Abstract: A sensor module mounted on a vehicle body includes a base plate, a sensor and a signal processing unit. The sensor includes a plurality of piezoelectric films for detecting an external force applied to the vehicle body. The signal processing unit is connected to the sensor for processing sensor signals output from the sensor. The sensor and the signal processing unit are attached to the base plate.

Abstract: The present invention provides systems and methods that can provide a high g-force to a test specimen. An exemplary system of the present invention includes a beam, rigidly fixed at one or both ends, on which a test specimen can be mounted. A loading device is preferably provided that can load the beam by using a ceramic column positioned between the beam and the loading device. A flywheel that has a cutter that can be deployed on command while the flywheel is rotating to fracture the ceramic column is also provided. The present invention also provides systems and methods for controllably damping the oscillation of a loaded beam at some point after the load on the beam is released to produce a high g-force event. For example, a damping device of the present invention may be engaged after the completion of the high g-force event. Such damping can prevent subsequent ringing or oscillation of the beam without affecting the magnitude of the high g-force event.

Abstract: A hybrid impact sensor and method of operating the same. One sensor includes a support containing one or more mounts; a first sensor with first sensing properties and configured to generate a first output signal; a second sensor with second sensing properties and configured to generate a second output signal, wherein the second sensing properties are different from the first sensing properties; and a housing encasing the first sensor and the second sensor.

Abstract: An impact test apparatus includes a holding device for holding a test piece at an arbitrary holding force, an impact applying device for applying an impact force to the test piece held by the holding device, a force sensor for sensing the impact force applied to the test piece by the impact applying device, a high-speed camera for detecting a displacement of the test piece when applied with the impact force by the impact applying device, and an output device for synchronizing a signal from the force sensor with a signal from the high-speed camera and outputting an impact stress-strain characteristic curve when the impact force is applied to the test piece.

Abstract: The present invention provides systems and methods that can provide a high g-force to a test specimen. An exemplary system of the present invention includes a beam, rigidly fixed at one or both ends, on which a test specimen can be mounted. A loading device is preferably provided that can load the beam by using a ceramic column positioned between the beam and the loading device. A flywheel that has a cutter that can be deployed on command while the flywheel is rotating to fracture the ceramic column is also provided. The present invention also provides systems and methods for controllably damping the oscillation of a loaded beam at some point after the load on the beam is released to produce a high g-force event. For example, a damping device of the present invention may be engaged after the completion of the high g-force event. Such damping can prevent subsequent ringing or oscillation of the beam without affecting the magnitude of the high g-force event.

Abstract: A sheet material detecting device for identifying the material of a sheet by utilizing an impact applied to the sheet has an impact applying unit which is supported to be rotatable and shiftable toward the sheet, and applies an impact onto the sheet, an impact receiving unit which is supported to be rotatable and shiftable in a state of being in contact with the sheet onto which the impact has been applied, arranged opposite the impact applying unit with a gap permitting the passage of the sheet in-between, and receives via the sheet the impact applied by the impact applying unit onto the sheet, and a signal output unit which outputs a signal in response to the impact applied onto the sheet.

Abstract: An anthropomorphic dummy head system is provided for measuring forces and moments applied to the back of the head and neck. The system includes a dummy head representing at least a portion of a human head and a force measuring device connected with the dummy head. The system also includes a skull cap attached to the force measuring device. The skull cap, representing a rear portion of a human head, may be free from direct attachment to the dummy head. The skull cap may further include a lower extension or nape extension configured to represent the back of a human neck.

Abstract: A multi-directional shock sensor including two masses arranged to move in directions, which are mutually perpendicular to one another. A moveable locking member prevents movement of a slider, which is used in the arming arrangement of a submunition. In response to an acceleration in a plane, one or both masses will move. The masses are operably coupled to the locking member to effect its movement out of its locking engagement with the slider, due to such acceleration.

Abstract: Certain example embodiments of the present invention provide a method for detecting a substrate crack by simple equipment and steps. A substrate crack inspecting method may include the steps of (1) producing a sound by providing vibration to a substrate, (2) determining a power spectrum by capturing the produced sound and carrying out an acoustic analysis for the captured sound, and (3) judging whether or not a substrate crack exists based on a spectral intensity of a predetermined frequency region.

