Ball Drop Test Research Articles

Improvement of windshield laminated glass model for finite element simulation of head-to-windshield impacts

The automotive windshield, with which pedestrians come into frequent contact during car accidents, has been identified as one of the main sources for severe pedestrian head injuries. Finite element simulation of head-to-windshield is widely used for the design and evaluation of car safety performance. Most of the windshield models used in the simulations for pedestrian head injury studies are simplified model. However, accurate modelling of windshield mechanical behaviour is necessary for good prediction of head injury during car-to-pedestrian collision. The purpose of this paper is to improve the model of automobile windshield for simulation of a collision between a pedestrian and a car. The laminated glass windshields of various thickness were tested according to UNECE R43. The deformation and crack pattern were recorded for validation of the finite element model. The finite element models of two layers and three layers laminate glass were developed. Element deletion method and share node techniques were employed for crack propagation pattern. Appropriate mesh size and shaped were obtained. The simulation results were compared with the experimental results of ball drop tests. The simulation results of the laminated glass model with two layers, lmm-triangle mesh shows good agreement with the experimental results. This laminated glass model was then implemented to the windshield of the car. Simulation of headform impact tests according to the EEVC protocol on pedestrian protection were performed. The results in terms of head deceleration, crack pattern and windshield energy absorption were compared with the test results. Good agreement can be seen.

잔향실에서의 고무공 충격음 반복성 평가

Real impact sound, such as child’s running and jumping in an apartment building, is best simulated using a rubber ball as this is the impact source established to be the most similar. As such, the rubber ball is the only heavy/soft impact source included the ISO standards, and a single numeric value for the rubber ball impact-sound is being standardized. However, it is necessary to check the repeatability of the results of a rubber ball drop from a 1 m height when using different operators, specifically a human operator and a rubber ball dropping machine. In this study, the repeatability of rubber ball drop-results was evaluated under reverberation conditions. Results indicated that the floor impact sound pressure level differed very little between the different operators. Testing using the rubber ball dropping machine showed that the reproducibility of the dropping machine’s sound was highest in the low-frequency band, excluding the 80 Hz band. Establishing results for a human operator dropping the rubber ball proved to be useful for improving the quality of the ball-drop test in the test room, and offers the additional benefit of extensibility into the field, as a human operator is easy to move and can check the impact force exposure level of the rubber ball.

Enhanced impact strength of injection-compression molded parts by controlling residual stress distribution

The objective of this study is to elucidate the relation between the results of ball drop tests and the residual stress distribution of an injection-compression molded part. To improve the ball drop property, a high impact material and a robust manufacturing process were employed. For the application to the transparent plastic window, it is of great importance to increase the impact strength of plastic products. Thin-walled plates were molded with use of rubber nanoparticles embedded poly(methyl methacrylate) (PMMA). Different compression gaps were considered during injection-compression molding (ICM) to adjust the residual stress distribution developed in the specimens. The ball drop tests were carried out to evaluate the impact strength of the prepared samples. In addition, the ICM was numerically simulated to predict the residual stress distribution in the parts.

Prediction model to estimate the specific energy and product particle size distribution of semi-autogenous mill

The optimal use of energy for grinding of ores in mills is one of the key objectives of this study. An attempt has been made to present an experimental model for the specific energy and product particle size distribution of semi-autogenous mills for the simulating of real conditions of the particles collision. A novel semi-autogenous mill test has been suggested in order to measure the required energy for grinding. The effect of the mill’s operation time and various energy levels on the particle size distribution and feed ore hardness has been investigated with samples collected from the Sarcheshmeh Copper Complex, Kerman, Iran. The obtained results demonstrated that there is a high congruence between the experimental product particle size distribution and energy, which are predicted by the proposed novel method and ball-drop test. Using the proposed analytic relationships, the required comminution energy and semi-autogenous mill operating time to achieve the specific product particle size distribution can be estimated with high accuracy ( R2 = 0.96). Finally, the accuracy of the results was evaluated by a ball drop-weight test.

Properties of Controlled Low Strength Material with Circulating Fluidized Bed Combustion Ash and Recycled Aggregates.

