Foundry Data Analytics to Identify Critical Parameters Affecting Mechanical Properties of Investment Castings

Besides shape fidelity and internal soundness, mechanical properties have become critical acceptance criteria for investment cast parts. These properties are mainly driven by the chemical composition of cast alloy as well as process parameters. It is however, difficult to identify the most critical parameters and their specific values influencing the mechanical properties. This is achieved in the present work by employing foundry data analytic based on Bayesian inference to compute the values of posterior probability for each input parameter. This is demonstrated on real-life data collected from an industrial foundry. Controlling the identified parameters within the specific range of values resulted in improved mechanical properties. Unlike computer simulation, artificial neural networks and statistical methods explored by earlier researchers, the proposed approach is easy to implement in industry for controlling and optimizing the parameters to achieve the desired range of mechanical properties. The current work also shows the way forward for building similar systems for other casting and manufacturing processes.

Phase Field Modeling of Solidification in Single Component Systems

Using phase field modeling simulation approach we investigate the effect of various parameters on the primary and secondary dendrite arm spacing during directional solidification in a single component system. In previous studies the effect of temperature gradient was assumed to be negligible in the transversal directions with a temperature rate equal to the product of thermal gradient and solidification rate. In our study the temperature field is obtained from energy conservation equation by considering the balance of latent heat released in the regions where solidification occurs and energy dissipation due to directional temperature gradient as boundary condition. In our simulations, we implemented a numerical method that enables the investigation of solidification in larger domains. Specifically, the temperature and the order parameter equations are solved only in the domains close to the solidification front; approach that reduces the computational costs significantly. We investigate the interplay and the effect of thermal gradient, solidification rate, undercooling temperature, and the cooling heat flux on arm spacing. By using a well-established power law relation the primary and secondary arm spacing are calculated for various solidification parameters. We also show that, for large heat fluxes, the secondary arm spacing is almost constant for different undercooling temperatures; behavior that demonstrates the need for correction of the power law relation by including the effect of heat flux.

Post-Fatigue Creep and Stress Relaxation Response of a Hybrid Polymer Composite

Polymer composites have a characteristic, composition specific visco-elastic property which influences the damage progression during fatigue cycling. While some researchers have studied the time dependent constitutive response of polymer composites during the first cycle of fatigue loading, very few have experimentally investigated the dependence of visco-elastic response of built-up polymer composite materials at various stages of fatigue cycling [1]. Our earlier studies on fatigue response of polymer composites focused primarily on the stiffness degradation as a function of applied cycles of loading, which represents the gross response of the material [2]. While doing such an experiment, complimentary experimental techniques to measure the temperature evolution was attempted through the use of infrared thermal imaging technique, which gave some insight into the change in temperature response as a function of fatigue cycling. However, there was no systematic measurement of creep and stress relaxation response of the composite material as a function of induced fatigue damage. The present paper describes the results of creep and stress-relaxation obtained during uni-axial fatigue loading of a hybrid polymer composite material. For this purpose, a woven carbon fiber mat was chosen as the synthetic fiber and Flax fiber in the unidirectional form was chosen as the natural fiber that is laid between the two layers of woven carbon fiber mat. Epoxy LY 556 and hardener Araldite® was used for building up of composite laminate by hand-lay-up technique. Dog-bone shaped tensile specimens with a gage width of 13 mm and gage length of 57 mm were extracted from the 250 × 250 mm sq. plate laminate of 2.1 mm thickness using a numerical controlled milling machine. The specimens were tested at 35% of their median tensile strengths under fatigue at a positive stress ratio (Pmin/Pmax) of 0.1 in tension-tension loading. Prior to start of fatigue loading, the specimens were held in load control and the strain in the gage length was measured for understanding the creep response over 2500 seconds. For stress-relaxation characterization, the specimens were held in extensometer control over a period of 2500 sec. The creep and stress relaxation tests were carried out after periodic intervals of fatigue cycling. It was observed that in the case of un-impacted specimens, the creep rate is consistent with the stiffness variation, which in turn, is dependent on the number of fatigue cycles - till it showed signs of de-lamination. Thereafter it was governed by the woven synthetic fiber response. Similarly, the stress relaxation response was found to decrease with increasing fatigue cycles. In case of impacted specimens, the local deformation had a prominent role in terms of creep and stress relaxation response.

