Mechanical Behavior of Sn1Ag0.5Cu and Sn3Ag0.5Cu Alloys at High Strain Rates

2012 ◽  
Author(s):  
Pradeep Lall ◽  
Sandeep Shantaram ◽  
Jeff Suhling ◽  
David Locker
Keyword(s):  
Strain Rate ◽  
High Speed ◽  
Prolonged Exposure ◽  
High Strain ◽  
Split Hopkinson Pressure Bar ◽  
Image Correlation ◽  
Constitutive Behavior ◽  
Strain Rates ◽  
High Strain Rates ◽  
Test Technique

Electronics may experience high strain rates when subjected to high g-loads of shock and vibration. Material and damage behavior of electronic materials at high strain rates typical of shock and vibration is scarce. Previously studies have shown that second-level interconnects have a high propensity for failure under shock and vibration loads in fine pitch electronics. Exposure to shock and vibration is common in a variety of consumer environments such as automotive and portable electronics. The low strain-rate properties of commonly used SnAgCu solders, including Sn1Ag0.5Cu and Sn3Ag0.5Cu, have been found to evolve with time after prolonged exposure to high temperatures. High strain rate properties of leadfree solder alloys in the strain-rate range of 1–100 sec−1 are scarce. Previous attempts at characterizing the high strain rates properties have focused on the use of the Split Hopkinson Pressure Bar (SHPB), which enables measurements of strain rates in the neighborhood of 1000 per sec. In this paper, a new test-technique developed by the authors has been presented for measurement of material constitutive behavior. The instrument enables attaining strain rates in the neighborhood of 1 to 100 per sec. Tests are conducted at strain rates 10, 35 and 50 per sec. High speed cameras operating at 75,000 fps have been used in conjunction with digital image correlation for the measurement of full-field strain during the test. Constancy of cross-head velocity has been demonstrated during the test from the unloaded state to the specimen failure. Solder alloy constitutive behavior has been measured for SAC105, SAC305 solders. Non-linear Ramberg-Osgood model has been used to fit the material data. The Ramberg-Osgood model available in Abaqus has been used for tensile test simulation and to correlate with DIC based experimental strain data.

Experimental Studies of the Behaviour at High Strain Rates of Unfilled and Filled Polypropylenes

2006 ◽  
Vol 3-4 ◽  
pp. 363-368 ◽  
Author(s):  
N. Temimi ◽  
Noelle Billon
Keyword(s):  
Strain Rate ◽  
High Speed ◽  
High Strain ◽  
Experimental Studies ◽  
Young Modulus ◽  
Video Camera ◽  
Image Correlation ◽  
Strain Rates ◽  
High Strain Rates ◽  
Low Velocity

Thermo mechanical behaviour of unfilled and filled polypropylenes are studied in tension from 10-4 to 102 s-1. Complementary low velocity compression and shear tests are also performed. A high-speed video camera (up to 2500 frames/s) combined with image analysis, image correlation and an infra red pyrometer allow measuring 3D-strain fields and temperature during tests. Thus, data can be processed without restrictive assumptions. Beside usual (for polymers) temperature and strain rate sensitivities it is found that plastic deformation in these materials does not obey incompressibility assumption. Voiding damage is evidenced in the polymer matrix by SEM observations that result in volume change and significant decrease in Young modulus for both materials. Moreover, an increase in the temperature of more than 10 °C is observed and is likely to modify the behaviour of each material at high strain rates. Shear and compression measurements demonstrate that yield criteria and constitutive equation depend on loading. It is concluded that apparent yield stress in semi-crystalline polypropylene can be a result of a combination of “non strain rate sensitive” “non-cohesive mechanisms” and “strain rate sensitive” “cohesive mechanisms”. Experimental characterisation on polymers should then be revisited as most of the usual assumptions are invalid and non monotonic tests should be generalized.

Constitutive Behavior of SAC Leadfree Alloys at High Strain Rates

2011 ◽  
Author(s):  
Pradeep Lall ◽  
Sandeep Shantaram ◽  
Mandar Kulkarni ◽  
Geeta Limaye ◽  
Jeff Suhling
Keyword(s):  
Constitutive Model ◽  
Solder Alloy ◽  
Failure Modes ◽  
High Strain ◽  
Image Correlation ◽  
Constitutive Behavior ◽  
Strain Rates ◽  
Mechanical Shock ◽  
High Strain Rates ◽  
Test Technique

