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31.
LOW-CYCLE FATIGUE UNDER NON-PROPORTIONAL LOADING 总被引:4,自引:0,他引:4
X. Chen Q. Gao X.-F. Sun 《Fatigue & Fracture of Engineering Materials & Structures》1996,19(7):839-854
A series of strain-controlled, low-cycle fatigue experiments have been conducted on 42CrMo steel under various loading paths including circular, square, cruciform, and rectangular paths. Present experiments have shown that there is additional hardening under non-proportional cyclic loading. Non-proportional cyclic additional hardening also results in a shorter life for multiaxial low cycle fatigue. A non-proportionality measure of strain path based on both a physical basis and macromechanical phenomena is proposed. The loading path effect on additional hardening is also described well. Low-cycle fatigue damage accumulation and the evolution process under non-proportional loading is analysed via the Continuum Damage Mechanics Model of Chaboche. A non-proportinality measure is introduced in the damage evolution equation and a modified Coffin-Manson type formula is derived. A novel fatigue life prediction approach based on the critical-plane concept of Brown and Miller is proposed. 相似文献
32.
Bituminous coal piles stored in the open air can undergo autocatalytic heating accompanied by the emission of small but appreciable amounts of molecular hydrogen. When the coal is contained in a confined space and the temperature reaches 40°C, accumulation of hydrogen is expected. This process has been observed for a wide variety of bituminous coals. The amount of hydrogen gas expected to accumulate in the air pocket above the coal cargo in ship holds (assuming that the coal's temperature approaches 40°C during the voyage) has been calculated. The results clearly indicate that in most cases the hydrogen concentration will be appreciably above the lower explosion limit in air. Hence when bituminous coals are stored in a confined space (e.g. a ship hold), the explosive risk of hydrogen should be taken into account. 相似文献
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34.
影响DT岩石粉状铵梯炸药爆速的因素探索 总被引:1,自引:1,他引:0
文章从DT岩石粉状铵梯炸药的原材料细度,复合油相,混药时间,投料顺序,混药药温,装药密度等方面,探讨了该炸药爆速的影响因素。 相似文献
35.
36.
A new method is outlined which aims to predict high-cycle fatigue behavior of components which fail from stress-concentrators. This involves examination of the stress field in the vicinity of the stress-concentrator, and comparison with stress fields for cracks at known stress intensities. Methods which are currently used for simple notch geometries can thus be generalised, making the approach applicable to stress concentrators of any geometry. The method of prediction is shown to be stable, providing a solution of good accuracy when compared to analytical methods for standard specimen geometries. Favourable comparisons with experimental data have been achieved both for standard notches and for a corner geometry which represents a typical component case. 相似文献
37.
Linear stress analysis without body force can be easily carried out by means of the boundary element method. Some cases of linear stress analysis with body force can also be solved without the domain integral. However domain integrals are generally necessary to solve the linear stress problems with complicated body forces. This paper shows that the linear stress problems with complicated body forces can be solved approximately without the domain integral. In order to solve these problems, the domain is divided into small areas using contour lines of body force. In these areas, the distributions of body force are assumed approximately to satisfy the Laplace equation. 相似文献
38.
Creep fracture by slow crack growth is studied in a medium density polyethylene at 60 °C and 80 °C. Whereas elastic-plastic fracture mechanics load parameters fail to provide a unique temperature-independent correlation, that of the fracture mechanics for creeping solids C∗ is proved to be relevant since this parameter correlates very well with the time to failure. Correlation established on both full notched creep tensile and double edge notched tensile tests was validated on cracked gas-pipe samples tested under hydrostatic pressure, extending the use of time to failure versus C∗ diagram to predict lifetime of engineering components. 相似文献
39.
利用AutoCAD求解机构运动学和动力学问题 总被引:1,自引:1,他引:0
提出采用AutoCAD求解机构运动学和动力学问题,并结合实例给出了方法与步骤。 此求解法既有图解法简单明了的特点,又能满足了现代机械设计对运动分析和动力分析的高精度 的要求,具有较高的可靠性和实用性。 相似文献
40.
Based on an analogy between thermodynamics and Bayesian inference,inverse halftoning was formulated using multiple halftone images based on Bayesian inference using the maximizer of the posterior marginal(MPM) estimate.Applying Monte Carlo simulation to a set of snapshots of the Q-Ising model,it was demonstrated that optimal performance is achieved around the Bayes-optimal condition within statistical uncertainty and that the performance of the Bayes-optimal solution is superior to that of the maximum-a-posteriori(MAP) estimation which is a deterministic limit of the MPM estimate.These properties were qualitatively confirmed by the mean-field theory using an infinite-range model established in statistical mechanics.Additionally,a practical and useful method was constructed using the statistical mechanical iterative method via the Bethe approximation.Numerical simulations for a 256-grayscale standard image show that Bethe approximation works as good as the MPM estimation if the parameters are set appropriately. 相似文献