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Artykuły w czasopismach na temat "Small scale mechanical testing for material behavior characterization"
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Kathavate, V. S., K. Eswar Prasad, Mangalampalli S. R. N. Kiran i Yong Zhu. "Mechanical characterization of piezoelectric materials: A perspective on deformation behavior across different microstructural length scales". Journal of Applied Physics 132, nr 12 (28.09.2022): 121103. http://dx.doi.org/10.1063/5.0099161.
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Piezoelectric materials (PEMs) find a wide spectrum of applications that include, but are not limited to, sensors, actuators, semiconductors, memory devices, and energy harvesting systems due to their outstanding electromechanical and polarization characteristics. Notably, these PEMs can be employed across several length scales (both intrinsic and extrinsic) ranging from mesoscale (bulk ceramics) to nanoscale (thin films) during their applications. Over the years, progress in probing individual electrical and mechanical properties of PEM has been notable. However, proportional review articles providing the mechanical characterization of PEM are relatively few. The present article aims to give a tutorial on the mechanical testing of PEMs, ranging from the conventional bulk deformation experiments to the most recent small-scale testing techniques from a materials science perspective. The advent of nanotechnology has led materials scientists to develop in situ testing techniques to probe the real-time electromechanical behavior of PEMs. Therefore, this article presents a systematic outlook on ex situ and in situ deformation experiments in mechanical and electromechanical environments, related mechanical behavior, and ferroelectric/elastic distortion during deformation. The first part provides significant insights into the multifunctionality of PEM and various contributing microstructural length scales, followed by a motivation to characterize the mechanical properties from the application's point of view. In the midst, the mechanical behavior of PEM and related mechanical characterization techniques (from mesoscale to nanoscale) are highlighted. The last part summarizes current challenges, future perspectives, and important observations.
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Tao, Ran, Kirk Rice, Anicet Djakeu, Randy Mrozek, Shawn Cole, Reygan Freeney i Aaron Forster. "Rheological Characterization of Next-Generation Ballistic Witness Materials for Body Armor Testing". Polymers 11, nr 3 (8.03.2019): 447. http://dx.doi.org/10.3390/polym11030447.
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Roma Plastilina No. 1 (RP1), an artist modeling clay that has been used as a ballistic clay, is essential for evaluation and certification in standards-based ballistic resistance testing of body armor. It serves as a ballistic witness material (BWM) behind the armor, where the magnitude of the plastic deformation in the clay after a ballistic impact is the figure of merit (known as “backface signature”). RP1 is known to exhibit complex thermomechanical behavior that requires temperature conditioning and frequent performance-based evaluations to verify that its deformation response satisfies requirements. A less complex BWM formulation that allows for room-temperature storage and use as well as a more consistent thermomechanical behavior than RP1 is desired, but a validation based only on ballistic performance would be extensive and expensive to accommodate the different ballistic threats. A framework of lab-scale metrologies for measuring the effects of strain, strain rate, and temperature dependence on mechanical properties are needed to guide BWM development. The current work deals with rheological characterization of a candidate BWM, i.e., silicone composite backing material (SCBM), to understand the fundamental structure–property relationships in comparison to those of RP1. Small-amplitude oscillatory shear frequency sweep experiments were performed at temperatures that ranged from 20 °C to 50 °C to map elastic and damping contributions in the linear elastic regime. Large amplitude oscillatory shear (LAOS) experiments were conducted in the non-linear region and the material response was analyzed in the form of Lissajous curve representations with the values of perfect plastic dissipation ratio reported to identify the degree of plasticity. The results show that the SCBM exhibits dynamic properties that are similar in magnitude to those of temperature-conditioned RP1, but with minimal temperature sensitivity and weaker frequency dependence than RP1. Both SCBM and RP1 are identified as elastoviscoplastic materials, which is particularly important for accurate determination of backface signature in body armor evaluation. The mechanical properties of SCBM show some degree of aging and work history effects. The results from this work demonstrate that the rheological properties of SCBM, at small and large strains, are similar to RP1 with substantial improvements in BWM performance requirements in terms of temperature sensitivity and thixotropy.
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Oliver, W. C., i G. M. Pharr. "Measurement of hardness and elastic modulus by instrumented indentation: Advances in understanding and refinements to methodology". Journal of Materials Research 19, nr 1 (styczeń 2004): 3–20. http://dx.doi.org/10.1557/jmr.2004.19.1.3.
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The method we introduced in 1992 for measuring hardness and elastic modulus by instrumented indentation techniques has widely been adopted and used in the characterization of small-scale mechanical behavior. Since its original development, the method has undergone numerous refinements and changes brought about by improvements to testing equipment and techniques as well as from advances in our understanding of the mechanics of elastic–plastic contact. Here, we review our current understanding of the mechanics governing elastic–plastic indentation as they pertain to load and depth-sensing indentation testing of monolithic materials and provide an update of how we now implement the method to make the most accurate mechanical property measurements. The limitations of the method are also discussed.
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Anton, Hadăr, Baciu Florin, Voicu Andrei-Daniel, Vlăsceanu Daniel, Tudose Daniela-Ioana i Adetu Cătălin. "Mechanical Characteristics Evaluation of a Single Ply and Multi-Ply Carbon Fiber-Reinforced Plastic Subjected to Tensile and Bending Loads". Polymers 14, nr 15 (7.08.2022): 3213. http://dx.doi.org/10.3390/polym14153213.