A Review of Challenges in Integrating Robot and Motion Control Into a Single System

Automation industries are trying to integrate and consolidate the operation of various processes that make up their production line. Most often, every one of those processes is controlled by unique controllers and hardware as the process demands. Each of these independently controlled units can be seen as “islands of automation”. It is indeed a challenge for the control engineer to ensure smooth communication between these islands. The challenge gets magnified many fold when the plant performs troubleshooting, maintenance, or an upgrade. Compatibility over time, between components that make up the line can never be guaranteed in today’s world dominated by software drivers where improvements and upgrades are frequent. It is generally agreed in the industry that controllers and software consolidation should be done as much as possible. In this paper, the authors would like to discuss the case of integration of two such islands of automation, i.e. motion control (traditional single axis control of servos) and robotics. Automation integrators working on applications such as packaging, converting, palletizing etc. use a combination of robots and independently acting servos to achieve their objective. Programming software and programming methods for these two elements have been quite different. There has been a push in the automation industry to consolidate the control programming of motion components and robots because the underlying control techniques that actuate motion are the same. However, there are challenges that must be overcome in order to ensure that this push brings about useful and substantial changes that reduce control programming, maintaining and troubleshooting efforts. Such challenges are listed in this paper. Potential solutions to overcome these challenges are also laid out in this work.

3D Printing of Medical Models: A Literature Review

Medical models are physical models of human or animal anatomical structures such as skull and heart. Such models are used in simulation and planning of complex surgeries. They can also be utilized for anatomy teaching in medical curriculum. Traditionally, medical models are fabricated by paraffin wax or silicone casting. However, this method is time-consuming, of low quality, and not suitable for personalization. Recently, 3D printing technologies are used to fabricate medical models. Various applications of 3D printed medical models in surgeries and anatomy teaching have been reported, and their advantages over traditional medical models have been well-documented. However, 3D printing of medical models bears some special challenges compared to industrial applications of 3D printing. This paper reviews more than 50 publications on 3D printing of medical models between 2006 and 2016, and discusses knowledge gaps and potential research directions in this field.

Numerical Analysis and Mechanical Properties of Nomex™ Honeycomb Core

This paper presents an investigation on the mechanical response of the Nomex honeycomb core subjected to flatwise compressive loading. Thin plate elastic in-plane compressive buckling theory is used to analyze the Nomex honeycomb core cell wall. A mesoscopic finite element (FE) model of honeycomb sandwich structure with the Nomex honeycomb cell walls is established by employing ABAQUS/Explicit shell elements. The compressive strength and compressive stiffness of Nomex honeycomb core with different heights and thickness of cell walls, i.e. double cell walls and single cell walls, are analyzed numerically using the FE model. Flatwise compressive tests are also carried out on bare honeycomb cores to validate the numerical method. The results suggest that the compressive strength and compression stiffness are related to the geometric dimensions of the honeycomb core. The Nomex honeycomb core with a height of 6 mm has a higher strength than that of 8 mm. In addition, the honeycomb core with lower height possesses stronger anti-instability ability, including the compressive strength and stiffness. The proposed mesoscopic model can effectively simulate the crushing process of Nomex honeycomb core and accurately predict the strength and stiffness of honeycomb sandwich panels. Our work is instructive to the practical applications in engineering.

FOCUS Headform Testing Used to Evaluate Head Injury Risk for Ejected Riders of Personal Watercraft

