CN103712532A - A method for detection and evaluation of shape and position errors for shells with skin frame-truss structures - Google Patents

Abstract

The invention belongs to a detection and evaluation method, and particularly relates to a shape and position error detection and evaluation method for a skin frame truss structure shell. It includes: the method comprises the following steps: adjusting the measuring table, and installing the transition ring on the measuring table by using a crown block, wherein the step two is as follows: according to the positioning marks of the transition ring and the product, the product is hung on the transition ring to be positioned and clamped, and the third step is that: measuring the radial error value of the product by using tools such as a dial indicator, a vernier caliper, a standard gauge block and the like, and recording, wherein the fourth step is as follows: and calculating and recording the form and position tolerance value, wherein the form and position tolerance value is the final detection result. The invention has the following remarkable beneficial effects: the results of form and position tolerance measurements made using the technique of the present invention were verified using a laser tracker. Verification results show that the measurement results of the technology have high reliability and can be used as a measurement method for form and position tolerance of a aerospace skin frame truss structure shell product. The technology can also be popularized and applied to the detection and evaluation of the form and position errors of parts with larger overall dimensions.

Description

A method for detection and evaluation of shape and position errors for shells with skin frame-truss structures

technical field

The invention belongs to detection and evaluation methods, and in particular relates to a form-position error detection and evaluation method for skin frame-truss structure shells.

Background technique

Skin frame truss structure (also known as semi-monocoque structure) has been widely used in aerospace shell products at home and abroad because of its high structural strength, light product quality, and easy assembly and production. In the field of aerospace, this kind of structural shell generally has the characteristics of a rotating body and has a large diameter, so it is difficult to measure its shape and position error. At present, the measurement methods of product shape and position errors are mostly for small workpieces (generally parts), and there is no detection technology specifically for the shape and position errors of skin frame-truss assembled structural shells. The shape and position tolerance requirements of the skin frame truss assembly structure shell is an important performance index of aerospace products. It directly affects the coordination and docking of the shells of each section of the product. Bit errors have always been a difficult problem for product inspectors.

With the rapid development of science and technology, the detection technology of product shape and position error presents the characteristics of diversification and high precision. Taking the roundness error as an example, the existing roundness detection methods are divided into contact measurement methods and non-contact measurement methods. Contact measurement methods mainly use measuring tools such as vernier calipers and dial indicators for detection. Commonly used are two-point method (diameter method) and three-point method (V-type method); these two methods are simple to operate but have low precision. The non-contact measurement method mainly uses some advanced digital measurement equipment to realize the measurement of shape and position errors, such as coordinate measuring instruments, etc.; this measurement method requires special measurement equipment and operating space, and the measurement accuracy is good but the measurement cost is high. Not suitable for on-site measurements in workshops. According to different sampling methods, the roundness measurement method can be divided into continuous measurement method and discrete sampling measurement method. Among them, the whole circle continuous measurement method is measured by a special roundness meter, which is divided into a rotary table type (table rotation) and a rotary shaft type (roundness meter rotation). The rotary table has stable performance and is suitable for measuring small workpiece parts. The rotating shaft type has strong bearing capacity and high rotation precision.

At present, there are mainly four kinds of roundness error evaluation methods commonly used in the world: ①Least square circle (LSC) method: the center of the circle whose square sum of the distances from the corresponding points on the contour of the circle to the circumference is the smallest is the center of the circle, The radius difference between the two concentric circles that contain the outline of the measured circle is the roundness error. ②Maximum inscribed circle (MIC) method: only applicable to inner circles. Taking the center of the inscribed circle that is inscribed in the contour of the measured circle and has the largest radius as the center, the radius difference between the two concentric circles that contain the contour of the measured circle is the roundness error. ③ Minimum circumscribed circle (MCC) method: only applicable to outer circles. Taking the center of the circumscribed circle that contains the outline of the measured circle and has the smallest radius as the center, the radius difference between the two concentric circles that contain the outline of the measured circle is the roundness error. ④Minimum zone circle (MZC) method: the radius difference of two concentric circles is evaluated as the roundness error with the radius difference containing the outline of the measured circle as the minimum error.

