Energy Absorbtion Research Articles

The effects of force application on the compressive properties of femoral spongious bone

BackgroundEnd artefacts play a major role in uniaxial compression tests with cancellous bone specimens. They lead to misinterpretation of mechanical parameters of bones due to uncontrolled introduction of bending moments into the free ends of trabeculae. This work aims to simplify current methods preventing end-artefacts and furthermore to investigate the influence of end artefacts on plateau stress. Methods176 cylindrical cancellous bone specimens were taken from human femoral condyles and tested in uniaxial compression. The specimens were divided into 2 groups (direct, end-cap) and compressive modulus, maximum stress, plateau stress, energy absorbtion as well as apparent density were evaluated. Density values are from separate specimens which are immediately adjacent to the mechanical specimen. FindingsAll mechanical parameters were significantly higher in the end-cap specimens than in the direct ones by about 30 – 40 %, thus reaching similar differences as the previous studies. Greatest differences between groups were determined for compressive modulus (45 %) and plateau stress (35 %). Energy absorbtion can be explained with great accuracy by plateau stress (P < 0.001; R2 = 0.95). Among all parameters plateau stress can be best explained by apparent density using an exponential function (P < 0.001; R2 = 0.38). InterpretationThe end-cap method used here to prevent end artefacts showed variations consistent with the literature when compared to the direct method. Additionally it was shown that the way in which the force is applied to the specimen has a major influence on the failure progression behavior, which was characterized using the plateau stress.

Impact Energy Absorbtion by Active Braking

Abstract Due to urbanization and the significantly increasing number of vehicles, urban roads are becoming more congested day by day, with the result that the rear-end collision has become the third most common type of collision. By developing and integrating active and passive safety systems, car manufacturers are working to prevent accidents and reduce the consequences of an accident. The present study examines a braking procedure and its applicability based on the integration of a passive and active safety system and provides development guidelines for the reduction of personal injuries and property damage in the event of a rear-end accident.

FEM model of protection bullet helmet made from composite material.

Damage evolution, mechanical behaviour, energy absorbtion, back-face deformation (BFD) and the perforation performance of Kevlar epoxy woven composite with and without foam (PU foam) were examined for various impact energies based on the drop weight test. The Kevlar woven composite induces different damage and deformation depending on its hybrid patterns. The Kevlar composite with PU foam decreases significantly, and the BFD of shell composite and transform locally deformation become a global nature. In addition, damage type - as fibres break - is primary dominant for Kevlar composite without PU foam. However, the role major damage as delamination, significantly appear for Kevlar composite with PU foam. In order to investigate the damage mechanism, energy absorbtion and BFD, FEM simulation were also performed. The FEM simulation is in very good agreement with the drop weight test. Finally, the FEM study showed that PU foam is able to decrease significantly, the BFD of composite shell, and the contact force on the skull, during ballistic impact.

Biobased insulating panels from mulberry stems

In this work, Mulberry Stems (MS) obtained as a by-product of sericulture have been used as reinforcement for Polypropylene (PP) composites intended for green building, furniture and automotive applications. Mulberry stems are lignocellulosic and are renewable and sustainable sources but remain unutilized and are usually discarded as waste by burning or burying. An attempt has been made to utilize mulberry stems as substitutes for commonly used non-biodegradable composites using a simple and clean fabrication technique. The effects of reinforcement percentage (80% to 95% w/w) of MS and density (0.5 g cm−3 to 1.25 g cm−3) of composites on the properties have been studied. Results revealed that, 90/10 (MS/PP w/w %) was the optimum ratio that provides highest mechanical strength. Increasing the density enhanced the strength, thermal insulation, sound transmission loss, water stability and flame retardancy. The 1.25 g cm−3, 90/10 ratio composite had a high sound transmission loss of 46.6 dB and thermal conductivity of 0.130 W/mK which is 70% lower than neat gypsum board used in false ceiling applications. The high insulation and sound barrier properties of mulberry stem based composites are due to the unique hollow morphology of MS which aids in efficient absorbtion and dissipation of the thermal energy and sound waves. Weight loss of MS/PP composite after soil burial test for 120 days varied between 8.9% and 31.4%. MS/PP composites could be potentially used as a green replacement for ply, particleboards, false ceiling, automotive parts and other applications.

