5052 aluminum alloy plate to SPCE steel plate were friction spot welded using a numerical controlled brake type friction welding machine. Microstructures and mechanical properties of friction spot welded joints were investigated The nugget such as a resistance spot welded joint was not observed, regardless of friction spot welding conditions. In case of friction time is longer, the intermetallic compound layer which had a thickness of 2-3 urn was observed at the weld interface. Hardness at SPCE steel side is no significant difference. However the softened area can be seen at the 5052 aluminum alloy side. The maximum tensile shear strength of welded joints was about 3.5kN. The test specimens which had the highest tensile shear strength were fractured at weld interface, and part of the 5052 aluminum alloy adhered to the SPCE steel side.

View full abstract

The 4-pipe-barzed specimen is used to obtain the strength of the brazed joint of the rocket nozzle skirt wall, which is made by the pipe works joined by brazing. The influence of the fillet shape to the strength of the 4-pipe-brazed specimen is numerically estimated by the finite element method with the non-linear static elastic-plastic analysis. The fillet shape is represented by the apparent fillet width and the clearance between the pipes. As far as the variation of the shape assumed in this research, the von Misee' equivalent stress in the fillet reaches to its tensile strength by the smaller nominal strain than the pipe, and rupture might always occur at the fillet. For the constant apparent fillet width of 1.0 and 2.0mm, the maximum nominal strain to rupture has the smaller extreme at clearance of 200μm.

View full abstract

Laser welding of lap joint between AZ31 and A5052 was studied. Formations of an intermetallic layer at the interface and under cutting were the main problems to weld the joint. In order to control the temperature distribution at the interface and the convection behavior of molten metal, effect of machined edge joint techniques was studied by FEM analysis. Laser welding experiment was carried out based on the result of FEM analysis. The strength of the welding joint obtained by the above method was comparable with the strength of joint made by solid state welding technique such as diffusion bonding and frictional welding.

View full abstract

Brazing of stainless steel to various aluminium alloys had been carried out using Al - Si filler and flux in air. The brazing properties changed remarkably with kinds of aluminium alloy. Also in the aluminium alloy of the same kind, brazing property changed remarkably by the change of a slight temperature. It was considered that these phenomena are due to the composition of base metals and the filler metal, the difference in the surface structure, and also the melting and solidification behavior by the reaction between the aluminium alloy base metal and the filler.

View full abstract

We developed an apparatus for the particle assemblage that makes it possible to deposit and to weld a fine particle on a desired position using a microprobe. We have already shown that gold and nickel alloy particles can be welded. In this report, other metal particles are welded at the point of Re-W needle of 125μm in diameter. Ag-Pd-Cu alloy particles of 40μm can be welded by replacing the probe of 35μm to that of 660μm. Defects were not observed at the welded interface. The heat affected zone is shown to be very narrow by EDX analysis.

View full abstract

Anodic bonding between ionic conductor ceramics and metals was attempted. Ionic conductors used are beta alumina and partially stabilized zirconia (YSZ) sheet, and metals are aluminum and silver sheet Anodic bonding was performed by the optimization of voltage and temperature conditions. But the bonding strength is low compared with the anodic bonding between ionic conductor glass and metals. Furthermore, the interracial structure was observed by election microscopy in order to clarify the interfacial reaction and bonding mechanism.

View full abstract

The erosion of Ni baaed alloy substrate to the convection of the molten 54mas8%Ag-21ma88%Cu-25masB%Pd (BPd-6) brazing filler metal is numerically analyzed. During the brazing process using BPd-6 with organic binder, the binder is heated by radiation to form the slag floating on the molten brazing filler metal surface. The slag becomes the heat spot which might induce the Marangoni convection of the molten brazing filler metal. The numerical analysis of flow and temperature fields of the molten brazing filler metal reveals that the Marangoni convection occur on the case of the slag temperature of 1,050℃ and 1,010℃ on the 1,000℃ molten BPd-6. The flow is the well-up type around the slag. The substrate is considered to be eroded by the combination of the metallurgical dissolution and the Marangoni convection. The eroded pif s depth is quantitatively estimated from the total flux of the molten BPd-6 flown over the substrate surface is quantitatively.

