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To avoid the open problems of the leading wheel and get a more rational structure, the paper uses PRO / E and the finite element software to analyze the leading wheel of JKM-3.25/4 multi-rope friction hoist. The results show that in the leading wheel the rib plates between the channel steel and wheel hub are removed or added the same ones will have little effect on the overall force situation, and only affect the stress of the weld bead. To solve the problem of open weld of rib plates, can consider the rib plates to be removed. When the radial angle between support wheel and drum is bigger than 6°, the overall force of the leading wheel is affected seriously. But when the radial angle is 5°, the amplitude of stress fluctuation is the minimum, which can improve the leading wheel working conditions and increase the service life of the leading wheel. Therefore the suggestion is to take the radial angle of 5° when to design the new multi-rope hoist. Study conclusions provide the theoretical supports for the leading wheel of multi-rope friction design and technical renovation.

AA6061 alloy is most widely used in aircraft fittings, marines fitting and automobile industries. This alloy can be joined by fusion welding process like Gas Tungsten Arc Welding (GTAW). An important metallurgical difficulty in arc welding of this alloy is hot cracking. As the name indicates, this kind of cracking occurs while the metal is still hot. It usually occurs in the fusion zone during solidification. The main aim of this work is to investigate the effect of vibratory treatment on hot cracking of AA6061 alloy. Houldcroft hot cracking test is used to determine the hot cracking tendency. Weld bead was made on AA6061 alloy specimen in the presence and absence of vibratory treatment. Vibratory treatment was carried out in the frequency range of 250 Hz to 900 Hz. Weldments made with and without vibratory treatment were compared using hot cracking tests. Test results show that by applying vibratory treatment, hot cracking can be largely controlled in AA6061 alloy.

The fracture toughness of different zones of X100 SAWL pipe was studied by three-point bend test method under different temperature. At the same temperature, the crack propagation resistance and tear modulus of X100 SAWL pipe distributed as: base metal>HAZ>weld bead, and the distribution of the CTOD value of X100 SAWL pipe is :base metal >weld bead >HAZ. Further investigation was conducted to analyze the decrease of fracture toughness (especially low temperature fracture toughness) and the occurrence of local unstable phenomenon in HAZ specimens.

The effect of TIG-dressing on fatigue strength in support of the fillet weld of offshore platform was investigated experimentally in the paper. According to the causes in which most cracks are produced in actual structure, the model tests have been performed based upon cruciform weld bead characteristic. The TIG-dressing technique parameters were established by the actual structure and the fatigue specimen tests were done also. The life estimation equation after TIG-dressing is presented by least square method. The fatigue life used by TIG-dressing has increased over 100%. Therefore the TIG-technique gives a big potential for engineering application.

Weld bead stability has an important effect on the quality of prototyped products .In the paper, hierarchy analytical theory, combined with the experiment, is employed to determine the weld bead stability synthesis evaluation weight coefficient of surface quality, weld reinforcement and weld width of weld bead. The membership degree tables of surface quality, weld reinforcement and weld width are created by using fuzzy theory. Thus a evaluation method of bead stability is established and applied to evaluate practical bead stability. It is approved that the calculation value accords with the actual result, which proves the evaluation method of bead stability is effective.