bluuebunny/crossref_metadata_2025 huggingface dataset:
A denture swallowed. Case report
Authors: Brunello Demetrio L. , Mandikos Michael N.
Published: May 2009

Swallowing and aspiration of dental foreign objects is often reported in the literature. Swallowing seems to be more common than aspiration, and is observed most often in the elderly. Too often the size and configuration of these objects compounds their impaction and removal. A 67‐year‐old man swallowed a unilateral removable partial denture which became lodged in his mid‐oesophagus. The denture was located by radiographic examination of his chest and removal by a rigid oesophagoscopy was performed under general anaesthetic.
Central calcifying odontogenic cyst. Case report
Authors: Tse K‐M , To E. W. H.
Published: May 2009

A case of central (intraosseous) calcifying odontogenic cyst affecting the mandible is reported. The clinical, radiographic, and histological features are reviewed and discussed.
The provision of orthodontic services by general dental practitioners. 2. Factors influencing variation in service provision
Authors: Lawrence A. J. , Wright F. A. C. , D'Adamo S. P.
Published: May 2009

Previous work has shown that variations exist amongst general dental practitioners in the volume and type of orthodontic services provided, the type of orthodontic appliances used, and the objectives of the orthodontic treatment. The aims of this survey were to identify practitioner characteristics that account for variations in the level of orthodontic services provided and which distinguish providers and non‐providers of orthodontic services. Multiple regression analysis revealed that four practitioner characteristics explained 41 per cent of the variance in the number of orthodontic patients treated. Dentists who treated more orthodontic patients: 1) treated more general practice patients; 2) frequently used multiple sources to keep up to date in orthodontics; 3) perceived their patient base to contain more children; and 4) were likely to have attended a Truitt course. Eleven variables best distinguished providers from non‐providers of orthodontic treatment; 1, 2 and 3 above had the highest correlation with the discriminant function. The Null Hypothesis that selected characteristics of dentists providing orthodontic services were no different from those of dentists not providing orthodontic services was rejected. The provision of orthodontic services was associated with a higher level of continuing orthodontic education as well as treating more general practice patients, especially children.
Cephalometric analysis of Deutero‐Malay Indonesians
Authors: Munandar Susanti , Snow Michael D.
Published: May 2009

A cephalometric study using Downs' analysis was undertaken with lateral cephalometric radiographs for a mixed sample of 50 child, adolescent and young adult Indonesians who presented with Angle Class I occlusions.

Significant differences between this study group and the published results from comparative racial types were found for Downs' angle of convexity, Y‐axis and incisor inclinations, indicating that Indonesians can be differentiated from other races with similar occlusions by using Downs' analysis.
Rehabilitation of the edentulous mandible with osseointegrated dental implants: 10 year follow‐up
Authors: Henry P. J. , Bower R. C. , Wall C. D.
Published: May 2009

Long‐term retrospective studies on the efficacy of implant retained bridgework are relatively few. In this study, 10 year follow‐up results are reported on the rehabilitation of the edentulous mandible with osseointegrated implant anchored bridges. Fifteen patients were closely maintained and monitored using the conventional indices used in longitudinal periodontal research, together with serial intraoral periapical and extraoral panoramic radiographs. The need for prosthetic maintenance and the effects of the treatment on soft tissues, supporting bone, opposing dentition and the behavioural aspects of such rehabilitation are discussed. Based on the reviewed results of the study and numerous other investigations, the treatment of mandibular edentulism with fixed bridges supported by osseointegrated implants ad modum Brånemark is a highly effective method, giving predictable long‐term results.
The gingival crevicular fluid Interleukin‐1β and tumour necrosis factor‐α levels in patients with rapidly progressive periodontitis
Authors: Yavuzyilmaz Ezel , Yamalik Nermin , Bulut Sule , Özen Seza , Ersoy Fügen , Saatpi Ümit
Published: May 2009

Cytokines are believed to play an important role in the pathogenesis of periodontal diseases. In the present study, gingival crevicular fluid (GCF) levels of two important cytokines, interleukin 1‐/3 (IL‐1β) and tumour necrosis factor‐α (TNF‐α) and, in addition, serum IL‐1β levels, were determined in patients with severe and rapid periodontal breakdown by use of ELISA. While IL‐1β was detected in all of the GCF samples studied, TNF‐α could only be detected in about half the samples. The mean GCF IL‐1β level was 38.45 ± 13.99 pg/mL, and the mean TNF‐α level was 3.20 ± 1.39 pg/mL, respectively. The GCF IL‐1β levels also presented a strong positive correlation with the mean pocket depths. Although weak, both of the cytokines also presented correlations with the presence of bleeding on probing. Additionally GCF samples contained increased IL‐1β levels when compared with the serum samples suggesting local production mechanisms. The findings of the present study suggest that these cytokines may be involved in the pathogenesis of periodontal diseases (IL‐1β being more significant), and also may help in defining the active phase of periodontal breakdown.
The Class V lesion — Aetiology and restoration*
Authors: Tyas Martin J.
Published: May 2009

The aetiology of non‐carious cervical lesions is discussed. These have been variously described as ‘abrasion’, ‘erosion’, ‘abrasion/erosion’, and ‘idiopathic cervical’. However, many lesions do not fit the classical appearance or location of an erosive and/or abrasive origin, and there is increasing interest in the possible role of occlusal stress in their aetiology.

