47 results about "Bending strain" patented technology

The invention provides a steel truss arch bridge suspender fatigue damage engineering evaluation method considering a bending effect, which comprises the following steps: firstly, distinguishing load working conditions according to a lane where a train is located and the number of carriages, comprehensively considering the influence of the bending effect, and simplifying the evaluation method by analyzing the influence degree of the transverse position of the train on suspender fatigue damage; then, axial strain epsilon < axial > and bending strain epsilon < bending > data of the shortest suspender under various working conditions are extracted and checked with health monitoring data, the influence of train bending behaviors, lanes where the train is located and the number of carriages on fatigue damage of the shortest suspender is determined, and the fatigue damage of the shortest suspender is determined based on a finite element model; evaluating fatigue damage of all suspenders of the full bridge under various load conditions when the bending effect is considered; finally, according to the accumulated fatigue damage rate, the fatigue damage grade and the maintenance period of the suspender are proposed, the fatigue performance of the steel truss arch bridge suspender is evaluated based on health data and numerical simulation, and a reference basis is provided for daily maintenance of the rigid suspender of the bridge.

The application provides a bending deformation pipe section identification method and device, electronic equipment and storage medium. The method comprises the following steps: obtaining first strain data measured by an inertial measurement unit (IMU); obtaining a bending strain curve according to the first strain data; determining a wave crest in the bending strain curve, wherein the bending strain value of the wave crest is greater than a preset value; obtaining a to-be-identified pipe section, wherein the to-be-identified pipe section is a pipe section corresponding to a preset interval on both sides of the wave crest in a pipeline; inputting second strain data corresponding to the to-be-identified pipe section into a pipe section type identification model to obtain a pipe section abnormal type of the to-be-identified pipe section. According to the method, the to-be-identified pipe section is determined according to the obtained first strain data, and the second strain data corresponding to the to-be-identified pipe section is input into the pipe section type identification model, so that the pipe section abnormal type of the to-be-identified pipe section can be obtained. The judgment of the pipe section abnormal type does not need to be manually performed, time and manpower can be saved, a unified judgment standard is provided, and the judgment efficiency of the pipe section abnormal type is improved.

A method for calculating the in-plane nonlinear deformation of an arch structure with axial defects in a Cartesian coordinate system is presented. This method is based on two states of the arch structure's curve element in the Cartesian coordinate system: an ideal axis and an actual axial defect. It derives the changes in the arc length and curvature of the curve element before and after deformation, obtaining expressions for the nonlinear compressive and bending strains in the in-plane of the arch structure with axial defects in the Cartesian coordinate system. The method also derives the nonlinear equilibrium differential equations in the in-plane of the arch structure with axial defects in the Cartesian coordinate system, obtaining solutions that satisfy the mechanical and geometric boundaries of the arch structure with axial defects. Finally, the method derives the nonlinear equilibrium governing equations in the in-plane of the arch structure with axial defects, ultimately obtaining the solution to the nonlinear mechanical problem in the in-plane of the arch structure with axial defects in the Cartesian coordinate system. This method can obtain the essence of the nonlinear mechanical problem of the arch structure with axial defects in the Cartesian coordinate system, filling the gap in the nonlinear strain-displacement expression for the in-plane of the arch structure with axial defects in the Cartesian coordinate system.

The invention belongs to the technical field of ship construction processes, and particularly discloses a detection method and an adjustment method for the centering state of a shaft system after ship launching, and the detection method specifically comprises the steps: carrying out the detection of the centering state of the shaft system after ship launching through the actual displacement and bearing load of a bearing in the to-be-detected shaft system before and after ship launching; a bearing load change value and an actual displacement change value caused by ship launching are obtained through calculation, and whether the shafting centering state is changed or not after ship launching is determined according to the bearing load change value and the actual displacement change value caused by ship launching; the actual displacement and the bearing load of the bearing in the to-be-measured shafting are obtained by the following steps: collecting the vertical bending strain of the shaft of the to-be-measured shafting at the strain measuring point, then calculating to obtain the actual vertical bending moment at the strain measuring point, and then calculating the actual displacement and the bearing load of the bearing in the to-be-measured shafting. On the premise that the construction difficulty and efficiency are not affected, the quality problem of shafting installation is controlled in the construction stage, and the shafting centering state of the naval vessel after being launched is greatly optimized.