Operators of personal watercraft (PWC) can perform maneuvers that may result in riders separating from the moving watercraft; the tested hypothesis was whether substantial brain injury concurrent with substantial facial and skull fractures can occur from contact with the PWC during a fall. The present study reports the potential for AIS2+ facial/skull fractures and AIS2+ traumatic brain injury (TBI) during a generic fall from the PWC in the absence of wave-jumping or other aggressive maneuvers. While it is well known that PWC can be used for wave-jumping which can result in more severe impacts, such impacts are beyond the scope of the present study because of the wide variability in occupant and PWC kinematics and possible impact velocities and orientations. Passenger separation and fall kinematics from both seated and standing positions were analyzed to estimate head impact velocities and possible impact locations on the PWC. A special purpose headform, known as the Facial and Ocular CountermeasUre Safety (FOCUS) device was used to evaluate the potential for facial fractures, skull fractures and TBI. Impacts between the FOCUS headform and the PWC were performed at velocities of 8, 10, and 12 miles per hour at 5 locations near the stern of a PWC. This study reports impact forces for various facial areas, linear and angular head accelerations, and Head Injury Criteria (HIC). The risk for facial fracture and TBI are reported herein. The results of this study indicate that concurrent AIS2 facial fractures, AIS2+ skull fractures, and AIS2+ TBI do not occur during a simple fall from a PWC.

Ball Drive Configurations and Kinematics for Holonomic Ground Mobility

Holonomic motion is desired for mobile ground robots and vehicles as it provides omnidirectional maneuvering capabilities, which can simplify the task of navigating around obstacles in confined spaces and unstructured environments. Mobility platforms that utilize spherical wheels are gaining popularity and interest due to the agile maneuvering and ground traversal capabilities they enable for mobility platforms. Ball-driven mobility platforms have a rich design space as various design parameters are available that can modify the physical and performance characteristics of the platforms. Various configurations for ball-driven mobility platforms are presented along with a generalized kinematic model that can be used for calculating motor velocities for a desired vehicle velocity. A naming convention is also presented in the paper for differentiating between configurations used for ball-driven mobility platforms. Metrics such as platform footprint, platform stability, and actuation force and efficiency are used to compare the configurations and to highlight some of the trade-offs associated with the selection of a configuration. Promising configurations are highlighted based on the metrics selected for the comparisons.

Numerical and Experimental Aerodynamic Evaluation of a Solar Vehicle

Solar car racing has created a competitive platform for research into alternative energy solutions and aids development in the green engineering space. The University of Johannesburg’s Solar Racing team developed a vehicle (Ilanga II) to compete in the 2014 South African Solar Car Challenge. This paper describes the numerical optimization of the vehicle’s body shape, utilizing Computational Fluid Dynamics (CFD) and finally compares the simulated results with the actual performance during the race. Motor control data is used to determine the aerodynamic drag coefficient of the vehicle. This work builds on the paper submitted in 2014 [1], which postulated the use of the Hermite cubic function in conjunction with the shape function analysis as a holistic design tool. By analyzing the motor control data it is possible to comment on the effectiveness of the shape function analysis technique. The final optimized design predicted a straight-line ACd 0.078. A yaw angle characterization study of ±25° degrees, in conjunction with historic weather data were used to fully characterize the vehicle with an average drag area coefficient of 0.119. The final comparative results of the simulated data and the race data show that the vehicle’s straight-line (Zero yaw) ACd was 11.2% higher than the simulated results, whereas the average aerodynamic characteristic ACd was 2.43% lower than the simulated results.

Cellulose Nanocrystals Assisted Preparation of Electrochemical Energy Storage Electrodes

Renewable energy sources demands sustainable energy storage technologies through the incorporation of low-cost and environment-friendly materials. In this regard, cellulose nanocrystals (CN), which are needle-shaped nanostructure derived from cellulose-rich resources, are extracted by sulfuric acid hydrolysis of biomass and used as both template and binder for the construction of electrochemical capacitors electrodes. A composite material is synthetized comprising CN and a conjugated electroactive polymer (CEP) to overcome the electrical insulating properties of cellulose as well as to exploit enhanced electrochemical activity by increased electrode surface-area. A one-step in-situ film synthesis protocol is evaluated by performing simultaneous polymerization and film deposition. The effect of proportion of starting components are evaluated through statistical Response Surface Methodology towards optimizing the electrochemical performance. Depending on the mass proportion of the starting components, a conducting network could be created by surface coating of the CEP on the whiskers during polymerization. Electrochemical measurements suggest an increase in specific surface area by at least a factor of two relative to bare CEP as a consequence of the template role of cellulose. Therefore, adjustment of the proposed one-step synthesis parameters allows tuning the material properties to meet specific application requirements regarding electrochemical performance.