This paper presents an experimental study carried out in order to assess the effects of the cutting parameters (cutting speed, feed and depth of cut) and also of cooling conditions on the cutting ...force and the surface quality during high speed face milling of a magnesium alloy. With its high ratio of strength to weight, good machinability and overall physico - mechanical properties magnesium has attracted a large interest upon itself, especially in fields such as automotive, aeronautics, electronics or biomaterials. On the other hand, there has been lately an increased interest for cooling techniques that are more environmentally friendly, which is why in this study two cooling systems were used: dry machining and minimum quantity lubrication (MQL). The tests have been organised according to design of experiment technique. By using the response surface methodology (RSM), a central composite experimental matrix was designed. Statistical analysis (ANOVA) has allowed to create mathematical models of the cutting force and surface roughness and to analyse the effects of the effects of the input parameters on these outcomes. It was thus revealed that the depth of cut and the feed, and the interactions feed - depth of cut and feed direction - cooling, respectively, have the most significant influence on the main cutting force, whereas when it comes to the surface roughness, the most significant factors were the feed, the feed direction and the interaction between feed direction and cooling type.
Stretch forming is a metal forming process that implies bending and stretching a sheet of metal over a die, with the sheet being plastically deformed into the desired shape. The purpose is to obtain ...large parts. One of the main aspects is that the metal sheet is locked into position by gripping jaws. A hydraulic ram is raised into the metal sheet, therefore increasing the tensile forces. This process is used to draw intro shape materials like aluminium, magnesium, titanium alloys, stainless steel, Inconel. These materials have in common the fact that they have poor formability or the elastic spring-back has unacceptable values. Taking this into consideration, the nature of the materials along with the fact that the metal sheet can crack, due to excessive strain, we propose a self-adaptive stretch forming process. Underlining this process is the stress-strain curve, that has three inputs: force, sample section area and strain. For each of these factors, our method uses a particular approach, as in a Python-based software and Android-based IoT solution, that uses stress and strain data. Furthermore, it controls, in real-time the hydraulic press to the point at which the material is stretch close to its ultimate yield strength.
3D printing is a maturing technology, that can be used from fast prototyping to industrial scale. A key aspect of 3D printing is the ability to control the material density, thus it's hardness. This ...factor assures that 3D printing is not only economical competitive, but it also provides parts with improved mechanical properties. Furthermore, it is a good alternative for manufacturing stretch-forming dies. Implementing 3D printed dies offers an economical advantage, as cost for producing are a fraction of the cost of standard metal die, and the technology behind the process is simpler. Therefore, in this paper we have chosen to study stretch forming on a die that has components 3D printed from polylactic acid (PLA). The length and width of the punch is maintained constant while the radius varied from R180 ÷ R1080 mm, with an increment of 180 mm. A total number of 6 punches were used in these experiments to stretch sheet metal stripes made of aluminium 2024-T0, a material specific for aircraft skin. In addition to the shape of the resulted part, in the present study other process parameters have been investigated (punch force, part radius and deviation from circularity).
The formability of magnesium alloy sheets at room temperature presents anisotropy in mechanical properties and difficulties in terms of occuring cracks easily, especially in regions with bend radius. ...In addition, the elastic spring-back is significant, leading to massive deviations from the desired shape. Recent studies conducted in this field lead to stretch forming magnesium alloys sheets using thermo-mechanical treatments at temperatures up to 400°C. The present study was conducted on 1 mm thick magnesium alloy AZ31B sheet to investigate its formability when stretching at room temperature by several dies with different radius. The stretching process was conducted on a hydraulic press, using 3D printed PLA dies with the following values: R180, R320, R540, R720, R900 and R1080. The samples were stretched until fracture to highlight the fracture force, distance to fracture, deviation from the die radius and bend angle.
•The sheet thickness variation in the case of mini drawn parts was analyzed.•New tools were made to minimize the sheet thickness variation and its effects.•The blankholder plate was made from two ...concentric rings with different widths.•The rings were made from different materials and were pressed with different forces.•The new tool geometries were verified/validated by simulation and experiment.
