Reduction In Impact Energy Research Articles

Study on the microstructure evolution and effect on mechanical properties of P92 steel during long term service

P92 heat-resistant steel is widely utilized in ultra-supercritical units due to its exceptional properties. This study examines the microstructure evolution and mechanical properties change of P92 during service spanning 0 to 93,000 h, while also exploring the correlation between microstructure changes and property variations. The results indicate that the matrix of P92 steel retains its characteristic tempered martensite structure, and the large-angle and small-angle grain boundaries in the steel remain nearly unchanged throughout extended service periods. However, the deterioration of P92 steel properties can mainly be attributed to alterations in precipitate size and martensitic lath width. The size of M23C6 and Laves particles increased from their initial dimensions of 150 nm and 0 nm to 260 nm and 370 nm, respectively. Moreover, the width of the martensitic lath increased from 350 nm to 700 nm. The martensitic lath contributes over 60 % of the theoretical tensile strength, playing a pivotal role in the exceptional strength of P92 steel during service. The presence of coarse Laves particles at the interface leads to a rapid reduction in impact energy, decreasing from approximately 130 J to 50 J, negatively affecting the impact energy of P92 steel.

HVOF-sprayed surface coating with various compositions of Co-NiCrAlY-Al2O3 to minimize sediment erosion in hydraulic turbines

The components of hydropower plants are susceptible to sediment erosion caused by hard particles in the water. These hard particles cause substantial material loss and a reduction in the performance of the hydraulic turbines. The present study deals with the mitigation of sediment erosion in hydraulic turbines by developing a protective coating (CoNiCrAlY-Al2O3 metal-ceramic composite) using a high-velocity oxygen-fuel (HVOF) coating technique. Hardness measurement, surface wettability analysis, and surface roughness measurement were conducted to characterize the coatings, whereas scanning electron microscopy (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDS) were performed for metallurgical characterization. The slurry/sediment erosion behavior of bare and coated substrate was investigated using a slurry erosion tester. Experiments were performed for five coating compositions at different impact angles (30° ≤ ϴ ≤ 90°) and velocities (6 ≤ v ≤ 12 m/s). The maximum improvement in erosion performance (reduction in erosion rate compared to bare substrate ≈ 28.12 % at 30°, 9.29 % at 45°, and 11.69 % at 90° impact angle) was obtained for the coating having 12 wt% alumina doped into Co-NiCrAlY. The coating's performance was improved due to increased hardness, high shielding effect, and reduction in impact energy on Al2O3 by using CoNiCrAlY-Al2O3 deposition. The empirical correlation between erosion rate and velocity for both bare and coated substrates has also been proposed.

Eggshell nanoparticle reinforced recycled low-density polyethylene: A new material for automobile application

Waste from low-density polyethylene products after lifespan accounts for 70% of solid waste in most dumpsites, contributing to environmental impacts. Eggshell foul smells are a threat to human and animal health. Before this study, there was no research documentation on transforming both wastes into green composites for engineering applications. This work developed composites using recycled low-density polyethylene (RLDPE) and eggshell Nanoparticles. They were evaluated structurally and mechanically. Straining, which affirms an improvement in the load-bearing capacity of the RLDPE due to the incorporation of eggshell Nanoparticles, was established by the composite XRD peak broadness. Structural integrities of the composites were confirmed with SEM. Maximum tensile strength was noted at 10% eggshell Nanoparticle additions to the RLDPE, equal to a 68% increase. About 52 and 19% enhancements in respective flexural strength and hardness value with a 0.85% reduction in impact energy were noted at 12% eggshell Nanoparticle additions. The probability value, 0.0481 <0.05 established the significance of the mono-variate regression model to estimate the tensile strength of RLDPE/eggshell Nanoparticle composites, and the model has 92.7% confidence. A bumper fascia prototype was fabricated from RLDPE/10% eggshell Nanoparticle composite possessing 10.64 Nmm−2 tensile strength, 21.964 Nmm−2 flexural strength, 21.69 J impact energy, and 59 VHN hardness value using sheet forming technique. Therefore, future usage of the developed RLDPE/10% eggshell Nanoparticle composite is established.

Experimental and numerical optimization study of shock wave damping in aluminum panel sandwich

Sandwich panels with polymer composite and light core composites are widely used in aircraft and spacecraft, vessels, trains, submarines, and cars. Due to their high strength to weight ratio, high stability, and high corrosion resistance, these structures have become particularly important in the industry. Reduction in impact energy, shock waves, and noise in many industries, including the automotive and military industries. Porous materials have always been the focus of attention due to their shock-reducing effects in various protective applications. For this reason, the study of physics governing shock propagation problems in porous media is of particular importance, and the complexity of the governing equations also results in the numerical solution of these equations with many computational problems and costs. In this paper, shock wave damping is investigated numerically and experimentally in aluminum blocks with porous grains scattered inside aluminum. The deformations of the specimens in numerical simulation and experimental testing have been compared. The results show that this material behaves similarly to the aluminum foam in both static loadings (practical pressure testing) and dynamic loading (explosion simulation) results, again similar to aluminum foam.

