Victor H. Mucino

Three-dimensional modeling and finite element analysis in treatment planning for orthodontic tooth movement

INTRODUCTION The objective of this study was to demonstrate the potential of 3-dimensional modeling and finite element analysis as clinical tools in treatment planning for orthodontic tooth movement. High stresses in bone and miniscrew implants under load can cause fractures and trauma for orthodontic patients, and treatments are typically planned by using clinical experience or simple 2-dimensional radiographs. METHODS Anatomically accurate 3-dimensional models reconstructed from cone-beam computed tomography scans were used to simulate the retraction of a single-rooted mandibular canine with a miniscrew placed as skeletal anchorage. Detailed stress distributions in the implant and peri-implant bone were found, in addition to the effect of the orthodontic bracket hook length and the angulation of retraction force on stress response in the periodontal ligament (PDL). RESULTS The numeric results showed that the equivalent von Mises stress on the miniscrew under a 200-cN tangential load reached 42 MPa at the first thread recession, whereas von Mises stress in the peri-implant bone only reached 11 MPa below the neck. High tightening loads of 200 N·mm of torsion and 460 cN of axial compression resulted in much greater bone and implant von Mises stresses than tangential loading, exceeding the yield strengths of the titanium alloy and the cortical bone. Increasing the hook length on the orthodontic bracket effectively reduced the canine PDL stress from 80 kPa with no hook to 22 kPa with a hook 7 mm long. Angulating the force apically downward from 0° to 30° had a less significant effect on the PDL stress profile and initial canine deflection. The results suggest that stresses on miniscrew implants under load are sensitive to changes in diameter. Overtightening a miniscrew after placement might be a more likely cause of fracture failure and bone trauma than application of tangential orthodontic force. The reduction of stress along the PDL as a result of increasing the bracket hook length might account for steadier tooth translation by force application closer to the center of resistance of a single-rooted canine. The relatively minor effect of force angulation on the PDL response suggests that the vertical placement of miniscrews in keratinized or nonkeratinized tissue might not significantly affect orthodontic tooth movement. CONCLUSIONS This model can be adapted as a patient-specific clinical orthodontic tool for planning movement of 1 tooth or several teeth.

Thermo-Mechanical Modeling of Friction Stir Spot Welding (FSSW) Process: Use of an Explicit Adaptive Meshing Scheme

This paper presents on-going finite element modeling efforts of friction stir spot welding (FSSW) process by an explicit finite element code. Adaptive meshing and advection schemes, which makes it possible to maintain mesh quality under large deformations, is utilized to simulate the material flow and temperature distribution in FSSW process. The predicted overall deformation shape of the weld joint resembles that experimentally observed. Temperature and stress graphs in the radial direction as well as temperature-deformation distribution plots are presented. However, refinements of several modeling aspects are needed for more realistic prediction of the FSSW process.

Energy Generation during Friction Stir Spot Welding (FSSW) of Al 6061-T6 Plates

Effective and reliable computational models would greatly enhance the study of energy dissipation during the friction stir spot welding (FSSW) process. Approaches for the computational modeling of the FSSW process, however, are still under development, and much work is still needed, particularly the application of explicit finite element (FE) codes for a verifiable simulation. The objectives of this work are to develop an FE modeling of FSSW of 6061-T6 aluminum alloy and analyze energy generation during the welding process. In this work, a three dimensional (3-D) FE coupled thermal-stress model of FSSW process has been developed in Abaqus/Explicit code. Rate dependent Johnson–Cook material model is used for elastic–plastic work deformations. Temperature profile and energy dissipation history of the FE model have been analyzed. The peak temperature at the tip of the pin and frictional dissipation energy are in close agreement with the experimental work done by Gerlich et al. [1], which is about 5.1% different.

Lateral sloshing in partially filled elliptical tanker trucks using a trammel pendulum

Fluid sloshing in partially filled tanker trucks is the problem herein being addressed. In these vehicles, lateral fluid sloshing during turning and sudden lane change manoeuvres is the main cause for low rollover threshold. Fluid models and equivalent mechanical spring-bob and pendulums models have been used to simulate the lateral fluid sloshing in various tank shapes. A novel idea of an elliptical trammel pendulum for elliptical tank geometries is proposed. The bases of selecting the parameters of this pendulum such as pendulum mass, length of arms, and location of fixed mass are derived and verified using a finite element approach.

A review of parameter estimators and controllers for induction motors based on artificial neural networks

Induction motors (IMs) are the most used electromechanic machines in industrial applications. Their control has become the subject of many studies since the 70s, and there have been several approaches to achieve high-performance adjustable speed drivers (ASDs). The review presented in this article can support the state of some related researches, since it deals with current state-of-the-art of Artificial Neural Networks (ANNs) oriented to experiments that perform motion control with induction motors. It summarizes many previous works focused on IM and can help the reader to have a starting point to begin their own research on choosing a correct type of Neural Network (NN). The paper provides a list of ANNs used to improve the ASD-control, extending the IM-driver life and achieving proper motor operation, their size and performance. A good match between IM parameter values and the data that the controller needs for the induction machine is imperative. Artificial Intelligence (AI) is a helpful tool to achieve this. The summary will also present an overview of different ANN-based drive approaches.

Finite element modeling of ROPS in static testing and rear overturns.