Non‐carious cervical lesions often require restoration, and there are essentially three options using tooth‐coloured materials: a restorative glass ionomer cement, a liner/base glass ionomer cement over‐layed with a resin composite, or a resin composite bonded by an enamel/dentine‐adhesive. The materials and techniques used in these options are discussed, indicating their advantages and disadvantages. Results of available clinical trials of these systems are given, and the link with the stress theory of cervical tooth loss is described. The preferred restorative approaches in order are: resin‐modified restorative glass ionomer; resin‐modified liner/base glass ionomer with a microfine resin composite overlay; enamel/dentine bonding agent with a micro‐fine resin composite.
Osseointegrated implants for single tooth replacement in general practice: A 1‐year report from a multicentre prospective study
Authors: Henry P. J. , Rosenberg I. R. , Bills I. G. , Chan R. W. , Cohen A. C. , Halliday K. G. , Kozeniauskas J. A.
Published: May 2009

The single tooth implant is a treatment option for the replacement of missing single teeth and in many cases is the treatment of choice. It is, however, an expensive treatment requiring a co‐ordinated approach to the surgical and restorative aspects of treatment. In this study, a group of dentists in general and restorative dental practice and with no previous experience in implant surgery underwent an intensive training course in all aspects of implant treatment for single teeth. Using a system of simplified instrumentation with a strict adherence to protocol, the group installed and restored single tooth implants ad modum Brånemark in a wide range of clinical situations. At the one year follow‐up period following crown insertion, the success rate of treatment compared favourably with results reported from centres using the specialist team approach to treatment. The results of this study indicate that further consideration should be given to the training of general dentists so that improved delivery of dental health care can be provided at a more economic level.
The use of autoclaves in the dental surgery
Authors: Savage N. W. , Walsh L. J.
Published: May 2009

Autoclaving is the absolute method of achieving instrument sterilization in any health care setting. However, it does rely on an effective pre‐sterilization routine for instrument handling and the subsequent correct loading and operation of the autoclave. This paper addresses the issue of correct autoclave use, the causes of failures and the regular monitoring.
Anterior crossbite correction in uncooperative or disabled children. Case reports
Authors: Olsen Christopher B.
Published: May 2009

Abstract— Uncooperative or disabled children who present with an anterior crossbite provide the clinician with a challenge to use innovative strategies to attempt crossbite correction. The following case reports provide possible treatment strategies as well as showing some pitfalls in both diagnosis and treatment of anterior crossbites in this difficult to treat group of patients.
The stability of facial osteotomies. Part 6. Chin setback
Authors: Hoffman Gary R. , Moloney Francis B.
Published: May 2009

Isolated horizontal osteotomy of the anterior mandible (genioplasty) to move the chin posteriorly can be used to improve facial profile. There has been an increasing tendency in practice to carry out this procedure in combination with maxillary and/or mandibular surgery. This is most appropriately undertaken when pre‐operative prediction techniques indicate that chin prominence will remain excessive following maxillary and/or mandibular advancement surgery.

This paper reviews surgical techniques applicable to posterior movement of the chin (‘the setback genioplasty’) and illustrates the clinical results achieved with its use.
A re‐evaluation of the importance of disc position in temporomandibular disorders
Authors: Dolwick M. Franklin , Dimitroulis George
Published: May 2009

During the 1970s there was a resurgence of interest in disc displacement as being central to the pathology of internal derangement. Since then it has been proposed that a displaced disc can result in pain, mandibular dysfunction, degenerative joint disease and mandibular growth disturbances. Two decades later, and with the introduction of sophisticated investigations and treatment modalities, doubts have emerged as to true pathological significance of disc position. Evidence derived from clinical observations, autopsy material, imaging studies and surgical findings has failed to establish strong support for the central role of disc displacement in internal derangement of the temporomandibular joint.
A preliminary study of the effects of laser radiation on collagen metabolism in cell culture
Authors: Skinner S. M. , Gage J. P. , Wilce P. A. , Shaw R. M.
Published: May 2009

A low power Ga‐As pulse laser was used to stimulate cultured human embryonic fibroblast cells. Energy fluencies varied from 0–1 J/cm2 over a period of 1–4 days. Fibroblast procollagen production was monitored by the synthesis of [3H] hydroxy‐proline, and DNA replication was assessed by [3H] thymidine incorporation. Following laser treatment, controlled pepsin digestion measured the increase in cell biostimulation. Maximum increase in collagen production and cell biostimulation occurred after 4 episodes of laser treatment at 24‐hour intervals. Laser doses between 0.099 and 0.522 J/cm2 had the most significant stimulatory effects on fibroblast function. Clinical efficacy of the low power Ga‐As pulse laser may be related to enhanced connective tissue repair.
The alterations of whole saliva constituents in patients with diabetes mellitus
Authors: Yavuzyilmaz Ezel , Yumak Ömür , Akdoǧanli Tuncay , Yamalik Nermin , Özer Nazmi , Ersoy Fügen , Yeniay İhsan
Published: May 2009

