Total Impact Energy Research Articles

Impact toughness behaviour of A516 GR. 60 steel welded joints

Impact fracture behaviour of welded joints made of A516 Gr. 60 is analysed as a commonly used carbon structural steel for welded structures. Impact testing on Charpy instrumented pendulum is performed using specimens with a notch at positions: the base metal (BM), heat-affected-zone (HAZ), and weld metal (WM). The total impact energy is presented as a sum of energies for crack initiation and crack propagation to make the analysis more sophisticated and comprehensive. The effect of temperature up to -60 °C was also analysed to prove the A516 Gr. 60 steel usability at subzero conditions.

Shear creep deformation of rock fracture distrubed by dynamic loading

The long-term stability of jointed rock masses is usually dominated by fault activation, which may be triggered by the dynamic disturbance generated by blasting during mining activities, leading to the occurrence of disasters such as landslides in open-pit and rockbursts in deep mining. The initial stress and dynamic disturbance are key factors that strongly affect the shear creep behavior of rock fractures. In this work, the shear failure instability of rock fractures of sandstone under creep-impact loading was experimentally investigated by using a creep-impact test machine, which allows for applying creep loading and an additional dynamic disturbance on rock fractures. Three stages of shear creep deformation, creep strain rate, and time-to-failure are examined under different creep stress levels and impact energies. Experimental results show that the tangential and normal creep rates increase with the increase of creep stress and impact energy, but the increment of tangential creep rate is higher than that of the normal creep rate. The time-to-failure of the creeping specimen is shortened under high creep stress and large impact energy, while the time-to-failure after the last dynamic disturbance of the specimen is determined by the total impact energy and creep stress level. By using high-speed photography, it is found that the failure types of rock depend on the magnitude of impact energy and creep stress level; that is, rock mainly slides with low stress levels and shears off with high stress levels. In addition, under different impact energy and creep stress levels, the variation of height is between 0.38 and 0.52, while the defined fracture factor, which describes the degree of failure of serrations, is between 0.30 and 0.54. The findings can provide deep insight into the fault sliding mechanism caused by mining activities, which provides theoretical support for the safe mining of ore in fault fracture zones.

Bi-functional hydrogen tungsten bronze/carbon composite catalysts towards biomass conversion and solar water purification

We presented a novel bi-functional catalyst composed of HxWO3 and carbon composites, which exhibits excellent catalytic activity in biomass conversion and has the ability to effectively purify water via a wide range of wavelengths in the light spectrum. The HxWO3/carbon composites were effectively produced from commercially available monoclinic tungsten trioxide (WO3) and polypropylene (PP) powders to a single-step mechanochemical reaction employing high-energy ball milling. We systemically investigated how different synthesis parameters, such as rotation speed, processing duration, and ball diameter, affect the mechanochemically-induced phase transformation to either tetragonal or cubic HxWO3 during planetary ball milling. The crystal phase of HxWO3 was controllable by altering the total impact energy in the ball milling. In addition, real-time monitoring of the pressure increment inside the pot and evaluation of the evolved gas revealed the degassing behavior through the oxidative degradation of PP assisted by WO3. The CV and Rietveld analysis proved that HxWO3 exhibited significant enhancement by two orders of magnitude in the rate of H+ diffusion compared to monoclinic WO3. This enhancement would be attributed to the expansion of a mechanically-formed tunnel along the a-axis, which facilitates the migration of H+ ions. The HxWO3/carbon composites performed approximately 12-fold higher efficiency in generating soluble solids (glucose and furfural derivatives) compared to untreated WO3 through the catalytic hydrolysis of cellulose, owing to the enhanced Brønsted acidity. Moreover, the composite particles showed broad light absorption in the UV–Vis–NIR range and demonstrated a considerable enhancement of over three orders of magnitude in the photocatalytic degradation of methyl orange pollutants when exposed to NIR and visible light.

