Effect of Grain Size on Change in Surface Roughness of Carbon Steels Through Polishing Processes

A mirror-like reflecting surface is an important characteristic in many industrial metallic parts. Polishing is done to form a mirror surface on metals. However, the effect of the grain size of metals on surface roughness through polishing processes is not clear. Specifically, mirror surface formation of ultrafine grained materials is still unknown. Ultrafine grained steels and coarse grained steels with 0.02, 0.10, and 0.60 wt% carbon contents were prepared by warm caliber rolling and annealing. Average grain sizes were 1–2 μm and 4–40 μm. The changes in surface roughness, Sa, were measured with an atomic force microscope (AFM) via eight polishing steps, using emery papers of type #600, #1000, #1500, #2000, #2500, #4000, and free abrasive grains of 3 μm and 1 μm diamond. As the polishing process progressed, the surface unevenness was removed and the surface roughness, Sa, decreased in all steels. The differences of Sa at each polishing step were analyzed from the point of carbon content, Vickers hardness, and grain size. Carbon contents and Vickers hardness have little effect on Sa. However, grain size has a considerable effect on Sa in all steels. Ultrafine grained steels have smaller Sa in all polishing steps in all steels. This is because ultrafine grained steels have very small work hardening rate. After final polishing, Sa is 2.5–3.6 nm in coarse grained steels and 2.0–2.6 nm in ultrafine grained steels. To obtain a mirror surface with smaller Sa, grain size control is important.

A New Approach For Calculating Inherent Strain and Distortion in Additive Manufacturing of Metal Parts

Additive manufacturing (AM) of metallic parts is widely utilized for industrial applications. However, quality issues of the printed parts, including part distortion and cracks caused by high temperature and fast cooling, result in high residual stress. This is a challenge that limits the industry acceptance of AM. To overcome this challenge, a numerical modeling method for predicting part distortion at the design stage plays an important role, and enables design engineers to remove failures before printing, as well as determine the optimal printing process parameters to minimize part deformation. This research proposes an inherent strain-based part deformation prediction method. To determine the inherent strain (IS) value, a micro-scale model for analyzing the temperature distribution is constructed. The IS value is calculated from the temperature gradient. Then, the IS value is used for determining the part deformation. The proposed methodology has been developed and evaluated, using a 316L stainless steel cantilever beam, in both simulations and experimental results.

Thermal Treatment under Vacuum for Obtaining a Quenchant from Rapeseed Oil

The aim of this study was to improve the quality of a vegetable oil, having in view its use as a quenchant for metallic parts in aircrafts. A process of pyrolysis under vacuum was applied to obtain a bio-oil with reduced viscosity and good quenching properties. Preliminarily, the rapeseed oil was fast pyrolyzed at temperature in the range of 300–375 °C and absolute pressure of 1 μbar. Some results such as viscosity and yields of bio-oil were obtained with a narrowing of the temperature range between 300–320 °C, for further processing. Quenching tests with bio-oils on stainless steel 25CD4 showed cooling curves closer to those of the standard mineral oil (Castrol IloquenchTM 1), by comparing them with unprocessed vegetable oil. The hardness of the steel after treatment rose from 29–30 HRC to 43–45 HRC, in accordance with requirements (35–45 HRC). Therefore, the conclusion is that bio-oils obtained by pyrolysis under vacuum are good quenchant proceeds from this study.

Surface and Interface Studies for Improved Performance of Metallic Parts and Devices

This work is to reveal and present some contemporary surface treatment methods used in view of improving performance of parts of a variety of metals and alloys. Stainless steels and titanium alloys are with the group of particular focus, important for medical implants in chirurgy and instruments used in dentistry. Improved, anti-corrosion properties and mechanical strength of materials are the primary features for examination.

Image processing method for delamination and fiber pull-out assessment during drilling of natural fiber composites

Natural fiber-reinforced composites are promising alternative materials in the manufacture of modern moderate-to-high-technology products. However, their heterogeneous structure causes processing defects uncommon with metallic parts. Drilling of composites is an essential machining process to facilitate assembly and fastening of composite components. The occurrence of delamination damage around the drilled hole and fiber pull-out within the hole are critical factors that affect the performance of these parts when assembled. A new image processing method using digital scanning and tracing for characterizing delamination and fiber pull-out induced by drilling has been developed to address the limitations in the existing methods of quantifying drilled hole qualities. The capability of the proposed method as a delamination and fiber pull-out assessment tool was verified using simulated and real images of drilled holes. The method was also used to investigate the effect of drilling parameters on delamination and fiber pull-out in jute reinforced epoxy composite produced via resin transfer molding. The results show that drill bit diameter, feed rate, and spindle speed have varying effects on both delamination areas and fiber pull-out within the drilled hole.

Increasing the Environmental Sustainability of an Over-Injection Line for the Automotive Component Industry

Thermoplastic injection is currently employed in different industrial fields. This process has significantly evolved over the years, and injection machine manufacturers are continuously forced to innovate, to improve the energetic efficiency, aiming to reduce costs, improve competitiveness, and promote environmental sustainability. This work focuses on the development of a novel, profitable, and environmentally friendly plastic over-injection equipment of small metallic parts for the automotive industry, to be applied in a bowden cable production line, to cover the zamak terminations with plastic, or produce terminations entirely made of plastic. The work is based on an over-sized existing solution. The operating parameters required for the work are quantified, and all machine parts are designed separately to achieve the required functionality. Known approaches are finally used to perform the cost analysis, calculate the return on investment (ROI), and energetic efficiency, to substantiate the replacement of the current solution. The new equipment was able to increase the energetic efficiency of the current assembly line while keeping the required injection rates. An efficient and sustainable solution was presented, with a ROI of 1.2 years over the current solution. The proposed design is also applicable to different automated production lines that require this technology. Nowadays, this concept can be extended to all fields of industry that employ injection molding in their processes, enabling to integrate new manufacturing systems, and increasing energetic efficiency while reducing production costs.

