Trockenumformung strukturierter Halbzeuge aus 16MnCr5 und 42CrMo4*/Dry forming of surface structured workpiece made of 16MnCr5 and 42CrMo4 - Determination of friction shear stress by means of a pin-on-cCylinder Tribometer

2016 ◽  
Vol 106 (10) ◽  
pp. 712-718
Author(s):  
R. Hild ◽  
D. Trauth ◽  
P. Mattfeld ◽  
S. Bastürk ◽  
T. Brögelmann ◽  
...  
Keyword(s):  
Shear Stress ◽  
Metal Forming ◽  
Shear Stresses ◽  
Bulk Metal ◽  
Bulk Metal Forming ◽  
Dry Forming ◽  
Tool Coatings ◽  
Green Factory

Der Einsatz von Schmierstoffen gestattet bisher die Umformung von Massivbauteilen. In der „Green Factory“ wird auf die Verwendung dieser Schmierstoffe verzichtet. Daraus resultieren unbekannte Anforderungen an das trockene Tribosystem. Selbstschmierende Werkzeugbeschichtung und strukturierte Halbzeuge ermöglichen das trockene Tribosystem und reduzieren die Reibschubspannung. Der Fachbeitrag zeigt die Auswirkungen von Oberflächenstrukturen auf Halbzeugen auf die Reibschubspannung.   Solid and liquid lubricants enable bulk metal forming processes. In the “Green Factory”, the application of lubricants is to be avoided. The absence of lubricants results in unknown demands on a dry tribosystem. Possible enablers of the dry tribosystem are self-lubricating tool coatings and structured workpieces that lower the friction shear stresses. This contribution shows how the workpiece structuring influences the friction shear stress.

scholarly journals Experimental Tooling for Contact Stress Measurement in Bulk Metal Forming Processes

2011 ◽  
Vol 36 (1) ◽  
pp. 9-16
Author(s):  
Dragiša Vilotić ◽  
Miroslav Plančak
Keyword(s):  
Experimental Determination ◽  
Contact Stress ◽  
Metal Forming ◽  
Stress Measurement ◽  
Contact Stresses ◽  
Axial Position ◽  
Bulk Metal ◽  
Bulk Metal Forming ◽  
Load Cells

Experimental Tooling for Contact Stress Measurement in Bulk Metal Forming Processes Knowledge of contact stresses in metal forming operations is essential not only for optimal die design, but also for theoretical and numerical analysis of the metal forming processes. Determination of contact stresses can be performed theoretically and experimentally. This paper presents a tool construction with built-in pin-load cells for experimental determination of contact stresses and friction coefficient at upsetting of prismatic specimen with cylindrical dies. This construction allows measurement of contact stresses in any point of the contact surface of specimen, due to adjustable location of pin-load cells. The adjustments are performed by turning cylindrical dies around its own axis in combination with the change of axial position of the specimen. Experimental determination of contact stresses in upsetting of Ck35 prismatic specimens using cylindrical tools was performed at the Laboratory for technology of plasticity, FTN Novi Sad.

A new test for determining the mechanical and fracture behavior of materials in sheet-bulk metal forming

2015 ◽  
Vol 231 (8) ◽  
pp. 693-703 ◽  
Author(s):  
CMA Silva ◽  
MB Silva ◽  
LM Alves ◽  
PAF Martins
Keyword(s):  
Fracture Toughness ◽  
Metal Forming ◽  
Three Dimensional ◽  
Strain Curve ◽  
Shear Zones ◽  
Shear Stresses ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Bulk Metal ◽  
Bulk Metal Forming

This paper presents a new experimental test for determining the stress–strain curve and the fracture toughness of sheets to be used in sheet-bulk metal forming (SBMF) applications. The test is based on the utilization of double-notched specimens loaded in shear and combines the plane stress loading conditions of sheet metal forming with the three-dimensional plastic flow conditions of bulk metal forming, which are commonly found in SBMF processes. The methodology to obtain the stress–strain curve involves calculation of the shear stresses and strains along the two symmetric plastic shear zones of the test specimens up to point where cracks start to propagate along the ligaments that connect each pair of opposite notches. The determination of fracture toughness involves characterization of the evolution of load with displacement for a number of test cases performed with specimens having different ligaments between the two symmetric opposite notches. The work is performed on aluminium alloy EN AW 5754 H111 sheets with 5 mm thickness and the results obtained by means of the new proposed test are compared against those from conventional mechanical and fracture characterization tests.

