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Impact Tests (impact + test)
Selected AbstractsA Double-Blind Comparison of OnabotulinumtoxinA (BOTOX®) and Topiramate (TOPAMAX®) for the Prophylactic Treatment of Chronic Migraine: A Pilot StudyHEADACHE, Issue 10 2009Ninan T. Mathew MD Background., There is a need for effective prophylactic therapy for chronic migraine (CM) that has minimal side effects. Objective., To compare the efficacy and safety of onabotulinumtoxinA (BOTOX®, Allergan, Inc., Irvine, CA) and topiramate (TOPAMAX®, Ortho-McNeil, Titusville, NJ) prophylactic treatment in patients with CM. Methods., In this single-center, double-blind trial, patients with CM received either onabotulinumtoxinA, maximum 200 units (U) at baseline and month 3 (100 U fixed-site and 100 U follow-the-pain), plus an oral placebo, or topiramate, 4-week titration to 100 mg/day with option for additional 4-week titration to 200 mg/day, plus placebo saline injections. OnabotulinumtoxinA or placebo saline injection was administered at baseline and month 3 only, while topiramate oral treatment or oral placebo was continued through the end of the study. The primary endpoint was treatment responder rate assessed using Physician Global Assessment 9-point scale (+4 = clearance of signs and symptoms and ,4 = very marked worsening [about 100% worse]). Secondary endpoints included the change from baseline in the number of headache (HA)/migraine days per month (HA diary), and HA disability measured using Headache Impact Test (HIT-6), HA diary, Migraine Disability Assessment (MIDAS) questionnaire, and Migraine Impact Questionnaire (MIQ). The overall study duration was approximately 10.5 months, which included a 4-week screening period and a 2-week optional final safety visit. Follow-up visits for assessments occurred at months 1, 3, 6, and 9. Adverse events (AEs) were documented. Results., Of 60 patients randomized to treatment (mean age, 36.8 ± 10.3 years; 90% female), 36 completed the study at the end of the 9 months of active treatment (onabotulinumtoxinA, 19/30 [63.3%]; topiramate, 17/30 [56.7%]). In the topiramate group, 7/29 (24.1%) discontinued study because of treatment-related AEs vs 2/26 (7.7%) in the onabotulinumtoxinA group. Between 68% and 83% of patients for both onabotulinumtoxinA and topiramate groups reported at least a slight (25%) improvement in migraine; response to treatment was assessed using Physician Global Assessment at months 1, 3, 6, and 9. Most patients in both groups reported moderate to marked improvements at all time points. No significant between-group differences were observed, except for marked improvement at month 9 (onabotulinumtoxinA, 27.3% vs topiramate, 60.9%, P = .0234, chi-square). In both groups, HA/migraine days decreased and MIDAS and HIT-6 scores improved. Patient-reported quality of life measures assessed using MIQ after treatment with onabotulinumtoxinA paralleled those seen after treatment with topiramate in most respects. At month 9, 40.9% and 42.9% of patients in the onabotulinumtoxinA and topiramate groups, respectively, reported ,50% reduction in HA/migraine days. Forty-one treatment-related AEs were reported in 18 onabotulinumtoxinA-treated patients vs 87 in 25 topiramate-treated patients, and 2.7% of patients in the onabotulinumtoxinA group and 24.1% of patients in the topiramate group reported AEs that required permanent discontinuation of study treatment. Conclusions., OnabotulinumtoxinA and topiramate demonstrated similar efficacy in the prophylactic treatment of CM. Patients receiving onabotulinumtoxinA had fewer AEs and discontinuations. [source] Analysis of Single Particle Attrition during Impact Experiments,PARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 5 2003Ramanan Pitchumani Abstract Particle breakage can be characterised as attrition, chipping, fracture, abrasion and wear. All these types of breakage mechanisms are the effect of the damage caused to these particles. These mechanisms can be differentiated not just on the basis of magnitude and direction of the force but also by the damage caused to the particles. The damage is measured by change in the size distribution and the change in shape of the particles. In the current research, experiments were performed on the newly developed Repeated Impact Test. The unique feature of this test is that about hundred particles can be subjected simultaneously to a monitored number of impacts, without particle-particle interactions at regulated velocities. The preliminary experiments were performed with single crystalline particles of different shapes and sizes. After fixed number of impacts, the images of the particles were taken. The volume and shape of the particles were determined by image analysis. It was observed that the rate of attrition was very high when the particles are irregular. The rate decreased as the particles became more