DE102023134724A1 - Method and apparatus for evaluating ultrasonic welding - Google Patents

Abstract

Method for evaluating ultrasonic welding of joining partners (100, 102), wherein at least one of the joining partners (100, 102) comprises a fiber-plastic composite material with a thermoplastic and reinforcing fibers, and working vibrations are introduced into a joining zone (106) formed between the joining partners (100, 102) with the aid of at least one sonotrode in order to heat and plasticize the plastic, wherein waves are initiated and/or modified by a change in state of the fiber-plastic composite material, in which signals based on the initiated and/or modified waves are detected and evaluated in order to evaluate a welding process and/or a welded connection, wherein a specific change in state of the plastic, the reinforcing fibers and/or an interaction between the plastic and the reinforcing fibers is taken into account, and device for evaluating ultrasonic welding which is designed to carry out such a method.

Description

The invention relates to a method for evaluating ultrasonic welding, wherein working vibrations are introduced into a joining zone formed between joining partners with the aid of at least one sonotrode in order to heat and/or plasticize a joining partner material, wherein waves are initiated and/or modified by changes in the state of the joining partner material. The invention also relates to a device for evaluating ultrasonic welding.

From the document EN 10 2014 105 110A1 A method is known for the non-destructive testing of components, in particular fiber composite components, with the aid of a testing device, the testing device having a transmitting device for transmitting ultrasound and a receiving device for receiving ultrasound, wherein firstly the transmitting device and/or the receiving device are adjusted taking into account a digital representation of a component to be tested and adapted to a respective test position and subsequently ultrasound is introduced into the component without contact.

• Beaufschlagen eines Werkstücks mit Ultraschallwellen, Erfassen von durch das Beaufschlagen des Werkstücks mit den Ultraschallwellen erzeugten Ultraschallsignalen, Erzeugen von Ultraschalltomogrammdaten des Werkstücks aus den Ultraschallsignalen, wobei das Werkstück zerspanend bearbeitet wird, insbesondere fräsbearbeitet wird und das Werkstück mit den davon hervorgerufenen Ultraschallwellen beaufschlagt wird.

From the document EN 10 2019 003 921 A1 A workpiece testing method is known, in particular for testing workpieces for internal defects, for example workpieces made of fiber-reinforced plastic, with the following steps:

• Exposing a workpiece to ultrasonic waves, detecting ultrasonic signals generated by exposing the workpiece to the ultrasonic waves, generating ultrasonic tomogram data of the workpiece from the ultrasonic signals, wherein the workpiece is machined, in particular milled, and the workpiece is exposed to the ultrasonic waves generated thereby.

The document US 2015/0369779 A1 concerns a method for checking the weld condition. The document US 2015/0369779 A1 It is proposed to measure energy transmitted during ultrasonic welding of a plurality of plate-like members stacked on the anvil while a vibrating horn is pressed against the plate-like members, and to determine a quality of a welding state of the plate-like members based on the energy measured in the measuring process.

The document EN 10 2019 109 263 A1 relates to a method for non-destructive testing of the quality of an ultrasonic weld, which is carried out by means of a welding process. In the document EN 10 2019 109 263 A1 It is proposed to record a time-dependent measured variable over a period of time, whereby the measured variable is characteristic of a mechanical or electrical vibration behavior of the welding process to be checked, to evaluate a measured variable curve of the recorded time-dependent measured variable by applying a Fourier analysis and to compare a result of the evaluation with a reference value in order to check the quality of the ultrasonic welding.

The document EN 11 2018 000 674 T5 relates to an ultrasonic bond inspection method for inspecting the bonding quality of a bonded portion obtained by interconnective bonding between a bonding target member and a bonding member using an ultrasonic wave, wherein the bonding target member is mounted on a fixed object fixed to a jig. In the document EN 11 2018 000 674 T5 proposes a detection signal monitoring step in the bonding process for the bonding target member and the bonding member for detecting a vibration propagating in the jig or a housing of an ultrasonic bonding machine equipped with the jig to thereby output a detection signal, and a bonded state determining step for determining a bonded state between the bonding target member and the bonding member on the basis of the detection signal output in the detection signal monitoring step.

