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According to the equation of shrunk interface pressure and the condition of diametrical ratio based on the theory of equal strength, it is found that the diametrical ratio isn’t true of the condition of diametrical ratio and the distribution of stress isn’t very equality through analyzing and calculating the diametrical ratio and stress to a super high pressure cylinder. Then aim at the problems existed in the super high pressure cylinder, it is taken the improved design. The super high pressure cylinder has much better than original one in distributing of stress. It is shown that the improved design project has a better technical result.

Through the analysis of stress in ultra high-pressure cylinders, found that its stress distribution is very uneven. In order to use the principle of autofrettage for improving design of the cylinders, first with Faupel-Furbe formula to calculate estimates of diameter ratio, and thus are inner and outer diameter of the cylinder block. Then the cylinder is determined parameter of autofrettage on the cylinder such as the optimum radius of elastic-plastic junction and the optimum autofrettage pressure. Finally, analysis and calculation of stress in improved design cylinder, the results show that the improved design of cylinder have a greater degree of improvement in weight, size and stress distribution of three areas. Key words: autofrettage; ultra-high pressure cylinders; diameter ratio; stress distribution.

The characteristics of stress distribution in high-pressure vessel are analyzed at first. Then the formula of inner pressure is derived. Through analysis the formula, a conclusion that the maximal inner pressure the high-pressure vessel can support goes steady under the diameter ratio is more than 5. Then the formula of equivalent stress at the dangerous position (inside wall) in high-pressure vessel is educed according to the fourth strength theorem and the quantitative relationship in the vessel’s inside pressure and diametrical ratio and the fatigue limit further is founded. Finally, the advice that proper structure is adopted to improve the cylinder’s inner pressure when design thick wall high-pressure cylinder according to relationships as above. These advices have a definite directive significance for how to design and use vessel effectively.

Mechanical analysis is carried out to the deformation of workpiece when turning slender shafts in the normal and reversed direction under two different conditions of clamping. Mathematical models are set up for the calculation of bending deformation resulting from cutting force in condition of normal and reversed turning. An example is given to show that bending deformation and the resulting machining error in conditions of reversed turning is much less than that in normal turning. The result has been verified by experiments. The mechanical model and numerical analysis can be used in the processing design of slender shaft turning.

Hollow parts with variable cross-section are widely used in the area of automotive and aerospace industries due to their excellent properties. Wrinkling is one of the most common forms of instability in the process of manufacturing the parts. The minimum curvature of the cross-section profile of bugled workpieces is proposed in this paper to as a wrinkling indicator to characterize the form and extent of the wrinkle. The wrinkle distribution of 1Cr13Mn9Ni1N stainless steel tube in hydroforming with radial crushing under linear and constant hydraulic pressures is analyzed and the influence of the bulging methods on the wrinkling is investigated via finite element simulation. The results indicate that wrinkling under constant hydraulic pressure is more obvious than that under linear one, wrinkling in hydroforming with radial crushing is more serious than that in free hydro-bugling, wrinkling on the cross-section away from the middle cross-section is more distinct and the wrinkling on the side edge is obvious than that on the bottom of the bugled workpiece.

Tube hydroforming with radial crushing (THFRC) process is particularly applicable to the tube which is difficult to shape due to lack of axial feeding. In this paper, the formability of the circular tube expanded into a triangle cross-section under the simple loading paths is explored by using the numerical simulation. The effect of the forming mode and the loading paths on bulged profile, wall-thickness distribution and the potential fracture location of the bulged tube are analyzed. The results showed that constraint conditions at tube ends have small influence on the bulged profile and wall-thickness distribution. Moreover, the larger the peak value of the internal pressure is, the better material filling ability and higher accurate the tube bulged profile are. Furthermore, the higher forming accuracy, the better material filling ability and wall-thickness distribution are gained in THFRC than those in free hydro-bulging (FHB) process, and they can be obtained under constant than linear pressure loading paths. Finally, the potential fracture location of the bulged tube in THFRC process is quite different from that in FHB process.

Based on the relation between the elastic disable pressure of the cylinder and the limit of yielding in material according to the elastic disable rule, a laboratorial method of determining elastic disable pressure of thick wall cylinder is designed and a set of experimental data are gained by the method. The elastic disable pressure of the cylinder is gained by analyzing the experimental data. The laboratorial method has a good reliability as the error between the experimental value and the theoretical value is small.