DE102022100378A1 - Procedure for determining the coefficient of friction of a screw connection - Google Patents

Abstract

Method (1) for determining a coefficient of friction of a screw connection (2), with the following method steps:
- Execution (100) of a screwing-in process, with an actuator (3) applying a torque (4) to a screwing means (6) to be screwed into a counter-thread (5) and the actuator (3) being operated as an impulse screwdriver,
- detecting (101) a torque (4) acting on the screw means (6) and generating torque information (20);
- detecting (102) a prestressing force (7) describing a prestressing force (7) of the screw connection (2) and generating prestressing force information (21),
- Determining (103) a friction value of the screw connection (2) imaging friction value information (22) as a function of the torque information (20) and prestressing force information (21).

Description

The invention relates to a method for determining a coefficient of friction of a screw connection.

Corresponding methods for determining a coefficient of friction of a screw connection are basically known from the prior art. The relationship between the coefficient of friction in the threads and in the head support are known as parameters when designing a screw connection. In the friction coefficient tests known from the prior art for determining the friction coefficients of a screw connection, the tension of a load cell and a drive torque or thread torque are determined. H. which is operated at constant speed. Such test methods and the information obtained from them about the coefficient of friction of the screw connection cannot be used, or can only be used to an insufficient extent, for the use of impulse screwing tools, since in particular static friction effects and/or static friction to sliding friction transitions are not taken into account.

The invention is based on the object of specifying a method which, in particular with regard to a simple, quick and cost-effective measure, increases the significance of a determined coefficient of friction be quantified.

The object is achieved by a method for determining a coefficient of friction of a screw connection according to claim 1. The claims dependent on this relate to possible embodiments of the method. Furthermore, the object is achieved by a device according to claim 11.

The invention relates to a method for determining or testing a coefficient of friction of a screw connection, with the following method steps: (a) Carrying out a screwing-in process, with an actuator applying a torque to a screw to be screwed into a counter-thread and the actuator being operated as an impulse screwdriver . The actuator can be designed as an impulse screw cell and/or as a servo motor that can be operated in the manner of an impulse screw driver. Here, (b) a torque acting on the screw means is detected and torque information is generated, and (c) a preload force describing a preload force of the screw connection is detected and preload force information is generated, with (d) a friction value information item depicting a friction value of the screw connection being determined as a function of the torque information and preload force information is performed. The mating thread can be worked into a test specimen, with the screw means being screwed into or onto the mating thread on the test specimen. In this case, the actuator is operated in such a way that its drive characteristics with regard to the screw means to be screwed are, in particular, similar or identical to those of an impulse screw driver. An impulse wrench is to be understood as an electrically and/or pneumatically and/or hydraulically driven screwing tool, which uses impulses to produce, i. H. performs a disc-continuous introduction of force to the screw means. Screwdriving tools of this type can, for example, emit ever stronger impulses as the screwing time increases, with the impulses being able to run asymptotically towards the maximum power output. In the context of the present invention, impulse wrenches can be understood as screwing tools which are operated by means of a compressed air motor or an electric motor and are used for screwing in and/or loosening screw means, ie screws or nuts. In this case, an impulse wrench can be designed without a reduction gear and thus achieve high screwing speeds. In this case, an impulse wrench can refer to screwing tools whose drive motor is not mechanically connected to an output spindle. Optionally, the term “impulse wrench” used here can also be understood to mean an impact wrench, which provides a mechanical coupling of the drive motor to the output spindle, so that it includes parts that are mechanically in contact and transmit an impulse.

The determination of the coefficient of friction information can, for example, be carried out partially or fully automatically and/or by means of a computer-implemented method. The coefficient of friction information can, for example, specify at least one coefficient of friction criterion for the screw connection. The type and/or quality, i. H. the quality of the screw connection, in particular in connection with the control parameters used for the impulse wrench used. In this way, for example, the quality of the screw means-counterthread connection can be clarified.

Contrary to conventional methods for detecting a coefficient of friction, the torque is detected and torque information is generated. In order to prevent damage to the detection device(s), which detects the torque in particular, the number of pulses, i.e. the pulse events of the actuator limited. The impulse event(s) occurring within the scope of detection can also occur at an early stage of the screwdriving process, i.e. e.g. within the first three quarters, preferably within the first two thirds, particularly preferably within the first half, most preferably within a first third, of the Screwing process for screwing or screwing a screw in or on a mating thread. Avoiding an execution of the detection in a late screwing stage can limit the maximum torque acting on the at least one detection device, in particular the torque which is again amplified by the pulse event.

