Influence of Processing Route on the Work-Hardening and Ductile Fracture of an AA6060 Aluminium Alloy

2014 ◽  
Vol 794-796 ◽  
pp. 284-289 ◽  
Author(s):  
Odd Sture Hopperstad ◽  
Ida Westermann ◽  
Ketill Olav Pedersen ◽  
Trond Furu ◽  
Tore Børvik
Keyword(s):  
Ductile Fracture ◽  
Aluminium Alloy ◽  
Work Hardening ◽  
Large Strain ◽  
Tensile Tests ◽  
Grain Structure ◽  
Processing Route ◽  
Stress Strain ◽  
Minimum Cross Section ◽  
Processing Step

Tensile tests on smooth and notched axisymmetric specimens were carried out to determine the large strain work-hardening curves and the ductile fracture characteristics of an AA6060 aluminium alloy for three different processing routes. The alloy was processed in three subsequent steps: 1) casting and homogenization, 2) extrusion, and 3) cold rolling and heat treatment to obtain a recrystallized grain structure. After each processing step, the material was tested after natural ageing for more than one week. A laser-based extensometer was used to continuously measure the average true strains to failure in the minimum cross-section of the specimens and the true stress-strain curves were calculated. Since these curves are influenced by necking, they do not represent the correct work-hardening of the material. Accordingly, finite element (FE) simulations of the tensile tests on the smooth axisymmetric specimens were conducted to determine the work-hardening curves to failure, using an optimization tool that interfaced with the nonlinear FE code and the experimental stress-strain curves as objectives. The microstructure of the alloy was characterized after the three processing steps by optical and scanning electron microscopy, and fractography was used to investigate the failure mechanisms.

scholarly journals On the Grain Microstructure–Mechanical Properties Relationships in Aluminium Alloy Parts Fabricated by Laser Powder Bed Fusion

Metals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1175
Author(s):  
Pavel A. Somov ◽  
Eugene S. Statnik ◽  
Yuliya V. Malakhova ◽  
Kirill V. Nyaza ◽  
Alexey I. Salimon ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Yield Strength ◽  
Aluminium Alloy ◽  
Young’S Modulus ◽  
Mechanical Performance ◽  
Young's Modulus ◽  
Grain Morphology ◽  
Tensile Tests ◽  
Grain Structure ◽  
Surface Finishing

Recent years witnessed progressive broadening of the practical use of 3D-printed aluminium alloy parts, in particular for specific aerospace applications where weight saving is of great importance. Selective laser melting (SLM) is an intrinsically multi-parametric fabrication technology that offers multiple means of controlling mechanical properties (elastic moduli, yield strength, and ductility) through the control over grains size, shape, and orientation. Targeted control over mechanical properties is achieved through the tuning of 3D-printing parameters and may even obviate the need of heat treatment or mechanical post-processing. Systematic studies of grain structure for different printing orientations with the help of EBSD techniques in combination with mechanical testing at different dimensional levels are the necessary first steps to implement this agenda. Samples of 3D-printable Al-Mg-Si RS-333 alloy were fabricated in three orientations with respect to the principal build direction and the fast laser beam scanning direction. Sample structure and proper-ties were investigated using a number of techniques, including EBSD, in situ SEM tensile testing, roughness measurements, and nanoindentation. The as-printed samples were found to display strong variation in Young’s modulus values from nanoindentation (from 43 to 66 GPa) and tensile tests (from 54 to 75 GPa), yield stress and ultimate tensile strength (100–195 and 130–220 MPa) in different printing orientations, and almost constant hardness of about 0.8 GPa. A further preliminary study was conducted to assess the effect of surface finishing on the mechanical performance. Surface polishing was seen to reduce Young’s modulus and yield strength but improves ductility, whereas the influence of sandblasting was found to be more controversial. The experimental results are discussed in connection with the grain morphology and orientation.