This study aims to investigate the effect of adding circulating fluidized bed combustion (CFBC) ash, desulfurization slag, air-cooled blast-furnace slag and coal bottom ash to the controlled low-strength material (CLSM). Test methods include slump flow test, ball drop test, water soluble chloride ion content measurement, compressive strength and length change measurement. The results show that (1) the use of CFBC hydration ash with desulfurization slag of slump flow is the best, and the use of CFBC hydration ash with coal bottom ash and slump flow is the worst; (2) CFBC hydration ash with desulfurization slag and chloride ion content is the highest; (3) 24 h ball drop test (diameter ≤ 76 mm), and test results are 70 mm to 76 mm; (4) CFBC hydration ash with desulfurization slag and compression strength is the highest, with the coal bottom ash being the lowest; increase of CFBC hydration ash can reduce compressive strength; and (5) the water-quenched blast furnace slag and CFBC hydration ash would expand, which results in length changes of CLSM specimens.

Effect of Nano-NiO Additive on Adhesion Strength and Bubble Structure of Vitreous Enamels

The effect of NiO nanopowder on the adhesion strength and formation of fish-scales in vitreous enamels has been investigated. The results of a ball drop test indicated that the adhesion strength was greatly increased by a mill addition of NiO nanopowder. The adhesion strength and bubbling microstructure of the enamel were studied using optical and scanning electron microscopy (SEM) in conjunction with energy dispersive spectroscopy (EDS) analysis. The results showed that, as a mill additive, NiO nanopowder changes the composition and structure at the enamel-steel interface and enables interdiffusion. In addition, as the amount of mill addition was increased, the size of the gas bubbles increased and the cracks of the enamel layer, generally referred to as fish-scaling, were reduced.

Hard body impact on glass panes and the fracture energy equilibrium

The Griffith theory describes the behavior of brittle materials. For the description of a crack creation, an energy equilibrium is used. At annealed glasses, this equilibrium is reduced to a simple formula containing the mechanical energy in the glass and the surface energy needed for crack creation. The paper deals with the question, whether ball drop test allows the demonstration of the crack creation principles. Furthermore, the specific surface energy is the coefficient that describes the energy needed to create cracks. Therefore it will be discussed here whether ball drop tests produce similar specific surface energy values like static tests, e.g. double cantilever of three-point-bending tests. The testing results show a constant surface energy coefficient at different drop height. Nevertheless, the measured coefficient showed a significant difference to statically determined surface energy coefficients. This was explained by the only partly use of the potential energy of the ball drop for the crack creation. The damping of the glass pane, that is supported in a gasket play a significant role in energy absorption. At a ball drop test the energy amount is defined and the energy input cannot be stopped during the experiment. Despite its easy build-up and conduction, the ball drop test seems not to be an appropriate investigation for the fracture mechanism of brittle glass.

On the effectiveness of incorporating shear thickening fluid with fumed silica particles in hip protectors

The objective of this research is to develop a smart hip protector by incorporating shear thickening fluid (STF) into conventional foam hip protectors. The shear thickening properties of fumed silica particles dispersed in liquid polyethylene glycol (PEG) were determined from rheological tests. Dynamic drop tests, using a 4 kg drop platen at 0.5 m drop height, were conducted to study how STF improves energy absorption as compared to unfilled foam and PEG filled foam. The results show that PEG filled foam reduces the mean peak force transmitted by a further 55% and mean peak displacement by 32.5% as compared to the unfilled foam; the STF filled foam further reduces mean peak force and displacement by 15% and 41% respectively when compared to the PEG filled foam. At a displacement of 22 mm, the STF filled foam absorbs 7.4 times more energy than the PEG filled foam. The results of varying the drop mass and drop height show that the energy absorbed per unit displacement for STF filled foam is always higher than that of PEG filled foam. Finally, the effectiveness of a prototype of hip protector made from 15 mm thick STF filled foam in preventing hip fractures was studied under two different loading conditions: distributed load (plate drop test) and concentrated load (ball drop test). The results of the plate and ball drop tests show that among all hip protectors tested in this study, only the prototype can reduce the mean peak impact force to be lower than the force required to fracture a hip bone (3.1 kN) regardless of the type of loading. Moreover, the peak force of the prototype is about half of this value, suggesting thinner prototype could have been used instead. These findings show that STF is effective in improving the performance of hip protectors.

