Deformation Of Brackets Research Articles

Zero-Velocity Update-Based GNSS/IMU Tightly Coupled Algorithm with the Constraint of the Earth's Rotation Angular Velocity for Cableway Bracket Deformation Monitoring.

Cableways have been widely used in industrial areas, cities, and scenic spots due to their advantages, such as being a convenient mode of transportation, time-saving, labor-saving, and low cost, as well as offering environmental protection. To ensure the safe operation of a cableway, based on the characteristic that the velocity of the cableway bracket is approximately zero in a static deformation monitoring environment, a deformation monitoring method called zero velocity update (ZUPT)-based GNSS/IMU tightly coupled algorithm with the constraint of the Earth's rotation angular velocity was proposed. The proposed method can effectively solve the problem of a single GNSS being unable to output attitude, which is directly related to the status of wire ropes and cable cars. Meanwhile, ZUPT is used to restrain the Kalman filter's divergence when IMU is stationary. However, the improvements of ZUPT on attitude are not obvious, so the constraint of the Earth's rotation angular velocity was applied. The performance of the proposed method was evaluated through monitoring the cableway bracket of the Yimeng Mountain Tourism area in Shandong. Compared with the ZUPT-based GNSS/IMU tightly coupled algorithm (ZUPT-TC), the proposed method can further constrain the error accumulation of IMU while stationary and, therefore, it can provide reliable position and attitude information on cableway brackets.

Comparative finite element analysis of bracket deformation in tie wings and slot region during simulated torque

Torque in orthodontics is the activation of the archwire for the third-order movement of teeth. During this force transfer mechanism from the twisted archwire, the bracket is prone to deformation. This study aimed to compare the deformation in tie wings and the slot region of the bracket during torque using finite element analysis. Three-dimensionally modeled 0.017×0.025-in and 0.019×0.025-in stainless steel (SS) and titanium molybdenum alloy archwires were assembled in 0.018-in and 0.022-in solid modeled SS edgewise brackets, respectively. The finite element model of the bracket-archwire combinations was developed with contact boundary conditions. The deformation between tie wings and the slot was analyzed for various angles of twist. For SS archwires at 30° angle of twist, the tie wings deformation in 0.018-in and 0.022-in brackets were 48.67μm and 34.87μm, respectively. The slot deformations of 0.018-in and 0.022-in brackets were 66.33μm and 45.69μm, respectively. Similarly, the amount of deformation in the bracket-titanium molybdenum alloy archwire combinations were also presented. The slot deformation was more than the tie wings deformation as the slot walls bear the immediate torque force. Thus, orthodontic researchers should know that the torque-relevant bracket deformation should ideally be evaluated in the slot region rather than the tie wings.

Ways to Correct the Errors in Posture of Multi-beam Sounding Resulted from Water Flow

Multi-beam bracket deformation is caused by factor like water flow and speed of ship. Such deformation also leads to the axle offset of relative attitude indicator of transducer, which may influence the accuracy of results. As for this phenomenon, the paper proposes a method that calculates water velocity and output speed of ship according to the navigation data, in order to fit the attitude deviation and correct the results of depth measurement. First of all, water velocity and output speed of ship of two adjacent stripes without abnormal sounding results in the testing zone in good sea condition are calculated respectively according to navigation data, and then the errors in posture of these two stripes in different time are worked out respectively based on discrepancy in elevation of the overlapping portions of the stripes; secondly, a modifier formula of water velocity, output speed of ship and errors in posture is formulated; finally, this formula is applied to solving errors in posture and correcting the sounding data of stripes in the testing zone. According to the experimental results, the proposed method can eliminate errors in posture effectively, with the average of discrepancy in elevation reduced from 0.188m (before) to 0.032m (after). The stripe splicing effect is improved and the data accuracy is enhanced enormously.

Finite Element Analysis of a Steel Bracket

With the development of the society, sheet metal filing cabinets have become popular in the office. When filing cabinets store too many paper documents, the interlayer splints often fail because of the failure of the small brackets below. The stress and deformation of brackets were studied by the theoretical method and the finite element method. Results show some small machining shape defects have little influence on the mechanical behavior of brackets. The failure reason of small brackets is not the strength, but the instability.

