Frequency characteristic-based nondestructive detection method of stress waves of wood

A frequency characteristic, non-destructive testing technology, applied in the processing of the detected response signal, the use of sonic/ultrasonic/infrasonic waves to analyze solids, etc., can solve the problem of large errors in the detection results, without considering the reflection, refraction, transmission, and mixed reflected waves of the stress wave signal , refracted wave signal, etc.

Inactive Publication Date: 2013-02-13
ZHEJIANG FORESTRY UNIVERSITY
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Problems solved by technology

[0012] The present invention provides a wood stress wave non-destructive detection method based on frequency characteristics, aiming to solve the non-destructive detection method using the frequency response characteristics of wood provided by the prior art, which do...

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  • Frequency characteristic-based nondestructive detection method of stress waves of wood
  • Frequency characteristic-based nondestructive detection method of stress waves of wood
  • Frequency characteristic-based nondestructive detection method of stress waves of wood

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specific Embodiment approach

[0057] A specific embodiment of the present invention is: a method for nondestructive detection of wood stress waves based on frequency characteristics, the specific method is:

[0058] Step 1: Install six piezoelectric acceleration sensors evenly around the log, and the output signal of the acceleration sensor is connected to the data acquisition card through the charge amplifier. The wiring diagram is as follows Figure 4 shown. see image 3 , use a pulse hammer to hit the 0th sensor, and the 6 sensors convert the received stress wave signal into an electrical signal and input it into the data acquisition card. Complete data conversion and other work under the control of the host computer software, and record the signal x 0 (n),x 1 (n),x 2 (n),x 3 (n),x 4 (n),x 5 (n). Select the sampling period as 1μs, and the recording signal length as 10ms.

[0059] Step two, for x 0 (n),x 1 (n),x 2 (n),x 3 (n),x 4 (n),x 5 (n) Do fast Fourier transform, select 1024 transform...

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Abstract

The invention discloses a frequency characteristic-based nondestructive detection method of stress waves of wood. The frequency characteristic-based nondestructive detection method comprises the following steps of: mounting piezoelectric type acceleration sensors around raw wood uniformly, knocking the No. 0 sensor by using a pulse hammer, and acquiring and storing output signals of the sensors by using a data acquisition card; carrying out K-point fast Fourier transform on the acquired signals and then solving an actual measurement frequency response function; establishing an observation matrix according to the actual measurement frequency response function and a frequency response function of healthy wood; carrying out blind source separation on the basis of second order statistic and establishing a frequency response function between a defect point and an observation point; and finally, judging whether the interior of the wood has defects as well as defect quantity and defect sizes according to a clustering result. The nondestructive detection method of the stress waves based on the frequency response function of the wood is not subject to interference from reflected wave and refracted wave signals and is more accurate in detection result, capable of automatically detecting information, such as whether the interior of the wood has defects as well as the defect sizes, and simple and convenient in detection process and strong in practicability.

Description

technical field [0001] The invention belongs to the technical field of wood quality detection, and in particular relates to a wood stress wave nondestructive detection method based on frequency characteristics. Background technique [0002] The basic principle of wood stress wave nondestructive testing technology is as follows: figure 1 As shown in Fig. 1, the pulse hammer is used to strike the wood to cause the propagation of stress wave inside, and the stress wave signal at each observation point can be collected through the sensors installed around the log, and the stress wave signal can be analyzed in time domain and frequency domain , to determine the properties of wood materials (such as elastic modulus and defects, etc.). [0003] The wood non-destructive testing technology based on stress wave has the advantages of simple implementation and convenient use, and has been widely used. However, the characteristic usually used to reflect the detection of internal defects...

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Application Information

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IPC IPC(8): G01N29/12G01N29/44
Inventor 冯海林方益明李光辉李剑
Owner ZHEJIANG FORESTRY UNIVERSITY
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