Engineering properties of controlled low-strength materials containing co-fired fly ash

In this study, it investigated the effects of adding a mixture of circulating fluidized bed co-fired fly ash and bottom ash on controlled low-strength material (CLSM). Experiment variables were as follows: (1) mixing of co-fired fly ash, cement, and pulverized coal fly ash in various proportions to evaluate the effectiveness of using co-fired fly ash as cementitious material in CLSM; (2) mixing of bottom ash and natural fine aggregate in various proportions to evaluate the effectiveness of using bottom ash mixture as aggregates in CLSM. The water-cement ratio of CLSM was fixed at 0.85. Assessments were conducted using a lump flow test, flow consistency test, ball drop test, chloride ion measurement, compression strength test, and length change test. Test results indicate the following: (1) increasing the replacement ratio of co-fired fly ash and bottom ash decreases flowability; (2) the addition of co-fired ash (containing chlorine), with bottom ash increases the amount of chloride ions in CLSM; (3) the addition of co-fired fly ash reduces setting time; (4) the CaO, SiO2, and Al2O3 in co-fired fly ash and bottom ash increase the compressive strength of CLSM; (5) the CaO contained in the mixture of co-fired fly ash and bottom ash causes CLSM to expand.

Impact force loss behavior of flocked surfaces

The impact force loss behavior of flocked energy absorbing materials (FEAM) was experimentally studied in the context of double-side flocked FEAM element layered structures. A ball drop test determined the force loss per cent (FL%) properties of various assembled panels. This study showed that: (a) FEAM layers are most effective when used in multiple layer configurations. (b) When fabricating multi-layer two-side flocked FEAM layer configurations, a film or fabric divider sheet should be placed between adjacent flocked layers to prevent the flocked fibers from intermeshing with each other during compressional deformation. (c) FEAM elements perforated with 6.4 mm (¼”) diameter holes, 12.7 mm (½”) off staggered centers, exhibit a higher FL% per areal density compared to non-perforated FEAM panels. (d) Promising improvements in FL% properties are found by sandwiching either foam or spacer fabric between two FEAM layers. These three-layer structures are found to have higher FL% values than individual foam or spacer fabric components. A possible synergistic effect might be operating. (e) Low strain rate (5 and 50 mm/min) compressional load deflection rate data on combination FEAM/ vinyl nitrile foam/FEAM layers have shown that the initial ‘hump’ in the foam’s stress–strain curve is eliminated. FEAM layers and their foam and spacer fabric combinations should lead to creating effective impact energy absorbing pads for sport, military and civil servant applications.

Analysis of Changes in the Surface Quality of a UD Prepregs Composite due to Mechanical Loading

Optimizing the mechanical properties of composites is very important for light low energy constructions. Unidirectional prepreg (UD prepreg) is an intermediate product synthesizing a unidirectional layer of carbon fibres with a matrix. This can be used in the production of continuous fibres of reinforced composites. The individual layers can be stacked on top of each other to precisely orientate the layers and attain the maximum properties in a given direction. The resulting composite is ultra thin with the highest possible fraction of fibres. Prepreg composites are very high quality and have very good mechanical properties. They can be applied in sectors where the requirements for mechanical resistance are very high. This paper presents an experimental and numerical analysis of the surface of a composite and the changes that may occur to it under the influence of loading. The Ball Drop Test (ASTM D6024-07 / DIN 52306) was used as a stress test. Test samples scanned by image analysis showed that the surface properties of the UD prepreg were not disrupted, while scanning with AXIO IMAGER M2 showed apparent surface disruptions. From the numerical simulations it was determined that a directional orientation of the fibres of +45°/0°/-45° significantly affects their elastic properties.

Dynamics behavior of flat glass panels under impact conditions: Experiments and numerical modeling

AbstractResponse of brittle plate‐like structures such as glass panels to impact loads has been the subject of many research studies. Different compositions of glass are used in wide variety of applications in daily life. Of interest in this study are the glass panels that are used in consumer electronics devices such as mobile phones, tablets, and televisions that help to protect the displays from every day wear and tear. Therefore, the requirement of this glass to resist scratches, drop impacts, and bumps from everyday use leads to the importance of investigation of the glass response under dynamic impact loading. Ball drop test is a widely accepted test for impact reliability in the industry. The test specifies the impact energy threshold as a qualification and prediction metric. Use of energy as the key parameter in impact testing is limited, because it does not account for the time spent in contact during the impact event. This study attempts to establish a reliable metric for impact testing based on a momentum change. The deformation and the strain of the glass will be obtained by the digital image correlation system, while the rebound velocity will be measured with the high‐speed cameras. The global and local measurements are conducted to verify the accuracy of the experimental results. Finite element analysis is conducted using ABAQUS to provide a comprehensive understanding of the dynamic response of the glass. Constitutive relationship for a tape, a hyperelastic material, is developed in this study. Good correlation in deflection time history is obtained between the measurements and predictions.

