On Using Stress Relaxation Tests to Characterize Material Behavior

1987 ◽  
Vol 54 (2) ◽  
pp. 346-350 ◽  
Author(s):  
J. L. Ding ◽  
W. N. Findley
Keyword(s):  
Stress Relaxation ◽  
Strain Rate ◽  
Testing Machine ◽  
Inelastic Strain ◽  
Material Behavior ◽  
Test Results ◽  
Creep Data ◽  
Total Stress ◽  
Initial Stage ◽  
Rate Relation

Stress relaxation tests, in which the gage length of the specimen was maintained constant by servocontrol, were performed on 2618-T61 aluminum. The test results, which were independent of the stiffness of the testing machine, were converted into a relation between stress and inelastic strain rate. It was found that the contribution by the anelastic component to the total stress relaxation was significant only in the initial stage. The validity of using the obtained stress versus inelastic-strain-rate relation to characterize the material behavior is also discussed. Results do not substantiate the concept of a “hardness” flow curve, but data were well predicted from the creep data by theory based on strain hardening and viscoelasticity.

A design of a new miniature device for solder joints’ mechanical properties evaluation

2016 ◽  
Vol 231 (20) ◽  
pp. 3818-3830 ◽  
Author(s):  
Quang-Bang Tao ◽  
Lahouari Benabou ◽  
Laurent Vivet ◽  
Ky-Lim Tan ◽  
Jean-Michel Morelle ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Shear Strength ◽  
Strain Rate ◽  
Solder Joints ◽  
Testing Machine ◽  
Testing Temperature ◽  
Material Behavior ◽  
Shear Strain Rate ◽  
Solder Alloys ◽  
Lap Shear

This paper makes a focus on the design of a micro-testing machine used for evaluating the mechanical properties of solder alloys. The different parts of the testing device have been developed and assembled in a manner that will facilitate the study of miniature solder joints as used in electronic packaging. A specific procedure for fabricating miniature lap-shear joint specimens is proposed in this work. The tests carried out with the newly developed machine serve to determine the material behavior of solder joints under different controlled loading and temperature conditions. Two new solder alloys, namely SACBiNi and Innolot, are characterized in the study, showing the influence of strain rate and temperature parameters on their respective mechanical responses. In addition, the as-cast and fracture surfaces of the solder joints are observed with a scanning electron microscope to reveal the degradation mechanisms. The SACBiNi solder alloy, which contains less Ni and Sb elements, is found to have smaller shear strength than the Innolot alloy, while its elongation to rupture is significantly improved at the same strain rate level and testing temperature. The highest shear strength is 58.9 MPa and 61.1 MPa under the shear strain rate of 2.0 × 10−2 s−1 and room temperature for the SACBiNi and Innolot solder joints, respectively. In contrast, the lowest shear strength values, 26.6 MPa and 29.5 MPa for SACBiNi and Innolot, respectively, were recorded for the strain rate value of 2.0 × 10−4 s−1 and at temperature of 125℃.

Analysis of Casting Materials under Thermal Fatigue

2015 ◽  
Vol 784 ◽  
pp. 95-103
Author(s):  
Holm Altenbach ◽  
Frank Laengler ◽  
Konstantin Naumenko ◽  
Mykola Ievdokymov
Keyword(s):  
Strain Rate ◽  
Low Cycle Fatigue ◽  
Kinematic Hardening ◽  
Inelastic Strain ◽  
Material Model ◽  
Material Behavior ◽  
Strain Rate Tensor ◽  
Inelastic Behavior ◽  
Damage Evolution Equation ◽  
High Temperature Components

High-temperature components, for example turbochargers, are often subject to complex thermal and mechanical loading paths. Non-uniform temperature distribution and constraints by neighboring components result in complex timely varying stress and strain states during operation. In this paper the inelastic behavior of a casting material Ni-resist D-5S in a wide stress, strain rate and temperature ranges is analyzed. The material model including a constitutive equation for the inelastic strain rate tensor, a non-linear kinematic hardening rule and a damage evolution equation is developed. To calibrate the model, experimental databases from creep and low cycle fatigue (LCF) tests are applied. For the verification of the model, simulations of the material behavior under uni-axial thermo-mechanical fatigue (TMF) loading conditions are performed. The results for the stress response and lifetime are compared with experimental data.

