Effect Of Shock Loading Research Articles

Effect of Shock and Vibration Loading on the Fracture Mechanisms of a VT23 Titanium Alloy

The structure nonuniformity a VT23 titanium alloy after shock and vibration loading is established to lead to larger plasticity of the material and changes in fracture mechanisms. Localization of deformation processes influences the sizes and quantitative distribution of tear dimples on the fracture surface. The approach was advanced to detect tear dimples on the fracture surface of the alloy, in particular after shock and vibration loading. The fractographic inspection was used to compute the dimple parameters, among them area, number, equivalent diameter, and visual depth. The above parameters for the conglomerates of detected dimples became the basis for statistical analysis and establishment of additional fracture mechanisms of the alloy at the microlevel. It provides the grounds the grounds for preliminary comparative evaluation of the cond of titanium alloys, modified by shock and vibration loading, using fractographic examination data.

Effects of transient 3-chloroaniline shock loading on the performance, microbial community and enzymatic activity of sequencing batch reactor

Chloroanilines from industrial wastewater can produce adverse effects on biological wastewater treatment systems due to their potential biotoxicity. The performance, nitrogen removal rate, microbial community and enzymatic activity of a sequencing batch reactor (SBR) were evaluated under transient 3-chloroaniline shock loading. After 40 mg/L 3-chloroaniline shock loading of 24 h on day 9, the chemical oxygen demand (COD) removal efficiency decreased from 90.71% on day 8 to 80.57% on day 11, and the NH4+-N removal efficiency reduced from 98.96% on day 8 to 35.51% on day 12. Subsequently, the COD and NH4+-N removal efficiencies gradually recovered to normal value. Compared with the absence of 3-chloroaniline shock loading, the ammonia-oxidizing rate (SAOR), nitrite-oxidizing rate (SNOR), nitrite-reducing rate (SNIRR) and nitrate-reducing rate (SNRR) decreased by 66.19%, 14.49%, 16.20% and 49.38% on day 11, respectively, and then they gradually recovered to normal value. The SAOR, SNOR, SNIRR and SNRR displayed the similar varying trends to the activities of ammonia monooxygenase, nitrite oxidoreductase, nitrite reductase and nitrate reductase, respectively. The appearance of 3-chloroaniline promoted the microbial reactive oxygen species production and lactate dehydrogenase release. The transient 3-chloroaniline shock loading distinctly impacted the microbial richness and diversity. The present research results can provide theoretical basis and technical support for evaluating the effects of transient 3-chloroaniline shock on biological wastewater treatment systems, which is beneficial to take reasonable preventable measures to decrease the adverse effects on the bioreactor performance.

Random Voids Generation and Effect of Thermal Shock Load on Mechanical Reliability of Light-Emitting Diode Flip Chip Solder Joints.

To make the light-emitting diode (LED) more compact and effective, the flip chip solder joint is recommended in LED chip-scale packaging (CSP) with critical functions in mechanical support, heat dissipation, and electrical conductivity. However, the generation of voids always challenges the mechanical strength, thermal stability, and reliability of solder joints. This paper models the 3D random voids generation in the LED flip chip Sn96.5–Ag3.0–Cu0.5 (SAC305) solder joint, and investigates the effect of thermal shock load on its mechanical reliability with both simulations and experiments referring to the JEDEC thermal shock test standard (JESD22-A106B). The results reveal the following: (1) the void rate of the solder joint increases after thermal shock ageing, and its shear strength exponentially degrades; (2) the first principal stress of the solder joint is not obviously increased, however, if the through-hole voids emerged in the corner of solder joints, it will dramatically increase; (3) modelling of the fatigue failure of solder joint with randomly distributed voids utilizes the approximate model to estimate the lifetime, and the experimental results confirm that the absolute prediction error can be controlled around 2.84%.

