A Theoretical Consideration of the Strength of Snow

AbstractA consideration of possible expressions for the number and size of bonds intersected by a potential failure surface leads to the following expression for the strength of snow, σf, which is age-hardening at a constant porosity n: where σi is the strength of ice, tf is the time at failure, α is a parameter specifically related to the mechanism of bonding, and ω is a temperature-dependent parameter. Allowing tf to become infinite provides the envelope of maximum strength for fully age-hardened snow at any porosity n.

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A Theoretical Consideration of the Strength of Snow

Journal of Glaciology ◽

10.1017/s0022143000019146 ◽

1966 ◽

Vol 6 (43) ◽

pp. 159-170 ◽

Cited By ~ 15

Author(s):

G. E. H. Ballard ◽

E. D. Feldt

Keyword(s):

Theoretical Consideration ◽

Failure Surface ◽

Maximum Strength ◽

Age Hardening ◽

Temperature Dependent ◽

Dependent Parameter ◽

Potential Failure ◽

Image Position

AbstractA consideration of possible expressions for the number and size of bonds intersected by a potential failure surface leads to the following expression for the strength of snow,σf, which is age-hardening at a constant porosityn:whereσiis the strength of ice,tfis the time at failure,αis a parameter specifically related to the mechanism of bonding, andωis a temperature-dependent parameter. Allowingtfto become infinite provides the envelope of maximum strength for fully age-hardened snow at any porosityn.

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Predicting Fusing Current for Encapsulated Wire Bonds under Transient Loads

International Symposium on Microelectronics ◽

10.4071/isom-2010-wa4-paper5 ◽

2010 ◽

Vol 2010 (1) ◽

pp. 000486-000493 ◽

Cited By ~ 1

Author(s):

Aditi Mallik ◽

Roger Stout

Keyword(s):

Single Pulse ◽

Element Model ◽

Current Response ◽

Temperature Dependent ◽

Wire Bonds ◽

Potential Failure ◽

Different Dimensions ◽

Transient Loads ◽

The Wire ◽

Set Up

For high power IC chips, as device size inevitably decreases, the wire diameter unfortunately must decrease due to the need of finer pitch wires. Fusing or melting of wirebonds thus increasingly becomes one of the potential failure issues for such IC's. Experiments were performed under transient loads on dummy packages having aluminum, gold, or copper wires of different dimensions. A finite element model was constructed that correlates very well with the observed maximum operating currents for such wirebonds under actual experimental test conditions. A qualitative observation of typical current profiles, as fusing conditions were approached, was that current would reach a maximum value very early in the pulse, and then fall gradually. One goal achieved through the modeling was to show that the current in the wire falls with time due to the heating of the wire material. Correspondingly, the wire reaches the melting temperature not at the peak current but rather at the end of pulse. Further, modeling shows that knowledge of external resistance and inductance of the experimental set up are highly significant in determining the details of a fusing event, but if known along with the temperature-dependent wire properties, the simulation can predict the correct voltage and current response of the part with 2% error. On the other hand, lack of external circuit characteristics may lead to completely incorrect results. For instance, the assumption that current is constant until the wire heats to fusing temperature, or that current and temperature both rise monotonically to maximum values until the wire fuses, are almost certain to be wrong. The work has been carried out for single pulse events as well as pulse trains.

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Temperature-dependent nanoindentation response of materials

MRS Communications ◽

10.1557/mrc.2018.19 ◽

2018 ◽

Vol 8 (01) ◽

pp. 15-28 ◽

Cited By ~ 11

Author(s):

Saeed Zare Chavoshi ◽

Shuozhi Xu

Keyword(s):

Temperature Dependent ◽

Image Position

Abstract

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An Efficient 2D Finite Element Procedure for the Quenching Analysis With Phase Change

Journal of Engineering for Industry ◽

10.1115/1.2901626 ◽

1993 ◽

Vol 115 (1) ◽

pp. 124-138 ◽

Cited By ~ 23

Author(s):

K. F. Wang ◽

S. Chandrasekar ◽

H. T. Y. Yang

Keyword(s):

