwisting torque tries to extend the rope (increase of ε), while twisting torque tries to compress it (decrease of ε), what is connected with influence of gap values between the rope elements (wires and layers) on distribution of the contact stresses between them during twisting.

Analysis of the stress-strain state of steel closed ropes under tension and torsion

The analysis of the stress-strain state of the closed rope elements under axial tension and torsion was carried out by the finite element method using the licensed software package SIMULIA/Abaqus. The closed rope consists of an outer layer of Z-profile wires, a subsurface layer of alternating round and H-profile wires, an intermediate layer, and a core of the structure 1 + 7 + 7/7 + 14 of round wires. Modeling made it possible to determine the values of the axial force P, the torque M, the relative elongation e, and the relative angle of torsion θ of the rope sample at the given values of the axial displacement and the rotation angle the cross-section. The results of the analytical calculation of the stress-strain state of a spiral rope using traditional approaches were compared with those obtained in the course of computer finite element modeling. The results of modeling the rope deformation under tension were verified by experimental data obtained by stretching the rope sample on a universal horizontal hydraulic test machine LabTest 6.2000N.7. The results of computer modeling of the rope pure tension correlate well with the results of the calculation by the method of M.F. Glushko, which more accurately takes into account the real construction of the ropes. Computer simulation of the stress-strain state of the closed rope elements made it possible to determine the contact stresses between shaped wires in layers and between layers at different values of the gap between shaped wires; therefore, it can be used to optimize the gaps. Computer simulation of the stress-strain state of the rope elements of a closed structure makes it possible to assess the consistency of the layers narrowing during axial tension by analyzing the contact stresses between adjacent wires in the cross-section of the rope.

The determination of the stresses in the wire of steel wire rope at clash on the block

The article considers the problem of determining the extra effort that occurs when the steel weir rope runsng and the bend on the block. In spite of that what questions of determining the strain in ropes of carrying machines dedicate very many of works different sciences to our time no definition method of calculation of additional strains of bend in rope in the time of bend on block. For define overall increase of length wire obtain at cover of rope on the block was examine site of rope from its point contact since block to exceed widen of elongation in side of straight rope. On transition site the rope have certain curvature which is small value in comparison since curvature rope at increase additional effort on transition site not create important influence. On this score extend additional effort on transition site examine however for the straight rope. On value overall increase of the length wire transition site can have considerable influence because on this site the wire can have considerable increase of the length which summarize with value elongation receipt widen which is in rope curve on block. Although the question of defining the forces of the ropes of Considered steel weir rope element, which goes from a straight section to the curved on the block is a subject of very many works. In this case there arise tensile force (or compression force), which leads to the destruction of weirs of the steel weir rope. The proposed new calculation, which is based on the classical theory, namely Hooke's law. A comparison of the calculated values with the experimental ones is made.

Development of analytical model of nonlinear stiffness bracing system for structures subjected to dynamic load

This paper reports the development of a numerical model for a nonlinear stiffness bracing (NCSB) system as a new lateral resisting technique for framed structures subjected to dynamic loading. The NCSB device is composed of two conical springs embedded into the device to limit the story drift through the attachment of cable bracings into the frame. This device can adapt the stiffness characteristic of the framed structures due to the dual action of conical spring and wire rope elements at varied displacement values. The derived mathematical and constitutive models were implemented in finite element program code for 3D analysis of reinforced concrete (RC) framed building. The competence of the NCSB device in RC frames was assessed using 3D pushover and time history analyses for a range of spring geometry configurations. The numerical analyses verified the effectiveness of the NCSB technique in enhancing the ultimate capacity of RC frame structures, in reducing plastic hinge formation in the main structural components, and in decreasing the maximum displacement in three directions. It also deduced drift ratio, critical shear, and moment values, when compared with bare RC framed buildings. It is evident that deployment of NCSB enhanced the seismic performance of RC buildings.

Обоснование правил подобия разрывной нагрузки рыболовных крученых изделий

The article focuses on the problem of physical modeling of the physical and mechanical properties of fishing twisted filamentary materials, in particular, the most important one – the breaking load. The problems arise because of conducting full-scale experiments, particularly when the ropes of large diameter are used to build the rope parts of fishing gear. The solution to the problem of determining the breaking load on filamentary parts can be found by using specialized tensile testing machines and modern software, which is an effective tool for predicting the reliability and a resource of a gear part operating in difficult conditions of dynamic and shock loads. However, de-signing of fishing gear must begin with large-scale modeling, which will help to correctly calculate the physical and mechanical properties of the designed object using the well-known parameters of the full-scale material. The similarity rules of breaking load of fishing twisted filamentary gear used for the construction of industrial fishing tools will make it possible to model new elements of these tools without conducting full-scale experiments. At the same time, they will already contain solutions to problems associated with studying the dynamic processes, deformation, fracture, as well as the prediction of reliability and resource of the material. The technique proposed based on determining the scale of similarity of filamentary gear made of polyamide fibers, will help to simu-late various net and rope elements from filaments gear of various sizes and structures, instead of conducting energy-intensive experimental studies on ropes of large diameter.

