CN115015103B - Real-time detection method and device for friction factor and microscopic morphology of material surface - Google Patents
Real-time detection method and device for friction factor and microscopic morphology of material surface Download PDFInfo
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- CN115015103B CN115015103B CN202210575660.7A CN202210575660A CN115015103B CN 115015103 B CN115015103 B CN 115015103B CN 202210575660 A CN202210575660 A CN 202210575660A CN 115015103 B CN115015103 B CN 115015103B
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Abstract
The invention discloses a real-time detection method and a device for a friction force factor and a microscopic morphology of a material surface. And when the loading tension is increased, obtaining a friction factor according to a loading tension value and a friction factor formula, scanning by the linear array CCD to obtain surface friction morphology image information of the bar-shaped test piece in a stretch bending forming state when the loading tension value is applied, and finally generating a real-time relation corresponding diagram of the friction factor and the surface friction morphology image information of the bar-shaped test piece in the stretch bending friction test and the loading pressure.
Description
Technical Field
The invention relates to the technical field of tribology, in particular to a method and a device for detecting a friction factor and a microscopic morphology of a material surface in real time.
Background
Friction is critical in the cold hot forming process, affecting the final quality of the part, and is also directly related to the wear of the surfaces of the part and the die. In recent years, the application of advanced steel, aluminum and composite materials on automobile bodies is rapidly expanded, and how to measure the friction factor of a plate and synchronously detect the surface appearance of the friction between the plate and a die in the metal cold stamping and hot stamping forming processes of the plate in the industry is an important scientific problem all the time, and a scientific method and a realization means are needed.
The existing testing mode is to test through a tensile bending test, and the conventional method for measuring the friction factor and analyzing the appearance of the friction surface of the sample are separately carried out. After the stretch bending friction test, the change of the friction surface of the sample is observed through secondary sampling of the friction test piece and subsequent microscopy, so that the relation between the friction factor and the appearance of the friction surface of the sample is obtained. However, because plastic strain occurs on the surface of the material during the tensile bending test, only the static morphology of the surface of the test piece with roughness change can be obtained after observation, the measurement error is very large, the dynamic change process of the friction morphology of the surface of the test piece during the tensile bending test cannot be observed, and the real-time change relationship between the friction factor and the surface morphology of the strip-shaped test piece cannot be revealed.
Disclosure of Invention
The invention aims to provide a method and a device for detecting a friction factor of a material surface and a microscopic morphology of the material surface in real time, which can reveal the relation between the friction factor and the real-time change of the surface morphology of a strip-shaped test piece.
In order to achieve the purpose, the invention provides a technical scheme that: a real-time detection method for friction factor and microscopic morphology of a material surface comprises the following steps:
step S1, respectively arranging roller supporting pieces on two sides of a sapphire mold with a rectangular upper half section and an arc lower half section, penetrating one end of a strip-shaped test piece into the upper side of the roller supporting piece on one side of the sapphire mold, penetrating the strip-shaped test piece out of the upper side of the roller supporting piece on the other side of the sapphire mold through the lower side of the lower half section of the sapphire mold, and pressing the sapphire mold downwards to enable the strip-shaped test piece to be tightly attached to the lower half section of the sapphire mold, so that a contact section of the strip-shaped test piece and the lower half section of the sapphire mold meets the wrap angle requirement of the sapphire mold;
s2, arranging a linear array CCD at the focus of a sapphire die, symmetrically arranging a plurality of groups of light sources on two sides of the linear array CCD, gathering interface reflected light of a bar-shaped test piece to the linear array CCD through the sapphire die by the aid of the light sources, and performing three-dimensional reconstruction on the surface geometry of the bar-shaped test piece by the aid of data acquired by the linear array CCD through an image signal preamplifier and a computer image processing system by means of ultra-depth-of-field measurement and a three-dimensional contour measurement method to obtain surface friction morphology image information of the bar-shaped test piece after stretch bending forming;
s3, applying a loading tension on one end of the bar-shaped test piece, detecting a pressure value in real time through a sensor, recording the pressure value as Fd, applying a fixed tension on the other end of the bar-shaped test piece as resistance generated by back pressure, recording the resistance as Ft, and calculating a friction factor mu between the bar-shaped test piece and the lower half face of the sapphire mold according to the Ft, the Fd and a wrap angle theta of the sapphire mold;
the friction factor is calculated by the formula: μ =2 (Fd-Ft-Fb)/(θ (Fd + Ft));
wherein Fb is the friction force between the strip-shaped test piece and the lower half surface of the sapphire mold, fb = μ Pav, pav is the average contact pressure of a friction pair, pav = (Ft + Fd)/2 wR, wherein R is the arc radius of the lower half part of the sapphire mold, and w is the width of the strip-shaped test piece;
and S4, when the loading tension is continuously increased, obtaining a current friction factor according to a current loading tension value and a friction factor calculation formula, and obtaining surface friction appearance image information of the bar-shaped test piece in the current stretch-bending forming state by scanning the linear array CCD when the current loading tension value is applied, and finally generating a real-time relation corresponding graph of the friction factor and the surface friction appearance image information of the bar-shaped test piece in the stretch-bending friction test and the whole loading pressure process.
