CN111735761A - Method and device for obtaining sliding friction coefficient of powder - Google Patents
Method and device for obtaining sliding friction coefficient of powder Download PDFInfo
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- CN111735761A CN111735761A CN202010409026.7A CN202010409026A CN111735761A CN 111735761 A CN111735761 A CN 111735761A CN 202010409026 A CN202010409026 A CN 202010409026A CN 111735761 A CN111735761 A CN 111735761A
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Abstract
The disclosure provides a method and a device for obtaining a sliding friction coefficient of powder, comprising the following steps: the device comprises a left female die and a right female die which are in flexible connection, wherein an upper piston, powder and a lower piston are sequentially arranged in a cavity formed by the left female die and the right female die from top to bottom; the powder, the upper piston and the lower piston integrally move linearly at a constant speed under the action of external force, the external force is the friction force of the piston, the powder and the female die, and the friction force of the powder and the inner wall of the female die is obtained based on the obtained friction force of the piston and the female die; the outer wall of the right female die is provided with lateral pressure measuring equipment for measuring lateral pressure generated by the powder and the inner wall of the die due to the lateral expansion tendency; and obtaining the sliding friction coefficient of the powder based on the friction force and the lateral pressure of the received powder and the inner wall of the female die. The friction coefficient between the powder particles and the wall surface of the die, which are not deformed, can be obtained.
Description
Technical Field
The disclosure belongs to the technical field of sliding friction, and particularly relates to a method and a device for obtaining a sliding friction coefficient of powder.
Background
The statements in this section merely provide background information related to the present disclosure and may not necessarily constitute prior art.
Aiming at powder with particle shape and fluidity or spherical solid with larger volume, such as iron powder, nickel powder, copper powder or small steel balls and glass balls, when the powder particles are not damaged, the friction coefficient of the powder particles and the sliding mold wall of the inner wall of the mold needs to be obtained, and the coefficient is applied to the analysis of the friction of the mold wall in the powder feeding process.
The inventor finds in research that most of the friction coefficients of the die wall measured by the existing device are after the powder particles are broken, and the existing device is unreasonable in measuring the lateral pressure of the powder and the die.
In addition, the conventional powder friction coefficient measuring device generally measures the friction coefficient between a powder pressed product and the wall surface of a mold through a macroscopic method, and the friction coefficient between powder particles which are not deformed and the wall surface of the mold cannot be obtained.
Specifically, there are two methods for measuring pressure. In the first direct measurement method, which measures the lateral pressure by the strain gauge on the side of the outer wall of the mold during pressing, there is a problem in that: the obtained lateral pressure value has larger error and the powder particles are damaged; the reason for this is: the existing die has larger wall thickness, so that larger errors exist in strain transmission.
The second indirect measurement method, as shown in FIG. 4, is to obtain a frictional force by pressing the upper end face of the pressed product against a friction test plate with a certain pressure and by dragging the friction test plate, and to use the pressure of the upper end of the pressed product as a frictional pressure. There are problems in that: the friction coefficient between the side face of the pressed product and the die cannot be obtained, and the friction pressure at this time is substantially different from the friction pressure at the time of pressing, which results from the following reasons: the lower end face of the pressed product is used as a friction coefficient measuring face, and the pressing conditions of the lower end face and the side face of the pressed product are greatly different.
Disclosure of Invention
In order to overcome the defects of the prior art, the disclosure provides a method for obtaining the sliding friction coefficient of the powder, which can obtain the friction coefficient between the powder particles without deformation and the wall surface of the mold.
In order to achieve the above object, one or more embodiments of the present disclosure provide the following technical solutions:
powder coefficient of sliding friction acquisition device includes:
the device comprises a left female die and a right female die which are in flexible connection, wherein an upper piston, powder and a lower piston are sequentially arranged in a cavity formed by the left female die and the right female die from top to bottom;
the powder, the upper piston and the lower piston integrally move linearly at a constant speed under the action of external force, the external force is the friction force of the piston, the powder and the female die, and the friction force of the powder and the inner wall of the female die is obtained based on the obtained friction force of the piston and the female die;
the outer wall of the right female die is provided with lateral pressure measuring equipment for measuring lateral pressure generated by the powder and the inner wall of the die due to the lateral expansion tendency;
and obtaining the sliding friction coefficient of the powder based on the friction force and the lateral pressure of the received powder and the inner wall of the female die.
