CN103557783B

CN103557783B - Method for vehicle stress non-discharging measurement

Info

Publication number: CN103557783B
Application number: CN201310544246.0A
Authority: CN
Inventors: 闫亚坤; 王文辉; 那景新; 麻文炎; 王童; 李婷婷; 张苹苹; 刘玉
Original assignee: Jilin University
Current assignee: Jilin University
Priority date: 2013-11-06
Filing date: 2013-11-06
Publication date: 2015-07-15
Anticipated expiration: 2033-11-06
Also published as: CN103557783A

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 method for measuring vehicle stress without unloading

技术领域technical field

本发明涉及一种车辆应力的测量方法，更具体而言，涉及一种不需要卸载车辆载荷的车辆应力测量方法。The invention relates to a method for measuring vehicle stress, and more particularly, relates to a method for measuring vehicle stress without unloading the vehicle load.

背景技术Background technique

强度条件是车辆产品及其它机械类产品必须满足的基本设计条件，车身结构与底盘结构的应力水平是车辆产品强度评价主要依据之一。尽管现代产品开发中已经大量引入CAE技术，对结构的强度、刚度及耐久性的指标进行全面的计算、分析，但最终的强度条件，仍然要以实车实验为准。The strength condition is the basic design condition that vehicle products and other mechanical products must meet. The stress level of the body structure and chassis structure is one of the main basis for the strength evaluation of vehicle products. Although a large number of CAE technologies have been introduced in modern product development to conduct comprehensive calculations and analyzes on the strength, stiffness and durability of structures, the final strength conditions still have to be based on actual vehicle experiments.

中国专利申请号201210236809.5公开了一种结构件应力应变的测量方法、装置及系统，用以实现对结构件的应力应变进行非接触式测量。但是该测量方法过程复杂，使用十分不方便。Chinese patent application number 201210236809.5 discloses a method, device and system for measuring stress and strain of structural parts, which are used to realize non-contact measurement of stress and strain of structural parts. However, the measurement process is complicated and inconvenient to use.

电阻应变片测量方法是目前应力测量的主要方法，其基本原理是首先在被测量结构上选取一定数量的测点，在测点上粘贴应变片，空载状态下将应变仪调平衡或记录初始值，然后加载，测试由载荷引起的应变，在根据胡克定律计算出测点处的应力。The resistance strain gauge measurement method is the main method of stress measurement at present. The basic principle is to select a certain number of measuring points on the structure to be measured, paste the strain gauges on the measuring points, and adjust the strain gauge to balance or record the initial stress under no-load conditions. Value, then load, test the strain caused by the load, and calculate the stress at the measuring point according to Hooke's law.

这种方法易于实施且技术成熟，在工程实践中应用非常广泛，但这种测试需要进行加卸载，即在测量前卸去结构的载荷，应变仪调平衡后再加载进行测量。由于结构自身的重量无法卸载，因此，由结构自重引起的应力也就无法测出。这给某些自重较大结构的测量带来困难。大量工程实践表明，由于车辆结构工作载荷很大，即使可以卸载的载荷，加卸载时间很长，因此很容易由测量仪器的零漂导致测试误差；此外，还有些载荷理论上可以卸载，但实际操作则非常不方便，如发动机、变速箱和离合器等。This method is easy to implement and the technology is mature, and it is widely used in engineering practice. However, this test needs to be loaded and unloaded, that is, the load of the structure is unloaded before the measurement, and the strain gauge is adjusted to balance and then loaded for measurement. Since the weight of the structure itself cannot be unloaded, the stress caused by the structure's own weight cannot be measured. This brings difficulties to the measurement of some structures with large self-weight. A large number of engineering practices have shown that due to the large working load of the vehicle structure, even if the load can be unloaded, the loading and unloading time is very long, so it is easy to cause test errors due to the zero drift of the measuring instrument; in addition, there are some loads that can be unloaded theoretically, but in practice It is very inconvenient to operate, such as engine, gearbox and clutch.

因为结构强度条件是所有车辆结构必须满足的必要条件之一，一种简单易行的应力测量方法，对车辆结构的强度设计与验证意义重大。Because the structural strength condition is one of the necessary conditions that all vehicle structures must meet, a simple and easy stress measurement method is of great significance to the strength design and verification of vehicle structures.

