Tooth Deformation Research Articles

Investigation on wear characteristic of biopolymer gear

Polymer is widely used in many mechanical components such as gear. With the world going to a more green and sustainable environment, polymers which are bio based are being recognized as a replacement for conventional polymers based on fossil fuel. The use of biopolymer in mechanical components especially gear have not been fully explored yet. This research focuses on biopolymer for spur gear and whether the conventional method to investigate wear characteristic is applicable. The spur gears are produced by injection moulding and tested on several speeds using a custom test equipment. The wear formation such as tooth fracture, tooth deformation, debris and weight loss was observed on the biopolymer spur gear. It was noted that the biopolymer gear wear mechanism was similar with other type of polymer spur gears. It also undergoes stages of wear which are; running in, linear and rapid. It can be said that the wear mechanism of biopolymer spur gear is comparable to fossil fuel based polymer spur gear, thus it can be considered to replace polymer gears in suitable applications.

Study of the effect of the expansion cone on the expansion process in solid expandable tubulars with thread joints

As the core technology of petroleum extraction engineering in the 21st century, Solid Expandable Tubular (SET) technology is applied to drilling, well completion, and cementing. However, the expansion process for tubulars in site operation may well lead to stress concentration, leakage, or even fracture failure in thread joints of the tubular assembly due to the irregular deformation of thread teeth. With the aim of studying the issue with regard to the thread joint of J55 steel expandable tubulars, this study extended a series of finite element models using the commercial software ABAQUS to investigate the structural response of tubulars during the expansion process. The simulation results include the stress evolution, deformation of the thread joint of the tubular assembly, and the effect of expansion cone geometry on the expansion consequences. A laboratory experiment was performed to validate the validity of the simulated solution. It was found from results that both the axial and hoop compressive stress concentrations were generated in the thread teeth edges near the contact surfaces of threads during the expansion process due to the mutual squeezing of box and pin thread teeth. An increase of the tubular diameter led to a reduction of wall thickness and axial length due to the law of volume-constancy. The expansion process resulted in a deterioration of the contact condition between the thread teeth. A cone angle of 9° and sizing section length of 65–75 mm were the optimal choice of the geometric size of the expansion cone according to their superior analytical results.

Research on the method to calculate deformation of curve-face gear

As a new type of face gear, the tooth deformation of curve-face gear has always been one of the research focuses. The conventional method of calculating the tooth deformation of face gear is widely focused on the basis of Buckingham's opinion, without considering the actual contact status. Therefore, in order to resolve this problem, a new calculation of curve-face gear tooth deformation is proposed. Firstly, the tooth distribution regularity of curve-face gear was analyzed. Then, a model for predicting the tooth elastic deformation of curve-face gear, taking into account the equivalent teeth, cross-section property, actual contact status and load distribution, was presented. Finally, the deformation variations were analyzed by taking into account the specific parameters such as eccentricity e, order number n1 and n2, and the correctness of the proposed mathematical model was verified by the results of the related experiment.

Optimization of Gear Modification for Boom and Crowing Mechanism Used in Large Mining Excavator

Aiming at the problems of pitting, shafts broken and so on in the process of the use of boom and crowning mechanism gear box of a large mining excavator, research found that the key problems of broken shafts and the large bearings clearance are caused by excessive shafts and gear teeth deformation, which result in serious corrosion occurred by partial load and serious bearing damage.