It is possible for an item of rotation angle information to be detected and assigned to the torque information and/or to the prestressing force information. The assignment of rotational angle information describing rotational angle values to the detected and generated torque information and/or to the preload force information can, for example, be an assignment or classification of individual torque values and preload force values to one another and/or a statement about the position and/or the progression of the torque and/or the preload force to at least one Enable impulse event. Torque information depicting a progression of the torque, in particular via the angle of rotation, and/or pretensioning force information depicting a progression of the pretensioning force, in particular via the angle of rotation, can preferably be generated and output. For example, the measurement setup has a rotational angle detection device, which makes it possible to specify rotational angle values that can be assigned to detected torque and/or preload force values.

The method can include, for example, determining at least one local minimum of the torque in the course of the torque information about the angle of rotation performed or a portion of the angle of rotation and outputting minimum torque information relating to the at least one local minimum of the torque. If a local minimum is assumed here, this means that the absolute minimum would always have to be assigned to the impulse event when considering the course of the torque or the torque information and/or the coefficients of friction or the coefficient of friction information, since the impulse event leads to a stop of the drive and/or leads to a significant delay/reduction in the drive of the drive movement exerted by the actuator on the screw means. However, this absolute minimum should not be included primarily or not at all in the determination of the coefficient of friction of the screw connection, since the focus of this investigation in particular should be the determination of a static friction component and/or a transition area from static to sliding friction. The local minimum thus describes the fact that the values during the impulse event itself are not used for the evaluation consideration, but that a local minimum is determined, which includes a significance with regard to, for example, static friction components of the screw connection that are to be quantified. If, in the following, a restriction of an observation or analysis area of a torque curve and/or friction coefficient curve to areas that exclude the impulse events is stated, the term local minimum is still used, even if in the observation area excluding the impulse events the local minimum or the local minima can form an absolute minimum for precisely this area of consideration. The same applies to the local maxima mentioned below.

It is possible to provide for determining at least one local minimum of the coefficient of friction in the course of the coefficient of friction information about the angle of rotation performed (angle of rotation section) and outputting minimum information of friction coefficient relating to the at least one local minimum of the coefficient of friction.

It is possible for the at least one determined local minimum to be determined in the course of the torque information and/or friction value information between two pulse events of the actuator. In this way, the course of the friction influence can be recorded and quantified during the screwdriving process. In particular, static friction components and/or transitions between static and sliding friction can be recorded and, in particular, evaluated. Here, for example, the rotation angle information can be used to locally localize the at least one pulse event and not to consider the values present at this rotation angle value (e.g. torque values and/or friction values) for determining the local minimum. In other words, the determined local minimum of the torque and/or the coefficient of friction represents a point or area within the screwing scenario, which results after an impulse event. In other words, the local minimum value should not reflect the switching off or sharp reduction in the drive power of the actuator that occurs in the course of the pulse event as a decreasing torque or friction coefficient result. Rather, a local minimum should be identified as a prominent point or area after restarting the driving of the screwing means by means of the actuator operated in the manner of an impulse wrench and for this purpose deliver meaningful values. It has been recognized here that when restarting, ie during the acceleration of the actuator and thus of the screw means, after its stop or deceleration phase there is initially a drop in torque and only after a first start-up phase does a then continuous (continued) course occur of the screw connection. This is due to the fact that in the first start-up phase, in addition to the sliding friction between the screw means and the counter-thread, there is a static friction component that affects static friction, which must first be overcome and in the course of the first start-up phase or loses its influence on the total coefficient of friction before a continuous and thus exclusively or predominantly due to the sliding friction resulting frictional influence on the friction pairing of the screw means and the mating thread.

In an advantageous development, it can be provided that at least two local minima of the torque information and/or the coefficient of friction information are determined and evaluation information describing these two minima is formed, with the at least two local minima each not including the at least one pulse event of the actuator, is performed. A first local minimum can be located between a starting point or an initial impulse event and a “first” impulse event and a further minimum between the first impulse event and another impulse event. In other words, the minima lie between two impulse events and thus represent a variable that is related to the transition from the static friction effect that initially occurs when restarting after the impulse event to the subsequent phase that predominantly or exclusively has a sliding friction effect.