Flexural behaviour of basalt fibred concrete slabs made with basalt fibre reinforced polymer rebars

In this paper, the flexural behaviour of M30 grade basalt fibred concrete slabs made with basalt fibre reinforced polymer rebars are studied and compared with slabs made with steel rebars. The optimum percentage of basalt is 0.3% for 50mm length basalt fibres. Due to high particle packing density in concrete made with basalt fibre micro cracks are prevented due to enhanced fatigue and stress dissipation capacity. Addition of basalt fibres to enhances the energy absorbtion capacity or toughness thereby enhancing the resistance to local damage and spalling. Addition of basalt fibres controlled the crack growth and crack width. Load at first crack of M30 grade basalt fibred concrete slabs made with basalt fibre reinforced polymer rebars is more than M30 grade conventional concrete slabs made with steel rebars because the with addition of basalt and BFRP bars will make either the interfacial transition zone (ITZ) strong or due to bond strength of concrete slabs made with basalt fibre reinforced polymer rebars. The ultimate strength in M30 grade basalt fibred concrete slabs made with basalt fibre reinforced polymer rebars is more than conventional concrete slabs made with steel rebars. Deflection at the centre of M30 grade basalt fibred concrete slabs made with basalt fibre reinforced polymer rebars is almost double than the conventional concrete slabs made with steel rebars. Toughness indices evaluated for M30 grade basalt fibred concrete slabs made with basalt fibre reinforced polymer rebars indicates that basalt fibre and BFRP bars will enhance the energy absorbtion capacity of slabs.

Bolster Barrier (BOLER) as a Guardrail Impact Device to Enhance Energy Absorbtion

Guardrails are the most important road furniture which prevent vehicles from going off the road or into the opposite lane. It also protects objects at the roadside and prevent vehicles from entering into dangerous areas such a ravine or river. Performance of guardrails is not only influenced by their own design, but also the design of the vehicle. The design of guardrails is mostly aimed to reduce serious effects towards vehicles and users in an event of an accident. Bolster Barrier (BOLER) is an impact device that enhances the existing W-shape guardrails that are intended to reduce the accident impact between road users and the guardrails themselves. The application of BOLER is focused at critical areas. The purpose of this device is to reduce the numbers of serious injuries and fatalities in an accident. BOLER involved an impact test known as dolly test at MIROS Lab, Provisional CRASE Crash Centre (PC3) of Ayer Molek, Melaka. The test measured the dolly’s velocity, W-beam guardrail bar’s deformation and the overall force overtime trace. The results for standard the W-beam guardrail with new impact device showed a lower peak force (47.6kN versus 51.5kN) and a delay in reaching peak force by 11.4 milliseconds as compared to guardrails without the new guardrail device. This delay of 11.4 milliseconds is crucial allowing airbags to inflate before full impact.

Effect of rubber particles on dynamic mechanical properties of ultra-lightweight cement composites

This paper develops a novel rubberized ultra-lightweight cement composites (RULCC) incorporated with different amount of rubber particles and investigates the static and dynamic mechanical properties of the RULCC experimentally. This study shows that the rubber particles have significant effect on the compressive strength, stress-strain curve and failure mode of the RULCC. A volume replacement of fine aggregates with 10% and 20% rubber particles results in a reduction in static compressive strength and elastic modulu. The dynamic experiments show the RULCC is a strain-rate sensitive material and the dynamic stress-strain curves illustrate that the capcity of energy absorbtion of RULCC is better than the composites without rubber particles. The experimental and analytical studies are essential to better understand the fundamental dynamic behaviour of RULCC for its further applications.

Energy characteristics of interfacial bridged cracks

Two energy characteristics of interfacial bridged cracks are considered: 1) the deformation energy release rate associated with the crack tip stress intensity factors; 2) the rate of the energy absorbtion by bonds associated with the energy necessary to create a unit of new surface of the bridged zone. The analysis of these energy characteristics (the last one - with more details) for interfacial straight bridged crack is performed numerically. The influence of materials and bonds mechanical properties on the energy characteristics of the bridged crack is studied. The limit equilibrium analysis of a crack is performed on the basis of the proposed nonlocal two-parametrical fracture criterion with the crack tip development condition which is based on the crack bridged zone energy characteristics (it is the necessary fracture condition) and the kinematic condition for the advancing of the trailing edge of the crack bridged zone (it is the sufficient fracture condition). The regimes of the equilibrium and quasi-static growth of the bridged zone and the crack tip are formulated.

