Method for material testing of a hot-formed part of a motor vehicle

Abstract

The invention relates to a method for material testing of a hot-formed part (1) of a motor vehicle, wherein a magnetic field and / or a gradient of a magnetic field of the hot-formed part (1) is detected by means of at least one quantum sensor (2) and evaluated by means of an evaluation device (3).

Description

[0001] The present invention relates to a method for material testing of a hot-formed part of a motor vehicle.

[0002] Hot-formed parts are high-strength structural components made of metal, such as the A- or B-pillars of a motor vehicle. These are manufactured by hot forming, which is also known as hot-forming or press hardening. In such hot-forming processes, manganese-boron steels are currently used almost exclusively in industry, which are heated in a furnace before forming. During the forming process, the material is rapidly cooled. This results in phase transformation processes at the material level, and the strength of the material increases significantly. Even small fluctuations in temperature or material composition can therefore lead to sporadic material defects, such as cracks or material inclusions, occurring during the hot-forming process.

[0003] The material testing of hot-formed metal parts installed in motor vehicles is a safety and quality-relevant test for the customer. It provides a precise overview of the quality of the hot-formed parts installed in the vehicle. This analysis is extremely important because it contributes to the calculation of the strength of a hot-formed part. This strength is essential to ensure that the hot-formed part remains reliably mechanically intact over the long term. However, in order to reliably test such hot-formed parts, they must be destroyed during many testing procedures. Therefore, in practice, only individual hot-formed parts can be tested for testing purposes, not those that are intended to be installed in the vehicle or have actually been installed.

[0004] CN 113567540 A discloses a device for the non-destructive testing of steel cables. It comprises two magnetic units arranged opposite one another, with a cavity for the steel cable between them. The first magnetic unit contains an NV color-nucleus quantum sensor. Each magnetic unit consists of two permanent magnets connected by an iron core. The device is housed in a casing consisting of an upper and a lower shell, between which the cavity lies. A guide wheel connected to the upper shell guides the movable steel cable. A displacement sensor is attached to the rear end of the guide wheel. The device is part of a system comprising a laser and a microwave system, both connected to the NV color-nucleus quantum sensor, as well as a CCD camera and a phase-locked amplifier, which are also connected to the CCD camera.

[0005] The invention aims to provide a method for material testing of a hot-formed part of a motor vehicle, which makes it possible to examine the hot-formed part non-invasively and thus non-destructively with regard to possible material defects, material cracks, inclusions or other quality defects.

[0006] The solution to this problem is provided by a method for material testing of a hot-formed part of a motor vehicle having the features of the characterizing part of claim 1. The subclaims relate to advantageous developments of the invention.

[0007] In a method according to the invention for material testing of a hot-formed part, it is provided that a magnetic field and / or a gradient of a magnetic field of the hot-formed part is detected by means of at least one quantum sensor and evaluated by an evaluation device. The method according to the invention advantageously allows for non-invasive and thus non-destructive testing of the hot-formed part by determining a magnetic field and / or the gradient of a magnetic field of the hot-formed part in order to be able to draw conclusions about possible material defects, material cracks, material inclusions, or other quality defects. Very different types of quantum sensors can be used in the method according to the invention. Depending on the type of quantum sensor, the non-invasive and non-destructive method can be used both before installation of the hot-formed part and subsequently after installation.The use of at least one quantum sensor advantageously provides very precise information about possible material defects, material cracks, material inclusions or other quality defects of the hot-formed part.

[0008] In one embodiment, it is proposed to use a quantum sensor comprising at least one atomic vapor cell. In an atomic vapor cell, atomic vapor of paramagnetic atoms (alkali metal atoms, such as potassium atoms, rubidium atoms, or cesium atoms) is held in a glass cell and optically pumped using a pump beam, resulting in spin polarization. As an optically pumped magnetometer, an atomic vapor cell can be used to detect the smallest magnetic fields of the molded part, from which the presence of material defects, cracks, inclusions, or other quality defects can be determined. A sensitivity in the range of approximately 700 pT / √Hz can be achieved.

[0009] In an alternative embodiment, it is proposed that a nuclear magnetic resonance sensor be used as the quantum sensor. Nuclear magnetic resonance, on which the nuclear magnetic resonance sensor is based, is a well-known physical effect in which the atomic nuclei of the molded part to be examined are exposed to a constant magnetic field and absorb and emit alternating electromagnetic fields. The measured variable to be evaluated is a magnetic field that can be recorded by inductive detection. The spins of the atomic nuclei of the material from which the molded part is made represent qubits that can be manipulated and read out using nuclear magnetic resonance. A sensitivity in the range of approximately 10 pT / √Hz can be achieved.