Enhanced mechanical properties of glass fibre-reinforced polymer composites with addition of AL2O3

ABSTRACT This paper depicts the mechanical behaviour of new class of multi-phase composites consisting of glass fibre-reinforced polyester composite filled with Al2O3 particles, Glass fibre-reinforced polyester composites was prepared by incorporating alumina particle at three different filler contents viz. 1 3 and 6%, and the mechanical properties of these composites are evaluated. The mechanical properties such as impact energy and hardness of the glass fibre-reinforced polyester composite was improved by adding alumina particles but increasing the percentage of filler content could be seen that there was reduction of impact energy, but increasing of hardness value. The macroscopic fracture surfaces of tensile specimens of all types of composites are studied briefly, However, the tensile strength and modulus of the Al2O3-filled glass fibre polyester composite was slightly lower than that of bare glass fibre-reinforced polyester composite, because of the tensile properties are more sensitive for how particles presented as network in the matrix.

Effects of a Phosphorus Flame Retardant System on the Mechanical and Fire Behavior of Microcellular ABS.

The present work deals with the study of phosphorus flame retardant microcellular acrylonitrile–butadiene–styrene (ABS) parts and the effects of weight reduction on the fire and mechanical performance. Phosphorus-based flame retardant additives (PFR), aluminum diethylphosphinate and ammonium polyphosphate, were used as a more environmentally friendly alternative to halogenated flame retardants. A 25 wt % of such PFR system was added to the polymer using a co-rotating twin-screw extruder. Subsequently, microcellular parts with 10, 15, and 20% of nominal weight reduction were prepared using a MuCell® injection-molding process. The results indicate that the presence of PFR particles increased the storage modulus and decreased the impact energy determined by means of dynamic-mechanical-thermal analysis and falling weight impact tests respectively. Nevertheless, the reduction of impact energy was found to be lower in ABS/PFR samples than in neat ABS with increasing weight reduction. This effect was attributed to the lower cell sizes and higher cell densities of the microcellular core of ABS/PFR parts. All ABS/PFR foams showed a self-extinguishing behavior under UL-94 burning vertical tests, independently of the weight reduction. Gradual decreases of the second peak of heat release rate and time of combustion with similar intumescent effect were observed with increasing weight reduction under cone calorimeter tests.

New generation of headgear for rugby: impact reduction of linear and rotational forces by a viscoelastic material-based rugby head guard

ObjectivesIn the aim to develop a usable and wearable head guard for rugby that could reduce impact energy and lessen the likelihood of concussive and subconcussive injury during play, a...

Effect of the As-Forged and Heat-Treated Microstructure on the Room Temperature Anisotropic Ductile Fracture of Inconel 718

The purpose of the present work was to investigate the effect of primary carbides and the δ-phase on the anisotropic ductile fracture of Inconel 718 in the forging process. Inconel 718 alloys were prepared by VIM + VAR processes with various carbon contents (0.009 and 0.027 wt.%). Then, the alloys were forged and annealed at temperatures of 980 and 1030 °C. The room temperature mechanical anisotropy of the alloys was evaluated at the longitudinal direction (LD) and transverse direction (TD). Tensile and impact tests were used to characterize the mechanical properties of the specimens. The microstructural characterization and the fractography of the alloys were carried out by FE-SEM. The obtained results showed that the fracture strain and the impact energy in the TD were 30-50% lower than the LD. The fracture was accelerated by the δ-phase, leading to the reduction of impact energy in the longitudinal and the lateral directions up to 50%. The low-carbon alloy indicated similar characteristics in both the LD and the TD. Aligned carbides changed the fracture path from a zigzag path in the LD to a fibrous path in the TD, while the δ-phase created a flat fracture path. The shear lip area ratio in the tensile fracture cross section was decreased by reducing ductility.

