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Friction stir welding (FSW) has many advantages rather than fusion welding, but details of internal phenomena during its processes have not yet been clarified. In this study, a thermo-mechanically coupled process model was developed to investigate FSW phenomena inside a tool and workpiece. As a workpiece, 6061-T6 aluminum alloy was employed. The system of FSW process model includes several thermal boundaries. Among heat flows through these boundaries, heat transfers into the exterior of the system become more sensitive to tool and workpiece temperatures than heat transfers within the system. This paper especially focused on a heat transfer coefficient at a workpiece bottom, and optimized it through experiments and finite element method (FEM) analyses. The tool temperatures during FSW were measured with a special tooling system with imbedded thermocouples within a tool. As a result, an analysis model that is able to investigate details at a wide range of traverse speeds was developed for practical high speed welding. Then, the accuracy of developed FEM model was validated with them. Finally, the temperatures and stress distribution around workpiece/tool interfaces were investigated with the developed model.

5083 aluminum alloy is increasingly used because of its excellent corrosion resistance, high work-hardening rate, and strength. In order to improve its weldability and feasibility, material behavior, material flow, and defects induced while friction stir welding 5083 should be studied. In this study, they were investigated by thermo-structural analysis. The flow stress of 5083-O has a high rate of sensitivity among high temperatures and wide strain rate ranges. Therefore, the details of the mechanical properties of 5083-O at high temperatures and wide strain rate ranges were investigated to obtain reasonable analysis results using a precise flow stress model. The tool/workpiece interface temperature during FSW is critical for accurate analysis results. This study used special equipment to measure tool temperature in order to investigate the interface temperatures precisely, and then the obtained data were used for optimization and verification of the thermal boundary conditions for analysis modeling. Using the developed model, the material behavior and material flow during FSW of 5083-O were analyzed. The tool and workpiece interface temperatures, flow stresses, strain rates, and velocities were investigated with the cylinder and threaded probes in detail. One of the analysis results indicated that the material flow rate on the rear side of a probe directly affected defect generation while joining.

Pultrusion is an easy molding method of fiber-reinforced polymer (FRP) to obtain a long composite material with a uniform cross-section at relatively low cost. In some cases, pultruded FRPs are now used in bridges and deck projects. Since the application of pultruded FRP as a structural material is increasing, a study on the durability of pultruded FRP under outdoor conditions is necessary in terms of safety. Some studies have shown that pultruded glass fiber-reinforced polymer (GFRP) exhibits a slight reduction in mechanical properties during outdoor exposure. Since pultruded GFRP consists of multi-layers, the change of mechanical properties in each layer is important to understand. In this study, an outdoor exposure test on pultruded GFRP for 10 years was conducted with three types of pultruded GFRP, which have different laminate systems, including surface-coated specimens of each type. Changes of strength and elastic modulus due to outdoor exposure were discussed with a focus on the contribution of each layer based on the rule of mixtures.

The ultrasonic welding of polymer optical fibres (POFs) onto carbon-fibre-reinforced polymers for advanced fibre-optic sensing is demonstrated. The relationships among the welding time, preload, optical loss, and adhesive force are fully evaluated. A high-speed camera to monitor changes in the cross section of the POF during the ultrasonic welding is also used.

The objective of this paper is to propose a new quality evaluation method for asphalt concrete mixture using X-ray CT scanner. To achieve this aim, asphalt mixtures should be subjected to the X-ray CT scanning and its characteristics should be clarified. The approach employed in this study was as follows: 1) Coarse aggregate, fine aggregate, filler and bitumen were prepared; 2) dense-graded, coarse-graded and porous asphalt mixtures were made; 3) materials and mixtures were subjected to the X-ray CT scanning; 4) frequency of CT-value, threshold value, average slice CT-value, average segment CT-value were computed. In the material examination, CT-value of aggregate becomes smaller in the order of coarse aggregate, fine aggregate and filler and CT image of bitumen was nearly homogeneous. In the mixture examination, histograms of CT-value and four segmentation images made from CT images expressed the material and mixture characterization such as particle size and the difference in bitumen content and mixture type visibly and the bitumen content varies with the threshold values. In addition, the average segment CT-value without threshold value by dividing the fine aggregate from the coarse aggregate and average CT-value of the coarse aggregate, especially is highly correlated with average CT-value of the bitumen.

The relaxation behavior of clamping force in friction-type FRP bolted joints is one of the significant subjects in application of FRP to structures. The aim of this paper is to obtain the factors of relaxation behaviors in the GFRP bolted joints based on the experimental results. The relaxation behaviors are due to both steel bolt and GFRP laminate. Steel bolt dominates the relaxed force immediately after initial loading but not reloading. The relaxation factors of GFRP laminate except matrix polymer could be both laminate surface geometry and laminate bond, considering the variance of relaxed force and more relaxed force for bonded laminate than single laminate observed in the experimental results. Boltzmann superposition principle can be hardly applicable to the relaxed forces for initial loading and reloading, suggesting that less relaxed force for reloading could be obtained by the strain hardening of bolt threads through the decrease of cross section area due to shear plastic deformation and that surface geometry could be modified by plastic and irreversible viscous deformation considering the viscoplastic property of matrix polymer. More relaxed force could be obtained for the surface geometry farther from the flat surface and the surface geometries could be categorized into the surface with either equal height protuberances or random height ones. Laminate bond dominates the relaxed force and its lower viscosity could give relaxed force more. The viscosity of laminate bond could be more variable than matrix polymer and increase through the modification of structure by plastic and irreversible viscous deformation. The minimum elapsed time could be required to complete the relaxation behavior for the flat surface and the bond viscosity as high as matrix polymer.

