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Investigation and Development of a Slip Model for a Basic Rigid Ring Ride Model
No full textWith the recent advances in rapid modeling and rapid prototyping, accurate simulation models for tires are very desirable. Selection of a tire slip model depends on the required frequency range and nonlinearity associated with the dynamics of the vehicle. This paper presents a brief overview of three major slip concepts including “Stationary slip”, “Physical transient slip”, and “Pragmatic transient slip”; tire models use these slip concepts to incorporate tire slip behavior. The review illustrates that there can be no single accurate slip model which could be ideally used for all modes of vehicle dynamics simulations. For this study, a rigid ring based semi-analytical tire model for intermediate frequency (up to 100 Hz) is used. The scope of this project is to investigate different steady state and transient slip models developed and used in industry and academia to find the most appropriate model, which could be added to this basic rigid ring tire model for capturing the tire behavior on uneven roads with relatively short and sharp unevenness. After a comprehensive investigation of all these existing tire models, this study presents the pragmatic transient tire modeling approach, which is best suited for performing vehicle ride simulation up to frequency range of 100 Hz. Then, the most appropriate relaxation length based pragmatic slip model is developed to capture the transient longitudinal slip behavior. Finally, pragmatic slip model is integrated into the rigid ring model and its response is analyzed against the road profiles with step obstacles of various shapes (triangular bump, large plank, small trapezium and large trapezium). This study concludes that the tandem cam enveloping model with pragmatic slip model makes a very accurate approximation of contact behavior of tire and this contact model coupled to rigid ring model make a good combination of complexity and simplicity, as they incorporate both physical and empirical approaches
The Effect of Booster Seat Use on Pediatric Injuries in Motor Vehicle Frontal Crashes
No full textBackground: Motor vehicle crashes are a significant source of pediatric mortality and morbidity. Studies indicate that booster seats significantly improve seat belt fit for children who have not attained a height of 145 cm (4’ 9”). This study examined injuries occurring in booster age children up to age 12, as the majority of children do not attain 145 cm until this age. The purpose of the study was to identify differences in injuries due to the type of restraint used, with attention to musculoskeletal injuries. Methods: Vehicle and occupant data were obtained from a publically available statistical sample of tow-away crashes. Frontal crashes over an 8-year period were examined. A data set of cases was created involving children ages 5 to 12 years who were unrestrained, restrained using the vehicle’s lap and shoulder belt, and restrained using a booster seat with the vehicle’s lap and shoulder seat belt. Injury severity, frequency, and patterns of distribution were compared. Results: Unrestrained children experienced moderate to severe injuries 3.8 to 19 times more frequently than children using restraints. There were more injuries to the head and face in unrestrained versus restrained children, but the head and face was the most frequently injured region for all groups. There were no serious cervical spine injuries reported for any group. Lower extremity fractures were not observed in booster seat users but occurred at similar rates in both unrestrained and seat belt restrained children. These fractures occurred in older children who were involved in more severe crashes. Conclusions: Unrestrained children were more likely to experience moderate and severe injuries than restrained children. The data sample suggests that booster use may reduce the risk of extremity fracture, as there were no extremity fractures in children restrained with booster seats. Clinical Relevance: This work provides evidence for the efficacy of booster use for preventing orthopaedic injury in children. This evidence can be used to inform parents and establish recommendations for best practices in transporting children
Experiences and Outcomes of Teaching Senior Capstone Course
No full textThe author taught a senor capstone design course during Fall 2017 in the Mechanical Systems design stream at Kettering University. The course duration for this course is approximately 11 weeks (Quarter system) that posed several challenges for handling the classes due to shorter academic term. The students are expected to perform detailed analysis and also validate the proof of concept of their designs by building prototypes. In all, there were 5 teams with 4 students each in each team. This paper discusses the course organization, topical selection policies and the final choice of a topic selected for each group to work on. Also, the appropriate assessment methods used to monitor weekly progress made by each group will be discussed. Finally, a brief description of work carried in each project along with the results from a sample project will be discussed
Near-room-temperature magnetocaloric properties of La1−xSrxMnO3 (x = 0.11, 0.17, and 0.19) nanoparticles
No full textThe growth of chemically stable magnetic materials showing a magnetic transition near room temperature with a strong magnetocaloric effect is important for the development of roomtemperature magnetic refrigeration technology. Single-phase nanoparticles of La1−xSrxMnO3 (x = 0.11, 0.17, and 0.19) (LSMO) materials in the rhombohedral crystal structure with particle sizes between 20 nm and 30 nm were prepared using the sol-gel method. The crystal structure, morphology, magnetic properties and magnetocaloric effect (MCE)were investigated. The ferromagnetic to paramagnetic phase transitions of these nanoparticles are of second order in nature and the transition temperatures(Tc)lie between 284 K and 327 K. The magnetic entropy change (ΔSM) and relative cooling power(RCP) exhibit a linear dependence on the applied magnetic field. All samples show relatively large cooling efficiency with ΔSM,max of 3.26 Jkg−1 K−1 for La0.89Sr0.11MnO3 at 297 K and RCP of 201 Jkg−1 for La0.81Sr0.19MnO3 both measured at H = 30 kOe. These results suggest that the LSMO nanoparticles have potential for room-temperature magnetic refrigeration