spherical. [source] Microabrasion of Coatings Investigated by the Inclined Impact Test at Various Loads under Dry and Lubricated ConditionsPLASMA PROCESSES AND POLYMERS, Issue S1 2007Konstantinos-Dionysios Bouzakis Abstract The impact test has clearly emerged as an important technology for the prediction of cohesive, adhesive, and fatigue failure of coatings, further enabling the establishment of Smith and Woehler diagrams of PVD films. In the present paper, the abrasive wear of a well-adherent (Ti46Al54)N coating was investigated by the inclined impact test, at impact loads higher, equal to or lower than the fatigue critical impact load of the applied film. These investigations were conducted for few thousands up to several millions of impacts both under dry and lubricated conditions. The obtained results suggest that the inclined impact test is a very efficient method for detecting coating resistance against impact microabrasion, with or without lubrication and according to the test conditions for the synchronous contribution of fatigue phenomena to the film wear. [source] A New Apparatus for Particle Impact TestsPARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 4 2003Yevgeny Petukhov Abstract Breakage and chipping of particles due to collision with a hard surface is a common occurrence in many conveying and handling systems, such as pneumatic conveying and jet-mills. Studies of the breakage mechanism of particles due to impact and the effect of impact velocity and the number of impacts have been investigated in depth both experimentally and theoretically. In this paper, a new concept and apparatus are introduced for conducting particle impact tests. In most of the published test rigs, particles were accelerated towards a target. In our apparatus, the target moves and hits the particles. Using this concept, the machine can operate in a vacuum, which will reduce errors caused by air streams and turbulence. The performance of the new apparatus is analyzed and the breakage phenomenon is discussed, to some extent, for two materials. The results are presented in terms of the increase in the weight percentage of the feed broken and the decrease in the weight median size as the impact velocity or number of impacts increases. [source] Damage Phenomena Observed on PVD Coatings Submitted to Repeated Impact TestsPLASMA PROCESSES AND POLYMERS, Issue S1 2007Florent Ledrappier Abstract Thin hard coatings obtained by PVD process are widely used to improve the mechanical and friction behaviour of industrial parts. Depending on the friction conditions, the failure mechanisms and resulting selection criteria may be very different. This study aims to investigate the endurance life of some PVD coatings under repeated impact conditions. Impact tests at controlled impact energy have been performed using a hemispherical tip. Long-term tests have been done to determine the coating endurance life while short tests enable us to identify the damage phenomena. Depending on the nature of the PVD coating, cracks, blisters or spalling may be observed under impact. These phenomena may worsen until the complete film rupture occurs. [source] Strain rate effect in the single-fiber-fragmentation testPOLYMER COMPOSITES, Issue 3 2001X. J. Gong The single fiber fragmentation test (SFVU) has been widely used to characterize the interface it fiber-reinforced polymers. The purpose of the work reported here was to determine the effect of strain rate on the fiber fragment lengths obtained in the SFFT. Three materials systems were used to make single-fiber-composite specimens: E-glass fiber/polycarbonate matrix, AS4-carbon fiber/polycarbonate matrix, and AS4-carbon fiber/polycarbonate matrix. The fiber-matrix adhesion in all three systems is based on physisorption rather than chemisorption. Each system was tested at strain rates ranging over four orders of magnitude. Results are reported in terms of fragment length, the dependent variable in this study, which is inversely related to the quality of the Interface. It was expected that the fragment length would show a systematic decrease with Increasing strain rate, but the expected trend was not found. Although the polycarbonate matrix exhibited rate-dependent viscoelastic behavior typical of amorphous polymers below Tg, the fragment length at saturation did not show a statistically significant variation with strain rate for any of the three materials systems. A major contributor to the lack of observed effect was the inherent random variability associated with the SFFT; random variability in average fragment length was equal or greater than the 19% effect of rate predicted for ideal elastic systems with no debonding at the interface. In addition, considerable interfacial debonding occurred during the SFFT, not surprising for Interfaces based on physisorption alone. Debonding Interferes with transfer of applied load from matrix to