Contact Analysis Research Articles

Meta-contact analysis based on contact theory in three-dimensional discontinuous deformation analysis

Accurate contact analysis between nonspherical blocks, such as polyhedral blocks, is crucial for modeling jointed rock masses. The Contact Theory provides a rigorous foundation for contact detection. However, designing a robust and efficient algorithm that conforms to the original Contact Theory remains challenging. This study introduces the meta-contact concept for polyhedral blocks, which corresponds to the contact cover on the entrance block of the Contact Theory. Using the meta-contact concept, contact type identification, determination of contact points and plans, and contact force calculation can be formulated while retaining the advantages of Contact Theory in dealing with irregular blocks with small edges and large penetration.

Ictal fast activity chirps as markers of the epileptogenic zone.

The identification of the epileptogenic zone (EZ) boundaries is crucial for effective focal epilepsy surgery. We verify the value of a neurophysiological biomarker of focal ictogenesis, characterized by a low-voltage fast-activity ictal pattern (chirp) recorded with intracerebral electrodes during invasive presurgical monitoring (stereoelectroencephalography [SEEG]). The frequency content of SEEG signals was retrospectively analyzed with semiautomatic software in 176 consecutive patients with focal epilepsies that either were cryptogenic or presented with discordant anatomoelectroclinical findings. Fast activity seizure patterns with the spectrographic features of chirps were confirmed by computer-assisted analysis in 95.4% of patients who presented with heterogeneous etiologies and diverse lobar location of the EZ. Statistical analysis demonstrated (1) correlation between seizure outcome and concordance of sublobar regions included in the EZ defined by visual analysis and chirp-generating regions, (2) high concordance in contact-by contact analysis of 68 patients with Engel class Ia outcome, and (3) that discordance between chirp location and the visually outlined EZ correlated with worse seizure outcome. Seizure outcome analysis confirms the fast activity chirp pattern is a reproducible biomarker of the EZ in a heterogeneous group of patients undergoing SEEG.

Average Force Applied for Individual Tooth in All Ceramic Restoration

Abstract Objectives Occlusion plays an important role in the retention and stability of dental restorations. Aim of this study was to analyze occlusal loading detected on dental elements in patients with unilateral partial edentulism—class III Kennedy, before and immediately after prosthetic treatment with a zirconia-based bridge in maximal intercuspation position with the help of electronic system T-scan III. Materials and Methods The research sample consisted of a total of 60 patients who, based on the preset selection criteria, were divided into two groups: control group with 30 (100%) patients with intact dentition (Gr1) and study group with 30 (100%) patients with unilateral partial edentulism—class III Kennedy, analyzed before prosthetic treatment (Gr2) and immediately after prosthetic treatment with a zirconia-based bridge (Gr3). Results In Gr1, the highest average force applied for individual tooth had the tooth numbers: 17–14.6 ± 9.9%, 26–11.9 ± 6.8%, and 27–11.7 ± 6.8%. The lowest average value was registered for the teeth number 22–1.4 ± 1.3%, 12–1.9 ± 3.8%, and 13–2.9 ± 2.7%. In the group Gr2, the highest average force applied for individual tooth had the tooth numbers: 17–12.9 ± 35.6 and 21–9.6 ± 13.9%, whereas the lowest in teeth 24–2.7 ± 5.2 and 27–3.4 ± 6.8. In Gr3, the highest average force applied for individual tooth had the tooth numbers: 17–11.8 ± 15.4 and 14–9.8 ± 10.9%, whereas the lowest in the tooth 22–2.1 ± 2.6. Conclusion This study demonstrated that all patients with the loss of teeth showed occlusal discrepancies and functional disharmony. During the delivery of zirconia restorations in the future a careful analysis of occlusal contacts should be performed. T-scan III technology reduces the subjective interpretation of occlusal analysis data allowing records and measures the contacts between the teeth.

Effect of Elevated Acetabular Cup on Contact and Failure Analysis in Hip Implants for Different Microseparations and Cup Inclinations Under Routine Gait Activities Using In Silico Approach.