Optionally, in step S2, the three-dimensional reconstruction of the surface geometry of the bar test piece by the linear array CCD includes:
and calculating the surface type of the mirror surface according to the measurement result and the mirror surface reflection geometrical relationship of the calibrated sapphire mold by adopting a three-dimensional profile measurement method and ultra-depth-of-field measurement.
Optionally, the central angle of the arc of the lower half of the sapphire mold is a wrap angle, and the wrap angle is between 30 ° and 120 °.
Optionally, the light source is a bar array adjustable light source.
Optionally, before the sapphire mold is placed on the surface of the bar-shaped test piece, the bar-shaped test piece is subjected to contact heating or induction heating.
Optionally, before the sapphire die is placed on the surface of the bar-shaped test piece, a lubricant is coated on the surface of the bar-shaped test piece.
Optionally, in step S4, after the linear array CCD scans the image information of the friction morphology of the bar-shaped test piece in the current stretch-bending forming state, the roughness of the bar-shaped test piece in the current stretch-bending forming state is obtained by matching and comparing the current image information with the standard image information on the standard roughness comparison table, and finally a corresponding graph of the whole process real-time relationship between the friction factor, the roughness, the surface friction morphology image information and the loading pressure of the bar-shaped test piece in the stretch-bending friction test is generated.
Optionally, when the linear array CCD acquires the surface friction topography image of the bar-shaped test piece below the sapphire mold, after acquiring a bar-shaped test piece of a unit length each time, the bar-shaped test piece moves to a next unit length, then the linear array CCD acquires the bar-shaped test piece of the next unit length, after continuous multiple acquisition, the acquired data are spliced into a two-dimensional image, and the surface geometry of the bar-shaped test piece is three-dimensionally reconstructed by combining an image signal preamplifier and a computer image processing system, and then by combining super depth of field measurement and a three-dimensional profile measurement method, the surface friction topography image information of the bar-shaped test piece after stretch bending is finally acquired.
The invention also provides a technical scheme that: a device applying the material surface friction force factor and the microscopic morphology real-time detection method comprises the following steps:
the sapphire die is provided with an upper half part and a lower half part, the cross section of the upper half part is rectangular, the cross section of the lower half part is arc-shaped, and the sapphire die is used for pressing a strip-shaped test piece;
the servo motor tension device is connected with one end of the strip-shaped test piece through a chuck and is used for applying loading tension to the strip-shaped test piece; a sensor is also connected between the servo motor tension device and the chuck and used for monitoring the loading tension in real time;
the backpressure weight is connected with the other end of the strip-shaped test piece through the holder and is used for applying fixed tension as resistance generated by backpressure; a steel wire rope is connected between the backpressure weight and the holder and supported by a steering roller;
the two groups of roller supporting pieces are positioned below the bar-shaped test piece and used for enabling the bar-shaped test piece to be tightly attached to the lower half part of the sapphire mold, so that the contact section of the bar-shaped test piece and the lower half part of the sapphire mold meets the wrap angle requirement of the sapphire mold, and the two groups of roller supporting pieces are distributed on two sides of the sapphire mold;
the linear array CCD is positioned at the focus of the sapphire mold and is used for acquiring surface friction topography image information of the strip-shaped test piece below the sapphire mold in real time;
the two light sources are symmetrically arranged on two sides of the linear array CCD and used for irradiating the strip-shaped test piece;
the image signal pre-amplifier is connected to the top of the linear array CCD and is used for amplifying surface friction topography image information collected by the linear array CCD;
and the computer image processing system is connected with the image signal pre-amplifier and is used for carrying out three-dimensional reconstruction on the surface geometric shape of the bar-shaped test piece by combining super depth of field measurement and a three-dimensional contour measurement method and finally obtaining the surface friction topography image information of the bar-shaped test piece after stretch bending forming.
Optionally, the device for detecting the microscopic morphology of the material surface further includes a data analysis system, the current friction factor is obtained according to a current tension value and a friction factor calculation formula, and the image information of the surface friction morphology of the bar-shaped test piece in the current stretch-bending forming state is obtained by scanning the linear array CCD when the current loading tension value is applied, so as to finally generate a corresponding graph of the whole process real-time relationship between the friction factor and the image information of the surface friction morphology of the bar-shaped test piece in the stretch-bending friction test and the loading pressure.
