木村 真晃

積層造形によって作製したAlSi12合金について，外周輪郭を照射する際のレーザ照射スパン長に注目し，それを種々変更して造形を行った．そして，引張試験を行い機械的性質を調べるとともに，表面性状の観察を行った．その結果，スパン長と外周輪郭の表面粗さには相関関係があり，表面粗さが低いほうが引張強さが高くなる傾向を示すことがわかった．

コネクティングロッドはエンジン部品の1つであり，大端孔内径は高い真円度が求められる．しかし，クランクシャフトへの組付け時に働くボルト締結力により，機械加工直後よりも真円度が低下してしまうことがある．斜め割りコンロッドは左右非対称の形状で，組付け後の内径も左右非対称となることが真円度低下に影響を及ぼすと考えられる．そこで本研究では，FEMを用いて斜め割りコンロッドモデルにボルト軸方向の軸力を与え，内径加工時，再締結時の2度のボルト締結を模擬した解析を行った．その結果，本研究で用いた斜め割りコンロッドにおける許容トルクの範囲を±1.0N･m広くとっても，真円度5μm以下を満たすことがわかった．また，内径加工時の2本のボルトに生じる軸力に左右差が生じたとき，ロッド軸側にあるボルトの軸力を変化させると真円度変化を小さくでき，再締結トルクを小さくすることで，軸力差による真円度の変化をより抑えられることが明らかとなった．

表面改質を目的とした皮膜コーティングが広く用いられているが，信頼性の観点から，皮膜のはく離強度を合理的に評価しておく必要がある．本研究では，混合モード荷重を受け大変形しながらはく離する皮膜のはく離強度評価パラメータとしてJ積分に着目し，形状非線形FEM解析と理論解析からJ積分のモード分離方法について検討した．その結果，はく離先端部のモーメントからモードⅠ成分のJ積分が，水平方向成分の荷重からモードⅡ成分のJ積分が求められ，それらの和が混合モードのJ積分に一致することを示した．すなわち，混合モードのJ積分を各モードのJ積分に分離できることを明らかにした．

混合モードを受けてはく離する皮膜の強度評価をする上ではモードⅠとモードⅡに分け，それぞれを破壊靱性値で評価する必要がある．本研究でははく離強度評価パラメータとしてJ積分に着目し，混合モードが発生するように皮膜に荷重を負荷したはく離モデルを用いて形状非線形FEM解析を行った．そして，はく離先端のモーメントと水平方向の荷重からそれぞれのモード成分を検討し，それらの和が混合モード成分のJ積分の値と一致することを確認し，モード分離が可能であることを明らかにした．

同じ圧接条件での接合端部直径と引張強さとの関係を調べるため，A6061中空材とAC8A中空材の2種類の大きさを用いて摩擦圧接した．外径30mm，内径24mmを大径，外径18mm，内径12mmを小径の組み合わせとし，各平均直径位置での周速度が誤差10%以内となる摩擦速度を設定して，継手の引張強度を調べた結果，初期トルクに到達した時間と引張強度はほぼ同じとなることが分かった．

A7075とS15CKの直接摩擦圧接は良好な継手を得ることが困難であるため，純Tiを挿入材とし，その厚さを種々変化させ摩擦圧接を行った．その結果，挿入材の厚みに対して圧接時の熱が足りず，S15CKの母材部分が破断するような継手を得られなかった．このことから，入熱量を増やすために摩擦時間を種々変化させて摩擦圧接を行った．その結果，摩擦時間が長い方が良好な継手得られる傾向にある事が分かった．

A5052挿入材を介してA5052とSS400との接合に摩擦スタッド接合を行い，圧接条件を種々変更して継手を作製し，継手強度に及ぼす圧接条件の影響について調べた．その結果，摩擦時間2.1s，アプセット圧力250MPa以上で高い強度を有する継手を得ることができた．また，アプセット圧力300MPa以上において，継手の破断位置をA5052間の圧接面からA5052挿入材とSS400との間の圧接面に変化させることができた．

ABS樹脂とSUS304との摩擦圧接を行った．摩擦速度および摩擦圧力を変化させて接合実験を行ったところ，部材が一体化するにはABSが溶ける必要があり，そのためには一定以上のエネルギーを要することがわかった．さらに，摩擦圧力1.0MPa，摩擦速度16.7s-1，摩擦時間を260sに設定することでABSが溶け出し，一体化することがわかった．しかし，ABSの溶け始める時間のばらつきが大きいという問題が生じた．

