•The studies on gear transmission efficiency and dynamics are reviewed.•The studies on gear contact fatigue and wear-contact fatigue competitive phenomenon are reviewed.•The conflicting gear ...performance requirements and implications on lubrication are discussed.
Increasingly demanding performance standards and operating requirements are driving the growing interest on lubrication technologies in gear transmission systems. Optimized gear lubrication methods and lubricant compositions are necessary to meet the industrial challenges of higher load, speed, temperature and performance expectations in multiple powertrain applications, including automotive, aeronautical and marine. Numerous theoretical and experimental studies have been dedicated to gear lubrication, especially on lubrication modelling and composition of lubricants. Improvements on lubrication methods and conditions can reduce friction, suppress wear and scuffing, and increase gear flank capacity and fatigue life. In order to compile and categorize key investigations in an expansive field with substantial recent research, this work reviews gear lubrication papers with focus on gear efficiency, contact fatigue and dynamics. Furthermore, some accompanying results obtained by the authors are included.
Background
Many studies have shown that robotic gastrectomy requires a longer operation time than laparoscopic gastrectomy. However, no study has analyzed the exact reason for this difference in ...detail. We therefore investigated the reasons why more time is needed in robotic gastrectomy.
Methods
Ten consecutive cases of robotic distal gastrectomy (RDG) performed in our institution were selected to measure the operation time in detail. Ten cases of laparoscopic distal gastrectomy (LDG) performed during the same period were chosen for comparison. The operation videos and electronic medical records of these 20 patients were retrospectively reviewed. The overall operation time, operation time in each step, and time required for instrument changes were measured. The number of intraoperative instrument changes and camera cleanings were also counted.
Results
The overall operation time (including effective time and junk time) was 56.8 min longer for RDG than LDG (273.7 vs. 216.9 min, respectively;
p
= 0.000). The effective time was only 15.3 min longer for RDG than LDG (145.9 vs. 130.6 min, respectively;
p
= 0.094). The time needed for the six technical steps was also not significantly different between the two groups. However, the junk time (instrument setup and docking or positioning of surgical arms) was 41.5 min longer for RDG than LDG (127.8 vs. 86.2 min, respectively;
p
= 0.001). The number of instrument changes was not different between RDG and LDG (
p
= 0.277), but the time required for each was longer for RDG than LDG (
p
= 0.000). The number of camera cleanings was lower for RDG than LDG (10.7 vs. 15.5 times, respectively;
p
= 0.005).
Conclusions
To reduce the operation time in RDG, a smarter and simpler system for setup should be developed to reduce the junk time. Additionally, a system for swifter instrument changes and more sophisticated energy devices are warranted to reduce the effective time.
SALM5, a synaptic adhesion molecule implicated in autism, induces presynaptic differentiation through binding to the LAR family receptor protein tyrosine phosphatases (LAR-RPTPs) that have been ...highlighted as presynaptic hubs for synapse formation. The mechanisms underlying SALM5/LAR-RPTP interaction remain unsolved. Here we report crystal structures of human SALM5 LRR-Ig alone and in complex with human PTPδ Ig1-3 (MeA
). Distinct from other LAR-RPTP ligands, SALM5 mainly exists as a dimer with LRR domains from two protomers packed in an antiparallel fashion. In the 2:2 heterotetrameric SALM5/PTPδ complex, a SALM5 dimer bridges two separate PTPδ molecules. Structure-guided mutations and heterologous synapse formation assays demonstrate that dimerization of SALM5 is prerequisite for its functionality in inducing synaptic differentiation. This study presents a structural template for the SALM family and reveals a mechanism for how a synaptic adhesion molecule directly induces cis-dimerization of LAR-RPTPs into higher-order signaling assembly.
FSH, a glycoprotein hormone, and the FSH receptor (FSHR), a G protein-coupled receptor, play central roles in human reproduction. We report the crystal structure of FSH in complex with the entire ...extracellular domain of FSHR (FSHR ED), including the enigmatic hinge region that is responsible for signal specificity. Surprisingly, the hinge region does not form a separate structural unit as widely anticipated but is part of the integral structure of FSHR ED. In addition to the known hormone-binding site, FSHR ED provides interaction sites with the hormone: a sulfotyrosine (sTyr) site in the hinge region consistent with previous studies and a potential exosite resulting from putative receptor trimerization. Our structure, in comparison to others, suggests FSHR interacts with its ligand in two steps: ligand recruitment followed by sTyr recognition. FSH first binds to the high-affinity hormone-binding subdomain of FSHR and reshapes the ligand conformation to form a sTyr-binding pocket. FSHR then inserts its sTyr (i.e., sulfated Tyr335) into the FSH nascent pocket, eventually leading to receptor activation.