Abstract: Method and device for sensing stress waves. One embodiment is a method that includes providing a bendable support with one or more mounts each located at an end of the support; attaching a semiconductor element containing a plurality of piezoresistors, each having impedance, to the support; connecting the support to the component by the mounts of the support; and sensing the impedance of the plurality of piezoresistors.

Abstract: A vehicle component test method includes measuring first acceleration data at discrete locations on a first vehicle frame during an actual road test of a first vehicle and measuring second acceleration data at the discrete locations on a second vehicle frame of a second vehicle mounted on a test fixture. The second acceleration data is compared to the first acceleration data and an acceleration error is generated. The test fixture is adjusted based on the acceleration error until the acceleration error is within a predetermined range.

Abstract: A multi-directional shock sensor having a central post surrounded by an omnidirectionally moveable toroidal mass. A plurality of anchor members surrounds the mass and carries one arm of a latching arm assembly. The other arm of each latching arm assembly is carried by, and radially extends from the mass to oppose a respective first arm. A shock event will cause the mass to move in a certain direction to an extent where one or more of the arm assemblies will latch. The latching may be determined by an electrical circuit connected to contact pads on the central post and on the anchor members.

Abstract: The present invention comprises an automated machine for testing the physical properties of spherical objects. Preferably, the apparatus comprises a firing mechanism that includes an inner and outer barrel. An object inside the firing mechanism is propelled towards a striking surface that faces the firing mechanism. Two sensors located at predetermined points between the firing mechanism and the striking surface measure the inbound and outbound velocity of the object. A computing device then uses an algorithm to determine the COR of a given set of objects. An angular device uses gravity to direct the objects to a retrieval chute, which uses a tubing system to direct the objects for re-testing or collection.

Abstract: The invention concerns a method for filtering signals (Vin) generated by a piezo-electric type accelerometer in response to detection of a shock applied to an object to which the accelerometer is connected, this method characterised in that it ensures, during a particular step, that the signal (Vin) generated by the accelerometer, after having increased and exceeded a first threshold value (VTH,ON) decreases and becomes lower than a second threshold value (VTH,OFF) lower than the first threshold value (VTH,ON) after a period of time (TP,ON) greater than a minimum period of time (TP,ON,MIN) and less than a maximum period of time (TP,ON,MAX). The invention also concerns a device for filtering signals generated by an accelerometer in response to detection of a shock applied to an object connected to the accelerometer. Finally, the invention concerns a portable object such as a wristwatch including a detection device of this kind.

Abstract: An instrument (“artificial athlete”) for characterizing, from the biomechanical standpoint, a treading surface, such as natural grass cover or synthetic grass flooring, is configured for: dropping a weight from a given height on the surface, producing the conversion of kinetic energy of falling of the weight into deformation energy of the surface, the deformation energy being able to be restored by the surface to the weight, bringing about its return/bouncing back upwards; and detecting at least one parameter representing the process of restitution of the deformation energy by the surface to the weight, the parameter identifying the characteristics of tread of the surface.

Abstract: An impact resistant portable personal computer apparatus having feet which support the personal computer, a protruding member protruding downwardly from a foot, an impact sensor in the personal computer and responsive to an impact on the member for providing an output, and an element responsive to the output for aborting an operation of the personal computer. The apparatus is responsive to a fall in which the personal computer pivots about the back feet and impact is transmitted through the front feet.

Abstract: A sheet material type detecting method for detecting a sheet material type has the steps of applying tension to at least a part of a sheet material, bounding an impact applying part on the part applied with the tension, a period detecting step of determining a period from a collision of the impact applying part with the sheet material to a specific state, and a sheet material identifying step of detecting a type of the sheet material based on the period.

Abstract: A magnetic disk device protection mechanism comprises a sensor that acquires information on changes in the environment of a magnetic disk device, a sensor driver, a shock manager that analyzes the information acquired by the sensor driver together with a history of the information to determine the status where the magnetic disk device is used to predict a shock, and an HDD filter driver that controls operations of the magnetic disk device including the escape of a magnetic head. The magnetic disk device can also comprise a diagnosis processing section that operates if a shock has occurred actually, to check whether or not the magnetic head could have completely escaped before the occurrence of this shock to carry out diagnosis as to whether or not a fault is occurring in the magnetic disk.

