Six-degree-of-freedom loading device used in drum-type geotechnical centrifuge

Abstract

The invention relates to a six-degree-of-freedom loading device used in a drum type geotechnical centrifuge, and belongs to the technical field of centrifugal test, the loading device comprises a centrifuge model box, an electric servo push rod, an angular displacement servo system, a linear displacement platform, a displacement sensor array, a six-degree-of-freedom positioning block, a basic model and a connector; the linear displacement platform is fixed above two parallel edges of the centrifugal machine model box; the linear displacement platform, the electric servo push rod and the angular displacement servo system are sequentially hinged, and the angular displacement servo system is connected with the six-degree-of-freedom positioning block and the basic model through a connector. According to the device, the six-degree-of-freedom loading test of a basic model can be realized through the combined movement of the electric servo push rod, the angular displacement servo system and the linear displacement platform.

Description

Technical Field

[0001] The invention belongs to the technical field of centrifugal testing and relates to a six-degree-of-freedom loading device used in a drum-type geotechnical centrifuge. Background Art

[0002] Scale model testing is a testing method that uses a reduced-scale physical model to simulate a real engineering or physical system. The basic idea of this method is to maintain geometric, material, and dynamic similarities between the model and the prototype by reducing the size, so that similar behavior to the prototype can be observed and measured in the model test.

[0003] In geotechnical engineering, the mechanical properties of soil vary with stress levels, and deadweight stress is the primary component of soil stress levels. Because the length-deadweight relationship is cubic, under conventional laboratory conditions, the deadweight stress of a smaller scale model will be much lower than that of the prototype, thus failing to reproduce the physical and mechanical properties of the prototype. Hypergravity centrifugal model testing simulates amplified gravitational acceleration through the action of centrifugal acceleration, compensating for the inconsistent stress levels caused by model scaling, thereby reproducing the properties of the prototype rock, soil, and structure. Soil materials used in hypergravity simulations can better reflect the prototype soil's granularity, stress correlation, frictional properties, strong nonlinearity, dilatancy, multiphase behavior, and stress history correlation.

[0004] A drum geocentrifuge is an experimental device used to simulate a hypergravity environment to study the mechanical behavior and engineering properties of soil. The centrifuge simulates hypergravity conditions by rotating a large cylinder (drum) to generate centrifugal acceleration. This equipment is commonly used to simulate the behavior of underground structures (such as foundations, tunnels, etc.) under different groundwater levels, soil densities, and stress conditions. In a drum geocentrifuge, soil samples are usually placed in a model that simulates the underground structure and then tested by the hypergravity generated by the high-speed rotating drum. By monitoring and measuring parameters such as the deformation and stress distribution of the soil in the model, researchers can obtain important information about the mechanical behavior of the soil under different conditions. Summary of the Invention

[0005] The present invention proposes a six-degree-of-freedom loading device for use in a drum geotechnical centrifuge, which is used to solve the problem of loading test of arbitrary spatial trajectory and arbitrary six-degree-of-freedom load of the basic model in centrifugal test. Through the combined movement of the electric servo push rod, the angular displacement servo system and the linear displacement platform, the device can plan the translation and rotation trajectory and load along the X, Y and Z axes, and can realize the load and displacement controlled loading test of the three-dimensional arbitrary trajectory of the basic model.

[0006] The present invention is achieved through the following technical solutions:

[0007] A six-degree-of-freedom loading device for a drum geotechnical centrifuge comprises a centrifuge model box, an electric servo push rod, an angular displacement servo system, a linear displacement platform, a displacement sensor array, a six-degree-of-freedom positioning block, a base model, and a connector;

[0008] The centrifuge model box is filled with soil, the basic model is arranged in the centrifuge model box, partially buried in the soil, and the top is connected to a six-degree-of-freedom positioning block;

[0009] The angular displacement servo system includes a rotary actuator, an angular displacement servo system base and a six-degree-of-freedom load sensor, wherein the middle portion of the angular displacement servo system base is hollow, the rotary actuator is embedded in the angular displacement servo system base, the six-degree-of-freedom load sensor is connected to the rotary actuator, and the six-degree-of-freedom load sensor is connected to the six-degree-of-freedom positioning block via a connector;

[0010] Two linear displacement platforms are provided, which are symmetrically arranged on two parallel edges outside the centrifuge model box. The linear displacement platforms include linear guide rails and slides, and the slides are slidably connected to the linear guide rails.

