Showing papers in "Tehnicki Vjesnik-technical Gazette in 2011"

Kinematic analysis of quick-return mechanism in three various approaches

Abstract: Mechanismshavebecomeapartofourlifeandaretobefound not only in technical practice, but along every step ofoureverydaylife[1,2,6]TheyhelpustodoourworkmoreeasilyandmorecomfortablyThemechanismisusuallyapartofamachinewheretwoor more pieces are combined, so that the motion of the firstcompels the motion of the others, according to a lawdepending on the nature of the combination The operationofanymachinedependsupontwothings:1 the transmission of certain forces,2 the production of determinate motionsIndesigning,dueconsiderationmustbegiventobothofthese, so that each part may be adapted to bear the stressesimposed on it, as well as have the proper motion relative totheotherpartsofthemachineThe structure that supports the moving parts andregulates the path motions, or kind of motion, is called theframe of a machine [3] In discussing the motions of themoving parts, they are considered in regard to the frameThe frame absorbs the forces or moments that originate atthe transformation of motions [7] The components whichactuate the mechanism are called the drivers, the othercomponents whose motions are caused are called thefollowersIt is often needed to define the velocity and accelerationof a rigid body or some point of mechanism inmanufacturingpractice,iftheinputparametersofdriverareknown The kinematic analysis is concerned with theproblemslistedbelowThe goal of the kinematic analysis is to investigate themotion of individual components of a mechanism (or itschosen points) in dependence on the motion of drivers To

Influence of cutting parameters on heat affected zone after laser cutting

Abstract: Přispěvek se zabýva metodou tepelneho děleni materialu, konkretně laserovou technologii. V teoreticke casti je popsan jeji princip, funkce, možnosti a využiti laseru při obraběni, předevsim postup řezani materialu pomoci laseroveho svazku. Experimentalni cast je zaměřena na řezani kobaltove slitiny kontinualnim CO2 laserem a vliv technologických parametrů při řezani na výslednou kvalitu řezne plochy. Na zakladě metalograficke analýzy byly stanoveny vhodne technologicke parametry, při kterých bylo dosaženo nejmensi tepelne ovlivněni materialu.

Simulation of production process reorganized with Value Stream Mapping

Abstract: The philosophy of Lean production offers a wide variety of advantages. Lean production concept is understood as the realization of Lean principle through the efficient application of methods and tools, with faster and more effective discovering of wastes and mistakes in the production systems. This article contains a presentation of the simulation application on production process previously analyzed with Value stream mapping tool. The model was applied for production line in the shipbuilding industry in Croatia. The production line current state is simulated with varying market requirements. Using Lean management tools, future improved state was developed and simulated. The simulation provides dynamic models with varying production performance results, unlike by applying only a Value stream mapping tool. During simulation runtime, adaptation of production process by varying resources assignment to continuous working cell were done to fulfill order requirements on time.

Development of a prototype for zrgb infraredesign device

Abstract: Infraredesign theory has developed a method of implementing graphics that carry two pieces of information, where the first one is seen in the visual spectrum (VS), and the other in the near infrared (NIR) spectrum. This paper introduces a prototype for a device which should record these two states: an image in the NIR as a Z monochrome record and image in the VS as a RGB record. These two independent images are representing properties of substance in the wavelengths region of the electromagnetic spectrum from 400 to 1000 nm. These can be paintings, reproductions, banknotes and secured documents, or even scenes from nature. With this device through developed software it will be possible to quantitatively determine the difference between information from RGB to the Z state of matter for each pictorial element. The device operates under the daylight, without a separate built-in IR source, which enables recording of close and very distant objects at the same time. :

Deformations after heat treatment and their influence on cutting process

Abstract: This paper deals with the influence of heat treatment on the deformation of parts and the following machining process. The regime of heat treatment significantly affects such aspects of material as structure, hardness and induced stress. Different process of heat treatment results in different deformation of parts and changes considering their dimensions. All these aspects are connected with the consecutive cutting operations such as grinding or hard turning, their stability, precision of produced parts, etc. Deformation of parts is also connected with the structure of material before heat treatment, placement in the furnace, regime of heat treatment and stress distribution around the parts. The results of the experimental study presented in this paper illustrate the connection between different heat treatment regimes and the following processing of parts.

