Mechanical Engineering Commons^™

Pre-Impact Lower Extremity Posture And Brake Pedal Force Predict Foot And Ankle Forces During An Automobile Collision, Elizabeth C. Hardin, Anne Su, Antonie J. Van Den Bogert

Mechanical Engineering Faculty Publications

Background: The purpose of this study was to determine how a driver’s foot and ankle forces during a frontal vehicle collision depend on initial lower extremity posture and brake pedal force. Method of Approach: A 2D musculoskeletal model with seven segments and six right-side muscle groups was used. A simulation of a three-second braking task found 3647 sets of muscle activation levels that resulted in stable braking postures with realistic pedal force. These activation patterns were then used in impact simulations where vehicle deceleration was applied and driver movements and foot and ankle forces were simulated. Peak rearfoot ground reaction …

The Non-Destructive And Nano-Microstructural Characterization Of Thermal-Barrier Coatings, Y. H. Sohn, B. Jayaraj, S. Laxman, B. Franke, J. W. Byeon, Anette M. Karlsson

Mechanical Engineering Faculty Publications

The durability of thermal barrier coatings (TBCs) plays an important role in the service reliability and maintainability of hot-section components in advanced turbine engines for aerospace and utility applications. Photostimulated luminescence spectroscopy (PSLS) and electrochemical impedance spectroscopy (EIS) are being concurrently developed as complimentary nondestructive evaluation (NDE) techniques for quality control and liferemain assessment of TBCs. This paper discusses recent achievements in understanding the residual stress, phase constituents, and electrochemical resistance (or capacitance) of TBC constituents—with an emphasis on the thermally grown oxide. Results from NDE by PSLS and EIS are correlated to the nano- and microstructural development of TBCs.

Multi-D Cfd Modeling Of Free-Piston Stirling Convertor At Nasa Grc, Scott D. Wilson, Rodger W. Dyson, Roy C. Tew, Mounir B. Ibrahim

Mechanical Engineering Faculty Publications

A high efficiency Stirling Radioisotope Generator (SRG) is being developed for possible use in long duration space science missions. NASA s advanced technology goals for next generation Stirling convertors include increasing the Carnot efficiency and percent of Carnot efficiency. To help achieve these goals, a multidimensional Computational Fluid Dynamics (CFD) code is being developed to numerically model unsteady fluid flow and heat transfer phenomena of the oscillating working gas inside Stirling convertors. Simulations of the Stirling convertors for the SRG will help characterize the thermodynamic losses resulting from fluid flow and heat transfer between the working gas and solid walls. …

Sagittal Plane Biomechanics Cannot Injure The Acl During Sidestep Cutting, Scott G. Mclean, Xuemei Huang, Anne Su, Antonie J. Van Den Bogert

Mechanical Engineering Faculty Publications

Background. Knee joint sagittal plane forces are a proposed mechanism of anterior cruciate ligament injury during sport movements such as sidestep cutting. Ligament force magnitudes for these movements however, remain unknown. The need to examine injury-causing events suggests elucidation via model-based investigations is possible. Using this approach, the current study determined whether sagittal plane knee loading during sidestep cutting could in isolation injure the anterior cruciate ligament.

Methods. Experiments were performed on subject-specific forward dynamic musculoskeletal models, generated from data obtained from 10 male and 10 female athletes. Models were optimized to simulate subject-specific cutting movements. Random perturbations …

Effect Of Gender And Defensive Opponent On The Biomechanics Of Sidestep Cutting, Scott G. Mclean, Susanne W. Lipfert, Antonie J. Van Den Bogert

Mechanical Engineering Faculty Publications

Purpose: Anterior cruciate ligament (ACL) injuries often occur in women during cutting maneuvers to evade a defensive player. Gender differences in knee kinematics have been observed, but it is not known to what extent these are linked to abnormal neuromuscular control elsewhere in the kinetic chain. Responses to defense players, which may be gender-dependent, have not been included in previous studies. This study determined the effects of gender and defense player on entire lower extremity biomechanics during sidestepping.

Methods: Eight male and eight female subjects performed sidestep cuts with and without a static defensive opponent while 3D motion and ground …

Cavitation Effects On The Stability Of A Submerged Journal Bearing, Jerzy T. Sawicki, T. V. V. L. N. Rao

Mechanical Engineering Faculty Publications

A computational procedure for the mechanism of shear between the liquid sublayer and air cavity in the cavitation zone of a submerged journal bearing is presented here. Using the mass conservation principle, Elrod's universal equation is modified to take into consideration the shear of the air cavity in the cavitation region. Results of steady state and transient response for the submerged journal bearing using the present approach are compared with the universal equation based on the striated flow in the cavitation region. At steady state, the angular extent of cavitation region predicted by the present approach is higher than that …

Foot And Ankle Forces During An Automobile Collision: The Influence Of Muscles, Elizabeth C. Hardin, Anne Su, Antonie J. Van Den Bogert

Mechanical Engineering Faculty Publications

Muscles have a potentially important effect on lower extremity injuries during an automobile collision. Computational modeling can be a powerful tool to predict these effects and develop protective interventions. Our purpose was to determine how muscles influence peak foot and ankle forces during an automobile collision. A 2-D bilateral musculoskeletal model was constructed with seven segments. Six muscle groups were included in the right lower extremity, each represented by a Hill muscle model. Vehicle deceleration data were applied as input and the resulting movements were simulated. Three models were evaluated: no muscles (NM), minimal muscle activation at a brake pedal …

On The Microstructural Development In Platinum-Modified Nickel-Aluminide Bond Coats, S. Darzens, Anette M. Karlsson

Mechanical Engineering Faculty Publications

A numerical procedure for simulating the distortions exhibited by a thermally grown oxide (TGO) upon temperature cycling has been adapted to incorporate the microstructure of the bond coat. The focus is on the dual phase β/γ′ microstructure that develops upon oxidation of a system with a Pt-aluminide bond coat. The results reveal that the presence of the γ′-phase next to the TGO reduces its distortion locally, because of the superior high-temperature strength of γ′, relative to β. Conversely, in regions where the β-phase exists adjacent to the TGO, it distorts and the TGO propagates downward, while simultaneously lengthening. These results …

A Nonlinear Model For Prediction Of Dynamic Coefficients In A Hydrodynamic Journal Bearing, Jerzy T. Sawicki, T.V.V.L. N. Rao

Mechanical Engineering Faculty Publications

This paper investigates the variation of nonlinear stiffness and damping coefficients in a journal orbit with respect to equilibrium position. The journal orbit is obtained by the combined solution of equations of motion and Reynolds equation. In the linearized dynamic analysis, dynamic pressure is written as a perturbation of static pressure and pressure gradients at equilibrium position. However, in order to obtain nonlinear dynamic coefficients about equilibrium position, the dynamic pressure gradients in the orbit are also written as the first order perturbation of static pressure gradients and higher order pressure gradients for displacement and velocity perturbations. The dynamic coefficients …