Showing papers in "Transactions of JWRI in 2009"

Prediction of Distortion Produced on Welded Structures during Assembly Using Inherent Deformation and Interface Element

Abstract: The objective of this research is to develop a practically useful finite element method for predicting distortions of structures under welding assembly. In this method, distortions produced by various thermal processes, such as the cutting, the forming, the welding and the straightening can be considered. These distortions are simulated using the inherent strain. On the other hand, the detail of how the gaps and the misalignments are controlled during the fitting process also has significant influence on the distortion. The gaps and the misalignments between parts are modeled using the interface element. The potential capability of the proposed method is demonstrated through simple examples.

Effect of Consolidation and Extrusion Temperatures on Tensile Properties of Hot Extruded ZK61 Magnesium Alloy Gas Atomized Powders via Spark Plasma Sintering

Abstract: The effects of powder consolidation and extrusion temperatures on the microstructure and the tensile properties of hot extruded ZK61 alloy powder were investigated. The powder was produced by the rapid solidification technique of spinning atomization. Consolidation of the powder was done using the spark plasma sintering process at 200, 300 and 400 ℃. Hot extrusion was then performed at 250, 300 and 400 ℃. The tensile properties were then evaluated and correlated to the Microstructural features, i.e. grain size. The results show that the use of rapidly solidified atomized powder could lead to improved mechanical response as a result of the refinement of both grain and precipitated compounds which are obtained through the use of powder metallurgy process. These results, along with other previously reported studies, prove that powder metallurgy technique can help to extend the applications of Mg-alloys in higher load carrying components.

Numerical Study of Joining Process in Magnetic Pressure Seam Welding

Abstract: The magnetic pressure seam welding is one of the candidate methods to join thin sheet multifunctional materials. In this research, to examine the mechanism of magnetic pressure welding from a dynamic viewpoint, numerical simulation of the impact was carried out by using a commercial Euler-Lagrange coupling software MSC.Dytran (MSC.Software) as a first step of the computational studies, where the joint between Fe and Al was employed according to the previous experimental researches. From the serial numerical results, it was found that the increase of temperature at the joint interface was not enough to melt Al or Fe in the range of collision velocity and angle studied in this report. Also, it was revealed that the very large mean stress occurring at the interface which could be considered as the pressure at joint interface and Al moved with high velocity along the interface. Moreover, it was found that there were two patterns of plastic strain distribution near the joint interface depending on the collision velocity and collision angle. Finally, it can be concluded that the plastic strain pattern might be related to the success of magnetic pressure seam welding.

Development of New Composites; Ceramic Bonded Carbon

Abstract: The new carbon composites which we named Ceramic Bonded Carbon (CBC) consist of carbon grains bonded with ceramic grainboundaries. The CBC structure can protect carbon against oxidation and improve the strength due to the three dimensional network of ceramic grainboundaries. We have developed two processing routes for different CBCs. One is for a SiC/CBC which was fabricated by SiC coating on carbon particles through the reaction of SiO vapor and carbon at 1500°C in vacuum and their consolidation at 2000°C for 20 min using a pulsed electric current sintering. Another approach is for a Si 3 N 4 /CBC by gelcasting, the preform of CBC and consolidation at 1500°C for 5 min. Both CBC compacts exhibited similar microstructures to the CBC model having the ceramic grainboundaries of SiC and Si 3 N 4 with thicknesses below 3 μm. They had the bulk density in the range of 2.2 to 2.5 g/cm 3 , relative density of about 90%, bending strength of 115 to 150 MPa, and electrical resistivity of 60 to 1800 μΩm. These results suggest that the CBCs have a large potential to extend the performance and application of carbon materials.

