Device and a method for performing a drop test

Abstract

The present invention relates to a device for performing a drop test, preferably for testing the landing gear of an aircraft, comprising a test stand, a sled for the controlled drop of a test specimen, and a base plate, wherein at least one means for digital measurement acquisition, preferably an optical measuring system, is provided, which is designed to perform a measurement of at least one property of the device and / or the test specimen during the drop test. Using the optical measuring system, additional information, for example regarding stiffness and deformation, can be acquired during the drop test itself, thus eliminating the need for additional tests to obtain this data.

Description

[0001] The present invention relates to a device and a method for performing a drop test.

[0002] Aviation construction regulations, such as CS25 / CS29, require a drop test for landing gear as a prerequisite for aircraft / helicopter certification. This drop test simulates the landing of an aircraft's landing gear under laboratory conditions. The test primarily verifies the functionality, energy absorption, and loads generated by the landing gear.

[0003] However, much of the information that could be gathered during the test is conventionally either not collected or not used in a case test, thus requiring additional effort in the form of further tests.

[0004] One example of such information is the recording of the test rig's inherent dynamics. Currently, dedicated, separate stiffness measurements are performed on the test rig for this purpose. This allows the test rig's stiffness to be determined using a designated procedure.

[0005] Information regarding stiffness is needed, for example, for correlation with simulation models of the chassis. These simulation models are created for the product development of a chassis and verified through drop tests.

[0006] Another example is the determination of the chassis's inherent dynamics. To verify the chassis's stiffness, it is conventionally measured on a special structural test rig.

[0007] Furthermore, to verify the stresses of the chassis structure, additional strain gauges are conventionally applied in the drop test and in a separate structural test and used for further model correlations.

[0008] Traditionally, classic length measurements are used during the drop test to record the deformation of wheels / tires, which entails a separate additional measurement process.

[0009] The current implementation of a prescribed case test thus leads to a rather high testing and evaluation effort for case tests, as many individual steps are required to carry out the respective tests.

[0010] At the same time, existing information from the tests is usually not reused. This means that reductions are not possible in other test campaigns, as the information has to be collected again.

[0011] Against this background, the present invention is based on the objective of mitigating or even completely eliminating the disadvantages of the prior art.

[0012] A specific objective of the invention is to utilize the full potential of the information generated by the drop test for product development. This information includes, for example, the complete deformations of the test rig and the chassis test specimen, including wheels, tires, and brakes, as well as the stress profiles of the associated structures.

[0013] This problem is solved by the device with the features of claim 1 and the further subject matter of the independent claims. Advantageous embodiments of the invention are the subject of the dependent claims.

[0014] The device for performing a drop test, preferably for checking the landing gear of an aircraft, is provided, comprising a measuring stand, a sled for controlled dropping of a test specimen and a base plate, wherein at least one means for digital measurement recording, preferably an optical measuring system, is provided, which is designed to perform a measurement of at least one property of the device and / or the test specimen during the drop test.

[0015] In other words, the invention utilizes the prescribed drop test to obtain additional information beyond the test procedures required by aerospace construction regulations. This information is recorded, for example, by suitable instrumentation, preferably optical sensors, during the drop test and can be used for further product development throughout the entire product lifecycle.

[0016] The means for digital measurement acquisition can, for example, include at least one digital camera. In other words, the means for digital measurement acquisition can include an optical measuring system with at least one camera and an evaluation unit for evaluating the images recorded by the camera.

[0017] A device according to the invention can have at least one sensor which is designed to perform at least one of the following measurements: pressure measurement on the test object and / or the environment, temperature measurement of the test object and / or the environment, strain measurement on the test object and / or the test stand, displacement measurement on the test object and / or the test stand, velocity measurement on the test object and / or the test stand, acceleration measurement on the test object and / or the test stand, force measurement on the test object and / or the test stand, relative humidity measurement of the environment.

