Numerical Fatigue Strength Evaluation of Inhomogeneous, Linear Flow Split Profiles

2008 ◽  
Author(s):  
Volker Landersheim ◽  
Chalid el Dsoki ◽  
Holger Hanselka ◽  
Thomas Bruder ◽  
Desislava Veleva ◽  
...  
Keyword(s):  
Residual Stresses ◽  
Plastic Material ◽  
Material Behavior ◽  
Fatigue Properties ◽  
Forming Process ◽  
Linear Flow ◽  
Local Material ◽  
Durability Analysis ◽  
Flow Splitting ◽  
Local Material Properties

The innovative sheet metal forming technology “Linear Flow Splitting” offers various new options for designing profile-like components. The forming process leads to severe changes in local material properties, inhomogeneities and residual stresses within the manufactured component. These effects influence the mechanical properties of the manufactured components. If the components are designed to endure cyclic mechanical loads, it is especially important to know the components fatigue properties. This paper focuses on a method to derive the fatigue properties of Linear Flow Split Profiles by nonlinear numerical FE analysis, including durability analysis and forming simulations. This numerical approach offers the possibility to estimate the fatigue properties of components before manufacturing physical prototypes, only based on material parameters derived from tests on smooth samples. The Finite-Element analysis of the Linear Flow Splitting Process provides distributions of local material deformation and residual stresses. These results are mapped by an appropriate interface on FE models, which allow simulating the component behavior under external loads. Thus, the inhomogeneous elastic-plastic material behavior and residual stresses are considered in the computed stresses and strains. Further on, a post-processing tool was implemented to interpret the FE results considering the inhomogeneous distribution of materials fatigue properties, the mean stress distribution and the statistical size effect.

Ontology-Based Approach to Transform Fatigue Properties of Branched Sheet Metal Products for Use in Algorithm-Based Product Development

2008 ◽  
Author(s):  
Nils Hirsch ◽  
Herbert Birkhofer ◽  
Volker Landersheim ◽  
Holger Hanselka ◽  
Ute Gu¨nther ◽  
...  
Keyword(s):  
Material Properties ◽  
Mathematical Optimization ◽  
Fatigue Properties ◽  
Continuous Manufacturing ◽  
Linear Flow ◽  
Simplified Approach ◽  
Local Material ◽  
Flow Splitting ◽  
Fatigue Evaluation ◽  
Local Material Properties

In order to shorten the design process of a multi-chambered profile, it is important to integrate the Technological Findings of the production and the evaluation of the manufactured product in a structured and systematic way, providing mathematical optimization. The development of profiles exposed to cyclic mechanical loading has to take into consideration their fatigue properties. This paper proposes a classification structure of the existing Technological Findings of Linear Flow Splitting and the continuous manufacturing line. The classification is realized by an ontology, modeling the manufacturing processes, machines, the geometry of the semi-finished product, sub-processes, engaged machine components and specific conditions for the employed material. A profile manufactured by linear flow splitting is subject to severe changes of local material properties. This affects the fatigue properties of the profile. The paper focuses on preparing the integration of these fatigue properties in a simplified approach into the mathematical optimization. The approach is developed by modeling examples of profiles with different material properties by methods of mathematical optimization. The examples are applied to a numerical fatigue evaluation. Results and conclusions drawn of this analysis are incorporated in the ontology as data and rules, serving as an input for the optimization.

Evaluation of Local Material Flow during Complex Deformation Conditions on the Basis of Multi Scale Analysis

2016 ◽  
Vol 682 ◽  
pp. 350-355
Author(s):  
Joanna Szyndler ◽  
Lukasz Madej
Keyword(s):  
Material Flow ◽  
Incremental Forming ◽  
Material Behavior ◽  
Scale Analysis ◽  
Forming Process ◽  
Complex Deformation ◽  
Multi Scale ◽  
Local Material ◽  
Scale Levels ◽  
Digital Material

Development of the multiscale numerical model of innovative incremental forming process, dedicated for manufacturing complex components for the aerospace industry is the main aim of the work. Description of the incremental forming concept based on division of large die into a series of small anvils subsequently pressed into the material is presented within the paper. Particular attention is put on material behavior at both, macro and micro scale levels, respectively. A Finite Element Method (FEM) supported by Digital Material Representation (DMR) concept was used during the investigation. Results in the form of strain distributions and shapes of grains obtained from different sample areas after incremental forming process are presented within the paper.

scholarly journals Properties of UFG HSLA Steel Profiles Produced by Linear Flow Splitting

