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Impact Loading (impact + loading)
Selected AbstractsAcceptable prior fatigue damage and failure threshold for impact loading of an aluminium alloyFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 1 2001T. Auzanneau In a competitive economic context that aims at gains in safety, some problems of combined fatigue-impact loadings are crucial, particularly in the case of light alloys used in the transport and aeronautical industries. One important challenge is to quantify the fatigue preloading effect on the residual dynamic plasticity of a 2017-A T3 aluminium alloy. From an experimental modal analysis, the change in mechanical properties of prefatigued material under impact loading allows us to define the best mechanical parameter for a limiting threshold between a no-damage state and weakened states due to fatigue predamage. For this situation a hybrid technique has been developed. A numerical model including voids (which represent surface micro-cracks produced by the fatigue preloading) is fitted to the results obtained by the modal analysis of the damaged sample. Hence, an acceptable damage threshold (i.e. a damage critical volume below which the impact toughness is not affected by fatigue preloading) and a failure threshold are established. On the basis of this methodology, it is possible to predict the energy required for the impact failure of prefatigued specimens and therefore to predict a safe or a dangerous mechanical state. [source] A hypersingular time-domain BEM for 2D dynamic crack analysis in anisotropic solidsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 2 2009M. Wünsche Abstract A hypersingular time-domain boundary element method (BEM) for transient elastodynamic crack analysis in two-dimensional (2D), homogeneous, anisotropic, and linear elastic solids is presented in this paper. Stationary cracks in both infinite and finite anisotropic solids under impact loading are investigated. On the external boundary of the cracked solid the classical displacement boundary integral equations (BIEs) are used, while the hypersingular traction BIEs are applied to the crack-faces. The temporal discretization is performed by a collocation method, while a Galerkin method is implemented for the spatial discretization. Both temporal and spatial integrations are carried out analytically. Special analytical techniques are developed to directly compute strongly singular and hypersingular integrals. Only the line integrals over an unit circle arising in the elastodynamic fundamental solutions need to be computed numerically by standard Gaussian quadrature. An explicit time-stepping scheme is obtained to compute the unknown boundary data including the crack-opening-displacements (CODs). Special crack-tip elements are adopted to ensure a direct and an accurate computation of the elastodynamic stress intensity factors from the CODs. Several numerical examples are given to show the accuracy and the efficiency of the present hypersingular time-domain BEM. Copyright © 2008 John Wiley & Sons, Ltd. [source] Optimized damage detection of steel plates from noisy impact testINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 7 2006G. Rus Abstract Model-based non-destructive evaluation proceeds measuring the response after an excitation on an accessible area of the structure. The basis for processing this information has been established in recent years as an iterative scheme that minimizes the discrepancy between this experimental measurement and sequence of measurement trials predicted by a numerical model. The unknown damage that minimizes this discrepancy by means of a cost functional is to be found. The damage location and size is quantified and sought by means of a well-conditioned parametrization. The design of the magnitude to measure, its filtering for reducing noise effects and calibration, as well as the design of the cost functional and parametrization, determines the robustness of the search to combat noise and other uncertainty factors. These are key open issues to improve the sensitivity and identifiability during the information processing. Among them, a filter for the cost functional is proposed in this study for maximal sensitivity to the damage detection of steel plate under the impact loading. This filter is designed by means of a wavelet decomposition together with a selection of the measuring points, and the optimization criterion is built on an estimate of the probability of detection, using genetic algorithms. Numerical examples show that the use of the optimal filter allows to find damage of a magnitude several times smaller. Copyright © 2006 John Wiley & Sons, Ltd. [source] Hair breakage during combing.INTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 6 2007Hair breakage during combing was evaluated by combing tresses and examining photographs of snags of hair fibers in combs. The resultant hair fiber arrangements suggest that breakage likely involves hair-on-hair interactions, and broken fragment size suggests that breakage occurs primarily at or near the hair-comb interface. Compression forces during combing were also measured, and impact loading of a hair fiber over another hair vs. a hair fiber over a comb tooth shows that compression and abrasion are important to breakage during combing and that impact loading of one hair fiber over another during snagging is a probable and important pathway for hair breakage. [source] The comparison of wear properties of different Fe-based hardfacing alloys in four kinds of testing methodsLUBRICATION SCIENCE, Issue 4 2008E. Badisch Abstract Iron-based hardfacing alloys are widely used to protect machinery equipment. A strong correlation is given between microstructure and chemical composition of welding deposit with the resulting wear behaviour. Concerning precipitation of metallurgical hard phases and synthetic added hard particles, the bonding strength of the hard phases in the metallic matrix seems to play a dominating role to obtain high wear resistance. The main objective of this study was to evaluate the wear behaviour for pure abrasion, combined impact/abrasion and high impact wear, respectively, for four different Fe-based hardfacing alloys. Tests were performed with a standard ASTM G65 dry-sand/rubber-wheel tester. An impeller,tumbler apparatus enabled investigation of impact abrasion wear tests. Additional wear tests with high impact loading were performed on a drop hammer apparatus. Fracture surface analysis was carried out after drop hammer testing and results were correlated with microstructure and interfacial bonding behaviour of precipitations in metallic matrix. Copyright © 2008 John Wiley & Sons, Ltd. [source] Experimental study of sharp-tipped projectile perforation of GFRP plates containing sand filler under high velocity impact and quasi-static loadingsPOLYMER COMPOSITES, Issue 10 2009Ali Reza Sabet Penetration and perforation behavior of glass fiber reinforced plastic (GFRP) plates containing 20% sand filler have been investigated via high velocity impact tests using sharp tipped (30°) projectile and quasi-static perforation tests. Two size sand filler (75 and 600 ,m) were used in 4-, 8-, and 14-layered laminated composite plates to study sensitivity of filler size toward loading system. Composite plates were examined for perforation load rate at 5 mm/min and high-velocity impact loading up to 220 m/s. Results indicated higher energy absorption for GFRP plates containing sand filler for both high-velocity impact and quasi-static perforation tests. Higher ballistic limits were recorded for specimens containing sand filler. The study showed clear role played by coarse-sized sand filler as a secondary reinforcement in terms of higher energy absorption as compared with nonfilled and specimens containing fine-sized fillers. The investigation successfully characterized behavior of quasi-static test during penetration and perforation of the sharp-tipped indenter as an aid for impact application studies. Residual frictional load in the specimens containing sand filler constituted considerable portion of load bearing during perforation in quasi-static tests. Delaminations followed by fiber and matrix fracture were major failure mode in high-velocity tests and the main energy absorbing mechanism in thick-walled plates, whereas in quasi-static tests the failures were more of matrix fracture and fiber sliding. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source] | |||||||||||||