To reduce weigh of the transportation machines, joining of the FRP and the light metal is considered as important technique. In this study, the punching rivet method was applied to make joints between a GFRP sheet and an aluminum alloy A6061 sheet and joint strength was examined. The punching rivet method is possible to join the sheets without drilling by using a rivet and a rivet holder. The punching-out process of the sheets using a rivet shank as a punch and the joining process of the sheets using the rivet and the rivet holder are continuously performed. From the experimental results of joining of the GFRP sheet and the A6061 sheet, the joints made by the punching rivet method had no large crack and out-of-plane deformation of the joints was suppressed. From the results of the joint strength tests, the joints made by the punching rivet method had almost the same joint strength as the bolted joints which were tightened by regulated torque. In addition, the fatigue life of the joints made by the punching rivet method was longer than that of bolted joints. It could be confirmed that the punching rivet method was effective to join the GFRP sheet and the A6061 sheet.

This paper describes the stud shape and joint strength of low carbon steel joints fabricated by friction stud welding with low load force requirement. To reduce the load force during the welding process, the stud side with the circular hole at the weld faying surface part was used. The outer diameter of a cylindrically shaped stud side had 12.0 mm and that was welded to the circular solid bar with a diameter of 24.0 mm as the work side. The joint was made with a friction speed of 27.5 rps, a friction pressure of 60 MPa, and a forge pressure of 60 MPa, which was determined as the low force condition for obtaining good joint in the previous study. When joints were made by a cylindrically shaped stud with a hole diameter of 6.0 mm and its depth of 0.5 mm, all joints at a friction time of 0.6 s, i.e. the friction torque reached to the initial peak, had the same tensile strength as that of the base metal with the base metal fracture. All joints with flash from the initial weld interface had the fracture on the base metal, the bend ductility of over 15° with no cracking at the initial weld interface through an impact shock bending test, and a high fatigue strength of the base metal. That is, the sound joint could be successfully achieved, and that could be obtained with the same friction stud welding condition of the circularly shaped solid stud. As a conclusion, the joining technique for the friction stud welding method with low load force requirement was proposed in accordance with using a cylindrically shaped stud that has the circular hole with the shallow depth at the weld faying surface part.

This paper describes the stud shape and joint strength of low carbon steel joints fabricated by friction stud welding with low load force requirement. To reduce the load force during the welding process, the stud side with the circular hole at the weld faying surface part was used. The outer diameter of a cylindrically shaped stud side had 12.0 mm and that was welded to the circular solid bar with a diameter of 24.0 mm as the work side. The joint was made with a friction speed of 27.5 s^-1, a friction pressure of 60 MPa, and a forge pressure of 60 MPa, which was determined as the low force condition for obtaining good joint in the previous study. When joints were made by a cylindrically shaped stud with a hole diameter of 6.0 mm and its depth of 0.5 mm, all joints at a friction time of 0.6 s, i.e. the friction torque reached to the initial peak, had the same tensile strength as that of the base metal with the base metal fracture. All joints with flash from the initial weld interface had the fracture on the base metal, the bend ductility of over 15 degrees with no cracking at the initial weld interface through an impact shock bending test, and a high fatigue strength of the base metal. That is, the sound joint could be successfully achieved, and that could be obtained with the same friction stud welding condition of the circularly shaped solid stud. As a conclusion, the joining technique for the friction stud welding method with low load force requirement was proposed in accordance with using a cylindrically shaped stud that has the circular hole with the shallow depth at the weld faying surface part.