Shift in bacterial community structure in response to salinity in a continuous anaerobic ammonium oxidation (anammox) reactor

The effect of gradual salt adaptation on nitrogen removal performance was examined in a continuous flow anaerobic ammonium oxidation (anammox) process. Specific anammox activity (SAA) batch test was conducted to observe the effect of salinity shock loads. SAA rapidly reduced from 100% to 2.3% when salinity increased from 0 g.L−1 to 5.0 g.L−1 NaCl. On the contrary, high total nitrogen removal efficiency (TNRE) of 85% was obtained when salt concentrations gradually increased up to 25.0 g.L−1 NaCl, after 264 d of the continuous anammox operation. Then, the additional increase of salinity by 2.5 g.L−1 resulted in critical negative effect of 63.8% reduction in TNRE. Candidatus Jettenia sp. was dominant as a salt-tolerant anammox species in the salt ranges of 0–27.5 g.L−1 NaCl. In contrast, Candidatus Kuenenia stuttgartiensis was observed at 10–27.5 g.L−1 NaCl with smaller relative abundance than that of Ca. Jettenia sp. This indicates that Ca. Kuenenia sp. would build limited niche in the competition with Ca. Jettenia sp. under sudden increase of salinity stress. Interestingly, heterotrophic bacteria became dominant in autotrophic nitrogen removal process in response to the increase in salt concentration, which could be a cause of anammox system failure.

Shock velocity-dependent elastic-plastic collapse of pre-existing stacking fault tetrahedron in single crystal Cu

Abstract Stacking fault tetrahedron (SFT) is a characteristic vacancy clustered defect which can cause deterioration of metals through plastic instability. Here, we have studied the effect of shock loading on the structural transformation of the SFT and subsequent damage production using molecular dynamics simulation. According to the investigation, at low shock intensity (0.2 km/s), the SFT collapses partially through inverse Silcox-Hirsch mechanism and re-evolve during the post shock recovery. With increasing the intensity of the shock (0.5 km/s), complete disruption of the tetrahedron structure occurs through dissociation of unfaulted Frank loop into perfect and partial dislocations causing plastic deformation. A threshold pressure value has been identified where the transformation transits from elastic to plastic collapse of SFT. At very high shock velocities (above 1.1 km/s), it is observed that amorphization and martensitic phase transition of the specimen occurs. However, the rarefaction wave generated from the presence of SFT has contributed towards the stabilization of the martensitic phase during shock wave propagation.

Fracture behavior of magnesia refractory materials under combined cyclic thermal shock and mechanical loading conditions

AbstractTo investigate the effect of cyclic thermal shock and mechanical loading on the fracture behavior of magnesia refractories showing different brittleness, the as‐received and cyclic thermally shocked specimens are subjected to monotonic and cyclic wedge splitting test. The whole duration of test is monitored by digital image correlation and acoustic emission. Both thermal and mechanical fatigue resistance increase with the reduction of brittleness. Repetitive thermal shock results in pronounced reduction of strength. However, the specific fracture energy and nonlinearity increase after exposure to thermal shock due to the expanded micro‐crack network inducing the development of a significant fracture process zone. Periodic loading mainly leads to the decrease of strain bearing capacity, as the fatigue loads favor the extension of crack tip instead of fracture process zone expansion. The combined application of periodic thermal shock and mechanical loads gives a new insight into the progressive damage behavior of refractory under critical conditions.

Centrifuge experiment and numerical analysis of an air-backed plate subjected to underwater shock loading

In this study, systematic centrifuge experiments and numerical studies are conducted to investigate the effect of shock loads due to an underwater explosion on the dynamic responses of an air-backed steel plate. Numerical simulations with three different models of pressure time history generated by underwater explosion were carried out. The first model of pressure time history was measured in test. The second model to predict the time history of shock wave pressure from an underwater explosion was created by Cole in 1948. Coefficients of Cole’s formulas are determined experimentally. The third model was developed by Zamyshlyaev and Yakovlev in 1973. All of them are implemented into the numerical model to calculate the shock responses of the plate. Simulated peak strains obtained from the three models are compared with the experimental results, yielding average relative differences of 21.39%, 45.73%, and 13.92%, respectively. The Russell error technique is used to quantitatively analyze the correlation between the numerical and experimental results. Quantitative analysis shows that the simulated strains for most measurement points on the steel plate are acceptable. By changing the scaled distances, different shock impulses were obtained and exerted on the steel plate. Systematic numerical studies are performed to investigate the effect of the accumulated shock impulse on the peak strains. The numerical and experimental results suggest that the peak strains are strongly dependent on the accumulated shock impulse.