Study of Aging-Induced Degradation of Fracture Resistance of Alloy 617 Toward High-Temperature Applications

For the Alloy 617, the effect of aging on the fracture energy degradation has been investigated after aging for different time periods at 1023 K (750 °C). A sharp reduction in impact energy (by ~55 pct vis-a-vis the as-received material) after 1000 hours of aging, as evaluated from room-temperature Charpy impact tests, has been observed. Further aging up to 10,000 hours has led to a degradation of fracture energy up to ~78 pct. Fractographic examinations using scanning electron microscopy (SEM) have revealed a change in fracture mode from fibrous-ductile for the un-aged material to intergranular mode for the aged one. The extent of intergranular fracture increases with the increasing aging time, indicating a tendency of the material to undergo grain boundary embrittlement over long-term aging. Analysis of the transmission electron microscopy (TEM) micrographs along with selected area diffraction (SAD) patterns for the samples aged at 10,000 hours revealed finely dispersed γ′ precipitates of size 30 to 40 nm, rich in Al and Ti, along with extensive precipitation of M23C6 at the grain boundaries. In addition, the presence of Ni3Si of size in the range of 110 to 120 nm also has been noticed. The extensive precipitation of M23C6 at the grain boundaries have been considered as a major reason for aging-induced embrittlement of this material.

FRP-confined concrete filled PVC tubes: A new design concept for ductile column construction in seismic regions

In their recent work Fakharifar and Chen (2016) [1] have introduced and validated a new ductile design concept of confined concrete-filled polyvinyl-chloride tubular (CCFPT) columns through experimental and analytical studies. Confinement was provided with the use of a polyvinyl-chloride (PVC) tube and fiber-reinforced polymer (FRP) wrappings or FRP with a sandwiched layer of foam to enhance impact energy reduction due to potential FRP rupture and PVC fracture. In the present paper, additional flexural tests on CCFPT columns were undertaken to further investigate the structural behavior of the proposed system for column construction in seismic regions. Axial and flexural behavior of CCFPT columns was investigated with compressive and flexural tests, respectively, and compared with those of their corresponding concrete-filled polyvinyl-chloride tubular (CFPT) and FRP-wrapped (FW) columns. Test results obtained from 152×305mm (6×12in.) stub columns under axial loads and 152×1524mm (6×60in.) flexural beams under four-point loads indicated that the CCFPT columns can significantly enhance strength over the CFPT columns and enhance ductility over the FW columns. The transverse confining pressure from FRP wrapping and the interface property between the FRP and PVC proved critical in CCFPT design. Furthermore, the idea of introducing a cushioning foam layer between FRP layers and PVC to lessen the brittleness of FRP rupture in seismic regions proved effective.

Lightweight sheet molding compound (SMC) composites containing cellulose nanocrystals

A scalable technique was introduced to produce high volume lightweight composites using sheet molding compound (SMC) manufacturing method by replacing 10wt% glass fibers (GF) with a small amount of cellulose nanocrystals (CNC). The incorporation of 1 and 1.5wt% CNC by dispersing in the epoxy matrix of short GF/epoxy SMC composites with 25wt% GF content (25GF/CNC-epoxy) produced 7.5% lighter composites with the same tensile and flexural properties of 35GF/epoxy composites with no CNC. The addition of 1wt% CNC in 25GF/CNC-epoxy SMC composites resulted in increases of 15% in elastic modulus, 11% in flexural modulus and 14% in flexural strength, reaching the corresponding properties of 35GF/epoxy SMC composites. Moreover, it was found that although addition of CNC did not alter the impact energy, removing 10wt% GF resulted in reduction of impact energy.

The Effect of Constant and Pulsed Current Gas Tungsten Arc Welding on Joint Properties of 2205 Duplex Stainless Steel to 316L Austenitic Stainless Steel

In this study, dissimilar 316L austenitic stainless steel/2205 duplex stainless steel (DSS) joints were fabricated by constant and pulsed current gas tungsten arc welding process using ER2209 DSS as a filler metal. Microstructures and joint properties were characterized using optical and electron scanning microscopy, tensile, Charpy V-notch impact and micro-hardness tests, and cyclic polarization measurements. Microstructural observations confirmed the presence of chromium nitride and delta ferrite in the heat-affected zone of DSS and 316L, respectively. In addition, there was some deviation in the austenite/ferrite ratio of the surface welding pass in comparison to the root welding pass. Besides having lower pitting potential, welded joints produced by constant current gas tungsten arc welding process, consisted of some brittle sigma phase precipitates, which resulted in some impact energy reduction. The tensile tests showed high tensile strength for the weld joints in which all the specimens were broken in 316L base metal.

