Coil Spring Research Articles

Maxillary anterior gingiva and dentoalveolar changes after en-masse retraction between thick and thin gingival biotypes

This study compared the changes of gingiva and alveolar bone parameters, including cortical and cancellous bones between thick and thin gingival biotypes after en-masse retraction. Thirty-two adult subjects (mean age, 20.6 years) with maxillary anterior teeth protrusion and proclination were studied and divided into 2 equal groups: thick gingival biotype (TKB) and thin gingival biotype (TNB). Maxillary anterior teeth were retracted using nickel-titanium coil springs at 150 g of force bilaterally for 4 months. Lateral cephalograms, study models, and cone-beam computed tomography scans were taken before retraction and 3 months after 4 months of retraction. Nonparametric tests compared the changes within the groups at these periods and between the groups. The gingiva gained thickness and length (P<0.01) on the labial and palatal sides. The gingival thickness gained more on the palatal side (P<0.01), whereas the length gained equally in both groups. Labial alveolar bone showed increased thickness and height (P<0.01) as opposed to the palatal alveolar bone that presented with loss of thickness and height (P<0.01). The height loss occurred more in TNB (P<0.01). Labial cortical bone increased in thickness and height (P<0.01), whereas palatal cortical bone thinned (P<0.01) at levels in which no cancellous bone was present at the crestal level for TKB and the crestal and midroot levels for TNB. TKB showed slower incisor movement and less retroclination than the TNB (P<0.01) with minimal incisor extrusion. Favorable gingiva and labial bone responses after en-masse retraction were found in both gingival biotypes, whereas more palatal alveolar bone height loss was presented in TNB. Cortical bone thickness decreased when cancellous bone was absent.

Multi-objective shape optimization of large strain 3D helical structures for mechanical metamaterials

The need for mechanical metamaterials with large strain range and lightweight properties are evidenced to engineering applications. In this regard, novel helical structures are proposed as suitable unit cell’s components of mechanical metamaterials. Three-dimensional helical structures composed of varying coil numbers, defined in a cylindrical spatial domain are shape optimized through genetic algorithm in a finite element script for conflicting objectives of minimum mass and maximum tensile range. The superior performance of the shape optimized helical structure is highlighted in terms of structural rigidity, large deformation capability, buckling and vibrational modal analysis in compare to equivalent coil springs of identical weight and comparable domain. Deformation mechanism is analyzed carefully to justify the improved performances of proposed structure. Tensile and compressive experimental analysis are undertaken to validate the enhanced strain ranges. One dimensional metamaterials implementations with various tessellation arrangements are simulated. Results show that the proposed design can effectively generate lightweight substitutes of metamaterials unit cells ligaments to improve the strain range performance. Planar and lattice metamaterial concepts employing shape optimized helical structure are illustrated to demonstrate the possibilities of promoting lightweight structural integrities in the design of mechanical metamaterials.

An experimental investigation of the mechanism and mitigation measures for the coil spring fracture of a locomotive

The fracture of coil springs occasionally appears in rail vehicles, which may severely jeopardise the train running safety. In this study, the fracture phenomenon of the locomotive coil spring is investigated mainly using the experimental methods. Field surveys are preliminarily carried out, including statistical analysis, visual observations, material properties tests, and measurement of the wheel out-of-roundness (OOR), all of which can help to discover the potential contributing factors to the coil spring fracture. To ascertain the root cause of the coil spring fracture, a well-designed modal test is carried out to determine the natural frequency of the coil spring. The dynamic stress of the coil spring is also measured to verify whether the structural resonance existed. Moreover, dynamic simulation is performed to reproduce the resonance phenomenon. The experimental results show that the 1st expansion modal of the coil spring will be motivated by the excitation frequency of the 17th order wheel OOR if the locomotive runs frequently in the speed of 75–80 km/h. Two mitigation measures are presented, including the wheel re-profiling and structure optimization for the coil spring. Furthermore, the proposed countermeasures are proved to be effective for reducing the risk of coil spring fracture according to the filed tracking tests.

