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In order to realize the high-quality work requirements of welding robots, based on the actual working conditions, the seven-degree-of-freedom series welding robot is taken as the research object, we design and determine the relevant technical parameters of it, and establish the kinematics model in D-H coordinate system. The micro-displacement synthesis method is introduced, and the static pose error model and reliability calculation model of the robot are established. The influencing factors of the accuracy of the welding robot's pose accuracy are analyzed and the sensitivity of the influencing factors was obtained. Finally, based on Monte-Carlo simulation method, the link parameters of the welding robot are taken as an example to verify the reliability of the position and accuracy of the welding robot, and the relevant results are obtained. The work in this paper is of some guiding significance in reliability design and assessment of a welding robot.

Escalators are now more and more widely used around the world. As escalator accidents occur from time to time, it is very important to analyze the structure and reliability of escalators. This paper studies the structure and reliability analysis methods of typical escalators. By applying parametric analysis methods, the efficiency and accuracy of escalator structure analysis are greatly improved. Because the failure of each structural member of the escalator truss system is dependent, this paper applies the dependent failure reliability modeling method and analyzes the reliability of the escalator truss system. The results show that the reliability analysis method of the truss system after considering the dependent failure is more reasonable. The above research work has certain reference significance for the design and analysis of escalators.

A new method based on Dynamic Bayesian Network (DBN) is proposed to assess the car engine reliability because of the limitation that the existing reliability analysis methods can only be used in static system reliability assessment. Firstly, define the failure mode and effect analysis table (FMEA) and the failure rates of the main components of the car engine and construct Bayesian network (BN) model. Secondly, combine the original BN model with time information and assess the reliability of the systems by using the advantages of BN in terms of the multi-state variables and uncertainly relations. The method is able not only to compute the reliability indices of car engine but also to carry out the fault detection easily to recognize the weakness of the system. This research is meaningful for reliability design and prediction of car engine.

Hexagon socket head bolts are widely used in many engineering fields as fasteners and are common and important parts for engineering, but for some hexagon socket head bolts it is still tedious to build the 3D models and assess their reliability. It is important for a hexagon socket head bolt to do reliability assessment, especially for some hexagon socket head bolt that under complex load conditions. In order to improve the reliability and stabilization, a hexagon socket head bolt reliability assessment method is introduced and an example is given, and the example shows that do reliability assessment is useful and effective.

A gear transmission system such as a gear train is a series system in sense of reliability evaluation, while it is different from a traditional series system such as a chain. Therefore, the conventional series system reliability model is not appropriate for gear transmission system. Based on the time-dependent configuration and the time-dependent loading path of a gear train, system specific reliability modeling technique is presented, by which a gear train is taken as a time-dependent series system, consisting of different components (gear teeth) in different time intervals. To illustrate the application of the reliability analysis method, several time-dependent series system reliability models are developed for different types of gear trains, the reliability estimation results are compared with those obtained by traditional series system reliability model.

A component with multiple weak sites is widely used in practical engineering and the existence of multiple weak sites can significantly decrease the component reliability. On the other hand, only a few components bear static loading and most components bear dynamic loading. In this paper, a reliability model of isomorphic component with multiple weak sites is built based on an order statistics model and the influences of strength decentrality and loading decentrality on isomorphic component with multiple weak sites are discussed. Furthermore the influence of loading times is studied in detail. The results show that unlike a component with only one weak site, not only does the failure of a component with multiple weak sites have a relationship with the safety margin, but there also exist relationships with the number of weak sites, the loading roughness, and loading times. The work in this paper is of some guiding significance in reliability design and assessment of a component with multiple weak sites under complex loading.

The propulsion system, comprising four hydraulic cylinders, is an important power supply assembly in tunnel boring machine, and fatigue is the major failure modes to concern for the hydraulic cylinders. To evaluate the reliability of the propulsion system, i.e. the hydraulic cylinder assembly, a reliability model capable of completely reflecting the effects of stochastic load environment and material property degradation is required. For such a purpose, this paper presents a method to describe the uncertainty of random load history at two levels, i.e. the macro-level characterizing the variation in the whole load history intensity over individual load historys, and the micro-level describing the fluctuation of load peaks inside one load history. Starting from random load history expression, a multi-layer, multi-variate dynamic (time-dependent) reliability model is developed through system-level load-strength interference analysis. By the multi-layer configuration, the model hierarchically expresses the role of the uncertainty in the intensity of load history, the randomness in load peaks within a specific load history, the uncertainty of load action number, and the uncertainty of component strength. By utilizing discrete time variable (i.e. load action number), product property degrading with load cycles can be exactly incorporated in failure criterion. The model, taking on either the form of multi-layer integral or the form of multilayer summation, can synthetically reflect the effects of the uncertainty of random load environment including statistical risk over operation period, the dependence among component failures, the uncertainty of load action number in a specified time interval, the uncertainty of material strength and its deteriorating path. Besides, this model incorporates both fatigue criterion and ultimate tensile failure criterion uniformally, and is applicable to both mechanical component and series system. Since no assumption on the independence between component failures, the reliability model can naturally reflect the effect of failure dependence, and the (conditional) probability distributions of the individual variates involved in the models can be easily determined.

Reliability concepts, models and methods have been developed in different fields and applied to a variety of engineering cases from component, system to process. Besides the great amount of successive applications, challenges are everywhere including the understanding to the role of random load environment, especially its uncertainty in reliability estimation and experiment, the mechanism to produce the bathtub type failure rate curve, the modeling of component/system reliability under complex load environment and with multiple failure modes, and so on. Focused in the present paper are general load-strength interaction analysis method and related failure rate modeling approach, statistical dependence among component failures, characterization and expression of the statistical property of random load environment, and the incorporation of the factors describing time, space and failure mechanism to develop comprehensive reliability models capable of reflecting stochastic load environment and material degradation behavior.

Electronic systems are widely used in many engineer and civil fields, such as aviation, energy, communication, military and automatic etc. Usually the more the components that a system includes the poorer the system reliability is. But the failures of components are usually dependent. In this paper, a reliability model of dependent failure of electronic system is built and the influences of strength decentrality and load decentrality is discussed. The results of two examples prove the validity and superiority of the method in the application of the reliability modeling and assessment of system and the model that considered failure dependent is more reasonable than those conventional reliability models.