Serpentine locomotion in snake robots is inherently susceptible to lateral slip induced by environmental interactions, leading to propulsion efficiency degradation and trajectory deviations. To address these tribodynamic coupling challenges, this study systematically investigates slip dynamics and parametric optimization strategies for high-efficiency serpentine propulsion. First, a hybrid Coulomb-viscous friction model is developed to characterize anisotropic contact constraints while ensuring numerical convergence. Based on this formulation, a generalized multibody dynamics framework incorporating passive wheel position parameters is established using planar rigid-body motion theorems. Numerical simulations comprehensively evaluate the sensitivity of frictional anisotropy, propulsion loss coefficient, and propulsion velocity to distinct control parameters. Subsequently, a genetic algorithm (GA) optimization framework is employed to determine optimal gait parameters, yielding an explicit empirical mapping between optimal initial angles and friction coefficient ratios to facilitate terrain-dependent parameter selection. Crucially, experimental validation on a physical prototype confirms the theoretical trends across varying friction conditions. Demonstrating significant enhancements in locomotion stability and efficiency, the proposed framework provides quantitative design guidelines and a theoretical basis for robust terrain-adaptive control of snake robots in unstructured environments.

The dimensional accuracy of CNC machining of frozen sand molds directly affects the accuracy of the resulting castings. This paper proposes a point cloud-based rapid 3D detection method to meet the measurement requirements for frozen sand molds during CNC machining. Using a general feature classification strategy, the 3D geometric features of sand molds are categorized as rectangular, circular, and planar, corresponding to dimensional information in the XY plane and the depth direction. Specific dimension-fitting strategies are developed for each feature type, enabling fast and accurate measurement of regular geometric structures in frozen sand molds. Experiments with dimensional standard parts show that the proposed method’s maximum measurement error is 0.34

The cold rolling process entails coupled elastoplastic deformation of the strip and elastic flattening of the work rolls. The complexity from nonlinear strain gradients and inhomogeneous contact conditions poses significant challenges to elucidating interfacial behaviors within the deformation zone. With the development of cold-rolled strip toward higher strength and thinner gauge, conventional analytical models based on simplified assumptions fail to adequately capture the intricate physical mechanism. In order to display the characteristics and behaviors within the deformation zone and enable fundamental exploration of deformation mechanism for the high-strength thin strip, a theoretical modeling framework is constructed: (1) Based on the elastoplastic deformation characteristics of the strip, the deformation zone is partitioned into entry elastic zone, plastic zone and exit elastic zone; (2) considering the slip or stick friction contact behaviors between the rolled strip and the work rolls, the plastic deformation zone is further subdivided into backward slip zone, stick zone and forward slip zone; (3) not using the traditional circular elastic flattening approach, the noncircular flattening curve is analytically expressed by combining the rolling stress distribution with the elastic half-space theory. Subsequently, a numerical iteration method driven by mechanism-data fusion is proposed to decouple the nonlinear roll-strip interactions and determine the key process parameters, which can characterize the distinct deformation zones, including rolling normal stress, friction tangential stress, roll flattening curve, contact arc length, total rolling force, and forward slip. Furthermore, an elastoplastic finite element method model for rolling process is established to verify the presented approach via rolling stress distribution and roll flattening curve, and the calculated parameters of rolling force and forward slip are validated by the actual process data. In addition, the influence of process parameters on interfacial behavior evolution is discussed, and the presented approach is effectively applied to investigate the industrial dynamic rolling process. The proposed approach enables accurate calculation and mechanistic explanation of negative forward slip phenomena, offering theoretical support for practical process optimization.

