System and method of measurement of fatigue for mechanical details of aircraft and aircraft maintenance method

The invention relates to a system and method for measuring fatigue of mechanical parts of the aircraft, such as aircraft, and to a method of maintenance of the aircraft.

Safety regulations require aviation companies to track the fatigue of parts of aircraft operated by them, as these parts are subject to a large number of mechanical stresses (or loads). For this reason, carry out regular and periodic inspections (or maintenance) parts.

For example, details of suspension turbojet engines for aircraft subjected to strict controls. However, each inspection suspension requires a break in the operation of the aircraft and the dismantling of its suspension for testing. The frequency of inspections is determined in advance and check produce systematically after each predetermined period of time (for example, every 2600 cycles flight (takeoff, flight and landing), regardless of the actual state of fatigue parts. To avoid the risk of the inspection through too long a period after the appearance of the state of fatigue requiring intervention, such as repair or replacement, this time period should be chosen (by calculation or empirically) minimum beyond which may appear the risk of breaking parts, even if it is statistically insignificant. This minimum period corresponds to the case of parts subjected to random voltage on Therefore, many examinations carried out on the parts which could be safely used longer because they are not subjected to accidental stresses. Ultimately, in the absence of the analysis of real stress that has undergone detail repelled from the worst-case scenario with possible damage this part, that often leads to premature inspection.

In addition, for safety reasons parts used shorter than it would be possible not to reach terms of operation in which the risk of damage exceeds a certain threshold. Again, in the absence of analysis of the real conditions of use of parts selected criteria corresponding to the worst case scenario, so traditionally in aviation item replaced in the middle of its theoretical life, regardless of the actual state of fatigue. Thus, the actual final margin parts (ratio of the actual time of use to its theoretical suitability) is about 50%, so there is a need to increase it.

Moreover, given the frequent inspections (requiring suspension of dismantling the plane, and then install it on another plane has a priori) and the different service lives of various parts of the aircraft, track the status of the suspension over time is complex. In particular, sometimes it happens that the serial number printed on the metal suspension, eventually erased; In this case, since it is impossible to trace the chronology of her life and to avoid any risk assessment of the duration of its operation should be carried out using the most pessimistic hypothesis, for example, assuming that the suspension installed on the first aircraft equipped with this type of suspension, and then operated continuously in flight conditions; In practice there are used much less than under this fictional pessimistic hypothesis, so replacing the suspension will be made too soon.

In addition, if there are currently proxies fatigue suspensions, they may only be approximate and give unreliable information. So, to assess the state of fatigue suspension, sometimes use the data measured inertial aircraft unit that determines whether the plane plunges exceptional stresses such as hard landing (usually denoted by the English expression "hard landing"); This is done by calculating the load transfer from the inertial unit to detail. However, if a hard landing can really build on the exceptional suspension load, it does not happen systematically, and inspection of the suspension sometimes produce, even if the landing did not have any real influence on the suspension, such as efforts have been absorbed and are not transferred to the suspension.

Known sources of information is not really addressed the issue of measurement of fatigue preceded inspections; they crack more considered detection parts, such as, for example, in patent application FR 2923540, filed in the name of the applicant.

The object of the invention is to overcome these drawbacks and to facilitate the measurement of fatigue mechanical parts of aircraft to ensure the timeliness of their shows and to optimize their use.

The invention finds its application in particular for suspensions of turbojet engines for airplanes, since these parts are subject to a large number of stresses. However, the applicant does not limit the scope of its claims to this single application, and the invention and its advantages generally apply to any part of the aircraft is subjected to stresses.

In connection with this aspect of the invention is a system for measuring fatigue parts of the aircraft are subjected to mechanical stresses, the system comprising a plurality of voltage sensors mounted on the parts, wherein each sensor is adapted to detect the predetermined threshold stress, and to output a data signal, reflecting exceeding this threshold, the system comprises means for registration of the data, wherein the sensors are adapted to detect different voltage threshold that enables us to calculate, based on data for the system fatigue evaluation items associated with mechanical stresses.

Preferably, the data recorded by the system, is the number of excess cases of each of the thresholds.

Thus, we can get a good estimate of the actual details of the fatigue associated with the stresses to which it is exposed. Sensors like "count" the number of cases voltages exceeding different thresholds and the system registers these events that leads to the conclusion which follows from damage (ie fatigue) parts. The collection is divided by the stress increments, with each increment threshold sensors Compliant.

