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The equivalent effects of initial temperature and dilution ratio on premixed combustion of natural gas in the constant volume combustion bomb are studied. The initial pressure pu and equivalence ratio  are set to be 0.3 MPa and 1.0 in experiment, respectively, and the ball type flame extension method by high speed schlieren photography is used in the experiment. Stretched flame propagation velocity Sn, unstretched flame propagation velocity SL, Markstein length Lb, laminar combustion velocity uL and NOx emission are analyzed in detail. The results show that SL, flame development duration and combustion duration are nearly identical, but the laminar burning velocity uL has a big difference at the operating points that have similar Sn value. The influence of dilution ratio on SL and uL is greater than that of initial temperature when the dilution ratio is small. Further research finds that the temperature difference ΔTu= 50 K has equivalent effect on combustion process compared with dilution ratio ΔDR=2%. Under the boundary conditions of the similar Sn, the NOx emission is lower under the conditions of higher initial temperature and dilution ratio compared with the smaller initial temperature and dilution ratio. [ABSTRACT FROM AUTHOR]

The eight-level spectrum of torque is established by using the stochastic loading history of torsion shaft of military vehicles on various types of standard road surface. In consideration of the randomness of factors such as material performance, and fatigue influence coefficient, etc.,the durability model is built by applying fatigue reliability theories. An optimization model, which takes the maximum durability of torsion shaft as the objective function when a vehicle travels for 6 000 km, is built based on the constraints such as rigidity reliability, structure dimension and so on. The approach that introduces the double-loop strategy for durability object conversion and the single-loop strategy for reliability bounds conversion is presented for this optimization model. The high computing accuracy of object value and the high efficiency of optimal computation are obtained. The results show that the durability of torsion shaft is improved obviously. [ABSTRACT FROM AUTHOR]

The quantitative reliability assessment of a MEMS-based safety and arming (MEMS S&A) device in fuze is performed based on the structural design and simulation. The structural design of MEMS S&A is then improved and verified through experiment. A primary design of MEMS S&A device is presented. The functional requirements of the key structures in the device are proposed according to the operating environment of small-caliber munition fuzes. Finite element (FE) simulation is adopted to evaluate the design. The structural reliability simulation method based on FE simulation and its implementation procedures are proposed, which can help to quantify the reliability of the device. An efficient CAE software integration method using ANSYS as an example is presented to facilitate the repetitive FE-based calculations. The reliability of the key structures of the device is evaluated, where the randomness of loading, geometric parameters and material properties are taken into account. The significant factors are also identified for further structural improvements. A prototype of MEMS-based S&A device is manufactured, which is delivered to centrifugal experiments. Experimental results demonstrate the feasibility of the design. [ABSTRACT FROM AUTHOR]

Based on the frequently-used engineering methods for fatigue life prediction and the performance measure approach, a reliable fatigue life model is built, and a set of methods for reliable life prediction and sensitivity analysis are proposed. By expressing fatigue life as the function of random variables, the reliable life prediction problem is converted into a spherical constraint optimization problem which can be solved using performance measure approach, and then the reliable life can be gotten directly. Moreover, the sensitivity factors for each random variable and deterministic variable can be calculated by using some intermediate variables in life prediction. The proposed method is demonstrated with a torsion shaft example. The results show that the proposed method has high efficiency and precision, and the different parameters have much different influences on reliable life. [ABSTRACT FROM AUTHOR]

The design of reliability sampling inspection program for the success or failure products is an issue to be solved in reliability test. Meta-heuristic algorithm provides a new idea to solve the problem. Cuckoo search algorithm is a new meta-heuristic algorithm, and has been widely used in many fields because of its simplicity but efficiency. A model for reliability sampling inspection program is developed to minimize the risk. The mechanism of the cuckoo search algorithm is expounded. For the local search efficiency of the algorithm, an adaptive detection probability is proposed to balance the global search and local search efficiencies. The result of a case study reveals that the proposed method is feasible and effective. [ABSTRACT FROM AUTHOR]