CN109668664B

CN109668664B - milli-Newton level surface friction force measuring device

Info

Publication number: CN109668664B
Application number: CN201811462644.7A
Authority: CN
Inventors: 任宗金; 杜瑞锋; 张军; 马露露; 赵顺义; 徐田国; 朱晓雨; 贾振元
Original assignee: Dalian University of Technology
Current assignee: Dalian University of Technology
Priority date: 2018-12-03
Filing date: 2018-12-03
Publication date: 2021-02-26
Anticipated expiration: 2038-12-03
Also published as: CN109668664A

Abstract

The invention provides a milli-Newton surface friction force measuring device, wherein four corners of a base of the measuring device are provided with four threaded holes so as to be conveniently fixed in a measured model; a certain cut piezoelectric quartz wafer is arranged in the sensor; the stud and the nut are used for connecting the base, the sensor and the upper cover; the polytetrafluoroethylene sleeve is positioned between the central hole of the sensor and the stud, plays a role in positioning, and ensures that the centers of the base, the sensor and the upper cover are on the same straight line; the dustproof plate is used for packaging and preventing dust from entering the connecting part; the adapter plate is used for connecting the upper cover and the long rod; the long rod is used for amplifying micro friction force; the upper surface of the sensing head is used for sensing air surface friction. The invention utilizes the piezoelectric torque sensor and the lever principle to be combined to measure the micro friction force on the surface of the aircraft, can effectively avoid the interference of force in the vertical direction, and simultaneously utilizes the lever principle to amplify the micro friction force on the surface, thereby realizing the rapid and accurate measurement of the milli-Newton friction force on the surface of the aircraft.

Description

milli-Newton level surface friction force measuring device

Technical Field

The invention belongs to the technical field of piezoelectric force measurement, is applied to wind tunnel tests of aircraft models, and particularly relates to a milli-Newton surface friction force measuring device which can measure milli-Newton surface friction force of an aircraft.

Background

The surface friction resistance is a large resistance source in the flight process of the aircraft, and researches show that the friction resistance of the subsonic aircraft in the cruising state accounts for 50% of the total resistance. Therefore, the research on drag reduction or the research on the friction resistance characteristics has an important influence on the performance of the aircraft, and the reduction of the friction resistance means that the voyage is increased under the same fuel consumption, or more effective loads can be carried under a certain condition of the voyage, and only by correctly measuring the friction resistance on the surface of the aircraft, a correct guidance mode can be provided for adopting a drag reduction measure. For the development of the aircraft, under the condition of hypersonic speed, the aerodynamic heat on the surface of the aircraft mainly comes from the surface friction resistance, and the accurate acquisition of the surface friction resistance of the aircraft can provide a reliable basis for the correct thermal protection design.

At present, most of devices for measuring friction force have the structural characteristics of adopting a cantilever beam structure, and a movable sensing head is arranged at the top of the cantilever beam to sense the friction force of air on the surface of an aircraft except for some methods for utilizing an oil film. Merit R J, Schetz J A, Marineau E C, et al direct Skin vibration Measurements at Mach 10in a Hypervelocity windpipe [ J ]. Journal of space and rolls, 2017,54(4):1-12. A funnel-shaped surface Friction force measuring device is introduced, a strain gauge is attached to a cantilever beam bending part to induce the Friction force in the horizontal direction, and experiments are carried out in an ultra-sonic Wind Tunnel. Although the method can measure the friction force in the horizontal direction, under actual conditions, the effect of the vertical force is also exerted during the flight process of the aircraft, and how to quickly and accurately measure the surface friction force in the horizontal direction under the condition of offsetting the interference of the vertical force becomes a great problem in the field of aerospace.

The invention measures the air friction force on the surface of the aircraft based on the piezoelectric torque sensor, takes the piezoelectric quartz crystal as a mechanical quantity sensitive element, has the characteristics of high rigidity, high natural frequency, high sensitivity and excellent stability, and is very suitable for measuring the force with high precision and good dynamic performance. The wafer with a certain cutting shape is selected, the wafer is not sensitive to force in the vertical direction due to a reasonable arrangement mode, the interference of the force in the vertical direction is eliminated, and meanwhile, the surface friction force in the horizontal direction is amplified and measured by combining a lever principle.

Disclosure of Invention

The invention aims to provide a device capable of quickly and accurately measuring the air friction force on the surface of an aircraft, eliminating the interference of force in the vertical direction and carrying out amplification measurement on the milli-Newton surface friction force.

