scholarly journals Effect of Hydrogen Content and Strain Rate on Hydrogen-induced Delay Cracking for Hot-Stamped Steel

Metals ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 798 ◽  
Author(s):  
Jia ◽  
Zhang ◽  
Xu ◽  
Sun ◽  
Li
Keyword(s):  
Strain Rate ◽  
Hydrogen Content ◽  
Great Influence ◽  
High Strength ◽  
Sample Surface ◽  
Tensile Tests ◽  
Strain Rates ◽  
Fracture Origin ◽  
Main Fracture ◽  
Hot Stamped Steel

Hot-stamped steel has been widely used in automobile bumper and other safety components due to its high strength. Therefore, this paper investigates the effect of hydrogen content and strain rate on hydrogen-induced delay cracking (HIDC) behavior. The results showed that the plasticity of the steel significantly decreased with an increase in hydrogen content or a decrease in the strain rate. Fractography was analyzed after tensile tests. It was found that all of the pre-charged specimens cracked at large-sized inclusions when stretched at a strain rate of 1 × 10−3 s−1, which indicates that, in this case, the defect itself in the material had great influence on the extend properties. No inclusions were found at the main fracture origin area for hydrogen steady-state specimens, when stretched at a strain rate of 1 × 10−6 s−1, which demonstrated that a slower strain rate causes greater influence by hydrogen. However, for the non-pre-charged samples, the fractures surface showed that cracking originated from the defect near the sample surface, which was independent of strain rates.

Influence of Temperature and Strain Rate on the Plastic Deformation of Two Commercial High Strength Al Alloys

2006 ◽  
Vol 519-521 ◽  
pp. 841-846 ◽  
Author(s):  
Magnus Johansson ◽  
Magnus Hörnqvist ◽  
Birger Karlsson
Keyword(s):  
Strain Rate ◽  
Temperature Sensitivity ◽  
Uniform Elongation ◽  
Rate Sensitivity ◽  
High Strength ◽  
Tensile Tests ◽  
Rate Dependence ◽  
Strain Rate Dependence ◽  
Strain Rates ◽  
Area Reduction

In the present study the influence of strain rate and temperature on the behaviour of two commercial aluminium alloys, 6063-T6 and 7030-T6, was investigated. Both alloys are high strength precipitation hardened alloys that are expected to have low strain rate and temperature sensitivity. Tensile tests were performed at room temperature at strain rates ranging from 10-4 to 102 s-1, and at -40°C and +60°C at strain rates of 10-4 and 10-1 s-1, due to equipment limitations. Both alloys showed low but positive strain rate sensitivity at all temperatures. Also the temperature sensitivity was low, showing negative values in all cases. The dependence of the flow stress on temperature was more pronounced than the strain rate dependence. The area reduction at fracture was higher in 6063 than 7030, although the uniform elongation was larger in 7030. 6063 showed almost no strain rate dependence of the ductility and a limited reduction with increased temperature. 7030 showed markedly increasing area reduction with increasing temperature and decreasing values with increasing strain rate. The energy absorption was higher in 7030 by a factor of approximately three.

scholarly journals New Approach In The Properties Evaluation Of Ultrafine-Grained OFHC Copper

2015 ◽  
Vol 60 (2) ◽  
pp. 605-614 ◽  
Author(s):  
T. Kvačkaj ◽  
A. Kováčová ◽  
J. Bidulská ◽  
R. Bidulský ◽  
R. Kočičko
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Tensile Tests ◽  
Coarse Grained ◽  
Wear Behaviour ◽  
Ofhc Copper ◽  
Strain Rates ◽  
Ultrafine Grained ◽  
Reduction Of Area ◽  
Pin On Disk

AbstractIn this study, static, dynamic and tribological properties of ultrafine-grained (UFG) oxygen-free high thermal conductivity (OFHC) copper were investigated in detail. In order to evaluate the mechanical behaviour at different strain rates, OFHC copper was tested using two devices resulting in static and dynamic regimes. Moreover, the copper was subjected to two different processing methods, which made possible to study the influence of structure. The study of strain rate and microstructure was focused on progress in the mechanical properties after tensile tests. It was found that the strain rate is an important parameter affecting mechanical properties of copper. The ultimate tensile strength increased with the strain rate increasing and this effect was more visible at high strain rates$({\dot \varepsilon} \sim 10^2 \;{\rm{s}}^{ - 1} )$. However, the reduction of area had a different progress depending on microstructural features of materials (coarse-grained vs. ultrafine-grained structure) and introduced strain rate conditions during plastic deformation (static vs. dynamic regime). The wear behaviour of copper was investigated through pin-on-disk tests. The wear tracks examination showed that the delamination and the mild oxidational wears are the main wear mechanisms.