Thus, it is possible to optimize the operation details. In particular, knowing her fatigue, you can decide to inspect parts, and this choice is made on the basis of actual fatigue detail, not in response to a general statistical conclusions applicable for all items, regardless of the stress that had a real impact (whether it the stresses in normal operation or accidental or exceptional stresses).

The data recorded by the system, also allow you to replace the parts only when required by its real damage, unlike the prior art, when the items were culled as a worn out after a predetermined time, and regardless of the actual state of fatigue.

It is also possible to equip aircraft test system in accordance with the invention, to further determine the size of parts based on the data recorded by the system. Thanks to the invention, can also confirm the values ​​submitted by aircraft manufacturers for certification of parts; in particular, if it is determined the complex spectrum of fatigue using the method according to the invention, this spectrum can be compared with a spectrum representing aircraft manufacturers.

Note that in the case of erasure of the serial number on the details of its valid lifetime can be determined based on its assessment of fatigue. Furthermore, in particular, the number is not exceptional stresses to which the item is exposed, a good approximation of its usable life.

Increments of one threshold voltage to another (that is, the intervals separating successive thresholds) can be constant or variable. This allows you to concentrate the number of sensors in specific voltage ranges.

According to a particular embodiment, the system comprises a processing unit comprising data recording means and the sensors comprise means for transmitting data to the processing unit.

The processing unit may include data analysis tools, allowing to calculate on the basis of evaluation items fatigue due to mechanical stresses.

According to another embodiment, each sensor comprises means for recording data.

Preferably, the system (specifically, the processing unit or the detector, depending on the embodiment) comprises means for transmitting data, preferably on request, remote means of analysis of these data to calculate the fatigue evaluation items. These remote means may for example comprise a portable device, located at the operator; the user simply receive data from the system to your device to know the state of fatigue detail.

According to a preferred embodiment, the sensors are sensors of mechanical deformation.

According to a preferred embodiment, the sensors are sensors of the type MEMS.

Abbreviation MEMS stands for English "microelectromechanical system", which translates as "microelectromechanical systems". Specialist usually calls such microsystems this reduction in MEMS, which will be used in the further description text. It is a system comprising a chip on a miniature scale (of the order of a millimeter or micrometer) not only electronic means for calculating, but also mechanical means for issuing data and computing facilities managed by the latter. These mechanical and electronic means serve to perform particular functions, in this case, at least the data collection function of the mechanical stresses and write function of data and / or data. MEMS-type system thus comprise means microelectronic and micromechanical means. Typically, they are fabricated using integrated circuits in the electronic part and using micromachining regarding mechanical means.

Because of the type of MEMS are tiny, they have little overall dimension, which is of particular interest to the details of the aircraft. Another consequence of the small size of the marker is that it is easy to provide a plurality of sensors on the same items and increase thereby the measurement accuracy, because the state of fatigue can be resolved into a larger number of threshold voltages.

According to a particular embodiment, provide at least two sensors to detect the same threshold voltage. Thus, in the event of failure of one Other sensors can continue to detect the reporting threshold voltage.

The invention can be well applied to metal parts, fatigue which is particularly sensitive to the existing mechanical stresses on it.

The invention also provides a method for measuring fatigue parts of the aircraft are exposed to mechanical stress, in which:

- Exceeding the threshold voltage is measured at certain points of detail, and the thresholds are different from one point to another,

- Record the number of each of the measurement exceeding the thresholds, and

- On the basis of the number of cases is calculated assessment of fatigue detail.

This method of measurement includes all the advantages of the system described above.

According to a preferred embodiment:

- For each threshold based on the calculated total number of cases of measurement of said threshold and less than the upper threshold, and

- For each threshold calculated equivalent fatigue items corresponding to the application of voltages in the range between the thresholds corresponding to said calculated number of cases, and

- Summarize the calculated equivalent fatigue for general fatigue detail.

According to a preferred embodiment, the method is applied using the system described above.

The invention is also a method of maintenance of the aircraft, comprising at least one item, is subjected to mechanical stress, fatigue and measurement system corresponding to the system described above, wherein:

- In transmitting a request to transmit data for the system,

- Receiving data, and

- On the basis of these data, calculate the fatigue assessment details associated with the mechanical stresses.