Analyses and solutions on technical and economical aspects of rapid prototyping technology

Abstract: This article deals with basic characteristics and problems in the area of technology of Rapid Prototyping using layered manufacturing technology. It belongs to progressive methods of model creation based on geometry obtained from CAD environment with application possibilities in different industrial spheres. Chapters are focused on optimization of Rapid Prototyping preparation process. There is also an algorithm that leads to the selection of suitable settings. Utilization of the algorithm is explained on a case of printing with the use of UPrint device and Catalyst software, a system created for the utilization of Fused Deposition Modelling technology. There are outputs in the form of graphs and tables accumulating information directly affecting economical aspect so f printing. Conclusion brings ideas on possible further progress in this area that would include a solution for the generation of database with stored information about previous printing results.

Preliminarni rezultati eksperimentalnog rezanja svinjske kosti abrazivnim vodenim mlazom

Abstract: Prikaz stanja The first medical applications of this technology were published in the eighties of the last century [1], when a jet of water [6, 7, 8, 9] was used for cutting soft tissues [1, 2]. There are currently no available relevant studies exploring in detail the use of abrasive waterjet cutting in orthopaedic surgery for the implantation and re-implantation of total hip and for knee replacement [4, 5]. The goal of this experimental research is to get a deeper comprehensive insight into the issue of identification and analysis of factors in relation to the surface topography of bone tissue. Achieving the desired surface quality is of great importance for the functional behaviour of a part.

Blasting design for obtaining desired fragmentation

Abstract: The empirical prediction of expected fragmentation is in most cases carried out by using the Kuz-Ram model. By doing this, the Rosin-Rammler theory is applied. This theory, first proposed by V. M. Kuznetsov (1973), gives a reasonable description of the blasted rock fragmentation. Using this approach, one calculates a rock factor that describes the nature and geology of the rock. The uniformity index is also obtained that characterizes the explosive loading and blast pattern type and dimensions. This allows the characteristic size and size distribution to be calculated according to the Rosin-Rammler procedure. Due to the amount of too many input rock mass parameters, that are not unambiguously determined, the rock factor may also not be satisfactory and this unfavorably influences the fragmentation prediction. The later work of others, particularly that of Lilly (1986) and Cunningham (1983, 1987) was useful for improving the efficiency of that approach. The authors have developed the program "SB" enabling the user to directly influence the blasted material size distribution by selecting a cumulative mass percentage of the required fraction size. By the required selection for the calibrated rock factor, the program computes the required drill hole pattern. The program is used for computing the drilling costs, the costs of machine crushing of larger blocks remaining after blasting and the costs of primary crushing. From the analysis of exploitation and primary processing costs it can be concluded that blasting is the cheapest method of rock fragmentation. The total costs for the required quantity of blasted material are significantly reduced by the use of smaller drill hole patterns. The costs for drilling and explosive do indeed increase in that way, but the costs of loading, transportation, crushing and grinding of the mineral are significantly smaller.

Modelling and simulations of elevator dynamic behaviour

Abstract: Electric drive elevators represent a special group of transport machines for vertical lifting of a load with stressed dynamic features. Special attention should be paid to the behaviour of these devices in exploitation, as early as in the projecting phase. The paper shows the process of forming adequate mechanical models for elevators grouped according to their features, and with this an analysis can be performed of the influence of certain parameters on their behaviou ri n operation. Based on the formed elevator models, simulations have been performed, and the obtained results are graphically shown through diagrams, with varying "dynamic" parameters (drive characteristics, velocity and acceleration, the height of lifting, rated load and the weight of the cabin, mechanical characteristics of the rope…) with the conclusions on their influence on elevator behaviour.

Numerical analysis of constraint effect on ductile tearing in strength mismatched welded CCT specimens using micromechanical approach

Abstract: In this paper, constraint effect on ductile fracture initiation and propagation has been studied. Three-dimensional finite element analyses of mismatched welded joints made of high strength steel, have been performed for centre-cracked tensile (CCT) specimens. Different weld widths and material mismatching ratios have been considered. Ductile fracture parameter, crack tip opening displacement at crack growth initiation (CTODi), has been obtained for centre-cracked tensile (CCT) specimens using local approach to fracture and compared with experimental results of single edge bend specimens. Micromechanical complete Gurson model has been applied to investigate fracture behaviour of cracked welded joints. Crack tip constraint has been analysed through stress triaxiality in order to study transferability of fracture parameters from one geometry to another.

A risk-assessment methodology in tunneling

Abstract: This paper introduces a process-driven risk- assessment methodology in tunneling. This methodology considers the construction process as a whole and covers all aspects of risk-management process, from risk identification to risk response. The application of the proposed methodology has been demonstrated on two phases of the construction project and was applied to tunnel construction. Risk assessment should follow the construction process. Each phase of the project has the goal that must be achieved. The goal of each phase depends on some activities that affect phase realisation. These activities are potential sources of risk and a cyclical risk assessment should be repeated for each phase of the project. It is necessary to take into account that executing a construction project is a process, and that risk management must follow that process.

