Effects of Strain Rate and Temperature on Ductile Damage of Metals

2018 ◽  
Author(s):  
Alexander Sancho ◽  
Mike J. Cox ◽  
Tim Cartwright ◽  
Paul A. Hooper ◽  
John P. Dear ◽  
...  
Keyword(s):  
Strain Rate ◽  
High Speed ◽  
Damage Accumulation ◽  
Tensile Tests ◽  
Ductile Damage ◽  
Metallic Materials ◽  
Stiffness Reduction ◽  
Strain Behaviour ◽  
Experimental Rig

Ductile damage appears in ductile metallic materials when these undergo sufficient plastic deformation, and it is caused by voids and microcracks that are formed within the material due to those severe conditions. The main interest of the present research is to experimentally characterise ductile damage in different conditions of strain rate (from quasi-static to 103s−1) and temperature (from −80°C to 180°C). Estimations of damage accumulation along the plastic regime have been taken by measuring the stiffness reduction of the material. The effects of strain localisation and necking have been accounted for by monitoring the changes in the geometry of the specimens during the test. At high speed these experiments have required the use of an in-situ shadowgraph method to monitor the sample silhouette and accurately calculate stress-strain behaviour throughout the test. The design of a novel experimental rig to perform high speed interrupted tensile tests has also been needed, in order to measure the damage accumulation in those conditions. The low and high temperature tests have been carried out inside an environmental chamber maintaining the rest of the technique unchanged. These experiments at varying strain rate and temperature have allowed to better understand the effect these conditions have on damage properties.

scholarly journals In Situ and Post-Mortem Characterizations of Ultrasonic Spot Welded AZ31B and Coated Dual Phase 590 Steel Joints

Metals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 899 ◽  
Author(s):  
Jian Chen ◽  
Yong Chae Lim ◽  
Donovan Leonard ◽  
Hui Huang ◽  
Zhili Feng ◽  
...  
Keyword(s):  
High Speed ◽  
Tensile Tests ◽  
Fatigue Tests ◽  
Image Correlation ◽  
Joint Interface ◽  
Welding Time ◽  
Cross Sectional ◽  
Welding Condition ◽  
Lap Shear

Ultrasonic spot welding using different welding conditions was applied to join dissimilar metals of galvanized DP590 steel and AZ31B magnesium sheets. In situ high-speed imaging, digital image correlation, and infrared thermography were utilized to quantitatively study the interfacial relative motion, surface indentation, and heat generation across the joint faying interface and the sheet/sonotrode interfaces under the welding condition of moderate welding power and short welding time. For welds made with high power and long welding time, lap shear tensile tests as well as fatigue tests were carried out. Different fracture modes were observed after the lap shear tensile tests and fatigue tests performed under different peak loads. Post-weld cross-sectional analysis with scanning electron microscopy coupled with energy dispersive X-Ray spectroscopy revealed the variation of morphology and chemical composition at the joint interface for welds made with different welding conditions.

Superplastic Deformation Behavior of Spray Formed High Speed Tool Steel at 820°C

2007 ◽  
Vol 561-565 ◽  
pp. 91-94
Author(s):  
Can Dong Zhou ◽  
Jun Fei Fan ◽  
Hai Rong Le ◽  
Jing Guo Zhang
Keyword(s):  
Dynamic Recrystallization ◽  
Strain Rate ◽  
Superplastic Deformation ◽  
High Speed ◽  
Tensile Axis ◽  
Tensile Elongation ◽  
High Speed Steel ◽  
Rate Sensitivity ◽  
Tensile Tests ◽  
Dislocation Creep

Being examined by tensile tests at 820°C with initial strain rates of 2.5×10-4 s-1, 5.0×10-3 s-1and 1.0×10-1 s-1, the hot-rolled spay formed high speed steel (SF-HSS) had superplastic properties. With έ=2.5×10-4 s-1and 5.0×10-3 s-1, the σ-ε curves indicate that there has occurred dynamic recrystallization at the later stage of deformation.The tensile elongation decreases monotonously with strain rate increasing. The strain rate sensitivity m =dlogσ/dlog έ is about 0.23. In the sub-surface of fractured SF-HSS samples with έ=2.5×10-4 s-1,, most of holes on the subsurface are observed to distribute near the carbides and arranged along the tensile axis direction. The interface between coarse carbides and matrix is very weak sites where the holes are easy to nucleate and connect to cracks during deformation. In the necked region, fine carbide particles on the grain boundary have pinned the slip of dislocations and formed dislocation wall inside the grain. Dynamic recrystallization and some climb of dislocations has occurred. The superplastic deformation mechanism with έ=2.5×10-4 s-1 was dislocation creep mechanism controlled by dynamic recrystallization. During deformation, the role of some carbide in the materials was to retard the grain growth and keep SF-HSS having fine equiaxed grain size and remain stable.

scholarly journals Analysis of Dynamic Plastic Deformation process on an Electrolytic Tough - Pitch copper (Cu-ETP): From material characterization to models improvement