The detection and evaluation method of coaxiality is basically the same as the detection and evaluation method of roundness. The degree of parallelism is mostly carried out by the meter method, and is evaluated according to the definition of parallelism. The measurement of flatness is measured and evaluated according to the definition of flatness. It is worth noting that with the advancement of detection technology, the detection methods of shape and position errors are also gradually improving.

Contents of the invention

The object of the present invention is to provide a form-position error detection and evaluation method for shells with skin frame and truss structures.

The present invention is achieved in this way: a form-position error detection and evaluation method for a skin frame-truss structure shell, comprising the following steps:

Step 1: Adjust the measuring platform, select different sizes of measuring transition rings according to different product diameters, and use the crown to install the transition rings on the measuring platform,

Step 2: According to the positioning marks of the transition ring and the product, hang the product on the transition ring for positioning and clamping,

Step 3: Use tools such as dial indicators, vernier calipers, and standard gauge blocks to measure the radial error value of the product (for roundness and coaxiality, for the parallelism between surfaces, a dial gauge should be used to measure the axial error of the end surface For flatness, the axial error value of the end face should be measured with a feeler gauge) and recorded,

Step 4: Calculate and record the geometric tolerance value, which is the final inspection result.

A method for detection and evaluation of form and position errors facing skin frame-truss structure shells as described above, wherein, after step four, the following steps are also included

Step 5: Repeat steps 3 to 4,

Step 6: Select the maximum shape and position tolerance obtained from repeated inspections as the final inspection result, and make a record.

A form error detection and evaluation method for shells with skin frame truss structures as described above, wherein, in the third step, for shell products with skin frame truss structures of different diameters, the number of sampling points during measurement should be Different, the smaller the diameter of the shell, the better the stiffness of the product, and the fewer the number of measurement sampling points can be set. For shells with a diameter below 2250mm, 8-point circumferential uniform sampling is sufficient to meet the testing requirements; for shells with a diameter of 3350mm or more 36 points are uniformly distributed in the circumferential direction; for products with a diameter between 2250mm and 3350mm, the number of measurement points can be appropriately increased.

A method for detection and evaluation of shape and position errors for shells with skin-frame-truss structures as described above, wherein,

The technical parameters of the geometric tolerance measurement method are shown in the table below

Flatness and parallelism between surfaces are evaluated by the method of difference between the maximum value and the minimum value.

As mentioned above, a method for detection and evaluation of shape and position errors oriented to shells with skin frame and truss structures, wherein the fifth step includes different measurement accuracy requirements for different shape and position tolerances, and different measurement times. For positional tolerance measurement, one measurement is sufficient. For products with high requirements for geometrical tolerance measurement accuracy, multiple measurements are taken to obtain the maximum value. The sampling point position for each measurement should be avoided as much as possible. The number of measurements is generally taken as 3 to 5 times is appropriate.

The obvious beneficial effect of the invention is that the results of shape and position tolerance measurement using the patented technology are verified by using the laser tracker. The verification results show that the measurement results of this technology have strong credibility and can be used as a measurement method for the shape and position tolerance of aerospace skin frame truss structure shell products. This technology can also be extended and applied to the detection and evaluation of shape and position errors of parts with large external dimensions.

Verification of measurement results of coaxiality shape and position tolerance of a certain type of skin frame truss structure product

Measurement methods 1st 2nd the 3rd time 4th 5th This patented technology 0.64 0.63 0.64 0.62 0.63 Laser tracker method 0.658 0.645 0.657 0.642 0.651 The difference between the measurement results of the two methods 0.018 0.015 0.017 0.022 0.021

Detailed ways

A form-position error detection and evaluation method for skin frame-truss structure shells, comprising the following steps:

Step 1: Adjust the measuring platform, select different sizes of measuring transition rings according to different product diameters, and install the transition rings on the measuring platform by using the crane.

