CN103743671B - Bonding strength checking method for vehicle adhesive - Google Patents

Abstract

A method for checking the bonding strength of an automotive adhesive, which calculates the total stress of the adhesive layer unit on the bonding plane: and ultimate stress Then calculate 1-R=1-p'/p" to judge whether it is safe; it can check the bonding strength of the vehicle bonding structure under any complex working conditions. When the working conditions of the bonding structure are determined According to the checking method of the present invention, it can be judged whether the bonded structure is safe, and by adjusting the form of the bonded structure, the bonded area, the amount of glue, etc., the bonded structure can reach a safe and reliable state.

Description

A method for checking the bonding strength of an automotive adhesive

technical field

The invention relates to the field of checking the bonding strength of adhesives, and more specifically, relates to a method for checking the bonding strength of vehicle adhesives applied in the fields of high-speed EMUs, railway passenger cars, road passenger cars and the like.

Background technique

Adhesive technology is a commonly used material connection technology in engineering. Using adhesive technology for connection and assembly has the advantages of neat appearance, relatively uniform load distribution in the connection area (compared with bolts and riveting), wide range of applicable materials and connection of dissimilar materials. and many other advantages.

In recent years, with the increasing application of new materials in the industry, the application of bonding technology has become more and more extensive. In the vehicle industry, most of the body structure and interior materials, sound insulation materials, heat insulation materials, windshields and windows are assembled by bonding.

Chinese Patent Application No. 201110183157.9 discloses a method for detecting the bonding strength of resins. By utilizing this solution, the detection accuracy of the bonding strength of brittle resins can be improved, and therefore, it is suitable for the detection of bonding strength of resins with brittle characteristics. However, there are problems such as complex operation process, not widely used and defects in detection.

Although the bonding technology has many advantages, judging from the current research status, there are still the following problems in the research on bonding technology: (1) The mechanical properties of bonded joints are not fully understood, the relevant basic experimental research is not perfect, and the accumulation is relatively large. There are few, and there is no unified and complete strength design standard. For example, GB-T7124-2008 "Determination of Tensile Shear Strength of Adhesives (Rigid Material to Rigid Material)" provides a test method for tensile shear strength of rigid material to rigid material adhesive joints, but there are also It stipulates that "this experimental process is not used as design information". (2) For the strength prediction and design methods of typical joints and important bonding parts of the car body, there is still a lack of effective research methods in engineering. (3) There is no effective strength evaluation model in the CAE numerical simulation analysis of the bonding structure, especially the bonding performance evaluation under complex stress states and different environments, which needs to be systematically explored.

Contents of the invention

The present invention aims at the problems existing in the existing vehicle adhesive bonding technology, and utilizes the thin adhesive layer thickness of the vehicle adhesive structure, and the adhesive layer is under various complicated stress conditions, especially the normal normal stress of the adhesive layer and the The in-plane shear stress is the most prominent feature, and a method for checking the bonding strength based on the normal normal stress of the bonding plane and the in-plane shear stress is proposed.

A method for checking the bonding strength of an automotive adhesive, step 1, making a plurality of groups of adhesive test pieces whose bonding angles are respectively α _n , and performing a tensile fracture test to it; step 2, according to the plurality of groups The normal stress σ and shear stress τ suffered by the vehicle bonded specimens at different bonding angles during fracture and failure are plotted in the coordinate system to form a critical broken line for adhesive fracture and failure based on normal stress and shear stress; step 3, Discretize the bonded test piece of the vehicle to be tested into units, that is, the adhesive layer unit, and calculate the normal normal stress of the adhesive layer unit as σ′ and the shear stress as τ′, and the total stress of the adhesive layer unit on the bonding plane: Step 4, the tension-shear ratio R' _στ = σ'/τ' of the adhesive layer unit, the expression of the connection line between the adhesive layer unit and the coordinate origin is: y=R' _στ x; the connection line and the critical broken line of fracture damage The normal normal stress of the intersection point is σ″ and the shear stress is τ″; the ultimate stress that the adhesive layer unit can bear Step 5, R=p′/p″, 1-R=1-p′/p″; take 0≤β ₁ <β ₂ <1, if 1-R<0, it means that the stress of the adhesive layer unit exceeds Ultimate stress, the adhesive layer unit is in the dangerous zone; if 0≤1-R<β ₁ , it means that the stress safety margin of the adhesive layer unit is insufficient, and the adhesive layer unit is in the warning zone; if β ₁ ≤1-R<β ₂ , which means that the stress safety margin of the adhesive layer unit is appropriate, and the adhesive layer unit is in the safe area; if β ₂ ≤1-R<1, it means that the stress safety margin of the adhesive layer unit is too large, and the adhesive layer unit is in the low stress area ; β ₁ and β ₂ are fixed constants.