The present study was undertaken in order to determine the possible alterations in whole saliva and the periodontal status in patients with diabetes mellitus (DM), and was conducted on 17 patients with DM and 17 systemically and periodontally healthy subjects. When the subjects were evaluated clinically, significantly increased probing depths were noticed in the DM group when compared with the healthy subjects. In whole saliva samples, sodium, potassium, total protein, amylase, thiocyanate, and secretory IgA levels were determined in both groups. Difference between the two groups regarding the mean salivary potassium levels were found to be statistically significant since the mean salivary potassium levels in the DM and the control groups were 2.470±9.04 mmol/L and 14.30±3.88 mmol/L, respectively. The mean salivary total protein, amylase and secretory IgA levels in the DM group were 2.41±1.0 mg/mL, 124.2±79.7 U/mL and 6.86±3.50 mg/L, all being significantly higher than the control group. However, no significant differences could be shown for the salivary sodium and thiocyanate levels. Nor was there any difference between non‐insulin dependent diabetes mellitus (NIDDM) and insulin‐dependent diabetes mellitus (IDDM). The findings of the present study suggest that, besides the clinical examinations, the determination of the possible alterations in the composition of whole saliva might also be helpful in understanding the increased severity of periodontal disease in diabetic patients.
Dentistry on the couch
Authors: Joffe Hugh
Published: May 2009

This article outlines some of the occupational stresses in dental practice. In a profession which combines skilful precision with aesthetics many dentists are vulnerable to stress ‐ yet most practitioners minimize or deny the suggestion that they face ‘bum‐out’. Regular seminars on pressures pertaining to dental practice would provide support to practitioners (at risk).
Gingival enlargement as a diagnostic indicator in leukaemia. Case report
Authors: Anil S. , Smaranayake Lakshman P. , Nair Raj G. , Beena V. T.
Published: May 2009

The acute leukaemias are a group of neoplastic diseases that are characterized by proliferation of immature white cells in the bone marrow and/or blood and are often associated with severe leukopenia, anaemia and thrombocytopenia. Oral manifestations are more common in patients with acute leukaemia. Oral bleeding, gingival enlargement, ulceration and infection in patients with leukaemia have been described. Leukaemic infiltrates in the gingivae are commonly seen in acute monocytic leukaemia. A case of acute monocytic leukaemia in a 34‐year‐old female who reported with gingival enlargement is presented here. The role of oral lesions as a diagnostic indicator is discussed.
Benign cementoblastoma. Case report
Authors: Mogi Kenji , Belal Essam , Kano Akio , Otake Katsuya
Published: May 2009

Benign cementoblastoma is a rare benign odontogenic tumour of mesenchymal origin. A case of a 24‐year‐old man with benign cementoblastoma is presented. The lesion manifested as a round, radiopaque mass attached to the root of the left first molar of the mandible. The tooth was extracted and the lesion was removed. A diagnosis of benign cementoblastoma was made microscopically. There has been no evidence of recurrence during the three‐year follow‐up period. A review of the literature and a discussion of the histologic feature of this case are included.
The stability of facial osteotomies. Part 5. Maxillary advancement with miniplate and screw fixation
Authors: Hoffman Gary R. , Moloney Frank B.
Published: May 2009

Surgical repositioning of the dento‐skeletal components of the middle‐third of the face, combined with appropriate orthodontic treatment, can be used to improve function and aesthetics. However, the attainment of three‐dimensional stability following corrective jaw surgery continues to be a major problem in the postsurgical period.

This paper examines the short‐term (six weeks postoperative) and long‐term (12 months postoperative) horizontal skeletal stability of Le Fort I maxillary advancement in 15 patients. The mean horizontal advancement of the maxilla was 8.76 ± 0.99 mm. Six weeks later, a mean relapse of 0.22 ± 0.19 mm was identified. The mean relapse at long‐term follow‐up was 0.61 ± 0.26 mm (6.96%).

