Effect of surface roughness and lubrication on the friction coefficient in deep drawing processes of aluminum alloy aa with fem analysis 1. Friction between the interface workpiece and tooling has considerable importance in sheet metal forming operations; an accurate description of the friction is necessary to analyze and design new workpieces and tooling. The results indicate that this methodology is consistent with reality. It is also observed that the software tends to diverge from the measured results because the software considers the COF to be constant along the process. Workpiece strain measurements were collected to compare with the numerical simulation results, and it was observed that they are generally in agreement.
Note also that there is a large fiction at the lower edge of The xxx adventures of maddison piece where the simulation predicts a tendency to wrinkle, which remains the same for all friction values. Because calculating the yield stress depends on the region, it is necessary to know how to calculate the strain. Fereshteh-Saniee and Montazeran [ 14 ] proposed a formulation to measure the maximum force of deep drawing and compare the Coefficiwnt with the simulation using ANSYS with viscoelastic solid elements, shell elements and the Panknin [ 11 ] formulation. Pfestorf, M. Kleinert, and R. This is probably because the software considers the friction to be constant throughout the process, and studies of COF measurements indicate that this is not true. The COF of Equation 9 should be different from that of Equation Chrome nipple ; however, in the present study, Coefficient friction stamp lube were considered to be the same throughout the process. The simulation demonstrates a difference stakp results compared to the real Coefficient friction stamp lube, and this difference tends to increase as the friction in the process increases.
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Journal of Vibration and Acoustics. Friction is an important factor in many engineering disciplines. Values outside this range are rarer, but teflonfor example, can have a coefficient as low as 0. It was shown that in AFM tip contacts both the sliding speed and the apparent contact area influence the friction force. Mountain climbers and sailing crews demonstrate a standard knowledge of belt friction when accomplishing basic tasks. It is commonly thought that the static coefficients of friction are Coefficient friction stamp lube than the dynamic or kinetic values. Computers and Structures. Rubber in contact Stories about boys masturbating other surfaces can yield friction coefficients from 1 to 2. This property can have dramatic consequences, as illustrated by the use of friction created Coefficient friction stamp lube rubbing pieces of wood together to start a fire. Limiting friction is usually the highest friction, meaning, it usually takes more force to get something moving than to keep it moving. Even though the sheet and the tool surfaces look smooth from an unassisted vision; under Cum on big breast microscope they show a complex shape. The understanding of friction was further developed by Charles-Augustin de Coulomb Frank Philip Bowden and David Tabor showed that, at a microscopic levelthe actual area of contact between surfaces is a very small fraction of the apparent area. Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity.
In stamping operations, wet oil-based or dry film lubricants are used to protect the surfaces of the sheet blanks, reduce friction during deep drawing, and minimize surface treatments before assembly.
- Friction is a force resisting relative motion and may occur at the interface between the bodies, but may also occur within the bodies.
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- Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other.
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- For an object pulled or pushed horizontally the normal force - N - is simply the gravity force - or weight :.
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Effect of surface roughness and lubrication on the friction coefficient in deep drawing processes of aluminum alloy aa with fem analysis 1.
Friction between the interface workpiece and tooling has considerable importance in sheet metal forming operations; an accurate description of the friction is necessary to analyze and design new workpieces and tooling. The results indicate that this methodology is consistent with reality. It is also observed that the software tends to diverge from the measured results because the software considers the COF to be constant along the process.
Workpiece strain measurements were collected to compare with the numerical simulation results, and it was observed that they are generally in agreement. Recently, increasing the knowledge about the friction in sheet metal forming operations has been a priority. Many methods of determining the coefficient of friction COF have been studied, and the current most commonly used method is the bending under tension test BUT.
In this test, a strip is bent and slid through a pin with a specific radius R to mimic the same conditions of the die radius in deep drawing. Lee et al. Ceretti et al. The BUT test, however, requires specific equipment built for this purpose; there is no such device manufacturer. Other authors like Darendeliler et al. Kim et al. Guillon et al. He found that a chrome surface alone is not enough to greatly reduce friction, it is necessary to apply a lubricant and the lowest friction was achieved with the use of Teflon.
Other important information was obtained by HAO et al. The various studies done with friction did not attempt to correlate real tests, numerical simulation, and analytical calculations. Articles focus on just one subject or another. Thus, the objective of this paper is to use Panknin's [ 11 ] analytical equations to determine the value of the friction coefficient by comparing it with a real test and uses it as input data in the LS-Dynaform Finite Element FE software.
With the simulation done, the force-displacement curve of the punch will be obtained and compared with the real test to verify the level of divergence that the friction can give. A cylindrical cup was used as the workpiece geometry, and the plot of punch force versus punch displacement was used to compare the true measurements and the simulation. The geometry was the same as that of the Swift cup test, which was described by Mielnik [ 12 ]. This test emulates the deep drawing process because there is tensile stress in the radial direction and compressive stress in the circumferential direction.
The tools used in the Swift test include a cylindrical punch, blank-holder and die. The dimensions are shown in Figure 1. The punch is then forced against the blank until the deep drawing ends or the material cracks.
