CN103557783A - Method for vehicle stress non-discharging measurement - Google Patents

Abstract

The invention provides a non-discharging indirect stress measurement method based on the inclination angle principle. Even under the circumstance of non-discharging, strain or stress caused by the structure of a vehicle is measured, and in particular, prominent effects on the strain or the stress caused by loads not capable of being discharged are achieved. According to the method, the vehicle inclines leftwards and rightwards by certain angles alpha and minus alpha, and changing of structural strain caused by means of changing of force in the horizontal and vertical direction of the weight of the front part of the vehicle and the back part of the vehicle is utilized to reversely push out structural stress.

Description

A kind of method that vehicle stress is measured without unloading

Technical field

The present invention relates to a kind of measuring method of vehicle stress, more specifically, relate to a kind of vehicle method for measuring stress that does not need discharge car load.

Background technology

Strength condition is the Basic Design condition that vehicle product and other machinery product must be satisfied, and the stress level of body structure and chassis structure is that vehicle product strength is evaluated one of Main Basis.Although introduced in a large number CAE technology in modern product development, the index of the intensity of structure, rigidity and permanance is comprehensively calculated, analyzed, final strength condition, still will be as the criterion with train experiment.

Chinese Patent Application No. 201210236809.5 discloses a kind of measuring method, Apparatus and system of structural member ess-strain, in order to realize, the ess-strain of structural member is carried out to non-contact measurement.But this measuring method process is complicated, uses very inconvenient.

Strain gage testing method is the main method of current stress measurement, its ultimate principle is first in measured structure, to choose the measuring point of some, on measuring point, paste foil gauge, under light condition by strainmeter balancing or record initial value, then load, the strain that test is caused by load, is calculating the stress at measuring point place according to Hooke's law.

Easy to implement and the technology maturation of this method, in engineering practice application very extensive, but this test need to add unloading, before measurement, sheds the load of structure, after strainmeter balancing, reloads and measures.Because the weight of structure self cannot unload, therefore, the stress being caused by dead load also just cannot be measured.This brings difficulty to some deadweight compared with the measurement of macrostructure.A large amount of engineering practices show, because vehicle structure operating load is very large, even if the load that can unload adds discharge time very long, are therefore easy to cause test error by the drift of surveying instrument; In addition, also some load can unload in theory, but practical operation is very inconvenient, as engine, wheel box and clutch coupling etc.

Because structural strength condition be all vehicle structures must be satisfied one of necessary condition, a kind of simple method for measuring stress, significant with checking to the Intensity Design of vehicle structure.

Summary of the invention

The present invention is directed to the shortcoming existing in prior art, utilize removable, the tiltable feature of automobile body, propose a kind of based on inclination angle principle without unloading indirect strain measurement method; Furthermore, also provide above-mentioned strainometer to calculate stress.

The method that vehicle stress is measured without unloading, mainly comprises the following steps: step 1, in the structure of vehicle, determine some measuring points, paste strain rosette, connect strainmeter; Step 2, described vehicle is placed at horizontal level, and strainmeter is returned to zero; Step 3, by vehicle deflection α angle to the left, measure the strain change amount { Δ ε } that is caused strain rosette on each measuring point of structure by the change of vehicle body Action of Gravity Field direction ^l; Step 4, vehicle rotate back to horizontal level, strainmeter rezeroing; Step 5, by the vehicle same angle-α of deflection to the right, again measure the strain change amount { Δ ε } of strain rosette on each measuring point of structure causing after being changed by vehicle body Action of Gravity Field direction ^r; Step 6, according to formula

obtain the strain value of strain rosette.

As further preferred, the scope at described α angle is between 15 to 25 degree.

As further preferably, also comprise step 7, calculate the principle stress of measured point.

As further preferred, described stickup strain rosette adopts three square bonding methods.

As further preferred, described stickup strain rosette adopts three equilateral triangle bonding methods.

