CN104122331B - A kind of nondestructive detection system based on piezo disc contact vibration and detection method thereof - Google Patents

Abstract

The invention discloses a non-destructive detection system and a detection method based on piezoelectric disc contact vibration. The nondestructive testing system of the present invention includes: a piezoelectric disc, a mobile bracket, a signal generator, a power amplifier, a strain gauge, a data acquisition card, and a computer; wherein the piezoelectric disc includes a disc substrate, a piezoelectric sheet, a probe and The strain gauge, the piezoelectric piece is located on the lower surface of the disk substrate and distributed symmetrically to the center, the probe is located at the center of the lower surface of the disk substrate and is perpendicular to the disk substrate, and the strain gauge is arranged on the upper surface of the disk substrate. The present invention is based on the contact vibration between the piezoelectric disc and the sample, and detects the local contact stiffness by tracking the vibration characteristics of the piezoelectric disc. The stiffness distribution of the structure can be obtained by point-by-point detection on the sample surface, and then the structural health can be completed. The degree of evaluation; the test principle used in the present invention is simple and reliable, and is suitable for non-destructive testing of thin plate structures such as composite material laminates or soft materials.

Description

A non-destructive testing system and testing method based on piezoelectric disk contact vibration

technical field

The invention belongs to the field of material structure safety monitoring, and in particular relates to a nondestructive testing system and a testing method based on piezoelectric disk contact vibration.

Background technique

Non-destructive testing technology can complete the damage detection and health evaluation of materials or structures, so it is of great significance in industrial development. In the case of a structure that may be damaged after a long period of use or by external effects, we need to understand the internal health of the structure to determine whether the structure can continue to work, or to repair it for specific damage conditions. Especially in the field of aerospace, with the development of industry, light-weight and high-strength composite sheet structures are more and more used, and composite sheet structures are prone to defects such as fracture, delamination, ply wrinkling, shedding, and separation. , for the aerospace industry with large loads and severe fatigue loading, how to complete the nondestructive testing of composite thin plate structures is an urgent problem to be solved.

At present, traditional non-destructive testing techniques such as ultrasonic, ray and magnetic particle testing methods can complete the testing of most industrial structures, but it is still difficult to detect structures such as new composite material sheets. For the ultrasonic method, the composite material is not suitable for the ultrasonic method due to the severe anisotropy of the material properties of the composite material and the obvious effect on the sound wave attenuation. Moreover, in the thin plate grid structure, there are often thickness blind areas in ultrasonic inspection, and the complex structure leads to complex propagation and reflection of sound waves, which in turn makes it difficult to realize ultrasonic testing in the grid thin plate structure. For a class of electromagnetic methods such as ray and magnetic particle testing, composite materials cannot be used in the non-destructive testing of grid thin plate structures due to their insensitivity to electromagnetics, great harm to the human body, and inconvenient in-situ testing. In order to complete the task of nondestructive testing of composite structures, it is necessary to develop methods suitable for nondestructive testing of thin plate structures.

Contents of the invention

In order to solve the problem that the non-destructive testing method in the prior art is difficult to complete the detection of the composite material thin plate structure, the present invention proposes a method based on the contact vibration between the piezoelectric disc and the sample, and detects the material or material by tracking the vibration characteristics of the piezoelectric disc. System and method for non-destructive testing of local contact stiffness of structures.

One object of the present invention is to propose a non-destructive testing system based on piezoelectric disk contact vibration.

The non-destructive testing system based on the piezoelectric disk contact vibration of the present invention includes: a piezoelectric disk, a mobile support, a signal generator, a power amplifier, a strain gauge, a data acquisition card and a computer; wherein the piezoelectric disk includes a disk substrate , piezoelectric sheet, probe and strain gauge, the piezoelectric sheet is located on the lower surface of the disc substrate and distributed symmetrically to the center, the probe is located at the center of the lower surface of the disc substrate and is perpendicular to the disc substrate, and the strain gauges are arranged in a circle The upper surface of the disc substrate; the circumference of the disc substrate of the piezoelectric disc is installed on the mobile support, and the piezoelectric disc is driven by the mobile support to move on the surface of the sample; the signal generator is connected to the power amplifier through the data line, and the power amplifier passes The wire is connected to the piezoelectric sheet of the piezoelectric disc; the strain gauge of the piezoelectric disc is connected to the strain gauge through the data line; the strain gauge is connected to the data acquisition card through the data line; and the data acquisition card is connected to the computer through the data line.