ABSTRACT In the process of replacing the guide with yarn in flexible‐guided 3D weaving, the frictional force of guide extraction exhibits unpredictable magnitude. This hinders the design of the automated device, reduces the progress efficiency, and restricts the universality of product application. This study developed a hybrid theory‐GBR (gradient boosting regressor) model for friction force prediction during the process of replacing the guide with yarn. The theoretical model accurately explained the mechanism between the friction force and the structure parameters (the number of fabric layers and fabric layer density), and the theoretical model was validated through experiments. GBR model was trained to capture the nonlinear residual between the theoretical friction force and the experimental friction force. Training data were obtained from experiments. The training method was leave‐one‐out cross‐validation. The prediction performance of the hybrid theory‐GBR model was compared with that of machine learning models, GBR and support vector regression, and a theoretical model. The results showed that the experimental results were consistent with the theoretical model that friction force increased linearly with the number of layers and nonlinearly with fiber volume fraction. The hybrid theory‐GBR model achieved better performance in predicting the pull‐out friction force. It combines the advantages of both theoretical and data‐driven approaches. This research provides a new method for predicting the friction force of guide rod removal, and it also provides data support for flexible‐guided 3D weaving.

Aiming at the problems of low efficiency, large yarn damage, and high labor cost during the traditional manual guide-to-yarn replacement process of flexible-guide three-dimensional preform, a novel method of multiple guide-to-yarn replacement is proposed. Firstly, the relationship between the height of the guide array and its deformation is explored by an image analysis method, and the principle of the multiple guide-to-yarn replacement method is clarified. And then, the four-wire method is used to quantify the fiber damage. The efficiency of the method is discussed by means of experiment and comparison. Further, the yarn locking ability is analyzed. Finally, three-dimensional composite samples are prepared to carry out compression tests. The results show that reducing the height of the guide array can increase the contact area from 0 to 0.49 mm2. Compared with the traditional method, the yarn damage of the multiple guide-to-yarn replacement method is relatively reduced by 22.47%, the yarn locking ability is equivalent, the forming efficiency is 8.05 times faster than that of the traditional manual method, and the compressive strength of the sample is increased by 12.64%-13.31%. The above work provides technical support for the efficient and high-quality production of the flexible-guide three-dimensional weaving.

Conventional mechanical metamaterials typically have fixed geometries, which limits their adaptability to complex service conditions. To address this limitation, this study proposes an electrically tuneable honeycomb structure with a variable Poisson's ratio, achieved by integrating macro fibre composite (MFC) actuators into the cell walls. A multi-field coupled analytical model was developed to describe the voltage-induced bending deformation, effective Poisson's ratio, in-plane equivalent elastic modulus, and out-of-plane bending stiffness of the structure. The underlying mechanism of the electrically driven geometric reconfiguration was systematically revealed. By switching the polarity of the applied voltage, the cell walls undergo a reversible transition between the convex and concave configurations, enabling controllable switching between auxetic (negative) and conventional (positive) Poisson's ratio regimes. Experimental results and finite element simulations demonstrate good agreement with the theoretical predictions, with deviations consistently within 5%. Notably, the Poisson's ratio can be reversibly switched between -11.5 and a positive value under +/- 1200 V. Although the out-of-plane bending stiffness is significantly tuned, the longitudinal equivalent elastic modulus varies by less than 3%, demonstrating an effective decoupling between deformation-mode regulation and axial load-bearing capacity. The proposed MFC-driven honeycomb structure provides a feasible strategy for programming mechanical properties through electrical stimuli, thereby offering a viable pathway for developing next-generation adaptive structures for aerospace, robotics, and vibration control applications.

The electrically assisted stretch bending (EASB) process enables the fabrication of components with complex cross-sections. However, defects such as springback, wrinkling, and necking typically emerge in this process. This study proposes a process parameter control methodology based on defect formation mechanisms and establishes an optimization framework to mitigate and prevent these defects and improve product quality. Analysis of the wrinkling and necking mechanisms elucidated the effects of process parameters on defect formation. Based on this foundation, defect prevention criteria were formulated as constraints, whose solution defined the feasible region of design variables. Subsequently, a springback optimization framework was developed using a response surface surrogate model. A case study on Y-section profile EASB demonstrates the framework’s implementation through five key steps: finite element modeling, stress-neutral layer determination, initial wall-thickness defect incorporation, feasible region definition, and springback optimization model construction and solution. Results demonstrate that optimizing process parameters within this framework effectively reduces springback while preventing wrinkling and necking.