The microstructure and mechanical properties of the AlSi12CuNi alloy fabricated by the additive manufacturing technique, laser powder bed fusion (L-PBF), were investigated. Several laser irradiation conditions were examined to optimize the manufacturing process to obtain a high volume density of the fabricated alloy. Good fabricated samples with a relative density of 99% or higher were obtained with no cracks. The fabricated samples exhibited significantly good mechanical properties, such as ultimate tensile strength, breaking elongation, and micro-hardness, compared to the conventional die casting AlSi12CuNi alloy. Fine microstructures consisting of the α-Al phase and a nano-sized eutectic Al-Si network were observed. The dimensions of the microstructures were smaller than those of the conventional die-casting AlSi12CuNi alloy. The superior mechanical properties were attributed to the microstructure associated with the rapid solidification in the L-PBF process. Furthermore, the influence of the building direction on the mechanical properties of the fabricated samples was evaluated. The ultimate tensile strength and breaking elongation were significantly affected by the building direction; mechanical properties parallel to the roller moving direction were significantly better than those perpendicular to the roller moving direction. In conclusion, AlSi12CuNi alloys with good characteristics were successfully fabricated by the L-PBF process.

To obtain multimaterial structures composed by various materials as the right man in the right place for improvement of the additional value of some products or parts, the easy manufacturing method of the dissimilar metal joint is necessary. This paper described the weldability and its improvement of the friction welded joint between ductile cast iron (JIS FCD400) and typical Al-Mg alloy (JIS A5052). When both materials welded, only the A5052 side was unilaterally deformed and that was exhausted as flash during the friction process regardless of the friction welding condition. The relatively high tensile strength of the joint was obtained when that was made with a friction speed of 27.5 s⁻¹, a friction pressure of 20 MPa, a friction time of 1.5 s, and a forge pressure of 270 MPa. However, the joint had approximately 77% in the tensile strength of the A5052 base metal and that was fractured at the weld interface. The tensile strength of joints, which were made with other friction welding conditions, was lower than that of this friction welding condition. Although the weld interface of the joint had no intermetallic compound interlayer, the fractured surface at the A5052 side had the C element as the graphite particles that were supplied from the FCD400 side. To improve the joint strength, the graphite particle was reduced from the weld faying surface at the FCD400 side by decarburization treatment before welding. The joints had approximately 97% in the tensile strength of the A5052 base metal, and one of joints was fractured at the A5052 base metal. Thus, the graphite particle at the FCD400 side influenced the weldability between FCD400 and A5052. In conclusion, the joint with high tensile strength as well as the possibility for the improvement of the fractured point of them could be obtained when they were made with an opportune friction welding condition and no graphite particles at the weld faying surface of the FCD400 side.

Joint strength of dissimilar thin pipe friction welded joints between 5052 Al alloy (A5052) and 304 stainless steel (SUS304) was investigated. Pipes had the outer diameter of 16 mm and the inner diameter of 12 mm, and those were welded with a friction speed of 27.5 s⁻¹, a friction pressure of 30 MPa, and a friction time of 1.2 s. When joints were made with as-received pipes, the joint strength at a forge pressure of 60 MPa had approximately 64% in the tensile strength of the A5052 base metal although that had scattering. Almost all joints fractured between the weld interface and the A5052 side though some joints fractured in the A5052 side. Thus, the fractured portion of joints had scattering at the same friction welding condition. On the other hand, the joint strength at a forge pressure of 50 MPa had approximately 77% in the tensile strength of the A5052 base metal when joints were made by pipes with the machined of the inner and outer diameter parts from solid bars. In addition, all joints fractured from the A5052 side. That is, to obtain good joint such as the fracture in the A5052 side without scattering of the fractured portion of joints, the joint should be made without the affected layer on the pipe surface at the manufacturing of itself.

Joining of plastics and light metals contributes to the reduction of a product weight. In this study, the punching rivet method was applied to joining of an acrylic resin sheet and an aluminum alloy sheet. The punching rivet method can join the sheets without drilling. The riveting process of this method is constituted of the punching process of the sheets using the rivet shank and the fastening process of the sheets using the rivet and the rivet holder. The sheets are fastened by using the plastic deformation of the rivet shank. From the observation of the joints made by the punching rivet method, it was found that the acrylic resin sheet of the joint had no crack and out-of-plane deformation of the joint was small. From the results of the joint strength tests, it was considered that the joint made by the punching rivet method had high strength due to the effect of the pressures on seating faces of the rivet and the rivet holder. As a result, the punching rivet method was effective to join the acrylic resin sheet and the aluminum alloy sheet.

