CN114543742B - Method for measuring real contact area of metal surface in friction process - Google Patents
Method for measuring real contact area of metal surface in friction process Download PDFInfo
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- CN114543742B CN114543742B CN202210183574.1A CN202210183574A CN114543742B CN 114543742 B CN114543742 B CN 114543742B CN 202210183574 A CN202210183574 A CN 202210183574A CN 114543742 B CN114543742 B CN 114543742B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B21/00—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant
- G01B21/28—Measuring arrangements or details thereof, where the measuring technique is not covered by the other groups of this subclass, unspecified or not relevant for measuring areas
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B15/00—Measuring arrangements characterised by the use of electromagnetic waves or particle radiation, e.g. by the use of microwaves, X-rays, gamma rays or electrons
- G01B15/02—Measuring arrangements characterised by the use of electromagnetic waves or particle radiation, e.g. by the use of microwaves, X-rays, gamma rays or electrons for measuring thickness
Abstract
The invention belongs to the technical field of tribology research, and provides a method for measuring the real contact area of a metal surface in a friction process. The measuring method of the invention fixes the metal material to be measured immovably under positive pressure F n Under the action of the sliding friction pair, the sliding friction pair reciprocates on the metal material to be tested to perform surface-to-surface sliding friction; after the surface is subjected to sliding friction, measuring the thickness T of a plastic deformation layer of the metal material to be measured; calculating to obtain the real contact area A of the surface of the metal material to be measured in the friction process according to the formula 1:
in formula 1, F n Is positive pressure in units of N; a is the real contact area of the surface of the metal material to be measured in the friction process, and the unit is m 2 ；σ s The yield stress of the metal material to be measured is expressed in Pa, and the T is the thickness of the plastic deformation layer and is expressed in m. The method provided by the invention is used for surface-surface sliding friction, and can be used for measuring the real contact area of metal materials with various roughness in the friction process.
Description
Technical Field
The invention relates to the technical field of tribology research, in particular to a method for measuring the real contact area of a metal surface in a friction process.
Background
For the surfaces of the metal structures to rub against each other,the real contact area tends to be small, as shown in fig. 1 (a), and the real contact area is only a shaded portion (1, 2,3 \8230; j) in fig. 1 (a), for j contact units, which results in a great possibility of plastic deformation and even abrasion at the contact surface when the load applied to the contact surface is small. For any one contact unit i, the contact of the friction pair is actually two convex contacts, and as shown in (b) of fig. 1, the contact area can be approximated by a radius r i As shown in fig. 1 (c). By obtaining the radius r of the true contact area of each contact element i The real contact area of the friction pair can be obtained
The load value in the actual pressing process can be guided through the real contact area, and the abrasion and the failure of the matching surface caused by overlarge load are effectively solved.
Because of the randomness and the multi-scale of the surface morphology, the theoretical calculation is very difficult, the measurement is usually carried out by adopting an experimental method, the main experimental method is an optical measurement method, and the optical measurement method has the advantages that the evolution of the real contact area of the friction interface can be observed in real time on line by means of a computer image processing technology, the real contact area ratio is calculated by using the image processing technology, but the method is only suitable for the surface with lower surface roughness. In practice, the surfaces of metal workpieces are obtained by milling, the surface roughness is high, and how to measure the real contact area of the metal workpieces in the friction process needs to be solved.
Disclosure of Invention
In view of the above, the present invention provides a method for measuring a real contact area of a metal surface during a rubbing process. The measuring method provided by the invention can be suitable for measuring the real contact area of the metal surface with various roughness surfaces in the friction process.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a method for measuring the real contact area of a metal surface in a friction process, which comprises the following steps:
fixing the metal material to be measured in a positive pressure F n Under the action of the sliding friction pair, the sliding friction pair reciprocates on the metal material to be detected to perform surface-surface sliding friction;
after the surface is subjected to sliding friction, measuring the thickness T of a plastic deformation layer of the metal material to be measured;
calculating to obtain the real contact area A of the surface of the metal material to be measured in the friction process according to the formula 1:
in formula 1, F n Is positive pressure in units of N; a is the real contact area of the surface of the metal material to be measured in the friction process, and the unit is m 2 ；σ s The yield stress of the metal material to be measured is expressed in Pa, and the T is the thickness of the plastic deformation layer and is expressed in m.
