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  • 1
    Electronic Resource
    Electronic Resource
    Free vibration analysis of delaminated composite pretwisted shells (2005)
    Bingley : Emerald
    Aircraft engineering and aerospace technology 77 (2005), S. 486-490 
    Details
    ISSN: 0002-2667
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Purpose - To investigate the effects of delamination on free vibration characteristics of graphite-epoxy composite pretwisted cylindrical shallow shells of various stacking sequences considering length of delamination as a parameter. Design/methodology/approach - A multipoint constraint algorithm which leads to unsymmetric elastic stiffness matrix is incorporated into an eight noded isoparametric plate bending finite element to satisfy the compatibility of deformation and equilibrium of resultant forces and moments at the delamination crack front. The study is focused upon long, intermediate and short cylindrical shells as defined by Aas-Jakobsen's parameters and considers symmetric and unsymmetric composite laminates. Findings - The non-dimensional fundamental natural frequencies are obtained for angle ply (45/-45/45, 45/-45) and cross ply (0/90/0, 0/90) configurations corresponding to different crack lengths and twist angles. The study implies the importance of the symmetric laminate as well as the long shell. Research limitations/implications - The standard eigenvalue computations using QR iteration algorithm for the present analyses take enormous time and hence, an efficient eigen-solver needs to be employed. Practical implications - New vibration modes are exhibited by the delaminated composite structures. The existence of invisible interlaminar cracking can be identified with the help of prior knowledge of natural frequencies for a delaminated composite pretwisted shell which can be idealized as a turbine blade with low aspect ratio. Originality/value - This paper presents a numerical approach for natural frequency determination of composite pretwisted shallow shells having delamination without taking care of the effect of dynamic contact between delaminated layers. The non-dimensional frequencies obtained could serve as reference solutions for future investigators.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1108/00022660510628480
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  • 2
    Electronic Resource
    Electronic Resource
    Crack Formation of Ceramic Thin Film on Polymer Substrate (2007)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 353-358 (Sept. 2007), p. 307-310 
    Details
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The aim of this paper is to investigate the effect of ultra-violet (UV) ray irradiation on thecrack formation of brittle ceramic coating on polymer substrate. It is well known that ultra-violet rayirradiation degrades the mechanical properties of polymer and polymer-based coating films. Wecarried out the tensile tests of PET/ITO film specimen after UV irradiation under the microscope andobserved the crack formation on ITO surface. Also, we carried out nano-indentation tests of PETsubstrate after removing ITO layer to characterize the change of the mechanical properties near theinterface between PET and ITO. The results show that the number of cracks vertical to loadingdirection and the rate of vertical crack formation decreased after UV irradiation. Hardness andYoung’s modulus of PET substrate increase due to the oxidation of PET after UV irradiation. Toexplain the relationship between the crack formation and mechanical property change, the energyrelease rates of the thin film channeling cracks are considered
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/55/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.353-358.307.pdf
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  • 3
    Electronic Resource
    Electronic Resource
    Compressive Deformation in Aluminum Foam Investigated Using a 2D Object Oriented Finite Element Modeling Approach (2007)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 353-358 (Sept. 2007), p. 651-654 
    Details
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The stochastic nature of aluminum foam structure, having a random distribution of voids,makes it difficult to model its compressive deformation behavior accurately. In this paper, a2-dimensional simplified modeling approach is introduced to analyze the compressive deformationbehavior that occurs in Alporas aluminum foam (Al foam). This has been achieved using imageanalysis on real undeformed aluminum foam images obtained by VHX-100 digital microscope. Finiteelement mesh for the cross sectional model is generated with Object Oriented Finite element (OOF)method combined with ABAQUS structural analysis. It is expected that OOF modeling enableprediction of the origin of failure in terms of localized deformation with respect to the microstructuraldetails. Furthermore, strain concentration sites leading to the evolution of the deformation band canbe visualized. Thus, this investigation addresses the local inhomogeneity in the Al foam structure.This study implies that the OOF modeling approach combined with experimental observations canprovide better insight into the understanding of aluminum foam compressive deformation behavior
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/55/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.353-358.651.pdf
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  • 4
    Electronic Resource
    Electronic Resource
    Study of Delamination of Thin Film Coating on Cyclic Nano-Indentation Test (2007)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 353-358 (Sept. 2007), p. 1842-1845 
    Details
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The aim of this paper is to evaluate the cyclic interfacial strength between thin film and itssubstrate by cyclic nano-indentation tests. The specimen used in this study is PET substrate/ITOcoatings layered specimen. From the indentation load and displacement curve, we proposed anevaluation method for the interfacial strength. The results are good agreement with the interfacialstrength evaluated by peel test. After cyclic indentations, the surface profile was observed by atomicforce microscope. The number of elongates increased with indentation cycles when the indentationload is low, whereas elongates number is almost constant under high load cases. These phenomenacan be explained by simple models. In this study, two types of fracture modes are proposed. They are“subsidiary fracture mode” and “buckling mode”
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/55/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.353-358.1842.pdf
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  • 5
    Electronic Resource
    Electronic Resource
    Peeling Rate Dependency of Delamination Behavior of Adhesives (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Advanced materials research Vol. 33-37 (Mar. 2008), p. 339-344 
    Details
    ISSN: 1662-8985