Dynamic analysis of rotating satellite de-spun using <?A3B2 ACK?>flexible brush

With the continuous exploration and expansion of human beings in space, the number of satellites in space is gradually increasing. In the process of catching the failed satellites, the rolling spin of the satellite has always been the main problem which is affecting the stability of the catching system between targets and servers. The derotation mechanism, a flexible deceleration brush, is proposed, which is placed at the end of a seven-degree-of-freedom manipulator to form a racemable space robot. The momentum of the rolling target is dissipated by the contact collision between the end flexible deceleration brush and the rolling target windsurfing board. The angular velocity deceleration of the freely rolling target is carried out. Based on the rope element of the large deformation cable beam element of the absolute nodal coordinate method (ANCF), the continuum model of the flexible deceleration brush is established. According to the Hertz theory, contact collision force between the flexible deceleration brush and the rolling target windsurfing board are calculated. For the non-cooperative target of free rolling in different speeds, the effects of the length, angle and other parameters of the flexible deceleration brush on the racemization effect are analyzed by dynamics simulation, and the optimal racemization parameters are obtained in the process of the dynamics simulation. Using these parameters to verify the simulation of the racemization, the results show that the strategy, which is using flexible deceleration brush to rack non-cooperative targets, can successfully eliminate the initial spin angular velocity and it is feasible and effective.

Estimation of the composition of the forced and free vibrations of the casing of the steel rope roof of Ukraine Cinema & Concert Hall located in Kharkov over the area of main line tunnel of working metropolitan railway

The paper discusses issues related to the dynamic parameters of the metro train influence on the building construction of Ukraine Cinema & Concert Hall complicated in terms of construction located in Kharkiv City. The hall roof is of peculiar complexity made in the shape of hyperbolic paraboloid hung to the cable roof system and supported by the inclining reinforced concrete arches. Using the equipment by DIAMEX 2000 LLC we have measured vertical and horizontal forced vibrations in the most relevant points of the casing. Natural vibrations were defined by creating dynamic impact of the falling load weighing 10 kg from a height og 2 m. The vibration parameter measurement was carried out by means of Ahat-M vibration analyzer. As a result we have obtained amplitude-frequency characteristics of the forced vibrations caused by metro train movements. The frequency of base and obertones is within 30-50 Hz. At the same time, vibration amplitudes is up 200-350 pm. Specific range of vibrations leads to the occurrence of the for framing roof framing (concrete and steel strand guy ropes), noise penetrating into the hall significantly worsens operating characteristics for the spectators. A special calculation of guy rope element taking into account fatigue factors has been made.

Braking Distance of Hoist Conveyances Required for Safe Stopping Under the Conditions of Emergency Braking

Abstract This study investigates selected aspects of the dynamic behaviour of mine hoists during the emergency braking in an event of overtravel. Characteristics of the braking force that needs to be applied in the headgear and in the pit bottom to arrest the conveyance in the event of an overtravel are derived from laboratory and industrial test data and recalling the results reported in literature. The real hoist installation is replaced by a model whereby the equations of motion of rope elements are written as for elastic strings, taking into account the variable length of the hoisting rope section between the Koepe pulley and the conveyance being arrested in the head tower. Analytical formulas are provided whereby the displacement of the top conveyance with the payload for the constant elasticity coefficient of the hoisting rope section between the conveyance being arrested in the head tower and the Koepe pulley is expressed as the function of the braking force and of the operational parameters of the hoist gear. The hoist operation is investigated in the event of emergency braking, taking into account the two aspects of the cycle: - the time required for the conveyance to be stopped, - the distance travelled by the conveyance until it is stopped. The results of the dynamic analysis of the hoist installation in the conditions of emergency braking may be utilised in selection of the effective and adequate braking system guaranteeing the safety of the system operation.