The document JP H11-174 033 A concerns a method for checking the welding zone in ultrasonic welding. In the document JP H11-174 033 A It is proposed to subject a part to be welded, which is placed on a support base, to ultrasonic welding while being pressed by an ultrasonic horn, to detect the sound generated during the ultrasonic welding, and to determine the quality of the welding state of the welding part by analyzing the waveform of the collected sound.

The document JP H11-197 854 A relates to an ultrasonic welding apparatus for performing ultrasonic welding by pressing an ultrasonic horn accompanied by ultrasonic vibration by an ultrasonic wave from an ultrasonic vibration device to an object to be welded held by a holding device. In the document JP H11-197 854 A vibration detection means are proposed which are arranged in a peripheral region of the object to be welded and are configured to detect vibrations during ultrasonic welding; and an arithmetic processing means for obtaining a relationship between an amplitude of a fundamental wave and an amplitude of an ultrasonic welding harmonic wave and an amplitude of a harmonic wave based on a detection result of the vibration detecting means, and for checking whether a welding state of the object to be welded is good or not.

The document EN 10 2013 222 876 A1 relates to a vibration welding system comprising: a vibration welding device having a welding horn and a welding anvil, which is configured to form a weld on a workpiece clamped between the welding horn and the welding anvil; a control station; a welding robot having an arm on which the welding horn and the welding anvil are arranged, the welding robot being configured to selectively move the welding horn and the welding anvil to the control station to determine a status condition of the vibration welding device; a first plurality of sensors positioned with respect to the vibration welding device while the workpiece is clamped between the welding horn and the welding anvil; a second plurality of sensors positioned with respect to the control station, the second plurality of sensors comprising a pressure sensitive arrangement; and a host device in communication with the first and second plurality of sensors, the host device comprising a processor and a tangible, non-transitory memory having instructions recorded therein for monitoring the vibration welding device to determine the status condition; the host device being configured to execute the instructions from the memory via the processor. In the document EN 10 2013 222 876 A1 it is proposed that the vibration welding system receive a first set of signals from the first plurality of sensors while the welding horn is actively forming the weld on the workpiece; selectively command the robot to move the welding horn and anvil to the control station; activate the second plurality of sensors when the welding horn and anvil reach the control station to thereby receive a second set of signals from the second plurality of sensors, the second set of signals comprising a measured force from the pressure sensitive assembly, and process the first and second sets of signals via the processor to thereby determine the status condition of the vibration welding apparatus.

The invention is based on the object of structurally and/or functionally improving a method mentioned at the outset. The invention is also based on the object of structurally and/or functionally improving a device mentioned at the outset.

The object is achieved by a method having the features of claim 1. Furthermore, the object is achieved by a device having the features of claim 11. Advantageous embodiments and/or further developments are the subject of the subclaims.

Ultrasonic welding can be designed for thermal joining. During ultrasonic welding, the joining partners can be plasticized on joining surfaces facing one another and/or adjacent to one another and an interpolymer bond can form. Ultrasonic welding can be designed for thermal joining of joining partners that contain a thermoplastic. The joining partners can consist of a composite material with a thermoplastic component or can contain a composite material with a thermoplastic component. The composite material can be a fiber composite material and/or a fiber-plastic composite material. The thermoplastic can be designed and/or arranged as a matrix material. The reinforcing fibers can be embedded in the matrix material. Mutual interactions can exist between the matrix material and the reinforcing fibers. The reinforcing fibers can be bound to the matrix by adhesive interactions. The reinforcing fibers can be organic fibers such as aramid fibers, carbon fibers, polyester fibers, nylon fibers, polyethylene fibers, polymethyl methacrylate fibers and/or inorganic fibers such as basalt fibers, boron fibers, glass fibers, ceramic fibers, silica fibers. The reinforcing fibers can be long fibers and/or short fibers. The reinforcing fibers can be arranged in a direction. The reinforcing fibers can be arranged as a bundle, woven fabric, knitted fabric, scrim or mat. The thermoplastic can be polyethylene (PE), polypropylene (PP), polyamide (PA), polyoxymethylene (POM), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), thermoplastic elastomer (TPE), polystyrene (PS), polyetheretherketone (PEEK), polyaryletherketone (PAEK), polyphenylene sulfide (PPS), polysulfone (PSU), polyetherimide (PEI) and/or polytetrafluoroethylene (PTFE).