Finite Element ◽

Phase Changes ◽

Age Hardening ◽

Infinite Cylinder ◽

Temperature Dependent ◽

Element Analysis ◽

Practical Applications ◽

Mixed Hardening ◽

Wide Range ◽

Finite Element Procedure

An efficient finite element procedure has been developed for the analysis of quenching problems involving nonisothermal phase changes. The finite element analysis includes temperature dependent material properties, a mixed hardening rule to describe the material constitutive model, and the incorporation of time-temperature-transformation (TTT) diagrams. The procedure is applied to the simulation of quenching of steel cylinders and an aluminum connector with temperature-dependent convection boundary conditions. First, the stress analysis of the quenching of an infinite cylinder is carried out and the predicted distributions of temperature and stresses are compared with an available numerical solution to validate the accuracy of the present formulation and procedure. To demonstrate the predictive capability and practical applicability of the developed procedure, the simulation of quenching of finite cylinders of various length-to-diameter ratios and of a square bar are presented. The role of edge effects and specimen geometry on the residual stress distribution is analyzed. In addition, the microstructures developed during the quenching of 1080 carbon steel cylinders are predicted using TTT diagram incorporated in the analysis. The final example addresses the simulation of age hardening in spray quenched 2024 aluminum connector. The example problems are directly related to many practical applications, such as the heat-treatment of solid piston pins used in automotive engines and the spray quenching of aluminum connector. They also illustrate the wide range of material transformations which can be modeled using the present finite element procedure.

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Numerical Study of Optimal Location of Non-Circular Segmented Failure Surface in Soil Slope With Weak Soil Layer

International Journal of Applied Metaheuristic Computing ◽

10.4018/ijamc.2021010107 ◽

2021 ◽

Vol 12 (1) ◽

pp. 111-141

Author(s):

Navneet Himanshu ◽

Avijit Burman ◽

Vinay Kumar

Keyword(s):

Numerical Study ◽

Soil Layer ◽

Failure Surface ◽

Detailed Comparison ◽

Global Optimum ◽

Weak Soil ◽

Critical Failure Surface ◽

Potential Failure ◽

Swarm Size ◽

Contemporary Standard

The article addresses stability analysis of complicated slopes having weak soil layer sandwiched between two strong layers. The search for critical failure surface and associated optimum/minimum factor of safety (FOS) among all potential failure surfaces can be posed as an optimization problem. Two different variants of particle swarm optimization (PSO) models, namely inertia weight-based PSO (IW-PSO) and contemporary standard PSO (CS-PSO), are used to obtain optimum global solution. Detailed comparison between the global optimum solutions obtained from two PSO variants and the effect of swarm size is studied. The performance of IW-PSO and CS-PSO are studied by observing the convergence behavior of the respective algorithms with respect to iteration count. The influence of velocity clamping on the optimized solution is investigated and its use is found beneficial as it prevents the solution from overflying the region with global best solution. The studies related to swarm diversity demonstrating the exploitation and exploration behaviors of the algorithms are also presented.

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Metallurgy for SiC Die Attach for Operation at 500°C

Additional Conferences (Device Packaging HiTEC HiTEN & CICMT) ◽

10.4071/hitec-rwjohnson-ta13 ◽

2010 ◽

Vol 2010 (HITEC) ◽

pp. 000008-000017 ◽

Cited By ~ 4

Author(s):

Ping Zheng ◽

Phillip Henson ◽

R. Wayne Johnson ◽

Liangyu Chen

Keyword(s):

High Temperature ◽

Thick Film ◽

Failure Surface ◽

Nano Particle ◽

Test Results ◽

Shear Tests ◽

Die Attach ◽

Film Layer ◽

Potential Failure ◽

Dc Bias

Metallurgy for high temperature SiC die attach involves the substrate metallization, die metallization, and die attach material. This paper examines off-eutectic Au-Sn as the die attach alloy with a PtAu thick film metallization on AlN substrates. A pure Au thick film layer was printed over the PtAu thick film layer. The SiC backside metallizations evaluated were Ti/TaSi/Pt/Au and Cr/NiCr/Au. Die shear tests were performed after aging at 500°C and after thermal cycling. The shear test results and failure surface analysis are discussed. Nanoparticle Ag and liquid transient phase bonding with Ag based metallurgies have been proposed for high temperature die attach. Data on the migration of sintered nano-particle Ag and thin film Ag dc bias during storage in air at 300°C and 375°C are presented. Migration of Ag is a potential failure mechanism for Ag based high temperature metallurgies.