As a further preference, according to vehicle operating conditions, β ₁ =20% and β ₂ =50%.

As a further preference, the α _n is greater than or equal to 0 and less than or equal to 90 degrees.

As a further preference, the bonding angles α _n are respectively 0°, 15°, 30°, 45°, 60°, 75°, and 90°.

Beneficial effect:

The method for checking the bonding strength of the vehicle adhesive of the present invention can check the bonding strength of the vehicle bonding structure under arbitrary complex working conditions.

In the case that the working conditions of the bonding structure are determined, it is possible to judge whether the bonding structure is safe according to the checking method described in the present invention, and by adjusting the bonding structure form, bonding area, glue amount, etc., to make The bonding structure reaches a safe and reliable state.

When conditions such as the form of the bonding structure, bonding area, and amount of glue are determined, the maximum safe load and limit load that the bonding structure can withstand can be calculated in reverse by using the checking method of the present invention.

Description of drawings

Figure 1 is a schematic diagram of the normal normal stress and plane shear stress of the specimen with the bonding angle α.

Fig. 2 is the bonding experiment specimens of different bonding angles adopted in the embodiment.

Figure 3 is the experimental data of tensile fracture failure of bonded specimens.

Figure 4 is the critical broken line of adhesive fracture failure.

Fig. 5 is a schematic diagram of the area division of the critical broken line strength state of adhesive fracture failure.

Figure 6 is a schematic diagram of the window bonding structure of a high-speed EMU

Fig. 7 is a schematic diagram of load application of the window bonding structure model.

Fig. 8 is a schematic diagram of checking the strength of a certain adhesive layer unit.

Figure 9 is the strength check result of the adhesive layer unit of the window bonding structure.

Among them, 1 is the experimental sample with a bonding angle of 0°, 2 is the experimental sample with a bonding angle of 15°, 3 is the experimental sample with a bonding angle of 30°, and 4 is the experimental sample with a bonding angle of 45°. Experimental specimen, 5 is the experimental specimen with the bonding angle of 60°, 6 is the experimental specimen with the bonding angle of 75°, 7 is the experimental specimen with the bonding angle of 90°, 8 is the low stress area, 9 10 is a warning area, 11 is a dangerous area, 12 is a side window glass, 13 is an aluminum alloy frame of a side window, 14 is an adhesive layer, and 15 is a vehicle body structure.

Detailed ways

The present invention is described in further detail below in conjunction with the embodiment given with accompanying drawing.

As shown in Figure 1, the ratio of the normal normal stress σ to the in-plane shear stress τ when the adhesive layer is fractured is the tension-shear ratio R _στ . Make n groups of bonded specimens with bonding angles of α _n , and conduct tensile fracture experiments on them. Taking the i-th group of bonded specimens as an example, the bonding angle is α _i , the normal normal stress at the time of fracture is σ _i , and the in-plane shear stress is τ _i , then:

(R _στ ) _i ＝tanα _i ＝σ _i /τ _i 1≤i≤n

For the convenience of subsequent calculations, the present invention defines:

0=α ₁ <α ₂ <...<α _n-1 <α _n =π/2 n≥2 and n is an integer

For exemplary illustration, seven sets of adhesive tensile test specimens with bonding angles of 0°, 15°, 30°, 45°, 60°, 75°, and 90° were established, as shown in Figure 2, each The number of bonded test pieces in each group is 15. As a preference, after the experiment is over, exclude individual invalid experimental data and take the average value of each group of experimental data as the normal stress σ and shear stress τ of adhesive layer failure at this bonding angle, as shown in the table in Figure 3 The data.