The invention provides a hierarchical mixture design index and optimization method according to functional requirements of different pavement layers (a surface layer, a middle surface layer and a lower surface layer) in combination with climate zoning and traffic load characteristics. According to the method, key mechanical parameters (the dynamic stability of a surface layer is greater than or equal to 6000 times / mm, and the low-temperature bending strain of a lower surface layer is greater than or equal to 2500 mu epsilon) are determined according to the horizon function, and then the mineral aggregate gradation and the special asphalt dosage are optimized through coupling analysis of volume parameters (the void ratio is 3%-5%, and the mineral aggregate void ratio is greater than or equal to 17%) and mechanical properties. And meanwhile, a bonding layer interface shear strength test (greater than or equal to 1.2 MPa) is introduced, so that the structural integrity is ensured.

This invention discloses a stress-reducing fixing structure for a sliding rotor, relating to the field of shaft support structure technology. It includes a rotor body sleeved around the outer periphery of a main shaft. Multiple pressure-relief grooves are spaced circumferentially on the cylindrical wall of the rotor body. These grooves extend radially inward from the inner periphery and spirally along the shaft hole axis, creating a deformation avoidance space within the rotor body. Multiple flexible support arms are formed between adjacent pressure-relief grooves. When the main shaft is heated and generates a radial expansion greater than that of the rotor body, the flexible support arms are radially compressed by the main shaft and undergo elastic bending deformation into the pressure-relief grooves, converting radial displacement into bending strain. This adaptively absorbs and reduces the stress between the main shaft and the rotor body. This invention effectively solves the stress concentration problem caused by differences in thermal expansion coefficients under high-temperature conditions without changing the materials or sacrificing assembly rigidity and rotational accuracy, significantly improving the reliability and service life of the equipment.

The application discloses a rotating machinery friction fault detection method based on a strain test technology, relates to the technical field of friction fault detection, and solves the technical problem of low recognition accuracy of friction faults, and the technical solution is characterized in that the strain test technology is used to convert a bending strain signal into a voltage signal, and the interference of other factors in the vibration signal is avoided. The strain technology has high precision and can reflect extremely tiny thermal bending deformation, and can identify the friction in the early stage. The bending strain of the rotor in the running state is collected, and the change trend is observed, and when periodic fluctuation or divergence occurs, the occurrence of the friction fault can be judged. Meanwhile, the friction range can be roughly judged according to the strain values of different sections, and the diagnosis reference for the rotor friction fault treatment is provided.

The application discloses a kind of ultra-high strength automobile steel plate limit tip cold bending strain calculation method, system and equipment, and it is related to the field of automobile.Based on the relationship between the strain and bending angle provided by the application, the fracture strain under the limit tip cold bending working condition can be predicted according to the measured cold bending angle, so as to quantitatively evaluate the bending resistance of the material according to the cold bending angle-strain relationship.Further, the cold bending angle-strain relationship calculated by the method of the application can be input into the finite element simulation model, and directly used for the fracture toughness evaluation of parts and the CAE analysis of the whole vehicle.The relationship between the strain and bending angle provided by the application only needs to be substituted by the pressing displacement, sheet thickness and cold bending angle to solve the critical fracture strain of the material, that is, through the simple and easy-to-measure cold bending angle parameter, the complex limit tip cold bending fracture strain parameter is obtained, which solves the problem of difficult fracture strain measurement and reduces the equipment investment and time cost of actual production.

The invention relates to the technical field of bridge engineering, and provides a multi-objective intelligent optimization method for finished cable force of a cable-stayed bridge. The multi-objective intelligent optimization method comprises the following steps: establishing a finite element model of the cable-stayed bridge, and primarily homogenizing the cable force by adopting a minimum bending energy method according to a principle that the cable force of a long cable is large and the cable force of a short cable is small; constructing a support vector machine regression small sample proxy model based on a radial basis kernel function, carrying out cross validation and tuning on hyper-parameters by adopting grid search and a leave-one-out method, and representing a mapping relation between cable force and structural responses such as bending moment and displacement; establishing a multi-objective optimization model taking bending strain energy and resultant displacement as optimization objectives; according to the multi-target intelligent optimization method based on the double-optimal strategy, comprehensive optimal cable force and partial optimal cable force are used as guidance, common cable force is guided to approach to two types of excellent cable force, iterative optimization is adjusted through a direction factor and a strength factor, a Pareto optimal cable force candidate set is updated through non-dominated sorting, hypercube grids and a congestion degree strategy, and the optimal cable force is obtained. And finally obtaining a comprehensive optimal cable force as a finished cable force of the cable-stayed bridge.

