Home About us Contact
|
Home About us Contact | ||
|
|
||
Impact Response (impact + response)
Selected AbstractsA lumped mass numerical model for cellular materials deformed by impactINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 11 2001Z. H. Tu Abstract When impacted by a relatively rigid body, cellular materials undergo severe deformation and extensive material failure. However, such behaviour may not be well described using traditional numerical approaches such as the finite element method. This paper presents a lumped mass numerical model which can accommodate high degrees of deformation and material failure. The essence of this model is to discretize a block of material into contiguous element volumes, each represented by a mass point. Interactions between a node and its neighbours are accounted for by defining ,connections' that represent their interfaces which transmit stresses. Strains at a node are calculated from the co-ordinates of the surrounding nodes; these also determine the stresses on the interfaces. The governing equations for the entire solution domain are then converted into a system of equations of motion with nodal positions as unknowns. Failure criteria and possible combinations of ,connection' breakage are incorporated to model the occurrence of damage. A practical contact algorithm is also developed to describe the contact interactions between cellular materials and rigid bodies. Simulations for normal and oblique impacts of rigid rectangular, cylindrical and wedge-tipped impactors on crushable foam blocks are presented to substantiate the validity of the model. The generally good correlation between the numerical and experimental results demonstrates that the proposed numerical approach is able to model the impact response of the crushable foam. However, some limitations in modelling crack propagation in oblique impacts by a rigid impactor on foam blocks are observed. Copyright © 2001 John Wiley & Sons, Ltd. [source] Impact behavior of hybrid composite platesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2010Metin Sayer Abstract This experimental study deals with the impact response of hybrid composite laminates. Two different hybrid composite laminates, aramid/glass and aramid/carbon, and two different stacking sequences, such as [0/0/90/90]A+ [90/90/0/0]G for AG1 and [0/90/±45]A+ [±45/90/0]G for AG2 and so on (see Table I), were chosen for impact testing. The impact energy was gradually increased until complete perforation took place, and an energy profiling method (EPM) was used to identify the perforation thresholds of composites. The damaged samples were visually inspected. The images of the several samples subjected to various impact energies were registered and used for comparison and identifying damage mechanisms. The perforation thresholds for [0/90/±45]s aramid/glass and aramid/carbon laminates were found to be approximately 5% higher than those for their counterparts with the [0/0/90/90]s stacking sequence. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Finite element analysis (FEA) applied to polyethylene foam cushions in package drop testsPACKAGING TECHNOLOGY AND SCIENCE, Issue 1 2005N. J. Mills Abstract Two designs of polyethylene (PE) foam cushions were compared, using a rigid ,product' of mass 5.6,kg, and an outer corrugated fibreboard box. The acceleration,time history for the product was measured when the box was dropped flat from 1,m onto a rigid floor. The data was processed to calculate the impact force as a function of the packaging deformation. Finite element analysis (FEA) predictions of the impact force vs. package deflection were accurate for end-cap designs using Ethafoam, but underestimated the slope of the experimental force vs. deflection relation for corner-cap designs. The corner-cap design is more efficient in reducing the peak product acceleration for multiple impacts. The contribution of the corrugated board box to the impact response appears to be small. The FEA results were compared with those from the cushion curve design method and were found to better predict the performance of complex shaped cushions. Copyright © 2004 John Wiley & Sons, Ltd. [source] Low velocity impact response of GFRP laminates subjected to cycling moisturesPOLYMER COMPOSITES, Issue 5 2000Guoqiang Li The low velocity impact response of laminated composites in ambient hygrothermal environments has been extensively investigated. This response, however, is not well understood when subjected to moisture cycling at elevated temperatures. In this current study, two types of glass fiber reinforced plastic (GFRP) laminates, unidirectional and crossply, were conditioned in a conditioning chamber for a maximum of eight moisture cycles at conditioning temperatures from 50°C to 100°C. Low velocity impact tests were conducted on the conditioned specimens and control specimens via an instrumented drop-weight impact testing machine. The tension after impact (TAI) strength was investigated using an MTS machine. The equivalent damage size is obtained using an average stress criterion found in the literature. The effect of moisture cycling and conditioning temperatures on the low velocity impact response and residual load carrying capacity of GFRP laminates are evaluated via the test results. [source] Pain interference impacts response to treatment for anxiety disordersDEPRESSION AND ANXIETY, Issue 3 2009Carrie Farmer Teh PhD Abstract Background: Anxiety disorders and pain are commonly comorbid, though little is known about the effect of pain on the course and treatment of anxiety. Methods: This is a secondary analysis of a randomized controlled trial for anxiety treatment in primary care. Participants with panic disorder (PD) and/or generalized anxiety disorder (GAD) (N=191; 81% female, mean age 44) were randomized to either their primary-care physician's usual care or a 12-month course of telephone-based collaborative care. Anxiety severity, pain interference, health-related quality of life, health services use, and employment status were assessed at baseline, and at 2-, 4-, 8-, and 12-month follow-up. We defined response to anxiety treatment as a 40% or greater improvement from baseline on anxiety severity scales at 12-month follow-up. Results: The 39% who reported high pain interference at baseline had more severe anxiety (mean SIGH-A score: 21.8 versus 18.0, P<.001), greater limitations in activities of daily living, and more work days missed in the previous month (5.8 versus 4.0 days, P=.01) than those with low pain interference. At 12-month follow-up, high pain interference was associated with a lower likelihood of responding to anxiety treatment (OR=.28; 95% CI=.12,.63) and higher health services use (26.1% with ,1 hospitalization versus 12.0%, P<.001). Conclusions: Pain that interferes with daily activities is prevalent among primary care patients with PD/GAD and associated with more severe anxiety, worse daily functioning, higher health services use, and a lower likelihood of responding to treatment for PD/GAD. Depression and Anxiety, 2009. © 2009 Wiley-Liss, Inc. [source] | |||||||||||||