The determination of the stresses in the wire of steel wire rope at clash on the blocks and drums

The article considers the problem of determining the extra effort that occurs when the steelweir rope winding on the drum and the bend on the blocks. Considered the steel weir rope element,which goes from a straight section to the curved on the block. In this case there arise tensile force(or compression force), which lead to the destruction of weirs of the steel weir rope. The proposednew calculation, which is based on the classical theory, namely Hooke's law. A comparison of thecalculated values with the experimental ones.

Loads Acting on the Mine Conveyance Attachments and Tail Ropes during the Emergency Braking in the Event of an Overtravel

Abstract It has now become the common practice among the design engineers that in dimensioning of structural components of conveyances, particularly the load bearing elements, they mostly use methods that do not enable the predictions of their service life, instead they rely on determining the safety factor related to the static loads exclusively. In order to solve the problem, i.e. to derive and verify the key relationships needed to determine the fatigue endurance of structural elements of conveyances expressed in the function of time and taking into account the type of hoisting gear, it is required that the values of all loads acting upon the conveyance should be determined, including those experienced under the emergency conditions, for instance during the braking phase in the event of overtravel. This study relies on the results of dynamic analysis of a hoisting installation during the braking phase when the conveyance approaches the topmost or lowermost levels. For the assumed model of the system, the equations of motion are derived for the hoisting and tail rope elements and for the elastic strings. The section of the hoisting rope between the full conveyance approaching the top station and the Keope pulley is substituted by a spring with the constant elasticity coefficient, equal to that of the rope section at the instant the conveyance begins the underwind travel. Recalling the solution to the wave equation, analytical formulas are provided expressing the displacements of any cross-profiles of hoisting and tail ropes, including the conveyance attachments and tail ropes, in the function of braking forces applied to conveyances in the overtravel path and operational parameters of the hoisting gear. Besides, approximate formulas are provided yielding: –loading of the hoisting rope segment between the conveyance braking in the headgear tower and the Keope pulley –deceleration of the conveyance during the braking phase. The results will be utilised to derive the function governing the conveyance load variations during the emergency braking, depending on the parameters of the hoisting installations and the braking systems. These relationships are required for adequate design of the frictional contact between the ropes and the pulley and will become the basic criteria for dimensioning and design of load-bearing components of conveyances in the context of improving their reliability and safety features.

Determination of a Real Strain-stress State of the Steel-wire Rope Elements

Today steel-wire ropes are used as a pre-stressed reinforcement for the large-span reinforced concrete structures that are considered as solid isotropic bars. Meanwhile, it's not taken into account that the rope represents a composite structure with the axial spiral anisotropy of properties, where a combined strain-stress state (SSS) occurs. On the basis of Kirchhoff differential equations for thin curved bars, the author develops a generic mathematical model of the steel twisted rope with a linear contact of wires. This model enables one to determine a combined strain-stress state of the rope elements taking into consideration its geometrical characteristics (wire size, twist angle of a twisted rope) and mechanical characteristics of steel (elasticity and shear moduli). The paper presents calculation of irregularity of stress distribution between a core and wires of the steel rope К-7 (1+6) in case of different rates of wire twisting. Knowing the real strain-stress state in the steel rope elements, one can specify an effective pre-stressing of the rope.

Numerical Simulation of Damage Localization in Polyester Mooring Ropes

This paper presents the derivation of a mechanical model to estimate the effects of damage on the response of ropes. Damage can be represented through a degradation of the properties of individual rope elements, and it can also include the complete rupture of one or more elements. The general assumptions made to estimate the length over which damage propagates along the length of a rope and how this length is considered in modeling damaged rope behavior are explained. Consistent with tests on damaged polyester (PET) mooring ropes, numerical simulations demonstrate the existence of strain localization around the failure region and, due to degradation of rope element properties, damage localization as well. This damage localization causes the premature failure of rope elements, reducing the maximum load capacity and maximum failure strain that a damaged rope is capable of resisting relative to that of an intact rope. The proposed model suggests that some of the variables that affect damaged rope behavior are the degree of damage present at a given cross-section, the location of broken rope elements, and the length over which damage propagates along the rope length. Experimental data are used to validate the model.

A Visco-hyperelastic Model for the Thermo-mechanical Behavior of Polymer Fibers

A visco-hyperelastic model for the thermo-mechanical behavior of polymer yarns is presented. The model assumes that the stress in a yarn during uniaxial deformation results from the superposition of strain rate hardening effects and the softening caused by filament damage. The filament damage accounts for the fracture of polymer chains and the failure of inter-chain bonds. The constitutive model was implemented in the finite element method as a 1D rope element, and was applied to the study of nylon 6.6 and Kevlar ® 29 behavior. Numerical simulations of fabrics subjected to ballistic impact were performed, and the model is shown to predict the fabric penetration resistance and the deformation characteristics during the dynamic event.