Effects of silicon content and test conditions on the dry wear behaviour of Zn–30Al–3Cu–(0–5)Si Alloys

ABSTRACT Dry sliding wear performance of Zn-30Al-3Cu-(0-5)Si alloys was studied using a block-on-disc type test apparatus. Their microstructure consisted of β dendrites, α, η, and ϵ (CuZn4) phases, and silicon particles. Hardness and tensile strength of the alloys increased with silicon content but above 1% Si the trend reversed for the tensile strength. Total percent elongation, impact energy, compressive strength, and quality index of the alloys decreased with silicon content. However, the friction coefficient and wear volume showed different changes with silicon content, sliding distance, contact pressure, and sliding velocity. Worn surface examinations indicated that the wear of these alloys occurs by both abrasion and adhesion. Non-linear regression analysis showed that the friction coefficient and wear volume of the alloys can be calculated in terms of silicon content and either sliding distance or contact pressure and sliding velocity using the empirical equations developed in this work. Zn-30Al-3Cu-0.5Si alloy exhibited the highest quality index and wear resistance among the alloys tested. It was concluded that the hardness and tensile strength of the alloys containing hard and brittle phases have opposite effects on their dry wear behaviour. The wear volume of such alloys decreases with increasing hardness but increases with tensile strength.

Understanding energy transformation mechanism of rockbursts through experimental and theoretical methods

Understanding the energy transformation mechanism in rockbursts is essential for predicting and mitigating potentially catastrophic rock failures. In this study, Double Springs Release Tests (DSRTs) were proposed in a laboratory setting to investigate the energy transformation of rockbursts from inception to development. High-speed cameras and image processing algorithms were utilized to calculate different types of energy throughout the duration of the burst. Theoretical analyses, grounded in structural dynamics and stress wave equations, was conducted and cross-referenced with the experimental results. The study found that wave impedance ρE is a key indicator of burst intensity. The research demonstrated that the impact energy in DSRTs originates from both the impact medium and the surrounding medium, and explored how these two components contribute to the total impact energy of the impact medium.

Segregation on small rubble bodies due to impact-induced seismic shaking

We present a framework to study regolith segregation on rubble-pile asteroids—self-gravitating granular aggregates—due to seismic shaking induced by impacts sustained during their lifetimes. We first relate the amplitude and frequency of surface vibrations to the location and severity of an impact, and the rubble body’s geometry and bulk properties. For illustration, the body is taken to be an ellipsoid with size and spin close to that of Itokawa, although more complex asteroid shapes may be incorporated. We then model the body’s collisional history stochastically given the variability in the impact activity on an asteroid. Finally, we use discrete element simulations to investigate the regolith’s response to impacts. In these simulations, in any sample collisional history, every time an impact occurs, a bin filled with a grain mixture and located at the region of interest on the asteroid is vibrated at that impact’s associated amplitude and frequency. Using this framework, we find that impact-driven seismicity is sufficient to drive size segregation on small rubble-piles, but the segregation quality depends on several aspects, e.g. total impact energy supplied, placement of the region of interest, bulk wave speed and seismic diffusivity.

Fatigue and Impact Behavior of Friction Stir Processed Dual-Phase (DP600) Steel Sheets

This study investigates the impact of friction stir processing (FSP) on the deformation behavior of 1.1 mm-thick DP600 steel sheets under both static and dynamic loading scenarios, with a focus on the automotive applications of the material. During the process, the large plastic shear strains imposed by FSP resulted in a maximum temperature of 915 °C, leading to a morphological transformation of the martensite phase from well-dispersed fine particles into lath martensite and grain refinement of the ferrite phase. DP600 steel showed an almost two-fold increase in static strength parameters such as the hardness value, yield strength, and ultimate tensile strength. As-received and processed DP600 steel exhibited a plastic deformation behavior governed by strain hardening. However, uniform elongation and elongation to failure after FSP took lower values compared to those of the as-received counterpart. Following the improvement in the static strength of the steel, the fatigue strength of the steel increased from 360 MPa to 440 MPa after the FSP. The finite-life fatigue fracture surfaces of the as-received samples were characterized by the formation of fine bulges due to the variation in the crack propagation path in the vicinity of the martensite particles/clusters. After FSP, the transformation of the martensite particles into coarser lath martensite also transformed the fracture surface into a step-like morphology. The microstructural evolution after FSP caused a decrease in the absorbed impact energy and maximum striker reaction force from 239 J and 37.6 kN down to 183 J and 33.6 kN, respectively. However, the energy absorption capacity of the processed steel up to failure was higher than the absorbed energy value of the as-received steel at the same impact displacement. The simultaneous decrease in both impact energy and reaction force is attributed to the higher cracking tendency of the processed microstructure due to the lower volume fraction of the ferrite phase. The experimental results reported in this study mainly show that FSP is an easy-to-apply and functional solution to significantly improve the static and cyclic strength of DP600 steel. However, it is clear that the reduced total impact energy absorption capacity after FSP may be taken into account in design strategies.