Preferably, the friction surface of the metal material to be measured comprises a plane or a curved surface.
Preferably, the determining the thickness of the plastically deformed layer of the metal material to be measured includes: and (3) making a longitudinal section in the plastic deformation area of the metal material to be detected, carrying out scanning electron microscope testing on the longitudinal section, and obtaining the thickness T of the plastic deformation layer according to the obtained scanning electron microscope picture.
The invention provides a method for measuring the real contact area of a metal surface in a friction process, which comprises the following steps: fixing the metal material to be measured in a positive pressure F n Under the action of the sliding friction pair, the sliding friction pair reciprocates on the metal material to be detected to perform surface-surface sliding friction; after the surface is subjected to sliding friction, measuring the thickness T of a plastic deformation layer of the metal material to be measured; calculating to obtain the real contact area A of the surface of the metal material to be measured in the friction process according to the formula 1:
in formula 1, F n Being positive pressure, sheetThe bit is N; a is the real contact area of the surface of the metal material to be measured in the friction process, and the unit is m 2 ；σ s The yield stress of the metal material to be measured is expressed in Pa, and the T is the thickness of the plastic deformation layer and is expressed in m. The measuring method of the invention calculates the real contact area of the metal surface in the friction process by measuring the thickness of the plastic deformation layer, and has no relation with the surface roughness of the metal material, so that the real contact area of the metal material with various roughness in the friction process can be measured.
Drawings
FIG. 1 is a schematic view of the condition of metallic structure surfaces rubbing against each other;
FIG. 2 is a schematic view of the operation of the present invention to perform surface-to-surface sliding friction;
FIG. 3 is a schematic diagram of a longitudinal cross-section of a plastically deformed region of a metal material to be tested according to the present invention;
FIG. 4 is a scanning electron microscope photograph of a longitudinal section of a metal material to be measured after surface-to-surface sliding friction;
FIG. 5 is a scanning electron microscope photograph of a longitudinal section of a metal material to be measured without surface sliding friction;
FIG. 6 is a schematic view of a face-to-face sliding friction contact unit according to the present invention.
Detailed Description
The invention provides a method for measuring the real contact area of a metal surface in a friction process, which comprises the following steps:
fixing the metal material to be measured in a positive pressure F n Under the action of the sliding friction pair, the sliding friction pair reciprocates on the metal material to be tested to perform surface-to-surface sliding friction;
after the surface is subjected to sliding friction, measuring the thickness T of a plastic deformation layer of the metal material to be measured;
calculating to obtain the real contact area A of the surface of the metal material to be measured in the friction process according to the formula 1:
in formula 1, F n Is positive pressure in units of N; a is the real contact area of the surface of the metal material to be measured in the friction process, and the unit is m 2 ；σ s The yield stress of the metal material to be measured is expressed in Pa, and the T is the thickness of the plastic deformation layer and is expressed in m.
In the present invention, the substances used in the present invention are preferably commercially available products unless otherwise specified.
Fixing the metal material to be measured in a positive pressure F n Under the action of the sliding friction pair, the sliding friction pair does reciprocating motion on the metal material to be measured to perform surface-to-surface sliding friction.
In the present invention, the friction surface of the metal material to be measured preferably includes a plane or a curved surface. In the invention, the roughness of the metal material to be measured is not required, and the polished surface with the surface roughness of a few nanometers can be measured, and the milled surface with the surface roughness of a few tens of micrometers can also be measured. The material of the metal material to be measured is not particularly limited, and the metal material to be measured can be set according to actual needs.
The material of the sliding friction pair is not particularly limited, and the sliding friction pair may be set according to actual conditions, and particularly preferably comprises metal, resin, rubber or glass. The material of the sliding friction pair is not particularly limited and can be set according to actual measurement; for example, when the real contact area of the aluminum block under the friction of the resin material needs to be studied, the aluminum block is fixed, the resin material is used as a sliding friction pair, and the surface sliding friction is carried out under the action of positive pressure.
