Search Results (3)

In this work, a laminate based on bioresin and natural fibers was produced. Flax fabric was selected as the natural fiber. The biocomposite was subjected to strength tests. Stress–strain characteristics and strength indicators were determined. The workability of the laminate produced was also tested using milling technology. The tests were carried out using five carbide shank cutters for different purposes. The cutters with the geometry used in the processing of polymer materials and composites, general purpose cutters, and cutters with the geometry for aluminum and with different numbers of blades were analyzed. In order to obtain information on the workability of the prepared material, machining tests with different configurations of technological parameters were carried out. For each cutter, the effect of cutting speed and feed rate on the quality of the machined surface was tested. Due to the small thickness of the laminate, the machining was carried out in one pass, as a result of which the cutting depth in each case was constant. Changes in cutting speed and feed were evenly distributed over five levels. The quality of machining was assessed in two stages. The first stage included a visual assessment of the machined surface, involving a preliminary qualification of the machining parameters. The criterion was the amount of chips, frays, burrs, etc., remaining after machining that adhered to the surface. The next stage was the measurement of the geometric structure of the surface, during which the roughness parameters were analyzed using an optical microscope with a roughness analysis attachment. Quantitative analysis was performed for the best quality composite surfaces from each measurement series. The studies showed a dependence of the quality of machining on the technological parameters used. High tool speed, regardless of the type, especially at low feed, led to the sticking of chips, which had a very delicate form. In turn, low tool speed and high feed, due to the chip thickness, favored the formation of burrs. Machining with different types of tools showed that the process progresses better for tools with sharp blade geometry. Machining with a regular and polished cutter did not show any differences in the scope of the process progress. Full article

Metal processing may benefit from innovative lean-and-green datacentric engineering techniques. Broad process improvement opportunities in the efficient usage of materials and energy are anticipated (United Nations Sustainable Development Goals #9, 12). A CO₂ laser cutting method is investigated in this study in terms of product characteristics (surface roughness (SR)) and process characteristics (energy (EC) and gas consumption (GC) as well as cutting time (CT)). The examined laser cutter controlling factors were as follows: (1) the laser power (LP), (2) the cutting speed (CS), (3) the gas pressure (GP) and, (4) the laser focus length (F). The selected 10mm-thick carbon steel (EN10025 St37-2) workpiece was arranged to have various geometric configurations so as to simulate a variety of real industrial milling demands. Non-linear saturated screening/optimization trials were planned using the Taguchi-type L₉(3⁴) orthogonal array. The resulting multivariate dataset was treated using a combination of the Gibbs sampler and the Pareto frontier method in order to approximate the strength of the studied effects and to find a solution that comprises the minimization of all the tested process/product characteristics. The Pareto frontier optimal solution was (EC, GC, CT, SR) = (4.67 kWh, 20.35 Nm³, 21 s, 5.992 μm) for the synchronous screening/optimization of the four characteristics. The respective factorial settings were optimally adjusted at the four inputs (LP, CS, GP, F) located at (4 kW, 1.9 mm/min, 0.75 bar, +2.25 mm). The linear regression analysis was aided by the Gibbs sampler and promoted the laser power and the cutting speed on energy consumption to be stronger effects. Similarly, a strong effect was identified of the cutting speed and the gas pressure on gas consumption as well as a reciprocal effect of the cutting speed on the cutting time. Further industrial explorations may involve more intricate workpiece geometries, burr formation phenomena, and process economics. Full article

The disc cutter is a key tool in shield machines that come into direct contact with rock while participating in the removal of rock. Therefore, the reasonable design of the geometric configuration of disc cutters greatly determines the tunnelling efficiency of the shield machine. In this paper, the factors influencing the rock-breaking behaviour of disc cutters are studied. Firstly, to ensure the accuracy of the rock-breaking simulation, the parameters of the Holmquist–Johnson–Cook model of the diorite in the Jinan area were determined. Secondly, using ANSYS/LS-DYNA to simulate the rock-breaking process, the influence of the geometric configuration, including blade width and blade fillet, on rock-breaking behaviour was analysed. The results show that with increasing depth of penetration, the contact force increases approximately linearly. The contact force and the rock-breaking influence range gradually decrease with increasing number of blade fillets. In addition, with increasing number of blade fillets, the shape of the influence range gradually transitions from an approximate circle to a trapezoid, and finally to a triangle. With increasing blade width, the contact force and the rock-breaking influence range both increase, but the shape of the influence range remains largely unchanged as a trapezoid. On the basis of these research results, this paper gives some suggestions for the selection and configuration of disc cutters in different strata, which can give some guidance for practical engineering. Full article