Empirical Study on Characteristics of Angled Spoke-Based Wheels on Granular Media

In this study, the optimal shape of angled spoke-based wheels (ASWs) was designed to maximize the driving speed of a mobile robot with ASWs on granular media. As a lightweight search and rescue mobile robot, it is required to have a high driving speed to reach the disaster site quickly. When granular media behave as fluids, slippage occurs, and the mobile robot slows down compared with when the media behave similarly to a solid ground. There are no exact criteria to explain the behavior of granular media. Therefore, the Taguchi method and L9(34) orthogonal array were employed to empirically optimize the shape of the ASW. The design variables evaluated were the motor RPM, width–height proportion of the foot, radius of curvature, and toe angle of the foot. The size of the ocher balls was adopted as the user condition. An orthogonal array and signal–to–noise (S/N) ratio were used to analyze the validity of the design variables. The optimal design variables of the ASW were a motor RPM of 6000, width–height proportion of 3:7, radius of curvature of 1.0×h, and toe angle of 15deg. Verification experiments were performed to evaluate the improved driving speed of the ASW. The angular velocity of the ASW increases by 2.79% for φ1 (mm) and 10.50% for φ6 (mm). Therefore, an optimized ASW design is expected to improve the driving speed of a mobile robot with ASWs.

Association between the toe angle and bony factors in the transverse plane for osteoarthritic knees compared with healthy knees

BACKGROUND: The association between the toe angle and bony rotational factors is critical to explain issues related to the onset and progression of knee osteoarthritis (OA). OBJECTIVE: The study aimed to clarify the association between the toe angle and each of the femoral and tibial transvers direction relative to gait direction, rotational knee alignment, and bony torsional deformity for the subjects with knee OA. METHODS: This study evaluated 58 knees in 24 healthy elderly (72 ± 5 years) and 34 varus knee OA (72 ± 6 years). A three-dimensional (3D) assessment system was used on 3D models and biplanar long-leg radiographs with the toe angle reflecting gait direction, applying a 3D-to-2D image registration technique. The main parameters on the transverse plane were: (1) toe angle, (2) transverse direction of the femur and tibia relative to the gait direction, (3) femoral neck anteversion, (4) condylar twist angle, (5) tibial torsion, and (6) rotational knee alignment. RESULTS: The alignment parameters, except for the tibial transverse direction, were different between healthy and osteoarthritic knees. In knee OA, the femoral neck anteversion - femoral transverse direction (p = 0.001), femoral transverse direction - tibial transverse direction (p < 0.001), and tibial transverse direction - toe angle (p < 0.001) were associated. CONCLUSIONS: The osteoarthritic knees showed that the femoral neck anteversion was associated with the femoral transverse direction, which determined the tibial transverse direction by adjusting the rotational knee alignment, leading to the toe angle.

Environmental Factors as a Cause of Differences in the Feet of Ecuadorian Children and Its Relation to Their Footwear

The objective of this study was to analyze the differences in foot measurements of Ecuadorian children according to their geographical location of residence, taking into account climatic differences (1). A total of 1662 children (2) participated in the study. Three groups were established: coast, mountains and amazonia. The type of footwear (3) used was recorded and the lengths, widths, perimeters, heights and angles of both (4) feet were analyzed with a 3D foot digitizer (5). The variable ‘fitting of the foot to footwear’ was also obtained. Children living in coastal areas presented greater lengths, widths, perimeters and heights compared to those living in the mountain (p > 0.001) and amazonia (p < 0.001) between ages 5 to 13. Mountain residents showed a greater first toe angle than coast residents (p > 0.001) aged 8 to 17. Children used shoes smaller than required by their foot length (p < 0.01). Ecuadorian children from the coast presented longer and wider feet with higher foot arches, whilst those from mountains presented greater first toe angle. The studied sample used footwear up to one size smaller than the size corresponding to their foot length. The fitting and type of footwear used according to climatic differences could be interfering with normal foot development.

