Low Strength Research Articles

Experimental Study on Plugging Behavior of Multitype Temporary Plugging Agents in Hydraulic Fractures

Summary Various types of temporary plugging agents are used in hydraulic fracturing to promote the uniform propagation of multicluster hydraulic fractures and increase the complexity of hydraulic fractures. However, the plugging behavior of these agents in hydraulic fractures has not yet been fully clarified, making the optimization of temporary plugging formulas challenging. In this study, dozens of plugging experiments were carried out to reveal the plugging behavior of pure fiber, pure particle, and fiber-particle combination materials in hydraulic fractures. The results indicate that the high fiber concentration and long fibers are beneficial to obtaining high maximum plugging pressures. However, the low tensile strength of fibers makes it difficult to form stable plugging layers under high pressure, especially for wide fractures. For particle plugging agents, the high rigidity of the particles prevents them from compacting tightly within the plugging layer, resulting in high permeability and low temporary plugging pressure. Excessive particle diameter and concentration tend to cause rapid blockage at the fracture entrance, leading to poor plugging performance. In contrast, the fiber-particle composite plugging scheme can form a stable and tight plugging layer at lower concentrations of both fibers and particles. Moreover, replacing single-size particles in composite with multisize particles can further enhance the plugging effect, allowing for a higher plugging pressure with a lower dosage of temporary plugging agents. Comprehensively considering the effects of material concentration and size on the plugging effect, the critical plugging quantitative characterization equations for pure fiber, pure particle, and fiber-particle combination plugging schemes are established respectively, with fracture width as the independent variable and the product of material concentration and size as the dependent variable. The temporary plugging schemes for various hydraulic fracture widths can be preliminarily determined using these equations. Based on the principle of economic optimization, the optimal temporary plugging schemes with consideration of the plugging pressure requirements were selected, which have shown good field application performance.

Preliminary study of synthesis and characterization of biodegradable avocado seed starch-chitosan plastic with glycerol plasticizer

Mechanical characteristics were studied for biodegradable plastics derived from avocado seed starch, emphasizing the influence of chitosan and glycerol. The extraction of starch from avocado seeds began with filtration. Different amounts of glycerol and chitosan were added to the extracted starch of up to 3% by weight. Because this method just uses distilled water instead of chemical chemicals, it was highly environmentally friendly. Tensile testing was done on the generated samples to assess the mechanical properties of this bioplastic; the results indicated that the samples’ elongation rates ranged from 21.9% to 134.7%. In spite of this, the bioplastic showed a comparatively low tensile strength, peaking at 3,381 MPa when chitosan-starch ratio was 2:1 and 1.5% glycerol was added.

Improving thermal stability and electrochemical performance of polymer solid electrolyte membranes with a novel TiO2@PA-APP composite additive

Polymer solid electrolytes (PSEs) are still under the safety risk because of flammability and low mechanical strength. Here a TiO2 coated piperazine-modified ammonium polyphosphate (TiO2@PA-APP) is synthesized and incorporated into poly (ethylene oxide) (PEO)-based PSE membranes to meet the above challenges. The thermal stability and ionic conductivity of PSE membrane incorporated with TiO2@PA-APP have been improved. Micro-scale combustion calorimetry experiments indicate a dramatic 70 % decrease in heat release rate, from 919 W g−1 to 267 W g−1. The lithium symmetric cell demonstrates remarkable durability, operating normally for 500 h with minimal polarization potential across various current densities at 60 °C. The all solid-state LiFePO4//Li battery using the cathode-supported TiO2@PA-APP/PEO-PSE membrane can reach a high discharge specific capacity of 153 mAh g−1 at 0.1 C and demonstrates good cycle performance, achieving a capacity retention rate of 88 % after 200 cycles at 0.2 C, along with an average coulombic efficiency of 99.24 %. These findings underscore the effectiveness of the TiO2@PA-APP flame retardant in fabricating solid-state lithium-ion batteries that provide enhanced safety and exceptional electrochemical performance.

