Metaphoric perceptions of pre-service teachers about ‘LEGO Robotic Instructional Practices,’ ‘Augmented Reality’ and ‘Flipped Classroom’ concepts

The aim of this study is to reveal perceptions of pre-service teachers about ‘LEGO robotic instructional practices,’ ‘augmented reality’ and ‘flipped classroom’ concepts through metaphors. The study is descriptive research that was conducted as a survey model. The study group consists of 37 pre-service teachers studying the undergraduate programme of Science Teaching, Faculty of Education of a university in the Western Black Sea Region in the spring semester of the academic year 2016–2017. A form consisting of three open-ended questions was used as a data collection tool during the study. The data acquired were analyzed through content analysis method. Following the study, 15 different metaphors created in relation to the LEGO robotic instructional practices concept were categorized as ‘edutainment tool,’ ‘a technological tool’ and a ‘development tool,’ while 24 different metaphors created in relation to the augmented reality concept were categorized as ‘Perception Of Reality’, ‘A Technological Tool’, ‘Change/Transformation Tool’ and ‘Entertainment Tool’. Moreover, 25 different metaphors created in relation to the flipped classroom concept were classified in two categories as a ‘form of education’ and ‘an education shaping tool’. Moreover, almost all of the metaphors created were observed to have positive features.

Plastic Flow Verification in a Tool Cavity for Production of Test Sample for Wettability Solders Measurement

The paper describes the structural design, simulation and proper manufacture of a tool for manufacturing of test samples in spherical form. This shape is essential for an innovative assessment of solder wettability, since the small sphere by its ideal shape represents the total non-wettability of substrate surface. In order to verify the design of the shaping tool, a simulation software, type Deform was used, which allowed the FEM analysis of plastic flow in the tool cavity. Just after successful computer simulation, a shaping tool was designed and then manufactured in laboratory conditions, thus the fabrication of test samples in spherical form was successfully tested.

Advanced Waterjet Technology for Machining Curved and Layered Structures

Considerable advancements in waterjet technology take advantage of its inherent merits as a versatile machine tool have been achieved in recent years. Such advancements include, but are not limited to, process automation, machining precision, multimode machining of most materials from macro to micro scales, and cost effectiveness with fast turnaround. In particular, waterjet as a cold cutting tool does not introduce heat-affected zones (HAZ) and preserves the integrity of parent materials. As such, for heat-sensitive materials, its cutting speed is over ten times faster than those of thermal-based tools, such as solid-state lasers, electric discharge machining (EDM), and plasmas cutting. Although waterjet is basically a 2D machined tool, novel multi-axis accessories were developed to enable 3D machining and for machining on workpieces with 3D geometry. For composites, waterjet unlike mechanical routers is capable of minimizing or mitigating tearing and fraying. CNC hard tools that are in direct contact with highly abrasive composite matrix often experience rapid wearing while the heat generated by machining processes induces thermal damage to the composite. This is a nonissue for waterjet as it is a noncontact tool. The only issue for machining composites with waterjet was the damage caused by large stagnating pressure developed inside blind holes during the initial piercing operation (before breakthrough). Considerable effort was made to understand and resolve the waterjet piercing damage issue. For extremely precise parts, waterjet can serve advantageously as a near-net shaping tool; the parts can then be finished by light trimming with proper precision tools. Since the bulk of the material is removed by waterjet, the operating lives of the precision tools can be greatly extended. This paper presents a collection of waterjet-machined samples to demonstrate many benefits by applying waterjet for multimode machining of curved and layered structures.

Parametric effects in the frictional interaction of a tool with a billet in the process of its treatment by pressure

Purpose. Justification of the influence of pulsating dynamic loads in the surface layers of parts obtained by plastic deformation methods on the quality of finished products during cold rolling, knurling, running in, drawing and stamping. Research methodology. A schematization was adopted in which the workpiece or part is an anisotropic medium elastically bonded along the surface of the junction of external reinforced layers with the internal mass of the part. On the basis of the proposed physical model, conditions were found under which under the action of cyclic surface loads, violations of the integrity of the appearance of fracturing and waviness of external fibers in the process of strengthening the treatment of semi-finished products and parts are possible. Findings. The obtained data allows us to establish the frequency characteristics of the process of unstable parametric oscillations caused by nonlinear friction between the forming element and the workpiece (part), which lead to a deterioration in the quality of finished products. In addition, for the steady-state operating modes of machines for cold metal forming, the dependence of the amplitudes of deformation waves, as functions of the maximum pulsations of the “periodic” components of surface forces, was obtained, and measures were proposed to reduce vibroactivity in the area of tool interaction with the workpiece and machine parts for cold processing. Originality. It consists in formulating and solving the second dynamic problem for the surface layers of the workpiece at the interface of the processed layers and the workpiece array. Depending on the occurring periodic forces for the surface layers, the conditions of steady and unstable operation of the shaping tool and the whole machine for metal forming by pressure, as a whole, are determined. Practical value of the work lies in the fact that safe modes of operation of metal forming machines have been identified, conditions for improving the design of machines for cold metal forming have been created, under which the possibility of occurrence of parametric oscillations, as well as the reduction of vibratory activity of machines for cold metal forming in minimized whole. Keywords: running in, knurling, drawing, plastic deformation, roller, tool, workpiece, the amplitude of oscillations, load, excitation coefficient, steady amplitude, deformation wave.

BACKGROUND TO THE ARRANGEMENT OF AUTOMATING AND VOLVOUS PROCESSES IN THE FORM-FORMING MACHINES WHEN TREATING THE PREPARATIONS AND DETAILS BY THE PLASTIC DEFORMATION METHOD

Purpose. Analysis of surface-hardening technology for cold processing of metals, taking into account the deformation-wave processes occurring in the area in front of the shaping tool. Methodology. To establish the reasons for obtaining finished products with increased roughness, insufficient contact strength, fracturing and peeling of the surface layers, as well as the occurrence of significant dynamic loads in the mechanisms of machines for machining parts using plastic deformation, a two-mass design model is used in which the working tool is connected by friction with the moving processed workpiece. Findings. The results of determining the conditions for the occurrence of self-oscillations in the system “workpiece - tool” are presented. Based on the analysis of the friction characteristics as a function of the mutual slip rate between the workpiece and the shaping tool, the range of slip speeds is set, at which the self-oscillating processes for the friction pair can be excited: "tool - workpiece". Originality consists in the fact that the influence of the variable friction force on the occurrence of sustained self-oscillations between the workpiece being processed and the tool in the machines for “cold” plastic deformation of the metal has been established. The conditions for the occurrence and absence of self-oscillations in the zone of contact between the tool and the workpiece are found. Practical value lies in the fact that the modes of operation of machines for processing products by plastic deformation have been revealed under which unregulated roughness, fracturing and “peeling” of the parts being machined can occur, as well as a high dynamic background during the operation of the shaping tool of driving and power mechanisms. Practical recommendations are given to improve the performance of finished products and reduce vibroactivity in the drive. Keywords: running in, dragging, knurling, plastic deformation, elastic deformation wave, roller, tool, blank.