The disc substrate is a thin plate, and the relationship between the thickness h and the radius R satisfies In this way, the disc substrate can excite the required overall bending vibration mode under the drive of the piezoelectric sheet. The probe located at the center of the disc substrate is in the shape of a cone, and its head is spherical; during the detection process, the boundary of the circumference of the disc substrate is a fixed support boundary condition, and the head of the probe is in contact with the surface of the sample. The relationship between the height H _Tan of the probe and the radius R of the disc substrate satisfies Therefore, under the premise of satisfying the mobility and freedom of the structure, the probe will not affect the vibration coordination of the piezoelectric disk itself. The piezoelectric sheet adopts a centrosymmetric structure, such as a centrally symmetrical sector of multiple pieces, or a ring concentric with the disc substrate. This centrosymmetric piezoelectric sheet ensures that the vibration of the excited piezoelectric disc is a centrosymmetric mode. The inner diameter R ₁ and the outer diameter R ₂ of the piezoelectric sheet satisfy 0.2R≤R ₁ <R ₂ ≤0.9R; the thickness t of the piezoelectric sheet is close to the disc substrate h, satisfying 0.5h≤t≤1.5h.

The signal generator sends out an excitation signal, which excites the piezoelectric sheet to vibrate and drives the disk substrate to vibrate, further driving the probe to vibrate in contact with the sample; the strain gauge located on the upper surface of the disk substrate senses the strain of the piezoelectric disk to obtain The contact resonance information of the piezoelectric disk is the strain signal; the strain gauge transmits the detected strain signal to the strain gauge through the data line. The excitation signal sent by the signal generator is divided into two types: fixed frequency signal and frequency sweep signal; correspondingly, the dynamic signal detected by the strain gauge is divided into two types: fixed frequency response signal and frequency sweep response signal.

The signal generator sends frequency sweep signals of multiple continuous frequency points, and the response of the piezoelectric disc is also frequency sweep. The strain gauge collects dynamic sweep frequency response signals, and finds the resonance frequency by extracting the frequency corresponding to the maximum amplitude among multiple frequency points. , the computer extracts the resonant frequency to calculate the local contact stiffness value, this mode is the frequency sweep test mode; the signal generator sends out a sinusoidal signal of a single frequency, the response of the piezoelectric disk is also a sinusoidal signal of a single frequency, and the strain gauge collects the dynamic constant Frequency response signal, the computer extracts the amplitude value of the sinusoidal signal to detect the local contact stiffness value of the material, this mode is the fixed frequency test mode. In the actual measurement process, the non-destructive testing of the sample can be completed by using the frequency sweep test mode or the fixed frequency test mode. The frequency sweep test mode is characterized by high precision but slow speed, and the fixed frequency test mode is characterized by fast speed but low precision. . Therefore, the combination of these two modes can better complete the detection of samples.

Strain gauges can detect both dynamic and static signals. The deformation of the piezoelectric disc can be divided into two parts: the overall static bending deformation, and the small-amplitude dynamic vibration deformation; the static bending deformation is the deformation caused by the contact force after the initial contact, and is detected by the static signal of the strain gauge; and The dynamic vibration deformation is caused by the excitation vibration of the piezoelectric sheet, which is sinusoidal and detected by the dynamic signal of the strain gauge. The contact force between the probe and the sample can be sensed through the static signal; the dynamic vibration characteristics of the piezoelectric disk such as resonance frequency (sweep frequency test mode) or vibration amplitude (fixed frequency test mode) can be tracked through the dynamic signal; further, By detecting the dynamic vibration characteristics of the piezoelectric disk, the local contact stiffness information of the contact point between the sample and the probe can be obtained.