[0011] The electric servo push rod includes a push rod and a linear motor. The two ends of the push rod are respectively hinged to the slide and the angular displacement servo system base. The linear motor is coaxially arranged with the push rod to drive the push rod to perform telescopic movement.

[0012] The displacement sensor array includes multiple laser displacement sensors arranged in the centrifuge model box, which are aligned with the marking points on the six-degree-of-freedom positioning block and are used to measure the horizontal, vertical, up and down displacements and pitch, roll, and yaw angles of the basic model during the loading process, a total of six degrees of freedom.

[0013] Furthermore, eight angular displacement servo system hinge supports are arranged circumferentially along the hollow outer side of the angular displacement servo system base, with two in each group and four groups arranged at equal intervals. The two angular displacement servo system hinge supports in each group are close to each other with an angle of 30°. The end of the push rod is a ball joint, which is hinged to the angular displacement servo system hinge support.

[0014] Furthermore, two linear displacement platform hinge supports are provided above the slide, and the end of the push rod is a ball joint, which is hinged to the linear displacement platform hinge supports.

[0015] Furthermore, the displacement sensor array includes 8 laser displacement sensors, namely 4 X-direction laser displacement sensors and 4 Y-direction laser displacement sensors. 4 are set on the front and side of the centrifuge model box, with the front being the Y-direction laser displacement sensor and the side being the X-direction laser displacement sensor. 4 marking points are set on the front and side of the six-degree-of-freedom positioning block, and the 8 laser displacement sensors are aligned with the 8 marking points respectively.

[0016] Furthermore, the six-degree-of-freedom positioning block is a thin-walled aluminum alloy cube, and the marking point is made of white titanium dioxide.

[0017] Furthermore, the basic model is an aluminum alloy thin-walled cylinder with a cover on the top.

[0018] Furthermore, the connector is a rigid connector or a flexible connector. The rigid connector is a group of six metal rods of equal length with threads at both ends, and the two ends are respectively connected to the six-degree-of-freedom positioning block and the six-degree-of-freedom load sensor; the flexible connector is composed of two metal connecting plates with bolt connection holes and a steel wire rope. A metal hanging ring is provided on the surface of the metal connecting plate, and the two ends of the steel wire rope are connected to the hanging ring. The metal connecting plate is respectively connected to the six-degree-of-freedom positioning block and the six-degree-of-freedom load sensor.

[0019] The beneficial effects of the present invention are:

[0020] Through the combined motion of the electric servo push rod, angular displacement servo system and linear displacement platform, the device can plan the translation and rotation trajectories and loads along the X, Y and Z axes, and can realize load and displacement controlled loading tests on arbitrary three-dimensional trajectories of the basic model. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural schematic diagram of the present invention;

[0022] Figure 2 It is a cross-sectional view from the main perspective of the present invention;

[0023] Figure 3 Detailed schematic diagram of one side linear displacement platform, electric servo push rod, and angular displacement servo system of the present invention;

[0024] Figure 4 Schematic diagram of the structure of the angular displacement servo system of the present invention;

[0025] Figure 5 Detailed schematic diagram of the angular displacement servo system, rigid connector, six-degree-of-freedom positioning block and basic model of the present invention;

[0026] Figure 6 Detailed schematic diagram of the angular displacement servo system, flexible connector, six-degree-of-freedom positioning block and basic model of the present invention;

[0027] Figure 7 This is a schematic diagram of the bolt connection between the six-degree-of-freedom positioning block and the basic model of the present invention.