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The luminescence thermometry based on analysing of 3P0-3H5 emission band of Pr3+ ions in Pr3+:LiYF4 nanoparticles and microparticles

EPJ Web of Conferences ◽

10.1051/epjconf/201922002011 ◽

2019 ◽

Vol 220 ◽

pp. 02011

Author(s):

Maksim Pudovkin ◽

Stella Korableva ◽

Elena Lukinova ◽

Darya Koryakovtseva ◽

Oleg Morozov ◽

...

Keyword(s):

Temperature Sensitivity ◽

Emission Band ◽

Absolute Temperature ◽

Temperature Dependent ◽

Temperature Range ◽

Dependent Parameter ◽

Luminescence Thermometry

The study is devoted to the possibility of using and Pr3+:LiYF4 microparticles and nanoparticles as luminescent thermometers in the temperature range of 80-320 K. The ratio of luminescence peaks corresponding to the transitions from the 3P0 state to two Stark sublevels of the 3H5 state of Pr3+ ions is considered as a temperature-dependent parameter. This system demonstrates an absolute temperature sensitivity of 0.0009 K-1 at a temperature of 185 K.

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ON θ VALUES IN METALS

Canadian Journal of Physics ◽

10.1139/p53-013 ◽

1953 ◽

Vol 31 (1) ◽

pp. 147-164 ◽

Cited By ~ 20

Author(s):

V. M. Kelly ◽

D. K. C. MacDonald

Keyword(s):

Data Analysis ◽

Specific Heat ◽

Characteristic Temperature ◽

Temperature Dependent ◽

Specific Heat Data ◽

Debye Theory ◽

Dependent Parameter ◽

Mathematical Derivation ◽

Sodium And Potassium ◽

Heat Data

Following a discussion of specific heat theories, it is suggested that, despite its limitations, the Debye theory is the most useful representation for general analysis. Four methods of calculating θD, the Debye characteristic temperature, are presented; specific heat data of lithium, sodium, and potassium are then analyzed and also compared with similar calculations of θR from resistance measurements made over a wide temperature range. It is shown that more realistic values of θ are obtained when θ is recognized as a temperature-dependent parameter in the mathematical derivation of the relevant equations. It appears that a considerable amount of useful information may be obtained from data analysis in this way.

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Ultimate Capacity Analysis and Determination of the Position of Failure Surface for Uplift Piles

Mathematical Problems in Engineering ◽

10.1155/2014/540143 ◽

2014 ◽

Vol 2014 ◽

pp. 1-6 ◽

Cited By ~ 1

Author(s):

Qian Su ◽

Xiaoxi Zhang ◽

Pingbao Yin ◽

Wenhui Zhao

Keyword(s):

Limit Equilibrium ◽

Failure Surface ◽

Equilibrium Analysis ◽

Soil Parameters ◽

Uplift Capacity ◽

Ultimate Capacity ◽

Potential Failure ◽

Coulomb Failure Criterion ◽

Slice Method

Ultimate capacity and failure surface position of uplift piles are dependent on soil parameters. In this paper, the horizontal slice method is used to discuss the relation among the ultimate uplift capacity, the failure surface position, and soil parameters with Mohr-Coulomb failure criterion. According to the limit equilibrium analysis, the ultimate uplift capacity is calculated by dividing soil around the pile into slices with considering the potential failure surface as a group of several sectional planes. Then the multivariate function used to calculate ultimate capacity is established and optimized by the sequential quadratic programming. Through the numerical calculation and comparison with the previous research, the results show that the method is reasonable and effective and can be used to determine the failure surface and the magnitude of the ultimate capacity of uplift piles.

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