CN103557783B - 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 not needing discharge car load.

Background technology

Strength condition is the Basic Design condition that production vehicles and other machinery product must meet, and the stress level of body structure and chassis structure is one of production vehicles intensity evaluation Main Basis.Although introduce CAE technology in a large number 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 carrying out non-contact measurement to the ess-strain of structural member.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 in measured structure, first choose the measuring point of some, measuring point pastes foil gauge, by strainmeter balancing or record initial value under light condition, then load, test the strain caused by load, calculate the stress at measuring point place according to Hooke's law.

Easy to implement and the technology maturation of this method, apply widely, but this test needs carries out adding unloading, namely shed the load of structure before measuring, reload and measure after strainmeter balancing in engineering practice.Because the weight of structure self cannot unload, therefore, the stress 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 practice shows, because vehicle structure operating load is very large, even if the load that can unload, adds discharge time very long, is 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 then very inconvenient, as engine, wheel box and clutch coupling etc.

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

Summary of the invention

The present invention is directed to the shortcoming existed in prior art, utilize removable, the tiltable feature of automobile body, propose a kind of indirect strain measurement method of nothing unloading based on inclination angle principle; Furthermore, above-mentioned strainometer is also provided to calculate stress.

The method that vehicle stress is measured without unloading, mainly comprises the following steps: step one, in the structure of vehicle, determine some measuring points, pastes strain rosette, connects strainmeter; Step 2, described vehicle to be placed at horizontal level, and strainmeter is returned to zero; Step 3, vehicle is deflected α angle to the left, measure the strain knots modification { Δ ε } being caused strain rosette on each measuring point of structure by the change in vehicle body Action of Gravity Field direction ^l; Step 4, vehicle rotate back to horizontal level, strainmeter rezeroing; Step 5, vehicle is deflected same angle-α to the right, again measure the strain knots modification { Δ ε } of strain rosette on each measuring point of structure that causes 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, provides a kind of nothing unloading indirect stress measuring method based on inclination angle principle.Be used for simplifying the stress measurement process of vehicle structure, particularly for the structure that own wt is larger, adopt conventional method to measure, adopt the inventive method to have unique advantage; For the load that some can unload in theory, the structure that practical operation is then very inconvenient, adopts method of the present invention also greatly can simplify test process, shortens test period.

Accompanying drawing explanation

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

Fig. 2 is that equilateral triangle strain rosette pastes 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 allows the vehicle body of measured vehicle respectively to the certain angle [alpha] of left and right inclination and-α, utilize forward and backward vehicle body to conduct oneself with dignity the change of power in the horizontal and vertical directions, cause the change of structural strain, the anti-stress released suffered by vehicle structure.

The structure of vehicle determines measuring point, the foil gauge (foil gauge is pasted in the mode of Fig. 1 or Fig. 2) needed for stickup, connect strainmeter.Tested vehicle is placed (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 on 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 on 0 °, 45 °, 90 ° directions is respectively { ε ^l, { ε ^r, ({ ε ^l, { ε ^rthe amount corresponding with { ε }, be all the vector comprising three components).

Arbitrary mode can be adopted (preferred as one, such as: hung up or jack-up on a tilting table or by vehicle side by storing cycle) vehicle is deflected α angle (as shown in Figure 4) to the left, measure and cause the strain knots modification of strain rosette on structure measuring point for { Δ ε } by the change of vehicle body Action of Gravity Field direction ^l.

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

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

{ε ^L} _X＝-{ε}sinα

{ε ^L} _Y＝{ε}cosα

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

{Δε} ^L＝{ε ^L}-{ε}

Vehicle rotates back to horizontal level, measuring system rezeroing.

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

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

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

{ε ^R} _X＝{ε}sinα

{ε ^R} _Y＝{ε}cosα

Strain { the ε recorded after body sway ^rand vehicle body horizontal positioned time strain { ε } 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 { 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 obtained ^l} _x=-{ ε ^r} _x, two formulas additions above can be obtained following equation:

{Δε} ^L+{Δε} ^R＝2{ε}(cosα-1)

Vehicle body deadweight can be obtained by above formula and cause the strain { ε } of strain rosette on structure measuring point namely:

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

So just obtain the value ε of each foil gauge in strain rosette ₀, ε ₄₅, ε ₉₀(ε ₀represent the strain value being pasted onto 0 degree of foil gauge, ε ₄₅represent the strain value being pasted onto 45 degree of foil gauges, ε ₉₀represent the strain value being pasted onto 90 degree of 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 maximum principal strain and minimum principal strain respectively. two parameters represent major principal stress and least principal stress respectively.

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

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

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

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

E is elastic modulus, and μ is the Poisson ratio of material. two parameters represent maximum principal strain and minimum principal strain respectively. two parameters represent major principal stress and least principal stress respectively.

Preferred as one, in one embodiment, the diverse location or different structure of vehicle same structure can mix above-mentioned two kinds of different strain rosette bonding methods, and those skilled in the art can realize completely.

Above-mentioned is can understand and apply the invention for ease of those skilled in the art to the description of embodiment.Person skilled in the art obviously easily can make various amendment to these embodiments, and General Principle described herein is applied in other embodiments and need not through performing creative labour.Therefore, the invention is not restricted to embodiment here, those skilled in the art, according to announcement of the present invention, do not depart from improvement that scope makes and amendment all should within protection scope of the present invention.

Claims (5)

1. vehicle stress is without a method for unloading measurement, it is characterized in that, mainly comprises the following steps:

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

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

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

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

Step 5, vehicle is deflected same angle [alpha] to the right, again measure the strain knots modification { Δ ε } of strain rosette on each measuring point of structure that causes 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. the method according to claim 1 or 3, is characterized in that: described stickup strain rosette adopts three square bonding methods.

5. the method according to claim 1 or 3, is characterized in that: described stickup strain rosette adopts three equilateral triangle bonding methods.