WO2021004851A1

WO2021004851A1 - Method for testing a fibre-reinforced composite component, device, computer program, and machine-readable storage medium

Info

Publication number: WO2021004851A1
Application number: PCT/EP2020/068503
Authority: WO
Inventors: Linda Klein
Original assignee: Robert Bosch Gmbh
Priority date: 2019-07-10
Filing date: 2020-07-01
Publication date: 2021-01-14
Also published as: DE102019210166A1

Abstract

The invention relates to a method for testing a fibre-reinforced composite component, in particular a body component for a vehicle, in which the fibre-reinforced composite component has a sensor device integrated in the fibre-reinforced composite component, the sensor device having a flexible circuit carrier with a sensor module, in particular with a micromechanical sensor module, for sensing an acceleration, the method having the steps: sensing a test signal by means of the sensor device, in particular as a result of the fibre-reinforced composite component being set in a test oscillation, in particular by introducing a test pulse at a test location of the fibre-reinforced composite component; comparing the test signal with a reference signal; characterised in that, in the comparing step, the comparison of the test signal and the reference signal is carried out using a spectral analysis in the frequency range, in particular in the discrete frequency range.

Description

description

title

Method for testing a fiber composite component, device,

Computer program and machine-readable storage medium

The present invention relates to a method for testing a

Fiber composite component, a corresponding device, a corresponding computer program and a corresponding machine-readable

Storage medium.

State of the art

DE 10 2016 220 032 A1 discloses a sensor device for a vehicle, in particular a motor vehicle, with at least one sensor module and with at least one connection line connected to the sensor module for making electrical contact with the sensor module.

It is provided that the connection line is designed as a conductor foil on which several different sensor modules are arranged and contacted by one or a common conductor foil.

A sensor module for detecting an acceleration, for example a

micromechanical acceleration sensor of the type

microelectromechanical systems (MEMS), usually emit a signal in the form of an acceleration over time, i.e. a signal in the time domain. A reaction to a test oscillation that is characteristic of the time signal, in particular due to the application of a defined test pulse, is successive signal amplitudes that decay over time into positive and negative

Direction of acceleration. Due to the measurement characteristics of the micromechanical

With the acceleration sensor, a changed state of the component in which the acceleration sensor is integrated in the form of a sensor device can possibly not be recognized with sufficient accuracy on the basis of a change in the course of the time signal (acceleration over time). This depends on the strength of the change in state of the component or the

Event.

Disclosure of the invention

Against this background, the present invention creates a method for testing a fiber composite component, the fiber composite component having a sensor device integrated into the fiber composite component, the

Sensor device has a flexible circuit carrier with a sensor module, in particular with a micromechanical sensor module for detecting an acceleration.

It is conceivable here for the flexible circuit carrier to have several sensor modules.

The procedure includes the following steps

Detecting a test signal by means of the sensor device.

It is conceivable that the test signal as a result of an offset of the

Fiber composite component is recorded in a test vibration. The transfer to a test oscillation can take place by introducing a test pulse to a test location of the fiber composite component.

Comparing the test signal with a reference signal.

The method is characterized in that in the step of comparing the comparison of the test signal with the reference signal using a

Spectral analysis in the frequency domain is carried out. Spectral analysis in the discrete frequency range is conceivable

perform.

The sensor signals in the frequency range, that is, the frequency spectra of the signals, can be analyzed qualitatively as well as quantitatively with regard to characteristic quantities. Significant changes in the characteristics are sought out:

For example, the location or frequency at which maximum spectral components occur can be considered.

For example, the size, i.e. the magnitudes, of the maximum spectral components can be considered.

For example, the appearance of the

Envelopes of the spectral components over the frequency response.

For example, the areas below the

Envelope over the frequency response in the vicinity of the maximum spectral components.

For example, the slope of the envelope over the frequency response in the vicinity of the maximum spectral components can be observed.

For example, the area sum over all spectral components can be considered, below the envelope of the spectral components over the frequency response.

The method has the advantage that the analysis of the test signal in the frequency range, i. H. After the spectral analysis, characteristics of the signal are more visible or even visible at all compared to the signal in the time domain.

This enables a more precise examination of the fiber composite component to be carried out. In this way, disadvantageous entries into the fiber composite component can be improved be recognized. Such entries can already have been made in the production process of the fiber composite component or later in the life cycle of the

Fiber composite component, for example. When used on a vehicle, if the fiber composite component is a body part of the vehicle.

In the present case, a fiber composite component can be understood to mean a component that consists of a fiber composite material. A

Fiber composite material is generally created by a

interacting composite of fibers or textile semi-finished product and a matrix between the fibers or the textile semi-finished product. The matrix is

Filler and adhesive for the fibers or for the semi-finished textile product. It is typical of fiber composite materials that the interaction of the composite creates a material that has higher-quality properties compared to the properties of the fibers and the filler.