View full abstract

Braze Pressure Welding (BPW) had been invented as the new joining method for the ordinary steel piping. BPW is the pressure welding with high frequency induction heating using the brazing filler as the interlayer metals. In the general idea of BPW, the liquid interlayer metals clear the joining surfaces, which are considered to be covered with the contamination layer of the oxide films and so on. The joining pressure discharges the liquid interlayer metals involving the oxide films from the joining interfaces. In addition, it forms the fillets around the joint. The base metals with cleared joining surfaces are pressure-welded by the relatively low joining pressure. Thus in BPW, the interlayer metals play an important role in welding the high performance joint. In this paper, the clearing property of the interlayer metals on the joining surfaces for clarifying the joining phenomenon was discussed. It was confirmed by the observation of the clearing effect, and the discharge of the inclusions produced by oxide films by the interlayer metals and the miniaturization of the inclusions by optical microscope and the EPMA analysis.

View full abstract

A new numerical method has been developed to estimate the transient distributions of temperature near a friction surface in friction welding. The present method consists of the finite element method applied to a non-steady heat conduction problem and the heat input model, that is the evaluation of friction heat. To find the most proper model of heat input, empirical formulae for coefficients of friction were examined comparing with experimental data. It was found that considering the dependence of friction coefficient on temperature and friction speed gives good results.

View full abstract

The temperature field during the friction welding process is numerically estimated. The friction welding process of SUS304 stainless steels is analyzed using the finite element method. The heat coefficient A_l is proposed for the frictional heating: q_o=A_l(3Q)/(4πR^6)r. The A_l value is deduced from the experimentally obtained temperature history of several points on the specimen's surface. The heat input surface is translated with time evolution to reflect the discharge of the weld flush from the joining interface. To decide the A_l value and the translation length of the heat input surface, the frictional joining experiment is conducted for SUS304 stainless steel bars, and the temperature history and the compression length of the specimen are measured. The obtained A_l values are varied with time. By using the Ai values and the compression length as the translation length of the heat input surface, the precisely identical temperature distribution can be calculated.

View full abstract

The mechanical properties of phase controlled friction welded joints of both 6063 aluminum alloys square bar and grooved square bar, which were friction welded by using a numerical controlled brake type friction welding machine, were examined. The phase controlled friction welding was using a servo motor positioning with hydraulic brake system. The burr was not generation from comer, and the burr occurred from the side. The burr of rotational side deviated to reverse side of the rotational direction, and the burr of fixed side inclined towards rotational side. The tensile strength of both square bar joint and center of grooved bar joint showed about 80% that of base metal, but the tensile strength of corner of grooved bar joint showed about 67% that of base metal. The elongation of joints was increased with increasing of friction time, but the elongation of all joints were lower than that of the base metal.

View full abstract

In the present study, concerning the coefficient of dynamic friction (i between stir rod and welded material which is quite important for clarifying heat transfer processes in friction stir welding, spot friction stir welding and so on, evaluation of the coefficient μ has been conducted based on torque measurement acting on the material. From the measured results using aluminum alloy A7075 as a welded material, it has been shown that the first approximate value of 0.76 can be evaluated for the coefficient of dynamic friction between the stir rod (high speed tool steel, SKH51) and A7075.

View full abstract

The present paper describes effect of indenter materials on Hertzian cracking of alumina ceramics. Two kinds of alumina ceramics having different density and 4 kinds of sphere indenters with different elastic modulus were used for the experiment. The crack initiation during the indentation was detected with acoustic emission. Experimental data showed that the fracture behavior such as the fracture load, ring crack radius and indentation strength were different depending on indenter material. In order to investigate the effect of indenter materials on the fracture behavior, numerical simulation (FEM) and observation of the crack growth below the indented surface were carried out. As results, it was confirmed that the frictional resistance at the interface influenced on the ring crack radius and that cone crack length was different depending on fracture load.

View full abstract

Diamond-like carbon (DLC) films are metastable amorphous carbon materials with superior tribological characteristics. As a kind of industrial application, it is very necessary to reduce the friction and wear of inner wall surface of many industrial components with holes and slots, such as microextrusion dies, etc. In this paper, we will discuss friction and wear characteristics of DLC films which were deposited on the inner wall surface of model dies with slots of 22 mm in length, 10 mm in width and 20 mm in depth by using pulse plasma CVD method.

View full abstract

Hard coatings, such as Hard Cr plating and CrN, show the excellent anti-wear properties under normal sliding test condition with lubricant. It is very difficult to evaluate the prepotency from the few differences in wear values, In order to detect significant variance, we tried to use the lubrication-oil which contains carbon soot for the reciprocating sliding test. Addition of carbon soot resulted to clear the differences of wear properties between the anti-wear hard coatings.