This paper described the tensile strength of friction welded joint between Al-Mg alloy (JIS A5052) and pure copper (OFC). In particular, the joining phenomena during the friction process and the effects of friction welding condition such as friction pressure, friction time and forge pressure on the joint strength have been investigated, and the metallurgical characteristics of joints have been also observed and analyzed. The adjacent region of the weld interface at the A5052 side was upset during the friction process, although that of the OFC side was hardly upset. When the joint was made with a friction pressure of 30 MPa, all joints fractured at the weld interface because those joints had the not-joined region at this portion. To reduce the not-joined region, the joint was made with increasing forge pressure. All joints did not have a joint efficiency of 100% (same tensile strength as the A5052 base metal) and the fracture on the A5052 base metal without crack at the weld interface, although the joint efficiency increased with increasing forge pressure. It was showed that the joint had the mechanically mixed layer as the lamellar structures of A5052 and OFC on the adjacent region of the weld interface at the A5052 side, and that layer influenced to the fractured point of the joint. The mechanically mixed layer decreased with decreasing friction time and with decreasing friction pressure after the initial peak. Then, the joint, which had the same tensile strength as the A5052 base metal, the fracture on the A5052 base metal with no crack at the weld interface, and less mechanically mixed layer with no the intermetallic compound (IMC) interlayer on the weld interface, could be successfully achieved. In conclusion, it was suggested that the joint should be made with a low friction pressures such as 20 MPa to prevent generating of the mechanically mixed layer, an opportune friction time such as 6.0 s without generating the IMC interlayer, and a high forge pressure such as 240 MPa in order to achieve completely joining of the weld interface and the fracture on the A5052 base metal.

In order to ensure the safety of passengers in the event of an accident, side member and crash box are mounted on automobiles. Cylindrical tubes, rectangular pipes and hat-shaped members have been examined as structural members that subjected to an axial compressive load. However, these structures have problems that the initial peak load is very high and the load rapidly decreases due to buckling during crushing. To solve the problems, we proposed a cellular solid with mimetic woody structure as a new structural member. Some woods have no initial sharp peak load and have a plateau region which the load is constant in the relationship between the load and the displacement, when the impulsive load are applied to them. We considered that those features were suitable for structural members like a side member or a crash box. The basic cell was a square block with a side length of 10 millimeters and it had a hole in the center. The cellular solid was constituted by combining some basic cells. Therefore, a homogeneous cellular solid was fabricated by making small holes in the aluminum cube. From results obtained from the impact crushing test and simulation by the FEM software LS-DYNA^®, it was demonstrated that the proposed cellular solid had crushing characteristics similar to the wood, and the energy absorption characteristics were influenced by the shape and arrangement of the cells. As a result, it was shown that the results of experiment and analysis substantially corresponded. Since the load during crushing depended on the shape and arrangement of the cells, the possibility of controlling the energy absorption characteristics was shown.

This paper described the tensile strength of friction welded joint between Al-Mg alloy (JIS A5052) and pure copper (OFC). In particular, the joining phenomena during the friction process and the effects of friction welding condition such as friction pressure, friction time and forge pressure on the joint strength have been investigated, and the metallurgical characteristics of joints have been also observed and analyzed. The adjacent region of the weld interface at the A5052 side was upset during the friction process, although that of the OFC side was hardly upset. When the joint was made with a friction pressure of 30MPa, all joints fractured at the weld interface because those joints had the not-joined region at this portion. To reduce the not-joined region, the joint was made with increasing forge pressure. All joints did not have a joint efficiency of 100% (same tensile strength as the A5052 base metal) and the fracture on the A5052 base metal without crack at the weld interface, although the joint efficiency increased with increasing forge pressure. It was showed that the joint had the mechanically mixed layer as the lamellar structures of A5052 and OFC on the adjacent region of the weld interface at the A5052 side, and that layer influenced to the fractured point of the joint. The mechanically mixed layer decreased with decreasing friction time and with decreasing friction pressure after the initial peak. Then, the joint, which had the same tensile strength as the A5052 base metal, the fracture on the A5052 base metal with no crack at the weld interface, and less mechanically mixed layer with no the intermetallic compound (IMC) interlayer on the weld interface, could be successfully achieved. In conclusion, it was suggested that the joint should be made with a low friction pressures such as 20MPa to prevent generating of the mechanically mixed layer, an opportune friction time such as 6.0s without generating the IMC interlayer, and a high forge pressure such as 240MPa in order to achieve completely joining of the weld interface and the fracture on the A5052 base metal.