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Chip formation is considered one important indicator to evaluate machining processes. In particular, geometric features of chips may provide important insights for the assessment of machining stability and productivity. In fixed-abrasive machining processes, such as grinding and honing, chips are simultaneously produced by many of the geometrically undefined cutting edges. Despite being "undefined," geometric features of abrasive grains can still be statistically characterized or described. Accordingly, it can be assumed that, under stable machining conditions, the geometric features of abrasive chips may also conform to certain statistical patterns. However, statistical characterization of abrasive chips can be very challenging due to their large quantity, irregular shapes, minuscule size, and sometimes tangled condition. In this study, an analysis method combining metallographic preparation and micro-computed tomography (micro-CT) has been developed to characterize abrasive chips produced by a honing stone. The results regarding the geometric characteristics of the obtained massive abrasive chips, i.e., their sizes and shapes, were presented and statistically described. It was found most chips had a size around 50 µm and the shape being a slightly elongated and curved cone. Most of the geometric features could meet a positive skewness distribution. [ABSTRACT FROM AUTHOR]

The design of machine parts of different sizes and shapes has become relevant in the manufacturing industry which requires five-axis machine tools of high dynamic performance; different machining test pieces have been used to test and reflect the machine tool's performance. The S-shaped is still under development and consideration of which a new test piece better than the S-shaped part has been recommended to be put forward making the NAS979 the only standardized test piece; however, it has some limitations. Hence, this study proposes a new test piece to objectively satisfy the demand for machine tools with higher dynamic performance, which shows much improvement over the standard NAS979 and is the best alternative to the S-shaped test piece, and it combines the geometric and kinematic features of both test pieces. Geometrically, it has non-uniform surface continuity, variable twist angle, and variable curvature; and the cutting tool moves in close and opened angles along the tool path; there is sudden rise and fall of axes' velocity, acceleration, and jerk with much impact during machining which makes the S-cone test piece be machined by only five-axis machine tools with high dynamic performance, and has a better dynamic performance identification effect than the S-shaped test piece based on the trajectory test. Detailed work on the validation of the machine tool's dynamic performance using the S-cone part will be captured next part of this study. [ABSTRACT FROM AUTHOR]

A dissimilar metal tube joint fabricated by magnetic pulse welding (MPW) usually has uneven mechanical properties and an uneven morphology along the welding direction due to the small discontinuous matching range of the collision parameters. In this work, inclined, concave, and convex wall features were prefabricated on the target tube to improve the uniformity of the mechanical properties. The effects of the types of features and the prefabricated angle on the collision parameters, the axial distribution of the strength, and the interfacial morphology were investigated by simulations, shear tests, and microscopic observations, respectively. The results show that the collision parameters were increased with the increase of the prefabricated angle under the three types of features. Compared with the case without features, the increment of the collision parameters was found to be the greatest under the convex wall feature, and the smallest under the concave wall feature. With the increase of the prefabricated angle under the three types of features, the average shear strength tended to be reduced. When the prefabricated feature was the concave wall with a prefabricated angle of 5°, the quality of the joint was the best; it had an average shear strength of 46.46 MPa, an increase of 87%, and a low standard deviation of 4.96 MPa, a decrease of by 81%, as compared with that without geometric features. The transition layer was found to be the largest under the concave wall feature, and the maximum thickness decreased with the increase of the prefabricated angle. [ABSTRACT FROM AUTHOR]

The aim of the cladding process is to improve mechanical, chemical, and physical features of the surface of metals. This laser process is frequently used to promote such alterations via deposition of metals/alloys with mechanical behavior superior to that of the substrate. In this contribution, an AISI 304 austenitic stainless steel is covered with an AISI 316 as powder filler metal using multiple laser deposition parameters. In the produced samples, the effect of the studied parameters on the geometry, surface appearance, dilution, and microstructural features was evaluated. The authors focus on metallurgical characteristics of cladding, seeking to explain the formation of three attributes: banding, columnar structure, and equiaxial grains. It was determined that banding is composed of a cellular-dendritic structure and is generated by changes in the microstructure size, derived from local variations in the solidification rate. The same applies for the columnar and equiaxial zones, but the appearance of equiaxial geometry is due to the change of the growth direction of the aforementioned columns, in the middle of the fusion zone. All the samples confirmed the formation of F/MA-type solidification mode, which indicates that the cooling rate is low and similar to those recorded in conventional fusion welding. [ABSTRACT FROM AUTHOR]

Nowadays, selective laser melting (SLM) technology features is somehow unknown mainly on the process parameters needed for each material. The main goal of this work is to give better process parameters combination when CoCrMo powders are utilized. A statistical methodology based on the experimentation has been applied. In this study, a full factorial design is used. It assesses the impact of process parameters on surface quality (Q), flatness, overlapping, and surface roughness. The distinguishing feature is the melting of single layers in variable layers powder with a continuous laser. Based on these results combined with visual observation of the solidified tracks, the effect of process parameters on the surface roughness for each case is investigated. The results show that surface roughness (Ra) is affected strongly by laser power, scan spacing, and scanning speed thereby giving an average roughness at 8 μm. In addition, other roughness parameters such as the peak height (Rp) and depth of the lowest point of the profile (Rv) are found to be useful tools for evaluation of top quality. The best layers have been showed when the laser powers are 300 and 400 W and the scanning space of 450 and 600 μm. These layers are classified with (Q) less than 2. [ABSTRACT FROM AUTHOR]