Papers by Keyword: Processing

Abstract: Direct compounding of long fiber thermoplastic (LFT-D) materials in compression molding are two complex processes in series linked by the plastificate. Continuous compounding and sequential compression create a time-dependent property progression along the extrusion direction of the plastificate. Under variation of secondary parameters, extruder die temperature, and die height of the LFT-D line, samples of plastificates, flow fronts and plates are manufactured and characterized. The plastificate density progression along the extrusion direction is primarily influenced by the temperature of the die. Lofting of the plastificate is higher at high temperatures while the density difference along the extrusion direction is lower. This density difference is known to influence fiber orientations and mechanical properties. The flow front of the material filling the mold is skewed because of the density difference. We show that the skewness is mainly influenced by the die height and is lower at high die heights. The fiber content distribution in the plate is discussed and found to be influenced by the length of the plastificate which is in turn determined by the secondary parameters. These secondary parameters of the LFT-D line can play a role in process optimization once the primary parameters are selected. This work provides clues and observations of principles for such optimizations.

Abstract: This study presents integrated methodology for using RTK and non-RTK UAV systems in open-pit mining surveying. Three experiments were performed using DJI Mavic 3E RTK and DJI Mini 3 Pro drones at an altitude of 61.5 m with an overlap of 80%×75% over identical sites. A network of 12 precisely located control points allowed for a comparative assessment of the accuracy between RTK+GCP, non-RTK+GCP, and RTK-only configurations. Statistical analysis using multivariate analysis of variance (ANOVA) confirmed the significance of the positioning technology for survey accuracy. The RTK system achieved RMS errors of 2.88-5.23 cm versus 17.27-22.94 cm for non-RTK systems, representing a 5-6-fold increase in accuracy. This comparison demonstrates that RTK without ground control points maintains comparable accuracy (5.23 cm) to RTK with control points (4.45 cm), while reducing operating costs by 84%. Analysis of camera position accuracy showed an accuracy of 2.04-2.06 cm RMS regardless of the use of control points. These results confirm that RTK methodology is cost-effective for standard surveying, achieving geodetic-grade accuracy without traditional field support infrastructure. The methodology allows for continuous monitoring of mining operations while reducing costs and increasing accuracy.

Abstract: One of the main problems with the use of steels for elevated temperatures is their limited weldability. This is mainly due to the fact that these materials may contain in their chemical composition. Due to the susceptibility to cold cracking, PWHT is necessary, especially in high-stiffness welded structures. In addition, depending on the condition after heat treatment or in the absence of heat treatment, precipitates may appear in the microstructure of the steel, affecting its mechanical properties. It is important in this case to ensure the high quality of welded joints, which means that the manufacturer has to demonstrate a very high technical culture. Currently, thin-walled pipe butt joints are welded manually using a tungsten electrode with solid wire material (TIG method). One of the solutions that can significantly speed up the welding process of components for work at elevated temperatures is the use of an electron beam welding. In addition, the ability to make welded joints without the use of filler material and to achieve narrow heat-affected zones may find application in the welding of modern materials used in the power industry. This paper presents the welding experience of materials assigned for the power industry (TEMPALOY AA1 and T92) by use of electron beam. In this article authors present the results of tests gained during first steps of welding welded joints. The article also includes preliminary results on the service life of the fabricated joints.

Abstract: This study details the design, assembly, and measurement processes of a modified test bench for examining sliding ring seals. We designed a test bench suitable for measuring mechanical seals, during which we first developed the concept and the design of the bench, defined the parameters to be measured and the measurement methods, and then implemented these objectives using an existing test bench. After procuring raw materials, I manufactured and assembled the necessary components, including acid-resistant and corrosion-resistant steel parts. Key machining operations were performed, such as drilling and threading, to accommodate the mechanical seals and ensure proper alignment. Following assembly, I conducted three reference measurements with varying compressive spring forces. The system's torque was measured at a consistent rotational speed of 200 RPM. Results from the frictional torque measurements revealed that the seals displayed sensitivity to compressive forces, confirming the effectiveness of the modified test bench for future seal evaluations.

Abstract: A novel approach for processing SiC wafers has been developed to grind then polish 150 and 200mm SiC wafers without lapping. The purpose of this work was to optimize the processing of SiC wafers sliced from boules to finished epi-ready wafers by grinding and chemical-mechanical polishing (CMP). Diamond vitrified wheels were used for coarse and fine grinding to correct the irregular shape of SiC wafers before reducing surface roughness by CMP. 4H-SiC wafers were sliced by diamond embedded/slurry wire saw and laser split techniques. Incoming wafer condition was seen to affect coarse grinding wheel performance depending on incoming surface roughness and shape. Wheel characteristics, including abrasive size, abrasive concentration, and bond structure, were adjusted to improve grinding efficiency based on incoming conditions. Coarse grinding wheels were able to reduce wafer total thickness variation to 3-5um and average surface roughness to 20-30nm (Ra). Fine grinding wheels were optimized to reduce total thickness variation (TTV) below 2um and surface roughness to 1-2nm Ra and peak-to-valley height of 20-30nm (Rt). Coarse and fine wafering time was less than 30 minutes total to remove 50 microns on both Si and C-face per wafer. Surface damage from grinding was removed after one hour of polishing each wafer by CMP, achieving surface roughness of 0.4nm Ra and 5-7nm Rt. The benefit of optimizing coarse and fine grinding of 150 and 200mm SiC wafers is demonstrated by producing flat wafers, which reduced overall processing time to prepare an epi-ready condition by CMP.