As further preferred, principle stress computing formula

$\begin{array}{c}{\mathrm{\σ}}_1\\ {\mathrm{\σ}}_2\end{array}=\frac{E}{2}[\frac{{\mathrm{\ϵ}}_0+{\mathrm{\ϵ}}_{90}}{1-\mathrm{\μ}}\±\frac{1}{1+\mathrm{\μ}}\sqrt{{({\mathrm{\ϵ}}_0-{\mathrm{\ϵ}}_{90})}^2+{({2\mathrm{\ϵ}}_{45}-{\mathrm{\ϵ}}_0-{\mathrm{\ϵ}}_{90})}^2}].$

As further preferred, principle stress computing formula

$\begin{array}{c}{\mathrm{\σ}}_1\\ {\mathrm{\σ}}_2\end{array}==E[\frac{{\mathrm{\ϵ}}_0+{\mathrm{\ϵ}}_{60}+{\mathrm{\ϵ}}_{120}}{3(1-\mathrm{\μ})}\±\frac{1}{1+\mathrm{\μ}}\sqrt{{({\mathrm{\ϵ}}_0-\frac{{\mathrm{\ϵ}}_0+{\mathrm{\ϵ}}_{60}+{\mathrm{\ϵ}}_{120}}{3})}^2+\frac{1}{3}{({\mathrm{\ϵ}}_{60}-{\mathrm{\ϵ}}_{120})}^2}].$

The present invention utilizes removable, the tiltable feature of automobile body, provide a kind of based on inclination angle principle without unloading indirect stress measuring method.Be used for simplifying the stress measurement process of vehicle structure, particularly for the larger structure of own wt, adopt conventional method to measure, adopt the inventive method to there is unique advantage; The load that can unload in theory for some, practical operation is very inconvenient structure, adopts method of the present invention also can greatly simplify test process, shortens test period.

Accompanying drawing explanation

Fig. 1 is that right-angle triangle strain rosette is pasted form;

Fig. 2 is that equilateral triangle strain rosette is pasted form;

Fig. 3 is vehicle horizontal positioned schematic diagram;

Fig. 4 is vehicle left bank schematic diagram;

Fig. 5 is the stressed isoboles of vehicle left bank;

Fig. 6 is vehicle right bank schematic diagram;

Fig. 7 is the stressed isoboles of vehicle right bank.

Embodiment

This measuring method is to allow the vehicle body of measured vehicle respectively to left and right certain angle [alpha] and the-α of tilting, the forward and backward vehicle body that utilizes the change of power in the horizontal and vertical directions of conducting oneself with dignity, cause the change of structural strain, the anti-suffered stress of vehicle structure of releasing.

In the structure of vehicle, determine measuring point, paste required foil gauge (foil gauge is pasted in the mode of Fig. 1 or Fig. 2), connect strainmeter.Tested vehicle is placed to (as shown in Figure 3) at horizontal level, and measuring system is returned to zero.If under vehicle body Gravitative Loads, the strain of strain rosette in 0 °, 45 °, 90 ° directions is { ε } during vehicle horizontal positioned.During the left and right inclination of vehicle, under vehicle body Gravitative Loads, the strain of strain rosette in 0 °, 45 °, 90 ° directions is respectively { ε ^l, { ε ^r, ({ ε ^l, { ε ^rthe amount corresponding with { ε }, be all the vector that comprises three components).

Can adopt arbitrarily mode (as a kind of preferably, for example: storing cycle is hung up or jack-up on a tilting table or by vehicle one side), by vehicle deflection α angle (as shown in Figure 4) to the left, measure by vehicle body Action of Gravity Field direction and change and cause that the strain change amount of strain rosette on structure measuring point is { Δ ε } ^l.

If the strain of strain rosette is respectively { ε on the vehicle body deadweight lower structure measuring point of two component Gsin α, Gcos α effect in the horizontal and vertical directions ^l} _x, { ε ^l} _y.

Comparison diagram 3 can obtain { ε }, { ε with Fig. 5 ^l} _x, { ε ^l} _ythere is following relation:

{ε ^L} _X＝-{ε}sinα

{ε ^L} _Y＝{ε}cosα

Strain { the ε recording after body sway ^land the strain { ε } during vehicle body horizontal positioned between strain differential { Δ ε } ^lcan be expressed as:

{Δε} ^L＝{ε ^L}-{ε}

Vehicle rotates back to horizontal level, measuring system rezeroing.