Abstract: A viscoelastic characteristic value-measuring apparatus, using a split Hopkinson's bar, having an impact bar, input bar, and an output bar. The input bar has a first strain gauge and a second strain gauge. The output bar has a third strain gauge and a fourth strain gauge. The input bar and the output bar are made of a viscoelastic material, and a specimen is in between the input bar and the output bar. The length of said output bar is set to a range from 500 mm to 2500 mm both inclusive. The length of said input bar is set to a range from 1500 mm to 2500 mm both inclusive.

Abstract: A method for measuring the acoustic damping capacity of a material or structure, such as a layered honeycomb structure, comprises tapping the honeycomb structure with a tapping rod. The tapping action imparts mechanical energy to the honeycomb structure. The method further comprises measuring, for a time interval, energy reflected from the honeycomb structure as a result of the tapping. The method further comprises creating a time-energy profile based on the energy reflected from the honeycomb structure during the time interval. The method further comprises evaluating the time-energy profile to determine the acoustic damping capacity of the honeycomb structure.

Abstract: A method for measuring the acoustic damping capacity of a material or structure, such as a layered honeycomb structure, comprises tapping the honeycomb structure with a tapping rod. The tapping action imparts mechanical energy to the honeycomb structure. The method further comprises measuring, for a time interval, energy reflected from the honeycomb structure as a result of the tapping. The method further comprises creating a time-energy profile based on the energy reflected from the honeycomb structure during the time interval. The method further comprises evaluating the time-energy profile to determine the acoustic damping capacity of the honeycomb structure.

Abstract: A control system is operable to selectably activate shock damping devices associated with a bicycle so as to eliminate bobbing encountered under extreme pedaling conditions. The system includes a crank axle torque detector which operates to detect a level of torque applied to a crank axle and provide a control signal corresponding to the level of torque. A shock damping device is coupled to the frame of the cycle, and functions to absorb and dampen mechanical shocks communicated to the frame. The shock damping device includes an activator for controlling its damping function. The activator is operable to receive the control signal from the crank axle torque detector and control the shock damping device in response thereto. The control signal may be an electrical or a mechanical signal.

Abstract: An apparatus and method for determining the shock characteristic of a suspension having a proximate portion, a distal portion and a spring portion therebetween has a rotatable structure having a mount for the suspension base portion such that the suspension distal portion is cantilevered over the rotatable structure, and a sensor carried on the rotatable structure for sensing the displacement of the suspension distal portion relative to the suspension proximate portion under shock load from centrifugal force imparted to the suspension by the rotatable structure. The shock characteristic value is determinable from the displacement value.

Abstract: In a method of detecting damage in materials or objects (4) the material or object is physically influenced to produce a physical change of the material or object inducing transient slow dynamics in case of damages in the material or object. Slow dynamics induced material elastic modulus changes are detected as indication of damages of the material or object. In a device for non-destructive detection of damage in materials or objects (4), an impact source (16) is provided to impact the material or object to physically influence the material or object to produce a physical change of the material or object inducing transient slow dynamics in case of damages in the material or object. A detector (2,8,10,12,14,6) is provided to detect by said slow dynamics induced material elastic modulus changes as indications of damages of the material or object.

Abstract: An electronic apparatus is provided that comprises a shock detector for detecting a shock received by an electronic apparatus such as a portable telephone, a controller for comparing the value of the shock as detected by the shock detector with a reference value, and a memory element for storing an identifying signal generated when the value of a shock has exceeded the reference value and the value of shock. This enabling easy determination as to whether or not a breakdown has been caused by shock.

Abstract: An inertial sensor with failure threshold includes a first body and a second body, which can move relative to one another and are constrained by a plurality of elastic elements, and a sample element connected between the first body and the second body and shaped so as to be subjected to a stress when the second body is outside of a relative resting position with respect to the first body. The sample element has at least one weakened region. The sensor may also include additional sample elements connected between the first and second bodies.

Abstract: A method for detecting cracks in a honeycomb structure includes the steps of: placing the honeycomb structure on the upper face of a first plate with the two end faces of the honeycomb structure facing up and down, respectively; applying to the honeycomb structure impact load adequately heavy to make powdery substance fall off the cracked portions of the honeycomb structure; and detecting the powdery substance having fallen off the cracked portions. The method enables the detection of cracks in the honeycomb structure to be simpler and easier and the honeycomb structure to be hardly damaged.