Compared with the prior art, the invention has the beneficial effects that:
1. the material surface friction factor and the microscopic morphology real-time detection method of the invention comprises the steps of placing a sapphire mold with a rectangular upper half section and an arc lower half section on the surface of a strip-shaped test piece, and enabling the strip-shaped test piece to cling to the lower half section of the sapphire mold, so that the contact section of the strip-shaped test piece and the lower half section of the sapphire mold meets the wrap angle requirement of the sapphire mold; the sapphire mould is made of transparent sapphire materials, and the design has the advantages that: the sapphire mold has the strength and the surface hardness of a metal mold, the surface roughness of the sapphire mold is processed to be the same level as that of a steel mold, the physical property requirement of an optical experiment method is met, the sapphire mold has the function of an optical lens, a plurality of groups of light sources can be emitted and transmitted to a strip-shaped test piece, and interface reflected light of the strip-shaped test piece is gathered to a linear array CCD.
2. The method comprises the steps of applying a loading tension on one end of a strip-shaped test piece, applying a fixed tension on the other end of the strip-shaped test piece as a resistance generated by a back pressure to deform the strip-shaped test piece, meanwhile, gathering interface reflected light of the strip-shaped test piece on a linear array CCD under the irradiation of a light source, performing three-dimensional reconstruction on the geometric shape of the surface of the strip-shaped test piece through the linear array CCD in combination with super-depth-of-field measurement and three-dimensional profile measurement, and acquiring surface friction morphology image information of the strip-shaped test piece after stretch bending forming through an image signal preamplifier and a computer image processing system. And when the loading tension is continuously increased, obtaining a current friction factor according to a current loading tension value and a friction factor calculation formula, and finally generating a real-time relation corresponding diagram of the friction factor of the bar-shaped test piece in the stretch bending friction test, the surface friction profile image information and the loading pressure in the whole process by scanning the linear array CCD when the current loading tension value is applied, so that the technical problems that the dynamic change process of the friction form of the surface of the test piece in the stretch bending test process cannot be observed, and the real-time change relation of the friction factor and the surface form of the bar-shaped test piece cannot be revealed in the prior art are solved.
3. The material surface friction factor and the microscopic morphology real-time detection method reduce friction and wear through the difference between the flowing and covering area of the lubricant and the friction behavior under the same load test condition.
4. According to the real-time detection method for the friction factor and the microscopic morphology of the surface of the material, disclosed by the invention, the strip-shaped test piece is subjected to contact heating or induction heating, and under the same load test condition, the morphologies of the strip-shaped test pieces at different temperatures are different, so that an observation experiment can be carried out.
5. The material surface friction force factor and the light source of the real-time detection method of the microscopic morphology are symmetrically distributed on two sides of the linear array CCD, so that the light source at the bottom of the sapphire die is uniform and convenient to collect.
6. The friction factor formula of the invention can calculate the friction factor between the strip-shaped test piece and the sapphire die only according to the applied tension data and the wrap angle, simplifies the complex friction factor formula and improves the precision of the friction factor formula.
7. The sapphire die adopts the semi-cylindrical optical lens and the male die, can be used in a stretch bending friction test, enables a bar-shaped test piece to move on the cylindrical surface for friction calculation, and is convenient for calculating a friction factor; the data acquired for a plurality of times can be spliced into a two-dimensional image.
8. The invention adopts an LED strip light source, alternately irradiates targets on two sides of a linear array CCD, can generate shadows with different target heights, can calculate the target height (because the incident angle is known) by measuring the shadow width through photography, alternately irradiates, can solve the shadow difference projected by the adjacent height difference of the targets, and obtains more continuous and accurate transition height. With the method of the invention, the subsequent three-dimensional profile measurement and super-depth-of-field measurement can obtain relevant mechanical data, which is of great significance and is a precondition that the existing instrument can not realize.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
FIG. 1 is a main flowchart of the method for real-time detection of the friction factor and the microstructure of the surface of the material according to the present invention;
FIG. 2 is a schematic view of the microstructure detecting apparatus for detecting the micro-topography of the surface of a material according to the present invention;
FIG. 3 is an enlarged view of a portion of the microstructure detecting apparatus for detecting the surface of a material according to the present invention;
FIG. 4 is a partial top view of an apparatus for detecting the microscopic topography of a material surface in accordance with the present invention;
FIG. 5 is a graph of friction factor versus mean pressure, and topographical images versus friction factor, in accordance with the present invention.
In the figure:
the method comprises the following steps of 1-a sapphire die, 2-a linear array CCD, 3-a strip-shaped test piece, 4-an image signal preamplifier, 5-a first light source, 6-a second light source, 7-a roller support, 8-a chuck, 9-a servo motor tension device, 10-a tension sensor, 11-a holder, 12-a steering roller, 13-a backpressure weight and 14-a computer image processing system.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.
In the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
A CCD (Charge-coupled Device) is a semiconductor Device, which uses the amount of Charge to represent the magnitude of a signal and transmits the signal in a coupled manner.