The invention provides a gravity angle sensor, a calibration method thereof and a gravity compensation method applying the gravity angle sensor, and belongs to the technical field of sensors and intelligent control. The sensor comprises a sensor frame, a flexible spring piece assembly, a mass block and a differential strain measurement unit, the flexible spring piece assembly is symmetrically connected with the mass block and the sensor frame, and the flexible spring piece assembly is configured to generate bending deformation perpendicular to the axial direction of the flexible spring piece assembly under the action of a gravity component; the differential strain measurement units are arranged on the convex side and the concave side when the flexible spring piece is bent and used for detecting the bending strain difference perpendicular to the axial direction. High-precision and real-time gravity compensation under a dynamic working condition is realized by calibrating a maximum strain difference value, measuring a current strain difference in real time, calculating a specific value and directly generating a gravity compensation amount without resolving an attitude angle and breaking through range limitation of a cosine function. According to the scheme, mechanical friction is eliminated, sensitivity and stability are improved, and the method is suitable for high-dynamic force control systems such as robots and precision platforms.

The utility model belongs to mechanical analysis equipment technical field provides a kind of engineering component internal force analysis appearance, the engineering component internal force analysis appearance includes mandrel and multiple component module;Multiple component module is successively sleeved on mandrel and mutually abuts and forms engineering component model, and component module is slidably engaged with mandrel;At least the outer peripheral surface or axial end surface of two adjacent component modules is respectively provided with angle scale stripe and pointer stripe;The outer peripheral surface of each component module is provided with grid stripe.The engineering component internal force analysis appearance provided by the utility model, the position of angle scale stripe is pointed to by pointer stripe, and torsion angle is directly and intuitively shown, and then torsion strain is directly and intuitively shown;When simulating the bending condition of engineering component, component module will turn over outward, and the outer side portion is mutually far away, and then bending strain is directly and intuitively shown.

The application provides a helicopter landing gear landing load measurement method, the method comprises the following steps: pasting at least 10 strain gauges at the wheel shaft position; obtaining the tensile strain, shear strain, bending strain and torsional strain of the strain gauges; determining the heading load, lateral load and / or vertical load when the helicopter landing gear lands based on the tensile strain, shear strain, bending strain and torsional strain of the strain gauges; the application realizes the analysis and calculation of the transmission of the three-directional ground loads to the landing gear wheel shaft during the landing of the helicopter, the reverse derivation process of strain to load is supplemented by the forward derivation of traditional load to strain, the interference of the nonlinear superposition of combined loads on the solution of ground load calculation is eliminated, the position requirement that the strain gauge layout needs to meet the unidirectional load sensitivity is reduced, and good universality is achieved.

The application belongs to the technical field of strain type multi-dimensional force sensor, and discloses a six-dimensional force sensor with four L-shaped elastic beam structures and a strain gauge arrangement method, aiming to solve the core problems of strain dispersion, low sensitivity, serious inter-dimension coupling and large mechanical hysteresis of the existing six-dimensional force sensor. The elastic body is an integral structure, and the core includes an outer circular ring, a central loading platform and four L-shaped elastic beams connecting the two, the four L-shaped elastic beams are distributed at equal intervals of 90 degrees along the circumference of the outer circular ring, and the beam body is mainly subjected to directional bending deformation when loaded, so that a stable strain concentration area can be formed; 12 strain gauges are accurately attached to the maximum bending strain area of the beam body based on finite element simulation, and cooperate with the half-bridge double-working-piece Wheatstone bridge to realize six-dimensional force / torque measurement. The application can effectively reduce the inter-dimension coupling error and mechanical hysteresis, improve the measurement sensitivity and long-term stability, and is suitable for high-precision six-dimensional force measurement scenes such as industrial robot precision assembly, aerospace measurement and control, medical minimally invasive surgery and the like.