Proposal of forceps force limiter design using leaf spring buckling

To prevent accidents in minimally invasive surgeries, force limiters have been developed for forceps grippers. When a force limiter is in use, if the absolute value of its spring constant is reduced, the risk of damage to the organs decreases. This paper proposes the use of a leaf spring buckling mechanism as a force limiter for forceps. The results obtained indicate that the spring constant of a buckled leaf spring is lower than that of a normal coil spring. Furthermore, the use of a leaf spring allows the independent adjustment of its thickness and width, based on the stress and force values. This enables an easy calibration of the threshold value. In the experiments, the spring constant of the buckled leaf spring was 1.5 times 10^{-1} N/mm, which is half of that of a normal coil spring. After calibrating the gripping force, it was confirmed that the force limiter reduced the extent of damage to the dummy organs in the ex vivo experiments.

The effect of micro-osteoperforations on orthodontic space closure investigated over 12 weeks: a split-mouth, randomized controlled clinical trial.

To evaluate the effects of minimally invasive micro-osteoperforations (MOPs) on orthodontic tooth movement and pain. Prospective, split-mouth, randomized controlled trial. Single-centre, university hospital. Twenty subjects requiring maxillary first premolar extractions were included. Right and left sides of the maxilla were randomly allocated into experimental and controls. Space closure was initiated following alignment on 0.20″ stainless steel archwires, using 150 g force, applied by coil springs on power arms. Nance-TPA was used for anchorage. On the experimental side, two 5 mm deep MOPs in vertical alignment on distal aspect of the maxillary canine mid-root region were performed prior to space closure. The primary outcome was the amount of tooth movement during space closure, measured every 4 weeks for 12 weeks (T1, T2, and T3). Secondary outcome was the pain levels related to MOP, measured using Visual Analogue Scale (VAS) questionnaires. Significance was set at P &lt; 0.01. Randomization was generated using a randomization table, and allocation was concealed in sequentially numbered, opaque, sealed envelopes. Blinding was not possible during the experiment but assessor was blinded during outcome assessment. All subjects completed the study, with tooth movement measurements available for all 20 patients for T0-T2. In three patients, space was closed on one side at T2. The average tooth movement between sides at three intervals (T0-T1, T1-T2, and T2-T3) were not significantly different. Overall difference following 12 weeks (T0-T3) was 0.69 mm higher on the experimental side (P &lt; 0.001). No harms were observed. Short-term study, cast measurements done with digital callipers. This 12-week randomized split-mouth controlled clinical trial showed two MOPs that are 5 mm deep, applied once prior to space closure, did not create clinically significant increase in maxillary premolar space closure. The protocol was not published before trial commencement. Trial was not registered. The Australian Society of Orthodontists Foundation for Research and Education.

Wear and leakage assessments of canted coil Spring–Energized polytetrafluoroethylene seals under Ultra-High cycle operations

Spring-energized polytetrafluoroethylene (PTFE) seals are typically utilized to meet requirements of long service life due to their excellent temperature and chemical resistance. After high-cycle operations, the contact pressure between the seal lip and the associated counterpart possibly decrease because of the wear on the contact surface and this eventually leads to loss of the sealing capability. Evaluations of the wear and resulting sealing performance of the seal are rather essential, however, the corresponding experiments are generally time consuming and costly. Simulation procedures for the seal based on the finite element analysis were therefore developed in the current study. Experimental and numerical investigations of mechanical behaviors of the canted coil spring and PTFE materials were first performed. A wear analysis model for the spring-energized PTFE seal used in a glue dispenser with reciprocating motions for semiconductor equipment was subsequently constructed. The modified Archard model was implemented into a self-coded user subroutine of commercial finite element software to assess the amount of wear on the seal. Simulation results revealed that the geometry dimensions of the worn seal are in fair agreement with those of the corresponding samples. Contact pressure distributions of the seal lip were also examined during the operations. Peak of the contact pressure was found to gradually decrease along with the increase of cycles due to the wear, and potential fluid leakage was then assessed via the Reynolds equation. Numerical calculations showed that no leakage would occur after ultra-high cycle operations which was consistent with practical observations.