fiber, and would thus interfere with transfer of the effect of rate from matrix to fiber. A tensile Impact test developed previously was also performed on single-fiber composite specimens made from the same three materials systems. The results of the Impact tests differed from those obtained at controlled strain-rates for only two of the materials systems. [source] Damage Phenomena Observed on PVD Coatings Submitted to Repeated Impact TestsPLASMA PROCESSES AND POLYMERS, Issue S1 2007Florent Ledrappier Abstract Thin hard coatings obtained by PVD process are widely used to improve the mechanical and friction behaviour of industrial parts. Depending on the friction conditions, the failure mechanisms and resulting selection criteria may be very different. This study aims to investigate the endurance life of some PVD coatings under repeated impact conditions. Impact tests at controlled impact energy have been performed using a hemispherical tip. Long-term tests have been done to determine the coating endurance life while short tests enable us to identify the damage phenomena. Depending on the nature of the PVD coating, cracks, blisters or spalling may be observed under impact. These phenomena may worsen until the complete film rupture occurs. [source] Strain rate effect in the single-fiber-fragmentation testPOLYMER COMPOSITES, Issue 3 2001X. J. Gong The single fiber fragmentation test (SFVU) has been widely used to characterize the interface it fiber-reinforced polymers. The purpose of the work reported here was to determine the effect of strain rate on the fiber fragment lengths obtained in the SFFT. Three materials systems were used to make single-fiber-composite specimens: E-glass fiber/polycarbonate matrix, AS4-carbon fiber/polycarbonate matrix, and AS4-carbon fiber/polycarbonate matrix. The fiber-matrix adhesion in all three systems is based on physisorption rather than chemisorption. Each system was tested at strain rates ranging over four orders of magnitude. Results are reported in terms of fragment length, the dependent variable in this study, which is inversely related to the quality of the Interface. It was expected that the fragment length would show a systematic decrease with Increasing strain rate, but the expected trend was not found. Although the polycarbonate matrix exhibited rate-dependent viscoelastic behavior typical of amorphous polymers below Tg, the fragment length at saturation did not show a statistically significant variation with strain rate for any of the three materials systems. A major contributor to the lack of observed effect was the inherent random variability associated with the SFFT; random variability in average fragment length was equal or greater than the 19% effect of rate predicted for ideal elastic systems with no debonding at the interface. In addition, considerable interfacial debonding occurred during the SFFT, not surprising for Interfaces based on physisorption alone. Debonding Interferes with transfer of applied load from matrix to fiber, and would thus interfere with transfer of the effect of rate from matrix to fiber. A tensile Impact test developed previously was also performed on single-fiber composite specimens made from the same three materials systems. The results of the Impact tests differed from those obtained at controlled strain-rates for only two of the materials systems. [source] A Comparative Study of Modal Parameter Identification Based on Wavelet and Hilbert,Huang TransformsCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 1 2006Banfu Yan Special attention is given to some implementation issues, such as the modal separation and end effect in the WT, the optimal parameter selection of the wavelet function, the new stopping criterion for the empirical mode decomposition (EMD) and the end effect in the HHT. The capabilities of these two techniques are compared and assessed by using three examples, namely a numerical simulation for a damped system with two very close modes, an impact test on an experimental model with three well-separated modes, and an ambient vibration test on the Z24-bridge benchmark problem. The results demonstrate that for the system with well-separated modes both methods are applicable when the time,frequency resolutions are sufficiently taken into account, whereas for the system with very close modes, the WT method seems to be more theoretical and effective than HHT from the viewpoint of parameter design. [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] Modeling of coat-hanger die under vibrational extrusionJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2008Jin-Ping Qu Abstract The distributions of the pulsatile pressure field, the pulsatile velocity field, and the pulsatile resident time of the polymeric melt in the coat-hanger die are derived by using the pulsation of volumetric flow rate and pressure. Subsequently, formulae of the manifold