Aluminum metal composites primed by fused deposition modeling-assisted investment casting: Hardness, surface, wear, and dimensional properties

Fused deposition modeling -based three-dimensional printing techniques, when merged with the investment casting process, is one of the most innovative techniques for developing functionally graded metal–matrix composites in high-performance industrial applications. In this study, Al–Al2O3 matrix composites have been prepared by the combined route of fused deposition modeling and modified investment casting processes. In the first step, the Al–Al2O3 particles have been reinforced into nylon 6 thermoplastics for the preparation of fused deposition modeling-based feedstock filaments (in two configurations: C1 (60% nylon 6–30% Al–10% Al2O3) and C2 (60% nylon 6–28% Al–12% Al2O3). In the next step, the investment casting patterns of the fused deposition modeling process of nylon 6–Al–Al2O3 composites were prepared. Furthermore, the investment casting has been performed by controlling the proportion of nylon 6–Al–Al2O3, the volume of pattern, the density of pattern, barrel finishing media weight, barrel fining time, and number of mold wall layers considering Taguchi L18-based experimental design. Finally, the functional aluminum matrix composites were subjected to testing to investigate average surface roughness ( Ra), deviation inside the cube, average wear, and average hardness. The study results have suggested that maintaining a higher proportion of Al2O3 in three-dimensional printed parts leads to higher Ra, higher dimensional deviation, and higher hardness of investment cast parts. On the contrary, solid patterns have provided low wear rates and low-density patterns resulting in increased wear rates in final investment casted products. Furthermore, the responses are optimized concurrently with the “technique for order of preference by similarity to ideal solution–Taguchi” technique while considering the analytical hierarchical process and entropy weights of significance.

Investigation into the surface integrity of crankshaft by barrel finishing

With the advancement of processing technology, the surface quality of crankshafts has become very demanding, especially in locations with severe friction and wear, such as the main shaft and connecting rod journals. Barrel finishing technology is widely applicable to the surface processes of large- and medium-sized parts as a typical free-grinding processing method with the characteristics of low processing cost, high processing efficiency, and simple processing equipment. In this study, a horizontal spindle barrel finishing machine is applied to the crankshaft parts. The surface integrity of the crankshaft is systematically evaluated before and after the finishing processing. The experimental results show that the surface integrity of the crankshaft is significantly improved after the finishing processing, which further improves the wear resistance of the part surface and increases the bearing capacity.

Amending Research on the Expression of the Contact Force of the Spindle Barrel Finishing Based on EDEM Simulation

The spindle barrel finishing is commonly used to improve the surface integrity of the important parts of the high-end equipment while it is difficult to provide enough test artifacts for the traditional trial and error experiment to obtain the desirable processing technology. The EDEM simulation of the spindle barrel finishing can provide effective help for the process design, however, the difference between the simulation and experiment is closely related to the selection of the contact model during simulation. In this paper, simulations and experiments are conducted based on the identical apparatus and conditions to facilitate the comparison and validation between each other. Based on the Hertz contact theory, the effect of the material properties of contact objects and the relative position of the workpiece on the contact force is qualified. The expression of the correlation coefficient of the contact model is deduced. Then the formula for calculating the contact force between the barrel finishing abrasive and the workpiece that includes influence coefficient of the material properties and the relative positions is established. Finally, the contact force calculation formula is verified by changing the rotating speed. The result shows that the material correction coefficient ranges from 1.41 to 2.38, which is inversely related to the equivalent modulus E. The position correction coefficient ranges from 2.0 to 2.3. The relative error value between the calculation result and the experimental test result is from 0.58% to 14.07%. This research lay a theoretical foundation for the correction theory of the core elements of the spindle barrel finishing process.

Effect of Industrial Heat Treatment and Barrel Finishing on the Mechanical Performance of Ti6Al4V Processed by Selective Laser Melting

Additive manufacturing is now capable of delivering high-quality, complex-shaped metallic components. The titanium alloy Ti6Al4V is an example of a printable metal being broadly used for advanced structural applications. A sound characterization of static mechanical properties of additively manufactured material is crucial for its proper application, and here specifically for Ti6Al4V. This includes a complete understanding of the influence of postprocess treatment on the material behavior, which has not been reached yet. In the present paper, the postprocess effects of surface finish and heat treatment on the mechanical performance of Ti6Al4V after selective laser melting were investigated. Some samples were subjected to barrel finishing at two different intensities, while different sets of specimens underwent several thermal cycles. As a reference, a control group of specimens was included, which did not undergo any postprocessing. The treatments were selected to be effective and easy to perform, being suitable for real industrial applications. Tensile tests were performed on all the samples, to obtain yield stress, ultimate tensile strength and elongation at fracture. The area reduction of the barrel-finished samples, after being tested, was measured by using a 3D scanner, as a further indication of ductility. Experimental results are reported and discussed, highlighting the effect of postprocessing treatments on the mechanical response. We then propose the optimal postprocessing procedure to enhance ductility without compromising strength, for structures manufactured from Ti6Al4V with selective laser melting.