The integrated control driver serves as the core actuator in control systems and is characterized by high structural integration and complex assembly. Under dynamic loading, strongly coupled vibration responses are likely to occur, posing risks to system stability and reliability. To address the inadequate consideration of complex internal assembly structures in conventional finite element modeling, this study establishes a hierarchical modeling and analysis approach from the component level to the system level. Differentiated equivalent strategies are adopted for PCB-mounted micro-components, bolted joints, and pre-compressed T-shaped rubber absorbers instead of a uniform rigid simplification. A multi-level validation chain is constructed through PCB modal hammer testing, absorber sine-sweep testing, and whole-system vibration testing. The coupling influence of absorber pre-compression on modal characteristics, random vibration response, and transient shock response is quantitatively revealed. The proposed methodology provides a validated route for the structural dynamic analysis and design of complex assembled electronic control devices.

Continuous fiber-reinforced thermoplastic composites (CFRTPs) have been limited by issues such as insufficient fiber-matrix bonding and high porosity, hindering performance enhancement. This study proposed a low-cost, high-efficiency ultrasonic-assisted printing (3DUAP) method. Multistage fiber-spreading filament-forming equipment was employed to prepare CAF/PA12 filaments with approximately 60 vol% fiber content. The effects of mold temperature, initial fiber-spreading tension, and traction speed on filament impregnation degree and mechanical properties were investigated. The prepared 3840D filament achieved 1664.25 MPa tensile strength. An ultrasonic-assisted additive manufacturing 3D printer was designed to investigate the effects of ultrasonic power and pressure on mechanical properties and surface precision of CAF/PA12 composites. Results showed that 3DUAP specimens exhibited maximum tensile strengths and tensile modulus of 1085.14 MPa and 32.79 GPa, respectively. Specimen porosity decreased to 1.85%. With increasing ultrasonic power and pressure, the tensile strength of both specimens first increased then decreased, while surface roughness values first decreased then increased. The high temperatures generated by the ultrasonic device's high-frequency vibration promoted the impregnation of the printed filament, enhancing the fiber-resin interfacial bonding strength. Simultaneously, it strengthened the interlaminar and intertrack bonding while reducing porosity in the printed specimens. This process achieved the printing of high-fiber content, high-performance CFRTPs, providing a technical reference for the additive manufacturing of high-performance composites.

Square guide rails, as typical ultra-long components, are prone to large deflection bending during machining. Therefore, accurate straightening is a prerequisite for ensuring assembly accuracy and in-service performance. Most existing straightening models are based on the plane-section assumption and are applicable to cases with small initial deflections. However, when straightening rails with large initial defects, the validity of the plane-section assumption declines significantly. Consequently, these models fail to accurately characterize the overall post-straightening morphology, and a dedicated evaluation framework and prediction model tailored to large-deflection scenarios are required. To address this challenge, this study proposes morphology descriptors for post-straightening profiles under large initial deflections, thereby overcoming the limitations of conventional indices that fail to comprehensively reflect the global rail shape. A finite element model of the pressure straightening process was developed using ABAQUS and validated against experimental measurements, demonstrating satisfactory reliability and accuracy. Subsequently, a parametric modeling strategy was adopted to build a dataset that covered combinations of initial deflection and straightening strokes. Finally, a deep neural network was developed to predict the straightening stroke. The application results indicate that the proposed model achieves favorable straightening performance and effectively improves the overall straightness of square guide rails with large initial defects.

