CN109781553B - Experimental device for compress sample at medium strain rate - Google Patents
Experimental device for compress sample at medium strain rate Download PDFInfo
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- CN109781553B CN109781553B CN201910179708.0A CN201910179708A CN109781553B CN 109781553 B CN109781553 B CN 109781553B CN 201910179708 A CN201910179708 A CN 201910179708A CN 109781553 B CN109781553 B CN 109781553B
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Abstract
The invention relates to an experimental device for carrying out medium strain rate compression on a sample, which comprises a transmitting tube, a guide sleeve, a striking rod assembly, a first transition rod, a second transition rod and an output rod assembly which are arranged on the same straight line, wherein one end of the transmitting tube is used for being connected with a high-pressure cylinder, and a push rod capable of axially moving along the transmitting tube is arranged in the transmitting tube; the striking rod assembly comprises a first cylinder and a striking rod body coaxial with the first cylinder; the other end of the transmitting tube is connected with the guide sleeve, a first cylinder in the striking rod component is movably embedded into the guide sleeve, and the bottom of the first cylinder is used for receiving the impact of the push rod; the first end of the first transition rod is arranged opposite to the second end of the striking rod body; the first end of the second transition rod is abutted to the output rod assembly, and a sample placing space is formed between the second end of the second transition rod and the second end of the first transition rod. The experimental device can enable the sample to be in a medium strain rate range so as to meet the requirement of sample performance research in the medium strain rate range.
Description
Technical Field
The invention relates to the technical field of stress wave experimental device design and production, in particular to an experimental device for carrying out medium strain rate compression on a sample.
Background
The mechanical behavior of a material is dependent on the strain rate, which varies significantly with the strength.
At present, the experimental device which is most widely applied and can obtain higher strain rate of materials is mainly a Hopkinson bar, and the strain rate of the experimental device for loading a sample can reach 102～103This falls within the high strain rate range, while the performance studies on samples with low strain rates are mainly obtained by means of MTS testers, which have a strain rate under load of less than 10-2In/s, which falls within the low strain rate range. However, the strain rate of the sample is between 101～102The experimental device in the medium strain rate range of/s is rarely reported at home and abroad.
The conventional Hopkinson bar is based on a one-dimensional stress wave theory, the pulse loading time of the Hopkinson bar depends on the length of the bar very much, the pulse loading time of the Hopkinson bar can be increased in order to research the performance of a sample in a medium strain rate state, but the Hopkinson bar needs to be modified, the length of the bar needs to be increased to 30m or more, obviously, the requirement on the experimental space is very high, and the realization is very difficult.
Therefore, it is an urgent technical problem to provide an experimental apparatus for performing medium-rate compression on a sample to satisfy the requirement of studying the performance of the sample at medium strain rate.
Disclosure of Invention
The invention aims to provide an experimental device for carrying out medium strain rate compression on a sample, so as to meet the requirement of researching the performance of the sample at the medium strain rate.
In order to achieve the above object, the present invention provides an experimental apparatus for performing medium strain rate compression on a sample, comprising a launching tube, a guide sleeve, a striking rod assembly, a first transition rod, a second transition rod and an output rod assembly, which are arranged on the same straight line along a horizontal direction, wherein,
one end of the launching tube is used for being connected with the high-pressure cylinder, and a push rod capable of moving along the axial direction of the launching tube is arranged inside the launching tube;
the striking rod assembly comprises a first cylinder and a striking rod body coaxial with the first cylinder, a first end of the striking rod body is embedded into the first cylinder and fixedly connected to the bottom of the first cylinder, and a second end of the striking rod body is exposed out of the first cylinder;
the other end of the transmitting tube is connected with the guide sleeve, a first cylinder in the striking rod assembly is movably embedded into the guide sleeve, and the bottom of the first cylinder is used for receiving the impact of the push rod;
the first end of the first transition rod is arranged opposite to the second end of the striking rod body and used for receiving the impact of the striking rod body;
the first end of the second transition rod is abutted to the output rod assembly, and a sample placing space is formed between the second end of the second transition rod and the second end of the first transition rod.
Preferably, the output rod assembly and the striking rod assembly are symmetrically arranged, the output rod assembly comprises a second cylinder and an output rod body coaxial with the second cylinder, the first end of the output rod body is embedded into the second cylinder and fixedly connected to the bottom of the second cylinder, and the second end of the output rod body is exposed out of the second cylinder.