Electronic products are subjected to high G-levels during mechanical shock and vibration. Failure-modes include solder-joint failures, pad cratering, chip-cracking, copper trace fracture, and underfill fillet failures. The second-level interconnects may be experience high-strain rates and accrue damage during repetitive exposure to mechanical shock. Industry migration to leadfree solders has resulted in proliferation of a wide variety of solder alloy compositions. Few of the popular tin-silver-copper alloys include Sn1Ag0.5Cu and Sn3Ag0.5Cu. The high strain rate properties of leadfree solder alloys are scarce. Typical material tests systems are not well suited for measurement of high strain rates typical of mechanical shock. Previously, high strain rates techniques such as the Split Hopkinson Pressure Bar (SHPB) can be used for strain rates of 1000 per sec. However, measurement of materials at strain rates of 1–100 per sec which are typical of mechanical shock is difficult to address. In this paper, a new test-technique developed by the authors has been presented for measurement of material constitutive behavior. The instrument enables attaining strain rates in the neighborhood of 1 to 100 per sec. High speed cameras operating at 300,000 fps have been used in conjunction with digital image correlation for the measurement of full-field strain during the test. Constancy of cross-head velocity has been demonstrated during the test from the unloaded state to the specimen failure. Solder alloy constitutive behavior has been measured for SAC105, and SAC305 solders. Constitutive model has been fit to the material data. Samples have been tested at various time under thermal aging at 25°C and 125°C. The constitutive model has been embedded into an explicit finite element framework for the purpose of life-prediction of leadfree interconnects. Test assemblies has been fabricated and tested under JEDEC JESD22-B111 specified condition for mechanical shock. Model predictions have been correlated with experimental data.

Stress–Strain Behavior of SAC305 at High Strain Rates

2015 ◽  
Vol 137 (1) ◽  
Author(s):  
Pradeep Lall ◽  
Sandeep Shantaram ◽  
Jeff Suhling ◽  
David Locker
Keyword(s):  
Constitutive Model ◽  
Solder Alloy ◽  
High Strain ◽  
Image Correlation ◽  
Lead Free ◽  
Constitutive Behavior ◽  
Strain Rates ◽  
Mechanical Shock ◽  
High Strain Rates ◽  
Test Technique

Electronic products are subjected to high G-levels during mechanical shock and vibration. Failure-modes include solder-joint failures, pad cratering, chip-cracking, copper trace fracture, and underfill fillet failures. The second-level interconnects may be experience high strain rates and accrue damage during repetitive exposure to mechanical shock. Industry migration to lead-free solders has resulted in proliferation of a wide variety of solder alloy compositions. One of the popular tin-silver-copper alloys is Sn3Ag0.5Cu. The high strain rate properties of lead-free solder alloys are scarce. Typical material tests systems are not well suited for measurement of high strain rates typical of mechanical shock. Previously, high strain rates techniques such as the split Hopkinson pressure bar (SHPB) can be used for strain rates of 1000 s−1. However, measurement of materials at strain rates of 1–100 s−1 which are typical of mechanical shock is difficult to address. In this paper, a new test-technique developed by the authors has been presented for measurement of material constitutive behavior. The instrument enables attaining strain rates in the neighborhood of 1–100 s−1. High-speed cameras operating at 300,000 fps have been used in conjunction with digital image correlation (DIC) for the measurement of full-field strain during the test. Constancy of crosshead velocity has been demonstrated during the test from the unloaded state to the specimen failure. Solder alloy constitutive behavior has been measured for SAC305 solder. Constitutive model has been fit to the material data. Samples have been tested at various time under thermal aging at 25 °C and 125 °C. The constitutive model has been embedded into an explicit finite element framework for the purpose of life-prediction of lead-free interconnects. Test assemblies has been fabricated and tested under Joint Electron Device Engineering Council (JEDEC) JESD22-B111 specified condition for mechanical shock. Model predictions have been correlated with experimental data.

A Dynamic Mechanical Analysis of T2 Copper at High Strain Rates

2019 ◽  
Vol 812 ◽  
pp. 38-44
Author(s):  
Shuai Chen ◽  
Wen Bin Li ◽  
Xiao Ming Wang ◽  
Wen Jin Yao
Keyword(s):  
Yield Strength ◽  
Strain Rate ◽  
High Strain ◽  
Split Hopkinson Pressure Bar ◽  
Pure Copper ◽  
Dislocation Slip ◽  
Strain Rates ◽  
High Strain Rates ◽  
Stress Strain ◽  
Shpb Test

This work compares the pure copper (T2 copper)’s stress-strain relationship at different strain rates in the uni-axial tension test and Split Hopkinson Pressure Bar (SHPB) test. Small samples were utilized in the high strain rate SHPB test in which the accuracy was modified by numerical simulation. The experimental results showed that the T2 copper’s yield strength at high strain rates largely outweighed the quasi static yield strength. The flow stress in the stress-strain curves at different strain rates appeared to be divergent and increased with the increase in strain rates, showing great strain strengthening and strain rate hardening effects. Metallographic observation showed that the microstructure of T2 copper changed from equiaxed grains to twins and the interaction between the dislocation slip zone grain boundary and twins promoted the super plasticity distortion in T2 copper.