To obtain different COF between tools and the sheet in the deep drawing test, the following methodology was used. Surface roughness variation of the die and blank-holder was induced by applying sandpaper with a specific grit in addition to four lubricants.
The unique varying parameters were surface finishing and lubricants; all other parameters remained constant. The sandpaper grit used was , and The application methodology consisted in adapting the matrices in a machining lathe with constant speed of rotation in the spindle "chuck".
Sandpaper applications were made from the inside out of the dies in just a single pass and slow enough to ensure a visible change in finish texture. The sandpapers were applied beginning with the largest and continuing to the smallest grit to remove the previous surface finish; for example, if it was necessary to use the sandpaper, then the and sandpapers were applied in sequence.
For these finishes, the average Ra and maximum Rmax roughness of the surfaces were evaluated after the application of each final sandpaper according to the ISO standard. The cut-off parameter adopted was 0.
Table 1 : Roughness measures for each finish. Analyzing table 1 , it can be observed that the roughnesses measured in all finishes applied had very close values.
The roughnesses Ra and Rmax, measured at the punch, were 0. This was done due to the fact that, for the geometry used, the punch comes into contact with the sheet only in the center of the sheet, where there is practically no deformation of the sheet and the slip between the surfaces is almost zero.
The lubricants used in this work are mineral based oils that are commonly used by sheet metal forming industries. The lubricants were labeled as the following: lub F, lub L, lub O and lub S.
Two other lubricants tested included grease and a 0. The condition without lubricant the dry condition was also tested, and the surface finish applied in this case was with sandpaper.
The lubricants were applied in abundance on the two sides of the blank and were not applied to the tools. The abundance of lubricant in the blank ensures that the tools will be well lubricated.
Acetone was used to remove the remaining lubricant before applying other lubricants, and it was used on all of the tools. The properties of the material used in this work, AA aluminum, or commercially pure aluminum, are described in Table 2. A cushion of 6-mm-thick Polyurethane was used to reduce the friction be-tween the aluminum AA and the tools. Figure 2 shows the result of the FLC test. This curve is used to determine the maximum strain limits that the sheet can have when subjected to certain deformation levels.
The curve line represents the possible values of the combinations of stain of the specimen that indicate signs of rupture start, the curve can be interpreted as a border between regions of failure and safety. The region above the curve is the region of failure or rupture. The region below the curve represents the safety region.
This curve was obtained to be used in the simulation as a criterion of failure of the material and will also be used for the comparison with the results of the simulation with the different frictions attributed between the sheet and the tools. There are several equations that are used to calculate the maximum drawing force in the deep drawing process.
These equations generally give limited information about the process or the material used because they are applied to simple geometries, or they make several simplifications that add uncertainty to the calculation. Some examples include the equations used to calculate the maximum force in a conventional stamping.
These equations are used to estimate the strength of the press needed to draw a piece. Siebel and Panknin [ 13 ] developed an analytical model based on the elementary theory of plasticity.
The model considers the main factors that contribute to the maximum force in the deep drawing of a cylindrical cup form. Figure 3 illustrates the parameters involved schematically. In Equation 1 , the medium yield stress kf m is calculated by:. Because calculating the yield stress depends on the region, it is necessary to know how to calculate the strain. The yield stress kf 1 and kf 2 can be calculated using Equation 8 , where C and n must be known and are determined according to the sheet material.
Thus, kf m can be determined. The COF of Equation 9 should be different from that of Equation 10 ; however, in the present study, both were considered to be the same throughout the process. Finally, to obtain the total force of the deep drawing though the Panknin [ 11 ] equations, it is necessary to add all the effects of the forces described above, i. This method of calculation will be used in this work because the COF is used as an input parameter to determine the maximum drawing force.
As mentioned above, three sandpapers and four types of lubricants were applied. For each condition of friction, three valid tests were performed and the average curve between the three was taken as the representative curve for the sandpaper and lubricant. The resulting force and displacement measurements of the punch are shown in Figure 4 , where they are grouped according to the sandpaper used and the applied lubricant. The lower right graph of Figure 4 shows the results for other lubricants with the sandpaper.
The dry conditions, Teflon film and grease are shown as well. For every graph in Figure 4 , the maximum force for each curve that occurs after an approximately 15 mm displacement of the punch is obtained. After this, the force measured on the punch decays to zero, which corresponds to the end of the drawing where the desired final shape of the piece is obtained.
It is possible to observe that as the surfaces of the dies are more polished, there is a decrease in the sheet metal forming forces. This is due to the fact that as there is a decrease in the size of peaks of the surface, there is a corresponding decrease in the force necessary to make the sheet to move, because there will be less amount of peaks meeting and thus the lubricant will have more acting in the separation interface. During the strain of a sheet metal the coefficient of friction is controlled by two different components, an adhesive force acting on the real areas of contact Figure 5a and a deformation force acting during the penetration of the roughening of the tool, which is harder, on the sheet, which is softer Figure 5b.
