Owing to high oil prices and environmental issues, the automobile industry has conducted considerable research and made large investments to manufacture a high-efficiency automobiles. In the case of automobile wheels in which a lightweight material is used to increase the fuel efficiency a mold is used to increase the production efficiency; however, the use of the molding method for this purpose is very expensive. Therefore an automobile wheel consists of two parts. In this study a two-piece automobile wheel is manufactured by the friction stir welding(FSW) of Al6061-T6 to reduce the manufacturing cost and process complexity. The FSW welding tool geometry and rotational speed, and the feed rate are key factors that significantly affect the weld strength. Therefore tensile tests were conducted on specimens produced using various welding conditions, and the optimal FSW welding conditions were applied to manufacture aluminum wheels. To ensure reliability, prototype aluminum wheels were manufactured and their mechanical reliability and safety were evaluated using a durability test, fatigue durability test, and impact test. Through this study, aluminum wheel production was made possible using the FSW method.

An optical defect detection method using ESPI(electronic speckle pattern interferometry) is proposed. ESPI is widely used as a non-contact measurement system which show deformation and phase map in real time. ESPI can be divided as the in-plane, out-of-plane and shearography by operation principle and target object and also divided with bulk type and optic fiber type by the optic configurations. This paper is focused on optic fiber type out-of-plane ESPI, which has the following advantages: (1) low cost; (2) reduction of the unreliable factors generated by separated optic components; (3) simplification of the optic configuration; (4) great reduction of volume; (5) flexibility, to be easily designed into different structures to adapt to inaccessible environments such as pipeline cavity and so on.

Pressure vessels in vehicle industries, power plants, and chemical industries are often affected by flaw and defect generated inside the pressure vessels due to production processes or being used. It is very important to detect such internal defects of pressure vessel because they sometimes bring out serious problems. In this paper, an optical defect detection method using digital shearography is used. This method has advantages that the inspection can be performed at a real time measurement and is less sensitive to environmental noise. Shearography is a laserbased technique for full-field, non-contacting measurement of surface deformation (displacement or strain). The ultimate goal of this paper is to detect flaws in pressure vessels and to measure the lengths of the flaws by using unwrapping, phase images which are only obtained by Phase map. Through this method, we could decrease post-processing (next processing). Real length of a pixel can be calculated by comparing minimum and maximum unwrapping images with shearing angle. Through measuring several specimen defects which have different lengths and depths of defect, it can be possible to interpret quantitatively by calculating gray level.

Laser ultrasonic testing is an advanced technique to extract crack information in nondestructive inspections. Though this testing is a fully non-contact detection technique, its application area was not wide until now because of the relatively low signal-to-noise ratio when compared with conventional contacting piezoelectric transducers. In this research, a common laser ultrasound was used to detect crack depth information in a thin aluminum plate. A laser ultrasonic inspection system was fabricated by using a pulse laser, a confocal Fabry-Perot laser interferometer (CFPI) with a CW laser beam, an iris, a high-pass filter, a dynamic stabilizer and a control computer. The laser ultrasonic signal was detected from the opposite epicenter position of an aluminum plate. Crack depth information was extracted from the corresponding wavelength frequency to the roundtrip length in the frequency domain. The results for the crack depth detected in a thin aluminum plate are described in this paper by using experimental data.

Nondestructive testing(NDT) and inspection of structural materials are becoming increasingly important to assure the safety level in the present industries. Nondestructive measuring techniques using an optical interferometer have emerged as a valuable tool for many industrial applications [1]. This non-contact optical method is a full-field measurement technique with high speed [2]. Recently, by virtue of the development of electronic technologies, a digital speckle pattern interferometer (DSPI) has been highly developed and widely used in many engineering applications to measure the deformation area of objects. The great advantage of this system is that the data processing can be done easily in real time and can provide highly accurate deformation data by using phase-analyzing techniques. In this paper, a DSPI based on remote communication is developed on a movable table for measuring 3D deformation of an object. Wrapped phase data of the deformed area can be measured by acquiring phaseshifted fringe images. The 3D deformation phase image can be extracted by applying an unwrapping algorithm to the wrapped phase data. Usually, many impulse pattern noises are included in the acquired wrapped phase image because these are produced from the interfered speckle pattern fringes. We developed an efficient phase unwrapping algorithm by developing an efficient removing filter. This filter is designed and applied to a phase map image that efficiently removes impulse noises. The filter improves the extracting efficiency of the phase information around the wrapping area. A fast unwrapping algorithm based on the discrete cosine transform (DCT) is adopted [4]. The hardware and software configurations of the developed DSPI are described in this paper.