For example, a rotation angle range value is defined for a determination phase, the rotation angle range value being defined as the rotation angle that occurs between two consecutive switch-off or deceleration events, i. H. Impulse events, the actuator results in executing the mode of operation of an impulse wrench. A first switch-off event can thus take place at a first angle of rotation value, e.g. B. at 70 ° angle of rotation, and a further switch-off event at a second angle of rotation value, z. B. at 210 ° result. It can be expedient if the range between the first and the second angle of rotation value is defined as the angle of rotation range value, it being preferable for the range to be reduced at the edges of the angle of rotation range, so that any influences on the immediate edge area are removed from the observation range or disregarded remain. This can be used to filter out or disregard any incorrect values, particularly for determining the local minimum. Thus the influence of the impulse events for the determination of the local minima within the considered areas, i. H. within the rotation angle range values, avoided.

Provision can be made, for example, for a maximum of 10%, preferably a maximum of 7.5%, particularly preferably a maximum of 5.0%, most preferably a maximum of 3.5%, more preferably a maximum of 2.5%, of the rotational angle range between two pulse events to be at least an edge area, in particular on both edges, of the rotation angle area for an observation area for determining the local minimum of the torque information and/or the determined coefficient of friction information are not taken into account and/or are disregarded. This means that any values of the pulse event that falsify influences are not taken into account when determining the local minimum of the torque information and/or the coefficient of friction information, and a statement on the static friction behavior of the screw connection is thus made possible.

If several local minima are determined or identified, an arithmetic mean and/or a median of at least two, preferably at least three, particularly preferably at least four, most preferably from all local minima recorded for a screw connection can be used to form the evaluation information the torque information and/or the coefficient of friction information are formed. It is also possible in the evaluation information to include the minimum values with a factor in a combined characteristic value, with each minimum value being taken into account a rotational angle range value of the rotational angle range assigned to the respective minimum value. For example, the angle of rotation ranges, which lie between two impulse events, can shorten until a final tightening point of the screw connection is reached. When considering the length or size of the angle of rotation ranges for the respective local minimum values recorded in the respective angle of rotation ranges, a further influencing variable that characterizes the specific screwing process can be taken into account in a later evaluation or in a quantification.

It is possible that the coefficient of friction information is evaluated by forming an integral from (a) the curve of a coefficient of friction of the coefficient of friction information and/or (b) the curve of a torque of the torque information and (c) the angle of rotation, in particular the coefficient of friction of the coefficient of friction information or the torque of Torque information about the angle of rotation takes place. By forming the integral, another variable that can be easily determined for the quantitative evaluation of the screw connection can be formed.

As an alternative or in addition to forming an integral, the friction information can be evaluated by determining a local maximum and/or a slope of a friction coefficient/angle of rotation diagram and/or a torque/angle of rotation diagram and this maximum value and/or these Slope is used to characterize a proportion of static friction and/or a transition from static friction to sliding friction during impulse screwing of the screw connection. The local maximum can be located, for example, between an impulse event and a subsequent local minimum in time. For example, a gradient between the local maximum and the local minimum can be determined.

The actuator can, for example, transmit a single drive pulse to the screw means in order to determine the coefficient of friction of the screw connection. In other words, provision can be made for the evaluation to be carried out using a single screw pulse. This reduces the load on the detection devices to a minimum. To determine the influence of static friction on a screw connection, the evaluation of the restart behavior after just a single pulse event can be sufficient. It is possible to use reference values or reference models to calculate progressive behavior of the course of the coefficient of friction based on the detection of the restart after the single impulse event.

Alternatively, the actuator can transmit only two or only three or only less than twenty or only less than twelve or only less than ten drive pulses or pulse events to the screw means to determine the coefficient of friction of the screw connection. Even with these numbers of impulse events, the evaluation of the restart behavior can be averaged or weighted or unweighted in at least one parameter in the individual restart scenarios after the respective (few) impulse events to determine the influence of static friction on the screw connection.

In an analysis step for determining a static friction component of the screwing-in process describing static friction information, for example, based on the friction coefficient information and/or the torque information, an analysis can be carried out such that values characterizing the static friction influence are selected and/or evaluated in order to determine the static friction influence and/or the transition between static friction - To depict and thus to quantify and/or to determine the characteristics of sliding friction during the screwing process, in particular during the restart of the actuator after an impulse event.