Another observation of figure 4 is that no matter what shape the surface has, the best lubricant performance will always be the same, that is, the one that generates less force in the sheet metal forming. In the graphs, that lubricant was the lub S, which under all conditions generated a lower sheet metal forming force. This is probably because the lubricant has additives such as teflon particles, for example that improve the ability to slip between surfaces and this will occur whenever the lubricant is able to remain between the contact surfaces.
In the lubricants used, the chemical composition was not evaluated, as this was not the objective of the study.
Table 3 shows the values of the maximum forces obtained from the plots in Figure 4. The values are measured in kN. It can be seen that the non-lubricated sheet metal forming had a lower force than when applying sandpapers and with some lubricants. This can be explained by the effect of adhesion of sheet material on the tools. When there is no lubrication at the materials interface, the aluminum tends to adhere to the dies and this happens early in the deformation, causing a peak of force.
The adhered material must then be sheared for the stamping to continue. This can be seen in figure 4 , on the dry graphic. After the adhered material has been sheared, the force does not increase as the material has flowed and itself functions as an interface lubrication. This condition may seem beneficial since it decreases the punch force, however adhesion of material will promote scratches on the sheet which is a surface defect. The adhered material will also make difficult the stamping of other parts in the same tooling in serial productions.
The geometric parameters obtained by the Swift cup test tools are shown in Table 4. Figure 1 shows a crosssection of the tooling with the dimensions of each component. The maximum force obtained from testing the equations of Panknin [ 11 ] can be used to obtain the COF. Thus, Table 5 shows the results of the COFs for each sandpaper and lubricating oil.
The blank holder force, Fn, was also measured and kept constant for all tests; its value was approximately 10 kN. The specific objective of the numerical simulation is to reproduce the experimental study, evaluate the COF and compare the values of force versus displacement of the punch with the measured results. Shell elements were used to define the material of the blank and the tools punch, die and blank holder.
This can be sinusoidal vibration as used in ultrasound-assisted cutting or vibration noise, known as dither. Some of the more common lubricants are silicone, molybdenum disulfide MoS2 , talc baby powder , graphite, carnuba wax. Friction is a non-conservative force - work done against friction is path dependent. With your hand start to push on the o-ring in the direction you want it to slide without actually making it move. Yelovoy, S. Hidden categories: CS1: long volume value Webarchive template wayback links CS1 maint: multiple names: authors list Articles with short description Wikipedia indefinitely semi-protected pages All articles with unsourced statements Articles with unsourced statements from June Articles with unsourced statements from December Articles containing potentially dated statements from All articles containing potentially dated statements Wikipedia articles incorporating a citation from the Encyclopaedia Britannica with Wikisource reference Wikipedia articles with GND identifiers Wikipedia articles with LCCN identifiers Wikipedia articles with NDL identifiers.
Coefficient friction stamp lube. Related Topics
In stamping operations, wet oil-based or dry film lubricants are used to protect the surfaces of the sheet blanks, reduce friction during deep drawing, and minimize surface treatments before assembly. Since most dry film lubricants are applied to steel or aluminum sheets before drawing operations, they also affect the assembly processes welding, riveting, clinching, and bonding.
Therefore, they must be evaluated not only for their deep-drawing characteristics, but also for their removability and their effect on assembly and painting operations. On complex-shaped body panels, dry film lubricants help improve performance in deep drawing, both in small-series production and on specific body parts of high-volume vehicles, especially aluminum-alloy parts.
One example of a high-volume car with aluminum body components is the Mercedes-Benz E-Class, launched in Its hood, front fenders, trunk, and some special inner body panels are madeof aluminum. In this case, the parts did not have to be washed before assembly. The deep-drawing process is used extensively to evaluate the performance of lubricants. However, during stamping of thin-gauge materials at high rates, the die and punch become warm, which can change the properties and behavior of the lubricant.
Therefore, drawing tests sometimes must be enhanced with heat to emulate realproduction conditions encountered in high-speed stamping presses. During deep drawing see Figure 3 , the most severe friction takes place at the flange area.
The lubrication condition in this flange area influences the thinning or failure in the side wall of a drawn cup. Therefore, lubricants can be evaluated in deep drawing by measuring the maximum applicable blank holder force without failure in the cup wall.
Two lubricants, one oil-based and one dry film see Figure 4 , were evaluated using the deep-drawing test for aluminum alloy AA The oil-based lubricant, KTLN 16, gave the maximum possible drawing depths of approximately 58 to 80 mm, depending on the blank holder force.
The dry film lubricant, E1, enabled sheet blanks to be drawn up to mm without part failures. For a specific drawing depth of 70 mm, the blank holder force could be increased up to 1 kN for dry lubricant; with the oil-based lubricant, blank holderforce was limited to 0. In this case, the dry lubricant gave a larger process window for obtaining larger drawing depths. Meiler, M. Pfestorf, M. Merklein, and M.
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Please sign into your acccount Email. Remember Me. Forgot Password. Figure 4 Two lubricants, one oil-based and one dry film, were evaluated using the deep-drawing test for aluminum alloy AA