Niels Bay - Academia.edu (original) (raw)

Papers by Niels Bay

Research paper thumbnail of Deformation Mechanisms in Tool–Workpiece Asperity Contact in Metal Forming

Forming the Future, 2021

The contribution to friction stemming from dissipation of plastic energy is studied by numerical ... more The contribution to friction stemming from dissipation of plastic energy is studied by numerical simulations and experiments. The geometrical setup consists of a single model asperity, which is first flattened against a tool with grooves on a smaller length scale. Relative, tangential sliding between the model asperity and the tool is induced subsequently until a steady state is reached. The flank angle of the grooves on the tool is varied. Comparison between the simulations and the experiments leads to validation of the simulations at low tool flank angles, while the current numerical implementation cannot handle the complicated flow around the tool grooves with a large flank angle. At low flank angles, the simulated tangential tool force is in agreement with experiments when keeping one determined friction factor. This proves that the change in tangential force, corresponding to a change in apparent friction factor, is only due to the dissipated energy from the plastic waves. The validated numerical model can be used to determine a wider range of apparent friction factors for strain hardening materials.

Research paper thumbnail of Numerical methods in simulation of resistance welding

Finite element simulation of resistance welding requires coupling between mechanical, thermal and... more Finite element simulation of resistance welding requires coupling between mechanical, thermal and electrical models. This paper presents the numerical models and their couplings that are utilized in the computer program SORPAS. A mechanical model based on the irreducible flow formulation is utilized to simulate plastic deformation and the resulting distribution of stress, a thermal model based on transient heat transfer is used to determine the distribution of temperature, and a steady-state electrical model is employed to calculate the distribution of electrical potential and current density. From a resistance welding point of view, the most essential coupling between the above mentioned models is the heat generation by electrical current due to Joule heating. The interaction between multiple objects is another critical feature of the numerical simulation of resistance welding because it influences the contact area and the distribution of contact pressure. The numerical simulation ...

Research paper thumbnail of A study of DLC coatings for ironing of stainless steel

Journal of Physics: Conference Series, 2017

View the article online for updates and enhancements. Related content Evaluation of resistance of... more View the article online for updates and enhancements. Related content Evaluation of resistance of diamond-like carbon coating to the corpuscular radiation in outer space conditions Elizaveta Tomilova, Valeriy Bashkov, Pavel Mikhalev et al.-Optimization and characterization of adhesion properties of DLC coatings on different substrates B Waseem, S Alam, M Irfan et al.

Research paper thumbnail of Acoustic emission monitoring of the bending under tension test

Procedia Engineering, 2017

 Users may download and print one copy of any publication from the public portal for the purpose... more  Users may download and print one copy of any publication from the public portal for the purpose of private study or research.  You may not further distribute the material or use it for any profit-making activity or commercial gain  You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

Research paper thumbnail of Analysis of lubricant performance in punching and blanking

Tribology International, 2019

 Users may download and print one copy of any publication from the public portal for the purpose... more  Users may download and print one copy of any publication from the public portal for the purpose of private study or research.  You may not further distribute the material or use it for any profit-making activity or commercial gain  You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

Research paper thumbnail of Effects of DLC/TiAlN-coated die on friction and wear in sheet-metal forming under dry and oil-lubricated conditions: Experimental and numerical studies

Wear, 2019

 Users may download and print one copy of any publication from the public portal for the purpose... more  Users may download and print one copy of any publication from the public portal for the purpose of private study or research.  You may not further distribute the material or use it for any profit-making activity or commercial gain  You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

Research paper thumbnail of Overview of friction modelling in metal forming processes

Procedia Engineering, 2017

 Users may download and print one copy of any publication from the public portal for the purpose... more  Users may download and print one copy of any publication from the public portal for the purpose of private study or research.  You may not further distribute the material or use it for any profit-making activity or commercial gain  You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

Research paper thumbnail of Review of friction modeling in metal forming processes

Journal of Materials Processing Technology, 2018

 Users may download and print one copy of any publication from the public portal for the purpose... more  Users may download and print one copy of any publication from the public portal for the purpose of private study or research.  You may not further distribute the material or use it for any profit-making activity or commercial gain  You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

