In order to obtain stable and reliable configuration transformation ability, reliability optimization design is regarded as an effective way to reduce the probability of kinematic function failure for the constrained metamorphic mechanism. Based on the structural composition principle of multi-configuration source metamorphic mechanism that can operate in an under-actuated state, the modularized calculation methods are established for the force analysis of augmented Assur groups including metamorphic kinematic joints. According to the equivalent resistance gradient model of metamorphic mechanisms, with considering the uncertainties in the link dimensions, masses, and compliance parameters et al., a probabilistic evaluation method for describing the configuration transformation ability of the constrained metamorphic mechanism is established. Based on reliability evaluation and reliability sensitivity analysis, a reliability optimization design method for improving the configuration transformation ability is proposed, and then the optimization design is carried out for tolerances of random variables focusing on those structural parameters with higher reliability sensitivity, so that the optimized results can satisfy the requirements of both reliability and economic simultaneously. Finally, the feasibility and effectiveness of the proposed method is verified by the illustration of a paper folding metamorphic mechanism. The research provides the foundation of reliability design of metamorphic mechanisms to obtain the high-probability repeated execution ability of configuration transformation, it also has theoretical and practical significance to promote the engineering application of metamorphic mechanisms.

The accumulation of emergency braking at high speed and heavy load may result in the initiation and expansion of thermal fatigue cracks on the surface of brake, then cause the potential risk such as brake wheel crack or even burst. Aiming at the emergency braking condition of the SBD80-A disc brake used in a company's port crane, a finite element analysis (FEA) simulation model was established for the thermal–mechanical performance analysis applying ABAQUS software. Firstly, FEA simulation was employed to obtain the variation process of thermal stress, and the stress cycle load of a single emergency brake was analysed by using the rain flow counting method simultaneously. And the stress–strain curve of the brake material was used to convert stress amplitude into the strain amplitude. Then, the strain life of one-time emergency brake was calculated under different strain amplitudes by utilizing the Manson-Coffin strain-life formula corresponding to the actual temperature. Finally, the Miner's rule was adopted to propose thermal fatigue life prediction method under emergency braking of disc brake considering the influence of high temperature. The research provides a theoretical basis for failure mechanism analysis and life prediction of thermal fatigue for the mechanical products with similar structures, offers a design guidance for determining the inspection and maintenance cycle of brakes under the condition of emergency braking.

In order to obtain stable and reliable configuration transformation ability, reliability optimization design is regarded as an effective way to reduce the probability of kinematic function failure for the constrained metamorphic mechanism. Based on the structural composition principle of multi-configuration source metamorphic mechanism that can operate in an under-actuated state, the modularized calculation methods are established for the force analysis of augmented Assur groups including metamorphic kinematic joints. According to the equivalent resistance gradient model of metamorphic mechanisms, with considering the uncertainties in the link dimensions, masses, and compliance parameters et al, a probabilistic evaluation method for describing the configuration transformation ability of the constrained metamorphic mechanism is established. Based on reliability evaluation and reliability sensitivity analysis, a reliability optimization design method for improving the configuration transformation ability is proposed, and then the optimization design is carried out for tolerances of random variables focusing on those structural parameters with higher reliability sensitivity, so that the optimized results can satisfy the requirements of both reliability and economic simultaneously. Finally, the feasibility and effectiveness of the proposed method is verified by the illustration of a paper folding metamorphic mechanism. The research provides the foundation of reliability design of metamorphic mechanisms to obtain the high-probability repeated execution ability of configuration transformation, it also has theoretical and practical significance to promote the engineering application of metamorphic mechanisms.