海津 浩一

純Al/軟鋼摩擦圧接継手において純Al側が破断しているにも関わらずアプセット圧力を増加させることによって継手強度が低下する現象がみられる場合があった．強度の低下を少なくするため，純Alの直径を変えることによる引張試験時に破断する位置にかかる圧力の変化させる方法と，純Alの調質状態を継手強度の低下を示したF材からH112材へと変更した方法で実験を行った結果，継手効率の低下を抑制することができた．

溶融溶接が難しいFCD400とA5052の異材継手作製に摩擦圧接法を適用し，圧接条件を種々変更して接合実験を行い，接合現象を観察するとともに，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，摩擦圧力が低く，アプセット圧力が高い条件の方が引張強度が高い継手を得られやすいことが分かった．また，引張試験後の継手破断面を観察したところ，FCD400に含まれる黒鉛が残留していることも分かった．

板材と棒材の組み合わせである摩擦スタッド継手は工業分野で広く用いられており，軟鋼の摩擦スタッド継手については良好な継手が得られる圧接条件が見出されている．しかし，負荷する推力が実際の施工現場では容易に出力できない場合がある．そこで，スタッド側を円筒形状として接合端面の面積を減少させ，接合時の圧力を変えずに推力を低下させた条件でも，良好な継手が作製できるかを検討した．

A6063/SUS304摩擦圧接継手を対象とし，この継手に対して種々の条件の後熱処理を施した．その結果，ある温度や時間を超えると継手はすべて圧接面から破断することがわかった．また，熱処理を施した継手の継手強度は熱効果という1つのパラメータで整理することが望ましく，熱効果がある一定の値を超えると，圧接面に中間層が生成されることで継手強度が著しく低下することもわかった．

A5052とSUS304の円管同士の摩擦圧接を行った．その結果，外径16mm，内径12mmの組み合わせでは，適切な摩擦圧力とアプセット圧力のときにA5052側から破断する継手を得ることはできたが，破断様相にバラつきがあった．一方，内径13mmとした場合では，アプセット圧力を75MPa以上に設定すると，破断様相にバラつきがなく，A5052側から確実に破断する良好な継手を得ることができた．

AZX611とA5083の摩擦圧接において，摩擦圧力を30MPaに設定して接合を行った結果，圧接面には金属間化合物が生成し継手は圧接面から破断した．そこで，圧接面への入熱を抑えるために摩擦圧力を60MPaに増加させ接合を行い，引張強度に及ぼす影響について調査した．その結果，アプセット圧力270MPaの場合，継手はAZX611母材の約30%の引張強度であり，30MPaの場合と差異は見られなかった．

<p>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.</p>

<p>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<sup>®</sup>, 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.</p>

In the punching rivet method, it is possible to fasten the sheets without drilling. The joint has high strength and out-of-plane deformation of the joint is also small because of the rivet and the rivet holder that are peculiar to this method, hi this study, the punching rivet method was applied to joining of an acrylic resin sheet and an aluminum alloy sheet. The fastening condition and the strength of the joints made by the method were examined. From obtained results, it was possible to fasten an acrylic resin sheet and an aluminum alloy sheet by an aluminum alloy rivet. The acrylic resin sheet of the joint after joining had no crack and joint strength was high. It was certified that the punching rivet method became new joining method for a resin sheet and a metal sheet.

Critical for the use of aluminum alloys for engine pistons are strength and durability behind customers demand high power and low fuel consumption to protect environment. In general, there are many case of generating cracks in a top part of the piston by thermal load of combustion during car driving. As a countermeasure, AC8A casting aluminum on a top part of the piston partially substitutes with A6061 wrought aluminum which is more strengthen than the ACS A. This paper deals with the joint characteristics of friction welded joint between the A6061 solid cylinder and the AC8A casting pipe. If the joint was made by a conventional friction welding machine, it was clarified that the friction welding of A6061 solid cylinder and ACS A casting pipe was difficult because the travelling phenomenon of the weld interface was cause by the combination of the shapes of the friction welding specimens. To prevent braking deformation until rotation stop, the joint was made by a continuous drive friction welding machine that has an electromagnetic clutch. In addition, the joining strength improved through the joining cross section of both specimens are the same shape of pipe by digging out the surface of the A6061 cylinder. As a result, the joining could be successfully achieved and that had the joint efficiency of 80 - 97% when the joint was made with a friction pressure of 25MPa, a friction time of 0.7s, and a forge pressure of 75MPa and post-weld heat treatment with the T6 of AC8A.