Infrasound analysis of the 2018-Dec-18 49 kiloton Bering Sea bolide: Misassociations and celerity-range models

Automatic detections at the International Data Centre (IDC) of the Comprehensive Nuclear-Test-Ban Treaty Organisation (CTBTO) are often misassociated. This occasionally leads to single events being split into multiple events. Infrasound signals generated from a large bolide over the Bering Sea on 2018-Dec-18 were recorded on more than 15 of the CTBTO International Monitoring System (IMS) stations. The bolide was also reported by the Center for Near Earth Object Studies (http://cneos.jpl.nasa.gov/fireballs) with a calculated total impact energy value of 49 kt. Signals from this bolide were automatically detected and associated at the IDC, into two different events, with the origin time differing by approximately 7.5 minutes and location by ∼125 km. To investigate why detections from this bolide event were misassociated in the automatic bulletins, we analyze infrasound observations from the IMS infrasound arrays and compare our arrival time observations to the automatic detections from the IDC. We use the Bayesian Infrasonic Source Localisation method and employ different celerity-range models, to investigate signal association for this event. Through comparison with the associations based on IDC detections, we aim to improve our understanding of the causes of misassociations and identify potential improvements to future event association algorithms.

Study of energy-power parameters of stamping hammers in manufactoring conditions of "Stupino Metallurgical Company" JSC

The results of experimental studies of the kinematic and energy-power parameters of stamping hammers with a falling parts mass of 10 and 13 tons carried out in the production conditions of "Stupino Metallurgical Company" JSC are presented. An experimental studies methodology is developed to determine the kinematic parameters and the actual total impact energy during hot upsetting of 12 control samples on stamping hammers with a falling parts mass of 10 and 13 tons. Processing of the experimental results allows to determine the speed of the falling parts upon impact on the workpiece and the actual total impact energy of the stamping hammers model M102 with a falling parts mass of 10 tons and model M109 with a falling parts mass of 13 tons.

Dynamic and Residual Static Behavior of Axially Loaded RC Columns Subjected to Low-Elevation Impact Loading

Columns can suffer heavy damage due to dynamic impact effects, which are ignored during their design. The impact effect could be a vehicle crash to columns of streetside buildings, parking garages or bridges. However, the effect of impact loading on the behavior of reinforced concrete columns has not been sufficiently studied. In this study, an experimental and numerical investigation is carried out on the impact behavior of axially loaded reinforced concrete columns. Dynamic experiments were carried out by dropping a mass from different heights to apply low-elevation impact on axially loaded, full-scale (30 × 30 × 320 cm) columns. After evaluating the performance of the columns under varied impact loadings, the residual load carrying capacities of the columns were also obtained by static loading. Additionally, a three-dimensional finite element model was developed and validated by using drop weight experimental results. The effect of increasing the impact energy on the behavior of RC columns was also examined numerically. As a result of the research, it has been observed that, as the applied impact energy increases, the dynamic damage/failure mode changes from flexure to shear. When a column was impacted by 75.8% of its total impact energy capacity, a decrease of 38.1% in its stiffness and a decrease of 49.7% in its load carrying capacity were determined compared to its previous unimpacted state. Additionally, the static energy dissipation capacity loss of the column was reached, up to 81.7% of its preloading state. The developed finite element model can also be utilized to determine the dynamic performance and the damage modes of columns under vehicle collision-type low-elevation impacts, which can be a guide for structural engineers in the design of such vulnerable columns and will contribute to safer structural designs.