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Carbon fiber-reinforced composites represent a broadly utilized class of materials in aeronautical applications, due to their high-performance capability. The studied CFRP is manufactured from a 3K carbon biaxial fabric 0°/90° with high tensile resistance, reinforced with high-performance thermoset molding epoxy vinyl ester resin. The macroscale experimental characterization has constituted the subject of various studies, with the scope of assessing overall structural performance. This study, on the other hand, aims at evaluating the mesoscopic mechanical behavior of a single-ply CFRP, by utilizing tensile test specimens with an average experimental study area of only 3 cm2. The single-ply tensile testing was accomplished using a small scale custom-made uniaxial testing device, powered by a stepper motor, with measurements recorded by two 5-megapixel cameras of the DIC Q400 system, mounted on a Leica M125 digital stereo microscope. The single-ply testing results illustrated the orthotropic nature of the CFRP and turned out to be in close correlation with the multi-ply CFRP tensile and bending tests, resulting in a comprehensive material characterization. The results obtained for the multi-ply tensile and flexural characteristics are adequate in terms of CFRP expectations, having a satisfactory precision. The results have been evaluated using a broad experimental approach, consisting of the Dantec Q400 standard digital image correlation system, facilitating the determination of Poisson’s ratio, correlated with the measurements obtained from the INSTRON 8801 servo hydraulic testing system’s load cell, for a segment of the tensile and flexural characteristics determination. Finite element analyses were realized to reproduce the tensile and flexural test conditions, based on the experimentally determined stress–strain evolution of the material. The FEA results match very well with the experimental results, and thus will constitute the basis for further FEA analyses of aeronautic structures.
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Oliver, Warren C., i George M. Pharr. "Nanoindentation in materials research: Past, present, and future". MRS Bulletin 35, nr 11 (listopad 2010): 897–907. http://dx.doi.org/10.1557/mrs2010.717.
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The method we introduced in 1992 for measuring hardness and elastic modulus by nanoindentation testing has been widely adopted and used in the characterization of mechanical behavior at small scales. Since its original development, the method has undergone numerous refinements and changes brought about by improvements to testing equipment and techniques, as well as advances in our understanding of the mechanics of elastic-plastic contact. In this article, we briefly review the history of the method, comment on its capabilities and limitations, and discuss some of the emerging areas in materials research where it has played, or promises to play, an important role.
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Lang, Anna, Oliver Focke i Axel S. Herrmann. "Mechanical Behavior of Loops with Small Diameters". Key Engineering Materials 742 (lipiec 2017): 374–80. http://dx.doi.org/10.4028/www.scientific.net/kem.742.374.
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To meet the comprehensive requirements of lightweight design, a material minded design method will be aimed. A fiber minded solution for load application in fiber reinforced plastics are loop joints, which are mainly applied for introducing high concentrated tensile loads, e.g. in mountings for rotor blades, or in pre-tensioned supporting structures. Usually, these loop joints consist of, diameters in centimeter scale. Miniaturized loop joints with diameters in millimeter scale are applied in transition structures for carbon reinforced plastic-aluminum multi material designs. Factors of miniaturization influencing the mechanical behavior are decoupled for tensile testing. Data from computer tomography provides information on the failure behavior of loop joints. To validate the non-destructive test method microsections will be used.
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Sancaktar, Erol. "Constitutive Behavior and Testing of Structural Adhesives". Applied Mechanics Reviews 40, nr 10 (1.10.1987): 1393–402. http://dx.doi.org/10.1115/1.3149541.
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Material characterization of structural adhesives in the bulk and bonded forms is discussed. Constitutive relations used for describing stress–strain data are reviewed. The difficulties associated with adhesive characterization in the bonded form are cited. Common testing procedures for adhesive characterization in the bulk and bonded forms are reviewed. In presenting the constitutive relations used in material characterization of structural adhesives, deformation theories introduced by Hencky are reviewed first. The modifications made in this theory to render it rate dependent and bilinear are discussed and applications to adhesive characterization are cited. Application of linear viscoelasticity, mechanical model characterization, and its use in describing the dependence of adhesive and cohesive strengths on rate, temperature, and bond thickness are presented. The time–temperature superposition principle and three-dimensional stress–strain relations in integral and differential operator forms are reviewed. Frequent assumptions for dilatation and distortion operations are presented. Procedures for describing nonlinear viscoelastic behavior are reviewed. It is pointed out that the extent of nonlinearity is dependent on both the stress level and the time scale. The use of nonlinear spring and dashpot elements, nonlinear differential operators, and perturbation of elastic and viscous coefficients are cited. Prandtl’s incremental theory of plasticity and its extension in the form of over-stress theory is presented. The incorporation of this over-stress idea into the viscoelastic mechanical model characterization is discussed. The modified Bingham model and the Chase–Goldsmith model developed in this fashion and their application to adhesive material characterization are presented. The use of empirical relations for the description of creep behavior is discussed. Prediction of shear behavior based on bulk tensile data is demonstrated. It is suggested that characterization of adhesive behavior in the bonded form should include the application of stress analysis, fracture mechanics, polymer chemistry and surface analysis techniques. In testing bonded samples the use of thick adherend symmetric single lap geometry or napkin ring test geometry is advised and it is suggested that the specimens should be prepared with the same surface preparation and cure techniques.