At least one of the joining partners can contain at least one energy director. The at least one energy director can be designed and/or arranged to concentrate, reflect, transmit and/or transport working vibrations. The at least one energy director can be designed and/or arranged as a functionally and/or structurally separate section of the at least one joining partner. The at least one energy director can be formed using a component of a composite material. A thermoplastic can be designed and/or arranged as an energy director. Reinforcing fibers can be designed and/or arranged as an energy director. The joining partners can be, in particular, automotive components, aircraft components or components for space travel.

The joining partners can have mutually assigned joining contact surfaces. The joining contact surfaces can be flat. The joining contact surfaces can be curved once or multiple times. The joining contact surfaces of the joining partners can lie against one another. The joining zone can be arranged on the joining contact surfaces of the joining partners. The joining zone can extend from the joining contact surfaces of the joining partners into the joining partner material.

In ultrasonic welding, at least two joining partners can be or have been connected to one another. In ultrasonic welding, a first joining partner and a second joining partner can be or have been connected to one another. In ultrasonic welding, the joining partners can be arranged with their joining contact surfaces next to one another, pressed against one another, moved relative to one another, positioned relative to one another and/or held. The working vibrations can be mechanical vibrations, in particular high-frequency mechanical vibrations. The working vibrations can be ultrasonic vibrations. The working vibrations can be waves and/or comprise waves. The working vibrations can have a frequency in the kHz range, in particular a frequency in the lower kHz range, in particular a frequency of 10 kHz to 1 50 kHz, in particular a frequency of 20 kHz to 90 kHz, in particular a frequency of 20 kHz to 35 kHz. The working vibrations can have a modulatable or modulated amplitude. The working vibrations can be impedance-adjustable or impedance-adjusted. The working vibrations can be introduced via a coupling medium. A gaseous medium, especially air, can be used as a coupling medium. A liquid medium, such as water, oil or gel, can be used as a coupling medium. A solid medium can be used as a coupling medium. Silicone can be used as a coupling medium.

In the present case, “evaluating” can include in particular a systematically planned description, examination, analysis and/or assessment. In the present case, “evaluating” can refer in particular to an ultrasonic welding method, an ultrasonic welding process, components used to carry out an ultrasonic welding method and/or an ultrasonic weld joint produced in an ultrasonic welding method.

During ultrasonic welding, the joining partner material in the joining zone can heat up, change from a solid to a deformable or flowable state, cool down again, and/or change from a deformable or flowable to a solid state. During ultrasonic welding, the material properties of the joining partner material in the joining zone can change. During ultrasonic welding, a crystal structure and/or an adsorbate structure of the joining partner material in the joining zone can change. During ultrasonic welding, waves can be initiated in the joining zone. During ultrasonic welding, a wave transmission and/or wave reflection behavior in the joining zone can change.

A specific change of state can be a phase transition and/or be based on a phase transition. The phase transition can be a phase transition of a thermoplastic. The phase transition can be a transition from solid to liquid, which can also be referred to as melting, a transition from liquid to solid, which can also be referred to as solidification or crystallization, a transition from liquid to gaseous, which can also be referred to as evaporation, a transition from gaseous to liquid, which can also be referred to as condensation.