The fiber composite component can be a body part for a vehicle; For example, a bumper component or a component on the long side of the vehicle.

The fiber composite component can include a component. from the field of mechanical and plant engineering, medical technology, the fields of aerospace technology, energy, offshore, robotic, sports equipment and consumer products.

Furthermore, the fiber composite component can be a piece of sports equipment.

The fiber composite component according to the present invention can in

primary forming process. For this purpose, a so-called liquid composite molding process (LCM process) can be used in the integration step in particular. LCM processes are characterized by the fact that there are comparatively moderate pressure and temperature loads.

A flexible circuit carrier can comprise silicones, polyurethanes, polyamides or thermoplastics. Thus, the flexible circuit carrier can easily be elastically or plastically deformed, in particular the integrated conductor track structure can be correspondingly plastically deformed, whereby the Essentially, the flexible circuit carrier can be adapted to a geometry or shape of the fiber composite component. The flexible circuit carrier can be a conductor foil.

In the present case, a sensor module can be an electronic or

electrical component for the detection of a physical quantity. A sensor module can be designed to detect an acceleration or a rotational acceleration.

In principle, it is conceivable for the sensor module to be designed to detect one or more physical effects.

It would be conceivable to design the sensor module to detect a pressure. However, such a design requires an open interface between the sensor module and the surroundings of the fiber composite component.

Other configurations of the sensor module could have further requirements with regard to integration into the fiber composite component. These requirements depend, among other things, on the physical effect to be detected.

The sensor module can be a micromechanical component for detecting an acceleration, thus a micromechanical acceleration sensor of the microelectromechanical system (M EMS) type.

The method according to the present invention forms an extended safety function of a fiber composite component with an in

Fiber composite component integrated sensor device. This safety function is particularly suitable for such fiber composite components as body components of a vehicle. Sensor values of the sensor device, in particular acceleration values of a corresponding sensor device

Acquisition of acceleration values could not only be used to implement a protective function for road users such as the occupants of the vehicle or other road users, but also beyond that can be used as an extended safety function for testing the fiber composite component.

This extended safety function comes into play against the background that mechanical energy input to fiber composite components can lead to internal damage in the component. This damage can be, for example, delamination, fiber cracks or so-called fiber pull-outs. This damage can have a detrimental effect on the properties of the component. If a fiber composite component is used as a body component, mechanical energy can be applied to the component in a variety of ways, for example through so-called parking bumps or other collisions. The resulting internal damage can generally change the character of the component. This can affect the vibration behavior of the component. I.e. Initiated impulses are diverted in a different way with a damaged component than with components in the

Original condition or in the undamaged condition. This other way, in other words, this difference can be determined by the method of the present invention and thus a direct conclusion about the state of the component or, more generally, about the character of the component.

The signal in the is used for determination or detection

Fiber composite component integrated sensor device, as this reacts directly to the changed component character.

The reference signal can be generated in that the

Fiber composite component is set in a reference oscillation and the

Reference vibration is detected by means of the sensor device and the detected signal or a signal derived therefrom is the reference signal.

The reference signal is used for follow-up examinations or tests of the fiber composite component.

It is advantageous if the reference signal is when the

Fiber composite component is generated. This can result in a later subsequent testing of the fiber composite component according to the method of the present invention by comparing the test signal with the

Reference signal a change in the component characteristics can be determined. Based on the determined component characteristics, conclusions can be drawn about the state or a change in state of the component at the time the method for testing the fiber composite component is carried out in comparison to its new state. With this information, an appropriate measure can be taken.

The state or this change of state of the fiber composite component determined in this way can be output by means of a state signal which suitably represents the state or the change in state.

In the case of body components for a vehicle, a suitable measure can be the recommendation to visit a workshop for inspection or repair. The vehicle is also conceivable as a suitable measure.

According to one embodiment of the method of the present invention, the spectral analysis is carried out by means of a discrete Fourier transform (DFT).

The starting point is the discrete sensor signal in the time domain z. B. by applying the Discrete Fourier Transform (DFT) in the discrete

Frequency range represented.

The use of a Fast Fourier Transformation is particularly suitable here. The advantage of using the Fast Fourier Transform is that this method can be carried out quickly. This compensates for any loss of accuracy that may be associated therewith.

The DFT can e.g. B. be done via a Fast Fourier Transformation (FFT). The FFT is a faster version of the DFT and has comparable properties. The representation is described mathematically as follows:

The formulas below represent the transformation of a

Acceleration signal in the frequency range (sinusodial):

It is also advantageous if zero padding takes place in the time domain before the application of the fast Fourier transformation.

In the present case, zero padding is understood to mean that the test signal im

Time range is padded with zeros. The observation interval can be increased as a result, whereby a narrower sampling can be achieved after the application of the Fast Fourier transform. Although this does not improve the quality of the signal, the closer sampling enables a better representation of the signal in the frequency domain.