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Vogel, D., R. Ku¨hnert, M. Dost i B. Michel. "Determination of Packaging Material Properties Utilizing Image Correlation Techniques". Journal of Electronic Packaging 124, nr 4 (1.12.2002): 345–51. http://dx.doi.org/10.1115/1.1506698.
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Thermo-mechanical reliability in advanced electronic packaging requires new materials testing approaches. The necessary understanding of the impact of very local material stressing on component reliability leads to the need of materials testing and characterization on microscopic scale. For example, defect initiation and propagation in multilayer structures as in WLP and flip chip technology, the influence of material migration to mechanical behavior or defect development in ultra-thin silicon dies often are not well understood. A key for micro materials testing and characterization is the measurement of strains and displacements inside microscopic regions. Correlation techniques (e.g., microDAC, nanoDAC) are one of the promising tools for that purpose. Their application potentials to micro testing for electronic packaging materials are demonstrated in the paper. More in detail, CTE measurement and crack testing are discussed. First attempts for testing under AFM conditions and their results are considered.
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Liu, Dong, Peter Heard, Branko Šavija, Gillian Smith, Erik Schlangen i Peter Flewitt. "Multi-scale characterization and modelling of damage evolution in nuclear Gilsocarbon graphite". MRS Proceedings 1809 (2015): 1–6. http://dx.doi.org/10.1557/opl.2015.433.
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ABSTRACTIn the present work, the microstructure and mechanical properties of Gilsocarbon graphite have been characterized over a range of length-scales. Optical imaging, combined with 3D X-ray computed tomography and 3D high-resolution tomography based on focus ion beam milling has been adopted for microstructural characterization. A range of small-scale mechanical testing approaches are applied including an in situ micro-cantilever technique based in a Dualbeam workstation. It was found that pores ranging in size from nanometers to tens of micrometers in diameter are present which modify the deformation and fracture characteristics of the material. This multi-scale mechanical testing approach revealed the significant change of mechanical properties, for example flexural strength, of this graphite over the length-scale from a micrometer to tens of centimeters. Such differences emphasize why input parameters to numerical models have to be undertaken at the appropriate length-scale to allow predictions of the deformation, fracture and the stochastic features of the strength of the graphite with the required confidence. Finally, the results from a multi-scale model demonstrated that these data derived from the micro-scale tests can be extrapolated, with high confidence, to large components with realistic dimensions.
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Field, J. S., i M. V. Swain. "Determining the mechanical properties of small volumes of material from submicrometer spherical indentations". Journal of Materials Research 10, nr 1 (styczeń 1995): 101–12. http://dx.doi.org/10.1557/jmr.1995.0101.
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The stress/strain behavior of bulk material is usually investigated in uniaxial tension or compression; however, these methods are not generally available for very small volumes of material. Submicrometer indentation using a spherical indenter has the potential for filling this gap with, possibly, access to hardness and elastic modulus profiles, representative stress/strain curves, and the strain hardening index. The proposed techniques are based on principles well established in hardness testing using spherical indenters, but not previously applied to depth-sensing instruments capable of measurements on a submicrometer scale. These approaches are now adapted to the analysis of data obtained by stepwise indentation with partial unloading, a technique that facilitates separation of the elastic and plastic components of indentation at each step and is able to take account of the usually ignored phenomena of “piling up” and “sinking in”.
Rozprawy doktorskie na temat "Small scale mechanical testing for material behavior characterization"
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Mahat, Raj Jung. "Extraction of Creep Parameters from Indentation Creep Experiment: An Artificial Neural Network- Based Approach". Thesis, 2021. https://etd.iisc.ac.in/handle/2005/5685.
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Conventional methods for extracting creep properties require conducting several uniaxial tests at different loads, which consumes an intensive amount of material and time. Indentation may minimize the material volume requirement; however, interpretation of indentation creep data in terms of uniaxial creep response, which is the standard practice, is quite challenging. Artificial neural network (ANN) may be used to obtain uniaxial creep parameters from indentation creep experiments; however, it has never been attempted. Here, we use fully connected sequential multi-layered ANN, trained using finite element (FE) indentation creep simulations, to map the observables (displacement, time) of indentation creep experiments to the corresponding uniaxial creep parameters. A constitutive law that relates the creep strain, 𝜖𝑐𝑟𝑒𝑒𝑝 to stress, 𝜎, and time, t, in form of a power-law (e.g., 𝜖𝑐𝑟𝑒𝑒𝑝 = 𝐴 𝜎𝑛𝑡𝛼) is used. Subsequently, multitude of indentation displacement-time curves are generated by conducting FE simulations with varying creep parameters (i.e., A, n and a) used in the constitutive relationship, while keeping the elastic and plastic properties of the material fixed. An indentation displacement-time (𝑑𝑐𝑟𝑒𝑒𝑝-t) curve obtained through FE simulations is fitted using a relationship comprising power-law and exponential terms in time (e.g., 𝑑𝑐𝑟𝑒𝑒𝑝 = 𝑑0 + 𝑚 𝑡𝑏 + 𝑝 𝑒−𝑐𝑡). The pre- processed fitting parameters, thus obtained, are provided as inputs to the ANN. ANN is trained using a back-propagation algorithm based on a batch gradient descent to map these inputs (i.e., 𝑑0, m, b, p and c) to the corresponding creep parameters (i.e., A, n and 𝛼) used in the FE simulations. Performance of the ANN is improved by optimizing its architecture using the Bayesian optimization approach and varying the fitting function, the parameters of which are the inputs to the ANN. The performance of ANN is evaluated based on its prediction on the validation set (size - 10% of the training set) and the learning is continued till the mean squared error of the prediction becomes ~10−3. Finally, the trained ANN is tested on the indentation creep data obtained by testing commercial purity Pb and its prediction is compared with the uniaxial creep parameters. A decent match between the experimental data and the ANN prediction for stress exponent (i.e., n) and time exponent (i.e., 𝛼) is noted.