A specific change in state can be a thermal expansion, which can also be referred to as thermal expansion, or a thermal shrinkage, which can also be referred to as thermal contraction, and/or be based on a thermal expansion and/or on a thermal shrinkage. A specific change in state can be an at least sectional movement within at least one of the joining partners or an at least sectional movement between the joining partners and/or be based on an at least sectional movement within at least one of the joining partners or on an at least sectional movement between the joining partners. A thermal expansion, a thermal shrinkage and/or an at least sectional movement as a specific change in state and/or a specific change in state based on thermal expansion, thermal shrinkage and/or at least sectional movement can be determined by an expansion coefficient and/or by a coefficient of friction must be determined and/or characterized.

A specific change in state can be based on mechanical and/or thermal stresses. A specific change in state can be a build-up of mechanical and/or thermal stresses and/or be based on a build-up of mechanical and/or thermal stresses. A specific change in state can be a reduction in mechanical and/or thermal stresses and/or be based on a reduction in mechanical and/or thermal stresses. A specific change in state can be a change in a material structure, a crack formation, for example a hot crack formation, such as solidification crack formation or melting crack formation, or a cold crack formation, and/or be based on a change in a material structure, a crack formation, for example a hot crack formation, such as solidification crack formation or melting crack formation, or a cold crack formation. A specific change in state based on mechanical and/or thermal stresses can be determined and/or characterized by material-related parameters.

A specific change in state can be a local or locally limited change in state of a joining partner and/or a joining partner material and/or be based on a local or locally limited change in state of a joining partner and/or a joining partner material. A specific change in state can be a change in a layer, position, distribution and/or concentration of reinforcing fibers and/or be based on a change in a layer, position, distribution and/or concentration of reinforcing fibers. A specific change in state can be a change in a mutual interaction between the thermoplastic and the reinforcing fibers and/or be based on a change in a mutual interaction between the thermoplastic and the reinforcing fibers.

Waves initiated and/or modified by a specific change in the state of the joining partners and/or the joining partner material can be mechanical waves. The waves can be transverse waves and/or longitudinal waves. The transverse waves can be polarized. The waves can be waves that propagate within the joining partners and/or the joining partner material and/or through a gas, in particular air. The waves can be irregular and/or non-periodic. The waves can have a structure that changes over time. The waves can be regular and/or periodic. The waves can have a precisely definable pitch. The waves can be sound waves, in particular ultrasonic waves, and/or be based on sound waves, in particular ultrasonic waves. The waves can have a structure that does not change over time. The waves cannot have a precisely definable pitch and/or can be perceived as noise.

Wave-based signals can be signals based on waves initiated by specific changes in the state of the joining partners and/or the joining partner material. Wave-based signals can be signals based on waves modified by specific changes in the state of the joining partners and/or the joining partner material. Wave-based signals can be signals based on working vibrations modified by specific changes in the state of the joining partners and/or the joining partner material.

A welding process and/or a welded joint can be evaluated based on the detected signals. A welding process and/or a welded joint can be evaluated based on the detected signals without further data and/or further signals, in particular comparison data and/or comparison signals, being used or required. A welding process and/or a welded joint can be evaluated based on the detected signals without comparison and/or without comparison signals. The detected signals can be suitable as such for evaluating a welding process and/or a welded joint. The detected signals can be suitable for evaluating a welding process and/or a welded joint without comparison and/or without comparison signals. The detected signals can be evaluated to determine whether the welding process and/or the welded joint appear suitable to fulfill a desired purpose. The detected signals can be evaluated to determine whether the welding process and/or the welded joint are suitable to meet predetermined criteria. The detected signals can be evaluated to determine whether the welding process meets predetermined quality criteria. The detected signals can be evaluated to determine whether the weld meets predetermined quality criteria and/or characteristics.

The recorded signals can be used to control the welding process. The term “control” can refer to both controlling and regulating control. The recorded signals can be used in particular to control the sonotrode and/or a movement of the sonotrode.

At least one step of the method can be carried out before, during and/or after the introduction of working vibrations in the joining zone. At least one step of the method can be carried out locally and/or temporally connected to the introduction of working vibrations in the joining zone. At least one step of the method can be carried out locally and/or temporally decoupled from the introduction of working vibrations in the joining zone.