The computer includes: a signal generating module, which is used to control the signal generator to generate an excitation signal for exciting the piezoelectric sheet; a signal acquisition module, which is used to control the data acquisition card to collect strain signals; and a calculation module, which is used to calculate the elastic properties of the sample and evaluate The health of the structure.

The computer is respectively connected to the signal generator and the data acquisition card through the data line. The signal generator generates an excitation signal to excite the piezoelectric sheet, and then drives the piezoelectric disc to vibrate in contact with the sample. The strain gauge collects the strain signal and transmits it to the strain gauge. The data acquisition card collects the strain signal conditioned by the strain gauge and transmits it to the computer.

The mobile support includes a circular fixed frame and a mobile device. The circumference of the disc substrate is fixed on the fixed frame, and the fixed frame is installed on the mobile device, thereby fixing the piezoelectric disk and driving the piezoelectric source disk to move on the surface of the sample, and then The detection of the target area of the sample is completed. The circumference of the piezoelectric disc is fixed on the ring-shaped fixing frame. This continuous large-rigidity structure is fixed, so that the entire circumference of the piezoelectric disc is in a good mechanically fixed boundary state, so the structure is more stable. The fixed frame is made of a material with high rigidity, such as stainless steel, and the rigidity of the fixed frame is realized by increasing the size and quality. The size (thickness) and quality of the fixed frame itself are much larger than that of the piezoelectric disk, and a stable fixed support boundary is provided by obtaining a larger inertia.

Another object of the present invention is to provide a non-destructive testing method based on piezoelectric disk contact vibration.

The non-destructive testing method based on piezoelectric disk contact vibration of the present invention comprises the following steps:

1) According to the size, structure and material of the piezoelectric disk, determine the mechanical model of the piezoelectric disk, so as to obtain the resonance frequency _fn of the piezoelectric disk or the vibration amplitude of the vibration system, and the local contact stiffness with the sample according to the mechanical model The relationship between k ^* ;

2) Place the mobile bracket equipped with the piezoelectric disc on the surface of the sample to be tested;

3) The static signal of the strain gauge is detected by the strain gauge to obtain the contact force between the probe and the sample, and the contact force between the probe and the sample is adjusted by adjusting the height of the moving bracket;

4) The computer-controlled signal generator sends an excitation signal to excite the piezoelectric sheet to drive the disc substrate to vibrate, thereby driving the contact vibration between the probe and the sample, and the piezoelectric disc performs steady-state resonance;

5) The strain gauge detects the strain signal and transmits it to the strain gauge, and the strain gauge adjusts the strain signal and then transmits it to the data acquisition card, and the data acquisition card acquires the adjusted strain signal;

6) The computer processes the strain signal collected by the data acquisition card, and then obtains the local contact stiffness information of the sample, and the health degree of the sample can be obtained through the local contact stiffness information.

The above detection method can adopt the frequency sweep test mode, the signal generator sends a dynamic frequency sweep signal, the strain gauge collects the dynamic sweep frequency response signal, the computer extracts the resonance frequency and calculates the local contact stiffness value, this mode is the frequency sweep test mode; The signal generator sends a fixed frequency signal, the strain gauge collects the fixed frequency response signal, and the computer extracts the vibration amplitude value and calculates the local contact stiffness value. This mode is the fixed frequency test mode.

Advantages of the present invention:

The detection method of the present invention adopts a piezoelectric disc with a centrally symmetrical structure, based on the contact vibration between the piezoelectric disc and the sample, and by tracking the vibration characteristics of the piezoelectric disc to detect the local contact stiffness of the material or structure, and further the piezoelectric disc The disk is integrated on a device that can move freely on the surface of the sample, and the stiffness distribution of the structure can be obtained by point-by-point detection on the surface of the sample, and then the evaluation of the health of the structure can be completed. Compared with the existing nondestructive testing methods, the testing principle used in the present invention is simple and reliable, and is suitable for nondestructive testing of thin plate structures such as composite material laminates or soft materials.