Improving the Performance of SBR WWTP under the Effect of Organic Shock Load using Stoat Software

Improving the Performance of SBR WWTP under the Effect of Organic Shock Load using Stoat Software

Thermal shock resistance of functionally graded materials with mixed-mode cracks

The thermal shock resistance of functionally graded materials (FGMs) is studied in the presence of periodic mixed-mode cracks as characterization of a typical damaging effect of thermal shock loading on FGMs. A methodology of assessing the thermal shock resistance of FGMs is proposed featuring consideration of both strength and fracture theories. The thermal shock resistance is modeled through three distinct failure criteria: (i) the maximum local tensile stress criterion (ii) the maximum thermal stress intensity factor criterion and (iii) the maximum hoop stress criterion. The finite-difference approximation of the transient temperature field is obtained firstly according to Fourier's law of heat conduction. The corresponding thermal stress field is then obtained through the finite element analysis of the mechanical problem involving thermal strain. With such a coupling between the finite element method (FEM) and finite difference method (FDM) resolving the thermomechanical response, the mixed-mode thermal stress intensity factors (TSIFs) are accordingly extracted through the interaction energy integral method (IEIM). Some typical examples of periodic mixed-mode cracks are presented with the influences of crack spacing, crack length and crack angle on the thermal shock resistance of FGMs studied. Furthermore, the distribution patterns of material properties in FGMs are discussed in terms of their effects on the thermal shock resistance. The results indicate that the proposed methodology provides an effective pathway to assessment of thermal shock resistance of FGMs showing great significance in design and fracture evaluation of such materials.

Phenol degrading and chromium (VI) reducing biofilm system : effect of shock-loading

Hexavalent chromium [Cr(VI)] which are discharged together with organic pollutants in effluent streams from industry pose a health hazard to humans. The present study observed the reduction of Cr(VI) in presence of phenol using microbial culture consortium originally obtained from Brits Waste Water Treatment Works (North West Province, South Africa) immobilised on ceramic beads in a packed bed reactor. The reactor was stabilised under a phenol feed of 1,500 mg/L and 30 mg/L of Cr(VI). After introducing a shock-loading of 40 mg/L of Cr(VI) and 1,500 mg/L of phenol, Cr(VI) concentration approached influent values in less than 3 HRTs (48-51 h). It took about 144 h for the system to recover after the feed conditions were re-established to 10 mg/L Cr(VI) and 400 mg/L of phenol, and the reactor achieved complete removal efficiency at operating condition of 10 mg/L Cr(VI) influent concentration. Results from this study also suggest that intermediates from the degradation of phenol served as electron donors in the reduction of Cr(VI), whilst the primary compound, which is phenol, remained relatively the same, thus, its degradation was inhibited by intermediates. The microbial culture consortium from Brits have the potential for efficient and simultaneous removal of organic pollutants and heavy metals in complex wastewaters.

Zeolite-amended microalgal-bacterial system in a membrane photobioreactor for promoting system stability, biomass production, and wastewater treatment efficiency to realize Environmental-Enhancing Energy paradigm

Efficiently producing biomass through microalgal-bacterial system (MBS) by using hydrothermal liquefaction wastewater (HTLWW) is a critical step to realize Environmental-Enhancing Energy (E2-Energy) paradigm. However, the toxicity and instability of HTLWW reduce biomass accumulation and further limit biocrude oil production. Here, zeolites were applied to investigate their role in improving MBS performance, which was challenged by four shock loadings, in a membrane photobioreactor (MPBR). Results demonstrated that zeolites effectively improved ammonium (NH4+) removal in both short and long term. After adding zeolites in 2# shock loading phase, NH4+ removal quickly increased to 99.5% in 9 days, which was higher compared with that after 1# shock loading (increase to 86.1% in 43 days). Even after zeolites were removed, it only took 5 days to remove 89.3% of NH4+ after 4# shock loading. Zeolites also promoted the total suspended biomass (TSB), especially the microalgae, from the negative effect of shock loadings. Contrast to 1# and 4# shock loading phases, shorter reduction time of chlorophyll (a + b) was observed after 2# and 3# shock loading with zeolites. With zeolite, the average chlorophyll (a + b) and TSB were 35.2 and 1577.2 mg L−1, which respectively increased by 67.2 and 34.2% compared with those in the phases without zeolites. Zeolites act as adsorbents relieving the NH4+ concentration and provide favorite habitats to form biofilms, which promote the tolerance of microorganisms to the high HTLWW concentrations and increased the biomass production. Adding zeolite is one suggested way to promote MBS stability, pollutant removal, and biomass production.