Investigation into the effects of stainless steel ligature ties on the mechanical characteristics of conventional and self-ligated brackets subjected to torque

Torque is applied to orthodontic brackets in order to alter the buccal-lingual angulation of a tooth. One factor that can affect torque is the ligation mode used to retain the archwire in the bracket slot. The objective of this study was to investigate the effects of stainless steel ligation on torque expression and bracket deformation. This study utilized 60 upper right central incisor Damon Q brackets and 60 Ormco Orthos Twin brackets. The brackets used in this study were subdivided into four groups: (1) Damon Q ligated with SS ligature; (2) Damon Q with the sliding bracket door; (3) Orthos Twin bracket ligated with SS wire; and (4) Orthos Twin ligated with elastic ties. All brackets were tested using an orthodontic torque simulating device that applied archwire rotation from 0° to 45°. All brackets ligated with stainless steel ties exhibited greater torque expression and less deformation than brackets without stainless steel ties. As well, Damon Q brackets exhibit less bracket deformation than Orthos Twin brackets. Stainless steel ties can reduce the amount of plastic deformation for both types of brackets used in this study.

A Deformation Analysis and Compensation Algorithm for Bracket Structure of Automatic Drill-Riveting System

Since the bracket deformation caused by its deadweight is too large, and the riveting of aircraft panel is always over-tolerance, a new algorithm for analysis and compensation of bracket deformation is presented in this paper. The algorithm is formed by combining finite element (FE) simulation with analytic method, which is fit for different combinations of supporting plates of bracket system. The formula is constructed through cubic spline interpolation and envelope surface fitting according to the FE simulation data. Meanwhile, a corresponding compensation method is proposed. Finally, a numerical simulation example with the software of ABAQUS shows that the algorithm and its results are valid and feasible.

Design of an Orthodontic Torque Simulator for Measurement of Bracket Deformation

The design and testing of an orthodontic torque simulator that reproduces the effect of archwire rotation on orthodontic brackets is described. This unique device is capable of simultaneously measuring the deformation and loads applied to an orthodontic bracket due to archwire rotation. Archwire rotation is used by orthodontists to correct the inclination of teeth within the mouth. This orthodontic torque simulator will provide knowledge of the deformation and loads applied to orthodontic bracket that will aide clinicians by describing the effect of archwire rotation on brackets. This will also impact that design on new archwire\bracket systems by providing an assessment of performance. Deformation of the orthodontic bracket tie wings is measured using a digital image correlation process to measure elastic and plastic deformation. The magnitude of force and moments applied to the bracket though the archwire is also measured using a six-axis load cell. Initial tests have been performed on two orthodontic brackets of varying geometry to demonstrate the measurement capability of the orthodontic torque simulator. The demonstration experiment shows that a Damon Q bracket had a final plastic deformation after a single loading of 0.022 mm while the Speed bracket deformed 0.071 mm. This indicates that the Speed bracket plastically deforms 3.2 times more than the Damon Q bracket for similar magnitude of applied moment. The demonstration experiment demonstrates that bracket geometry affect the deformation of orthodontic brackets and this difference can be detected using the orthodontic torque simulator.

Three-dimensional deformation comparison of self-ligating brackets

Archwire rotation is used in orthodontic treatment to alter the labiolingual orientation of a tooth. Measurement of the 3-dimensional (3D) motion of the orthodontic brackets requires a new configuration of the orthodontic torque simulator. The orthodontic torque simulator was coupled with a stereo microscope and 2 cameras to allow for the 3D bracket motion to be determined during wire twisting. The stereo camera images were processed with a 3D digital image correlation technique to determine the 3D deformation of the orthodontic brackets. Three self-ligating brackets (Damon Q, Ormco, Orange, Calif; In-Ovation R, GAC, Bohemia, NY; and Speed, Strite Industries, Cambridge, Ontario, Canada) were compared by using the 3D digital image correlation method to demonstrate the difference in 3D motion of self-ligating brackets components. Contour plots of the 3 brackets demonstrate the 3D motion of the bracket tie-wings and the archwire retentive component. The 3D motion of the bracket tie-wings and archwire retentive component were quantified. The displacement values of the archwire retentive component measured with the 3D orthodontic torque simulator were found to be 2.0 and 3.5 times less for the In-Ovation and Damon Q brackets than the values in previous studies that examined the compliance of the archwire retentive component. The 3D digital image correlation method used to quantify bracket deformation showed the 3D motion of the bracket tie-wings and the motion of the archwire retentive component. The use of a 3D optical measurement system is useful to understand the motion of the archwire retentive component but is not necessary to quantify bracket tie-wing motion. This measurement technique can be used to evaluate brackets of varying designs.

