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For some industries such as automotive, defence, aerospace, pharmaceutical manufacturing, dynamic pressure measurement is an important requirement. In a primary level dynamic pressure measurement system with a drop weight method, the dynamic pressure value is calculated using parameters such as the effective area value depending on the piston cylinder unit, the maximum acceleration value measured by a laser interferometer. On the other hand, the type of liquid used in the measuring head is another important factor affecting repeatability and providing ease of measurement. In this study, a new measurement head, piston and cylinders were designed, manufactured and the Taguchi method was used to accurately determine some parameters affecting the measurements in a dynamic primary pressure measurement system operating with the drop weight method. In the studies carried out, four pistons, four cylinders, four sampling frequency values and two liquid types were considered. By using the Taguchi method, the optimum parameters of the dynamic pressure measurement system with drop weight method were determined with only sixteen experiments instead of one hundred and twenty-eight. [ABSTRACT FROM AUTHOR]

Some of the desirable properties of concrete include high impact resistance and great energy-sucking capacity to name a few. These properties can be improved through the use of sustainable materials. This study investigated the effects of partly replacing fine aggregate with linear low-density polyethylene (LLDPE) and waste rubber (WR) as fine aggregates on the efficiency of concrete under impact loading. Two water to binder ratio (W/B) percentages of (0.40 and 0.55) were selected, with six (LLDPE-R) replacement grades (0%, 5%, 10%, 15%, 20%, and 30%) and two silica fume (SF) replacement grades (0% and 15%). Six cylinders with 150 and 60 mm were subjected to an impact by a 4.45 kg hammer striking. Test results indicated that impact resistance for the first visible crack and the ultimate failure increased with LLDPE-R content, where it increased by 4.76 times. This study also demonstrated that the impact resistance for the first visible crack of LLDPE-R concrete was improved by an average of 295% for specimens without SF and 292% for specimens containing SF. This enhancement for the ultimate failure is 291% and 290% for specimens without SF and containing SF, respectively.

• Different mixed-mode SIFs measurements in low and high loading rate conditions. • Classical caustics interpretation is suitable for drop weight loading condition. • Modified caustics interpretation is verified for reflected P wave loading condition. • Loading time and crack-tip stress field influence mixed-mode SIFs measurements. Mixed-mode crack-tip stress field is different in low and high loading rate conditions, resulting in different mixed-mode stress intensity factors (SIFs) measurements. How to correctly measure mixed-mode SIFs in different loading rate conditions is of critical importance. To this end, mixed-mode SIFs are measured and compared by optical caustics method with high-speed photography, specifically by the interpretation of crack-tip optical image, i.e., caustics pattern which reflects crack-tip stress field. Different mixed-mode caustics patterns in shape are observed in drop weight and blast loading conditions, indicating that corresponding crack-tip stress field and mixed-mode SIFs measurements are different. Under drop weight loading, mixed-mode caustics patterns are consistent with the classical caustics interpretation for SIFs measurements, while those under reflected P wave loading in blasts are not consistent. Therefore, a modified mixed-mode caustics interpretation is proposed and verified to be available for SIFs measurements in blast loading condition. Finally, underlying reasons for different mixed-mode SIFs measurements in low and high loading rate conditions are discussed, and it is concluded that in low loading rate condition, a longer loading time results in crack-tip K-dominated stress field which is suitable for the classical caustics interpretation, while in high loading rate condition, the loading time is too short to form K-dominated stress field in the crack tip, hence a modified caustics interpretation is necessary. This paper benefits correct applications of caustics method to mixed-mode SIFs measurements in different loading rate conditions. [ABSTRACT FROM AUTHOR]

• Generated experimental t n of copper ore from drop weight impact tests. • Fitted various t n functions via t n -fitted and t n -regenerated B ij approaches. • PBM with t n -based B ij fitted product PSD under wide range of milling conditions. • Use of size-dependent t n functions led to much better fits to drop weight t n data. • t n -regenerated B ij achieved improved PBM fits than t n -fitted B ij. This study aimed at assessing various energy-based breakage distribution functions B ij within the context of a population balance model (PBM) of copper ore milling in a wet stirred media mill (WSMM). First, drop weight impact tests were performed to determine the size distribution parameters, t n. Second, various t n models called t n -fitted and t n -regenerated approaches were used to fit experimental t n , and their goodness-of-fits were compared. They were then used to construct the matrices of the cumulative breakage distributions, B ij , of the PBM, while a power-law form of the specific breakage rate function, S i , was assumed. By fitting the PBM to the product particle size distributions (PSDs) obtained under various rotor speeds, suspension volumetric flow rate, and solids content, we estimated the S i parameters. Results suggest that except the Napier-Munn model, all t n models fitted the experimental drop weight data reasonably well, which was reflected in the PBM fitting of the product PSDs. The PBM fits with B ij constructed with the t n -regenerated approach were more accurate than those with the t n -fitted approach. The PBM was validated with additional tests that were not considered in the parameter estimation. Overall, we have established that the choice of t n function and the methodology to determine B ij can affect the PBM predictions of the WSMM process significantly. [ABSTRACT FROM AUTHOR]

