The bending fatigue limit moment and crack initiation life of 4105 crankishaft in five groups of bending moments are obtained by resonant bending fatigue tests first. Then, the static finite element calculation using sub-model is performed to get the strain distributions in every test load. The results show that in the region where stress concentrate, the strain field could be seen as plane strain state. So two dimensional strain field intensity model is selected. In order to remove the influences of size and surface conditions, the radius of strain field is determined with the strain distribution under the low-life test load. After that, the local strain field intensities under each test load are calculated with the radius of strain field. Finally, the strain-life curve of material is modified by the fatigue intensity limit of crankshaft, and the predicted life agree with the test results.

Here we report experimental results of propagating characteristics of ultrasonic wave and explain it in light of existing theories. First, we study the relaxation process after magnetic field built up. It is known that the particles form chain-like clusters when the magnetic field is applied. The process of the cluster for mation is a relaxation process. The ultrasonic velocity v as a function of magnetic field at field angle　θ= 0 and π/2 at 4MHz were measured. We have studied the dependence of velocity on. Concentrations of the magnetic particles and frequency. The experimental results can be explain by Tarapov's theory rather than th approach used by Parsons.

High hardness and abrasiveness, low ROP and seriously deviation are the features of Shanle block Xishanyao formation in Turpan-Hami Oilfield, whose lithology was conglomerate, glutenite, interbedded sandstone, large angle of bedding and many fractures. To enhance ROP at this high hardness and abrasive region, designing of PDC bit is introduced based on crown shape, blade, teeth, bit hydraulics and so on. The designed bit had a good performance in the test of Well He-3 at Shanle block.

Based on the geological configuration and formation lithology of igneous rock stratum of Santanghu, optimized design methods of PDC (polycrystalline diamond compact) bit are used to design PDC bit crown shape, cutting angle, the distribution of cutters and hydraulic structure, etc. Especially, these methods, which are design methods of gentle crown profile, spiral blade, high-density distribution of cutters, suitable back rake angle, and hydraulic structures which are more flexible nozzles of asymmetric arrangement and deeper fluid course layout, are fit for high hardness, multiple interbed and high abrasiveness of the igneous rock formation. The bit designed in this paper has turned out to be much better in the experiment of Horse 36 well of Santanghu.