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In this case study, exploiting a theoretical infinite length broaching model, analytic and numeric asymptotic stability predictions are derived to forecast the transient dynamic behaviour of the real, time-limited machining operation. These stability assessments are then validated both numerically and empirically. As instabilities are generally difficult to induce in conventional broaching machines, for conducting cutting experiments, a small scale laboratory test bench is established. To do so, a three-axis milling machine is retrofitted with a custom tool holder, integrated with a stiff, four-axis, strain-gauge-based load cell. This configuration allows accurate monitoring of the process dynamics, and a high degree of control over the operation parameters.

Manufacturers show great interest in all technological processes and methods that provide high productivity. The analytical method of modelling the productivity rate of the broaching operation was problematic because of the multi-cutting processes. The broaching operation is highly productive and implemented by one expensive multi-cutter tool. The specificity of the broach designs and processes is well-described in publications. The broaching process is fulfilled by the axial motion of the group of cutters with simultaneous action. The cutters of the broach are involved serially with the interrupted cutting process of the blank. The known model for the productivity rate of the broaching machine tool does not consider the reliability indices of the broach and machine tool units from the change in machining regimes. The proposed mathematical model comprises the broaching operation’s main factors that influence the machine tool’s productivity rate. This model enables the definition of the maximal productivity of the machine tool and the broaching process’ optimal cutting speed, which is an important economic index for manufacturers. The research paper considers the derivation of the mathematical model for the broaching process, which shows a higher productivity rate with the magnitude of the cutting speed that is less than the handbooks prescribe.

The article intends to bring back to light old perceptions about the “broaching-to” behaviour of ships. The signature of broaching-to is the sudden loss of controllability. The phenomenon sometimes ends with vessel capsize. The findings of an investigation into old bibliographical sources are reported, spanning more than 300 years of use of the term. Several citations have been identified in texts of nautical or related content, including voyagers’ records, nautical journals, training manuals, old encyclopaedias and even literary sources and leisure magazines. At a time when broaching-to is considered in the currently formulated new ship stability criteria at IMO, this paper provides a historical perspective on a problem that has maintained relevance despite the changes in ship technology and design.

The turbine mortise is a critical structural feature of turbine disks, and its manufacturing quality directly determines the performance and service life of aircraft engines. With the increasing application of advanced nickel-based superalloys, severe tool wear in conventional mechanical broaching of turbine mortises has emerged as a key limitation, substantially elevating production costs. Electrochemical broaching (ECB), which removes material through anodic dissolution reactions, eliminates tool wear and thus offers low cost and efficiency advantages, making it a promising method for turbine mortise fabrication. In this study, COMSOL Multiphysics 6.2 was employed to simulate the multiphysics field comprising the electric field, flow field, temperature field, bubble ratio, and dynamic mesh and elucidate the evolution of the electric field during the ECB process. ECB experiments of specimens on Inconel 718 were conducted under different feed speeds. On this basis, optimal processing parameters were identified. The results of the mid-position ECB experiments revealed five distinct dissolution states: pre-processing, pre-transition, stable dissolution, post-transition, and post-processing stages. A material dissolution mechanism model for the ECB process was established. Finally, fir-tree turbine mortises were successfully manufactured on Inconel 718 using a self-developed specialized electrochemical machining system at a feed speed of 70 mm/min. The mortise profile demonstrated dimensional deviations of (+16 to −21) μm, with working surface variations maintained within ±5 μm. The machined surfaces exhibited uniform and dense morphology with a surface roughness of Ra 0.275 μm. Three sets of mortise specimens processed under identical parameters showed excellent consistency, presenting a maximum deviation in profile removal thickness of +4.1 μm. The tool cathode was repeatedly reused without any detectable wear.

The amplitude of tooth passing frequency in frequency spectrum is an important indicator to judge machining quality and tool wear. In comparison to the amplitude of tooth passing frequency in acceleration spectrum, broaching force more directly reflects the tool wear and machining quality, but the broaching force measurement equipment is expensive and can change the dynamic structure of the machine. Therefore, this paper establishes a frequency spectrum prediction model of the broaching process using theoretical cutting force time history. This model combines the advantages of easy acquisition of vibration data, low cost, and no change in machine structure by the acceleration sensor, with the benefits of directly reflecting tool wear and machining quality through broaching force measurement equipment. In this paper, the theoretical cutting force model is developed based on the Johnson–Cook material law. Compared to the traditional method of directly applying FFT to obtain the broaching force spectrum, this paper innovatively divides the broaching force into square waves of equal width but varying amplitudes in the time domain. The frequency domain waveform of broaching force can be regarded as the vector superposition between the harmonic series corresponding to these time-domain square waves. Through the waveform image of numerical simulation, it can be concluded that the amplitude of tooth passing frequency used for tool wear diagnosis depends on the shape of tooth passing area in cutting force time history, which is affected by factors like tool wear and lubrication conditions. Any force changes caused by tool wear and broaching quality can be reflected in the broaching force spectrum. According to the characteristics of the dynamic equation, the frequency spectrum of acceleration can be obtained by substituting the broaching force in frequency domain into the dynamic equation. Through experimental analysis, it is shown that the numerical acceleration frequency spectrum obtained by the present model is consistent with the experimental acceleration frequency spectrum.