The response of plain and fibrous concrete to the scenario of fired structures exposed to repeated impacts from falling fragmented building elements and other objects is experimentally investigated in this study. The experimental program included the casting and testing of specimens with 0%, 0.5%, and 1.0% hooked-end steel fibers (SFs) under the ACI 544-2R repeated-impact test. The impact test was conducted using cylindrical disk specimens, while 100 mm cubes were used to evaluate the residual compressive strength and weight loss. From each mixture, six disks and three cubes were heated to high temperatures of 200, 400, and 600 °C, while a similar set of specimens were tested without heating as a reference group. The results show that SF could significantly improve cracking impact resistance and dramatically boost failure impact numbers. The retained percentage improvements were the highest for specimens heated to 600 °C, which were approximately 250% at the cracking stage and 1680% at the failure stage for specimens with 1.0% SF. The test results also show that the repeated-impact resistance dramatically deteriorated at high temperatures, where the maximal residual cracking and failure impact numbers after exposure to 200, 400, and 600 °C were approximately 20% and 40%, 4% and 7%, and 2.2% and 4%, respectively. [ABSTRACT FROM AUTHOR]

Particulate Al2O3 matrix nanocomposites containing 1 vol.%Ni were prepared by the heterogeneous precipitation method and the addition of 5 vol.% ZrO2 (ANZ) or 1 vol.% Cr2O3 (ANC). The prepared samples were subjected to the low energy drop weight impact tests to compare the behaviour of the composites under low energy impact and to investigate the damage mechanisms. The pure Al2O3, Al2O3/Ni, Al2O3/ZrO2 and Al2O3/Cr2O3 compositions with the same additive ratios were also produced to make the comparison systematically. Also, the Vickers hardness measurements were carried out and a significant increase in hardness was attained for both ANZ and ANC composites. The average hardness value around 24.8±1.0GPa was measured for the ANZ and ANC composites which means ~15% improvement compared to the pure Al2O3. Between all the compositions, the maximum force (Fmax) value was obtained for the ANZ (for 12 J impact energy level Fmax = 26617N) according to the low energy drop weight impact test results. Tensile radial crack network formation, cone formation, fracture and crushing of the cone structure were observed as damage mechanisms for all compositions. The volume of conical frustum structure was evaluated for each composition and the effect of microstructure on possible ballistic performance was also discussed.

In 2011, the percentage of the American population affected by Noise Induced Hearing Loss (NIHL) was 15.3%. Unlike most forms of hearing loss, this can be prevented by limiting exposure to certain magnitudes of noises for varying amounts of time. The present study, using six calibrated smartphones, aims to assess the sound given off from dropping free weights in the gym, at the University of Birmingham, which can be contributing to NIHL. A relationship between drop weight and vibration is also constructed. For vibration, it is found that vibration level (m/s2) increases with the drop weight, whereas the average noise level for each drop weight only varies by a range of 4.4 dB between 102.7 and 98.3 dB. Note that all the sound levels recorded are over 85 dB, which is the range where NIHL can be contributed to. This study reminds us that measures need to be taken to reduce the sound level from the drops of loaded barbells in any sports and fitness centers. [ABSTRACT FROM AUTHOR]

The most attractive structural feature of the three-dimensional (3D) angle-interlock woven structure is that the straight weft yarns are bundled by the undulated warp yarns, which induces the overall good structural stability and a stable fabric structure. Thus the 3-D angle-interlock woven composite (3DAWC) prepared by the vacuum-assisted resin transfer molding (VARTM) curing process has excellent mechanical properties by using the fabric and epoxy resin as the reinforcement and matrix, respectively. The low-velocity impact damage properties of the composites under different drop-weight energies (70, 80, and 100 J) were tested experimentally. The load–displacement curves, energy–time curves, and the ultimate failure modes were obtained to analyze the performance of resistance to low-velocity impact, as well as the impact energy absorption effect and failure mechanism, especially the structural damage characteristics of the 3DAWC subjected to the low-velocity impact of drop weight. By analyzing the obtained experimental results, it is found that the fabric reinforcement is the primary energy absorption component and the impact energy mainly propagates along the longitudinal direction of the yarns, especially the weft yarn system, which is arranged in a straight way. In addition, as the impact energy increases, the energy absorbed and dissipated by the composite increases simultaneously. This phenomenon is manifested in the severity of deformation and damage of the material, i.e., the amount of deformation and size of the damaged area.