By the vehicle same angle-α of deflection (as shown in Figure 6) to the right, again measure after being changed by vehicle body Action of Gravity Field direction and cause that the strain change amount of strain rosette on structure measuring point is { Δ ε } ^r.

If the strain of strain rosette is respectively { ε on the now vehicle body deadweight lower structure measuring point of two component Gsin α, Gcos α effect in the horizontal and vertical directions ^r} _x, { ε ^r} _y.

Comparison diagram 3 can obtain { ε }, { ε with Fig. 7 ^r} _x, { ε ^r} _ythere is following relation:

{ε ^R} _X＝{ε}sinα

{ε ^R} _Y＝{ε}cosα

Strain { the ε recording after body sway ^rand the strain { ε } during vehicle body horizontal positioned between strain differential { Δ ε } ^rcan be expressed as:

{Δε} ^R＝{ε ^R}-{ε}

Because vehicle body is identical to the angle of two edge run-outs, so { ε ^l} _x, { ε ^l} _y, { ε ^r} _x, { ε ^r} _ythere is following relation:

{ε ^L} _X＝-{ε ^R} _X

{ε ^L} _Y＝{ε ^R} _Y

Comprehensive above various can be { Δ ε } ^l, { Δ ε } ^rbe expressed as:

{Δε} ^L＝{ε ^L} _X+{ε ^L} _Y-{ε}＝{ε ^L} _X+{ε}cosα-{ε}

{Δε} ^R＝{ε ^R} _X+{ε ^R} _Y-{ε}＝{ε ^R} _X+{ε}cosα-{ε}

By the relation { ε having obtained ^l} _x=-{ ε ^r} _x, two formulas additions above can be obtained to following equation:

{Δε} ^L+{Δε} ^R＝2{ε}(cosα-1)

By above formula, can obtain strain { ε } that vehicle body deadweight causes strain rosette on structure measuring point:

$\left\{\mathrm{\ϵ}\right\}=\frac{{\left\{\mathrm{\Δ\ϵ}\right\}}^L+{\left\{\mathrm{\Δ\ϵ}\right\}}^R}{2(\cos \mathrm{\α}-1)}$

So just obtained the value ε of each foil gauge in strain rosette ₀, ε ₄₅, ε ₉₀(ε ₀represent to stick on the strain value of 0 degree foil gauge, ε ₄₅represent to stick on the strain value of 45 degree foil gauges, ε ₉₀represent to stick on the strain value of 90 degree foil gauges).

The stickup form of three square strain rosettes as shown in Figure 1, according to principal strain in the mechanics of materials and principle stress computing formula, can try to achieve principal strain and principle stress.

$\begin{array}{c}{\mathrm{\ϵ}}_1\\ {\mathrm{\ϵ}}_2\end{array}=\frac{{\mathrm{\ϵ}}_0+{\mathrm{\ϵ}}_{90}}{2}\±\frac{1}{2}\sqrt{{({\mathrm{\ϵ}}_0-{\mathrm{\ϵ}}_{90})}^2+{({2\mathrm{\ϵ}}_{45}-{\mathrm{\ϵ}}_0-{\mathrm{\ϵ}}_{90})}^2}$

$\begin{array}{c}{\mathrm{\σ}}_1\\ {\mathrm{\σ}}_2\end{array}=\frac{E}{2}[\frac{{\mathrm{\ϵ}}_0+{\mathrm{\ϵ}}_{90}}{1-\mathrm{\μ}}\±\frac{1}{1+\mathrm{\μ}}\sqrt{{({\mathrm{\ϵ}}_0-{\mathrm{\ϵ}}_{90})}^2+{({2\mathrm{\ϵ}}_{45}-{\mathrm{\ϵ}}_0-{\mathrm{\ϵ}}_{90})}^2}]$

E is elastic modulus, and μ is the Poisson ratio of material.

two parameters represent respectively maximum principal strain and minimum principal strain.

two parameters represent respectively major principal stress and least principal stress.