Using higher rates of stabilization of a wet-spun pan fibre to understand the effect of microstructure on the tensile and compressive properties of carbon fibre

The transformation of a polyacrylonitrile (PAN) precursor fibre into carbon fibre using varying stabilization times during carbon fibre manufacture is presented in this work. The wet-spun precursor fibre is a specifically designed PAN co-polymer made up of acrylonitrile, methyl acrylate and 3 wt% itaconic acid. The residence or stabilization times in the oxidation ovens are varied from 32, 64 and 96 min, enabling investigation of the impact upon microstructure upon tensile and compressive properties. Using a continuous pilot scale carbonization line for faster cyclization and dehydrogenation, the precursor fibres exhibited lower oxygen uptake contributing to the formation of a less dense and more amorphous carbon fibre. Synchrotron based SAXS-WAXS characterisation and Raman spectroscopy of the carbon fibre microstructure displays lower orientation and crystallinity, with higher void concentration. This led to lower electrical conductivity, lower tensile strength (19 %) but higher compressive strength (27 %) when reducing stabilisation times from 96 to 32 min.

Adaptive reuse of waste plastic as binders in composites for sustainable construction

Effective and efficient handling of solid waste remains a significant issue, particularly in low- and middle-income countries, and densely populated urban areas. Waste plastic is identified as a major contributor to solid waste streams. This study highlighted the viable reuse of waste Linear low-density polyethylene (LLDPE) plastic as a binder and full replacement for cement in composite blocks. An extrusion technique was adopted to melt the plastic and mix it with the sand fillers to create a homogenous waste plastic binder composite block. Composite block samples were produced at various mixture ratios of 1:1, 1:2, and 1:3 with waste plastic or cement as binder and sand as filler. The composite samples' compressive strength, flexural strength, tensile strength, UPV, thermal conductivity, skid resistance, Cantabro mass loss, and morphology were investigated. In addition, the thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analysis of the composites were carried out. The results showed that composite blocks containing waste LLDPE plastic as binder exhibited lower compressive strength, higher flexural strength, and tensile strength, better thermal insulation, and abrasion resistance compared to composite blocks containing cement as binder. Meanwhile, the cement binder composite gave better skid resistance when the surface was wet than the waste plastic binder composite. However, the waste LLDPE plastic composite mixes considered gave compressive strength above 5 N/mm2, which is the minimum requirement for building bricks according to BS 3921: 1985.

Optimizing engineering potential in sustainable structural concrete brick utilizing pond ash and unwashed recycled glass sand integration

The Australian construction sector faces a dual challenge of high demand for concrete bricks and the need for sustainable materials. This research investigates eco-friendly structural concrete brick formulations, incorporating pond ash and unwashed recycled glass sand. It aims to provide scientific evidence on their engineering performance as per AS/NZS 4455.1:2008 standard, thermal insulation, and fire resistance properties. Additionally, microstructural, chemical, and pore-structure analyses are carried out to gain insights into the reaction mechanisms and the evolution of their properties. Findings indicate that bricks with 15% pond ash and 20% unwashed glass sand meet structural requirements with compression strength of 29.63MPa at 28 days. Enhanced thermal insulation is observed due to the lower densities of pond ash and glass sand. After a 2-hour exposure to elevated temperatures, the unexposed surface of these bricks remains below 180°C, satisfying fire resistance criteria for wall elements. However, microstructure and chemistry analyses suggest lower compression and tensile strength comparable conventional bricks because of low reactivity of the pond ash and the smooth surface of the glass sand.

The impact of 45S5 bioglass vs. β-TCP nanoparticles ratio on rheological behavior of formulated printing inks and 3D printed polycaprolactone-based scaffolds final properties

