31 results about "Geometrical nonlinearity" patented technology

The invention discloses a passive suspension vibration isolation method and device with zero stiffness characteristics, and relates to the fields of gravity environment ground simulation, low-frequency vibration isolation, ultralow-frequency vibration isolation and the like. The passive suspension vibration isolation method and device with the zero stiffness characteristics are put forward to meetincreasingly higher requirements for space gravity ground simulation experiments in aerospace engineering, and to solve the existing technical problems in the low-frequency and ultralow-frequency vibration isolation. According to the suspension vibration isolation device, based on geometric nonlinear negative stiffness characteristics and the adjustability of geometrical parameters thereof, a vertical elastic element, sliding rails, sliding blocks, horizontal elastic elements and connecting rods are connected to a load, the characteristic of accurate zero-inherent frequency in a design rangeof the device is realized through parameter configuration, and a constant force that is collinear with the direction of gravity of the load and has no relation with displacement of the load can be provided for the load. The resultant force acting on the load in the design range is fixed in value, so that the load is enabled to be in a certain specific gravity environment. The full-frequency-band immunity of the load to the vibration environment is realized, and ultralow-frequency vibration isolation, the zero-rigidity suspension of a modal test and the ground simulation of the spatial gravityenvironment are realized.

A method for predicting compression rigidity and compression strength of a composite material spiral structure by considering geometrical nonlinearity comprises the following four steps: step 1, defining the geometrical shape and size of the spiral structure of the composite material, and determining a mathematical expression of a relationship among geometrical parameters; 2, carrying out stress analysis on any cross section A, and calculating the deformation and compression rigidity of the composite material spiral structure based on an energy principle; 3, through the compression deformationincrement and the compression load increment in the cumulative loading process, establishing a load displacement relation considering geometric nonlinearity of the composite material spiral structure, and linearly fitting a load displacement curve according to a least square method; 4, deriving a composite material helical structure compression strength analytical expression by adopting principaldirection stress and a TsaiHill failure criterion; the invention is convenient and efficient, and the compression rigidity and the compression strength of the spiral structure of the composite material can be conveniently and quickly predicted only by determining performance parameters and geometrical parameters of component materials.

The invention belongs to the field of structural dynamics and aeroelastic mechanics analysis, and particularly relates to a nonlinear aeroelastic dynamic response analysis method based on a structuralreduced-order model. The method includes: solving a structural nonlinear stiffness coefficient in a given form by adopting a method for carrying out regression analysis on an input test load and corresponding structural deformation, constructing a large-deformation structural kinetic equation by utilizing the nonlinear stiffness coefficient, and on the basis, constructing the test load by utilizing a mode of multiplying a proportionality coefficient by a mode combination; accurately recovering the spanwise displacement of the wing by constructing a displacement residual basis function; and finally, constructing a geometric nonlinear aeroelastic gust response solving process in combination with a kinetic equation given by the structure reduced-order model and an unsteady curved surface vortex lattice method. The method gives consideration to the solving precision, the calculation efficiency and the applicability of a complex model, and can be applied to the analysis and calculation ofthe geometrical nonlinear aeroelastic gust response of aerospace aircrafts.

The invention relates to a design method of an initial prestress state of a spoke type cable bearing grid steel structure. The design method comprises the following steps of performing calculation according to the self-weight condition borne by the spoke type cable bearing grid steel structure to obtain the magnitude of load effect borne by nodes of radial cables and ring cables; obtaining the initial pretension estimated value of each radial cable under the self-weight and the cable force distribution condition of the radial cables and the ring cables; determining the diameters of the radialcables and the ring cables according to the pretension, inputting the initial pretension obtained by comparison into a finite element structure model, and checking and adjusting the structure shape until the requirement of the building appearance is met after geometric nonlinear static calculation; and determining the pretension of the radial cables and the ring cables, and obtaining the diametersof new radial cables and new ring cables at the same time, thereby determining the initial prestress state of the structure. The design method of the initial prestress state of the spoke type cable bearing grid steel structure of the invention is suitable for the design of the spoke type cable bearing grid steel structure.