发明内容Contents of the invention

本发明针对现有技术中存在的缺点，利用车辆车身可移动、可倾斜的特点，提出一种基于倾角原理的无卸载间接应变测量方法；进一步而言，还提供上述应变计算出应力。Aiming at the shortcomings in the prior art, the present invention utilizes the movable and tiltable characteristics of the vehicle body, and proposes an indirect strain measurement method without unloading based on the principle of inclination; furthermore, it also provides the above-mentioned strain to calculate the stress.

一种车辆应力无卸载测量的方法，主要包括以下步骤：步骤一、在车辆的结构上确定若干测点，粘贴应变花，连接应变仪；步骤二、将所述车辆在水平位置放置，并对应变仪调零；步骤三、将车辆向左侧偏转α角，测出由车身重力作用方向的改变引起结构各测点上应变花的应变改变量{Δε}^L；步骤四、车辆旋转回水平位置，应变仪重新调零；步骤五、将车辆向右侧偏转同样角度-α，再次测量由车身重力作用方向改变后引起的结构各测点上应变花的应变改变量{Δε}^R；步骤六、根据公式求出应变花的应变值。A method for measuring vehicle stress without unloading mainly includes the following steps: Step 1, determining a number of measuring points on the structure of the vehicle, pasting strain rosettes, and connecting strain gauges; Step 2, placing the vehicle in a horizontal position, and Set the strain gauge to zero; step 3, deflect the vehicle to the left by an angle α, and measure the strain change {Δε} ^L of the strain rosettes on each measuring point of the structure caused by the change in the direction of gravity of the vehicle body; step 4, rotate the vehicle back to the horizontal position, the strain gauge is re-zeroed; Step 5, deflect the vehicle to the right by the same angle -α, and measure the strain change {Δε} ^R of the strain rosette on each measuring point of the structure caused by the change of the gravity direction of the vehicle body again; Step Six, according to the formula Find the strain value of the rosette.

作为进一步的优选，所述α角的范围是15至25度之间。As a further preference, the angle α ranges from 15 to 25 degrees.

作为进一步的优选，还包括步骤七、计算被测点的主应力。As a further preference, it also includes step 7, calculating the principal stress of the measured point.

作为进一步的优选，所述粘贴应变花采用三片直角形粘贴方式。As a further preference, the pasting rosette adopts a three-piece right-angle pasting method.

作为进一步的优选，所述粘贴应变花采用三片正三角形粘贴方式。As a further preference, the pasting rosette adopts the pasting method of three regular triangles.

作为进一步的优选，主应力计算公式As a further optimization, the principal stress calculation formula

$\begin{matrix} {σ σ}_{11} \\ {σ σ}_{22} \end{matrix} = = \frac{E E.}{22} [[\frac{{ϵ ϵ}_{00} + + {ϵ ϵ}_{9090}}{11 - - μ μ} &PlusMinus; &PlusMinus; \frac{11}{11 + + μ μ} \sqrt{{(({ϵ ϵ}_{00} - - {ϵ ϵ}_{9090}))}^{22} + + {(({22 ϵ ϵ}_{4545} - - {ϵ ϵ}_{00} - - {ϵ ϵ}_{9090}))}^{22}}]] . .$

$\begin{matrix} {σ σ}_{11} \\ {σ σ}_{22} \end{matrix}= = = E E. [[\frac{{ϵ ϵ}_{00} + + {ϵ ϵ}_{6060} + + {ϵ ϵ}_{120120}}{33 ((11 - - μ μ))} &PlusMinus; &PlusMinus; \frac{11}{11 + + μ μ} \sqrt{{(({ϵ ϵ}_{00} - - \frac{{ϵ ϵ}_{00} + + {ϵ ϵ}_{6060} + + {ϵ ϵ}_{120120}}{33}))}^{22} + + \frac{11}{33} {(({ϵ ϵ}_{6060} - - {ϵ ϵ}_{120120}))}^{22}}]] . .$

本发明是利用车辆车身可移动、可倾斜的特点，提供一种基于倾角原理的无卸载间接应力测量方法。用来简化车辆结构的应力测量过程，特别是对于自身重量较大的结构，采用常规方法无法测量，采用本发明方法具有独特的优势；对于一些理论上可以卸载的载荷，实际操作则非常不方便的结构，采用本发明的方法也可以大大简化测试过程，缩短测试周期。The invention utilizes the movable and tiltable characteristics of the vehicle body to provide a non-unloading indirect stress measurement method based on the principle of inclination. It is used to simplify the stress measurement process of the vehicle structure, especially for the structure with a large weight, which cannot be measured by conventional methods, and the method of the present invention has unique advantages; for some loads that can be unloaded in theory, the actual operation is very inconvenient structure, adopting the method of the present invention can also greatly simplify the testing process and shorten the testing cycle.