Części książek na temat "Small scale mechanical testing for material behavior characterization"
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Trigui, Abdelwaheb. "Techniques for the Thermal Analysis of PCM". W Phase Change Materials - Technology and Applications [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.105935.
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Thermal Energy Storage (TES) technologies based on Phase Change Materials (PCMs) with small temperature differences have effectively promoted the development of clean and renewable energy. Today, accurate thermal characterization is needed to be able to create an optimal design for latent heat storage systems. The thermo-physical properties of PCMs, namely latent heat, phase-change temperatures, enthalpy and specific heat capacity are obtained by means of differential scanning calorimetry (DSC), which is one of the most widely used techniques to study reactions related to the transformation of a material subjected to temperature constraints. This method presents some limitations due, among other things, to the fact that only a very small quantity (less than 90 mg) of material can be tested. Indeed, the small mass samples, taken out of the large testing specimen and out of testing system, is not representative of the thermal behavior of a material on a large scale. The Transient Guarded Hot Plate Technique (TGHPT) presents several advantages when compared to the commercially available thermal analysis methods (DSC, DTA) to determine PCM thermophysical properties. The most significant are large sample amount, optimized measuring time and a simple and economical built up.
Streszczenia konferencji na temat "Small scale mechanical testing for material behavior characterization"
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Hasnine, Mohammad, Muhannad Mustafa, Jing Zou, Jeffrey C. Suhling, Barton C. Prorok, Michael J. Bozack i Pradeep Lall. "Nanomechanical Characterization of Aging Effects in Solder Joints in Microelectronic Packaging". W ASME 2013 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/ipack2013-73234.
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The mechanical properties of a lead free solder are strongly influenced by its microstructure, which is controlled by its thermal history including solidification rate and thermal aging after solidification. Due to aging phenomena, the microstructure, mechanical response, and failure behavior of lead free solder joints in electronic assemblies are constantly evolving when exposed to isothermal and/or thermal cycling environments. Through uniaxial testing of miniature bulk solder tensile specimens, we have previously demonstrated that large changes occur in the stress-strain and creep behaviors of lead free solder alloys with aging. Complementary studies by other research groups have verified aging induced degradations of SAC mechanical properties. In those investigations, mechanical testing was performed on a variety of sample geometries including lap shear specimens, Iosipescu shear specimens, and custom solder ball array shear specimens. While there are clearly aging effects in SAC solder materials, there have been limited prior mechanical loading studies on aging effects in actual solder joints extracted from area array assemblies (e.g. PBGA or flip chip). This is due to the extremely small size of the individual joints, and the difficulty in gripping them and applying controlled loadings (tension, compression, or shear). In the current work, we have explored aging phenomena in actual solder joints by nano-mechanical testing of single SAC305 lead free solder joints extracted from PBGA assemblies. Using nanoindentation techniques, the stress-strain and creep behavior of the SAC solder materials have been explored at the joint scale for various aging conditions. Mechanical properties characterized as a function of aging include the elastic modulus, hardness, and yield stress. Using a constant force at max indentation, the creep response of the aged and non-aged solder joint materials has also been measured as a function of the applied stress level. With these approaches, aging effects in solder joints were quantified and correlated to the magnitudes of those observed in testing of miniature bulk specimens. Our results show that the aging induced degradations of the mechanical properties (modulus, hardness) of single grain SAC305 joints were similar to those seen previously by testing of larger “bulk” solder specimens. However, due to the single grain nature of the joints considered in this study, the degradations of the creep responses were significantly less in the solder joints relative to those in larger uniaxial tensile specimens. The magnitude of aging effects in multi-grain lead free solder joints remains to be quantified. Due to the variety of crystal orientations realized during solidification, it was important to identify the grain structure and crystal orientations in the tested joints. Polarized light microscopy and Electron Back Scattered Diffraction (EBSD) techniques have been utilized for this purpose. The test results show that the elastic, plastic, and creep properties of the solder joints and their sensitivities to aging are highly dependent on the crystal orientation. In addition, an approach has been developed to predict tensile creep strain rates for low stress levels using nanoindentation creep data measured at very high compressive stress levels.
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Breedlove, Evan L., Mark T. Gibson, Aaron T. Hedegaard i Emilie L. Rexeisen. "Evaluation of Dynamic Mechanical Test Methods". W ASME 2016 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/imece2016-65742.