According to the technical scheme, the lateral pressure measuring devices are at least three pressure sensors, one side of each pressure sensor is fixed on the outer wall of the right female half die along the axis, and the other side of each pressure sensor is fixed on a vertical plate surface capable of extending the guide rail to move transversely along the axis.
On the other hand, the method for obtaining the sliding friction coefficient of the powder comprises the following steps:
when only the upper piston and the lower piston are positioned in a cavity formed by the left female die and the right female die, downward force is applied to the upper piston, the force is the friction force between the piston and the female die when the lower piston and the upper piston integrally move at a constant speed, and the side pressure between the upper piston and the die wall and the side pressure between the lower piston and the die wall in the pressing process are obtained;
applying a downward force to the upper piston, wherein the force is the friction force of the piston, the powder and the female die when the lower piston, the powder and the upper piston integrally move at a constant speed, and meanwhile, the side pressure of the powder and the die wall in the pressing process is obtained;
subtracting the friction force of the piston and the female die from the friction force of the piston, the powder and the female die to obtain the friction force of the powder and the inner wall of the female die;
subtracting the measured pressure of the piston and the female die from the side pressure of the piston, the powder and the female die to obtain the side pressure of the powder and the inner wall of the female die;
the sliding friction coefficient of the powder is obtained based on the friction force between the powder and the inner wall of the female die and the side pressure between the powder and the die wall.
According to the further technical scheme, when downward force is applied to the upper piston, different applied forces are obtained by adding different weights.
The above one or more technical solutions have the following beneficial effects:
according to the powder-injection molding device, the powder, the upper piston and the lower piston integrally move linearly at a constant speed under the action of external force, the external force is the friction force of the piston, the powder and the female die, and the friction force of the powder and the inner wall of the female die is obtained based on the obtained friction force of the piston and the female die; the outer wall of the right female die is provided with lateral pressure measuring equipment for measuring lateral pressure generated by the powder and the inner wall of the die due to the lateral expansion tendency; and obtaining a powder sliding friction coefficient based on the friction force and the lateral pressure of the received powder and the inner wall of the female die, wherein the measured die wall friction coefficient is the corresponding powder sliding friction coefficient when no relative sliding occurs among the powder particles, no rolling occurs in the powder particles, no damage occurs in the powder particles, and the powder sliding friction coefficient is in plastic deformation.
The right half female die capable of moving slightly and the lateral pressure measuring device can accurately measure the lateral pressure. The lateral pressure is helpful for calculating the sliding friction coefficient of the powder, and the size of the upper pressure and the lower pressure can be accurately adjusted by matching the weight with the piston without deforming the powder.
Drawings
The accompanying drawings, which are included to provide a further understanding of the disclosure, illustrate embodiments of the disclosure and together with the description serve to explain the disclosure and are not to limit the disclosure.
FIG. 1 is a schematic diagram of the overall structure of an embodiment of the present disclosure;
FIG. 2 is a schematic diagram of the powder stress according to the embodiment of the disclosure;
FIG. 3 is a cross-sectional view of the overall structure of an embodiment of the present disclosure;
FIG. 4 is a diagram of a prior art test structure according to an embodiment of the present disclosure;
in the figure, 1, a box body; 2. a lower piston; 3. a left half-female die; 4. powder; 5. a weight; 6. an upper piston; 7. a right half female die; 8. tightening and loosening the bolts; 9. a pressure sensor; 10. a vertical baffle; 11. a guide rail.
Detailed Description
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
The embodiments and features of the embodiments in the present disclosure may be combined with each other without conflict.