It is possible for an item of advisory information to be output as a function of a comparison of the coefficient of friction information with predefined reference coefficient of friction information. The coefficient of friction reference information, in particular as a function of rotational angle values and/or torque values, can indicate that a coefficient of friction for a screw connection is too high. Optionally, the advisory information can contain instructions for action, according to which, depending in particular on defined parameter values of the screw connection, a change in the screw means and/or the mating thread and/or the use or application of a lubricant to the contact area of the screw means and mating thread is displayed. The action information can, for example, be dependent on at least one operating parameter information item describing at least one operating parameter of the actuator. Operating parameter comparison information is preferably taken into account, which depicts at least one comparison of operating parameter information with reference operating parameter information. Alternatively or additionally, the action information can be dependent on at least one parameter value of the screw connection, so that action information taking this circumstance into account can be output depending on the material and/or condition (e.g. surface condition or coating).

In addition to the method for determining a coefficient of friction of a screw connection, the invention also relates to a device for testing a screw connection using a method described herein. The device can, for example, comprise an actuator which is operated as an impulse wrench or executes the mode of operation of an impulse wrench and consequently, like an impulse wrench, acts in a torque-transmitting manner on a screwing means. Furthermore, the device comprises a torque detection device that detects a torque acting on the screw means and a preload force detection device that detects a preload force of the screw connection.

All advantages, details, designs and/or features of the method according to the invention can be transferred or applied to the device according to the invention and vice versa.

• 1 eine Prinzipdarstellung eines Diagramms, welches die erfasste Vorspannkraft, das Drehmoment und den Drehwinkel darstellt;
• 2 eine Prinzipdarstellung einer aus den Werten des Diagramms nach 1 ermittelten und in Diagrammform dargestellten Reibwertinformation, welche den Reibwert bzw. die Reibzahl über den Drehwinkel ausgibt;
• 3 eine Prinzipdarstellung einer Vorrichtung zur Ausführung eines Verfahrens zur Ermittlung der Reibzahl einer Verschraubung;
• 4 eine schematische Darstellung eines Verfahrens zur Ermittlung der Reibzahl einer Verschraubung.

The invention is explained in more detail using exemplary embodiments in the drawings. It shows:

• 1 a schematic diagram of a diagram showing the detected preload force, the torque and the angle of rotation;
• 2 a schematic representation of one of the values of the diagram 1 friction coefficient information determined and presented in the form of a diagram, which outputs the coefficient of friction or the coefficient of friction over the angle of rotation;
• 3 a schematic diagram of a device for performing a method for determining the coefficient of friction of a screw;
• 4 a schematic representation of a method for determining the coefficient of friction of a screw connection.

The basic steps of method 1 for determining a coefficient of friction of a screw connection 2 are in 4 The following method steps are carried out: (a) Execution 100 of a screwing-in process, with an actuator 3 applying a torque 4 to a screw means 6 to be screwed into a counter-thread 5 and the actuator 3 being operated as an impulse screwdriver, (b) detecting 101 a torque 4 acting on the screw means 6 and generating torque information 20 and (c) detecting 102 a prestressing force 7 describing a prestressing force 7 of the screw connection 2 and generating prestressing force information 21. Based on this, a friction value information item 22 depicting a friction value of the screw connection 2 is determined 103 in Dependency of the torque information 20 and pretensioning force information 21.

The method can optionally include detecting 104 a rotation angle 8 and generating rotation angle information 23 describing the detected rotation angle 8 and assigning the rotation angle information 23 to the torque information 20 and/or to the prestressing force information 21 . Torque information 23 depicting a progression of the torque 4, in particular via the angle of rotation 8, and/or pretensioning force information 21 depicting a progression of the preload force 7, in particular via the angle of rotation 8, is preferably generated and output. The torque information 20 and/or the prestressing force information 21 can in this case include the rotational angle information 23 as its component.

In an optional method step, at least one local minimum 9 of the torque 4 can be determined 105 in the course of the torque information 23 via the executed angle of rotation 8 and outputting minimum torque information 24 relating to the at least one local minimum 9 of the torque 4 . As an alternative or in addition, at least one local minimum 9 of the coefficient of friction can be determined 105 in the course of the coefficient of friction information 22 via the angle of rotation 8 performed and output of minimum friction coefficient information 25 relating to the at least one local minimum 9 of the coefficient of friction. How from the 2 As can be seen, the local minimum 9 can be localized in the first tenth of the rotation angle range between a first and a further pulse event 10, 10'. It is possible that individual or all method steps comprising a determination 103, 105 (a) are carried out in a partially automated or fully automated manner and/or (b) are carried out on the basis of computer-implemented methods.

