Hailong Deng

Accurate remaining useful life (RUL) prediction of rolling bearings was essential for condition-based maintenance because bearing service degradation was primarily governed by progressive rolling-contact fatigue at the rollingelement–raceway interface, whereas vibration signals provided measurable responses to this degradation rather than being its physical cause. However, reliable RUL prediction remained challenging because vibration measurements were noisy, nonlinear, stage-dependent, and sensitive to operating-condition shifts. In this study, a health-indicator-guided temporal-attention framework was developed for bearing RUL prediction using public run-to-failure vibration datasets. The novelty of this work lay in integrating degradation-consistent health indicator construction, sliding-window life-cycle representation, and HI-guided temporal attention into a unified and interpretable prediction framework. First, degradation-sensitive vibration features were extracted and fused into a compact health indicator (HI) to represent the progressive deterioration trend. Then, sliding-window sequences were generated and processed by a Transformer-based temporal-attention network, through which long-range temporal dependencies were captured and higher weights were assigned to informative degradation segments near stage transitions and late-life acceleration. Experiments on the XJTU-SY and IMS datasets showed that the proposed method improved prediction stability, reduced late-life error amplification, and achieved better performance than baseline variants without HI or temporal attention. Ablation analysis confirmed that HI construction mitigated cross-stage drift, whereas temporal attention enhanced transition sensitivity during accelerated degradation. Robustness and cross-domain tests further indicated that the method maintained acceptable degradation-following behavior under noise perturbations and operating-condition changes, although explicit domain-adaptation mechanisms were still required for strongly shifted target domains.

This article proposes a dual motor anti backlash rack and pinion transmission mechanism for the longitudinal feed system of CK61250 heavy-duty CNC lathe. This mechanism is different from fixed preloading and simple master-slave tracking electric preloading dual motor schemes. It adopts a master-slave control architecture that integrates real-time adjustable preloading force, disturbance observer, and stiffness error compensation framework. The force position decoupling dual motor layout is adopted, and mechanical preloading is not set. The control layer includes adaptive preloading adjustment and active cutting force suppression content. The relevant content has been verified through frequency domain stability margin analysis, interference suppression ratio evaluation, and comparison with single motor system simulation. The single motor system has problems such as transmission clearance, elastic deformation, and vibration noise. The maximum thrust of the system is 50 kN, the fast moving speed is 12 m/min, and the full stroke positioning accuracy is better than ±0.015 mm. A comprehensive error mathematical model has been developed, and sensitivity analysis shows that thermal deformation and control errors account for 38% and 22% of the overall positioning error.

This research analyzes the very high cycle fatigue behavior of two kinds of Cr–Ni alloy steel, including a surface‐carburized variant, through fatigue tests under R  = −1 and 0. The tested results reveal the effects of carburizing treatment and microstructure on failure mechanism. First, carburizing treatment cannot alter S – N characteristic of Cr–Ni alloy steel due to the fact that S – N curves are invariably characterized by single linear under R  = −1 and bilinear under R  = 0. Second, carburizing treatment and microstructure can impact the formation of fine granular area (FGA). Most notably, residual stresses would inhibit crack nucleation close to carburization layer, which can make internal crack nucleation much deeper. Furthermore, damage tolerance assessment (DTA) model and multiparametric Kitagawa–Takahashi diagram (K–T diagram), which can be widely applied on Cr–Ni alloy steel in different failure modes, are constructed according to the theory of stress concentration and statistic, synergistically considering the effect of carburization and stress–crack–life on failure mechanisms. DTA model significantly improves the accuracy of prediction for critical size, and multiparametric K–T diagram of internal failure with FGA not only contains a crack stagnation region corresponding to the formation of FGA but also makes the safety region more conservative. This research provides important theoretical support and practical guidance for engineering applications.

The welded joint of TC4 titanium alloy is easy to form coarse grain, and there is a large residual stress and residual deformation after welding. By applying ultrasonic aid in the conventional TIG welding process, the ultrasonic amplitude converter is directly contacted with the TC4 titanium alloy plate, and the ultrasonic cavitation effect generated by ultrasonic vibration and the mechanical vibration stirring effect are used to influence the flow and solidification process of liquid metal in the weld pool, so as to refine the microstructure and grain of the weld and reduce the residual stress of the weld. The grain size and residual tensile stress of welded TC4 titanium alloy joints under different ultrasonic power were measured. Compared with conventional TIG welding, the average grain size of the weld is reduced by 22.70 % and the average residual stress release rate is 82 % when 2000 W ultrasonic power is applied. Grain refinement can increase grain boundary number and improve material strength. Reducing the residual stress of weld can further reduce the fatigue crack propagation rate of weld. Therefore, it is of practical significance to improve the weld microstructure and reduce the residual stress of welded joints by ultrasonic assisted welding technology to improve the strength and reliability of welded structures.

