Search

The development of 3D printing technologies has introduced new possibilities in producing multi-material parts, and Fused Filament Fabrication (FFF) is one of these technologies. Typically, multi-material parts are made of different blends of the same material, also known as multi-color 3D printing, or from materials with good chemical compatibility. Conventionally, a simple face-to-face bonding interface between part components and chemical bonding between thermoplastics define the mechanical performance of multi-material components. In this regard, the paper aimed to investigate the contact interface strength of multi-material specimens using a geometric approach. Therefore, several geometrical interfaces, such as dovetail, omega, T-shape, and others, were used to interlock pars of low-compatibility thermoplastic polymers, styrene-acrylonitrile acrylic (ASA), and thermoplastic polyurethane (TPU). In the case of one of these interfaces, modeling by the finite element method was resorted to obtain additional information regarding the processes that develop at the interface level between the two components of the joint during the tensile loading. The results showed that the macroscopic interlocking interfaces significantly improved the mechanical properties of the multi-material specimens.

In industrial practice, there are situations where friction processes are developed, one of the components involves in the process being made of polymeric materials. In such situations, it may be necessary to know more information regarding the magnitude of the friction coefficient for polymer–polymer or polymer–metal material pairs. A relatively simple equipment is designed and materialized, starting from the idea of moving a sled on which there is a strip of known material and on which a sample of the material to be tested is pressed with a force of known magnitude. The processing of the results of some experimental tests carried out on this equipment, using specialized software, allows the determination of an empirical mathematical model to highlight the influence exerted by some input factors in the experiment on the size of the friction coefficient. It is thus found that, for the available experimental conditions, the nature of the couple of materials in contact and the thickness of the polymer layer deposited by 3D printing exert the greatest influence on the magnitude of the friction coefficient. [ABSTRACT FROM AUTHOR]

To evaluate the sound insulation capacity of small panels made of polymeric materials by 3D printing, a Taguchi L18-type factorial experiment with eight independent variables was designed and materialized. The independent variables were the panel thickness, polymer material type, 3D printing speed, infill percent, infill pattern, layer thickness, frequency, and sound volume. Empirical mathematical models were determined through the mathematical processing of the experimental results using specialized software. These empirical mathematical models highlight the meaning and intensity of the influence exerted by the input factors in the process on the acoustic pressure level of the energy absorbed after the passage of sounds through the small panels manufactured by 3D printing from polylactic acid and polyethylene terephthalate glycol. The factor with the strongest influence was the frequency of the sounds, with a maximum of the sound pressure level for a frequency of 13,000 Hz. A polylactic acid panel between the sound source and the sound-receiving sensor reduces the sound pressure level by about 45% from 95.8 to 65.8 dB. The power function type mathematical model in the case of the energy absorbed by the panel highlights the fact that the highest values of the exponents are those attached to the sound frequency (exponent equal to 1.616) and, respectively, to the thickness of the panel (exponent equal to −0.121). [ABSTRACT FROM AUTHOR]

A process currently under researchers' attention in terms of making holes is the so-called friction drilling. The process is based on pressing a conical-shaped tool, driven in rotation, into the workpiece to be drilled. The analysis of the process highlights that there will be a variation of the axial force to the physical-mechanical properties of the workpiece material. To highlight the axial force variation, it was necessary to select, among several alternatives, a device that would make this possible. In this sense, the method of analytic hierarchy process was used. It was possible, thus, a justified selection of the device intended to allow obtaining additional information on the friction drilling process [ABSTRACT FROM AUTHOR]

Increased interest in the study of plastics has led to the development of processing technologies using such materials. The variety of plastics has led to a diversification of the technical processes through which the finished plastic products can be obtained. We approached the idea of designing plastic injection equipment, considering that various research could be made on the phenomena involved during the process, as well as the observation of the technological properties of the plastics. To design such equipment, some known methods used in conception processes could be applied. Optimizing the equipment design process is one of the elements that can ensure high efficiency of the entire injection molding process. Thus, the method chosen in this case was the analytic hierarchy process (AHP) method, which is one of the methods that offer the possibility to choose a solution when there are many alternatives. The relative simplicity and precision of this method are some of the arguments behind this method. The combination of required equipment and application of the AHP method allowed the choice of an optimal solution for testing injection molding. The result of design activity was an alternative to equipment that can be used for developing future research.

When a technical problem is approached, as a direct consequence of analyzing certain distinct existing solutions, an improved solution of the problem could be elaborated. Over the years, some methods able to help the designers were identified and developed. The purpose of this paper was to take into consideration and to develop a succinct comparison of some creative considered methods of solving research problems in the field of industrial processes. The first group of analyzed design method was based on the initial use of the so-called ideas diagram. The results of the analysis were used to propose solutions concerning a device for investigation of the effects developed on sharp peaks by the electrical discharges. The axiomatic design was applied as a creative design method in the case of equipment for the investigation of degradation in time of the subsystems of the computers. The reverse engineering method was considered in the case of a device for supporting the tablet in a convenient position for the user. A final succinct comparison of the three ways of synthesizing an improved solution of a technical problem from the field of industrial processes highlights the essential characteristics of the approached methods.