Research paper thumbnail of Three-dimensional simulations of resistance spot welding

Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, 2014

This paper draws from the fundamentals of electro-thermo-mechanical coupling to the main aspects ... more This paper draws from the fundamentals of electro-thermo-mechanical coupling to the main aspects of finite element implementation and three-dimensional modelling of resistance welding. A new simulation environment is proposed in order to perform three-dimensional simulations and optimization of resistance welding together with the simulations of conventional and special-purpose quasi-static mechanical tests. Three-dimensional simulations of resistance welding consider the electrical, thermal, mechanical and metallurgical characteristics of the material as well as the operating conditions of the welding machines. Simulations of the mechanical tests take into account material softening due to the accumulation of ductile damage and cover conventional tests, such as tensile–shear tests, cross-tension test and peel tests, as well as the possibility of special-purpose tests designed by the users. The overall presentation is supported by numerical simulations of electrode misalignment caus...

Research paper thumbnail of Revisiting liquid lubrication methods by means of a fully coupled approach combining plastic deformation and liquid lubrication

Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, 2017

This paper presents a new approach based on a fully coupled procedure in which the lubricant flow... more This paper presents a new approach based on a fully coupled procedure in which the lubricant flow and the plastic deformation of the metallic material in metal forming are solved simultaneously. The proposed method is an alternative to conventional modelling techniques which allow studying the effect of a broad range of parameters directly on the friction conditions. The approach is applied to strip reduction of a sheet with mesoscopic surface pockets in order to investigate the escape of lubricant from the pocket by means of Micro Plasto HydroDynamic Lubrication and Micro Plasto HydroStatic Lubrication. For the investigation on Micro Plasto HydroStatic Lubrication, the friction along the tool–workpiece contact interface and the back tension are taken as parameters, and the backward escape Micro Plasto HydroDynamic Lubrication is investigated by variations in lubricant viscosity by means of a combined numerical and analytical model, and by variations in drawing speed. Good agreement...

Research paper thumbnail of Modelling of real area of contact between tool and workpiece in metal forming processes including the influence of subsurface deformation

CIRP Annals, 2016

New equipment for testing asperity deformation at various normal loads and subsurface elongations... more New equipment for testing asperity deformation at various normal loads and subsurface elongations is presented. Resulting real contact area ratios increase heavily with increasing subsurface expansion due to lowered yield pressure on the asperities when imposing subsurface normal stress parallel to the surface. Finite element modelling supports the presentation and contributes by extrapolation of results to complete the mapping of contact area as function of normal pressure and one-directional subsurface strain parallel to the surface. Improved modelling of the real contact area is the basis for estimating friction in the numerical modelling of metal forming processes.

Research paper thumbnail of The Influence of Tool Texture on Friction and Lubrication in Strip Reduction Testing

While texturing of workpiece surfaces to promote lubrication in metal forming has been applied fo... more While texturing of workpiece surfaces to promote lubrication in metal forming has been applied for several decades tool surface texturing is rather new. In the present paper tool texturing is studied as a method to prevent galling. Adopting a strip reduction test longitudinal pocket geometries oriented perpendicular to the sliding direction, with shallow pocket depth, small pocket angle to the workpiece surface and varying distance between pockets are investigated. The experiments reveal that the distance between pockets should be larger than the pocket width thereby creating a topography similar to flat table mountains to avoid mechanical interlocking in the valleys; otherwise an increase in drawing load and pick-up on the tools is observed. The textured tool surface lowers friction and improves lubrication performance provided that the distance between pockets is 2-4 times larger than the pocket width. Larger drawing speed facilitates escape of the entrapped lubricant in the pocke...

