Objective This paper depicts a testing technology of nondestructive infrared imaging for acquiring internal structure information of metal Buddha head. Methods applying active infrared thermal imaging nondestructive testing technology Results Data which was collected by IR camera was processed, the typical time thermograph and the curve of logarithmic temperature-time can be. get information of relative thickness in metal Buddha face. Conclusion Infrared thermal imaging technology can be detect the inside information of metal Buddha head . It is feasible to conserve heritage in infrared imaging method.
In sonic infrared (SonicIR) imaging, heat is generated in defect areas during the sonic pulse; the heat appears bright in SonicIR images as the indication of a defect. However, in practical applications of SonicIR, there are lots of disturbing bright areas in infrared images, such as heat reflection and paint problem. When crack size is small, the generated heat appears not bright enough to be recognizable. Based on heat diffusion properties in the one-dimensional temporal and two-dimensional spatial domain, a method is developed to automatically recognize defect signals from SonicIR image sequences. The algorithm is verified with the SonicIR image sequences of 100 metal plates which may have different thickness, materials, or crack sizes.
Pulsed-heating infrared thermography non-destructive testing is one of the most common used technology in industial NDT/NDE. It has an advantage on simple instrument and easy operation among method for NDT/NDE. To get an persuasive result, properties of heating pulse should be adjusted to testing condition, such as depth of defect and thermal conductivity of material. This paper tries to derive a method for optimization of heating pulse. The method is based on theory of thermal wave. The pulse should be chosen to make itself contain more effective thermal frequency components for NDT. The effect of this method can be verified by simulation and NDT experiments in this paper.
Chopper is widely used in optical system to produce a series of optical
pulses which has particular shape and frequency. This paper presents a way to make
a simple chopper based on Labview. Labview and NI DAQ are widely available in
universities. So with this method chopper system can be easily constructed for
temporary use. NI DAQ uses counter tools to detect the frequency of modulated
laser and produce several feedback signal to drive the location and rotate speed of
modulation plate, which leads to the change of modulation frequency and duty. This
paper can provide a reference for experiment work in optics and other natural
science.
The glue defects of the wind turbine blades which are composed of the glass fiber reinforced plastic (GFRP)
composite plates make its strength greatly reduced, so security issues could be caused. To improve the safety of wind
turbine blades, nondestructive testing technique using pulsed thermography is being investigated in this study. The
results of ultrasonic C scan test were compared with the results of thermography. The current results indicated that both
methods can successfully detect two gluing situations. However, the inspect specimens need to be putted in the water in
the detection process by ultrasonic C scan, and the detection time lasts much longer than pulsed thermography. And in
situ applications, the measured wind turbine blades are normally in the size of several tens meter, and also only one side
is available for the inspection especially at the tip of blades. Thus, ultrasonic C scan of current experimental setup is not
suitable for the applications in the field. Pulsed thermography is not necessary to contact with inspected specimens. The
infrared results by pulsed thermography indicate that the shape and size of deficiency glue defects in the specimens show
good agreement with the real situation, so it is more suitable for the inspection in the field. The preliminary results in this
study indicate that pulse thermography can be used to detect glue faults of GFRP which are not too thick.
In pulse thermography, pulsed flash energy is applied to the surface and the temperature of the surface
is recorded and analysed. Generally the the flash duration is short and the heating could be taken as
impulse function. After the surface is heated instantaneously, heat goes down by conduction. If an area
has defect below, the temprature of this area will be different from the temprature of defect free area.
Analytic solution indicates that the time at which the temperature descending curve of the area with
defect below separate from the curve of the defect free area is proportional to the square of the defect
depth. Thus, if the deviation time is determined, the defect depth could be calculated.
In real inspection, different from theoretical model, the temperature decay curve may be noisy and
sometimes fluctuating. And due to the effect of three-dimentional conduction and different boundary
conditions the temperature decay curve is different from the theoretical solution under ideal conditions.
All these affect the identification of the deviation time and then affect the accurary of the depth
measurement. Peak temperature contrast and peak slope of temperature contrast methods are popularly
used in depth measurement, but all these two methods require the prior determination of a reference
point that is known to be on sound material. Peak second derivative method in log scale is a reference
free method which can somehow decrease the influence of noisy data and three-dimentioanl conduction.
To reduce the noise induced by derivation, fitted data instead of raw data is offten used. However, the
global data fitting is not suitable in some situation. In this paper, peak second derivative method based
on patial data fitting is proposed and results are discussed. The results show that this method could
improve the accuracy of depth measurement for CFRP specimen.
