WO2017128496A1

WO2017128496A1 - Thin-walled energy-absorbing cylinder and buckling mode control method thereof

Info

Publication number: WO2017128496A1
Application number: PCT/CN2016/076040
Authority: WO
Inventors: 魏延鹏; 杨喆; 黄晨光
Original assignee: 中国科学院力学研究所
Priority date: 2016-01-26
Filing date: 2016-03-10
Publication date: 2017-08-03
Also published as: CN105715724A

Abstract

A thin-walled energy-absorbing cylinder. The thin-walled energy-absorbing cylinder comprises a cylinder body, which comprises a front end for receiving an axial impact load and a rear end opposite to the front end, and starting from the front end of the cylinder body, a plurality of circumferential annular grooves are alternately arranged on the outer and inner walls of the cylinder body. By arranging initial defects, that is, the annular groove, in the longitudinal direction on the thin-walled cylinder, the device can effectively control the buckling mode and plastic hinge forming position of the thin-walled cylinder, and then through control of depth change, width, spacing, and the like of the groove, the buckling collapsing process can be effectively controlled, achieving controlled optimization of axial compressional buckling energy absorption space of the thin-walled cylinder. A buckling mode control method for the thin-walled energy-absorbing cylinder is also provided.

Description

Thin wall energy absorbing cylinder and buckling mode control method thereof

Technical field

The present invention relates to the field of thin wall energy absorption, and more particularly 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 cars and high-speed trains and the continuous increase in driving speed, the collision problem has become more and more prominent. The rapid increase of collision accidents will cause major personal injury and property damage, and crashworthiness has become a car and high-speed train. The primary consideration of structural design.

It has long been noted that thin-walled cylinders generally have a stable progressive failure mode under axial compression, absorbing energy by plastic buckling. The thin-walled cylinder is a traditional buffered energy absorbing structure and one of the most widely used cushioning energy absorbing structures, which absorbs considerable energy when subjected to axial impact loads. Dynamic elastoplastic buckling of thin-walled cylinders subjected to axial impact loads is a complex phenomenon. There are three types of instability modes according to the geometric parameters of the thin-walled cylinder, load and material properties: dynamic plastic buckling mode, Generally, in the case of high-speed impact, the thin-walled cylinder is wrinkled along the entire length before the occurrence of large radial displacement; the dynamic progressive buckling mode, in the case of low-speed impact, the deformation process is similar to the static situation, wrinkles It is formed from one end and gradually develops to the other end. This mode is the ideal energy absorption mode; and the Euler bending mode.

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

Summary of the invention

The invention provides a thin wall energy absorbing tube and a buckling mode control method of the thin wall energy absorbing tube, so as to reduce the initial peak buckling load on the one hand and effectively control the thin wall tube on the one hand, aiming at the deficiencies in the prior art. Buckling mode.

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

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

Preferably, the thin walled energy absorbing cylinder is a cylinder, an elliptical cylinder or a polygonal cylinder.

Preferably, starting from the front end of the barrel, the maximum depth of the groove tends to decrease over at least a portion of the length of the barrel.

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

Preferably, the axial section of the groove is rectangular, semi-circular or curved.

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

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

1. Controlling the buckling mode of the thin-walled energy absorbing cylinder by the magnitude of 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 barrel and the barrel The ratio of the wall thickness of the body.

2. Controlling the buckling mode of the thin-walled energy absorbing cylinder by 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 is located in the cylinder The ratio of the sum of the maximum depths of the initial grooves of the front end of the body.

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

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

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

Where H is the minimum spacing between adjacent grooves, W is the maximum width of the groove, h is the wall thickness of the cylinder, and sqrt(Dh) is the axisymmetric buckling mode of the complete cylindrical barrel portion without the groove The theoretical half wavelength.

The invention adopts an initial defect along the length direction, that is, an annular groove, on the thin-walled cylinder, which effectively controls the buckling mode of the thin-walled cylinder, the plastic hinge forming position, and further controls the groove depth variation and the groove width of the groove. The groove spacing, etc., effectively control the buckling and crushing force history, thus achieving the purpose of controllable optimization of the thin-walled cylinder buckling energy absorption space.