Should a Vehicle Always Deviate to the Tire Blowout Side? - A New Tire Blowout Model with Toe Angle Effects

As a severe tire failure, tire blowout during driving can significantly threaten vehicle stability and road safety. Tire blowout models were developed in the literature to conclude that a vehicle always deviates to the tire blowout side. However, this conclusion is proved to be inaccurate in this paper, since one important factor was largely ignored in the existing tire blowout models. Toe angle, as a basic and widely-applied setup on ground vehicles, can provide preset and symmetric lateral tire forces for normal driving. However, when tire blowout occurs, different toe angle setups can impact vehicle motions in different ways. For the first time, the toe angle is explicitly considered and integrated into a tire blowout model in this paper. For different tire blowout locations, driving maneuvers, and drivetrain configurations, the impacts of different toe angle setups on the variations of tire friction forces and vehicle motions are analyzed. The developed tire blowout model with toe angles is validated through both high-fidelity CarSim® simulation results and experimental results of a scaled test vehicle. Both simulation and experimental results show that a vehicle may not deviate to the tire blowout side, depending on the toe angle setups and driving maneuvers. Moreover, the experimental results also validate that the proposed tire blowout model can accurately evaluate the tire blowout impacts on vehicle dynamics.

Evaluation of the Stress Concentration Factor in Butt Welded Joints: A Comparative Study

Surface cracks in butt-welded joints usually occur in places with increased stress concentrations. The stress concentration factor (SCF) can be calculated using an empirical equation, with five geometric parameters of a butt-welded joint (thickness of the base material, toe radius, weld toe angle, weld width, and reinforcement height). However, in an industrial environment, it is impractical and sometimes even impossible to measure all five geometric parameters with sufficient accuracy. In this study, eight experiments on butt-welded joints were performed. All samples were scanned with a 3D scanner, and the geometric sizes of the welded joints were measured using computer software. A modified empirical expression proposed by Ushirokawa and Nakayama was used to calculate the SCF; the expression was adjusted in such a way that the SCF was calculated by knowing only the toe radius. In addition, four new expressions were proposed for the calculation of the SCF by knowing the toe radius in relation to the weld toe angle; the expressions were then compared and analyzed. Additionally, the values of the stress concentrations in the butt-welded joints were obtained using a finite element method (FEM). The SCFs calculated using the four methods were compared and further discussed. Our data suggested a new accurate and straightforward approach for calculating the SCF by knowing only the weld toe radius.

Difference in hoof conformation between shod and barefoot-managed hooves

Reasons for performing the studyHoof conformation is linked to biomechanics of the hoof and injury occurrence. There is no scientific data if conformation differs between shod and barefoot-managed hooves.ObjectivesTo investigate if and how shod and barefoot hooves differ in conformation.Study designRetrospective cohort study.MethodsStandardised lateral, dorsopalmar/dorsoplantar and solar photographs of 98 shod and 69 barefoot-managed hooves were included. Thirty-six of the barefoot horses were farrier-managed, 33 were podiatrist-managed. Length and angular measurements produced nine conformation parameters; dorsopalmar/plantar balance, solar symmetry, toe angle, heel angle, heel/toe angle difference, heel width, splaying index, flaring index and frog size.ResultsBarefoot hooves showed significantly fewer underrun heels, steeper heel angles, wider heels, increased splaying, increased flaring and larger frog size compared to hooves of shod horses. Solar symmetry showed a significant difference in front hooves but not hind hooves (P=0.038, P=0.104) and toe angle was not significantly different (P=0.368, P=0.425). There was no significant difference in the conformation of barefoot farrier and podiatrist-managed front hooves, however there was a significant difference in the hind hooves: farrier-managed hooves had longer frogs and shorter toes, compared to podiatrist-managed hooves.ConclusionsThe significant differences in hoof conformation found should be considered when managing the individual horse, since hoof conformation affects loading of the internal structure of the hoof and hence influences aetiopathogenesis of hoof pathology.

