• Journal of Ocean Engineering and Technology
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• v.21 no.1 s.74
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• pp.40-44
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• 2007

This paper presents the experimental results on slamming phenomenon. The air pressure cylinder was used to ensure repeatability of the impact. The results showed that the adopted experimental technique was excellent in terms of repeatability, compared to that of the free drop tests. The pressure time histories, magnitude of peak pressure and the behavior of jetspray were obtained. The flat specimen was tested for various incident angles. To estimate the incident speed of the specimen, a high-speed camera was used. The high-speed camera was also a useful tool in understanding the behavior.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.6
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• pp.135-141
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• 1997

Low velocity impact test and compressive residual strength test after impact were performed by using Hercules AS4/3501-6[45/0/-45/90]$_{2s}$ laminated plate to investigate the low velocity impact damage behavior and the post-impact strength degradation on orthotropic composite laminate plate. Due to the lateral impact losd, the load path showed "" shape according to the laminate central deflection. Damage in a laminate occurs by inclined matrix crack at the damage initiation load stage and vertical matrix crack, occurs on the outer surface. Evaluating the compressive residual strength after the low velocty impact test, it could be found that there is a transient range where the compressive residual strength drop suddenly in the initial damage which is in the matrix crack range and the initial delamination area. is in the matrix crack range and the initial delamination area.

• Steel and Composite Structures
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• v.20 no.5
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• pp.983-997
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• 2016

The aim of this study is to investigate the impact behavior and impact-induced damage of sandwich composites made of E-glass/epoxy face sheets and PVC foam. The studies were carried out on square flat and curved sandwich panels with two different radius of curvatures. Impact tests were performed under impact energies of 10 J, 25 J and 80 J using an instrumented drop-weight machine. Contact force and displacement versus time and contact force- displacement graphs of sandwich panels were presented to determine the panel response. Through these graphs, the energy absorbing capacity of the sandwich panels was determined. The impact responses and failure modes of flat and curved sandwich panels were compared and the effect of curvature on sandwich composite panel was demonstrated. Testing has shown that the maximum contact force decrease while displacement increases with increasing of panel curvature and curved panels exhibits mixed failure mode, with cylindrical and cone cracking.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.10
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• pp.80-87
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• 2006

Metallic sandwich plate with a truss core has metallic inner structures which have low relative density between a pair of metal skin sheets or face sheets. In this work, low impact tests have been carried out to examine the behavior of sandwich plates with a pyramidal truss core. For the low velocity impact, the impact apparatus of drop weight type has been fabricated. From the results of the experiments, maximum energy absorption is found to happen when the upper sheet fails. The sandwich plate loses its absorption ability as soon as the inner structures have been crashed completely and optimal core thickness has existed to maximize energy absorption. Comparing the metallic sandwich plate with the monocoque plate, the absorbed energy has been improved up to 160 % and the deflection decreased by up to 76%. As a result, the metallic sandwich plate with a truss core is shown to have good material for impact resistance and energy absorption.

• Composites Research
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• v.26 no.2
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• pp.116-122
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• 2013

In this study, impact behavior of aluminium and glass-fiber structure is studied under low impact velocity. Compression test is carried out to investigate the compressive strength of the specimens. The degree of damage is observed using microscopy and compared with the experimental analysis data. The maximum load capacity, impact strength and elastic energy of glass-fiber honeycomb sandwich panel are more than the aluminium honeycomb sandwich panel.

• Journal of the Microelectronics and Packaging Society
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• v.15 no.4
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• pp.77-86
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• 2008

The reliability of leaded and lead-free solders of BGA type packages on a printed circuit board was investigated by employing the standard drop test and 4-point bending test. Tested solder joints were examined by optical microscopy to identify associated failure mode. Three-dimensional finite element analysis(FEM) with ANSYS Workbench v.11 was carried out to understand the mechanical behavior of solder joints under the influence of bending or drop impact. The results of numerical analysis are in good agreement with those obtained by experiments. Packages in the center of the PCB experienced higher stress than those in the perimeter of the PCB. The solder joints located in the outermost comer of the package suffered from higher stress than those located in center region. In both drop and bending impact tests, the lead-free solder showed better performances than the leaded solders. The numerical analysis results indicated that stress and strain behavior of solder joint were dependent on various effective parameters.