Effects of Mn and Al contents on cryogenic-temperature tensile and Charpy impact properties in four austenitic high-Mn steels

Abstract Effects of Mn (19 and 22 wt.%) and Al (0 and 2 wt.%) contents on tensile and Charpy impact properties in four austenitic high-Mn steels were investigated at room and cryogenic temperatures. The cryogenic-temperature tensile test results indicated that the yield strength was higher in the Al-added steels than non-Al-added steels, which could be explained by a stress-induced martensitic transformation in the non-Al-added steels. The reduction in ductility was largest in the 19Mn steel, where the transformations to e- and α′-martensites occurred and their fraction was highest. Charpy impact energies of the 19Mn and 22Mn steels rapidly dropped with decreasing temperature, whereas those of the 19Mn2Al and 22Mn2Al steels slowly decreased. According to the EBSD analysis data of the cryogenic-temperature Charpy impact specimen, the transformation to e- and α′-martensites readily occurred in the 19Mn and 22Mn steels, which resulted in the large reduction in impact energy. In the 19Mn2Al steel composed of highly stable austenite, the time needed for sufficient deformation to trigger the martensitic transformation was very short under the impact testing condition. In the Al-added steels, any martensites were not found, while many deformation twins were formed, thereby leading to high Charpy impact energy.

Manganese Supplementation in Deer under Balanced Diet Increases Impact Energy and Contents in Minerals of Antler Bone Tissue.

Bone ash, collagen, Ca and P composition, are considered the main factors affecting mechanical properties in bones. However, a series of studies in bone and antler have shown that some trace minerals, such as manganese, may play a role whose importance exceeds what may be expected considering their low content. A previous study showed that a reduction in manganese in antlers during a year of late winter frosts led to generalized antler breakage in Spain, which included a reduction of 30% of cortical thickness, 27% reduction in impact energy, and 10% reduction in work to peak force. Starting for this observation, we experimentally studied the effects of manganese supplementation in adults and yearling (yearlings) red deer under a balanced diet. Subjects were 29 deer of different age classes (adult n = 19, yearlings n = 10) that were divided in a manganese injected group (n = 14) and a control group (n = 15). Antler content in ashes and minerals, intrinsic mechanical properties and cross section structure were examined at 4 points along the antler beam. A one way ANOVA (mean per antler) showed that in yearlings, manganese supplementation only increased its content and that of Fe. However, in adults, Mn supplementation increased the mean content per antler of Ca, Na, P, B, Co, Cu, K, Mn, Ni, Se (while Si content was reduced), and impact work but not Young’s modulus of elasticity, bending strength or work to peak force. A GLM series on characteristics in the uppermost part examined in the antler, often showing physiological exhaustion and depletion of body stores, showed also a 16% increase in work to peak force in the antlers of the treated group. Thus, manganese supplementation altered mineral composition of antler and improved structure and some mechanical properties despite animals having a balanced diet.

Impact Strength of Carbon Reinforced Epoxy Composite at Different Temperatures

Charpy impact tests were conducted on carbon reinforced epoxy composites fabricated by hand lay-up method using 0.47, 0.56 and 0.66 carbon fiber volume fractions; tests were conducted at temperatures between -60oC to 60oC. The impact strength was found, in general, to increase when the samples were fractured at temperatures above 0oC and the impact strength decreased with the increase of fiber content. The impact energy absorption was highest of 270 KJm-2 with 47 vol% fiber when fractured at +60oC and it reduced to 130 KJm-2 at -60oC. With decreasing the fracture temperature and increasing the fiber content the impact strength reduced significantly. The reduction of impact energy was from 235 KJm-2 to 107 KJm-2 for 56 vol% fiber and from 196 KJm-2 to 90 KJm-2 for 66 vol% fiber when fractured at +60oC and -60oC, respectively. Failure occurred mostly by fiber delamination; fiber splitting and matrix cracking were also present. Delamination was more in specimens tested at -60oC while fiber splitting and matrix cracking were more when fractured at +60oC.

알루미늄 폼을 사용한 자동차 범퍼 빔의 설계 및 충돌해석

본 논문에서는 알루미늄 폼을 사용한 자동차 범퍼 빔을 설계하고 충돌해석을 수행하였다. 해석모델은 B형 단면 구조를 갖는 실제 크기의 범퍼 빔이다. 저속 정면충돌 시 알루미늄 범퍼 빔의 변형량 및 내부 에너지 거동을 예측할 수 있는 ANSYS AUTODYN을 이용하였다. 7075-T6 알루미늄 합금을 사용하여 철강 재질의 빔보다 55 %의 중량 감소를 얻을 수 있었으며 알루미늄 폼을 사용한 범퍼 빔의 변형량은 철강 빔과 비슷하지만 충돌에너지의 감소가 더 큰 것을 확인할 수 있었다. 또한, 알루미늄 폼의 완충보다는 50 % 충진 시 충돌에너지 흡수가 더 좋았다. In this paper, the automotive beam using aluminium foam is designed and the impact analysis is carried out. The analysis model is the beam of actual size with B- type section structure. At the frontal crash of low speed, ANSYS AUTODYN is used by predicting the behavior of deformation and its internal energy. By the use of 7075-T6 aluminum alloy, the weight is reduced as much as 55% than steel. The deformation at the bumper foam of aluminum is similar with that of steel and the impact energy reduction at aluminum is more than steel. The foam filled with aluminum as much as 50 % has more impact energy absorption than the completely filled aluminum foam.