The invention discloses a modeling method of a two-dimensional airfoil nonlinear flutter time domain model, which comprises the following steps of: simplifying a system by taking the system that a rudder blade is connected with a torsion spring as an object, and deducing a bending-torsion coupling beam transfer matrix based on MSTMM; determining a transfer matrix of each element, assembling the transfer matrixes into a total transfer matrix, and establishing a system overall dynamic model; superposing a rigid center and a mass center in the transfer matrix, and solving the kinetic model to obtain key parameters of a binary flutter model, namely rudder blade pure bending and pure torsion frequencies; taking a cross section of a 3 / 4 blade extension part, and establishing a binary airfoil nonlinear flutter model; solving the two-dimensional airfoil nonlinear flutter model, and solving the time domain response of the two-dimensional airfoil nonlinear flutter model. According to the method,key kinetic parameters, namely pure bending and pure torsion frequencies of the rudder system, required by the binary flutter model are calculated by adopting the MSTMM, a modeling thought of the binary airfoil flutter model considering gap nonlinearity and geometric nonlinearity is provided, and an effective technical approach is provided for nonlinear hydroelasticity research of the rudder system.

The invention discloses a load controllable transmission structure topological optimization method based on geometric nonlinearity. The method is used for solving the technical problem that an existing load controllable transmission structure topological optimization method is poor in practicability. According to the technical scheme, the method comprises the steps that firstly, an auxiliary rod unit is added, constraint node loads are converted into constraint node displacement, and then load controllable transmission is achieved through the ratio of constraint node displacement, so that load controllable transmission can be achieved in geometric nonlinearity topological optimization, the technical problem that in the prior art, only the integral rigidity performance is considered and the structural partial performance is neglected in geometric nonlinearity topological optimization is solved, meanwhile, constraint modeling optimization and rapid model modification are promoted, and the method has the high flexibility, universality and accuracy and the good practicability.

The invention discloses a nonlinear calculation method for a guyed tower stay wire. The geometric nonlinearity of the stay wire is equivalent to a multi-linearity material nonlinear problem through the method, and the method includes the following steps that (1), according to the theoretical calculation relation between the chordwise stress and the chordwise deformation of the stay wire, a series of discrete coordinate points related to the chordwise deformation and the chordwise stress of the stay wire are obtained; (2), the stay wire is equivalent to a material nonlinear rod unit, the stress of the rod unit is a piecewise linear function of strain, and the piecewise linear function is constructed according to the discrete coordinate points in the step (1); (3), according to the piecewise function of the nonlinear material constitutive relation in the step (2), a multi-linearity piecewise function of the rigidity of the stay wire is constructed; (4), a nonlinear balance equation of a stay wire system is used for iteration solution. The nonlinear calculation method is a method for simplifying and processing the stay wire in the finite element calculation process of a guyed tower, the calculation process is simple, the number of iterations is small, accuracy is high, and the nonlinear calculation method can be used for analytical calculation of the guyed tower stay wire.

The invention discloses a passive suspension vibration isolation method and device with zero stiffness characteristics, and relates to the fields of gravity environment ground simulation, low-frequency vibration isolation, ultralow-frequency vibration isolation and the like. The passive suspension vibration isolation method and device with the zero stiffness characteristics are put forward to meetincreasingly higher requirements for space gravity ground simulation experiments in aerospace engineering, and to solve the existing technical problems in the low-frequency and ultralow-frequency vibration isolation. According to the suspension vibration isolation device, based on geometric nonlinear negative stiffness characteristics and the adjustability of geometrical parameters thereof, a vertical elastic element, sliding rails, sliding blocks, horizontal elastic elements and connecting rods are connected to a load, the characteristic of accurate zero-inherent frequency in a design rangeof the device is realized through parameter configuration, and a constant force that is collinear with the direction of gravity of the load and has no relation with displacement of the load can be provided for the load. The resultant force acting on the load in the design range is fixed in value, so that the load is enabled to be in a certain specific gravity environment. The full-frequency-band immunity of the load to the vibration environment is realized, and ultralow-frequency vibration isolation, the zero-rigidity suspension of a modal test and the ground simulation of the spatial gravityenvironment are realized.