Prediction of the microstructural grain evolution during selective laser melting by a cellular automata method

The mechanical properties of additively fabricated metallic parts are closely correlated with their microstructural texture. Knowledge about the grain evolution phenomena during the additive manufacturing process is of essential importance to accurately control the final structural material properties. In this work, a two-dimensional model based on the cellular automata method was developed to predict the grain evolution in the selective laser melting process. The effectiveness of this presented model is proven by comparing the simulated and reported results. The influence of process parameters, like the scanning strategy, laser power, and scanning speed, on the microstructural grain morphology, are numerically evaluated.

Design and validation of integrated clamping interfaces for post-processing and robotic handling in additive manufacturing

Additive manufacturing (AM), particularly laser-based powder bed fusion of metals (LPBF), enables the fabrication of complex and customized metallic parts. However, 20–40% of the total manufacturing costs are usually attributed to post-processing steps. To reduce the costs of extensive post-processing, the process chain for AM parts has to be automated. Accordingly, robotic gripping and handling processes, as well as an efficient clamping for subtractive machining of AM parts, are key challenges. This study introduces and validates integrated bolts acting as a handling and clamping interface of AM parts. The bolts are integrated into the part design and manufactured in the same LPBF process. The bolts can be easily removed after the machining process using a wrench. This feasibility study investigates different bolt elements. The experiments and simulations conducted in the study show that a force of 250 N resulted in a maximum displacement of 12.5 µm. The milling results of the LPBF parts reveal a maximum roughness value, Ra, of 1.42 µm, which is comparable to that of a standard clamping system. After the bolt removal, a maximum residual height of 0.067 mm remains. Two case studies are conducted to analyze the form deviation, the effect of bolts on build time, and material volume and to demonstrate the application of the bolts. Thus, the major contribution of this study is the design and the validation of standardized interfaces for robotic handling and clamping of complex AM parts. The novelties are a simple and clean interface removal, less material consumption, less support structure required, and finally an achievement of a five-side tool accessibility by combining the interfaces with a three-jaw chuck.

Keep Your ESPs Running: Case Studies Exhibiting a Holistic Methodology for Run-Life Improvement

Build a more robust ESP or reduce the stress it endures? Run-life improvement requires finding the right balance to suit the local well conditions and economics. Utilizing key case studies, the paper examines how operational stress caused by low flow rates can be avoided with the correct utilization of instrumentation, surveillance, and automation thereby providing practical solutions for extending the run life of already installed ESPs. The method starts with an extensive review of ESP failure mechanisms and their causes, supported by case studies and pictures illustrating the symptoms that can be observed during dismantling. This holistic technique is supported by several case studies. The common "thread" found on most failure mechanisms is temperature rise inside the ESP, which deteriorates properties of materials, including polymer insulation, elastomer seals, and metallic parts. Heat rise is attributed to three main causes: motor thermal losses, pump hydraulic losses, and frictional heat. Case studies and data sets are provided to confirm that a paradigm shift in mitigation improvement can be achieved by automating the identification of low flow events utilizing a downhole real-time flowmeter. Three reasons are given. Firstly, it is a leading indicator, whereas surface flow meters and temperature sensors are lagging indicators due to pump-up time and heat exchange respectively. Secondly, automation enables more consistent and cost-effective identification in large ESP populations. Thirdly, it enables deeper diagnostics of the cause of low flow (i.e., gas lock versus slugging, and even the source of slugging such as horizontal lateral versus production tubing). The authors provide an exhaustive list of case studies identifying sand fallback and scale as well as low flow causes and how they can be diagnosed, including differentiation between ESP, wellbore hydraulics, and reservoir inflow causes (e.g. depletion and skin.) Over the last 30 years, improvements in design and materials have tripled ESP run lives. Therefore, many fields attain six-year average run lives and 90-day survivability of 98%. Nevertheless, economics have tightened, which has raised the bar, and therefore, many operators still suffer uneconomical run lives. Case studies indicate that the next step-change in run life improvement will require a reduction in environmental stresses by mitigating the effect of low-flow events, scale, and sand.

Investigation on Bidirectional Pulse Electrochemical Micromachining of Micro Dimples

Through-mask electrochemical micromachining (TMEMM) is a promising method to prepare micro dimples on the surface of metallic parts. However, the workpiece is machined one by one in traditional TMEMM. This paper introduced bidirectional pulse to TMEMM to improve the machining efficiency. Two masked workpieces were placed face to face, and connected to the ends of the bidirectional pulse power supply. Along with the change of the pulse direction, the polarities of the two workpieces were interchanged periodically, and micro dimples could be prepared on both workpieces at one time. The simulation and experiment results indicated that with bidirectional pulse mode, micro dimples with same the profile can be prepared on two workpieces at one time, and the dimension of micro dimple was smaller than that with unidirectional pulse mode. In bidirectional pulse current, the pulse frequency and pulse duty cycle played an important role on the preparation of micro dimple. With high pulse frequency and low pulse duty cycle, it is useful to reduce the undercut of micro dimple and improve the machining localization. With the pulse duty cycle of 20% and pulse frequency of 10 kHz, micro dimples with etch factor (EF) of 3 were well prepared on both workpieces surface.