As a vital component of electronic products, the quality of the printed circuit board (PCB) assembly directly affects the applications and service life. During the reflow soldering process, the PCB assembly may suffer excessive warpage. Therefore, in order to avoid such a failure, this paper conducts the finite element simulation of the PCB assembly temperature change and the deformation process according to a theoretical model for heat transfer and then explores the causes of warpage and predicts the percentage of warpage that occurs during the reflow soldering. A reliability sensitivity analysis is creatively applied in the PCB assembly warpage study in order to uncover the quantitative influence of multiple factors with random errors on warpage. Moreover, the reliability calculation provides a theoretical basis for the allowable error range of geometric dimensions, material properties and process parameters of the PCB assembly. This research has a remarkable significance and is valuable to engineering in promoting quality and reliability, and increasing the yield of PCB assembly in mass production.

This paper presents a queuing system model that incorporates multiple priorities, multiple abandonments, and heterogeneous servers. Waiting for service easily leads to impatient behaviors. The impact of two kinds of impatient behaviors, balking and reneging, on queueing system performance is examined. The problem is formulated as continuous-time Markov chains. It also introduces a special state called the non-sojourn state to record the number of customers who abandon the system. The state transition rate matrix is transformed into a block tridiagonal matrix by appropriately setting the state numbers. A novel indicator called interstate transition frequency is proposed, which aids in distinguishing state transitions during the system evaluation process. Based on the interstate transition frequency, a set of indicators is derived to offer additional analytical perspectives for the queuing system. Finally, the proposed model is applied to an automobile repair shop to validate its effectiveness in practical scenarios.

Grind-hardening processing is an emerging approach that combines the grinding and surface quenching process. During the process, the hardened layer—mainly martensite—is produced on the surface of the workpiece to achieve the purpose of surface strengthening. Above all, the surface temperature field of the hypoeutectoid-1045 steel workpiece was determined by finite element method for fully revealing the formation mechanism of the hardened layer. Further, the cellular automata approach was applied to dynamically simulate the transformation of both austenitization and martensitization from the initial microstructure. The hardness penetration depth was also predicted. Finally, a grind-hardening experiment was conducted to assess the theoretical study. Results showed that a combination of the finite element method and the cellular automata approach can effectively simulate the microstructure transformation of hardened layer. The microstructure and the hardness penetration depth were affected by the maximum grinding temperature and the heating rate. Research on the influence of grinding parameters showed that the hardness penetration depth increased as the depth of the wheel cut and feeding speed increased. Experiments revealed that the difference between predicted value and experimental value of the hardness penetration depth varied between 2.83% and 7.31%, which confirmed the effectiveness of the predicted model.

Cavitation erosion is induced by the penetrating pressure from implosion of cavitation bubbles nearby solid boundary. The bubble evolution and the subsequent collapse pressure are especially important to evaluate the erosion degradation of solid boundary materials. The bubble dynamics equation taking into account the influence of distance between bubble and solid boundary is formulated to investigate the effect of boundary wall on bubble evolution process. The pressure fluctuation induced by slapping forces is adopted to evaluate the bubble dynamic characteristics. Negative pressure period which reflects the effect of vibration velocity and gap clearance also has large influence on bubble dynamics. The effects of standoff distance, initial radius and negative pressure period on bubble evolution and collapsing shock pressure are discussed. Maximum bubble radius increases with standoff distance and initial radius, while shock pressure increases with distance and decreases with bubble initial radius, and both of them increase with negative pressure period.

The missions of weapon systems are becoming increasingly complex. Thus, more mechanism motions than one are required to complete one mission. Under such conditions, a sort of mission has emerged, that needs a few mechanism motions to be executed in sequence. This means that the mission is not completed until all the motions have been executed successfully in strict sequence. This sequence motion system can be considered as a traditional series system with the motions treated as subsystems. Then, the system reliability can be analyzed with the traditional series system reliability method. However, this method cannot fully reflect the characteristics of a sequence. In this work, a reliability model of sequence motions and its solving idea are proposed. In this reliability model, the influence factors of each motion are included. Particularly, the performance function of the former motion is regarded as just one of the influence factors of the next motion, which is the most significant feature for the sequence motion system. Afterward, a solving idea with characteristics of a gradually shrinking sample space is proposed based on Monte-Carlo simulation. Finally, the reliability model of sequence motions and its solving idea are illustrated with a case study on the automatic chain shell magazine sequence motions of a self-propelled artillery.