Numerical and Experimental Study on Nugget Formation in Resistance Spot Welding for High Strength Steel Sheets in Automobile Bodies

Abstract: Resistance spot welding is the most popular joining process in automobile body assembly production lines. There have been many researches concerned with spot welding for two pieces of sheets. In order to reduce the cost and improve the strength of the lightweight automobile bodies, resistance spot welding for multi-pieces of sheets has to be investigated before production. In this paper, resistance spot welding for three pieces of high strength steel sheets is mainly taken as an object and the nugget formation process is firstly investigated by experiments. Then the spot welding process is simulated by FEM program JWRIAN developed by the authors with the coupling of the electrical field, thermal field and mechanical field. The nugget size and its formation process predicted by FEM agree very well with experimental results. Based on the simulation results, weldable conditions (current, cycles and force) of spot welding for both two pieces and three pieces of high strength steel sheets can estimated with a good accuracy. 1. Background Finite Element Method (FEM) has been routinely applied in automobile industries for the analysis of structural strength and component design because of the spread of computers with high performance, low price and development of FEM software. It has also been playing a significant role in predicting the behavior of the weld cracking, weld distortion and residual stress in a welding area 1) .

Visualizations of 2D Temperature Distribution of Molten Metal in Arc Welding Process

Abstract: In the present research, a general-purpose method for measurement and visualization of the temperature distribution of an object in arc welding, such as a tungsten electrode and a weld pool in GTA welding, and also a metal droplet and a weld pool in GMA welding, was conducted. Two-color pyrometry is utilized to obtain the temperature of the object. The object is photographed by high speed camera during arc welding. Two wave lengths (950 nm and 980 nm) in the infrared range are selected from the thermal radiation emitted from the object by using an imaging spectroscope, and the temperature is obtained from the intensity ratio of the two waves of radiation. Consequently, it was seen that in CO 2 arc welding, the 2D temperature distribution of the metal droplet is not uniform, namely, ranging from 2000 K to over 3000 K, while the 2D temperature distribution of the weld pool is more uniform, about 1800 K. It was found that there is a great difference between the temperature of the metal droplet and that of the weld pool in GMA welding process.

Polysaccharide Hydrolysis and Metallic Impurities Removal Behavior of Rice Husks in Citric Acid Leaching Treatment

Abstract: Rice husk is one of the representative non-eatable biomasses, and contains 70~75 mass% organics such as cellulose and hemi-cellulose and 15~20 mass% silica (SiO 2 ) elements. From a viewpoint of the wide use of the biomass energy, its cost reduction is strongly required by selecting suitable raw materials as biomass fuels and optimizing the operating conditions. In the present study, rice husk was selected as input raw fuel materials because after extracting the above organics as the biomass energy from rice husks, their residues consisting of high-purity amorphous silica would be an industrial resource with added value, and resulted in the total cost reduction of the biomass energy. For high-purification of silica materials originating in rice husk residues, the citric acid leaching treatment and the following water rinsing process of rice husks were used to remove metallic impurities such as Na, K, Ca, Mg, Fe, Cu, etc. In this study, the optimization of the operating parameters such as the concentration and temperature of citric acid solution, the stirring time in the acid leaching and water rinsing treatment, and combustion temperature were examined out for the removal of metallic impurities and the hydrolysis reaction of the polysaccharides. XRF and ICP analysis were used to quantitatively evaluate the residual content of impurities and carbon elements. GC-MS and FT-IR analysis of rice husks after leaching were conducted to examine their hydrolysis behavior.

Mechanical Properties and Machinability of Extruded Cu-40%Zn Brass Alloys with Bismuth via Powder Metallurgy Process

Abstract: In this paper, the uniform distribution process of bismuth particles in Cu-40Zn brass alloy by powder metallurgy (P/M) and machinable lead-free P/M brass with bismuth are described. Cu-40Zn Brass with bismuth powders produced by the rapid solidification processing were used as raw materials, having mean particle sizes of 150 μm. Three kinds of billets were prepared for the extrusion, namely green compact, sintered billets by using spark plasma sintering (SPS) and cast ingot. Bismuth dispersed in brass powder formed grains and dissolved into the powder surface by the heat treatment at the temperature over the melting point of bismuth. The behavior of bismuth existing in the primary particle boundary caused a decrease in the elongation of the extruded brass. Drill cutting ability was improved for the extruded material with the continuous machining chip. The shape of the machining chip was affected by the combination of brass matrix and the distribution of bismuth.