The signals can be recorded on at least one of the joining partners. The signals can be recorded on a single joining partner. The signals can be recorded on several joining partners. The signals can be recorded on a first joining partner and/or on a second joining partner. The signals can be recorded in direct contact. The signals can be recorded in force-locking and/or positive contact. When signals are recorded in direct contact or in force-locking and/or positive contact, a liquid, gel-like or solid coupling medium can be used. The signals can be recorded using at least one vibration sensor.

The signals can be recorded from the joining partners at a distance. The signals can be recorded from airborne sound. The signals can be recorded using at least one microphone.

The signals can be recorded in a constant position relative to the joining partners. The signals can be recorded in a changing position relative to the sonotrode. The signals can be recorded in a constant position relative to the sonotrode. The signals can be recorded in a changing position relative to the joining partners.

The signals may be processed to obtain information, reduce data, and/or prepare for evaluation. The signals may be processed to obtain information about the welding process and/or the weld joint. The signals may be processed to prepare for automated or machine evaluation. The signals may be processed to prepare for human evaluation. The signal processing may include a linear time-frequency transform. The signal processing may be configured to enable simultaneous extraction of local spectral and temporal information. The signal processing may be configured to enable processing while avoiding segmentation. The signal processing may include a wavelet transform. The signal processing may include an integral transform. The signal processing may include a Fourier transform.

The at least one sonotrode can be arranged fixedly relative to the joining partners during ultrasonic welding in order to connect the joining partners to one another using a welding point. The at least one sonotrode can be moved relative to the joining partners during ultrasonic welding in order to connect the joining partners to one another using a weld seam.

The at least one vibration sensor and/or the at least one microphone can be arranged fixedly relative to the joining partners during ultrasonic welding. The at least one vibration sensor and/or the at least one microphone can be moved relative to the joining partners during ultrasonic welding.

The at least one sonotrode, the at least one vibration sensor and/or the at least one microphone can be moved during ultrasonic welding using a robot. The at least one sonotrode, the at least one vibration sensor and/or the at least one microphone can be moved along a predetermined path during ultrasonic welding. The signals can be assigned to a sonotrode position. The signals can be assigned to a changing sonotrode position. The signals can be assigned to a sonotrode position moving along a path.

Useful signals and interference signals can be differentiated. The signals can be classified into useful signals and interference signals. Interference signals can be at least partially reduced or removed. The useful signals can be taken into account at least in the main. The useful signals can be taken into account at least in the main during the evaluation and/or assessment.

A welding process and/or a weld joint can be evaluated automatically or by machine. A welding process and/or a weld joint can be evaluated using an algorithm. A welding process and/or a weld joint can be evaluated by a person.

The device comprises at least one sonotrode, at least one vibration sensor, at least one microphone and/or a device for signal processing, evaluation and/or assessment.

The at least one sonotrode can be designed to introduce the working vibrations into the joining zone. The at least one sonotrode can be designed to establish a connection between an ultrasonic generator and the at least one joining partner. The at least one sonotrode can have a specifically adapted or adaptable impedance. The at least one sonotrode can have a specifically adapted geometry. The at least one sonotrode can be made of metal, in particular of aluminum, titanium, steel, alloys containing these metals or other metals or alloys.

The at least one vibration sensor can be an ultrasonic sensor. The at least one vibration sensor can be designed as a piezoelectric sensor. The at least one microphone can be designed to convert airborne sound as alternating sound pressure vibrations into corresponding electrical voltage changes or capacitance changes as a signal. The at least one microphone can be designed as a laser microphone.

The device for signal processing, evaluation and/or assessment can have at least one processor, at least one main memory, at least one data memory, at least one signal input and/or at least one signal output. The device for signal processing, evaluation and/or assessment can be designed to control the at least one sonotrode. The device for signal processing, evaluation and/or assessment can have signals from the at least one vibration sensor and/or the at least one microphone available.