2008 ◽  
Vol 584-586 ◽  
pp. 661-666 ◽  
Author(s):  
Enrico Bruder ◽  
Tilman Bohn ◽  
Clemens Müller
Keyword(s):  
Mechanical Properties ◽  
Hsla Steel ◽  
Recrystallization Temperature ◽  
Forming Process ◽  
Cold Forming ◽  
Linear Flow ◽  
Metal Structures ◽  
Local Strength ◽  
Flow Splitting ◽  
Processing Zone

Linear flow splitting is a new cold forming process for the production of branched sheet metal structures. It induces severe plastic strain in the processing zone which results in the formation of an UFG microstructure and an increase in hardness and strength in the flanges. Inbuilt deformation gradients in the processing zone lead to steep gradients in the microstructure and mechanical properties. In the present paper the gradients in the UFG microstructure and the mechanical properties of a HSLA steel (ZStE 500) processed by linear flow splitting are presented, as well as a calculation of local strength from hardness measurements on the basis of the Ludwikequation. In order to investigate the thermal stability of the UFG microstructure heat treatments below the recrystallization temperature were chosen. The coarsening process and the development of the low angle to high angle grain boundary ratio in the gradient UFG microstructure were monitored by EBSD measurements. It is shown that heat treatment can lead to a grain refinement due to a strong fragmentation of elongated grains while only little coarsening in the transverse direction occurs. A smoothing of the gradients in the UFG microstructure as well as in the mechanical properties is observed.

Taguchi Grey Relational Approach for Optimizing Process Parameters of Laser Peening on Titanium Alloy to Induce Enhanced Compressive Stress based on Finite Element Simulation

2020 ◽  
Vol 19 (02) ◽  
pp. 365-387
Author(s):  
G. Ranjith Kumar ◽  
G. Rajyalakshmi
Keyword(s):  
Finite Element ◽  
Residual Stresses ◽  
Compressive Stress ◽  
Process Parameters ◽  
Surface Deformation ◽  
Material Behavior ◽  
Laser Spot ◽  
Fatigue Properties ◽  
Fe Model ◽  
Grey Relational

Laser Shock Peening (LSP) turned out to be the most efficient surface engineering process for advanced materials to induce beneficial deep compressive residual stress which helps in improving mechanical, fatigue properties and surface damage resistance. But, analyzing the nonuniform distribution of residual stresses in the treated sample with X-ray diffraction (XRD) is much time taking and a costly process. This problem can be resolved with LSP finite element numerical simulation model which is feasible with the realistic experimental process. The FE model allows the user to control the laser parameters in order to achieve the optimal level of all controllable parameters. This study is intended to analyze and optimize the influence of laser processing parameters that assists in inducing the residual compressive stress with minimal surface deformation. A Ti6Al4V material model with Johnson–Cook’s visco-elastic–plastic material behavior law is prepared for LSP simulation. Gaussian pressure profile is utilized for uniform loading of the targeted zone for the proposed model. Taguchi Grey Relational Analysis (TGRA) with L27 orthogonal array is applied to LSP simulation, and the results were analyzed with consideration of multiple response measures. It is noted that surface deformation is increased with the rise in a number of laser shots and pressure pulse duration. Maximum compressive residual stresses are falling for higher levels of laser spot diameter, laser spot overlap and laser power density. The correlation is observed between the FE simulation and the published results. The optimal set of process parameters are obtained for improving the LSP on Ti alloys.

Texture Based Finite Element Simulation of a Two-Step Can Forming Process

2012 ◽  
Vol 504-506 ◽  
pp. 655-660 ◽  
Author(s):  
Vedran Glavas ◽  
Thomas Böhlke ◽  
Dominique Daniel ◽  
Christian Leppin
Keyword(s):  
Finite Element ◽  
Finite Element Simulation ◽  
Plastic Material ◽  
Large Strain ◽  
Material Model ◽  
Material Behavior ◽  
Flow Rule ◽  
Forming Process ◽  
Aluminum Sheets ◽  
Element Simulation

Aluminum sheets used for beverage cans show a significant anisotropic plastic material behavior in sheet metal forming operations. In a deep drawing process of cups this anisotropy leads to a non-uniform height, i.e., an earing profile. The prediction of this earing profiles is important for the optimization of the forming process. In most cases the earing behavior cannot be predicted precisely based on phenomenological material models. In the presented work a micromechanical, texture-based model is used to simulate the first two steps (cupping and redrawing) of a can forming process. The predictions of the earing profile after each step are compared to experimental data. The mechanical modeling is done with a large strain elastic visco-plastic crystal plasticity material model with Norton type flow rule for each crystal. The response of the polycrystal is approximated by a Taylor type homogenization scheme. The simulations are carried out in the framework of the finite element method. The shape of the earing profile from the finite element simulation is compared to experimental profiles.