Abstract: With the COVID 19 pandemic and the rise of polymerase chain reaction (PCR) testing in its wake, affordable large-scale testing became necessary. A thermal cycler for PCR has been developed that is affordable, fast, and accurate. The thermocycler must follow a specific temperature profile consisting of three different temperature levels. To ensure the success of any PCR, the tempering elements must accurately follow the tempering profile and be stable heat sources to maintain any given temperature. A control mechanism is required to approximate this prescribed temperature behavior. The basis for this is a Proportional-Integral-Differential (PID) controller, whose functionality is ensured by a feedback mechanism consisting of a temperature sensor. The PID controller provides precise attainment and maintenance of the temperature levels. A high performance Peltier element is used to heat and cool the PCR system. This is controlled by a programmable power supply and, in combination with a heat dissipation system, achieves heating and cooling powers in excess of 200 W. In addition, different design variants of the thermal cycler were created and their temperature behavior was simulated. These were then implemented, tested and the PID controller tuned accordingly. These tests help to find the best design for the thermal cycler with the optimal heat distribution.

Abstract: Organ models that resemble the original anatomy are needed in the education and training of human and veterinary doctors. The organs should be as close as possible to the original in shape, colour and feel. Furthermore, these organ models must be able to be handled in such a way that they can be examined by palpation and imaging (ultrasound, X-ray, CT and endoscopy). The diagnostic procedures should detect pathologies such as cysts, tumours, ruptures, haemorrhages or air collections. Following the diagnostic measures, it must be possible to initiate a therapy. Possible therapeutic measures are surgery with a scalpel, electrosurgery or puncture. The present work deals with the production of training models by means of a casting process. With this method, the models can be produced quickly and at low cost. Different compositions of hydrogels and other biomaterials are investigated. These gels are examined for the following properties, among others: thermostability, electrical conductivity and dimensional stability under pressure. Other parameters such as pot life, cross-linking time and durability in relation to mould formation will also be considered.

Abstract: Ni-cellulose nanofiber (CNF) composite plated films were fabricated by electroless plating method. The deposition conditions and basic properties of the Ni-CNF composite film were investigated. A C1100 plate was used as the plated material, and a Ni-P electroless plating bath was prepared as the plating solution. 5 g/L of 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) oxidized CNF or carboxymethyl cellulose was added to the plating solution. Sodium dodecyl sulfate (SDS) was added as a surfactant. It was confirmed that CNFs were complexed on the surface of the plated film, and the addition of SDS made CNFs disperse into the plated film. The surface of the plated film obtained by adding both TEMPO oxidized CNF and SDS had the highest Vickers hardness among all conditions investigated.

Abstract: Fire though an important component of life, the devastating effect of fire accidents is a threat to life and materials. Thus, the prevention and control of fire are becoming a serious concern. Hence, it is no wonder that fire retardant materials (FRMs) are slowly becoming ubiquitous in our daily lives. To control the fire in an unexpected fire accident or to prevent fire accidents FRMs are becoming essential requirements. To save material or life, fire retardant materials have been used for long knowingly or unknowingly. However, the understandings of chemistry and thermochemistry of materials helped for the development of efficient FRMs. Diversified materials, processing methods, and application modes have been developed, and all of them become specific depending on the nature and origin of the fire. In this regard, the inorganic FRMs form a distinct category due to their low cost, easier processing and wider choice of application mode without leaving any additional environmental burden either to land or the atmosphere. In this paper, different fire retardant materials and their properties with the abilities to tackle the fire at different temperatures are reviewed. The primary characteristics of fire and the thermal behaviours of FRMs as well as changes in behaviour/properties when FRMs are treated with certain synergistic systems are discussed. The importance of composition, morphology and structure of FRMs on the efficiency and applicability are discussed. Recent developments on the synthesis and characterisation of different types of FRMs and their composites have been elaborated. The effective applications and the commercial products based on their properties are also briefly covered. Overall, the review provides an overview of existing information on fire retardant materials in terms of their synthesis, processing, usability and limitations, with a prime attention on the process-structure-property relations of these materials.

Abstract: Soybean for tempeh preparation is generally peeled by wet milling of cooked soybean seeds. This technique is time consuming and requires a lot of water. Instead, peeling can be done by dry milling prior to cooking to save processing time and water usage. This research aims to evaluate the characteristics of tempeh prepared from local Indonesian soybean as influenced by peeling techniques. The characteristics of peeled and unpeeled-soybean were also evaluated. Characterization of tempeh was done on proximate composition, textural properties, color, and organoleptic acceptances. The proximate characteristics of tempeh made from dry-peeled and wet-peeled soybean had no significant differences. Tempeh prepared by dry peeling had a softer texture (1.79 N) than that prepared by wet peeling (2.04 N). The color of tempeh with dry-peeled soybean was lighter than that with wet-peeled soybean, both its outer and inner part. Tempeh prepared by dry peeling had a better sensory acceptance in chewiness (4.3) than that by wet peeling (3.0), and no differences in taste, cohesiveness, aroma, and color. These results provide an alternative of a more environmentally friendly tempeh preparation with a dry peeling technique.