The Effects of Physical Ageing and of Prior Immersion on the Esc Behaviour of Polycarbonate in Ethanol

1993 ◽  
Vol 305 ◽  
Author(s):  
J. C. Arnold ◽  
A. R. Eccott
Keyword(s):  
Strain Rate ◽  
Immersion Time ◽  
Constant Strain Rate ◽  
Tensile Tests ◽  
Strain Rates ◽  
Physical Ageing ◽  
Diffusion Effects ◽  
Craze Initiation ◽  
Comparison Of Tests

AbstractThe effects of physical ageing and prior immersion time on the ESC behaviour of polycarbonate in ethanol were studied. Constant strain rate tensile tests were performed at a range of strain rates for samples with ageing times varying from 100 hours to 3000 hours and for prior immersion times of between 1 hour and 500 hours. Comparison of tests performed in ethanol and in air gave a good indication of the point of craze initiation. The results showed that there was a reduction in strain to crazing as the strain rate decreased, apart from with the lowest strain rate used. A longer prior immersion time also promoted craze formation. Both of these results are attributable to diffusion effects. Physical ageing had little effect on the ESC behaviour, due to the large amounts of deformation encountered in this system.

scholarly journals Experimental Investigation into Corrosion Effect on Mechanical Properties of High Strength Steel Bars under Dynamic Loadings

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Hui Chen ◽  
Jinjin Zhang ◽  
Jin Yang ◽  
Feilong Ye
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Dynamic Loading ◽  
High Strength Steel ◽  
High Strength ◽  
Tensile Tests ◽  
Reinforcing Steel ◽  
Test Results ◽  
Cross Sectional ◽  
Steel Bars

The tensile behaviors of corroded steel bars are important in the capacity evaluation of corroded reinforced concrete structures. The present paper studies the mechanical behavior of the corroded high strength reinforcing steel bars under static and dynamic loading. High strength reinforcing steel bars were corroded by using accelerated corrosion methods and the tensile tests were carried out under different strain rates. The results showed that the mechanical properties of corroded high strength steel bars were strain rate dependent, and the strain rate effect decreased with the increase of corrosion degree. The decreased nominal yield and ultimate strengths were mainly caused by the reduction of cross-sectional areas, and the decreased ultimate deformation and the shortened yield plateau resulted from the intensified stress concentration at the nonuniform reduction. Based on the test results, reduction factors were proposed to relate the tensile behaviors with the corrosion degree and strain rate for corroded bars. A modified Johnson-Cook strength model of corroded high strength steel bars under dynamic loading was proposed by taking into account the influence of corrosion degree. Comparison between the model and test results showed that proposed model properly describes the dynamic response of the corroded high strength rebars.

Strain-Rate Effect on the Tensile Behaviour of High Strength Alloys

2011 ◽  
Vol 82 ◽  
pp. 124-129 ◽  
Author(s):  
Ezio Cadoni ◽  
Matteo Dotta ◽  
Daniele Forni ◽  
Stefano Bianchi
Keyword(s):  
Strain Rate ◽  
Rate Sensitivity ◽  
High Strength ◽  
Constitutive Law ◽  
Tensile Behaviour ◽  
Strain Rates ◽  
Cross Sectional ◽  
Split Hopkinson Tensile Bar ◽  
Wide Range ◽  
First Results

In this paper the first results of the mechanical characterization in tension of two high strength alloys in a wide range of strain rates are presented. Different experimental techniques were used for different strain rates: a universal machine, a Hydro-Pneumatic Machine and a JRC-Split Hopkinson Tensile Bar. The experimental research was developed in the DynaMat laboratory of the University of Applied Sciences of Southern Switzerland. An increase of the stress at a given strain increasing the strain-rate from 10-3 to 103 s-1, a moderate strain-rate sensitivity of the uniform and fracture strain, a poor reduction of the cross-sectional area at fracture with increasing the strain-rate were shown. Based on these experimental results the parameters required by the Johnson-Cook constitutive law were determined.