Also is off 2 It can be seen that the coefficient of friction drops shortly after the impulse event 10, i.e. shortly after the torque 4 has been transferred from a significantly reduced or completely canceled drive state of the actuator 3 to a renewed drive state, see arrow 14. This reduction in the coefficient of friction, which is due to a falling torque 4, is due to the fact that after a torque 4 is applied again, the actuator 3 must first “work” against the static friction that occurs in the temporary idle state of the screw means/counterthread pairing. in the in 2 In the diagram shown, after the local minimum 9 (here: approx. at an angle of rotation of 85°), a continuous course and increase in the torque or the coefficient of friction can be seen, which then indicates a subordinate or non-existent influence of any static friction and a predominant one or total influence of sliding friction.

The at least one determined local minimum 9 can be determined, for example, in the course of the torque information 23 and/or friction value information 22 between two pulse events 10, 10' of the actuator 3. In particular, it can be provided that to determine the coefficient of friction, recorded values are taken into account which have at least one predefined and subsequent position to an impulse event 10, 10'. For example, a rotation angle range of 28 to 8°, preferably up to 5°, particularly preferably up to 3.5°, most preferably up to 2.5°, more preferably up to 1.5°, after the impulse event 10, 10' can remain unconsidered.

It is also possible to determine a local maximum 15 which is after an impulse event 10, 10' and before a local minimum 9 that has been determined. For example, to determine the Friction coefficient values that lie between the impulse event 10 and the local maximum 15 are not taken into account. An evaluation can also take place between the local maximum 15 and the subsequent local minimum 10 and, in particular exclusively, based on an evaluation of values that lie between the local maximum 15 and the local minimum 10, the coefficient of friction or the coefficient of friction information 22 can be determined to be executed.

Preferably, for example, at least two local minima 9 of the torque information 23 and/or the coefficient of friction information 22 can be determined 105 and evaluation information 26 describing these two minima 9 can be formed, with the at least two local minima 9 each not representing the at least one pulse event 10, 10' of the Actor 3 includes.

In an optional development, it may prove useful if, to form the evaluation information 26, an arithmetic mean and/or a median of at least two, preferably at least three, particularly preferably at least four, local minima 9 and/or local maxima 15 of the Torque information 23 and/or the coefficient of friction information 22 is formed.

Optionally, the coefficient of friction information 22 can be evaluated by forming an integral from the curve of a coefficient of friction of the information item 22 of friction coefficient and the angle of rotation 8 , in particular the coefficient of friction of the coefficient of friction information 22 over the angle of rotation 8 . In this way, the area below the torque curve over the rotation angle 8 and/or the friction coefficient curve over the rotation angle 8 can be considered in the evaluation and in particular in the quantification of an influence of static friction on the screwing process and/or on the screw connection 2.

The actuator 3 can, for example, transmit a single drive pulse to the screw connection and thus to the screw means 6 in order to determine the coefficient of friction of the screw connection 2 . In other words, the determination of the coefficient of friction includes a single pulse event 10, 10' of the actuator 3 driving the screw means 6.

In an optional analysis step 106, static friction value information 27 describing a static friction component of the screwing-in process can be determined based on the friction value information and/or the torque information 23, for example. In this case, this can be done in particular on the basis of minimum friction value information 25 and/or minimum torque information 24 and/or evaluation information 26 .

In 3 1 shows a device 11 for testing a screw connection 2 while executing a method 1 described herein, the device comprising an actuator 3 which can be operated as an impulse wrench. The actuator 3 is thus able to drive a screw means 6 in the manner of an impulse screwdriver for screwing into a counter-thread 5 . Furthermore, the device 11 comprises a torque detection device 12 that detects a torque 4 acting on the screw means 6 and a preload force detection device 13 that detects a preload force 7 of the screw connection 2. The preload force device 13 is designed, for example, in such a way that between a contact plate 16 and the element 17 having the mating thread 5 Detecting means 18, 18' detecting compressive forces are placed, the compressive force detected in this way mapping the prestressing force 7 prevailing in the screw connection and in particular in the screwing means. In this case, the pretensioning force detection device 13 can be designed in such a way that there is at least extensive, in particular complete, decoupling of the detection means 18, 18′ with regard to rotational movement components of the screwing process. In other words, the detection means 18, 18' are mounted in such a way that they are not twisted or twisted and are therefore not subjected to a torque 4, but only detect an axially acting force component.