Experimental investigations on the repeated low velocity impact and compression‐after‐impact behaviors of woven glass fiber reinforced composite laminates

AbstractIn this paper, the repeated low velocity impact responses and compression‐after‐impact (CAI) behaviors of woven glass fiber‐reinforced composite laminates were studied at the same total impact energy. Three types of impact energies, 30, 40, and 60 J, were chosen for the repeated impact tests relative to the single 120 J impact event. The impact behaviors including impact contact force–displacement and energy–time curves during the impact testing were recorded. The variations of the impact mechanical characteristics such as peak impact force, maximum displacement, and energy absorption were evaluated. The methods of visual inspection and stereo microscope were applied to identify the damage morphology of the impacted laminates. The damage accumulation was evaluated employing the absorbed energy fraction and normalized maximum displacement. It was found that the influences of impact energy on the repeated impact mechanical response are more remarkable than that of the impact number, and the impact events with fewer impact numbers cause more damage to the laminates for the same accumulative impact energy. Furthermore, the load–displacement and the CAI strength versus impact number curves were compared for the CAI testing. The ultimate load and the resulted CAI strength decrease with the increase of impact number owing to the influence of damage accumulation in repeated impacts.Highlights Repeated impact responses were studied at the same total impact energy. The impact energy makes significant influence on the impact dynamic responses. The impact events with fewer impact numbers cause more damage to the composites. The CAI behavior was explored considering the effect of damage accumulation. The CAI strength of damaged laminates decreases with impact number increasing.

Predicting the crushing behavior of pebbles: Theoretical model and experiment verification

In this paper, a theoretical model is established to describe pebble-crushing behavior, and the fractal theory was introduced to describe the relationship between original particles and fractures. Considering the size effect and random variation of crushing strength, the Weibull theory was used to characterize the strength variation, and the correlation between the Weibull modulus and fractal dimension was derived. The impact test was performed to verify the established theoretical model’s validity. Results showed that the theoretical model was verified to be valid for crushing behavior description, and the slope of the fitted straight line could be used to calculate the fractal dimension, which is the most critical parameter in fractal theory and could describe the extent of crushing in the pebble bed. The crushing behavior of pebble beds under impact loading was also studied, and test results identified limited evidence of fractal dimension limitation as the impact times increased. The crushing degree could not increase by only increasing the impact times. The extent of crushing had a limitation at a certain drop height. The evolution rate of crushing behavior negatively correlated with total impact energy, and the extent of crushing changed more drastically in a single-layer bed. The established theoretical model and findings presented in this paper add to our understanding of granular material physics, especially the mechanism of particle crushing behavior in a packed bed for fusion blankets.

Regulating the binder phase of polycrystalline diamond compact by adding tantalum to enhance the mechanical properties

In this study, PDC added with tantalum was successfully prepared via high pressure and high temperature (HPHT, 7.7GPa and 1650 °C) with the Cubic-Anvil Press. The effect of tantalum on the mechanical properties and thermal stability was systematically investigated by hardness, abrasion resistance, impact resistance and coefficient of thermal expansion (CTE) tests. The results showed that the hardness, wear ratio, total impact energy and initial expansion temperature increased by 21.7%, 45.5%, 55.2% and 20 °C with the addition of tantalum, respectively. The Ta-PDC material binder phase consisted of Ta-phases (TaC, (Ta,W)CX) and cobalt phase after sintering. In elemental quantification observe that the addition of Ta facilitated cobalt infiltration which was benefit to diamond-diamond bonding. The improvement of mechanical properties and thermal stability can be attributed to the reinforced binder, refined and deagglomerated WC grains at the interface between PCD layer and substrate, and better sintering quality. Further optimization of the Ta additive phase content, mixing methodology, or sintering conditions could be explored to further improve the mechanical properties and thermal stability of this novel PDC material.