B7 大学相撲選手における立会いの3次元動作分析(動作解析2)

We examined the characteristics of sumo wrestling using three-dimensional motion analyzer. Two kinds of college sumo wrestler, including the type of pushing the body (Tsukioshi) and grabbing the Mawashi (Yotsu), performed sumo match in circle area consisted of packed cry and straw bales (Dohyo) wearing only loincloth (Mawashi). Body motion of wrestler was analyzed during the starting phase of match (Tachiai). During Tachiai, Tsukioshi wrestlers raised their upper-body after the impact using their heads. In contrast, Yotsu wrestlers extended their knees and twisted upper-body up-down or left-right after the impact using chests. The present results suggest that there is some relationship between the reduction of impact energy and the movement such as moving the upper-body up-down and twisting left-right.

Effects of various fillers on CEM-1 laminate punchability

The primary objective of this study is to emphasize the modification of the epoxy resin formulation by implementing falling weight test to discuss reduction of impact energy and apply the thesis to improve the punchability on the CEM-1 copper clad laminate. Experimental results demonstrate that the core structure can be modified with different phenolic resin; when phenolic resin PF-440 of a smaller molecular weight is used as the modified agent, the impact energy can be lowered by 17%. In addition, three kinds of inorganic fillers, such as TiO2, Al(OH)3, SiO2, are added and the core and face structure were modified separately. Adding these fillers has a small effect on lowering the impact energy and no clear evidence of tendency, while the phenolic resin has significant effect. When 10 phr TiO2 is added to face, the impact energy can be lowered around 60% and has a visible effect on improving the punchability improvement of CEM-1 copper clad laminate. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3381–3386, 2006

フラクトグラフィ 熱間工具鋼の計装化シャルピー衝撃特性と破面解析

The effects of hardness and prior austenite grain size on the impact property of hot work tool steel JIS-SKD6 at room temperature were investigated by the analyses of impact fracture surface and of load-deflection diagrams obtained from instrumented Charpy impact test. In order to vary hardness and the grain size, the specimens of SKD6 produced by ingot and powder metallurgy were quenched from different temperatures, i.e., 1303K and 1403K, and then tempered twice at 873K. It was found that most of impact energy was exhausted in crack initiation for every material and the impact fracture modes were divided into three groups. Although the impact energy tended to decrease with increasing hardness, fine-grained structure suppressed the reduction in impact energy due to the enhancement of the resistance to the crack initiation.

Modal and Temporal Analysis of Head Mathematical Models

The basic hypotheses used during these investigations were based on the vibration analysis of the head, which demonstrated that the head is not a solid nondeformable body, but a complex structure including deformable elements. Laboratoire des Systemes Biomecanique (LSBM) has recently proposed three mathematical models: a lumped model, a finite element model of the head in its sagittal plane, and a three-dimensional finite element model. These models were validated by their modal behavior and enabled the lesion mechanisms to be distinguished as a function of the spectral characteristics of the shock. The objective of this study is to complete these modal results by temporal analysis of the models by calculating the evolution of the intracranian mechanical parameters under shock conditions. To describe the head's dynamic behavior in the temporal domain, constant energy shocks of variable duration were simulated to evaluate their influence on different quantities as the intracerebral stresses in terms of compression, tensile, and shearing stresses, the relative brain-skull displacement, and the skull deformation. The importance of modal behavior of the head is illustrated by analyzing its temporal response to variable duration impacts, thus exciting very different frequencies. For a triangular shock, the critical duration times are between 10 and 15 x 10(-3) s, which correspond to impacts that excite the first resonance frequency of the head. Taking modal behavior into consideration in developing the finite element model leads to a harmonization of the calculated intracerebral stresses, even for short duration shocks. So, when the head is considered as a complex structure made up of several deformable elements, risk limitation is conditioned by an impact energy reduction for frequencies close to the natural frequencies of the structure. In the time field, the objective will be to avoid a number of impact shapes and durations. Therefore, the aim will not be to dampen the impact at any cost, but to damper it in an "intelligent" manner. In the future, this will allow the reduction of an injury mechanism-related risk, without increasing the risk of an injury generated by another mechanism.