Complex profile broaches are widely used in the manufacture of complex parts of aero-engines, but the forces in the broaching process are difficult to predict and control. A new numerical model for broaching force with complex profile tools was presented, which considered the area and arc length of the curved shear zone boundary. The area and arc length were calculated by the curve function of the boundary, which is firstly predicted by FEM simulation. Then, an experimental device was set up to carry out the broaching experiment with straight profile tools and complex profile tools in accordance with the progressive depth of the cut. Based on the experiments, the traditional broaching model and the modified model with the complex profile tool have been established. Compared with the traditional force model, the accuracy of the modified model has been moderately improved. Furthermore, the modified main broaching force ( Y direction) model and the normal force ( Z direction) model show a significant improvement in accuracy of 4.8% and 9.7%, respectively, which suggests that the projection area of curved shear zone A 1 and the projection arc length of curved shear zone l 1 have a big impact on the broaching process. It is firmly believed that the modified model proposed in this paper can provide guidance for the design of complex profile tools and facilitate the efficient and high-precision machining of complex parts.

This paper presents a breakthrough in activating the skin effect at conventional broaching speeds (1–8 m/min) by using laser defocus gradient modification to induce surface embrittlement in martensitic stainless steel Z10C13. Through controlled defocusing, a 50 μm gradient remelting layer was created, which features ultrafine grains (0.8 μm) and a high-density geometrically necessary dislocation (GND) zone (ρGND = 2.27 μm−3). The quasi-cleavage fracture was triggered via dislocation pinning by non-oriented low-angle grain boundaries (28.4% LAGBs). Multiscale characterization confirms that this microstructural transformation enhances surface hardness by 12.95% (reaching 31.4 HRC), reduces cutting force by 34.07%, and improves surface roughness by 63.74% (Sz = 28.80 μm). Simultaneously, a parallel crack-deflection mechanism restricts subsurface damage propagation, resulting in a crack-free subsurface zone. These results demonstrate the effectiveness of the embrittlement–toughening dichotomy for precision machining of difficult-to-cut materials under low-speed constraints.

The optimization of a broach surface is of great significance to improve the cutting performance of the tool. However, the traditional optimization method (surface texture, coating, etc.) destroys the stress distribution of the tool and reduces the service life of the tool. To avoid these problems, four kinds of flocking surfaces (FB1, FB2, FB3, and FB4), imitating the biological structure of Daphniphyllum calycinum Benth (DCB), were fabricated on the rake face of the broach by electrostatic flocking. The broaching experiment, wettability, and spreading experiment were then conducted. Moreover, the mathematical model of the friction coefficient of the bionic broach was built. The effect of broaches with different flocking surfaces on the broaching force, chip morphology, and surface quality of workpieces was studied. The results indicate that the flocked broaches (FB) with good lubricity and capacity of microchips removal (CMR) present a smaller cutting force (Fc) and positive pressure (Ft) compared to the unflocked broach (NB), and reduce the friction coefficient (COF). The chip curl was decreased, and the shear angle was increased by FB, which were attributed to the function of absorbing lubricant, storing, and sweeping microchips. Its vibration suppression effect enhanced the stability in the broaching process and improved the surface quality of the workpiece. More importantly, the FB2 with the most reasonable fluff area and spacing exhibited the best cutting performance. The experimental conclusions and methods of this paper can provide a new research idea for functional structure tools.

In modern day industry of heavy engineering, parts made from billets comprising large-sized pipe forgings are widely used. The paper presents results of the study of various methods of broaching on mandrel of large-sized pipe forgings and presents the results of industrial testing of the developed methods of broaching and designs of mandrels.

This study comprehensively addresses the machining of nickel alloys, focusing its attention on crucial aspects related to chip formation and tool wear. Detailed characterization of the morphology and the chip formation process was performed by analyzing parameters such as chip segmentation ratio and variables such as shear band thickness and strain rate. Additionally, a numerical model was used to quantify stresses and temperatures at the tool/chip interface and to evaluate damage, thus contributing to the understanding of the development of chip formation. A transition in chip shapes as the toothing increases is highlighted, evidenced by segmentation ratio values below 0.5, indicative of the presence of discontinuous chips. The increase in cutting-edge radius is associated with a gradual increase in the compression ratio, indicating a higher plastic energy requirement in chip formation. Numerical simulations support this theory of failure. A significant correlation of 80% was identified between flank wear and the increase in shear force oscillation amplitude, indicating that flank wear contributes to system vibration. It is also noted that the adiabatic shear bands (ASB) are narrow, revealing a marked plastic deformation in the primary shear zone. Consequently, the remarkable incidence of wear with cutting parameters on chip formation is demonstrated, affecting the cutting force amplitude and, hence, the workpiece topography.