scholarly journals Influence of Mechanical Anisotropy on Micro-Voids and Ductile Fracture Onset and Evolution in High-Strength Low Alloyed Steels

Metals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 224 ◽  
Author(s):  
Francesco Iob ◽  
Luca Cortese ◽  
Andrea Di Schino ◽  
Tommaso Coppola
Keyword(s):  
Large Diameter ◽  
High Strength ◽  
Tensile Tests ◽  
Mechanical Anisotropy ◽  
Anisotropic Behavior ◽  
Notched Specimens ◽  
Void Distribution ◽  
Void Evolution ◽  
Spiral Line ◽  
Stress States

In this paper results of a wide and innovative mechanical assessment, that was performedon large diameter spiral line pipes for gas transportation, are reported. The anisotropic materialhardening has been characterized by tensile (smooth and notched specimens), torsion, andcompression tests. Tests were performed in the pipe of the pipe with specimens machined alongseveral orientations, taking into account the pipe through thickness direction. The influence ofdifferent triaxiality stress states on anisotropic behavior of the material have also been analyzed bymeans of tensile tests on notched specimens. After the experiments, the material was assessed bymeasuring the void distribution on the material as is, and on many deformed and fracturedspecimens, including tensile tests at different triaxiality, and torsion tests. The results showed that insuch a class of materials, the experimental void fraction is fully negligible and not related to theapplied plastic strain, even at the fracture proximity. As a consequence it can be concluded that, theplastic softening hypothesis may be dropped and damage due to void evolution hypothesis is notadequate.

scholarly journals Numerical-Experimental Plastic-Damage Characterisation of Additively Manufactured 18Ni300 Maraging Steel by Means of Multiaxial Double-Notched Specimens

2021 ◽  
Vol 5 (3) ◽  
pp. 84
Author(s):  
Tiago Silva ◽  
Afonso Gregório ◽  
Filipe Silva ◽  
José Xavier ◽  
Ana Reis ◽  
...  
Keyword(s):  
Maraging Steel ◽  
High Stress ◽  
Stress Triaxiality ◽  
High Strength ◽  
Viable Option ◽  
Notched Specimens ◽  
Stress States ◽  
Data Gap ◽  
Structural Parts ◽  
High Degree

Additive manufacturing (AM) has become a viable option for producing structural parts with a high degree of geometrical complexity. Despite such trend, accurate material properties, under diversified testing conditions, are scarce or practically non-existent for the most recent additively manufactured (AMed) materials. Such data gap may compromise component performance design, through numerical simulation, especially enhanced by topological optimisation of AMed components. This study aimed at a comprehensive characterisation of laser powder bed fusion as-built 18Ni300 maraging steel and its systematic comparison to the conventional counterpart. Multiaxial double-notched specimens demonstrated a successful depiction of both plastic and damage behaviour under different stress states. Tensile specimens with distinct notch configurations were also used for high stress triaxiality range characterisation. This study demonstrates that the multiaxial double-notched specimens constitute a viable option towards the inverse plastic behaviour calibration of high-strength additively manufactured steels in distinct state of stress conditions. AMed maraging steel exhibited higher strength and lower ductility than the conventional material.

scholarly journals Characterization of High-Strength Packaging Steels: Obtaining Material Data for Precise Finite Element Process Modelling

Metals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1683
Author(s):  
Fabian Knieps ◽  
Benjamin Liebscher ◽  
Ioana Moldovan ◽  
Manuel Köhl ◽  
Johannes Lohmar
Keyword(s):  
Finite Element ◽  
Flow Curve ◽  
Material Selection ◽  
Biaxial Tension ◽  
Selection Process ◽  
High Strength ◽  
Tensile Tests ◽  
Bulge Test ◽  
Hardening Law ◽  
Stress States

The steadily increasing demand for downgauging to reduce costs in packaging steel applications requires the development of high-strength packaging steel grades to meet strength requirements. At the same time, the demand for a simulative, computer-aided layout of industrial forming processes is growing to reduce costs in tool constructions for downgauging manners. As part of this work, different high-strength packaging steels were characterized for use in a finite element based process layout and validated using application-oriented experiments. Due to a low hardening rate and the occurrence of Lüders bands, high-strength packaging steels show a low amount of elongation in tensile tests, while for other stress states higher degrees of deformation are possible. Thus, common extrapolation methods fail to reproduce the flow curve of high-strength packaging steels. Therefore, a new approach to extrapolate the flow curve of high-strength packaging steels is presented using the tensile test and bulge test data together with a combined Swift–Voce hardening law. Furthermore, it is shown that the use of complex anisotropic yield locus models such as Yld2000-2d is necessary for high-strength packaging steels in order to be able to precisely simulate application-oriented loads in between plane strain and biaxial tension in validation experiments. Finally, the benefit of a material selection process for packaging steel applications guided by finite element simulations based on precisely characterized material behaviour is demonstrated.