The machining quality of frozen sand molds is closely related to the casting process and the final quality of high-end equipment components. To enable intelligent manufacturing of sand molds while reducing resource consumption, this study proposes a multi-objective online inspection system for CNC machining of frozen sand molds. A segmented machining-inspection strategy based on a moving sand mold is developed, enabling stage-wise online inspection on the machining line of three key quality metrics: sand removal rate, surface roughness, and dimensional accuracy. Experimental evaluation using multi-material frozen sand molds demonstrates that the relative error in sand mold forming induced by the two reciprocating motions of the proposed online inspection platform remains within 1

The quality of profiles produced by porthole-die extrusion depends strongly on the bonding behavior of separated metal flows. This macroscopic bonding behavior is closely associated with micro-void closure at the bonding interface. However, how stress states relevant to porthole die extrusion govern micro-void closure remains unclear, and their effects have not been adequately incorporated into welding quality evaluation criteria. This study combines porthole-die extrusion experiments, microstructural characterization, finite element simulations, and representative volume element (RVE) modeling to establish a link between the local stress state, micro-void evolution, and longitudinal weld quality. The stress triaxiality and Lode parameter obtained from the welding plane were mapped to the RVE model to relate the mechanical state during extrusion to void closure behavior. The results show that stress triaxiality controls void-volume reduction, whereas the Lode parameter affects void shape evolution and the critical strain required for complete closure, indicating that shear-related stress effects should be considered in welding criteria. Accordingly, an L criterion incorporating hydrostatic pressure and maximum shear stress effects was proposed to evaluate longitudinal weld quality. The proposed criterion captures the radial variation in longitudinal weld quality observed in the extruded profiles. This work provides a micromechanically motivated basis for evaluating longitudinal welds under combined compressive and shear stress conditions in porthole die extrusion.

In the past decade, a novel composite fluid, i.e., microencapsulated phase change material latent functional thermal fluid (MPCM-LFTF), which consists of nano/microsized core-shell microencapsulated phase change material (MPCM) and base fluid, has attracted increasing research attention, as it is capable of facilitating rapid heat transfer by virtue of both the phase transition properties of MPCM and the flow characteristics of base fluid. To improve the heat transfer capability and promote the practical application of MPCM-LFTFs, it is essential to fully figure out the complicated process of heat transfer in the whole composite fluid. In this review, a concept of multiscale interfacial modulation in MPCM-LFTFs is firstly proposed based on their composite structures and heat transfer characteristics. Specifically, the multiscale interfaces in MPCM-LFTFs include the nanoscale interface in core-shell architecture of MPCM (Interface I), the microscale interface between MPCM and base fluid (Interface II), and the macroscale interface between the composite fluid and the internal surface of container (Interface III). The typical preparation methods of MPCMs and composite fluids are further introduced, and the significance of some typical physical property parameters in evaluating the heat transfer efficiency across the three interfaces is emphasized. Quantitative analyses from the literatures indicate that systematically optimizing these interfaces can enhance the effective thermal conductivity of MPCM-LFTFs by up to 120

The multiredundant degrees-of-freedom (DoF) in snake robots present substantial challenges in attaining oriented movement toward target directions. Under the coupled influence of various factors, these systems progressively deviate from desired trajectories, thereby diminishing locomotion precision. This paper systematically investigates head orientation strategies and their effects on orientation control and stability during the snake robot's serpentine locomotion. First, through biomechanical analysis and mechanistic simplification of biological snakes' orientation mechanisms, a dynamic model of the snake robot and a central pattern generator (CPG) control network based on Hopf oscillators are established. Building on this foundation, we implement head orientation algorithms under different strategies and propose a multimetric evaluation framework. The methodology comprises three steps: (1) formulation of distinct head orientation strategies considering the characteristics of signal continuity and joint angular patterns; (2) definition of state variables for serpentine locomotion and corresponding orientation evaluation metrics; (3) parametric investigation of control parameters' impacts on head orientation accuracy through the proposed framework. Finally, comprehensive simulations and prototype experiments demonstrate the approach's effectiveness. This work provides theoretical and practical guidance for achieving precise orientation control of snake robots in complex operational scenarios.

