Rolling Mechanism Research Articles

Using the kinematic radius in the mechanics of elastic wheel rolling

As you know, in the mechanics of a wheel with an elastic tire, both dynamic (rd) and kinematic (rk) radius are widely used. At the same time, specialists in the theory of the motion of wheeled vehicles still do not have a clear understanding of the scope of their application. Keywords: elastic wheel, kinematic radius, circumferential force, dynamic radius, wheel traction force, instantaneous center of speeds, torque, solid, rolling resistance

Molecular Dynamics Simulation Study on Allosteric Regulation of CD44-Hyaluronan Binding as a Force Sensing Mechanism.

CD44 protein exists on surfaces of a variety of human cells, acts as a receptor for the hyaluronan (HA) molecule, and mediates cell adhesion via the HA binding in leukocyte trafficking, cell rolling, and so on. The molecular structures of both CD44 and HA are well known, and the previous work shows that the external-mechanical force induces the partially disordered (PD) conformation from the ordered (O) conformation of CD44. The PD conformation has the higher HA affinity compared to the O conformation. However, the details of force-sensing mechanics have remained unclear. This study provides new insights into allosteric regulation of HA binding by conformational shift from the O to the PD conformation of the CD44 HA binding domain by using the classical molecular dynamics simulations. The O conformation was more favorable than the PD conformation under the equilibrium state, and the O conformation showed weak HA-binding affinity. Our simulation suggests that the PD conformation induced by the external force can refold to a compact structure similar to the O conformation keeping the bound HA. This new conformation showed a higher affinity than the O and PD conformations. Our results show that the unfolding of a remote disordered region from the ligand binding site by the external force allosterically regulates the HA affinity. This study promotes understanding not only the mechanism of CD44-mediated cell rolling but also the allosteric regulation induced by the external mechanical force.

Droplet rolling angle model of micro-nanostructure superhydrophobic coating surface.

The droplet rolling angle is one of the important indicators to measure the coating's hydrophobic performance, but the specific factors affecting the droplet rolling angle on the micro-nanostructured superhydrophobic coating surface are not yet known. Based on the rolling mechanism of droplets on rough surfaces, and from the perspective of coating microscopic energy conservation, this paper points out that the micron-scale morphology and the nanoscale morphology can comprehensively affect the droplet rolling angle. From the above perspective, a mathematical model of the droplet rolling angle on the micro-nanostructure superhydrophobic coating surface was established. The model shows that the droplet rolling angle is positively correlated with the ratio of nano-sized pillar width to spacing, the ratio of micron-sized papilla radius to spacing, and the liquid-gas interfacial tension, and is negatively correlated to the droplet intrinsic contact angle, droplet volume and droplet density. The droplet rolling angle calculated by the presented model is in good agreement with the experimentally tested results. This model can provide good accuracy in predicting the droplet rolling angle on the micro-nanostructured superhydrophobic coating surface.

A hybrid rolling grey framework for short time series modelling

Time series modelling is gaining spectacular popularity in the prediction process of decision making, with applications including real-world management and engineering. However, for short time series, prediction has to face unavoidable limitation for modelling extremely complex systems. It has to apply inadequate and incomplete data from short time to predict unknown observations. With such limited data source, existing techniques, such as statistical modelling or machine learning methods, fail to predict short time series effectively. To address this problem, this paper provides a global framework for short time series modelling predictions, integrating the rolling mechanism, grey model, and meta-heuristic optimization algorithms. In addition, dragonfly algorithm and whale optimization algorithm are investigated and deployed to optimize the framework by enhancing its predicting accuracy with less computational costs. To verify the performance of the proposed framework, three industrial cases are introduced as simulation experiments in this paper. Experimental results confirm that the framework solves corresponding short time series modelling predictions with greater accuracy and speed than the standard GM(1,1) models. The source codes of this framework are available at: https://github.com/zhesencui/HybridRollingGreyFramework.git .

Analytical determination of application point and normal reaction arm when rolling a wheel on a drum

Evaluation of the rolling resistance of car tires is now often performed on drum stands like car tests. This necessitates the study of the mechanics of interaction between the wheel and the drum in order to determine its force and kinematic characteristics, including the values and points of application of tangential and normal forces in contact with the drum. These problems can be solved taking into account that the mechanics of elastic wheel rolling on a drum is the same as when rolling on a flat rigid support surface. In this paper, from consideration of the mechanics of interaction between an elastic wheel and a drum, using the equations of power balance and force equilibrium of the wheel, the equations for determining the point of normal reaction in contact and its arm relative to the wheel axis during its rolling along one and two drums have been derived.. These dependencies have a simple form and can be applied when considering the rolling of both a single wheel and the car as a whole on a drum stand.