The core of the linear CCD is a photosensitive array composed of a row of photodiodes (each photodiode has its own integration circuit, which is called as a pixel), a row of integration capacitors are arranged behind the array, the photodiodes generate photocurrent under the impact of light energy to form an active integration circuit, and then the integration capacitors are used for storing charges converted from the light energy. The more charges stored in the integrating capacitor, the greater the light intensity collected by the corresponding photodiode in front, and when the light intensity is close to saturation, the gray level of the pixel point is close to full white and is white level. It can be seen that the linear CCD extraction signal is passively received by the reflected light.
Referring to fig. 1 to 5, the invention provides a real-time detection method for a friction factor and a micro-topography of a material surface, which comprises the following steps:
step S1, the cross-section of the upper half part is rectangular, the cross-section of the lower half part is arc-shaped sapphire mold 1 (namely, the upper half part of the sapphire mold 1 is a cuboid, the lower half part is a half cylindrical surface), two sides are respectively provided with a roller support member 7, one end of a strip-shaped test piece 3 penetrates from the upper part of the roller support member 7 on one side of the sapphire mold 1, the strip-shaped test piece 3 penetrates out from the upper part of the roller support member 7 on the other side of the sapphire mold 1 and is pressed downwards, the strip-shaped test piece 3 is tightly attached to the lower half part of the sapphire mold 1, and the design of the structure can enable the contact section of the strip-shaped test piece 3 and the lower half part of the sapphire mold 1 to meet the requirement of the wrap angle of the sapphire mold 1.
As shown in fig. 2, the central angle of the lower half arc of the sapphire mold 1 is a wrap angle θ, cos θ = H/R, where H is the height of the upper half rectangle of the sapphire mold 1 and R is the radius of the lower half arc of the sapphire mold 1.
The sapphire die 1 can be designed into different models according to different wrap angles theta, wherein the wrap angles theta are from 30 degrees to less than or equal to 120 degrees and can be 60 degrees, 90 degrees and the like.
The sapphire mould 1 is made of transparent sapphire materials, and the design has the advantages that: the sapphire die 1 has the strength and the surface hardness of a metal die, the surface roughness of the sapphire die is processed to be the same level as that of a steel die, the physical property requirements of an optical experiment method are met, the sapphire die has the function of an optical lens, a plurality of groups of light sources can be emitted to be transmitted to a strip-shaped test piece 3, and interface reflected light of the strip-shaped test piece 3 is gathered to a linear array CCD 2.
S2, arranging a linear array CCD2 above the sapphire mold 1, symmetrically arranging a plurality of groups of light sources on two sides of the linear array CCD2, enabling interface reflected light of the strip-shaped test piece 3 to be gathered to the linear array CCD2 through the sapphire mold 1 by the aid of light emitted by the plurality of groups of light sources, enabling data collected by the linear array CCD2 to pass through an image signal preamplifier 4 and a computer image processing system 14, carrying out three-dimensional reconstruction on the surface geometry of the strip-shaped test piece 3 by combining super depth of field measurement and a three-dimensional profile measurement method, adopting a three-dimensional profile measurement method and super depth of field measurement, and calculating the surface shape of a mirror surface according to a measurement result and a calibrated mirror reflection geometry relation of the sapphire mold 1, so that surface friction profile image information of the strip-shaped test piece 3 after stretch bending is obtained.
In the process of the tensile bending test, the acquisition of dynamic image information of the change of the surface morphology of the test piece caused by the friction between the strip test piece 3 and the sapphire die 1 is as follows:
(1) There is relative motion between bar test piece and the sapphire mould 1, and bar test piece 3 receives the tensile force of two directions in this experiment and makes it produce deformation, and bar test piece surface and sapphire mould 1 contact under the tensile force effect. Meanwhile, under the action of a tensile force, the strip-shaped test piece generates an average contact pressure Pav of a friction pair on the surface of the sapphire die 1, and when the difference of the generated tensile force is greater than a friction force Fb, the test piece moves; when the linear array CCD2 collects images at high speed, after one line is collected each time, the bar-shaped test piece just moves to the next unit length, and the collection of the next line is continued. The data acquired continuously for a plurality of times can be spliced into a two-dimensional image. The accuracy of the line array image acquisition depends on the resolution of the line array and the speed of the scan.
(2) The speed V of the stretch bending movement of the friction test only needs to meet the stamping speed of the actual die plate, and is generally V = 0.1-10 mm/Sec.
(3) The resolution accuracy of the linear array CCD2 is required to be from 0.01 to 0.001mm as required for the degree of fineness of image observation.
(4) Since the bar specimen 3 to be measured is opaque, it is necessary to take illumination light above the lens. Two groups of light sources (preferably, LED strip array light sources) are used as incident light and are irradiated on the strip-shaped test piece 3 in contact with the semi-cylindrical surface through the semi-cylindrical surface of the sapphire mold 1. The reflected light of the strip-shaped test piece 3 and the interface is focused on the linear array CCD2 by the cylindrical lens and is photoelectrically converted into a digital image signal. In order to resist interference and transmit signals in a long distance, the digital image signals are amplified through an image signal preamplifier 4 and transmitted to a computer image processing system through a line.