The technical scheme of the invention is as follows:

a milli-Newton surface friction force measuring device comprises a measuring device base 1, a sensor 2, a stud 3, a polytetrafluoroethylene sleeve 4, an upper cover 5, a nut 6, a dust-proof plate 7, an adapter plate 8, a long rod 9 and a sensing head 10; the main structures of the base 1 and the upper cover 5 are the same, and four corners of the base are respectively provided with a threaded hole for fixing in a tested model; a certain cut piezoelectric quartz wafer is arranged in the sensor 2, the sensor 2 is arranged between the base 1 and the upper cover 5, and the connection is realized through the matching of the stud 3 and the nut 6; the polytetrafluoroethylene sleeve 4 is positioned between the central hole of the sensor 2 and the stud 3, plays a role in positioning and ensures that the centers of the base 1, the sensor 2 and the upper cover 5 are on the same straight line; a stepped hole is formed in the center of the upper cover 5 and used for placing a nut 6 and a dust guard 7; the dust-proof plate 7 is used for packaging and preventing dust from entering the connecting part; the adapter plate 8 is fixed on the upper cover 5 and is used for connecting the upper cover 5 and the long rod 9; the long rod 9 is used for amplifying small force; the upper surface of the sensing head 10 is used for sensing air surface friction, and the lower surface is in threaded connection with the long rod 9.

The invention has the beneficial effects that: the invention utilizes the piezoelectric torque sensor and the lever principle to be combined to measure the micro friction force on the surface of the aircraft, can effectively avoid the interference of force in the vertical direction, and simultaneously utilizes the lever principle to amplify the micro friction force on the surface, thereby realizing the rapid and accurate measurement of the milli-Newton friction force on the surface of the aircraft.

Drawings

Fig. 1 is a force-bearing schematic diagram of a surface friction force measuring device.

FIG. 2 is a schematic diagram of a surface friction device.

In the figure: 1 measuring a device base; 2, a sensor; 3, a double-end stud; 4, a polytetrafluoroethylene sleeve; 5, covering the cover; 6, a nut; 7, a dust guard plate; 8, an adapter plate; 9 long rods; 10 sense the head.

Detailed Description

The technical scheme and the attached drawings of the invention are combined to further implement the specific implementation mode of the invention.

Four corners of a base 1 are provided with four threaded holes so as to be conveniently fixed in a measured model; a certain cut piezoelectric quartz wafer is arranged inside the sensor 2; the stud 3 and the nut 6 are used for connecting the base 1, the sensor 2 and the upper cover 5; the polytetrafluoroethylene sleeve 4 is positioned between the central hole of the sensor 2 and the stud, plays a role in positioning, and ensures that the centers of the base 1, the sensor 2 and the upper cover 5 are on the same straight line; four corners of the upper cover 5 are provided with four threaded holes which are convenient for connecting with other parts, and a stepped hole at the center is used for placing a nut 6 and a dust guard 7; the dust-proof plate 7 is used for packaging and preventing dust from entering the connecting part; the adapter plate 8 is used for connecting the upper cover 5 and the long rod 9; the long rod 9 is used for amplifying small force; the upper surface of the sensing head 10 is used for sensing air surface friction, and the lower surface is in threaded connection with the long rod 9.

The measuring principle of the surface friction measuring device is as follows: through the reasonable arrangement of the wafer with surely cutting the type, make measuring device insensitive to the power of vertical direction, with this measuring device reasonable built-in the model of being surveyed, make sense head flush in the model surface of being surveyed, the air current direction perpendicular to stock, sense head 10 response air surface friction, reachs aircraft surface friction through lever principle and statics analysis. The measuring device can realize measurement of the friction force of the surface of the model in principle.

Although the present invention has been described in detail with reference to the preferred embodiments, the present invention is not limited to the embodiments. It will be appreciated by those skilled in the art that additions may be made to the technology and substitutions of equivalent elements in the field without departing from the technical features and scope of the present invention as set forth in the claims.

Claims

1. A milli-Newton surface friction force measuring device is characterized by comprising a measuring device base (1), a sensor (2), a stud (3), a polytetrafluoroethylene sleeve (4), an upper cover (5), a nut (6), a dust-proof plate (7), an adapter plate (8), a long rod (9) and a sensing head (10); the main structures of the base (1) and the upper cover (5) are the same, and four corners of the base are respectively provided with a threaded hole for fixing the base in a tested model; a certain-section piezoelectric quartz wafer is arranged in the sensor (2), the sensor (2) is arranged between the base (1) and the upper cover (5), and connection is realized through the matching of the stud (3) and the nut (6); the polytetrafluoroethylene sleeve (4) is positioned between the central hole of the sensor (2) and the stud (3) to play a role in positioning, and the centers of the base (1), the sensor (2) and the upper cover (5) are ensured to be on the same straight line; a step hole is formed in the center of the upper cover (5) and used for placing a nut (6) and a dust guard (7); the dust-proof plate (7) is used for packaging and preventing dust from entering the connecting part; the adapter plate (8) is fixed on the upper cover (5) and is used for connecting the upper cover (5) and the long rod (9); the long rod (9) is used for amplifying small force; the upper surface of the sensing head (10) is used for sensing the surface friction of air, and the lower surface of the sensing head is in threaded connection with the long rod (9); the sensor (2) is a piezoelectric torque sensor.