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Low-frequency vibrations (0.5–5 Hz) that harm drivers occur in off-road vehicles. Thus, researchers have focused on finding methods to effectively isolate or control low-frequency vibrations. A novel nonlinear seat suspension structure for off-road vehicles is designed, whose static characteristics and seat-human system dynamic response are modeled and analyzed, and experiments are conducted to verify the theoretical solutions. Results show that the stiffness of this nonlinear seat suspension could achieve real zero stiffness through well-matched parameters, and precompression of the main spring could change the nonlinear seat suspension performance when a driver’s weight changes. The displacement transmissibility curve corresponds with the static characteristic curve of nonlinear suspension, where the middle part of the static characteristic curve is gentler and the resonance frequency of the displacement transmissibility curve and the isolation minimum frequency are lower. Damping should correspond with static characteristics, in which the corresponding suspension damping value should be smaller given a flatter static characteristic curve to prevent vibration isolation performance reduction.

Gear transmission is the most basic transmission component in mechanical transmission system. Many scholars have done a lot of research on gear reliability. When the variation coefficient is used to calculate and optimize the reliability of bevel gear, in order to calculate the reliability of bevel gear, it is often assumed that the gear works under constant torque, that is, the coefficient of variation (COV) is zero, but this is not the case in practice. In this paper, a gear reliability method based on discrete element simulation is proposed. The purpose of this method is to simulate the actual working conditions of gears, calculate more accurate coefficient of variation in the real world, and improve the accuracy of gear reliability design. Firstly, the real working conditions of the bevel gear transmission are simulated by discrete element method (DEM), and in the transmission system, the tangential force COV of the bevel gear is proved to be equal to the torque COV of the crusher central shaft. Secondly, the multi-objective function model of the gear transmission system is established based on the double tooth roll crusher (DTRC). The optimal volume and reliability of the bevel gear transmission are taken as the objective function, and the teeth number, module and face width factor of basic parameters of gear are optimized by genetic algorithm (GA). Finally, the accuracy of the optimization results is verified by Monte Carlo method. The main purpose of the manuscript is to analyse the effect of actual conditions (DEM simulation) on the optimization results. The results show that the COV of nominal tangential load of bevel gear is about 0.65 under actual working conditions, so in order to guarantee the same reliability, total volume need to be increased by 34.4%. This method is similar to the selection of gear safety factor. In practical production, the selection of safety factor is often based on experience. This paper provides a new method to optimize the reliability of bevel gear, combining with DEM simulation, which provides theoretical guidance for optimal design of bevel gear.

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In order to support the industry goal of zero fuel failures by 2010 and beyond, established by the Institute of Nuclear Power Operations (INPO), this paper describes how the Crud Induced Power Shift (CIPS) and Crud Induced Localized Corrosion (CILC) risk is being addressed by Westinghouse Electric Company LLC. As one of the key fuel failure mechanisms, CIPS/CILC risk assessments are being targeted, and the relationship between the CIPS/CILC mechanisms, fuel reliability, and plant operating conditions will be discussed. Plant and experimental data will be presented to show the current state of CIPS/CILC risk assessments for Westinghouse fuel. Finally, suggestions and other initiatives that specifically target reducing CIPS/CILC risk will be described for Pressurized Water Reactors (PWRs) supported by test and/or analysis results.