An Analytical Interpretation of High Strain Rate Material Behavior During Early Time Plastic Deformation in the Taylor Impact Test

1992 ◽  
Author(s):  
S. E. Jones ◽  
Paul J. Maudlin ◽  
Peter P. Gillis ◽  
Joseph C. Foster
Keyword(s):  
Plastic Deformation ◽  
Strain Rate ◽  
Impact Test ◽  
Early Time ◽  
Material Behavior ◽  
Deformation Phase ◽  
Taylor Impact ◽  
Taylor Impact Test ◽  
Rate Relation ◽  
The Continuum

Abstract Using information from experiments and continuum mechanics code calculations, an analytical stress/strain-rate relation is developed. This relation is valid during the early time plastic deformation phase of the Taylor impact test. The results show good correlation between experiment and the continuum code predictions.

Study of Solder/Copper Interface Behavior Under Varying Strain Rates

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
Y. W. Kwon ◽  
A. M. Luteran ◽  
J. M. Didoszak ◽  
A. S. Kwon
Keyword(s):  
Strain Rate ◽  
Room Temperature ◽  
Fracture Strain ◽  
Peak Stress ◽  
Absolute Error ◽  
Material Behavior ◽  
Interface Fracture ◽  
Strain Rates ◽  
Test Results ◽  
Strain Rate Loading

This paper investigates the mechanical behavior of a copper–solder interface when subjected to varying strain rate loading between 0.05 s−1 and 10.0 s−1. The copper is alloy 101, and the solder is lead-free type with a composition of 96% tin and 4% silver. Both uniform and nonuniform two-level strain rate loadings were applied. For the two-level strain rate loading, the strain rate was changed from one level to another during the loading process as a step change. The strain rate tests were performed at room temperature as well as at an elevated temperature of 65 °C. The test results showed significant effects of uniform and nonuniform strain rates as well as temperature on fracture surface, peak stress, fracture strain, modulus, and stored energy density until fracture. Generally, a higher strain rate increased the peak stress and fracture strain, but decreased the modulus. The heated specimens showed significantly reduced strength and fracture strain at high strain rates when compared to the specimens tested at room temperature. For the two-level strain rates, the sequence of the loading rates affected the material behavior significantly. The peak stress under the two-level strain rates might be located outside the range that was determined by the two individual uniform strain rates occurring in the two-level rates. On the other hand, the fracture strain under two-level strain rate loading always fell inside that range. An expression was proposed to predict the interface fracture strains for the case of a two-level strain rate loading based on the data of each respective single-level strain test. The prediction was reasonable when compared to the experimental data with an average absolute error of 10%.

scholarly journals Strain Rate Effect on the Compressive Behaviour of Reinforced Cork Agglomerates

2018 ◽  
Vol 183 ◽  
pp. 03018 ◽  
Author(s):  
Louise Le Barbenchon ◽  
Jérémie Girardot ◽  
Jean-Benoît Kopp ◽  
Philippe Viot
Keyword(s):  
Strain Rate ◽  
Testing Machine ◽  
Compressive Loading ◽  
Material Behavior ◽  
Large Set ◽  
Strain Rates ◽  
Average Strain Rate ◽  
Plane Direction ◽  
Mechanical Performances ◽  
Energy Absorbing

The demand for bio-sourced materials is currently increasing. Cork material because of its unique properties (fire resistant, energy absorbing, …) is then an excellent candidate for a large set of applications. In order to widen its possible uses, cork agglomerates with reinforcements at a 0.48 density were studied to compare their mechanical performances with classical cork agglomerates. This paper investigates the effect of these foreign reinforcements on the properties of agglomerated cork under a compressive loading. The material behavior has been determined as a function of the average strain rate and the direction of solicitation. The microstructure was first observed through optical and scanning electronic microscopy, spotting charges between each cork bead. The characterisation of cork at different strain rates was then carried out. An electromechanical testing machine was used to apply an uniaxial compression at quasi-static strain rates. Reinforced agglomerated cork was found to be anisotropic and strain-rate dependant. Its micro-structure reveals at complex composite material influencing strongly mechanical properties. Both Young's modulus and absorbed energy density at 0.6 strain increase with the cross-head speed displacement. From 12.7 MPa and 0.77 J.mm-3 when compressed at 0.05 mm·min-1 to 19.9 MPa and 1.44 J·mm-3 at 500mm·min-1 in the Off-plane direction.