DRAWINGS

1 is a schematic view showing the arrangement of groove defects of a thin-walled cylinder according to an embodiment of the present invention;

Figure 2 is a schematic view showing the control of the groove defect to the plastic hinge in the embodiment shown in Figure 1;

Figure 3 is a schematic illustration of a buckling fold model at the groove of the embodiment of Figure 1;

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

In the figure: D: thin wall tube diameter, L: thin wall tube length, h: thin wall tube wall thickness, h0: initial groove depth, t: groove depth change value, H: adjacent groove pitch, W: Groove width, m: specific model parameters, F: crushing force.

Preferred embodiment of the invention

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that the embodiments in the present invention and the features in the embodiments may be arbitrarily combined with each other without conflict.

The thin-walled energy absorbing cylinder provided by the present invention may be a cylinder, an elliptical cylinder or a polygonal cylinder, and includes a cylinder body including a front end receiving an 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 a front end that receives an axial impact load, and the bottom end is the rear end opposite to the front end.

Referring to Fig. 1, circumferential annular grooves are alternately arranged on the outer and inner walls of the thin-walled cylinder along the length L direction of the thin-walled cylinder. The axial section of the groove is rectangular, semi-circular or curved, and FIG. 1 shows a groove of rectangular cross section. For grooves of different axial sections, the depth and width of the groove and the spacing between two adjacent grooves may be varied, and therefore, although the embodiment shown in FIG. 1 takes a groove of a rectangular cross section as an example, H0 represents the depth of the initial groove (first groove), H represents the spacing between two adjacent grooves, and W represents the width of the groove, but for the purposes of the present invention, It is understood that h0 actually represents the maximum depth of the initial groove, and H actually represents the two adjacent grooves. The minimum spacing between the two, W actually represents the maximum width of the groove.

From the front end of the barrel, the depth of the groove changes in a decreasing trend over at least part of the length of the barrel. As shown in Fig. 1, it is preferred that the adjacent groove depths are gradually reduced by a fixed groove depth variation value t, and preferably the spacing H between any two adjacent grooves is equal.

Due to the thin wall thickness at the groove, the groove is more prone to buckling than the full cylinder. Therefore, by 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 the load that obviously exceeds the average crushing force does not appear in the whole process of buckling. The ideal rectangular energy absorbing space is formed, which can significantly improve the energy absorption effect of the device. At the same time, the buckling is started by using the deep groove defect at the front end, and the order of buckling is controlled. Further, since the depth of the groove along the length of the cylinder is different, the buckling start point can be more precisely controlled at the deepest groove at the front end, and gradually Developed to a lower depth of the groove.

Figure 2 shows a buckling fold formed by a thin-walled cylinder under the action of the crushing force F. For each buckling fold formation, the impact kinetic energy is absorbed by the plastic bending of the three plastic hinges as shown in Figure 2 and the stretching and compression of the material between the plastic hinges. The buckling force of each buckling pleat is equivalent, and the crushing force characteristic can be stabilized, so that a controllable optimized energy absorbing space (rectangular energy absorbing space) can be created, and the energy absorbing space can maximize the energy absorbing structure. Energy efficiency. It can be seen that the groove defect can effectively control the plastic hinge formation at the defect, and can also control the precise axisymmetric buckling mode (in the case where the thin wall cylinder is a cylinder, it is a ring buckling mode). At the same time, by using the depth variation of the defect, the order of plastic hinge formation can be effectively controlled, that is, from the deeper groove to the shallower groove.

From the entire length L of the cylinder, the depth of the groove does not have to be reduced all the time. As shown in Fig. 1, the depth of the groove does not change at h0-mt. At this time, the top-down buckling order has been Smooth start and controllable, the buckling mode is also stable and will not change due to no change in groove depth. Where m is a specific model parameter, which is constant for a particular model and can be determined by routine experimentation.

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

(1) dimensionless groove depth parameter h0/h

This parameter is the ratio of the depth h0 of the initial groove to the wall thickness h of the thin-walled cylinder. If the ratio is too large, since the local buckling energy is less than the energy of the overall buckling, local buckling easily occurs in the groove region. (ie, the wall at the groove is buckling as a local small thin-walled cylinder), so this parameter should not be too large, and the upper limit should be set according to the specific conditions of the model so that local buckling does not occur.