Ductile Fracture Property of Structural Steels With a Surface Flaw Under Large Deformation

2002 ◽  
Author(s):  
Satoshi Igi ◽  
Hiroyuki Sumi ◽  
Masayoshi Kurihara
Keyword(s):  
Ductile Fracture ◽  
Large Deformation ◽  
Deformation Behavior ◽  
Shape Change ◽  
Three Dimensional ◽  
Tensile Tests ◽  
Surface Flaw ◽  
Stress Strain ◽  
Crack Shape ◽  
Critical Flaw

Tensile tests using plate specimens with a surface flaw were conducted in order to study the large deformation behavior of steels with a flaw. Steels prepared for examination had tensile strengths of 470–490MPa with different stress-strain relationships. The strain distribution during loading and the maximum strain at fracture were measured in order to investigate the influence of stress-strain properties on ductile fracture. The crack shape changes during ductile crack growth were also examined and compared with empirical formulae for estimating fatigue crack shape change. In order to assess test results, three dimensional elastoplastic finite element analyses were carried out which included detailed analysis of the influence of stress-strain properties on deformation behavior. In addition, a simplified analytical model to estimate fracture strain and critical flaw size was proposed using the stress-strain relationship of Swift’s equation. The results from the model show fairly good agreement with experimental results.

scholarly journals Experimental Analysis and Behaviour Modelling of the Deformation Mechanisms of a Ti-6242S Alloy under Hot and Superplastic Forming Conditions

Metals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1599
Author(s):  
Longqiu Song ◽  
Anzu Ii ◽  
Laurie Despax ◽  
Hatsumi Onishi ◽  
Hiroaki Matsumoto ◽  
...  
Keyword(s):  
Strain Rate ◽  
Strain Hardening ◽  
Grain Growth ◽  
Superplastic Forming ◽  
Tensile Tests ◽  
Thin Layers ◽  
Grain Structure ◽  
Stress Strain ◽  
Fine Grained ◽  
Β Phase

In this work, the hot deformation characteristics of a near-α Ti-Al-2SnZr-2Mo alloy (Ti6242 alloy) with a Fine-Grained (FG) microstructure (dα = 2.86 μm) were investigated at two levels of temperature, T = 730 ∘C and T = 840 ∘C. The initial microstructure consists of equiaxed nodules of the α phase as well as some α lamellae sparsely distributed and separated by thin layers of the BCC β phase. For both temperatures, three strain rates (10−4,10−3,10−2s−1) were analysed during loading. Moreover, the microstructural evolution (α size and morphology) was also evaluated by conducting interrupted tensile tests. The different tensile testing conditions greatly influence the stress-strain response of the material as well as the microstructure evolution. Indeed, various phenomena can take place such as elongation of the grain structure, globularization, dynamic recrystallization and grain growth of the equiaxed areas depending on the temperature, the strain rate and the strain level. The FG Ti6242 alloy exhibits interesting superplastic ductility at T = 840 ∘C. At this temperature either a very gradual flow softening (at higher strain rate) or flow hardening (at lower strain rate) can be observed and are related respectively to one or more of the following mechanisms: lamellae globularization, DRX and grain growth. At the intermediate strain rate, both mechanisms, strain hardening and softening, coexist. At T = 730 ∘C, the onset of the α lamellae globularization was only promoted at low strain rate. A mechanical behavior model was developed in the temperature range of 730–840 ∘C, which was able to take into account all the observed phenomena: viscosity, softened behavior and strain hardening. Constitutive equations were calibrated from the stress-strain responses and microstructural observations, and the computed results were in good agreement with the experiments.