2018 ◽  
Vol 183 ◽  
pp. 03023
Author(s):  
Jérôme Mespoulet ◽  
Bermane Beucia ◽  
David Tingaud ◽  
Pierre-Louis Hereil ◽  
Hervé Couque ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Strain Rate ◽  
High Speed ◽  
Structural Changes ◽  
Tensile Tests ◽  
Video Camera ◽  
Post Mortem ◽  
Structural Investigations ◽  
Impact Compression ◽  
Dynamic Plastic Deformation

This paper presents a comprehensive study of a direct impact compression loading on an Electrolytic Tough-Pitch copper (Cu-ETP). The aim of the study is to provide reliable experimental data in this dynamic loading using high-speed video camera records and real time projectile deceleration profiles. Test set-up has been optimized to ensure an efficient recovery of the samples after the Dynamic Plastic Deformation (DPD) process in the 103 to 104 s-1 strain rate range regime. Structural investigations have been made on post-mortem samples: microstructure investigations of recovered samples have shown more structural changes in terms of crystallographic texture and grain sizes. Post-mortem tensile tests have also been carried out to evaluate yield strength behavior of the Cu-ETP copper after the DPD process. Numerical simulations have been performed to evaluate the ability of empirical models to reproduce recorded signals. In-situ results (time evolution of strain, strain rate, temperature, etc.) given by the numerical analysis have contributed to enrich the post-mortem analysis.

scholarly journals GTN Model-Based Material Parameters of AZ31 Magnesium Sheet at Various Temperatures by Means of SEM In-Situ Testing

Crystals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 856
Author(s):  
Thorsten Henseler ◽  
Shmuel Osovski ◽  
Madlen Ullmann ◽  
Rudolf Kawalla ◽  
Ulrich Prahl
Keyword(s):  
Void Nucleation ◽  
Thin Sheet ◽  
Void Formation ◽  
Tensile Tests ◽  
Image Correlation ◽  
Ductile Damage ◽  
Material Parameters ◽  
Model Based ◽  
Simple Tension

Magnesium alloys are primarily associated with complex forming mechanisms, which yield ductility at high temperatures. In sheet metal forming, high triaxiality stress states that favor the ductile damage mechanisms of void formation and growth are known to malleable metals. The formulation of coupled damage models has so far failed, due to the incomplete experimental determination of damage parameters for magnesium AZ31 thin sheet. A quantitative investigation was conducted to determine the ductile damage behavior of twin-roll cast, hot rolled, and annealed AZ31 thin sheet. Results on the mechanisms of void nucleation-, coalescence- and growth-rate were established at temperatures ranging from room temperature to 350 °C. In-situ tensile tests were carried out in a scanning electron microscope with three different specimen types: Simple tension specimens, notched specimens for high triaxiality stress state testing, and shear specimens. Through a comparative analysis of local strains measured by digital image correlation and local void volume fractions determined through post-mortem analysis of specimen cross-sections, GTN (Gurson–Tvergaard–Needleman) model-based material parameters were determined by experiment, representing a novel departure in the magnesium research landscape. The procedure developed in this context should also be transferable to other metals in the form of thin sheets.

Dynamic Tensile Tests of Auto-Body Steel Sheets with the Variation of Temperature

2006 ◽  
Vol 116-117 ◽  
pp. 259-262 ◽  
Author(s):  
Hee Jong Lee ◽  
Jung Han Song ◽  
Hoon Huh
Keyword(s):  
Flow Stress ◽  
Tensile Test ◽  
Strain Rate ◽  
Mechanical Behavior ◽  
High Speed ◽  
Mechanical Response ◽  
Rate Sensitivity ◽  
Tensile Tests ◽  
Static State ◽  
Steel Sheets

This paper is concerned with the thermo-mechanical behavior of steel sheet for an autobody including the temperature dependent strain-rate sensitivity. Tensile tests have been carried out with the high strength steel sheets such as SPRC35R, SPRC45E and TRIP60. The tensile tests were performed with the variation of the strain-rates from 0.001/s to 200/s and with the variation of environmental temperatures from -40 to 200. The thermo-mechanical response at the quasi-static state is obtained with the static tensile test and the one at the intermediate strain-rate is obtained with the high speed tensile test. Both the strain-rate and the temperature sensitivity of the flow stress are calculated for the quantitative evaluation of thermo-mechanical behavior of steel sheets. The results demonstrate that as the strain-rate increases, the variation of the flow stress becomes more dependent on the temperature. The results also indicate that the material properties of SPRC35R are more sensitive to the strain-rate and the temperature than those of SPRC45E and TRIP60.

scholarly journals Thermomechanical tensile properties of deposited Inconel 718 superalloy over a wide range of strain rate and temperature

2021 ◽  
Vol 250 ◽  
pp. 05017
Author(s):  
Martina Scapin ◽  
Lorenzo Peroni ◽  
Kangbo Yuan ◽  
Weiguo Guo
Keyword(s):  
High Temperature ◽  
High Strain Rate ◽  
Strain Rate ◽  
High Speed ◽  
High Strain ◽  
Heating System ◽  
Tensile Tests ◽  
Significant Drop ◽  
Nominal Strain Rate ◽  
Wide Range

