JPS6330752A - Method of sensing strain and crack throgh conductor patterning machining of surface of mechanical part - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention provides a new method for detecting distortions and cracks whenever they occur in parts of aircraft or other machines. It concerns a mechanical anomaly sensing method.

Conventional technology The design of machines that are subject to localized high stress or pressure, such as aircraft or some types of construction machinery, requires double-wall construction, etc.
Measures are being taken to prevent rupture. In addition, periodic inspections are carried out to prevent material fatigue from developing into rupture and causing an accident while the machine is in use.

In addition, research aimed at investigating or predicting vibrations, fatigue, and other phenomena in mechanical parts in use is
Most of the results are based on mock tests in the laboratory.

Problems to be Solved by the InventionDouble structures such as those for certain machines, especially aircraft,
It can cause increased weight and impede high performance.

In addition, a huge amount of money and time is spent on periodic inspection and maintenance, and it is almost impossible to discover all the cracks in all parts. It is true that catastrophes can occur due to

In contrast, the purpose of this invention is to eliminate distortions and cracks in structural parts at all times, that is, even while the machine is in use.
Moreover, the aim is to enable sensing through automatic driving. This has the advantages of improving safety, saving costs for operation and maintenance, and facilitating the collection of data on the dynamic characteristics of mechanical parts in actual usage conditions.

Means for Solving the Problem In order to make such sensing possible, conductive wires are attached to the surface of the structural parts used in the machine by a suitable method that does not significantly reduce the strength of the parts. In this case, it is desirable that the conductive wire be made of a material that has a large gauge factor (ratio of change in electrical resistance value ΔR/R to ratio of change in length Δβ/l) and has a small temperature dependence of electrical resistance. In addition to this, it is desirable that the stress and strain characteristics of the conducting wire be close to those of the base material. Specifically, it is desirable that the yield point of the conducting wire is the same as or slightly higher than that of the base material. It is also essential that the conductor has strong adhesion to the surface of the base material. Changes in the electrical resistance of the conductor are measured by microprocessor control or by human intervention.

The amount of strain in the component is measured according to the principle of a resistance wire strain meter.
It is proportional to the change in resistance value. This electrical resistance measurement does not require the high precision of a normal resistance strain meter measurement, and can be significantly greater than a reference value that has already been measured, or if the resistance measurement is infinite. only the results of the measurement are considered meaningful. Of course, a base material that is susceptible to brittle fracture requires higher precision.

Operation Periodically, a voltage is applied to both ends of the conductor, and its electrical resistance is measured from the flowing current. If the result is significant, an alarm device etc. is used to notify that something is wrong. Based on this, a human inspection is performed on the area through which the conductive wire passes to determine the location of defects such as distortions or cracks, and appropriate countermeasures are taken.

As an example, an overview of mechanical anomaly detection by applying this surface conductor patterning to parts used in the fuselage of an airplane will be described.

The fuselage of current jumbo aircraft includes A2024 and A7075.
Aluminum alloys such as are often used. Since aluminum is the main component, the conductor wire is preferably made of a material that has mechanical behavior similar to aluminum, such as aluminum or an aluminum alloy, as mentioned above.

The stringers of jumbo aircraft must withstand repeated stresses consisting exclusively of tensile loads.

For this reason, A7075, which has high tensile strength, is often used. Moreover, A7075 has poor cutting toughness and is prone to stress corrosion cracking even in the atmosphere, so early detection of crack occurrence is a serious issue.

Therefore, in FIG. 1 (cross-sectional view), an insulating oxide film 2 is formed by heat-treating the A7075 base material 1, and a conducting wire 3 made of an aluminum film with a thickness of about several tens of microseconds is formed on the insulating oxide film 2 by sputtering.
Make (plural). These conductors are placed perpendicular to the expected tensile stress direction. This wire is insulated by subjecting it to a heat treatment as described above or by forming another film. Finally, it is protected with paint 4.

This surface-treated stringer was installed in a jumbo machine, and the electrical resistance of each conductive wire made of aluminum film was measured in advance. The result is called the reference value.

During the flight of the jumbo aircraft, a microprocessor (5 in FIG. 2) is connected to the conductors through the connector 6, thereby measuring the resistance of each conductor periodically, for example every 5 minutes. Each measurement consists of several hundred current pulses per -second,
Then, take the average of several hundred resistance values and use this as the electrical resistance value.

If this resistance value differs significantly from the standard value, measure the resistance value again, and if the second measurement result also differs greatly from the standard value, record the result or sound an alarm. Notify the technician immediately.

When determining the arrangement and number of conducting wires, the larger the number, the more effective it will be in finding short cracks, and will also be useful in identifying the location where they occur. On the other hand, if there are too many conductive wires, the measurement process will be complicated and the effort and cost involved in surface processing will increase. Therefore, details regarding the conductors, such as their shape, arrangement, total number, etc., are determined by taking into account their overall effectiveness and economic constraints.

Further, a developed version of the above method is shown in FIG.

That is, the surfaces of two or more parts 7 connected by means such as welding are subjected to a similar patterning process, and when the parts are connected, the conductive wire 3 is electrically connected and insulated. This also helps in detecting cracks and other irregularities in the seam 8 through the resistance measurement described above.

Finally, I will introduce two examples of changing the conductor pattern. When the wires are arranged in a zigzag shape as shown in FIG. 4, sensing can be performed over a wide area using a circuit made up of minus conductive wires 3. or,
As shown in Figure 5, area 9 where stress is expected to be concentrated
Efficiency can be increased by arranging the conductors so that distortions and cracks can be detected in a focused manner.

Effect of the invention The effects of this invention can be roughly divided into two types.

First, it enables early detection and repair of distortions and cracks in machines such as aircraft that are actually operated, and has related effects (reduced maintenance inspections, more thorough safety, etc.).

Second, it helps collect data about the strains and cracks that occur during use of a particular machine.

4. Brief Description of the Figures FIG. 1 is a cross-sectional view of the surface of a component processed with a conductor pattern specified by the present invention, and FIGS. 2-5 show various types of conductor patterns.

1: Part base material, 2: Insulating film, 3: Conductive wire (film), 4: Protective layer, 5: Mix processor, 6: Connector, 7: Parts connected to other parts, 8: Seam, 9: Stress Concentrated area %S morning A change Kenel ¥13 \2 4 da ω 5 Procedural amendment document October 16, 1985 October 151, 1985” Submitted

Claims (1)

[Claims] 1. By electrically insulating several conductive wires and forming them on the surface of the base material, the electrical resistance value of which changes depending on the strain or crack in the base material, it is possible to measure the resistance change. A mechanical anomaly detection method that detects distortions and cracks. 2. When several mechanical parts are connected to each other, similar conductor patterning is applied to their surfaces so that the resistance value of the conductor changes in response to distortions and cracks at the joints of the parts, and by measurement. A mechanical anomaly detection method that also detects distortions and cracks in seams. 3 A similar mechanical anomaly sensing method using a component made of laminated materials whose surfaces are patterned with conductive wires as in 1 and 2 above.