Force Of Rod Research Articles

Dynamic Characteristic Analysis on the Rod Fastening Rotor Bearing System

Modern large-scale gas turbine’s rotor is the main form rod fastening rotor. The contact friction between wheels, the pre-tightening force of the rod and bearing system have an effect on rotor dynamics. According to the structure characteristics of rod fastening rotor, contacting model is established. In the rotor modal, contacting friction, the pre-tightening force of rod and bearing system is included to get natural frequency and the mode. Through the analysis of rotor, with increasing the pre-tightening force, the overall stiffness and natural frequency has increased. The natural frequency is increase fast when the pre-tightening force is small. With the increase of the pre-tightening force, speed of the natural frequency is slow. Bearing system with changes in speed, its oil film dynamic coefficients varieties also have some impact on the inherent characteristics of the rotor.

ANALYSIS OF THE DEFLECTION OF A TRUSS WITH A DECORATIVE LATTICE

Introduction. A scheme is proposed for a planar symmetric statically determinate beam truss with a rectilinear lower belt, struts, multidirectional braces and a polygonal outline of the upper belt. The belts of the truss are rectilinear, the hinges are ideal. The truss belongs to the class of regular trusses having periodic cells. The supporting rods are not deformable. The truss is evenly loaded around the nodes of the lower belt. Materials and methods. The task is to deduce the dependence of the deflection of the truss on the number of panels in the span. The deflection is obtained from the Maxwell-Mora formula under the assumption that all the rods have the same rigidity. Forces in the structural rods from the effective uniform load and from the unit vertical in the middle of the span are determined by the method of cutting the nodes. The matrix of the system of linear equations of node equilibrium is made up of the cosines of the forces with the coordinate axes. To compile a system of equations and solve it, the program of symbolic mathematics Maple is used. To obtain the general formula, a number of problems of trusses with a number of panels from 2 to 29 are solved. Sequences of the coefficients of the deflection formula have common terms for which homogeneous recurrence equations are also compiled using the methods of the Maple system using specialized operators. Results. The solutions of recurrence equations have the form of polynomials with coefficients that depend on the parity of the number of panels and contain trigonometric functions. The graphs of the solutions obtained are constructed and analysed. Sharp changes of deflection characteristic for such truss and their non-monotonic character are noted. It is shown that for a fixed, independent on the number of panels, length of the span and the total load, the relative deflection with increasing number of panels first decreases, then varies little. Conclusions. The asymptotic property of the solution is obtained by the methods of the Maple system: an inclined asymptote is found. The slope is calculated using the analytical capabilities of Maple. A simple formula is derived for the horizontal displacement of the mobile support from the action of the load. The dependence is monotonic. The height of the truss is included in the denominator of the formula.

The impact of configuration of the Ilizarov fixator on its stiffness and the degree of loading of distraction rods

BackgroundThe mechanical parameters of the Ilizarov fixator are influenced by many factors related to its spatial configuration. The aim of this study was to experimentally evaluate the impact of the type of implant and the number of distraction rods on the uniformity of loading of distraction rods and stiffness coefficients of the Ilizarov fixator. MethodsThe tests were carried out on a physical model. The model was mounted in a universal loading station MTS 858 Mini Bionix. Forces in distraction rods are measured with the use of strain gauge force transducers. Displacements of bone fragments were measured by means of digital image correction. FindingsIn the case of a fixator with 3 distraction rods, configuration of implants has no statistically significant effect on the forces occurring in distraction rods. In the case of a fixator with 4 distraction rods, there are statistically significant differences in the forces in distraction rods. The highest transverse stiffness coefficients occurs in the system with 4 distraction rods and the configuration of 1K1S implants, while the smallest transverse stiffness coefficients occurs in the fixator with 4 distraction rods and the configuration of 0K1S implants. InterpretationBased on the results of experiments on the physical model, we observed an asymmetry in the distribution of forces transmitted through distraction rods. The configuration with 3 distraction rods provides more uniform distribution of forces in distraction rods and reduces the impact of the implant configuration on transverse stiffness coefficients. The use of a configurations with 4 rods may be advantageous when we want to obtain greater transverse stiffness coefficients of a system consisting of the fixator and fragments of the lengthened bone.