Comparative Analysis of Vehicle Crash Box of Different Shapes for Maximum Collision Energy Absorbtion

Comparative Analysis of Vehicle Crash Box of Different Shapes for Maximum Collision Energy Absorbtion

THE STUDY OF MECHANICAL PROPERTIES OF LAMINATED BAMBOO STRIP (LBS) FROM GIGANTOCHLOA LEVIS TYPE MIXED WITH EPOXY

This study about laminated bamboo strip from gigantochloa levis type mixed with epoxy composite. Due to the existence of demand for products that are comfortable, healthy and environmentally friendly, this research has focused on the use of renewable sources that is bamboo. Bamboos are some of fastest growing plant in the world and also have a higher compressive strength than wood, brick or concrete and a tensile strength that rivals steel. Certain species of bamboo can grow 35 inchies within 24 hour period, at a rate of 3 cm/h. That means bamboos can growth of approximately 1 mm every 2 minutes. In this study, the bamboo strip reinforced with epoxy was processed through hand lay-out method. Bamboo strips are combined with epoxy for a total sample thickness of 3 mm. This study is performed using the impact test that is Charpy (ASTM D-6110) and Izod (ASTM D-256) to measure the mechanical properties of energy absorbtion, followed by hardness test (ASTM D-1037). The 0, 60 and 90 degree of laminated bamboo strip epoxy composite with two types of load 7 kg and 14 kg has been tested. It is found that the 0 degree specimen Charpy test give the best value is 4.79 Joule energy absorbtion for 14 kg load. While for the Izod test, the best composition is also 0 degree with 4.51 Joule energy absorbtion for 14 kg load. It is shown that when the degree of bamboo laminate configuration increases, the impact absorbtion decrease. The result also shown that, when the load is increase the impact also increases. It means that got relative significant between bamboo strip configuration and load. The impact properties relate to the loading weight. The hardness test also shown that the laminated bamboo strip for 14 kg load resulting 91 rating, that is more higher than 7 kg load that is 84. It is shown that more loads will result more hardness rating for the laminated bamboo strip.

A Comparative Study of the Damping Force and Energy Absorbtion Capacity of Regenerative and Conventional-Viscous Shock Absorber of Vehicle Suspension

This paper presents a comparative study of the damping force and energy absorbtion capacity of a typical conventional-viscous and a regenerative shock absorber for vehicle suspension. Regenerative shock absorber (RSA) is a shock absorber which can regenerate the dissipated vibration energy from vehicle suspension into electricity. In this research, a prototype of regenerative shock absorber was developed, its damping force and energy absorbtion capacity were tested, and the results were analized and compared with those of a typical conventional-viscous shock absorber. The regenerative and viscous shock absorber were compressed and extended in various excitation frequency using damping force testing equipment to obtain force-velocity and the force-displacement curves. The force-velocity and force-displacement curves indicate the damping force and energy absorbtion capacity of the shock absorber. The results show that the damping force of the typical-viscous shock absorber closed to linear at all exciation frequencies. For regenerative shock absorber, nonlinearity and large hysteresis area of the damping force occur at all excitation frequencies. Further, the energy absorbtion capacity of the typical-viscous shock absorber shows an elliptical area with the compression part bigger than the extension one, while those of the regenerative shock absorber shows an asymmetric square area, which indicates a smaller energy absorbtion capacity. These phenomena indicate the significant effect of implementing dry friction damper and elctrical damper to the characteristics of regenerative shock absorber.

The Effect of Using Current Stabilizer to the Dynamic Characteristic of a Regenerative Shock Absorber

Most of the energy from the vehicle is wasted in the form of heat energy and vibration. On vehicles, the largest vibration occurs in the suspension system. The development of a mechanism which can recover the vibration energy and convert it into electrical energy, named Regenerative Shock Absorber (RSA), will be detailed in this paper. The prototype of RSA which consist of gear transmission and an electromagnetic type electric generator was studied and analyzed. Electrical circuit signal conditioner / stabilizer is added into the RSA system to stabilize the output current of the generator so that the generated electrical energy can be stored in the battery of 6 volts. The characteristics of the RSA are obtained by testing the value of the damping coefficient, the energy absorbtion capacity, and the generated electrical energy before and after going through a series of signal conditioner. Experiment was also performed by measuring the acceleration response time of the sprung and un-sprung suspension system that uses RSA with damping ratio value of 0.6. From this research, it is found that RSA design with stabilizer circuit can produce more stable electric current and voltage. The measurement results show the value of the electrical voltage output through the generator is fluctuating with an average value of 15 volts and a constant 6 volts output is obtained through the signal conditioning circuit. Furthermore, the dynamic response is obtained in the form of acceleration time-value of less than 0.2 m/s2 in a corresponding ISO 2631 standard is stated very comfortable.

