The Influence of Technological Factors of Centrifugal Planetary Treating the Roughness of the Internal Channels of Small-Sized Parts

Surface integrity in abrasive flow machining (AFM) of internal channels created by selective laser melting (SLM) in different building directions

Abrasive flow machining (AFM) finishing of conformal cooling channels created by selective laser melting (SLM)

Selective laser melting (SLM) is an additive manufacturing process for producing metallic components with complex geometries. A drawback of this process is the process-inherent poor surface finish, which is highly detrimental in materials submitted to fatigue loading situations. The goal of this work is to analyze the fatigue behavior of Ti-6Al-4V specimens with internal axial channels under the following different conditions: hole drilled, hole as manufactured, and hole threaded M4 × 0.7. All the cases studied showed a lower fatigue performance as compared with solid samples due to the surface roughness and geometry effect that produced a surface stress concentration leading to a reduction in fatigue strength. The fractography revealed that crack initiation occurred from the internal surface in all specimens with internal channel mostly from defects as unfused particles and lack of fusion zones, while for the solid specimens crack initiation was observed from the external surface due to insufficient fusion defect. The application of the Smith-Watson-Topper energy-based parameter was revealed to be a good tool for fatigue life prediction of the different series studied.

Controlled hydrodynamic cavitation abrasive finishing (HCAF) process is presented as a new approach for surface finishing the internal surfaces of mechanical components. A recirculating hydrodynamic apparatus is designed and developed to generate controlled cavitation. Experiments are conducted on the internal channels fabricated using electric discharge machining (EDM). Firstly, the surface wear arising from the combined effects of controlled hydrodynamic cavitation and abrasive particles are investigated at (a) non-cavitating condition without abrasive particle, (b) cavitating condition without abrasive particles (c) abrasion condition without cavitation and (d) combined cavitation and abrasion condition. The effect of various operating conditions on the material removal are discussed. Lastly, the improvements in profile surface roughness (Ra) of the internal channels is characterized using optical profilometer. The results obtained (Ra < 1 µm) clearly shows that the combined effect of controlled cavitation and abrasive particles has a significant effect on the surface roughness reduction of internal surfaces.

Additive manufacturing (AM) is able to create engineering components with internal features that are unmeasurable using conventional tactile and optical methods; new methods for measuring internal inaccessible features in a non-destructive manner are required. In this work a metal additively manufactured (AM) component with an internal channel is fabricated and scanned via X-ray computed tomography (XCT) before and after undergoing internal surface polishing by means of abrasive flow machining (AFM). The internal surface roughness of the AM channel is characterised in 3D to better understand and control the AFM process. The results show that XCT is able to reveal the complex internal surface texture of metal AM components and to quantify the changes caused by the AFM process.

Surface finishing of additively manufactured Inconel 625 complex internal channels: A case study using a multi-jet hydrodynamic approach

To solve the problem of poor surface quality of internal channel parts in additive manufacturing, the internal electrode electrolyte plasma polishing technology was used to improve the surface quality of the workpiece. The influence of different process parameters on the surface roughness of the internal channel was studied by orthogonal test. The experimental results show that for small caliber channels, polishing is more suitable for low voltage conditions. Under the conditions of polishing voltage 40 V, electrolyte temperature 80°C, moving speed of cathode wire 3 mm/min, and peristaltic pump speed 100 rpm, the roughness of the GH3536 inner channel sample is reduced from 15.1 to 2.793 μm. The order of influence of each factor is as follows: firstly voltage, secondly electrolyte temperature, then cathode wire traveling speed, and finally peristaltic pump speed. The roughness of GH4169 was reduced from 6.724 to 0.47 μm by polishing experiment. The results of the internal surface performance test show that the spherical powder on the surface of the workpiece disappears after polishing through the internal flow channel, the electrolyte component residue is not detected on the surface of the internal flow channel, and the corrosion resistance is significantly improved.

Study of Internal Channel Surface Roughnesses Manufactured by Selective Laser Melting in Aluminum and Titanium Alloys

On the effect of internal channels and surface roughness on the high-cycle fatigue performance of Ti-6Al-4V processed by SLM

This article introduces a new biomedical / open surgical instrument to assist surgeon in applying surgical clips to patient’s body tissue and blood vessel during surgical processes. The new clip delivery system is designed to better the clip’s distal advance through internal clip channel, jaw guiding track, and all other transition areas to keep surgical clip from accidental shooting out during clip’s distal move into jaws. Currently the clip distal move in normal surgical instrument is usually driven by compression springs and some complains of clip accidental drop-off were recorded in surgical procedures. Because higher request of dimensional tolerance and better component surface quality are needed in case the compression springs are used as driven force, a little dimensional devia-tion or less qualified part surface produced from manufacturing processes will potentially cause surgical clip device malfunction or misfiring of the clips. It is clearly known that the jaws can seriously sever or damage patient’s blood ves-sel or body tissue if there is no clip inside the jaws due to accidental clip drop-off, when surgeons close instrument handles. The improved internal system design in this new open surgical instrument can prevent clip from accidental drop-off because of well guided and controlled clip distal move through internal clip channel and track. Besides the operational force to fully form clip is lower than existing surgical clip devices due to better mechanical advantage in this new instrument design. In addition to the above, manufacturing and product cost can be decreased since lower requirement of dimensional tolerance and surface quality of instrumental parts is allowed in this new surgical instrument design. This new instrumental prototype is build upon the analysis of computer aided modeling and simulation to prove its good mechanical advantage, feasible function, reliable performance. The preliminary results of instrument fir-ing force from both computer aided modeling and prototype testing are very close to each other, and preliminary prototype testing shows no accidental clip drop-off in this new biomedical / surgical clip instrument.