THE EFFICIENCY OF THE USE OF INDIVIDUAL REMOVABLE DENTAL BITE SPLINTS FOR CORRECTION OF DENTAL DEFORMATIONS DEGREE IN PATIENTS WITH DENTURE DEFECTS

Objective: introduction of prevention methods and increase of the treatment efficacy of teeth deformations using individual dental bite splints. Materials and methods: The results of clinical examination of 67 patients of different age (20 to 59 years) with the existing dentition defects before and after use of individual removable dental bite splints are given in this article. The results of the work: the objective study showed a difference in data of the distances between certain points of the teeth surrounding the defect without dentition deformations and in their presence (distances АВ in the control and experimental groups was respectively 7.16 ± 0.19 mm and 4.32 ± 0.19 mm, АD -7.62 ± 0.19 mm and 4.16 ± 0.20 mm, ВС - 7.49 ± 0.19 mm and 4.07 ± 0.19 mm, СD – 6.96±0.19 mm and 3.67±0.19 mm). After the performance of the preparation of the patients with the dentition defects and deformations of the teeth with the use of individual dental bite splints to the prosthetic repair in several stages, it became possible to reduce significantly indexes of the distances in the presence of pathology and bring them closer to physiological data (АВ - 5.85 ± 0.21 mm, AD - 6.09 ± 0.18 mm, BC - 6.22 ± 0.19 mm, and СD- 5.73±0.19mm). Conclusions: The use of individual removable dental bite splints gave the possibility to improve significantly the prosthetic efficacy by normalizing the occlusal relations and chewing load onto the displaced teeth in the area of dentition defect.

Load sharing by tooth pairs in involute toothed harmonic drive with conventional wave generator cam

A harmonic drive is a two gear epicyclic drive with a gear set of circular ring gear (RG), a flex rimmed external toothed gear (FG) and an oval cam. FG, with oval cam inside, takes non-circular gear shape encounters improper teeth mating with RG, having only two teeth difference. Consequently, interferences occur at several tooth pairs even at no load. These are inherent and obvious. Overcoming such interferences and further with applied load estimation of load sharing by tooth pairs poses a complex problem. In solving it, first, tooth stiffness of internal gear and external gear are derived in the present investigation. A method of estimating the load shared by the multiple tooth pairs in contact is proposed. The load distribution pattern in proportion to the tooth deformation is considered. Load shared by contacting tooth pairs is estimated and stresses in FG cup are found out using FEM. Finally, such results are compared with experimental results, which have good agreement.

Numerical Simulation of Root Longitudinal Stresses and Tooth Deformations Under Irregularly Distributed Loads

Gear strength analysis is important to the drive design of gear. Because of the considerable effect of the precise modeling on the numerical simulation of gear strength, APDL(ANSYS Parametric Design Language)- MATLAB parametric modeling approach is used. Gear tooth model is built by reducing tooth profile curve exactly. Based on the invariable position of gear engagement stiffness and linear elastic model of a pair of gears engagement stiffness, the engagement stiffness formula in the highest location of one-pair teeth is deduced under regularly distributed load. Considering the influence of surface hardness, running-in effects and the end stiffness on distribution of longitudinal load, a simulation method is given, which supposed that contact load is linear before running-in and parabolic after running-in. Then longitudinal stress curves are deduced. The maximum root stresses and tooth deformations are contrasted under linear and regular distribution load, linear and irregular distribution load and parabolic distribution load. The end stiffness effect and the continuity of root stresses and tooth deformations are validated. Under irregularly distributed load, root longitudinal stresses and tooth deformations are simulated. The results show that maximum root stress increases whereas tooth deformations decreased due to existing irregularly longitudinal load and end constraint. And the conclusions have some value on optimizing tooth profile and improving longitudinal load distribution.

A review on failure characteristics of polymer gear

Polymer are now widely used as substitute material for steel gear in low load devices. Its failure differs from gears made of steel, thus it is important to categorize the failures shown by polymer gears. Several previous studies noted that wear detection, microstructure surface condition monitoring, weight loss and temperature detection can be used in detecting failure of polymer gear. This article reviews the failure detection method mentioned above. Other researcher works were studied and their findings were extracted in order to identify the methods they used. The most common method used was wear detection and it was supplemented by other methods such as microstructure surface condition monitoring. Failures shown by polymer can be concluded to be tooth breakage, tooth deformation, material removal and surface fatigue.