The invention relates to the technical field of optical fiber real-time monitoring, in particular to a steel structure platform health monitoring system and method based on optical fiber sensing, and the method comprises the following steps: respectively monitoring a steel beam and a bolt node of a steel structure platform by using an FBG strain sensor and a temperature sensor, and independently monitoring the bending strain of the steel beam by using an FBG curvature meter; after strain and temperature are decoupled, a real strain value is obtained, the steel beam curvature is measured by combining three gratings of a curvature meter, an eccentric threshold value is set, and when the steel beam curvature anomaly exceeds the eccentric threshold value, a steel beam deformation early warning is generated; the pre-tightening force loss rate is calculated by using the real axial strain of the bolt, the node state is dynamically evaluated by combining the curvature anomaly of the steel beam, a yellow alarm and a red alarm are set, maintenance is planned when the yellow alarm is triggered by the loss rate, and emergency disposal is performed when the red alarm is triggered. According to the system and method, thermal expansion and cold contraction errors are eliminated through strain and temperature decoupling, the bending degree of the steel beam is effectively evaluated by means of the FBG curvature meter, safety and stability of the platform are guaranteed, and a maintenance strategy is optimized.

The present application relates to the technical field of bridge engineering, and provides a cable-stayed bridge completion cable force multi-objective intelligent optimization method: a finite element model of the cable-stayed bridge is established, the minimum bending energy method is adopted, and the cable force is initially uniform according to the principle of "long cable force is large, and short cable force is small"; a small sample support vector machine regression proxy model based on a radial basis kernel function is constructed, grid search and leave-one-out cross-validation are adopted to optimize the super parameters, and the mapping relationship between the cable force and the bending moment, displacement and other structural responses is represented; a multi-objective optimization model with bending strain energy and combined displacement as optimization objectives is established; and a multi-objective intelligent optimization method based on a double optimization strategy is used to guide the general cable force to approach the two types of excellent cable forces, the iteration optimization is adjusted through a direction factor and a strength factor, the Pareto optimal cable force candidate set is updated through a non-dominated sorting, a hypercube grid and a crowding degree strategy, and finally a comprehensive optimal cable force is obtained as the cable-stayed bridge completion cable force.

The invention discloses a dynamic bending self-adaptive flexible connection electrophoresis insulation process, and belongs to the technical field of electrical insulation. According to the process, a miniature strain gauge is embedded in the surface of an electrical flexible connection main body, the dynamic bending strain is detected in real time, and the current bending curvature radius is calculated; the control unit dynamically adjusts the electric field intensity of the electrophoresis system according to a preset curvature-electric field mapping relation; the flexible connection main body is arranged in epoxy-silicon dioxide sol, the sol is directionally deposited under the action of an electric field to form an insulating layer, and the thickness of the insulating layer is dynamically adjusted along with the bending curvature radius and is in a negative correlation relationship. Self-adaptive distribution of the thickness of the insulating layer is achieved, the thickness is increased in a violent bending area to resist tensile stress, the thickness is reduced in a smooth area to maintain flexibility, and the insulation reliability and mechanical durability of flexible connection under the dynamic working condition are effectively improved.

An inertial-based method and system for detecting bending strain in a pipeline, a device, and a medium. The method comprises: acquiring position information of a pipeline of a preset length, collected by an IMU (S1); performing a wavelet transformation on the position information to obtain an initial target position information (S2); performing sliding filtering on the initial target position information through a sliding window according to a preset sequence and window width, and determining a data window at each sliding of the sliding window on the initial target position information (S3); determining a fit coefficient by the minimum mean squared error depending on the respective data windows (S4).Using a numerical value at the center of each data window as a filter value, determining a filter sequence based on the respective filter values ​​and the fit coefficient, and using the filter sequence as the second target position information (S5); determining a pipe bending strain force based on the second target position information (S6); detecting the pipe bending strain based on the pipe bending strain force (S7). This method removes noise twice, thereby improving the accuracy of the position information calculated by an inertial measurement unit (IMU) and solving the problem of noise affecting the position information calculated by the IMU.