PENGARUH SUSUNAN PIPA LALUAN TERHADAP PEMANFAATAN KALOR PADA KOLEKTOR SURYA PELAT DATAR ABSORBER GRANITE

The collector of solar energy can be used for heating fluidssuch as liquid or gas. The optimize absorbtion of solar energy depends on the collectordimention and component, e.g.the width, body of collector, tube formation, cover and isolation system. This research usesa granite absorber with a variation of tube formations and water flow rates. The aim of the research is tofind out the optimal tube formation. To achieve the aim of the research,theexperiments of water heating usingthree collectorswith a granite absorber 80 Cm x 100 Cm and three way tube formatians have been done.The variation of water flow rates had beenperformed toinvestigate the maximal performance. The water flow rates used were200, 250 and 300 cc/minute.The result of research achieved value of heat utilization of solar collector influenced by: arrangement inlet tube, flow rates of water and time. The maksimal heat utilization occur at parallel 7 for each flow rate. The flow rate 300 cc/minute show maximal heat utilization.

Experimental analysis of normal and oblique high velocity impacts on carbon/epoxy tape laminates

In this work, the effect of high velocity impacts on carbon/epoxy tape quasi-isotropic laminates is studied. Experimental test were carried out at two different impact angles and in a wide range of velocities (from 80 to 490m/s). Both parameters, the residual velocity and the damaged area, are used to evaluate the effect of the kinetic energy of the projectile on the laminate response. In addition it has been proposed a simplified analytical model which allows to identify the different energy absorbtion mechanisms and predict the residual velocity of the projectile. Finally the energy absorbed by the laminate during the impact is studied.

A desalination plant with solar and wind energy

The shortage of freshwater resources has become a worldwide problem. China has a water shortage, although the total amount of water resources is the sixth in the world, the per capita water capacity is the 121th (a quarter of the world's per capita water capacity), and the United Nations considers China one of the poorest 13 countries in the world in terms of water. In order to increase the supply of fresh water, a realistic way is to make full use of China's long and narrow coastline for seawater desalination. This paper discusses a sea water desalination device, the device adopts distillation, uses the greenhouse effect principle and wind power heating principle, and the two-type start is used to solve the problem of vertical axis wind turbine self-starting. Thrust bearings are used to ensure the stability of the device, and to ensure absorbtion of wind energy and solar energy, and to collect evaporation of water to achieve desalination. The device can absorb solar and wind energy instead of input energy, so it can be used in ship, island and many kinds of environment. Due to the comprehensive utilization of wind power and solar power, the efficiency of the device is more than other passive sea water desalting plants, the initial investment and maintenance cost is lower than active sea water desalting plant. The main part of the device cannot only be used in offshore work, but can also be used in deep sea floating work, so the device can utilise deep sea energy. In order to prove the practicability of the device, the author has carried out theory of water production calculations. According to the principle of conservation of energy, the device ais bsorbing solar and wind power, except loose lost part which is used for water temperature rise and phase transition. Assume the inflow water temperature is 20 °C, outflow water temperature is 70 °C, the energy utilization is 60%, we can know that the water production quantity is 8 kg/ m2 per hour. Comparing with the disk solar distillation apparatus, of which water production quantity is only 3-4kg/m2 per hour only in sunny day, but can't be used at night, the water production quantity is highly increased. So the device should have a good application prospect.

P 19. Threshold for neurodegeneration and microstructural changes in different cell types induced by anodal transcranial direct current stimulation