Evaluating the Effect of Dental Filling Material and Filling Depth on the Strength and Deformation of Filled Teeth

ackground and aim: It is important to evaluate the effect of the type of filling material on deformation and strength of tooth after filling and also the effect of filling depth on quality of restoration of a decayed tooth. Material and Methods: The Orthopantomogram (OPG) of the first and second molars of a 28-year-old man was made and the teeth were 3D modeled. The stress-deformation analysis was then performed on the models in the three states of normal tooth, tooth filled with amalgam and tooth filled with composite using finite element method under a distributed load of 400N equivalent to chewing force. Two values (1/2 and 1/3 of the tooth height) were considered for filling depth in the analyses. Results: The results showed that the normal first molar was exposed to a 7.2% greater risk of dental injuries compared to the normal second molar and also a greater stress is created in it when it is filled with composite. The first molar filled with a composite material is 13.7% weaker than the normal tooth while it is almost as strong as a normal tooth when it is filled with amalgam. The effect of the type of filling material on the strength and deformation of the second molar was trivial. Conclusion: Amalgam is a more proper dental filling material for the first molar although a 16.7% change in drilling depth is needed for tooth preparation. Dental filling material and filling depth have a small effect on the strength and deformation of filled second molars.

Dynamic analysis of torus involute gear including transient elastohydrodynamic effects

The torus involute gear can compensate large axial misalignments and may possess good meshing characteristics without lead correction. In order to study its dynamic characteristics and verify its feasibility of the practical application, a new efficient rigid-elastic coupling dynamic model of multi-tooth is established which includes effects of lubrication oil film and tooth deformations directly in contact simulation of gears. In this model, each tooth is connected with the gearwheel by a rotatable spring-damper element whose stiffness is calculated through analysis of tooth deformation. The normal tooth contact force is determined via Lankarani and Nikravesh model. Variation of contact stiffness and rotatable spring stiffness with contact points are both taken into account. Combined with tooth contact analysis, the computation of friction coefficient is implemented with high efficiency by introducing the average lubrication oil film height. A three-dimension multi-body model of a torus involute gear pair is employed and verified by an impact experiment. The simulated results provide useful information about tooth impacts, dynamic transmission error and lubrication conditions like oil film heights and friction coefficients, and show that this type of gear can work with good meshing characteristics. The contributions in this paper lay theoretical basis for the application of the torus involute gear.

A formulation of tooth deformation and its error compensation for worm gear transmission mechanisms

Milling head and rotary table are the key components in five-axis CNC machine tools. However, tracking and positioning precision of these rotary axes based on worm gear mechanisms are affected by the backlash, friction, elastic deformation, and other nonlinearities. Therefore, finding out a simple and universal principle to predict the tooth deformation in an initial design is quite significant. A novel deformation calculation and compensation method with finite element analysis and circular plate theory is proposed for the worm gear transmissions. When the relationship (form factor) between the solutions of circular plate theory and finite element analysis is derived, deformation calculation with finite element analysis can be replaced by multiplying the solution of circular plate theory and the form factor. Analysis and calculation results show that the presented method can provide a reference for the compensation control of the positioning errors.

Oral phenotype and variation in focal dermal hypoplasia.

Focal dermal hypoplasia (FDH) or Goltz Syndrome (OMIM# 305600) is an X-linked dominant ectodermal dysplasia caused by mutations in the PORCN gene. This gene encodes an endoplasmic reticulum transmembrane protein that is involved in processing the embryonically critical WNT signaling proteins. Individuals diagnosed with FDH were recruited to participate in the study through the National Foundation for Ectodermal Dysplasia. Individuals were evaluated to characterize the FDH phenotype. Each participant completed a brief dental survey and oral evaluation using artificial light. To identify the oral soft and hard tissue findings 19 individuals (16 female and 3 male) participated with a median age of 10 years (range 2-56 years). Soft and hard tissue defects were present in 68% (13) and 94% (18) of the patients, respectively. Dental anomalies were highly prevalent with 68% (13) demonstrating vertical enamel grooving, 52% (10) having peg shaped tooth deformities, and 78% (15) having enamel hypoplasia with or without discoloration. Cleft lip and cleft palate presented in 15% (3) of the participants. Other findings included 57% (11) having intra-oral lipoma or papilloma with no site predilection. Dental malocclusions were common with 63% (12) having some degree of malocclusion with 15% (3) of participants having class III malocclusion with an anterior dental cross bite. Participants frequently reported speech problems or difficulty with chewing (73%; N = 14). This study shows there is marked variation in the oral phenotype of individuals with FDH and underscores the important role of WNT signaling in oro-facial development.