The invention is a method for obtaining the curved displacement of a flexible structure by using strain measurements obtained by strain sensors. By obtaining the displacement of structures in this manner, one may accurately construct the deformed shape of the structure under large geometric nonlinear deformations and display said deformed shape in real-time, enabling active control of the structure shape if desired.

The invention discloses a method for calculating the ultimate bearing capacity value of a double-layer cylindrical pressure-resistant shell, and relates to the technical field of deep sea engineering.The method comprises the following steps: firstly, establishing an initial geometric model of the double-layer cylindrical shell, then establishing a finite element model of the double-layer cylindrical shell, determining elastic-plastic parameters of a double-layer cylindrical shell material, defining section parameters and boundary conditions of the finite element model of the double-layer cylindrical shell, and then performing nonlinear solving calculation by adopting a Newton iteration method; and finally, extracting a calculation result of the double-layer cylindrical shell. According tothe invention, inner and outer layer cylindrical shell grid nodes are in one-to-one correspondence, a one-dimensional gap unit is used, a complex contact nonlinear problem is converted into a simplesmall slip model, and the calculation efficiency is improved; meanwhile, geometric nonlinearity, material nonlinearity and boundary nonlinearity are considered, the arc length method is adopted for carrying out nonlinear buckling calculation on the ultimate bearing capacity of the double-layer cylindrical pressure-resistant shell, and the calculation precision is improved.

The invention relates to a thermal axial force measuring device of a framed structure component, comprising a pressure tester with a pressure sensor, a component positioning device, a loading cylinderand a control system thereof, a heating and temperature-controlling device and a restrained beam system, wherein, the restrained beam system is installed on one side of the loading cylinder; a component is positioned on the component positioning device and disposed in the heating and temperature-controlling device; and the mid-span middle point of the restrained beam, the loading cylinder, the component and the pressure are arranged on the same horizontal axial line. The thermal axial force measuring device of the framed structure component has the advantages that the device can directly measure the thermal axial force considering factors of the material nonlinearity, temperature nonlinearity, geometrical nonlinearity, etc. of the component, and the measurement result is accurate. The thermal axial force of the component can be easily calculated by establishing the relationship among the thermal axial force of the component, the load-bearing level, the slenderness ratio of the component, and the rigidity and the temperature of the restrained beam and then determining the total restraint rigidity of the component, thus improving the calculation accuracy of fireproof design and evaluation of building structures.

The invention relates to a nonlinear modal calculation method of a tire structure, and belongs to the field of tire structure design. Comprising the following steps: 1, establishing a tire finite element model, and performing inflation analysis on a tire; 2, performing finite element analysis on the basis of tire inflation to obtain a tangent stiffness matrix of the last step of inflation, and assembling a total mass matrix to form a characteristic value equation; 3, solving a generalized eigenvalue and an eigenvector of the equation, and drawing a vibration mode cloud picture of the tire; and 4, performing tire dynamic performance evaluation according to a result solved in the step 3. An effective calculation method is provided for nonlinear modal analysis of the tire structure, compared with an existing linear modal analysis method, the method provides a nonlinear modal analysis theory, and can be used for solving modal problems such as geometric nonlinearity and material nonlinearity.