The acetabular cup design plays a critical role in reducing contact stress between femur head acetabular cup. Many studies used ellipsoidal and spheroidal geometry in acetabular cup design to effectively reduce contact stress. The present study focuses on elevated acetabular cup rim with round corner design to reduce contact stress with round corner geometry. The cobalt chromium femur head and cup are considered for finite element (FE) model of hip resurfacing. The gait loads of routine activities of humans like normal walking, stair ascending and descending and sitting down and getting up gait activities are applied to the developed 3D FE model. Five microseparations of 0.5, 1, 1.5, 2 and 2.5mm are considered in the present study. The acetabular cup inclination angle considered for this study are 35°, 45°, 55°, 65° and 75°. The contact stress and von Mises stress plot for each gait activities under these microseparations are analyzed for betterment of longevity of implants. Overall elevated cup rim design helped in reducing contact stress to a greater extent than conventional cup with different geometries. Also, the predicted von Mises stress for all the parameters considered in the current study are well within the yield strength of CoCr material. Therefore, elevated cup rim could be used as a better alternative to spline and, ellipsoidal and circular geometries of cup.

A Systematic Review of Isogeometric Contact Analysis and Its Applications

A Systematic Review of Isogeometric Contact Analysis and Its Applications

An improved tolerance analysis method for gear mechanisms considering form deviations and elastic-plastic contact behaviors

The contact quality between geometric features significantly affects the assembly accuracy and dynamic performance of mechanical products. However, accurate and efficient contact problem solving is currently a common challenge in the fields of tolerance analysis and tooth contact analysis (TCA). In this paper, a tolerance analysis method for gear mechanisms considering form deviations and elastic-plastic contact behaviors is proposed. Specifically, tolerance modeling of systematic and random deviations on tooth surfaces is represented by skin model shapes (SMS). Elastic-plastic contact behaviors including contact deformation, status, and stress distribution are modeled and calculated by a modified boundary element method (BEM). The accuracy and efficiency of this BEM algorithm are verified by comparing with the finite element method (FEM), indicating that the BEM can greatly improve the computational efficiency while maintaining high solution accuracy. A case study for a pair of spur gears demonstrates the significant effects of contact behaviors on transmission performance. This research provides an effective method to introduce mechanical contact behaviors in tolerance analysis of gear mechanisms. In addition, the contact simulation results can also be adopted in the analysis of vibration, reliability, and other aspects.

Modeling and contact analysis for spur gear pair with modification and localized crack failure

The modified teeth are deliberately manufactured to mitigate the stress concentration generated by offset components, which makes equipment more susceptible to localized failures. Therefore, this paper presents a model aimed at investigating the meshing characteristic of gear pair with modification and crack failure. In this model, the tooth deformation and force transmission are determined based on slice coupling theory. The torsional deformation of teeth produced by eccentric load distribution is considered and complemented to the calculation method. Finally, the approach is proven through the experimental tests and FE model. The result shows that when the equipment is operated in misalignment condition, eccentric load distribution, and stress concentration at tooth edge are generated, the meshing stiffness will be reduced drastically, which can be suppressed by appropriate modification, and the rapid decline of meshing stiffness is weakened by increasing the effective contact length. Although the contact stiffness would be further reduced by the crack failure and the tooth surface deformation is increased, it seems to alleviate the stress concentration and eccentric load effectively.

Comparative Study on Energy Yield of Tunnel Oxide Passivated Contact (TOPCon) and Passivated Emitter and Rear Contact (PERC) Solar Cells and Analysis of Optimal Installation Method for Vertical Photovoltaics

Photovoltaic (PV) installations have traditionally relied on a conventional south-facing orientation, which maximizes energy production at noon but has lower energy generation in the morning and afternoon. Vertical photovoltaic (VPV) systems have emerged as promising alternatives to address this inconsistency. Vertical photovoltaic systems can enhance energy generation by facing east in the morning and west in the afternoon. We compared the performance of n-tunnel oxide passivated contact (n-TOPCon) and p-passivated emitter and rear contact (p-PERC) cells in vertical photovoltaic systems to determine whether the optimal installation direction of bifacial vertical photovoltaics is east or west. Our findings indicated that n-TOPCon cells exhibited higher energy yields than p-PERC cells, with a difference of approximately 8%, attributed to the superior bifaciality and lower temperature coefficient of power of n-TOPCon. Additionally, the energy yield was higher for n-TOPCon modules when the front faced east, whereas the PERC modules performed better with a west-facing front. This contributes to the knowledge of the factors for energy production in vertical photovoltaic systems and the optimization of installation configurations.

