scholarly journals The behaviour of a single crystal of aluminium under alternating torsional stresses while immersed in a slow stream of tap water

1932 ◽  
Vol 135 (827) ◽  
pp. 392-411 ◽  
Keyword(s):  
Single Crystal ◽  
Fatigue Test ◽  
Corrosion Fatigue ◽  
Tap Water ◽  
Present Report ◽  
Cycle Number ◽  
Corrosion Fatigue Crack ◽  
Mechanical Methods ◽  
Wide Range ◽  
Number Of Cycles

The characteristics of the deformation and fracture of metals under repeated cycles of stress, generally described as “fatigue phenomena,” have received very considerable attention, both experimental and theoretical. Usually, consideration has been devoted exclusively to conditions in which the metal subjected to fatigue has its free surface exposed to the ordinary atmosphere. In many cases in actual practice, however, metals are subjected to fatigue action while surrounded by a fluid—either gaseous or liquid—which is of a corrosive nature and the endurance or “life” of the metal is controlled by the simultaneous conjoint action of the applied stresses and the corrosive agent. To such conditions the term “corrosion-fatigue” has been applied. Attention was first directed to this aspect of fatigue phenomena in 1917 by Haigh, who demonstrated experimentally that, in general, fatigue stresses and corrosive influences may be mutually accelerative, producing more destructive effects than either influence when acting separately, or when the stressing is applied subsequent to the corrosion stage. The subject then appeared to escape further attention for a period of about nine years, after which the results of the first of a series of important researches were published; in this connection reference should be made to the work of Lehmann, McAdam, Speller, McCorkle and Mumma, Binnie, Fuller, Haigh and Jones, etc. From the researches of these investigators, and particularly from those of McAdam, a very large amount of data is now available regarding the corrosion-fatigue resistance of a wide range of metals and alloys, and the separate effects of such variables as frequency of stress cycle, number of cycles, corrosion time, applied range of stress, etc., also of corrosion inhibitors and accelerators. No attention has apparently been given hitherto to the changes in microstructure occurring during a corrosion-fatigue test and, as a result, no information existed on such fundamental points as (i) the general course of a corrosion-fatigue crack; whether intercrystalline or transcrystalline; (ii) the actual point of initiation of the crack; whether it is situated at a crystal boundary, or on the site of previous slip bands, or at local corrosion pits bearing no distinct relation to these special positions. In planning a research with these general objects in view it was decided to make experiments, under corrosion-fatigue conditions, on ( a ) a single crystal, ( b ) a specimen consisting of two large crystals with the separating boundary, and ( c ) a specimen consisting of the usual finely-divided aggregate of crystals. By using single crystals and large crystal specimens and employing X-ray, microscopical and mechanical methods, it was hoped to correlate corrosion-fatigue phenomena with the fine structure. The present report describes the observations made on what is believed to be the first corrosion-fatigue test on a single crystal.

SnAgCu Micro-Ball Grid Array (BGA) Solder Joint Evaluation Using a Torsion Mechanical Fatigue Test Method

2005 ◽  
Author(s):  
Claire Ryan ◽  
Bryan A. Rodgers ◽  
Jeff M. Punch
Keyword(s):  
Fatigue Test ◽  
Solder Joints ◽  
Fatigue Testing ◽  
Ball Grid Array ◽  
Test Method ◽  
Superior Performance ◽  
Cycle Number ◽  
Mechanical Fatigue ◽  
Number Of Cycles ◽  
Cycles To Failure

