FG Fügetechnik

27 Items

Recent Submissions
Influence of oscillating magnetic field on the keyhole stability in deep penetration laser beam welding

Üstündağ, Ömer ; Bakir, Nasim ; Gumenyuk, Andrey ; Rethmeier, Michael (2020-11-10)

The stability of the keyhole decreases for deep penetrated high-power laser beam welding. The keyhole tends to collapse with increasing laser power and e.g. keyhole induced porosity can occur. This study deals with the observation of the keyhole during high-power laser beam welding in partial penetration mode by means of a high-speed camera. A butt configuration of 25 mm thick structural steel ...

Finite element analysis of in-situ distortion and bulging for an arbitrarily curved additive manufacturing directed energy deposition geometry

Biegler, Max ; Marko, Angelina ; Graf, Benjamin ; Rethmeier, Michael (2018-10-05)

With the recent rise in the demand for additive manufacturing (AM), the need for reliable simulation tools to support experimental efforts grows steadily. Computational welding mechanics approaches can simulate the AM processes but are generally not validated for AM-specific effects originating from multiple heating and cooling cycles. To increase confidence in the outcomes and to use numerical...

Investigation of liquid metal embrittlement of dual phase steel joints by electro-thermomechanical spot-welding simulation

Frei, Julian ; Biegler, Max ; Rethmeier, Michael ; Böhne, Christoph ; Meschut, Gerson (2019-02-22)

A 3D electro-thermomechanical model is established in order to investigate liquid metal embrittlement. After calibration to a dual phase steel of the 1000 MPa tensile strength class, it is used to analyse the thermo-mechanical system of an experimental procedure to enforce liquid metal embrittlement during resistance spot welding. In this procedure, a tensile stress level is applied to zinc coa...

Sensitivity analysis of the residual stress state in friction stir welding of high strength aluminum alloy

Bachmann, Marcel ; Rethmeier, Michael ; Wu, Chuan Song (2016-01)

In this paper, the friction stir welding process was numerically investigated for 6 mm thick aluminum alloy AA2024-T3. The finite element software COMSOL Multiphysics was used to calculate the transient thermal field during welding and the mechanical reaction depending on different mechanical clamping conditions and hardening models subsequently. A thermal pseudo-mechanical (TPM) heat source wa...

Numerical assessment and experimental verification of the influence of the Hartmann effect in laser beam welding processes by steady magnetic fields

Bachmann, Marcel ; Avilov, Vjaceslav ; Gumenyuk, Andrey ; Rethmeier, Michael (2015-11-18)

Controlling the dynamics in the weld pool is a highly demanding challenge in deep-penetration laser beam welding with modern high power laser systems in the multi kilowatt range. An approach to insert braking forces in the melt which is successfully used in large-scaled industrial applications like casting is the so-called Hartmann effect due to externally applied magnetic fields. Therefore, th...

Experimental and numerical assessment of weld pool behavior and final microstructure in wire feed laser beam welding with electromagnetic stirring

Meng, Xiangmeng ; Bachmann, Marcel ; Artinov, Antoni ; Rethmeier, Michael (2019-07-25)

Advantages such as element homogenization and grain refinement can be realized by introducing electromagnetic stirring into laser beam welding. However, the involved weld pool behavior and its direct role on determining the final microstructure have not been revealed quantitatively. In this paper, a 3D transient heat transfer and fluid flow model coupled with element transport and magnetic indu...

Assessment of thermal cycles by combining thermo-fluid dynamics and heat conduction in keyhole mode welding processes

Artinov, Antoni ; Karkhin, Victor ; Khomich, Pavel ; Bachmann, Marcel ; Rethmeier, Michael (2019-07-07)

A numerical framework for simulation of the steady-state thermal behaviour in keyhole mode welding has been developed. It is based on the equivalent heat source concept and consists of two parts: computational thermo-fluid dynamics and heat conduction. The solution of the thermo-fluid dynamics problem by the finite element method for a bounded domain results in a weld pool interface geometry be...

Numerical and experimental investigation of thermo-fluid flow and element transport in electromagnetic stirring enhanced wire feed laser beam welding

Meng, Xiangmeng ; Artinov, Antoni ; Bachmann, Marcel ; Rethmeier, Michael (2019-09-06)

The introduction of electromagnetic stirring to laser beam welding can bring several beneficial effects e.g. element homogenization and grain refinement. However, the underlying physics has not been fully explored due to the absence of quantitative data of heat and mass transfer in the molten pool. In this paper, the influence of electromagnetic stirring on the thermo-fluid flow and element tra...

Avoidance of liquid metal embrittlement during resistance spot welding by heat input dependent hold time adaption

Böhne, Christoph ; Meschut, Gerson ; Biegler, Max ; Rethmeier, Michael (2020-07-20)

Liquid metal embrittlement (LME) cracking can occur during resistance spot welding (RSW) in zinc-coated advanced high-strength steels (AHSS) for automotive production. In this study, a methodological variation of hold time is performed to investigate the process-related crack influence factors. A combination of numerical and experimental investigations confirms, that the extent of heat dissipat...

Lamé curve approximation for the assessment of the 3D temperature distribution in keyhole mode welding processes

Artinov, Antoni ; Karkhin, Victor ; Bakir, Nasim ; Meng, Xiangmeng ; Bachmann, Marcel ; Gumenyuk, Andrey ; Rethmeier, Michael (2020-05-04)

A novel approach for the reconstruction of an equivalent volumetric heat source from a known weld pool shape is proposed. It is based on previously obtained weld pool geometries from a steady-state thermo-fluid dynamics simulation. Hereby, the weld pool dimensions are obtained under consideration of the most crucial physical phenomena, such as phase transformations, thermo-capillary convection,...