scholarly journals Laboratory Study on Changes in Gas Desorption Properties of Anthracite after Cyclic Loading

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Tie Li ◽  
Dong Wang ◽  
Mei-Hua Liu ◽  
Liang Chen ◽  
Hao Liu
Keyword(s):  
Diffusion Coefficient ◽  
Cyclic Loading ◽  
Testing Machine ◽  
Coal Mass ◽  
Shanxi Province ◽  
Loading Frequency ◽  
Test Results ◽  
Gas Desorption ◽  
Initial Stage ◽  
Desorption Capacity

Coal mass is subjected to cyclic loading during pulsating hydraulic fracturing (PHF), and changes in its gas desorption properties affect gas drainage. Therefore, it is of great importance to correctly understand the influences of cyclic loading on the gas desorption properties of coal mass. Firstly, loading tests with different frequencies and amplitudes were performed on anthracite from Qinshui Basin (Shanxi Province, China) using a fatigue testing machine. Secondly, gas desorption tests were performed to determine the associated curves for each test group at different equilibrium pressures, and the initial desorption capacity and diffusion coefficient of the gas were calculated. Finally, the influence of different loading conditions on the gas desorption laws were analyzed. The test results demonstrate that a greater loading frequency increases the ratio of the initial desorption capacity so that the desorption rate of coal samples is higher, and the gas desorption properties become increasingly better in the initial stage. However, variations in the amplitude have minimal impact on the ratio of the initial desorption capacity. When the amplitude is too large in the initial stage, the diffusion coefficient decreases and the gas desorption properties worsen. In addition, the above test results are used to discuss the selection of the amplitude and frequency in the PHF process from a macroperspective. The contained research results provide an important theoretical basis for the field application of PHF technologies in coal mines.

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.

Prediction of Stress Relaxation in Power Plant Components Based on a Constitutive Model

2017 ◽  
Author(s):  
Y. Kostenko ◽  
K. Naumenko
Keyword(s):  
Power Plant ◽  
Stress Relaxation ◽  
Constitutive Model ◽  
Evolution Equations ◽  
Material Behavior ◽  
Assessment Procedure ◽  
Reliable Prediction ◽  
Inelastic Material ◽  
Plant Components

Many power plant components and joint connections are subjected to complex thermo-mechanical loading paths under severe temperature environments over a long period. An important part in the lifetime assessment is the reliable prediction of stress relaxation using improved creep modeling to avoid possible integrity or functionality issues and malfunction in such components. The aim of this work is to analyze the proposed constitutive model for advanced high chromium steels with the goal of predicting stress relaxation over the long term. The evolution equations of the constitutive model for inelastic material behavior are introduced to account for hardening and softening phenomena. The material properties were identified for 9–12%CrMoV steels in the creep range. The model is applied to the stress relaxation analysis of power plant components. The results for long-term assessment, which are encouragingly close to reality, will be presented and discussed. An outlook on further developments of the model and assessment procedure is also provided.

Tensile Ductility of Ultra-Fine Grained Copper at High Strain Rate

2010 ◽  
Vol 160-162 ◽  
pp. 260-266 ◽  
Author(s):  
Tao Suo ◽  
Kui Xie ◽  
Yu Long Li ◽  
Feng Zhao ◽  
Qiong Deng
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
Testing Machine ◽  
Coarse Grained ◽  
Dislocation Dynamic ◽  
Pressing Method ◽  
Fine Grained ◽  
Angular Pressing ◽  
Split Hopkinson

In this paper, ultra-fine grained copper fabricated by equal channel angular pressing method and annealed coarse grained copper were tensioned under both quasi-static and dynamic loading conditions using an electronic universal testing machine and the split Hopkinson tension bar respectively. The rapture surface of specimen was also observed via a Scanning Electron Microscope (SEM). The experimental results show that the ductility of polycrystalline copper decreases remarkably due to the grain refinement. However, with the increase of applied strain rate, ductility of the UFG-Cu is enhanced. The fracture morphologies also give the evidence of enhanced ductility of UFG-Cu at high strain rate. It is believed the enhanced ductility of UFG materials at high strain rate can be attributed to the restrained dislocation dynamic recovery.

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