Analysis of long-range chromatin contacts, compartments and looping between mouse embryonic stem cells, lens epithelium and lens fibers

BackgroundNuclear organization of interphase chromosomes involves individual chromosome territories, “open” and “closed” chromatin compartments, topologically associated domains (TADs) and chromatin loops. The DNA- and RNA-binding transcription factor CTCF together with the cohesin complex serve as major organizers of chromatin architecture. Cellular differentiation is driven by temporally and spatially coordinated gene expression that requires chromatin changes of individual loci of various complexities. Lens differentiation represents an advantageous system to probe transcriptional mechanisms underlying tissue-specific gene expression including high transcriptional outputs of individual crystallin genes until the mature lens fiber cells degrade their nuclei.ResultsChromatin organization between mouse embryonic stem (ES) cells, newborn (P0.5) lens epithelium and fiber cells were analyzed using Hi-C. Localization of CTCF in both lens chromatins was determined by ChIP-seq and compared with ES cells. Quantitative analyses show major differences between number and size of TADs and chromatin loop size between these three cell types. In depth analyses show similarities between lens samples exemplified by overlaps between compartments A and B. Lens epithelium-specific CTCF peaks are found in mostly methylated genomic regions while lens fiber-specific and shared peaks occur mostly within unmethylated DNA regions. Major differences in TADs and loops are illustrated at the ~ 500 kb Pax6 locus, encoding the critical lens regulatory transcription factor and within a larger ~ 15 Mb WAGR locus, containing Pax6 and other loci linked to human congenital diseases. Lens and ES cell Hi-C data (TADs and loops) together with ATAC-seq, CTCF, H3K27ac, H3K27me3 and ENCODE cis-regulatory sites are shown in detail for the Pax6, Sox1 and Hif1a loci, multiple crystallin genes and other important loci required for lens morphogenesis. The majority of crystallin loci are marked by unexpectedly high CTCF-binding across their transcribed regions.ConclusionsOur study has generated the first data on 3-dimensional (3D) nuclear organization in lens epithelium and lens fibers and directly compared these data with ES cells. These findings generate novel insights into lens-specific transcriptional gene control, open new research avenues to study transcriptional condensates in lens fiber cells, and enable studies of non-coding genetic variants linked to cataract and other lens and ocular abnormalities.

Mathematical model for mesh analysis of gear pair in gear-shaft-bearing systems with localized failure on raceway

To investigate the influence of bearing failures on the mesh characteristics of gear pairs, this paper presents a mathematical model for gear-shaft-bearing systems. Within this simulation method, the model of defective bearings and the contact analysis methodology of gear pairs are integrated into the system equations. Additionally, the coupling mechanism between system components is determined by addressing the misaligned shafts induced by asynchronous bearing vibrations. Furthermore, the torsional deformation of gear teeth generated by uneven load distribution is considered, and a calculation method for mesh stiffness in complex environments is developed. By employing the comprehensive model, the effect of raceway failures on the mesh behavior is lucidly explained, the real-time distribution of contact stress and load on the tooth surface can be obtained, and the optimal modification strategies for gears are formulated. Finally, the proposed model is confirmed through the finite element (FE) model and experimental observation, which provides a potent tool for the performance optimization of gearboxes.

Rear Axle Whine Reduction by Gear Contact Patch Optimization

In-cab whine is a highly annoying phenomena in all the category of vehicles. The in-cab noise of passenger vehicle with Rear Wheel Drive ( RWD) considered for this study consist of axle whine noise. The whine noise is heard at multiple speeds during Wide Open Throttle (WOT) as well as coasting. To resolve the issue of whine noise, series of measurement are carried out to identify the source and transfer path of the whine. The noise measurement revealed that rear axle pinion mesh order is responsible for in-cab whine. It is confirmed through measurement that the whine is structure borne. The order based operational deflections shapes of rear axle show excessive vibration on differential nose in affected speed zones. It is thus learnt that whine is due to poor contact pattern of pinion and crown wheel of the rear axle. The three resonances in operation range amplify this mesh order resulting in whine. It is decided to work on noise source i.e. gear rather than transfer path. The hypoid gear design is optimized through Tooth Contact Analysis (TCA). The lapping and heat treatment processes of gear manufacturing are modified. The contact pattern of optimized gear is identified on gear tester machine. Significant improvement is observed in contact pattern. The in-cab noise measurement is carried out with optimized hypoid gear and it is found that the whine is completely eliminated.
 Keywords: Rear axle, Whine reduction, Gear contact, Patch optimization, Rear Wheel Drive, Whine Source, Vibration on Transfer Paths, Noise Generation, Hypoid Gear, Heat Treatment

Classical molecular dynamics simulation identifies catechingallate as a promising antiviral polyphenol against MPOX palmitoylated surface protein