Mechanical properties of masonry as required for the seismic resistance verification

Abstract: Despite the extensive use of masonry in different types of construction, this material has not been investigated as much as other materials. Results obtained from different sources are general and for each particular use its characteristics have to be determined separately. Although the stress state in masonry is very complex and cannot be easily simulated in experiments, the properties obtained by simple experiments that investigate the basic failure modes of masonry could be used for a more accurate prediction of its non-linear behavior and failure. The outlined extended testing of masonry mechanical properties in plane has been necessary for obtaining the parameters needed for the non-linear numerical analysis of the masonry behavior under in-plane lateral loading. Presented data could be used as initial required values for masonry as used in Croatia. They represent the main input data for any further analysis of masonry buildings made of hollow-clay blocks and they could be used as a good reference for designers, brick industry and masonry builders in Croatia.

Numerical and experimental strength analysis of fire-tube boiler construction

Abstract: Norms, such as EN 12952-3 and EN 12953-3 handle the issues concerned with calculation of the pressurized boiler components, not however considering the influences of thermal strains that are often of vital importance for the integrity of boiler's construction.Application ofFEMin boiler design inENis suggested in calculating all components that are not covered by the norm. In this way, the calculation of thermal stress is left to the free will of designer and technical inspectorate which supervises and approves placement of a boiler into operation. This paper demonstrates that the influence of thermal stresses is great and that it must be taken into consideration when the boiler's construction is designed and its working life evaluated. It is shown that for every construction a numericalexperimental behaviour diagnostics should be conducted prior to putting it into operation. First, a numerical model must be experimentally verified and then it can be used in considering different parameters of strength diagnostics, such as distribution of membrane and bending stresses for substructures, and distribution of deformation energy. They indicate, in an optimal way, root causes of insufficiently good behaviour of the construction. Also, a dynamical calculation of natural oscillations should always be suggested.

Implementing genetic algorithms to cuda environment using data parallelization

Abstract: Computation methods of parallel problem solving using graphic processing units (GPUs) have attracted much research interests in recent years. Parallel computation can be applied to genetic algorithms (GAs) in terms of the evaluation process of individuals in a population. This paper describes yet another implementation method of GAs to the CUDA environment where CUDA is a general-purpose computation environment for GPUs provided by NVIDIA. The major characteristic point of this study is that the parallel processing is adopted not only for individuals but also for the genes in an individual. The proposed implementation is evaluated through eight test functions. We found that the proposed implementation method yields 7 6-18 4 times faster results than those of a CPU implementation.

Electrostatic separation of pet/pvc mixture

Abstract: Nowadays, due to their favorable properties, plastic materials replace other materials in many industries, especially packaging industries, therefore the generation of plastic waste is constantly increasing. Waste plastics can be recycled, which decreases potential harmful influence on the environment and saves lanfill space and natural resources. The aim of the research presented in this article was to evaluate the performance of the electrostatic separator when separating a PET/PVC mixture. The effect of electrode potential and rotor speed on the separation efficiency was studied on three different particle size classes (4/3.15 mm, 3.15/2 mm and 2/1 mm). Indicators of separation efficiency for the two-component plastic mixture were the concentrate grade and recovery. The best result (grade of 100% and recovery of 87% ) was obtained by separating coarse grain size 4/3.15 mm after two separation stages at the electrode potential of 15.5 kV and rotor speed of 35 m/min.

Taguchi-fuzzy based mapping of EDM-machinability of aluminium foam

Abstract: Conventional machining of aluminium foams is a difficult task because of the fact that their cells and cell edges are damaged and/or collapsed during the machining processes and thereby their original properties deteriorated. This problem can be overcome to a certain extent by machining this material by Electro Discharge Machining (EDM) process. The present paper deals with identifying the various control parameters responsible for effective machining of aluminium foam. Taguchi-Fuzzy Logic based technique is used for parameter design of performance characteristics to determine optimal machining parameters for maximum Material Removal Rate (MRR) and minimum Tool Wear Rate (TWR) in EDM. Taguchi-fuzzy based mapping of MRR and TWR with productivity revealed that in order to achieve higher productivity while machining aluminium foam, the two parameters, pulse current and pulse-On time are required to be set high in combination with the low setting of duty cycle.