Furthermore, the device 11 can include a rotation angle detection device 19 which is set up to describe or specify the rotation angle θ of the screwing means 6 during the screwing process.

Reference List

1

Proceedings

2

screw connection

3

actuator

4

torque

5

counter thread

6

screw means

7

preload force

8th

angle of rotation

9

local minimum

10, 10`

impulse event

11

contraption

12

torque detection device

13

preload force detection device

14

arrow (waste)

15

local maximum

16

attachment plate

17

element

18, 18`

detection means

19

rotation angle detection device

20

torque information

21

preload information

22

friction coefficient information

23

torque information

24

Torque minimum information

25

Friction minimum information

26

evaluation information

27

Static friction information

28

rotation angle range

100

Carry out

101

Capture 4

102

Capture 7

103

Determine

104

Capture 8

105

Identify 9

106

analysis step

Claims (11)

Method (1) for determining a coefficient of friction of a screw connection (2), with the following method steps: - Execution (100) of a screwing-in process, with an actuator (3) applying a torque (4) to a screwing means (6) to be screwed into a counter-thread (5) and the actuator (3) being operated as an impulse screwdriver, - detecting (101) a torque (4) acting on the screw means (6) and generating torque information (20); - detecting (102) a prestressing force (7) describing a prestressing force (7) of the screw connection (2) and generating prestressing force information (21), - Determining (103) a friction value of the screw connection (2) imaging friction value information (22) as a function of the torque information (20) and prestressing force information (21). Method (1) according to claim 1 , characterized by detecting (104) a rotation angle (8) and generating a rotation angle information (23) describing the detected rotation angle and assigning the rotation angle information (23) to the torque information (20) and/or to the pretensioning force information (21), preferably one Torque information (23) depicting the progression of the torque (4), in particular via the angle of rotation (8), and/or pretensioning force information (21) depicting a progression of the pretensioning force (7), in particular via the angle of rotation (8), is generated and output. Method (1) according to claim 1 or 2 , characterized by determining (105) at least one local minimum (9) of the torque (4) in the course of the torque information (23) about the executed angle of rotation (8) and outputting the at least one local minimum (9) of the torque (4). Torque minimum information (24). Method (1) according to one of the preceding claims, characterized by determining (105) at least one local minimum (9) of the coefficient of friction in the course of the coefficient of friction information (22) about the angle of rotation (8) carried out and outputting the at least one local minimum (9) minimum information (25) relating to the coefficient of friction. Method (1) according to claim 3 or 4 , characterized in that the at least one determined local minimum (9) is determined in the course of the torque information (23) and/or friction value information (22) between two pulse events (10, 10') of the actuator (3). Method (1) according to one of claims 3 until 5 , characterized by determining (105) at least two local minima (9) of the torque information (23) and/or the friction value information (22) and forming evaluation information (26) describing these two minima (9), the at least two local minima (9 ) does not include the at least one impulse event (10, 10') of the actuator (3). Method (1) according to claim 6 , characterized in that to form the evaluation information (26) an arithmetic mean and / or a median of at least two, preferably at least three, particularly preferably at least four, local minima (9) of the torque information (23) and / or the friction information (22) is formed. Method (1) according to one of the preceding claims, characterized by evaluation the coefficient of friction information (22) by forming an integral from the course of a coefficient of friction of the coefficient of friction information (22) and the angle of rotation (8), in particular the coefficient of friction of the coefficient of friction information (22) over the angle of rotation (8). Method (1) according to one of the preceding claims, characterized in that the actuator (3) transmits a single drive impulse to the screw means (6) in order to determine the coefficient of friction of the screw connection (2). Method (1) according to one of the preceding claims, characterized by an analysis step (106) for determining static friction information (27) describing a static friction component of the screwing process, starting from the friction information and/or the torque information (23). Device (11) for testing a screw connection (2) using a method (1) according to one of the preceding claims, characterized by - an actuator (3) which is set up to be operated as an impulse wrench and to drive a screw means (6), - a a torque detection device (12) that detects the torque acting on the screw means (6), and - a preload force detection device (13) that detects a preload force (7) of the screw connection (2).

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