Rotational behavior of exposed column bases with different base plate thickness

Exposed column base connections are used in low- to mid-rise steel moment resisting frames. This paper is to investigate the effect of the base plate thickness on the exposed column base connection strength, stiffness, and energy dissipation. Five specimens with different base plate thickness were numerically modelled using ABAQUS software. The numerical model is able to reproduce the key characteristics of the experimental response. Based on the numerical analysis, the critical base plate thickness to identify the base plate and anchor rod yield mechanism is proposed. For the connection with base plate yield mechanism, the resisting moment is carried by the flexural bending of the base plate. Yield lines in the base plate on the tension side and compression side are illustrated, respectively. This type of connection exhibits a relatively large energy dissipation. For the connection with anchor rod yield mechanism, the moment is resisted through a combination of bearing stresses of concrete foundation on the compression side and tensile forces in the anchor rods on the tension side. This type of connection exhibits self-centering behavior and shows higher initial stiffness and bending strength. In addition, the methods to predict the moment resistance of the connection with different yield mechanisms are presented. And the evaluated moment resistances agree well with the values obtained from the FEM model.

Refined Finite Element Analysis of Crack Causes in SRC Arch Rib Bridges considering Multiple Factors

The SRC (steel-frame reinforced concrete) arch bridge is an important part of the development of arch bridges. Scholars worldwide have studied it from various aspects because of its stronger stiffness and stability than other types of bridges especially when crossing the canyon. The steel frame is a stress bracket during construction. Concrete becomes the main axial-pressure bearing structure when it fills the inner pipe and the encased frame. This article mainly focuses on the crack problems of SRC arch bridging during the postconstruction operation, local model of the midspan arch rib, and the equivalent relationship between the coefficient of expansion and the temperature of concrete. This study uses a cooling method to simulate the shrinkage process with detailed analysis of three properties including concrete shrinkage, temperature gradients, and concentrated hanger rod force. It is concluded that the SRC arch bridge will have large tensile stress on both inner and outer surfaces of slab and web when the temperature changes, and it is the main cause of cracks. The results agree well with measured data. At last, we come up with some reference suggestions in the design and construction of similar bridges in the future.

Dynamic behavior analysis of reciprocating compressor with subsidence fault considering flexible piston rod

Subsidence wear is inevitable in a reciprocating compressor system, but how to induce body vibration is not clear. We investigated the dynamic behavior of a reciprocating compressor system with subsidence fault considering a flexible piston rod. The flexible piston rod was modeled as a cantilever beam. The dynamic model, in which the influence of the subsidence size, variational cylinder pressure, impact effects and piston rod flexibility are taken into account, was established. Influences of the four parameters including subsidence size, vertical force of flexible piston rod, cylinder pressure and crankshaft speed were analyzed in the dynamic response. Numerical results reveal that with the change of the four parameters, the existence of subsidence fault has a significant effect on the displacement, velocity and acceleration of the crosshead in the transverse direction, but only conspicuously affects the acceleration in the longitudinal direction. In addition to cylinder pressure, the larger the values of the other three parameters, the greater the influences. The cylinder pressure is a time-varying working load. Not only the cylinder pressure but also the open/close time of the valves and change rate of the pressure all affect the dynamic behavior of the system with subsidence. Meanwhile, the change in the vertical force of the flexible piston rod has a remarkable effect on the jump position of the crosshead, but the effect of other parameters is not obvious. In addition, the changes of parameters produce obvious influences on the impact force and the impact range of the crosshead. The stability of the reciprocating compressor system was studied using Poincare portraits method. The result shows that the system with subsidence fault has chaotic behavior.

Asymptotic analysis of the clamped-pinned elastica

Asymptotic solutions for the clamped-pinned elastica when the displacement of the pinned end is small (immediately after buckling) and when it approaches its limiting displacement (when the force in the rod tends to infinity) are presented. Simple leading order relationships describing the force as a function of the pinned end’s displacement are derived. Those approximate the force-displacement behaviour of the clamped-pinned elastica for small and limiting end displacements. All our results are valid for the clamped-pinned elastica in any mode.

Thermal effects on the tensile forces of rods in rod-fastened rotor of heavy-duty gas turbine

Circumferential tie-rods fastened rotor is a common structure widely used in gas turbine. The preloads of rod groups are of great importance to ensure the strength, stiffness, and stability of the rotor in gas turbine. The tensile force of rods obtained through preload may change due to inconsistent axial thermal expansions between rods and discs during transient startup and shutdown processes, and the change should be within the safety margin. Based on the finite element method, thermal-structural analyses of a gas turbine are carried out to quantify the effect of temperature field on tensile force of rods under multiple operating conditions including steady state, shutdown process, turning gear operation, startup, and standstill. Results show that the maximum increase of the tensile force of rods reaches about 33% and 25% for the compressor and turbine shafts during startup. The tensile force of rod-groups presents nonuniform distribution with sine wave shapes during the standstill condition, and the unevenness is highly relative to the time on turning gear. The quantitative results provide a theoretical reference for the preload design of rods in gas turbine.