topography method is a well-known non-contacting 3-D measurement method. Recently, the automatic 3-D measurement by topography has been required, since the method was frequently applied to the engineering and medical fields. The 3-D measurement using projection topography is very attractive because of its high measuring speed and high sensitivity. In this paper, using two-wavelength method of projection topography was tested to measuring object with problems. The experimental results prove that the proposed scheme is capable of finding absolute fringe orders, so that the problems can be effectively overcome so as to treat large step discontinuities in measured objects.

This paper describes an optical nondestructive testing technique for honeycomb composite material, which has been used as structural material in aeronautics and space transportation. The inspection of a honeycomb composite structure by the conventional NDT technique is difficult and complex. Optical NDT can give a solution about problems of previous technique. Optical NDT basically provides non-contact, whole-field inspection and easy interpretation. Representative techniques are X-ray, Thermography, Electronic Speckle Pattern Interferometry (ESPI), Shearography, Neutron Radiography and so on. They each have strengths and weaknesses with respect to system preparation, field application and inspection target. ESPI, ultrasonic testing and Thermography in this paper are applied to detect an artificial defect of 30 mm in diameter and an impact- induced delamination inside the honeycomb composite plate, which consists of an aluminum core and carbon fiber reinforced plate skin. Inspection conditions in the experiment are compared with each other, and results are discussed.

The ESPI (Electronic Speckle Pattern Interferometry) is a real-time, full-field, non-destructive optical measurement technique. In this study, ESPI was proposed for the purpose of vibration analysis for new and composite materials. Composite materials have various complicated characteristics according to the materials, orientations, stacking sequences of the ply and boundary conditions. Therefore, it was difficult to analyze composite materials. For efficient use of composite materials in engineering applications the dynamic behavior (i.e., natural frequencies and nodal patterns) should be informed. With the use of Time-Average ESPI, one could analyze vibration characteristics of composite material by real time easily. We manufactured two kinds of laminated composites (i.e., symmetry and asymmetry) which were consisted of CFRP (Carbon Fiber Reinforced Plastics) and the shape of the test piece was of rectangular form.

Shearography is one of optical methods that has been applied to nondestructive testing (NDT) and strain/stress analysis. The technique has the merit of the directly measuring relative displacement, which is insensitive to environmental vibration disturbance. Previous studies about the method have emphasized on extending its application to new fields and lack insufficient research on effective parameters for qualitative and quantitative evaluation of defects. In this paper, the influence of shearing amount on the detection of an internal defect is investigated. In experiment, slender defects along longitudinal direction of pipeline are artificially designed and detection results according to the change of shearing amount are analyzed. Based on the investigation, we propose the technique for the determination of defect size and accurate source location.

A new dimension measuring method for the measurement of diameter of an object has been developed using laser triangulation. The 3 D data of an object was calculated from the 2 dimensional image information obtained by the laser stripe using the laser triangulation. The system that use existing theory can measure the diameter of hole not only in a normal plane but also in an incline plane. However, in the existing theory, since the lens with fixed focal length was used, the area of measurement was fixed. The simplest way to solve this problem is to change distance between a CCD camera and object. Other way is to use a zoom lens having variable focal length. In this paper, the zoom lens with variable focal length was used. Therefore, we can experiment with magnification that is optimized according to size of object using zoom lens with variable focal length.

Recently, laser interferometry is widely used as a measuring system in many fields because of its high resolution and its ability to measure a broad area in real-time all at once. In conventional laser interferometry, for example Out-of-plane ESPI (Electronic Speckle Pattern Interferometry), In plane ESPI, Shearography and Holography, it uses PZT or other components as a phase shift instrumentation to extract 3-D deformation data, vibration mode and others. However, in most cases PZT has some disadvantages, which include nonlinear errors and limited time of use. In the present study, a new type of laser interferometry using a laser diode is proposed. Using Laser Diode Sinusoidal Phase Modulating (LD-SPM) interferometry, the phase modulation can be directly modulated by controlling the laser diode injection current thereby eliminating the need for PZT and its components. This makes the interferometry more compact.