Reliability of MEMS shallow arches based actuator under the combined effect of mechanical shock and electric loads

Critical issues for the development of MEMS devices are their performance, reliability and survivability when subjected to unwanted loads, such as when dropped on a hard surface. These active forces can lead to tremendous destruction in these tiny mechanisms, such as stiction and all related short circuit problems in MEMS devices. Investigating the reliability of micro-structures under mechanical shock loads is a challenging job, driven, in part, by the large deflections that exacerbate system nonlinearities, such as those due to geometric (such as mid-plane stretching) and also the actuating nonlinear electric load. The proposed work aims to establish computationally efficient approaches that are capable of analyzing the transient dynamics of bi-stable MEMS devices, such as shallow arches, to mechanical shock and electric loadings. This investigation aims to improve the understanding of how mechanical shock loads can deteriorate the bi-stability of MEMS shallow arches. To this end, a Galerkin expansion reduced-order modeling (ROM) will be exploited. The capability of the ROM in simulating the bi-stable dynamical response of such devices to the combined effect of electrostatic force and shock load is thoroughly studied and analyzed. The ROM is utilized to explore the effect of several design parameters on the dynamic response of initially curved microbeams to shock loads: such as the shock amplitude, the shock duration, the beam initial curvature, and the DC voltage. Universal curves for the snap-through and pull-in voltages thresholds versus shock amplitude for various values of the nondimensional design constraints of the ROM are generated. These curves will present valuable information about the interaction between the shock and electrostatic forces and how to utilize this interaction to build new devices and propose new technologies.

Vibrational Response of Initially Deformed Bistable Microbeams Under the Combined Effect of Mechanical Shock Loads and Electrostatic Forces

This paper focuses on the influence of sudden drop tests on the nonlinear structural behavior of electrically actuated bi-table shallow microelectromechanical system (MEMS) arches. The assumed structure consists of an initially bell-shaped doubly clamped microbeam with a rectangular cross section. The Euler–Bernoulli beam theory is assumed to model the nonlinear structural behavior of the bistable system under the combined effect of both the direct current (DC) actuating load and the shaking waves. Moreover, the structural model takes into account both geometric midplane stretching and electric actuation nonlinear terms. A multimode Galerkin-based decomposition is used to discretize the beam equations to extract a reduced-order model (ROM). The convergence of the ROM simulations are first verified and furthermore compared to published experimental data. A thorough ROM parametric study showed that the effect of increasing the shallow arch initial rise alter drastically the system behavior from undergoing a uninterrupted snap-through motion to a sudden snap-through instability. Moreover, the arch rise relationship with its shock spectrum response (SSR) is investigated and it was concluded that as increasing the rise value can cause the system to collapse under the combined DC and shock wave loadings if the shock wave duration is lower or near the system fundamental natural period. All the presented graphs in this investigation represent some robust numerical approaches and design tools to help MEMS designers in improving both the reliability and efficiency of these bistable-based microdevices under shaking dynamic environments.

Performance and stability of an expanded granular sludge bed reactor modified with zeolite addition subjected to step increases of organic loading rate (OLR) and to organic shock load (OSL).

This paper shows the effect of organic shock loads (OSLs) on the anaerobic digestion (AD) of synthetic swine wastewater using an expanded granular sludge bed (EGSB) reactor modified with zeolite. Two reactors (R1 and R2), each with an effective volume of 3.04 L, were operated for 180 days at a controlled temperature of 30 °C and hydraulic retention time of 12 h. In the case of R2, 120 g of zeolite was added. The reactors were operated with an up-flow velocity of 6 m/h. The evolution of pH, total Kjeldahl nitrogen, chemical oxygen demand (COD) and volatile fatty acids (VFAs) was monitored during the AD process with OSL and increases in the organic loading rate (OLR). In addition, the microbial composition and changes in the structure of the bacterial and archaeal communities were assessed. The principal results demonstrate that the presence of zeolite in an EGSB reactor provides a more stable process at higher OLRs and after applying OSL, based on both COD and VFA accumulation, which presented with significant differences compared to the control. Denaturing gradient gel electrophoresis band profiles indicated differences in the populations of Bacteria and Archaea between the R1 and R2 reactors, attributed to the presence of zeolite.