Thickness variation is a major defect of the drawn parts made from sheet metals, which influences the intensity of part defects and may cause part failure. In the case of mini deep drawing, sheet thickness variation along part's profile has the following effects on the drawn part geometry: increased non-uniformity of diameter variation, variation of springback parameters (part edge radius deviations and angle of wall inclination), different wrinkling intensities, and part cracking and fracture. The present paper analyses the experimental results of the investigations concerning the sheet thickness variation in the case of mini cylindrical drawn parts made from a copper alloy. Some constructive solutions of tool components that allow the control and minimization of sheet thickness variation by controlling the blank holder force, contact and friction forces (especially in the part flange zone) are also proposed and tested by simulation and experiment. The constructive solutions of the new tools were obtained by constructing the blank holder plate from two concentric rings made from different materials with equal or unequal widths.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Milling is an important industrial common machining operation used to produce complex surfaces. Surface quality in milling operation is influenced by various factors such as cutting speed, cutting ...feed, depth of cut and chemical composition of the material. Surface quality is defined by roughness, residual stress and microhardness and is important in determining corrosion resistance and in fatigue crack initiation. The aim of the present paper is to analyse the influence of above-mentioned cutting parameters (cutting feed, cutting speed, depth of cut) on surface microhardness. Tests were conducted using a Coro mill 490 with a single insert that was indexed for every experiment, thus eliminating the influence of tool wear. Al 6061-T6, a material widely utilised in aircraft, defence, automobiles, and marine areas due to its good proprieties (good strength and lightweight) was used. Microhardness was measured on workpiece surface but also in the cross section of the workpiece, up to a depth of 1mm, in order to observe material state in subsurface layer. It was observed from the results that an increase of cutting speed have led to an increase of microhardness while a higher value for depth of cut has led to a lower value of microhardness. Feed rate has generated similar results with the depth of cut.
An important problem encountered in the deep drawing processes of sheet metals is represented by the sheet thickness variation that can influence and affect the quality of drawn parts, may cause ...stress concentration in different zones of drawn parts or may conduct part fracture. The variation of sheet thickness during cold formation can have a greater importance when the drawn parts are made with small dimensions from metal sheets having small thickness. The present paper analyses experimental and numerical simulation results concerning the thickness variation in the case of micro/milli-cylindrical drawn cups made from sheets, called foils, having thicknesses from 0.05 to 0.20mm. A mathematical model for predicting the thickness variation is also developed, based on the variation of the unit radial forces developed in foil thickness, as a function of part geometry and material yielding trajectory. On this basis it is possible to control and minimise the thickness variation in the following part zones where such phenomena can generate negative effects: part wall where the variations of part diameter, wall inclination and wall curvature are the negative effects caused or influenced by the foil thickness variation and wall–bottom connexion zone where a negative effect can occur if the foil thickness variation results in the loss of material integrity.
► The analysis was performed based on experimental and simulation results using the DynaForm software. ► The factors that influence sheet thickness variation for micro/mili drawn parts were analysed. ► A model for the thickness variation prediction was developed based on the radial forces variation. ► The developed model was used to optimise process parameters and tools geometry.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Abrasive water jet machining is an emerging non-conventional technology widely used in different industrial sectors due to its multiple economic and environmental benefits. The quality of processed ...surface depends on process parameters, abrasive material properties and processed material properties and is mainly expressed by surface roughness, shape and dimensional accuracy of cut, presence of striations and/or burr. The current paper aims to present the influence of water jet pressure and traverse speed on the quality of processed surfaces in the case of AL-EN AW 2017A - T4 aluminium alloy abrasive water jet cutting.
The current paper presents the influence of different working regimes on the quality of cuts performed by abrasive water jet processing on S 235 steel. Four process parameters were varied: pressure ...(P), feed rate (Vf), quantity of abrasive material (Q) and distance between the cutting head and workpiece (h). Four quality parameters were analysed: width of the processed surface at the jet inlet (Li), width of the processed surface at the jet outlet (Lo), inclination angle of cut (α) and surface roughness (Ra). The analysis was done for three material thicknesses: 1mm, 6.5mm and 10mm.
Today major metal cutting companies in industrial countries, looking to gain time and reduce manufacturing costs while respecting the environment. There are many phenomena which affect the quality ...and production costs of the product, including cutting efforts, cutting temperature, residual stresses, etc. A better understanding of these phenomena will reduce production costs and maximize productivity. The aim of this work is to analyze the effect of machining conditions (cutting speed, feed speed and cutting depth) on cutting temperature and residual stresses, during the milling operations using the response surface method. A good accuracy between predicted and measured values of the cutting temperature was found, the cutting speed and the depth of cut are parameters whose effect is most sensitive to the residual stresses and the cutting temperature.However, little influence has been registered in the case of an increase of the feed rate. The percentage of error is 4.57%, indicating that the numerical approach can accurately predict the cutting temperature of the AISI 1045.
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