Effects of misalignment on the pre-macroyield region of the uniaxial stress-strain curve

Christ, Bruce W

doi:10.1007/bf02665424

Cited by 17 publications

(12 citation statements)

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“…Numerical prediction for the limits of the scatter band according to equations such as (30) require the determination of the bending error (ACb/Atc) at conditions corresponding to the (tensile and compressive) peaks of stress/strain in the fatigue test. This is not current practice, and therefore reported values of percent bending [ 15-1 71 or the so-called "precision of alignment" [ 18,191 at arbitrary elastic-loading conditions are of little value. The present work suggests that there should be a reappraisal of the British Standard BS 7270:1990 [20] and ASTM Standards E606-80 and It can be seen that equations (24) to (30) predict that there will be no effect on fatigue life due to a non-reversed bending (angular or lateral offsets, Fig.…”

Section: Discussionmentioning

confidence: 91%

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The Influence of Load Misalignment During Uniaxial Low‐cycle Fatigue Testing—i: Modelling

Kandil

Dyson

1993

Fatigue Fract Eng Mat Struct

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A quantitative model has been proposed which predicts the extent of lifetime scatter in low-cycle fatigue due to the influence of bending caused by load misalignment. The main components of the model are the mechanism of bending, the type of extensometer used to control strain and the fatigue characteristics of the material being assessed. Three mechanisms of bending have been studied and it is F. A. KANDIL and B. F. DYWN tb = maximum bending strain tbx = bending strain at point x cbe = maximum bending strain at axial compressive peak strain tb, = maximum bending strain at axial tensile peak strain cC = control-strain amplitude t, = strain amplitude at point x L,, = strain amplitude at the centre of testpiece t , = maximum strain amplitude t2 = minimum strain amplitude A6 = strain range Atb = bending strain range ( = t b t f k ) = control-strain range Act = elastic strain range AcP = plastic strain range Au = stress range ub =bending stress 8 = angle in the circular cross-section between the intersections of the maximum bending plane and the extensometer plane

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Section: Discussionmentioning

confidence: 91%

“…(18) In this case the maximum and minimum strain amplitudes become t I = t, + (tb -tbx) and t2 = t, -(6b + tbx), respectively. Substituting equation (1 5) and noting that t, = t,, then 61 = 6 , + t b ( 1 -cos 8 ) -€2 = 6, -tb( 1 + cos 0).…”

Section: Single Extensometermentioning

confidence: 98%

The Influence of Load Misalignment During Uniaxial Low‐cycle Fatigue Testing—i: Modelling

Kandil

Dyson

1993

Fatigue Fract Eng Mat Struct

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“…Transverse and rotational misalignment may occur between the specimen's longitudinal axis and the setup's loading axis. This can cause significant bending stresses, invalidating the assumed stress and strain state [58,61,[63][64][65] and possibly leading to premature failure.…”

Section: Design Principlementioning

confidence: 99%

On-wafer time-dependent high reproducibility nano-force tensile testing

Bergers¹,

Hoefnagels²,

Geers³

2014

J. Phys. D: Appl. Phys.

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Time-dependent mechanical investigations of on-wafer specimens are of interest for improving the reliability of thin metal film microdevices. This paper presents a novel methodology, addressing key challenges in creep and anelasticity investigations through on-wafer tensile tests, achieving highly reproducible force and specimen deformation measurements and loading states. The methodology consists of a novel approach for precise loading using a pinin-hole gripper and a high-precision specimen alignment system based on three-dimensional image tracking and optical profilometry resulting in angular alignment of <0.1 mrad and near-perfect co-linearity. A compact test system enables in situ tensile tests of on-wafer specimens under light and electron microscopy. Precision force measurement over a range of 0.07 µN to 250 mN is realized based on a simple drift-compensated elastically-hinged load cell with high-precision deflection measurement. The specimen deformation measurement, compensated for drift through image tracking, yields displacement reproducibility of <6 nm. Proof of principle tensile experiments are performed on 5 µm-thick aluminum-alloy thin film specimens, demonstrating reproducible Young's modulus measurement of 72.6 ± 3.7 GPa. Room temperature creep experiments show excellent stability of the force measurement and underline the methodology's high reproducibility and suitability for time-dependent nanoforce tensile testing of on-wafer specimens.

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“…Function F 2 is surely much more difficult to achieve, and an efficient misalignment adjustment also appears strictly related to the satisfaction of the technical requirements cited above. The first option to be considered was to make use of a spherical coupling: 16 in this case, the specimen should be connected to a hemispherical collar. Such a solution could be acceptable, as it is able to prevent any bending contribution, but it does have two serious drawbacks.…”

Section: Conceptual Design and Final Construction Of The Loading‐consmentioning

confidence: 99%

A New Loading-Constraining Device for Mechanical Testing With Misalignment Auto-Compensation

Olmi

2010

Experimental Techniques

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ABSTRACT. Experimental testing represents the basic approach for mechanical characterization. Due to the high costs for test execution, the research is often developed with the collaboration of several laboratories, finally collating al the results. At this stage problems may arise due to data scattering, often due to (lateral or angular) misalignments between the fixed and the moving machine crossheads. The object of this work is to manufacture and experimentally validate a novel loading-constraining device for misalignment compensation. Conceptual design is applied to investigate on the optimal technical solution. The developed device achieves misalignment reduction with the use of a thrust bearing with sphered housing washers. The bearing is mounted under one of the specimen heads: the inverted orientation of the upper ring, allowing relative lateral displacement between the two rings, and the spherical shape of the washer compensate for offset and angular misalignments. Experimental results showed that such misalignments are respectively reduced to less than 0.02 mm and 0.05°, while the bending strain is lowered to just 6% of the nominal one, so that requirements in different standards for mechanical testing can be fulfilled.

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Effects of misalignment on the pre-macroyield region of the uniaxial stress-strain curve

Cited by 17 publications

References 1 publication

The Influence of Load Misalignment During Uniaxial Low‐cycle Fatigue Testing—i: Modelling

The Influence of Load Misalignment During Uniaxial Low‐cycle Fatigue Testing—i: Modelling

On-wafer time-dependent high reproducibility nano-force tensile testing

A New Loading-Constraining Device for Mechanical Testing With Misalignment Auto-Compensation

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