If the magnetic field acts on the electrically conductive adhesive containing a ferromagnetic metal filler in the process of curing, the filler is oriented and the conductivity of the adhesive is expected to be increased. In this paper, the effects of the orientation of filler on the electrical conductivity of the adhesive and the adhesive bond strength are investigated. Iron powder and silver-plated iron powder were used as a filler and epoxy adhesive was used as matrix resin. The resistivity change with time in the curing process of the electrically conductive adhesive under magnetic field revealed some characteristic features. This is due to not only the orientation of the filler but also the change of the electrical resistance or other physical properties of epoxy matrix with the progress of curing. It was made clear that the alternating magnetic field was more effective than direct magnetic field on the increase of electrical conductivity of the electrically conductive adhesive. The filler particles were hardly observed on the interface between adherend and adhesive. Hence the existence of the filler in the adhesive did not influence upon the bond strength of the adhesive to adherend.
This paper deals with a quantity of heat to be transported into a substrate by plasma spraying. The quantity of heat was measured by means of a calorimeter. It is clear that a kinetic energy of powder particles is almost neglected when a velocity of the particles is less than 400 m per second. The quantity of heat transported by powder became a constant value which required for melting the powder. Total quantity of heat given by a plasma gas was extremely dependent of spray apparatus. Total quantity of heat by a plasma gas was estimated, but a distribution of heat quantity was not clear. When the distribution is assumed as Gaussian distribution, a heat input is estimated less than 25% errors.
It is very difficult to obtain high quality without cracks and charring by heat affection in the field of materials processing on ceramics or fibre reinforced plastics (FRP) by conventional CO2 laser owing to its low peak power and long pulse duration. A high peak and rectangular pulse CO2 laser excited by 1 MHz-silent discharge has developed. With the development of a new electrode system utilizing high dielectric constant ceramics plate, homogeneous discharge of power density up to 355 W/cm3 is obtained. An output peak power of 5 kW and pulse duration of 30 to 150 μs in a stable TEM00 mode operation is attained. A profile of focused beam can be measured by adopting 'Straight Edge Method' and it was made clear that the laser beam has a performance of convergency based on diffraction theory.
Change in focus position and focus power density caused by thermally induced optical distortion were analyzed theoretically and experimentally by physical optics and measurement using a beam measurement system, respectively, when high power CO2 laser beam having Gaussian intensity profile is focused by edge-cooled ZnSe lens. A simple equation was also derived to predict steady focus change on the basis of geometrical optics. Results obtained are summarized as follows: (1) Focus position was determined at a precision of ±0.2 mm by means of the beam measurement system using a slit probe and a pyroelectric detector, even when power ripple of incident laser beam is as high as 30%. (2) Focus change is predicted on the basis of the physical optics and the thermal conduction theory, when absorptivity of the lens and intensity distribution of incident beam are known. (3) At absorption powers less than 5W, original power density can be almost recovered by adjusting focus position of lens having thermally induced optical distortion. However, at absorption powers higher than 10W, power density cannot be recovered by focus adjustment any more. (4) Thermally induced optical distortion makes the slope of power density along optical axis smaller at lens side, which is opposite to the case of spherical aberration, and also focus depth deeper.
Since aluminum and its alloys possess many excellent properties, such as light weight, high thermal and electrical conductivity, high corrosion resistance, high specific strength and so on, they have been widely used in various fields. In order to make the most of them in future, it should be indispensable to develop a new joining technology for them. With the aid of ultrasonic vibration, a new soldering method for aluminum was proposed and investigated in this study. Commercial pure aluminum was attempted to be soldered in air using zinc as a filler metal. The effects of the ultrasonic vibration and several joining parameters on the soldered joints were examined. The aluminum could not be well soldered without ultrasonic vibration, and more than approximately 10μm vibration amplitude made the soldering possible. The stable and sound joining was achieved over the eutectic temperature between Al- and Zn- solid solution, however, the tensile strength of the joints soldered at the temperature in the vicinity of the melting point of zinc was apt to be lowered. The joints performed at the appropriate joining temperature, such as 673K, was sound when the applying time of the ultrasonic vibration was shorter than approximately 10 second.