Thin-rim gears are widely used in industrial fields such as aerospace and electric vehicles due to the advantage of light weight. Yet, the root crack fracture failure of thin-rim gears significantly ...limits their application and further affects the reliability and safety of high-end equipment. In this work, the root crack propagation behavior of thin-rim gears is experimentally and numerically investigated. The crack initiation position and crack propagation path for different backup ratio gears are simulated using gear finite element (FE) models. The crack initiation position is determined using the maximum gear root stress position. An extended FE method coupled with commercial software ABAQUS is used to simulate the gear root crack propagation. The simulation results are then verified by conducting experimental tests for different backup ratio gears based on a dedicated designed single-tooth bending test device.
Human periostin plays a multifaceted role in remodeling the extracellular matrix milieu by interacting with other proteins and itself in both a heterophilic and homophilic manner. However, the ...structural mechanism for its extensive interactions has remained elusive. Here, we report the crystal structures of human periostin (EMI‐Fas1I–IV) and its Cys60Ala mutant. In combination with multi‐angle light‐scattering analysis and biochemical assays, the crystal structures reveal that periostin mainly exists as a dimer in solution and its homophilic interaction is mainly mediated by the EMI domain. Furthermore, Cys60 undergoes cysteinylation as confirmed by mass spectroscopy, and this site hardly affects the homophilic interaction. Also, the structures yield insights into how periostin forms heterophilic interactions with other proteins under physiological or pathological conditions.
Coating is an effective way to reduce friction and wear and to improve the contact-fatigue lives of gear components, which further guarantees a longer service life and better reliability of ...industrial machinery. The fact that the influence coefficient linking the tractions and stress components could not be expressed explicitly increases the difficulty of coated solids contact analysis. The complicated tribological behavior between tooth surfaces influenced by lubrication and surface roughness further adds difficulty to the coated gear pair contact problems. A numerical elastohydrodynamic lubricated (EHL) contact model of a coated gear pair is proposed by considering the coupled effects of gear kinematics, coating properties, lubrication, and surface roughness. The frequency response function and the discrete convolute, fast Fourier transformation (DC-FFT) method are combined to calculate the surface deformation and the subsurface stress fields at each meshing position along the line of action (LOA). The Ree-Eyring fluid is assumed to incorporate the non-Newtonian effect, which is represented in the generalized Reynolds equation. Influences of the ratio between the Young’s modulus of the coating and the substrate on the contact performance, such as pressure, film thickness, tooth friction coefficient, and subsurface stress field, are studied. The effect of the root mean square (RMS) value of the tooth surface roughness is studied by introducing the roughness data, deterministically measured by an optical profiler.
Abstract
Digitally-enhanced technologies are set to transform every aspect of manufacturing. Networks of sensors that compute at the edge (streamlining information flow from devices and providing ...real-time local data analysis), and emerging Cloud Finite Element Analysis technologies yield data at unprecedented scales, both in terms of volume and precision, providing information on complex processes and systems that had previously been impractical. Cloud Finite Element Analysis technologies enable proactive data collection in a supply chain of, for example the metal forming industry, throughout the life cycle of a product or process, which presents revolutionary opportunities for the development and evaluation of digitally-enhanced lubricants, which requires a coherent research agenda involving the merging of tribological knowledge, manufacturing and data science. In the present study, data obtained from a vast number of experimentally verified finite element simulation results is used for a metal forming process to develop a digitally-enhanced lubricant evaluation approach, by precisely representing the tribological boundary conditions at the workpiece/tooling interface, i.e., complex loading conditions of contact pressures, sliding speeds and temperatures. The presented approach combines the implementation of digital characteristics of the target forming process, data-guided lubricant testing and mechanism-based accurate theoretical modelling, enabling the development of data-centric lubricant limit diagrams and intuitive and quantitative evaluation of the lubricant performance.
Contact fatigue issues become more and more crucial in gear industry as they significantly affect the reliability and service life of associated mechanical systems such as wind turbine gearboxes. The ...contact fatigue behavior is mostly determined by the mechanical properties of materials and stress fields near the contact area, which is further influenced by the lubrication and surface roughness due to pressure fluctuations. In this study, a numerical model incorporating the lubrication state, tooth surface roughness, residual stress, and mechanical properties of the material is developed to determine the contact fatigue behavior of a megawatt level wind turbine carburized gear. The variations of the hardness and residual stress along the depth were characterized by the Vickers hardness measurement and X-ray diffraction test, respectively. The elastohydrodynamic lubrication theory was applied to predict the contact pressure distribution, highlighting the influence of the surface roughness that stemed from the original measurement through an optical profiler. The stress histories of the studied material points during a complete contact loading cycle were fast calculated using the discreteconcrete fast Fourier transformation (DC-FFT) method. Modified Dang Van diagrams under different working conditions were determined to estimate the contact fatigue failure risk. The effect of the root mean square (RMS) value of the surface roughness on the failure risk at critical material points were discussed in detail. Results revealed that the surface roughness significantly increases the contact fatigue failure risk within a shallow area, and the maximum risk appears near the surface.
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