radius and the slope of the manifold are deduced via volumetric flow rate pulsation. Polypropylene (PP) was employed for the experiments of the vibrational extrusion. The results indicate that the average extrusion pressure declines with frequency or amplitude decreasing; the distribution of residence time along the width of the coat-hanger die performs uniformly during the vibrational extrusion process; the theoretical extrusion pressure well agrees with the experimental pressure; the experiments of tensile test, impact test implicate that vibration improves the mechanical properties of products; differential scanning calorimetry testing demonstrates that the melting point of PP is moved to a higher temperature value, and the endothermic enthalpy and the crystallinity are improved as well when superimposing the vibrational force field. Accordingly, the model of the coat-hanger die under vibrational extrusion is well consistent with the experiments. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Effect of molecular relaxation of acrylic elastomers on impact toughening of polybutylene terephthlateJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2007Nafih Mekhilef Abstract In this study, we examined the performance of two core-shell acrylic-based impact modifiers (AIM) prepared by emulsion polymerization. The rubber core was prepared from ethyl hexyl acrylate (EHA) and n -octyl acrylate (n -OA). In such as process, the particle size and particle-size distribution of the modifiers were precisely controlled, so that performance differences observed in polybutylene terephthlate (PBT), used as matrix resin, could only be interpreted in terms of the nature of the elastomeric component of the modifiers. When isolated, the rubber core of the modifiers showed identical glass transition temperatures (Tg) by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) despite the fact that they were made from two different acrylic monomers. Temperature-frequency superposition principle inferred from the classical WLF equation showed that the rubber components exhibit the same Tg at all frequencies including at the time scale at which mechanical impact typically occurs. However, significant differences in low temperature impact performance measured at ,30°C using notched Izod impact test according to ASTM D 256 were obtained even though their rubber components had identical Tg. Such differences were attributed to the dynamic relaxation behavior of the rubber components and identified as inherent properties of the elastomers due to the structure of the monomers' repeat units. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] A study on the behavior of a cylindrical type Li-Ion secondary battery under abnormal conditions. Über das Verhalten eines zylindrischen Li-Ionen Akkumulators unter abnormalen BedingungenMATERIALWISSENSCHAFT UND WERKSTOFFTECHNIK, Issue 5 2010S. Kim zylindrische Li-Ionen Akkumulatoren; mechanisches Verhalten; abnormale Bedingungen; Separator Abstract Li-ion (lithium ion) secondary batteries are rechargeable batteries in which lithium ions move between the cathode and the anode. Lithium is not as safe as nickel cadmium (NiCd), and the Li-ion battery can under some conditions increase in temperature and ignite abnormal conditions which includes overcharging, being subjected to an impact, or being hit by a projectile. Before studying causes of Li-ion battery explosions, the term "abnormal condition" was defined. Next, to check the mechanical conditions, an impact test by a free falling object of 9.1 kg weight made of steel was carried out. After the impact test, the damage of the separator around the hollow of the jelly roll in the cell was observed. Following this, the same cell's electrochemical conditions were assessed through a heating test to determine the potential thermal runaway. Finally, to analyze the mechanical damage to the Li-ion batteries during the charging and the impact test, a finite element analysis was performed using LS-DYNA and ABAQUS software. A cylindrical type Li-ion secondary battery was selected for the impact test, heating test, and simulation. The test and simulation results provided insights into the extent to which cylindrical cells can endure abnormal conditions. [source] Microabrasion of Coatings Investigated by the Inclined Impact Test at Various Loads under Dry and Lubricated ConditionsPLASMA PROCESSES AND POLYMERS, Issue S1 2007Konstantinos-Dionysios Bouzakis Abstract The impact test has clearly emerged as an important technology for the prediction of cohesive, adhesive, and fatigue failure of coatings, further enabling the establishment of Smith and Woehler diagrams of PVD films. In the present paper, the abrasive wear of a well-adherent (Ti46Al54)N coating was investigated by the inclined impact test, at impact loads higher, equal to or lower than the fatigue critical impact load of the