Finite element simulations of high-frequency crash signals for robust crash discrimination

This work presents finite element simulations of a crash-management system and a body-in-white vehicle structure under low-speed crash conditions. The simulation models can be used to predict the excitation of high-frequency acceleration signals due to the initial impact and deformation of the crash-management system. In recent years, modern crash detection systems started to use frequency crash signals up to 20 kHz to distinguish between different crash severity levels and to trigger the restraint systems accordingly. The parameterization and application of such crash detection systems to new vehicle models require extensive testing of vehicle prototypes. The discussed approach allows assessment of the virtual components with respect to the signal quality at an early design stage. The first part of the study covers a ball-drop test to identify and isolate relevant modelling parameters. The second part discusses a crash-management system model and a low-speed crash with a body-in-white vehicle structure. Although finite element method crash simulations have already become a standard tool for assessment of the vehicle safety, no published work was found on the excitation of crash signals in that particular frequency range. The results show that the present-day finite element method is already capable of simulating frequency signals up to 20 kHz, which are excited through complex deformation processes. The simulation results are validated by experimental data and are within the measuring accuracy and the experimental repeatability. Simulations of crash signals allow simultaneous design optimization of the vehicle components and the crash detection system.

이온강화법을 이용한 소다라임 글라스 강화에 관한 연구

ABSTRACT lass used for mobile display windows is requireThe g d to have high strength. Chemical strengthening by means of ion exchange is widely used glass. The depth of the layer and the compressed stress are affected by tempering temperature and time. The purpose of this study is to investigate the range of DOL and CS, which to less breakage during reliability tests such as the ball drop test, hole drop test, 3-point bending test, drop test, and tumble test with Soda-lime Glass. Key Words : Chemical Strengthening glass(화학강화 글라스), Sodalime(소다라임), Mobile display window, Aluminosilicate(알루미노실리케이트), Depth of Layer(DOL), Compressed Stress(압축응력, CS) *Samsung Electorics Co Ltd Mobile Comm.** Department of intelligent Mechanical Engineering, Kumoh Institute of Technology # Corresponding Author : Department of intelligent Mechanical Engineering, Kumoh Institute of Technology E-mail : sdchoi@kumoh.ac.kr 1.서 론 Mobile device의 display window는 높은 강도와 투과율을 확보하기위해 강화글라스를 채용하게 되었다. glass는 일반적으로 압축응력보다 인장응력에 취약하다는 것으로 인식되고 있어서 강화유리는 인장응력에 대응하도록 유리 표면에 압축응력이 구성되어 있다.

Crack Initiation Tendency of Chemically Strengthened Glasses

The relationship between crack initiation tendency before chemical strengthening and fracture strength of chemically strengthened glass was investigated. Four kinds of glass compositions were used in this study: soda‐lime silicate (SLS), aluminosilicate (ALS‐1,ALS‐2), and aluminoborosilicate (ALBS) glasses. The fracture strength of sheet glass was measured by the four‐point bending test, the ring‐on‐ring test, the ball drop test, and the predamaged four‐point bending test.ALBSglass, which has the lowest crack formation probability before chemical strengthening, is more damage tolerant than other glasses, and one of the best candidates for chemical strengthening.

Experimental study and strength formulation of soil-based controlled low-strength material containing stainless steel reducing slag

Using stainless steel reducing slag (SSRS), a byproduct generated from stainless steel making process, as a cement substitute in production of soil-based controlled low-strength material (CLSM) is a major aim of this study. In the present work, surplus soil and concrete sand were blended well together with a sand–soil proportion of 6:4 by volume in order to produce fine aggregate. Totally, twelve mixtures were prepared for experiment when we changed in turn percentages of Portland cement replacement with SSRS of 0%, 10%, 20%, and 30% by weight and the water-to-binder ratio of 3.4, 3.6, and 3.8. Meanwhile, the binder content in each mixture was fixed at 100kg/m3. Fresh and hardening properties of the CLSM were experimentally investigated via flowability, hardening time, ball drop, compressive strength, and pulse velocity test. Testing results indicate that SSRS with the specific surface area of 4551cm2/g can substitute for Portland cement up to 30% in production of excavatable CLSM, commonly classified by the 28-day compressive strength of 1.034MPa or less. In addition, increasing SSRS substitution level would result in effectively improving workability, extending setting time, decreasing pulse velocity, as well as reducing gradually compressive strength, being necessary to control the excavatability of CLSM. Moreover, based on the testing data, an analytical model for predicting compressive strength of the CLSM from one to 56days has been developed with high reliability.

