CN105715724A - Thin-wall energy absorption cylinder and buckling mode controlling method thereof - Google Patents

Abstract

The invention discloses a thin-wall energy absorption cylinder and a buckling mode controlling method thereof. The thin-wall energy absorption cylinder comprises a cylinder body, wherein the cylinder body is composed of a front end which accepts axial impulse load and a back end arranged opposite to the front end; and a plurality of circumferential annular grooves are alternately formed in the outer wall and the inner wall of the cylinder body starting from the front end of the cylinder body. According to the thin-wall energy absorption cylinder, with adoption of initial imperfections, i.e. the annular grooves, formed in the thin-wall cylinder in the length direction, a buckling mode and a plastic hinge formation position of the thin-wall cylinder are effectively controlled, the buckling crushing force course is further effectively controlled by controlling the groove depth variations, the groove widths, pitch of the grooves and the like of the grooves, and thus the purpose of controllably optimizing the axial pressure buckling energy absorption space of the thin-wall cylinder is reached.

Description

Thin-walled energy-absorbing cylinder and its buckling mode control method

technical field

The invention relates to the thin-wall energy-absorbing field, in particular to a thin-wall energy-absorbing structure containing initial defects.

Background technique

For vehicles such as automobiles and high-speed trains, the impact phenomenon has always been an extremely important and unavoidable problem. In recent years, with the rapid increase in the number of automobiles and high-speed trains and the continuous increase in driving speed, the collision problem has become more and more prominent. The rapidly increasing collision accidents will cause heavy personal casualties and property losses. The primary consideration in structural design.

It has long been noted that thin-walled cylinders generally have a stable progressive failure mode under axial compression, absorbing energy through plastic buckling. The thin-walled tube is a traditional energy-absorbing structure and one of the most widely used energy-absorbing structures. It can absorb considerable energy when subjected to axial impact loads. The dynamic elastoplastic buckling of thin-walled cylinders under axial impact loads is a very complex phenomenon. According to the joint influence of geometric parameters, load conditions and material properties of thin-walled cylinders, there are three types of instability modes: dynamic plastic buckling mode, Generally, in the case of high-speed impact, before a large radial displacement occurs, the thin-walled tube will wrinkle along the entire length direction; in the dynamic progressive buckling mode, in the case of low-speed impact, the deformation process is similar to the static case, and the wrinkle It is formed from one end and gradually develops to the other end. This mode is an ideal energy absorption mode; and the Euler bending mode.

Although the energy-absorbing structure of the thin-walled tube has been widely studied and widely used, there are still some problems under the axial impact: 1. The initial peak buckling load is too high, generally more than twice the average crushing load, which will As a result, the effective energy-absorbing space cannot be completely filled; 2. The buckling mode is not completely controllable. In some cases, there will be a mixed mode transitioning from the ring mode (axisymmetric mode) to the diamond mode (non-axisymmetric mode), which is impossible The controlled buckling mode will lead to uncontrollable buckling crush force and instability in the buckling process; 3. The uncontrollable buckling sequence will lead to model instability in some models with relatively large length diameters, and Euler instability is prone to occur .

Contents of the invention

Aiming at the deficiencies in the prior art, the present invention provides a thin-walled energy-absorbing cylinder and a buckling mode control method of the thin-walled energy-absorbing cylinder, thereby reducing the initial peak buckling load on the one hand, and effectively controlling the buckling mode of the thin-walled energy-absorbing cylinder on the other hand. buckling mode.

The scheme of the thin-walled energy-absorbing cylinder is as follows:

A thin-walled energy-absorbing cylinder, comprising a cylinder body, the cylinder body includes a front end receiving an axial impact load and a rear end opposite to the front end, from the front end of the cylinder body, on the outer wall and the inner wall of the cylinder body A plurality of circumferential annular grooves are alternately arranged on the top.

Preferably, the thin-walled energy-absorbing cylinder is a cylinder, an ellipse or a polygon cylinder.