The Transient Dynamics of a Beam Mounted on Spring Supports and Equipped with the Nonlinear Energy Sink

The transient dynamics of a beam mounted on springer-damper support and equipped with a nonlinear energy sink (NES) is investigated under the effects of shock loads. The equations of motion are derived using the Hamilton’s principle leading to four hybrid ordinary and partial differential equations and descritized using the Galerkin method. An adaptive Newmark method is employed for accurate and efficient numerical simulation and the results are used to assess the efficiency of the NES by conducting various parametric studies. The mechanisms of targeted energy transfer from the beam to the NES are indicated using the wavelet transform and Hilbert–Huang transform of the responses. Numerous modes are recognized to contribute to the response and the modes with smaller particiaption of the rigid-body motions are found to be strongly engaged in the transient resonance capture (TRC) at the initial stage of the motion. The modes with dominant rigid-body motions are, however found to be less engaed in an effective TRC. The enhanced empirical mode decomposition, with different masking signals are used to extract narrow-band intrinsic mode functions (IMFs) and simultaneous 1:1 transient resonances are observed between different IMFs of the responses especially at the initial stage of the motion.

Impact of phenol shock loads on the performance of a combined activated sludge-moving bed biofilm reactor system

The effect of phenol shock loads (100–3000 mg phenol/L) on the performance of an activated-sludge (AS) – moving bed biofilm reactor (MBBR) system was assessed. The AS-MBBR system could well withstand phenol shocks up to 500 mg phenol/L (organic load of 2.72 kgCOD/(m3d)), above which its performance was disturbed, more or less intensely depending on the phenol load. Nevertheless, acclimation of microorganisms to the increasing phenol levels was observed, and full phenolic COD removal was reached at 2000 mg phenol/L. Ammonium removal occurred by both bacterial assimilation and nitrification. Nitrifiers showed higher sensitivity to phenol than heterotrophs, being already impaired at 250 mg phenol/L. However, further adaptation of ammonium oxidizers allowed stable ammonium oxidation activity to be reached up to 1500 mg phenol/L. Nevertheless, nitrite oxidizers were severely affected above 250 mg phenol/L, leading to nitrite build-up. At 3000 mg phenol/L, phenol toxicity strongly limited microbial activity. Meanwhile, COD and ammonium removal performance was dramatically impaired. Moreover, the increasing phenol loads led to the development of filamentous organisms, deteriorating the biomass settling properties. The MBBR, employed downstream of the AS reactor, was frequently subjected to low (sometimes nil) phenol loads, not being therefore acclimated to this compound. Once phenol reached this reactor during some shocks, it accounted for less than 23% of the overall COD removal. The results indicated that the use of a non-acclimated biofilm reactor as a polishing step under phenol stress conditions did not always render improvements to the overall treatment and its implementation is only recommended under certain shock loads.

The effect of organic shock loads on the stability of anaerobic granular sludge

ABSTRACTThis study investigated the effect of organic shock loads on the stability of anaerobic granular sludge (AnGS). At double and triple shock intensity (8 and 12 kg COD/m3d organic loading rate (OLR), respectively), the accumulation of volatile fatty acids resulted in the decreasing pH of the reactors. The unstable performances of AnGS also appeared in the macroscopic properties, including the decreasing contents of relative hydrophobicity (RH), granular strength and diameter, and the fluctuation of EPS production. Noteworthily, the contents of loosely bound and tightly bound polysaccharide increased obviously and were higher than that in the control under double and triple OLR shock load. However, the growing trend of protein content was only found in the double OLR shock reactor. In addition, the N-hexanoyl-homoserine lactone (C6-HSL) content increased following the shock and then decreased during the recovery. The autoinducer-2 (AI-2) content gradually decreased under OLR shock conditions, and then rapidly increased during the recovery phase. The behaviour of the diffusible signal factor (DSF) was opposite that of AI-2. The combination of C6-HSL, AI-2 and DSF had a degraded effect on the properties of AnGS. The results provide a new reference for further research into the inter-effects among multiple signal molecules in anaerobic sludge.Abbreviations: 3-oxo-C6-HSL: N-3-oxo-hexanoyl-homoserine lactone; AHLs: acyl-homoserine lactone; AI-2: auto-inducers-2; AnGS: anaerobic granular sludge; C4-HSL: N-hydroxybutanoyl-homoserine lactone; C6-HSL: N-hexanoyl-homoserine lactone; COD: chemical oxygen demand; DSF: diffusible signal factor; EPS: extracellular polymeric substance; HPLC: High-performance liquid chromatography; HRT: hydraulic retention time; IC: integrity coefficient; LB-: loosely bound; MLSS: mixed liquor suspended solids; MLVSS: mixed liquor volatile suspended solids; OLR: organic loading rate; PN: protein; PS: polysaccharide; QS: quorum sensing; RH: Relative hydrophobicity; SS: suspended solids; TB-: tightly bound; UPLC–MS/MS: ultra-performance liquid chromatography–tandem mass spectrometry; VFAs: volatile fatty acids