Research paper thumbnail of New tribo-systems for sheet metal forming of advanced high strength steels and stainless steels

 Users may download and print one copy of any publication from the public portal for the purpose... more  Users may download and print one copy of any publication from the public portal for the purpose of private study or research.  You may not further distribute the material or use it for any profit-making activity or commercial gain  You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

Research paper thumbnail of Modelling of Damage During Hot Forging of Ingots

 Users may download and print one copy of any publication from the public portal for the purpose... more  Users may download and print one copy of any publication from the public portal for the purpose of private study or research.  You may not further distribute the material or use it for any profit-making activity or commercial gain  You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

Research paper thumbnail of 3D Modeling and Testing of Contact Problems in Resistance Welding

MPa The last two drawbacks apply if the dynamic explicit formulations are used in the ''high-spee... more MPa The last two drawbacks apply if the dynamic explicit formulations are used in the ''high-speed-mode''.

Research paper thumbnail of Strategies and limits in multi-stage single-point incremental forming

The Journal of Strain Analysis for Engineering Design, 2009

Multi-stage single-point incremental forming (SPIF) is a state-of-the-art manufacturing process t... more Multi-stage single-point incremental forming (SPIF) is a state-of-the-art manufacturing process that allows small-quantity production of complex sheet metal parts with vertical walls. This paper is focused on the application of multi-stage SPIF with the objective of producing cylindrical cups with vertical walls. The strategy consists of forming a conical cup with a taper angle in the first stage, followed by three subsequent stages that progressively move the conical shape towards the desired cylindrical geometry. The investigation includes material characterization, determination of forming-limit curves and fracture forming-limit curves (FFLCs), numerical simulation, and experimentation, namely the evaluation of strain paths and fracture strains in actual multi-stage parts. Assessment of numerical simulation with experimentation shows good agreement between computed and measured strain and strain paths. The results also reveal that the sequence of multi-stage forming has a large e...

Research paper thumbnail of Analysis of fluid lubrication mechanisms in metal forming at mesoscopic scale

CIRP Annals, 2012

 Users may download and print one copy of any publication from the public portal for the purpose... more  Users may download and print one copy of any publication from the public portal for the purpose of private study or research.  You may not further distribute the material or use it for any profit-making activity or commercial gain  You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

Research paper thumbnail of Testing and Prediction of Limits of Lubrication in Sheet Metal Forming

 Users may download and print one copy of any publication from the public portal for the purpose... more  Users may download and print one copy of any publication from the public portal for the purpose of private study or research.  You may not further distribute the material or use it for any profit-making activity or commercial gain  You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

Research paper thumbnail of Backward can extrusion with conical, rotating punch as a cold forging tribology test

A new, simulative test of friction and lubrication in cold forging is developed by the authors. T... more A new, simulative test of friction and lubrication in cold forging is developed by the authors. The test is based on a backward can extrusion process in which the workpiece rotates. An analytical model is presented determining the friction stress from the measured torque during testing combined with an analysis of the sliding velocity distribution along the punch nose. The latter is determined by FE analysis of the test. Results show friction stress for unalloyed low C-steel provided with different types of lubricants, e.g. phosphate coating plus soap, phosphate coating plus MoS 2 and single bathe lubrication with PULS. The new test is so severe, that it is possible to break down the best lubrication systems for cold forging, such as phosphate coating plus soap and MoS 2 .

Research paper thumbnail of Influence of surface texture on the galling characteristics of lean duplex and austenitic stainless steels

Two simulative test methods were used to study galling in sheet forming of two types of stainless... more Two simulative test methods were used to study galling in sheet forming of two types of stainless steel sheet: austenitic (EN 1.4301) and lean duplex LDX 2101 (EN 1.4162) in different surface conditions. The pin-on-disc test was used to analyse the galling resistance of different combinations of sheet materials and lubricants. The strip reduction test, a severe sheet forming tribology test was used to simulate the conditions during ironing. This investigation shows that the risk of galling is highly dependent on the surface texture of the duplex steel. Trials were also performed in an industrial tool used for high volume production of pump components, to compare forming of LDX 2101 and austenitic stainless steel with equal thickness. The forming forces, the geometry and the strains in the sheet material were compared for the same component. It was found that LDX steels can be formed to high strain levels in tools normally applied for forming of austenitic steels, but tool adaptations are needed to comply with the higher strength and springback of the material.