Preferably starting from the front end of the barrel, the maximum depth of the grooves decreases over at least part of the length of the barrel.

Preferably, the maximum depth reduction values between any two adjacent grooves with depth variation are equal.

Preferably, the axial section of the groove is rectangular, semicircular or arc-shaped.

Preferably, the minimum spacing between any two adjacent grooves is equal.

The method of controlling the buckling mode of the above-mentioned thin-walled energy-absorbing cylinder is as follows:

1. The buckling mode of the thin-walled energy-absorbing cylinder is controlled by the size of the dimensionless groove depth parameter, wherein the dimensionless groove depth parameter is the maximum depth of the initial groove located at the front end of the cylinder and the maximum depth of the cylinder The ratio of the wall thickness of the body.

2. Control the buckling mode of the thin-walled energy-absorbing cylinder through the size of the dimensionless groove width parameter, wherein the dimensionless groove width parameter is the maximum width of the groove and the wall thickness of the cylinder and the The ratio of the sum of the maximum depths of the initial grooves at the front end of the body.

The dimensionless groove width parameter is preferably greater than or equal to π/2.

3. Control the buckling mode of the thin-walled energy-absorbing cylinder through the size of the dimensionless half-wavelength parameter, the thin-walled energy-absorbing cylinder is a cylinder, and the dimensionless half-wavelength parameter is represented by the following ratio:

(H+W-h)/sqrt(Dh)

Among them, H is the minimum distance between two adjacent grooves, W is the maximum width of the groove, h is the wall thickness of the cylinder, sqrt(Dh) is the axisymmetric buckling mode of the complete cylinder without grooves under the theoretical half-wavelength.

The present invention arranges the initial defects along the length direction on the thin-walled tube, that is, the annular groove, effectively controls the buckling mode of the thin-walled tube and the position of the plastic hinge formation, and further controls the change of the groove depth and the groove width of the thin-walled tube , groove spacing, etc., effectively control the buckling and crushing force history, so as to achieve the purpose of controllable optimization of the axial buckling energy-absorbing space of the thin-walled cylinder.

Description of drawings

Fig. 1 is a schematic diagram of groove defect arrangement of a thin-walled cylinder according to an embodiment of the present invention;

Fig. 2 is a schematic diagram of the control of groove defects on the formation of plastic hinges in the embodiment shown in Fig. 1;

Fig. 3 is a schematic diagram of the buckling fold model at the groove of the embodiment shown in Fig. 1;

Fig. 4 is a graph of crushing force-displacement curve of a thin-walled cylinder.

In the figure: D: diameter of thin-walled tube, L: length of thin-walled tube, h: wall thickness of thin-walled tube, h ₀ : initial groove depth, t: variation value of groove depth, H: distance between adjacent grooves, W : groove width, m: specific model parameters, F: crushing force.

detailed description

Embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings. It should be noted that, in the case of no conflict, the embodiments of the present invention and the features in the embodiments can be combined arbitrarily with each other.

The thin-walled energy-absorbing cylinder provided by the present invention may be a cylinder, an ellipse or a polygonal cylinder, and includes a cylinder body. The cylinder body includes a front end receiving axial impact load and a rear end opposite to the front end. As shown in FIG. 1 , the thin-walled energy-absorbing cylinder of the embodiment of the present invention is described by taking a cylinder as an example. The upper end of the cylinder is the front end receiving the axial impact load, and the bottom end is the rear end opposite to the front end.

Referring to FIG. 1 , along the length L direction of the thin-walled cylinder, circumferential annular grooves are alternately arranged on the outer wall and the inner wall of the thin-walled cylinder. The axial cross-section of the groove is rectangular, semicircular or arc-shaped, and Fig. 1 shows a groove with a rectangular cross-section. For grooves with different axial sections, the depth and width of the grooves and the distance between two adjacent grooves may have variable values. Therefore, although the embodiment shown in FIG. 1 takes a groove with a rectangular cross-section as an example, where What h ₀ represented was the depth of the initial groove (the first groove), what H represented was the spacing between two adjacent grooves, and what W represented was the width of the groove, but for the present invention, it should be respectively It is understood that h ₀ actually represents the maximum depth of the initial groove, H actually represents the minimum distance between two adjacent grooves, and W actually represents the maximum width of the groove.