Preferably, the first cylinder and the second cylinder have the same structure, and the outer side surfaces of the bottoms of the first cylinder and the second cylinder are both planes.
Preferably, the first cylinder and the second cylinder have the same structure, wherein the outer side surface of the bottom of the first cylinder is a first curved plate, the first curved plate forms a first central concave point by taking the first end of the striking rod body as a center, and the periphery of the first central concave point is raised and is connected with the side wall of the first cylinder after being turned over towards the second end of the striking rod body;
the outer side face of the bottom of the second cylinder is a second curved plate, the second curved plate forms a second central concave point by taking the first end of the output rod body as a center, and the periphery of the second central concave point is raised and is connected with the side wall of the second cylinder after being turned over towards the second end of the output rod body.
Preferably, a plurality of strain gauges for recording waveforms are attached to the first transition rod and the second transition rod, and a space is provided between any two adjacent strain gauges.
Preferably, three strain gauges are attached to the first transition rod, two of the strain gauges are arranged close to two ends of the first transition rod and are called end strain gauges, and the other strain gauge is arranged at the midpoint of a connecting line of the two end strain gauges.
Preferably, the second transition rod is attached with two strain gauges, and the two strain gauges are respectively arranged near two ends of the second transition rod.
Preferably, the striking rod body has a diameter D0The inner diameter of the first cylinder is D1Outer diameter of D2Between the inner wall of the first cylinder and the striking rod bodyWhen the distance is h, the following relation is satisfied: d0 2＝D2 2-D1 2Or D0 2＝4h(D2-2h)。
Preferably, the diameter of the output rod body is D3The inner diameter of the second cylinder is D4Outer diameter of D5The distance between the inner wall of the second cylinder and the output rod body is h1Then the following relationship is satisfied: d3 2＝D5 2-D4 2Or D3 2＝4h1(D5-2h1)。
It can be seen from the above technical solutions that the experimental apparatus disclosed in the present invention actually improves the existing hopkinson bar, and particularly, the striking bar is replaced by a striking bar assembly from an original single bar, and the striking bar assembly is composed of a first cylinder and a striking bar body, a first end of the striking bar body is embedded into the first cylinder and fixedly connected to the bottom of the first cylinder, a second end of the striking bar body is exposed out of the first cylinder, compared with the single bar, after the push rod strikes the bottom of the first cylinder, because the stress wave is propagated in the first cylinder and the striking bar at the same time, the occurrence time of the stress wave unloading stage is delayed due to the existence of the first cylinder, the loading time width of the stress wave is significantly increased, thereby effectively increasing the loading time of the stress wave on the sample, which enables the deformation of the sample to be within the range of medium strain rate, the study of the sample performance in the medium strain rate range is realized.
Drawings
FIG. 1 is a schematic structural diagram of an experimental apparatus disclosed in the embodiment of the present invention;
FIG. 2 is a cross-sectional view of the striking rod assembly of FIG. 1;
FIG. 3 is a schematic cross-sectional view of the output rod assembly of FIG. 1;
fig. 4 is a right side view of the striking rod assembly of fig. 2.
The device comprises a high-pressure cylinder 1, a transmitting tube 2, a push rod 3, a guide sleeve 4, a striking rod assembly 5, a first transition rod 6, a sample 7, a second transition rod 8, a strain gauge 9, an oscilloscope 10, an output rod assembly 11, a striking rod body 51, a first cylinder 52, an output rod body 111 and a second cylinder 112, wherein the transmitting tube 2, the push rod 4, the guide sleeve 5, the first transition rod, the second transition rod, the sample 7, the second transition rod, the strain gauge 9, the oscilloscope 10, the output rod assembly 11, the striking rod.
Detailed Description
The core of the invention is to provide an experimental device for compressing a sample at a medium strain rate so as to meet the requirement of researching the performance of the sample at the medium strain rate.
