Part dimensional errors in free upsetting due to the elastic springback

Pojava elastičnog vraćanja materijala radnog predmeta prisutna je u svim procesima plastičnog deformiranja metala. Ovaj faktor prepoznat je kao jedan od glavnih čimbenika dimenzijske (ne)točnosti. Stoga, da bi se proizveli dijelovi sukladno zahtjevima koji se odnose na njihovu geometriju ovaj fenomen se mora dobro razumjeti i uzeti u obzir prilikom projektiranja alata i procesa deformiranja. Nažalost, znanje vezano za ovaj fenomen je ograničeno te stoga predviđanje i proračun iznosa elastičnog vraćanja ponekad predstavlja vrlo težak zadatak. U ovom članku predstavljeno je opće analitičko rješenje za izračun elastičnog vraćanja. Izvedene analitičke jednadžbe mogu se primijeniti za različite procese oblikovanja pod uvjetom da su vrijednosti glavnih naprezanja na samom kraju procesa deformiranja poznate. Koristeći ovaj pristup izračunate su elastične deformacije i amplituda elastičnog vraćanja radnog komada kod procesa slobodnog prešanja cilindrične gredice. Dobiveni rezultati provjereni su pomoću MKE analize.Elastic springback of workpiece material which occurs in any forming process has been recognized as one of most relevant factors regarding part dimensional accuracy. Therefore, in order to manufacture component in accordance with the geometrical specifications engineers must have a good understanding of this phenomenon and take it into account during the design tool and forming process. Unfortunately, this knowledge is often insufficient and therefore the prediction of elastic springback is sometimes a very tough task. The paper presents a general approach for the calculation of elastic recovery. Given analytical equations can be applied for different forming processes under the condition that values of the principal stresses at the very end of forming process are known. By using this approach elastic strains and amplitude of elastic springback of workpiece in case of free upsetting of cylindrical billet were calculated. Obtained results were verified by FEM analysis

DEEP DRAWING TECHNOLOGY WITH WALL IRONING IN MASS PACKAGING INDUSTRY

Aluminum is a metal that is being increasingly used in the packaging industry in the modern metal forming technology, but it also provides a good opportunity for effective advertising and product promotion. Processing technologies for aluminum plastic deformation ensure superior packaging that meets the most rigorous demands in the food, pharmaceutical, chemical, and other industries. It is the case of mass production with very little material loss that offers the possibility of multiple recycling. On the other hand, today's products for general purpose consumers cannot be imagined without aggressive advertising that has a major impact on customers. Modern graphics techniques for printing images and different basic surfaces offer great opportunities that manufacturers use widely in the promotion and sale of their products

Evaluation of the behavior of welded structures under low-cycle fatigue loading

Welded structures are exposed to constant variable loads during their exploitation in real conditions. A variable load affects the integrity and life of a welded structure; therefore, it is of practical importance to understand fatigue behavior, especially the behavior of welded structures under the impact of low-cycle fatigue. The effect of low-cycle fatigue is very prevalent in structures and an assessment of cyclic loading of a material entails modifications of its properties and characteristics related to the dependence of stress and strain. Since the stress-strain response during low-cycle fatigue is in the form of a hysteresis loop, this paper presents the application of one of the two most common relations for testing resistance to low-cycle fatigue, the Ramberg-Osgood relation, which is used to evaluate the behavior of a material, in this case a high-strength low-alloy steel welded joint

Industry 4.0 and New Paradigms in the Field of Metal Forming

Over the last few year, the metalworking sector has been undergoing rapid and radical transformations driven by global competition and the revision of the production focus that is being moved from mass customization to mass individualization. A results of this is introduction of new manufacturing strategies such as Industry 4.0, a concept that combines cyber-physical systems and promote communication and connectivity. Therefore, this concept changes not only the face of the manufacturing systems but also causes transformation of existing business models and the society as a whole. This paper deals with the recent trends and paradigms in the field of metal forming, resulting from the concept of Industry 4.0 and the modern market challenges. The maim attention is paid on the flexibility of manufacturing systems and recent developments in design of smart forming tools

Experimental examination of the applicability of additive technologies in the field of rapid tooling - injection molding