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Dynamic mechanical properties are critical in the evaluation of materials with viscoelastic behavior. Various techniques, including dynamic mechanical analysis (DMA), rheology, nanoindentation, and others have been developed for this purpose and typically report complex modulus. Each of these techniques has strengths and weaknesses depending on sample geometry and length scale, mechanical properties, and skill of the user. In many industry applications, techniques may also be blindly applied according to a standard procedure without optimization for a specific sample. This can pose challenges for correct characterization of novel materials, and some techniques are more robust to agnostic application than others. A relative assessment of dynamic mechanical techniques is important when considering the appropriate technique to use to characterize a material. It also has bearing on organizations with limited resources that must strategically select one or two capabilities to meet as broad a set of materials as possible. The purpose of this study was to evaluate the measurement characteristics (e.g., precision and bias) of a selection of six dynamic mechanical test methods on a range of polymeric materials. Such a comprehensive comparison of dynamic mechanical testing methods was not identified in the literature. We also considered other technical characteristics of the techniques that influence their usability and strategic value to a laboratory and introduce a novel use of the House of Quality method to systematically compare measurement techniques. The selected methods spanned a range of length scales, frequency ranges, and prevalence of use. DMA, rheology, and oscillatory loading using a servohydraulic tensile tester were evaluated as traditional bulk techniques. Determination of complex modulus by beam vibration was also considered as a bulk technique. At a small length scale, both an oscillatory nanoindentation method and AFM were evaluated. Each method was employed to evaluate samples of polycarbonate, polypropylene, amorphous PET, and semi-crystalline PET. A measurement systems analysis (MSA) based on the ANOVA methods outlined in ASTM E2782 was conducted using storage modulus data obtained at 1 Hz. Additional correlations over a range of frequencies were tested between rheology/DMA and the remaining methods. Note that no attempts were made to optimize data collection for the test specimens. Rather, typical test methods were applied in order to simulate the type of results that would be expected in typical industrial characterization of materials. Data indicated low levels of repeatability error (<5%) for DMA, rheology, and nanoindentation. Biases were material dependent, indicating nonlinearity in the measurement systems. Nanoindentation and AFM results differed from the other techniques for PET samples, where anisotropy is believed to have affected in-plane versus out-of-plane measurements. Tensile-tester based results were generally poor and were determined to be related to the controllability of the actuator relative to the size of test specimens. The vibrations-based test method showed good agreement with time-temperature superposition determined properties from DMA. This result is particularly interesting since the vibrations technique directly accesses higher frequency responses and does not rely on time-temperature superposition, which is not suitable for all materials. MSA results were subsequently evaluated along with other technical attributes of the instruments using the House of Quality method. Technical attributes were weighted against a set of “user demands” that reflect the qualitative expectations often placed on measurement systems. Based on this analysis, we determined that DMA and rheology provide the broadest capability while remaining robust and easy to use. Other techniques, such as nanoindentation and vibrations, have unique qualities that fulfill niche applications where DMA and rheology are not suitable. This analysis provides an industry-relevant evaluation of measurement techniques and demonstrates a framework for evaluating the capabilities of analytical equipment relative to organizational needs.
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Roan, Esra, Alex Bada i Randy Buddington. "Mechanical Characterization of Preterm Neonate Pig Liver as a Function of High-Density Lipoprotein (HDL)". W ASME 2010 International Mechanical Engineering Congress and Exposition. ASMEDC, 2010. http://dx.doi.org/10.1115/imece2010-39363.
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Elastography, a non-invasive imaging modality, utilizes mechanical properties of tissue as markers for disease diagnosis or staging. In the case of liver, there have been a number of studies focusing on the relationship between elastic mechanical properties and underlying disease, i.e. fibrosis and cirrhosis. In summary, these studies indicate the feasibility of elastographic tools in detecting liver diseases such as fibrosis and steatosis. There have not been any studies looking at the mechanical properties of the preterm neonate liver to date, which is important, because preterm neonates are at a greater risk for developing liver complications due to their aggressive dietary needs that are met with total parenteral nutrition (TPN). They use of elastography may be less from the use of elastographic tools since the concerns over noise levels in measurements resulting from abdominal wall thickness may be less influential. Therefore, it is necessary to establish basic preterm neonate liver mechanical properties. In this study, we measured the nonlinear (hyperelastic) mechanical properties of livers from preterm pigs that were fed common neaonatal diets, i.e. colostrum, total parenteral nutrition (TPN). 16 neonate pigs survived the feeding regime. Mechanical evaluation of 15 of these neonatal pigs was achieved with the use of uniaxial compression experiments at 0.01 s−1 strain rate. The livers averaging a weight of 34.7±7.0 (SD), were stored in phosphate buffered saline solution at 4°C until experimentation, which occurred within 30 minutes of the animal sacrifice. A minimum of three specimens from each liver was required for the computation of averaged mechanical properties. In addition to mechanical testing samples, blood serum was also obtained from these animals and common chemical parameters for liver health were measured (bilirubin, ALT, AST, HDL, LDL, etc.) Exponential form of the hyperelastic strain energy function, W = b1exp[b2(L2 + 2/L-3)], where bi are the material parameters and L is the stretch ratio, was utilized to describe the hyperelastic mechanical behavior of the preterm neonate pig livers. With the use of E = 6b1b2, a small-strain regime estimate of the elastic modulus of the neonate liver tissue was also computed. The mean b1 and b2 parameters are determined to be 97.00±44.15(SD) Pa and 1.90±0.28(SD) (n = 71). The mean elastic modulus exhibited an linear dependence on the HDL values obtained from chemical analysis of the blood serum. Moreover, although relatively weak, the ratio of the HDL over LDL also correlated with the elastic modulus. To our knowledge, this is the only study to date that has focused on the mechanical properties of preterm neonatal pigs and its correlation with liver lipid profile in neonates. Future work will focus on correlating this information with histology and then devising multi-scale material characterization approaches that link underlying neonatal liver structure to its overall mechanical properties.