In order that those skilled in the art will better understand the disclosure, the invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
Referring to fig. 1, the experimental apparatus for performing medium strain rate compression on a sample disclosed in the embodiment of the present invention includes a launching tube, a guide sleeve, a striking rod assembly, a first transition rod, a second transition rod, and an output rod assembly, wherein axes of the launching tube, the guide sleeve, the striking rod assembly, the first transition rod, the second transition rod, and the output rod assembly are located on a same straight line in a horizontal direction, one end of the striking rod assembly is connected to a high pressure cylinder, and a push rod capable of fixing along an axial direction of the launching tube is disposed inside the launching tube, the striking rod assembly includes a first cylinder and a striking rod body disposed coaxially with the first cylinder, a first end of the striking rod body is embedded in the first cylinder and fixedly connected to a bottom of the first cylinder, as shown in fig. 1 and 2, a second end of the striking rod body is exposed out of the first cylinder, another end of the launching tube is connected to the guide sleeve, and the first cylinder in the striking rod assembly is embedded in the guide, the first end of first transition pole is just to the second end setting of striking rod body to accept the striking of striking rod body, the first end of second transition pole offsets with the output rod subassembly, and the second end constitutes the sample with the second end of first transition pole and places the space.
When carrying out the experiment, place the sample in the sample space of placing, high-pressure cylinder aerifys to the atmospheric pressure value of settlement, then the push rod in the drive launching tube gos forward, and the push rod pushes away the first transition pole of impact pole subassembly common and the striking speed striking after striking with the striking pole subassembly, and the stress wave that the striking produced is acted on the sample through first transition pole, and the projection wave transmits to the output pole subassembly through the second transition pole, and the back wave passes back again to the striking pole subassembly through first transition pole.
It can be seen from the technical solutions disclosed in the above embodiments that the experimental apparatus disclosed in the present invention actually improves the existing hopkinson bar, and particularly, the striking bar is replaced by a striking bar assembly from an original single bar assembly, and the striking bar assembly has the following specific form: the striking rod component comprises a first cylinder and a striking rod body, wherein the first end of the striking rod body is embedded into the first cylinder and fixedly connected to the bottom of the first cylinder, and the second end of the striking rod body is exposed out of the first cylinder.
In order to further optimize the scheme in the foregoing embodiment, the output rod assembly and the striking rod assembly in this embodiment are consistent in form and symmetrically arranged, the output rod assembly specifically includes a second cylinder and an output rod body coaxially arranged with the second cylinder, a first end of the output rod body is embedded into the second cylinder and fixedly connected to the bottom of the second cylinder, and a second end of the output rod body is exposed out of the second cylinder.
In the embodiment of the invention, the first cylinder and the second cylinder have the same structure, and the technical personnel in the field can understand that the outer side surfaces of the bottoms of the first cylinder and the second cylinder can be both planes, so that the structural form is easy to manufacture, the process is simpler, but the time domain width enhancement effect on the stress wave is not obvious enough; therefore, the scheme can be further optimized, as shown in fig. 1 to 3, the outer side surface of the bottom of the first cylinder is provided with a first curved plate, the first curved plate and the first end of the striking rod body are used as centers to form a first central concave point, and the periphery of the first central concave point is raised, is turned towards the second end of the striking rod body and then is connected with the side wall of the first cylinder; the outer side face of the bottom of the second cylinder body is a second curved plate, the second curved plate forms a second central concave point by taking the first end of the output rod body as a center, the periphery of the second central concave point is raised and faces the second end of the output rod body, and then the second central concave point is folded and connected with the side wall of the second cylinder body.
Preferably, the striking rod body has a diameter D0The inner diameter of the first cylinder is D1Outer diameter of D2The distance between the inner wall of the first cylinder and the striking rod body is h, and the following relations are satisfied: d0 2＝D2 2-D1 2Or D0 2＝4h(D2-2h)；
The diameter of the output rod body is D3The inner diameter of the second cylinder is D4Outer diameter of D5The distance between the inner wall of the second cylinder and the output rod body is h1Then the following relationship is satisfied: d3 2＝D5 2-D4 2Or D3 2＝4h1(D5-2h1)。
Furthermore, in order to actually calculate whether the strain rate of the sample is within the set intermediate strain rate range, in this embodiment, a plurality of strain gauges for recording waveforms are attached to the first transition rod and the second transition rod, and any two adjacent strain gauges are arranged at intervals, and more specifically, three strain gauges are attached to the first transition rod, two of the strain gauges are arranged near two ends of the first transition rod and are called end strain gauges, the other strain gauge is arranged at a midpoint position of a connecting line of the two end strain gauges, two strain gauges are attached to the second transition rod, and the two strain gauges are respectively arranged near two ends of the second transition rod.