Recently, the development of the recycled resource is active in the background of effective use of the resource and the depletion of the final disposal dump, etc. Especially, the development of the technology used for the pavement of those recycled resources is active. Using these recycled resources comes to recycle certainly. However, whether it has contributed to the environmental load decrease in total until abandoning since using these manufactures it is not clarified. Then, the resource consumption, the saving resource, and the environmental load when using it for pavement were provisionally calculated for scrap tire and waste plastics, and LCA evaluation was examined. As a result, it was shown overall might decrease the environmental load though the recycled resource pavement might partially increase the load.

In Japan, several mix design methods for the recycled porous asphalt are being developed and proposed. These methods include the one to use Cantabro test and the one by the extraction recovery of asphalt. However, they have not been established yet, because they have some problems. The authors studied the mix design method using asphalt mortar, the new method evaluating several properties without extraction. As a result, the new mortar method was a method of not only appreciable of servicing temperature but also appreciable of constructing temperature. In addition, the labor of the method was also light.

本研究は, 遮水シートの耐久性評価を目的とし, 室内促進暴露実験と実暴露実験を実施し, 遮水シートの力学特性 (硬さ, 引張強さ, 伸び率) や表面状態の変化を追跡評価したものである。室内促進暴露実験の結果, 伸び率は経過時間とともに徐々に低下し5, 000時間では初期値のおおむね80%程度となり, そのとき遮水シート表面には亀甲状の微小亀裂が発生していることが確認された。一方10年間の実暴露実験を行った遮水シートの力学特性の変化は小さく, ある種類の遮水シート表面には室内促進暴露実験と同様の亀甲状の微小亀裂が観察されたが, 最終処分場の標準的な供用期間である15年に対して遮水シートの耐久性は充分余力あるものと推測された。また両実験結果を比較検討した結果, 2, 000時間強の室内促進暴露実験の結果が実暴露実験10年間に相当することが確認された。さらに遮光性保護材を用いると, 遮水シートの劣化の主要因とされる紫外線を遮断することができ, 遮水シートの耐久性が大幅に向上することも確認できた。

Focusing on sunlight that has severe effects on the degradation of asphalt pavement during service, this study examined the relationships between the film thickness of asphalt and the states of photodegradation. The results confirmed that thinner films had a higher modulus of elasticity, lower viscosity, and increased production of carbonyl groups, which is an indicator of oxidative degradation. The degree of degradation rapidly increased especially at thicknesses below 200 μm. The wavelength dependence of spectral photodegradation was also examined. Visual observations and the carbonyl index confirmed that ultraviolet irradiation in the range of 300 to 400 nm caused severe photodegradation of asphalt. Carbon black blocked light near the surface of the asphalt layer, where the damage caused by light is most severe. Addition of carbon black helps to prevent photodegradation by ultraviolet irradiation in the wavelength range of 300 to 400 nm., アスファルト舗装の供用中の劣化現象に影響の大きい光に注目し，この劣化におけるアスファルト単体の膜厚の影響を調査した。その結果，膜厚が薄くなるにつれて，特に200 μm以下の領域で，弾性率の増大や粘性の喪失，また酸化劣化を示すカルボニル基生成の増大など，劣化の程度が急激に著しくなることが確認された。また，分光劣化試験による波長依存性を調査した結果，外観変化やカルボニル指数の挙動より，アスファルトの光による劣化には波長範囲300～400 nmの紫外線の影響が大きいことを明らかにした。さらに，遮光性フィラーとして知られるカーボンブラックは，光による劣化の著しいアスファルト層の表面付近で機能し，波長300～400 nmの紫外線による劣化を抑える効果のあることが見出された。

In this research, to establish the method of recycling porous asphalt mixture, the propriety of two mixing design methods being proposed was examined. The result is shown below. 1) The problem was found in the deciding method of the amount of rejuvenators of recycled porous asphalt mixture and the deciding method of optimal asphalt content 2) It has been understood might not obtain satisfactory properties about mixture properties not so examined when mixing is designed. 3) It has been understood that there is a possibility to be improved from present methods by adding easy tests.