Description of drawings

Fig. 1 is a structural schematic diagram of a non-destructive testing system based on piezoelectric disc contact vibration of the present invention;

Fig. 2 is the schematic diagram of an embodiment of the piezoelectric disc of the non-destructive testing system based on the piezoelectric disc contact vibration of the present invention, wherein, (a) is the schematic diagram of the upper surface of the piezoelectric disc, (b) is the piezoelectric disc The electric sheet is a schematic diagram of the lower surface of a plurality of centrally symmetrical fan-shaped piezoelectric discs;

Fig. 3 is a schematic diagram of the lower surface of the piezo disc whose piezoelectric sheet is ring-shaped in the non-destructive testing system based on the piezoelectric disc contact vibration of the present invention;

4 is a cross-sectional view of the first-order vibration mode excited by the centrosymmetric piezoelectric sheet of the nondestructive testing system based on piezoelectric disc contact vibration of the present invention;

5 is a schematic diagram of the mechanical model of the piezoelectric disk vibration system of the nondestructive testing system based on piezoelectric disk contact vibration of the present invention;

6 is a graph showing the relationship between the resonant frequency f _n of the piezoelectric disk and the local contact stiffness k ^* of the sample in the nondestructive testing system based on the piezoelectric disk contact vibration of the present invention;

Figure 7 (a) is a schematic diagram of the contact between the probe and the sample of the local contact stiffness detection system of the cantilever beam type, and (b) is the probe of the piezoelectric disc of the nondestructive testing system based on the piezoelectric disc contact vibration of the present invention Schematic diagram of contact with the sample.

detailed description

The present invention will be further elaborated below through specific embodiments in conjunction with the accompanying drawings.

As shown in Figure 1, the non-destructive testing system based on piezoelectric disk contact vibration of the present invention includes: piezoelectric disk 2, mobile support, signal generator 4, strain gauge 5, data acquisition card 6 and computer 7; Wherein, The piezoelectric disk 2 includes a disk substrate 21, a piezoelectric sheet 22, a probe 23 and a strain gauge 24. The piezoelectric sheet 22 is located on the lower surface of the disk substrate and is a centrally symmetrical pattern, and the probe 23 is located on the lower surface of the disk substrate. At the center of the surface and perpendicular to the disk substrate 21, as shown in Figure 2 (b), the strain gauge 24 is arranged on the upper surface of the disk substrate 21, as shown in Figure 2 (a); the disk of the piezoelectric disk 2 The circumference of the substrate 21 is installed on the movable support, and the piezoelectric disc 2 is driven by the movable support to move on the surface of the sample 1; the signal generator 4 is connected to the power amplifier 41 through a data line, and the power amplifier 41 is connected to the piezoelectric disc through a wire The piezoelectric sheet 22; the strain gauge 24 of the piezoelectric disk 2 is connected to the strain gauge 5 through the data line; the strain gauge 5 is connected to the data acquisition card 6 through the data line; the data acquisition card 6 is connected to the computer 7 through the data line.

The moving device 32 of the mobile support adopts a universal wheel set, which is evenly installed under the annular fixed frame 31 .

In this embodiment, both the disc substrate 21 and the fixing frame 31 are made of stainless steel; the piezoelectric sheet 22 is made of PZT-5H piezoelectric material. The radius R of the disc substrate 21 is 100 mm, and the thickness h is 2 mm; the height H _Tan of the probe is 20 mm; the thickness t of the piezoelectric disc is 2 mm, and the inner diameter R ₁ and outer diameter R ₂ are 40 mm and 80 mm respectively.