As shown in Figure 4, a coordinate system is established with the in-plane shear stress τ as the abscissa and the normal normal stress σ as the ordinate. σ and shear stress τ are drawn in the coordinate system, and n coordinate points (τ ₁ ,σ ₁ ), (τ ₂ ,σ ₂ )...(τ _n ,σ _n ) can be drawn sequentially, and the n coordinate points They are connected in sequence to form a critical broken line for adhesive fracture failure based on normal stress and shear stress.

As shown in Figure 4 and Figure 5, connect the coordinate origin and n coordinate points on the critical fold line respectively to obtain n line segments, which form n-1 triangle areas with n-1 line segments on the critical fold line. The meaning of the slope of the n line segments is the tension-shear ratio R _στ , and the length of the line segment represents the ultimate stress of the adhesive layer in the state of the tension-shear ratio R _στ , which is defined as p, so

$\mathrm{<span\; class="notranslate">\; p</span>}<span\; class="notranslate">\; =</span>\sqrt{{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}$

The experimental specimen to be tested is discretized into units, that is, the adhesive layer unit. According to the mechanics of materials, the stress state of any center point of the adhesive layer unit can be obtained, namely σ _x , σ _y , σ _z , τ _yz , τ _zx , τ _xy . According to the relationship between the local coordinate system of the adhesive layer unit and the global coordinate system of the adhesive structure model, the stress value of the center point of the unit is changed in coordinates to obtain the normal stress in the normal direction of the adhesive layer unit and the shear stress in the plane. Assuming that the outer normal direction of the bonding plane of a glue layer unit is n′, its direction cosine is:

cos(n',x)=l,cos(n',y)=m,cos(n',z)=n

Define the total stress of the adhesive layer unit on its bonding plane as p', and the projection on the coordinate axis is represented by p' _x , p' _y , p' _z . According to the equilibrium condition, we can get

p′ _x ＝ lσ _x + mτ _xy + nτ _zx

p′ _y = mσ _y + nτ _yz + lτ _xy

p′ _z = nσ _z + lτ _zx + mτ _yz

Assuming that the normal normal stress of the bonding plane of the adhesive layer unit is σ′, and the shear stress is τ′, then

σ'=lp' _x +mp' _y +np' _z

${\mathrm{<span\; class="notranslate">\; \&tau;</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>\sqrt{{\mathrm{<span\; class="notranslate">\; p</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}^{<span\; class="notranslate">\; \&prime;</span>\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; p</span>}}_{\mathrm{<span\; class="notranslate">\; the\; y</span>}}^{<span\; class="notranslate">\; \&prime;</span>\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; p</span>}}_{\mathrm{<span\; class="notranslate">\; z</span>}}^{<span\; class="notranslate">\; \&prime;</span>\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}^{<span\; class="notranslate">\; \&prime;</span>\mathrm{<span\; class="notranslate">\; 2</span>}}}$

${\mathrm{<span\; class="notranslate">\; p</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>\sqrt{{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}^{<span\; class="notranslate">\; \&prime;</span>\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}^{<span\; class="notranslate">\; \&prime;</span>\mathrm{<span\; class="notranslate">\; 2</span>}}}$

The tension-shear ratio R′ _στ =σ′/τ′ of the adhesive layer unit is compared with the tension-shear ratio R _στ corresponding to n coordinate points on the critical broken line, if:

(R _στ ) _n-1 ≤R′ _στ ≤(R _στ ) _n

Then the adhesive layer unit (τ′, σ′) is in the n-1th triangular area, and the line segment on the critical fold line corresponding to this area can be defined by coordinate points (τ _n-1 , σ _n- 1), (τ _n ,σ _n ), the straight line expression is:

$\mathrm{<span\; class="notranslate">\; the\; y</span>}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>\frac{{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; x</span>}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}}{{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}}$

The expression of the connection line between the adhesive layer unit and the coordinate origin is: y=R′ _στ x

According to the above straight line expression, find the intersection point (τ″,σ″):

${\mathrm{<span\; class="notranslate">\; \&tau;</span>}}^{<span\; class="notranslate">\; \&prime;</span><span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span>}$

${\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}^{<span\; class="notranslate">\; \&prime;</span><span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span>}$

${\mathrm{<span\; class="notranslate">\; p</span>}}^{<span\; class="notranslate">\; \&prime;</span><span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>\sqrt{{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}^{<span\; class="notranslate">\; \&prime;</span><span\; class="notranslate">\; \&prime;</span>\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}^{<span\; class="notranslate">\; \&prime;</span><span\; class="notranslate">\; \&prime;</span>\mathrm{<span\; class="notranslate">\; 2</span>}}}$

p″ is the ultimate stress that the adhesive layer unit can bear, which is taken as:

R=p'/p"

1-R=1-p'/p"

The meaning of 1-R is the safety margin of the stress of the adhesive layer unit, and the strength check result of the adhesive layer unit is determined according to the value of 1-R. Take 0≤β ₁ <β ₂ <1, if 1-R<0, it means that the stress of the adhesive layer unit exceeds the limit stress, and the adhesive layer unit is in the dangerous zone; if 0≤1-R<β ₁ , it means that the adhesive layer unit If the stress safety margin of the layer unit is insufficient, the adhesive layer unit is in the warning area; if β ₁ ≤1-R<β ₂ , it means that the stress safety margin of the adhesive layer unit is appropriate, and the adhesive layer unit is in the safe area; if β ₂ ≤1-R<1, it means that the stress safety margin of the adhesive layer unit is too large, and the adhesive layer unit is in the low stress area. The values of β ₁ and β ₂ should be determined according to the specific working conditions of the bonded structure.

As a preference, according to the engineering design experience of automotive adhesives, in this embodiment, β ₁ = 20%, β ₂ = 50%, that is, the safety margin of the adhesive layer unit should be 50% ≤ 1-R The area of <100% is the low stress area 8, the area of 20%≤1-R<50% is the safe area 9, the area of 0≤1-R<20% is the warning area 10, and the area of 1-R<0 is The danger zone 11 is shown in FIG. 5 .

Exemplary, seven groups of adhesive tensile test specimens with bonding angles of 0°, 15°, 30°, 45°, 60°, 75°, and 90° respectively; τ is the abscissa, and the normal normal stress σ is the ordinate to establish a coordinate system, draw points and connect lines in the coordinate system according to the experimental data shown in the table in Figure 2, and obtain the critical broken line of adhesive fracture and failure as shown in Figure 3 , connecting the seven coordinate points to the origin of the coordinates respectively, the broken line diagram of the adhesive fracture failure can be divided into six regions, as shown in Figure 4, the tension-shear ratio R _στ corresponding to the seven connecting lines is as follows:

(R _στ ) ₁ =0 (R _στ ) ₂ =0.27 (R _στ ) ₃ =0.58 (R _στ ) ₄ =1

(R _στ ) ₅ ＝1.73 (R _στ ) ₆ ＝3.73 (R _στ ) ₇ ＝∞

For exemplary illustration, the present invention selects the window structure in the high-speed EMU as the bonding structure to be checked. The vehicle window structure mainly includes two parts, a side window glass (12) and a side window aluminum alloy frame (13). As a sub-assembly, the window structure is assembled by bonding the side window aluminum alloy frame (13) to the vehicle body structure (15), as shown in Figure 6.

According to the main stress conditions of the window structure during the operation of the high-speed EMU, loads are applied to the window structure model: in order to simulate the force acting on the window glass due to the pressure difference between the inside and outside of the window during the high-speed operation of the EMU , apply a uniform load on the glass unit in the middle of the window structure model, as shown in Figure 7(a); in order to simulate the residual shear force that may exist after the window structure is bonded to the car body structure, A pair of opposing forces are applied in the diagonal direction, as shown in Fig. 7(b).

According to the mechanics of materials, the stress state of each unit of the adhesive layer is obtained through calculation. Select any glue-line unit from it, and check the glue-line unit according to the method for checking the strength of the bonded glue-line. Calculate the stress value of the glue layer element:

σ _x =5.715264e-5Pa τ _xy =1.086516e-5Pa

σ _y =5.747150e-5Pa τ _yz =2.545583e+6Pa

σ _z =3.131656e+6Pa τ _zx =2.545575e+6Pa

The cosine of the normal direction of the bonding surface of the unit is:

l＝0.00 m＝0.00 n＝1.00

According to the solution method for the normal normal stress and in-plane shear stress of the adhesive layer unit, it can be obtained:

τ′=3.60MPa σ′=3.13MPa

R' _στ = σ'/τ' = 0.8694

${\mathrm{<span\; class="notranslate">\; p</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>\sqrt{{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}^{<span\; class="notranslate">\; \&prime;</span>\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}^{<span\; class="notranslate">\; \&prime;</span>\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 4.77</span>}\mathrm{<span\; class="notranslate">\; MPa</span>}$