This paper described the joining phenomena and joint strength of friction welded joint between Ti-6Al-4V and low carbon steel (S15CK) . When the joint was made with a friction pressure of 30MPa, the adjacent region of the weld interface reached to about 1,075 ℃ at a friction time of 8.0s or longer. This joint had the intermetallic compound layer (IMC interlayer) at the weld interface, and the joint efficiency of 100% was not achieved. It was demonstrated that the joint inhibited the generating of the IMC interlayer on the weld interface by increasing friction pressure, because the temperature at the weld interface was able to estimate a propensity to decrease with increasing friction pressure. Then, the joint, which was made with a friction pressure of 120MPa, a friction time of 7.0s or longer, and a forge pressure of 330MPa, had the 100% joint efficiency and it fractured from the S 15CK base metal with no cracking at the weld interface. This joint did not have the IMC interlayer on the weld interface. In conclusion, the joint should be made with the opportune high friction pressure and opportune long friction time for it without IMC interlayer with the high forge pressure for completely joining of the weld interface.

Crash safety of a vehicle is based on impact energy absorbed by crashing the structure in a situation that a cabin is protected. Side impact is extremely dangerous for passengers of vehicles. Energy absorption capabilities of the vehicle in side impact are low because there is little room for large deformation of the safety element to absorb impact energy. On the other hand, weight reduction of the vehicle is also important for the fuel efficiency. The purpose of this study is to develop a light and effective energy absorbing member for side impact. In this paper, an energy absorbing tubular member made by a combination of a thin-walled circular tube and a thin-walled square tube was proposed. The effect of the cross-sectional shape of the tubular member on energy absorption capacities under bending impact was investigated by the experiment and the analysis of the finite element code LS-DYNA. From the obtained results, bending strength decreased significantly when the cross section of the member which was subjected to impact bending load was crushed in flat shape. Therefore, energy absorption capacities were able to be improved by preventing flattening deformation of the cross section. Energy absorption capacities of the tubular member were able to be improved by changing its cross-sectional shape without increasing of the weight.

This paper described the effect of friction welding condition on joining phenomena and tensile strength of ABS resin friction welded joint. When the joint was made with a friction speed of 4.2 s^-1 and a friction pressure of 0.3 MPa, the temperature at the weld interface at a friction time of about 45 s or longer exceeded 130 ℃. That is, the temperature at the weld interface of the ABS resin friction welding exceeded the glass transition temperature of its resin. When the joint was made with a friction time of 60.0 s, it obtained approximately 67% joint efficiency. However, the joint efficiency decreased with increasing friction speed, and it also decreased with decreasing friction speed. The joint efficiencies with other friction pressures showed a similar change although the friction speed differed. When the joint was made with a friction speed of 2.5 s^-1, a friction pressure of 0.3 MPa and a friction time of 180.0 s, it obtained over approximately 90% joint efficiency. However, the joint efficiency decreased with increasing friction time, and it also decreased with decreasing friction time. Furthermore, the joint efficiency increased with decreasing parallel part diameter of the joint tensile test specimen, and that achieved 95% joint efficiency. In conclusion, to obtain the higher joint efficiency, the joint should be made with opportune friction speed, friction pressure and friction time, and the friction welding should be completed when the whole weld interface became melting state.

The joining phenomena during the friction process and the joint tensile strength of ABS resin friction welded joint were investigated. When the joint was made with a friction pressure of 0.5MPa or lower, the temperatures at the weld interface during the friction process exceeded 130 ℃. This temperature was higher than that of the glass transition temperature of ABS resin. That is, the temperature at the weld interface of the ABS resin friction welding exceeded the glass transition temperature, of which was differed with the friction welding of various metals. When the joint was made with a friction speed of 4.2s^<-1> and a friction pressure of 0.3MPa or a friction speed of 3.3s^<-1> and a friction pressure of 0.5MPa, it was obtained about 67% joint efficiency. However, the joint efficiency decreased with increasing friction time, and that also decreased with decreasing friction time. The joint efficiencies with other friction pressures were showed with similar change although the friction speed differed. In conclusion, to obtain the higher joint efficiency, the joint should be made with opportune friction speed and friction pressure.