Further, the hand-held handle 8 is installed on the ring-shaped fixed frame 31 to form a handle-type detection structure. The two ends of the hand-held handle 8 are installed on the ring-shaped fixed frame 31 and the line connecting two points passes through the center of the circle. The detection structure can be moved on the surface of the sample by moving the handle 8; during the movement, the probe 23 of the piezoelectric disc is kept in contact with the sample 1; by moving on the surface of the sample 1, the detection of interest can be completed Non-destructive testing of the area.

The piezoelectric sheet 22 adopts a centrosymmetric structure, which can be a plurality of centrosymmetric sectors, as shown in Figure 2 (b); or a ring concentric with the disc substrate, as shown in Figure 3, this centrosymmetric The structure of can excite the mode of central vibration, as shown in Figure 4.

The non-destructive testing method proposed by the present invention detects the local contact stiffness of the structure to be tested based on the contact vibration of the piezoelectric disc, and the basic principle of the present invention is described in detail here.

The boundary of the piezoelectric disk is: the boundary condition of the circumference is a fixed support; the center of the circle is in contact with the sample through a probe, and the boundary condition of the center of the circle is an elastic support. The circumference of the piezoelectric disc is fixed and the probe in the center vibrates in contact with the sample to form a piezoelectric disc vibration system, which is obtained from the theory of vibration mechanics. The vibration system can be simplified as a mechanical model with fixed support around and elastic support at the center. As shown in FIG. 5 , in this mechanical model, a spring is used to simulate the interaction between the probe and the sample. The elastic coefficient of the spring is k ^* , and the elastic coefficient k ^* is the local contact stiffness k ^* of the sample.

According to the knowledge of vibration mechanics, in the above-mentioned piezoelectric disk vibration system, the relationship between the resonance frequency f _n of the piezoelectric disk and the local contact stiffness k ^* of the sample can be described by an analytical expression f _n = H(k ^* ) , and, when the elastic coefficient k* of the spring is higher, the resonant frequency f _n of the vibration system is also larger, and the relationship between the resonant frequency f _n of the piezoelectric disc and the local contact stiffness k ^* of the sample satisfies similarity as shown in Figure 6 the curve shown. The relationship between the resonant frequency f _n and the local contact stiffness k ^* is related to the size, structure and material of the piezoelectric disk, and corresponds to the only analytical solution.

By using a frequency sweep signal to excite the piezoelectric disc, tracking the resonance frequency f _n of the piezoelectric disc, and then tracking to obtain the information of the local contact stiffness k ^* of the sample, such a test mode is a frequency sweep test mode. Also, by using a fixed frequency signal to excite the piezoelectric disc, the vibration amplitude of the vibrating system is different when the local contact stiffness k* of the sample is different. Therefore, the system can be excited by a signal with a fixed frequency, and the vibration amplitude of the vibration system can be tracked to obtain the local contact stiffness information of the sample. This mode is a fixed frequency test mode.

Compared with the cantilever beam type local contact stiffness detection system, the disc type local contact stiffness detection device proposed by the present invention has the following differences and advantages:

1. The torsional stiffness of the cantilever beam design is very low. When the needle tip of the probe moves on the sample surface, the existing lateral force will distort the cantilever beam, which will affect the structural attitude and detection signal. The disc design forms a A new centrosymmetric structure, when the structure moves on the surface of the sample, due to the high structural stiffness in all directions, the lateral interference will be much reduced compared with the cantilever beam design, and the interference to the detection signal will be less or even completely eliminated , which solves the problem of lateral force in contact detection, so the disc design is more suitable for moving monitoring on the sample surface;

2. The cantilever beam design only has one fixed point at one end, while the surrounding of the piezoelectric disk is fixed with a continuous high-rigidity structure, and the entire periphery of the disk is in a good mechanically fixed boundary state, so the structure is more stable and the signal-to-noise The ratio is also higher, so the disc design is more suitable for application in vibration methods than the cantilever beam design;

3. The design of the cantilever beam adopts the design of the whole beam made of piezoelectric material or the design of piezoelectric sheets arranged on the lower surface of the cantilever beam. Centrally symmetrical piezoelectric sheet group or ring design, the centrally symmetrical design helps to excite the required "first-order central vibration" mode, as shown in Figure 4, and suppresses the appearance of unwanted interference modes , so the disk design is more suitable for the application in the contact vibration method than the cantilever beam design;