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Brown, Alexander L., Amanda B. Dodd i Brent M. Pickett. "Intermediate Scale Composite Material Fire Testing". W ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-63725.
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Composite materials are increasingly being used in aviation applications. As the quantity of composite material increases, there is a corresponding need to develop a better understanding of composite material response in fire environments. We have recently developed a program to examine this problem experimentally and computationally. Although Sandia National Laboratories and Air Force Research Laboratories at Tyndall have slightly different focuses, we are collaborating to focus on understanding duration, intensity, and the underlying physics during composite fires, as well as the technology and procedures to safely manage composite fire events. In the past year, we have been performing both small and intermediate scale testing to understand the behavior of composite materials used in aviation applications. The current focus is on a set of intermediate scale tests to generate data useful for understanding the behavior of carbon fiber epoxy composites in adverse thermal environments. A series of tests has been performed in a 90 cm cubic enclosure with 25–40 kg of composite materials to generate a severe fire environment fueled mostly by the composites. Preliminary results of these tests will be reported to provide data on the severity of the environment in terms of thermal intensity, duration, and chemical products.
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Karjadi, Erwan, Helen Boyd, Harm Demmink i Philippe Thibaux. "Reeling Pipeline Material Characterization: Testing, Material Modeling and Offshore Measurement Validation". W ASME 2015 34th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/omae2015-41919.
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It is a fact that when a pipeline is installed by the reeling method, it will undergo cyclic plastic straining and the pipe will plastically deform. Due to the applied plastic bending moment, the residual deformation in terms of residual pipe ovality after reeling is difficult to predict by Finite Element Analyses (FEA) without a thorough understanding of the material characterization and changes under cyclic plastic straining. The paper describes how the material behavior of seamless pipe under plastic strain reeling cycle has been characterized by a comprehensive material testing program including Bauschinger tests and perpendicular loading pre-straining tests. It turns out that for seamless pipe, by looking at the yield stress locus of the material after plastic straining, the reeled pipe material which initially shows isotropic behavior in the un-strained condition will change and evolve to show anisotropic behavior. The material in the hoop direction of the pipe will become more hardened than the material in the longitudinal direction of the pipe. The cross hardening characteristics of material under cyclic plastic deformation have been modeled using the “distortional plasticity” principle and implemented in a user subroutine of an FEA software package. This paper includes the validation of the ovality prediction by FEA model using the developed material model against the ovality measurement from full scale bend tests at Heriot-Watt University as well as ovality measurements taken during the spooling test and trial of 16″OD pipeline at Carlyss spool base in 2013. The material testing of a sample cut out from Spoolbase test and trial, undergoes spool and un-spool 5 cycles, has been performed to confirm the distortional plasticity hardening behavior obtained from the small scale Bauschinger and perpendicular loading tests.
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Wang, Jingyu, Nyree Mason, Firas Akasheh, Gul Kremer, Zahed Siddique i Yingtao Liu. "Implementation of Multi-Scale Characterization and Visualization on Enhancement of Solid Mechanics Education". W ASME 2019 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/imece2019-10747.
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Abstract This paper presents the implementation and preliminary analysis of a multi-scale material and mechanics education module for the improvement of undergraduate solid mechanics education. 3D printed and conventional wrought aluminum samples were experimentally characterized at both the micro- and macro-scales. At the micro-scale, we focus on the visualization of material’s grain structure. At the macro-scale, standard material characterization following ASTM standards is conducted to obtain the macroscopic behavior. Digital image correlation technology is employed to obtain the two-dimensional strain field during the macro-scale testing. An evaluation of students understanding of solid mechanics and materials behavior concepts is carried out in this study to obtain the student data and use it as baseline for further evaluation of study outcomes. We plan to use the established multi-scale mechanics and materials testing dataset in a broad range of undergraduate courses, such as Solid Mechanics, Design of Mechanical Components, and Manufacturing Processes. Our current effort is expected to demonstrate the real materials’ multi-scale nature and their mechanical performance to undergraduate engineering students. The successful implementation of this multi-scale approach for education enhances students’ understanding of abstract solid mechanics theories and establishing the concepts between mechanics and materials. In addition, this approach will assist advanced solid mechanics education, such as the concept of fracture, in undergraduate level education throughout the country.
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Cox, Martijn A. J., Jeroen Kortsmit, Niels J. B. Driessen, Carlijn V. C. Bouten i Frank P. T. Baaijens. "Inverse Mechanical Characterization of Tissue Engineered Heart Valves". W ASME 2008 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2008. http://dx.doi.org/10.1115/sbc2008-192521.
