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The theoretical research shows that brittle materials can realize ductile cutting at the nanometer scale and avoid cracks on the machined surface. However, the decrease of machining scale changes the load state and material behavior, which makes the classical shear model fail. Therefore, based on modern physical research methods such as molecular dynamics, the nano-cutting process of the monocrystalline γ-TiAl alloy is studied in this paper. The essential difference between nano-cutting and macro-cutting is analyzed, and the material removal mechanism at nanoscale is explained, which provides theoretical support for the plastic domain machining of brittle materials. The results show that the ductile cutting process of the brittle γ-TiAl alloy at the nanometer scale is implemented by the phase transformation under the high hydrostatic pressure near the tool. The phase transformation during the cutting process can be divided into high stress-induced amorphization (HSIA) and elastic stress-induced dislocation (ESID). Compared with shear cutting, the material removal under extrusion cutting is achieved by continuous plastic deformation in the HSIA region above the stagnation zone. The ESID process leads to the formation of subsurface defects and does not contribute to the formation of amorphous chips.

The use of multi-movable containers for extrusion cutting of low-alloy materials can enhance the mechanical properties of cold extrusion. The grain structure becomes denser during extrusion and deformation, and the cross-sectional metal streamlines, which align with the product’s geometric contour, remain continuously distributed and unbroken. However, grain size uniformity at the edges can be further improved. This study proposes the utilization of a movable extrusion die to better control the grain size, enhancing the hardening effects of the material as it enters the die through extrusion cutting. The process employs a movable and a stationary container with a step at the boundary near the die discharge port. As the material is pushed inward and downward during forming, multiple cycles induce severe plastic deformation (SPD), altering the grain direction and refining the grain structure. DEFORM-3D simulations and calculations using the Tabor equations were performed, with results subject to experimental evaluation. Both predicted and experimental increases in hardness were similar, confirming the viability of the movable container design. Additionally, the movable container was used to form a bimetal billet comprising a copper core and an aluminum shell, yielding satisfactory results. Product test results confirmed that grain refinement occurred and hardness increased in all experiments.

Center cracks frequently occur during extrusion cutting. These cracks are often caused by uneven material flow velocities, which may also increase the material’s hardness and cause surface fractures and unevenness. In this study, simulations and experiments were performed to determine whether a novel grooved punch can stabilize the material flow velocity of a billet during extrusion cutting. The relationship between the punch and die outlet geometry was also investigated. If the punch dimensions are smaller than those of the die outlet, the product shrinks and fractures. Larger punches can prevent these defects but increase the material flow velocity, causing sinking at the center. Finite element analysis and experiments conducted with grooved punches revealed that both shallow and deep grooves can improve the control of material flow and delay acceleration. Punches with greater volume both increase and stabilize the material’s acceleration. The dimensions of the grooved punch must be similar to those of the die outlet to ensure optimal material flow.

This study explores the feasibility of using polyurethane (PU) elastomer as a flexible punch-filling medium in cold forming. Microforming processes encounter challenges such as size effects and friction effects, which can lead to defects including fractures, distortions, and central depressions. The proposed method incorporates a high-hardness PU plate (95A) with excellent elasticity and near-incompressibility to address these issues. By compensating for axial compression through lateral expansion, the PU plate distributes pressure uniformly, reduces central stress, mitigates central acceleration effects, and minimizes defects caused by velocity gradients. Experiments and simulations using aluminum alloy Al 1050-O demonstrate that the PU-assisted extrusion–cutting process improves material flow, redistributes forming pressure, and enhances forming stability compared to conventional methods. This approach shows significant potential for advancing microforming technologies, particularly in industries requiring high-precision components.

In this study, a new process of axial ultrasonic vibration-assisted extrusion cutting (AUV-EC) is proposed to prepare Al6061 alloy ultrafine-grained chip strips. The principles of AUV-EC are analyzed. The cutting motion trajectory equations of the main tool and the constraint tool during the AUV-EC process are established, and the theoretical cut marks on the chip surface are predicted. AUV-EC experiments are conducted to verify the theoretical cut marks on the chip surface and characterize the surface topography and microstructure of the chip strip samples. The results show that applying ultrasonic vibration with a frequency of 33 ~ 34.5 kHz and an amplitude of 1 ~ 6 μm in the AUV-EC process can improve the chip strip’s surface quality. Compared with traditional extrusion cutting (EC) chip samples, AUV-EC chip samples have better surface flatness and smoothness and lower surface defect ratios. The average grain sizes of the traditional EC and AUV-EC chip samples are approximately 164 nm and 135 nm, respectively. Many dynamic recovery grains are distributed in traditional EC chips, but there is only a small amount in AUV-EC chips. The x-ray diffraction (XRD) test finds that the AUV-EC chip has a higher dislocation density.