The invention discloses an inhaul cable equivalent pretension determination method which is based on a nonlinear implicit equation structure and a steffensen iteration method, and under the condition that a structural load and a supporting state are known, a cable force value of an inhaul cable in a load state is taken as a target, a geometric nonlinear effect is considered, and the equivalent pretension of the inhaul cable is determined. The method comprises the following steps: converting an inhaul cable equivalent pretension determination problem into a problem of solving a plurality of relatively independent nonlinear implicit equations, constructing an iterative formula of equivalent pretension based on a steffensen iterative method principle, and carrying out loop iteration solving to obtain a group of inhaul cable equivalent pretension of which the cable force error is within an allowable error range. The method has the advantages of few iterations, short solving time, convergence efficiency of more than two orders, high applicability and outstanding calculation efficiency and stability, and is widely suitable for determining the equivalent pretension of the inhaul cables of various prestressed structures.

The invention discloses a method and device for determining the axial force loss of a front steering knuckle ball head connecting structure, and relates to the technical field of automobiles, in particular to a method and device for determining the axial force loss of a double-wishbone type front steering knuckle ball head connecting structure under the misuse working condition. According to the method, finite element models of the steering knuckle, the ball head and the bushing are established by means of finite element analysis, the interference fit relation between the steering knuckle and the bushing is considered, and the contact relation of all contact surfaces and the conical surface fit pre-tightening axial force of the bushing and the ball head are considered; in the calculation process, geometric nonlinearity and material nonlinearity are considered, the axial force loss of the double-wishbone type front steering knuckle ball head connecting structure under the misuse working condition is determined according to the change of the axial force of the ball head bolt of the steering knuckle ball head connecting structure along with time under the misuse load effect, and the method has the advantages of being high in calculation precision, high in calculation speed and high in applicability.

The invention discloses a method for calculating the offset of a neutral layer in the bending forming process of a thick plate, and the bending forming process of the thick plate is complex and changeable and comprises nonlinearity of an elastoplastic material, geometric nonlinearity of large deflection and the like and the change condition of stress and strain in the deformation process. At present, the factor of deviation of a neutral layer is not considered in bending forming of a thick plate, and the factor is that the deviation of the neutral layer cannot be accurately given, so that the bending forming quality is poor. In order to improve the bending forming quality, reduce the production cost and improve the productivity, the invention provides a method for calculating the offset of a neutral layer in the bending forming process of a thick plate. A thickness-direction strengthening linear distribution curve is obtained through experimental measurement, then according to an elastic-plastic mechanics theory and a medium-thickness plate bending theory, a limit state is discussed by taking a differential unit body for mechanical analysis when a thick plate is bent, and a calculation formula of theoretical neutral layer deviation is deduced.

The invention belongs to the technical field of polar region engineering material strength calculation, and particularly relates to an ice and structure dynamic coupling calculation method considering geometric nonlinearity. Dynamic coupling calculation of the ice body and the cantilever beam structure is carried out in a mode of combining near-field dynamics and a finite element method, coupling of nonlinear dynamic effects of ice and the structure can be achieved, and the method has the advantages of being high in efficiency, accurate in calculation result and the like. The ice body impact load is solved according to a near-field dynamics method, the ice load acts on a cantilever surface element in a point-to-surface mode, a total stiffness matrix and an equivalent node force are formed by using a nonlinear dynamic finite element, a stress and strain of a cantilever beam are calculated by using the nonlinear finite element method, the new configuration of the cantilever beam is taken as a contact boundary to resolve the ice load, the stiffness matrix and the unbalanced force of the deformed cantilever beam are continuously solved, iterative calculation is carried out, and a final nonlinear dynamic coupling result of the ice body and the cantilever beam is calculated by judging whether the unbalanced force is converged or not.

The invention discloses a method for analyzing angular motion characteristics of a double-spinning projectile under geometric nonlinearity. The method comprises the following steps: step 1, establishing a nonlinear angular motion equation of the double-spinning projectile about an attack angle alpha, a sideslip angle beta, a pitch angle speed omega z and a yaw angle speed omega y; 2, taking a pitching rudder deflection angle delta z and a yawing rudder deflection angle delta y as parameters, and determining a Jacobian matrix of the angular motion system corresponding to the nonlinear angular motion equation established in the step 1 in a balanced state; 3, determining the necessary and sufficient conditions of the angular motion system in a stable balance state; 4, determining boundary conditions required to be met by the deflection angle of the yawing rudder when the angular motion system is stable; and 5, carrying out dimension reduction processing on the angular motion system, and determining motion characteristics of the double-spin projectile near a bifurcation point in a balanced state by carrying out reduction analysis on the nonlinear angular motion equation described in the step 1.