View full abstract

In this study the influence of micro structure of wear resistant materials consisting of hard phase and metal matrix on particle erosion rate at high temperature was investigated. High temperature erosion tests were carried out by a centrifugal erosion tester, and worn surfaces were observed by SEM to clarify the wear mechanism. From the results of the tests and the observation, it was found that erosion was caused by the platelet mechanism of the metal matrix. A new erosion model was discussed and a new parameter Spm, which represents severity of the platelet formation in the metal matrix, was proposed. To decrease erosion rate of a material, it is necessary to design a material whose value of Spm is small.

View full abstract

At high pressures or at low temperatures lubricating oils cause the solidification First, phase diagrams of paraffinic mineral oils (PN), traction oils (SN), polybutene (PB), DOS and BBPH were drawn in pressure-temperature plots of three different states (liquid, viscoelastic solid and elastic-plastic solid). Next, the four-ball tests were used to evaluate anti-wear characteristics of lubricating oils in boundary lubrication regime. The SNs showed the minimum wear scar in four-ball wear test The anti-wear characteristics of oils was closely related with EHL film thickness and the oil molecular packing parameter T_<VE>-T (T_<VE> : viscoelastic solid transition temperature at pressure p of wear test condition, T: oil temperature).

View full abstract

Effects of graphite size and volume fraction on mechanical and tribological properties of Cu-Sn-graphite composites produced by a powder metallurgy process were investigated in order to develop a suitable self-lubricating material. The graphite size and volume fraction were varied from 3μm to 2.3mm, and from 0 to 40 vol%, respectively. The density, microstructure, bending strength, wear rate and coefficient of friction of the sintered composites were examined. It was found that the composite containing 20 vol% graphite of 100μm in size showed the best performance in mechanical and wear properties.

View full abstract

The cobalt alloys "Stellite No.6 and No.21 " are welding materials and have excellent properties to resist corrosion, wear and erosion. On this account these alloys are applied to the valves and many other machinery parts. However, these alloys show unexpected erosion damages under a certain kind of fluid conditions. The preceding study clarified that the good erosion properties of these alloys may be attributed to the features of the t phase transformations. On the contrary, these alloys show greater erosion damages comparing with other alloys under the slight or no E phase transformed fluid conditions. The iron contents of these alloys are increased by the improper welding conditions. This study is carried out to clarify the effects of the iron contents to the cobalt base alloys erosion properties by the room and hot water jet impact tests. Test results suggest that the quantity of iron to prevent the formation of ε phase accelerate the erosion of these alloys.

View full abstract

Observation of stress distribution in an adhesive layer was carried out to mix a mecanoluminesence material. The novel material is ceramic powders which consist of SrAl_20_2:Eu and shows luminescence when loads are applied. Specimens of joints having transparent adherends of acrylic plates bonded with the adhesive including the mecanoluminesence material were prepared. Quasi static load or repeated load were applied to the specimen The luminescence of the adhesive layer were observed through the transparent adherend. Bright parts were found around the both edges of the joints. Therefore, it seems that the stress distribution along the bond line can be visualized by the method.

View full abstract

Combined tension-torsion experiments of an adhesively bonded butt-joint were performed using a highly ductile acrylic adhesive. From the experiments, it was found that the multi-axial flow stresses and fracture limits are strongly dependent on shear strain rate and stress multiaxiality. The multi-axial flow stresses are calculated with an extended version of the present authors'constitutive model, and they are compared with the corresponding experimental data Furthermore, fracture limit curves expressed in the normal and shear stress plane is discussed based on the experimental data and the numerical predictions.

View full abstract

An experimental method was proposed for evaluating the modes I+II fracture toughness of CF/concrete adhesive interface. The validity of the evaluation formula was confirmed by numerical analysis using the finite element method. The mixed mode fracture toughness decreased remarkably by increasing the mode I component. The microscopic crack path was not in the adhesive interface but in the concrete. However, the fracture toughness of CF/concrete adhesive interface almost corresponded to that of steel/steel adhesive interface.