Cumulative global prevalence of the emergent monkeypox (MPX) infection in the non-endemic countries has been professed as a global public health predicament. Lack of effective MPX-specific treatments sets the baseline for designing the current study. This research work uncovers the effective use of known antiviral polyphenols against MPX viral infection, and recognises their mode of interaction with the target F13 protein, that plays crucial role in formation of enveloped virions. Herein, we have employed state-of-the-art machine learning based AlphaFold2 to predict the three-dimensional structure of F13 followed by molecular docking and all-atoms molecular dynamics (MD) simulations to investigate the differential mode of F13-polyphenol interactions. Our extensive computational approach identifies six potent polyphenols Rutin, Epicatechingallate, Catechingallate, Quercitrin, Isoquecitrin and Hyperoside exhibiting higher binding affinity towards F13, buried inside a positively charged binding groove. Intermolecular contact analysis of the docked and MD simulated complexes divulges three important residues Asp134, Ser137 and Ser321 that are observed to be involved in ligand binding through hydrogen bonds. Our findings suggest that ligand binding induces minor conformational changes in F13 to affect the conformation of the binding site. Concomitantly, essential dynamics of the six-MD simulated complexes reveals Catechin gallate, a known antiviral agent as a promising polyphenol targeting F13 protein, dominated with a dense network of hydrophobic contacts. However, assessment of biological activities of these polyphenols need to be confirmed through in vitro and in vivo assays, which may pave the way for development of new novel antiviral drugs.

Mesh Characteristic Analysis of Spiral Bevel Gear Pairs Considering Assembly Errors and Tooth Tip Chipping Faults

Due to machining errors, location inaccuracies, human error, and various other factors, it is challenging to avoid assembly errors during the production of spiral bevel gears (SBGs). When SBG assembly errors occur, it can cause the appearance of edge contact and may even lead to severe tooth tip chipping. In this study, we propose an improved method based on loaded tooth contact analysis (LTCA) to examine mesh characteristics, including time-varying mesh stiffness (TVMS), unloaded transmission error, and contact stress. Furthermore, we explore the effects of assembly errors and tooth tip chipping. Moreover, it is observed that assembly errors can alter the contact area of SBGs and potentially reduce the peak-to-peak value of TVMS. Additionally, the occurrence of tooth tip chipping decreases TVMS within the chipping region, lowers transmission error, and increases maximum contact stress. Notably, when assembly errors are present, the reduction in TVMS due to tooth tip chipping exceeds that of a properly assembled SBG pair.

Assembly accuracy prediction method of planetary gear train considering bolt-bearing-shaft-gear coupling effects

Planetary gear train (PGT) is a complex transmission system composed of gears, shafts, bearings and bolted joints, of which the assembly accuracy affects the transmission accuracy and dynamic behavior. In this paper, a new assembly accuracy prediction method is proposed for PGT considering gear-shaft-bearing-bolt coupling effects. The new method is formulated by establishing three models for bolt assembly, shaft error motion and assembly accuracy (transmission error) of PGT. The model for bolt assembly is an original FE-analytical model to analyze the bolt assembly effect on elastic deformation of bearing cap, which is developed by finite element (FE) method and analytical method for addressing the elastic effect of bearing cap and elastic interaction between bolts. The models for shaft error motion and assembly accuracy are performed by the three-dimensional contact analysis with errors and preload of bearing cap based on analytical method and kinematic geometry relationship. Combining the three models, the assembly accuracy can be predicted by simulations. The simulations indicate that the proper bolt assembly parameters can alleviate the influence of manufacturing errors on assembly accuracy. The assembly accuracy tests of PGT are conducted. The results well agree with the simulations’, and the assembly accuracy is improved by the proper bolt assembly parameters.

Structural Origins of the Anisotropic Thermal Expansion of BINOL Crystals

Measurement of the unit cell of (R)-BINOL over a 200° temperature range (300–100 K) reveals an anisotropic contraction where the c-axis contracts ca. 2.3% compared to a ca. 0.45% contraction of the a and b axes, a ca. six-fold difference in linear thermal expansion coefficient. This contraction corresponds to a decrease in the helical pitch of the 31 screw axis in the [001] direction. The anisotropic nature of the contraction is rationalised by a thorough analysis of intermolecular contacts within the crystal and their impact on the conformation of the molecule and crystal packing.Graphical The crystal structure of (R)-BINOL exhibits a pronounced anisotropic thermal expansion.