Numerical Analysis of Current Attachment at Thermionic Cathode for Gas Tungsten Arc at Atmospheric Pressure

Abstract: In a gas tungsten arc at atmospheric pressure, electrons are emitted from a thermionic cathode of the tungsten electrode, of which the work function would be reduced by generally adding an emitter material such as thorium oxide (ThO 2 ), lanthanum oxide (La 2 O 3 ), and so on. However, there is still a lack of practical understanding of the physical behavior in the electrode region. For example, current attachment at a thermionic cathode is not yet clear. The present paper presents a methodology for predicting the current attachment at a thermionic cathode for the gas tungsten arc at atmospheric pressure in argon. It is suggested that the current attachment at thermionic cathode is dependent on work function, melting point and the Richardson constant of emitter materials.

Microstructure and Hardness of Tungsten Coating for High Heat Resistant Material Produced by Means of Gas Tunnel Type Plasma Spraying

Abstract: Tungsten (W) is the metal which has the highest melting point of 3422 °C, therefore when deposited as a coating it can protect the substrate surface from high heat flux. The W composite produced by coating methods will be a superior candidate for aerospace materials which require high heat resistance (such as TBC). Thermal spraying method is one of potential candidates to produce W composites. In this study, pure W coatings were produced on stainless steel substrates by gas tunnel type plasma spraying at a short spraying distance (40-50mm). Regarding the microstructure, the W coating contained some pores. The Vickers micro-hardness of the W coating was measured as the mechanical property. The W coating had a hardness of Hv=260-320 along its cross section, which is a little lower than the hardness for bulk tungsten. The results of X ray Diffraction showed that the coating consists of pure tungsten, without oxidation.

Titanium Matrix Composite Reinforced with In-situ Formed TiC Using Carbon Black Nano Particles via a Wet Process

Abstract: Powder metallurgy (P/M) titanium matrix composite (TMC) reinforced with carbon black particles was produced by spark plasma sintering (SPS) and the hot extrusion process. Carbon black particles were added for the in –situ formation of TiC dispersoids in the SPS process. Two kinds of titanium (Ti) powders, sponge and fine Ti, were coated with carbon black particles via a wet process using the zwitterionic solution containing carbon black particles. The distribution of the particles on the Ti powder surface before the consolidation process was observed by scanning electron microscopy (SEM). The morphology and distribution of in-situ TiC phases were investigated by optical microscope and SEM equipped with an EDS analyzer. The mechanical properties of extruded pure Ti composites reinforced with in-situ formed TiC particles were evaluated. The mechanical properties of these composites were remarkably improved by adding a small amount of carbon black from 0.07 ~ 0.16wt.%. Finally, the fractured surfaces of TMC specimens after the tensile test were observed.

Tribological Properties of WC/12Co Cermet - Fe-Based Metallic Glass Spray Coating

Abstract: A composite coating containing WC/12Co cermet and Fe 43 Cr 16 MO 16 C 15 B 10 metallic glass was successfully deposited onto type 304 stainless steel by high-velocity oxygen fuel (HVOF) spraying, and the microstructure and tribological properties were investigated. The microstructure of the coating was characterized by scanning electron microscopy/electron probe micro-analysis (SEM/EPMA) and X-ray diffractometry (XRD). The hardness and tribological properties of the coating were tested with a Vickers hardness tester and reciprocating wear tester, respectively. The composite coating, in which flattened WC/12Co was embedded in amorphous Fe 43 Cr 16 MO 16 C 15 B 10 layers, exhibited high hardness, good wear resistance and a low friction coefficient compared to the monolithic coating. The addition of 8% WC/12Co to the Fe 43 Cr 16 MO 16 C 15 B 10 matrix increased the cross-sectional hardness from 660 to 870 HV and reduced the friction coefficient from 0.65 to 0.5. WC/12Co reinforcement plays an important role in improving the tribological properties of the Fe 43 Cr 16 Mo 16 C 15 B 10 coating.

Friction Stir Welding of High Carbon Tool Steel (SK85) below Eutectoid Temperature

Abstract: The present study is concerned with applying FSW to a high carbon tool steel (0.85 wt % carbon, JIS-SK85, AISI-1080) with below and above A 1 (726° C) welding conditions and analyzing the joints as well as evaluating the joint quality. Defect-free joints can be successfully fabricated and the joint structure and the mechanical properties were investigated for both conditions. The microstructures of the above A 1 joints mainly consisted of martensite. Therefore, the micro-hardness of the above A 1 joints is significantly higher at more than 1000HV. The tensile tests results are scattered and some of the joints are fractured at the stir zone while others are fractured the base metal. On the other hand, the microstructures of the below A 1 joints consist of ferrite with globular cementite, and grain-refinement occurs because no phase transformation to the martensite structures occurs. The high carbon tool steel was successfully friction-stir was welded below the A 1 and a method has been established to obtain sound joints which show a stable fracture and a good strength.