附图说明Description of drawings

图1是直角三角形应变花黏贴形式；Fig. 1 is the pasting form of the right-angled triangle rosette;

图2是正三角形应变花黏贴形式；Fig. 2 is the pasting form of equilateral triangle rosette;

图3是车辆水平放置示意图；Figure 3 is a schematic diagram of the horizontal placement of the vehicle;

图4是车辆左倾斜示意图；Fig. 4 is a schematic diagram of a vehicle tilting to the left;

图5是车辆左倾斜受力等效图；Fig. 5 is the force equivalent diagram of the left tilt of the vehicle;

图6是车辆右倾斜示意图；Fig. 6 is a schematic diagram of a vehicle tilting to the right;

图7是车辆右倾斜受力等效图。Fig. 7 is the force equivalent diagram of the vehicle tilted to the right.

具体实施方式Detailed ways

该测量方法是让被测量车辆的车身分别向左、右倾斜一定的角度α与-α，利用倾斜前、后车身自重在水平和竖直方向上力的改变，引起结构应变的改变，来反推出车辆结构所受的应力。The measurement method is to let the body of the vehicle to be measured tilt to the left and right at a certain angle α and -α, and use the change of the weight of the body before and after the tilt in the horizontal and vertical directions to cause a change in the structural strain to reflect Educe the stresses on the vehicle structure.

在车辆的结构上确定测点，粘贴所需的应变片（应变片以图1或者图2的方式黏贴），连接应变仪。将被测车辆在水平位置放置（如图3所示），并对测量系统调零。设车辆水平放置时在车身自重作用下应变花在0°、45°、90°方向上的应变为{ε}。车辆左、右倾斜时在车身自重作用下应变花在0°、45°、90°方向上的应变分别为{ε^L}、{ε^R}，（{ε^L}、{ε^R}是与{ε}相对应的量，都是包含三个分量的向量）。Determine the measuring points on the structure of the vehicle, paste the required strain gauges (the strain gauges are pasted in the manner shown in Figure 1 or Figure 2), and connect the strain gauges. Place the vehicle under test in a horizontal position (as shown in Figure 3), and zero the measurement system. Suppose the strain of the rosette in the directions of 0°, 45°, and 90° under the weight of the vehicle body is {ε} when the vehicle is placed horizontally. When the vehicle is tilted left and right, the strains of the rosette in the directions of 0°, 45°, and 90° under the weight of the vehicle body are respectively {ε ^L }, {ε ^R }, ({ε ^L }, {ε ^R } are the The quantities corresponding to {ε} are all vectors containing three components).

可采用任意的方式（作为一种优选，例如：将车辆停放在一倾斜台上或将车辆一侧挂起或者顶起）将车辆向左侧偏转α角（如图4所示），测出由车身重力作用方向改变引起结构测点上应变花的应变改变量为{Δε}^L。Any way (as a preference, for example: parking the vehicle on an inclined platform or hanging or jacking up the vehicle side) can be used to deflect the vehicle to the left by an angle α (as shown in Figure 4), and the measured The strain change of the rosette on the structural measuring point caused by the change of the gravity direction of the vehicle body is {Δε} ^L .

设车身自重在水平和竖直方向上的两个分力Gsinα、Gcosα作用下结构测点上应变花的应变分别为{ε^L}_X、{ε^L}_Y。Assume that the strains of the strain rosette on the structural measuring point under the two component forces Gsinα and Gcosα of the body weight in the horizontal and vertical directions are respectively {ε ^L } _X , {ε ^L } _Y .

对比图3与图5可得到{ε}、{ε^L}_X、{ε^L}_Y存在以下关系：Comparing Figure 3 and Figure 5, it can be obtained that {ε}, {ε ^L } _X , {ε ^L } _Y have the following relationship:

{ε^L}_X＝-{ε}sinα{ε ^L } _X ＝-{ε}sinα

{ε^L}_Y＝{ε}cosα{ε ^L } _Y ＝{ε}cosα

车身倾斜后测得的应变{ε^L}与车身水平放置时的应变{ε}之间的应变差{Δε}^L可表示为：The strain difference {Δε} L between the strain {ε ^L } measured after the body ^is tilted and the strain {ε} when the body is placed horizontally can be expressed as:

{Δε}^L＝{ε^L}-{ε}{Δε} ^L ＝{ε ^L }-{ε}

车辆旋转回水平位置，测量系统重新调零。The vehicle rotates back to a horizontal position and the measurement system is reset to zero.