The device can have at least one robot. The at least one robot can be designed as an industrial robot. The at least one robot can have a manipulator. The at least one robot can have at least one effector or end effector. The at least one robot can have a control device. The control device can have at least one processor, at least one main memory, at least one data memory, at least one signal input and/or at least one signal output. The control device can be designed to control the at least one robot. The control device and the device for signal processing, evaluation and/or assessment can be connected to one another in a signal-conducting manner. The control device and the device for signal processing, evaluation and/or assessment can be structurally designed to be at least partially separate from one another. The control device and the device for signal processing, evaluation and/or assessment can be structurally and/or functionally at least partially integrated.

The at least one sonotrode, the at least one vibration sensor and/or the at least one microphone can be arranged on the robot. The at least one sonotrode, the at least one vibration sensor and/or the at least one microphone can be arranged on the at least one effector or end effector.

In summary and in other words, the invention thus results, among other things, in a noise emission measurement for quality assurance in the process of stationary/continuous ultrasonic welding.

Noise is understood here in particular to be a sound wave that travels through the air to a sensor, such as a microphone, and is measured there. Acoustic emission (AE) is understood to be a wave that originates from a change in the state of a material, such as melting, cracking, etc., and inevitably travels through the material until it is either measured by a sensor lying on top of it or can be measured by a sensor floating above the material when the vibrations pass into the air. With AE, the wave can be caused by a change in the state of the material, such as cracking, melting, rubbing, etc. AE sensors can enable a particularly fine resolution of the vibrations. A microphone measurement can be particularly simple.

Acoustic signals can be measured for quality evaluation of spot or continuous ultrasonic welding/ultrasonic welded joints. AE data can be used for quality evaluation of ultrasonic spot welding and/or continuous ultrasonic welding process.

The invention improves quality evaluation in ultrasonic spot welding and/or continuous ultrasonic welding. The quality of an ultrasonic welded joint can be evaluated. The reliability of an evaluation can be increased.

• 1 zwei zum Ultraschallschweißen mit Signalerfassung vorbereitete Fügepartner in seitlicher Ansicht und
• 2 zwei zum Ultraschallschweißen mit Signalerfassung vorbereitete Fügepartner in Draufsicht.

In the following, embodiments of the invention are described in more detail with reference to figures described, showing schematically and by way of example:

• 1 two joining partners prepared for ultrasonic welding with signal detection in side view and
• 2 Two joining partners prepared for ultrasonic welding with signal detection in top view.

1 shows two joining partners 100, 102 prepared for ultrasonic welding with signal detection in a side view. 2 shows the joining partners 100, 102 in a top view. The joining partners 100, 102 each consist of a composite material with a thermoplastic matrix material and reinforcing fibers embedded in the matrix material. The joining partners 100, 102 each have a joining contact surface. The joining partners 100, 102 lie on a working surface 104 and with their joining contact surfaces in a joining zone 106.

The vibration sensor 108 is fixed to the joining partner 100 using a clamping lever 110 designed as a horizontal clamp, so that signal detection is possible in direct force-locking and/or form-locking contact. The vibration sensor 108 is coupled to the joining partner 100 via a silicone layer.

Ultrasonic welding is carried out using a robot (not shown here) that has an end effector with a sonotrode and a microphone. The sonotrode is pressed onto the joining zone 106 using the robot and working vibrations are initiated so that the matrix material of the joining partners 100, 102 is heated in the joining zone 106 and changes from a solid to a deformable or flowable state. The matrix material of the joining partners 100, 102 bonds in a material-locking manner, whereby the reinforcing fibers can also be mutually embedded. After the sonotrode is switched off, the matrix material of the joining partners 100, 102 cools down again and changes back to a solid state.

While the working vibrations are introduced into the joining zone 106, and possibly also before and after, signals are recorded at a distance from the joining partners 100, 102 using the vibration sensor 108 on the joining partner 100 and the microphone arranged on the robot. These signals are based on mechanical waves that are initiated and/or modified by changes in the state of the joining partner material during the welding process. The vibration sensor 108 arranged on the joining partner 100 is used to record waves that propagate within the joining partners 100, 102. The microphone is used to record waves that propagate through the air.