[0028] In the picture:

[0029] Centrifuge model box 1, electric servo push rod 2, push rod 21, linear motor 22, angular displacement servo system 3, rotary actuator 31, angular displacement servo system base 32, six-degree-of-freedom load sensor 33, angular displacement servo system hinge support 321, linear displacement platform 4, linear guide rail 41, slide 42, linear displacement platform hinge support 421, displacement sensor array 5, six-degree-of-freedom positioning block 6, marking point 61, basic model 7, connector 8, rigid connector 801, flexible connector 802, metal connecting plate 8021, wire rope 8022. DETAILED DESCRIPTION

[0030] The following further describes the structure of the present invention or the technical terms used in the present invention. These descriptions are merely examples of how the present invention is implemented and do not constitute any limitation to the present invention.

[0031] In the description of the present invention, it should be understood that the terms "upper," "lower," "front," "back," "left," and "right" and the like, indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the indicated positions or components must have a specific orientation, be constructed, or operate in a specific orientation, and are therefore not to be construed as limitations of the present invention. Furthermore, the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

[0032] In the description of the present invention, unless otherwise specified or limited, the terms "connected" and "fixed" should be understood in a broad sense. For example, "fixed" can mean fixed connection, detachable connection, or integration; it can mean direct connection or indirect connection through an intermediate medium; it can mean internal communication between two elements or interaction between two elements, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0033] like Figure 1-7 As shown, a six-degree-of-freedom loading device for a drum geotechnical centrifuge includes a centrifuge model box 1, an electric servo push rod 2, an angular displacement servo system 3, a linear displacement platform 4, a displacement sensor array 5, a six-degree-of-freedom positioning block 6, a basic model 7 and a connector 8.

[0034] like Figure 1 As shown, the cross section of the centrifuge model box 1 is arc-shaped to adapt to the curvature of the centrifugal drum of the drum-type geotechnical centrifuge, and the top is open.

[0035] like Figure 2As shown, soil is contained within centrifuge model box 1. In this embodiment, the soil is standard sand, which is quartz sand processed to meet the requirements of GB / T 14684-2022, "Construction Sand." Foundation model 7 is secured to the bottom of six-degree-of-freedom positioning block 6. Depending on the project's needs, foundation model 7 can be pre-buried or driven into the soil within centrifuge model box 1. Alternatively, foundation model 7 can be directly secured beneath connector 8 for penetration testing.

[0036] like Figure 3 and Figure 4 As shown, the angular displacement servo system 3 includes a rotary actuator 31, an angular displacement servo system base 32, and a six-degree-of-freedom load sensor 33. The center of the angular displacement servo system base 32 is hollow, with the inner diameter of the hollow area slightly larger than the diameter of the rotary actuator 31. The rotary actuator 31 is embedded in the angular displacement servo system base 32. After embedding, the rotary actuator 31 can be fixed by methods including, but not limited to, bonding and welding. Eight angular displacement servo system hinge supports 321 corresponding to the ends of the electric servo actuator 2 are circumferentially welded to the outer side of the hollow area. Each group of two angular displacement servo system hinge supports 321 are arranged at equal intervals. The two angular displacement servo system hinge supports 321 in each group are close to each other, with an angle of 30°. During use, the electric servo actuator 2 can select an angular displacement servo system hinge support 321 from each group for connection according to the load amplitude requirement. Four of the hinge supports are left vacant to switch the maximum load amplitude. The rotary actuator 31 can move with the extension and retraction of the electric servo actuator 2. The six-degree-of-freedom load sensor 33 is connected to the rotary actuator 31 by bolts and can move with the rotation of the rotary actuator 31, that is, rotate around the Z axis, and is used to measure the load on the basic model 7 during the loading process.

