Prediction Of The Coefficient Of Friction In The Single Point Incremental Forming Of Truncated Cones From A Grade 2 Titanium Sheet

The aim of this paper is to analyze the effect of the process parameters on the coefficient of friction (COF) in the single-point incremental forming process. This investigation may be useful for further FEM analyses where the tool-workpiece contact must be set appropriately to obtain adequate results. The friction was analyzed between a solid tungsten carbide ⌀8 hemispherical ended tool with a radius of 4 mm and a grade 2 pure titanium sheet. As a lubricant, 10W40 engine oil was used. The experiment was of a central composite design and 20 runs in random order were carried out. The influence of input factors, namely spindle speed, tool feed and incremental step depth, was analyzed for the COF response. Two type of equations founded in the literature have been acquired to calculate COF values. An investigation of COF analysis was done for initial tool contact, the first tool full depth contact and stabilized forming region. Additionally, single components of the horizontal force (X-axis and Y-axis) were taken into account. Analysis of variance shows that there is no correlation between the input factors and the COF responses. However, the mean model fitted to the results obtained allows for the prediction of the COF by using the vertical force component and only one horizontal force component. The resulting mean value of the COF between the tool and the workpiece equals 0.4 for Eq. (1) initial contact, stabilized forming: Eq. (1) 0.656 and Eq. (2) 0.469

Properties of low-alloy high-speed steel at elevated temperature

This paper presents the results of research on the determination of the coefficient of thermal conductivity and hot hardness of cutters made of selected grades of low-alloy high-speed steels, HS 6-5-2 and HS3-1-2. The investigations of hot hardness and yield stress values of HS6-5-2 steel at elevated temperatures have shown that the hot hardness value decreased to 650 – 700 HV (59 – 60 HRC) in the temperature range of 500 – 550 °C. However, the hardness of the samples preheated to the temperature of 500 – 550 °C and measured at room temperature does not change. A decrease of the hot hardness of the steel is correlated with decreasing yield stress at elevated temperature

Current Concepts for Cutting Metal-Based and Polymer-Based Composite Materials

Due to the variety of properties of the composites produced, determining the choice of the appropriate cutting technique is demanding. Therefore, it is necessary to know the problems associated with cutting operations, i.e., mechanical cutting (blanking), plasma cutting plasma, water jet cutting, abrasive water jet cutting, laser cutting and electrical discharge machining (EDM). The criterion for choosing the right cutting technique for a specific application depends not only on the expected cutting speed and material thickness, but it is also related to the physico-mechanical properties of the material being processed. In other words, the large variety of composite properties necessitates an individual approach determining the possibility of cutting a composite material with a specific method. This paper presents the achievements gained over the last ten years in the field of non-conventional cutting of metal-based and polymer-based composite materials. The greatest attention is paid to the methods of electrical discharge machining and ultrasonic cutting. The methods of high-energy cutting and water jet cutting are also considered and discussed. Although it is well-known that plasma cutting is not widely used in cutting composites, the authors also took into account this type of cutting treatment. The volume of each chapter depends on the dissemination of a given metal-based and polymer-based composite material cutting technique. For each cutting technique, the paper presents the phenomena that have a direct impact on the quality of the resulting surface and on the formation of the most important defects encountered. Finally, the identified current knowledge gaps are discussed.publishedVersio

Development of Harvesting Machines for Willow Small-Sizes Plantations in East-Central Europe

The production of plant biomass in small farms within the Central and Eastern European countries requires the application of agricultural machines adjusted to the scale of production. In the article, new machines for small-sized plantations of energy crops have been presented. Furthermore, the results of strength analysis of three-point linkage mower frame are presented by finite element method. The advantage of the proposed solutions is their simple construction, which is connected with low production cost and simple machine operation. The energy-crop harvesting machines are especially intended for small biomass producers in East-Central Europe, and the purchase of professional machines is financially inaccessible. The proposed machines are mounted in front or at the back of a typical farm tractor and the chipping units are power-take-off driven. The numerical simulation was carried out using finite element method to study the structural strength of a mower frame. All machine designs proposed by the Rzeszow University of Technology are legally protected by patents and utility models. The presented agricultural solutions have been worked out by authors and a part of them is still being developed in cooperation with biomass producers

Artificial neural networks and experimental analysis of the resistance spot welding parameters effect on the welded joint quality of AISI 304

The automobile industry relies primarily on spot welding operations, particularly resistance spot welding (RSW). The performance and durability of the resistance spot-welded joints are significantly impacted by the welding quality outputs, such as the shear force, nugget diameter, failure mode, and the hardness of the welded joints. In light of this, the present study sought to determine how the aforementioned welding quality outputs of 0.5 and 1 mm thick austenitic stainless steel AISI 304 were affected by RSW parameters, such as welding current, welding time, pressure, holding time, squeezing time, and pulse welding. In order to guarantee precise evaluation and experimental analysis, it is essential that they are supported by a numerical model using an intelligent model. The primary objective of this research is to develop and enhance an intelligent model employing artificial neural network (ANN) models. This model aims to provide deeper knowledge of how the RSW parameters affect the quality of optimum joint behavior. The proposed neural network (NN) models were executed using different ANN structures with various training and transfer functions based on the feedforward backpropagation approach to find the optimal model. The performance of the ANN models was evaluated in accordance with validation metrics, like the mean squared error (MSE) and correlation coefficient (R2). Assessing the experimental findings revealed the maximum shear force and nugget diameter emerged to be 8.6 kN and 5.4 mm for the case of 1–1 mm, 3.298 kN and 4.1 mm for the case of 0.5–0.5 mm, and 4.031 kN and 4.9 mm for the case of 0.5–1 mm. Based on the results of the Pareto charts generated by the Minitab program, the most important parameter for the 1–1 mm case was the welding current; for the 0.5–0.5 mm case, it was pulse welding; and for the 0.5–1 mm case, it was holding time. When looking at the hardness results, it is clear that the nugget zone is much higher than the heat-affected zone (HZ) and base metal (BM) in all three cases. The ANN models showed that the one-output shear force model gave the best prediction, relating to the highest R and the lowest MSE compared to the one-output nugget diameter model and two-output structure. However, the Levenberg–Marquardt backpropagation (Trainlm) training function with the log sigmoid transfer function recorded the best prediction results of both ANN structures