For skin frame and truss structure shell products with different diameters, the number of sampling points should be different during measurement. The smaller the shell diameter, the better the rigidity of the product, and the fewer the number of measurement sampling points can be set. For shells with a diameter below 2250mm, 8-point circumferential uniform sampling is sufficient to meet the detection requirements; for shells with a diameter above 3350mm, 36 points are used for circumferential uniform sampling; for products with a diameter between 2250mm and 3350mm, the number of measurement points can be appropriately increased .

Step 2: According to the positioning marks of the transition ring and the product, hang the product on the transition ring for positioning and clamping.

Step 3: Use tools such as dial indicators, vernier calipers, and standard gauge blocks to measure the radial error value of the product (for roundness and coaxiality, for the parallelism between surfaces, a dial gauge should be used to measure the axial error of the end surface For flatness, feeler gauge should be used to measure the axial error value of the end face) and record.

The technical parameters of the geometric tolerance measurement method of this patent are shown in the table below

Note: The flatness and the parallelism between surfaces are evaluated by the method of difference between the maximum value and the minimum value

Step 4: Input the recorded value into the computer geometric tolerance calculation software, calculate the geometric tolerance value and make a record.

The geometric tolerance calculation software is a calculation software that uses existing data for data fitting to obtain results. As long as those skilled in the art know fitting mathematical formulas such as the least square method, they can easily write such a program.

For different geometric tolerance measurement accuracy requirements, the number of measurements is different. For general-precision geometric tolerance measurement, only one measurement is required. For products with high requirements for geometric tolerance measurement accuracy, it is generally necessary to perform multiple measurements to obtain the maximum value. The position of the sampling point for each measurement should be avoided as much as possible. The number of measurements is generally 3 to 5 times. Too few times are not enough to eliminate random errors; too many times are not economical and practical.

Step 5: When the detection accuracy is high, repeat steps 3 to 4 (generally 3 to 5 times are enough).

Step 6: Select the maximum shape and position tolerance obtained from repeated inspections as the final inspection result, and make a record.

Claims (5)

1. A form and position error detection and evaluation method facing skin frame truss structure shell, it is characterized in that: comprise the following steps: Step 1: Adjust the measuring platform, select different sizes of measuring transition rings according to different product diameters, and use the crown to install the transition rings on the measuring platform, Step 2: According to the positioning marks of the transition ring and the product, hang the product on the transition ring for positioning and clamping, Step 3: Measure the radial error value of the product with tools such as dial indicators, vernier calipers, and standard gauge blocks, and make records. Step 4: Calculate and record the geometric tolerance value, which is the final inspection result. 2. A method for detection and evaluation of shape and position errors facing skin frame-truss structure shells as claimed in claim 1, characterized in that: after step 4, the following steps are also included Step 5: Repeat steps 3 to 4, Step 6: Select the maximum shape and position tolerance obtained from repeated inspections as the final inspection result, and make a record. 3. A method for detection and evaluation of shape and position errors facing skin frame-truss structure shells as claimed in claim 2, characterized in that: in step 3, for skin frame-truss structure shells with different diameters For products, the number of sampling points should be different when measuring. The smaller the diameter of the shell, the better the rigidity of the product, the less the number of sampling points for measurement can be set. For shells with a diameter below 2250mm, 8-point circumferential uniform sampling is sufficient to meet the testing requirements; For shells with a diameter of 3350mm or more, 36 points are uniformly distributed in the circumferential direction; for products with a diameter between 2250mm and 3350mm, the number of measurement points can be appropriately increased. 4. A method for detection and evaluation of shape and position errors facing skin frame-truss structure shells as claimed in claim 3, characterized in that: The technical parameters of the geometric tolerance measurement method are shown in the table below

Flatness and parallelism between surfaces are evaluated by the method of difference between the maximum value and the minimum value. 5. A method for detection and evaluation of shape and position errors facing skin frame and truss structure shells as claimed in claim 4, characterized in that: said step 5 includes the measurement accuracy requirements for different shape and position tolerances, the number of measurements Different, the number of measurements is generally 3 to 5 times is appropriate.