Dynamic Response Analysis of 2.5MW Wind Turbine Gearbox with Flexible Pins

This study is concerned with the numerical investigation of dynamic characteristics of 2.5MW-class wind turbine gearbox in which the misalignment improvement of plenary gear shafts by the flexible pins and the dynamic impact response are analyzed by the finite element method. The tooth contact between gears is modelled using the line element having the equivalent tooth stiffness and the contact ratio to accurately and effectively reflect the load transmission in the internal complex gear system. The equivalent tooth stiffness is calculated by utilizing the tooth deformation analysis and the impulse torque is applied to the input shaft for the dynamics response characteristic analysis. Through the numerical experiments, the equivalent tooth stiffness model was validated and the misalignment improvement of planetary gear shafts was confirmed from the comparison with the cases of fixed shafts at one and both ends.

Theoretical and experimental study on gear-coupling contact and loads considering misalignment, torque, and friction influences

A new analytic model addresses the tooth contact and induced loads of gear couplings that are affected by misalignment, torque, and friction. The contact model accounts for Hertzian, bending, and shear deformations of coupling teeth considering crown modifications. For a specified torque and shaft misalignment, the model calculates the number of teeth in contact, tooth load, stiffness, stress, deformation, and safety factors. The tooth load distribution around the circumference compares well with high fidelity finite-element/contact-mechanics analyses. Simulation time with the analytic model is orders of magnitude less. Using the local contact characteristics, the model computes coupling loads that are primarily caused by the disrupted tooth contact and sliding friction caused by axial motions. This analytic model was validated by experiments. The load amplitude depends on the misalignment, torque, and friction. At low torque, coupling motion was induced by the eccentricity between the hub and sleeve even with nearly perfect alignment. This eccentricity was caused by its self-weight. When torque was larger than a threshold, the motion amplitude was greatly reduced. This torque threshold was analytically derived and validated by experiments.

マシニングセンタを用いて抽出した竹繊維のみの成形歯車のかみあいモニターと考察

A plastic gear has the advantages that it is light and can be used without any lubricant, and the disadvantages that its strength is low and that it has a large environmental impact. Therefore, the development of a new gear that maintains the advantages while negating the disadvantages has been proposed. The development of sustainable and reproducible natural materials is especially desired in order to address environmental problems. In this study, a method was therefore devised to extract high quality and highly precise bamboo fibers using a machining center. The hot press method was then used to produce a spur gear, which is a machine element with a complicated shape. Therefore, the present paper describes characteristics of the bamboo fiber gears investigated in some experiments. The results of a strength test showed that the bamboo fiber gear can be used as an alternative to the Mc nylon gear. The results of a meshing test showed that the teeth of a bamboo fiber gear underwent transformation because of the meshing load. In addition, we calculated travel value of meshing point by teeth deformation and compared experimental value of travel value with calculated value. Results show that the experimental deformation value is greater than the calculated value.