The more specific experimental principle is as follows:
(1) the high-pressure cylinder is inflated to a set air pressure value to drive the push rod to advance; the push rod system carries a striking rod component to impact a first transition rod at a preset speed;
(2) generating a stress wave signal at the interface of the striking rod assembly and the first transition rod: the stress wave signal is transmitted to the striking rod assembly leftwards, firstly passes through the solid round rod, then smoothly passes through the gradual change transition section (the curved surface bottom), and finally is transmitted in the hollow first cylinder body until the end part of the first cylinder body is emitted, and the stress wave signal is basically not attenuated in the process; the stress wave signal propagates to the right in the first transition rod, when the stress wave signal passes through a sample, a reflected wave and a transmitted wave are generated, the reflected wave reversely propagates to the striking rod assembly, the transmitted wave propagates to the second transition rod and the output rod assembly, and the propagation characteristic of the transmitted wave in the output rod assembly is consistent with that in the striking rod assembly.
In a putter assembly:
striking rod body diameter D0Inner and outer diameters D of the first cylinder1And D2Satisfies the relationship:
(3) Meanwhile, the superposed waveforms of the incident wave and the reflected wave recorded by the strain gauge on the first transition rod from left to right are respectively1(t)、2(t)、3(t); the wave forms of the transmitted waves recorded by the strain gauge on the second transition rod from left to right are respectively4(t)、5(t), the generation and display of the waveform may be accomplished by a strain gauge and an oscilloscope.
Calculating to obtain the incident wave waveformI(t) reflected wave waveformR(t) and transmitted wave waveformT(t), the calculation process is not discussed herein since it is described in detail in the stress wave base (king etiquette, national defense industry press).
Transmitted wave waveform:T(t)＝4(t) orT(t)＝5(t)，4(t) and5(t) should be substantially the same, however, for viscoelastic materials,4(t) and5(t) unlike the above, the analysis can be carried out by the method of ZHao H, which is well accepted as the viscoelastic wave and thus is not shown in detail.4(t) and5(t) is specifically designed for viscoelastic stems.
Based on the recorded waveforms of the second and third strain gauges on the first transition rod, the incident wave waveformI(t) and reflected wave waveformR(t) is determined by the following procedure.
Firstly, when
When the temperature of the water is higher than the set temperature,I(t)＝2(t); the process represents the process that the stress wave is transmitted to the sample from the second strain gage on the first transition rod, and then a part of the stress wave is reflected to the second strain gage on the first transition rod;
R(t′)＝3(t)-2(t) wherein,
and t' is not less than 0;
② when
When the temperature of the water is higher than the set temperature,I(t)＝2(t)-R(t'); the process is that the stress wave is transmitted to the sample from the third strain gage on the first transition rod, and then a part of the stress wave is reflected to the third strain gage on the first transition rod;
R(t′)＝3(t)-2(t) wherein,
in the formula, C0The elastic wave velocity, L, of the striking rod assembly and the output rod assembly (both of the same material)2sAnd L3sThe distances from the second strain gage and the third strain gage on the first transition rod to the sample respectively.
To be provided with
Repeating the solving step of step two for the time step length, solving the incident wave and the reflected wave section by section until the integral loading and unloading process is obtainedI(t) andR(t)。
to check the calculation result, the incident wave waveform can be calculated based on the recorded waveforms of the first strain gauge and the third strain gauge on the first transition rod and the above processI(t) and reflected wave waveformR(t) comparing the results with the above results.
(4) Determining the axial strain of the test piece under a certain constant strain rate by combining the incident wave waveform, the reflected wave waveform and the transmitted wave waveformsAnd stress σs。
The calculation formula of the axial strain rate of the test piece is as follows:
the calculation formula of the axial strain of the test piece is as follows:
the calculation formula of the axial stress of the test piece is as follows:
wherein L issFor sample length, AsIs the cross-sectional area of the sample, A0The sectional areas of the striking rod body and the output rod body (the sectional areas of the striking rod body and the output rod body are equal).
The experimental apparatus for performing medium strain rate compression on a sample provided by the present invention is described in detail above. The principles and embodiments of the present invention are explained herein using specific examples, which are presented only to assist in understanding the method and its core concepts. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.