Such a method of service includes all the advantages of the system described above. In particular, it allows you to make a decision on the timeliness of inspection without dismantling parts, as sufficient to adopt the system registered data, to know the state of fatigue detail.

According to a preferred embodiment, the request transmission and reception of data is performed by a wireless communication with a portable transceiver apparatus.

Use of such a portable device is extremely simple and allows the user to stay close to the aircraft and simply send requests and receive data, in particular for control inspections parts.

In particular, one can consider the use of the same portable device to receive data from multiple measurement systems fatigue installed on different details. Thus, inspections can control all of these components.

According to a preferred embodiment, the portable device comprises processing means to allow for the calculation of the fatigue evaluation items.

The present invention will be more apparent from the following description of a preferred embodiment of the system and method according to the invention with reference to the accompanying drawings, in which:

FIG. 1 - a schematic rear perspective view of a turbojet suspended from the structure of the aircraft by a first type of suspension;

FIG. 2 - a schematic front perspective view of the second type suspension used for a turbojet engine;

FIG. 3 - scheme of the system according to the invention with a representation of rules governing the mechanical response of the sensor voltage;

FIG. 4 - histogram data for the sensor system according to the invention for a certain period of time.

As shown in FIG. 1 and is known to the skilled person, the turbojet engine 1 comprises a fan 2, through which outside air is drawn into the turbofan engine, a low pressure compressor to the high pressure compressor adapted to compress air at the outlet of which compressed air is directed into the combustion chamber where it is burnt together with compressible and fuel; combustion gases are sent to the high-pressure turbine, then into the low-pressure turbine, the outlet of which they exit the jet through the turbojet exhaust nozzle.

Different parts of the turbojet engine is smiling in the case. FIG. 1 turbojet engine 1 comprises, in particular, at the input of the fan case and the so-called intermediate casing 3 and the outlet 4. The outlet housing intermediate casing 3 and a discharge casing 4 are structural housings included in the structure of the turbojet engine 1.

The intermediate body 3 comprises an outer mantle 3a, 3b connected by radial struts from the hub 3c on which the front through journal bearings of the rotors shafts mounted enclosures the low pressure and high pressure turbojet engine 1. Similarly, the outlet housing 4 comprises an outer mantle with bushing 4a 4c which through the rear support bearings mounted rotor shaft casings of low pressure and high pressure.

The engine 1 is suspended from a structure not shown in the aircraft by means of the front suspension and rear suspension 5, 6 which are fixed to a pylon or the front engine mount P, which in turn is fixedly connected to the aircraft structure.

The front suspension 5 comprises a crossbar 7 installed in the appropriate mounting slot of the intermediate casing 3. The rear suspension 6 comprises a beam 8, mounted directly on the exhaust housing 4. Such suspension are well known, so there is no need for a detailed description thereof.

Some details of the suspension device of the turbojet to the aircraft system 10 a measure of fatigue. In particular, the system is placed on each of the items on which to perform the measurement of fatigue, related to the stresses to which the item is exposed. Each measurement system comprises n sensors Ci (i = 1 to n), installed on the workpiece.

In the example shown in FIG. 1, the measurement system 10 is provided on the crosspiece 7, the front suspension 5, 8 on the beam rear axle 6, for each rod connecting girder 8 of the rear suspension 6 from intermediate casing 4a and pylon P.

FIG. 2 shows some of the elements involved in the suspension of the turbojet engine according to a second type of suspension, wherein the system 10 can provide measurement of fatigue in accordance with the invention. FIG. 2 shows only the beam P 'and front 5' and back 6 'suspension of the turbojet engine, these elements being shown alone, but in its context, and two circumferences Ca, Cb schematically showing the locations of buildings turbojet, which set the suspension 5' 6 '. The front suspension 5 'comprises a straight beam 9a coupled rods with intermediate beam 9b, experts called "traverse", which, in turn, is connected to rods with intermediate casing of the turbojet engine; Suspension of this type are well known in the art. With regard to the rear axle 6 ', it contains only a single beam.