Due to the hazard which lead poses to health and the environment the EU is banning its use in electrical and electronic equipment from July 2006. This ban along with the market drive to more environmentally friendly products means that tin-lead solders must be replaced with lead-free alternatives. This paper presents the results of an experimental investigation of the mechanical fatigue properties of tin-silver-copper (SnAgCu) solder joints with a baseline of tin-lead (SnPb). The test vehicle comprised of an 8-layer FR4 printed circuit board (PCB) mounted with four micro-ball grid array (BGA) components — each with a total of 100 solder balls in a 10×10 array. The solder joints were formed using surface mount reflow processes optimised for both solder types. A torsion mechanical fatigue test was employed to evaluate the solder joints — the principle of which was to stress the solder joints repetitively in order to determine the number of cycles to failure. The BGA components were daisy-chained — the resistance across each daisy-chain was monitored continuously during the cyclic defection of the test board. A profile of the increase in resistance with cycle number was established and the number of cycles to failure determined. The failure mechanism induced by the cycling was examined using cross-section and scanning electron microscopy (SEM) techniques. The results for SnAgCu joints show a superior performance during torsion mechanical fatigue testing than SnPb joints; giving a greater number of cycles to failure. The results from the tests presented in this paper show that the torsion test method provides a viable alternative to ATC as a qualification method for solder joints, while also providing substantial time savings — taking weeks rather than months to complete.

scholarly journals In vitro cell cycle oscillations exhibit a robust and hysteretic response to changes in cytoplasmic density

2021 ◽  
Author(s):  
Minjun Jin ◽  
Franco Tavella ◽  
Shiyuan Wang ◽  
Qiong Yang
Keyword(s):  
Cell Cycle ◽  
Oscillatory Behavior ◽  
Cycle Number ◽  
Biochemical Processes ◽  
Cellular Processes ◽  
Wide Range ◽  
A Cell ◽  
Xenopus Egg ◽  
Number Of Cycles

Cells control the properties of the cytoplasm to ensure the proper functioning of biochemical processes. Recent studies showed that the density of the cytoplasm varies in both physiological and pathological states of cells undergoing growth, division, differentiation, apoptosis, senescence, and metabolic starvation. Little is known about how cellular processes cope with these cytoplasmic variations. Here we study how a cell cycle oscillator comprising cyclin-dependent kinase (CDK1) responds to cytoplasmic density changes by systematically diluting or concentrating a cycling Xenopus egg cytoplasm in cell-like microfluidic droplets. We found that the cell cycle maintains robust oscillations over a wide range of deviations from the endogenous density by as low as 0.2x to more than 1.22x. A further dilution or concentration from these values will arrest the system in a low or high steady-state of CDK1 activity, respectively. Interestingly, diluting a concentrated arrested cytoplasm recovers its oscillatory behavior but requires a significantly lower concentration than 1.22x. Thus, the cell cycle switches reversibly between oscillatory and stable steady states at distinct thresholds depending on the direction of density tuning, forming a hysteresis loop. We recapitulated these observations by a mathematical model. The model predicted that Wee1 and Cdc25 positive feedback do not contribute to the observed robustness, confirmed by experiments. Nevertheless, modulating these feedback strengths and cytoplasmic density changes the total number of cycles, revealing a new role of Wee1 and Cdc25 in controlling the cycle number of early embryonic extracts. Our system can be applied to study how cytoplasmic density affects other cellular processes.

scholarly journals A review study on Corrosion Fatigue and its related testing methodologies

2019 ◽  
Vol 2 (1) ◽  
Author(s):  
Farshad Abbasi
Keyword(s):  
Fatigue Test ◽  
Corrosion Fatigue ◽  
Crack Detection ◽  
Fatigue Testing ◽  
Fatigue Behavior ◽  
International Standards ◽  
Mechanical Degradation ◽  
Damage Mechanisms ◽  
Corrosion Fatigue Crack ◽  
Set Up

Corrosion Fatigue is the mechanical degradation of a material under the joint action of damage mechanisms corrosion and fatigue. Corrosive nature of the seawater puts severe durability requirements on materials of which are often exposed to corrosion fatigue and abrasive conditions simultaneously. Therefore, identification of the combined effects of both corrosion and fatigue damage mechanisms is necessary to improve predictive models for the corrosion fatigue phenomenon. Present article is the result of a desktop study (scientific literature and standards) with the aim of study the feasibility of designing and manufacturing of a corrosion fatigue testing set-up that would allow the designer to compare the performance of different materials exposed to corrosion fatigue, permitting also the comparison with results from dry fatigue testing. The corrosion fatigue mechanism is described in more detail and a short presentation of some typical lab-scale corrosion fatigue test setups is given. This is followed by illustration of international standards and guidelines which will be used to design a new corrosion fatigue test set-up for evaluating the fatigue behavior of material in seawater environment. Finally the experimental techniques for corrosion fatigue crack detection and propagation along with the fundamental basic of corrosion fatigue modeling are illustrated.

