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%.

Stress-Strain Behavior of an Aluminum Alloy Under Transient Strain-Rates

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Y. W. Kwon ◽  
Y. Esmaeili ◽  
C. M. Park
Keyword(s):  
Aluminum Alloy ◽  
Strain Rate ◽  
Fracture Strain ◽  
Strain Curve ◽  
Strain Rates ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Single Strain ◽  
Transient Strain ◽  
Strain Rate Loading

Because most structures are subjected to transient strain-rate loading, an experimental study was conducted to investigate the stress-strain behaviors of an aluminum alloy undergoing varying strain-rate loading. To this end, uniaxial tensile loading was applied to coupons of dog-bone shape such that each coupon underwent two or three different strain-rates, i.e., one rate after another. As a basis, a series of single-strain-rate tests was also conducted with strain-rates of 0.1–10.0 s−1. When the material experienced multistrain-rate loading, the stress-strain curves were significantly different from any single-strain-rate stress-strain curve. The strain-rate history affected the stress-strain curves under multistrain-rate loading. As a result, some simple averaging of single-strain-rate curves did not predict the actual multistrain-rate stress-strain curve properly. Furthermore, the fracture strain under multistrain-rate loading was significantly different from that under any single-strain-rate case. Depending on the applied strain-rates and their sequences, the former was much greater or less than the latter. A technique was proposed based on the residual plastic strain and plastic energy density in order to predict the fracture strain under multistrain-rate loading. The predicted fracture strains generally agreed well with the experimental data. Another observation that was made was that the unloading stress-strain curve was not affected by the previous strain-rate history.

scholarly journals Experimental Study on Biaxial Dynamic Compressive Properties of ECC

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1257
Author(s):  
Shuling Gao ◽  
Guanhua Hu
Keyword(s):  
Strain Rate ◽  
Lateral Pressure ◽  
Deformation Modulus ◽  
Strain Curve ◽  
Peak Stress ◽  
Pressure Level ◽  
Strain Rates ◽  
Peak Strain ◽  
Stress Strain Curve ◽  
Toughness Index

An improved hydraulic servo structure testing machine has been used to conduct biaxial dynamic compression tests on eight types of engineered cementitious composites (ECC) with lateral pressure levels of 0, 0.125, 0.25, 0.5, 0.7, 0.8, 0.9, 1.0 (the ratio of the compressive strength applied laterally to the static compressive strength of the specimen), and three strain rates of 10−4, 10−3 and 10−2 s−1. The failure mode, peak stress, peak strain, deformation modulus, stress-strain curve, and compressive toughness index of ECC under biaxial dynamic compressive stress state are obtained. The test results show that the lateral pressure affects the direction of ECC cracking, while the strain rate has little effect on the failure morphology of ECC. The growth of lateral pressure level and strain rate upgrades the limit failure strength and peak strain of ECC, and the small improvement is achieved in elastic modulus. A two-stage ECC biaxial failure strength standard was established, and the influence of the lateral pressure level and peak strain was quantitatively evaluated through the fitting curve of the peak stress, peak strain, and deformation modulus of ECC under various strain rates and lateral pressure levels. ECC’s compressive stress-strain curve can be divided into four stages, and a normalized biaxial dynamic ECC constitutive relationship is established. The toughness index of ECC can be increased with the increase of lateral pressure level, while the increase of strain rate can reduce the toughness index of ECC. Under the effect of biaxial dynamic load, the ultimate strength of ECC is increased higher than that of plain concrete.

scholarly journals Strain-Rate and Grain‒Size Effects in Ice

1987 ◽  
Vol 33 (115) ◽  
pp. 274-280 ◽  
Author(s):  
David M. Cole
Keyword(s):  
Grain Size ◽  
Strain Rate ◽  
Transition Point ◽  
Boundary Migration ◽  
Peak Stress ◽  
Strain Rates ◽  
Thin Sections ◽  
Fine Grained ◽  
Lower Strain ◽  
Polycrystalline Ice