Friction modeling of Al-Mg alloy sheets based on multiple regression analysis and neural networks

This article reports a proposed approach to a frictional resistance description in sheet metal forming processes that enables the determination of the friction coefficient value under a wide range of friction conditions, without performing time-consuming experiments. The motivation for this proposal is the fact that there exists a considerable amount of factors that affect the friction coefficient value and as a result building analytical friction model for specified process conditions is practically impossible. In this proposed approach, a mathematical model of friction behaviour is created using multiple regression analysis and artificial neural networks. The regression analysis was performed using a subroutine in MATLAB programming code and STATISTICA Neural Networks was utilized to build an artificial neural networks model. The effect of different training strategies on the quality of neural networks was studied. As input variables for regression model and training of radial basis function networks, generalized regression neural networks and multilayer networks, the results of strip drawing friction test were utilized. Four kinds of Al-Mg alloy sheets were used as a test material.publishedVersio

Investigation of contact phenomena in turning using tools made of low-alloy high-speed steels

U ovom se radu daju rezultati ispitivanja raspodjele temperaturnog polja i trošenja alata tijekom tokarenja čelika C60. Provedena su ispitivanja otpornosti na abrazivno trošenje tokarskih noževa izrađenih od niskolegiranog brzoreznog čelika. Uzorci čelika su toplinski obrađeni i zatim podvrgnuti ionskom nitriranju, oblaganju TiN ili kompleksnoj obradi. Analiziran je utjecaj brzine rezanja na vrijednost osnovnih parametara karakterističnih za pojave u graničnoj površini alat-obradak, t.j. rezni omjer, faktor trenja i dužina zone dodira. Porast vrijednosti kuta nagiba dovodi do porasta vrijednosti faktora trenja. Nadalje, vrijednost faktora trenja se smanjuje kako raste debljina reznog sloja. Ispitivanja trajnosti rezne oštrice potvrđuju da je u definiranju radnih uvjeta alata, najvažnija otpornost na gubitak tvrdoće kod porasta temperature na temperaturama višim i nižim od temperature popuštanja.In this paper, the results of investigations of the temperature field distribution and tool wearing during C60 steel turning are presented. Abrasive wear resistance tests were carried out for cutters made of low-alloy high-speed steel. Steel samples were heat treated, and then were subjected to ion nitriding, TiN coating, or to complex treatment. The influence of cutting speed on the value of basic parameters characterising the phenomena in the tool-workpiece interface i.e., cutting ratio, friction coefficient, and length of contact zone, is analysed. An increase of the rake angle value causes an increase in the value of the friction coefficient. Furthermore, the value of the friction coefficient decreases as the thickness of the cut layer increases. Investigations of the durability of cutting edges confirm that to define the working conditions of the tool, resistance against hardness loss with increasing temperature at temperatures higher and lower than the tempering temperature is the most significant

FINITE ELEMENT BASED PREDICTION OF DEFORMATION IN SHEET METAL FORMING PROCESS

In this paper the sheet forming process of cylindrical drawpieces was sim-ulated based on the finite element method by the explicit approach in the pres-ence of contact conditions with isotropic and anisotropic friction. The ex-perimental and numerical results obtained in the Abaqus finite element (FE) based program are presented. The aim of the experimental study is to analyse material behaviour under deformation and in addition to use the results to verify numerical simulation results. It was found that, although, the anisotropy of resistance to friction affects the height of ears, the influence of the friction formulation is relatively small in comparison with material anisotropy. The study indicates that FE analysis with 3-node triangular shell element S3R elements ensures the best approximation of the numerical results to the real process when both material and friction anisotropy are taken into account

Investigation of frictional conditions of steel sheets using pin-on-disk tribometer

This paper presents a method of determining the anisotropic friction model for sheet metal forming processes based on experimental data obtained from the pin-on-disk tribometer test. Friction coefficient value was measured as a function of angular position with respect to the rolling direction of the sheet metal. The frictional investigations presented in this work were conducted for deep drawing quality cold-rolled steel sheet with a sheet thickness of 1 mm

Recent Developments and Future Challenges in Incremental Sheet Forming of Aluminium and Aluminium Alloy Sheets

Due to a favourable strength-to-density ratio, aluminium and its alloys are increasingly used in the automotive, aviation and space industries for the fabrication of skins and other structural elements. This article explores the opportunities for and limitations of using Single- and Two Point Incremental Sheet Forming techniques to form sheets from aluminium and its alloys. Incremental Sheet Forming (ISF) methods are designed to increase the efficiency of processing in low- and medium-batch production because (i) it does not require the production of a matrix and (ii) the forming time is much higher than in conventional methods of sheet metal forming. The tool in the form of a rotating mandrel gradually sinks into the sheet, thus leading to an increase in the degree of deformation of the material. This article provides an overview of the published results of research on the influence of the parameters of the ISF process (feed rate, tool rotational speed, step size), tool path strategy, friction conditions and process temperature on the formability and surface quality of the workpieces. This study summarises the latest development trends in experimental research on, and computer simulation using, the finite element method of ISF processes conducted in cold forming conditions and at elevated temperature. Possible directions for further research are also identified