将车辆向右侧偏转同样角度-α（如图6所示），再次测量由车身重力作用方向改变后引起结构测点上应变花的应变改变量为{Δε}^R。The vehicle is deflected to the right by the same angle -α (as shown in Figure 6), and the strain change of the strain rosette on the structural measuring point caused by the change of the gravity direction of the vehicle body is measured again as {Δε} ^R .

设此时车身自重在水平和竖直方向上的两个分力Gsinα、Gcosα作用下结构测点上应变花的应变分别为{ε^R}_X、{ε^R}_Y。Assume that the strains of the strain rosettes on the structural measuring point under the action of the two component forces Gsinα and Gcosα of the body’s self-weight in the horizontal and vertical directions are {ε ^R } _X , {ε ^R } _Y , respectively.

对比图3与图7可得到{ε}、{ε^R}_X、{ε^R}_Y存在以下关系：Comparing Figure 3 and Figure 7, it can be obtained that {ε}, {ε ^R } _X , {ε ^R } _Y have the following relationship:

{ε^R}_X＝{ε}sinα{ε ^R } _X ＝{ε}sinα

{ε^R}_Y＝{ε}cosα{ε ^R } _Y ＝{ε}cosα

车身倾斜后测得的应变{ε^R}与车身水平放置时的应变{ε}之间的应变差{Δε}^R可表示为：The strain difference {Δε ^} R between the strain {ε ^R } measured after the body is tilted and the strain {ε} when the body is placed horizontally can be expressed as:

{Δε}^R＝{ε^R}-{ε}{Δε} ^R ＝{ε ^R }-{ε}

由于车身向两边偏转的角度相同，所以{ε^L}_X、{ε^L}_Y、{ε^R}_X、{ε^R}_Y存在以下关系：Since the body deflects at the same angle to both sides, {ε ^L } _X , {ε ^L } _Y , {ε ^R } _X , {ε ^R } _Y have the following relationship:

{ε^L}_X＝-{ε^R}_X {ε ^L } _X ＝-{ε ^R } _X

{ε^L}_Y＝{ε^R}_Y {ε ^L } _Y ＝ {ε ^R } _Y

综合以上各式可把{Δε}^L、{Δε}^R表示为：Combining the above formulas, {Δε} ^L and {Δε} ^R can be expressed as:

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

由已求出的关系{ε^L}_X＝-{ε^R}_X，把上面两式相加可得到如下等式：According to the obtained relationship {ε ^L } _X =-{ε ^R } _X , the following equation can be obtained by adding the above two equations:

{Δε}^L+{Δε}^R＝2{ε}(cosα-1){Δε} ^L +{Δε} ^R ＝2{ε}(cosα-1)

由上式可以求出车身自重引起结构测点上应变花的应变{ε}即：From the above formula, the strain {ε} of the strain rosette on the structural measuring point caused by the self-weight of the vehicle body can be obtained, namely:

${{ϵ ϵ}} = = \frac{{{Δϵ Δϵ}}^{L L} + + {{Δϵ Δϵ}}^{R R}}{22 ((cos cos α α - - 11))}$

这样就求出了应变花中各个应变片的值ε₀、ε₄₅、ε₉₀（ε₀表示粘贴在0度应变片的应变值，ε₄₅表示粘贴在45度应变片的应变值，ε₉₀表示粘贴在90度应变片的应变值）。In this way, the values ε ₀ , ε ₄₅ , and ε ₉₀ of each strain gauge in the strain rosette are obtained (ε ₀ represents the strain value pasted on the 0-degree strain gauge, ε ₄₅ represents the strain value pasted on the 45-degree strain gauge, and ε ₉₀ Indicates the strain value pasted on the 90-degree strain gauge).

由图1所示的三片直角形应变花的粘贴形式，根据材料力学中主应变和主应力计算公式，可求得主应变和主应力。From the paste form of three rectangular strain rosettes shown in Figure 1, the principal strain and principal stress can be obtained according to the calculation formulas of principal strain and principal stress in material mechanics.