Analysis on temperature-dependent deployment behavior of bi-stable composite rods

Bi-stable composite rods attract many researchers to investigate the mechanical and deployment behaviors for possible application to space deployable structures. Operation requires the bi-stable composites to be in a compact form prior to deployment. The deployment behavior is influenced by the storage conditions and the environmental temperature, of which, the latter is focused on in the present study. This study utilizes plain woven carbon fabrics composites to make bi-stable composites. Temperature-dependent mechanical properties of bi-stable composites are measured, and temperature-dependent deployment forces of bi-stable rods are evaluated using analytical formulations and finite element simulations with the measured properties.

An improved technique for measuring piston-assembly friction and comparative analysis with numerical simulations: Under motored condition

Abstract Robust and accurate measurement techniques are essential to studying the piston-assembly friction of Internal Combustion (IC) engines. Based on the instantaneous Indicated Mean Effective Pressure (IMEP) method, this paper develops an improved measurement technique to evaluate the piston-assembly friction in engines. Wireless telemetry technology is employed in the measurement of connecting rod axial force, which greatly minimizes the engine modifications and enhances the measurement stability compared to the conventional wired way. The measurement system, which is composed of computer, data acquisition system, sampling trigger apparatus and sensors, is exploited with special attention given to the sampling synchronization of signal channels including cylinder pressure, connecting rod force and crank angle position. Engineering implementations are carried out on a four-stroke gasoline engine under motored condition. The measurement results are compared with numerical results from a newly developed numerical coupling model system, and it shows that the two agree well. In addition, the piston-assembly friction under different engine speeds and inlet lubricant temperatures are also measured, and analyses indicate that these results are in good correlation with the well-known Stribeck curve. This improved measurement technique provides an accurate and reliable option for the friction evaluation of piston-assembly components in engine designs.

The Influence of Using the Traction Booster of the Semi-Mounted Plough on the Performance Parameters of the Ploughing Set

The objective of this article is to verify the influence of the use of the traction cylinder of the semi‑mounted plough on the performance parameters of the ploughing set., Claas Axion 850 set, equipped with Hexashift mechanical stepped gearbox, fully geared under the load of Pöttinger semi-mounted plough was used for the purposes of the measurement. Assessed parameters included force in the upper rod, slip, effective performance of the set and fuel consumption. The results of the measurement clearly indicate the positive influence of the traction booster on the performance and energetic parameters of the ploughing set. By increasing the force in the upper rod, the torque is transferred to the land-wheel which partially relieves the furrow wheel and transfers the weight pertaining to this wheel to the land-wheel. This has decreased the slip (between 0 – 15 MPa: 7.5 % for plant-bed wheel and 2 % for furrow wheel) and increased the performance of the set (hectare efficiency was increased by 3.7 %) while reducing consumption and eliminating the undesirable compaction. The difference of effective consumption was between the pressure 0 and 15 MPa 0,6 l/ha which corresponds to a decrease of 2.6 % and 2.89 ml/m3, equal to a decrease of 3.9 %. Except for some exceptions, the changes of the monitored parameters were not statistically significant. This was caused especially due to the conditions of the measurement and also due to the chosen aggregation. The measured values fluctuated due to soil non-homogeneity, which was subsequently reflected in the size of the confidence intervals and due to the fact that the tractor was under-dimensioned for the given conditions and the plough construction, the influence of the traction booster has not been proven to such an extent.

Dynamic performance of reciprocating compressor with capacity regulation system

Regulating capacity by holding suction valves open in the partial compression stroke has a great application value for reciprocating compressors, which can reduce the power consumption proportionally with respect to the decrease of capacity. To allow this method to be widely applicable, it is important to analyze the changes in the dynamic performance of reciprocating compressors. This study focuses on the dynamic performance in an M-type reciprocating compressor with capacity regulation system. When the compressor’s capacity is regulated, the connecting rod force and normal force are within a reasonable range. The capacity regulation system has little effect on the shaft speed irregularity of compressor when the capacity regulation ratio is below 100%. The designed flywheel moment can satisfy the compressor’s safe operation under variable capacity regulation conditions. The results show that the application of the capacity regulation system has little negative influence on the compressor’s dynamic performance.

Analysis of inter-channel sweeping flow in wire wrapped 19-rod bundle

Helical wire spacers are widely used in sodium cooled fast reactors. One of the main effects of wire spacers is enhancing the inter-channel cross flow in triangular arrayed rod bundles. To study the characteristic of sweeping flow rate across the gaps between the sub-channels, the computational fluid dynamics (CFD) method is used in the present study to analyze the flow field in a 19-rod bundle with wire wraps. This CFD work only considers the fluid zone of one section of the rod bundle. The height of the CFD model with periodic inlet and outlet boundary conditions is one wire pitch. The k-ω SST model is used as the turbulent model. The wire effect on the velocity distribution of the flow across the interface between two sub-channels is investigated in the CFD study. Based on the force balance equation between the wire wake force and the surface friction force of rods in the circumferential direction, a theoretical model for estimating the average swirling flow rate driven by one single wire is proposed. The simulation shows that the ratio of rod pitch (P) to rod diameter (D) has a strong effect on the velocity of the sweeping flow. The flow rate increases with the P/D ratio. The simulation agrees well with the proposed model. In addition, the effect of the ratio of wire pitch (H) to rod diameter has also an influence on the cross flow rate: A small H/D ratio leads to higher cross flow rate. A correlation as a function of both P/D ratio and H/D ratio is proposed to predict the sweeping flow velocity by the present study.

