Papers by Keyword: Material Testing

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Authors: Radim Halama, Lukáš Horňáček, Luboš Pečenka, Martin Krejsa, Jiří Šmach
Abstract: The presented paper introduces the application of the Electronic Speckle Pattern Interferometry (ESPI) technique for measurements of contours of strains and stresses on 3-D surfaces. The paper focuses on three selected applications. Firstly, the methodology for determining the Poisson ratio of a material from tensile tests is described. Secondly, results of calibration verification of a biaxial extensometer used for measurements of shear strain in comparison with the ESPI measurements are presented. Finally, the experimental analysis of stresses in welds is discussed. As mentioned in the paper, the method is very useful for material testing, as well as for measurements on structural parts in service.
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Authors: Marion Merklein, M. Biasutti
Abstract: The finite element method is a widely used tool in sheet metal forming. The quality of the results of such an analysis depends largely on the applied constitutive model and its material parameters, which have to be determined experimentally. These data are relevant on the choice of the yield criterion among the wide range of options available in the commercial applications implementing the finite element method. Since the accuracy of material parameters estimation is therefore crucial, investigations were performed with an Al-Mg sheet alloy and a mild steel sheet to optimize a Miyauchi-based simple shear test. This method is one of the basic ways to investigate the plastic properties of a sheet metal up to large strains, which is very important for numerical analysis of sheet metal forming processes. Aim of the test is to determine the shear stress-strain correlation. In order to enhance the quality of the experimental results the detection of the deformation’s field, trough an optical measurement system, and the methodology for its evaluation are focus of the present study.
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Authors: Atsumi Ohtsuki
Abstract: This report deals with an innovative method (Own-Weight Cantilever Method) to measure Young’s modulus of flexible thin materials. A newly developed method is based on the large deformation theory considering large deformation behaviors due to own-weight in flexible thin materials. Analytical solutions are derived by using Bessel Functions. By means of measuring the horizontal displacement or the vertical displacement at a free end of a cantilever, Young’s modulus can be easily obtained for various flexible thin and long materials. Measurements were carried out on a piano wire. The results confirm that the new method is suitable for flexible thin wires.
371
Authors: K. Sirivedin
Abstract: Optical strain analysis system plays an important role in tools and dies design, particularly in the phase of die design and die tryout. The objective of this paper is to present the information of the application by using the optical strain measurement device in tools and dies design and material testing. Therefore, two cases in mechanical testing and one case of tools and dies design are demonstrated. The AutoGrid® Compact strain measuring device is applied for all cases. The determination of Forming Limit Diagram (FLD) by using tensile testing machine and U-bending test supported by the optical strain measuring technique is performed and illustrated. In this paper, the procedure of material testing is developed and applied from related literatures. The result obtained from several cases shows the powerful performance of using the strain measurement device for providing the strain information in each situation of forming material as required so that the engineer can tackle the problem and find the solution to improve the production processes in a short time.
317
Authors: Yasuhide Shindo, Fumio Narita
Abstract: We present numerical and experimental results on the nonlinear bending behavior due to domain wall motion in functionally graded piezoelectric actuator under alternating current (ac) electric fields. A nonlinear finite element method is employed to analyze the dynamic response of functionally graded piezoelectric actuator. A phenomenological model of domain wall motion is used in computation, and the effects of ac electric field amplitude and frequency, number of layers, and property gradation on the deflection of the cantilever actuators are examined. Experimental results, which verify the model, are presented using a functionally graded bimorph. The numerical results agree very well with the experimental values.
2619
Authors: Shigeo Saimoto, S. Subbaiyan, C. Gabryel
Abstract: In dynamic dislocation-defect analysis, the thermodynamic deformation-mode signatures are examined as the ageing proceeds. In this method, the activation volume (ν) and the mean slip distance (λ) is simultaneously determined with the flow stress (τ) such that the inverse workhardening slope (1/θ) can be plotted versus b2λ/ν where b is the Burgers vector. The slope of this almost linear locus is directly proportional to the activation distance (d). Calibration with a model alumina-dispersed high conductivity copper reveals that punched-out loops are produced up to failure and is represented by a linear locus from 0.1 to 11 % strain. Artificial ageing of AA6111 at 180°C follows this pattern but the naturally-aged specimen manifest a distinctly different signature which shows a transition as the GP zone-type precipitates are sheared. Furthermore by selecting a suitable tensile-test temperature below 250K, the particle size and volume fraction can be determined if particle shearing does not take place. The optimum size and volume fraction necessary for sufficient strength and ductility can be assessed using this method.
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Authors: Marcela Karmazínová, Jindrich Melcher
Abstract: The paper is generally focused on yield and ultimate strengths of structural steels. The attention is mainly paid to the testing and subsequent determination of steel strengths, especially from the viewpoint of the statistical evaluation aimed to obtain the strength values leading to the reliable structural design, in the meaning of general rules given by the European Standard for the structural design of civil engineering constructions. The presented paper deals with the actual yield and ultimate strengths obtained from material tests and their characteristic and design values based on the test results evaluation, versus nominal and design values considered according to European Standard rules and used for the structural design in the usual cases if the steel grade is known. But in the case of existing constructions, sometimes there are no information about the material that the actual steel properties shall be determined using the material tests and their statistical evaluation to obtain such steel properties values which can lead to the reliable structural design. However, approaches of the determination of characteristic and design steel strengths using actual test results are different from the determination of the nominal and design steel strengths given by standard rules. As an illustration the paper summaries the results and evaluations of tests of structural steel performed on the specimens taken from the load-carrying roof structure of the sport stadium aged about 40 years, within the steel construction diagnostics.
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Authors: Masaya Miura, Yasuhide Shindo, Tomo Takeda, Fumio Narita
Abstract: This paper studies the damage behavior and interlaminar shear properties of hybrid composite laminates subjected to bending at cryogenic temperatures. Cryogenic short beam shear tests were performed on hybrid laminates combining woven glass fiber reinforced polymer (GFRP) composites with polyimide films, and microscopic observations of the specimens were made after the tests. A progressive damage analysis was also conducted to simulate the initiation and growth of damage in the specimens and to determine the interlaminar shear strength based on the maximum shear stress in the failure region. The predicted load-deflection curve and damage pattern show good agreement with the test results, and the numerically determined interlaminar shear strength is higher than the apparent interlaminar shear strength.
565
Authors: Ondrej Rozum, František Zahálka, Michaela Kašparová, Šárka Houdková
Abstract: High quality methods of designing the experiments (DOE) seem to be a very useful exploratory tool at many points of material engineering. Designing the experiments is a natural way to find a systematic influences in the process. It is necessary to have a clear view on how the things are to have the processes under controll. Therefore the importance of DOE increases in management and industry all over the world. In this work, a general use in branch of thermal spraying is shown.
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