The invention relates to the technical field of submarine cable bending measurement, and discloses a submarine cable laying curvature measuring device, which comprises a head end annular block and a submarine cable sleeve, and further comprises a connecting mechanism, and the connecting mechanism comprises a plurality of circular connecting blocks and a tail end connecting block which are sequentially arranged behind the head end annular block. Bending strain of the submarine cable is monitored in real time through the fiber grating sensor, wavelength offset is converted into curvature data, seawater in the hollow rubber blocks can generate pressure when the adjacent hollow rubber blocks are in contact due to the fact that the water outlet apertures of the circular water spraying holes are small, and therefore buffering force generated when the adjacent hollow rubber blocks are in contact is increased, and the submarine cable is prevented from being damaged. And the damage caused by rapid bending of the device is further reduced, water sprayed out of the circular water spraying holes correspondingly impacts the outer wall of the submarine cable sleeve, algae and shellfish organisms entering the device from gaps between the circular connecting blocks are removed, and therefore the algae and shellfish organisms are prevented from influencing the submarine cable.

A force detection bone screw device includes a bone screw body, a spring structure, a detection module, and an antenna module. The bone screw body includes a cylinder. The spring structure, the detection module and the antenna module are respectively arranged in the accommodation portion of the column. The spring structure includes a body, a bearing part, a fixing part and at least one bending strain structure. One end of the body is connected to the bearing part, and the other end of the body is connected to the fixing part, and the fixing part is fixed in the cylinder. Each bending strain structure is respectively provided on the body. The body has an axial direction, and each bending strain structure has deformation in at least one direction different from the axial direction. The detection module includes at least one strain element and a sensing component.

According to the present disclosure, an optical cable can be fixed such that the bending strain applied to the periphery of a portion of the optical cable from which an optical fiber is drawn is reduced. This optical panel (100) is provided with: a gripper (13) that grips an optical cable (22); the optical cable connector includes an optical cable (22), and a housing (10) in which an optical fiber (21) led out from the optical cable (22) is routed, the housing (10) is provided with a plurality of attachment portions (16), the gripper (13) has a plurality of fixing portions (46) capable of engaging with the attachment portions (16) of the housing (10), and the number of the attachment portions (16) is greater than the number of the fixing portions (46).

The application discloses a fiber acceleration detector based on a shape-variable cylinder and a method for detecting vibration acceleration. One end of the cylindrical shape-variable cylinder is used as a mounting end. Three axial grooves are arranged on the side wall of the shape-variable cylinder in a circumferential direction and are distributed at an angle of 120 degrees. An optical fiber with a certain pre-stress is fixed in each axial groove by using glue. A grating is engraved on the optical fiber. The shape-variable cylinder detector is mainly made of silica gel, is easy to deform, has good bending strain performance, and has higher sensitivity than common metal structures under the same conditions. The application has the advantages of convenient production, simple structure and accurate measurement.

A device for accurately measuring bending strain of a superconducting strand is provided. The bending strain precision measuring device includes a support frame. A driving mechanism is installed on the upper part of the support frame. An output end of the driving mechanism is sequentially connected with a weighing sensor and a pressure transmission module from top to bottom along the vertical direction. A bending strain module is installed on the lower part of the support frame. In a case that the output end of a driving mechanism moves downwards, the pressure transmission mechanism is capable of applying pressure to the superconducting strand placed on the bending strain module.

The invention discloses a displacement sensor for a micro-Newton-level variable thruster, and belongs to the field of precision measurement. The displacement sensor comprises a polymer film substrate, a strain gate resistor and three compensation resistors, the compensation resistors are all arranged at the top section of the substrate, and the strain gate resistor is arranged at the middle section of the substrate; the length of the bottom section of the substrate is larger than the sum of the length of the top section and the length of the middle section, so that the displacement sensor is of an asymmetric U-shaped bent structure when being installed and used. During use, the displacement sensor converts the relative displacement of the two ends into the change of the bending strain of the polymer film, thereby causing the change of the resistance value of the strain gate resistor. The sensor has the characteristics of high precision, low cost and light weight, can be stably used in a wide temperature range environment, and is easy to install and suitable for various application scenes.

The invention is applicable to the technical field of coaxiality measurement, and provides a detection instrument for coaxiality measurement, which comprises a sensor, an instrument and software, a sensor elastomer is provided with a protective shell, the top end of the sensor elastomer is connected with a connecting plate through a first fixing plate and a second fixing plate, the shell is fixed through the connecting plate, and the cylindrical centering sensor is connected with the instrument. Clamping parts at the two ends are provided with high-precision threads, replacement is convenient, and the service life of the sensor is prolonged. According to the detection instrument for coaxiality measurement, the non-measurement strain gauge is arranged in the detection instrument, and the non-measurement strain gauge and the measurement strain gauge on the centering sensor elastomer are located in the same environment, so that the situation of measurement errors caused by different environment influences is avoided, and the measurement accuracy is improved; the coaxiality is mainly calculated according to the ratio of the maximum bending strain to the average axial strain, the accuracy of the measurement result is improved, the accuracy and the qualified rate of the coaxiality sensor are improved, and the measurement result is more reliable.