AbstractThis paper presents and discusses the results of constant deformation-rate tests on laboratory-prepared polycrystalline ice. Strain-rates ranged from 10−7to 10−1s−1, grain–size ranged from 1.5 to 5.8 mm, and the test temperature was −5°C.At strain-rates between 10−7and 10−3s−1, the stress-strain-rate relationship followed a power law with an exponent ofn= 4.3 calculated without regard to grain-size. However, a reversal in the grain-size effect was observed: below a transition point near 4 × 10−6s−1the peak stress increased with increasing grain-size, while above the transition point the peak stress decreased with increasing grain-size. This latter trend persisted to the highest strain-rates observed. At strain-rates above 10−3s−1the peak stress became independent of strain-rate.The unusual trends exhibited at the lower strain-rates are attributed to the influence of the grain-size on the balance of the operative deformation mechanisms. Dynamic recrystallization appears to intervene in the case of the finer-grained material and serves to lower the peak stress. At comparable strain-rates, however, the large-grained material still experiences internal micro-fracturing, and thin sections reveal extensive deformation in the grain-boundary regions that is quite unlike the appearance of the strain-induced boundary migration characteristic of the fine-grained material.

The effect of strain rates on tensile deformation of ultrafine-grained copper

2017 ◽  
Vol 31 (16-19) ◽  
pp. 1744014
Author(s):  
M. Li ◽  
Q. W. Jiang
Keyword(s):  
Strain Rate ◽  
Deformation Behavior ◽  
Room Temperature ◽  
Tensile Deformation ◽  
Strain Rates ◽  
Roll Bonding ◽  
Fracture Elongation ◽  
Tensile Deformation Behavior ◽  
Ultrafine Grained ◽  
Flow Stress Level

Tensile deformation behavior of ultrafine-grained (UFG) copper processed by accumulative roll-bonding (ARB) was studied under different strain rates at room temperature. It was found that the UFG copper under the strain rate of 10[Formula: see text] s[Formula: see text] led to a higher strength (higher flow stress level), flow stability (higher stress hardening rate) and fracture elongation. In the fracture surface of the sample appeared a large number of cleavage steps under the strain rate of 10[Formula: see text] s[Formula: see text], indicating a typical brittle fracture mode. When the strain rate is 10[Formula: see text] or 10[Formula: see text] s[Formula: see text], a great amount of dimples with few cleavage steps were observed, showing a transition from brittle to plastic deformation with increasing strain rate.

Local Investigations of the Mechanical Properties of Ultrafine Grained Metals by Nanoindentations

2006 ◽  
Vol 503-504 ◽  
pp. 31-36 ◽  
Author(s):  
Johannes Mueller ◽  
Karsten Durst ◽  
Dorothea Amberger ◽  
Matthias Göken
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Room Temperature ◽  
Rate Sensitivity ◽  
Strain Rates ◽  
Fcc Metals ◽  
Angular Pressing ◽  
Ultrafine Grained ◽  
Indentation Strain

The mechanical properties of ultrafine-grained metals processed by equal channel angular pressing is investigated by nanoindentations in comparison with measurements on nanocrystalline nickel with a grain size between 20 and 400 nm produced by pulsed electrodeposition. Besides hardness and Young’s modulus measurements, the nanoindentation method allows also controlled experiments on the strain rate sensitivity, which are discussed in detail in this paper. Nanoindentation measurements can be performed at indentation strain rates between 10-3 s-1 and 0.1 s-1. Nanocrystalline and ultrafine-grained fcc metals as Al and Ni show a significant strain rate sensitivity at room temperature in comparison with conventional grain sized materials. In ultrafine-grained bcc Fe the strain rate sensitivity does not change significantly after severe plastic deformation. Inelastic effects are found during repeated unloading-loading experiments in nanoindentations.

Constitutive Modeling for Elevated Temperature Flow Behavior of ZHMn34-2-2-1 Manganese Brass

2017 ◽  
Vol 872 ◽  
pp. 30-37
Author(s):  
Meng Han Wang ◽  
Kang Wei ◽  
Xiao Juan Li
Keyword(s):  
Constitutive Model ◽  
Strain Rate ◽  
Flow Behavior ◽  
Peak Stress ◽  
Strain Rates ◽  
Hollomon Parameter ◽  
Prediction Ability ◽  
Absolute Relative Error ◽  
Deformation Behaviors ◽  
State Stress