[0037] like Figure 3 As shown, the linear displacement platform 4 includes a linear guide rail 41 and a slide 42. The slide 42 is embedded above the linear guide rail 41 and can be driven by the linear guide rail 41 and slide along the direction of the linear guide rail 41, that is, the Y direction at a specified speed. The slide 42 is provided with two linear displacement platform hinge supports 421 arranged along the Y direction above the slide 42 for connecting with the electric servo push rod 2. Figure 2 As shown, two linear displacement platforms 4 are provided, which are respectively installed above two parallel edges outside the centrifuge model box 1 and are arranged in a bilaterally symmetrical manner.

[0038] like Figure 3 As shown, the electric servo actuator 2 comprises a actuator 21 and a linear motor 22. The actuator 21 has ball joints at both ends. The actuator 21 passes through the sleeve of the linear motor 22 and is hinged to the linear platform hinge support 421 and the angular servo system hinge support 321, respectively. The four electric servo actuators 2 extend and retract independently, driving the angular servo system 3 in the X direction and around the X and Y axes.

[0039] like Figure 1 and Figure 2 As shown, the displacement sensor array 5 includes 8 laser displacement sensors, namely 4 X-direction laser displacement sensors and 4 Y-direction laser displacement sensors. Four are set on the front and left side of the centrifuge model box 1, with the front being the Y-direction laser displacement sensor and the left side being the X-direction laser displacement sensor. Four marking points 61 are set on the front and left side of the six-degree-of-freedom positioning block 6, and the 8 laser displacement sensors are aligned with the 8 marking points 61 respectively, for measuring the horizontal, vertical, up and down displacements and pitch, roll, and yaw angles of the basic model 7 during the loading process, a total of six degrees of freedom.

[0040] like Figure 5 and Figure 6 As shown, the six-degree-of-freedom positioning block 6 is a thin-walled aluminum alloy cube with six bolt connection holes on the top and bottom respectively; the marking point 61 is made of white titanium dioxide. Because white titanium dioxide is whiter, the marking point 61 needs to reflect the light beam emitted by the laser sensor. Four are set on the front and left side of the six-degree-of-freedom positioning block 6, arranged in a square.

[0041] The connector 8 is divided into two types, a rigid connector 801 and a flexible connector 802. Figure 5 As shown, the rigid connector 801 is a set of six metal rods of equal length with threads at both ends, and the two ends are screwed into the bolt connection holes of the six-degree-of-freedom positioning block 6 and the six-degree-of-freedom load sensor 33 respectively. Figure 6 As shown, flexible connector 802 consists of two metal connecting plates 8021 with bolt holes and a steel wire rope 8022. Metal connecting plates 8021 are provided with metal eyelets, with both ends of wire rope 8022 connected to the eyelets. Metal connecting plates 8021 are bolted to the bolt holes of the six-degree-of-freedom positioning block 6 and the six-degree-of-freedom load sensor 33, respectively. While rigid connector 801 can transmit both torque and force, measuring the six degrees of freedom of displacement and the three degrees of freedom of bending moment of load, flexible connector 802 transmits only force, not torque. The six degrees of freedom of displacement remain unaffected, while the three degrees of freedom of bending moment of load are reset to zero.

[0042] like Figure 7 As shown, the basic model 7 is a thin-walled aluminum alloy cylinder with a cover on the top. The cover is provided with six bolt connection holes. The basic model 7 is bolted to the six-degree-of-freedom positioning block 6. The cover and the cylinder are integrally formed.