Research paper thumbnail of Deformation Mechanisms in Tool–Workpiece Asperity Contact in Metal Forming

Forming the Future, 2021

The contribution to friction stemming from dissipation of plastic energy is studied by numerical ... more The contribution to friction stemming from dissipation of plastic energy is studied by numerical simulations and experiments. The geometrical setup consists of a single model asperity, which is first flattened against a tool with grooves on a smaller length scale. Relative, tangential sliding between the model asperity and the tool is induced subsequently until a steady state is reached. The flank angle of the grooves on the tool is varied. Comparison between the simulations and the experiments leads to validation of the simulations at low tool flank angles, while the current numerical implementation cannot handle the complicated flow around the tool grooves with a large flank angle. At low flank angles, the simulated tangential tool force is in agreement with experiments when keeping one determined friction factor. This proves that the change in tangential force, corresponding to a change in apparent friction factor, is only due to the dissipated energy from the plastic waves. The validated numerical model can be used to determine a wider range of apparent friction factors for strain hardening materials.

Research paper thumbnail of Numerical methods in simulation of resistance welding

Finite element simulation of resistance welding requires coupling between mechanical, thermal and... more Finite element simulation of resistance welding requires coupling between mechanical, thermal and electrical models. This paper presents the numerical models and their couplings that are utilized in the computer program SORPAS. A mechanical model based on the irreducible flow formulation is utilized to simulate plastic deformation and the resulting distribution of stress, a thermal model based on transient heat transfer is used to determine the distribution of temperature, and a steady-state electrical model is employed to calculate the distribution of electrical potential and current density. From a resistance welding point of view, the most essential coupling between the above mentioned models is the heat generation by electrical current due to Joule heating. The interaction between multiple objects is another critical feature of the numerical simulation of resistance welding because it influences the contact area and the distribution of contact pressure. The numerical simulation ...

Research paper thumbnail of A study of DLC coatings for ironing of stainless steel

Journal of Physics: Conference Series, 2017

View the article online for updates and enhancements. Related content Evaluation of resistance of... more View the article online for updates and enhancements. Related content Evaluation of resistance of diamond-like carbon coating to the corpuscular radiation in outer space conditions Elizaveta Tomilova, Valeriy Bashkov, Pavel Mikhalev et al.-Optimization and characterization of adhesion properties of DLC coatings on different substrates B Waseem, S Alam, M Irfan et al.

Research paper thumbnail of Acoustic emission monitoring of the bending under tension test

Procedia Engineering, 2017

 Users may download and print one copy of any publication from the public portal for the purpose... more  Users may download and print one copy of any publication from the public portal for the purpose of private study or research.  You may not further distribute the material or use it for any profit-making activity or commercial gain  You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

Research paper thumbnail of Analysis of lubricant performance in punching and blanking

Tribology International, 2019

 Users may download and print one copy of any publication from the public portal for the purpose... more  Users may download and print one copy of any publication from the public portal for the purpose of private study or research.  You may not further distribute the material or use it for any profit-making activity or commercial gain  You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

Research paper thumbnail of Effects of DLC/TiAlN-coated die on friction and wear in sheet-metal forming under dry and oil-lubricated conditions: Experimental and numerical studies

Wear, 2019

 Users may download and print one copy of any publication from the public portal for the purpose... more  Users may download and print one copy of any publication from the public portal for the purpose of private study or research.  You may not further distribute the material or use it for any profit-making activity or commercial gain  You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

Research paper thumbnail of Overview of friction modelling in metal forming processes

Procedia Engineering, 2017

 Users may download and print one copy of any publication from the public portal for the purpose... more  Users may download and print one copy of any publication from the public portal for the purpose of private study or research.  You may not further distribute the material or use it for any profit-making activity or commercial gain  You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

Research paper thumbnail of Review of friction modeling in metal forming processes

Journal of Materials Processing Technology, 2018

 Users may download and print one copy of any publication from the public portal for the purpose... more  Users may download and print one copy of any publication from the public portal for the purpose of private study or research.  You may not further distribute the material or use it for any profit-making activity or commercial gain  You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