$\begin{matrix} {ϵ ϵ}_{11} \\ {ϵ ϵ}_{22} \end{matrix} = = \frac{{ϵ ϵ}_{00} + + {ϵ ϵ}_{9090}}{22} &PlusMinus; &PlusMinus; \frac{11}{22} \sqrt{{(({ϵ ϵ}_{00} - - {ϵ ϵ}_{9090}))}^{22} + + {(({22 ϵ ϵ}_{4545} - - {ϵ ϵ}_{00} - - {ϵ ϵ}_{9090}))}^{22}}$

$\begin{matrix} {σ σ}_{11} \\ {σ σ}_{22} \end{matrix} = = \frac{E E.}{22} [[\frac{{ϵ ϵ}_{00} + + {ϵ ϵ}_{9090}}{11 - - μ μ} &PlusMinus; &PlusMinus; \frac{11}{11 + + μ μ} \sqrt{{(({ϵ ϵ}_{00} - - {ϵ ϵ}_{9090}))}^{22} + + {(({22 ϵ ϵ}_{4545} - - {ϵ ϵ}_{00} - - {ϵ ϵ}_{9090}))}^{22}}]]$

E是弹性模量，μ是材料的泊松比。两个参数分别表示最大主应变和最小主应变。两个参数分别表示最大主应力和最小主应力。E is the modulus of elasticity and μ is the Poisson's ratio of the material. The two parameters represent the maximum principal strain and the minimum principal strain, respectively. The two parameters represent the maximum principal stress and the minimum principal stress, respectively.

作为另一个实施例，如果按图2所示三片正三角形黏贴应变片，可根据上述推导过程求出ε₀、ε₆₀、ε₁₂₀（ε₀表示粘贴在0度应变片的应变值，ε₆₀表示粘贴在60度应变片的应变值，ε₁₂₀表示粘贴在120度应变片的应变值）。As another example, if the three equilateral triangles are pasted with strain gauges as shown in Figure 2, ε ₀ , ε ₆₀ , and ε ₁₂₀ can be obtained according to the above derivation process (ε ₀ represents the strain value pasted on the 0-degree strain gauge, ε ₆₀ represents the strain value pasted on the 60-degree strain gauge, ε ₁₂₀ represents the strain value pasted on the 120-degree strain gauge).

按照以下计算公式，可求出相应的主应力和主应变According to the following calculation formula, the corresponding principal stress and principal strain can be obtained

$\begin{matrix} {ϵ ϵ}_{11} \\ {ϵ ϵ}_{22} \end{matrix} = = \frac{{ϵ ϵ}_{00} + + {{ϵ ϵ}_{6060} + + ϵ ϵ}_{120120}}{33} &PlusMinus; &PlusMinus; \sqrt{{(({ϵ ϵ}_{00} - - \frac{{ϵ ϵ}_{00} + + {ϵ ϵ}_{6060} + + {ϵ ϵ}_{120120}}{33}))}^{22} + + {\frac{11}{33} (({ϵ ϵ}_{6060} - - {ϵ ϵ}_{120120}))}^{22}}$

$\begin{matrix} {σ σ}_{11} \\ {σ σ}_{22} \end{matrix}= = = E E. [[\frac{{ϵ ϵ}_{00} + + {ϵ ϵ}_{6060} + + {ϵ ϵ}_{120120}}{33 ((11 - - μ μ))} &PlusMinus; &PlusMinus; \frac{11}{11 + + μ μ} \sqrt{{(({ϵ ϵ}_{00} - - \frac{{ϵ ϵ}_{00} + + {ϵ ϵ}_{6060} + + {ϵ ϵ}_{120120}}{33}))}^{22} + + \frac{11}{33} {(({ϵ ϵ}_{6060} - - {ϵ ϵ}_{120120}))}^{22}}]]$

作为一种优选，在一个实施例中，在车辆同一结构的不同位置或者不同结构上可以混合上述两种不同的应变花粘贴方式，本领域技术人员完全能够实现。As a preference, in one embodiment, the above two different methods of pasting rosettes can be mixed at different positions of the same structure of the vehicle or on different structures, which can be fully realized by those skilled in the art.

上述的对实施例的描述是为便于该技术领域的普通技术人员能理解和应用本发明。熟悉本领域技术的人员显然可以容易地对这些实施例做出各种修改，并把在此说明的一般原理应用到其他实施例中而不必经过创造性的劳动。因此，本发明不限于这里的实施例，本领域技术人员根据本发明的揭示，不脱离本发明范畴所做出的改进和修改都应该在本发明的保护范围之内。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

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.