PERANCANGAN SISTEM AIR SUSPENSION PADA SEPEDA MOTOR HONDA VARIO 110

This study discusses the suspension on motorcycles by changing the standard suspension system, namely spring suspension / Coil Spring by designing an air suspension system to be applied to the Honda Vario 110 motorcycle. There are several problems with the suspension of spring-type motorcycles, namely when adjusting the suspension and the level of comfort. The purpose of this study is toknow the construction design, design and know the ratio of damping values pthere is an air suspension system and coil spring applied to the initial design of the motorcycle. The design and simulation method carried out is using Autodesk Inventor 2020 Software. In this design process, there are additions to the construction, namely the holder for the suspension as an air suspension support and changes to the size of the engine mounting which is extended to increase the suspension water storage space. As a result of the Autodesk Inventor 2020 simulation, the Air Suspension made of rubber with a load of 300 kg with a damping value of 7,744 N/m is greater than the initial suspension made of steel wire spring (SW) with a value of 7,500 N/m.

Effect of Caffeine Injection on Orthodontic Tooth Movement in Rats: An Experimental Study on Rats.

Objectives Several studies have investigated the effects of different medications on orthodontic tooth movement (OTM). This study assessed the effect of caffeine injection on OTM in rats. Materials and Methods Thirty-five male Wistar rats were randomly divided into five groups. Their first molars and central incisors were attached with a nickel-titanium closed coil spring with 50 g load. The rats in the three experimental groups received 25, 50, and 75 mg/kg caffeine intraperitoneally for 21 days. The negative control group did not receive any injection and did not undergo orthodontic treatment. The positive control group underwent orthodontic treatment and received 0.9% NaCl (saline) injection. After 21 days, all rats were sacrificed by chloroform inhalation, and the maxilla was resected. The mean number of Howship's lacunae, blood vessels, osteoclasts, and root resorption lacunae was histologically measured. The bone volume-to-total volume ratio (BV/TV) in maxillary molars was calculated by microcomputed tomography (micro-CT) to quantify bone loss. Results The amount of OTM and the number of osteoclasts, blood vessels, and Howship's lacunae significantly increased in rats under caffeine therapy, while the number of root resorption lacunae did not increase. Lower BV/TV in the caffeine groups was in accord with the increased count of osteoclasts. Conclusion Caffeine injection can significantly increase OTM in rats.

A Simple Technique Using a Modified Nance Appliance as Anchorage for Maxillary Molar Distalization—Two Case Reports

Maxillary molar distalization to correct a dental Class II molar relationship and to create space to relieve crowding has been a long-lasting subject of debate in orthodontics. Generally, to distalize maxillary molars, an intra-arch distalization appliance is favored over an inter-arch appliance since it does not utilize mandibular dentition as an anchorage, so some unwanted side effects on mandibular incisors can be avoided. A variety of intra-arch appliances have been developed to distalize maxillary molars, such as the pendulum, Jones jig, first class appliance, distal jet, and modified C-palatal plate. Although they could achieve efficient molar distalization, the learning curve of proper appliance insertion and activation is relatively long. In addition, the appliances are not comfortable for the patients due to the bulky activation units, especially when the activation units are designed in the palatal area. The current manuscript describes a novel and effective maxillary intra-arch molar distalization appliance—a modified Nance appliance technique, which consists of: (1) palatally, a big acrylic button against the palatal rugae and connected to the premolars with wide mesh pads; (2) buccally, regular brackets on maxillary premolars and first molars with sectional round stainless steel archwires and open coil springs between the second premolar and first molar. Either bilateral or unilateral maxillary molar distalization can be achieved with this appliance, and the Class II elastics are not needed. It is simple to be fabricated, delivered, and activated, and it is comfortable for patients.