Research paper thumbnail of Three-dimensional simulations of resistance spot welding

Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, 2014

This paper draws from the fundamentals of electro-thermo-mechanical coupling to the main aspects ... more This paper draws from the fundamentals of electro-thermo-mechanical coupling to the main aspects of finite element implementation and three-dimensional modelling of resistance welding. A new simulation environment is proposed in order to perform three-dimensional simulations and optimization of resistance welding together with the simulations of conventional and special-purpose quasi-static mechanical tests. Three-dimensional simulations of resistance welding consider the electrical, thermal, mechanical and metallurgical characteristics of the material as well as the operating conditions of the welding machines. Simulations of the mechanical tests take into account material softening due to the accumulation of ductile damage and cover conventional tests, such as tensile–shear tests, cross-tension test and peel tests, as well as the possibility of special-purpose tests designed by the users. The overall presentation is supported by numerical simulations of electrode misalignment caus...

Research paper thumbnail of Revisiting liquid lubrication methods by means of a fully coupled approach combining plastic deformation and liquid lubrication

Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, 2017

This paper presents a new approach based on a fully coupled procedure in which the lubricant flow... more This paper presents a new approach based on a fully coupled procedure in which the lubricant flow and the plastic deformation of the metallic material in metal forming are solved simultaneously. The proposed method is an alternative to conventional modelling techniques which allow studying the effect of a broad range of parameters directly on the friction conditions. The approach is applied to strip reduction of a sheet with mesoscopic surface pockets in order to investigate the escape of lubricant from the pocket by means of Micro Plasto HydroDynamic Lubrication and Micro Plasto HydroStatic Lubrication. For the investigation on Micro Plasto HydroStatic Lubrication, the friction along the tool–workpiece contact interface and the back tension are taken as parameters, and the backward escape Micro Plasto HydroDynamic Lubrication is investigated by variations in lubricant viscosity by means of a combined numerical and analytical model, and by variations in drawing speed. Good agreement...

Research paper thumbnail of Modelling of real area of contact between tool and workpiece in metal forming processes including the influence of subsurface deformation

CIRP Annals, 2016

New equipment for testing asperity deformation at various normal loads and subsurface elongations... more New equipment for testing asperity deformation at various normal loads and subsurface elongations is presented. Resulting real contact area ratios increase heavily with increasing subsurface expansion due to lowered yield pressure on the asperities when imposing subsurface normal stress parallel to the surface. Finite element modelling supports the presentation and contributes by extrapolation of results to complete the mapping of contact area as function of normal pressure and one-directional subsurface strain parallel to the surface. Improved modelling of the real contact area is the basis for estimating friction in the numerical modelling of metal forming processes.

Research paper thumbnail of The Influence of Tool Texture on Friction and Lubrication in Strip Reduction Testing

While texturing of workpiece surfaces to promote lubrication in metal forming has been applied fo... more While texturing of workpiece surfaces to promote lubrication in metal forming has been applied for several decades tool surface texturing is rather new. In the present paper tool texturing is studied as a method to prevent galling. Adopting a strip reduction test longitudinal pocket geometries oriented perpendicular to the sliding direction, with shallow pocket depth, small pocket angle to the workpiece surface and varying distance between pockets are investigated. The experiments reveal that the distance between pockets should be larger than the pocket width thereby creating a topography similar to flat table mountains to avoid mechanical interlocking in the valleys; otherwise an increase in drawing load and pick-up on the tools is observed. The textured tool surface lowers friction and improves lubrication performance provided that the distance between pockets is 2-4 times larger than the pocket width. Larger drawing speed facilitates escape of the entrapped lubricant in the pocke...