Factor analysis of the abrasive waterjet factors affecting the surface roughness of titanium

Abstract: The paper focuses on experimental research and evaluation of the abrasive waterjet cutting technology process in order to evaluate the technology factors affecting the microgeometry (average roughness) of workpiece surface of titanium of 10 mm thickness using a full factorial design. The significance of four selected process factors – independent variables (traverse speed, abrasive mass flow rate, angle of attack, depth of cut) affecting the surface quality was evaluated by a two level full factorial design. The surface quality was evaluated by , and surface roughness parameters. A multiple nonlinear regression equation obtained fromANOVAgives the level quality as a function of the machining factors.Adifferent significance of these factors has been found. Ra Rq Rz Ra abrasive waterjet, surface roughness, titanium

Eksperimentalno ispitivanje kvalitete polimernih tvorevina proizvedenih LOM postupkom

Abstract: Rapid prototyping procedures make it possible to produce relatively complicated geometries based on the computer 3D model of products in relatively short time. This requires that the respective product features have good quality, good mechanical properties, dimensional accuracy and precision. However, the number of available materials that can be used for prototyping is limited and their properties can differ significantly from the properties of the finished product. However, RP parts are not inexpensive and sometimes it is difficult to decide which procedure to use to manufacture them in order to obtain their maximal usability. The Laminated Object Manufacturing (LOM) procedure can be used to produce low cost polymeric products (from poly(vinyl chloride)) that have to meet certain mechanical properties, especially if they are used to perform functional tests. Past studies in LOM procedure have been carried out mainly with paper, and a few on metal. The paper deals with testing the influence of the position of products in the machine working area on the mechanical properties (tensile and flexural properties) of the product.

Uporaba vodenog mlaza u obrnutim logističkim operacijama kod obrade odbačenog streljiva

Abstract: This paper deals with presenting a manufacturing cutting process of munitions disposal by abrasive waterjet in order to increase safety of operator, environmental protection and material utilization. The paper aims at proposing an automatic line with abrasive waterjet cutting of unused munitions in order to utilize raw materials, increase safety and environment protection and exclude workers from the process. In order to find out and analyze the cutting process behaviour a non-thermal experimental cutting was performed of 100 mm antitank bullet Nk 100 ShK 44 TK by abrasive jet. Based on experimental results the structure of AWJ automated cutting system for discarded munitions was proposed. This unconventional technology can be easily implemented by this system. Increased effectiveness is also possible during munitions processing with the utilization of obtained metal scraps.

Experimental investigation of the added mass of the cantilever beam partially submerged in water

Abstract: The phenomena of added (virtual) mass of submerged structures are analyzed numerically and experimentally in this paper. The classical concept of modal added mass is analyzed in parallel with local added mass that is evaluated using pseudo-residual force vector. A finite element structure model is used to determine the local added mass. The model update and the model reduction techniques are necessary, and their respective roles are described and applied in determining the local added mass. The procedure is implemented to the cantilever beam partially submerged into water. Experimental modal analysis is performed on a cantilever beam in the air and on the same beam partially submerged in the water. This results in two sets of modal parameters, and the cause of their differences is presented and explained by the added mass. The results obtained this way can be used as benchmark for further study and comparison with other simulations.

Delta roboti – roboti za rukovanje velikom brzinom

Abstract: Delta roboti Mechanical systems that allow a rigid body (called endeffector) to move with respect to a fixed base play a very important role in numerous applications. A rigid body in space can move in various ways, in translation or rotary motion. These are called its degrees of freedom (DOF). The position and the orientation of the end-effector (called its pose) can be described by its generalized coordinates. As soon as it is possible to control several degrees of freedom of the end-effector via a mechanical system, this system can be called robot [1, 3]. From this aspect, consisting of three subsystems: sensorial, control and decision-making, and actuation subsystem. The sensorial subsystem establishes a feedback with the environment. The control and decision-making subsystem represents the 'thinking' centre of the robot, its 'brain'. Together, the sensorial and control subsystems make up a cognitive system. Finally, the actuation subsystem is used to affect the environment, making such an impact on it that the environment changes [2]. It was concluded that the serial robots are inappropriate for tasks requiring either the manipulation of heavy loads, or a good positioning accuracy, or to work with high dynamic parameters.