Introduction Transcranial direct current stimulation (tDCS) has been shown to modulate cortical excitability and to improve motor learning (Nitsche and Paulus, 2000; Reis et al., 2009; Fritsch et al., 2010). To date there is no data available on the safety aspects of tDCS covering a broad range of stimulation intensities, thus limitations for dosages applied to humans are still based empirically on other types of electrical brain stimulation (Agnew and McCreery, 1987). Objectives The aim of this study was to investigate lesion threshold, accompanying neurodegeneration and possible microstructural changes in glial cells in an animal model of tDCS. Methods The tDCS electrode was placed in a screw tube surgically fixed on the skull above the left primary motor cortex of 47 Male Sprague Dawley rats. Anodal tDCS was applied in different intensities (254.8, 127.4, 63.7, 31.8, 15.9 and 8A/sqm) or as sham stimulation for 20min under slight isoflurane anesthesia. For each intensity animals were sacrificed either 24h (acute effects) or 7days (chronic effects) after intervention. Histological analyses of neurodegeneration (HE-staining, Fluoro-Jade C), astrocyte (anti-GFAP) and microglial (anti-CD11b [OX-42]) cell counts/density and/or morphological changes were evaluated. Results Macroscopical lesions could be observed at tDCS intensity of 127A/sqm and above whereas the lesion dose 50 (LD 50) for microscopical neurodegeneration was determined at 60A/sqm. Threshold for damage in neuronal and glial cells and change in morphology (activation) was identical. These changes could be detected both in the acute and chronic group. Notably, signs of still ongoing neurodegeneration, though to a slighter extent, were seen 7days after stimulation. Brain swelling, which was seen underneath the stimulation electrode 24h following the highest intensity used, was not present one week after stimulation. Conclusions Our results demonstrate that the LD 50 intensity of anodal tDCS for unwanted structural effects is 75 times higher than the intensities applied to humans to date. Additional safety derives from the fact that structures between brain and stimulation electrode, which lead to energy absorbtion, are thicker in humans compared to rats. Cell death, as a trigger for glial reaction, continues even 7days after the intervention. Based on our results we conclude that higher tDCS intensities in human studies can be applied without risking structural damage.

Vibration Energy Harvesting on Vehicle Suspension Using Rotary and Linear Electromagnetic Generator

In this paper, we discuss comparation of vehicle vibration energy harvesting between rotary and linear electromagnetic generator. We construct the two model of energy harvester mechanism and then analyze both of energy absorbtion and vehicle comfortability. Furthermore, we analyze both of energy absorbtion and vehicle comfortability. Vehicle is modeled as quarter car. Rotarty generator harvests 2.5 x 10-4 Watt. The other hand, linear generator has viscous characteristic and capable to generates 90 Watts with 12 Volt power supply for 0.03 m amplitude of bumpy road input. Linear generator reduces oscillation with 1.2 sec settling time. It is more comfort than the angular which has 3 sec in settling time. With unnevenees road input, mean power of this generator is 64 Watt.

Development and Mechanical Behavior of FML/Aluminium Foam Sandwiches

In this study, the Fiber-Metal Laminates (FMLs) containing glass fiber reinforced polypropylene (GFPP) and aluminum (Al) sheet were consolidated with Al foam cores for preparing the sandwich panels. The aim of this article is the comparison of the flexural properties of FML/Al foam sandwich panels bonded with various surface modification approaches (silane treatment and combination of silane treatment with polypropylene (PP) based film addition). The FML/foam sandwich systems were fabricated by laminating the components in a mould at 200 °C under 1.5 MPa pressure. The energy absorbtion capacities and flexural mechanical properties of the prepared sandwich systems were evaluated by mechanical tests. Experiments were performed on samples of varying foam thicknesses (8, 20 and 30 mm). The bonding among the sandwich components were achieved by various surface modification techniques. The Al sheet/Al foam sandwiches were also consolidated by bonding the components with an epoxy adhesive to reveal the effect of GFPP on the flexural performance of the sandwich structures.

Crash Analysis of Vehicle Front Bumper and Its Optimization

The objective of this paper is to investigate the crash energy absorbtion of bumper-crash box system subjected to 40% offset impact loading. Nonlinear finite element model was created and impact test was simu- lated using Ls-Dyna software. Design of experiment method is used to construct approximated design functions then size optimization technique is defined to solve the problem of minimization of the total weight. Matlab was used to solve the size optimization problem and optimum sheet thickness value was determined for the impact condition of 40% offset. The study also has shown that crushing initiator geometry on the crash box significantly decrease the maximum initial reaction force but its effect on energy absorbing capacity was relatively small.

The Effect of Colloidal Silica Dispersions on the Energy Absorbtion of Polyethylene Nonwoven

In this study, the effect of colloidal silica dispersions on the energy absorbtion of different weight in grams polyethylene nonwoven interfacing material is investigated. By this aim; three different (18, 28 ve 45 gr/m 2 ) weight in grams interfacing materials are padded with five different concentrated (0,20, 30, 40 ve 50 gr/lt) silica dispersions so the variation of interfacing material's energy absorbtion is measured. According to research results, interfacing material's energy absorption increases with the increase in silica dispersions concentration and the wight in grams of interfacing material.