Towards 3D self-assembled rolled multiwall carbon nanotube structures by spontaneous peel off.

Controlling the 3D assembly of individual nanomaterials can be a challenging task. However, it opens up opportunities for the production of increasingly complex nanostructures. Unusual rolled multiwall carbon nanotube structures are synthesized here by simply inducing a change of precursor composition during the growth of multiwall carbon nanotube forests. The multiwall carbon nanotube structures are comprised of nitrogen-doped and undoped sections, and are obtained via a detailed peel off and roll mechanism. These results open new doors for the development of increasingly complex nanostructures.

Prediction-based analysis on power consumption gap under long-term emergency: A case in China under COVID-19

With the coronavirus pandemic wreathing havoc around the world, power industry has been hit hard due to the proposal of lockdown policies. However, the impact of lockdowns and shutdowns on the power system in different regions as well as periods of the pandemic can hardly be reflected on the foundation of current studies. In this paper, a prediction-based analysis method is developed to point out the electricity consumption gap resulted from the pandemic situation. The core of this method is a novel optimized grey prediction model, namely Rolling IMSGM(1,1) (Rolling Mechanism combined with grey model with initial condition as Maclaurin series), which achieves better prediction results in the face of long-term emergencies. A novel initial condition is adopted to track data with various characteristics in the form of higher-order polynomials, which are then determined by intelligent algorithms to realize accurate fitting. Historical power consumption data in China are utilized to carry out the monthly forecasts during COVID-19. Compared with other competitive models’ prediction results, the superiority of IMSGM(1,1) are demonstrated. Through analyzing the gap between predicted consumption values and the actual data, it can be found that the impact of the pandemic on electricity varies in different periods, which is related to its severity and the local lockdown policies. This study helps to understand the impact on power industry in the face of such an emergency intuitively so as to respond to possible future events.

Design of a Nonlinear Roll Mechanism for Airplanes Using Lie Brackets for High Alpha Operation

A nonlinear controllability analysis for fixed-wing aircraft has been performed in an earlier effort by the authors, which revealed a novel roll mechanism due to a nonlinear interaction between elevator and aileron control inputs. In this effort, we perform a detailed investigation of this novel roll mechanism, called Lie Bracket Roll Augmentation (LIBRA). First, we show the nonlinear flight physics associated with the LIBRA mechanism. Second, using the Fliess functional expansion, we perform a theoretical study of the effectiveness (degree of controllability) of the LIBRA mechanism in comparison to the conventional mechanism (using ailerons only). Third, to simulate the airplane response to a LIBRA input, we cast the problem of executing the LIBRA mechanism as a nonholonomic motion planning problem. In such a problem, a Lie bracket input is applied to generate motion along an unactuated direction. A Lie bracket input represents a nonlinear interaction between two (or more) control inputs to steer the system along a direction that is not directly actuated by any of these inputs (or their linear combinations). In this language, the LIBRA mechanism is simply a Lie bracket interaction between the elevator and aileron control inputs. We modify existing nonholonomic motion planning algorithms for systems with drift to be more feasible for flight control applications with bounded controls. We show that the LIBRA novel roll mechanism is superior compared to the conventional one during stall, where the aileron sensitivity degrades. In particular, the novel roll mechanism can provide an order of magnitude enhancement in the rolling capability over the conventional roll mechanism near stall.

Electrically Activated Soft Robots: Speed Up by Rolling.

Soft robots show excellent body compliance, adaptability, and mobility when coping with unstructured environments and human-robot interactions. However, the moving speed for soft locomotion robots is far from that of their rigid partners. Rolling locomotion can provide a promising solution for developing high-speed robots. Based on different rolling mechanisms, three rolling soft robot (RSR) prototypes with advantages of simplicity, lightweight, fast rolling speed, good compliance, and shock resistance are fabricated by using dielectric elastomer actuators. The experimental results demonstrate that the impulse-based and gravity-based RSRs can move both stably and continuously on the ground with a maximum speed higher than 1 blps (body length per second). The ballistic RSR exhibits a high rolling speed of ∼4.59 blps. And during its accelerating rolling process, the instantaneous rolling speed of the robot prototype reaches about 0.65 m/s (13.21 blps), which is much faster than most of the previously reported locomotion robots driven by soft responsive materials. The structure design and implementation methods based on different rolling mechanisms presented can provide guidance and inspiration for creating new, fast-moving, and hybrid mobility soft robots.