Fatigue Test for Thick Wire Bonds

2014 ◽  
Author(s):  
Turker Dagdelen ◽  
Karim El-Rayes ◽  
Sangtak Park ◽  
Mahmoud Khater ◽  
Resul Saritas ◽  
...  
Keyword(s):  
Fatigue Test ◽  
Mechanical Load ◽  
Life Time ◽  
Wheatstone Bridge ◽  
Wire Bonds ◽  
Power Modules ◽  
Wide Range ◽  
Bonding Wires ◽  
Number Of Cycles ◽  
Thick Wire

Thick bonding wires used in power modules experience a wide range of temperature and mechanical load cycling conditions. This leads to cracks at the wire heel due to fatigue. In this study, a new type of thick wire bonds, Aluminum coated copper, was subjected to fatigue test to investigate its durability. Unlike traditional thermal cycling, this test involves applying a pattern of repetitive prescribed displacements to a wire foot while fatigue failure is detected via a Wheatstone bridge. The aim is to compare different wire materials to the number-of-cycles-to-failure, thereby quantifying the reliability and life time of thick wire bond.

Mechanical Properties and Dislocation Structure of Single Crystal Cdte Deformed in Compression at 300°C

1976 ◽  
Vol 34 ◽  
pp. 592-593
Author(s):  
Ernest L. Hall ◽  
J. B. Vander Sande
Keyword(s):  
Mechanical Properties ◽  
Single Crystal ◽  
Dislocation Structure ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Strain Curve ◽  
Optical Devices ◽  
Semiconductor Compound ◽  
Wide Range ◽  
Sample Orientation

The present paper describes research on the mechanical properties and related dislocation structure of CdTe, a II-VI semiconductor compound with a wide range of uses in electrical and optical devices. At room temperature CdTe exhibits little plasticity and at the same time relatively low strength and hardness. The mechanical behavior of CdTe was examined at elevated temperatures with the goal of understanding plastic flow in this material and eventually improving the room temperature properties. Several samples of single crystal CdTe of identical size and crystallographic orientation were deformed in compression at 300°C to various levels of total strain. A resolved shear stress vs. compressive glide strain curve (Figure la) was derived from the results of the tests and the knowledge of the sample orientation.

Epitaxial ferroelectric thin films

1994 ◽  
Vol 52 ◽  
pp. 572-573
Author(s):  
S. G. Ghonge ◽  
E. Goo ◽  
R. Ramesh ◽  
R. Haakenaasen ◽  
D. K. Fork
Keyword(s):  
Single Crystal ◽  
Work Function ◽  
Nonvolatile Memory ◽  
Ferroelectric Properties ◽  
Electrical Contact ◽  
Memory Devices ◽  
Ferroelectric Films ◽  
Si Substrates ◽  
Electro Optic ◽  
Wide Range

Microstructure of epitaxial ferroelectric/conductive oxide heterostructures on LaAIO3(LAO) and Si substrates have been studied by conventional and high resolution transmission electron microscopy. The epitaxial films have a wide range of potential applications in areas such as non-volatile memory devices, electro-optic devices and pyroelectric detectors. For applications such as electro-optic devices the films must be single crystal and for applications such as nonvolatile memory devices and pyroelectric devices single crystal films will enhance the performance of the devices. The ferroelectric films studied are Pb(Zr0.2Ti0.8)O3(PLZT), PbTiO3(PT), BiTiO3(BT) and Pb0.9La0.1(Zr0.2Ti0.8)0.975O3(PLZT).Electrical contact to ferroelectric films is commonly made with metals such as Pt. Metals generally have a large difference in work function compared to the work function of the ferroelectric oxides. This results in a Schottky barrier at the interface and the interfacial space charge is believed to responsible for domain pinning and degradation in the ferroelectric properties resulting in phenomenon such as fatigue.