Currently, the field of microgear manufacturing faces various processing challenges, particularly in terms of size reduction; these challenges increase the complexity and costs of manufacturing. In this study, a technique for microgear manufacturing is aimed at reducing subsequent processing steps and enhancing material utilization. This technique involves the use of trough dies with extrusion-cutting processing, which enables workpieces to undergo forming in a negative clearance state, thus reducing subsequent processing time for micro products. We conducted finite element simulations using microgear dies, measuring stress, velocity, and flow during the forming process of four types of dies-flat, internal-trough, external-trough, and double-trough dies. The results indicated that the buffering effect of the troughs reduced the rate of increase in the material’s internal stress. In the cavity, the material experiences a significant increase in hydrostatic pressure, leading to the formation of a “hydrostatic pressure wall”. This pressure barrier imposes substantial constraints on the flow of the material during dynamic processes, making it difficult for the material to move into the remaining areas. This effectively enhances the blockage of material flow, demonstrating the critical role of hydrostatic pressure in controlling material distribution and movement. In addition, combining the characteristics of both into a double-trough die enhances the overall stability of forming velocity, reduces forming load and energy consumption, and maximizes material utilization. Results further revealed that microgears manufactured using double-trough dies exhibited defect-free surfaces, with a dimensional error of less than 5 μm and tolerances ranging from IT5 to IT6. Overall, this study offers new insights into the traditional field of microgear manufacturing, highlighting potential solutions for the challenges encountered in current microstamping processes.

This study proposed and evaluated a highly precise method employing various diameters and shapes of punch to manufacture right-angled square-bodied products. In this method, a trough is not only engraved on the die but also designed into the punch. Five diameters and shapes of the punch were collocated with a circular trough around the square shape of a die cavity. In the tests, a ram descended to a fixed level, and part of the billet was forced into the trough without touching its bottom. This causes high hydrostatic stress on the cutting edge of the die. The pressure substantially reduces the occurrence of fractures in test products. The punch with a square trough engraved on its face produced a product with favorable shape and precision compared with other punch shapes. The results revealed that the proposed method can produce a product with a long and burnished surface with a roughness of 0.02–0.12 μm. The tolerance band for the width and thickness ranges from IT1 to IT3, and that for the right angle is 0.02–0.06°. The proposed method is a new rapid prototyping technology and has greater levels of precision than conventional manufacturing methods.

A huge number of metal scraps are produced every year, while the existing recycling methods are featured with disadvantages such as high melting loss, cumbersome processes, or high cost. Instead of reprocessing the chips, forming extrusion cutting (FEC) can turn the cutting-away material directly into finished/semifinished products, which makes this novel process radically different from other available recycling methods, and can avoid their disadvantages. Therefore, FEC has great potential, and the research and improvement of FEC are significant. During the FEC process, several key parameters of the tool including the chip compression ratio λ , the rake angle of the cutting tool α , and the constraining tool corner radius  r c obviously affect the material deformation and forming performance. In this study, effects of these three parameters are investigated by combining the experiment with 3-D finite element simulation. According to the study, the increase of λ leads to the decrease of the materials’ deformation degree and the forming properties, and  r c shows a positive correlation while α shows a negative correlation with the main cutting force respectively. Besides, while α varies from 10° to 30°, the samples show steady forming performance. The results indicate that, to obtain a better forming performance during the high-efficiency and low-cost FEC process, λ and  r c should be set small, while α prefers a large value.

A high-precision technology with negative punch clearance for manufacturing a cycloid pump is proposed in this paper. Notably, the manufacturing process for this technology is similar to extrusion, except that a substantially different die and punch design was developed. Specifically, a trough engraved in a die was designed around the gear shape of a cycloid pump, and a ram with a hole through which the punch can penetrate was developed to press the billet. Thus, when the ram descends to a certain level, a portion of the billet is forced into the cave of the trough and keeps the ram from touching the bottom of the trough. In such situations, very high hydrostatic stress on the cutting edge of the die is produced. The diameter of the punch was designed to be larger than the hole of the die, but smaller than the diameter of die. Thus, when the punch descends to extrude the billet, the hydrostatic pressure around the cutting edge of the punch and die is increased; this can also substantially reduce product fracturing. An experimental test for two types of cycloid pump shapes was conducted and the results showed that a long and well-burnished product surface can be obtained within a few minutes. Notably, the mechanical clearance that effectively prevented fluid from leaking backward was measured to be less than 10 μm, which is considerably smaller than that of conventional products and verifies the potential of this technology.