Towards a Numerical Design Tool for Composite Crack Arrestors on High Pressure Gas Pipelines

2010 ◽  
Author(s):  
F. Van den Abeele ◽  
L. Amlung ◽  
M. Di Biagio ◽  
S. Zimmermann
Keyword(s):  
High Pressure ◽  
Large Scale ◽  
Steel Wire ◽  
Large Diameter ◽  
High Strength ◽  
Tensile Tests ◽  
Design Tool ◽  
Pipe Material ◽  
Gas Pipelines ◽  
Numerical Design

One of the major challenges in the design of ultra high grade (X100) high pressure gas pipelines is the identification of a reliable crack propagation strategy. Ductile fracture propagation is an event that involves the whole pipeline and all its components, including valves, fittings, flanges and bends. Recent research results have shown that the newly developed high strength large diameter gas pipelines, when operated at severe conditions (rich gas, low temperatures, high pressure), may not be able to arrest a running ductile crack through pipe material properties. Hence, the use of crack arrestors is required in the design of safe and reliable pipeline systems. A conventional crack arrestor can be a high toughness pipe insert, or a local joint with higher wall thickness. Steel wire wrappings, cast iron clamps or steel sleeves are commonly used non-integral solutions. Recently, composite crack arrestors have enjoyed increasing interest from the industry as a straightforward solution to stop running ductile cracks. A composite crack arrestor is made of (glass) fibres, dipped in a resin bath and wound onto the pipe wall in a variety of orientations. In this paper, the numerical design of composite crack arrestors will be presented. First, the properties of unidirectional glass fibre reinforced epoxy are measured and the micromechanic modelling of composite materials is addressed. Then, the in-use behaviour of pipe joints with composite crack arrestors is covered. Large-scale tensile tests and four point bending tests are performed and compared with finite element simulations. Subsequently, failure measures are introduced to predict the onset of composite material failure. At the end, the ability of composite crack arrestors to arrest a running fracture in a high pressure gas pipeline is assessed.

scholarly journals Microstructural Characterization and Mechanical Property of Al-Li Plate Produced by Centrifugal Casting Method

Metals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 966
Author(s):  
Qingle Tian ◽  
Kai Deng ◽  
Zhishuai Xu ◽  
Ke Han ◽  
Hongxing Zheng
Keyword(s):  
Centrifugal Casting ◽  
High Strength ◽  
Microstructural Characterization ◽  
Fracture Morphology ◽  
Total Elongation ◽  
Mechanical Anisotropy ◽  
Tensile Fracture ◽  
Casting Method ◽  
Scanning Calorimetry ◽  
Strengthening Phases

Using a centrifugal casting method, along with deformation and aging, we produced a high-strength, low-anisotropy Al-Li plate. The electron probe microanalysis, transmission electron microscope, differential scanning calorimetry, and X-ray diffraction were used to clarify the evolution of strengthening phases. Experimental results showed that centrifugal-cast Al-Li plate consisted of intragrain δ′—(Al,Cu)3Li precipitate and interdendritic θ′—Al2Cu particles. After cold-rolling to a reduction ratio of 60% and annealing at 800 K for 90 min, both primary θ′ and δ′ were dissolved in solid solution. Aging at 438 K for 60 h led to the formation of two kinds of precipitates (needle-like T1—Al2CuLi and spherical δ′ in two sizes), which acted as the main strengthening phases. The average values of ultimate tensile strength and yield strength for the anneal-aged plate reached 496 MPa and 408 MPa, with a total elongation of 3.9%. The anneal-aged plate showed mechanical anisotropy of less than 5%. The tensile fracture morphology indicated a typical intergranular fracture mode.

scholarly journals Heat Treatment Design for a QP Steel: Effect of Partitioning Temperature

Metals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1136
Author(s):  
Marcel Carpio ◽  
Jessica Calvo ◽  
Omar García ◽  
Juan Pablo Pedraza ◽  
José María Cabrera
Keyword(s):  
Retained Austenite ◽  
High Strength Steels ◽  
High Strength ◽  
Tensile Tests ◽  
Quenching Temperature ◽  
Advanced High Strength Steels ◽  
New Family ◽  
Automotive Parts ◽  
Fresh Martensite ◽  
Industry Needs

Designing a new family of advanced high-strength steels (AHSSs) to develop automotive parts that cover early industry needs is the aim of many investigations. One of the candidates in the 3rd family of AHSS are the quenching and partitioning (QP) steels. These steels display an excellent relationship between strength and formability, making them able to fulfill the requirements of safety, while reducing automobile weight to enhance the performance during service. The main attribute of QP steels is the TRIP effect that retained austenite possesses, which allows a significant energy absorption during deformation. The present study is focused on evaluating some process parameters, especially the partitioning temperature, in the microstructures and mechanical properties attained during a QP process. An experimental steel (0.2C-3.5Mn-1.5Si (wt%)) was selected and heated according to the theoretical optimum quenching temperature. For this purpose, heat treatments in a quenching dilatometry and further microstructural and mechanical characterization were carried out by SEM, XRD, EBSD, and hardness and tensile tests, respectively. The samples showed a significant increment in the retained austenite at an increasing partitioning temperature, but with strong penalization on the final ductility due to the large amount of fresh martensite obtained as well.