SAG usage wear-resistant steel with rare retained austenite achieve trade-off between impact toughness and strength

The impact toughness is the key to determine the service life of high strength wear-resistant steel for the lining boards of large-scale semi-autogenous grinding mill (SAG). It is difficult to predict the impact fracture failure of lining boards when SAG is running, which can cause damage to equipment once it occurs. Therefore, novel high strength wear-resistant steel was designed to improve impact toughness in this study. It is interestingly found that the microstructure contained finer bainite/martensite, and rare retained austenite (around 2 vol.%), which achieved trade-off between impact toughness and strength after the optimal heat treatment scheme (900 °C normalizing → 900 °C quenching → 300 °C tempering). The element segregation of Al and Si was improved and the start temperature of martensitic transformation during quenching was reduced, resulting in the refinement of martensite laths. Thus, the higher density of high-angle grain boundary (HAGB) and dislocation were obtained, which contributed to excellent impact toughness. Based on the instrumented impact curve, the total impact energy can be divided into four parts: elastic deformation energy (Ee), plastic deformation energy (Ed), crack stable propagation energy (Ep1) and crack unstable propagation energy (Ep2). Traditional toughening mechanisms focus on Ep1, which was based on the tortuous crack propagation path. Our experimental results show that Ed was another effective control unit to ensure the toughness. The difference between Ed and Ep1 in improving absorption energy was discussed in detail by combining HAGB density and dislocation density.

Effect of Temperature on S32750 Duplex Steel Welded Joint Impact Toughness.

The search for alternative materials that can be used for parts of aircraft hydraulic systems has led to the idea of applying S32750 duplex steel for this purpose. This steel is mainly used in the oil and gas, chemical, and food industries. The reasons for this lie in this material's exceptional welding, mechanical, and corrosion resistance properties. In order to verify this material's suitability for aircraft engineering applications, it is necessary to investigate its behaviour at various temperatures since aircrafts operate at a wide range of temperatures. For this reason, the effect of temperatures in the range from +20 °C to -80 °C on impact toughness was investigated in the case of S32750 duplex steel and its welded joints. Testing was performed using an instrumented pendulum to obtain force-time and energy-time diagrams, which allowed for more detailed assessment of the effect of testing temperature on total impact energy and its components of crack initiation energy and crack propagation energy. Testing was performed on standard Charpy specimens extracted from base metal (BM), welded metal (WM), and the heat-affected zone (HAZ). The results of these tests indicated high values of both crack initiation and propagation energies at room temperature for all the zones (BM, WM, and HAZ) and sufficient levels of crack propagation and total impact energies above -50 °C. In addition, fractography was conducted through optical microscopy (OM) and scanning electron microscopy (SEM), indicating ductile vs. cleavage fracture surface areas, which corresponded well with the impact toughness values. The results of this research confirm that the use of S32750 duplex steel in the manufacturing of aircraft hydraulic systems has considerable potential, and future work should confirm this.

Behaviour of hybrid polypropylene and steel fibre reinforced ultra-high performance concrete beams against single and repeated impact loading

The high cost of steel fibres limited the application of ultra-high performance concrete (UHPC) in practical construction. To balance the performance and cost, hybrid polypropylene and steel fibre reinforced UHPC was proposed. The material properties of UHPC that contained 2 vol% polypropylene fibre and 1 vol% steel fibre were measured by the four-point bending tests and uniaxial compression tests. Three large-sized hybrid fibre reinforced UHPC beam specimens were tested against repeated and single impact loading. The weight of the drop hammer was 641 kg and the impact location was at the mid-span, the impact velocity varied from 3.13 to 4.43 m/s. The UHPC beams showed the flexural response in all the impact scenarios. With the same total impact energy, single impact loading was noted to be less hazardous than the repeated impact loadings. Based on the test results, a concrete numerical model of hybrid fibre reinforced UHPC was developed. The bond-slip relationship between UHPC and steel bars was incorporated into the structural model. Compared to the simulation considering the bond-slip relationship, the simulation with perfect bonding assumption exhibited an overall smaller mid-span displacement, where the maximum and residual displacement were 11.41% and 9.43% smaller, respectively. The numerical drop weight tests were reproduced and validated with experimental data. Finally, the failure mechanism and energy absorption of the test specimen under the repeated impact loading scenario was analysed.