Development and studies of new rolling screw-type mechanisms

One of the tendencies in mechanical engineering is the transition from sliding friction to rolling friction in part joints moving under load, motor assemblies and machinery. For the present time, planetary roller screws (PRS), which are rolling mechanisms, possess the biggest potential as converters of rotational motion to linear motion. However production of high-precision parts for PRS requires special expensive equipment. The emerging world tendency for reduction of technological costs is to develop nutless roller screws (NRS), which is the most complex PRS part to manufacture. Its production requires an additional machine tool or a universal grinding machine for external and internal grinding. The new rolling NRS has been developed in line with this tendency. This paper focuses on the design and operation of the mechanism and on theoretical studies. A test model and a testing rig have been developed to confirm the results of the theoretical studies and to determine operation parameters of the new NRS. The experiments showed that the newly developed NRS loses to PRS in some parameters, while outperforming it in other. It is also simpler and cheaper to produce and after additional studies and tests rational applications for the newly developed NRS can be found.

Size segregation of granular materials during Paul-Wurth hopper charging and discharging process

In an ironmaking blast furnace top, raw granular materials such as iron ore and coke are delivered to the parallel Paul-Wurth (PW) hoppers first and then discharged to the furnace. In this work, the effects of variables such as filling positions and filling angles on the size segregation during PW hopper charging and discharging processes are examined. Results illustrate that small particle gathering area appears near the filling points due to the rolling mechanism, and the area size is related to the distance of filling position to the side wall. Trajectory is another main segregation mechanism related to different filling angles. Steep filling angle changes particle trajectories significantly and large particles tend to gather in the side wall region. Increasing flow rate decreases the segregation. During the discharging process, a depression appears and large particles are engulfed in the depression, leading to the segregation at the last stage of discharging.

Forecasting China's energy intensity by using an improved DVCGM (1, N) model considering the hysteresis effect

PurposeThe purpose of this paper is to examine the effectiveness of an improved dummy variables control grey model (DVCGM) considering the hysteresis effect of government policies in China's energy intensity (EI) forecasting.Design/methodology/approachEnergy consumption is considered as an important driver of economic development. China has introduced policies those aim at the optimization of energy structure and EI. In this study, EI is forecasted by an improved DVCGM, considering the hysteresis effect of energy-saving policies of the government. A nonlinear optimization method based on particle swarm optimization (PSO) algorithm is constructed to calculate the hysteresis parameter. A one-step rolling mechanism is applied to provide input data of the prediction model. Grey model (GM) (1, N), DVCGM (1, N) and ARIMA model are applied to test the accuracy of the improved DVCGM (1, N) model prediction.FindingsThe results show that the improved DVCGM provides reliable results and works well in simulation and predictions using multivariable data in small sample size and time-lag virtual variable. Accordingly, the improved DVCGM notes the hysteresis effect of government policies and significantly improves the prediction accuracy of China's EI than the other three models.Originality/valueThis study estimates the EI considering the hysteresis effect of energy-saving policies in China by using an improved DVCGM. The main contribution of this paper is to propose a model to estimate EI, considering the hysteresis effect of energy-saving policies and improve forecasting accuracy.

The effect of outer ring elastodynamics on vibration and power loss of radial ball bearings