Exploration of accessibility of internal pore surface by using rigid nanoparticles as a probe for constructing the integrated nanocomposites

In contrast to a large number of publications about the influence of interstitial elements (O, N) on the physical-mechanical properties of zirconium alloys, insufficient attention at present is paid to examining their influence on the characteristics of near-surface layers of the shells of heat generating element (HGE). Therefore, it is expedient to widen the knowledge about the influence of interstitial elements on the properties of zirconium HGE tubes. Authors experimentally established the influence of treatment in the controlled oxygen- and nitrogen-containing gas media on the mass increment and properties of the near-surface layer of samples-rings, cut out of the shells of heat generating elements. Differences in the saturation of internal and external surfaces of zirconium pipes were described. It was shown that roughness of the internal surface is less compared to that of the external surface. Results of examining the hardness of external and internal surfaces of the samples-rings after oxidizing and nitriding are presented here. For example, treatment of the samples-rings in the oxygen-containing medium (T=650 °C, t=20 h) leads to the formation of hardness at the external surface HV0.49=1190±90, and at the internal surface HV0.49=1190±90. However, after treatment in the nitrogen-containing medium (T=650 °C, t=20 h), the hardness on external surface is HV0.49=615±35, while on the internal surface it is HV0.49 =445±35.For example, after treatment in the oxygen-containing medium (T=650 °C, t=20 h), depth of the strengthened layer at the external surface is l=70…75 μm and at the internal surface, it reaches l=60…65 μm. Treatment in the nitrogen-containing medium (T=650 °С, t=20 h) causes the formation of a strengthened layer on the external surface l=60…65 µm and on the internal surface – l=55…65 µm.The duration of isothermal holding in the oxygen mixture, which can lead to the crack initiation at the internal surface of zirconium HGE pipes, was experimentally discovered. Results of present work may be taken into account for the development of modes of treatment of zirconium alloys.

In the management of communications under the conditions of the development of an industrial enterprise, there are continuous violations in communications due to the poor quality of communication channels or due to unexpected changes in the environment with which communication channels can not exist. To solve this problem, a scientific and methodical approach to controlling the stability of communication channels has been developed in the management of the development of an industrial enterprise, which is based on the consideration of the peculiarities of different types of internal and external communication channels and the use of which makes it possible to identify problems in communications in a timely manner and adapt communication channels to changes in external environment or to the features of internal communications. The methods of formalizing the estimation of the stability of communication channels of an industrial enterprise are developed, providing the basis for their correction or for adjusting managerial decisions in case of distortion of the information received through insufficiently stable communication channels. In order to assess the stability of the communication channels, it is proposed to distinguish between internal and external communication channels. In turn, the internal communication channels can be upright and horizontal. Vertical channels combine subdivisions or individual workers at different levels of the hierarchy, and horizontal channels combine subdivisions or employees of an enterprise that are at the same level of the hierarchy. In addition, it is proposed to distinguish between symmetric and asymmetric channels as well as unitary and binary communication channels.Models for estimating stability are developed for each of the proposed communication channel types. An analysis of the stability of communication channels of an industrial enterprise allows them to be adapted to changes in the external environment or characteristics of internal communications.

The considered operating ferrous metallurgy enterprise uses three different technological modes of steel smelting, each of which is characterized by an individual composition of the ingredients of chemical pollutant emissions into the atmosphere affecting the state of the forest areas around this enterprise. Based on the decoding of satellite pixel photographs of forest areas, the technological mode with the least impact on forest areas was determined. It corresponds to the condition of the minimum area of ecological zones around the ferrous metallurgy enterprise. The authors propose an assessment of the impact of chemical pollution of ferrous metallurgy enterprises on forests in the form of areas of ecological zones of the state of forest vegetation and the volume of biomass in its various parts. The mosaic of ecological zones of forest areas is determined from their satellite pixel photographs using an original algorithm of “controlled cluster analysis”. The main recommendation for ferrous metallurgy enterprises to choose one of several alternative technological modes is as follows: the choice of technological mode should be based on a comparison of sizes of the areas of ecological zones. In this case, the technological mode with the smallest dimensions of the area is selected. Assessment of the damage caused by the chemical pollution of the plant to forest areas was determined by the area of ecological zones and the volume of biomass loss in forest areas in comparison with the background areas. The boundaries of ecological zones can be determined according to the “dose-effect” dependencies typical for the considered region.

This paper presents both an experimental study and a theoretical discussion on the relevant faults resulting from progressive creeping discharge. Pressboard ageing, voltage amplitude, and pressboard type are configured to generate the faults under divergent creeping stresses. The fault progression is recorded by high-resolution camera, partial discharge (PD) device, and optic-fiber thermometer. The damaged pressboards are scrutinized by microscopy and image-processing techniques, and gas chromatography is used to analyze the gas compositions. The progression of internal treeing shows distinct stages of different interface phenomena, such as spark discharge, white marks, and bubbling effect, as well as varying discharge patterns. In contrast, the progression of surface tracking is a simple but hardly noticeable process due to the PD disappearance. The internal carbonization channels are believed the fundamental causes of the interface phenomena pertinent to internal treeing. A theoretical model is proposed to expound the development of the internal carbonization channels, which considers the charge emission, the pressboard pyrolysis, and the percolation theory. The failure mode of internal treeing is schematically illustrated using a four-phase model, and the effects of thermal ageing and field distribution on surface tracking are discussed. Lastly, a detailed comparison is made between internal treeing and surface tracking in terms of the occurrence condition, initiation mechanism, growth driver, and growth characteristics.