(5) The light source adopts an LED strip light source, the targets are alternately irradiated on two sides of the linear array CCD, shadows with different target heights can be generated, the target height (because the incident angle is known) can be calculated by measuring the shadow width through photography, the shadow difference projected by the adjacent height difference of the targets can be solved through alternate irradiation, and the more continuous and accurate transition height can be obtained. This method is a non-contact method for measuring roughness. The application purpose of the invention is to measure macroscopic friction force (calculate friction factor) and observe the appearance of the friction test piece. With the method, the subsequent three-dimensional profile measurement and super-depth-of-field measurement can obtain related mechanical data, which is significant and also a precondition that the existing instrument cannot realize.
S3, applying a loading tension on one end of the strip-shaped test piece 3, detecting a pressure value in real time through a sensor, marking the pressure value as Fd, applying a fixed tension on the other end of the strip-shaped test piece 3 as resistance generated by back pressure, marking the resistance as Ft, and calculating a friction factor mu between the strip-shaped test piece 3 and the lower half face of the sapphire mold 1 according to the Ft, the Fd and a wrap angle theta of the sapphire mold 1;
the friction factor is calculated by the formula:
μ＝2(Fd-Ft-Fb)/(θ(Fd+Ft))， (1)；
wherein, fb is the frictional force of bar test piece 3 and sapphire mould 1 the latter half face:
Fb＝μPav， (2)；
pav is the average contact pressure of the friction pair:
Pav＝(Ft+Fd)/2wR， (3)；
wherein, R is the arc radius of the lower half part of the sapphire die 1, and w is the width of the strip-shaped test piece 3;
obtaining the following through formula transformation: μ =4wR θ (Fd-Ft)/(θ (1 +2wr θ) (Fd + Ft)), (4).
Through the formula (4), the friction factor between the strip-shaped test piece and the sapphire die 1 can be calculated only according to the applied tension data and the wrap angle, the complex friction factor formula is simplified, and the precision of the friction factor formula can be improved.
And S4, when the loading tension is continuously increased, obtaining a current friction factor according to a current loading tension value and a friction factor calculation formula, scanning the current loading tension value by the linear array CCD2 to obtain the surface friction appearance image information of the bar-shaped test piece 3 in the current stretch-bending forming state, and finally generating a real-time relation corresponding graph of the friction factor and the surface friction appearance image information of the bar-shaped test piece 3 in the stretch-bending friction test and the loading pressure in the whole process.
In an embodiment of the present invention, the plurality of light sources may be two groups of light sources, the two groups of light sources include a first light source 5 and a second light source 6, and the first light source 5 and the second light source 6 are both LED strip array light sources and are symmetrically arranged on two sides of the linear array CCD2, so that the light sources at the bottom of the sapphire mold 1 are relatively uniform and convenient to collect, and the brightness thereof can be adjusted according to the use requirement.
In another embodiment of the present invention, before step S1, a lubricant may be coated on the surface of the strip-shaped test piece 3, so as to reduce friction and wear through the difference between the flowing and coverage area of the lubricant and the friction behavior under the same load test condition, and also to test the morphology under different lubricants.
In the experimental process, the lubrication characteristic of the interface between the strip-shaped test piece 3 and the sapphire mold 1 can be measured, and when the average contact pressure of the strip-shaped test piece 3 is low, the surface roughness rises to the dominant position, and the friction factor becomes constant. Further, increasing the average contact pressure of the strip-shaped test piece 3 causes flattening of the surface roughness, thereby lowering the friction factor.
Before step S1, before placing the sapphire mold 1 on the surface of the bar-shaped test piece 3, the bar-shaped test piece 3 may be subjected to contact heating or induction heating, and by heating the bar-shaped test piece 3, the bar-shaped test pieces 3 at different temperatures have different morphologies under the same load test condition, so that the observation experiment can also be performed.
The device and the method are suitable for cold stretch bending test of metal plates and composite material (GFRP/CFRP) test. In the preamble of a cold stretch bending friction device, an induction heating method is added to realize a metal friction appearance observation experiment at different temperatures, and the device can be used for testing friction factors and surface appearances of metal plates below 550 ℃, particularly high-strength aluminum alloy plates in a hot stretch bending process.
In step S4, after the linear array CCD2 scans the image information of the friction profile of the bar-shaped test piece 3 in the current stretch-bending forming state, the roughness of the bar-shaped test piece 3 in the current stretch-bending forming state is obtained by matching and comparing the current image information with the standard image information on the standard roughness comparison table, and finally a corresponding graph of the friction factor, the roughness, the surface friction profile image information and the whole process real-time relationship of the loading pressure of the bar-shaped test piece 3 in the stretch-bending friction test is generated.