Nickel-based superalloys show high strength retained also at high temperature and they are widespread used for structural components exposed during services to high temperature combined with high strain rate or impact loading conditions. The objective of this study was the investigation of the plastic flow behaviour of Laser Metal Deposited Nickel-based superalloy Inconel718. The material was manufactured at Northwestern Polytechnical University in China. Specimens with three different heat treatment conditions were investigated: as-deposited, directly aged and aged after homogenization and solution. High strain rate tensile tests were performed on the direct Hopkinson bar setup developed at DYNLab laboratory at Politecnico di Torino. At a nominal strain rate of 1500 s-1 the temperature sensitivity was investigated between 20 and 1000°C. An induction heating system was adopted, and the temperature was monitored by thermocouples and infrared pyrometer and high-speed camera. The results showed the materials strength decreases as a function of temperature with a significant drop starting from 800 °C. An asymmetric tension-compression behaviour was found by comparing the results with data in compression. The strain rate influence was investigated at room temperature and very limited or negligible sensitivity was found covering six orders of magnitude in strain rate.

Temperature and Strain Rate Dependent Simulation of High Speed Tensile Tests of I-PP

2005 ◽  
Vol 25 (5) ◽  
Author(s):  
M. Keuerleber ◽  
N. Woicke ◽  
S.R. Raisch ◽  
P. Eyerer
Keyword(s):  
Strain Rate ◽  
High Speed ◽  
Tensile Tests ◽  
Rate Dependent

Evaluation of Dynamic Deformation Properties of Metallic Materials with Different Crystal Structures Using Taylor Impact Test

2014 ◽  
Vol 566 ◽  
pp. 146-151 ◽  
Author(s):  
Kyung Oh Bae ◽  
Hyung Seop Shin ◽  
Hoon Huh ◽  
Lee Ju Park ◽  
Hyung Won Kim
Keyword(s):  
Strain Rate ◽  
Deformation Behavior ◽  
High Speed ◽  
Impact Test ◽  
Dynamic Deformation ◽  
Metallic Materials ◽  
Dynamic Yield Strength ◽  
Taylor Impact ◽  
Dynamic Yield ◽  
The Impact

Investigations on dynamic deformation behavior of metallic materials under high strain rate have been conducted. In this study, the deformation behaviors of metallic materials with different crystal structures were examined through Taylor impact test. As representative materials, HSA800 (body-centered cubic: BCC), OFHC (face-centered cubic: FCC) and Ti-6Al-4V (hexagonal close-packed : HCP) were adopted. Taylor impact tests were carried out in the impact velocity range of 100~270 m/s for BCC and FCC materials and 150~330 m/s for Ti-alloy one. In addition, an 8-Ch high-speed photography system was used to provide a series of images representing the plastic deformation behavior of a projectile during Taylor test. The dynamic yield strength and the strain rate were calculated based on the contact time duration of projectile determined from high-speed images. From the result, the strain rate dependency of the dynamic yield strength varied depending on the material adopted. Bulging occurred at the impact part was more significant in FCC material than in BCC one, while a shear band occurred in the Ti-alloy specimen when the impact velocity of projectile exceeded 270 m/s.

Strain-rate dependent material properties of selective laser melted AlSi10Mg and AlSi3.5Mg2.5

2020 ◽  
Vol 62 (6) ◽  
pp. 573-583
Author(s):  
Andreas Lutz ◽  
Lukas Huber ◽  
Claus Emmelmann
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
High Speed ◽  
Treatment Strategies ◽  
High Strength ◽  
Tensile Tests ◽  
Rate Dependent ◽  
Shaping Process ◽  
Behavior Modifications ◽  
Structural Parts

Abstract This paper investigates the mechanical properties of two selective lasermelted aluminum alloys (AlSi10Mg and AlSi3.5Mg2.5) under high strain-rate uniaxial loading. Accelerated tensile tests were performed under various strain-rate decades (.ε = 4.7 × 10-3 up to 250 s-1) to determine the load-speed-specific changes in the mechanical properties. As a result of the primary laser-based shaping process, the microstructure and characteristics change was entirely comparable to the conventional manufacturing of aluminum parts. Based on an ultrafine microstructure, parts achieve high strength along with a brittle fracture behavior. Modifications for applications requiring high ductility (e. g., the crashloaded structural parts of a car body) can be made through specific heat treatment strategies. The experimental results demonstrate that a significant increase in ductility (factors 4-5) with a concurrent decrease in strength can be obtained compared to the as-built state. In high-speed tests, the tensile strength of both alloys rose strain-rate dependently around 10 %, and the elongation at break increased relatively by ≈ 15 % for AlSi10Mg and ≈ 10 % for AlSi3.5Mg2.5.

Sign in / Sign up

Export Citation Format

Share Document