The surface roughness of CNC-machined frozen sand molds strongly influences the resultant surface quality of the final casting. In this paper, the surface roughness detection and prediction method of CNC machining of frozen sand mold is studied, and a surface roughness detection method based on surface-structured light is proposed to achieve the low-temperature rapid detection of CNC machining of frozen sand mold with complex structure. Planar array structured light is adopted to detect the roughness of frozen sand molds made from different materials under multiple process parameters, and the significant impact of these parameters is determined through extreme difference analysis. This analysis serves as the basis for process judgment in the online regulation of surface roughness during CNC machining of frozen sand molds. In the study, the angular coefficient is introduced as a parameter to characterize the different material sand molds, combined with the CNC machining process parameters of spindle speed, cutting speed, cutting depth, and cutting width as inputs, and the surface roughness of the frozen sand pattern as outputs, to build a BP neural network prediction model with five inputs and one output, and to realize the prediction of the surface roughness of the different material sand molds under the multi-processing process with prediction error of 2.75

The retention of frozen sand chips generated during CNC machining of frozen sand molds can accelerate tool wear and compromise casting quality. To address the challenges of chip accumulation and incomplete removal during pneumatic-assisted CNC machining of these molds, this study investigates a detection method based on 3D point cloud data. The proposed approach enables efficient and accurate quantification of sand removal rates in molds with complex geometries, offering a practical solution for enhancing machining performance and casting reliability. The grid projection method was employed to measure the volume of various known structural models. An optimal grid size of 2.6 mm resulted in a volume measurement error of only 0.58

The latent heat thermal energy storage system with solid–liquid phase-change material (SLPCM-LHTES) as energy storage medium provides outstanding advantages such as system simplicity, stable temperature control, and high energy storage density, showing great potential toward addressing the energy storage problems associated with decentralized, intermittent, and unstable renewable energy sources. Notably, effective heat transfer within the SLPCM-LHTES is crucial for extending its application potential. Therefore, a comprehensive understanding of the heat transfer processes in SLPCM-LHTES from a theoretical perspective is necessary. In this review, we propose a three-stage heat transfer pathway in SLPCM-LHTES, including external heating, interfacial heat transfer, and intrinsic phase transition processes. From the perspective of this three-stage pathway, the theoretical basis of heat transfer processes and typical efficiency enhancement strategies in SLPCM-LHTES are summarized. Moreover, an overview of the typical applications of SLPCM-LHTES in various fields, such as building energy efficiency, textiles and garments, and battery thermal management, is presented. Finally, the remaining challenges and possible avenues of research in this burgeoning field will also be discussed.

In dual-phase alloys, the alpha/beta phase boundary plays a critical role in determining their phase transformation and deformation behavior. Here, our TEM observation confirmed that a hexagonal close-packed to face-centered cubic phase transformation was induced by the alpha/beta phase boundary migration. Results indicated the interface between alpha and beta phase can promote the dissociation of misfit dislocations, thereby providing a source of partial dislocations for FCC phase formation. More precisely, the mechanical drag force caused by the migration of phase boundary facilitate the activation of partial dislocations that required for FCC nucleation. Atomic-scale analysis indicated that the phase transformation from HCP to FCC was achieved through the 12 R intermediate structure. The present study not only provides new insights into the HCP to FCC phase transformation mechanism in Group IVB metals and alloys, but also sheds light on the critical role of alpha/beta phase interface migration in this phase transformation.

The effects of contact pressure, die temperature and interface gap on cooling rate and strengthening law of 2195 Al-Li alloy sheet in the die were systematically analyzed by the interface heat transfer experiment and simulation. The results shows that when the contact pressure and die temperature were 15 MPa and 25 degrees C, respectively, the cooling rate of sheet was 135 degrees C/s, the tensile strength of sheet reached 550 MPa; which indicated that effective quenching of the sheet in the die could be achieved in this situation, thereby ensuring aging strengthening effect. The precipitations of strengthening phases in quenched specimens under varying heat transfer parameters was observed by TEM. Combined with the information on precipitation morphology, diameter, and number density of strengthening phases, the quenching strengthening mechanism of the 2195 AlLi alloy in die was revealed. When the contact pressure was greater than 15 MPa, the specimen was rapidly cooled in the die, which inhibited the early precipitation of theta ' during the cooling process and promoted precipitation of uniformly fine strengthening phase T1 in the aging treatment process, thereby ensuring the heat treatment strengthening effect of 2195 Al-Li alloy.