These results indicate that rigid miniplate and screw fixation of Le Fort I osteotomy undertaken to correct horizontal mid‐dentofacial deficiency is both statistically and surgically predictable and stable when reviewed up to twelve months after surgery.
A laboratory study of dimensional changes for three elastomeric impression materials using custom and stock trays
Authors: Boulton Justin L. , Gage John P. , Vincent Peter F. , Basford Kaye E.
Published: May 2009

Clinical success of fixed prosthodontic procedures is dependent in part upon the dimensional accuracy of elastomeric impression materials and impression procedures. Three elastomeric impression materials were used in custom and stock trays to determine the accuracy of impressions taken from an experimental stainless steel model representing premolar and molar bridge abutment preparations. Horizontal and vertical individual abutment and interabutment dimensions were measured on die stone replicas, and the measurements compared with those obtained from stainless steel master models. The results of this study demonstrate polysulphide is the least accurate impression material for both vertical and horizontal individual abutment dimensions. However, for interabutment horizontal dimensions, no statistical differences were noted between impression material types when using a custom tray. Stock trays produced unreliable results for all the materials tested.
Active Vibration Control With Modified Positive Position Feedback
Authors: Mahmoodi S. Nima , Ahmadian Mehdi
Published: May 2009

A novel active vibration control technique based on positive position feedback method is developed. This method, which is a modified version of positive position feedback, employs a first-order compensator that provides damping control and a second-order compensator for vibration suppression. In contrast, conventional positive position feedback uses a single second-order compensator. The technique is useful for strain-based sensors and can be applied to piezoelectrically controlled systems. After introducing the concept of modified positive position feedback, this paper investigates the stability of the new method for locating gain limits. Stability conditions are global and independent of the dynamical characteristics of the open-loop system. Using root locus plots, proper compensator frequency is identified and damping of the closed-loop system is studied. The performance of the modified positive position feedback for both steady-state and transient dynamic control is studied. The experimental and numerical results show that the proposed method is significantly more effective in controlling steady-state response and slightly advantageous for transient dynamics control, as compared with conventional positive position feedback.
Topology Synthesis of Extrusion-Based Nonlinear Transient Designs
Authors: Patel Neal M. , Penninger Charles L. , Renaud John E.
Published: May 2009

Many practical structural designs require that the structure is easily manufactured. Design concepts synthesized using conventional topology optimization methods are typically not easily manufactured, in that multiple finishing processes are required to construct the component. A manufacturing technique that requires only minimal effort is extrusion. Extrusion is a manufacturing process used to create objects of a fixed cross-sectional profile. The result of using this process is lower costs for the manufacture of the final product. In this paper, a hybrid cellular automaton algorithm is developed to synthesize constant cross section structures that are subjected to nonlinear transient loading. The novelty of the proposed method is the ability to generate constant cross section topologies for plastic-dynamic problems since the issue of complex gradients can be avoided. This methodology is applied to extrusions with a curved sweep along the direction of extrusion as well. Three-dimensional examples are presented to demonstrate the efficiency of the proposed methodology in synthesizing these structures. Both static and dynamic loading cases are studied.
Integrated Product and Process Design for a Flapping Wing Drive Mechanism
Authors: Bejgerowski Wojciech , Ananthanarayanan Arvind , Mueller Dominik , Gupta Satyandra K.
Published: May 2009

Successful realization of a flapping wing micro-air vehicle (MAV) requires development of a light weight drive mechanism that can convert the continuous rotary motion of the motor into oscillatory flapping motion of the wings. The drive mechanism should have low weight to maximize the payload and battery capacity. It should also have high power transmission efficiency to maximize the operational range and to minimize weight of the motor. In order to make flapping wing MAVs attractive in search, rescue, and recovery efforts, they should be disposable from the cost point of view. Injection molded compliant drive mechanisms are an attractive design option because of manufacturing scalability and reduction in the number of parts. However, realizing compliant drive mechanism using injection molding requires use of multipiece multigate molds. Molding process constraints need to be considered during the design stage to successfully realize the drive mechanism. This paper describes an approach for determining the drive mechanism shape and size that meets both the design and molding requirements. The novel aspects of this work include (1) minimizing the number of mold pieces and (2) the use of sacrificial shape elements to reduce the impact of the weld-lines on the structural performance. The design generated by the approach described in this paper was utilized to realize an operational flapping wing MAV.
Quantifying Aesthetic Form Preference in a Utility Function
Authors: Orsborn Seth , Cagan Jonathan , Boatwright Peter
Published: May 2009

One of the greatest challenges in product development is creating a form that is aesthetically attractive to an intended market audience. Market research tools, such as consumer surveys, are well established for functional product features, but aesthetic preferences are as varied as the people that respond to them. Additionally, and possibly even more challenging, user feedback requires objective measurement and quantification of aesthetics and aesthetic preference. The common methods for quantifying aesthetics present respondents with metric scales over dimensions with abstract semantic labels like “strong” and “sexy.” Even if researchers choose the correct semantics to test, and even if respondents accurately record their responses on these semantic scales, the results on the semantic scales must be translated back into a product shape, where the designer must take the consumers’ numerical scores for a set of semantics and translate that into a form which consumers will find desirable. This translation presents a potential gap in understanding between the supply and demand sides of the marketplace. This gap between designer and user can be closed through objective methods to understand and quantify aesthetic preferences because the designer would have concrete directions to use as a foundation for development of the product form. Additionally, the quantification of aesthetic preference could be used by the designer as evidence to support certain product forms when engineering and manufacturing decisions are made that might adversely affect the aesthetics of the product form. This paper demonstrates how the qualitative attribute, form, cannot only be represented quantitatively, but also how customer preferences can be estimated as utility functions over the aesthetic space, so that new higher utility product forms can be proposed and explored. To do so, the form is summarized with underlying latent form characteristics, and these underlying characteristics are specified to be attributes in a utility function. Consumer surveys, created using design of experiments, are then used to capture an individual’s preference for the indicated attributes and thus the form. Once preference is summarized in the utility function, the utility function can be used as the basis for form generation and modification or design verification.
Analysis of General Characteristics of Transmission Error of Gears With Convex Modification of Tooth Flank Form Considering Elastic Deformation Under Load
Authors: Mohamad Edzrol Niza , Komori Masaharu , Murakami Hiroaki , Kubo Aizoh , Fang Suping
Published: May 2009