The response of plain and fibrous concrete to the scenario of fired structures exposed to repeated impacts from falling fragmented building elements and other objects is experimentally investigated in this study. The experimental program included the casting and testing of specimens with 0%, 0.5%, and 1.0% hooked-end steel fibers (SFs) under the ACI 544-2R repeated-impact test. The impact test was conducted using cylindrical disk specimens, while 100 mm cubes were used to evaluate the residual compressive strength and weight loss. From each mixture, six disks and three cubes were heated to high temperatures of 200, 400, and 600 °C, while a similar set of specimens were tested without heating as a reference group. The results show that SF could significantly improve cracking impact resistance and dramatically boost failure impact numbers. The retained percentage improvements were the highest for specimens heated to 600 °C, which were approximately 250% at the cracking stage and 1680% at the failure stage for specimens with 1.0% SF. The test results also show that the repeated-impact resistance dramatically deteriorated at high temperatures, where the maximal residual cracking and failure impact numbers after exposure to 200, 400, and 600 °C were approximately 20% and 40%, 4% and 7%, and 2.2% and 4%, respectively.

The most attractive structural feature of the three-dimensional (3D) angle-interlock woven structure is that the straight weft yarns are bundled by the undulated warp yarns, which induces the overall good structural stability and a stable fabric structure. Thus the 3-D angle-interlock woven composite (3DAWC) prepared by the vacuum-assisted resin transfer molding (VARTM) curing process has excellent mechanical properties by using the fabric and epoxy resin as the reinforcement and matrix, respectively. The low-velocity impact damage properties of the composites under different drop-weight energies (70, 80, and 100 J) were tested experimentally. The load–displacement curves, energy–time curves, and the ultimate failure modes were obtained to analyze the performance of resistance to low-velocity impact, as well as the impact energy absorption effect and failure mechanism, especially the structural damage characteristics of the 3DAWC subjected to the low-velocity impact of drop weight. By analyzing the obtained experimental results, it is found that the fabric reinforcement is the primary energy absorption component and the impact energy mainly propagates along the longitudinal direction of the yarns, especially the weft yarn system, which is arranged in a straight way. In addition, as the impact energy increases, the energy absorbed and dissipated by the composite increases simultaneously. This phenomenon is manifested in the severity of deformation and damage of the material, i.e., the amount of deformation and size of the damaged area. [ABSTRACT FROM AUTHOR]

• The influence of drop weight geometry on impact behavior. • The effect of interlayer on impact behavior. • The effect of initial inclination angle on impact behavior. • Effective contact area affects contact stiffness. • The impact response characteristics are derived. A number of drop weight tests on reinforced concrete (RC) beams have been reported in literature. These tests conducted by different researchers used drop weight of different geometries. Some researchers also placed an interlayer between the drop weight and RC beam in the tests, while others directly dropped the weight on the beam. These different testing configurations surely affect the testing results. However, only very limited studies have been conducted to investigate their effects on the impact behavior of RC beams. In this study, the influence of drop weight geometry and interlayer on the impact behavior of RC beams is numerically investigated by using explicit finite element code LS-DYNA. The numerical models of RC beams subjected to drop weigh impact are verified by available testing data. With the calibrated model, the responses of RC beams impacted by five commonly used drop weights are analyzed and discussed. The effect of steel plate or rubber pad interlayer between drop weight and RC beam is also investigated. It is found that both the drop weight geometry and interlayer property significantly affect the impact loading profile and the failure mode of RC beams. Furthermore, although most drop-weight tests assume vertical impact, small inclination angles of drop weight impacting on beams might occur. The influence of this small testing error on testing results is also investigated. [ABSTRACT FROM AUTHOR]