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Over the last few years, research interest in tissue engineering as an alternative for current treatment and replacement strategies for cardiovascular and heart valve diseases has significantly increased. In vitro mechanical conditioning is an essential tool for engineering strong implantable tissues [1]. Detailed knowledge of the mechanical properties of the native tissue as well as the properties of the developing engineered constructs is vital for a better understanding and control of the mechanical conditioning process. The nonlinear and anisotropic behavior of soft tissues puts high demands on their mechanical characterization. Current standards in mechanical testing of soft tissues include (multiaxial) tensile testing and indentation tests. Uniaxial tensile tests do not provide sufficient information for characterizing the full anisotropic material behavior, while biaxial tensile tests are difficult to perform, and boundary effects limit the test region to a small central portion of the tissue. In addition, characterization of the local tissue properties from a tensile test is non-trivial. Indentation tests may be used to overcome some of these limitations. Indentation tests are easy to perform and when indenter size is small relative to the tissue dimensions, local characterization is possible. We have demonstrated that by recording deformation gradients and indentation force during a spherical indentation test the anisotropic mechanical behavior of engineered cardiovascular constructs can be characterized [2]. In the current study this combined numerical-experimental approach is used on Tissue Engineered Heart Valves (TEHV).
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Acton, Katherine, Bahador Bahmani i Reza Abedi. "Mesoscale Material Strength Characterization for Use in Fracture Modeling". W ASME 2018 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/imece2018-88249.
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To accurately simulate fracture, it is necessary to account for small-scale randomness in the properties of a material. Apparent properties of Statistical Volume Elements (SVE), can be characterized below the scale of a Representative Volume Element (RVE). Apparent properties cannot be defined uniquely for an SVE, in the manner that unique effective properties can be defined for an RVE. Both constitutive behavior and material strength properties in SVE must be statistically characterized. The geometrical partitioning method can be critically important in affecting the probability distributions of mesoscale material property parameters. Here, a Voronoi tessellation based partitioning scheme is applied to generate SVE. Resulting material property distributions are compared with those from SVE generated by square partitioning. The proportional limit stress of the SVE is used to approximate SVE strength. Superposition of elastic results is used to obtain failure strength distributions from boundary conditions at variable angles of loading.
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Hasnine, Md, Jeffrey C. Suhling, Barton C. Prorok, Michael J. Bozack i Pradeep Lall. "Characterization of the Effects of Silver Content on the Aging Resistance of SAC Solder Joints". W ASME 2015 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems collocated with the ASME 2015 13th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/ipack2015-48623.
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In the current study, we have extended our previous work on nanoindentation of joints to examine a full test matrix of SAC solder alloys. The effects of silver content on SAC solder aging has been evaluated by testing joints from SACN05 (SAC105, SAC205, SAC305, and SAC405) test boards assembled with the same reflow profile. In all cases, the tested joints were extracted from 14 × 14 mm PBGA assemblies (0.8 mm ball pitch, 0.46 mm ball diameter) that are part of the iNEMI Characterization of Pb-Free Alloy Alternatives Project (16 different solder joint alloys available). After extraction, the joints were subjected to various aging conditions (0 to 12 months of aging at T = 125 C), and then tested via nanoindentation techniques to evaluate the stress-strain and creep behavior of the four aged SAC solder alloy materials at the joint scale. The observed aging effects in the SACN05 solder joints have been quantified and correlated with the magnitudes observed in tensile testing of miniature bulk specimens performed in prior studies. The results show that the aging induced degradations of the mechanical properties (modulus, hardness) in the SAC joints were of similar order (30–40%) as those seen previously in the testing of larger “bulk” uniaxial solder specimens. The creep rates of the various tested SACN05 joints were found to increase by 8–50X due to aging. These degradations, while significant, were much less than those observed in larger bulk solder uniaxial tensile specimens with several hundred grains, where the increases ranged from 200X to 10000X for the various SACN05 alloys. Additional testing has been performed on very small tensile specimens with approximately 10 grains, and the aging-induced creep rate degradations found in these specimens were on the same order of magnitude as those observed in the single grain joints. Thus, the lack of the grain boundary sliding creep mechanism in the single grain joints is an important factor in avoiding the extremely large creep rate degradations (up to 10,000X) occurring in larger bulk SAC samples. All of the aging effects observed in the SACN05 joints were found to be exacerbated as the silver content in the alloy was reduced. In addition, the test results for all of the alloys show that the elastic, plastic, and creep properties of the solder joints and their sensitivities to aging are highly dependent on the crystal orientation. Due to the variety of crystal orientations realized during solidification, it was important to identify the grain structure and crystal orientations in the tested joints. Cross-polarized light microscopy and Electron Back Scattered Diffraction (EBSD) techniques have been utilized for this purpose. The test results show that the elastic, plastic, and creep properties of the solder joints and their sensitivities to aging are highly dependent on the crystal orientation. In addition, an approach has been developed to predict tensile creep strain rates for low stress levels using nanoindentation creep data measured at very high compressive stress levels.
