Design of a Micro Tensile Testing Structure to Restrain Non-Axial Alignment Errors

Accurate mechanical properties measurements in the micro scale are very important for the design and the fail-safe analysis of MEMS. And the tensile test, as one of the micromechanical experimental techniques, has the advantage of uniform stress and strain fields. In this paper, a new tensile testing structure is presented to solve the non-axial alignment problem in microscale tensile test. The testing structure integrates the specimen and the suspended spring beams on a chip. The function of the additional spring beams is to balance the non-axial loading component and so the specimen is uniaxial tensile. As the spring constant of the tensile specimen in the axial direction is much smaller than the spring constant of the testing structure in the vertical direction, the spring beams could specimen caused by non-axial force. Meanwhile, the spring constant of the specimen in axial direction is much larger than that of the spring beams in the same direction so that the loading shared in the spring beams can be ignored. The performance of the tensile testing structure is confirmed by FE simulations. When the loading force has 2° angle with the axial direction, the stress distribution of the specimen is almost identical with that of under axial loading. The axial stress of the specimen is considerably uniform. That is to say the specimen is uniaxially tensile, although the loading direction is offset the axial. And the force shared in the suspended spring beams is below 3.2% of the loading force. The tensile testing structure could greatly weaken the errors caused by disalignment, and would have big potential to be used in the microscale tensile test.

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Mechanical Properties of Kevlar® KM2 Single Fiber

Journal of Engineering Materials and Technology ◽

10.1115/1.1857937 ◽

2005 ◽

Vol 127 (2) ◽

pp. 197-203 ◽

Cited By ~ 195

Author(s):

Ming Cheng ◽

Weinong Chen ◽

Tusit Weerasooriya

Keyword(s):

Isotropic Material ◽

Axial Stress ◽

Axial Loading ◽

Strain Range ◽

Transversely Isotropic ◽

Axial Direction ◽

Strain Response ◽

Transversely Isotropic Material ◽

Stress Strain ◽

Strain Behavior

Kevlar® KM2 fiber is a transversely isotropic material. Its tensile stress-strain response in the axial direction is linear and elastic until failure. However, the overall deformation in the transverse directions is nonlinear and nonelastic, although it can be treated linearly and elastically in infinitesimal strain range. For a linear, elastic, and transversely isotropic material, five material constants are needed to describe its stress-strain response. In this paper, stress-strain behavior obtained from experiments on a single Kevlar KM2 fiber are presented and discussed. The effects of loading rate and the influence of axial loading on transverse and transverse loading on axial stress-strain responses are also discussed.

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Biomechanical and Elastographic Analysis of Mesenchymal Stromal Cell Treated Tissue Following Surgery

Journal of Biomechanical Engineering ◽

10.1115/1.4001382 ◽

2010 ◽

Vol 132 (7) ◽

Cited By ~ 1

Author(s):

Hazel Marie ◽

Yong Zhang ◽

Jeremy Heffner ◽

Heath A. Dorion ◽

Diana L. Fagan

Keyword(s):

Mechanical Property ◽

Tensile Test ◽

Tensile Testing ◽

Recovery Period ◽

Strain Analysis ◽

Biomechanical Properties ◽

Uniaxial Tensile ◽

Uniaxial Tensile Test ◽

Ongoing Research ◽

Uniaxial Tensile Testing

Hernia repair continues to be a problem facing surgeons today, particularly because of the high incidence of reoccurrence. This work presents preliminary data of a pioneering effort to investigate the effect of mesenchymal stromal cells (MSCs) on mechanical property enhancement in full thickness fascial defects. Heparinized MSCs harvested from a rabbit’s tibia/iliac crest were applied to two fascial defects on the rabbit’s abdominal wall, with two other defects acting as controls (no MSCs added). After an 8 week recovery period, the entire abdominal fascia was harvested for mechanical property testing and elastographic strain analysis. Preliminary results from uniaxial tensile testing indicate a significant increase in the modulus of toughness strain energy, with at least a 50% increase in the MSC treated defects as compared with the control defects. Results from the elastographic strain analysis show excellent correlation in the calibration of the elastography to the uniaxial tensile test, with nearly identical moduli of elasticity. In addition, the elastographs clearly show tissue property heterogeneity at all stages of tensile testing. The MSC treated tissue demonstrates promise of enhanced material properties over that of the nontreated tissue; testing and analysis is ongoing. The elastography provides pixel-level description of tissue property variations providing critical information on wound healing effectiveness that would be impossible with other methods. In the ongoing research, optical elastography, in combination with the traditional tensile test and tissue histology, will be used to characterize localized biomechanical properties directly within the defect area and to locate “crack” initiation and propagation sights as the material is strained to rupture.

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Influence of Lode Angle on the ASME Local Strain Failure Criterion

Volume 5: High-Pressure Technology; Rudy Scavuzzo Student Paper Symposium and 24th Annual Student Paper Competition; ASME Nondestructive Evaluation, Diagnosis and Prognosis Division (NDPD); Electric Power Research Institute (EPRI) Creep Fatigue Workshop ◽

10.1115/pvp2016-63067 ◽

2016 ◽

Author(s):

Kumarswamy Karpanan ◽

William Thomas

Keyword(s):