[0018] A device according to the invention can further comprise a computing unit which is designed to verify at least one model of the test object, preferably a chassis model, on the basis of at least one measurement carried out by means of the device.

[0019] The computing unit can also be designed to generate at least one proposal for the further development of the test specimen based on at least one measurement performed by means of the device.

[0020] The device can further be designed to completely and preferably fully automatically store and electronically document all data generated during the execution of a drop test, in particular measurement data from measurements performed.

[0021] The means for digital measurement acquisition can be designed to view at least one measuring point on the measuring stand, the sled and / or the base plate and / or on the test object, preferably on a chassis, a wheel, a tire or a brake, and to perform a local measurement there.

[0022] Furthermore, the present invention relates to a method for carrying out a drop test, preferably for testing the landing gear of an aircraft, wherein the method is preferably carried out with a device according to the present invention, comprising the steps: - Controlled dropping of a test specimen into a measuring stand using a sled, and, - Measuring, during the drop test, at least one property of the device and / or the test specimen, preferably using an optical measuring system.

[0023] Within the framework of a method according to the invention, at least one of the following measurements can be carried out: pressure measurement on the test object and / or the environment, temperature measurement of the test object and / or the environment, strain measurement on the test object and / or the measuring stand, displacement measurement on the test object and / or the measuring stand, velocity measurement on the test object and / or the measuring stand, acceleration measurement on the test object and / or the measuring stand, force measurement on the test object and / or the measuring stand, relative humidity measurement of the environment.

[0024] Based on the at least one measurement performed using the device, preferably at least one model of the test object, preferably a chassis model, is verified using a computing unit.

[0025] Furthermore, the measurement data of the at least one measurement carried out using the device are preferably used for product development and preferably, for example by means of a computing unit, at least one proposal for the further development of the test object is generated.

[0026] In a method according to the invention, preferably all data generated during the execution of a drop test, in particular measurement data from measurements performed, are completely and preferably fully automatically stored and electronically documented.

[0027] In a method according to the invention, preferably at least one measuring point on the measuring stand, the sled and / or the base plate of a device for carrying out the drop test and / or on the test specimen, preferably on a chassis, a wheel, a tire or a brake, is viewed by means of the optical measuring system and a local measurement is carried out there.

[0028] Furthermore, the present invention relates to the use of a device and / or a method according to the present invention for carrying out a drop test, preferably in the context of an official approval of a component of an aircraft, preferably a landing gear for an aircraft.

[0029] Furthermore, the present invention relates to the use of a device and / or a method according to the present invention in the manufacture of an aircraft, preferably an airplane.

[0030] Other aspects of the present invention can be described in other words as follows: Preferably, a test rig (also referred to as a test stand) of a test stand according to the invention and / or the test object (in this example the chassis) is instrumented with at least one sensor for the following measurements during the drop test: pressure measurements on the test object and the environment, temperature measurements of the test object and environment, strain gauges on the test object and possibly on the test rig, classic displacement measurements on the test object and test rig, velocity measurements of the test object and test rig, acceleration measurements on the test object and test rig, force measurements on the test object and test rig, relative humidity measurement of the environment.

[0031] The acquired sensor data is preferably forwarded to a processing unit and used there, for example, to correlate and ultimately verify landing gear simulation models. These landing gear simulation models are used, for instance, to determine design loads for the landing gear and the aircraft.

[0032] In addition, in a test rig according to the invention, the static and / or dynamic state of the test rig and / or the test specimen is recorded and determined using a means for digital measurement acquisition. For this purpose, for example, an optical measurement method can be used.

[0033] Preferably, all geometric information and data are recorded and further processed by the computing unit.

[0034] From the measured deformations of the test rig, the computing unit can, for example, use analytical methods to generate a model that describes the inherent dynamics of the test rig. This is needed, for instance, for correlation with a chassis simulation model.

[0035] The recorded deformations of the chassis can, for example, be used to check the chassis's inherent dynamics using the computing unit and verified with chassis simulation models.