• Steel and Composite Structures
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• v.48 no.3
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• pp.305-320
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• 2023

The mechanical properties of polymeric composites are degraded under elevated temperatures due to the effect of temperature on the mechanical behavior of the resin and resin fiber interfaces. In this study, the effect of temperature on the impact response of the carbon fiber reinforced plastics (CFRP) was investigated at low-velocity impact (LVI) using a drop-weight impact tester machine. All the composite plates were fabricated using a vacuum infusion process with a stacking sequence of [45/0_2/-45/90_2]s, and a thickness of 2.9 mm. A group of the specimens was exposed to an environment with a temperature cycling at the range of -30 ℃ to 65 ℃. In addition, three other groups of the specimens were aged at ambient (28 ℃), -30 ℃, and 65 ℃ for ten days. Then all the conditioned specimens were subjected to LVI at three energy levels of 10, 15, and 20 J. To assess the behavior of the damaged composite plates, the force-time, force-displacement, and energy-time diagrams were analyzed at all temperatures. Finally, radiography, optical microscopy, and scanning electron microscopy (SEM) were used to evaluate the effect of the temperature and damages at various impact levels. Based on the results, different energy levels have a similar effect on the LVI behavior of the samples at various temperatures. Delamination, matrix cracking, and fiber failure were the main damage modes. Compared to the samples tested at room temperature, the reduction of temperature to -30 ℃ enhanced the maximum impact force and flexural stiffness while decreasing the absorbed energy and the failure surface area. The temperature increasing to 65 ℃ increased the maximum impact force and flexural stiffness while decreasing the absorbed energy and the failure surface area. Applying 200 thermal cycles at the range of -30 ℃ to 65 ℃ led to the formation of fine cracks in the matrix while decreasing the absorbed energy. The maximum contact force is recorded under cyclic temperature as 5.95, 6.51 and 7.14 kN, under impact energy of 10, 15 and 20 J, respectively. As well as, the minimum contact force belongs to the room temperature condition and is reported as 3.93, 4.94 and 5.71 kN, under impact energy of 10, 15 and 20 J, respectively.

• Tribology and Lubricants
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• v.27 no.3
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• pp.140-146
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• 2011

A miniature pendular type impact testing machine was designed and developed, adopting a magnetic powder brake in order to investigate tensile and shear behavior of a small solder ball at high speed. In this testing system, the potential energy of the pendulum is transferred into the impact energy during its drop. Then, the impact energy is transmitted through the striker which is connected to the push rods to push the specimen for tensile loading. The tensile behavior of lead-free solder ball in diameter of 760 ${\mu}m$ was successfully investigated in a speed range of 0.15 m/s~1.25 m/s using this designed device. The maximum tensile strength of the solder joint decreases with the loading speed in the testing condition. The maximum tensile strength of the joint was 56 MPa in the low speed region.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.4
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• pp.826-833
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• 1998

The energy-absorbing characteristic of impact limiters affects the cask design so significantly that it should be evaluated as accurate as possible. The objective of this study is to find the influence of the impact limiter's steel case and gusset plates which enclose the shock absorbing cellular material on the impact energy absorption. The influence of impact limiter's steel case and gusset plate stiffeners on the impact energy absorption behavior under horizontal drop impact was evaluated for a radioactive isotope transport cask. Though the impact limiters mitigate the impact damage of the cask, the impact limiter's steel case and gusset plate stiffeners increase the impact force so significantly that should be designed as soft as possible. The impact analysis without considering impact limiter's steel case and gusset plates stiffener gives non-conservative results, so the stiffness of the steel case and gusset plates should be considered in impact analysis.

• Structural Engineering and Mechanics
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• v.76 no.4
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• pp.465-477
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• 2020

This paper presents an investigation on the dynamic behavior of SRC columns with built-in cross-shaped steels under impact load. Seven 1/2 scaled SRC specimens were subjected to low-speed impact by a gravity drop hammer test system. Three main parameters, including the lateral impact height, the axial compression ratios and the stirrup spacing, were considered in the response analysis of the specimens. The failure mode, deformation, the absorbed energy of columns, as well as impact loads are discussed. The results are mainly characterized by bending-shear failure, meanwhile specimens can maintain an acceptable integrity. More than 33% of the input impact energy is dissipated, which demonstrates its excellent impact resistance. As the impact height increases, the flexural cracks and shear cracks observed on the surface of specimens were denser and wider. The recorded time-history of impact force and mid-span displacement confirmed the three stages of relative movement between the hammer and the column. Additionally, the displacements had a notable delay compared to the rapid changes observed in the measured impact load. The deflection of the mid-span did not exceed 5.90mm while the impact load reached peak value. The impact resistance of the specimen can be improved by proper design for stirrup ratios and increasing the axial load. However, the cracking and spalling of the concrete cover at the impact point was obvious with the increasing in stiffness.