Distribution characterisation of spring durability for road excitations using maximum likelihood estimation

This paper presents the determination of a suitable probability function for fatigue-related reliability assessment of automotive coil springs under various road excitations using maximum likelihood estimation (MLE). The fatigue-related reliability assessment is a critical element for determining the component warranty period. The fatigue lives of the coil spring under various road excitations were obtained from experimental analysis using strain life approaches. The parameters for various distribution approach were estimated through maximum likelihood estimation (MLE). The Akaike information criterion (AIC) was used to determine the most suitable approach for fitting. As the outcome, the Nakagami distribution has shown the lowest AIC value at 330 which indicating as the most suitable fitting among other distributions. For reliability assessment, the mean time to failure (MTTF), reliability function and hazard rate was analysed. Based on these results, the suitable distribution for fatigue-related reliability characterisation were determined for improving spring life cycle assessment.

Vibration control of an unbalanced system using a quasi-zero stiffness vibration isolator with fluidic actuators and composite material: An experimental study

In this study, a new type of vibration isolator based on fluidic actuators and a composite slab was tested experimentally with an unbalanced disturbance. Quasi-zero stiffness vibration isolation techniques are advanced and provide effective isolation performance for non-nominal loads. The isolation performance of the proposed isolator was compared to that of a nonlinear vibration isolator equipped with fluidic actuators and a mechanical coil spring (NLVIFA). The NLVIFA system is better suited to non-nominal loads; however, the mechanical spring axial deflection leads to limited amplitude reduction in the system. To address this issue, a cross buckled slab was developed to replace a mechanical coil spring for absorbing vertical deflection by transverse bending, which is made of a specially developed composite material of Basalt fiber reinforced with epoxy resin and enhanced with graphene nano pellets. This current study was concerned with the theoretical analysis and experimental investigations of the proposed nonlinear vibration isolator with fluidic actuators and composite material (NLVIFA-CM), which performs under quasi-zero stiffness characteristics. Because of its reduced axial deflection, the theoretical and experimental results show that the NLVIFA-CM system outperforms the NLVIFA system and other linear type vibration isolators in terms of isolation performance. Furthermore, the proposed vibration isolator makes a significant contribution to low-frequency vibration.

A Systematic Way of using Preference Selection Index Methodology for Selecting Suspension Coil Spring Material

Material selection serves as a foundation for all engineering applications. Inappropriate material selection would create a huge impact which in turn would affect the quality of the product in whole. In this work, the best material for suspension coil spring is selected by using a novel method. Fatigue failure of a shock absorber coil spring occurs mainly due to the improper selection of material. To improve the performance and efficiency of the shock absorber coil spring, suitable material is to be selected based on its application with considerations of the desired properties. Preference selection Index (PSI), a systematic multi-criteria decision-making approach is presented in this study for selecting the appropriate material which is considered as best. This technique is used to select the best alternatives without defining the proportionate significance of attributes. ASTM A231 steel, AISI 9255 steel, 302 Stainless Steel, ASTM A228 Steel and Beryllium Copper UNS C17200 are the various materials suitable for suspension coil spring. Through PSI method, ASTM A228 Steel is selected as a best material among the alternative materials. The PSI results are validated using the numerical analysis, basic analytical analysis and verified using the average validation method with respect to the desired attributes.

The MH-WIRE, a novel coil-springe wire system: A prototype design.

OBJACTIVE:The authors introduced a novel wire system aiming to achieve optimal goals of tooth movement without multiple wire changes or sophisticated wire bending.MATERIALS AND METHODS:The system was composed of a single wire for all phases of treatment. The archwire was composed of NiTi coil springs connecting delta-shaped segments of 0.018˝ × 0.025˝ Titanium Molybdenum Alloy (TMA) segments to fit the 0.018˝ × 0.025˝ bracket slot, or 0.022˝ × 0.028˝ TMA segments to fit the 0.022˝ × 0.028˝ bracket slot. The coil spring was closed and packed in design. The coil-spring loops were constructed with 3 mm lumen. The wires were designed in three sagittal forms and the system provided nine forms of archwires.RESULTS:The wire systems have been an important component of treatment since the development of orthodontic science. Over time, the philosophy has evolved from endorsing wire bending to straight-wire treatment and then to custom-made archwires.CONCLUSION:This wire system was designed to be used as a “single-wire for the case” across all stages of treatment to achieve the ideal goals without any biological damage.