Analysis of Residual Stresses in the Transition Zone of Tube-to-Tubesheet Joints

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Abdel-Hakim Bouzid ◽  
Mohammad Pourreza
Keyword(s):  
Residual Stresses ◽  
Transition Zone ◽  
Analytical Model ◽  
Plastic Material ◽  
Plastic Region ◽  
Material Behavior ◽  
Maximum Expansion ◽  
Perfectly Plastic ◽  
Major Interest ◽  
Comparison Of The Results

The rigorous stress analysis of tube-to-tubesheet joints requires a particular attention to the transition zone of the expanded tube because of its impact on joint integrity. This zone is the weakest part of the joint due to the presence of high tensile residual stresses produced during the expansion process, which coupled to in-service loadings and harsh corrosive fluids results in joint failure. In fact, it is often subjected to stress corrosion cracking caused by intergranular attack leading to plant shutdown. Therefore, the evaluation of the residual stresses in this zone is of major interest during the design phase and its accurate assessment is necessary to achieve a reliable joint in service. In this study, an analytical model to evaluate the residual axial and hoop stresses in the transition zone of hydraulically expanded tubes based on an elastic perfectly plastic material behavior has been developed. The model is capable of predicting the stress state when maximum expansion pressure is applied and after its release. Three main regions are identified in the transition zone: the fully plastic region, the partially plastic region, and the elastic region. Therefore, various theories have been applied to analyze the stresses and deformations neglecting the elastoplastic region because of simplicity. The validation of analytical model is conducted by comparison of the results with those of 3D finite element models of two typical joints of different geometries and mechanical properties. The effect strain hardening and reverse yielding of the expansion zone are also investigated.

scholarly journals Investigations into Manufacturing Composite Profiles Having Local Magnesium-Foam Reinforcements

2010 ◽  
Vol 137 ◽  
pp. 129-160 ◽  
Author(s):  
Tillmann Plorin ◽  
Dirk Bormann ◽  
Torsten Heidenblut ◽  
Friedrich Wilhelm Bach
Keyword(s):  
High Strength ◽  
Mechanical Tests ◽  
Absorption Capacity ◽  
Roll Forming ◽  
Metallic Foams ◽  
Forming Process ◽  
Research Results ◽  
Foaming Process ◽  
Local Material ◽  
Local Material Properties

Owing to their mechanical properties, metallic foams possess the outstanding ability to considerably improve a structure's stiffness and energy absorption capacity with low increases in weight. In the research results from the sub project A4 "Foam filled, rolled, closed profiles” of the CRC 675 "Creation of high strength metallic structures and joints by setting up scaled local material properties" introduced here, both the manufacture as well as the reinforcement of magnesium foams, which are produced by means of powder metallurgy, are described. The potential for increasing their strengths using reinforcements are demonstrated and the results of mechanical tests are presented. In addition to this, research results are presented which have contributed to achieving the main objectives of developing a combined technology for producing profiles which are locally reinforced using magnesium foam. The developed technology is characterised by integrating the foaming process into the roll forming process.

scholarly journals Development of a Standard for New Passenger Car Wheel Designs

2006 ◽  
Author(s):  
Brandon Talamini ◽  
Benjamin Perlman ◽  
Jeff Gordon
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Residual Stresses ◽  
Public Transportation ◽  
Fatigue Cracking ◽  
Material Behavior ◽  
Fatigue Properties ◽  
Element Analysis ◽  
Design Standard ◽  
In Transit