Within the university study program that trains of the future engineers in the field of manufacturing engineering, in the Romanian technical universities, there are matters that aim at familiarizing students with the way of solving certain problems of constructive and/or technological design. Such a matter, called cold pressing technology, has been included in the last years of the license studies. In the context of the project activity at this matter, as a theme to be solved, the student usually receives the responsibility of designing a mold for the cold-pressing of pieces of various shapes, for large series production, starting from sheet type workpiece. The passing of successive design stages gradually leads the student to elaborate a project that includes an assembly drawing and some mechanical drawings as final documents related to the received project theme. It was considered that by using some principles of axiomatic design, it is possible to investigate and define more clearly the objectives of the project activity in the field of cold pressing technology. The analysis allowed a clearer definition of functional requirements and the identification of solutions to improve the quality of future engineer training activities concerning to project activity in the field of cold pressing technology.

The phonic pollution is a problem of interest in the mechanical workshops. Various solutions could be applied in order to diminish the intensity level of the sound generated by various noise sources. The research presented in this paper aimed to highlight some aspects concerning the measuring of the sound intensity level in a mechanical workshop and some possibilities of decreasing the sound intensity level by using fences made of distinct materials. The sound intensity level corresponding to the use of a universal lathe was experimentally measured by means of an adequate apparatus. The results of experimental research were mathematically processed and some empirical mathematical models were determined. The analysis of the experimental results and empirical mathematical models highlighted the influence exerted by some factors on the sound intensity level and some possibilities of diminishing the phonic pollution by using various phonic fences.

The vibrorolling could be sometimes applied as a finishing method to diminish the height of the surface asperities. It is expected that the mechanical characteristics of the workpiece material affect in a certain extent the generation of the new profiles corresponding to the surface roughness and distinct values of the surface roughness parameters could be obtained. An experimental research was designed and achieved taking into consideration some vibrorolling process input factors and distinct steels as materials for the test samples. The experimental results were mathematically processed and empirical models were determined. These mathematical empirical models highlight the distinct behavior of the studied steels evaluated by means of the Ra surface roughness parameter.

When the threads are obtained by using turning tools, various factors are able to affect the machining accuracy. In order to reveal the way in which these factors exert influence on the threading accuracy, an analysis of some proper situations of obtaining threads on universal lathes and using turning tools was developed. The analysis showed that the thread profile error could be essentially affected by the position of the cutting tool active edges relative to the workpiece. Taking into consideration the results of analysis, some aspects concerning the requirements to be met during the design of a device that could be used in experimental investigation of influence exerted by some factors on the threading accuracy are presented.

Electrochemical machining is usually included in the wider group of non-conventional machining methods. This method is based on the material removal from the workpiece as a result of chemical reactions between the electrolyte and the material of the workpiece, under conditions where the tool electrode and the workpiece are immersed in an electrolyte and connected to the poles of a direct current source. Using principles from axiomatic design, specialized equipment was designed. This equipment could be used to experimentally investigate the influence of working gap size on the material removal rate from a test sample made of an electroconductive material. The development of the design matrix led to the observation that, in the proposed version, the condition imposed by the first axiom is not strictly respected. This requires the independence of the functional requirements valid for different components of the equipment, which means that there are possibilities for future improvement of the proposed constructive solution. [ABSTRACT FROM AUTHOR]

The study of residual stresses in metal parts can be performed by making slits where such stresses are assumed to exist. Measuring the width of the slits can provide information on the type and size of residual stresses. The slits must be made by machining processes that do not introduce other stresses in the part's material. One of the methods that can be used in this regard is electrochemical cutting. In the paper, the ideas diagram method was used to analyze the possibilities of contouring some alternatives for the different components of electrochemical cutting equipment. An equipment structure was designed to allow the realization of slits in metal parts to evaluate the internal stresses in parts made of metal. [ABSTRACT FROM AUTHOR]

Punching is a cold deformation process by which holes are obtained in the workpiece in sheets or plates. The part of interest is the separate part of the workpiece or that which remains after separating an area from the plate or sheet. A systemic analysis of the punching process was first performed to investigate the punching processes better. The analysis revealed the parameters of interest in the case of such processes and the factors that influence the values of the parameters of interest. The use of the first axiom in the axiomatic design facilitated the identification of some components of a device that would fulfill the different functional requirements of the device. A variant of the device was designed to facilitate a more detailed study of the material's behavior in the area affected by the plastic deformation process. The device considers the specific components of a die, being adaptable to some of the existing universal machine tools in a mechanical workshop. [ABSTRACT FROM AUTHOR]

The wire electrical discharge machining is a nonconventional machining method applied to machine ruled surfaces in plate type workpieces made of electroconductive materials. There are various methods to establish the optimal values for the process input factors in the case of the wire electrical discharge machining. One of these methods is the gray relational analysis that takes into consideration distinct weightings for some of the process output parameters. The method was applied considering the pulse on time, pulse off time and average current intensity as process input factors. The process output parameters were the surface roughness and the machining speed of penetration in the plate type workpiece. In this way, distinct combinations of the process input factors values were established for different weightings of the output parameters. [ABSTRACT FROM AUTHOR]