Claims (6)
1. The experimental device for performing medium strain rate compression on a sample is characterized by comprising a launching tube, a guide sleeve, a striking rod component, a first transition rod, a second transition rod and an output rod component which are arranged on the same straight line along the horizontal direction, wherein,
one end of the launching tube is used for being connected with the high-pressure cylinder, and a push rod capable of moving along the axial direction of the launching tube is arranged inside the launching tube;
the striking rod assembly comprises a first cylinder and a striking rod body coaxial with the first cylinder, a first end of the striking rod body is embedded into the first cylinder and fixedly connected to the bottom of the first cylinder, and a second end of the striking rod body is exposed out of the first cylinder;
the other end of the transmitting tube is connected with the guide sleeve, a first cylinder in the striking rod assembly is movably embedded into the guide sleeve, and the bottom of the first cylinder is used for receiving the impact of the push rod;
the first end of the first transition rod is arranged opposite to the second end of the striking rod body and used for receiving the impact of the striking rod body;
the first end of the second transition rod is abutted against the output rod assembly, and a sample placing space is formed between the second end of the second transition rod and the second end of the first transition rod;
the output rod assembly and the striking rod assembly are symmetrically arranged, the output rod assembly comprises a second cylinder and an output rod body coaxial with the second cylinder, the first end of the output rod body is embedded into the second cylinder and fixedly connected to the bottom of the second cylinder, and the second end of the output rod body is exposed out of the second cylinder;
the structure of the first cylinder is the same as that of the second cylinder, wherein the outer side surface of the bottom of the first cylinder is a first curved plate, the first curved plate forms a first central concave point by taking the first end of the striking rod body as a center, and the periphery of the first central concave point is raised and is connected with the side wall of the first cylinder after being turned over towards the second end of the striking rod body;
the outer side face of the bottom of the second cylinder is a second curved plate, the second curved plate forms a second central concave point by taking the first end of the output rod body as a center, and the periphery of the second central concave point is raised and is connected with the side wall of the second cylinder after being turned over towards the second end of the output rod body.
2. The experimental device as claimed in claim 1, wherein a plurality of strain gauges for recording waveforms are attached to the first transition rod and the second transition rod, and a space is provided between any two adjacent strain gauges.
3. The experimental device as claimed in claim 2, wherein three strain gauges are attached to the first transition bar, two of the strain gauges are disposed near two ends of the first transition bar and are called end strain gauges, and the other strain gauge is disposed at a midpoint of a connecting line of the two end strain gauges.
4. The experimental device as claimed in claim 3, wherein two strain gauges are attached to the second transition rod, and the two strain gauges are respectively disposed near two ends of the second transition rod.
5. The experimental device as claimed in any one of claims 1 and 3 to 4, wherein the diameter of the striking rod body is D0The inner diameter of the first cylinder is D1Outer diameter of D2The distance between the inner wall of the first cylinder and the striking rod body is h, and the following relations are satisfied: d0 2＝D2 2-D1 2Or D0 2＝4h(D2-2h)。
6. The device of claim 1, wherein the device is a disposable unitThe diameter of the output rod body is D3The inner diameter of the second cylinder is D4Outer diameter of D5The distance between the inner wall of the second cylinder and the output rod body is h1Then the following relationship is satisfied: d3 2＝D5 2-D4 2Or D3 2＝4h1(D5-2h1)。
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| CN103234844B (en) * | 2013-03-29 | 2016-01-20 | 东北大学 | A kind of pendulum loads mid strain rate Hopkinon depression bar test unit and method |
| CN203811463U (en) * | 2014-03-10 | 2014-09-03 | 东北大学 | Split Hopkinson pressure bar suitable for test pieces with various standards |
| US9863859B2 (en) * | 2014-04-23 | 2018-01-09 | Mississippi State University Research And Technology Corporation | Serpentine load monitoring apparatus |
| CN107505189B (en) * | 2017-09-30 | 2020-08-11 | 安徽理工大学 | A support and protection and fragment collect integrative device for hopkinson experiment |
| CN108717024B (en) * | 2018-03-16 | 2020-06-23 | 太原理工大学 | Variable pressure head dynamic pressing-in test device based on Hopkinson pressure bar system |
| CN108548942B (en) * | 2018-05-09 | 2021-01-05 | 西北工业大学 | Hopkinson pressure bar system with true triaxial dynamic loading and testing functions and method |
| CN109001053B (en) * | 2018-06-13 | 2021-01-12 | 安徽工业大学 | Coal rock dynamic impact damage test system under confining pressure and damp-heat coupling condition |
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