Example one
The embodiment discloses a powder sliding friction coefficient obtaining device, which is shown in fig. 1 and 3 and comprises:
an upper piston 6, powder 4 and a lower piston 2 are sequentially arranged in a cavity formed by the left female die and the right female die from top to bottom through a left female die 3 and a right female die 7 which are in flexible connection;
the powder, the upper piston and the lower piston integrally move linearly at a constant speed under the action of external force, the external force is the friction force of the piston, the powder and the female die, and the friction force of the powder and the inner wall of the female die is obtained based on the obtained friction force of the piston and the female die;
the outer wall of the right female die is provided with lateral pressure measuring equipment for measuring powder and lateral pressure generated by the piston and the inner wall of the die due to the lateral expansion tendency;
and obtaining the sliding friction coefficient of the powder based on the friction force and the lateral pressure of the received powder and the inner wall of the female die.
In the concrete embodiment, the left female die and the right female die are in flexible connection through the rubber pads, the left female die and the box body 1 are fixed, the left female die and the right female die are connected to form sealing, so that the right female die can realize rightward small displacement in the pressing process and keep the overall sealing performance of the die, the flexible connection has certain elasticity, the sealing performance, the stretching amount and the compression amount are small, the upper piston, the powder and the lower piston are axially distributed in the female die, the left sides of the three pressure sensors are fixed on the outer wall of the right female die along the axis, the right sides of the pressure sensors 9 are fixed on a vertical plate surface 10 capable of moving along the guide rail transversely along the axis, and the plate surface can be adjusted to.
In a specific implementation example, a cylindrical tubular female die is divided into two parts at a central axis to obtain a left female die and a right female die, and the place where the rubber pad is arranged is the original connection position of the left female die and the right female die;
the rubber pad connection is a soft connection, and the purpose of the connection is to accurately transmit the lateral pressure received by the right female half die to the pressure measuring device in the pressing process.
In a specific embodiment, the axial direction, the longitudinal direction and the vertical direction are all the axial directions of the cylindrical female die, and the transverse direction is the horizontal direction.
The guide rail is positioned on the bottom plate of the box body, and the right half female die is placed in the guide rail 11; satisfying the slight displacement of the right half female die.
The vertical baffle is arranged on the right side wall surface of the box body; the displacement is adjusted by the length of the adjusting screw by rotating the tightening bolt 8; and when the friction force between the piston and the mold is measured under the condition that the powder is not added, the right half female mold is fixed on the vertical baffle through the adjusting screw.
When the whole device is operated, the weight 5 is added on the upper piston to apply force. The axial force is obtained by reading the weight of the weight, the lateral pressure is read by a pressure sensor, G2 is the friction force between the upper piston and the inner wall of the female die and between the three lower pistons and the inner wall of the female die in the experimental data measured by the device, and G1 is the friction force between the upper piston and the inner wall of the female die and between the upper piston and the powder and between the three lower pistons and the inner wall of the female die. That is, G1-G2 is the friction force between the powder and the inner wall of the female mold.
When weights are added on the upper piston, weights with smaller mass are used and added one by one.
Wherein an upper piston and three lower pistons are longitudinally placed in a female mold and weights are gradually added above the upper piston. When the piston and the weight integrally move at a constant speed, the weight of the weight is G2, and the weight is the friction force between the piston and the female die.
And adding weights with smaller mass one by one, wherein the weights and the piston integrally start to move at a constant speed.
And sequentially placing the lower piston, the powder and the upper piston in the female die, and gradually adding weights on the upper piston. When the whole body moves at a constant speed, the weight is G1, and the weight is the friction force of the piston, the powder and the female die.
Specifically, the powder downstream under the piston effect, the weight can constantly increase, and the powder compaction when the weight increases to a definite weight continues to increase the weight, and the powder can whole downstream, when reaching the certain degree greatly, overcomes the frictional force of following three piston, and powder, weight and four pistons are uniform linear motion together. The stress condition of the powder at this time is shown in fig. 2.
f＝F1-F2 (1)
f＝μN (2)
Here, F2 is the friction force between the three lower pistons and the female die, and F1 is the gravity of the weight G1 minus the friction force between one piston and the female die. f is the friction force between the powder and the mold wall. And N is the lateral pressure of the powder and the inner wall of the female die. μ is the coefficient of friction.