(2) dimensionless groove width parameter W/(h+h0)

This parameter determines whether or not extrusion occurs between the complete cylinders on either side of the groove when the buckling fold is formed. Referring to the theoretical model shown in Fig. 3, when the buckling fold is formed, a semicircular arc is formed at the groove, and when the parameter is greater than or equal to π/2, no extrusion occurs, 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 collide with each other, which will affect the optimization of the energy absorption space.

(3) dimensionless half-wavelength parameters

Taking a cylinder as an example, this parameter is (H+W-h)/sqrt(Dh). Where (H+Wh) is the half-wavelength controlled by the model, and sqrt(Dh) is the half-wavelength of the theoretical axisymmetric buckling mode of the complete cylindrical cylinder. The ratio between the active control and the intrinsic quantity will cause buckling. The mode change, when this 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 the buckling fold does not occur at the groove, which is beyond the control range of the method.

Figure 4 shows the crushing force-displacement curve of a complete thin-walled cylinder, with the X-axis representing the displacement and the Y-axis representing the crushing force. Its higher initial peak load results in an undesired energy absorption space (space below the wavy line), and the energy absorption efficiency is much lower than the expected energy absorption efficiency. Through 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, so that the load area is uniform and a rectangular controllable energy absorption space is formed. The space below the dotted line) can most effectively exert the function of the energy absorbing structure.

Through the above method of the invention, the controllable energy absorption space optimization of the thin-walled cylinder impact buckling energy absorbing structure can be optimized, and can be applied to the optimization design of the energy absorbing device of the automobile and the high speed train, and the optimization of the soft landing device of the aircraft and the spacecraft. Design and so on.

The above is only the preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes can be made to the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and scope of the present invention are intended to be included within the scope of the present invention.

Industrial applicability

The thin-walled energy absorbing cylinder and the buckling mode control method provided by the invention can be manufactured and used industrially to meet the requirements of industrial applicability.

Claims

A thin-walled energy absorbing cylinder comprising a cylinder comprising a front end receiving an axial impact load and a rear end opposite to the front end, wherein:

From the front end of the cylinder, a plurality of circumferential annular grooves are alternately arranged on the outer and inner walls of the cylinder.
The thin walled energy absorbing cylinder of claim 1 wherein:

The thin walled energy absorbing cylinder is a cylinder, an elliptical cylinder or a polygonal cylinder.
A thin walled energy absorbing cylinder according to claim 2, wherein:

Starting from the front end of the barrel, the maximum depth of the groove tends to decrease over at least a portion of the length of the barrel.
A thin walled energy absorbing cylinder according to claim 3, wherein:

The maximum depth reduction between any two adjacent grooves where there is a depth change is equal.
A thin walled energy absorbing cylinder according to any one of claims 1 to 4, wherein:

The axial section of the groove is rectangular, semi-circular or curved.
A thin walled energy absorbing cylinder according to any one of claims 1 to 4, wherein:

The minimum spacing between any two adjacent grooves is equal.
A buckling mode control method for a thin-walled energy absorbing cylinder according to any one of claims 1 to 6, wherein:

Controlling the buckling mode of the thin-walled energy absorbing cylinder by the magnitude of 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 barrel and the barrel The ratio of wall thickness.
A buckling mode control method for a thin-walled energy absorbing cylinder according to any one of claims 1 to 6, wherein:

Controlling the buckling mode of the thin-walled energy absorbing cylinder by 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 is located in the cylinder The ratio of the sum of the maximum depths of the initial grooves of the front end.
The control method according to claim 8, wherein:

The dimensionless groove width parameter is greater than or equal to π/2.
A buckling mode control method for a thin-walled energy absorbing cylinder according to any one of claims 1 to 6, wherein said 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 size of the dimensionless half-wavelength parameter, which is represented by the following ratio:

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

Where H is the minimum spacing between adjacent grooves, W is the maximum width of the groove, h is the wall thickness of the cylinder, and sqrt(Dh) is the axisymmetric buckling mode of the complete cylindrical barrel portion without the groove The theoretical half wavelength.