Abstract: A method for measuring the acoustic damping capacity of a material or structure, such as a layered honeycomb structure, comprises tapping the honeycomb structure with a tapping rod. The tapping action imparts mechanical energy to the honeycomb structure. The method further comprises measuring, for a time interval, energy reflected from the honeycomb structure as a result of the tapping. The method further comprises creating a time-energy profile based on the energy reflected from the honeycomb structure during the time interval. The method further comprises evaluating the time-energy profile to determine the acoustic damping capacity of the honeycomb structure.

Abstract: A device for testing the rebound quality of a golf ball is described. The device includes a substrate of hard, dense material with a level, flat upper surface, the substrate being attached to an accelerometer that is capable of sensing the impact of a golf ball dropped onto the substrate's upper surface. In turn, the accelerometer is connected to a pulse period measuring module capable of determining the period of time between successive impacts as the golf ball freely and repeatedly bounces against the substrate. Further, a computational module capable of determining from three or more successive bounces the mechanical loss the golf ball experiences on each bounce. Three successive impacts against the substrate result in two time period measurements. The first time period is that which elapses between the first and second impacts and the second time period is that which elapses between the second and third impacts.

Abstract: An impact force is applied to a sensing element to enlarge the size of a hidden crack to a visible level to reveal the presence of a hidden crack. To apply the impact force to a sensing element, a gas sensor is supported by a holder which is fixed to a distal end of a shaft. The shaft swings about a proximal end thereof serving as a pivot. The holder, with the gas sensor held at its end, is released from a predetermined higher position so as to swing downward about the pivot of the shaft due to gravity. The holder hits a striking plate disposed on a swing path of the holder.

Abstract: A device and a method, which, upon triggering of the restraint devices via a control device, allow a systematic testing of the triggering characteristics of restraint devices in a motor vehicle under conditions as realistic as possible. For that purpose, the device includes an ambiency simulator, connectable to the control device, for stipulating defined peripheral states, an acceleration device for accelerating the control device, a detector for recording the triggering characteristics of the restraint devices in response to acceleration of the control device, and an evaluator for evaluating the recorded triggering characteristics. In accordance with the method, the control device is programmed for a particular constellation of restraint devices. A defined peripheral state is predefined for the control device thus programmed with the aid of an ambiency simulator. The control device is then accelerated, in this manner provoking a triggering of the restraint devices.

Abstract: A vehicle impact testing device (10, 100, 500) is provided with a towing device (16, 116, 516) for running a test car (11) along a running road surface (12, 112, 521) to collide with a barrier (13, 113, 513). The towing device is movably suspended from a pair of guide rails (26, 126, 514) received in a recess (15, 115, 523) formed below the running road surface. The towing device is disposed between the guide rails, thereby making effective use of the space between the guide rails. Further, the towing device is disposed at a position below the running road surface, so that it does not interfere with the running of the test car.

Abstract: An instrumented torso model that simulates anatomical features and measures the effects on a body caused by various types of impacts. Simulated bone having material properties similar to that of healthy human bone is surrounded by simulated tissue. At least one sensor array is attached to either or both of the simulated bone and the simulated tissue for measuring the effects of the impacts.

Abstract: An ice ball launcher simulates the impact of a storm-generated hailstone falling onto a test specimen or structural component exhibit such as a roofing shingle, skylight, automobile panel, aircraft fuselage panel, aircraft wing panel and the like. The launcher includes a tripod base, a rail, a sled, an ice ball holder cup, a manually operable trigger latch assembly, an elastic band and a laser beam aiming device. The ice ball launcher consistently and repeatably projects ice balls at a predetermined velocity and impact energy onto the component sample. The velocity of each ice ball is measured as it transits from the ice ball launcher to the installation mockup, verifying that the ice ball velocity is within a predetermined velocity tolerance range. The measured velocity and known mass of the ice ball are used to calculate the kinetic impact energy on the component sample material, and to determine whether the calculated impact energy is within a predetermined impact energy tolerance range.

Abstract: The present invention discloses a method for evaluating the sound speed and dynamic modulus of elasticity of wood by non-destructive stress wave testing, wherein a timber specimen of long post is placed steadily on a sensor near the center with friction, acting on the interfaces of the sensor and the timber specimen, which resists the timber specimen from moving. Pounding one end of the timber specimen with a striking instrument sends a compression pulse stress wave down the post toward the other end, thereby generating a tension pulse wave back along the post till friction exponentially dissipates the energy of the stress waves. The changing signals of friction received by a receiver support the analyzer to measure longitudinal fundamental frequency of timber specimen; therefore, sound speed and dynamic modulus of elasticity are then calculated.