Referring to fig. 2, an embodiment of the present disclosure provides an apparatus for detecting a micro-topography of a material surface, including: the device comprises a sapphire mold 1, a servo motor tension device 9, a backpressure weight 13, two groups of roller supporting pieces 7, a linear array CCD2, two groups of light sources, an image signal preamplifier 4 and a computer image processing system 14, wherein the sapphire mold 1 is provided with an upper half part and a lower half part, the cross section of the upper half part is rectangular, the cross section of the lower half part is arc-shaped, and the sapphire mold 1 is used for pressing a strip-shaped test piece 3; the servo motor tension device 9 is connected with one end of the strip-shaped test piece 3 through the chuck 8 and used for pulling the strip-shaped test piece 3; a sensor is also connected between the servo motor tension device 9 and the chuck 8; the backpressure weight 13 is connected with the other end of the bar-shaped test piece 3 through the holder 11 and is used for pulling the bar-shaped test piece 3; a steel wire rope is connected between the backpressure weight 13 and the holder 11 and supported by the steering roller 12; the two groups of roller supporting pieces 7 are positioned below the bar-shaped test piece 3 and used for supporting the bar-shaped test piece 3, and the two groups of roller supporting pieces 7 are distributed on two sides of the sapphire die 1; the linear array CCD2 is positioned at the focus of the sapphire mold 1 and used for collecting the appearance of a strip-shaped test piece 3 below the sapphire mold 1; the two light sources are symmetrically arranged on two sides of the linear array CCD2 and are used for irradiating the strip-shaped test piece 3; the image signal preamplifier 4 is connected to the top of the linear array CCD2 and is used for amplifying the appearance collected by the linear array CCD 2; the computer image processing system 14 is connected with the image signal preamplifier 4 and is used for acquiring the feature amplified by the image signal preamplifier 4.
The working principle is as follows: the detection device can be executed and controlled by a servo motor tension device 9, the speed of the detection device can be adjusted steplessly (V = 0.1-20 mm/Sec) to meet the accurate requirement of the test, the tension range (50-500N) detected by a backpressure weight 13 is input into a computer image processing system 14, a bar-shaped test piece 3 is supported by two roller supporting pieces 7 (supporting rollers with rolling bearings), the sapphire mold 1 is pressed to a certain degree under the condition that the roller supporting pieces 7 are not moved, the contact section of the bar-shaped test piece 3 and the sapphire mold 1 meets the wrap angle requirement, a chuck 8 and a holder 11 are connected to two ends of the bar-shaped test piece 3, the holder 11 is connected with a flexible steel wire rope, the steel wire rope is turned by a turning roller 12, and the tail end of the flexible steel wire rope is connected with the backpressure weight 13. Thereby exert loading pulling force through servo motor tension device 9, backpressure weight 13 applys fixed pulling force, and bar test piece 3 can rub on sapphire mould 1, and the surface appearance of bar test piece 3 can take place deformation during the friction.
Meanwhile, under the irradiation of a light source, interface reflected light of the bar-shaped test piece 3 is gathered on the linear array CCD2, when the linear array CCD2 collects a surface friction topography image of the bar-shaped test piece 3 below the sapphire mold 1, after one unit length bar-shaped test piece 3 is collected each time, the bar-shaped test piece 3 moves to the next unit length, then the linear array CCD2 collects the bar-shaped test piece 3 of the next unit length, after continuous multiple collection, the collected data are spliced into a two-dimensional image, and the surface geometry of the bar-shaped test piece 3 is subjected to three-dimensional reconstruction through the image signal preamplifier 4 and the computer image processing system 14 by combining super depth of field measurement and a three-dimensional contour measurement method, and finally surface friction topography image information of the bar-shaped test piece 3 after stretch bending forming is obtained; and when the loading tension is continuously increased, obtaining a current friction factor according to a current loading tension value and a friction factor calculation formula, and scanning by the linear array CCD2 to obtain surface friction morphology image information of the bar-shaped test piece 3 in a current stretch bending forming state when the current loading tension value is applied, and finally generating a real-time relation corresponding diagram of the friction factor and the surface friction morphology image information of the bar-shaped test piece 3 in the stretch bending friction test and the whole loading pressure process.
The device for detecting the microscopic morphology of the material surface further comprises a data analysis system, a current friction factor is obtained according to a current tension value and friction factor calculation formula, surface friction morphology image information of the bar-shaped test piece 3 in the current stretch-bending forming state is obtained by scanning the linear array CCD2 when the current loading tension value is applied, and finally a corresponding graph of the friction factor of the bar-shaped test piece 3 in the stretch-bending friction test, the surface friction morphology image information and the loading pressure in the whole process real-time relation is generated.
The specific case of the invention is as follows:
(1) A practical case is shown in figure 4. The sapphire die 1 is characterized in that a cylindrical surface A =40mm and a cylindrical surface width B =20mm. Is made of transparent sapphire material, and the surface roughness of the sapphire material is processed to the same level as that of a steel mould. The central angle of the cylindrical surface of the lens is 90 degrees, and the wrap angle requirement of a test piece and a die in a stretch bending experiment is met. The focus of the cylindrical lens is a linear array CCD device 2.