Even with the technological advances of the last several decades, agricultural production remains one of the most hazardous occupations in the United States. Death due to tractor rollover is a prime contributor to this hazard. Standards for rollover protective structures (ROPS) performance and certification have been developed by groups such as the Society of Automotive Engineers (SAE) and the American Society of Agricultural Engineers (ASAE) to combat these problems. The current ROPS certification standard, SAE J2194, requires either a dynamic or static testing sequence or both. Although some ROPS manufacturers perform both the dynamic and static phases of SAE J2194 testing, it is possible for a ROPS to be certified for field operation using static testing alone. This research compared ROPS deformation response from a simulated SAE J2194 static loading sequence to ROPS deformation response as a result of a simulated rearward tractor rollover. Finite element analysis techniques for plastic deformation were used to simulate both the static and dynamic rear rollover scenarios. Stress results from the rear rollover model were compared to results from simulated static testing per SAE J2194. Maximum stress values from simulated rear rollovers exceeded maximum stress values recorded during simulated static testing for half of the elements comprising the uprights. In the worst case, the static model underpredicts dynamic model results by approximately 7%. In the best case, the static model overpredicts dynamic model results by approximately 32%. These results suggest the need for additional experimental work to characterize ROPS stress levels during staged overturns and during testing according to the SAE standard.

Flight Simulation of a Hybrid Projectile to Estimate the Impact of Launch Angle on Range Extension

A Hybrid Projectile (HP) currently under design at West Virginia University was simulated to estimate the effects of barrel launch angle and flight position of wing deployment. The projectile is similar to a standard 60mm mortar, except that is has been equipped to achieve extended range. A Simulink model was developed based upon external ballistics. The flight performance of the WVU-HP-60 was compared to a standard M720 60mm mortar. The developed HP was considered to be a tube-launched UAV, that transforms, not directly after launch but sometime after for optimal gliding, and must be modeled with different flight profiles because after transformation the aerodynamics drastically change. Two models of the UAV were created to allow for design of controllers. They were the launch model and the projectile flight model. It was found that the projectile may exit the barrel with a two degree variation of launch angle. The simulations show that range extension is still viable, with this barrel exit variation, to within 10% of the maximum achievable range. A confidence area was also developed to determine how far the launch angle and wing deployment position could stray and still maintain a significant amount of range extension.Copyright

Finite element vibration analysis of a helically wound tubular and laminated composite material beam

Finite element stiffness and consistent mass matrices are derived for helically wound, symmetrical composite tubes. The tubular element is considered to have constant cross-section and small deformations restricted to a plane. Each node has three degrees of freedom: axial and transverse displacement and rotation (slope of transverse displacement). Shell theory and lamination theory are used to formulate element stiffness matrices. The stiffness and mass matrices derived from the helically wound tubular composite material are reduced to symmetrically laminated composite beam. The free vibration and natural frequency are investigated for five different materials: steel, aluminum, carbon/N5280, Kevlar-49/epoxy and graphite/epoxy composites and various layup configurations. One application of a rotating flexible beam is investigated. The dynamic model of the flexible rotating beam includes the coupled effect between the rigid body motion and the flexible motion. The inverse dynamic simulation is performed by a prescribed driving torque in the numerical simulation. The influence of flexibility on rigid body motion are presented and discussed. From the numerical results, the composite material strongly possesses the lower power consumption and the passive control in damping the vibration of the structure.

An Approach to Motion Control Applications Based on Advanced Programmable Devices

In this article a methodology for constructing a simple servo loop for motion control applications which is suitable for educational applications is presented. The entire hardware implementation is demonstrated, focusing on a microcontroller-based (μC) servo amplifier and a field programmable gate array-digital signal processor (FPGA-DSP) motion controller. A novel hybrid architecture-based digital stage is featured providing a low-cost servo drive and a high performance controller, which can be used as a basis for an industrial application. Communication between the computer and the controller is exploited in this project in order to perform a simultaneous adaptive servo tuning. The USB protocol has been put into operation in the user front-end because a high speed sampling frequency is required for the PC to acquire position feedback signals. A software interface is developed using educational software, enabling features not only limited to a motion profile but also the supervisory control and data acquisition (SCADA) topology of the system. A classical proportional-integral-derivative controller (PID) is programmed on a DSP in order to ensure a proper tracking of the reference at both low and high speeds in a d.c. motor. Furthermore, certain blocks are embedded on an FPGA. As a result, three of the most important technologies in signal processing are featured, permitting engineering students to understand several concepts covered in theoretical courses.

Speed dependent rolling resistance evaluation of a twin roller chassis dynamometer for heavy-duty vehicles

The current interest in quantifying real-world emissions from heavy-duty vehicles has led to a far more extensive use of chassis dynamometers than ever before. Depending upon the objectives of chassis dynamometer testing, a range of different driving schedules could be employed to operate vehicles on the dynamometer. This paper addresses the losses associated with tyre-roller interaction on a chassis dynamometer. In this paper, a theoretical analysis has been conducted to evaluate the rolling resistance, as a function of vehicle speed, experienced by heavy-duty vehicle tyres on a twin-roller chassis dynamometer. This study focuses on the constant torque method to more accurately evaluate the parasitic losses of the dynamometer. Thus, a more accurate dynamometer control scheme could be implemented to simulate the road load for better assessment of a vehicles performance and exhaust gas emissions measurements.