scholarly journals Influence of strain rate and heat treatments on tensile and creep properties of Zn-0.15Cu-0.07Ti alloys

DYNA ◽  
2016 ◽  
Vol 83 (195) ◽  
pp. 77-83 ◽  
Author(s):  
María José Quintana Hernández ◽  
José Ovidio García ◽  
Roberto González Ojeda ◽  
José Ignacio Verdeja
Keyword(s):  
Strain Rate ◽  
Room Temperature ◽  
Rolling Direction ◽  
Tensile Tests ◽  
Strain Rates ◽  
Creep Tests ◽  
Design Problems ◽  
Creep Properties ◽  
Heat Treated ◽  
Zn Alloys

The use of Cu and Ti in Zn alloys improves mechanical properties as solid solution and dispersoid particles (grain refiners) may harden the material and reduce creep deformation. This is one of the main design problems for parts made with Zn alloys, even at room temperature. In this work the mechanical behavior of a Zn-Cu-Ti low alloy is presented using tensile tests at different strain rates, as well as creep tests at different loads to obtain the value of the strain rate coefficient m in samples parallel and perpendicular to the rolling direction of the Zn strip. The microstructure of the alloy in its raw state, as well as heat treated at 250°C, is also analyzed, as the banded structure produced by rolling influences the strengthening mechanisms that can be achieved through the treatment parameters.

Tensile Stress-Strain Curves Modeling of Four Kinds of Solders with Temperature and Rate Dependence

2005 ◽  
Vol 297-300 ◽  
pp. 905-911 ◽  
Author(s):  
Xu Chen ◽  
Li Zhang ◽  
Masao Sakane ◽  
Haruo Nose
Keyword(s):  
Tensile Stress ◽  
Constitutive Model ◽  
Strain Rate ◽  
Constant Strain Rate ◽  
Tensile Tests ◽  
Strain Rate Range ◽  
Rate Dependence ◽  
Strain Rates ◽  
Stress Strain ◽  
Rate Range

A series of tensile tests at constant strain rate were conducted on tin-lead based solders with different Sn content under wide ranges of temperatures and strain rates. It was shown that the stress-strain relationships had strong temperature- and strain rate- dependence. The parameters of Anand model for four solders were determined. The four solders were 60Sn-40Pb, 40Sn-60Pb, 10Sn-90Pb and 5Sn-95Pb. Anand constitutive model was employed to simulate the stress-strain behaviors of the solders for the temperature range from 313K to 398K and the strain rate range from 0.001%sP -1 P to 2%sP -1 P. The results showed that Anand model can adequately predict the rate- and temperature- related constitutive behaviors at all test temperatures and strain rates.

Anisotropic Behavior of Aluminum Alloy 2024-Graphene Composites at Varying Strain Rates

2017 ◽  
Author(s):  
M. Anthony Xavior ◽  
Prashantha Kumar Hosamane ◽  
Jeyapandiarajan Paulchamy
Keyword(s):  
Aspect Ratio ◽  
Strain Rate ◽  
Ball Milling ◽  
High Strength ◽  
Uniaxial Tensile ◽  
Strain Rates ◽  
Strain Sensitivity ◽  
Anisotropic Behavior ◽  
Dimple Size ◽  
Processing Methods

In fabrication of high strength materials coupled with improved mechanical properties; focus on integration of multifunctional reinforcements are increasing along with novel processing methods. Single layer 2-D material Graphene are among one such novel material with huge aspect ratio, posse’s high strength. But the real challenge is processing and incorporation of these reinforcements with appropriate content in metals or its alloys matrix. Current research work focus to study the anisotropic behavior on addition of pristine Graphene/MWCNT and processing methods like ball milling under constant ball to powder precursor ratio (BPR) of AA 2024 nanocomposites. The extent change in aspect ratio, size of the nanoparticle mixtures during ball milling were analyzed under SEM and Raman spectroscopy. Thus obtained (ball milled) precursors are consolidated through vacuum hot press and hot extruded to get typical flat specimen at optimized processing parameters. XRD analysis, relative density and hardness measurement is done on extruded composites. Thus developed composites are subjected to study the anisotropic behavior at various orientations and strain rates (0.5, 1.0, 1.5 mm/min) using uniaxial tensile testing instrument and corresponding stress strains graphs were obtained. The fracture surfaces were characterized by scanning electron microscope (SEM) and its shows the nucleation of the dimple size are varies with increasing the strain rate and also deeper dimple size were noticed. Negative strain sensitivity were observed for the lower strain rate (0.1 and 0.3 mm/min) and positive strain sensitivity for higher strain rates. Microstructural anisotropy infers that AA2024-Graphene/MWCNT composites are sensitive to strain rate and shear type of failure is observed on increasing the strain rate.