As another embodiment, if paste foil gauge by three equilateral triangles shown in Fig. 2, can obtain ε according to above-mentioned derivation ₀, ε ₆₀, ε ₁₂₀(ε ₀represent to stick on the strain value of 0 degree foil gauge, ε ₆₀represent to stick on the strain value of 60 degree foil gauges, ε ₁₂₀represent to stick on the strain value of 120 degree foil gauges).

According to following computing formula, can obtain corresponding principle stress and principal strain

$\begin{array}{c}{\mathrm{\ϵ}}_1\\ {\mathrm{\ϵ}}_2\end{array}=\frac{{\mathrm{\ϵ}}_0+{{\mathrm{\ϵ}}_{60}+\mathrm{\ϵ}}_{120}}{3}\±\sqrt{{({\mathrm{\ϵ}}_0-\frac{{\mathrm{\ϵ}}_0+{\mathrm{\ϵ}}_{60}+{\mathrm{\ϵ}}_{120}}{3})}^2+{\frac{1}{3}({\mathrm{\ϵ}}_{60}-{\mathrm{\ϵ}}_{120})}^2}$

$\begin{array}{c}{\mathrm{\σ}}_1\\ {\mathrm{\σ}}_2\end{array}==E[\frac{{\mathrm{\ϵ}}_0+{\mathrm{\ϵ}}_{60}+{\mathrm{\ϵ}}_{120}}{3(1-\mathrm{\μ})}\±\frac{1}{1+\mathrm{\μ}}\sqrt{{({\mathrm{\ϵ}}_0-\frac{{\mathrm{\ϵ}}_0+{\mathrm{\ϵ}}_{60}+{\mathrm{\ϵ}}_{120}}{3})}^2+\frac{1}{3}{({\mathrm{\ϵ}}_{60}-{\mathrm{\ϵ}}_{120})}^2}]$

E is elastic modulus, and μ is the Poisson ratio of material.

two parameters represent respectively maximum principal strain and minimum principal strain.

two parameters represent respectively major principal stress and least principal stress.

As a kind of, preferably in one embodiment, on the diverse location of vehicle same structure or different structure, can mix above-mentioned two kinds of different strain rosette bonding methods, those skilled in the art can realize completely.

The above-mentioned description to embodiment is can understand and apply the invention for ease of those skilled in the art.Person skilled in the art obviously can easily make various modifications to these embodiment, and General Principle described herein is applied in other embodiment and needn't passes through performing creative labour.Therefore, the invention is not restricted to the embodiment here, those skilled in the art are according to announcement of the present invention, and not departing from the improvement that category of the present invention makes and revise all should be within protection scope of the present invention.

Claims (5)

1. the method that vehicle stress is measured without unloading, is characterized in that, mainly comprises the following steps:

Step 1, in the structure of vehicle, determine some measuring points, paste strain rosette, connect strainmeter;

Step 2, described vehicle is placed at horizontal level, and strainmeter is returned to zero;

Step 3, by vehicle deflection α angle to the left, measure the strain change amount { Δ ε } that is caused strain rosette on each measuring point of structure by the change of vehicle body Action of Gravity Field direction ^l;

Step 4, vehicle rotate back to horizontal level, strainmeter rezeroing;

Step 5, by the vehicle same angle [alpha] of deflection to the right, again measure the strain change amount { Δ ε } of strain rosette on each measuring point of structure causing after being changed by vehicle body Action of Gravity Field direction ^r;

Step 6, according to formula

obtain the strain value of strain rosette.

2. method according to claim 1, is characterized in that: the scope at described α angle is between 15 to 25 degree.

3. method according to claim 1, is characterized in that: also comprise step 7, calculate the principle stress of measured point.

4. according to the method described in claim 1 or 3, it is characterized in that: described stickup strain rosette adopts three square bonding methods.

5. according to the method one of claim 1-4 Suo Shu, it is characterized in that: described stickup strain rosette adopts three equilateral triangle bonding methods.

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