CN102169065A - Method for measuring normal rigidity of large contact interface by completely considering plastic influence - Google Patents

Abstract

The present invention discloses a method for measuring normal rigidity of a large contact interface by completely considering plastic influence. The method comprises the steps of adopting a contact system of two rough bodies as a measuring object and the complete equivalence of the system as a principle, using laser to mark three straight lines which fulfill the measuring requirement on the two rough bodies, and obtaining the normal rigidity of the contact interface by observing normal displacements of the three straight lines during a loading procedure. The method considers the influence of the contact interface shape degree on the normal contact rigidity on the basis of a prior method, and uses a simple and easy laser mark method to measure the normal rigidity of the large contact interface without being influenced by contact areas. Moreover, the method, which breaks using limits of the prior method, can be used not only in laboratories, but also in practical engineering conveniently.

Description

A kind of big contact interface normal stiffness measuring method of taking into account the plasticity influence fully

Technical field

The invention belongs to laser scanning and field of measuring technique, relate to the power equivalence and the friction properties of system, be specifically related to a kind of measuring method of taking into account the big contact interface normal stiffness of plasticity influence fully.

Background technology

High speed development along with heavy mechanical equipments such as high precision machine tool, heavy duty gas turbine and carrier rockets, the accurate measurement of contact interface rigidity more and more obtains paying attention in its structure, and this is because the rigidity of contact interface can produce significant impact to the kinematic behavior of these heavy mechanical equipments.If ignore the influence of damping, contact interface can equivalence become the homogeneous spring in essence, so the accurate equivalence of contact system is the accurate based measurement of contact interface rigidity.

Existing contact interface normal stiffness equivalent method all is based on T.R.Thomas﹠amp; The computing formula that R.S.Sayles proposes (is seen document THOMAS T R, SAYLES R S.Stiffnessof machine tool j oints:A random-process approach[J] .ASME J.Eng.Ind, 1977,99:250-256), it is by investigating under the different normal loads in essence, change in displacement rule between uneven surface average line and rigid face draws this regional normal direction equivalent stiffness, and it is defined the normal stiffness of contact interface for this reason.

Because the investigation zone of the method does not comprise all plastic ranges, make and to be difficult to realize complete power equivalence the elasto-plastic Contact system, therefore, two class experiments of measuring based on existing equivalent method, it is direct loading experiment and ultrasonic investigation experiment, can accurately not measure the contact interface normal stiffness, existing simultaneously measuring method has only considered that contact interface roughness and percent ripple to the influence of normal direction contact stiffness, do not consider the influence of its shape degree.In addition, directly the uneven surface average line investigated of loading experiment is illusory, and can change along with the variation of contact condition, thereby accurate mark; The ultrasound wave experiment is owing to focus on, and the area of its measurement is limited, can't obtain the normal stiffness of big contact interface.Therefore, a kind ofly can comprise material plasticity influence fully to be convenient to the measuring method of big contact interface again very necessary.

Summary of the invention

The objective of the invention is to overcome the shortcoming of above-mentioned prior art, a kind of big contact interface normal stiffness measuring method of taking into account the plasticity influence fully is provided, this method adopts two asperities contact systems as measuring object, complete equivalence with this system is a principle, utilize laser three straight lines that satisfy measurement requirement of mark on two asperities, by investigating the normal stiffness that this three lines normal direction displacement in loading procedure obtains contact interface.This method can comprise the influence of material plasticity fully and can measure big contact interface again.

The objective of the invention is to solve by the following technical programs:

This big contact interface normal stiffness measuring method of taking into account the plasticity influence fully is characterized in that, comprises following steps:

(1), utilize Finite Element Method to set up and the on all four contact model of its parameter at two asperities A and the B that adopted in the normal stiffness measurement;

(2), draw the plastic region scope of contact model in the pressurized contact process of two asperities, and the maximal value of plastic region thickness in the full load range is made as u by finite element contact analysis _Cl

When (3) placing two asperities A, B, make the contact of two uneven surfaces, with laser straight line L parallel of difference mark on two asperities A, B with contact interface ₁And L ₂, make straight line L ₁, L ₂Between part can comprise plastic region fully, measure straight line L ₁To straight line L ₂Distance and be made as h ₁Another straight line L parallel of mark on asperities A with contact interface ₃, straight line L ₃With straight line L ₁Do not overlap, measure straight line L ₁To straight line L ₃Distance and be made as h ₂

(4) asperities A is applied the normal pressure load p _Nom, measure three straight line L ₁, L ₂And L ₃The normal direction displacement and be made as δ ₁, δ ₂And δ ₃

(5) the normal direction displacement δ by three straight lines ₁, δ ₂And δ ₃Measured value and pressure load P _NomJust can obtain contact interface normal stiffness K _c:

$K_c=\frac{{\mathrm{<figure-callout\; id="2"\; label="h"\; filenames="HDA0000044397930000023.png"\; state="\{\{state\}\}">h</figure-callout>}}_2\&CenterDot;{\mathrm{<figure-callout\; id="2"\; label="P\; nom\; h"\; filenames="HDA0000044397930000023.png"\; state="\{\{state\}\}">P</figure-callout>}}_{\mathrm{nom}}}{h_{}}.$

Above-mentioned three straight line L ₁, L ₂And L ₃Live width is all less than 1 micron.