The vibration/noise of power transmission gears is a serious problem for vehicles including automobiles, and therefore many studies on gear vibration have been reported. These studies, however, were carried out by investigation using numerical simulations in which gears with specific dimensions and tooth flank modifications under specific loading were considered. Therefore, the general characteristics of the transmission error of gears have not been clarified theoretically. In this report, a general model for the tooth meshing of gears is proposed; in which a quasi-infinite elastic model composed of springs with stiffness peculiar to the gear is incorporated. The transmission error of gears is formulated by theoretical equations. An investigation on the factors affecting the general characteristics of transmission error is accomplished using the formulated equations. The qualitative characteristic of the transmission error of gears with convex tooth flank form deviation is determined by the actual contact ratio and qualitative elements of gears, i.e., tooth flank form deviation and the distribution of stiffness. Even if the amplitude of torque, the amount of tooth flank form deviation, and other quantitative elements are not determined, the qualitative characteristic of transmission error can be derived. The peak-to-peak value of transmission error increases proportionately to the amount of tooth flank form deviation.
Automotive Thermostat Valve Configurations: Enhanced Warm-Up Performance
Authors: Mitchell T. , Salah M. , Wagner J. , Dawson D.
Published: May 2009

The automotive cooling system has unrealized potential to improve internal combustion engine performance through enhanced coolant temperature control and reduced parasitic losses. Advanced automotive thermal management systems use controllable actuators (e.g., smart thermostat valve, variable speed water pump, and electric radiator fan) that must work in harmony to control engine temperature. One important area of cooling system operation is warm-up, during which fluid flow is regulated between the bypass and radiator loops. A fundamental question arises regarding the usefulness of the common thermostat valve. In this paper, four different thermostat configurations were analyzed, with accompanying linear and nonlinear control algorithms, to investigate warm-up behaviors and thermostat valve operations. The configurations considered include factory, two-way valve, three-way valve, and no valve. Representative experimental testing was conducted on a steam-based thermal bench to examine the effectiveness of each valve configuration in the engine cooling system. The results clearly demonstrate that the three-way valve has the best performance as noted by the excellent warm-up time, temperature tracking, and cooling system power consumption.
Steady-State Biodiesel Blend Estimation via a Wideband Oxygen Sensor
Authors: Snyder David B. , Adi Gayatri H. , Bunce Michael P. , Satkoski Christopher A. , Shaver Gregory M.
Published: May 2009

A substantial opportunity exists to reduce carbon dioxide (CO2) emissions, as well as dependence on foreign oil, by developing strategies to cleanly and efficiently use biodiesel, a renewable domestically available alternative diesel fuel. However, biodiesel utilization presents several challenges, including decreased fuel energy density and increased emissions of smog-generating nitrogen oxides (NOx). These negative aspects can likely be mitigated via closed-loop combustion control provided the properties of the fuel blend can be estimated accurately, on-vehicle, in real-time. To this end, this paper presents a method to practically estimate the biodiesel content of fuel being used in a diesel engine during steady-state operation. The simple generalizable physically motivated estimation strategy presented utilizes information from a wideband oxygen sensor in the engine’s exhaust stream, coupled with knowledge of the air-fuel ratio, to estimate the biodiesel content of the fuel. Experimental validation was performed on a 2007 Cummins 6.7 l ISB series engine. Four fuel blends (0%, 20%, 50%, and 100% biodiesel) were tested at a wide variety of torque-speed conditions. The estimation strategy correctly estimated the biodiesel content of the four fuel blends to within 4.2% of the true biodiesel content. Blends of 0%, 20%, 50%, and 100% were estimated to be 2.5%, 17.1%, 54.2%, and 96.8%, respectively. The results indicate that the estimation strategy presented is capable of accurately estimating the biodiesel content in a diesel engine during steady-state engine operation. This method offers a practical alternative to in-the-fuel type sensors because wideband oxygen sensors are already in widespread production and are in place on some modern diesel vehicles today.
Linear Estimation of the Rigid-Body Acceleration Field From Point-Acceleration Measurements
Authors: Cardou Philippe , Angeles Jorge
Published: May 2009