As in the previous case, seeks to enable the evaluation of the fatigue of some parts of the device to the suspension of the turbojet aircraft. For this purpose a system 10 measuring fatigue in accordance with the invention each of the items for which a track fatigue, for example, on the pylon P ', on the beam 9a of the front suspension 5' on the intermediate girder 9b (traverse) of the front suspension 5 'and rear axle 6 '. In addition, system 10 may be provided on some measurement devices the suspension rods.

FIG. 1, as in Fig. 2 are denoted by the system 10 only, and not shown sensors Ci because of their very small size.

Ultimately, it is clear that, given its simplicity, the system 10 measuring fatigue in accordance with the invention can be installed on various parts of the aircraft turbojet engine.

According to a particular embodiment, a single motor mounted in several different measurement systems 10, each measuring system 10 is specifically designed to measure the fatigue associated with current voltages, depending on the degree of freedom of the engine. The engine has six degrees of freedom, as a rule, during the forward movement in three orthogonal directions and rotation about these directions; These six degrees of freedom can be modeled as a six rods working in tension-compression; as the system's sensors measure 10 measured tensile force, compression, each system 10 can track fatigue-related stresses on a rod. Thus, the motor can provide more systems 10, each system 10 measures the fatigue one rod; According to a particular embodiment, the system 10 include one for each rod, and thus can keep track of all degrees of freedom.

Preferably Ci sensor system 10 arranged in the area of ​​measurement items, wherein the location of the various sensors n Ci (i = 1 to n) are subjected to the same type of strain, and preferably tensile stresses and / or compression. For example, if the system is designed to measure fatigue rod, preferably a middle sensors Ci traction.

Note that if the part is symmetrical about a plane and measuring system fatigue set thereon for measuring fatigue-related stresses perpendicular to this plane, the sensors Ci can be positioned on either side of the plane of symmetry, preferably interleaved thresholds sensors Ci from one side to the other. For example, since the pylon P ', shown in FIG. 2, extends generally along the axis W and is substantially symmetrical about the plane of symmetry Ps, containing the axis W, Ci sensors may be distributed on both sides of the plane Ps, alternating successive thresholds with one and the other side of this plane Ps.

Ci sensors can be mounted on parts where fatigue is measured by different methods, for example by adhesive, screws, or by immersing them directly into the material. For details, you can also fasten a small plate, which is attached sensors Ci.

Next, referring to FIG. 3 and 4 is a more detailed description of the measurement system 10 as such, and with reference to any component.

The system 10 comprises a plurality of n sensor voltages Ci, in this case, in the example shown in FIG. 3 and 4, the five sensors C1, C2, C3, C5 (n = 5). These sensors C1-C5 are set to detail, which will make the measurement of fatigue associated with existing mechanical stresses on it.

To simplify the description of the system 10 in accordance with the invention, the values ​​associated with sensors are conventional and are intended only for the understanding of the system. The skilled person may adapt the system (in particular, the number of sensors, the value of threshold voltages that are detected and the number of found thresholds) to a part at which it sets the system 10, in particular, depending on the materials used.

In this case Ci sensors are strain gauges, with the deformation part in response to a voltage is expressed as a dimensionless quantity called "micro-deformation", denoted "μdef" and are well known; This value corresponds to the elongation per unit length of the well-known formula: μdef = ΔL / L. For example, the elongation of 1 mm to 1 m long parts corresponds to the deformation of 0.001 / 1 = 1,000 μdef.

Thus, the voltage of the test materials are expressed in parts deformations and consequently to μdef (according to Hooke's law). Consequently, the strain gauges are voltage sensors. Therefore, in the future of the description will use the concept of equivalent stress or strain, threshold voltage or threshold strain as deformation of the display can be directly applied voltage.

As an example, below is an approximate match between the thresholds of the deformation sensor of FIG. 3 (and described in more detail below), and the respective voltages to become (or Inconel or "INCO") and titanium; As follows from the table, the stress associated with this deformation (and vice versa) is not the same for these two types of materials.

Steel or INCOTitanDeformatsiya (μdef) corresponding voltage (MPa) Deformation (μdef) corresponding voltage (MPa) 10002101000110200042020002203000630300033040008404000440500010505000550

Each sensor C1-C5 adapted to detect a predetermined level or threshold stress and to output the data signal (in this case one bit) in the case of exceeding the threshold. In other words, each of the sensors C1-C5 is a certain threshold voltage sensor and each sensor allows to count the number of cases voltages exceeding the threshold voltage.