scholarly journals Development of a numerical compensation framework for geometrical deviations in bulk metal forming exploiting a surrogate model and computed compatible stresses

2021 ◽  
Author(s):  
Lorenzo Scandola ◽  
Christoph Büdenbender ◽  
Michael Till ◽  
Daniel Maier ◽  
Michael Ott ◽  
...  
Keyword(s):  
Finite Element ◽  
Surrogate Model ◽  
Metal Forming ◽  
Computer Aided Design ◽  
Transition Process ◽  
Reference Points ◽  
Compensation Method ◽  
Tool Geometry ◽  
Bulk Metal ◽  
Bulk Metal Forming

AbstractThe optimal design of the tools in bulk metal forming is a crucial task in the early design phase and greatly affects the final accuracy of the parts. The process of tool geometry assessment is resource- and time-consuming, as it consists of experience-based procedures. In this paper, a compensation method is developed with the aim to reduce geometrical deviations in hot forged parts. In order to simplify the transition process between the discrete finite-element (FE) mesh and the computer-aided-design (CAD) geometry, a strategy featuring an equivalent surrogate model is proposed. The deviations are evaluated on a reduced set of reference points on the nominal geometry and transferred to the FE nodes. The compensation approach represents a modification of the displacement-compatible spring-forward method (DC-SF), which consists of two elastic FE analyses. The compatible stress originating the deviations is estimated and subsequently applied to the original nominal geometry. After stress relaxation, an updated nominal geometry of the part is obtained, whose surfaces represent the compensated tools. The compensation method is verified by means of finite element simulations and the robustness of the algorithm is demonstrated with an additional test geometry. Finally, the compensation strategy is validated experimentally.

Fundamental investigations on the material flow at combined sheet and bulk metal forming processes

CIRP Annals ◽  
2011 ◽  
Vol 60 (1) ◽  
pp. 283-286 ◽  
Author(s):  
M. Merklein ◽  
J. Koch ◽  
S. Opel ◽  
T. Schneider
Keyword(s):  
Metal Forming ◽  
Material Flow ◽  
Bulk Metal ◽  
Bulk Metal Forming

Amorphous Carbon Coatings for Locally Adjusted Tribological Properties in Sheet Bulk Metal Forming

2012 ◽  
Vol 504-506 ◽  
pp. 969-974 ◽  
Author(s):  
Harald Hetzner ◽  
Stephan Tremmel ◽  
Sandro Wartzack
Keyword(s):  
Amorphous Carbon ◽  
Tribological Properties ◽  
Metal Forming ◽  
Friction And Wear ◽  
Wear Properties ◽  
Carbon Coatings ◽  
Bulk Metal ◽  
Bulk Metal Forming ◽  
Friction And Wear Properties ◽  
Amorphous Carbon Coatings

In sheet bulk metal forming, locally adapted friction properties of the contact tool/workpiece are an appropriate means for the targeted enhancement of the material flow, enabling an improved form filling and lowered forming forces. However, the implementation of desirable friction conditions is not trivial. And further, friction is inseparably linked to wear and damage of the contacting surfaces. This calls for a methodological approach in order to consider tribology as a whole already in the early phases of process layout, so that tribological measures which allow fulfilling the requirements concerning local friction and wear properties of the tool surfaces, can already be selected during the conceptual design of the forming tools. Thin tribological coatings are an effective way of improving the friction and wear properties of functional surfaces. Metal-modified amorphous carbon coatings, which are still rather new to the field of metal forming, allow tackling friction and wear simultaneously. Unlike many other types of amorphous carbon, they have the mechanical toughness to be used in sheet bulk metal forming, and at the same time their friction properties can be varied over wide ranges by proper choice of the deposition parameters. Based on concrete research results, the mechanical, structural and special tribological properties of tungsten-modified hydrogenated amorphous carbon coatings (a-C:H:W) are presented and discussed against the background of the tribological requirements of a typical sheet bulk metal forming process.

scholarly journals Development of a Constitutive Model for Friction in Bulk Metal Forming

Lubricants ◽  
2018 ◽  
Vol 6 (2) ◽  
pp. 42 ◽  
Author(s):  
Marco Lüchinger ◽  
Igor Velkavrh ◽  
Kerstin Kern ◽  
Michael Baumgartner ◽  
Stefan Klien ◽  
...  
Keyword(s):  
Constitutive Model ◽  
Metal Forming ◽  
Bulk Metal ◽  
Bulk Metal Forming
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