Experimental-Based Optimization of Injection Molding Process Parameters for Short Product Cycle Time

This paper presents a framework for optimizing injection molding process parameters for minimum product cycle time subjected to constraints on the product defects. Two product defects, namely, volumetric shrinkage and warpage, as well as seven process parameters including injection speed, injection pressure, cooling time, packing pressure, mold temperature, packing time, and melt temperature, were considered. Injection molding experiments were conducted on specifically chosen test points and results were used to compute the volumetric shrinkage and warpage (at each test point). Thereafter, three relationships between the product cycle time (one relationship), the two product defects (two relationships), and the injection molding parameters were constructed using the kriging technique. An optimization problem to minimize the product cycle time (described by the first relationship) subject to constraints on the product defects (described by the latter two relationships) was then formulated. A combination set of points between the lower and upper extreme values of acceptable product defect was generated to serve as constraints for the two product defects. The optimization problem was then solved using the Fmincon function, available in the Matlab optimization toolbox. A plot of the optimization results revealed an appreciable tradeoff between the cycle time and the two product defects. To validate the optimization, an additional injection molding experiment was conducted for one of the optimization results. Results from the additional experiment showed reasonably close agreement with simulation optimization results differing in the cycle time, the warpage and volumetric shrinkage by 6.7%, 3.2%, and 8%, respectively

Computer Simulation/Prediction of Wear in Mechanical Components

In this paper, a state of the art on computer simulation and prediction of wear in mechanical components is reviewed. Past and recent developments as well as approaches employed in the simulation and prediction of wear are reviewed. In particular, the wear models, contact analysis schemes, and wear evolution prediction procedures as well as their application to the mechanical components (including cam-follower, gears, bearings, and cylinder/piston/piston ring wear) are reviewed. Recommendations and suggestions on possible directions for further research studies are also presented

Surface Modelling of Nanostructured Copper Subjected to Erosion-Corrosion

The last decade has witnessed considerable advancements in nanostructured material synthesis and property characterization. However, there still exists some deficiency in the mechanical and surface property characterization of these materials. In this paper, the erosion corrosion (E-C) behavior of nanostructured copper was studied. The nanostructured copper was produced through severe plastic deformation (SPD) by applying four passes of equal channel angular pressing (ECAP). The combined effects of the testing time, impact velocity, and concentration of erosive solid particles (i.e., sand concentration) on the E-C behavior of nanostructured copper were then examined. Based on a defined domain for the testing time, impact velocity, and sand concentration, E-C tests were performed for numerous combinations of test points via the slurry pot method. The test points were selected using the face-centered center composite design of experiments to enable visualization of the test results through surface plots. The extent of E-C on the test specimens was determined by measuring the mass loss. Polynomial regression and Kriging were used to fit surfaces to the experimental data, which were subsequently used to generate surface plots. The results showed that the E-C of nanostructured copper is best described by a quadratic function of testing time, velocity, and erosive solid particle concentration. The results also revealed that E-C increases with an increasing testing time, impact velocity, and erosive solid particle concentration. In addition, it was observed that the effect of the erosive solid particles on E-C is further intensified by an increased impact velocity

Recent advances and challenges in controlling quadrotors with suspended loads

Quadrotors have been utilized in a variety of applications where the payload needs to be transferred from one location to another, such as in mine detection, load delivery through hazardous environments, or locations that are inaccessible to ground vehicles. In these applications, the payload will be suspended underneath the vehicle and is subjected to large oscillations due to external disturbances or the acceleration of the vehicle itself. In this article, the most recent advancements in controlling the quadrotors vehicles with suspended loads are presented including control algorithms and techniques to implement these controllers. These techniques include the hardware and sensors besides the testing techniques for the developed control algorithms