Theoretical study of influence of electromagnetic stirring on transport phenomena in wire feed laser beam welding

Meng, Xiangmeng ; Artinov, Antoni ; Bachmann, Marcel ; Rethmeier, Michael (2020-04-29)

The additional element from the filler wire in the laser beam welding is usually distributed inhomogeneously in the final weld due to the high solidification rate of weld pool. It has been found that the electromagnetic stirring produced by an external oscillating magnetic field can enhance the material mixing in the weld pool to achieve a more uniform element distribution. However, the magneti...

Mathematical modeling of the geometrical differences between the weld end crater and the steady-state weld pool

Artinov, Antoni ; Karkhin, Victor ; Bachmann, Marcel ; Rethmeier, Michael (2020-04-28)

The geometrical characteristics of the weld end crater are commonly used as a means of validating numerical results in welding simulations. In this paper, an analytical model is developed for calculating the cooling stage of the welding process after the moving energy source is turned off. Solutions for various combinations of heat sources and heated bodies are found. It is shown that after tur...

Influence of welding parameters on electromagnetic supported degassing of die-casted and wrought aluminum

Fritzsche, André ; Hilgenberg, Kai ; Rethmeier, Michael (2020-04-29)

Laser beam welding of aluminum die casting is challenging. A large quantity of gases (in particular, hydrogen) is absorbed by aluminum during the die-cast manufacturing process and is contained in the base material in solved or bound form. After remelting by the laser, the gases are released and are present in the melt as pores. Many of these metallurgic pores remain in the weld seam as a resul...

Full penetration laser beam welding of thick duplex steel plates with electromagnetic weld pool support

Avilov, Vjaceslav ; Fritzsche, André ; Bachmann, Marcel ; Gumenyuk, Andrey ; Rethmeier, Michael (2016-03-31)

Full penetration high power bead-on-plate laser beam welding tests of up to 20 mm thick 2205 duplex steel plates were performed in PA position. A contactless inductive electromagnetic (EM) weld pool support system was used to prevent gravity drop-out of the melt. Welding experiments with 15 mm thick plates were carried out using IPG fiber laser YLR 20000 and Yb:YAG thin disk laser TruDisk 16002...

Finite element modeling of an alternating current electromagnetic weld pool support in full penetration laser beam welding of thick duplex stainless steel plates

Bachmann, Marcel ; Kunze, Richard ; Avilov, Vjaceslav ; Rethmeier, Michael (2016-03-31)

An electromagnetic weld pool support system for 20 mm thick duplex stainless steel AISI 2205 was investigated numerically and compared to experiments. In our former publications, it was shown how an alternating current (AC) magnetic field below the process zone directed perpendicular to the welding direction can induce vertically directed Lorentz forces. These can counteract the gravitational f...

Increasing Performance and Energy Efficiency of Gas Metal Arc Welding by a High Power Tandem Process

Sproesser, Gunther ; Pittner, Andreas ; Rethmeier, Michael (2016-02-19)

Standard Gas Metal Arc Welding (Standard GMAW) and a high power Tandem GMAW (TGMAW) process are evaluated with respect to energy efficiency. Current, voltage and overall equipment power are measured and energy consumption is determined. The new key performance indicator Electrical Deposition Efficiency is introduced to reflect the energy efficiency of GMAW processes. Additionally, wall-plug eff...

Sustainable Welding Process Selection Based on Weight Space Partitions

Sproesser, Gunther ; Schenker, Sebastian ; Pittner, Andreas ; Borndörfer, Ralf ; Rethmeier, Michael ; Chang, Ya-Ju ; Finkbeiner, Matthias (2016-02-19)

Selecting a welding process for a given application is crucial with respect to the sustainability of part manufacturing. Unfortunately, since welding processes are evaluated by a number of criteria, preferences for one or the other process can be contradictory. However, the prevalent procedure of weight assignment for each criterion is subjective and does not provide information about the entir...

Laser Metal Deposition as Repair Technology for a Gas Turbine Burner Made of Inconel 718

Petrat, Torsten ; Graf, Benjamin ; Gumenyuk, Andrey ; Rethmeier, Michael (2016-09-19)

Maintenance, repair and overhaul of components are of increasing interest for parts of high complexity and expensive manufacturing costs. In this paper a production process for laser metal deposition is presented, and used to repair a gas turbine burner of Inconel 718. Different parameters for defined track geometries were determined to attain a near net shape deposition with consistent build-u...

Experimental and numerical study on the influence of the laser hybrid parameters in partial penetration welding on the solidification cracking in the weld root

Bakir, Nasim ; Üstündağ, Ömer ; Gumenyuk, Andrey ; Rethmeier, Michael (2020-01-27)

The aim of the present study is to investigate the influence of the laser hybrid welding parameters on the solidification cracks in the weld root for partial penetration welding. Welding trials were performed on thick-walled high-strength steels of grade S690QL under the same critical restraint intensity, with a variation of the welding velocity, wire feeding rate, and the focal position of the...

Automated Tool‐Path Generation for Rapid Manufacturing of Additive Manufacturing Directed Energy Deposition Geometries

Biegler, Max ; Wang, Jiahan ; Kaiser, Lukas ; Rethmeier, Michael (2020-05-08)

In additive manufacturing (AM) directed energy deposition (DED), parts are built by welding layers of powder or wire feedstock onto a substrate with applications for steel powders in the fields of forging tools, spare parts, and structural components for various industries. For large and bulky parts, the choice of tool‐paths influences the build rate, the mechanical performance, and the distort...