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Adhesives are widely used in our life and industrial world. However, it is difficult tocharacterize their mechanical properties because those strongly depend on environmental andmechanical conditions such as temperature, humidity or strain rate. In this paper, we focus on thestrain rate dependence of the interfacial strength and investigate the interfacial strength by peel testsunder several peel rates. The results show that, in lower rate region (under 1.0 mm/s), the interfacialstrength is constant and, in transition region (1.0 to 10 mm/s) the interface strength increased with thepeel rate. In middle rate region (10 to 103 mm/s), the interfacial strength is constant again. Over 103mm/s region, the interfacial strength drops and became lower than those in middle rate cases. Fromthe observation of peeling front by a high speed video camera, the deformation behavior of adhesiveschanges with the peel rate.??Finite element analysis by using cohesive zone model is also conducted,and influence of the rate dependency of adhesive and base material is discussed
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/40/transtech_doi~10.4028%252Fwww.scientific.net%252FAMR.33-37.339.pdf
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  • 6
    Electronic Resource
    Electronic Resource
    Evaluation and Characterization of Plastics-Made Sheet Type Components under Impact (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Advanced materials research Vol. 33-37 (Mar. 2008), p. 381-386 
    Details
    ISSN: 1662-8985
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Experimental works using a drop weight impact test method have been performed on acircular sheet specimen to evaluate and to characterize the impact resistance of the sheet-type plasticcomponents designed for automotive wheel covers. Evaluation has been conducted for a set ofengineering plastics: polycarbonate (PC), acrylonitrile-butadiene-styrene (ABS) and their blend(PC/ABS). The testing results showed that the PC/ABS blend specimens failed in brittle mannerunder higher impact speeds with very few of whitening zones. Secondary cracks capturedperpendicular to fracture surface were also found in the mid-plane of the scattered PC/ABS blendspecimens. Investigation is then focused on this blend and the testing results describe that impactresistance of the specimen made of this alternative material is determined by ABS not by PC.Combination of structures between PC and ABS through the thickness in the core due to theirimmiscibility was observed by scanning electron microscope (SEM) on the etched PC/ABS specimen.This latter result well correlates the results obtained from the testing. It therefore reveals thatimmiscibility between PC and ABS in the blend plays an important role in determining the impactresistance of the components. This paper also presents simulative results of the test obtained from aFEA work by introducing a 3D- layered finite element (FE) model of the PC/ABS specimen to takeinto account effect of a layer in the core on the behavior of the blend
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/40/transtech_doi~10.4028%252Fwww.scientific.net%252FAMR.33-37.381.pdf
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  • 7
    Electronic Resource
    Electronic Resource
    Behavior of Thin-Walled Square Tube and Tubular Hat Sections Subjected to Low Velocity Impact Loading (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Advanced materials research Vol. 33-37 (Mar. 2008), p. 387-394 
    Details
    ISSN: 1662-8985
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: In this paper, the prediction and comparison of the behavior of thin-walled prismaticstructures (square tube, top-hat and double-hat sections) in absorbing energy using theoretical andnumerical analysis are presented. Equations to predict crushing length and dynamic mean crushingforce of top-hat and double-hat sections were applied for material mild steel St37 and the effect ofspot weld positions are also figured out. For comparison, an explicit non-linear commercial finiteelement code LS-DYNA was used to predict the response of the structures subjected to axialcrushing. It was found that results of numerical methods and theoretical prediction have goodagreement. Assuming that the failure of spot-weld is neglected, mean dynamic crushing force ofdouble-hat section is 90% higher compared to that of square tube
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/40/transtech_doi~10.4028%252Fwww.scientific.net%252FAMR.33-37.387.pdf
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of Initial Stress on the Behavior of Love Waves in an Elastic Half-Space with a Functionally Graded Layer (2008)
    s.l. ; Stafa-Zurich, Switzerland
    Advanced materials research Vol. 33-37 (Mar. 2008), p. 669-674 
    Details
    ISSN: 1662-8985
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The propagation behavior of Love waves in a functionally graded material layeredhalf-space with initial stress is taken into account. The Wentzel-Kramers-Brillouin (WKB)asymptotic technique is adopted for the theoretical derivations. The analytical solutions are obtainedfor the dispersion relations and the distributions of mechanical displacement and stress alongthickness direction in the layered structure. Firstly, these solutions are used to study effects of theinitial stress on the dispersion relations and phase velocities, then influences of the initial stress on thedistributions of mechanical displacement and shear stresses along thickness direction are discussed indetail. Numerical results obtained indicate that the phase velocity of Love wave increases with theincrease of the magnitude of the initial tensile stress, while decreases with the increase of themagnitude of the initial compression stress. The effects on the dispersion relations of the Love wavepropagation are negligible as the magnitudes of the initial stress are less than 100MPa. Some otherresults are shown for distributions of field quantities along thickness direction. The results obtainedare not only meaningful for the design of functionally graded structures with high performance butalso effective for the evaluation of residual stress distribution in the layered structures
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/40/transtech_doi~10.4028%252Fwww.scientific.net%252FAMR.33-37.669.pdf
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  • 9
    Electronic Resource
    Electronic Resource
    The Near Crack Tip Deformation and Fracture Initiation of a Ductile Material under Mixed Mode Loading (1991)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 51-52 (Jan. 1991), p. 325-330 
    Details
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/58/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.51-52.325.pdf
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  • 10
    Electronic Resource
    Electronic Resource
    Fracture Behavior of ABS Resin under Mixed Mode Loading (1997)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 145-149 (Oct. 1997), p. 743-748 
    Details
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/44/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.145-149.743.pdf
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