| 1. |
- Andersson, Daniel C., et al.
(författare)
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Inverse modeling applied for material characterization of powder materials
- 2015
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Ingår i: Journal of Testing and Evaluation. - 0090-3973 .- 1945-7553. ; 43:5, s. 1005-1019
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Tidskriftsartikel (refereegranskat)abstract
- An investigation is performed concerning the applicability of inverse procedures, using optimization and simple experiments, for characterization of WC/Co powder materials. The numerical procedure is combined with uniaxial die-compaction experiments using an instrumented die, which allows direct measurement of the distribution of radial stress during the experiments. Finite-element (FE) methods and an advanced constitutive description of powder materials are relied upon to model the compaction experiment. Optimization using a surrogate model is used to determine some of the parameters in the constitutive description. These parameters in the material model are said to be found (with some accuracy) if the output from the FE simulation is similar to the experimental data. It is found that even though a complete constitutive description of the powder materials investigated cannot be achieved using this approach, many important material parameters can be determined with good accuracy.
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| 2. |
- Brenner, Richard, et al.
(författare)
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Evaluation of a humidity sensor for use in an environment exposed to radiation
- 2007
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Ingår i: Journal of Testing and Evaluation. - 0090-3973 .- 1945-7553. ; 35:5, s. 469-476
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Tidskriftsartikel (refereegranskat)abstract
- Humidity sensors tolerant to ionizing radiation are used in high-energy physics experiments where radiation doses are large and the sensors are inaccessible for replacement due to the highly activated environment. Other fields that have to meet the same demands are nuclear industry and space technology. In this paper cellulose crystallite humidity sensors that have been qualified by the manufacturer for use in radiation environments have been characterized and calibrated with the purpose of evaluating their suitability for use in the CERN ATLAS experiment for high-energy physics research. The impact of protons on the sensor was studied up to a fluence of 2∙1014 p/cm2.
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| 3. |
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| 4. |
- Dinegdae, Yared, et al.
(författare)
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Reliability-based specification for asphalt concrete pavements
- 2020
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Ingår i: Journal of Testing and Evaluation. - : ASTM International. - 0090-3973 .- 1945-7553. ; 48:1, s. 41-51
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Tidskriftsartikel (refereegranskat)abstract
- The use of volumetric-based specifications that utilize air void and asphalt content for the quality control of asphalt pavements is a major concern as there is a lack of fundamental correlation between these mixture properties and long-term pavement performance. In addition to that, the input variabilities' influence on target reliability and pavement performance is not addressed in these volumetric-based specifications. The aim of this article is to introduce a reliability-based specification for the quality control of top-down cracking in asphalt concrete pavements. The reliability-based specification criteria are developed for two traffic level categories and using design inputs such as hourly equivalent single axle load traffic, asphalt layer thickness, base modulus, and dissipated creep strain energy limit. For the development of the reliability-based specification, several field pavement sections with well-documented performance history and high-quality laboratory and field data were analyzed using the mechanics-based design framework for variability conditions that are representative of actual field conditions. Variation in dissipated creep strain energy limit and asphalt concreter layer thickness has been observed to influence target reliability and overall pavement performance significantly, in comparison with base modulus and hourly equivalent single axle load traffic. The proposed reliability-based specification can complement existing performance-based specifications for the quality control of top-down cracking in asphalt concrete pavements.
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| 5. |
- Edvardsson, Sverker, et al.
(författare)
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A Note on Wet Paper Web Adhesion Strength
- 2012
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Ingår i: Journal of Testing and Evaluation. - 0090-3973 .- 1945-7553. ; 40:4, s. 682-686
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Tidskriftsartikel (refereegranskat)abstract
- This work is concerned with the determination of the adhesion strength between a paper web and an adhesive surface. Edvardsson et al. [Edvardsson, S., Gradin, P., and Isaksson, P., "On Dissipative Effects of Paper Web Adhesion Strength," Int. J. Solids Struct., Vol. 48(1), 2011, pp. 24-30] suggested recently a model that takes into account the energy dissipation caused by elastic plastic deformation in the bent structure of a paper specimen. This model is further developed and investigated in the present work. A linear relation in plastic dissipation is discovered facilitating a novel analysis of the peeling tension and a more convenient determination of the proper adhesion strength. Industrial relevant examples are made with wet newsprint and kraft stock. A straightforward experimental procedure for determining the consistent adhesion strength is suggested. It is found that the agreement between the model and the experimental observations is good.
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| 6. |
- Eskner, Mats, et al.