Ductile Fracture Evaluation of Welded Joints With a Surface Flaw Under Large Deformation

2005 ◽  
Author(s):  
Satoshi Igi ◽  
Takahiro Kubo ◽  
Masayoshi Kurihara
Keyword(s):  
Ductile Fracture ◽  
Large Deformation ◽  
Analytical Model ◽  
Welded Joint ◽  
Three Dimensional ◽  
Base Material ◽  
Tensile Tests ◽  
Surface Flaw ◽  
Stress Strain ◽  
Joint Specimen

Tensile tests using welded joint specimens with a surface flaw were conducted in order to study the large deformation behavior and ductile fracture of welded structural component with a flaw. Two types of 490MPa class steel plates with different yield strength are prepared for this study. The surface flaw was introduced at the center of welded metal of welded joint specimen. Strain distribution during loading and the maximum strain at ductile fracture of specimen were measured in order to investigate the influence of stress-strain properties on ductile fracture behavior of the welded joint. Three dimensional elastoplastic finite element analyses were also carried out by using the welded joint specimen models in order to calculate the detailed stress and strain distributions around notch tip. In addition, a simplified analytical model to estimate fracture strain and critical flaw size of the welded joint was proposed using the stress-strain relationship combination between base material and welded metal by Swift’s equation. The results from the analytical model show fairly good agreement with experimental results.

scholarly journals Consequences of large strain anisotropic work-hardening in cold forging

2021 ◽  
Author(s):  
Felix Kolpak ◽  
Oliver Hering ◽  
A. Erman Tekkaya
Keyword(s):  
Work Hardening ◽  
Strain Path ◽  
Large Strain ◽  
Constitutive Models ◽  
Numerical Data ◽  
Tensile Tests ◽  
Cold Forging ◽  
Cold Forming ◽  
Process Forces ◽  
Multi Stage

AbstractThe influence of anisotropic work-hardening on the component properties and process forces in cold forging is investigated. The focus is on the material behaviour exhibited after strain path reversals. The work-hardening of three steels is characterized for large monotonic strains (equivalent strains up to 1.7) and subsequent strain path reversals (accumulated strains up to 2.5). Tensile tests on specimens extracted from rods forward extruded at room temperature reveal an almost linear work-hardening for all investigated steels. The application of compressive tests on extruded material gives insights into the non-monotonic work-hardening behaviour. All previously reported anisotropic work-hardening phenomena such as the Bauschinger effect, work-hardening stagnation and permanent softening are present for all investigated steels and intensify with the pre-strain. Experimental results of 16MnCrS5 were utilized to select constitutive models of increasing complexity regarding their capability to capture anisotropic work-hardening. The best fit between experimental and numerical data was obtained by implementation of a modified Yoshida-Uemori model, which is able to capture all observed anisotropic work-hardening phenomena. The constitutive models were applied in simulations of single- and multi-stage cold forming processes, revealing the significant effect of anisotropic hardening on the predicted component properties and process forces, originating in the process-intrinsic strain path reversals as well as in strain path reversals between subsequent forming stages. Selected results were validated experimentally.

Hysteresis loss of ultra-large off-the-road tire rubber compounds based on operating conditions at mine sites

2021 ◽  
pp. 095440702110155
Author(s):  
Shaosen Ma ◽  
Guangping Huang ◽  
Khaled Obaia ◽  
Soon Won Moon ◽  
Wei Victor Liu
Keyword(s):  
Large Strain ◽  
Tensile Tests ◽  
Operating Conditions ◽  
Hysteresis Loss ◽  
Strain Rates ◽  
Test Results ◽  
Tire Rubber ◽  
The Road ◽  
Rubber Compounds ◽  
Mine Sites

The objective of this study is to investigate the hysteresis loss of ultra-large off-the-road (OTR) tire rubber compounds based on typical operating conditions at mine sites. Cyclic tensile tests were conducted on tread and sidewall compounds at six strain levels ranging from 10% to 100%, eight strain rates from 10% to 500% s−1 and 14 rubber temperatures from −30°C to 100°C. The test results showed that a large strain level (e.g. 100%) increased the hysteresis loss of tire rubber compounds considerably. Hysteresis loss of tire rubber compounds increased with a rise of strain rates, and the increasing rates became greater at large strain levels (e.g. 100%). Moreover, a rise of rubber temperatures caused a decrease in hysteresis loss; however, the decrease became less significant when the rubber temperatures were above 10°C. Compared with tread compounds, sidewall compounds showed greater hysteresis loss values and more rapid increases in hysteresis loss with the rising strain rate.

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