applied film. These investigations were conducted for few thousands up to several millions of impacts both under dry and lubricated conditions. The obtained results suggest that the inclined impact test is a very efficient method for detecting coating resistance against impact microabrasion, with or without lubrication and according to the test conditions for the synchronous contribution of fatigue phenomena to the film wear. [source] Characterization and properties of activated nanosilica/polypropylene composites with coupling agentsPOLYMER COMPOSITES, Issue 11 2009Ong Hui Lin In this work, nanosilica/polypropylene composites containing 1 wt% of silica nanoparticles were prepared by melt mixing in a Thermo Haake internal mixer. Prior compounding, nanosilica was subjected to surface activation using sodium hydroxide (NaOH) solution. The effectiveness of the activation process was evaluated by measuring the amount of hydroxyl groups (OH) on the surface of nanosilica via titration method and supported by FTIR analysis. Two coupling agents namely 3-aminopropyl triethoxysilane (APTES) and neopentyl (diallyl)oxy, tri(dioctyl) phosphate titanate (Lica 12) were used for surface treatment after activation process. The mechanical properties of polypropylene matrix reinforced with silica nanoparticles were determined by tensile and impact test. Hydroxyl groups on the nanosilica surface played an important role in enhancing the treatment with silane coupling agents. To increase the amount of hydroxyl groups on the nanosilica surface, the optimum concentration of NaOH is 1 mol%. Tensile strength, tensile modulus, and impact strength of nanosilica/PP composites improved with activation process. As the coupling agent is concerned, APTES coupling agent is more pronounced in enhancing the mechanical properties of the composites when compared with Lica 12 coupling agent. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [source] Das Geschäft mit den Schutzplanken , Wissenschaftliche und andere InteressenBAUTECHNIK, Issue 3 2008Hans-A. Als Schutzeinrichtungen am Rande von Straßen und Brücken konnten Stahlschutzplanken fast ein halbes Jahrhundert lang einen unangefochtenen Spitzenplatz einnehmen. Zu ihrer erfolgreichen Vermarktung haben eine wirksame Interessenvertretung sowie unkritische Betrachtungen des Anprallvorgangs beigetragen. Unter Vernachlässigung der an einer Schnittstelle von Bau-, Fahrzeug- und Verkehrstechnik notwendigen interdisziplinären Zusammenarbeit kam auf europäischer Ebene eine fragwürdige Norm zustande. Daran geäußerte Kritik störte das gesicherte Geschäft mit Schutzplanken und wurde mit disziplinarischen Maßnahmen beantwortet. Nachdem auch auf deutschen Straßen Vorteile von Schutzwänden aus Beton sichtbar werden, bedürfen frühere Fehleinschätzungen und Festlegungen einer Korrektur. Business on guardrails , scientific and other interests. For about half a century steel guardrails could rank in first place among safety devices at the borders of roads and bridges. An effective lobby as well as an uncritical observation of the impact test contributed to a successful marketing. Disregarding the need of interdisciplinary cooperation concerning road construction, motor vehicles, and traffic a questionable standard on European level has been accepted. Criticism of that standard seemed to be out of line with safe business on guardrails and was responded by disciplinary measures. After advantages of concrete safety walls are visible on German highways, too, former wrong assessments and agreements should go under review. [source] Evaluation of a new fiber-reinforced resin compositeJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2006S. Suzuki Abstract Efficacy of the usage of an experimental fiber-reinforced composite (FRC) on mechanical properties of an indirect composite was investigated by means of three-point bending and Charpy impact tests. Bond strength between the FRC and the indirect composite was also evaluated by tensile testing. The FRC consisted of a matrix resin with 25% silanized milled glass fiber (11-,m diameter, 150-,m length) and 5% colloidal silica. The values of strain of proportional limit, total strain, and fracture energy of the FRC during the bending test (1.2%, 10.4%, and 41.6 × 10,3 J) were significantly higher than those of the indirect composite (0.1%, 2.5%, and 11.9 × 10,3 J). The impact strengths of the 1-mm specimens with FRC ranged from 15.2 to 15.9 kJ/m2, and were significantly higher than that of the control (3.1 kJ/m2). The 2-mm specimens showed significant difference from the control when the FRC thickness was equal or greater than 0.5 mm. The bond strength after the thermocycling was 15.2 MPa, and all of the specimens exhibited cohesive fracture inside the indirect composite. Based upon the results, it was concluded that the FRC tested in this study improved toughness and impact resistance of the indirect composite. The interfacial bonding between the FRC and the indirect composite was strong enough to prevent delamination. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2006 [source] Morphological, mechanical, and rheological studies of PVC/ABS blends in the presence of maleic anhydrideJOURNAL OF VINYL & ADDITIVE TECHNOLOGY, Issue 2 2010Pegah Mohammad Hosseinpour A novel method of enhancing compatibility in PVC/ABS blends is the use of ABS-grafted-(maleic anhydride) (ABS- g -MAH) as a compatibilizer. In this study, maleic anhydride was grafted onto ABS (initiated by peroxide) in an internal mixer. Grafting degree was determined by a back-titration method, and certain amounts of the resultant ABS- g -MAH were added to PVC/ABS blends during their melt blending in the mixer. The weight ratio of PVC to ABS was kept at 70:30. Evaluation of compatibilization was accomplished via tensile and notched Izod impact tests, scanning electron microscopy (SEM), and rheological studies. According to the SEM micrographs, better dispersion of the rubber phase and its finer size in properly compatibilized blends were indications of better compatibility. Besides, in the presence of a proper amount [5 parts per hundred parts of PVC (php)] of ABS- g -MAH, PVC/ABS blends showed significantly higher impact strengths than uncompatibilized blends. This result, in turn, would be an indication of better compatibility. In the presence of 5 php of compatibilizer, the higher complex viscosity and storage modulus, as well as a lower loss modulus and loss factor in the range of frequency studied, indicated stronger interfacial adhesion as a result of interaction between maleic anhydride and the PVC-SAN matrix. J. VINYL ADDIT. TECHNOL., 2010. © 2010 Society of Plastics Engineers [source] High-pressure short time behavior of traction fluidsLUBRICATION SCIENCE, Issue 1 2006Nobuyoshi Ohno Abstract The squeeze film formation ability of traction fluids is studied under impact load by dropping a steel ball-bearing against a flat anvil made of mild steel. The effect of the pressure,viscosity coefficient and of the viscosity is investigated for plastic impact. The depth difference between the lubricated surface dent and the dry dent increases linearly with the product ,, of the pressure,viscosity coefficient , and the viscosity ,. The importance of the lubricant parameter ,, is observed under the squeeze film formation ability from contact voltage or elastohydrodynamic lubrication central film thickness measurement at rolling condition. The intensity of each impact collision is measured by means of an acoustic emission (AE) sensor. The high-pressure short-time solidification of traction fluids was confirmed by dent analysis after the impact tests and AE analysis under impact loads. Copyright © 2006 John Wiley & Sons, Ltd. [source] A New Apparatus for Particle Impact TestsPARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 4 2003Yevgeny Petukhov Abstract Breakage and chipping of particles due to collision with a hard surface is a common occurrence in many conveying and handling systems, such as pneumatic conveying and jet-mills. Studies of the breakage mechanism of particles due to impact and the effect of impact velocity and the number of impacts have been investigated in depth both experimentally and theoretically. In this paper, a new concept and apparatus are introduced for conducting particle impact tests. In most of the published test rigs, particles were accelerated towards a target. In our apparatus, the target moves and hits the particles. Using this concept, the machine can operate in a vacuum, which will reduce errors caused by air streams and turbulence. The performance of the new apparatus is analyzed and the breakage phenomenon is discussed, to some extent, for two materials. The results are presented in terms of the increase in the weight percentage of the feed broken and the decrease in the weight median size as the impact velocity or number of impacts increases. [source] Tailoring mechanical properties of nano-structured Eurofer 97 steel for fusion applicationsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 5 2010M. Kozikowski Abstract EUROFER 97 steel is a candidate structural material for future fusion reactors and Test Blanket Modules (TBMs). In the present work microstructure of Eurofer 97 was modified by hydrostatic extrusion in multi-step process with total true strain exceeding 3. TEM observations showed that HE causes significant grain refinement from about 400 to 80 nm. This is accompanied by improvement of the tensile mechanical properties and microhardness. On the other hand, there is a clear decrease in the resistance to brittle fracture as measured in the Charpy impact tests. In order to improve strength/ductility/fracture toughness balance, the extruded samples were annealed for 1 hour at temperature range of 473-1073K. The results obtained for samples after post-extrusion annealing are discussed in terms of mechanical properties of Eurofer 97 steel. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Effect of clay modification on the morphological, mechanical, and thermal properties of polyamide 6/polypropylene/montmorillonite nanocompositesPOLYMER COMPOSITES, Issue 7 2010Kusmono Polyamide 6/polypropylene (PA6/PP = 70/30 parts) blends containing 4 phr (parts per hundred resin) of organophilic montmorillonite (OMMT) were prepared by melt compounding. The sodium montmorillonite (Na-MMT) was modified using three different types of alkyl ammonium salts, namely dodecylamine, 12-aminolauric acid, and stearylamine. The effect of clay modification on the morphological and mechanical properties of PA6/PP nanocomposites was investigated using x-ray diffraction (XRD), transmission electron microscopy (TEM), tensile, flexural, and impact tests. The thermal properties of PA6/PP nanocomposites were characterized using thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), and heat distortion temperature (HDT). XRD and TEM results indicated the formation of exfoliated structure for the PA6/PP nanocomposites prepared using stearylamine modified montmorillonite. On the other hand, a mixture of intercalated and exfoliated structures was found for the PA6/PP nanocomposites prepared using 12-aminolauric acid and dodecylamine modified montmorillonite. Incorporation of OMMT increased the stiffness but decreased the ductility and toughness of PA6/PP blend. The PA6/PP nanocomposite containing stearylamine modified montmorillonite showed the highest tensile, flexural, and thermal properties among all nanocomposites. This could be attributed to better exfoliated structure in the PA6/PP nanocomposite containing stearylamine modified montmorillonite. The storage modulus and HDT of PA6/PP blend were increased significantly with the incorporation of both Na-MMT and OMMT. The highest value in both storage modulus and HDT was found in the PA6/PP nanocomposite containing stearylamine modified montmorillonite due to its better exfoliated structure. POLYM. COMPOS., 31:1156,1167, 2010. © 2009 Society of Plastics Engineers [source] Repeated impact behavior of glass/epoxy laminatesPOLYMER COMPOSITES, Issue 11 2009Bulent Murat Icten The response of glass,epoxy composites to repeated impact for various impact energies ranging from 5 to 15 J was investigated. Specimens with two different stacking sequences were studied; [0/90/0/90]S and [0/90/+45/,45]S. In addition to the room temperature, impact tests were also performed at ,40°C environmental test temperature for impact energy of 15 J. Contact force-deflection and energy-time curves at each test and the number of impacts to failure (Nf) were obtained for each experiment. Compression after impact (CAI) tests were also conducted to determine the residual load carrying capacity of the damaged specimens. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers [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] 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] Impact properties and microhardness of double-gated glass-reinforced polypropylene injection moldingsPOLYMER ENGINEERING & SCIENCE, Issue 9 2009Matias Martinez Gamba Injection moldings with weld lines were produced in glass reinforced polypropylene grades differing in filler content using a two-gated hot runner injection mold. The skin-core microstructure developed during injection molding was qualitatively analyzed by means of optical and scanning electronic microscopy techniques. The load bearing capacity of the moldings was assessed by uniaxial tensile-impact and biaxial instrumented falling dart impact tests. Microhardness was also used to ascertain the possibility of using it as a simple nondestructive technique for characterizing glass fiber-reinforced injection moldings. The properties were monitored at various points to evaluate their variation at the bulk and the knit region. The biaxial impact test highlights the 10-fold reduction of the impact strength caused by the weld line. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers [source] Impact fracture toughness of polyethylene/polypropylene multilayersPOLYMER ENGINEERING & SCIENCE, Issue 9 2004Luisa Moreno In a number of applications, a brittle polymeric surface layer is deliberately molded onto a tough substrate for decorative or protective purposes. This can increase the susceptibility of the tough polymer to premature failure. Similar problems arise when a surface layer becomes embrittled by environmental effects. Choosing a surface material that has good mechanical properties without having this effect can be difficult. In this work the fracture resistances of two polyethylenes and an ethylene/propylene copolymer, and of symmetrical two-component multilayers of these polymers, were determined as a function of temperature, using