The size and depth of defects significantly affect fatigue performance; the main purpose of this article is to clarify the effect of stress correction factors caused by defects on the fatigue life of α + β Type titanium alloy welded joints. In order to investigate the fatigue characteristics of α + β Type titanium alloy welded joints, axial constant amplitude loading fatigue tests were performed with a stress ratio of −1. The test results show that the fatigue life continues to increase as the stress amplitude decreases, and the failure modes can be classified into two types: interior failure and surface failure. A fatigue parameter (λ) determined by both defect depth and size was proposed which allowed for a good generalization of the data point distribution in short and long-life regions. The stress correction factor (W) related to the S–N characteristics was constructed by combining the λ and average defect size, and it effectively improved the dispersion of the test data. Continuing, the fatigue life prediction model was established under the condition that the defect type and size can be estimated or detected on the basis of the dislocation energy method. The results indicated that the evaluated values of the new life model associated with W are in good agreement with the test results.

As a metal material with superior mechanical properties, high-strength carburized steel is of great value for the production and manufacture of components in various fields. In this work, based on axial loading tests at stress ratios of −1, 0, and 0.3, the fatigue behaviors of high-strength carburized steels from high cycle to very high cycle are systematically investigated. For defect-fine granular area (FGA)-fisheye induced failure exhibiting long fatigue life, it is verified that the transition sizes between small and long cracks can be approximately equivalent to FGA size. Combined with extreme value estimation, a new mathematical model based on Weibull distribution was proposed to describe the competition among different failure modes. The results show that the probability of interior failure will decrease significantly with the increase of the maximum surface defect size under the condition that the maximum stress exceeds about 900 MPa. Additionally, larger surface defects are more beneficial to the occurrence of surface failure. Finally, combined with the stress correction factor proposed for optimizing the data with large dispersion, the fatigue life is predicted based on the crack initiation and propagation behavior, and the prediction results are in good agreement with the experimental results.

Carburized Cr-Ni steel is widely used in the manufacture of components in many fields due to excellent performance, of which the service life has been a concern. In order to investigate the high-cycle-fatigue and very-high-cycle-fatigue properties of carburized Cr-Ni gear steel, axial loading fatigue tests were performed by QBG-100 with stress ratios of −1, 0 and 0.3. The Generalized Pareto distribution was used to evaluate the inclusion size of carburized Cr-Ni gear steel. Based on the stress ratio and the evaluated crack size, a new fatigue life prediction model for carburized Cr-Ni gear steels was constructed. The results show that the S–N characteristics of carburized Cr-Ni gear steel represent the continuously descending tendency. Based on the long crack propagation threshold and the instability propagation threshold of carburized Cr-Ni gear steel, the sizes of FGA, fisheye and surface smooth area (SSA) can be evaluated, respectively. In addition, the maximum size of surface and interior inclusion of carburized Cr-Ni gear steel are 17.50 μm and 6.46 μm with a cumulative probability of 99.9%. By validating the new established model, the prediction result is acceptable according to the good consistency between the predicted life and the experimental life.

The variable amplitude loading fatigue test with interior Inclusion-FGA-Fisheye induced failure under R = 0 was carried out on carburized 12CrNi ₃ steel in very high-cycle fatigue regime. Comparing with S-N curve of constant amplitude loading, the total life is inevitably longer under variable amplitude loading. And, the surface morphology of FGA is coarser under same order of magnitude of fatigue life. Simultaneously, it can be determined that the formation micro-mechanism of FGA is caused by the continuous debondings of refined grains due to stress concentration around interior micro-defects, and variable amplitude loading will aggravate the formation of FGA. Furthermore, the life prediction model based on double nonlinear fatigue damage, which considers the coupling effect of local equivalent stress (surface residual stress, maximum stress and local stress concentration by RVE model), loading sequence and failure mechanism is established, and predicted life has good accuracy within the factor-of-three lines for experimental life.