According to one embodiment of the method of the present invention, in the step of comparison in the spectral analysis, the test signal and the reference signal are only considered on one side.

This is useful because the periodicity of the signal is used so that with the (discrete) Fourier transformation the spectrum of the signal is considered over only one period. A period extends over the frequency range from 0 to the sample rate of the sensor signal. Since, after the (discrete) Fourier transformation, the spectrum of the signal is symmetrical about the center point, the information obtained is also redundant, so that a one-sided view is sufficient.

According to one embodiment of the method of the present invention, in the step of determining the determination takes place as a function of significant changes in the characteristic of the frequency spectrum.

According to the present invention, significant is understood to mean all changes that go beyond the scope of the - known per se - measurement accuracy of the integrated sensor device and thus not affect the

Measurement uncertainty. According to one embodiment of the method of the present invention, the test oscillation lies within a measurement range under consideration

Sensor device and is dependent on a natural frequency of the environment of the fiber composite component.

In the present case, an environment can include, for example

Clamping device for the fiber composite component, the suspension device for the fiber composite component on a vehicle, but also others

Frequency transmissions that have an influence on the detection of the test signal can be understood.

For an exact signal analysis, the natural frequencies of the environment outside of the

Measuring range (frequency range) of the sensor module. Especially if the acceleration sensor has a high or low pass filter. This can be done, for example, by means of vibration isolation.

This ensures that when analyzing the frequency response of the

Acceleration sensor signal no frequency components are superimposed by natural oscillation of the environment.

Another aspect of the present invention is a device which is designed to carry out all steps of the method according to the present invention.

Another aspect of the present invention is a computer program which is designed to carry out all steps of the method according to the present invention.

Another aspect of the present invention is a machine-readable storage medium on which the computer program according to the present invention is stored.

drawings Embodiments of the present invention are explained below with reference to drawings.

Show it:

1 shows a flow diagram of an embodiment of the method of the present invention.

FIG. 1 shows a flow chart of an embodiment of the method 100 for testing a fiber composite component according to the present invention.

In step 101, the fiber composite component is subjected to a test vibration

Generation of a test signal offset. The setting into a test vibration can be done by introducing a test pulse to a test location of the

Fiber composite component take place. The process step is shown in dashed lines in the flowchart, since this step does not represent an essential step of the claimed process.

In step 102, the test signal is recorded by means of a sensor device integrated into the fiber composite component. The test signal can be used as a discrete sensor signal in the time domain, i. H. for example, as acceleration over time.

In the optional step 103, the recorded is zero-padding

Sensor signal in the time domain.

In step 104, the acquired test signal is transformed in the discrete time domain for representation in the discrete frequency domain. These

Transformation can, for example, by means of a discrete Fourier transformation (DFT) z. B. be performed by applying the Fast Fourier Transform (FFT).

In step 105, the frequency spectrum of the test signal is examined in the frequency range, in particular one-sided, in particular the real part. In step 106, the test signal is compared in the frequency range with respect to characteristic variables with a reference signal.

In step 107, based on the comparison from step 106, a state or a change of state is determined.

Claims

Expectations

1. A method (100) for testing a fiber composite component, in particular a body component for a vehicle, the fiber composite component having a sensor device integrated into the fiber composite component, the sensor device having a flexible circuit carrier with a sensor module, in particular with a micromechanical sensor module for detecting acceleration , with the steps:

- Detecting (102) a test signal by means of the sensor device,

in particular as a result of a displacement (101) of the fiber composite component in a test vibration, in particular by introducing a

Test pulse to a test location of the fiber composite component;

- Comparing (106) the test signal with a reference signal, characterized in that

in the step of comparing (106) the comparison of the test signal and the reference signal on the basis of a spectral analysis (105) in

Frequency range, especially in the discrete frequency range, is carried out.

2. The method (100) according to claim 1, wherein the spectral analysis is carried out by means of a (discrete) Fourier transformation (104), in particular by using a fast Fourier transformation.

3. The method (100) according to claim 2, wherein a zero padding (103) takes place in the time domain before the application of the fast Fourier transformation.

4. The method (100) according to any one of the preceding claims, wherein in the step of comparing (106) in the spectral analysis the test signal and the reference signal are only considered on one side.

5. The method (100) according to any one of the preceding claims, with a step of determining (107) the state and / or the

Change in state of the fiber composite component, the determination taking place in the determining step (107) as a function of significant changes in the characteristic of the frequency spectrum.

6. The method (100) according to any one of the preceding claims, wherein the test vibration is within an observed measurement range of the

Sensor device is and is dependent on a natural frequency of the environment of the fiber composite component.

7. Device which is designed to carry out all steps of the method (100) according to one of the preceding claims.

8. A computer program which is designed to carry out all the steps of the method (100) according to any one of claims 1 to 6.

9. Machine-readable storage medium on which the computer program according to claim 8 is stored.