An investigation into the mechanical characteristics of select self-ligated brackets at a series of clinically relevant maximum torquing angles: loading and unloading curves and bracket deformation

Edgewise orthodontic treatment utilizes a force couple in order to achieve labial-lingual tooth angulation. Two self-ligating brackets (Damon Q and Speed) were examined across a range of clinically relevant torques in order to assess the loading and unloading curves and bracket deformation. A previously developed torquing and load measurement system was utilized to rotate a 0.199 × 0.25 in stainless steel wire in a fixed bracket slot to the following angles: 16, 20, 24, 28, 32, and 40 degrees. The torque on the bracket was measured during both wire loading and unloading cycles. The torque play for the Damon brackets was determined to increase by less than 0.4 degrees when torqued to 70 Nmm, whereas the increase for the Speed brackets was 2.1 degrees at the same torque magnitude. The deformation curves for the Damon and Speed brackets were found to be different for loading and unloading. Speed brackets were found to start to plastically deform when torqued to 24 degrees (26 Nmm of torque), while Damon brackets did not plastically deform until 28 degrees (38 Nmm of torque). Damon brackets were found not to plastically deform as easily and to have a smaller increase in torque play than Speed brackets. Both the Damon and the Speed brackets demonstrated minimal effect of plastic deformation and torque play at maximum angles of twist less than 20 degrees. Torque measured in the brackets was different for loading and unloading.

Finite Element Idealization of a Cold-Formed Steel Portal Frame

A simple linear beam idealization of a cold-formed steel portal frame is presented in which beam elements are used to idealize the column and rafter members, and rotational spring elements are used to represent the rotational flexibility of the joints. In addition, the beam idealization takes into account the finite connection length of the joints. Deflections predicted using the beam idealization are shown to be comparable to deflections obtained from both a linear finite element shell idealization and full-scale laboratory tests. Using the beam idealization, deflections under rafter load are divided into three components: Deflection due to flexure of the column and rafter members, deflection due to bolt-hole elongation, and deflection due to in-plane bracket deformation. Of these deflection components, the deflection due to bolt-hole elongation is the most significant and cannot, therefore, be ignored. Using the beam idealization, engineers can analyze and design cold-formed steel portal frames, including making appropriate allowances for connection effects, without the need to resort to expensive finite element shell analysis.

Comparison of load transmission and bracket deformation between titanium and stainless steel brackets

This study measures the load transmitted and structural integrity of stainless steel and titanium brackets on application of torsional forces. Both 0.018 and 0.022 inch slot size edgewise brackets were tested in a specially designed apparatus that applied a torque value of 45°. The load generated was measured by an Instron Universal Testing Machine at intervals of 15°, 30°, and 45° of torque application. The structural stability of the brackets was evaluated by measuring the bracket slot width with a traveling stereoscopic microscope before and after the brackets were subjected to torsional forces. The specimen population was composed of 80 brackets and 80 wire specimens. An independent sample t test was used for comparison of mean load generated at 45° of torque application. Repeated measures ANOVA (one-way) comparison was used to evaluate changes in load at different torque levels for the stainless steel and titanium brackets. A paired t test (two-tail) was used to determine the difference between initial and final bracket slot width at 45° of torque applied for the two bracket types. The titanium brackets transmitted higher loads at 15° and 30° torque and lower load at 45° torque on application of torsional forces in comparison to stainless steel brackets. The titanium brackets demonstrated superior dimensional stability compared to stainless steel brackets ( P < .0001). (Am J Orthod Dentofacial Orthop 1999;116:275-8)

A stratigraphic and structural reappraisal of Central Malawi:Results of a geotraverse

The Precambrian Malawi Basement Complex, metasediments and orthogneisses of central Malawi are discussed. Three metasedimentary associations, intruded by a suite of low TiO 2, olivine tholeiite gabbros, are recognised and interpreted as a continental shelf-rise assemblage. A fourth unit, the psammitic Mchinji Group, is reinterpreted as a proximal facies equivalent of the other paragneisses. Widespread, early granitoid and alkaline plutonism is recognised and interpreted as an anorogenic magmatic province. Metamorphic transformations and deformational styles are locally controlled, probably by variable H 20. The first deformation produced migmatitic fabrics in aweu> paragneisses while water-deficient orthogneisses retained their igneous textures orrecrystall ised to granoblastic aggregates, locally with granulite-facies mineralogy. Anhydrous, kelyphitic rims formed around olivine in the metagabbros. Later deformation produced tectonte fabrics with lower- amphibolite, locally greenschist, mineralogy. Fold vergence and stretching lineations suggest N or NW tectonic transport directions and the overall structure is interpreted as a foreland fold and thrust zone with steep structures produced by imbricatlon. Previous isotope studies bracket deformation between c.1100Ma and c.450Ma, contemporary with deformation of the Muva Supergroup in the Irumide Belt of Zambia which may be the foreland-ward extention of the studv area.