Decomposition and spectrum analysis of surge impact pressures on a vertical wall based on the Hilbert–Huang transform

In this study, two individual dam-break induced surge impact pressure datasets are analyzed using the Hilbert–Huang transform method, which is capable of adaptively decomposing the impulsive, oscillatory, and quasi-steady pressure components from the measured raw pressure data. Time-frequency characteristics of these three pressure components are analyzed. Applying the empirical mode decomposition method, the intrinsic mode function (IMF) series extract the local periodic features, including the impulsive and oscillatory pressures, whereas the non-periodic residual series reveal the general variation characteristics of the surge impact pressure, i.e., the quasi-steady pressure. Subsequently, the Hilbert spectrum analysis is conducted to the individual IMF series. The impulsive pressure components are found to be high-frequency (over 5 Hz in this study), and the oscillatory pressure components have frequency ranging from 20 to 60 Hz. It is confirmed that the quasi-steady pressure contributes the dominant amount of the total surge impact energy in both the bottom impact zone and the upper outer zone on the wall. The impulsive pressure-induced instantaneous energy is large in the bottom impact zone shortly after the impact, whereas the oscillatory pressures only lead to a small local instantaneous energy peak. In addition, the impulsive pressure impulses are calculated, which are more test-stable than those of peak pressures. These findings indicate that impulsive pressures induced by surge impact can be rather destructive, especially near the toe of the structure, thus deserve particular attention in the safe design of coastal structures.

Multi-hit damage and perforation of plates inspired by the attacks of the mantis shrimp

The crustacean Odontodactylus scyllarus, known as peacock mantis shrimp, employs its hammer-like appendages to attack and destroy the shells of prey with a sequence of two strikes. The first strong strike of about 480 N triggers a cavitation bubble in the seawater, which provokes a successive hit (about twice weaker than the first one and with a time delay of ≈0.5 ms) on the prey upon collapsing. Inspired by this double-impact strategy, this paper presents a set of parametric finite element simulations of single, double and triple mechanical hits, using elastic-plastic targets and rigid-body projectiles, to compute the damage energy of the target. Several sequences of combinations (strong, weak and equal impact energy), different diameters of the projectile, (3, 4, 6) mm, and various time delays between consecutive impacts, taken in the range 0.0–0.8 ms, are tested by keeping the total impact energy of the projectile fixed and equal to 2.27 J. Our results reveal that: (i) the single-impact strategy is the most damaging, (ii) among the double-impact cases the crustacean attack strategy has the most damaging effect, (iii) the triple-impact strategy shows more complex scenarios and different optimal solutions. Our results could be of interest for designing bio-inspired armours.

Ocjena sklonosti ka krtom lomu zavarenog spoja

Welded structures place increasing demands on the level of increased resistance to fracture. A large number of fractures of welded structures, which occur during exploitation at a stress level below of the allowable, indicates the danger of brittle fracture. The assessment of brittle fracture susceptibility was analyzed by testing Sharpy specimens, and the total impact energy, components of total impact energy (crack energy initiation and crack energy propagation) were used as parameters in the analysis.

Study on crashworthiness of nature-inspired functionally graded lattice metamaterials for bridge pier protection against ship collision

Lightweight lattice metamaterials can effectively enhance the impact resistance of thin-walled structures. With the aim of further investigating the potential of lattice-filled composite structures, an innovative nature-inspired functionally graded lattice filled protection structure (FGLPS) is proposed in this paper to enhance structural energy absorption characteristics under ship impact loadings. At this point, two different graded patterns (i.e. increasing graded pattern and decreasing graded pattern with partition design) for lattice metamaterial fillers are established, then the effects of gradient model and impact angle on energy absorption characteristics of lattice-filled structures are studied using ship impact finite element model with multiple collision conditions. The results show that the novel functionally graded lattice filled thin-walled structure can significantly reduce the peck impact force, prolong the impact time and play prominent protective role. Especially, the peak impact force generated during the vessel impact on bridge pier can be reduced by up to 60.01% through zonal gradient design. Besides, FGPLS can absorb up to 33.15% of total impact energy by plastic deformation, and both increasing and decreasing gradient structure have the potential ability to significantly reduce the impact damage. The findings of this study provide a new approach to the engineering applications of collision-resistant structures with high energy absorption capacity.