Investigation of the Damage-Dependent Response of Mooring Ropes

The focus of this paper is on the development of an analytical damage model for predicting the deterioration of the mechanical properties of polyester (PET) ropes subjected to static tension loading. Experimental data on small PET ropes are used to estimate the evolution of damage using the effective stress concept and the principle of strain equivalence. The proposed damage model relies on an empirically based cumulative scalar damage function, which is founded on the assumption that the strain range experienced by rope elements is the main source of damage under static tension loading conditions. In this particular study, the evolution of the damage function is represented by both power law and polynomial forms. Based on experimental observations, softening behavior is developed by rope elements after reaching their maximum load-carrying capacities. This softening behavior is captured by the damage function through an asymptotic expansion technique (perturbation method). Comparisons between predicted rope responses and experimental data are provided to illustrate the use of the proposed damage model to estimate PET rope response.

Statics of a gillnet placed in a uniform current

The configuration and tension distribution of a gillnet are very important for catching fish. A nonlinear mixed method is employed to determine the equilibrium configuration and tension distribution of a gillnet set in a uniform current, based on a finite element formulation a gillnet composed of mesh bars and ropes can be modeled as an infinitely flexible, straight rope element, connected at each end to other elements by a frictionless hinge. The basic nonlinear equations describing the equilibrium state of the gillnet system are solved by the Newton–Raphson method. The numerical solutions are obtained by a loading iteration in addition to a common shape iterative procedure. The method has excellent global convergence and good accuracy by comparing the numerical values with measured results from circulating water tank model testing.

A static analysis of the tension and configuration of submerged plane nets

A non-linear finite element method is employed to determine the equilibrium configuration and tension distribution of a net set in a uniform current. The method models each mesh bar in the net as an infinitely flexible rope element connected at each end to other elements by a frictionless hinge. The Newton-Raphson method is used to solve the basic non-linear simultaneous equations with respect to tension in mesh bar and knot displacements. Global convergence to the correct solution from an initially estimated state is ensured using a loading iteration in addition to the common configuration iterative procedure in order to accurately model the shape-dependent characteristic of hydrodynamic forces. The method is shown to predict the shape and tension distribution of fishing nets with reasonable accuracy in the case examined in the present study.

A method for analyzing the static response of submerged rope systems based on a finite element method

: A method is presented for determining the equilibrium configuration and tensions of submerged rope systems in a uniform current based on a non-linear finite element formulation. A standard straight rope element is adopted to model rope segments of the system. Rope stretch is included in the formulation, and a hydrodynamic model is introduced for the rope. The structural and hydrodynamic models are coupled in order to account for the interaction between the structural response and hydrodynamic load acting on the rope itself. The Newton–Raphson method is employed in the formulation, ensuring the global convergence of the iteration to the correct response (and hence to the correct equilibrium configuration and tension of the rope system) from any set of initially estimated responses. Good agreement between this numerical simulation and experimental behavior was revealed in an application of this method to a long-line model.

Wear and Fatigue of Nylon and Polyester Mooring Lines

Wear and fatigue in synthetic fiber lines depend on a multitude of mechanisms, including cumulative creep to rupture, hysteretic heating due to cyclic loading of filaments or to relative displacement of structural rope elements, internal wear caused by relative movement between yarns or strands, and external abrasion against deck hardware or rough surfaces. Studies undertaken to evaluate fiber, yarn, and rope responses to each of these mechanisms, singly or in combination, vary significantly with the test conditions including cyclic load level (both axial and transverse), cyclic strain level, and ambient conditions, i.e., temperature and moisture content (whether dry or wet in fresh water or salt). Cyclic load limits depend on wave height, wind velocity, and mooring line dimensions and properties. The relative durability of nylon versus polyester lines is considered as the lines are subjected to tensile cycling under storm conditions. While tensile fatigue as a creep phenomenon is operative over the free length of the mooring line, the more critical location of rope deterioration is at its interactive contact with deck hardware. An ideal mooring system is composed of two segments. The one between the elements of deck hardware (cleats and chocks) should possess maximum abrasion resistance and high tensile stiffness. The other segment should possess high tensile compliance so as to minimize cyclic load levels induced by waves and wind. A review of yarn/yarn wear tests and rope abrasion tests is provided to form the foundation for recommendations.