Abstract: A sheet material type detecting method for detecting a sheet material type has the steps of applying tension to at least a part of a sheet material, bounding an impact applying part on the part applied with the tension, a period detecting step of determining a period from a collision of the impact applying part with the sheet material to a specific state, and a sheet material identifying step of detecting a type of the sheet material based on the period.

Abstract: In a method of detecting damage in materials or objects (4) the material or object is physically influenced to produce a physical change of the material or object inducing transient slow dynamics in case of damages in the material or object. Slow dynamics induced material elastic modulus changes are detected as indication of damages of the material or object. In a device for non-destructive detection of damage in materials or objects (4), an impact source (16) is provided to impact the material or object to physically influence the material or object to produce a physical change of the material or object inducing transient slow dynamics in case of damages in the material or object. A detector (2,8,10,12,14,6) is provided to detect by said slow dynamics induced material elastic modulus changes as indications of damages of the material or object.

Abstract: A method for measuring the acoustic damping capacity of a material or structure, such as a layered honeycomb structure, comprises tapping the honeycomb structure with a tapping rod. The tapping action imparts mechanical energy to the honeycomb structure. The method further comprises measuring, for a time interval, energy reflected from the honeycomb structure as a result of the tapping. The method further comprises creating a time-energy profile based on the energy reflected from the honeycomb structure during the time interval. The method further comprises evaluating the time-energy profile to determine the acoustic damping capacity of the honeycomb structure.

Abstract: A damage detection device is used to detect damage in bonded and laminated composite structures. A tap hammer or tap coin containing an acceleration sensor is connected to a circuit that can measure the width of an impact signal and then display the result. The result correlates to local stiffness of a structure. A method of determining the desired signal width and the method of using the damage detection device, includes tapping a known good region and then tapping a suspect region. Readings from the two areas are used to determine whether the suspect region is within an acceptable range. The circuit determines the desired signal width by measuring from the time the impact signal exceeds a threshold to the time it falls below the threshold.

Abstract: A damping performance evaluation apparatus for damping devices including: a support member detachably supporting a damping device in a state enabling the device to exhibit a damping effect thereof; a hammer member for applying oscillation force to the device caused by gravitational descent to strike the device; a double-strike preventing member for preventing the hammer member from dropping a second time due to rebound after initially striking the device, to prevent double-strike of the device by the hammer member; a vibration sensor installed at a vibration zone caused to vibrate through oscillation force applied by said hammer member, for outputting an electrical signal in response to vibration at the vibration zone; and a sensing member for sensing a vibration mode in the vibration zone on the basis of an output of said vibration sensor. A damping performance evaluation method is also disclosed.

Abstract: A collision protection system for protecting a pedestrian that uses a sensor that provides a width output signal that varies in relation to the width of an object contacting the vehicle. The sensor includes a resistive conductor that is shorted out by a conductive conductor of a portion of the length of the resistive conductor. A second sensor may be provided that provides an output only upon exceeding an impact threshold. Several sensors may be used to provide an indication of the location and width of the object contacted.

Abstract: The present invention generally relates to a tensile impact apparatus that is designed to give dynamic stress-strain curves and fracture characteristics for a rubber specimen undergoing tensile impact loading. More particularly, this invention relates to a tensile impact apparatus that is capable of achieving strains of up to fracture. The apparatus is also capable of visually recording fracture phenomena.

Abstract: An impact sensor for indicating exposure of an electronic equipment to a predetermined impact force is described. The impact sensor has a hollow case, a mass within the case, and a number of wire filaments supporting the mass within the case. Exposure of the sensor to the predetermined impact force results in a force acting on the mass sufficient to cause at least one of the filaments to break. The breaking of at least one of the filaments indicates to a repairer that the electronic equipment has been exposed to the predetermined impact force.