Compressive Behavior of Plain and Fiber-Reinforced High-Strength Concrete Subjected to High Strain Rate Loading

2011 ◽  
Vol 82 ◽  
pp. 57-62 ◽  
Author(s):  
Sha Sha Wang ◽  
Min Hong Zhang ◽  
Ser Tong Quek
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
High Strength Concrete ◽  
High Strain ◽  
Split Hopkinson Pressure Bar ◽  
High Strength ◽  
Strain Rates ◽  
Compressive Behavior ◽  
High Strain Rates ◽  
Strength Concrete

This paper presents a laboratory experimental study on the effect of high strain rate on compressive behavior of plain and fiber-reinforce high-strength concrete (FRHSC) with similar strength of 80-90 MPa. Steel fibers, polyethylene fibers, and a combination of these were used in the FRHSC. A split Hopkinson pressure bar equipment was used to determine the concrete behavior at strain rates from about 30 to 300 s-1. The ratio of the strength at high strain rates to that at static loading condition, namely dynamic increase factor (DIF), of the concretes was determined and compared with that recommended by CEB-FIP code. Fracture patterns of the specimens at high strain rates are described and discussed as well. Results indicate that the CEB-FIP equation is applicable to the plain high strength concrete, but overestimates the DIF of the FRHSC at strain rates beyond a transition strain rate of 30 s-1. Based on the experimental results, a modified equation on DIF is proposed for the FRHSC.

Dynamic Testing at High Strain Rates of AZ31 Magnesium Alloys on SHPB Equipment

2013 ◽  
Vol 303-306 ◽  
pp. 2648-2651
Author(s):  
Xu Qing Chang ◽  
Tie Hua Ma
Keyword(s):  
Strain Rate ◽  
Optical Microscopy ◽  
Strain Hardening ◽  
High Strain ◽  
Split Hopkinson Pressure Bar ◽  
Mg Alloy ◽  
Strain Rates ◽  
Hopkinson Pressure Bar ◽  
High Strain Rates ◽  
Az31 Mg Alloy

The mechanical behaviour of as-cast AZ31 Mg alloy has been investigated at strain rates up to 2.0×103s-1. Dynamic tests were carried out at room temperature using a Split Hopkinson Pressure Bar (SHPB) apparatus. Microstructural characteristic were analysed by Image MAT A1 optical microscopy. The results demonstrated that AZ31 Mg alloy exhibited obvious yield phenomena and strain hardening behaviour at high strain rates. The basically same curvature of stress-strain curves exhibited an similar strain hardening rate. The dynamic yield strength changes little and the peak stress increases with the strain rates. An examination by optical microscopy after high strain rate deformation reveals the occurrence of twinning and twin area percentage increases with the strain rate increasing.

Influence of Temperature and Strain Rate on the Mechanical Behaviour of Aluminium Alloy AA6060

2014 ◽  
Vol 794-796 ◽  
pp. 520-525
Author(s):  
Vincent Vilamosa ◽  
Arild H. Clausen ◽  
Odd Sture Hopperstad ◽  
Tore Børvik ◽  
Svein Skjervold
Keyword(s):  
Strain Rate ◽  
High Speed ◽  
High Strain ◽  
True Strain ◽  
Constitutive Models ◽  
Local Deformation ◽  
Minor Effect ◽  
Strain Rates ◽  
High Strain Rates ◽  
A Minor

In an attempt to improve the constitutive models for 6xxx aluminium alloys at high temperatures and high strain rates, a comprehensive test series has been carried out for AA6060. Uniaxial tension tests were performed at various strain rates from 0.01 s-1to 1000 s-1and temperatures from 20 °C to 350 °C. The tests were carried out using a standard tensile machine for low to moderate strain rates and a split-Hopkinson tension bar (SHTB) system for high strain rates. In both cases, an induction apparatus was used to heat the sample while local deformation measurements were obtained with a high-speed camera and used to estimate the true strain beyond necking. Strong coupling between the influence of strain rate and temperature on the stress-strain behaviour was found. At room temperature, the strain rate has a minor effect on the behaviour of AA6060. On the other hand, a significant increase of the yield stress and work-hardening with strain-rate is observed for temperatures above (K), being the melting temperature; i.e., above 673 K.