The sliding friction coefficient of the powder can be obtained by equation (3).
If the side pressure of the piston and the inner wall can be ignored, the device adopts three or more side pressure measuring devices which are positioned on the path of the powder body moving at a constant speed, and the measured force is the side pressure of the powder body; n is the average of three pressure sensors.
In addition, the sliding friction coefficient is calculated by using the measured pressure, the pressure sensor positioned on the outer wall of the female die measures the side pressure of the powder and the die wall in the pressing process, and the method can be widely applied to measuring the friction coefficient of various powders and the die wall of a die.
Side pressure measurement analysis:
in the pressing process of the powder, the powder and the piston generate transverse pressure with the inner wall of the die due to the transverse expansion tendency. The right half female die and the left half female die are in flexible connection, and the right half female die is not directly fixed. A plurality of pressure sensors are installed between the right female half die and the vertical plate surface, in the process of the forced movement of the powder, the right female half die generates a trend of moving rightwards, the trend is transmitted to the pressure sensors in a force mode, and the reading of the pressure sensors is the lateral pressure N of the powder in the pressing process.
On the other hand, the embodiment discloses a method for obtaining a sliding friction coefficient of powder, which comprises the following steps:
when only the lower piston of the upper piston is positioned in a cavity formed by the left female die and the right female die, downward force is applied to the upper piston, and the force is the friction force between the piston and the female die when the lower piston and the upper piston integrally move at a constant speed;
applying a downward force to the upper piston, wherein the force is the friction force of the piston, the powder and the female die when the lower piston, the powder and the upper piston integrally move at a constant speed, and meanwhile, the side pressure of the powder and the die wall in the pressing process is obtained;
subtracting the friction force of the piston and the female die from the friction force of the piston, the powder and the female die to obtain the friction force of the powder and the inner wall of the female die;
the sliding friction coefficient of the powder is obtained based on the friction force between the powder and the inner wall of the female die and the side pressure between the powder and the die wall.
When downward force is applied to the upper piston, different applied forces are obtained by adding different weights.
The above description is only a preferred embodiment of the present disclosure and is not intended to limit the present disclosure, and various modifications and changes may be made to the present disclosure by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present disclosure should be included in the protection scope of the present disclosure.
Although the present disclosure has been described with reference to specific embodiments, it should be understood that the scope of the present disclosure is not limited thereto, and those skilled in the art will appreciate that various modifications and changes can be made without departing from the spirit and scope of the present disclosure.
Claims (10)
1. Powder coefficient of sliding friction acquisition device, characterized by includes:
the device comprises a left female die and a right female die which are in flexible connection, wherein an upper piston, powder and a lower piston are sequentially arranged in a cavity formed by the left female die and the right female die from top to bottom;
the powder, the upper piston and the lower piston integrally move linearly at a constant speed under the action of external force, the external force is the friction force of the piston, the powder and the female die, and the friction force of the powder and the inner wall of the female die is obtained based on the obtained friction force of the piston and the female die;
the outer wall of the right female die is provided with lateral pressure measuring equipment for measuring lateral pressure generated by powder and a piston due to the lateral expansion tendency and the inner wall of the die;
and obtaining the friction coefficient between the undeformed powder particles and the wall surface of the die based on the friction force and the lateral pressure between the received powder and the inner wall of the female die.
2. The powder sliding friction coefficient obtaining device according to claim 1, wherein the side pressure measuring means is at least three pressure sensors, one side of each pressure sensor is fixed to the outer wall of the right female half along the axis, and the other side of each pressure sensor is fixed to a vertical plate surface capable of moving laterally along the guide rail along the axis.
3. The apparatus for obtaining the sliding friction coefficient of powder according to claim 2, wherein the vertical plate surface is adjustable in lateral displacement.
4. The apparatus for obtaining a sliding friction coefficient of powder according to claim 2 or 3, wherein a vertical plate is installed on the right wall surface of the box body, and the feed length of the adjustment screw adjusts the displacement when the vertical plate adjusts the lateral displacement.
5. The apparatus for obtaining powder sliding friction coefficient according to claim 1, wherein the left and right female molds have guide rails at the bottom.