The present invention has following beneficial effect than prior art:

The first, the investigation scope h1 that the invention enables the normal direction contact stiffness is greater than plastic range ucl, thereby comprised the whole plasticity influences of material in loading procedure, allows the more approaching reality of measurement result;

The second, the present invention has utilized simple laser labeling method, makes its influence that is not subjected to contact area, can measure the normal stiffness of big contact interface;

The 3rd, the present invention has considered the influence of contact interface shape degree to the normal direction contact stiffness on the basis of existing method;

The 4th, the present invention has broken through the use limitation of existing method, can not only use in the laboratory, and can be used for engineering reality easily.

Description of drawings

The two asperities contact model synoptic diagram of Fig. 1 for setting up, wherein A is the left side asperities, and C is two asperities contact models, and B is the right side asperities;

Fig. 2 is the plastic region synoptic diagram under certain load pressure, and E is a plastic region;

Fig. 3 is the Changing Pattern synoptic diagram of plastic region in the full load range;

Fig. 4 is two straight line synoptic diagram with laser mark on asperities;

Fig. 5 needs three straight-line methods of measurement to displacement diagram;

Fig. 6 is the inventive method and the contrast of existing contact interface normal stiffness measuring method.

Embodiment

The present invention takes into account the big contact interface normal stiffness measuring method of plasticity influence fully, specifically comprises following steps:

(1), utilize Finite Element Method to set up and the on all four contact model of its parameter at two asperities A and the B that adopted in the normal stiffness measurement;

(2), draw the plastic region scope of contact model in the pressurized contact process of two asperities, and the maximal value of plastic region thickness in the full load range is made as u by finite element contact analysis _Cl

When (3) placing two asperities A, B, make the contact of two uneven surfaces, with laser straight line L parallel of difference mark on two asperities A, B with contact interface ₁And L ₂, make straight line L ₁, L ₂Between part can comprise plastic region fully, measure straight line L ₁To straight line L ₂Distance and be made as h ₁Another straight line L parallel of mark on asperities A with contact interface ₃, straight line L ₃With straight line L ₁Do not overlap, measure straight line L ₁To straight line L ₃Distance and be made as h ₂

(4) asperities A is applied the normal pressure load p _Nom, measure three straight line L ₁, L ₂And L ₃The normal direction displacement and be made as δ ₁, δ ₂And δ ₃

(5) the normal direction displacement δ by three straight lines ₁, δ ₂And δ ₃Measured value and pressure load P _NomJust can obtain contact interface normal stiffness K _c:

$K_c=\frac{{\mathrm{<figure-callout\; id="2"\; label="h"\; filenames="HDA0000044397930000023.png"\; state="\{\{state\}\}">h</figure-callout>}}_2\&CenterDot;{\mathrm{<figure-callout\; id="2"\; label="P\; nom\; h"\; filenames="HDA0000044397930000023.png"\; state="\{\{state\}\}">P</figure-callout>}}_{\mathrm{nom}}}{h_{}}.$

Below in conjunction with accompanying drawing the present invention is done and to describe in further detail:

Referring to shown in Figure 1, set up model according to the asperities correlation parameter of using in the inventive method, these parameters comprise length L, width W, the height H of two asperities, elastic modulus E, material yield limit σ, Poisson ratio v, density p, surfaceness R _a, protruding peak density D _sAnd load pressure P _NomDeng.

Referring to shown in Figure 2, obtain the plastic region of asperities under certain load pressure by contact analysis.

Referring to shown in Figure 3, change load p _NomSize just can obtain plastic region Changing Pattern in the full load range, its maximal value is made as u _Cl

Referring to shown in Figure 4, when placing two asperities A, B, make the contact of two uneven surfaces, with laser straight line L parallel of difference mark on asperities A, B with contact interface ₁And L ₂(live width is less than 1 micron) makes the part between it can comprise plastic region fully, measures L ₁To L ₂Distance and be made as h ₁, obvious h ₁Greater than u _ClAnother straight line L parallel of mark on asperities A with contact interface ₃(L ₃And L ₁Do not overlap), measure L ₁To L ₃Distance and be made as h ₂L ₁With L ₂Between this part normal stiffness be K _Cl, L ₁With L ₃Between this part normal stiffness be K _l

Referring to shown in Figure 5, asperities A is applied the normal pressure load p _Nom, measure three straight line L ₁, L ₂And L ₃The normal direction displacement and be made as δ ₁, δ ₂And δ ₃

According to relation stressed and distortion, L ₁With L ₂Between this part normal stiffness K _ClCan pass through δ ₁, δ ₂And normal load P _NomTry to achieve:

$k_{\mathrm{cl}}=\frac{P_{\mathrm{nom}}}{|{\mathrm{\&delta;}}_1-{\mathrm{\&delta;}}_2|}---\left(2\right)$

In like manner, L ₁With L ₃Between this part normal stiffness K _lCan pass through δ ₁, δ ₃And normal load P _NomTry to achieve:

$K_l=\frac{P_{\mathrm{nom}}}{|{\mathrm{\&delta;}}_1-{\mathrm{\&delta;}}_3|}---\left(3\right)$

K _ClFor the normal stiffness of interface block, h are arranged ₂*/K _l/ h ₁For with the normal stiffness of the no interface block of its equal length, both difference are caused by contact interface, so K _Cl, h ₂*/K _l/ h ₁And K _cBetween satisfy following relation:

$\frac{1}{K_{\mathrm{cl}}}=\frac{1}{K_c}+\frac{h_1}{{\mathrm{<figure-callout\; id="2"\; label="h"\; filenames="HDA0000044397930000023.png"\; state="\{\{state\}\}">h</figure-callout>}}_2\&CenterDot;K_l}---\left(4\right)$

(2) and (3) two formula substitutions (4) just can be tried to achieve contact interface normal stiffness K _c:

$K_c=\frac{{\mathrm{<figure-callout\; id="2"\; label="h"\; filenames="HDA0000044397930000023.png"\; state="\{\{state\}\}">h</figure-callout>}}_2\&CenterDot;{\mathrm{<figure-callout\; id="2"\; label="P\; nom\; h"\; filenames="HDA0000044397930000023.png"\; state="\{\{state\}\}">P</figure-callout>}}_{\mathrm{nom}}}{h_{}}---\left(5\right)$

Embodiment:

Be checking the inventive method: take into account the big contact interface normal stiffness measuring method of plasticity influence fully, with existing load measuring method and the ultrasonic wave measuring method object as a comparison that directly adds.Wherein, the numerical value of ultrasonic wave measuring method is obtained (seeing document Gonzalez-Valadez M by the experiment that people such as Gonzalez-Valadez M do, Baltazar A, Dwyer-Joyce R S.Study of interfacialstiffness ratio of a rough surface in contact suing a spring model[J] .Wear, 2010,268:373-379); The numerical value that directly adds load measuring method and the inventive method obtains by finite element simulation, and its model as shown in Figure 1.For can and ultrasonic wave measuring method effectively contrast, the size of two asperities and material unanimity, and one of them surface of contact is smooth flat, correlation parameter is as shown in table 1.

The realistic model correlation parameter	Numerical value (unit)
		Length L	0.2mm
Width W	0.2mm
		Height H	0.6mm
Elastic modulus E	200GPa
		Yield limit σ	835MPa
Poisson ratio v	0.3
		Density p	7800Kg/m 3
Surfaceness R a	1.58μm
		Protruding peak density D s	7813/mm 2
Load pressure P nom	0～400MPa

Table 1

Referring to shown in Figure 6, because ultrasonic method does not almost count the influence of material plasticity, directly loading method has partly counted the plasticity influence, and the inventive method has counted the plasticity influence fully, therefore, and in full load range, the normal direction contact stiffness value maximum that ultrasonic method obtains, directly Loading Method secondly, the inventive method minimum, and the difference between this three increases along with the increase of load.This explanation the inventive method is owing to counted the influence of material plasticity fully, and measured value is more accurate.

The above example obtains at a certain contact area, but the present invention is not subjected to the limitation of contact area size.So, everyly do not break away from the equivalence of finishing under the spirit disclosed in this invention or revise, all fall into the scope of protection of the invention.

Claims (2)

1. a big contact interface normal stiffness measuring method of taking into account the plasticity influence fully is characterized in that, comprises following steps:

(1), utilize Finite Element Method to set up and the on all four contact model of its parameter at two asperities A and the B that adopted in the normal stiffness measurement;

(2), draw the plastic region scope of contact model in the pressurized contact process of two asperities, and the maximal value of plastic region thickness in the full load range is made as u by finite element contact analysis _Cl

When (3) placing two asperities A, B, make the contact of two uneven surfaces, with laser straight line L parallel of difference mark on two asperities A, B with contact interface ₁And L ₂, make straight line L ₁, L ₂Between part can comprise plastic region fully, measure straight line L ₁To straight line L ₂Distance and be made as h ₁Another straight line L parallel of mark on asperities A with contact interface ₃, straight line L ₃With straight line L ₁Do not overlap, measure straight line L ₁To straight line L ₃Distance and be made as h ₂

(4) asperities A is applied the normal pressure load p _Nom, measure three straight line L ₁, L ₂And L ₃The normal direction displacement and be made as δ ₁, δ ₂And δ ₃

(5) the normal direction displacement δ by three straight lines ₁, δ ₂And δ ₃Measured value and pressure load P _NomJust can obtain contact interface normal stiffness K _c:

$K_c=\frac{h_2\&CenterDot;P_{\mathrm{nom}}}{h_2\&CenterDot;|{\mathrm{\&delta;}}_1-{\mathrm{\&delta;}}_2|-h_1\&CenterDot;|{\mathrm{\&delta;}}_1-{\mathrm{\&delta;}}_3|}.$

2. the big contact interface normal stiffness measuring method of taking into account the plasticity influence fully according to claim 1 is characterized in that described three straight line L ₁, L ₂And L ₃Live width is all less than 1 micron.

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