Magnetic Quantum Oscillations from Surface States of Bi Nanowires

2011 ◽  
Vol 1350 ◽  
Author(s):  
L. A. Konopko ◽  
T. E. Huber ◽  
A. A. Nikolaeva
Keyword(s):  
Single Crystal ◽  
Low Temperatures ◽  
Surface States ◽  
Charge Carriers ◽  
Quantum Oscillations ◽  
Wide Range ◽  
Spin Orbit Interactions ◽  
Conducting Tube ◽  
Magnetic Quantum Oscillations ◽  
Strong Spin

ABSTRACTIn this work, we report the results of studies of the transverse magnetoresistance (MR) of single-crystal Bi nanowires with diameter d<80 nm. The single-crystal nanowire samples were prepared by the Taylor-Ulitovsky technique. Due to the semimetal-to-semiconductor transformation and high density of surface states with strong spin-orbit interactions, the charge carriers are confined to the conducting tube made of surface states. The non monotonic changes of transverse MR that are equidistant in a direct magnetic field were observed at low temperatures in a wide range of magnetic fields up to 14 T. The period of oscillations depends on the wire diameter d as for the case of longitudinal MR. An interpretation of transverse MR oscillations is presented.

The Effect of Distraction on Schizophrenic Performance (2) Psychomotor Ability

1965 ◽  
Vol 111 (474) ◽  
pp. 391-398 ◽  
Author(s):  
Andrew McGhie ◽  
James Chapman ◽  
J. S. Lawson
Keyword(s):  
Present Report ◽  
Sensory Modality ◽  
Preceding Paper ◽  
Auditory Distraction ◽  
Psychomotor Tests ◽  
Motor Responses ◽  
Wide Range ◽  
Schizophrenic Patients ◽  
Psychomotor Ability ◽  
Experimental Findings

In the preceding paper the effect of experimental distraction was examined and the findings discussed. The present report is concerned with a similar study of the effect of distraction on tests which involve another aspect of schizophrenic performance, that of psychomotor ability. Earlier studies (Chapman and McGhie, 1961, 1962) produced both clinical and experimental evidence that auditory distraction disrupted the motor responses of some schizophrenic patients. As the previous experimental findings were based on two tests involving only very limited areas of psychomotor performance, it was necessary to examine patients on a wide range of psychomotor tests. A second aim of the present investigation was to assess any differential effects due to variation in the sensory modality of the distracting stimuli.

On The Optimized Nucleation of Near-Single-Crystal Cvd Diamond Film

1995 ◽  
Vol 416 ◽  
Author(s):  
L. C. Chen ◽  
C. C. Juan ◽  
J. Y. Wu ◽  
K. H. Chen ◽  
J. W. Teng
Keyword(s):  
Single Crystal ◽  
Photoelectron Spectroscopy ◽  
Morphological Evolution ◽  
Present Report ◽  
Ex Situ ◽  
Nucleation Density ◽  
Induced Current ◽  
Current Time ◽  
Single Crystal Diamond

ABSTRACTNear-single-crystal diamond films have been obtained in a number of laboratories recently. The optimization of nucleation density by using a bias-enhanced nucleation (BEN) method is believed to be a critical step. However, the condition of optimized nucleation has never been clearly delineated. In the present report, a novel quantitative technique was established to monitor the nucleation of diamond in-situ. Specifically, the induced current was measured as a function of nucleation time during BEN. The timedependence of induced current was studied under various methane concentrations as well as substrate temperatures. The optimized nucleation condition can be unambiguously determined from the current-time plot. Besides the in-situ current probe, ex-situ x-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) were also used to investigate the chemical and morphological evolution. Characteristic XPS and AFM features of optimized nucleation is discussed.

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