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Warren, Maria, Marc Sanborn i Lauren K. Stewart. "Characterization of A325 Structural Bolts Subjected to Impulsive Loads". W ASME 2021 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/imece2021-71763.
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Abstract Structural connections must maintain strength and ductility during and after impulsive loading to prevent widespread failure of a structure. However, a decrease in ductility in response to impulsive loads has been observed both experimentally and in situ. Further, experimental data on the residual capacity of steel structures is limited, especially the residual capacity of impulsively-damaged steel connections. To ensure the safe design of structures, it is necessary to characterize the dynamic and residual capacity of steel connections. To address the lack of data in this realm, an experimental method has been developed to determine the dynamic and residual behavior of A325 high-strength structural steel bolts in single-shear. A high-speed hydraulic actuator is employed for structure-scale experimentation, with impact energies varied from 760 J – 1370 J. Then, surviving bolts are quasi-statically loaded to failure to evaluate their residual capacity properties. Results demonstrate that, below a critical impact energy, A325 steel structural bolts have residual strength commensurate to undamaged bolts, but lessened residual ductility and energy absorption capacity. These data suggest that metrics other than residual strength should be explicitly included in residual capacity analyses. Further, above a critical impact energy, dynamic bolt fracture with a significant loss of ductility has been observed. A loss of deformation capacity at high impact energies (and thus, capacity to absorb energy through plasticity) may increase the susceptibility of a structure to progressive collapse. Therefore, these results prompted further investigation into the dynamic behavior of A325 bolts. Specifically, the sensitivity of material behavior to strain rate is studied using a Split-Hopkinson Pressure Bar (SHPB) testing apparatus. These results, in tandem with the single-shear bolt impulsive test data, are used to evaluate the role of strain hardening in the loss of ductility observed in A325 bolts at high impact energies.
Raporty organizacyjne na temat "Small scale mechanical testing for material behavior characterization"
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Snyder, Victor A., Dani Or, Amos Hadas i S. Assouline. Characterization of Post-Tillage Soil Fragmentation and Rejoining Affecting Soil Pore Space Evolution and Transport Properties. United States Department of Agriculture, kwiecień 2002. http://dx.doi.org/10.32747/2002.7580670.bard.
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Tillage modifies soil structure, altering conditions for plant growth and transport processes through the soil. However, the resulting loose structure is unstable and susceptible to collapse due to aggregate fragmentation during wetting and drying cycles, and coalescense of moist aggregates by internal capillary forces and external compactive stresses. Presently, limited understanding of these complex processes often leads to consideration of the soil plow layer as a static porous medium. With the purpose of filling some of this knowledge gap, the objectives of this Project were to: 1) Identify and quantify the major factors causing breakdown of primary soil fragments produced by tillage into smaller secondary fragments; 2) Identify and quantify the. physical processes involved in the coalescence of primary and secondary fragments and surfaces of weakness; 3) Measure temporal changes in pore-size distributions and hydraulic properties of reconstructed aggregate beds as a function of specified initial conditions and wetting/drying events; and 4) Construct a process-based model of post-tillage changes in soil structural and hydraulic properties of the plow layer and validate it against field experiments. A dynamic theory of capillary-driven plastic deformation of adjoining aggregates was developed, where instantaneous rate of change in geometry of aggregates and inter-aggregate pores was related to current geometry of the solid-gas-liquid system and measured soil rheological functions. The theory and supporting data showed that consolidation of aggregate beds is largely an event-driven process, restricted to a fairly narrow range of soil water contents where capillary suction is great enough to generate coalescence but where soil mechanical strength is still low enough to allow plastic deforn1ation of aggregates. The theory was also used to explain effects of transient external loading on compaction of aggregate beds. A stochastic forInalism was developed for modeling soil pore space evolution, based on the Fokker Planck equation (FPE). Analytical solutions for the FPE were developed, with parameters which can be measured empirically or related to the mechanistic aggregate deformation model. Pre-existing results from field experiments were used to illustrate how the FPE formalism can be applied to field data. Fragmentation of soil clods after tillage was observed to be an event-driven (as opposed to continuous) process that occurred only during wetting, and only as clods approached the saturation point. The major mechanism of fragmentation of large aggregates seemed to be differential soil swelling behind the wetting front. Aggregate "explosion" due to air entrapment seemed limited to small aggregates wetted simultaneously over their entire surface. Breakdown of large aggregates from 11 clay soils during successive wetting and drying cycles produced fragment size distributions which differed primarily by a scale factor l (essentially equivalent to the Van Bavel mean weight diameter), so that evolution of fragment size distributions could be modeled in terms of changes in l. For a given number of wetting and drying cycles, l decreased systematically with increasing plasticity index. When air-dry soil clods were slightly weakened by a single wetting event, and then allowed to "age" for six weeks at constant high water content, drop-shatter resistance in aged relative to non-aged clods was found to increase in proportion to plasticity index. This seemed consistent with the rheological model, which predicts faster plastic coalescence around small voids and sharp cracks (with resulting soil strengthening) in soils with low resistance to plastic yield and flow. A new theory of crack growth in "idealized" elastoplastic materials was formulated, with potential application to soil fracture phenomena. The theory was preliminarily (and successfully) tested using carbon steel, a ductile material which closely approximates ideal elastoplastic behavior, and for which the necessary fracture data existed in the literature.