6. The apparatus for obtaining the sliding friction coefficient of powder according to claim 1, wherein the left female half-mold is fixed to the housing, and the left and right female molds are flexibly connected by a rubber pad, so that the lateral pressure applied to the right female half-mold during pressing can be transmitted to the pressure measuring apparatus, and the left and right female molds are connected to form a sealing structure.
7. The apparatus for obtaining the sliding friction coefficient of powder according to claim 5, wherein the guide rail is located on the bottom plate of the box body, and the right female mold half is placed in the guide rail so as to satisfy the slight displacement of the right female mold half.
8. The method for obtaining the sliding friction coefficient of the powder is characterized by comprising the following steps:
when only the lower piston of the upper piston is positioned in a cavity formed by the left female die and the right female die, downward force is applied to the upper piston, and the force is the friction force between the piston and the female die when the lower piston and the upper piston integrally move at a constant speed;
applying a downward force to the upper piston, wherein the force is the friction force of the piston, the powder and the female die when the lower piston, the powder and the upper piston integrally move at a constant speed, and meanwhile, the side pressure of the powder and the die wall in the pressing process is obtained;
subtracting the friction force of the piston and the female die from the friction force of the piston, the powder and the female die to obtain the friction force of the powder and the inner wall of the female die;
the friction coefficient between the powder particles and the wall surface of the die without deformation is obtained based on the friction force between the powder and the inner wall of the female die and the side pressure between the powder and the die wall.
9. The method for obtaining the sliding friction coefficient of powder according to claim 8, wherein when the downward force is applied to the upper piston, different applied forces are obtained by adding different weights.
10. The method for obtaining the sliding friction coefficient of powder according to claim 8, wherein the cylindrical tubular female mold is divided into two parts along the central axis to obtain left and right female molds, the place where the rubber pad is arranged is the original connection place of the left and right female molds, and the right female mold is kept fixed when the friction force between the powder measuring piston and the mold is not added.
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| CN202010409026.7A CN111735761B (en) | 2020-05-14 | 2020-05-14 | Powder sliding friction coefficient acquisition method and device |
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Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5736630A (en) * | 1997-02-11 | 1998-04-07 | Welner; Jerome M. | Slip friction measurement and recording apparatus |
| CN201527393U (en) * | 2009-11-20 | 2010-07-14 | 北京理工大学 | Measuring device for particle surface friction coefficient |
| CN205067308U (en) * | 2015-10-15 | 2016-03-02 | 济南大学 | Experimental device for acquire granular material suppression power and mould wall frictional force |
| CN105928871A (en) * | 2016-05-30 | 2016-09-07 | 北京理工大学 | Forming explosive friction testing system and testing method thereof |
| CN106940231A (en) * | 2017-04-09 | 2017-07-11 | 河南工业大学 | A kind of test method and device for measuring silo bulk material pressure and sidewall friction power |
| CN109900410A (en) * | 2019-04-22 | 2019-06-18 | 兰州理工大学 | Slide valve pollutes frictional force real-time accurate measuring device and measuring method |
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2020
- 2020-05-14 CN CN202010409026.7A patent/CN111735761B/en active Active
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5736630A (en) * | 1997-02-11 | 1998-04-07 | Welner; Jerome M. | Slip friction measurement and recording apparatus |
| CN201527393U (en) * | 2009-11-20 | 2010-07-14 | 北京理工大学 | Measuring device for particle surface friction coefficient |
| CN205067308U (en) * | 2015-10-15 | 2016-03-02 | 济南大学 | Experimental device for acquire granular material suppression power and mould wall frictional force |
| CN105928871A (en) * | 2016-05-30 | 2016-09-07 | 北京理工大学 | Forming explosive friction testing system and testing method thereof |
| CN106940231A (en) * | 2017-04-09 | 2017-07-11 | 河南工业大学 | A kind of test method and device for measuring silo bulk material pressure and sidewall friction power |
| CN109900410A (en) * | 2019-04-22 | 2019-06-18 | 兰州理工大学 | Slide valve pollutes frictional force real-time accurate measuring device and measuring method |
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