FIG. 3 in front of each of the sensors C1-C5 system 10 is a diagram of a signal Si (i = 1 to 5), emitted by the sensor Ci depending on acting on a voltage, i.e. the deformation μdef (Ci) (i = 1 to 5) . As indicated above, each sensor Ci (i = 1 to 5) Si outputs a signal depending on the voltage to which it is subjected:

- Si = 0 (in this case in fact corresponds to no signal), if the deformation μdef (Ci) is less than the response threshold Ci sensor, and

Si = 1 (corresponding to one bit), if the deformation μdef (Ci) of the sensor exceeds the threshold Ci.

In this case, as shown in FIG. 3:

- A first sensor C1 has a threshold equal to S (C1) = 1,000 μdef (Ci);

- A second sensor C2 has a threshold equal to S (C2) = 2,000 μdef (Ci);

- A third sensor C3 has a threshold equal to S (C3) = 3,000 μdef (Ci);

- Fourth sensor threshold C4 is equal to S (C4) = 4,000 μdef (Ci);

- The fifth sensor S5 has a threshold equal to S (C5) = 5,000 μdef (Ci);

When the item on which the sensors Ci, is subjected to distortion, each sensor substantially Ci undergoes the same deformation. If the deformation is less than the threshold, the sensor signal does not issue; if the deformation exceeds the threshold, the sensor outputs a signal (bit). Furthermore, in the described embodiment, in the case of prolonged load sensor Ci yields only one bit; Ci sensor outputs a new bit only when the voltage level drops below its threshold S (Ci) and then rises again above the threshold.

For example, assume that the item is subjected to a strain of 3.300 μdef; in this case the sensors C1, C2 and C3 output the bits and gauges C4 and C5 this bit is not given.

These sensors C1-C5 (i.e., the number of bits issued by each of them) during operation of the aircraft equipped with these probes are recorded and stored in the memory unit 11, processing system 10 measurements, wherein the processing unit 11 can be, for example, is near the zone where the sensors are installed C1-C5, and communicate with them using radio waves 12, as schematically shown in FIG. 3. In particular, when the sensor outputs Ci of bits it transmits data using radio waves 12 in processing unit 11, wherein the sensor signal comprises identifying Ci; processing unit 11 may then increment the counter of the sensor under consideration Ci. Electronic registration of sensor data is known, so there is no need for a detailed description; its application is a classic. Processing unit 11 may be installed on a computing device of a turbojet engine, well known by the acronym or FADEC "Full Authority Digital Engine Control". As indicated above, data transmission between the sensors Ci and processing unit 11 takes place by means of radio waves, but, of course, possible to provide any other means of communication, either wired or wireless, and according to any communications protocol.

In an alternative embodiment, data logging sensors may make Ci funds held directly in the sensors.

Regardless of the method of recording data after a certain period of operation of the system comprises data concerning the number of deformation which each sensor subjected to C1 and C5 that exceed their respective thresholds.

FIG. 4 is a histogram of data recorded sensor system 10 for a certain period of time (for example, the commissioning items equipped with sensors C1-C5). The abscissa of the histogram shown viewed sensors C1-C5, and the ordinate - number of N signals, equal one, are transferred in each sensor within a certain period of time.

Thus, the first sensor C1 has transferred 8,000 bits (which means that he was subjected to 8,000 strains exceeding the threshold of his trip 1,000 μdef), a second sensor C2 passed 4,000 bits (which means that he was subjected to 4,000 strains exceeding the threshold of his trip 2,000 μdef), third sensor C3 passed the 2,000 bits, four sensors transmit 1,000 bits, and a fifth sensor S5 passed 1,000 bits.

Based on data recorded sensors C1-C5, we can calculate the total damage (or damage) DTOTAL details, ie its fatigue (tiredness corresponding damage).

Usually (and as it is known), injury or damage to parts D, subject to certain voltage A (or strain A) is determined by the following formula (Equation Miner):

D = n (A) / N (A),

where n (A) denote the number of cases (cycles) of events leading to the applied voltage (deformation) A and

N (A) denote the number of cases (cycles) of events leading to the applied voltage (strain) A piece which can withstand before its breakdown (this is usually determined using the so-called curves Weller).