Both recorded signals are evaluated to assess the welding process and/or the welded joint created in the welding process. The evaluation provides data that can be evaluated by algorithms or by a specialist so that a statement can be made about the quality of the joint.

During continuous ultrasonic welding, the vibration sensor 108 is guided over the sample and the detected signal is assigned to the location of the weld via position and/or movement information of the robot.

The term "can" refers in particular to optional features of the invention. Accordingly, there are also further developments and/or embodiments of the invention which additionally or alternatively have the respective feature or features.

If necessary, isolated features can also be selected from the combinations of features disclosed here and used in combination with other features to define the subject matter of the claim, dissolving any structural and/or functional connection that may exist between the features.

Reference symbols

100

Joining partner

102

Joining partner

104

Work surface

106

Joining zone

108

Vibration sensor

110

Clamping lever

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• DE 102014105110 A1 [0002]
• DE 102019003921 A1 [0003]
• US 20150369779 A1 [0004]
• DE 102019109263 A1 [0005]
• EN 112018000674 T5 [0006]
• JP H11174033 A [0007]
• JP H11197854 A [0008]
• DE 102013222876 A1 [0009]

Claims (13)

Method for evaluating ultrasonic welding of joining partners (100, 102), wherein at least one of the joining partners (100, 102) comprises a fiber-plastic composite material with a thermoplastic and reinforcing fibers, and with the aid of at least one sonotrode, working vibrations are introduced into a joining zone (106) formed between the joining partners (100, 102) in order to heat and plasticize the plastic, wherein waves are initiated and/or modified by a change in the state of the fiber-plastic composite material, characterized in that signals based on the initiated and/or modified waves are recorded and evaluated in order to evaluate a welding process and/or a welded connection, wherein a specific change in the state of the plastic, the reinforcing fibers and/or an interaction between the plastic and the reinforcing fibers is/are taken into account. Procedure according to Claim 1 , characterized in that when evaluating the welding process and/or the welded connection, a phase transition of the plastic, a thermal expansion of the plastic and/or the reinforcing fibers, an at least sectional movement within at least one of the joining partners (100, 102) or an at least sectional movement between the joining partners (100, 102), mechanical and/or thermal stresses, a build-up of mechanical and/or thermal stresses, a reduction in mechanical and/or thermal stresses, a change in a location, position, distribution and/or concentration of reinforcing fibers, and/or a change in a mutual interaction between the thermoplastic plastic and the reinforcing fibers are/are taken into account. Method according to at least one of the preceding claims, characterized in that the signals are detected at at least one of the joining partners (100, 102). Method according to at least one of the preceding claims, characterized in that the signals from the joining partners (100, 102) are detected at a distance. Method according to at least one of the preceding claims, characterized in that the signals are detected in a constant position relative to the joining partners (100, 102) and/or in a constant position relative to the sonotrode. Method according to at least one of the preceding claims, characterized in that the signals are processed in order to obtain information, reduce data and/or prepare an evaluation. Method according to at least one of the preceding claims, characterized in that the signal processing comprises a wavelet transformation. Method according to at least one of the preceding claims, characterized in that the signals are assigned to a sonotrode position. Method according to at least one of the preceding claims, characterized in that useful signals and interference signals are differentiated and at least substantially the useful signals are taken into account. Method according to at least one of the preceding claims, characterized in that a welding process and/or a welded joint are evaluated using an algorithm. Device for evaluating ultrasonic welding, characterized in that the device is designed to carry out a method according to at least one of the preceding claims. Device according to Claim 11 , characterized in that the device has at least one sonotrode, at least one vibration sensor (108), at least one microphone and/or a device for signal processing, evaluation and/or assessment. Device according to at least one of the Claims 11 until 12 , characterized in that the device has at least one robot and the at least one sonotrode, the at least one vibration sensor (108) and/or the at least one microphone is arranged on the robot.

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