instrumented impact tests. The law of mixtures accounts adequately for the fracture resistance of multilayer structures where there is no mechanical interaction between skin and core. However, it gave misleading results for a structure in which high skin modulus at low temperatures appeared to influence the fracture resistance of the core through a constraint effect. Polym. Eng. Sci. 44:1627,1635, 2004. © 2004 Society of Plastics Engineers. [source] Association between plasticized starch and polyesters: Processing and performances of injected biodegradable systemsPOLYMER ENGINEERING & SCIENCE, Issue 5 2001Luc Avérous Different formulations of wheat thermoplastic starch (TPS) have been processed with various plasticizer/starch ratios and moisture contents. The biodegradable polyesters tested are polycaprolactone (PCL), polyester amide (PEA), polybutylene succinate adipate (PBSA) and polybutylene adipate co terephtalate (PBAT). TPS and polyesters are melt blended in different proportions by extrusion and then injected to obtain dumbbell specimens. Various properties are evaluated such as the mechanical properties (tensile and impact tests), and the hydrophilic character with contact angle measurements. Additionally, uniaxial shrinkage is evaluated. Results show that the addition of polyester to TPS increases the dimensional post-injection stability. Blend modulus values are close to the results of the classical rule of mixture. Elongation at break, resilience values and SEM observations seem to give some indications about the compatibility between both polymeric systems. PBAT and PEA present better results than PCL and PBSA. Contact angle measurement show that we have a drastic increase of the hydrophobic character from 10% of polyester in the blend. The different combinations of TPS and polyesters give a wide range of mechanical behavior for compostable materials, to be developed in specific applications. [source] Synthesis of sub-micrometer core,shell rubber particles with 1,2-azobisisobutyronitrile as initiator and deformation mechanisms of modified polystyrene under various conditionsPOLYMER INTERNATIONAL, Issue 10 2009Rujun Dai Abstract BACKGROUND: Sub-micrometer core-shell polybutadiene- graft -polystyrene (PB- g -PS) copolymers with various ratios of polybutadiene (PB) core to polystyrene (PS) shell were synthesized by emulsion grafting polymerization with 1,2-azobisisobutyronitrile (AIBN) as initiator. These graft copolymers were blended with PS to prepare PS/PB- g -PS with a rubber content of 20 wt%. The mechanical properties, morphologies of the core-shell rubber particles and deformation mechanisms under various conditions were investigated. RESULTS: Infrared spectroscopic analysis confirmed that PS could be grafted onto the PB rubber particles. The experimental results showed that a specimen with a ,cluster' dispersion state of rubber particles in the PS matrix displayed better mechanical properties. Transmission electron micrographs suggested that crazing only occurred from rubber particles and extended in a bridge-like manner to neighboring rubber particles parallel to the equatorial plane at a high speed for failure specimens, while the interaction between crazing and shear yielding stabilized the growing crazes at a low speed in tensile tests. CONCLUSION: AIBN can be used as an initiator in the graft polymerization of styrene onto PB. The dispersion of rubber particles in a ,cluster' state leads to better impact resistance. The deformation mechanism in impact tests was multi-crazing, and crazing and shear yielding absorbed the energy in tensile experiments. Copyright © 2009 Society of Chemical Industry [source] Thermal and mechanical properties of diglycidylether of bisphenol A/ trimethylolpropane triglycidylether epoxy blends cured with benzylpyrazinium saltsPOLYMER INTERNATIONAL, Issue 5 2002Soo-Jin Park Abstract The effect of blend composition on thermal stability and mechanical properties of diglycidylether of bisphenol A (DGEBA)/trimethylolpropane triglycidylether (TMP) epoxy blends cured with benzylpyrazinium salts (N -benzylpyrazinium hexafluoroantimonate, BPH) as a thermal latent catalyst was investigated. The thermal stability, characterized by the initial decomposition temperature, temperature of maximum rate of weight loss, integral procedural decomposition temperature, and activation energy for decomposition, increase in DGEBA-rich compositions. This could be due to the long repeat unit and stable aromatic ring in the DGEBA. The mechanical properties are also discussed in terms of the fracture toughness (KIC), flexural and impact tests for the blend composition studied. The addition of TMP into DGEBA gives systematic improvements in fracture toughness, which results from the increase in aliphatic and flexible chain segments of TMP. © 2002 Society of Chemical Industry [source] | ||||||||||||||||||||||||||||