30 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 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 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 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 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 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.

The invention discloses a low-frequency quasi-zero-stiffness vibration isolator integrated with double geometric nonlinear structures, belongs to the field of low-frequency quasi-zero-stiffness vibration isolation devices, and aims to solve the problem that an existing nonlinear quasi-zero-stiffness vibration isolation system cannot achieve the vibration isolation effect at a lower frequency, a larger working interval and a wider frequency range. According to the low-frequency quasi-zero stiffness vibration isolator integrated with the double geometric nonlinear structures, an X-shaped structure serves as a supporting body, and it is guaranteed that the vibration isolator has the better bearing capacity and stability in the working process; a horizontal spring (or two inclined springs) structure is introduced to provide positive stiffness to eliminate negative stiffness existing in the structure, it is guaranteed that the structure cannot be unstable and damaged in the working process, meanwhile, the quasi-zero stiffness interval of the structure is widened, the vibration isolation effect can be achieved in lower frequency, a larger working interval and a wider frequency range, and the service life of the vibration isolator is prolonged. And the structural stability is ensured while low-frequency vibration isolation is performed.