Ball bearings are an integral part of many machines and mechanisms and often determine their performance limits. Vibration, friction and power loss are some of the key measures of bearing performance. Therefore, there have been many predictive analyses of bearing performance with emphasis on various aspects. The current study presents a mathematical model, incorporating bearing dynamics, mechanics of rolling element-to-races contacts as well as the elastodynamics of the bearing outer ring as a focus of the study. It is shown that the bearing power loss in cage cycles increases by as much as 4% when the flexibility of the outer ring is taken into account as a thick elastic ring, based on Timoshenko beam theory as opposed to the usual assumption of a rigid ring in other studies. Geometric optimisation has shown that the lifetime power consumption can be reduced by 1.25%, which is a significant source of energy saving when considering the abundance of machines using rolling element bearings. The elastodynamics of bearing rings significantly affects the radial bearing clearance through increased roller loads and generated contact pressures. The flexible ring dynamics is shown to generate surface waviness through global elastic wave propagation, not hitherto taken into account in contact dynamics of rollers-to-raceways which are generally considered to be subjected to only localised Hertzian deflection. The elastodynamic behaviour reduces the elastohydrodynamic film thickness, affecting contact friction, wear, fatigue, vibration, noise and inefficiency.

Flexible Recruitment of Balance Mechanisms to Environmental Constraints During Walking

Background: Humans need to actively control their upright posture during walking to avoid loss of balance. We do not have a comprehensive theory for how humans regulate balance during walking, especially in complex environments. The nervous system must process many aspects of the environment to produce an appropriate motor output in order to maintain balance on two legs. We have previously identified three balance mechanisms that young healthy adults use to maintain balance while walking: 1) The ankle roll mechanism, a modulation of ankle inversion/eversion; 2) The foot placement mechanism, a shift of the swing foot placement; and 3) The push-off mechanism, a modulation of the ankle plantar flexion angle during double stance. We know that these mechanisms are inter dependent and can be influenced by internal factors such as the phase of the gait cycle and walking cadence. Here we seek to determine whether there are changes in neural control of balance when walking in the presence of environmental constraints. Methods: Subjects walked on a self-paced treadmill while immersed in a virtual environment that provides three different colored pathways. Subjects were instructed not to step in the No-Step Zone, which appeared either on the right or left side of the subject. While walking, subjects received balance perturbations in the form of galvanic vestibular stimulation,providing the sensation of falling sideways, either toward the No-Step zone or toward the Neutral zone on the other side. Results: The results indicate that the use of the balance mechanisms are altered depending on whether the perceived fall is toward the No-Step or the Neutral zone. Participants increased the use of the lateral ankle and foot placement mechanisms for No-Step stimuli resulting in a larger shift of the center of mass (CoM) compared to the Neutral stimuli. Conclusion:This experiment provides further evidence that the balance control system during walking is extremely flexible, recruiting multiple mechanisms at different times in the gait cycle to adapt to environmental constraints.

A deformable tetrahedron rolling mechanism (DTRM) based on URU branch

The purpose of this paper is to put forward a novel deformable tetrahedron rolling mechanism (DTRM). This new reconfigurable mobile mechanism with the external tetrahedral shape can be regarded as a parallel mechanism with a variable platform, that is constructed by four vertices and six edges corresponding to four platforms and six URU chains. Mechanical design is introduced, and the degree of freedom (DOF) is analyzed. Equivalent planar mechanism analysis method is proposed for the symmetrical mechanical structure to simplify the theoretical analysis process. Based on the symmetric-drive rolling locomotion, impact and non-impact rolling gait are planned, respectively corresponding to different joints workspace, to reduce the displacement error. Aiming at non-impact rolling gait, the motion strategy is established instead of moving with pre-set driving parameters, as the basis of the control system. Then a trajectory optimization of the center of mass (CM) based on actuator torque analysis is carried out to reduce the actuator torque. To verify the rolling locomotion, we present the results of a series of experiments, performed on a manufactured prototype.

Winding Microtubes: Highly Symmetric and Extremely Compact Multiple Winding Microtubes by a Dry Rolling Mechanism (Adv. Mater. Interfaces 13/2020)

A novel dry rolling technique enables rolled-up nanotechnology to create highly symmetric and extremely compact multiple winding microtubes. The technique exploits hydrophobicity of fluorocarbon polymers and thermal expansion mismatch of polymers and inorganic films upon thermal treatment. It opens up possibilities to fabricate highly complex device architectures, which conventional wet chemical etching technologies have not been able to engineer. More details can be found in article number 1902048 by Somayeh Moradi, Oliver G. Schmidt, and co-workers.

