Josef Sedlák

Phenomenological Modelling of Cyclic Plasticity

The stress-strain behaviour of metals under a cyclic loading is very miscellaneous and needs an individual approach for different metallic materials. There are many different models that have been developed for the case of cyclic plasticity. This chapter will address only so called phenomenological models, which are based purely on the observed behaviour of materials. The second section of this chapter describes the main experimental observations of cyclic plasticity for metals. Material models development for the correct description of particular phenomenon of cyclic plasticity is complicated by such effects as cyclic hardening/softening and cyclic creep (also called ratcheting). Effect of cyclic hardening/softening corresponds to hardening or softening of material response, more accurately to decreasing/increasing resistance to deformation of material subjected to cyclic loading. Some materials show very strong cyclic softening/hardening (stainless steels, copper, etc.), others less pronounced (medium carbon steels). The material can show cyclic hardening/softening behaviour during force controlled or strain controlled loading. On the contrary, the cyclic creep phenomenon can arise only under force controlled loading. The cyclic creep can be defined as accumulation of any plastic strain component with increasing number of cycles and can influence the fatigue life of mechanical parts due to the exhaustion of plastic ability of material earlier than the initiation of fatigue crack caused by low-cycle fatigue is started.

Material Analysis of Titanium Alloy Produced by Direct Metal Laser Sintering

This paper focuses on the testing of samples made by Direct Metal Laser Sintering (DMLS). This additive method is based on the continuous melting of fine layers of metal powder by laser beam. The paper focuses on the DMLS process description, analysis of the titanium alloys and experimental procedures. The experimental section is a structural comparison of the materials produced by hot forming and powder metallurgy (DMLS) using scanning electron microscopy (SEM) analysis. Results from the DMLS technology and conventional powder metallurgy are compared to show the advantages of the former technology.

Shaped Glued Connection of Two Parts Made by Rapid Prototyping Technology

An increasing number of designs and subsequent production of parts created by the Rapid prototyping (RP) [1] technology led to a problem with the maximum workspace of the 3D printer. Due to this reason, it was necessary to work on the solution of joining the parts to overcome the limited workspace of the printer. This article is devoted to glue joints analysis of two parts made by RP technology. A great emphasis is given to the load capacity testing of the parts made this way. The measured values than may serve as a lead for the construction design of the outlined joints. The article builds on the knowledge gained during the previous testing of the screw connections of parts made by 3D printing technology [2].

Machining Issues of Titanium Alloys

This paper deals with the machining issues of two titanium alloys using two cutting tools. With respect to the given issue, a larger part of the article is devoted to metallographic analysis of both materials. The following is a description of the tools and machining conditions. Further, there is a description of a milling test of both alloys by end mills while sensing the force load by piezoelectric dynamometer. The last section evaluates and compares the obtained data. Based on the information obtained, the conclusion evaluates the problems encountered when machining, which correspond to the material properties.

CHANGES IN THE SURFACE LAYER OF ROLLED BEARING STEEL

This paper describes changes observed in bearing steel due to roller burnishing. Hydrostatic roller burnishing was selected as the most suitable method for performing roller burnishing on hardened bearing steel. The hydrostatic roller burnishing operation was applied as an additional operation after standard finishing operations. All tests were performed on samples of 100Cr6 material (EN 10132-4), and changes in the surface layer of the workpiece were then evaluated. Several simulations using finite element methods were used to obtain the best possible default parameters for the tests. The residual stress and the plastic deformation during roller burnishing were major parameters that were tested.

On the Cutting Performance of Nano-(Tix,Al1-x)N PVD Coatings

It is well known that hard coatings can extend the lifetime of production tools in many industrial applications significantly [1]. Higher cutting speeds, dry cutting or a better quality of machined surface can present the typical benefits of the protective surfaces so hard coatings receive a great interest from industrial and research organizations. Among the most important parameters of the coatings belong properties such as resistance to oxidation, thermal and abrasion, and good adhesion and tribological properties. The hard coatings based on (Tix,Al1-x)N prevails with unique properties belong to the most used coatings today. These coatings are deposited by PVD technology using either arc technologies or magnetron sputtering systems. New nanocomposite coatings (Ti,Al)N and (Ti0.4,Al0.6)N were tested in dry and wet cooling conditions and this paper deals with material analyses of the coating, testing of the cutting performance for a grooving technology in hardened low-alloyed steel.

REVERSE ENGINEERING METHOD USED FOR INSPECTION OF STIRRER´S GEARBOX CABINET PROTOTYPE

Reverse engineering is a technology that enables acceleration of data acquisition for CAD, CAM, CAE systems and thus greatly reduces the time of development, design and production of components. In general, reverse engineering technology can be considered as the conversion of analog data to digital data, which is further processed. Individual industries are still increasing their demands for accuracy, size, quality, and so, therefore the use of digitization is found in many manufacturing areas such as the automotive, aerospace, shipping, medicine, industrial design, design, and so on. The paper deals with the analysis of the prototype component of the agitator gearbox in the form of a rough and chip-machined casting. The inspection of the shape of the gearbox consisted in reading the reference CAD model, establishing the digitized shape with respect to this reference model, checking the dimensions and creating a color map of the variations at selected points.

APPLICATION OF MODERN TECHNOLOGIES IN PRODUCTION DESIGN OF CAR COMPONENT PROTOTYPE

An article deals with a design and production of a prototype component for an automotive industry. A theoretical part defines a technology of plastics injection from the point of view of selection, preparation and use of appropriate materials for plastic components fabrication. There is also principle of activities of an injection moulding machine with a subsequent description of an issue of design and construction of injection moulds. A practical part of the article deals with a 3D model formation of the car component prototype (PC modelling in a parametric CAD software Autodesk Inventor, a control of entry data) and its production using an additive technology of Rapid Prototyping (a method of Fused Deposition Modelling – a 3D Printer uPrint). The practical part also focuses on production of the real prototype casts of the car component casted from a special binary resin. The final prototype casts casted to a silicon mould that is made using system. The article also includes a metrological measurement of the prototype components (components made injection moulding machine, the 3D printer and the silicon mould) using the 3D measuring device in order to evaluate of production tolerances to a given technical document article ends with evaluation of production of the prototype component with recommendations and an analysis of the most economical solution (modern technological procedures versus the aluminium mould), including final summarization of costs on the car component production.

PRODUCTION OF PROTOTYPE PARTS USING DIRECT METAL LASER SINTERING TECHNOLOGY

Unconventional methods of modern materials preparation include additive technologies which involve the sintering of powders of different chemical composition, granularity, physical, chemical and other utility properties. The technology called Rapid Prototyping, which uses different technological principles of producing components, belongs to this type of material preparation. The Rapid Prototyping technology facilities use photopolymers, thermoplastics, specially treated paper or metal powders. The advantage is the direct production of metal parts from input data and the fact that there is no need for the production of special tools (moulds, press tools, etc.). Unused powder from sintering technologies is re-used for production 98% of the time, which means that the process is economical, as well as ecological.The present paper discusses the technology of Direct Metal Laser Sintering (DMLS), which falls into the group of additive technologies of Rapid Prototyping (RP). The major objective is a detailed description of DMLS, pointing out the benefits it offers and its application in practice. The practical part describes the production and provides an economic comparison of several prototype parts that were designed for testing in the automotive industry.