Microstructural and Mechanical Properties of Ti Composite Reinforced with TiO2 Additive Particles

Abstract: Titanium (Ti) alloys can be applied to various products in aircraft, automotive and motor cycles industries because of their weight reduction effects, superior mechanical responses and high corrosion resistance. Ti-6Al-4V (Ti64) is one of the most common Ti alloys used in structural components. It shows a high tensile strength of 900MPa or more. On the other hand, the poor elongation of about 10% is one of the disadvantages of Ti64 alloys. In addition, high cost additional elements such as vanadium and difficult melting processes increase the total material cost of Ti64. That is why its applications are limited to high-performance products. In this study, a highly strengthened pure titanium has been developed using high-purity titanium powder (HP-Ti) by elemental mixing with titanium oxide (TiO 2 ) powder and avoiding the melting process. The main strengthening mechanism of this material is the oxide dispersion strengthening (ODS) by elementally mixed TiO 2 in fine dispersoids. Elementally mixed powder of HP-Ti and TiO 2 was consolidated by the spark plasma sintering (SPS) process. To improve the ductility of sintered material, hot extrusion was applied to sintered HP-Ti. For example, the extruded HP-Ti mixed with 0.8wt% of TiO 2 particles indicated a high tensile strength of 863 MPa and good elongation of 26.7%.

Effect of Different La Additions on the Microstructure and Mechanical Properties of Hot Extruded SWAP Mg-Al-Zn-Ca Powder

Abstract: The microstructure and mechanical properties of hot extruded Mg-Al-Zn-Ca alloys with different Lanthanum additions were investigated. Both rapidly solidified powders, produced via Spinning Water Atomization Process, and cast billets were extruded at 573, 623 and 673 K to optimize the processing conditions for obtaining better mechanical response. Powders were consolidated to prepare the extrusion billets using both cold compaction and Spark Plasma Sintering at 473, 573 and 623 K. The tensile properties of the extruded alloys were then evaluated and correlated to the observed microstructure. The results show that the use of rapidly solidified Mg-Al-Zn-Ca powder with La additions could lead to effective grain refinement, which in turn resulted in the improved mechanical response, especially compared to the extruded conventional cast material. The La content of 1.5% has shown superior tensile properties compared to that of 1.3%, and to other Mg alloys like AMX602, especially the elongation, as shown in Fig. 1. This may help extend the applications of Mg alloys to higher load carrying parts while maintaining the excellent advantage of light weight parts.

Microstructure and Hardness Distribution of Friction Stir Welded 1050 Al and IF Steel with Different Original Grain Size

Abstract: In this study, 2mm-thick commercial 1050-Al plates and IF steel plates with three different kinds of original grain size were subjected to the friction stir welding process. These three kinds of samples with different grain sizes were obtained by accumulative roll bonding after a 5 cycles process, 5 cycles ARB process plus annealing and fully annealing, respectively. The microstructure evolution and Vickers hardness in the stir zone of all the samples were investigated. For both 1050-Al and IF steel, the ARB plus annealed samples with an intermediate original grain size finally produced the most refined microstructure and highest Vickers hardness in the stir zone. While for the ARB processed samples with ultrafine grained structure, significant grain growth and decrease in hardness occurred in the stir zone. The microstructure coarsening in the stir zone is suggested to be caused by the heating of the unstable structure in the ultrafine grained materials during friction stir welding process.

Mechanism and Effect of Stress-induced Transformation on Improvement of Fracture Toughness

Abstract: To study the influence of expansion under phase transformation on ductility of the material, a finite element method employing interface element is developed. It is applied to the fracture problem of a rectangular specimen with a center crack and a three point bending of specimen with initial crack. The effectiveness of the expansion accompanied by the phase transformation is clarified from the aspects of toughness level of a reference material.