Due to the comparison of the ratio of tension to shear (R _στ ) ₃ <R′ _στ <(R _στ ) ₄ , the adhesive layer unit is located in the third triangular area, and the intersection point (τ″,σ″ ):

τ″=5.76MPa σ″=5.00MPa

${\mathrm{<span\; class="notranslate">\; p</span>}}^{<span\; class="notranslate">\; \&prime;</span><span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; =</span>\sqrt{{\mathrm{<span\; class="notranslate">\; \&tau;</span>}}^{<span\; class="notranslate">\; \&prime;</span><span\; class="notranslate">\; \&prime;</span>\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&sigma;</span>}}^{<span\; class="notranslate">\; \&prime;</span><span\; class="notranslate">\; \&prime;</span>\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 7.63</span>}\mathrm{<span\; class="notranslate">\; MPa</span>}$

R=p'/p"=0.625

1-R＝0.325＝32.5%

Therefore, it can be judged that the adhesive layer unit is located in a safe area, that is, the stress state of the adhesive layer unit is in a safe state. In the same way, the strength of other adhesive layer units can be checked to obtain the strength check result of the adhesive layer unit of the window bonding structure as shown in FIG. 9 .

The above description of the embodiments is for those of ordinary skill in the art to understand and apply the present invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments, and apply the general principles described here to other embodiments without creative effort. Therefore, the present invention is not limited to the embodiments herein. Improvements and modifications made by those skilled in the art according to the disclosure of the present invention without departing from the scope of the present invention should fall within the protection scope of the present invention.

Claims (4)

1. a bonding strength check method for vehicle adhesive, is characterized in that:

Step 1, the bonding angle of the many groups of making are respectively α _nautomobile-used bonding test specimen, tension failure experiment is carried out to it;

Step 2, normal stress σ, the shear stress τ in a coordinate system described point suffered when rupture failure according to the automobile-used bonding test specimen of many group different bonding angles, form a critical broken line of bonding agent rupture failure based on normal stress and shear stress;

Step 3, change into unit, i.e. glue-line unit by discrete for automobile-used bonding test specimen to be detected, to calculate glue-line unit mormal stress be σ ' and shearing stress is τ ', and glue-line unit is in the total stress of bonding plane: $p^{\&prime;}=\sqrt{{\mathrm{\&tau;}}^{\&prime;2}+{\mathrm{\&sigma;}}^{\&prime;2}};$

Step 4, drawing of glue-line unit are cut than R ' _{σ τ}=σ '/τ ', the line expression formula of glue-line unit and true origin is: y=R ' _{σ τ}x; The mormal stress of the intersection point of this line and the critical broken line of described rupture failure is σ " and shearing stress is τ "; The ultimate stress that glue-line unit can bear

$p^{\&prime;\&prime;}=\sqrt{{\mathrm{\&tau;}}^{\&prime;\&prime;2}+{\mathrm{\&sigma;}}^{\&prime;\&prime;2}};$

Step 5, R=p '/p ", 1-R=1-p '/p "; Get 0≤β ₁< β ₂< 1, if 1-R < 0, represent the stress that glue-line unit bears and exceeded ultimate stress, this glue-line unit is in explosive area; If 0≤1-R < is β ₁, the stress margin of safety representing glue-line unit is not enough, and this glue-line unit is in warning area; If β ₁≤ 1-R < β ₂, the stress margin of safety representing glue-line unit is suitable, and this glue-line unit is in place of safety; If β ₂≤ 1-R < 1, the stress margin of safety representing glue-line unit is excessive, and this glue-line unit is in low stress area; β ₁, β ₂for fixed constant.

2. the bonding strength check method of vehicle adhesive according to claim 1, is characterized in that: according to automobile-used operating mode, described β ₁=20% and β ₂=50%.

3. the bonding strength check method of vehicle adhesive according to claim 1 and 2, is characterized in that: described α _nfor being more than or equal to 0 and being less than or equal to 90 degree.

4. the bonding strength check method of vehicle adhesive according to claim 3, is characterized in that: bonding angle [alpha] _nbe respectively 0 °, 15 °, 30 °, 45 °, 60 °, 75 °, 90 °.