4. The cantilever-beam-designed probe contacts the sample under pressure. Since the pressure is transmitted by the cantilever beam, the force on the probe is asymmetrical and often bends off-axis, as shown in Figure 7(a). It is shown that this deviation will lead to complex mode shapes of the probe and bring in interference signals, while in the disc design, the probe is located at the central axis of the centrosymmetric structure, so the force is uniform, and the probe will remain perpendicular to the sample, as shown in As shown in Figure 7(b), there is no problem with the cantilever beam design, so the disc design is more beneficial to increase the stability of detection;

5. The lateral force will be more obvious when the cantilever beam design probe moves laterally on the curved surface, and the disc design and the universal wheel set will make the disc design more suitable for complex surfaces such as machines. Hand-held motion detection of curved surfaces of wings, etc.

The non-destructive testing method based on piezoelectric disk contact vibration of the present invention comprises the following steps:

1) According to the size, structure and material of the piezoelectric disk, determine the mechanical model of the piezoelectric disk, so as to obtain the resonance frequency _fn of the piezoelectric disk or the vibration amplitude of the vibration system, and the local contact stiffness with the sample according to the mechanical model The relationship between k ^* satisfies the curve shown in Figure 6;

2) placing the mobile support equipped with the piezoelectric disc on the surface of the sample to be tested;

3) Measure the static signal of the strain gauge through the strain gauge to obtain the contact force between the probe and the sample, and adjust the contact force between the probe and the sample by adjusting the height of the universal wheel set;

4) The computer controls the signal generator to send an excitation signal, which excites the piezoelectric plate to drive the disc substrate to vibrate, thereby driving the contact vibration between the probe and the sample under the probe, and the piezoelectric disc performs steady-state resonance;

5) The strain gauge detects the strain signal and transmits it to the strain gauge, and the strain gauge adjusts the strain signal and then transmits it to the data acquisition card, and the data acquisition card acquires the adjusted strain signal;

6) The computer processes the strain signal collected by the data acquisition card, and then obtains the local contact stiffness information of the sample at the measurement point, and the health degree of the sample can be obtained through the local contact stiffness information.

Finally, it should be noted that the purpose of the disclosed embodiments is to help further understand the present invention, but those skilled in the art can understand that various replacements and modifications can be made without departing from the spirit and scope of the present invention and the appended claims. It is possible. Therefore, the present invention should not be limited to the content disclosed in the embodiments, and the protection scope of the present invention is subject to the scope defined in the claims.

Claims (10)

1. a nondestructive detection system based on piezo disc contact vibration, it is characterised in that described nondestructive detection system includes: pressure Electricity disk (2), traversing carriage, signal generator (4), power amplifier (41), deformeter (5), data collecting card (6) And computer (7)；Wherein, described piezo disc (2) includes disk substrate (21), piezoelectric patches (22), probe (23) With foil gauge (24), piezoelectric patches (22) be positioned at disk substrate lower surface and centered by symmetrical, probe (23) is positioned at The lower surface circle centre position of disk substrate and be perpendicular to disk substrate (21), foil gauge (24) is arranged in disk substrate (21) Upper surface；The circumference of the disk substrate (21) of described piezo disc (2) is arranged on traversing carriage, traversing carriage drive Piezo disc (2) moves on the surface of sample (1)；Described signal generator (4) is connected to power amplification by data wire Device (41), power amplifier (41) is connected to the piezoelectric patches (22) of piezo disc through wire；Described piezo disc (2) Foil gauge (24) be connected to deformeter (5) by data wire；Described deformeter (5) is connected to data acquisition by data wire Truck (6)；Described data collecting card (6) is connected to computer (7) by data wire.