The American Public Transportation Association (APTA) is seeking to develop specifications to ensure that wheels used in transit and commuter applications perform safely under the service conditions to which they are exposed. To this end, a design standard has been conceived to ensure that new wheel designs proposed for such applications are not susceptible to fatigue cracking in the wheel plate and hub. Historically, the Association of American Railroads (AAR) Standard S-660 has been applied in the industry for the purposes of qualifying wheel designs for use in passenger applications. The standard stipulates particular loads to apply in a simple finite element analysis of the new wheel design. The basis for approval is an empirical comparison (by an independent third party) of the results with those in a database of previous analysis results of other qualified wheels. The proposed "S-660 equivalent" design standard is envisioned to be self-qualifying, in that results of the analysis will directly determine whether the wheel design will perform safely in service; a review or approval body will not be required. The new standard is needed to overcome limitations embodied in the current wheel qualification process, namely, the assumption of purely elastic material behavior, the omission of residual stresses due to manufacturing, and the use of comparative approval criteria. The Union Internationale des Chemins de Fer (UIC) introduced a wheel design requirement based on finite element analysis, the results of which are subjected to a fatigue criterion in order to achieve acceptance of the wheel design. As in the current S-660 methodology, a set of thermal and mechanical loads are prescribed. This methodology is essentially self-qualifying as the results of the analysis (obtained following a prescribed procedure) determine whether the wheel design will perform safely in service. The proposed design standard is envisioned to be a combination of the current S-660 analysis requirements and the fatigue calculation-based approach of the UIC. The task force developing the standard is still resolving the specific details of the thermal and mechanical loading requirements. This paper explores the underlying methodology behind the developing standard. A finite element calculation forms the basis of the qualification procedure. Initial (asmanufactured) residual stresses present in a new wheel are determined. Mechanical and thermal loading representative of passenger operations are applied. The analysis yields three characteristic stress distributions: as-manufactured, mechanical, and thermal. The Sines criterion, with temperature-dependent material fatigue properties obtained from testing, is applied to infer whether the candidate wheel design is fatigue-prone. Results are presented for a wheel design currently in transit/commuter service. The APTA committee is currently investigating the thermal and mechanical load levels to be prescribed in the proposed standard.

scholarly journals Directing the Material Flow and Form Filling through a Multi-axis Forming Process

2021 ◽  
Author(s):  
Birk Wonnenberg ◽  
Felix Gabriel ◽  
Klaus Dröder
Keyword(s):  
Material Properties ◽  
Material Flow ◽  
Motion Path ◽  
Work Piece ◽  
Forming Process ◽  
Local Material ◽  
Standard Linear ◽  
Tool Motion ◽  
Six Degree Of Freedom ◽  
Local Material Properties

Multi-axis forming is a six degree of freedom forming process. This process influences actively the material flow by defining a six dimensional tool motion path and the corresponding tool velocity. Within this process, it is possible to combine a linear forming movement followed by a rolling movement and therefore tailor the induced local material properties of the work piece. The research objective of this work is to observe and quantify the interaction between tool motion and material flow for the purpose of process planning. Experiments are conducted to examine the horizontal material flow within a multi-axis forming process of a plane L-shaped work piece. Three different punches form the material: Flat, cylindrical and cone-shaped. The horizontal material flow is recorded through a transparent die by a camera to measure the material flow for different tool motions. It is shown, that a multi-axis forming process can adjust the local material flow. The resulting redirection of the material flow after the sharp inward facing edge of the L-shape is analyzed and compared. With a smaller active zone compared to a standard linear pressing, the multi-axis forming forces are reduced. In addition, the reservoir with the remaining material is more concentrated. Finally, it is possible to direct the material flow with the punch motion, which can be used to determine local part properties.

scholarly journals Formation of residual stresses in austenitic stainless steels by infeed and recess rotary swaging

2020 ◽  
Author(s):  
Holger Hoche ◽  
Fabian Jaeger ◽  
Alessandro Franceschi ◽  
Matthias Oechsner ◽  
Peter Groche
Keyword(s):  
Residual Stresses ◽  
Stainless Steels ◽  
Austenitic Stainless Steels ◽  
Phase Changes ◽  
Austenitic Steels ◽  
Coarse Grained ◽  
Fatigue Properties ◽  
Forming Process ◽  
Cold Forming ◽  
Rotary Swaging

The austenitic stainless steels 1.4307 and 1.4404 significantly benefit from cold forming, due to their high work hardening capability. Great potential to improve the component's fatigue properties is expected by optimizing the forming process chain such that specific residual stresses are induced in critical component areas. In this work, an analysis of the formation of residual stresses during rotary swaging is carried out. Through this incremental forming process, high strain hardening and a complex material flow history are induced in the workpieces. Therefore, measuring strategies for the residual stress measurement of cold de-formed austenitic steels by X-Ray diffraction, using the sin2Ψ-method, were developed. Here, especially the 1.4307 is a challenging material due to cold forming induced martensite formation. Despite phase changes, both cold formed materials exhibit anisotropic microstructures as well as coarse grained areas. Moreover, particular notched geometries are produced on the workpieces by rotary swaging. The measuring techniques are further developed for these complex geometries and the residual stresses are investigated.

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