scholarly journals Adapted tool design for the cold forging of gears from non-ferrous and light metals

2021 ◽  
Author(s):  
Andreas Rohrmoser ◽  
Hinnerk Hagenah ◽  
Marion Merklein
Keyword(s):  
Process Model ◽  
Manufacturing Sector ◽  
Flow Behavior ◽  
High Strength Steels ◽  
High Strength ◽  
Cold Forging ◽  
Light Metals ◽  
Resource Saving ◽  
Die Filling ◽  
Wide Range

AbstractDue to growing competitive pressure within the manufacturing sector, there have been increasing attempts to establish resource saving production methods in gear manufacturing within recent years. Cold forging offers the potential—in addition to a high material and energy efficiency—to produce gears with an excellent surface quality, increased hardness as well as a load adapted fiber orientation. With regard to the wide range of applications there is a broad demand for gear materials, ranging from high-strength steels to non-ferrous and light metals. The flow behavior of the material has a significant influence on the cold forging process. Therefore, no consistent process result is achieved when forming different materials. Challenges exist due to deficient die filling and poor resulting geometrical accuracy. In this contribution, material-specific challenges during the full forward extrusion of gears from non-ferrous and light metals have been identified and suitable tool-sided measures were derived. A validated numerical process model was used to determine the underlying mechanisms of action and to verify the derived measures. A reduced yield stress leads to inflow formation, insufficient die filling, and low achievable strain hardening, as well as gearing accuracy. The tool-sided measures achieved a significant increase of resulting die filling and gearing accuracy as well as the mechanical properties. That provides the basis for the production of ready-to-use gears from various metal materials.

Investigations on the Mechanical Properties and Formability of Friction Stir Welded Tailored Blanks

2007 ◽  
Vol 344 ◽  
pp. 143-150 ◽  
Author(s):  
Gianluca Buffa ◽  
Livan Fratini ◽  
Marion Merklein ◽  
Detlev Staud
Keyword(s):  
Mechanical Properties ◽  
Stress Condition ◽  
Research Effort ◽  
High Strength Steels ◽  
High Strength ◽  
Tensile Tests ◽  
Friction Stir ◽  
Tailored Blanks ◽  
Sheet Stamping ◽  
Wide Range

Tight competition characterizing automotive industries in the last decades has determined a strong research effort aimed to improve utilized processes and materials in sheet stamping. As far as the latter are regarded light weight alloys, high strength steels and tailored blanks have been increasingly utilized with the aim to reduce parts weight and fuel consumptions. In the paper the mechanical properties and formability of tailored welded blanks made of a precipitation hardenable aluminum alloy but with different sheet thicknesses, have been investigated: both laser welding and friction stir welding have been developed to obtain the tailored blanks. For both welding operations a wide range of the thickness ratios has been considered. The formability of the obtained blanks has been characterized through tensile tests and cup deep drawing tests, in order to show the formability in dependency of the stress condition; what is more mechanical and metallurgical investigations have been made on the welded joints.

Frictional Behaviors of a Mild Steel and a TRIP780 Steel Under a Wide Range of Contact Stress and Sliding Speed

2014 ◽  
Vol 136 (2) ◽  
Author(s):  
Chongmin Kim ◽  
Jeong-Uk Lee ◽  
F. Barlat ◽  
Myoung-Gyu Lee
Keyword(s):  
Mild Steel ◽  
Contact Pressure ◽  
High Strength Steels ◽  
Diffraction Method ◽  
High Strength ◽  
Contact Stresses ◽  
Minor Amount ◽  
Sliding Speed ◽  
Normal Contact ◽  
Wide Range

The application of advanced high-strength steels (AHSS) generally makes it necessary to use higher tool-sheet contact pressures compared with those used for forming low-strength steel, and it leads to significant changes in frictional behavior, which in turn change the final product characteristics. In order to understand frictional behaviors between steel sheets and tool materials under high contact stresses present in real stamping conditions, a novel friction tester was conceived, fabricated, and used. This tester can generate high normal loads, as high as 625 MPa, whereas traditional friction testers were limited to 10 MPa or less. A mild steel and a TRIP780 steel were paired with Cr-coated D2 tool steel, and friction behaviors were observed under various conditions, including the use of two lubricants, wide ranges of sliding speeds, and normal contact stresses. The coefficient of friction (COF) decreased at a low contact pressure as the sliding velocity increased. The contact pressure had a significant effect, albeit too complex to be explained by simple models. It was also evident that lubricant effects must be studied coupled with the contact pressure and sliding speed. In a nonlubricated condition at normal stresses roughly half of the steel’s yield strength, the friction event caused plastic deformation that reached up to 0.2 mm from the surface. In this deformed region, the amount of retained austenite in the TRIP steel decreased substantially, and significant residual compressive stress, reaching 350 MPa, also developed in the ferrite phase (plus a minor amount of martensite, which is undistinguishable from ferrite by the X-ray diffraction method used herein). The magnitude of change of friction constant due to changes in contact conditions was enough to significantly affect springback of automotive body panels.