The invention relates to the technical field of star sensor support systems, in particular to a star sensor support system deformation field reconstruction method, device and equipment based on strain measurement and a computer storage medium. According to the method for reconstructing the deformation field of the star-sensitive support system, the deformation of the star-sensitive support system is decomposed into three parts of mounting plate deformation, support deformation and support displacement caused by the mounting plate deformation, and reconstruction analysis is carried out on the three parts; solving the relation between the bending strain and the deformation field and between the tension and compression strain and the deformation field through a strain field reconstructed by an inverse distance weighting method; simplifying the star sensor bracket into a beam structure, and deducing a bracket deformation field by using a curvature iteration method based on a strain field reconstructed by a least square method; establishing a geometric relational expression of the deformation of the support and mounting plate assembly, and obtaining a displacement expression of the support on the deformed mounting plate; according to the method, the calculation complexity and the calculation time of a deformation reconstruction technology are effectively reduced.

The present invention discloses a monitoring device for uneven settlement of a steam turbine foundation, comprising a control unit, a mounting base plate, a cylinder, a support plate disposed within the cylinder, an inclined plate, a counterweight, and a strain sensor. The top of the inclined plate is connected to the support plate, and the bottom of the inclined plate is connected to the counterweight. The strain sensor is disposed at one end of the inclined plate near the support plate. The strain sensor is used to collect bending strain data of the inclined plate, and the control unit is used to collect data and perform calculations. The monitoring device for uneven settlement of a steam turbine foundation of the present invention is based on strain measurement technology and has an accuracy of up to 1*10 ‑6 The device has high stability and can be used to monitor the tilt of steam turbine platforms during their long service life.

The invention belongs to the technical field of mine hydrogeology and engineering geology, and particularly discloses a method for calculating the permeability of an aquitard under a high hydraulic gradient condition, electronic equipment and a storage medium. Comprising the following steps: S1, determining initial parameters of an aquitard; s2, calculating bending strain of the aquitard caused by mining; s3, substituting the bending strain into a fracture expansion equation to calculate equivalent permeability; s4, substituting the equivalent permeability into a Forchhemer nonlinear flow equation, and solving the seepage velocity and pressure distribution under the high hydraulic gradient; s5, through iterative updating, the local pressure gradient and the flow velocity obtained through calculation are fed back to the fracture evolution equation at each time step, and the equivalent permeability and the hydraulic condition are updated until a steady state or a preset time step is reached; s6, parameter inversion is carried out, and it is ensured that a calculation result is consistent with a low-gradient experiment result k0. According to the invention, the dynamic evolution characteristics of permeability can be reflected, and the limitation of average permeability is overcome.

The titanium porous body according to the present invention is in a form of a sheet, and has a thickness of 0.3 mm or less, and a bending strain at break of 0.005 or more, wherein, for a three-dimensional surface texture of at least one surface of the titanium porous body, an arithmetic mean height Sa is 2.5 μm or less, a maximum height Sz is 30 μm or less, an aspect ratio Str of the surface texture is 0.93 or more, and an arithmetic mean curvature Spc of a peak is 4.8 (1 / μm) or less.

This application provides a stretchable device and its manufacturing method, relating to the field of display technology, to reduce the risk of fracture of the bending strain layer during stretching. The stretchable device includes: a stretching region and a non-stretching region; a substrate; at least one bending strain layer located on one side of the substrate, covering the stretching region and the non-stretching region in a direction perpendicular to the plane of the substrate; wherein, the surface of the bending strain layer away from the substrate is the upper surface, and the surface closer to the substrate is the lower surface; the portion of the bending strain layer located in the stretching region is the stretching portion, the stretching portion including at least one stretching part, at least a portion of each stretching part having an arc-shaped bending shape, in the portion of the stretching part having an arc-shaped bending shape, the upper surface and the lower surface are concentric arcs, and the central angle corresponding to the arc of the upper surface is the same as the central angle corresponding to the arc of the lower surface.