Analytical modeling of subsurface damage depth in machining of SiCp/Al composites

SiC particle reinforced aluminum matrix (SiCp/Al) composite has been one of the key light metal matrix composites, which is widely used in aerospace and electronics industries due to its excellent material properties. However, the abrasive particles within the materials easily lead to severe tool wear during machining, and the subsequent machining-induced subsurface damage (SSD) will significantly affect the fatigue properties of composite structures. In this paper, an analytical model considering the effects of reinforced particle, thermal-mechanical coupling, and tool wear is first proposed to predict the SSD depth during cutting of SiCp/Al composites. The two-body abrasion and three-body rolling mechanisms are introduced to describe the effects of the particles on the tool-chip interface friction. The mechanical stress and thermal stress induced by mechanical load and thermal load, respectively are simultaneously taken into account. Meanwhile, the tool wear is considered in modeling of friction characteristic of tool flank-workpiece. The SSD depth is evaluated as a measure of variation in microhardness along the depth normal to the cross-section of the machined surface. The correctness of the proposed model was validated by the orthogonal cutting experiments of SiCp/Al composites under different tool wear values and feed rates. A good agreement is found by comparing the predicted and experimental results, which proves that the proposed model can accurately predict the SSD depth with an error of 7.8% in average. Furthermore, the results indicate that even a new tool is used, the SSD depth can reach to hundred micros level during machining of SiCp/Al composites, which is significantly greater than homogeneous metal machining.

Material removal and wear mechanism in abrasive polishing of SiO2/SiC using molecular dynamics

The effect of the sliding and rolling motions of the abrasive particle on the silicon carbide substrate covered by a thin film of silica atoms is investigated in this paper using molecular dynamics simulation. The influence of the sliding depth, sliding speed, rolling depth and rolling speed on the material removal and wear mechanism are surveyed. The results represent that increasing the sliding depth gives rise to higher forces, a higher temperature, a deeper groove, deeper subsurface damage (SSD) layer, and a higher amount of atoms erased. Improving the sliding velocity results in a higher fraction of atoms removed out of the pathway and a larger number of atoms erased. In the rolling mechanism, improving the depth and the rolling speed leads to the same effect as in the sliding mechanism but with a lower rate. Notably, the number of atoms erased in the rolling motion is greatly lower than the sliding one. In the ploughing regime, the silica film is effectively removed out of the SiC substrate, especially at a high sliding speed. The ploughing regime in the rolling motion requires a deeper depth to achieve, and the ploughing indications are weaker than the sliding motion. This report also considers both mechanical and chemical effects as some models with pure SiC workpiece or with different silica thickness are constructed and investigated. With the same removing conditions, the pure SiC sample suffers higher forces, a higher level of deformation and a larger number of atoms erased as compared to the sample covered by a silica thin film. The ploughing regime does not only require a sufficient penetration depth but also needs a suitable silica thickness to happen.

Mixing character in the head part of a gravity current

The mixing within a full depth lock-exchange gravity current was investigated experimentally with planar laser-induced fluorescence PLIF. The scalar edge of the gravity current was identified via an edge detection algorithm. A strong mixing region located along this edge was extracted from the flow field and analyzed. A dimensionless background potential energy was defined to characterize the local mixing rate in this region, which showed a two-stage behavior. In the section near the nose, mixing rate oscillates strongly under the influence of the lobe and cleft shifting, while in the upper part, the mixing rate grows gradually under the mechanism of billows rolling up.

Highly Symmetric and Extremely Compact Multiple Winding Microtubes by a Dry Rolling Mechanism

AbstractRolled‐up nanotechnology has received significant attention to self‐assemble planar nanomembranes into 3D micro and nanotubular architectures. These tubular structures have been well recognized as novel building blocks in a variety of applications ranging from microelectronics and nanophotonics to microbatteries and microrobotics. However, fabrication of multiwinding microtubes with precise control over the winding interfaces, which is crucial for many complex applications, is not easy to achieve by existing materials and technologies. Here, a dry rolling approach is introduced to tackle this challenge and create tight windings in compact and highly symmetric cylindrical microstructures. This technique exploits hydrophobicity of fluorocarbon polymers and the thermal expansion mismatch of polymers and inorganic films upon thermal treatment. Quality parameters for rolled‐up microtubes, against which different fabrication technologies can be benchmarked are defined. The technique offers to fabricate long freestanding multiwinding microtubes as well as hierarchical architectures incorporating rolled‐up wrinkled nanomembranes. This work presents an important step forward toward the fabrication of more complex but well‐controlled microtubes for advanced high‐quality device architectures.