Synthesis of NiO/YSZ Nanocomposite Particles using Co-precipitation Method

Abstract: NiO/Yttria-stabilized zirconia (YSZ) composite particles were synthesized via a co-precipitation of hydroxides. The effect of precipitation and agglomeration behaviors of the hydroxides in an aqueous solution on the morphology of the composite particles was investigated by varying pH from 11 to 13. The particles synthesized at pH 12, or lower, involved large angular NiO particles with the size > 1μm due to slower precipitation or agglomeration of Ni(OH) 2 , while NiO/YSZ nanocomposite particles with the primary particle size of < 100 nm were obtained at pH 13. This can be attributed to rapid precipitation as well as better dispersion of the hydroxides in the aqueous solution.

Direct Observation of Solidification and Phase Transformation in Pure Titanium

Abstract: Unidirectional-solidification and phase transformation in the weld metal of commercial pure-titanium in Gas Tungsten Arc welding was observed by using Time-Resolved X-Ray Diffraction (TRXRD) system with two-dimensional pixel detector. An undulator beam was used as a probe. A larger area of a cone of half apex angle 2θ made by diffracted beam could be detected in the time-resolution of 0.05 seconds, in unidirectional solidification and subsequent phase transformation process of pure-titanium weld metal. The constrained growth of weld metal in solidification processes and rapid change of phase ratio in β-α transformations were clearly shown.

Application of Natural Nano Silicate Powder in Advanced Smart Nanocomposite Coating

Abstract: Applying nano technology in smart coatings is a new field of interest for industry and technology. A smart coating using nano materials has been applied using different types of metallic materials such as Zirconia or Metal glass. It has been applied using different technologies such as plasma spray tunnelling systems or nowadays microwave coating technologies. The current research studies a new advanced material with super properties based on the powder of nano silicate-polymer nanocomposite. This new material can produce sustainable and durable coatings with super properties and low cost in addition to good maintenance and environmentally green performance. It can be applied as hot coating or cold coatings. The efficiency of this type of coating material is very high for corrosion resistance, impact resistance, wear resistance, fracture resistance, thermal stability, impermeability for gas and water, hardness,.....etc. This research introduces it as a new technology for coating industries.

Structure and Analyses of Natural Nano-silicate Layers Based on (RM-K) Fracture Theory

Abstract: Current research is intended to study the structure phenomenon of natural nano silicate layers. The research studies the effect of water on the structure of the material and also, the stresses due to the effect of drying of the material. The research includes a study of the change of structure, fracture, cracking mechanism, crack propagation, crack branching and bifurcations. The results conclude that the silicate layers are very sensitive to temperature. Cracks and fracture will be produced due to the loss of water due to shrinkage as the effect of heat loss or temperature changes. One of the most important properties of the nano silicate is the hydrophilic property. This property makes it very sensitive for absorbing water or losing it. As a result of absorbing water the silicate volume changes by swelling while due to loss of water or drying the silicate will shrink. If the silicate is dried, it will be fractured. It is found that if the nano silicate is added to another matrix material representing filler or reinforcement for that main material temperature stability and temperature resistant material. If it is mixed with polymers under certain conditions it can produce high quality material of nanocomposite. A mechanism of silicate cracking is proposed. A new and special version of directional fracture theory called (RM-K) theory is proposed for the application of silicate cracking since it follows different behavior than the normal fracture approach.

Influence of Spraying Conditions on Properties of Zr-Based Metallic Glass Coating by Gas Tunnel Type Plasma Spraying

Abstract: Metallic glass has excellent functions such as high strength and high corrosion resistance. However, as metallic glass is an expensive material, a composite material is preferred for the cost performance. The gas tunnel type plasma spraying is useful for obtaining high quality metallic glass coatings. In this study, Zr-based metallic glass (Zr55Cu30Al10Ni5) coatings were produced by gas tunnel type plasma spraying, and the influence of spraying conditions on the properties of Zr-based metallic glass coatings were investigated. The Zr-based metallic glass coatings of about 200 Pm in thickness were dense with a Vickers hardness of about Hv =500-600 at a plasma current of about 250A. The amorphous phase of this metallic glass coatings seem to be maintained in good condition.