View full abstract

The mechanical properties of adhesives are determined either from bulk material samples from adhesively bonded joints. For many years there has been controversy as to whether the mechanical properties obtained through testing bulk material are representative of the adhesive in its thin-film form. The use of adhesive bonding as a method of joining structural members in advanced structures is increasing. A major advantage of adhesive bonding is that it enables dissimilar materials to be joined and reduces the localized stresses encountered when using mechanical fastening such as bolts and rivets. In design process it is important to know unambiguously the mechanical properties of the materials being used. Because the adhesive is used in thin-film from, to obtain the mechanical characteristics of the adhesive in situ is hoped. In several papers it has been found that the adhesive material has different mechanical properties when tested in the thin-film form and bulk form, and further that a thickness effect exists, causing the properties to depend on the thickness of the bondline. However, the good agreement between thin-film and bulk properties is obtained in other papers. Moreover, the existence of the boundary layer in the adhesive layer is reported. In this paper, nano-indentation testing is carried out for the calibration specimens and two kinds of the specimens of adhesive. And the method in the former paper applied to know the distribution of local mechanical properties in the adhesive layers and the bulk material.

View full abstract

In order to investigate the effect of tensile shear-induced bending deformation of sheet metals in adhesively bonded single-lap joint on the shear strength of adhesive, in the present work, tensile lap shear experiments on an aluminium sheet joint bonded with the acrylic adhesive were performed at room temperature. Since this type of adhesive has strong rate sensitivity in flow stress, bending deformation becomes larger with increasing tensile speeds. For the prediction of bending deformation, a numerical analysis of elastic-plastic bending deformation of singlelap sheet metals is presented.

View full abstract

The expansion behavior of dismantlable adhesives including thermally expansion agents was investigated experimentally. The adhesives have capability to be separated after use by heating and is quite useful for the recycling of adhered materials. To investigate the expansion mechanism of the adhesive, the volume change of an expansion agent was measured under hydrostatic pressures. Only few MPa of expansion pressure of the agent could be measured at the condition of being included in the cured resin. Using the other organic expansion agents such as ADCA and OBSH, experiments to check their dimantability were carried out. In some cases, separation of the adherends was observed on the specimens bonded with the adhesives.

View full abstract

The measurement method of the crack growth rate for an adhesive layer under impact load was evaluated by adding impact load to a tubular butt joint. The material of adherends used was aluminum alloy A5052-H34, and the acrylic bonded Hardloc M-372-20 was used as the adhesive. In this experiment we conducted measurements of stresses by observing the stress wave pattern, where the specimens are subjected to two different kinds of impact loads, one under the free-fall impact of the striker and another is under accelerated striker using compressed air. By accelerating the striker using compressed air, only the first wave of the stress wave can be measured. In addition, the crack growth rate was about 7mm/μs. From the above result, it can be concluded that we can obtain the stress value when a crack occurs under the impact loading test.

View full abstract

A measurement method for the absorbed energy to the adhesive joints fractured by subjecting impact loads was studied. One-dimensional elastic wave theory was used for the calculation of the absorbed energy. The experimental equipment which can apply the theory was developed. The performance of the experimental equipment was investigated. Specimens were manufactured using the adhesion tape. The absorbed energy when this adhesion tape is fracturing is small. As a result of the experiments, It found that the measurement of energy is possible even if the value of fracture energy was very small. As the above result, it was thought that the precision of this measurement method is high sufficiently.

View full abstract

The Charpy impact test machine is used for the measurement of fracture energy under impact load. However, as the energy for the specimen to be displaced is also contained in the measurement value, it is difficult to measure the energy used only for the fractured specimen. Therefore, we used the Hopkinson pressure bar method, where dynamic stress and strain can directly be gained. From the stress waveform obtained, the fracture energy of the adhesion under impact load was computed. Consequently, the fracture energy between the adhesion tape and the adherend joints interface was 2.5J/m^2.

View full abstract

Using C/C composite materials fabricated by preformed yarn method, we plan to observe the initial state of this materials. And conducting the tensile tests for several temperature we keep records of fracture strength and observe the state after heating and testing. And based on these results, we want to analyze the strength of this materials.

View full abstract

We developed a small fatigue testing machine using a Piezoelectric actuator. The fatigue testing machine was designed on the concept of micro-factory. Fatigue tests have been carried out on high strength Ni-based metallic glass. The fatigue strength of the material is about 350MPa, and this strength is 13% of the tensile strength of 2.7GPa. Fracture has been occurred for a moment due to the glassy structure after the crack propagation initiated at the inside of a specimen. Striation due to the crack propagation during the reated cycles has been observed and the vein pattern has been recognized at the fractured surface.