Stress-Strain Equations for Some Near-Eutectic Tin-Lead Solders

1991 ◽  
Vol 113 (4) ◽  
pp. 475-484 ◽  
Author(s):  
K. P. Jen ◽  
J. N. Majerus
Keyword(s):  
Strain Rate ◽  
Printed Circuit Boards ◽  
Volume Fraction ◽  
Total Error ◽  
Tensile Tests ◽  
Elastic Behavior ◽  
Plastic Behavior ◽  
Strain Rates ◽  
Stress Strain ◽  
Engineering Strain

This paper presents the evaluation of the stress-strain behavior, as a function of strain-rate, for three tin-lead solders at room temperature. This behavior is critically needed for reliability analysis of printed circuit boards (PCB) since handbooks list minimal mechanical properties for the eutectic solder used in PCBs. Furthermore, most handbook data are for stable eutectic microstructure whereas PCB solder has a metastable microstructure. All three materials were purchased as “eutectics.” However, chemical analysis, volume fraction determination, and microhardness tests show some major variations between the three materials. Two of the materials have a eutectic composition, and one does not. The true stress-strain equations of one eutectic and the one noneutectic material are determined from compressive tests at engineering strain-rates between 0.0002/s and 0.2/s. The second eutectic material is evaluated using tensile tests with strain-rates between 0.00017/s and 0.042/s. The materials appear to exhibit linear elastic behavior only at extremely small strains, i.e., less than 0.0005. However, this “elastic” behavior showed considerable variation, and depended upon the strain rate. In both tension and compression the eutectic alloy exhibits nonlinear plastic behavior, i.e., strain-softening followed by strain-hardening, which depends upon the strain rate. A quadratic equation σy = σy(ε˚/ε˚0) + A(ε˚/ε˚0)ε + B(ε˚/ε˚0)ε2 fit to the data gives correlation coefficients R2 > 0.91. The coefficients σy(ε˚/ε˚0), A(ε˚/ε˚0), B(ε˚/ε˚0) are fitted functions of the normalized engineering strain rate ε˚/ε˚0. Replicated experiments are used at each strain-rate so that a measure of the statistical variation could be estimated. Measures of error associated with the regression analysis are also obtained so that an estimate of the total error in the stress-strain relations can be made.

scholarly journals High Strain Rate Superplasticity in Al-Zn-Mg-Based Alloy: Microstructural Design, Deformation Behavior, and Modeling

Materials ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2098 ◽  
Author(s):  
Olga Yakovtseva ◽  
Maria Sitkina ◽  
Ahmed O. Mosleh ◽  
Anastasia Mikhaylovskaya
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
Superplastic Deformation ◽  
High Strain ◽  
Flow Behavior ◽  
Constant Strain Rate ◽  
Superplastic Forming ◽  
High Strength ◽  
Strain Rate Range ◽  
Strain Rates

Increasing the strain rate at superplastic forming is a challenging technical and economic task of aluminum forming manufacturing. New aluminum sheets exhibiting high strain rate superplasticity at strain rates above 0.01 s−1 are required. This study describes the microstructure and the superplasticity properties of a new high-strength Al-Zn-Mg-based alloy processed by a simple thermomechanical treatment including hot and cold rolling. The new alloy contains Ni to form Al3Ni coarse particles and minor additions of Zr (0.19 wt.%) and Sc (0.06 wt.%) to form nanoprecipitates of the L12-Al3 (Sc,Zr) phase. The design of chemical and phase compositions of the alloy provides superplasticity with an elongation of 600–800% in a strain rate range of 0.01 to 0.6/s and residual cavitation less than 2%. A mean elongation-to-failure of 400% is observed at an extremely high constant strain rate of 1 s−1. The strain-induced evolution of the grain and dislocation structures as well as the L12 precipitates at superplastic deformation is studied. The dynamic recrystallization at superplastic deformation is confirmed. The superplastic flow behavior of the proposed alloy is modeled via a mathematical Arrhenius-type constitutive model and an artificial neural network model. Both models exhibit good predictability at low and high strain rates of superplastic deformation.

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