2. nondestructive detection system as claimed in claim 1, it is characterised in that the thickness h of described disk substrate (21) and radius R Between relation meet

3. nondestructive detection system as claimed in claim 1, it is characterised in that the height H of described probe_TanRadius with disk substrate Relation between R meets

4. nondestructive detection system as claimed in claim 1, it is characterised in that the internal diameter R of described piezoelectric patches (22)₁With external diameter R₂ Meet 0.2R≤R₁＜ R₂≤0.9R；The thickness t of piezoelectric patches meets 0.5h≤t≤1.5h, and wherein, R is the radius of disk substrate, H is the thickness of disk substrate.

5. nondestructive detection system as claimed in claim 1, it is characterised in that the accumulation signal that described signal generator (4) sends It is divided into signal and the swept-frequency signal two kinds of fixed frequency；Correspondingly, the Dynamic Signal that described deformeter (5) detects is divided into determines frequency Response signal and frequency sweep response signal two kinds.

6. nondestructive detection system as claimed in claim 1, it is characterised in that described computer includes: control signal generator produces The signal generating module of the accumulation signal of excitation piezoelectric patches；Control data collecting card and gather the signal acquisition module of strain signal；With And calculate the elastic property of sample and the computing module of the health status of evaluation structure.

7. nondestructive detection system as claimed in claim 1, it is characterised in that described traversing carriage includes the fixed mount (31) of annular With mobile device (32), the circumference of described disk substrate (21) is fixed on fixed mount (31), and described fixed mount (31) is pacified It is contained in mobile device (32).

8. nondestructive detection system as claimed in claim 1, it is characterised in that farther include hand-held handle (8), described hand-held hands Handle (8) is arranged on traversing carriage.

9. a lossless detection method based on piezo disc contact vibration, it is characterised in that comprise the following steps:

1) according to size, the structure and material of piezo disc, determine the mechanical model of piezo disc, thus obtain according to mechanical model Resonant frequency f to piezo disc_nOr the vibration amplitude of vibrational system, with localized contact rigidity k of sample^*Between Relation；

2) traversing carriage being provided with piezo disc is placed on sample surfaces to be measured；

3) by the stationary singnal of deformeter detection foil gauge, the contact force between probe and sample is obtained, by adjusting mobile The height of frame, thus adjust the contact force between probe and sample；

4) computer control signal generator sends accumulation signal, and excitation piezoelectric patches drives the vibration of disk substrate, thus drives probe And coming in contact vibration between sample, piezo disc carries out stable state resonance；

5) transmission of deformeter detection strain signal is to deformeter, transmits to data collecting card, data after deformeter conditioning strain signal The strain signal of capture card collection conditioning；

6) strain signal that computer disposal is gathered by data collecting card, and then obtain the localized contact rigidity information of sample, logical The localized contact rigidity information crossed just can obtain the health degree of sample；

Wherein, piezo disc includes disk substrate, piezoelectric patches, probe and foil gauge, and piezoelectric patches is positioned at the lower surface of disk substrate also Centered by and symmetrical, probe is positioned at the lower surface circle centre position of disk substrate and is perpendicular to disk substrate, foil gauge arrange Upper surface at disk substrate；The circumference of the disk substrate of piezo disc is arranged on traversing carriage, by traversing carriage band dynamic pressure Electricity disk moves on the surface of sample；Signal generator is connected to power amplifier through data wire, and power amplifier passes through wire It is connected to the piezoelectric patches of piezo disc；The foil gauge of piezo disc is connected to deformeter by data wire；Deformeter passes through data Line is connected to data collecting card；Data collecting card is connected to computer by data wire.

10. lossless detection method as claimed in claim 9, it is characterised in that described detection method uses sweep check pattern, letter Number generator sends swept-frequency signal, and deformeter gathers frequency sweep response signal, and computer extracts resonant frequency and to calculate localized contact firm Degree；Or using fixed frequency test pattern, signal generator sends the signal of fixed frequency, and frequency response induction signal is determined in deformeter collection, Computer extracts vibration amplitude value and calculates localized contact rigidity.