A Comparison of the Geometrical Accuracy of Thin-Walled Elements Made of Different Aluminum Alloys

In modern constructions, especially aircraft, the aim is to minimize the weight of the components used. This necessitates the use of innovative construction materials, or the production of these parts with ever-decreasing wall thicknesses. To simplify assembly and improve strength properties, so-called structural elements are being used in the form of monolithic elements, which are replacing the assemblies of parts joined by, for example, riveting. These structures often have a complex, thin-walled geometry with deep pockets. This paper attempts to assess the accuracy of manufacturing thin-walled elements, in the shape of walls with different geometries, made of various aluminum alloys. Machining tests were conducted at different cutting speeds, which allowed comparisons of the geometric accuracy of parts manufactured under conventional and high-speed cutting conditions. Based on the result obtained, it was found that the elements made of EN AW-7075 T651 alloy underwent the greatest deformations during machining in comparison to that of other two materials (EN AW-6082 T651 and EN AC-43000). An increase in the geometrical accuracy of the manufactured elements was also observed with the increase in the cutting speed for the HSC range. Hence, to minimize the postmachining deformation of thin-walled elements, the use of high-speed cutting is justified.

Investigation on the Machinability of Metastable β Titanium Alloy M28

Oriented to the application of new generation strategic aircraft, M28 (Ti-4Al-5Mo-5V-6Cr-1Nb) is a novel metastable β titanium alloy with outstanding strength. A better understanding of its machinability is the cornerstone of the manufacture. In this work, milling experiments were made with the uncoated WC-Co carbide insert to investigate its machinability. Compared with milling Ti-6Al-4V, the cutting force is much higher and the tool life is considerably shorter in the milling of M28, especially in the high-speed cutting. Serious edge breaking is found at normal cutting speed. While a continuous band of flank wear with significant chip adhesion, which covers comb cracks in the cutting edge, is found in the high-speed cutting tool. The machinability of M28 is considerably poorer than that of Ti-6Al-4V. The hard-to-machine performance of M28 is considered to be subject to the material property of the metastable β titanium alloy as well as the competing mechanism among work hardening, strain rate hardening and the thermal softening in the cutting. According to the detection of the scanning electron microscope (SEM) and the energy dispersive spectrometer (EDS), the diffusion of C and Co generates a negative influence on the cutting edge and accelerates the tool wear.

The use of assembled cutting tool with damping elements to reduce mechanical vibrations

Aspects of vibration reduction during machining on metal-cutting machines to improve the quality of machined surfaces at moderate and high-speed cutting modes are considered. End mills with damping elements made of different materials, which provide the control of tool rigidity, are developed. Keywords: vibrations, end mill, vibrations, machined surface, damping. [email protected]

Low and High Speed Orthogonal Cutting of AA6061-T6 under Dry and Flood-Coolant Modes: Tool Wear and Residual Stress Measurements and Predictions

The present research work aimed to study the effects of cutting environments and conditions on tool wear and residual stresses induced by orthogonal cutting of AA6061-T6. Cutting environments included dry- and flood-coolant modes and cutting conditions consisted of cutting speed and feed rate. A 2D finite element (FE) model was developed to predict tool wear and residual stresses and was validated by experimental measurements including machining forces, tool wear, and residual stresses. This was obtained by exploring various magnitudes of the shear friction factor and heat transfer coefficient and choosing proper coefficients using the calibration of the predicted results with the measured ones. The experimental results showed that the effect of cutting environment including dry and flood-coolant modes was negligible on machining forces. The experimental investigation also demonstrated that increasing feed rate raised machining forces, tool wear and residual stresses in both cutting environments. Low Speed Cutting (LSC) led to the highest value of tool wear and High Speed Cutting (HSC) provided the lowest values of resultant machining forces and residual stresses in both modes. Flood-coolant mode reduced tool wear and slightly decreased tensile residual stresses in comparison with dry mode. As a result, low feed rate and high-speed cutting under flood-coolant mode were proposed in order to improve tool wear and residual stress in orthogonal cutting of AA6061-T6.

Modeling of Heat Phenomenon in Rolling Kinematic Pairs Using the Finite Element Method

In the spindles of HSC (High Speed Cutting) machines with rolling bearings, higher temperatures in the bearings can be expected, which may affect the resistance to movement of the bearing itself. Therefore, to estimate these resistances, it is necessary to know the temperatures of the bearing components. The article presents the results of FEM simulation tests of temperature distribution in a rolling bearing. These studies were focused on assessing the influence of such features as the distribution of heat sources, the geometric form and size of the contact areas of the balls with the raceways, the conditions of heat convection to the environment and heat conduction inside the bearing. It has been recognized that FEM simulations for the default conditions offered by most commercial FEM systems can lead to out-of-the-box results. As part of the experimental research, conclusions from the simulation studies were verified.

Validating Continuum Model for Onset of Adiabatic Shear Banding during High Speed Cutting by Finite Element Method

High-speed cutting (HSC) is frequently adopted to manufacture parts in many industries, including aerospace and automotive. To manufacture high-quality parts, adiabatic shear banding (ASB), often observed on serrated chips of various metallic materials during the HSC process, should be suppressed and studied. ASB is formed due to work hardening of metallic materials and work softening induced by adiabatic heating. The onset of ASB during the orthogonal cutting of Ti6Al4V is modeled based on the continuum mechanics, taking both work hardening and work softening into considerations. The model is validated by finite element method (FEM) and experiments. Moreover, the ASB onset process is simulated in FEM to reveal the ASB formation mechanism. The effect of the mechanical properties of Ti6Al4V on the onset of ASB is investigated based on the Johnson-Cook model. The investigation reveals the main factors that affect the onset of ASB during the HSC process. Future work includes characterizing the mechanical behavior of Ti6Al4V after the onset of ASB during a cutting process by coupling the continuum mechanics and micromechanics.