scholarly journals Thermal Diffusivity of Traditional and Innovative Sheet Steels

2010 ◽  
Vol 297-301 ◽  
pp. 893-898
Author(s):  
Elena Campagnoli ◽  
Paolo Matteis ◽  
Giovanni M.M. Mortarino ◽  
Giorgio Scavino
Keyword(s):  
Thermal Diffusivity ◽  
Deep Drawing ◽  
Process Model ◽  
Twip Steel ◽  
Welding Process ◽  
High Strength Steels ◽  
High Strength ◽  
Carbon Steels ◽  
Low Carbon ◽  
Low Carbon Steels

The low carbon steels, used for the production of car bodies by deep drawing, are gradually substituted by high strength steels for vehicle weight reduction. The drawn car body components are joined by welding and the welded points undergo a reduction of the local tensile strength. In developing an accurate welding process model, able to optimized process parameters and to predict the final local microstructure, a significant improvement can be given by the knowledge of the welded steels thermal diffusivity at different temperatures. The laser-flash method has been used to compare the thermal diffusivity of two traditional deep drawing steels, two high strength steels already in common usage, i.e. a Dual Phase (DP) steel and a TRansformation Induced Plasticity (TRIP) steel, and one experimental high-Mn austenitic TWIP (Twinning Induced Plasticity) steel. The low carbon steels, at low temperatures, have a thermal diffusivity that is 4-5 times larger than the TWIP steel. Their thermal diffusivity decreases by increasing temperature while the TWIP steel shows an opposite behaviour, albeit with a lesser slope, so that above 700°C the TWIP thermal diffusivity is larger. The different behaviour of the TWIP steel in respect to the ferritic deep drawing steels arises from its non ferro-magnetic austenitic structure. The DP and TRIP steels show intermediate values, their diffusivity being lower than that of the traditional deep drawing steels; this latter fact probably arises from their higher alloy content and more complex microstructure.

Observations on the Stress Corrosion Crack Propagation Characteristics of High Strength Steels

CORROSION ◽  
1971 ◽  
Vol 27 (11) ◽  
pp. 471-477 ◽  
Author(s):  
C. S. CARTER
Keyword(s):  
Stress Intensity ◽  
Stress Corrosion ◽  
Stress Corrosion Crack ◽  
Crack Velocity ◽  
High Strength Steels ◽  
High Strength ◽  
Testing Procedure ◽  
Crack Morphology ◽  
Wide Range ◽  
The Relationship

Abstract The relationship between stress corrosion crack velocity and crack-tip stress intensity is discussed. In most high strength steels, there is a wide range of stress intensity over which crack velocity is essentially constant. Methods of estimating this velocity are described. Values for a variety of high strength steels are presented and the effects of metallurgical variables are indicated. Implications with regard to testing procedure, crack morphology, and service performance are outlined.

Analytical Prediction of Large Radius Bending by Circular Approximation

2018 ◽  
Vol 140 (12) ◽  
Author(s):  
Vitalii Vorkov ◽  
Richard Aerens ◽  
Dirk Vandepitte ◽  
Joost R. Duflou
Keyword(s):  
High Strength Steels ◽  
High Strength ◽  
High Ratio ◽  
Coefficient Of Determination ◽  
Engineering Practice ◽  
Analytical Prediction ◽  
Large Radius ◽  
Forming Process ◽  
Air Bending ◽  
Wide Range

An accurate analytical method is normally the preferred choice in engineering practice since this approach usually does not require additional software and can be applied for different situations. A number of analytical methods have been proposed for the air bending process, however, none of them has the capacity to deal with large radius bending. Large radius bending is characterized by a high ratio of the punch radius to the die opening and it is often applied for high-strength steels because of their limited bendability. This bending mode is used to fulfill the imposed level of maximum strain during the forming process. This contribution develops an analytical solution based on the assumption that the bent plate profile can be represented by two straight lines and a circular segment. Three different hardening laws—linear, Swift, and Aerens—are used for the bending moment calculation. Unit moment measurements are used in order to avoid extrapolation of hardening curves obtained by tensile testing. The model is compared with a wide range of experiments using the coefficient of determination, relative and absolute average errors, in addition to the mean standard error. The analytical prediction based on the circular approximation is found to be an accurate and robust tool for the calculation of the major bending characteristics for large radius air bending of high-strength steels.

Strain Hardening Behaviour of PM Alloys with Heterogeneous Microstructure

2007 ◽  
Vol 534-536 ◽  
pp. 741-744 ◽  
Author(s):  
Giovanni Straffelini
Keyword(s):  
Plastic Deformation ◽  
Strain Hardening ◽  
Flow Behavior ◽  
High Strength Steels ◽  
High Strength ◽  
Acoustic Resonance ◽  
Matrix Microstructure ◽  
The Matrix ◽  
Heterogeneous Matrix ◽  
Localized Plastic Deformation

Tensile stress-strain and dynamic acoustic resonance tests were performed on Fe-C-Ni- Cu-Mo high-strength steels, characterized by a heterogeneous matrix microstructure and the prevalence of open porosity. All materials display the first yielding phenomenon and, successively, a continuous yielding behavior. This flow behavior can be described by the Ludwigson equation and developes through three stages: the onset of localized plastic deformation at the pore edges; the evolution of plastic deformation at the pore necks (where the austenitic Ni-rich phase is predominant); the spreading of plastic deformation in the interior of the matrix. The analytical modeling of the strain hardening behavior made it possible to obtain the boundaries between the different deformation stages.

