Tribological Characterization of the Heat-Assisted Single Point Incremental Forming Process Applied to the Ti6Al4V Alloy with the Definition of An Adhesion Parameter for the Tool Surface

Heat-assisted single point incremental forming or HA-SPIF has a great potential for producing one-piece batches of hard-to-form materials such as Ti6Al4V alloy for medical and aeronautical applications. One of the limitations of the process is the difficulty in achieving a reasonable surface finish, which makes essential the characterization of the tribological process in the tool–sheet contact. In fact, not much work can be found at this point in literature. In this research, a novel procedure for evaluating the adhesion on the tool surface is proposed and the influence of the temperature is determined. The surface finish of parts is analyzed, and the changes promoted by HA-SPIF appearing in the morphology of the external surface layer are characterized by SEM.

A study of wire tool surface topography and optimization of wire electro-spark machined UNS N06690 using the federated mode of RSM-ANN

PurposeThe purpose of this study is to examine the postprocessed wire tool surface using scanning electron microscopy and find out the streamlined conditions of input process variables using multi-objective optimization techniques to get minimum wire wear values.Design/methodology/approachA federated mode of response surface methodology (RSM) and artificial neural network (ANN) is used to optimize the process variables during the machining of a nickel-based superalloy.FindingsThe study explores that with the rise in spark-off time and spark gap voltage, the rate of wire tool consumption also escalates.Originality/valueMost of the researchers used the RSM technique for the optimization of process variables. The RSM generates a second-order regression model during the modeling and optimization of a manufacturing process whose major limitation is to fit the collected data to a second-order polynomial. The leading edge of ANN on the RSM is that it has comprehensive approximation capability, i.e. it can approximate virtually all types of nonlinear functions, including quadratic functions also.

Modeling the Effects of Various Liquid Droplet Sizes in Acoustic Deliquification Techniques

Liquid loading is a major challenge in natural gas wells. Enhancing the production in liquid loading natural gas wells using an acoustic liquid atomizer tool is proposed as a possible artificial lift method. The effect of different droplet sizes on the transport efficiency and the performance of the proposed technique during production are studied using Computational Fluid Dynamics (CFD) simulation. Also, the liquid behavior and fluid dynamics after applying the atomization mechanism are reviewed. In the model, the tool is placed axially in the middle of the gas/air flowing wellbore. To reduce computational time, the tool and pipe are cut symmetrically. The pipe diameter is 4 in, and the four injectors diameters are each 0.04 in. The orientation of the injectors is set to 90° with the sprayers facing sideways, while water liquid droplets are injected from the tool surface into the air flow at angles from 45° to the flow direction. Unstructured hybrid mesh is used to allow the cells to assemble freely within the complex geometry. Sensitivity tests were conducted with droplet sizes ranging between 30-300 µm. The CFD results showed that water liquid droplets of size 30 µm followed the pathway along the tool surface due to the low mass of the droplets and high air velocity. This phenomenon is called wall impingement and occurs where the droplets are very small and clustering on the wall. The 200 and 300 µm water liquid droplets kept their inertial high chaotic movements in all directions within the computational fluid domain due to the increased weight of the droplets. These larger sized droplets withstand the backpressure from high turbulent air velocity and tend to keep their inertial turbulent movement. This research presents a set of CFD results to further evaluate acoustic atomization as a possible artificial lift technique. This technique has never been commercially applied in the oil and gas industry, and continued evaluation of such methods is a vital addition to the industry as it brings the potential for new lower cost artificial lift technologies. If completely developed, this technique can bring a cost-effective solution compared to conventional artificial lift methods.

On Force-Displacement Characteristics and Surface Deformation in Piezo Vibration Striking Treatment (PVST)

This paper presents an experimental study on a novel mechanical surface treatment process, namely piezo vibration striking treatment (PVST), which is realized by a piezo stack vibration device installed on a CNC machine. Unlike other striking-based surface treatments, PVST employs non-resonant mode piezo vibration to induce controllable tool strikes on workpiece surface. In this study, an experimental setup of PVST is implemented. Four types of experiments, i.e., tool-surface approaching, single-spot striking, 1D scan striking, and 2D scan striking, are conducted to investigate the relationships among the striking force, tool vibration displacement, and surface deformation in PVST. The study shows that PVST can induce strikes with consistent intensity in each cycle of tool vibration. Both the striking intensity and striking location can be well controlled. Such process capability is particularly demonstrated by the resulting texture and roughness of the treated surfaces. Moreover, two linear force relationships have been found in PVST. The first linear relationship is between the striking force and the reduction in vibration amplitude during striking. The second one is between the striking force and the permanent indentation depth created by the strike. These linear force relationships offer the opportunity to realize real-time monitoring and force-based feedback control of PVST. This study is the first step towards developing PVST as a more efficient deformation-based surface modification process.