The invention is opposite to the positive pressure F n The size of the reciprocating motion, the reciprocating motion speed and the time of the surface sliding friction are not particularly limited and can be set according to actual conditions.
In the present invention, an operation diagram for performing the surface sliding friction is shown in fig. 2.
After the surface is subjected to sliding friction, the thickness T of the plastic deformation layer of the metal material to be measured is measured.
In the present invention, the determining the thickness of the plastically deformed layer of the metal material to be measured preferably includes: and (3) making a longitudinal section in the plastic deformation area of the metal material to be tested, carrying out scanning electron microscope test on the longitudinal section, and obtaining the thickness T of the plastic deformation layer according to the obtained scanning electron microscope photo.
In the present invention, the longitudinal cross section of the plastic deformation region of the metal material to be measured is shown in fig. 3, where T in fig. 3 is the thickness of the plastic deformation layer.
Fig. 4 is a scanning electron microscope photograph of a longitudinal section of a metal material to be measured after surface-to-surface sliding friction is performed, and fig. 5 is a scanning electron microscope photograph of a longitudinal section of a metal material to be measured without surface-to-surface sliding friction. As can be seen by comparing fig. 4 and 5: the surface after the surface-to-surface sliding friction had an obvious plastic deformation layer, which appeared white and high in brightness, and the thickness T of the plastic deformation layer was measured. And the longitudinal section scanning electron microscope photo of the metal material to be measured without surface sliding friction does not have a white highlight layer, namely a plastic deformation layer.
After the thickness T of the plastic deformation layer is obtained, the invention calculates and obtains the real contact area A of the metal surface in the friction process according to the formula 1:
in formula 1, F n Is positive pressure in units of N; a is the real contact area of the surface of the metal material to be measured in the friction process, and the unit is m 2 ；σ s The yield stress of the metal material to be measured is expressed in Pa, and the T is the thickness of the plastic deformation layer and is expressed in m.
In the present invention, for any one of the contact units i, the contact state of the contact unit and the surface of the metal material to be measured can be simplified to the contact of a sphere and a plane, as shown in fig. 6. During the surface-to-surface sliding friction, the plastic flow diffuses into the surrounding material, centered on the contact area, and the plastic strain gradually decreases during the diffusion process until it reaches the radius T j And there is only elastic strain in the metal material, which forms the plastic-elastic deformation boundary.
In the plastic deformation region (r) shown in FIG. 6 i ≤r≤T i ) Internal, stress can be expressed as:
wherein σ ri : in a polar coordinate system, the stress of the metal material to be measured along the polar axis direction has the unit: pa;
σ θi : in a polar coordinate system, the stress of the metal material to be measured along the polar angle direction has the unit: pa;
σ s : the yield stress of the metal material to be measured can be obtained by looking up a table, and the unit is as follows: pa.
In the elastically deformed region (r ≧ T) shown in FIG. 6 i ) Internal: the stress can be expressed as:
wherein σ ri : in a polar coordinate system, the stress of the metal material to be measured along the polar axis direction has the unit: pa;
σ θi : in a polar coordinate system, the stress of the metal material to be measured along the polar angle direction has the unit: pa;
σ s : the yield stress of the metal material to be measured can be obtained by looking up a table, and the unit is as follows: pa.
At hydrostatic pressure zone boundary (r = r) i )：
The above two formulas can be used to obtain the T for the plastic deformation layer i Radius of true contact r i The relationship of (1) is:
in the formula, F ni : load acting on any one contact unit i, unit: n;
σ s : the yield stress of the metal material to be measured can be obtained by looking up a table, and the unit is as follows: pa;
T i : thickness of the plastic deformation layer, unit: and m is selected.
In the course of real experiments, the thickness of the plastically deformed layer was the result of the interaction of all contact elements (1, 2,3 \8230; \8230j), so that the thickness of the plastically deformed layer in FIG. 4 was the result of
Sum of loads for the entire real area of the metallic material to be measured
The total radius of the whole real area of the metal material to be measured is
Therefore, the whole real contact area of the metal material to be measured
Further, it is found that:
the following will describe the method for measuring the actual contact area of the metal surface during the rubbing process in detail with reference to the examples, but they should not be construed as limiting the scope of the present invention.