Starting from the front end of the barrel, the depth of the groove decreases over at least part of the length of the barrel. As shown in FIG. 1 , it is preferable that the variation value t of the groove depth gradually decreases between adjacent grooves, and the distance H between any two adjacent grooves is preferably equal.

Due to the thinner walls in the grooves, buckling is more likely to occur in the grooves than in a full cylinder. Therefore, using the initial defect on the thin-walled cylinder, that is, the setting of the annular groove, the initial peak buckling load can be effectively removed, so that the initial load is equivalent to the average load level, and no load that significantly exceeds the average crushing force will appear during the entire buckling process. , forming an ideal rectangular energy-absorbing space, which can significantly improve the energy-absorbing effect of the device. At the same time, the buckling sequence is controlled by using the deep groove defect at the front end, and the buckling starting point can be more precisely controlled at the deepest groove at the front end due to the different depths of the grooves along the length of the cylinder, and gradually It develops toward the place where the depth of the groove is small below.

Figure 2 shows a buckling fold formed by a thin-walled cylinder under the action of crushing force F. For the formation of each buckling fold, the impact kinetic energy is absorbed by the plastic bending of the three plastic hinges shown in Figure 2 and the stretching and compression of the material between the plastic hinge lines. The crushing force levels of each buckling fold are equal, which can stabilize the crushing force characteristics, so a controllable and optimized energy-absorbing space (rectangular energy-absorbing space) can be created. Such an energy-absorbing space can maximize the energy-absorbing structure’s ability to absorb energy utility. It can be seen that the groove defect can effectively control the formation of plastic hinges at the defect, and can also control the precise axisymmetric buckling mode (when the thin-walled cylinder is a cylinder, it is the ring buckling mode). At the same time, the sequence of plastic hinge formation can be effectively controlled by using the depth variation of the defect, that is, buckling gradually from deeper grooves to shallower grooves.

From the perspective of the entire length L of the cylinder, the depth of the groove does not have to decrease all the time. As shown in Figure 1, the depth of the groove does not change at h ₀ -mt. At this time, the buckling sequence from top to bottom It has started up smoothly and is controllable, and the buckling mode has stabilized and will not change due to no change in groove depth. Among them, m is a specific model parameter, which is a constant for a specific model and can be determined by conventional experimental methods.

The control method of the buckling mode of the thin-walled energy-absorbing cylinder of the present invention is described below from the perspective of optimizing the energy-absorbing space, which is specifically realized by controlling the following important dimensionless parameters:

(1) Dimensionless groove depth parameter h ₀ /h

This parameter is the ratio of the depth h ₀ of the initial groove to the wall thickness h of the thin-walled cylinder. When the ratio is too large, local buckling easily occurs in the groove area because the energy of local buckling is less than the energy of overall buckling (ie The wall at the groove buckles as a local small thin-walled cylinder), so this parameter cannot be too large, and the upper limit needs to be set according to the specific conditions of the model so that local buckling does not occur.

(2) Dimensionless groove width parameter W/(h+h ₀ )

This parameter determines whether compression occurs between the intact cylinders on either side of the groove when buckling folds form. Referring to the theoretical model shown in Figure 3, when the buckling folds are formed, a semicircle arc is formed at the groove, then when this parameter is greater than or equal to π/2, extrusion will not occur, and when it is less than π/2, due to the width W If the space is not enough to form a semi-circular arc, the complete cylinders on both sides will squeeze each other, which will affect the optimization of the energy-absorbing space.

