Model plitkog gravurnog kovanja temeljen na veličini kristalnog zrna

Poznato je da se proces plitkog gravurnog kovanja može uvrstiti u skupinu procesa mikro oblikovanja deformiranjem. Kod takvih procesa mikrostruktura i red veličine geometrije gravure imaju značajan utjecaj na mehanizam deformiranja te se mikro procesi fundamentalno razlikuju od klasičnih procesa oblikovanja. Zbog toga je potrebno odrediti utjecaj efekta veličine na silu kovanja i pomak alata kod procesa plitkog gravurnog kovanja. U tu svrhu istražen je utjecaj veličine kristalnog zrna materijala na elastični povrat materijala nakon prestanka djelovanja sile oblikovanja, popunjavanje gravure i silu kovanja otkovaka materijala. Materijal sirovaca (rondela) je 99,5% aluminij i koristi se gravura relativno složene geometrije. Predloženi model plitkog gravurnog kovanja uzima u obzir utjecaj efekata veličine na naprezanje plastičnog tečenja preko geometrije gravure te daje procjenu konačne sile kovanja i pripadajućeg pomaka alata. Time je omogućen kontroliran utjecaj veličine kristalnog zrna na silu kovanja i pomak alata, kao i pouzdana predikacija konačne sile kovanja i pomaka alata kod kojeg se postiže potpuno popunjavanje gravurne šupljine

Multirotor UAV Design and Development – Case Study

This paper proposes the development and production of multirotor UAV parts using additive manufacturing. A new smart design approach is needed to take advantage of additive manufacturing in terms of reducing the product weight and making the product more customizable and specific purpose-oriented while also reducing the time and cost of product development and production. This paper provides a brief overview of three additive technologies: fused deposition modelling, stereolithography, and selective laser sintering. Two different UAV modules, the avionics module and GPS holder assembly, are described and produced. Also, some design ideas and approaches are explained, such as snap-fit joints and thread joints using hex bolt pockets and metal screws. The goal of this paper is to develop and manufacture special purpose UAV parts that are durable, sustainable, and low cost. For this purpose, the additive manufacturing process is proposed and described, from the idea to the final product

Prototyping and Integration of Educational Low-Cost Mobile Robot Platform

This paper describes the process of designing and prototyping a low-cost robotic platform based on existing equipment and projects that enable extracurricular STEM activities in Croatia and beyond. A robotic platform with a differential drive configuration was chosen for education from an early age due to its simplicity and a wide range of cheap and compatible components from which it can be made. From the aspect of integration into extracurricular or curricular activities, the BBC micro:bit ecosystem was considered, enabling block-based visual programming. Components with printable parts make up the assembly of the educational robot. The main steps in designing and creating a robot prototype are presented, which consist of the modelling, 3D printing of robot parts, and assembly into a functional system. After several stages of testing, an interactive workshop was held with 7th-grade primary school pupils. Further work is planned to create educational material for extracurricular STEM workshops

Mathematical Modelling of Unmanned Aerial Vehicles with Four Rotors

Mathematical model of an unmanned aerial vehicle with four propulsors (quadcopter) is indispensable in quadcopter movement simulation and later modelling of the control algorithm. Mathematical model is, at the same time, the first step in comprehending the mathematical principles and physical laws which are applied to the quadcopter system. The objective is to define the mathematical model which will describe the quadcopter behavior with satisfactory accuracy and which can be, with certain modifications, applicable for the similar configurations of multirotor aerial vehicles. At the beginning of mathematical model derivation, coordinate systems are defined and explained. By using those coordinate systems, relations between parameters defined in the earth coordinate system and in the body coordinate system are defined. Further, the quadcopter kinematic is described which enables setting those relations. Also, quadcopter dynamics is used to introduce forces and torques to the model through usage of Newton-Euler method. Final derived equation is Newton’s second law in the matrix notation. For the sake of model simplification, hybrid coordinate system is defined, and quadcopter dynamic equations derived with the respect to it. Those equations are implemented in the simulation. Results of behavior of quadcopter mathematical model are graphically shown for four cases. For each of the cases the propellers revolutions per minute (RPM) are set in a way that results in the occurrence of the controllable variables which causes one of four basic quadcopter movements in space

Micromachining – Review of Literature from 1980 to 2010

Trend of miniaturization of products and consequently its components nowadays can be evident in almost every production field. To accomplish requirements imposed by miniaturization micromachining proved to be a satisfied manufacturing technique. Herein the term micromachining refers to mechanical micro cutting techniques where material is removed by geometrically determined cutting edges. The aim of this review article is to summarize existing knowledge and highlight current challenges, restrictions and advantages in the field of micromachining

Design Considerations for Autonomous Cargo Transportation Multirotor UAVs

Unmanned aerial vehicles (UAVs) have proven to be an advanced tool for a variety of applications in the civilian and military sectors. Different categories of UAVs are used in various missions and are also the subject of numerous researches. Due to their characteristics and potential in specific conditions, multirotor UAVs imposes itself as a solution for many tasks, including transport. This chapter presents a conceptual solution of autonomous cargo transportation where the primary research objective is the design of a heavy lift multirotor UAV system. The process of designing a multirotor UAV that can carry heavy lift cargo is quite challenging due to many parameters and constraints. Five selected series of electric propulsion systems are analyzed, with different multirotor configurations, and results are graphically displayed for payloads from 10 kg up to 100 kg

In-Crystal Dislocation Behaviour and Hardness Changes in the Case of Severe Plastic Deformation of Aluminium Samples

The presence of dislocations significantly modifies the mechanical properties of crystalline solids. Severe plastic deformation (SPD) and the most used SPD process – the Equal Channel Angular Pressing (ECAP), affect the multiplication and localized accumulation of dislocations. This research is related to the observation of dislocation pile-up and significant reduction of the crystalline grain size caused by severe deformations in the ECAP process of the widely used aluminium material (Al 99.5%). Because of its lightweight, the application of Al 99.5 % can pose a challenge for the aviation and space industry, especially since its mechanical properties limit its application. Improving these mechanical properties can extend its applicability in cases of demanding constructions as well as influence the final product cost. As a confirmation of SPD in-fluence on mechanical properties, material hardness has been examined and described. Dislocation monitoring is enabled using the light and electron microscopy and AFM (Atomic Force Microscope) device. A numerical simulation of the Equal Channel Angular Pressing process using the ABAQUS software package determined the representative area of the most severe deformation