We have been studying on soldering aluminum with the aid of ultrasonic vibration. In the previous paper, the effects of ultrasonic vibration, joining temperature and pressure on the properties of the joint were examined. In this paper, the effects of faying surface roughness and filler metal thickness on the joint properties were investigated. Furthermore, we discussed the joining process of this soldering method and referred the corrosion resistance of the joint. The Paying surface roughness and a polishing paper influenced considerably on the joint strength. Especially, when the polishing emery paper of # 1500 was used the SiC particle, which was the main component of the emery paper, was caught in the polished surface and caused the joint strength to decrease. The thickness of the filler metal also had much influence on the strength of the joint soldered at relatively low temperature. The strength was decreased with the filler metal thickness. The corrosion test revealed that the eutectic microstructure in the soldered part had low resistance to corrosion, and that the corrosion resistance increased with the increase of Al-solid solution volume in the microstructure. Referring to the joining process of this soldering method, it was known that the eutectic liquid formed at the Paying interface played the roles of not only wetting and bonding but also putting broken oxide films out of the interface.
Weld quality of spot welds was examined by a newly developed ultrasonic testing with a focussed probe. This method is based on the composite effects of convergence of the ultrasonic beam and attenuation of reflected waves due to the multiple reflection, and the back wall echo in the welded region is distinguished from the interface echo in the faying surface. In this study, the weld quality and weld size were evaluated by the parallel line scannings over the spot weld. In the scanning graphs of sound spot weld, the periphery of spot weld is given by the sharp minimum pattern and the welded region is represented by the protrusive pattern surrounded by the sharp minima. When the spot weld includes the expulsion, crack and shrinkage cavity or blow hole in the welded region, different patterns appear in the scanning graphs. The expulsion gives lower echo height region linearly distributed around the protrusive pattern, and the crack and shrinkage cavity give the depressed and small protrusive pattern in the protrusive one. Besides, irregular shaped nugget and mechanical or solid bonding interspersed around the welded region are evaluated by the irregular and banded shape of minimum pattern, respectively. These patterns were confirmed by the macroscopic observation of fracture surface. The imaging technique was also developed for the twodimensional representation of nugget and shrinkage cavity, from which the diameter and area of nugget were measured, precisely.
This paper deals with some problems concerning the sensing and controlling of the weld pool. A good quality of the welding result can be obtained by keeping the weld pool shape constant. The system for sensing and controlling the weld pool is proposed. First, authors tried to take an image of the weld pool with a CCD shutter camera. A new method is proposed to clearly take the weld pool. The method is to reduce the welding current as small as possible while the shutter of the CCD camera opens for 1 [ms]. The weld pool shape can be obtained by the image processing. Next, the method is discussed for controlling the weld pool. It may be difficult to describe the state equations of the weld pool shape, since welding phenomena are described by partial differential equations. Therefore, authors control the weld pool shape with the fuzzy controller. In fuzzy control, it is important to determine the control rule and the fuzzy variables. A new method is proposed for designing the fuzzy controller. The weld pool width w (t) for the welding current u(t) is approximated by a first order system with the time delay T : dw(t)/dt=-λw(t)+bu(t-T). In the system with the time delay, when the gain of the conventional fuzzy controller increase, the response of the plant may become unstable. In order to improve the control performance, the fuzzy variables and the control rules are constructed from design knowledge of the controller for the first order system with the time delay. Namely the deviation e[n], its variation Δe[n], the prior manipulating variable Δu[n-1], and the manipulating variable Δu[n] are used as the fuzzy variables. The validity of proposed method was verified by the experiments.
A type 329J1 duplex stainless steel was welded by gas tungsten arc welding in argon-nitrogen gas mixture atmospheres. The penetration depth of weld metal increased with an increase of the nitrogen partial pressure of atmosphere. No porosity was observed in the weld metals. The nitrogen content and microstructure of the weld metal were studied. The nitrogen content increased and the ferrite content decreased with an increase of the nitrogen partial pressure of atmosphere. The ferrite content decreased linearly with an increase of nitrogen content. Fine chromium nitride precipitates were observed in ferrite grains of weld metals, and the amount of precipitates decreased with increases of nitrogen and ferrite contents.