Among other applications, accelerometer arrays have been used extensively in crashworthiness to measure the acceleration field of the head of a dummy subjected to impact. As it turns out, most accelerometer arrays proposed in the literature were analyzed on a case-by-case basis, often not knowing what components of the rigid-body acceleration field the sensor allows to estimate. We introduce a general model of accelerometer behavior, which encompasses the features of all acclerometer arrays proposed in the literature, with the purpose of determining their scope and limitations. The model proposed leads to a classification of accelerometer arrays into three types: point-determined; tangentially determined; and radially determined. The conditions that define each type are established, then applied to the three types drawn from the literature. The model proposed lends itself to a symbolic manipulation, which can be readily automated, with the purpose of providing an evaluation tool for any acceleration array, which should be invaluable at the development stage, especially when a rich set of variants is proposed.
Modeling of a Cartwheel Flexural Pivot
Authors: Shusheng Bi , Hongzhe Zhao , Jingjun Yu
Published: May 2009

A cartwheel flexural pivot has a small center shift as a function of loading and ease of manufacturing. This paper addresses an accurate model that includes the loading cases of a bending moment combined with both a horizontal force and a vertical force. First, a triangle flexural pivot is modeled as a single beam. Then, the model of cartwheel flexural pivot based on an equivalent model is developed by utilizing the results of the triangle pivot. The expressions for rotational displacement and center shift are derived to evaluate the primary motion and the parasitic motion; the maximum rotational angle is simply formulated to predicate the range of motion. Finally, the model is verified by finite element analysis. The relative error of the primary motion is less than 1.1% for various loading cases even if the rotational angle reaches ±20 deg, and the predicted errors for the two center shift components are less than 15.4% and 7.1%. The result shows that the model is accurate enough for designers to use for initial parametric design studies, such as for conceptual design.
Kinematic and Dynamic Analyses of Tripod Sliding Universal Joints
Authors: Wang X. F. , Chang D. G.
Published: May 2009

The kinematic and dynamic equations of the tripod sliding universal joint were established in order to understand the kinematic and dynamic properties thereof, and then the effects of the joint angle, the rotating radius of the slide rods, the length of the output shaft on the fluctuation of the joint angle, the output angle error, and the relative displacements of the slide rods were investigated. Meanwhile, the main dynamic curves were also obtained. In this work, each obtained curve is basically similar to a sinusoid. The joint angle, the output angle error, the forces or torques of two bearings of the input and output shafts as well as the load torque have a threefold frequency. The relative displacement of the slide rod to the tripod has a twofold frequency. The relative displacement of the slide rod to the hole of the input shaft and each component force acting on the tripod arms and holes of the input shaft have a simple frequency. The fluctuation amplitudes of the joint angle and relative displacements of the slide rods as well as the output angle error increase with the increase of the joint angle or the rotating radius of the slide rod. Increasing length of the output shaft decreases the fluctuation amplitudes of the joint angle and output angle error. However, the relative displacements of the slide rods hardly depend on this length.
A Systematic Model for Dynamics and Control of Dual Clutch Transmissions
Authors: Liu Yonggang , Qin Datong , Jiang Hong , Zhang Yi
Published: May 2009

This paper focuses on the dynamic modeling and analysis of dry dual clutch transmissions (DCTs) during vehicle launch and shifts. The system model incorporates the clutch torque control strategies for DCT vehicle launch and shifts. This model is capable of quantitatively analyzing and predicting dual clutch transmission dynamic characteristics and performance metrics, such as launch response and shift patterns, thus providing an analytical tool for DCT torque control and calibration. The model is applied for a test vehicle equipped with a dry dual clutch transmission. The simulation data on vehicle launch and shift dynamic characteristics are highly agreeable to the data obtained on the test vehicle.
Simulations of Dynamic Braking of Railroad Vehicles Using Trajectory Coordinates
Authors: Mellace Claudio , Gugliotta Antonio , Sinokrot Tariq , Shabana Ahmed A.
Published: May 2009

One of the important issues associated with the use of the trajectory coordinates in railroad vehicle simulations is the ability of such coordinates in dealing with braking and traction scenarios. In existing specialized railroad computer algorithms, the trajectory coordinates instead of the absolute Cartesian coordinates are often used. In these algorithms, track coordinate systems that travel with constant speeds are employed to define the configuration of the components in railroad vehicle systems. As the result of using a prescribed motion for these track coordinate systems, the simulation of braking and/or traction scenarios becomes difficult or even impossible, as reported in recent investigations [2]. The assumption of the prescribed motion of the track coordinate systems can be relaxed, thereby allowing the trajectory coordinate systems to be effectively used in modeling braking and traction scenarios. It is the objective of this investigation to demonstrate that by using track coordinate systems that can have an arbitrary motion, the trajectory coordinates can be used as the basis for developing computer algorithms for modeling braking and traction scenarios. To this end, a set of six generalized trajectory coordinates is used to define the configuration of each rigid body in the railroad vehicle system. This set of coordinates consists of one absolute coordinate, which is an arc length that represents the distance traveled by the body, and five relative coordinates. The arc length parameter defines the location of the origin and the orientation of a track coordinate system that follows the motion of the body. The other five relative coordinates are two translations that define the position of the origin of body coordinate system with respect to the track coordinate system in directions lateral and normal to the track, and three Euler angles that define the orientation of the body coordinate system with respect to its track coordinate system. The independent state equations of motion associated with the trajectory coordinates are identified and integrated forward in time in order to determine the trajectory coordinates and velocities. The results obtained in this study show that when the track coordinates systems are allowed to have an arbitrary motion, the resulting set of trajectory coordinates can be used effectively in the study of braking and traction conditions. The numerical examples presented in this paper include two different vehicle models subjected to several braking conditions. The results obtained are compared with the results obtained using the absolute Cartesian coordinate based formulations which allow modeling braking and traction scenarios.
New Approach to the Local Synthesis of Spiral Bevel Gears
Authors: Akimov Vasiliy V. , Lagutin Sergey A. , Volkov Andrey E.
Published: May 2009