Abstract: A gravelometer (20) includes a base unit (30) comprising compressed air receiver tank (40) having wheels (42) and feet (44). Main frame (46) connects tank (40) to a media gun frame or mount (50) and includes a bore (52) for releasably receiving and supporting a media gun (54) having a mounting flange (70) so that media inlet (56) is upwardly oriented and gun barrel or media outlet (57) extends through gun mount (50). Media inlet (56) interconnects via elongated con-duit (58) to a media supply system (60) which includes media supply hopper (62) and vibratory feeder assembly (64). A control system (80) having operator control panel (82) controls operations. A modular target box or chamber (90) is aided in being releasably connected to base unit (30) by locator pins (102). Chamber (90) includes media inlet (92), media outlet (94), which connects to spent media reclaim chamber (100), and specimen window (96) having a target holding toggle clamp (98).

Abstract: In a viscoelastic characteristic value-measuring apparatus, using a split Hopkinson's bar, a first strain gauge (7) and a second strain gauge (9) are installed on an input bar (3) which is hit with a impact bar. A third strain gauge (11) and a fourth strain gauge (13) are installed on an output bar (5) which is connected with the input bar (3) through a specimen (20) put between the input bar (3) and the output bar (5). The length of the input bar is set to not less than 1000 mm nor more than 2500 mm. The length of said output bar is set to not less than 700 mm nor more than 2200 mm. The propagation speed of a strain in the input bar and the output bar is set to not less than 1200 m/s nor more than 1800 m/s.

Abstract: The present invention comprises an automated machine for testing the physical properties of spherical objects. Preferably, the apparatus comprises a firing mechanism that includes an inner and outer barrel. An object inside the firing mechanism is propelled towards a striking surface that faces the firing mechanism. Two sensors located at predetermined points between the firing mechanism and the striking surface measure the inbound and outbound velocity of the object. A computing device then uses an algorithm to determine the COR of a given set of objects. An angular device uses gravity to direct the objects to a retrieval chute, which uses a tubing system to direct the objects for re-testing or collection.

Abstract: A shaped charge tubing cutter performance test apparatus and procedure comprises a plurality of test coupons, preferably fabricated from a pipe wall section of the test subject. The coupons are configured with a height greater than the axial length of the shaped charge device and a width greater than the nine wall thickness. These coupons are secured around a circular perimeter with the width plane radiating from the perimeter and the thickness edges in parallel alignment. The circular perimeter diameter corresponds to the shaped charge diameter. A shaped charge cutter is centrally positioned within the coupon encirclement and discharged. Penetration of the cutter plasma into the coupons is measured directly. In variation, the entire assembly is encased, subjected to hydraulic pressure corresponding to a desired well depth and discharged.

Abstract: These objects are achieved by a method of acoustically inspecting a one-piece bladed wheel in which the wheel is driven in rotation; each blade of the wheel is subjected to mechanical excitation; its acoustic response is picked up and a corresponding electrical signal is generated; its frequency response is determined by computing a FFT; the electrical signal and the associated frequency response are stored; the characteristic frequencies of each blade of the wheel are identified; and a wheel is rejected or accepted depending on whether or not the frequency distribution obtained in this way matches a predetermined set of forbidden frequency distributions. Advantageously, an additional step is provided in which the defects of a blade are determined by comparing its frequency response with predetermined frequency responses that are characteristic of various types of defect.

Abstract: Disclosed is a damping performance evaluation apparatus for damping devices comprising: a support member detachably supporting a damping device in a state enabling the device to exhibit a damping effect thereof; a hammer member for applying oscillation force to the device caused by gravitational descent to strike the device; a double-strike preventing member for preventing the hammer member from dropping a second time due to rebound after initially striking the device, to prevent double-strike of the device by the hammer member; a vibration sensor installed at a vibration zone caused to vibrate through oscillation force applied by said hammer member, for outputting an electrical signal in response to vibration at the vibration zone; and a sensing member for sensing a vibration mode in the vibration zone on the basis of an output of said vibration sensor. A damping performance evaluation method is also disclosed.

Abstract: The invention relates to a nonlinear method that permits simple, fast and accurate detection of defects in a body made from brittle materials. In the case of the method, at least two temporally offset operations (A, B) are used such that the body is set vibrating (1a, 1b) with a different intensity, a vibrational response of the body in the time domain is picked up (2a, 2b), the vibrational response is normalized (3a, 3b), the beginning of the vibration is determined (4a, 4b) and a section of the vibrational response is determined (5a, 5b) whose start is formed by the previously determined beginning of the vibration, and which has a specific length, a correlation coefficient of the sections of the respective vibration responses of the at least two operations being formed as feature value for the detection of defects (6).