Surfacing on aluminum alloy has been investigated by gas metal arc welding (GMAW) process using a newly developed Al-Cu seamless type cored electrode wire of 1.2 mm in diameter. Two types of cored wires were tested, one is copper sheath type with alminum solid wire as inside core, and the other alminum sheath type. Their chemical compositions were both 30Al-70%Cu. Investigation were performed on metal droplet transfer phenomena, microstructure and hardness distribution versus arc current, effect of weld heat input on porosity formation, analysis of hydrogen gas from porosities. The copper sheath cored wire showed far superior quality to the aluminum sheath one. It has excellent arc stability, uniform and stable metal transfer, uniform hardness distribution in the surfacing weld metal. The overlay hardness 220-280 HV decreased with increasing weld heat input. Hydrogen gas causes porosity formation, which is reduced by increasing weld heat input readily to a low level of total area 1% in transverse cross section of surfacing weld metal. The porosities were very small in size, mostly less than 0.2 mm in diameter. Oxygen also seems to cause porosity formation.
Vibration of molten puddle is achieved with the low frequency pulsed MIG welding process of new current waveform to switch over two preset unit nulse conditions alternately. The degree of this vibration depended on switching frequency of unit pulse conditions, fs and there was an optimum frequency range of fs=10-30 Hz, and moreover large difference between two pulse current values promoted the molten puddle vibration. It was made clear that the stirring effect of molten puddle was expected by this process and this resulted in the remarkable grain refinement of weld structure of commercial avairable Al-Mg alloy base metal and wire within the optimum frequency range, especially fs=30 Hz. Moreover, this process.had a beneficial effect to improve the solidification crack susceptibility of Al-Mg alloy weld metal due to the grain refinement.
In this study, the authors have investigated on fatigue properties of titanium-matrix composites reinforced with SiC (CVD) fiber (FRM). The fatigue properties were examined for as-fabricated FRM, thermal-exposed FRM and unreinforced commercial pure titanium(CPTi) and Ti-21V-4Al alloy matrix. The fatigue strength of the as-fabricated FRM is three times higher than unreinforced CPTi and Ti-21V-4Al alloy. It is because the impeding effect of the fiber leads to low crack growth rates. After long thermal exposure (12h for CPTi FRM and 24h for Ti-21V-4Al FRM) at 1123 K, the FRM crack growth resistance is reduced mainly due to fiber degradation and notch effect of reaction zone. The fatigue properties of the Ti-21V-4Al FRM was lower than CPTi FRM because of coarsening of the grain of matrix. The fatigue properties of FRM is rarely determined as the deciding factor in that of matrix.
Highly mixed and bonded Ti-Al powders were made by mechanical alloying (MA) method, and these powders were plasma sprayed on the mild steel substrate under the reduced pressure conditions. Moreover, to fabricate the intermetallic matrix composite coatings, Ti-Al/Si3N4 MA pre-composite powders were made and plasma sprayed. Mo-Si system was also applied to make the intermetallic coating. The results obtained are summarized as follows; (1) The moderate MA powders, which have moderate powder size and highly mixed structure between two metal materials, could be prepared by selecting the moderate MA conditions. (2) Ti3Al intermetallic coatings were made by just plasma spraying of MA powders without after heat treatment. Intermetallic matrix composite coatings were also made by the similar spray process. The Ti3Al matrix composite coating had a Vickers hardness of about 1000. (3) The phase obtained by spraying of Mo-Si MA powder was fairly complicated. More detailed observation was required in this system.
CO2 laser deposition apparatus was newly developed, which enabled the high power laser- and the long time deposition without breaking window. Alumina thin films were deposited on stainless steel using a continuous CO2 laser (λ=10.6μm) for ablation of the alumina target. In this paper, the effect of various deposition parameters on hardness, deposition rate and adhesive strength of alumina films were investigated. Alumina films were analyzed using a scanning electron microscope (SEM), a X-ray diffractometer, an Auger electron spectroscope (AES) and a X-ray photoelectron spectron spectroscope (XPS). The results are summarized as follows. (1) Crack free films were formed at the substrate temperature of more than 673 K, although many cracks were observed in the films formed at room temperature. (2) Hard films more than Hk 1000 were formed under the pressure of less than about 1.33 Pa. (3) Depositon rate was controlled in the range of 10-3-8×10-2μm/s by varying the laser power, the ambient pressure and the distance between target and substrate. Deposition rate of this deposition method was much higher than that of Ion plating. (4) Film hardness had an excellent correlation with the deposition rate. Hard films more than Hk 2000 were formed with deposition rate of less than 3.3×10-3 μm/s. (5) Adhesive strength of hard films more than Hk 1000 by tensile test were higher than 40 MPa. (6) The deposition by a CO2 laser deposition resulted in stoichiometry close to the target. (7) Crystal structures of these films were found to be amorphous.