The significance of grain morphology, moisture, and strain rate on the rapid compaction of silica sands

There is considerable interest in the high-rate compaction of brittle granular materials such as sand. However, the vast majority of studies focus on a single granular system, limiting our ability to make comparisons between materials to discern how granular structure manifests as bulk material response. Here, three different silica sands with similar grain size and shape are studied: we compare a rough quarry sand, a smoother-grained sand, and a sandy loam. Quasi-static compaction and planar shock loading responses are compared, and recovered samples analyzed. The combination provides information regarding the interplay between granular properties, loading conditions, and material response. We show that the fundamental grain-scale behaviour depends on loading conditions: At low strain rates compaction behaviour is dominated by grain morphology, and in particular, smoothness and particle size distribution. Under shock loading, grain rearrangement and force chain effects are suppressed, and the nature of inter-granular contact points, modified by the presence of moisture or fines, is most important. Furthermore, grain fracture under shock loading is substantially reduced with increasing moisture content.

Substrate removal kinetics and performance assessment of a vermifilter bioreactor under organic shock load conditions.

In the present study, the effect of short-term organic shock loads (675, 799, 1,084 and 1,410 mg COD/L) on the treatment performance of a pilot-scale vermifilter (VF), employing an epigeic earthworm Eisenia fetida and treating synthetic domestic wastewater is investigated. The effect of organic shock loads on the performance and stability of vermifiltration reactor was evaluated to identify its feasibility in actual field conditions. Prior to the application of each organic shock load, normal loading conditions were maintained to achieve the pseudo steady state (PSS) conditions. The results showed satisfactory endurance against imposed organic shock loads with negligible reduction in chemical oxygen demand (COD) removals and it was almost similar to PSS condition with removal efficiencies of ∼ 66, 71, 67 and 68%, respectively. The experimental COD data fit well to first-order kinetic model, with a regression value of 0.95. At the end of all shock loads, the nutritional analysis of vermicompost obtained from the top layer of VF, showed increased concentration of total nitrogen (∼31 g/Kg) and total phosphorus (29 g/Kg). Besides, an augmented earthworm biomass, ∼23.2% on weight basis and ∼22% on number basis, was observed at the end of the study.

Effect of Shock Loads on the Process Stability and Behavior of an Anammox Hybrid Reactor

The process stability of laboratory scale anammox hybrid reactor (AHR) was studied at different substrate and hydraulic shock loadings. The substrate shock load (SSL) was given by increasing the nitrogen concentration from 500–1750 mg/L, while the hydraulic shock loads (HSLs) were given by increasing the flow rates to 1.5‐, 2.5‐, and 3.5‐fold, respectively. Performance analysis of AHR dictated that the reactor was relatively more tolerant to HSLs but showed increased sensitivity to SSLs. Polynomial model and Gaussian model were applied to simulate the effect of overloads on the anammox bioreactor. Higher values of sensitivity index (1.96–12.86) and response factor (95.36–152.44) indicated higher degree of perturbations during SSLs than hydraulic shocks. This may be attributed to lower recovery rate (3.3–6.2 mg/mg h) during substrate shocks than HSLs. The modified Stover‐Kincannon model predicted the recovery potential of AHR with fair degree of accuracy.