The generating of two spiral bevel gears by the plane-top generating wheel with essentially different parameters of the head-cutter installation and motion is considered. For this case the necessary and sufficient conditions providing coincidence of normal vectors and surface curvatures in the designed point are presented as the vector equations system. The relations among blade pressure angle, head-cutter radius, radial distance, tool installation angle, machine centre to back, blank offset and velocity ratio are obtained. The developed methods make the opportunity to design equivalent machine-tool settings, to extend manufacturing possibilities of gear-cutting machines and to raise the load rating of the gear drive.
Dynamics of Hypoid Gears With Emphasis on Effect of Shaft Rotation on Vibratory Response
Authors: Peng Tao , Lim Teik C.
Published: May 2009

The effect of large displacement rotational motion of the shafting system on the higher frequency, small displacement vibratory motion primarily excited by gear transmission error and variation of gear mesh stiffness is examined in this paper. Traditional hypoid gear dynamic analysis based on a pure vibration model assumes that the system perturbs about its mean position without coupling to the large displacement rotational motion. To improve on this approach and understanding of the influences of the dynamic interaction, a coupled multi-body dynamic and vibration simulation of the hypoid geared rotor system is performed. In the proposed formulation, a multi-degrees-of-freedom, multi-body hypoid geared rotor system dynamic model is developed to calculate the combined motion of the large displacement rotation of the shaft and small vibratory motion of the gear pair. The formulation may be generalized to other forms of gearing because hypoid gears have more complicated geometry and time-varying mesh characteristics when compared to parallel axis gears. Numerical simulation results are compared to those derived from the classical analytical method that only considers pure vibration effect. The proposed theory also provides new approaches to investigate both steady-state and transient geared rotor system dynamics.
Effect of Preshaved Form and Cutter Performance in Plunge Cut Shaving
Authors: Nakada Shimpei , Moriwaki Ichiro
Published: May 2009

The present paper describes a new method of simulation program for plunge cut gear shaving. The developed program estimates the shaved form as follows. First is generation of tooth flanks of the work gear and the shaving cutter from gear data. Second is estimation of initial mismatches between tooth flanks of the work gear and the shaving cutter as depth of cut. Third is calculation of stock removal of work tooth flanks from the depth of cut. The program can simulate in consideration of an effect of preshaved form and the cutter tooth form modification. In addition, the program can simulate in consideration of an effect of cutter performance. The cutter performance has been evaluated from slide velocity between the tooth flanks of the work gear and the shaving cutter. The effect of accuracy of preshaved form and cutter performance on the shaved form was investigated using the developed program. As a result, requirement of accuracy of preshaved form and cutter performance are proposed.
Mathematical Model for Parametric Tooth Surface of Cylindrical Gears Based on Kinematic Synthesis
Authors: Garci´a-Masia´ Carlos , Morillas-A´lvarez Juan D.
Published: May 2009

A generalized approach for parametrizing conjugate tooth surfaces in cylindrical gears is presented in this work. Developed are the polynomials expressions to define the tooth surfaces of pinion and gear based on kinematics synthesis for planar gears. The polynomials expressions incorporate the motion generation (points or positions of precision) and function of transmission errors. It is interesting to note that if the desired pressure angle for the tooth profile is constant, the output polynomial of profile becomes a conventional involute. Polynomials expressions are given for the profile modifications necessary to compensate for any specified or anticipated errors of assembly and/or manufacturing. In addition property of rack as the limits of zone active, transverse contact ratio and contact asymmetry ratio are analysed.
Observation of Fatigue Damage to Gear Tooth Using Image Processing
Authors: Masuyama Tomoya , Ikeda Takuya , Yoshiizumi Satoshi , Inoue Katsumi
Published: May 2009