Thus, if the damage D is equal to 1, the item breaks down; if the damage is 0, the item is not damaged.

The number of signals issued by each sensor Ci, expresses fatigue exerted on it, as it depends on the number of cases of various deformations which undergoes item. The data for the sensors Ci, can derive equivalent damage Di Ci for each sensor; This corresponds to an equivalent damage Di damage by applying voltage exceeding the threshold S (Ci) Ci sensor, but smaller than the upper threshold S (Ci + 1).

According to the laws of fatigue, general damage DTOTAL part a result of all the stress acting on it can be expanded linearly equivalent to the amount of damages for each voltage range. In other words, if the set voltage divided into ranges of voltages corresponding to the intervals between successive thresholds of sensors Ci, get a good approximation of the damage DTOTAL details in the form of a sum equivalent Di damages for each voltage range, ie DTOTAL = Σ1nDi.

<IMG>

To calculate DTOTAL, for each sensor Ci on the basis of data registered sensors Ci (i = 1 to 5), calculates the number n (Ci), the voltage being in the range between the threshold S (Ci) of the sensor and an upper threshold S (Ci 1). Then you can calculate the equivalent damage Di sensor Ci based on this number n (Ci), using it to stress or stresses, characterizing the considered range of voltages. Not knowing the exact distribution of stresses in the voltage range, it is possible to make an approximation; thus it is possible to provide a plurality of solutions:

- You can use the average value of the strain between the two thresholds (μdef (mean) = (S (Ci) + S (Ci + 1)) / 2) and assume the resulting damage Di as damage as a result of n (Ci) of cases this average strain μdef ( average);

- It is possible to apply statistical analysis to determine the weighted average value between the thresholds used, and use a weighted average value;

- For safety reasons, you can take the upper limit (S (Ci + 1)) of the voltage range and assume that the equivalent damage Di corresponds to n (Ci) of cases of deformation corresponding to the upper limit of S (Ci + 1) (the so-called "conservative" assumption ).

There are other possible approximations. In a preferred embodiment of the invention, to comply with the most stringent safety criteria in the field of aviation, choose the latter approximation (conservative assumption). Thus, the calculated deformation D exceeds the real deformation.

To determine the number n (Ci) of cases counted sensor Ci, should be out of the total N (Ci) bit sensor Ci to deduct all of the signals that correspond to a voltage exceeding the threshold S (Ci + 1) in excess of the threshold S (Ci) of the sensor Ci .

To determine all cases n (Ci) are beginning to gauge the C5, which has the highest threshold.

For example, in FIG. 4:

- N (C5) = N (C5) = 1,000, that is, the sensor S5 averaged 1,000 voltages exceeding its threshold S (C5) = 5,000 μdef;

- N (C4) = N (C4) -N (C5) = 0, that is not counted sensor C4 any voltage in a range between its threshold S (C4) = 4,000 μdef upper threshold and S (C5) (indeed, all Bits sensor C4 corresponds to the voltage exceeding S (C5), ie already counted sensor C5);

- N (C3) = N (C3) -N (C4) = 2,000-1,000 = 1,000, i.e. sensor C3 averaged 1,000 stress in a range between its threshold S (C3) = 3,000 μdef upper threshold and S (C4);

- N (C2) = N (C2) -N (C3) = 4,000-2,000 = 2,000, that is, the sensor C2 has counted 2,000 stress in a range between its threshold S (C2) = 2,000 μdef upper threshold and S (C3);

- N (C1) = N (C1) -N (C2) = 8,000-4,000 = 4,000, i.e. sensor C3 averaged 4,000 stress in a range between its threshold S (C1) = 1,000 μdef upper threshold and S (C2).

For each of the thus calculated n (Ci) display equivalent damage D to items (Di = n (Ci) / N (S (Ci + 1))), where N (S (Ci + 1)) is the number of cases of stress corresponding deformation of the upper threshold S (Ci + 1), which leads to the destruction of the details (see. approximation above).

Finally, as noted above, the total damage DTOTAL, the test piece is equal to the sum of the damages corresponding to each voltage range, ie DTOTAL = Σ1nDi of n sensors.

<IMG>

As an example, the system was presented with five sensors. Of course, it may contain more or fewer sensors and, in general, the number n of sensors. Thus, for i = 1 to n using various formulas above.