(författare)
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Mechanical property evaluation using the small punch test
- 2004
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Ingår i: Journal of Testing and Evaluation. - 0090-3973 .- 1945-7553. ; 32:4, s. 282-289
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Tidskriftsartikel (refereegranskat)abstract
- The small punch (SP) test technique is an attractive method for evaluating mechanical behavior in materials where only small volumes of materials are available. An SP-test machine was developed where miniature disc specimens 5 and 3 mm in diameter and with thickness ranging between 50 to 400 mum can be investigated. For two materials, a 1Cr-0.5Mo low alloy steel and an 18Cr-9Ni austenitic stainless steel, the stress-strain flow curve was assessed and compared with that in tensile tests. The yield strength was determined from the SP-test by analyzing the initial elastic deformation with help of classical plate bending theory. The effective flow properties in the biaxial stress state were evaluated through analytical modelling of the stretching deformation. Good agreement between the uniaxial and biaxial flow properties was found for the 1wCr-0.5Mo steel and acceptable agreement for the 18Cr-9Ni steel.
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| 7. |
- García, A., et al.
(författare)
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Influence of steel wool fibers on the mechanical, termal, and healing properties of dense asphalt concrete
- 2014
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Ingår i: Journal of Testing and Evaluation. - 0090-3973 .- 1945-7553. ; 42:5
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Tidskriftsartikel (refereegranskat)abstract
- This paper summarizes the main results of experimental research on the induction healing of dense asphalt concrete with steel wool fibers. Different physical properties of dense asphalt concrete, as the steel wool fibers distribution, mechanical properties, thermal conductivity, and healing via induction heating have been analysed. The main results show that short and thick fibers disperse very well in the mixture, while long and thin fibers produce clusters. It was also observed that fibers can be damaged during the mixing and compaction processes. In addition, it was found that steel wool fibers do not significantly improve the mechanical properties and damage resistance of dense asphalt concrete. Moreover, steel wool fibers slightly increase the thermal conductivity of dense asphalt concrete. Furthermore, the temperature reached due to induction heating increases with the number of fibers in the mixture and with their diameter. Finally, it was found that dense asphalt concrete heals through the increase of temperature and that the type and diameter of fibers do not influence the healing properties of dense asphalt concrete.
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| 8. |
- Jelagin, Denis, et al.
(författare)
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Mechanical Characterization of Granite Rock Materials : On the Influence from Pre-Existing Defects
- 2018
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Ingår i: Journal of Testing and Evaluation. - : ASTM International. - 0090-3973 .- 1945-7553. ; 46:2, s. 540-548
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Tidskriftsartikel (refereegranskat)abstract
- The length, orientation, and population of pre-existing cracks play an important role in the mechanical response of quasi-brittle materials, such as granite. Specifically, Bohus granite rock is at issue in the present investigation. The aims of this study are (1) to demonstrate the existence and characteristics of pre-existing defects (cracks) in granite rock specimens, and (2) to determine the influence from these defects at characterization of such materials. In doing so, X-ray tomography was the method used to visualize the cracking of three-point bending specimens in the context of pre-existing defects. It was also the intention to relate the experimentally determined effect of these cracks at three-point bending testing with corresponding results from numerical methods and specifically finite-element calculations. In the latter case, the location of these cracks was of primary interest and it was shown that this feature can be of considerable importance at material characterization.
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| 9. |
- Larsson, Per-Lennart
(författare)
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Correlation of global quantities for material characterization by sharp indentation testing of elastoplastic materials
- 2016
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Ingår i: Journal of Testing and Evaluation. - : ASTM International. - 0090-3973 .- 1945-7553. ; 44:6, s. 2293-2301
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Tidskriftsartikel (refereegranskat)abstract
- Indentation problems pertinent to sharp indenters were examined. The analysis concerned classical elastic-plastic materials and, especially so, the details of the behavior of global contact quantities, such as mean contact pressure and the size of the contact area, in the transition region where elastic and plastic effects are of equal magnitude. The global contact quantities were correlated accurately using a single parameter, comprising both geometrical and mechanical properties, and presented using closed form expressions directly applicable to material characterization or measurements of residual mechanical fields by sharp indentation tests, but also for situations such as contact in gears or in electronic devices. The derived relations were based on highly accurate previous results from finite element studies of sharp indentation problems.
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| 10. |
- Larsson, Per-Lennart, 1961-
(författare)
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Determination of residual stresses utilizing the the variation of hardness at elastic-plastic indentation
- 2019
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Ingår i: Journal of Testing and Evaluation. - West Conshohocken, Pennsylvania USA. - 0090-3973 .- 1945-7553. ; 47:4, s. 3174-3184
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Tidskriftsartikel (refereegranskat)abstract
- Material hardness is independent of residual stresses at predominantly plastic deformation in the region of contact between an indenter and the material. This is an important fact, as such a situation is relevant for most metals and alloys. It has, however, been established that when elastic and plastic deformations are of equal magnitude, this independence is lost. This fact complicates residual stress determination in such a situation, pertinent to materials such as ceramics and polymers, but it also provides additional important information for performing such a task in an accurate manner. Presently, a relevant formula for taking advantage of this information is presented. The formula is based on previous results pertinent to indentation analyses of stress-free materials. The predictions are compared to finite element results from previous studies describing cone indentation of materials with residual stresses. The analysis is restricted to classical elastoplasticity.
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