Lightweight design of steel sprocket for roller chain drive using explicit dynamic simulation

Roller chain drives are frequently applied in a variety of machinery for mechanical motion and power transmission. The roller engagement location on the sprocket tooth contour and the resulted contact behavior is governed by the wear of components and pretension of the chain. Therefore, the influence of extension of chain resulted from wear and pretension of chain on contact behavior was investigated numerically using explicit dynamics module of ABAQUS software. The contact angles evaluated from the numerical simulation were assessed relative to those obtained from the basic rigid body analytical formulation. The chain elongation of 3% increased the maximum contact force up to 52% during engagement with the driver sprocket. The contact force raised to 400% when the pretension in the chain drive was increased from 200 to 1000 N, leaving the force distribution pattern unaltered. The optimal design of a steel sprocket is realized through equivalent static finite element contact analysis of a sprocket engaged with 3% extended roller chain. The dynamic finite element analysis in conjunction with topology optimization reduced the weight of the sprocket by 24%.

Comparison between quasi-static and multibody dynamic simulations for wheel-rail contact analysis

Comparison between quasi-static and multibody dynamic simulations for wheel-rail contact analysis

Antifungal plant flavonoids identified in silico with potential to control rice blast disease caused by Magnaporthe oryzae.

Rice blast disease, caused by the fungus Magnaporthe oryzae, poses a severe threat to rice production, particularly in Asia where rice is a staple food. Concerns over fungicide resistance and environmental impact have sparked interest in exploring natural fungicides as potential alternatives. This study aimed to identify highly potent natural fungicides against M. oryzae to combat rice blast disease, using advanced molecular dynamics techniques. Four key proteins (CATALASE PEROXIDASES 2, HYBRID PKS-NRPS SYNTHETASE TAS1, MANGANESE LIPOXYGENASE, and PRE-MRNA-SPLICING FACTOR CEF1) involved in M. oryzae's infection process were identified. A list of 30 plant metabolites with documented antifungal properties was compiled for evaluation as potential fungicides. Molecular docking studies revealed that 2-Coumaroylquinic acid, Myricetin, Rosmarinic Acid, and Quercetin exhibited superior binding affinities compared to reference fungicides (Azoxystrobin and Tricyclazole). High throughput molecular dynamics simulations were performed, analyzing parameters like RMSD, RMSF, Rg, SASA, hydrogen bonds, contact analysis, Gibbs free energy, and cluster analysis. The results revealed stable interactions between the selected metabolites and the target proteins, involving important hydrogen bonds and contacts. The SwissADME server analysis indicated that the metabolites possess fungicide properties, making them effective and safe fungicides with low toxicity to the environment and living beings. Additionally, bioactivity assays confirmed their biological activity as nuclear receptor ligands and enzyme inhibitors. Overall, this study offers valuable insights into potential natural fungicides for combating rice blast disease, with 2-Coumaroylquinic acid, Myricetin, Rosmarinic Acid, and Quercetin standing out as promising and environmentally friendly alternatives to conventional fungicides. These findings have significant implications for developing crop protection strategies and enhancing global food security, particularly in rice-dependent regions.

Forecasting model for hypoid gear elastohydrodynamic lubrication considering entrainment effect

In full consideration of time-varying meshing performance and oil film characteristics, entrainment effect on elastohydrodynamic lubrication (EHL) is developed for establishing accurate forecasting model of the complex hypoid gears. Firstly, dynamic loaded tooth contact analysis (DLTCA) is employed to determine the meshing interface kinematics, load distribution and entrainment speed under dynamic load condition. Then, entrainment speed is introduced into the EHL governing equation and accurate forecasting model is established. With accurate discretization of EHL governing equation, discrete convolution and fast Fourier transformation (DC-FFT) method is employed to compute the flank elastic deformation. Finally, a hypoid gear set in automotive industrial application is exercised to verify entrainment effect on EHL assessment in the proposed model.

Investigation into the analysis method for assessing contact stress in joint prosthesis

Contact stress is the important cause of wear and failure of knee joint prostheses implanted in the human body during movement. The calculation of contact stress on joint prostheses is often inaccurate due to the deviation of joint position during activity. This paper proposes a correction method for contact stress based on finite element results. Firstly, the contact stress and contact radius between femoral and tibial prostheses of knee joint were calculated and analyzed by Hertz contact theory. Then, individualized finite element models based on the individualized geometry of the joint prosthesis and individualized loading were constructed, and the finite element contact stress was analyzed. The finite element results were calibrated utilizing the Hertz contact theory. Additionally, this study investigated the impact of three gait patterns (normal gait, medial thrust gait, and bouncing gait) on the contact stress experienced by the tibial insert. The research methods and results can provide ideas for theoretical analysis and finite element simulation of prosthetic joint contact, as well as offer theoretical support and analysis methods for evaluating the lifespan of prosthetic joints.