Can now again more synthetically present application the preferred embodiment of the method according to the invention for n sensors. In this case, the method comprises the following steps:

1) n Ci sensors measure the incidence of N (Ci) stresses above their threshold S (Ci);

2) the data N (Ci) is recorded during the period t;

3) for each sensor Ci based on the plurality of cases N (Ci) (i = 1 to n) calculate the number of n (Ci), the respective voltages in a range between the threshold S (Ci) sensor Ci and an upper threshold S (Ci + 1 ), according to the formula:

- N (Cn) = N (Cn);

- If i <n, n (Ci) = N (Ci) -N (Ci + 1);

4) for each sensor Ci calculate equivalent damages D to parts corresponding to the voltage range of between threshold S (Ci) of the sensor Ci and an upper threshold S (Ci + 1);

5) calculated the total damage DTOTAL details on the formula: DTOTAL = Σ1nDi.

<IMG>

In other words, thanks to a system and method according to the invention, for the part equipped with the incremental sensors Ci (i = 1 to n), wherein each sensor is adjusted to the threshold voltages S (Ci) (and the voltage decomposed into n successive voltage ranges) You can obtain a comprehensive range of fatigue, which allows you to determine the total fatigue (total damage DTOTAL) based on its decomposition into equivalent fatigue (equivalent damages Di), corresponding to each voltage range.

This makes it possible to use simplified maintenance methods.

For example, the operator can have at his disposal device 13 receiving data for the sensors Ci. In the example shown in FIG. 3, the apparatus 13 is adapted to establish communication by radio waves 12 to the block 11 processing system; of course, possible to provide any other method of communication.

Of course, if the system 10 does not include the processing unit for storing data measured by sensors Ci, the apparatus 13 may be configured to establish a direct connection with the sensors Ci, to the last pass in the individually recorded their findings.

The apparatus 13 comprises a processing unit with a program (algorithm) calculating allowing it based on the registered data (bits N (Ci) (i = 1 to n) of sensors Ci) calculating damage DTOTAL corresponding parts in accordance with the method described above.

Thus, the operator brings his device 13 to the parts (for example, to the suspension of the aircraft), and this unit remotely loaded automatically or on command data registered by sensors Ci, and calculates the damage DTOTAL, ie fatigue suspension that allows the operator to take appropriate action. For example:

- If the damage DTOTAL is from 0 to 0.3, there is no need for inspection;

- If the damage DTOTAL is from 0.3 to 0.8, it is necessary to inspect;

- If the damage DTOTAL exceeds 0.8, the item must be replaced.

You can provide that analysis is made not the operator and the machine automatically 13. So, if the inspection is not required, the apparatus 13 does not give a signal (or outputs, such as signal light green), or if you want to inspect, the device will sound 13 signal (or outputs, for example, red light signal).

It is also possible to provide the transmission of information gathered apparatus 13, either automatically or on operator request to the information server or any other appropriate device adapted to receive this information and processing it.

Depending on the wishes of the users may be provided any other method of use. In particular, it can be provided that monitoring of fatigue details is done automatically processing unit 11 (for example, FADEC), which automatically triggers an alarm (designed for the pilot of the aircraft, the aircraft manufacturer, the operator of the aircraft, the information server, etc.) from exceeding a certain level of fatigue.

Ultimately the system 10 in accordance with the invention allow to calculate the stresses to which the item is exposed, and on this basis to build the complex spectrum fatigue. The system 10 can also have a reliable picture of the chronology of events in the operation details. Sensors with weak amplitude thresholds given, in particular, information about normal use items, that is, the actual operating time since its first use. Sensors with high amplitude thresholds provide, inter alia, information on exceptional stresses which may be subject to detail, such as a hard landing. Thus, the system is an excellent tool for the maintenance of end-user details.

According to a particular embodiment, the sensor may comprise a clock synchronizer, causing them to give out one bit at regular intervals, and this bit is 0 if the sensor is not exposed to exceeding its threshold voltage and is equal to 1 if the sensor is subjected to voltage exceeding its threshold. This option is made possible with the use of digital sensors.

In a preferred embodiment utilizes mechanical sensors outputs a signal only when the excitation voltage exceeding their threshold; advantage of mechanical sensors is their ease of use, as well as their energy supply.