scholarly journals Effects of Sc and Zr on the Texture and Mechanical Anisotropy of High Strength Al–Zn–Mg Alloy Sheets

2016 ◽  
Vol 48 (1) ◽  
pp. 39-48 ◽  
Author(s):  
Y. Deng ◽  
Z. M. Yin ◽  
G. F. Xu ◽  
Y. J. Wang ◽  
L. Y. Lu ◽  
...  
Keyword(s):  
High Strength ◽  
Mechanical Anisotropy ◽  
Mg Alloy

Investigations on the Mechanical Properties and Formability of Friction Stir Welded Tailored Blanks

2007 ◽  
Vol 344 ◽  
pp. 143-150 ◽  
Author(s):  
Gianluca Buffa ◽  
Livan Fratini ◽  
Marion Merklein ◽  
Detlev Staud
Keyword(s):  
Mechanical Properties ◽  
Stress Condition ◽  
Research Effort ◽  
High Strength Steels ◽  
High Strength ◽  
Tensile Tests ◽  
Friction Stir ◽  
Tailored Blanks ◽  
Sheet Stamping ◽  
Wide Range

Tight competition characterizing automotive industries in the last decades has determined a strong research effort aimed to improve utilized processes and materials in sheet stamping. As far as the latter are regarded light weight alloys, high strength steels and tailored blanks have been increasingly utilized with the aim to reduce parts weight and fuel consumptions. In the paper the mechanical properties and formability of tailored welded blanks made of a precipitation hardenable aluminum alloy but with different sheet thicknesses, have been investigated: both laser welding and friction stir welding have been developed to obtain the tailored blanks. For both welding operations a wide range of the thickness ratios has been considered. The formability of the obtained blanks has been characterized through tensile tests and cup deep drawing tests, in order to show the formability in dependency of the stress condition; what is more mechanical and metallurgical investigations have been made on the welded joints.

Experimental Investigation of Ti-6Al-4V with a Biaxial Tensile Test Setup at Elevated Temperature

2014 ◽  
Vol 622-623 ◽  
pp. 273-278 ◽  
Author(s):  
Marion Merklein ◽  
Sebastian Suttner ◽  
Adam Schaub
Keyword(s):  
Elevated Temperature ◽  
Elevated Temperatures ◽  
Tensile Tests ◽  
Advanced Materials ◽  
Uniaxial Tensile ◽  
Plastic Yielding ◽  
Characterization Methods ◽  
Specific Strength ◽  
Biaxial Tensile ◽  
Stress States

The requirement for products to reduce weight while maintaining strength is a major challenge to the development of new advanced materials. Especially in the field of human medicine or aviation and aeronautics new materials are needed to satisfy increasing demands. Therefore the titanium alloy Ti-6Al-4V with its high specific strength and an outstanding corrosion resistance is used for high and reliable performance in sheet metal forming processes as well as in medical applications. Due to a meaningful and accurate numerical process design and to improve the prediction accuracy of the numerical model, advanced material characterization methods are required. To expand the formability and to skillfully use the advantage of Ti-6Al-4V, forming processes are performed at elevated temperatures. Thus the investigation of plastic yielding at different stress states and at an elevated temperature of 400°C is presented in this paper. For this reason biaxial tensile tests with a cruciform shaped specimen are realized at 400°C in addition to uniaxial tensile tests. Moreover the beginning of plastic yielding is analyzed in the first quadrant of the stress space with regard to complex material modeling.

A Study on the Coupled Thermal and Damage Effects in Deforming Solids

2011 ◽  
Vol 312-315 ◽  
pp. 229-234
Author(s):  
M. Vaz ◽  
Pablo A. Muñoz-Rojas ◽  
M.R. Lange
Keyword(s):  
Metal Forming ◽  
Ductile Failure ◽  
Tensile Tests ◽  
Thermal Softening ◽  
Mechanical Degradation ◽  
Material Behaviour ◽  
Temperature Variations ◽  
Damage Models ◽  
Notched Specimens ◽  
Fully Coupled

Mechanical degradation and ductile failure in metal forming operations can be successfully modelled using fully coupled damage models. In addition, it has been largely reported in the literature that temperature variations affect material behaviour, especially thermal softening. This paper presents a numerical discussion of the coupled effects between ductile damage and temperature evolution based on the simulation of tensile tests of notched specimens.

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