Example 1
Determination of die Steel (Friction surface planar, roughness R) a 183.1 nm) determination of the real contact area during rubbing under an aluminum sliding friction couple:
the experimental conditions are as follows:
friction experiment machineLoad applied to: f n ＝100mN；
Speed of reciprocating motion: s =4mm/S;
the reciprocating motion period is as follows: 10;
the reciprocating motion path is as follows: 5mm;
the sliding friction pair is made of the following materials: al;
the metal material to be measured: die steel;
time of face sliding friction: 12.5s;
and (3) making a longitudinal section of the plastic deformation area of the die steel according to the figure 3, and scanning by using a scanning electron microscope to obtain the thickness T of the plastic deformation layer of the longitudinal section of the die steel after the surface sliding friction is obtained: 10.6 μm.
Calculating to obtain the real contact area of the die steel in the process of friction under the aluminum sliding friction pair by using a formula 1: a =8.98 μm 2 。
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (3)
1. A method for measuring the real contact area of a metal surface in a friction process is characterized by comprising the following steps:
fixing the metal material to be measured in a positive pressure F n Under the action of the sliding friction pair, the sliding friction pair reciprocates on the metal material to be tested to perform surface-to-surface sliding friction;
after the surface is subjected to sliding friction, measuring the thickness T of a plastic deformation layer of the metal material to be measured;
calculating to obtain the real contact area A of the surface of the metal material to be measured in the friction process according to the formula 1:
in formula 1, F n Is positive pressure in units of N; a is the real contact area of the surface of the metal material to be measured in the friction process, and the unit is m 2 ；σ s The yield stress of the metal material to be measured is expressed in Pa, and the T is the thickness of the plastic deformation layer and is expressed in m.
2. The measurement method according to claim 1, wherein the friction surface of the metal material to be measured includes a flat surface or a curved surface.
3. The method of claim 1, wherein the determining the thickness of the plastically deformable layer of the metallic material to be measured comprises: and (3) making a longitudinal section in the plastic deformation area of the metal material to be tested, carrying out scanning electron microscope test on the longitudinal section, and obtaining the thickness T of the plastic deformation layer according to the obtained scanning electron microscope photo.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2008134184A (en) * | 2006-11-29 | 2008-06-12 | Nippon Avionics Co Ltd | Method and apparatus for evaluating joining properties/connectivity of surface of metal |
| JP2010266297A (en) * | 2009-05-14 | 2010-11-25 | Nippon Telegr & Teleph Corp <Ntt> | Friction coefficient measuring instrument |
| JP2016138330A (en) * | 2015-01-26 | 2016-08-04 | 明 小豆島 | Metal material having surface shape allowing low friction coefficient |
| CN110619164A (en) * | 2019-09-05 | 2019-12-27 | 北京工业大学 | Modeling method for friction coefficient of contact surface based on fractal theory and Florida theory |
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- 2022-02-28 CN CN202210183574.1A patent/CN114543742B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2008134184A (en) * | 2006-11-29 | 2008-06-12 | Nippon Avionics Co Ltd | Method and apparatus for evaluating joining properties/connectivity of surface of metal |
| JP2010266297A (en) * | 2009-05-14 | 2010-11-25 | Nippon Telegr & Teleph Corp <Ntt> | Friction coefficient measuring instrument |
| JP2016138330A (en) * | 2015-01-26 | 2016-08-04 | 明 小豆島 | Metal material having surface shape allowing low friction coefficient |
| CN110619164A (en) * | 2019-09-05 | 2019-12-27 | 北京工业大学 | Modeling method for friction coefficient of contact surface based on fractal theory and Florida theory |
Non-Patent Citations (2)
| Title |
|---|
| Contact analysis of elastic-plastic fractal surfaces;W. Yan et.al;《Journal of Applied Physics》;19981031;第84卷(第7期);第3617-3624也 * |
| Plastic deformation and contact area of an elastic–plastic;J. Jamari et.al;《Tribology International》;20071231(第40期);第1311-1318页 * |
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