ANALYSIS OF THE IMPACT OF VARIOUS PRESSURES IN THE VEHICLE WHEELS ON THE WHEEL GEOMETRY

The steering system in a vehicle is one of the main systems that ensures its controllability and is important for road safety. The steering system consists of two main mechanisms, namely the steering gear, the task of which is to convert the rotary motion into reciprocating motion, and the steering gear, the task of which is to ensure the correct steering of the vehicle. In this case, the steering system is interconnected with the suspension of the car, in which there are four main angles of the wheels that are responsible for the correct maneuverability of the vehicle, namely: camber angle, toe angle, angle of rotation of the axle of the fist and the angle of inclination of the pivot axis of the fist. Measuring the geometry of a vehicle's suspension has several interrelated purposes. One of them is the modification of the stability of the vehicle, that is, the effective impact on the maintenance of the vehicle on the road. Handling also depends on the geometry setting and ensures proper maintenance on the road. Well adjusted geometry ensures even tire wear on each axle. The purpose of the steering system is to maintain the correct position of the steering wheel in relation to the steering wheels. The tests were carried out in stationary conditions at the diagnostic station of the Rzeszow University of Technology using an automatic device for measuring and regulating the air pressure in the tires of the Unitrol PA-10K car and the Launch X-631 car wheel alignment system. The object of the study was a passenger car of the Opel Agila brand. The tests were carried out for various values of air pressure in the car wheels. Based on the above, the task was set - to demonstrate how incorrect air pressure in the wheels of a car changes the angles of inclination of the wheels of the car. When analyzing the obtained test results, it was found that the pressure in the wheels, different from the nominal, but the same in each wheel, does not significantly affect the change in the values of the parameters of the angles of inclination of the vehicle wheels. If the pressure in the wheels on one side of the vehicle drops by 1 bar, there is a significant difference in the camber angles of the front axle. Changes in the air pressure in one of the rear wheels of the car do not significantly affect the angles of inclination of the car wheels. KEY WORDS: AIR PRESSURE IN THE WHEELS, UNEVEN PRESSURE, WHEEL MOUNTING ANGLES, CAMBER AND TOE ANGLES, STEERING.

New Methods for Stress Concentration Factor Calculation in Butt Welded Joints: A Comparative Study

Surface cracks in butt-welded joints usually occur in places with increased stress concentrations. The stress concentration factor (SCF) can be calculated using an empirical equation, with five geometric parameters of a butt-welded joint (thickness of the base material, toe radius, weld toe angle, weld width, and reinforcement height). However, in anindustrial environment, it is impractical and sometimes even impossible to measure all five geometric parameters with sufficient accuracy. In this study, eight experiments on butt-welded joints were performed. All samples were scanned with a 3D scanner, and the geometric sizes of the welded joints were measured using computer software. A modified empirical expression proposed by Ushirokawa and Nakayama was used to calculate the SCF; the expression was adjusted in such a way that the SCF was calculated by knowing only the toe radius. In addition, four new expressions were proposed for the calculation of the SCF by knowing the toe radius in relation to the weld toe angle; the expressions were then compared and analysed. Additionally, the values of the stress concentrations in the butt-welded joints were obtained using afinite element method (FEM). The SCFs calculated using the four methods were compared and further discussed. Our data suggested a new accurate and straightforward approach for calculating the SCF by knowing only the weld toe radius.

Effects of Boot-Shaped Rib On Heat Transfer Characteristics of Internal Cooling Turbine Blades

Gas turbine engine has been widely applied to many heavy industries, such as marine propulsion and aerospace fields. Increasing turbine inlet temperature is one of the major ways to improve the thermal efficiency of gas turbines. Internal cooling for gas turbine cooling system is one of the most commonly used approaches to reduce the temperature of blades by casting various kinds of ribs in serpentine passages to enhance the heat transfer between the coolant and hot surface of gas turbine blades. This paper presents an investigation of boot-shaped rib design to increase the heat transfer performances in the internal cooling turbine blades for gas turbine engines. By varying the design parameter configuration, the airflow is taken with higher momentum, and the minor vortex being at the front rib is relatively removed. The object of this investigation is increasing the reattachment airflow to wall and reducing the vortex occurring near the rib for improving the performances of heat transfer using three-dimensional Reynolds-averaged Navier-Stokes with the SST model. A parametric study of the boot-shaped rib design was performed using various geometric parameters related to the heel-angle, toe-angle, slope-height and rib-width to find their effect on the Nusselt number, temperature on the ribbed wall, friction factor ratio of the channel and thermal performance factor. The numerical results showed that the heat transfer performances are significantly increased with the heel-angle, toe-angle, slope-height, while that remained relatively constant with the rib-width.