The real defects in composite structures are detected by using laser techniques. Several types of real defects, that is, delamination in laminated composites, debond in a honeycomb structure, free-edge delamination, and debond in an adhesive joint, are investigated by laser techniques. To make the different type of real defects, impact and fatigue tests were carried out on composite specimens. Laser techniques such as ESPI and shearography are used to detect those defects. Thermal loading method, which can easily induce the surface deformation of specimen, is used to detect the defects. Not only the location of defects, but also the approximate size can be estimated. Experimental results show that the real defects in composite structures can be easily detected by laser techniques. Moreover, it seems to be effective to the detection of defects in various kinds of composite structures.

A phase shifting pulsed holographic interferometer was applied to the experimental study of the propagation of laser-induced shock waves over metal plates. A double-pulsed ruby laser was used to generate the shock waves and to make a holographic interferogram of the wave fields. The phase shifting method with a dual-reference beam solved the sign ambiguity problem in holographic fringe patterns and allowed a quantitative evaluation of the phase of the interference patterns. The transient surface profile and propagation behavior of the shock wave over plates were investigated from the holographic fringe patterns.

Moire topography method is a well-known non-contacting 3-D measurement method. Recently, the automatic 3-D measurement by moire topography has been required since the method was frequently applied to the engineering and medical fields. The 3-D measurement using projection moire topography is very attractive because of its high measuring speed and high sensitivity. In this paper, using the two-wavelength methods of projection moire topography was tested to a measuring object with 2pi-ambiguity problems. Also, rapid measurement can be accomplished by the synchronization between CCD camera and projector. The experimental results prove that the proposed scheme is capable of finding absolute fringe orders, so that the 2pi-ambiguity problems can be effectively overcome so as to treat large step iscontinuities in measured objects.

Moire topography method is a well-known non-contacting 3-D measurement method. Recently, the automatic 3-D measurement by moire topography has been required since the method was frequently applied to the engineering and medical fields. 3-D measurement using projection moire topography is very attractive because of its high measuring speed and high sensitivity. In this paper, using two-wavelength methods of projection moire topography was tested to a measuring object with 2pi -ambiguity problems. Experimental results prove that the proposed scheme is capable of finding absolute fringe orders, so that the 2pi -ambiguity problems can be effectively overcome so as to treat large step discontinuities in measured objects.

It is very important that we understand the dynamic behaviors of the laser induced plume in welding, because the laser induced plume has considerable effects on welding efficiency and the quality of materials. Many experimental studies have been performed in order to observe the plume behaviors using a visualization method. In this paper, we describe the visualization and quantification of the laser induced plumes by pulse holographic interferometry. A pulsed Nd:YAG laser was used for the generation of laser induced plume and a Q-switched Ruby laser was employed to record the weld plume. For qualitative visualization of the laser induced plume, we used the double-exposure holographic interferometry. Then, we chose the quasi-heterodyne holographic interferometry with the dual-reference-beam and phase shifting in order to visualize the plume quantitatively. The experimental results show the visible behavior of the laser induced plume according to a change in the output power of the pulsed Nd:YAG laser and the time delay of Q-switched Ruby laser. Finally, we obtained the quantitative results by using the dual-reference-beam.

In the world, there are several types of vibration, and these vibrations especially affect the mechanical industry. In this paper, experimental analysis of vibration modes of plates is discussed. Electronic speckle pattern interferometry (ESPI) is one of the optical nondestructive testing techniques. By using the ESPI, vibration modes of plates with various excitation points, ratio of longitudinal and lateral length, and materials are measured and qualitatively compared with the results of theoretical analysis proposed by Warburton. Finally, these vibration modes are quantitatively compared with the result of FEM analysis. The results of this study are as follows: (1) By comparing the theoretical and experimental frequencies, we confirmed qualitatively that deviations of frequencies are within 10% in accuracy. (2) By comparing the experimental vibration mode shapes with the numerical ones of the FEM analysis, we can conclude quantitatively that measuring vibration modes by using the ESPI has high accuracy.

There are many optical interferometric methods for measuring vibration, such as holography, speckle and moire interferometer. The electronic shearography technique has a lot of advantages in practical use1): low sensitivity for mechanical unstability, low limit in laser coherence, simple setup, etc.. The fringe patterns obtained by time-average shearography represent derivatives of amplitude of vibration2). Therefore, through a proper integration technique, the useful information of vibration modes can be obtained from shearograms.