In this paper, an experimental examination/analyzing applicability and machinability of the polymer material’s core and cavity formed using additive technology (rapid tooling) was conducted. Achieving the price reduction of the final product, as well as the price of the mold for plastic injection through the introduction of rapid tooling injection molding can be applied, not only to mass production, but also to small series production. This research is limited to obtaining plane parts of simpler geometry from polypropylene polymer material. Obtained results showed that, at this point, it is not directly possible to completely produce a core and cavity only through additive technologies. In order to achieve some tolerances at specific places, it is still necessary that the core and cavities are machined with conventional methods. On the other hand, it turned out that by using a polymer core and cavity, it is possible to produce a smaller series of the parts

Cold Radial Extrusion of a Gear-Like Element with Flow Relief Opening

When divided material flow is enabled during extrusion process, the required forming load is lower compared to a conventional process. The reduction of forming load leads to higher quality of extruded part and longer tool life. One way to achieve divided material flow is the application of a relief opening, either in the billet or in the tool. In this paper, theoretical solution based upon the Upper bound theorem was used to determine the forming load for radial extrusion of a gear-like element with straight parallel flank profile. Two possible positions of relief openings were analysed - in the centre of the billet and in the centre of the punch. Theoretical solution was compared to experimental results. Material of billets was Al 99,5. Comparison between theoretical and experimental values of the forming load showed fairly good agreement. Further development of the proposed theoretical solution should lead to better process description and more accurate value of the forming load

Finite element simplifications and simulation reliability in single point incremental forming

Single point incremental forming (SPIF) is one of the most promising technologies for the manufacturing of sheet metal prototypes and parts in small quantities. Similar to other forming processes, the design of the SPIF process is a demanding task. Nowadays, the design process is usually performed using numerical simulations and virtual models. The modelling of the SPIF process faces several challenges, including extremely long computational times caused by long tool paths and the complexity of the problem. Path determination is also a demanding task. This paper presents a finite element (FE) analysis of an incrementally formed truncated pyramid compared to experimental validation. Focus was placed on a possible simplification of the FE process modelling and its impact on the reliability of the results obtained, especially on the geometric accuracy of the part and bottom pillowing effect. The FE modelling of SPIF process was performed with the software ABAQUS, while the experiment was performed on a conventional milling machine. Low-carbon steel DC04 was used. The results confirm that by implementing mass scaling and/or time scaling, the required calculation time can be significantly reduced without substantially affecting the pillowing accuracy. An innovative artificial neural network (ANN) approach was selected to find the optimal values of mesh size and mass scaling in term of minimal bottom pillowing error. However, care should be taken when increasing the element size, as it has a significant impact on the pillow effect at the bottom of the formed part. In the range of selected mass scaling and element size, the smallest geometrical error regarding the experimental part was obtained by mass scaling of 19.01 and tool velocity of 16.49 m/s at the mesh size of 1 × 1 mm. The obtained results enable significant reduction of the computational time and can be applied in the future for other incrementally formed shapes as well

Influence of Process Parameters on the Characteristics of Additively Manufactured Parts Made from Advanced Biopolymers

Over the past few decades, additive manufacturing (AM) has become a reliable tool for prototyping and low-volume production. In recent years, the market share of such products has increased rapidly as these manufacturing concepts allow for greater part complexity compared to conventional manufacturing technologies. Furthermore, as recyclability and biocompatibility have become more important in material selection, biopolymers have also become widely used in AM. This article provides an overview of AM with advanced biopolymers in fields from medicine to food packaging. Various AM technologies are presented, focusing on the biopolymers used, selected part fabrication strategies, and influential parameters of the technologies presented. It should be emphasized that inkjet bioprinting, stereolithography, selective laser sintering, fused deposition modeling, extrusion-based bioprinting, and scaffold-free printing are the most commonly used AM technologies for the production of parts from advanced biopolymers. Achievable part complexity will be discussed with emphasis on manufacturable features, layer thickness, production accuracy, materials applied, and part strength in correlation with key AM technologies and their parameters crucial for producing representative examples, anatomical models, specialized medical instruments, medical implants, time-dependent prosthetic features, etc. Future trends of advanced biopolymers focused on establishing target-time-dependent part properties through 4D additive manufacturing are also discussed