Approaches to Synchronise Conventional Measurements with Optical Techniques at High Strain Rates

2011 ◽  
Vol 70 ◽  
pp. 75-80 ◽  
Author(s):  
Duncan A. Crump ◽  
Janice M. Dulieu-Barton ◽  
Marco L. Longana
Keyword(s):  
Polymer Composites ◽  
High Speed ◽  
High Strain ◽  
Image Correlation ◽  
Test Machine ◽  
Strain Rates ◽  
High Strain Rates ◽  
Optical Techniques ◽  
Specific Loading ◽  
Military Applications

Polymer composites are increasingly being used in high-end and military applications, mainly due to their excellent tailorability to specific loading scenarios and strength/stiffness to weight ratios. The overall purpose of the research project is to develop an enhanced understanding of the behaviour of fibre reinforced polymer composites when subjected to high velocity loading. This is particularly important in military applications, where composite structures are at a high risk of receiving high strain rate loading, such as those resulting from collisions or blasts. The work described here considers an approach that allows the collection of full-field temperature and strain data to investigate the complex viscoelastic behaviour of composite material at high strain rates. To develop such a data-rich approach digital image correlation (DIC) is used to collect the displacement data and infra-red thermography (IRT) is used to collect temperature data. The use of optical techniques at the sampling rates necessary to capture the behaviour of composites subjected to high loading rates is novel and requires using imaging systems at the far extent of their design specification. One of the major advantages of optical techniques is that they are non-contact; however this also forms one of the challenges to their application to high speed testing. The separate camera systems and the test machine/loading system must be synchronised to ensure that the correct strain/temperature measurement is correlated with the correct temporal value of the loading regime. The loading rate exacerbates the situation where even at high sampling rates the data is discrete and therefore it is difficult to match values. The work described in the paper concentrates on investigating the possibility of the high speed DIC and synchronisation. The limitations of bringing together the techniques are discussed in detail, and a discussion of the relative merits of each synchronisation approach is included, which takes into consideration ease of use, accuracy, repeatability etc.

Dynamic Characteristics of the Sinter-Forged Cu-Cr Alloys with the Variation of Chrome Content

2006 ◽  
Vol 116-117 ◽  
pp. 255-258
Author(s):  
Jung Han Song ◽  
Hoon Huh
Keyword(s):  
Dynamic Response ◽  
Dynamic Characteristics ◽  
High Speed ◽  
High Strain ◽  
Split Hopkinson Pressure Bar ◽  
Testing Machine ◽  
Impact Behavior ◽  
Stress Wave Propagation ◽  
Strain Rates ◽  
High Strain Rates

This paper is concerned with the dynamic characteristics of sinter-forged Cu–Cr alloy for various strain-rates. The amount of the chrome content is varied from 10 %wt to 30 %wt in order to investigate the influence of the chrome content on the dynamic characteristics. The dynamic response at the corresponding level of strain-rate should be obtained with an adequate experimental technique and corresponding apparatus due to the inertia effect and the stress wave propagation. In this paper, the high speed tensile testing machine is utilized in order to identify the dynamic response of the Cu–Cr alloy at the intermediate strain-rates and the split Hopkinson pressure bar is used at the high strain-rates. Experimental results from both the quasi-static and the high strain-rates up to the 5000/s are interpolated with respect to the amount of the chrome content in order to construct the Johnson–Cook and the modified Johnson–Cook model as the constitutive relation for numerical simulation of the dynamic impact behavior of electrodes.

Material Behaviors of PBX Simulant with Various Strain Rates

2013 ◽  
Vol 535-536 ◽  
pp. 117-120 ◽  
Author(s):  
Chung Hee Park ◽  
Seh Wan Jeong ◽  
Hoon Huh ◽  
Jung Su Park
Keyword(s):  
Strain Hardening ◽  
High Speed ◽  
High Strain ◽  
Split Hopkinson Pressure Bar ◽  
Testing Machine ◽  
Materials Testing ◽  
Strain Rates ◽  
High Strain Rates ◽  
Material Behaviors ◽  
Compressive Tests

This paper is concerned with the material behaviors of PBX(Polymer Bonded eXplosive) simulant at various strain rates ranging from 0.0001/sec to 3150/sec. Material behaviors of PBX at the high strain rates are important in the prediction of deformation modes of PBX in a warhead which undergoes severe impact loading. Inert PBX stimulant which has analogous material behaviors with PBX was utilized for material tests due to safety issues. Uniaxial compressive tests at quasi-static and intermediate strain rates were conducted with cylindrical specimen using a dynamic materials testing machine, INSTRON 8801. Uniaxial compressive tests at high strain rates ranging from 1200/sec to 3150/sec were conducted using a split Hopkinson pressure bar. Deformation behaviors were investigated using captured images obtained from a high-speed camera. The strain hardening behaviors of PBX simulant were formulated by proposed strain rate-dependent strain hardening model.

Sign in / Sign up

Export Citation Format

Share Document