Nonlinear elastic plastic load deflection curves in NiTi shape memory alloy helical coils

Reversible deflection of coil spring due to shape memory effect was examined. Coil springs were prepared by winding the wire of Nickel -50.at.% Titanium alloy followed by the annealing at 800 C for 1h to set the coil shape. The Mf and Af temperatures were 30 C and 87 C and the spring was deformed in the fully martensite state at room temperature. A tough pitched spring with the coil diameter of 6.6 mm and the element diameter of 0.6 mm showed shape memory effect after extension larger than 1,000 %. The load-deflection curves measured showed nonlinear relationship with rapid increase of load at a certain extension. It was found that the shape memory strain of coil spring is not limited by that of element wire but by the geometry of coil spring against the extension. Noted that and the deflection was accompanied with the rotation around the coil axis. Elastic plastic deflection analysis was performed, and the prediction of the theory was compared with the experimental curves.

Railway vehicle vibration mechanism induced by offsetting axlebox suspension elements position

This paper describes railway vehicle vibration mechanism whereby offset suspension elements position affect bogieframe vibration response. Primary suspension elements are often set on offset position from center of axlebox, so we hypothesized that offset primary damper position trigger axlebox rotation around axlebox bearing, which play pivotal role in inducing bogie-frame pitching via coil spring. To address this hypothesis, we conducted whole vehicle vibration analysis, focusing on axlebox damper vertical damping force and coil spring horizontal force applied on the offset position from center of axlebox. Analysis results showed that the mechanisms are suggested to involve bogie-frame vibration response mediated by axlebox rotation as well as coil spring horizontal force.

Finite Element Study on Forming Helical Springs by Wire Bending with a Plate

Coil springs, widely used as mechanical elements, will enter another new production outlook due to the application of CNC wire bending machines and as the era of On-Demand Manufacturing is approaching. This article tries to follow the trend and use finite element analysis investigating parameters, such as the angle, shift distance, and wire diameter, applied in a CNC bending machine with a swivel plate as the die on the formed cylindrical helical coil springs. The results show that the angle of the swivel plate normal to the wire feeding direction and shift distance have a significant effect on the spring diameter, while the wire diameter has a significant effect on the spring pitch. The result will be used as a reference for the industry to develop On-Demand Manufacturing machinery applications in the future.

Variations of Stress Intensity Factors of Surface Cracks with Wrapping Location in Compression Coil Springs

This study has investigated the effects of coil turn position on the principal stresses and the correction factors, Fi (i=I, II and III) of the three modes of the stress intensity factors for a semi-elliptic surface crack on the outer surface of a compression coil spring. For this purpose, 3D finite element stress analyses have been made on a compression coil spring having a surface crack on the outer surface of its wire at every 0.5 turn from n=0.5 to n=4.5. The maximum principal stress, σ1, was also calculated by FEM and found to vary as cosine function of number of turns, n. The value of σ1 took maxima for half integer coil turns, i.e., n=0.5, 1.5, 2.5, …, whereas minima for every coil turn, i.e., n=1, 2, 3, … The principal stress fluctuation range was found as small as 4.6 % of its center value. The correction factor FI for the mode I stress intensity factors of the semi-elliptic surface crack also varied as cosine functions of n in the same manner as σ1 at all the positions of crack peripheries investigated. The largest mode I correction factor fluctuation range was as large as 22.9 % of its fluctuation center value. The variations of FI value with n can be distinguished into 5 groups according to the distance from the wire surface. This tendency was caused by the variations of FI value with the eccentric angle φ of the crack which are expressed as quartic functions of φ almost symmetric with the φ=90° (deepest point). The FI value took minima at the wire surface and second minima at the deepest point of the crack, and the value increased as the point got closer to the surface. The FI value varied from 0.47 to 0.69 with the geometrical parameters n and φ. The FI value was found dominant among the three modes of correction factors, since the values of the correction factors of the other modes, i.e., FII and FIII, were at most 8.3 % and 14.3 % of the FI value, respectively.