It should be noted that the system 10 was provided with the positive strains (μdef takes only positive values). According to another embodiment, the system may comprise sensors with a positive threshold (μdef> 0) and / or sensors with a negative threshold (μdef <0), which allows counting of voltage, for example, in one direction (tensile) and in the other direction (compression) .

It should be noted that it is possible to provide a plurality of sensors (at least two) with the same threshold voltage. Due to this, in the event of failure of one of the other sensors can continue to count cases of a voltage corresponding to this threshold. In passing, it should be noted that in the case where the sensor or all sensors associated with a single threshold, denied, the presence of multiple sensors allows to reduce error to a minimum, since voltage incapacitated one threshold sensors are counted sensors lower threshold.

Of course, the greater the number of sensors, the higher the level of security in the event of failure of certain sensors and the more accurate the calculation of the total fatigue given smaller increments between successive thresholds. All growth rates may be identical or may vary; advantage is the ability to change the increments of more precise measurements in the most common range of voltage and less accurate measurements for exceptional stress (which in any case are very high voltage). Preferably, a detail from 2 to 50 sensors, depending on the desired level of accuracy in determining the damage.

For example, the minimum detectable deformation may be equal to 1.000 μdef (threshold of the first sensor C1) and maximum detectable deformation is 5,000 μdef (threshold last sensor Cn) when the difference between the successive thresholds of 200 μdef (in this case include 21 detector thresholds which respectively equal to 1.000, 1.200, 1.400, ..., 5.000).

System 10 was presented in the case of placing on the workpiece, but it can be positioned on a structure containing several parts, which allows monitoring the fatigue of the entire assembly.

As applied to the preferred field of aircraft sensors must withstand temperatures ranging from -55 ° to 600 ° C (in particular, for the suspension of the turbojet engine) and emissions may be exposed to oil and fuel. Furthermore, they must be resistant to corrosion and fouling, in particular relating to emissions of water, salt, sand and dirt. In addition, they should preferably not withstand the destructive inspection, such as penetrant, eddy current application, X-rays, etc. Preferably, they should have different electromagnetic compatibility waves (radio waves, sound waves, etc.). Furthermore, the sensors have to withstand the mechanical vibrations of the turbojet engine which can reach several tens of kHz, in particular, the vibrations associated with the rotation of the rotating parts of the turbojet (0 to 5,500 rev / min in the case of the shaft and low pressure from 0 to 20,000 rev / min in the case of the high pressure shaft) and can withstand shocks with acceleration from a few dozen to a few tens of thousands of g (9,81 m · s-2). Moreover, preferably they should withstand static and quasi-static deflection under loads of various types.

In addition, preferably the sensors must have a shelf life at least equal to the lifetime of items on which they are installed, since they are designed to track its fatigue during its entire lifetime. For example, their service life can exceed 60 years, or 70 years or 70 or 80,000 flight cycles (take-off and landing flight).

Preferably, the sensors have to withstand more than 109 cases of stress in excess of the threshold. During the whole period of operation and the application to them of dynamic load sensors do not have to show deterioration in their work.

Preferably, the sensor supply is not dependent on the supply of the aircraft.

The system according to the invention is of particular interest to the suspension devices turbojet engines, in particular for the linkage of these devices, the beams or uprights fastening. The system according to the invention preferably also have on the chassis or on their aircraft brake pads. In general, it can be placed on any instrumental parts (ie sensors which can be placed), which during use is subjected to an alternating voltage is required to obtain an integrated spectrum of fatigue; it just refers to the various drafts and earrings turbojet.

The sensors according to the invention allow you to track different types of fatigue under stress, for example, classically referred to curves Weller oligotsiklicheskoy area fatigue (under heavy stress, where the destruction takes place after a very small number of cases, and preceded by a large plastic deformation), a zone of fatigue (or limited fatigue strength where the destruction is achieved after a number of cycles, which increases when the voltage is reduced) and the area unrestricted fatigue; Of course, an unlimited zone fatigue strength of less interest since the item is usually replaced before its destruction can occur, given the voltages corresponding to this zone.

According to a preferred embodiment of the invention, sensor system 10 is mounted in the devices (or transducers) type MEMS, already mentioned at the outset.