Cutting tool life tests of ceramic inserts for car engine sleeves

Abstract: Ovaj na eksperimentalno trajnosti alata za indeksiranje reznih uložaka. Postavljen je kriterij trosenja alata = 0,6 mm (sukladno ISO 3685) ili 30 komada tuljaka. Kada je postignut barem jedan od ovih parametara, ispitivanje je zaustavljeno i procijenjeno. Ispitivane su dvije vrste reznog materijala tvrtke Saint Gobain Advanced Ceramics s.r.o. – ZTA7 NI i D 250. Pratili smo njihovu trajnost kod istih parametara obrade. Eksperimenti su izvedeni na alatnom stroju – CHEMNITZ NILES N22 lijevano željeza 25P koje se koristi za motore automobila.Trosenje alata je za svaki peti tuljak. Mjerena je mikrogeometrija nakon ispitivanja trosenja alata na svakom petom tuljku. Cilj je bio odrediti toleranciju profila, visinu profila i vanjski promjer . Mjerenje je provedeno puta, je izvedena naknadno i prikazana je u tablicama.

The design and verification of experimental machine for real journal bearings testing

Abstract: The article presents the design of a machine for determining basic tribological features of real journal bearings. Thus, the article aims at presenting the principle of the machine and the kinematic scheme of the machine. The device is tested by a set of experiments with real journal bearings determined to be applied in automotive industry. The journal bearings on the base of bronze type B70 were tested. The experiment conditions resulted from the chosen application, steering servo unit.

Sustav potpore neizrazitom AHP utemeljenom odlučivanju u izboru tehnologije u procesu rezanja abrazivnim vodenim mlazom

Abstract: Due to its remarkable abilities, the studies about abrasive water jet cutting process are rapidly increased in recent years. One of the main problems about this brilliant technology is to find the appropriate technology to use in cutting processes to increase surface quality. In this paper a fuzzy/crisp AHP based decision support system is proposed for the selection of appropriate technology for the cutting process of titanium. An application of the proposed models and their results are presented with comparisons. The results illustrated that both methods used in decision support pointed out the same technology with similar weights.

Drevna logistika – povijesna distanca i etimologija

Abstract: The capital work "Logistics Systems" [1] synthesized all human activities and demonstrated that each was a separate logistic sub-system. Furthermore, the origin of the word "logistics" is based on the view that its genesis temporally correlates with the invention of steam engine in the eighteenth century (1764). Thus, the genesis of the concept of logistics is directly related to industrial revolution, although the phenomenon of production and trade dates back to much earlier times. Presently, the prevalent view is that the term logistics was first used by the Swiss General Baron de Jomini (1779 − 1869). There are two versions of the genesis of the word logistics, both of French origin. The first, , is derived from military rank and refers to the organization of the military support troops. The other, refers to a spatial military organization − camping. At the end of the nineteenth century, the term logistics "arrived" to the United States, and their military literature adopted the term "logistics", referring to the science of military support services, i.e. transport and supply for the troops. In the Second World War, the term "logistics" was used in relation to the planning and management process in providing (re-populating) and supplying the allied troops. During the 1960s, the term logistics was first used in the civilian sector in the trade industry. In the United States, the term logistics referred to planning and implementation of physical distribution. In 1974, HansChristian Pfohl provided the characteristic areas of logistics tasks, conceptualized and shaped logistic axiomatics and developed logistics as a science. The obvious ancient genesis of logistics contains in its root the Greek word "logos", primarily used in the context "logistique" "Marechal de logis"

A discussion on assuring software quality in small and medium software enterprises: an empirical investigation

Abstract: Under the studies of general core activities including software inspection, review and testing to achieve quality objectives in small-medium size enterprises (SMEs), the paper presents a contemporary view of such companies against quality measures. The results from a local empirical investigation of quality standards in the Turkish software industry are reported. Around 150 software companies have been approached from which 17 detailed feedback inform that in order to ensure software quality, standards including internationally recognized International Standards Organization (ISO) and Capability Maturity Model Integration (CMMI) are given credit. However the substantial workload and resources required to obtain them are also reported as serious; downscaled frameworks of such large models proposed in the literature are not well known by the SMEs either. The paper also discusses "work around" that bypasses such standards to ease delivery of products while keeping certificates as labels just to acquire new jobs for the business.

Application of variations of the lms adaptive filter for voice communications with control system

Abstract: U ovom se radu opisuje predložena metoda za optimalno podesavanje parametara varijacija LMS adaptivnog filtera kod prigusenja aditivne buke iz govornog signala. Izabrana varijacijaLMSadaptivnog ponista a buke je implementirana naTMS320C6713 DSK.Upraksi je ovo primijenjeno na govornu komunikaciju s upravlja kim sustavom za pra enje operativno-tehni kih funkcija u zgradama.