(2) The linear array CCD2 device has the width B =20mm, the precision E =0.01mm and the speed Vmax =50mm/s; pixel 2000 (actual choice 2048); the actual precision is 0.009766 mm/pixel; the camera scan frequency was calculated to be 5.12KHz (2048 pixels is preferred, linear array CCD array device with frequency 6-10 KHz).
(3) The two groups of light sources are selected to be LED strip array light sources which are symmetrically arranged on two sides of the linear array CCD, and the brightness of the linear array CCD can be adjusted.
(4) The image preprocessing amplifier 4 has the bandwidth of 10kHz, the input of 0-50mv and the output of 0-5V, and the USB electrical and cable standard.
(5) The data image processing system selects a microcomputer and a Window operating system and is provided with a USB interface.
(6) The motion and load testing system is executed and controlled by a digital servo ball screw tension system 9, and the speed of the motion and load testing system can be steplessly regulated (V = 0.1-20 mm/Sec) so as to meet the accurate requirement of the test. The sensor 10 detects the tensile force range (0-500N) of the test piece and inputs data into the data processing computer system 14;
(7) The strip test piece is an A1100 aluminum plate, the thickness of the strip test piece is 1mm, the strip width (W) of the strip test piece is 18mm, and the length of the strip test piece is 500mm. The moving speed of the test piece relative to the die is 5-10 mm/Sec.
(8) Typical results of the measurements of friction factors and surface topography are shown in FIG. 5. The ordinate is the friction factor μ of the test, the abscissa is the average pressure Pav (N), and the images in the figure are surface topography images of the test piece at an average contact stress of 50n,100n,180n and 250N, respectively. According to the obtained image, the surface roughness can be further calibrated and processed into corresponding surface roughness so as to adapt to the requirements of engineering measurement.
In the description of the present invention, it is to be understood that the indicated orientations or positional relationships are based on the orientations or positional relationships shown in the drawings, which are merely for convenience in describing the present invention and for simplicity in description, and are not intended to indicate or imply that the indicated devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be construed as limiting the present invention.
In the description of the specification, reference to the description of "one embodiment," "some embodiments," "an example," "a specific example," or "some examples" or the like means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (10)
1. A real-time detection method for friction factors and microscopic topography of a material surface is characterized by comprising the following steps:
step S1, respectively arranging roller supporting pieces on two sides of a sapphire mold with a rectangular upper half section and an arc lower half section, penetrating one end of a strip-shaped test piece into the upper side of the roller supporting piece on one side of the sapphire mold, penetrating the strip-shaped test piece out of the upper side of the roller supporting piece on the other side of the sapphire mold through the lower side of the lower half section of the sapphire mold, and pressing the sapphire mold downwards to enable the strip-shaped test piece to be tightly attached to the lower half section of the sapphire mold, so that a contact section of the strip-shaped test piece and the lower half section of the sapphire mold meets the wrap angle requirement of the sapphire mold;
s2, arranging a linear array CCD at the focus of a sapphire mold, symmetrically arranging a plurality of groups of light sources on two sides of the linear array CCD, gathering interface reflected light of a bar-shaped test piece to the linear array CCD through light emitted by the plurality of groups of light sources by the sapphire mold, and performing three-dimensional reconstruction on the surface geometry of the bar-shaped test piece by the data acquired by the linear array CCD through an image signal preamplifier and a computer image processing system by combining super depth of field measurement and a three-dimensional contour measurement method to obtain surface friction topography image information of the bar-shaped test piece after stretch bending forming;
s3, applying a loading tension on one end of the strip-shaped test piece, detecting a pressure value in real time through a sensor, recording the pressure value as Fd, applying a fixed tension on the other end of the strip-shaped test piece as resistance generated by a back pressure, recording the resistance as Ft, and calculating a friction factor mu between the strip-shaped test piece and the lower half face of the sapphire mold according to the Ft, the Fd and a wrap angle theta of the sapphire mold;
the friction factor is calculated by the formula: μ =2 (Fd-Ft-Fb)/(θ (Fd + Ft));
wherein Fb is the friction force between the strip-shaped test piece and the lower half surface of the sapphire mold, fb = μ Pav, pav is the average contact pressure of a friction pair, pav = (Ft + Fd)/2 wR, wherein R is the arc radius of the lower half part of the sapphire mold, and w is the width of the strip-shaped test piece;
and S4, when the loading tension is continuously increased, obtaining a current friction factor according to a current loading tension value and a friction factor calculation formula, and obtaining surface friction appearance image information of the bar-shaped test piece in the current stretch-bending forming state by scanning the linear array CCD when the current loading tension value is applied, and finally generating a real-time relation corresponding graph of the friction factor and the surface friction appearance image information of the bar-shaped test piece in the stretch-bending friction test and the whole loading pressure process.