Carbon black, used as a reinforcing filler for rubber materials, was evaluated for asphalt binders in pavements. Carbon black added to straight asphalt within 20 wt% caused an increase in the elastic modulus and a decrease in the viscosity of the asphalt, especially at temperatures higher than room temperature. Addition of carbon black raised the maximum service temperature of asphalt in the category of the binder performance grade according to the SHRP (Strategic Highway Research Program) specifications. On the other hand, addition of carbon black also increased the failure strain at low temperatures. Furthermore, addition of carbon black reduced the coefficient of thermal expansion (CTE) of asphalt to closer to that of aggregates. In asphalt mixtures, tensile stress occurs at the boundary between asphalt and aggregate with decreasing temperature due to the CTE difference. Addition of carbon black reduced this stress. Carbon black addition to asphalt has the potential to improve both deformation resistance in the high temperature region and crack resistance in the low temperature region, which were empirically considered to be contradictory. Therefore, carbon black is an effective filler for improving the durability of asphalt pavements.

With high corrosion resistance, high tensile strength, electromagnetic neutrality, and lightweight, the newly emerged aramid and carbon fibre-reinforced plastic (FRP) tendons are being used for prestressed ground anchors. FRP ground anchors can be used when the corrosion protection of steel tendons becomes expensive or difficult to achieve, or where electromagnetic insulation is required. Although FRP tendons are more expensive than steel tendons, the total cost on transportation, handling, fabrication, drilling, installation, and maintenance can be significantly reduced due to lightweight and no requirement for corrosion protection. In addition, optical fibre sensors can be integrated into FRP tendons for permanent monitoring of ground anchors. This paper gives an introduction of the currently available aramid and carbon FRP tendons and an overview of the important properties of FRP tendons and their constituent materials. The design, fabrication, installation, and field applications of aramid and carbon FRP ground anchors are described. (A)

Polymer-modified asphalt binder is applied for the heavy trafficked pavement because the asphalt is superior in terms of plastic flow and abrasion resistance. Recently, the development of warm-mix polymer modified asphalt has proceeded. Then, it is necessary to evaluate the characteristics of these asphalt binders. In general, the authors have estimated the physical behavior of polymer-modified asphalt by DSR test. However, it seems to difficult for DSR test to estimate the nonlinear viscoelastic behavior such as warm-mix polymer-modified asphalt. In this study, the authors validated the availability of MSCR test for the characteristics of the widely distributed warm-mix polymer-modified asphalts. ポリマー改質アスファルトバインダは塑性変形抵抗性や摩耗抵抗性、はく離抵抗性等に優れており，重交通路を中心に普及している．近年では，CO₂排出量削減や作業環境改善策として中温化ポリマー改質アスファルトバインダの開発も進んでおり，既に複数メーカーから市販されている．一般的に，アスファルトバインダの物理性状はDSR試験から得られるパラメータによって評価されてきたが，改質アスファルトバインダの非線形粘弾性状を適切に評価できないことが指摘されている．本研究では，国内で流通している複数の中温化ポリマー改質アスファルトバインダの性状を調査し，基本性状の相違を明らかにするとともに，物理性状評価に対して繰り返しクリープ試験(MSCR試験)の有効性を検証したので報告する．

Hexavalent chromium is sometimes eluted from cement concrete recycled base course material. Therefore, hexavalent chromium eluted restraint technology is developed. The concentration analysis of hexavalent chromium is difficult, when a reducer coexists. There were not that standard measurement methods. The authors have already developed the analysis method of hexavalent chromium when a return substance coexists. When using this way, even if there is a return substance, hexavalent chromium is measured right. So hexavalent chromium reduction technologies were studied using accessible materials. As a result, hexavalent chromium eluted restraint technologyreducing sugar has been developed. セメントコンクリート再生路盤材からは六価クロムが溶出する可能性があるため，溶出の確認が行われるようになっている．これに伴い，六価クロム溶出低減技術も開発されるようになっているが，還元物質を用いる対策の場合，JISの分析法を用いることができず，評価が難しいのが現状である．本研究では，独自に開発した還元物質共存下でも容易に六価クロムを分析できる方法を用いて，自然由来の物質や入手が容易な物質の中から，還元効果が期待できる物質を選定し，六価クロムの溶出低減効果を検討した．その結果，比較的入手が容易な一部の果汁や還元糖の中に六価クロム溶出低減効果が高いものがあることを把握した．

The warm-mix asphalt technics have been applied to the hot asphalt pavements to improve the quality of constructions and to reduce CO₂ emission. Although many studies have reported that the warm-mix additives affected the physical characteristics of asphalt mixtures, the basic characteristics of the warm-mix asphalt binder has not been revealed. In this investigation, the authors measure the differential scanning calorimetry (DSC) and the viscoelastic property of the warm-mix asphalt binder in a wide range of temperature. Also, they discuss the validity of the thermal analysis to detect the physical change of the asphalt binder. 施工性改善やCO₂排出削減などを目的として，加熱アスファルト舗装に対する中温化技術の開発や利用が進んでいる．これまで，中温化剤の添加によるアスファルト混合物の物理的性状の変化は多く報告されているが，アスファルトバインダの基礎的な物理性状については十分な言及がなされていない．本研究では，中温化剤によるアスファルトバインダの性状変化を把握することを目的として，示差走査熱量測定によりアスファルトや中温化剤の広範囲の温度域での熱特性や，これに対応した粘弾性状を調べた．さらに，熱特性と粘弾性状の関係について検討した．