The detection of damage in early stage of fatigue is important for a reliable evaluation of gear life and strength. From this point of view, the variation of strain distribution in a tooth due to cyclic load contains useful information because the fatigue crack will initiate as a result of the accumulation of plastic strain. Meanwhile, digital image equipments are widely used in our life and the performance is in progress. We took digital pictures of cyclic loaded tooth by the digital camera and compared with the picture of no load to find displacement. The strain distribution of tooth is calculated by the correlation method using those pictures. The initiation of a micro crack is observed by the method. It is also confirmed by the detection of acoustic emission wave with higher energy. The variation of stress-strain diagram in fatigue process is presented, and this illustrates the increase of strain in the final stage of fatigue.
Expansion of Ratio Range of Shaft Drive CVT by Using Zero-Spin Disk
Authors: Narita Yukihito , Yamanaka Masashi , Inoue Katsumi
Published: May 2009

The novel mechanism CVT (Shaft Drive CVT, S-CVT) was developed by the authors. It transmits power by a traction drive same as the half toroidal CVT. S-CVT has parallel input/output shafts with conical or concave disks and the idler shaft having conical rollers at both ends, which is placed perpendicularly to the input/output shafts. All disks and rollers can move along each axis directions, and these movements produce the ratio changing by the changes of the rotational radii. The efficiency is the key evaluation function of CVT. To improve the efficiency, the backup roller mechanism was devised. Its effectiveness was confirmed by the experiment, and the efficiency of 95% was obtained by modified prototype S-CVT. This paper deals with the expansion of ratio range of S-CVT. In case of using the present disks, S-CVT has a difficulty to expand the narrow ratio range of 4 (0.5 to 2) because of the large slip brought by the spin. To expand the ratio range, the zero-spin disk/roller was devised. The shape of zero-spin disk/roller satisfies the condition that the spin does not occur at any speed ratio. According to the calculation, the slip rate becomes less than 1% at any speed ratio. To confirm the effectiveness, the prototype S-CVT with zero-spin disk was manufactured. It has the ratio range of 0.43 to 2.35. To obtain the slip rate the experiments were carried out at the speed ratio of 0.43, 1 and 2.35. At each speed ratio, the slip rate of less than 1% was obtained, and the effect of the zerospin disk was confirmed.
Analytical and Numerical Dynamic Analysis of Gears in the Presence of Engine Acyclism
Authors: Sika G. , Velex P.
Published: May 2009

A one degree of freedom model is set up which incorporates time-varying mesh stiffness functions and the influence of unsteady input rotations due to engine acyclism. In order to investigate spur and helical gears, a piecewise and a sine function are used to simulate mesh stiffness fluctuations. Contact conditions are considered in order to deal with contact losses and back strikes, i.e., when contacts occur on the back flanks of the teeth. The dynamic response is determined by combining several analytical and numerical techniques. It is shown that acyclism modulations can generate additional response peaks on either side of the main resonance area. This is due to frequency and amplitude modulations between the mesh excitations and the harmonics of the engine rotational speed. The analytical results compare particularly well with those delivered by a time-step numerical integration by Newmark’s method with controlled variable time-step coupled with a contact algorithm. This excellent agreement shows that Newmark’s method can be extended to the dynamic simulation of geared drives with unsteady rotational speeds provided that time-steps are carefully calibrated and readjusted. Finally, the influence of gear geometry (module, tooth number, speed ratio) along with the acyclism parameters (frequencies, amplitudes) is studied and some general trends are presented concerning the resulting dynamic tooth loads.
Virtual Clutch Development Model
Authors: Lundquist Lina J. , Eberle Franz , Mohlin Mikael B. , Sponsel Rainer
Published: May 2009

In a world of constant development and where competition grows stronger for every minute, there is a need to work smart to stay on the market. Product development in the automotive business is not an exception. It is though not enough to adapt new technology and new ideas, one has to apply it to the organization in the smartest way to be able to achieve one of the most wanted goals; shortened lead-time in combination with improved product quality. As well known, virtual prototyping is a mean to achieve the above stated goal. This paper describes how this method has been the basis for a new product development approach in the clutch system area in an automotive company. The new virtual development approach is enabled by creation of the Virtual Clutch Development Model (VCDM). The main benefit of the simulation model is that several clutch performance phenomena can easily be investigated at once to get an overview of the performance of the clutch system, this in an early phase of the development process. This will facilitate trade off decisions and avoid suboptimization and thus shorten lead-times and improve product quality.
Numerical and Experimental Study of Loaded Transmission Error of Worm Gear With a Plastic Wheel
Authors: de Vaujany Jean-Pierre , Guingand Miche`le , Remond Didier
Published: May 2009

Nowadays, the wheels of worm gears with a low module can be made of plastic, thus classical modeling can no longer be used satisfactorily. The present paper describes an original method for studying the quasi-static loaded behavior of a worm gear, with a steel worm and a nylon wheel. A generalized Kelvin model is proposed and the computation of load sharing is described by using an equation of displacement compatibility. The history of previous deformation and the effect of the nylon’s structural damping are also taken into account. Experimental measurements of the Loaded Transmission Error are performed with the help of optical encoders rigidly connected to the worm and gear shafts, giving access to their instantaneous angular positions. The numerical simulations fit quite well with the experimental results.