2. The method for detecting the friction factor and the micro-morphology of the material surface in real time according to claim 1, wherein in the step S2, the three-dimensional reconstruction of the surface geometry of the bar-shaped test piece by the linear array CCD comprises the following steps:
and calculating the surface type of the mirror surface by adopting a three-dimensional profile measurement method and super-depth of field measurement according to the measurement result and the calibrated mirror surface reflection geometrical relationship of the sapphire mold.
3. The method for real-time detection of the friction factor and the microstructure of the material surface according to claim 1, wherein the central angle of the arc of the lower half portion of the sapphire mold is a wrap angle, and the wrap angle is between 30 ° and 120 °.
4. The method for detecting the friction factor and the micro-morphology of the material surface according to claim 1, wherein the light source is a strip array adjustable light source, the targets are alternately irradiated on two sides of a linear array CCD (charge coupled device), shadows with different target heights are generated, the shadow widths are measured through photography, and the target heights are calculated.
5. The method for detecting the friction factor and the micro-morphology of the material surface in real time according to claim 1, wherein the strip-shaped test piece is subjected to contact heating or induction heating before the sapphire mold is placed on the surface of the strip-shaped test piece.
6. The method for detecting the friction factor and the micro-topography of the surface of the material in real time according to claim 1, wherein a lubricant is coated on the surface of the bar-shaped test piece before the sapphire mould is placed on the surface of the bar-shaped test piece.
7. The method for detecting the material surface friction force factor and the microscopic morphology thereof in real time according to claim 1, wherein in step S4, after the linear array CCD scans the obtained image information of the friction morphology of the bar-shaped test piece in the current stretch-bending forming state, the roughness of the bar-shaped test piece in the current stretch-bending forming state is obtained by matching and comparing the current image information with the standard image information on the standard roughness comparison table, and finally a real-time relation map of the friction factor, the roughness and the surface friction morphology image information of the bar-shaped test piece in the stretch-bending friction test and the loading pressure in the whole process is generated.
8. The method for detecting the material surface friction force factor and the microscopic morphology thereof according to claim 1, wherein when the linear array CCD collects the surface friction morphology image of the bar-shaped test piece below the sapphire mold, after each unit length bar-shaped test piece is collected, the bar-shaped test piece moves to the next unit length, then the linear array CCD collects the bar-shaped test piece of the next unit length, after continuous multiple collection, the collected data are spliced into a two-dimensional image, and through an image signal preamplifier and a computer image processing system, the surface geometry of the bar-shaped test piece is three-dimensionally reconstructed by combining with super depth of field measurement and a three-dimensional profile measurement method, and finally the surface friction morphology image information of the bar-shaped test piece after stretch bending is obtained.
9. An apparatus for applying the material surface friction factor and the method for detecting the microscopic morphology thereof in real time according to any one of claims 1 to 8, comprising:
the sapphire die is provided with an upper half part and a lower half part, the cross section of the upper half part is rectangular, the cross section of the lower half part is arc-shaped, and the sapphire die is used for pressing a strip-shaped test piece;
the servo motor tension device is connected with one end of the strip-shaped test piece through a chuck and is used for applying loading tension to the strip-shaped test piece; a sensor is also connected between the servo motor tension device and the chuck and used for monitoring the loading tension in real time;
the back pressure weight is connected with the other end of the bar-shaped test piece through the holder and used for applying a fixed pulling force as resistance generated by the back pressure; a steel wire rope is connected between the backpressure weight and the holder and supported by a steering roller;
the two groups of roller supporting pieces are positioned below the bar-shaped test piece and used for enabling the bar-shaped test piece to be tightly attached to the lower half part of the sapphire mold, so that the contact section of the bar-shaped test piece and the lower half part of the sapphire mold meets the wrap angle requirement of the sapphire mold, and the two groups of roller supporting pieces are distributed on two sides of the sapphire mold;
the linear array CCD is positioned at the focus of the sapphire mold and is used for acquiring surface friction morphology image information of the strip-shaped test piece below the sapphire mold in real time;
the two light sources are symmetrically arranged on two sides of the linear array CCD and used for irradiating the strip-shaped test piece;
the image signal pre-amplifier is connected to the top of the linear array CCD and is used for amplifying surface friction topography image information collected by the linear array CCD;
and the computer image processing system is connected with the image signal pre-amplifier and is used for carrying out three-dimensional reconstruction on the surface geometric shape of the bar-shaped test piece by combining super depth of field measurement and a three-dimensional profile measurement method and finally obtaining the surface friction morphology image information of the bar-shaped test piece after stretch bending forming.
10. The device according to claim 9, further comprising a data analysis system, wherein the data analysis system obtains a current friction factor according to a current tension value and a friction factor calculation formula, obtains surface friction topography image information of the bar-shaped test piece in a current stretch-bending forming state by scanning of the linear array CCD when the current loading tension value is applied, and finally generates a real-time relation corresponding graph of the friction factor and the surface friction topography image information of the bar-shaped test piece in the stretch-bending friction test and the loading pressure in the whole process.
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