(3) Dimensionless half-wavelength parameter

Taking a cylinder as an example, this parameter is (H+W-h)/sqrt(Dh). where (H+W-h) is the half-wavelength controlled by this model, sqrt(Dh) is the half-wavelength of the axisymmetric buckling mode of the theoretical complete cylinder, the ratio between this active control quantity and the intrinsic quantity will lead to the buckling When the value is less than a certain range, the axisymmetric buckling mode can be completely controlled; when the value is relatively large, the axisymmetric buckling mode cannot be controlled, and buckling folds do not occur at the groove, which is beyond the control range of this method.

Figure 4 shows the crushing force-displacement curve of a complete thin-walled cylinder, the X-axis represents the displacement, and the Y-axis represents the crushing force. Its high initial peak load will result in an unsatisfactory energy-absorbing space (the space below the wavy line), and the energy-absorbing efficiency is much lower than the expected energy-absorbing efficiency. After the reasonable arrangement and control of the groove defects, the peak load and the average load are adjusted to the same level, which stabilizes the crushing load of each fold during the progressive buckling process, makes the load area uniform, and forms a rectangular controllable energy-absorbing space ( The space below the dotted line), can play the role of the energy-absorbing structure most effectively.

Through the above-mentioned method of the present invention, the controllable energy-absorbing space optimization of the impact buckling energy-absorbing structure of the thin-walled tube can be achieved, and can be applied to the optimized design of energy-absorbing devices for automobiles and high-speed trains, and the optimization of soft landing devices for aircraft and spacecraft design etc.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. A thin-walled energy-absorbing cylinder, comprising a cylinder, the cylinder comprising a front end that accepts an axial impact load and a rear end opposite to the front end, characterized in that: Starting from the front end of the barrel, a plurality of circumferential annular grooves are alternately arranged on the outer wall and the inner wall of the barrel. 2. The thin-walled energy-absorbing cylinder according to claim 1, characterized in that: The thin-walled energy-absorbing cylinder is a cylinder, an ellipse or a polygon cylinder. 3. The thin-walled energy-absorbing cylinder according to claim 2, characterized in that: Starting from the front end of the barrel, the maximum depth of the groove decreases over at least part of the length of the barrel. 4. The thin-walled energy-absorbing cylinder according to claim 3, characterized in that: The maximum depth reduction value between any two adjacent grooves with depth variation is equal. 5. The thin-walled energy-absorbing cylinder according to any one of claims 1-4, characterized in that: The axial section of the groove is rectangular, semicircular or arc-shaped. 6. The thin-walled energy-absorbing cylinder according to any one of claims 1-4, characterized in that: The minimum spacing between any two adjacent grooves is equal. 7. The buckling mode control method of the thin-walled energy-absorbing cylinder according to any one of claims 1-6, characterized in that: The buckling mode of the thin-walled energy-absorbing cylinder is controlled by the dimensionless groove depth parameter, wherein the dimensionless groove depth parameter is the maximum depth of the initial groove at the front end of the cylinder and the maximum depth of the cylinder ratio of wall thickness. 8. The buckling mode control method of the thin-walled energy-absorbing cylinder according to any one of claims 1-6, characterized in that: The buckling mode of the thin-walled energy-absorbing cylinder is controlled by the dimensionless groove width parameter, wherein the dimensionless groove width parameter is the maximum width of the groove and the wall thickness of the cylinder and the The ratio of the sum of the maximum depths of the initial grooves of the front end. 9. The control method according to claim 8, characterized in that: The dimensionless groove width parameter is greater than or equal to π/2. 10. The buckling mode control method of the thin-walled energy-absorbing cylinder according to any one of claims 1-6, wherein the thin-walled energy-absorbing cylinder is a cylinder, characterized in that: The buckling mode of the thin-walled energy-absorbing cylinder is controlled by the dimensionless half-wavelength parameter expressed by the following ratio: (H+W-h)/sqrt(Dh) Among them, H is the minimum distance between two adjacent grooves, W is the maximum width of the groove, h is the wall thickness of the cylinder, sqrt(Dh) is the axisymmetric buckling mode of the complete cylinder without grooves under the theoretical half-wavelength.