Strength of High Manganese Non-magnetic Steel / Carbon Steel Hybrid Girder † - Investigation for Applying Dissimilar Materials to Steel Structures (Report IV)-

Abstract: The strength of a hybrid girder with a high manganese non-magnetic (Hi-Mn) steel / carbon (SM490; SM) steel (Hybrid girder) was investigated based on the results of the elastic-plastic large deformation analysis. The yield stress and Young’s modulus of Hi-Mn steel were 16% larger and 20% smaller compared with those of SM steel. When the upper half was assembled with Hi-Mn steel and the lower half of the cross section of the Hybrid girder was assembled with SM steel, the yielding moment was 2% and 18% larger than those of the girder with only Hi-Mn steel and the girder with only SM steel. The bending stiffness was 8% larger and 11% smaller than those of Hi-Mn and SM girders. The out-of-plane deformation of the web was larger than those of Hi-Mn and SM girders. By moving the position of the horizontal stiffener of the Hybrid girder 10% lower, the out-of-plane deformation of the web was controlled to smaller than those of Hi-Mn and SM girders.

In-Process Monitoring and Adaptive Control in Micro Welding with a Single-Mode Fiber Laser

Abstract: A fiber laser has excellent beam quality, enough to be applied for micro welding of electronics or automobile parts, and thus is regarded as a promising heat source for adaptive control since the laser peak power can be changed within a sub-micro-second period. This research was undertaken with the objective of obtaining a fundamental knowledge of in-process monitoring and adaptive control for the stable bead widths of full penetrations under the conditions that surround heat transfer or rapid change in welding speed when drastically changed in the micro welding of thin metal sheets with a continuous wave (CW) single-mode fiber laser beam. Concerning the surrounding conditions of heat transfer in bead-on-plate welding of a 0.1 mm-thick type 304 stainless steel sheet, the bead width was so influenced with or without aluminum heat sink that the bead width increased from 320 μm to 790 μm at 10 mm/s welding speed and 75 W laser power. It was found that the heat radiation was sensitive to such a rapid growth of the molten pool diameter. Moreover, the desired bead width was produced regardless of the existence of the heat sink by controlling the laser power adaptively on the basis of heat radiation intensity. As for welding speed in lap seam micro-welding of 0.1 mm-thick pure titanium, it was revealed that the geometry of the full penetration weld was drastically changed from narrow to wide, or to partial penetration during rapid deceleration in welding speed from 50 mm/s to 10 mm/s and the corresponding laser power of 75 W to 47 W. Prediction of the weld bead width on the bottom surface was difficult when utilizing monitoring of the heat radiation signal. Therefore, the designed stable full-penetration welds were made by controlling the laser power adaptively according to the heat radiation signal in order to adjust the weld bead width on the laser-irradiated surface to the target weld geometry affected by thermal storage. Consequently, it was confirmed that adaptive control was effective with drastic changes of surrounding conditions of heat transfer or welding speed during lap seam micro-welding process with a CW single-mode fiber laser beam.

Erosion Behavior and Interfacial Reaction of Stainless Steels in Molten Lead-free Solder

Abstract: The dissolution of iron and stainless steel during soldering presents a serious issue for manufacturing equipment such as wave soldering baths and soldering-iron tips. Severe erosion damage of stainless steel wave solder equipment has been encountered in operation. So, it is necessary to study the erosion behavior of stainless steel by molten lead-free solders. In this study, to investigate the erosion behavior of stainless steel in molten lead-free solder, an immersion test on 304 and 316 stainless steels was performed. It was found that the maximum erosion depth of the stainless steel was affected by the immersion conditions. A reaction phase was formed at the interface between the Sn-3.0Ag-0.5Cu solder and stainless steel during the immersion test.

Measurement of Three Dimensional Residual Stresses in Rolled Clad Plates and Welded Joints of a Chemical Tank Structure