The hot compressive deformation behaviors of ZHMn34-2-2-1 manganese brass are investigated on Thermecmastor-Z thermal simulator over wide processing domain of temperatures (923K-1073K) and strain rates (0.01s-1-10s-1). The true stress-strain curves exhibit a single peak stress, after which the stress monotonously decreases until a steady state stress occurs, indicating a typical dynamic recrystallization. A revised constitutive model coupling flow stress with strain, strain rate and deformation temperature is established with the material constants expressed by polynomial fitting of strain. Moreover, better prediction ability of the constitutive model is achieved by implementation of a simple approach for modified the Zener-Hollomon parameter considering the compensation of strain rate and temperature increment. By comparing the predicted and experimented values, the correlation coefficient and mean absolute relative error are 0.997 and 2.363%, respectively. The quantitative statistical results indicate that the proposed constitutive model can precisely characterize the hot deformation behavior of ZHMn34-2-2-1 manganese brass.

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.

Failure Criterion for Varying Strain Rates

2010 ◽  
Author(s):  
Kian Sing Tan ◽  
Young W. Kwon
Keyword(s):  
Aluminum Alloy ◽  
Structural Material ◽  
Strain Rate ◽  
Failure Criterion ◽  
Loading Condition ◽  
Strain Rates ◽  
Main Question ◽  
Loading Conditions ◽  
Failure Envelopes ◽  
Strain Rate Loading

Strain rate affects the behaviors of engineering structural materials, such as metals and composites, in terms of their stiffness and strength. In particular, yield and failure strengths and strains depend on the strain rate applied to the materials. When a structural material is subjected to a typical dynamic loading, the material usually undergoes various strain rate loading conditions. Then, the main question is whether the material is going to fail or not. To the authors’ best knowledge, there has been no failure criterion proposed for a varying strain rate loading condition. This paper presents a failure criterion under non-uniform strain rate conditions. Experiments were also conducted to support the proposed failure criterion using aluminum alloy AA3003-H14. This study also investigated the failure envelopes in terms of strain rates and the normalized failure strengths. Furthermore, evaluations of various stressstrain relations under different strain rate loading conditions were also undertaken.

Effects of Continuous Strain Rate Changing on Environmental Fatigue for Stainless Steels in PWR Environment

2010 ◽  
Author(s):  
Yuichiro Nomura ◽  
Seiji Asada ◽  
Takao Nakamura ◽  
Masakazu Tanaka
Keyword(s):  
Fatigue Life ◽  
Strain Rate ◽  
Water Environment ◽  
Sine Wave ◽  
Fatigue Tests ◽  
Integral Model ◽  
Strain Rates ◽  
Test Results ◽  
Approach Method ◽  
The Difference

The strain rates in actual transients of operating plants are not constant and changing momentarily. A large number of fatigue tests under stepwise strain rate changing conditions were performed to develop a method for evaluating fatigue life under varying strain rate conditions. Based on these test results, a strain base integral model known as the named the modified rate approach method was developed and verified. However it was reported recently that in the case of sine wave fatigue tests in BWR environment, the fatigue life was two to six times longer than the fatigue life predicted by the modified rate approach method. For this paper, in order to confirm whether the same tendency is observed in PWR environment, fatigue tests of sine wave were performed of SS316 in simulated PWR water environment. As the result, the difference of fatigue life by sine wave test reported in BWR environment was not observed between experimental and predicted life in PWR environment and the modified rate approach method was applicable under continuous strain rate changing condition.

Strain rate sensitivity of a mild steel at room temperature and strain rates of up to 105s−1

1980 ◽  
Vol 15 (4) ◽  
pp. 201-207 ◽  
Author(s):  
M S J Hashmi
Keyword(s):  
Finite Difference ◽  
Mild Steel ◽  
Strain Rate ◽  
Strain Hardening ◽  
Strain Rate Sensitivity ◽  
Elastic Strain ◽  
Room Temperature ◽  
Numerical Technique ◽  
Rate Sensitivity ◽  
Strain Rates

Experimental results on a mild steel are reported from ballistics tests which gave rise to strain rates of up to 105 s−1. A finite-difference numerical technique which incorporates material inertia, elastic-strain hardening and strain-rate sensitivity is used to establish the strain-rate sensitivity constants p and D in the equation, σ4 = σ1 (1+(∊/D)1/ p). The rate sensitivity established in this study is compared with those reported by other researchers.

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