Experimental Data ◽

Stress State ◽

Tensile Testing ◽

Failure Strain ◽

Axial Stress ◽

Equivalent Stress ◽

Ductile Material ◽

Uniaxial Tensile ◽

Lode Angle ◽

Triaxiality Factor

Failure strain at any point on a structure is not a constant but is a function of several factors, such as stress state, strain rate, and temperature. Failure strain predicted from the uniaxial tensile testing cannot be applied to the bi-axial or tri-axial stress state. ASME Sec VIII-Div-2, and −3 codes give methods to predict the failure strain for multi-axial stress state by considering the triaxiality factor, which is defined as the ratio of mean stress to the equivalent stress. Failure strain predicted by the ASME method (based on the Rice-Tracey ductile failure model) is an exponential curve that relates the failure strain to the triaxiality factor. The ASME VIII-3 method also gives procedures to calculate failure strain for various material types: ferritic, stainless steel, nickel alloy, aluminum, etc. Experimental results of failure strain at various stress states show that the failure strain is not only a function of the triaxiality factor, but also a function of the Lode angle. The Lode angle takes on the value of 1, 0, and −1 for tension, pure shear, and compression stress state, respectively. Experimental data shows that the failure strain is a 3D surface which has an exponential relation with triaxiality and a parabolic relation with the Lode angle. To validate the ASME failure strain prediction, this paper compares experimental failure strain test data from literature with the ASME predictions. The ASME predictions are non-conservative especially for moderately ductile materials such as aluminum and high strength carbon steel. A reduction factor on failure strain for low ductile material is presented using the relation between the R (yield/ultimate) and the stress ratio (shear/tensile stress). The ASME method does not account for the environmental effects while calculating the failure strain. High pressure, high temperature (HPHT) subsea components designed using ASME VIII-3 code are subjected to various environments in subsea, such as seawater, seawater with cathodic protection (CP) and production fluid (crude oil). Experimental data shows that the Elongation (EL) and/or Reduction in Area (RA) from tensile testing decrease in these environments. Therefore, to account for any environment effect on the failure strain, reduced EL and RA can be used to predict the failure strain.

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Numerical Simulations and Experimental Results of Tensile Test Behavior of Laser Butt Welded DP980 Steels

Journal of Engineering Materials and Technology ◽

10.1115/1.2969256 ◽

2008 ◽

Vol 130 (4) ◽

Cited By ~ 44

Author(s):

S. K. Panda ◽

N. Sreenivasan ◽

M. L. Kuntz ◽

Y. Zhou

Keyword(s):

Tensile Test ◽

Numerical Simulations ◽

Tensile Testing ◽

High Strength Steels ◽

High Strength ◽

Experimental Results ◽

Uniaxial Tensile ◽

Vehicle Performance ◽

Soft Zone ◽

Uniaxial Tensile Testing

Laser welding of advanced high strength steels for fabrication of tailor welded blanks is of increasing interest for continued improvements in vehicle performance and safety without an increase in weight. Experimental results have shown that formability of welded dual-phase (DP) steels is significantly reduced by the formation of a softened region in the heat-affected zone (HAZ). In this study, a finite element simulation of welded DP980 samples undergoing transverse uniaxial tensile testing was used to evaluate the effects of soft zone width and strength on formability characteristics. Both the strength and the ductility of laser welded blanks decreased compared with those of unwelded blanks due to the formation of a softened outer-HAZ, where strain localization and final fracture occurred during tensile testing. The magnitude of softening and the width of the HAZ depend on the laser specific energy. It was observed from tensile test experiments and numerical simulations that both a decrease in strength and an increase in width of the softened HAZ were responsible for a decrease in the overall strength and ductility of the welded blanks.

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Tensile Testing for Determining Sheet Formability

10.31399/asm.tb.tt2.t51060101 ◽

2004 ◽

pp. 101-114

Keyword(s):

Tensile Test ◽

Plane Strain ◽

Sheet Metal ◽

Tensile Testing ◽

Large Family ◽

Uniaxial Tensile ◽

Uniaxial Tensile Test ◽

Accurate Indication ◽

Complex Shapes ◽

Sheet Formability

Abstract Sheet metal forming operations consist of a large family of processes, ranging from simple bending to stamping and deep drawing of complex shapes. Because sheet forming operations are so diverse in type, extent, and rate, no single test provides an accurate indication of the formability of a material in all situations. However, as discussed in this chapter, the uniaxial tensile test is one of the most widely used tests for determining sheet metal formability. This chapter describes the effect of material properties and temperature on sheet metal formability. Information on the types of formability tests is also provided. The chapter discusses the processes involved in uniaxial and plane-strain tensile testing. Examples include the uniaxial tensile test and the plane-strain tensile test which are subsequently described.

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Numerical Simulation of Failure Mode and Crack Propagation of Marble with Pre-Existing Fissure

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.236-237.153 ◽

2012 ◽

Vol 236-237 ◽

pp. 153-157

Author(s):

Wei Song

Keyword(s):

Numerical Simulation ◽

Laboratory Experiments ◽

Axial Stress ◽

Vertical Direction ◽

Axial Loading ◽

Particle Flow Code ◽

Propagation Mode ◽

Particle Model ◽

Bonded Particle Model ◽

Joint Contact

Laboratory experiments and numerical simulations, using Particle Flow Code (PFC2D ), were performed to study the behavior of marble under tri-axial loading and pre-existing fissure uniaxial compression. The laboratory tri-axial compression results of marble was analyzed, and the calibration of the micro-properties of BMP (Bonded particle model ) in PFC2D with the test data was carried out successfully. The pre-existing fissure was simulated by smooth joint contact, and the cracking propagation mode of pre-existing fissure was carried out with the calibrated BMP properties and single smooth joint contact. The simulation show that the tensile crack firstly initiated along the vertical direction to pre-existing fissure, and then gradually departs towards the direction of axial stress, and finally develops along the direction of axial during compression. The numerical simulation coincide with our understanding of fracture mechanics.

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