Forming Limit Curves and Forming Limit Stress Curves for Advanced High Strength Steels

2013 ◽  
Vol 773-774 ◽  
pp. 109-114 ◽  
Author(s):  
Sansot Panich ◽  
Frédéric Barlat ◽  
Vitoon Uthaisangsuk ◽  
Surasak Suranuntchai ◽  
Suwat Jirathearanat
Keyword(s):  
Yield Criterion ◽  
Flow Behavior ◽  
Constitutive Models ◽  
High Strength Steels ◽  
High Strength ◽  
Forming Limit ◽  
Advanced High Strength Steels ◽  
Hardening Law ◽  
Limit Stress ◽  
Forming Limit Curves

Experimental and numerical investigations using Forming Limit Curve (FLC) and Forming Limit Stress Curve (FLSC) were carried out for two Advanced High Strength Steel (AHSS) grades DP780 and TRIP780. The forming limit curves were experimentally determined by means of Nakazima stretching test. Then, both FLC and FLSC were analytically calculated on the basis of the Marciniack-Kuczinsky (M-K) model. The yield criteria Barlat2000 (Yld2000-2d) were employed in combination with the Swift and modified Voce strain hardening laws to describe plastic flow behavior of the AHS steels. Hereby, influence of the constitutive models on the numerically determined FLCs and FLSCs were examined. Obviously, the forming limit curves predicted by the M-K model applying the Yld2000-2d yield criterion and Swift hardening law could fairly represent the experimental limit curves. The FLSCs resulted from the experimental data and theoretical model were also compared.

Energy Efficient Servo Controlled Roll Levelling Machines

2016 ◽  
Vol 716 ◽  
pp. 413-419
Author(s):  
Eneko Sáenz de Argandoña ◽  
Elena Silvestre ◽  
Daniel Garcia ◽  
Joseba Mendiguren ◽  
Lander Galdos
Keyword(s):  
Energy Consumption ◽  
Residual Stresses ◽  
Sheet Metal ◽  
Energy Efficient ◽  
High Strength Steels ◽  
High Strength ◽  
Important Process ◽  
Process Improvements ◽  
Wide Range ◽  
Ultra High Strength Steels

The roll levelling and coil straightening facilities are becoming one of the most important process steps when forming Ultra High Strength Steels. The correct levelling and straightening of these materials are the main responsible for the stabilization of the residual stresses through the thickness and post forming springback of sheet metal formed components.Due to the arrangement of the rolls in roll levellers, micro-sliding occurs between the rolls and the sheet and the first rolls are subjected to high torques and high forces since they are responsible for the plastification of the material to a high extent. In order to reduce these drawbacks and optimize the energy consumption avoiding energy loses due to friction, the use of servo technology in levelling processes is studied in this paper.A wide range of materials are levelled using the conventional and the new servo controlled strategy that uses two servo motors and the process improvements are quantified.

Experimental Investigations on Development of Rapid Die Wear Tests for Stamping of Advanced High Strength Steels

2007 ◽  
Author(s):  
O¨mer Necati Cora ◽  
Yusuf Usta ◽  
Muammer Koc¸
Keyword(s):  
Low Cost ◽  
High Strength Steels ◽  
Wear Test ◽  
High Strength ◽  
Test Method ◽  
Experimental Investigations ◽  
Lightweight Materials ◽  
Die Wear ◽  
Wide Range ◽  
Aluminum And Magnesium Alloys

In a quest to achieve low-mass vehicles (i.e., higher fuel economy and lower emission), the automotive industry has been actively investigating the use of lightweight materials for a wide range of body panels and structural parts. Among the lightweight materials considered, Advanced and Ultra High Strength Steels (A/UHSS) hold promise as a prominent choice for the near future due to their relatively high formability and low cost compared to Aluminum and Magnesium alloys. However, due to their significantly higher strength than mild steel, in addition to the springback, blanking and joining issues, serious problems with the die wear are expected to arise during manufacturing. Although the die wear literature for the forming of conventional steels is prevalent, tribological issues of high strength steels have not been understood well yet. This study aims to develop a new, rapid and automated wear test for the die materials used in sheet metal forming operations of high strength steels (mainly DP and TRIP steels) and to investigate the wear, friction, and lubrication issues. With this test, the actual stamping conditions such as contact pressure, temperature, and sliding velocity can be represented well. Our preliminary tests on two different extreme contact conditions (soft-soft, hard-hard) indicate that this novel wear test method results in relatively reasonable wear rate estimations/measurements when compared to the results in the literature.

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