[0043] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent replacements for some of the technical features therein. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A six-degree-of-freedom loading device for a drum geotechnical centrifuge, characterized in that: It includes a centrifuge model box (1), an electric servo push rod (2), an angular displacement servo system (3), a linear displacement platform (4), a displacement sensor array (5), a six-degree-of-freedom positioning block (6), a basic model (7) and a connector (8); The centrifuge model box (1) is filled with soil, and the base model (7) is arranged in the centrifuge model box (1), partially buried in the soil, and connected to a six-degree-of-freedom positioning block (6) on the top; The angular displacement servo system (3) comprises a rotary actuator (31), an angular displacement servo system base (32) and a six-degree-of-freedom load sensor (33); the middle portion of the angular displacement servo system base (32) is hollow; the rotary actuator (31) is embedded in the angular displacement servo system base (32); the six-degree-of-freedom load sensor (33) is connected to the rotary actuator (31); and the six-degree-of-freedom load sensor (33) is connected to the six-degree-of-freedom positioning block (6) via a connector (8); Two linear displacement platforms (4) are provided, and are symmetrically arranged on two parallel edges outside the centrifuge model box (1). The linear displacement platforms (4) include a linear guide rail (41) and a slide (42), and the slide (42) is slidably connected to the linear guide rail (41); The electric servo push rod (2) comprises a push rod (21) and a linear motor (22), the two ends of the push rod (21) are respectively hinged to the slide (42) and the angular displacement servo system base (32), and the linear motor (22) is coaxially arranged with the push rod (21) and is used to drive the push rod (21) to perform telescopic movement; The displacement sensor array (5) includes a plurality of laser displacement sensors arranged in a centrifuge model box (1), which are aligned with the marking points (61) on the six-degree-of-freedom positioning block (6) and are used to measure the horizontal, vertical, up-and-down displacements and pitch, roll, and yaw angles of the base model (7) during the loading process, a total of six degrees of freedom.

2. The six-degree-of-freedom loading device for a drum geotechnical centrifuge according to claim 1, characterized in that: Eight angular displacement servo system hinge supports (321) are arranged circumferentially along the hollow outer side of the angular displacement servo system base (32), with two forming a group and four groups being arranged at equal intervals. The two angular displacement servo system hinge supports (321) in each group are close to each other with an angle of 30 degrees. The end of the push rod (21) is a ball joint, which is hinged to the angular displacement servo system hinge support (321).

3. The six-degree-of-freedom loading device for a drum geotechnical centrifuge according to claim 1, characterized in that: Two linear displacement platform hinge supports (421) are provided above the slide (42), and the end of the push rod (21) is a ball joint, which is hinged to the linear displacement platform hinge supports (421).

4. The six-degree-of-freedom loading device for a drum geotechnical centrifuge according to claim 1, characterized in that: The displacement sensor array (5) includes eight laser displacement sensors, four X-direction laser displacement sensors and four Y-direction laser displacement sensors, four of which are arranged on the front and side of the centrifuge model box (1), the front being a Y-direction laser displacement sensor and the side being an X-direction laser displacement sensor. Four marking points (61) are arranged on the front and side of the six-degree-of-freedom positioning block (6), and the eight laser displacement sensors are aligned with the eight marking points (61).

5. The six-degree-of-freedom loading device for a drum geotechnical centrifuge according to claim 4, characterized in that: The six-degree-of-freedom positioning block (6) is a thin-walled aluminum alloy cube, and the marking point (61) is made of white titanium dioxide.

6. The six-degree-of-freedom loading device for a drum geotechnical centrifuge according to claim 1, characterized in that: The basic model (7) is an aluminum alloy thin-wall cylinder with a cover on the top.

7. The six-degree-of-freedom loading device for a drum geotechnical centrifuge according to claim 1, characterized in that: The connector (8) is a rigid connector (801) or a flexible connector (802). The rigid connector (801) is a group of six metal rods of equal length with threads at both ends, and the two ends are respectively connected to the six-degree-of-freedom positioning block (6) and the six-degree-of-freedom load sensor (33); the flexible connector (802) is composed of two metal connecting plates (8021) with bolt connection holes and a steel wire rope (8022). Metal rings are provided on the surface of the metal connecting plate (8021), and the two ends of the steel wire rope (8022) are connected to the rings. The metal connecting plate (8021) is respectively connected to the six-degree-of-freedom positioning block (6) and the six-degree-of-freedom load sensor (33).

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