Abstract In this study, we investigate the effect of drop weight shape, bed mass and drop height on the impact breakage of a run-of-mine platinum group metals (PGM) ore collected from the Great Dyke region in Zimbabwe. The three drop weight shapes used were spherical balls, semi-ellipsoids and cubes. We then applied a model-free optimization tool called the Attainable Region (AR) technique to analyze and optimize the impact energy on a bed of PGM particles. We observed that different drop weight shapes produce products of different levels of fineness, hence an interesting area for research. A higher mass fraction of a preselected desired product fineness (−850 + 150 μm) was obtained from use of spherical balls and semi-ellipsoids compared to cubes. We also observed that the bed mass had a significant effect on the impact breakage process and an optimal bed mass gave result to a maximum amount of the desired size class. Graphical abstract Unlabelled Image Highlights • We do drop weight tests using different media shapes on a platinum ore sample. • We vary the drop height, number of drops and the mass of the bed of platinum ore particles. • We apply the AR method to experimental data in order to optimize impact tests. • We use the AR technique to specify the optimum operating conditions. [ABSTRACT FROM AUTHOR]

Highlights • An impact strength measurement method based on high speed photography was introduced. • A reverberation application of dynamic impedance mismatch method was used. • The method only involved the known dynamic impedance properties and the velocity measurements of the impactor. • Different types of porous concretes at different frame rates were tested to verify the method. Abstract In this study, an impact strength measurement method based on high speed photography, that has been developed for testing porous concrete, was introduced. In the experiments, a drop weight impact test set-up instrumented with a high speed camera was used. The impact strength analyses were conducted using impedance mismatch method, where the wave reverberations were investigated in detail. The measurement configuration carries the advantage of being a fast, non-contact and accurate experimental method where only the known material properties and particle velocity data of the drop weight are required. The target cementitious material itself is not actually involved in the measurements or the subsequent analyses. The method also facilitates the observation of the crack patterns throughout the experiment. The measurement method was verified to be accurate and consistent by testing different types of porous concretes and by comparing the results with those from other dynamic monitoring techniques, such as laser Doppler velocimetry and direct stress gauge measurements. [ABSTRACT FROM AUTHOR]

PET (Polythene terephthalate) bottles and cans are mostly discarded after a single use cycle, creating environmental and waste management concerns. This study reports an experimental work carried out, in which PET bottles were shredded and used as aggregate (fine and coarse) in concrete at various replacement percentages, i.e., 5%, 10%, 15% and 20% by weight of concrete. Concrete parameters such as compressive strength, impact resistance and energy absorption capacity of concrete containing PET waste were studied. In addition, the residual compressive strength of concrete containing PET waste was investigated for exposure to 300 °C and 600 °C elevated temperatures. The analysis of test results indicated lower compressive strength of concrete containing waste plastic PET aggregate. However, results showed better resistance to impact loading in case of plastic concrete when compared to control concrete. [ABSTRACT FROM AUTHOR]

Composite tubes may be subjected to impact loads during placement or operation. By determining the impact properties of composite tubes and using them in the design process, the accuracy of the behavior of these structures in the loading condition is guaranteed. In this study, the behavior of glass/epoxy composite tubes under dynamic axial loading was experimentally investigated. Also, the effects of parameters such as fiber density, fiber alignment angle, internal diameter of the tube and impact energy on the amount of pipe damage were also studied. To prepare composite specimens, E-type glass fiber was used with two different densities of 200 gr⁄m2 and 400 gr⁄m2. The specimens were placed on a drop weight machine of Tafresh University by a fixture, and the Impactor was released from the height of 2 meters. The force -displacement diagrams for each test were extracted and compared with each other. Also, a parameter called specific energy absorption was calculated for all samples in order to compare the efficiency of the samples as energy absorber. The results of this study showed that increasing the fiber density, number of layers and diameter of the tube increases the specific energy absorption. It was also observed that with the increase of the axial dynamic impact energy, the mechanical properties of the specimen will be changed and the specimen will be firmly established. [ABSTRACT FROM AUTHOR]

The performance of the newly developed soft-hard-soft (SHS) cement based composite system under multiple impact loading was investigated using a combined numerical and experimental study. Such a composite consists of three layers including Geogrid (GST) reinforced asphalt concrete (AC) on the top, high strength concrete (HSC) layer in the middle, and fiber reinforced cementitious composites (FRCC) at the bottom. A Hard-Soft-Hard (HSH) composite pavement was also proposed and tested for comparison purpose. In addition, the experimental results were compared with standard rigid and flexible pavements. The SHS composite system exhibits minimum damage, higher energy absorption and significant improved impact resistance against multiple impact loading compared with the other three types of pavements. A 3D finite element (FE) model was also established and confirmed the experimental results for the SHS composite pavement. Following the FE model, intensive parametric study was conducted to investigate the factors to enhance the impact resistance of the SHS composite system. The results can guide the upgrade options for runway pavement and be used for further development of the protective composite. [ABSTRACT FROM AUTHOR]