DEFORMATION AND STIFFNESS OF SPUR GEAR TEETH AND THEIR INFLUENCE ON GEAR NOISE

Summary. Gear teeth are deformed due to the load. The deformation of gear teeth is causing some negative as well as positive effects. A tooth has a complex shape and due to the complex shape of the teeth, a theoretical determination of the deformation is difficult. The existing experimental techniques are based on static deflection measurements gearing loaded of constant force or seismic measurement deviations at slow rotation. Recently, at ever faster evolving computer technology and the available literature, we can encounter modern numerical methods, such as finite element method (FEM), which can serve as methods for the determination of teeth of gearing. The article is devoted to the problems of gearing stiffness analysis. The problem is solved for spur gears. Deformation analysis solved by FEM is used for calculations of the gearing stiffness. There are many influences that cause vibrations in the gearbox and that have to be taken into account already in the phase of design, manufacture, installation and operation. Detailed analysis of gearboxes manufacturers have shown that improving of the gear accuracy cannot reduce the transmission unit noise to the desired level. Only fundamental changes to the shape of the tooth and changes in production technology can achieve stronger noise reduction of gear mechanism.

Robust tooth surface reconstruction by iterative deformation

Digital design technologies have been applied extensively in dental medicine, especially in the field of dental restoration. The all-ceramic crown is an important restoration type of dental CAD systems. This paper presents a robust tooth surface reconstruction algorithm for all-ceramic crown design. The algorithm involves three necessary steps: standard tooth initial positioning and division; salient feature point extraction using Morse theory; and standard tooth deformation using iterative Laplacian Surface Editing and mesh stitching. This algorithm can retain the morphological features of the tooth surface well. It is robust and suitable for almost all types of teeth, including incisor, canine, premolar, and molar. Moreover, it allows dental technicians to use their own preferred library teeth for reconstruction. The algorithm has been successfully integrated in our Dental CAD system, more than 1000 clinical cases have been tested to demonstrate the robustness and effectiveness of the proposed algorithm.

Influence Gearing Parameters on the Tooth Deformation of Spur Gears

Gear teeth are deformed due to the load. The tooth deformation of spur gears is not constant for all examined teeth of gears. Tooth deformation is depends on the shape of the teeth, on the basic parameters of examined spur gear, such as the number of teeth, module gearing, pressure angle, gearing width, correction and modification of gearing.

Analysis and research on teeth thermodynamic coupling contact of gear transmission system

In the gear meshing process, gear temperature field concerns the meshing surface friction, the friction heat depends on the contact pressure, the contact pressure is affected by the elastic deformation of gears and the temperature field caused by the thermal deformation, so the temperature field, stress field and displacement field should be mutual coupling. It is necessary to consider in meshing gear pair in the operation process of thermodynamic coupling contact stress (TCCS) and thermodynamic coupling deformation (TCD), and based on thermodynamic coupling analysis (TCA) of gear teeth deformation.

Secondary dentoalveolar deformations in children, its prevention and treatment

Secondary dentoalveolar deformation due to premature removal of deciduous teeth and delayed tooth prosthesis occur in children 10 times faster than in adults. The main method of prevention of their occurrence is replacement of dentition defects. Development of relevant sustainable to the children's oral structures of child dentures is actual. Aim. Improving prevention and treatment of secondary dentoalveolar deformations in children due to early loss of teeth, through the development of children's rational constructions of dentures. Material and methods. We examined and taken for treatment of 48 people from 3 to 17 years old with dentition defects. Patients were divided into three age groups, namely: I group – 12 children from 3 to 5.5 years with a temporary occlusion, II group – 22 children from 6 to 13 years with a variable occlusion and III group – 14 teenagers from 14 to 17 years with permanent occlusion. Results. Given the shortcomings of existing designs, we have developed partial dentures, which base is made from a combination of polyester material that can be used in all periods of occlusion as a prophylactic and therapeutic purposes and adhesion bridge-like denture on tabs with holes for the prevention of secondary teeth deformations during permanent occlusion for temporary or permanent prosthetic of children. Conclusions. Clinical examinations have shown that our proposed design of children's dentures have significant advantages over traditional and can be used successfully in orthodontic practice for the prevention and treatment of secondary dentoalveolar deformities of dentition in children