The invention discloses a zero-frequency vibration reduction device and a manufacturing method. The zero-frequency vibration reduction device comprises a plurality of yoke plates (1), a protective shell (2), an elastic piece (3) and a heavy block (4). The elastic piece (3) can extend and is arranged in the hollow part of the protective shell (2), and the heavy block (4) is suspended on the elasticpiece (3). The yoke plate (1) is hinged to the protective shell (2). The device is suspended on a multi-split transmission conductor through a yoke plate (1). The geometric nonlinear elastic piece isintroduced to reduce vibration in a wide vibration frequency domain, the yoke plate can be connected to a wire and can also be connected with the wire through the eight-split wire clamp, vibration reduction of multiple strands of wires through a single device is achieved, and the application range is wide. The device has the characteristic of multidirectional vibration, the heavy block not only can move up and down, but also can move vertically and move in other directions due to the sum of orthogonal vectors of the heavy block and the heavy block, vibration in all directions caused by external factors to the power transmission wire can be absorbed, and the device can be installed and used under various working conditions.

The invention relates to the technical field of anti-seismic structures, and discloses a force-displacement hybrid control method for a three-degree-of-freedom loading system. It includes the following process: issue the target displacement, target rotation angle and target axial force commands to the three-degree-of-freedom loading system, obtain the target displacements of the three actuators through nonlinear transformation, and act on the specimen; Set the LVDT displacement sensor, collect the displacement of the LVDT displacement sensor, and collect the displacement and output of each actuator at the same time; obtain the actual displacement and rotation angle of the test piece through the nonlinear transformation of the displacement of the LVDT displacement sensor, and convert the actual displacement of the actuator to The actual axial force of the specimen is obtained through nonlinear transformation with the output force; the actual displacement, rotation angle and axial force are transmitted to the loading system for feedback control, and the above process is repeated through the correction of the PI controller to achieve the target command of the specimen. This scheme adopts LVDT displacement sensor, and considers the geometric nonlinearity of the loading system at the same time, which improves the accuracy of the test system.

The invention discloses a method for predicting the coupled response of vortex-induced vibration in the cross-flow direction and the downstream direction of a rigid cylinder, which mainly includes the following steps: 1) establishing a vibration control equation in which the cross-flow direction and the downstream direction are mutually coupled; 2) based on the finite difference method Solve the coupled vibration governing equations; 3) Calculate and analyze the examples based on the analyzed data. The invention studies the coupled vibration response of the rigid cylinder in the cross-flow and forward-flow directions. A complete cross-flow and downstream coupled vibration model is established to analyze the vortex-induced vibration response prediction problem of a rigid cylinder considering both cross-flow vibration, downstream vibration and structural geometric nonlinearity. The model can well simulate the structure locking and displacement catastrophe.

The invention discloses a method for constructing an undercarriage model and a device thereof, and the method comprises the steps: building a first undercarriage beam equation based on a partial differential equation according to a geometric nonlinear composite beam which is a strut part of an undercarriage; projecting the first undercarriage beam equation onto a modal basis to convert the first undercarriage beam equation based on the partial differential equation into a second undercarriage beam equation based on an ordinary differential equation; and performing linear order reduction on the second undercarriage beam equation to obtain a low-order undercarriage model. According to the method, deformation load information of each point of the undercarriage can be directly obtained in the model, the vibration condition of the undercarriage can be analyzed conveniently, the equation is projected to a modal basis, a nonlinear partial differential equation is converted into an ordinary differential equation which is easy to solve in time, the model order reduction process is simplified to a great extent, and the model accuracy is greatly improved, so that the method has guiding significance on design model predictive control.