INDUCTIVE ANALYSIS OF THE DEFORMATION OF THE ARCHED TRUSS

An analytical solution to the problem of the deflection of a flat arched statically determinate truss un-der the action of a uniformly distributed and concentrated load is obtained and analyzed. To obtain the depend-ence of the deflection on the number of panels, an induction method was used in two parameters — the number of panels in the crossbar and the number of panels in the supporting side trusses. All transformations and analysis are performed in the system of computer mathematics Maple. Expressions for the forces in individual rods are found. The asymptotic approximation of solutions is obtained.

Analytical calculation of the deflection of a beam truss with double bracing

A statically determinate planar truss has rectilinear belts and a triangular lattice consisting of double braces. The four links make it seemingly statically indeterminate. The derivation of the formula for the dependence of the deflection on its dimensions and the number of panels is given. Forces in rods are determined in symbolic form by cutting out nodes from the solution of a system of linear equations in the system of computer mathematics Maple. To determine the deflection, the Maxwell - Mohr’s formula is used. Rods (except all rigid support) are assumed to be elastic with the same rigidity. The generalization of individual solutions to an arbitrary number of panels is done by induction. Operators of the Maple system from the calculation data yield linear homogeneous recurrence equations for the coefficients of the desired formula. The solutions of these equations give the general terms of the obtained sequences. Formulas for three types of loads are obtained and compared (the uniform loading of the nodes of the lower and upper belts and the concentrated force in the middle of the span). Curves of the dependence of deflection on the number of panels have weakly expressed minima. The dependencies of the forces in the most compressed and stretched rods on the number of panels are derived. Also given are asymptotic estimates for solutions in accordance with the number of panels in fixed spans of the construction and at a given total load.

Construction Simulation Analysis of 60m-span Concrete Filled Steel Tube arch bridge

The construction process of the CFST arch bridge is complicated. The construction process not only affects the structural stress in the installation, but also determines the form a bridge and internal force of the bridge. In this paper, a 60m span concrete filled steel tube tied arch bridge is taken as the background, and a three-dimensional finite element simulation model is established by using the MIDAS/Civil bridge structure analysis software. The elevation of the main arch ring, the beam stress, the forces in hanger rods and the modal frequency of the main arch during the construction stage are calculated, and the construction process is simulated and analyzed. Effectively and reasonably guide the construction and ensure that the line and force conditions of the completed bridge meet the design requirements and provides a reliable technical guarantee for the safe construction of the bridge.

Вычисление критических сил в упругих стержнях переменного сечения прямым интегрированием дифференциального уравнения изгиба

Вычисление критических сил в упругих стержнях переменного сечения прямым интегрированием дифференциального уравнения изгиба

Простая приближенная формула для критической силы в упругом стержне переменного сечения

Простая приближенная формула для критической силы в упругом стержне переменного сечения

An Optimization Method for Design of Acoustic Metamaterial Structure

Pentamode (PM) metamaterial is a kind of acoustic metamaterial generally designed from a general material and made by a periodic array of micro-truss structures. The paper presents an optimization method for the design of PM metamaterial structure, and this kind of structure has usually special physical properties to guide the acoustic wave to propagate according to the design path. In order to construct the optimization model, the micro-truss unit cell is firstly investigated deeply, and the relationship between the effective elastic modulus of PM materials and the structural parameters of micro-truss unit cells is established. With incorporating the transformation acoustics algorithm into the optimization process to predict the theoretic material parameters of the current design structure, the constraint of the material property in the design structure is converted into the rod size constraint of micro-truss. As a result, the design of PM material structures can be realized as a problem of structure size optimization, and the optimized result can meet the requirement of PM metamaterial property and the theory of transformation acoustics. And also, the total stability of the PM material structure is also ensured by the balance rod forces constraints in the optimization process. Finally, a numerical example of PM material structure is presented.

Control of membrane drives

A method is proposed for increasing the efficiency of membrane drives by adjusting the effective area of the membrane. A device with adjustable effective area of the membrane is developed, with variation in the rod force by changing the working pressure in the chamber.