Comparison of Rate of Tooth Movement, Root Resorption and Pulp Vitality during En masse Anterior Retraction with Micro-osteoperforation and Low Level Laser Therapy: A Randomised Clinical Trial

Introduction: Micro-osteoperforation (MOP) and Low Level Laser Therapy (LLLT) are rapidly gaining popularity in clinical practice due their proven success in accelerating tooth movement and acceptable patient compliance. However, literature shows an inconsistent and variable evidence of their iatrogenic effects on the root and pulp due to biological variations of the samples chosen by the previously studies. Aim: To evaluate and compare the rate of tooth movement, changes in amount of external root resorption and pulp vitality in teeth during en masse anterior retraction associated with MOP and LLLT using split mouth technique. Materials and Methods: This was a double blinded, single center split mouth randomised clinical trial conducted at Faculty of Dental Sciences, MS Ramaiah University of Applied Sciences, Bangalore, Karnataka, India from March 2019 to October 2019. Total of 11 patients with bimaxillary dentoalveolar protrusion which required all four first premolar extractions were included in the study. Nickel Titanium (NiTi) closed coil springs were used for en masse retraction in upper and lower arches with force of 150g per side. Root resorption of all anterior teeth was evaluated using Cone Beam Computed Tomography systems (CBCT) and pulp vitality was checked using cold test after 4 months. The data was entered in Microsoft excel and the Statistical Package for Social Sciences software (SPSS) version 18.5 (SPSS Inc, Chicago) software was used for data entry and statistical analysis. A p-value of less than 0.05 was considered as statistically significant. Results: Total of 11 patients in which 9 were females and 2 males aged between 18-30 years with mean age 19±4.21 year, participated in this trial. LLLT (4 mm) and MOP (4.05 mm) showed similar performance in acceleration of tooth compared to each other. The overall root resorption was more in the experimental groups (LLLT- 2.60 mm, MOP- 2.84 mm) compared to the allotted controls. However, the canine showed less root resorption in both the experimental groups compared to the control. The overall root resorption was similar in both the experimental groups. The canine in LLLT group (0.30 mm) showed less root resorption compared to canine in MOP group (0.59 mm). There was no change in the pulp vitality status in both the experimental groups and the control groups. Conclusion: The overall root resorption in a given quadrant increases with increased rate of tooth movement. The tooth which was subjected to acceleratory orthodontic technique showed less root resorption compared to control. The tooth subjected to LLLT showed less root resorption as compared to the tooth subjected to MOP.

Research of Coil Spring for Refrigeration Linear Compressor

Research of Coil Spring for Refrigeration Linear Compressor

A CBCT assessment of bone density changes after accelerated orthodontic retraction of canine by microosteoperforations.

AIM:The study was conducted to assess the changes in bone density before and after performing accelerated orthodontic maxillary canine retraction by microosteoperforations (MOPs).MATERIALS AND METHODS:Forty patients (120 cone-beam computed tomography [CBCT] images) within the age group of 15 to 25 years undergoing fixed orthodontic treatment with bilateral maxillary first premolar extraction were enrolled in this study. The right and left sides of the maxillary jaw in the same patients were selected as experimental and control sites. To accelerate the tooth movement, MOPs were performed distal to the canine root in the extraction space under local anesthesia with a miniscrew. Thereafter, the maxillary canine retraction was initiated using a NiTi closed coil spring. The CBCT images were taken and evaluated at the following time intervals: 1 week before MOPs(T0);1 week after MOPs(T1);3 weeks after MOPs(T2).RESULTS:A statistically significant reduction in bone density was observed at the center of resistance of canine on the experimental site (after MOPs) at 1 week and 3 weeks (T0-T1 = 0.000,0.115; T1-T2 = 0.0025,0.0117), whereas a statistically non-significant difference was found 1 week before and 3 weeks later in the control group.CONCLUSION:Accelerated orthodontics by MOPscan result in a substantial reduction in bone density during canine retraction, leading to an increase in the tooth movement rate, hence lowering the overall orthodontic treatment time.