Abstract: To evaluate the safety of welded joints in a chemical tank before manufacture, the rolling residual stress in steel plates and welding residual stress in welded joints need be measured. In this paper, firstly, the rolling residual stresses in a stainless plate (SUS304) and a clad plate (SUS304/MB410) used in a chemical tank are measured. Then, the welding residual stresses in a simple bead-on-plate weld and a practical filled weld are measured by the inherent strain method. Lastly, the total residual stresses in the welded joints are discussed. KEY WORDS: (Three Dimensional Residual Stress), (Rolled Clad Plates), (Measurement) 1. Introduction Clad steel is widely used in pressure vessels and chemical tanks because it has advantages of both the strength and resistance to corrosion. On the other hand, since the base metal and the clad metal have different physical and mechanical properties, residual stresses are often induced by the cladding process and the following welding process. The residual stresses may induce interface peeling at the clad plates, fatigue cracking, stress corrosion cracking during service. Figure 1 shows a chemical tank in which stainless steel (SUS304), high strength steel (MB410) and thermally rolled clad steel (SUS304/MB410) are used. Before production, residual stresses in a fillet welded joint, shown in Fig. 1, need to be measured. In this paper, firstly, the rolling stresses in both a stainless steel plate (SUS304) and a clad steel plate (SUS304/MB410) are carried out by the layer removal method

Applicability of Thin Steel Plate with a Crack to Estimating of Fatigue Damage on Bridges (Report II) -Effect of delayed retardation and applicability under fluctuating amplitude loads-

Abstract: Thin steel plates, which have initial crack at the center, are used as “Sacrificial Test Pieces” in this study The Sacrificial Test Piece is attached to a bridge member in order to evaluate the damage before appearance of a crack in the member The purpose of this study is to clarify the effect of delayed retardation and to show the applicability of the thin steel plates as sacrificial test pieces under fluctuating amplitude loads The fatigue damage parameters calculated by crack propagation length of thin steel plates under some fluctuating amplitude loads are compared with those calculated by the stress measurement From the results, the crack propagation lengths in the thin steel plates are affected by the delayed retardation of the crack propagation under fluctuating amplitude loads However, it is shown that the relation between the fatigue damage parameter and the crack propagation length is almost linear through the hastening of the crack propagation after delayed retardation And it is verified that the absolute value of the fatigue damage parameter can be monitored by the crack propagation length of the thin steel plates even under fluctuating amplitude loads

Anodic Bonding of Zirconium-based Metallic Glass

Abstract: Zirconium-based metallic glass was anodically-bonded to soda-lime glass as a trial. Faying surfaces of the joint pieces were finished by buffing and bonded in a pure argon atmosphere with a bonding voltage of 500 V. At a bonding temperature of 473 K intimate contact all over the joint interface was achieved with a bonding time of 7200 s. The bonding process was accelerated with increase of the bonding temperature. The obtained bond interfaces were strong, but cracks occurred in the soda-lime glass due to the residual stress caused by the difference in expansion coefficients of the metallic glass and the soda-lime glass. By transmission electron microscopy, it was found that the metallic glass kept its amorphous nature through the anodic bonding process. An oxidation layer ~100 nm thick was found at the bond interface. The oxidation layer was composed of a crystalline sublayer contacting to the metallic glass and an amorphous sublayer contacting to the soda-lime glass.

Terahertz Wave Resonance Profiles in Micro Patterns of Dielectric Tablets Fabricated by Using Stereolithography of Structural Joining Process

Abstract: Materials tectonics is new concept to control energy flows form environmental field to human beings through spatial patterns of ceramics or metals fabricated by using structural joinings Recently, we have developed two dimensional micro patterns composed of dielectric ceramics in order to control terahertz waves effectively by using stereolithography In this process, photosensitive resin pastes with titania particles dispersion were spread on a glass substrate with 10 μm in layer thickness by moving a knife edge, and two-dimensional images of ultra violet rays were exposed by using a digital micro-mirror device with 2 μm in part accuracy Through the layer by layer stacking, periodic structures composed of micro polygon tablets were formed Dielectric constant of these tablets was measured as 40 Subsequently, the electromagnetic wave properties of these samples were measured by using a terahertz spectroscopic device In transmission spectra, forbidden bands were observed form 033 to 057 THz through electromagnetic wave diffractions Moreover, a localized mode of a transmission peaks was formed in the band gap frequency range Through transmission line modeling simulations at the peak frequency, electromagnetic energies were concentrated strongly into the thin micro patterns The terahertz waves are well known to resonate with various types of protein molecules, and expected to control the biological material syntheses through the frequency excitements Fabricated dielectric ceramic micro patterns are considered to be applied for the new types of reactors to create the useful materials as artificial interfaces between the electromagnetic energy and the biological materials