Fabrication of micro-structured tools for the production of curved metal surfaces by pulsed electrochemical machining

A new, scalable process chain for the fabrication of curved micro-structured metallic tools is developed and evaluated. Arrays of arrows, circles, semicircles and rings with final lateral dimensions of 124 to 819 µm are realised on the tools and successfully transmitted in one process step to stainless steel workpieces with a functional area of 6.5 cm2 using pulsed electrochemical machining. Photolithography-etching or micromilling are applied as initial micro-structuring processes, resulting in micro-structured master forms. These forms are copied into reusable silicon forms. This is followed by epoxy casting and electroforming to obtain the final tools. The tools are made of Nickel and have a diameter of 34 mm. Whilst micromilling, photolithography, silicon casting, epoxy casting and electroforming copy the structures very precisely, the wet etching process induces a widening of the dimensions due to the isotropic character of the process. The advantage of the process chain is the reusability of the master as well as of the silicone forms, which can be copied very precisely and easily with scalable processes to get precision tools with relatively large micro-structured areas. The reusability of the forms makes the fabrication of micro-structured tools relatively cost-efficient. The use of photolithography as the initial structuring process enables the generation of arbitrary, user-defined geometries for the micro-structures on the tool surface. The process chain described has the potential to fabricate lateral structure sizes on tools down to one micrometre.

Effect of Punch Surface Grooves on Microformability of AA6063 Backward Microextrusion

In order to apply conventional forming processes at the micro scale, the size effects caused by material properties and frictional effects must be taken into account. In this research, the effects of tool surface properties such as punch surface grooves on microextrudability, assessed using extrusion force, shape of the extrusion, and Vickers hardness, were investigated using an AA6063 billet. Microscale grooves of 5 to 10 µm were fabricated on the punch surface. The extrusion force increased rapidly as the stroke progressed for all the grooves. Comparing the product geometries showed that, the smaller the groove size, the lower the adhesion and the longer the backward extrusion length. The results of material analysis using EBSD showed that a 5 µm groove depth punch improved the material flowability and uniformly introduced more strain. On the other hand, material flowability was reduced and strain was applied nonuniformly when a mirror-finish tool was used. Therefore, the tribology between the tool and the material was controlled by changing the surface properties of the punch to improve formability.

STRENGTHENING OF PIPE TOOLS FOR COLD ROLLER ROLLING OF CORROSION-RESISTANT PIPES BY APPLICATION OF AMORPHOUS ALLOYS

In the production of pipes from corrosion-resistant steels on pipe rolling plants, the current problem is the low stability of the pipe tool. Therefore, the creation of high-performance and durable tools is associated primarily with the production and processing of materials that could withstand harsh working conditions. The technology of heat hardening of the pipe tool for cold roller rolling of corrosion-resistant pipes (rollers and support laths of HPTR mills) from 4Х5МФ1С steel which excludes the third holiday and uses drawing of a covering from powders of amorphous alloys 100…150 µm thick is offered in the work. As a result of the offered technology durability, wear resistance, and also hardness to HV0.1 950–1050 (in comparison with HV 587–690 on existing technology of heat treatment in factory conditions) increases. A wide range of studies of the structure of the coating and industrial tests of rollers and support bars. It is shown that gas-plasma coating of amorphous alloy based on Fe–Si–B system increases the hardness of the tool surface by 1.3–1.6 times and their stability by ~ 30…50%.

Design of an Experimental Injection Moulding Tool for Testing Microstructured Cavity Surfaces

This research is based on the impact assessment of the active element of injection moulding tools. The quality of the tool surface has a significant effect on the filling and cooling efficiency. Our goal is to create a uniform structure on the cavity’s surface that results in a high degree of orientation during the injection moulding process. A special experimental tool is needed for the research. Our design was based on the results of previous experimental research and preliminary criteria. The design was based on the size and position tolerances of the A side of the tool. As the previous study has shown, there are three main points to consider when designing an experimental moulding tool. These are the applied manufacturing technology, Design for Assembly, and the expansion of the measurement possibilities by using different sensors. The small beam size of the femtosecond laser also allows the machining of microscopic-sized details, a technology used to structure the cavity surface. The success of this was analyzed by microscopic examination.

REPRESENTATION, CHARACTERIZATION AND SIMULATION OF TOOL-PART INTERACTION AND ITS EFFECTS ON PROCESS-INDUCED DEFORMATIONS IN COMPOSITES

The interaction between a tool and part during composites processing contributes to the formation of residual stresses and dimensional changes. A resultant mismatch of part geometries during assembly can cause a potential loss of mechanical performance in aerospace structures. Costly shimming steps are needed to compensate for processinduced deformations and satisfy specifications on mechanical performance. Due to difficulties associated with accurate measurement of interfacial shear stresses, current analysis methods fail to represent the interaction between a tool and part throughout processing. A combined approach to represent, characterize, and simulate tool-part interaction and its effects on dimensional changes is proposed. First, a characterization method was established using a custom Dynamic Mechanical Analysis (DMA) shear test setup to measure tool-part interfacial stress development in a simulated autoclave curing environment. Tool-part interfacial stresses were characterized for Toray T800S/3900-2 UD prepreg as a function of temperature, degree of cure, strain rate, and tool surface condition. Then, a previously developed numerical model was modified to include the effects of tool-part interaction in predicting dimensional changes of L-shape parts. For validation, composite parts were fabricated on tools with different surface conditions and successfully compared to simulation results. This paper demonstrates that tool-part interaction significantly impacts the spring-in of angled composite parts. The proposed method is a comprehensive and practical approach to study and simulate the effects of tool-part interaction. The results of this paper can be used to understand the complex interaction between a tool and part throughout processing and potentially mitigate processinduced deformations.