Study of Specific energy of mechanical destruction of ice for calculation of ice load on ships and offshore structures

Analysis of scenarios of transportation oil and gas which produced in the Arctic and others cold seas shows that in the near-term there will be a significant increase of tonnage of tankers for oil and gas and number of ships which should be exploited in difficult ice conditions. For the construction of ice-resistant structures (IRS) intended for production of oil and gas and transportation of these products at ice-class vessels, calculating the load from ice to board the ship and on surface of supports of the platforms are the actuality and urgent tasks. These tasks have one basis in both cases: at beginning of the contact occurs fracture of edge of ice, then occurs compressing of rubble shattered of ice, then they extruding from contact area, after this next layer of ice begin to destruct. At calculating the strength of plating and elements construct of vessels, icebreakers and ice-resistant platforms the specific energy of mechanical destruction ice ? cr is an important parameter. For the whole period of study of physical and mechanical characteristics of sea ice have been not many experimental studies various researchers to obtain numerical values of this energetic characteristic of the strength of ice by a method called Ball Drop Test. This study shows that the destruction of the ice from dynamic loading in zone of contact occurs in several cycles, and the ice destructed with a minimum numerical values of ? cr . The author offer this energy characteristic to take as a base value for the calculation of ice load on ships and offshore structures.

P.154L: Late News Poster: Establishment of Evaluation Method of Surface Fracture Mode with Front‐side‐origin for Cover Glass

AbstractRecently, thinner cover glass is required, therefore to prevent fracture becomes more important. Sandpaper Ball Drop Test was newly established to evaluate front‐side‐origin fracture. It was found that CT and glass thickness are important parameters for front‐side‐origin fracture. This evaluation method contributes to designing glass with sufficient balance.

Comparison study on reliability performance for polymer core solder balls under multiple reflow and HTS stress tests

Drop ball reliability for Ball Grid Array (BGA) package on lead-free product is a major reliability concern. Integrating a polymer core in the solder ball could be a good strategy to dissipate stress better compared to the purely metallic solder ball. However, the diffusion rate of the copper is much faster than the diffusion rate of the solder. Hence, Kirkendall voids starts forming and causing crack between the interface of copper and solder. This could affect the solder joint as well as the solder ball drop reliability especially when subjected to high temperature stress. The new polymer core solder ball with 1μm thickness of nickel (Ni) coated on the copper (polymer core/copper/nickel/solder) could offer better solder ball joint and drop reliability performance. This work studies the effects of IMC growth, solder ball shear strength and drop test reliability. Subsequently, the failure modes were observed after multiple reflow (up to 5 times) and HTS stress tests. The IMC formation was observed under the high power scope with magnification 50× via the mechanical cross-section and was measured using an analytical software tool. Solder ball shear test was carried out to measure the solder joint performance after multiple reflow and HTS stress tests via the Dage 4000 series bond tester. Drop reliability test was carried out via the packing drop test. From this study, we could conclude that the polymer core solder ball with an additional Ni layer coating demonstrates better performance than the polymer core solder ball without Ni layer. The same observation applies to the solder ball shear strength, drop reliability performance in multiple reflow and HTS stress tests. The IMC thickness for polymer core solder ball without additional Ni layer is much thicker than the polymer core solder ball with an additional Ni layer, most probably because Ni could limit the Cu diffusion into the solder, thus resulting in better reliability performance.

50.3: Finite Element Analysis of Ball Drop on LCD Panels

AbstractA ball drop test is amongst the tests used to assess the response of an LCD device under impact conditions. Two different glass thicknesses − 0.5 mm and 0.7 mm ‐ were submitted to this test in consideration for this paper. The result of the testing demonstrated that when a ball is dropped onto the outside surface of color‐filter glass, the peak stress occurs on the bottom of color‐filter glass, and not on the bottom of the TFT glass. In addition to this, we studied an extreme case where the back plate is rigid, since most LCD displays have a diffuser plate or back plate behind the panel. The rigid plate restricts the panel deflection when impacted by a ball. The findings from this study can be used as guidelines to go for thinner panels by balancing panel thickness, diffuser / back plate stiffness and the distance between the panel and the back plate. When appropriately implemented, panels made with 0.5 mm glass substrates may experience lower stress when compared to those made with 0.7 mm glass.