View full abstract

It is well known that Shape Memory Alloys (SMAs) recover the original shapes after deformation when heated. SMAs also show excellent damping properties compared with other materials. In this study the attenuation property of NiTiCu alloy in the small strain region is investigated using the inverted torsion pendulum. As the temperature goes up, phase transformation from martensite into austenite occurs, when the extent of attenuation decreases. This nhenomenon is different frnm those of other materials.

View full abstract

A method for fatigue damage evaluation was investigated to detect fatigue damage and estimate fatigue life of steels with optical method using laser. In fatigue of mild steels, fatigue damage occurs from material surface, slipbands appear anddensity of the slipbands increases with progress of fatigue damage. In this method, surface change due to slipbands is detected by change in light intensity distribution of diffusion pattern of the reflected laser light from surface of the fatigued steel. Using this method, we are able to detect fatigue damage before crack initiation by observing difiusion pattern change, In this study, we investigated relation between change of difiusion pattern and number of loading cycles and we devised a method to estimate fatigue life of the object material by observing change of the diffusion patterns during fatigue loading.

View full abstract

Specimens were subjected to testing to elongate to required plastic strains, and then subjected to the ultrasonic measurement with immersion and local immersion method. The ultrasonic measurement was carried out by using a probe of 20MHz, in the tensile and transverse directions. Surface wave velocities were obtained by immersion method and local immersion method were almost the same. Velocities in the tensile direction were larger than that in the transverse direction. Velocities changed largely with residual strain. Surface waves were also measured using two probes by immersion method and local immersion method.

View full abstract

This paper describes the basic study on measurement of guided waves using piezoelectric film. Over the past few years, nondestructive inspections using guided waves were performed. In the inspection, piezoelectric ceramics are used mainly. Since a piezoelectric film also has a piezoelectric effect and flexibility, it is available for the inspection. Then, an experiment using the piezoelectric film was performed. The results show that the echo obtained by piezoelectric film agrees with those obtained by the conventional method.

View full abstract

In this study, a temperature insensitive damage evaluation parameter is proposed. Ultrasonic wave velocity was measured for different propagation direction in order to evaluate angular dependence of ultrasonic wave propagation. Every experiment was conducted at constant temperature to eliminate influence of temperature variation. Consequently, it was found that anisotropy of wave velocity does not change even if temperature changes, although wave velocity itself changes with temperature. It was also found that formation of cracks causes significant change in ultrasonic anisotropy therefore it can be used as a temperature independent damage evaluation parameter for FRP laminates.

View full abstract

A time domain boundary element method (T-D BEM) is discussed for the visualization of ultrasonic wave fields. The T-D BEM needs considerable computational memory capacity because of a stepby-step time marching calculation. To save the memory size we introduce an interpolation method into the calculation of coefficient matrices (fundamental solutions). The advantage of the memorysaved technique is shown in the scattering analyses. In this study, the memory-saved technique is then applied to a dynamic water-solid coupling problem.

View full abstract

The in service inspection (ISI) of MONJU fast breeder reactor vessel is performed at elevated temperature (about 200℃). A horizontally polarized shear (SH) wave electromagnetic acoustic transducer (EMAT) is used to perform the volumetric inspection of the MONJU reactor vessel. In this paper, the magnetic flux density distributions of a SH wave EMAT with a so-called Halbach magnet structure is analyzed from room temperature up to 240℃. The relative reduction of the magnetic flux density is less than 15% and the thermal demagnetization is about 5%, respectively. As a result, the Halbach magnet structure can be used at elevated temperatures without large performance reduction as compared to its performance at room temperature. This new structure EMAT is suitable for MONJU reactor vessel ISI.

View full abstract

A newly developed ultrasonic high temperature sensor and its application to an m-situ monitoring of a solid/liquid interface during unidirectional solidification of an aluminum alloy (Al-12.6%Si) are presented. The developed sensor mainly consists of a piezoelectric ultrasonic transducer (UT), a cooling system and a clad titanium (Ti) buffer rod. The longitudinal velocity monitoring during melting and solidifying processes of the Al alloy is successfully performed using the developed sensor. Then, attempts to monitor the solid/liquid interface of the alloy have been made at frequency of 2.25 MHz. A reflected echo from a stable solid/liquid interface has been clearly observed. Furthermore, The behavior of the echoes from the growing interface during unidirectional solidification process has been monitored. From the behavior of the echoes, the location and growth rate of the advancing interface can be determined.

View full abstract