The cement treated aggregate (CTA) is increasingly used as base or sub-base layer for pavement to withstand various traffic and dynamic loads. Under extreme events, the CTA layer of the pavement is expected to absorb significant amount of impact energies subjected to different loading conditions including accidents, mobile vehicles, heavy aircrafts, machinery, or even terrorist attack. However, no research has been found on the resistance of CTA under drop weight impact load. To fill up this gap, a detailed study was carried out to investigate the impact resistance of CTA under impact loading through both experimental and finite element analysis (FEA). Moreover, detailed parametric studies were carried out based on the validated model to determine the significance of selected key parameters on the impact resistance of CTA. [ABSTRACT FROM AUTHOR]

In this paper we study a new type of interlocking brick recently proposed by the authors. The brick has a symmetrical geometry with four concavo-convex side surfaces for the interlocking purpose. Drop weight tests have been conducted to investigate the mechanical response of interlocking assembly plates by applying different levels of impact force and lateral confining load. The results show that, compared with monolithic plates, the new interlocking assembly plates have significantly improved flexural performance in terms of impact energy absorption capacity. The fracture of individual bricks during the impact always occurs along a load transmission path that is determined by the geometrical constraints of the interlocking bricks. Most importantly, the interlocking design of the plate-like assembly can effectively prevent the propagation and spread of the cracks, so that the damage to a single brick will not lead to a catastrophic failure of the entire structure. [ABSTRACT FROM AUTHOR]

The drop weight test was usually used to evaluate the impact performance of fiber-reinforced concrete. However, there is no uniform parameters about the weight and the drop height of the hammer in the drop weight test. In this paper, the effect of the weight and the drop height of the hammer on the impact performance of steel fiber and polypropylene fiber reinforced concrete was studied. The results show that, for both polypropylene fiber and steel fiber reinforced concrete, the initial impact strength (S i ) and the final impact strength (S f ) exponentially decrease with the increase of the drop height. S i and S f increase with the increase of the drop weight when the impact energy is a constant value in each impact test. However, the damage of the polypropylene fiber reinforced concrete is still a brittle fracture at this condition. The addition of steel fiber improves the ductility and impact resistance of concrete. [ABSTRACT FROM AUTHOR]

The strain rate effect influences the mechanical properties on most construction materials and its investigation is critical for structural engineering. Current materials such as steel or concrete have been intensively investigated. However, similar studies on the dynamic properties of masonry or masonry components such as clay brick or mortar are scares. This paper intends to study the behavior of masonry and its usual components (clay brick and mortar) when subjected to high strain rates. A drop-weight impact machine is used at different heights and weights introducing different levels of strain rate. Empirical relations of dynamic increase factors (DIFs) are derived from the experimental results and the strain rate effect on compressive strength, compressive fracture energy, strain at peak strength, and Young's modulus are determined and presented. [ABSTRACT FROM AUTHOR]

Ultra-high molecular weight polyethylene (UHMWPE) fibre reinforced composite materials are widely used in ballistic impact and collision scenarios due to their extremely high specific strength and stiffness. Exceptional levels of protection are provided by controlling the damage and deformation mechanisms over several length scales. In this study, the role of UHMWPE fibre architecture (cross-ply, quasi-isotropic and rotational “helicoidal” layups) is considered on the damage and deformation mechanisms arising from low velocity impacts with 150 J impact energy and clamped boundary conditions. Dyneema ® panels approximately 2.2 mm thick were impacted with a fully instrumented hemi-spherical impactor at velocities of 3.38 m/s. Full field deformation of the panels was captured through digital image correlation (DIC). The results indicate that the cross-ply laminate [0°/90°] had the largest back face deflection, whilst quasi-isotropic architectures restricted and reduced the central deflection by an average of 43%. In the case of the [0°/90°] panel, the deformation mechanisms were dominated by large amounts of in-plane shear with limited load transfer from primary fibres. Conversely, the failure of the quasi-isotropic panels were dominated by large amounts of panel buckling over various length scales. The observed mechanisms of deformation with increasing length scale were; through thickness fibre compression, fibre micro-buckling, fibre re-orientation with large matrix deformation, lamina kink band formation, and laminate buckling. The helicoidal panels showed that bend-twist and extension-twist coupling were important factors in controlling clamped boundary conditions and the laminate buckling/wrinkling shape. Further examination of the impact zone indicated that the damage mechanisms appear to be fibre orientation dependent, with quasi-isotropic laminates having up to 37.5% smaller impact damage zones compared with [0°/90°]. The experimental observations highlight the importance of fibre orientation in controlling the deformation mechanisms under dynamic impact, in particular limiting the shear deformation of Dyneema ® panels. [ABSTRACT FROM AUTHOR]