[0036] Both deformations must be determined in separate, costly test campaigns on a conventional test rig without the means of digital measurement. The test rig according to the invention thus reduces the effort required for the verification of components.

[0037] At the same time, the deformation and movement of wheels / tires / brakes can be recorded using a test rig according to the invention without additional separate tests.

[0038] The stresses in the chassis structure can be recorded, for example, during dynamic loading using digital measurement equipment.

[0039] This allows for the correlation / verification of, for example, finite element models in this test. This comparison is conventionally determined in complex static structural tests using strain gauges.

[0040] The information acquired by means of a test bench according to the invention can, for example, be used by the computing unit in further product development, verification of the models, use of the models in the life cycle of a chassis in the case of product changes and improvements.

[0041] An advantage of the present invention is that a test which is mandatory according to aviation construction regulations is used to obtain additional information about the test specimen.

[0042] In addition, the invention simplifies the test procedure and eliminates the need for additional tests such as stiffness tests inside and outside the drop test.

[0043] It should be noted here that the terms "ein" and "eine" do not necessarily refer to exactly one of the elements, although this is a possible interpretation, but can also denote a plurality of elements. Likewise, the use of the plural also includes the presence of the element in question in the singular, and conversely, the singular also includes several of the elements in question.

[0044] Furthermore, all features of the invention described herein can be combined with one another or claimed separately from one another; the disclosure is therefore not limited to explicitly mentioned combinations of features.

[0045] Further details and advantages of the invention will be explained in more detail with reference to the exemplary embodiments shown in the drawing.

[0046] They show: Fig. 1: a conventional test bench for a drop test; Fig. 2: a test rig according to the present invention; and Fig. 3: a comparison of a test procedure using conventional and an exemplary procedure according to the invention.

[0047] Fig. Figure 1 shows a conventional test rig for performing a drop test with a measuring rig / test rig 1 and a slide 2 stored therein, which is weighted with a mass 3.

[0048] The test rig contains a test specimen 4 in the form of a chassis with wheels, tires, and brakes. As indicated by arrow 5, the test specimen 4 undergoes a free fall to a preset height in the test rig before landing on the base plate 5.

[0049] Fig. Figure 2 shows a test rig according to the invention, in which an optical measuring system (not shown in the figure) is provided. The optical measuring system performs a measurement at the measuring points indicated by stars in the figure.

[0050] The optical measuring system is designed to observe a measuring point 6 on the measuring stand 1, a measuring point 7 on the carriage 2 and a measuring point 8 on the base plate 5.

[0051] The test specimen 4 has a measuring point 9 on the chassis and a measuring point 10 on a wheel, a tire or a brake (only one star is shown as an example in the figure) where a local measurement is carried out.

[0052] The digital instrumentation of the test rig, in particular measuring point 6 on the test rig, allows the deformations during the drop tests to be recorded without the need for separate stiffness tests.

[0053] The optical measuring system is also used to detect the position of the slide 2.

[0054] Fig.Figure 3 shows a comparison of a test procedure using conventional (left branch of the flowchart) and an exemplary procedure according to the invention (right branch of the flowchart).

[0055] Conventionally, to perform a drop test of a chassis, a separate stiffness measurement of the test rig and chassis is first carried out. Separate chassis structure tests are also performed.

[0056] The data from the stiffness measurement and chassis structure tests can be used for model validation of the drop test.

[0057] The drop test is then performed separately. The data from the drop test can be used for model validation of the drop test.

[0058] In the conventional approach, the data from the stiffness measurement and chassis structure tests, as well as the data from the drop test, are collected and processed separately.

[0059] In contrast, in the new method according to the invention, the data from the stiffness measurement and chassis structure tests as well as the data from the drop test are collected together during the drop test as part of a drop test on a test rig with additional instrumentation.

[0060] Therefore, only one test is required to collect the data in one step.

[0061] The data is then stored together and is available for model validation and further product development.

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