[0010] In a further alternative embodiment, it is proposed that a neutron sensor be used as the quantum sensor. Due to their magnetic moment, neutrons are very sensitive to magnetic fields, while due to their charge neutrality, they can penetrate even solid samples, in particular the hot-formed parts to be installed or already installed in motor vehicles. Spin-polarized neutrons are used here, whose spin is polarized by a polarization device before they impact the hot-formed part to be tested. The spin polarization of the neutrons can be obtained in particular by Bragg reflection from a magnetic crystal. During testing, the hot-formed part is exposed to a magnetic field, which causes the neutron spin to rotate in the magnetic field of the hot-formed part and approach a polarization analyzer in a non-parallel orientation.The angle of the final spin rotation depends on the magnetic field along the neutron trajectory. Changes in polarization alter the neutron transmission through the polarization analyzer, which can be measured.

[0011] In another alternative embodiment, it is proposed that an ion trap be used as a quantum sensor. For example, a Paul trap or a Penning trap can be used. The ion trap acts as a magnetometer, with the ions trapped in the ion trap forming the qubits. The resonant frequency of an ion trapped in the ion trap depends on the strength of the magnetic field. An external magnetic field induced by the molded part under investigation changes the resonant frequency, which can be measured accordingly. Furthermore, magnetic field gradients can also be measured if multiple ions are present in the ion trap.

[0012] In another alternative embodiment, it is proposed to use a quantum sensor based on spin-dependent photoluminescence of nitrogen vacancy centers. Nitrogen vacancy centers (NV centers) in an optically excited diamond react very sensitively to magnetic fields and can then serve as a quantum sensor to examine the structure of the molded part for possible material cracks, material defects, inclusions, or other quality defects. This is because the defects in the diamond's crystal lattice detect NMR signals from atoms in their surroundings. This information can be read optically. A sensitivity in the range of 100 pT / √Hz can be achieved. In this variant of the process, the qubits are formed by the spin states of the diamond's electrons.

[0013] Further features and advantages of the present invention will become clear from the following description of preferred embodiments with reference to the enclosed Fig. 1, which shows a measuring arrangement 100 for carrying out a method for material testing of a metallic hot-formed part 1 of a motor vehicle in a very simplified schematic form.

[0014] Hot-formed parts 1 are high-strength structural components made of metal, such as the A and B pillars of a motor vehicle. These are manufactured by hot forming, which is also known as form or press hardening. In such hot forming processes, manganese-boron steels are currently used almost exclusively in industry, which are heated in a furnace before forming. During the forming process, the material is cooled rapidly. This results in phase transformation processes at the material level, and the strength of the material increases considerably. Even small fluctuations in temperature or material composition can therefore lead to sporadically occurring material defects, such as cracks 10 or material inclusions 11, or other quality defects during the form hardening process, which are to be detected using the method described here.

[0015] The measuring arrangement 100 comprises a quantum sensor 2, which, through a physical interaction 4 with the hot-formed part 1, is capable of detecting a magnetic field of the hot-formed part 1 and / or a gradient of a magnetic field of the hot-formed part 1. The measuring arrangement 100 further comprises an evaluation device 3, which is designed to evaluate the measurement signals of the quantum sensor 2 and to determine whether the hot-formed part has, for example, cracks 10, material inclusions 11, or other material defects or quality defects.

[0016] The process presented here can be used with very different types of quantum sensors 2. Depending on the type of quantum sensor 2, the process can be applied both before the hot-formed part is installed and subsequently in the installed state of the hot-formed part 1.

[0017] In one embodiment, a quantum sensor 2 may be used which comprises at least one atomic vapor cell.

[0018] According to a further embodiment, a nuclear magnetic resonance sensor can be used as quantum sensor 2.

[0019] In a further embodiment, a neutron sensor can be used as quantum sensor 2.

[0020] According to a further embodiment, an ion trap can be used as quantum sensor 2.

[0021] In a further embodiment, a quantum sensor 2 can be used which is based on spin-dependent photoluminescence of nitrogen vacancy centers.

[0022] The method presented here advantageously allows for the non-invasive and thus non-destructive testing of the hot-formed part 1 by determining a magnetic field and / or the gradient of a magnetic field of the hot-formed part 1, thereby allowing conclusions to be drawn about possible material defects, material cracks, material inclusions, or other quality defects. The use of at least one quantum sensor 2 advantageously provides very precise information about possible material defects, material cracks, material inclusions, or other quality defects of the hot-formed part 1. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] CN 113567540 A

[0004]

Claims

[1] Method for material testing of a hot-formed part (1) of a motor vehicle, characterized by that a magnetic field and / or a gradient of a magnetic field of the hot-formed part (1) is detected by means of at least one quantum sensor (2) and evaluated by means of an evaluation device (3). [2] Method according to claim 1, characterized by that a quantum sensor (2) is used which comprises at least one atomic vapor cell. [3] Method according to claim 1, characterized by that a nuclear magnetic resonance sensor is used as the quantum sensor (2). [4] Method according to claim 1, characterized by that a neutron sensor is used as the quantum sensor (2). [5] Method according to claim 1, characterized by that an ion trap is used as quantum sensor (2). [6] Method according to claim 1, characterized bythat a quantum sensor (2) is used which is based on a spin-dependent photoluminescence of nitrogen vacancy centers.

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