Although active thermography has traditionally been regarded as a qualitative NDT method, its potential for
quantitative measurement of thermophysical properties including wall thickness, defect size and depth, thermal
diffusivity has been the subject of numerous investigations. An investigation into the effect of depth on the quantitative
estimation of defect size in metalic specimen has been undertaken using pulsed thermography. A 3D model based on
finite element method was used to simulate the heat conduction in a flat metal plate containing articial defects. The plate
is made of steel with known thermal properties. The defects of different depth are flat bottom holes simulating areas
damaged by corrosion. The goal of the1 research was to find if there is a possibility to combine pulsed thermography and
numberical modeling to determine the effect of depth on the quantitative estimation of defect size. The temperature
distribution on the metal surface can provide proper threshold value to extract edge of defect in thermography. A series of
specimen with circular defect of varying diameter and depth were tested. To solve this problem, we analysis the FEM
simulation results, investigate the relationship between measured value and true value, and introduce a correction factor
related to depth. Using this correction factor, its measured value in the thermography is quite close to the design size of
defect in the specimen.
Pulsed thermography is a technique in which pulsed flash energy is applied to the surface and the
temperature of the surface is recorded and analysed. Generally the temperature above the defect areas
is different from that of the surrounding area. However, when the surface of the specimen is highly
reflective, artifact of fixed pattern could be introduced which comes from the reflection of the heated
lamp tube. Several methods were used to eliminate the artifact, including spatial filtering, image
subtraction and frequency domain filtering. Results show that spatial filtering may be the best method
of the fixed pattern artifact elimination.
Conventional ultrasonic thermography (thermosonic or sonic infrared imaging) is a technique in which acoustic energy is
coupled to the structure by means of an acoustic transducer in contact with the sample, the captured temperature at the
defect areas by an infrared camera is relatively higher than that of the surrounding area. The primary problem of this
technique is that the acoustic horn must be mechanically in contact against the tested sample with an applied force.
Therefore, the potential for damaging the structure especially for the filmy, brittle and fragile structure can't be ignored.
In this paper, a new NDE technique based on a non-contact ultrasonic excitation thermography has been presented. The
technique utilizes a redesigned ultrasonic horn to excite the sample in a non-contact fashion, and an infrared camera to
monitor the variation of the surface temperature. The presented experimental results show that the non-contact ultrasonic
excitation thermography has some potential in NDE application.
The applications of ultrasonic infrared thermal wave nondestructive evaluation for crack detection of several
materials, which often used in aviation alloy. For instance, steel and carbon fiber. It is difficult to test cracks interfacial or
vertical with structure's surface by the traditional nondestructive testing methods. Ultrasonic infrared thermal wave
nondestructive testing technology uses high-power and low-frequency ultrasonic as heat source to excite the sample and
an infrared video camera as a detector to detect the surface temperature. The ultrasonic emitter launch pulses of
ultrasonic into the skin of the sample, which causes the crack interfaces to rub and dissipate energy as heat, and then
caused local increase in temperature at one of the specimen surfaces. The infrared camera images the returning thermal
wave reflections from subsurface cracks. A computer collects and processes the thermal images according to different
properties of samples to get the satisfied effect. In this paper, a steel plate with fatigue crack we designed and a juncture
of carbon fiber composite that has been used in a space probe were tested and get satisfying results. The ultrasonic
infrared thermal wave nondestructive detection is fast, sensitive for cracks, especially cracks that vertical with structure's
surface. It is significative for nondestructive testing in manufacture produce and application of aviation, cosmography
and optoelectronics.
The optical characteristic of Nd:YAG ceramic was introduced, and a LD pumped high efficiency Nd:YAG ceramic laser was demonstrated. The laser threshold is 48mW with R=97% output coupler. With 2W LD pumping, 812mW CW laser output at 1064 nm has been obtained, and the corresponding optical-to-optical efficiency is as high as 45.6%. A LD pumped high efficiency high repetition rate A-O Q-switched Nd:YAG ceramic laser was also demonstrated. With a 2W LD pumping, the obtained narrowest pulse width, highest peak power and highest energy per pulse are 16.4ns, 2.46kW and 40.5μJ, respectively. The experimental study about the influence of repetition rate on the performance of A-O Q-switched pulse laser was emphasized, and the experiment results were analyzed and discussed.
By combining the techniques of AO (acousto-optic) Q-switching and EO (electro-optic) cavity-dumping, a new type of diode-pumped nanosecond pulsed laser was proposed for the first time. The Q- switched pulses at 1.06micrometers with a peak power of 5.02kW and a pulse width 3.1ns pumped a 1W laser diode on the Nd:YVO4 microchip at the 1kHz repetition rate were obtained. The temporal characteristics of the pulses were analyzed numerically. The experiment results are shown to be in good agreement with theoretical predictions.
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