Research paper thumbnail of New tribo-systems for sheet metal forming of advanced high strength steels and stainless steels

 Users may download and print one copy of any publication from the public portal for the purpose... more  Users may download and print one copy of any publication from the public portal for the purpose of private study or research.  You may not further distribute the material or use it for any profit-making activity or commercial gain  You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

Research paper thumbnail of Modelling of Damage During Hot Forging of Ingots

 Users may download and print one copy of any publication from the public portal for the purpose... more  Users may download and print one copy of any publication from the public portal for the purpose of private study or research.  You may not further distribute the material or use it for any profit-making activity or commercial gain  You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

Research paper thumbnail of 3D Modeling and Testing of Contact Problems in Resistance Welding

MPa The last two drawbacks apply if the dynamic explicit formulations are used in the ''high-spee... more MPa The last two drawbacks apply if the dynamic explicit formulations are used in the ''high-speed-mode''.

Research paper thumbnail of Strategies and limits in multi-stage single-point incremental forming

The Journal of Strain Analysis for Engineering Design, 2009

Multi-stage single-point incremental forming (SPIF) is a state-of-the-art manufacturing process t... more Multi-stage single-point incremental forming (SPIF) is a state-of-the-art manufacturing process that allows small-quantity production of complex sheet metal parts with vertical walls. This paper is focused on the application of multi-stage SPIF with the objective of producing cylindrical cups with vertical walls. The strategy consists of forming a conical cup with a taper angle in the first stage, followed by three subsequent stages that progressively move the conical shape towards the desired cylindrical geometry. The investigation includes material characterization, determination of forming-limit curves and fracture forming-limit curves (FFLCs), numerical simulation, and experimentation, namely the evaluation of strain paths and fracture strains in actual multi-stage parts. Assessment of numerical simulation with experimentation shows good agreement between computed and measured strain and strain paths. The results also reveal that the sequence of multi-stage forming has a large e...

Research paper thumbnail of Analysis of fluid lubrication mechanisms in metal forming at mesoscopic scale

CIRP Annals, 2012

 Users may download and print one copy of any publication from the public portal for the purpose... more  Users may download and print one copy of any publication from the public portal for the purpose of private study or research.  You may not further distribute the material or use it for any profit-making activity or commercial gain  You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

Research paper thumbnail of Testing and Prediction of Limits of Lubrication in Sheet Metal Forming

 Users may download and print one copy of any publication from the public portal for the purpose... more  Users may download and print one copy of any publication from the public portal for the purpose of private study or research.  You may not further distribute the material or use it for any profit-making activity or commercial gain  You may freely distribute the URL identifying the publication in the public portal If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.

Research paper thumbnail of Backward can extrusion with conical, rotating punch as a cold forging tribology test

A new, simulative test of friction and lubrication in cold forging is developed by the authors. T... more A new, simulative test of friction and lubrication in cold forging is developed by the authors. The test is based on a backward can extrusion process in which the workpiece rotates. An analytical model is presented determining the friction stress from the measured torque during testing combined with an analysis of the sliding velocity distribution along the punch nose. The latter is determined by FE analysis of the test. Results show friction stress for unalloyed low C-steel provided with different types of lubricants, e.g. phosphate coating plus soap, phosphate coating plus MoS 2 and single bathe lubrication with PULS. The new test is so severe, that it is possible to break down the best lubrication systems for cold forging, such as phosphate coating plus soap and MoS 2 .

Research paper thumbnail of Influence of surface texture on the galling characteristics of lean duplex and austenitic stainless steels

Two simulative test methods were used to study galling in sheet forming of two types of stainless... more Two simulative test methods were used to study galling in sheet forming of two types of stainless steel sheet: austenitic (EN 1.4301) and lean duplex LDX 2101 (EN 1.4162) in different surface conditions. The pin-on-disc test was used to analyse the galling resistance of different combinations of sheet materials and lubricants. The strip reduction test, a severe sheet forming tribology test was used to simulate the conditions during ironing. This investigation shows that the risk of galling is highly dependent on the surface texture of the duplex steel. Trials were also performed in an industrial tool used for high volume production of pump components, to compare forming of LDX 2101 and austenitic stainless steel with equal thickness. The forming forces, the geometry and the strains in the sheet material were compared for the same component. It was found that LDX steels can be formed to high strain levels in tools normally applied for forming of austenitic steels, but tool adaptations are needed to comply with the higher strength and springback of the material.