Extrusion based 3-D printing has been extensively applied to create geometrically complex composite polymer-ceramic structures as bone tissue substitute. The rheological features of the formulated bioink that regulate the printability and resolution of the printed scaffolds, rely on physicochemical properties of ink components, mainly their composition and chemical structure. The aim of this study was to evaluate the effect of different content of 45S5 bioglass (BG) and β-tricalcium phosphate (β-TCP) nanoparticles on the rheological behavior of printing inks and final composite scaffolds based on polycaprolactone (PCL)/BG/β-TCP. Ceramic nano-powders were first characterized and the composite bioinks were prepared by mixing various ratios of BG and β-TCP powders into the 50% w/v of PCL solution (β-TCP/BG: 70/30, 50/50, 30/70, and 10/90 w/w %). All formulated inks showed a thixotropic behavior and viscosity significantly increased by applying higher fraction of BG. Interestingly highly loaded β-TCP ink (β-TCP/BG: 70/30) revealed a rubbery nature with high surface tension which reduced final scaffolds resolution. All printed scaffolds possessed highly porous structure with interconnected pores. However, porosity percentage and shape stability improved by increasing BG content which was accompanied with lower mechanical strength and superior biodegradation and bioactivity of scaffolds. The biological performance of the printed scaffolds was evaluated using osteoblast cell line MG-63. MTT assay and cell attachment observation by SEM confirmed that printed scaffolds are well biocompatible and properly support cell colonization and proliferation. In overall, besides more appropriate materialistic properties, scaffolds with β-TCP/BG: 30/70 composition provided the most favorable microenvironment for cell colonization and growth.

Study on the Mechanical Response Behavior of X80 Pipeline Steel Welding Structure under Tensile Stress

Abstract The weld joint is composed of the weld area and the heat-affected area. The heterogeneity of the organizational structure will lead to local strain mismatch and affect its mechanical properties. This paper studies the strain distribution characteristics of the weld area and the heat-affected area under tensile stress, and reveals the respective strain response mechanism of the two regions. It is found that the weld area has lower yield strength and hardness, greater uniform elongation and strain hardening index. The plastic strain of the weld joint under tensile stress is highly heterogeneous, and the strain response mechanism is mainly based on the processing hardening effect. The strain response of the heat-affected area is weak and is affected by grain-oriented hardening. The research results provide a theoretical basis and experimental basis for the design of pipeline steel welding process and the safety evaluation under plastic deformation conditions.

Correlations of Postural Stability to Proprioception, Tactile Sensation, and Strength Among People With Chronic Ankle Instability.

The static and dynamic correlations of postural stability to its three potential contributors, namely, proprioception, tactile sensation, and strength remain unclear among people with chronic ankle instability (CAI). This study aimed to compare static and dynamic postural stability, along with proprioception, tactile sensation, and strength between people with and without CAI and explore their correlations. Sixty-seven participants with CAI and 67 participants without CAI were enrolled in this study. Ankle proprioception, plantar tactile sensation, and lower limb strength were measured by a proprioception test device, a set of monofilaments, and a strength testing system, respectively. Static and dynamic postural stability were measured during standing and jump landing on a force plate and indicated by the root mean square of center of pressure and time to stability. Compared to people without CAI, people with CAI had poorer postural stability, proprioception, tactile sensation, and strength. Both groups demonstrated correlation between proprioception and static postural stability, but only people without CAI showed correlation between proprioception and dynamic postural stability. Both groups demonstrated a correlation between tactile sensation and static postural stability, but not with dynamic stability. Both groups demonstrated a correlation between strength and both static and dynamic postural stability. People with CAI had deficits in static and dynamic postural stability, proprioception, tactile sensation, and strength. Among people with CAI, proprioception, tactile sensation, and strength can help maintain static postural stability; strength can help maintain dynamic postural stability, whereas proprioception may not provide sufficient information for dynamic postural stability.

Lower Limb Strength Asymmetries Predicts Perceptions Of Limb Function In University Athletes

Lower Limb Strength Asymmetries Predicts Perceptions Of Limb Function In University Athletes

Damage monitoring on inter-lamination of GFRP via the resistance change of the MWCNT@GF sensor

The paper aimed to investigate the performance of multi-walled carbon nanotube-coated GF (MWCNT@GF) sensors on interlayer shear damage monitoring and sensing capability of glass fiber-reinforced polymers (GFRPs) based on the resistance change under short beam shear (SBS) load. The MWCNT@GF sensor, manufactured by physical vapor deposition (PVD), was embedded into the neutral layer of laminates to form an in-situ sensing network in different directions and positions. “The MWCNT@GF sensor, manufactured by physical vapor deposition (PVD), was embedded into the neutral layer of laminates to form an in-situ sensing network.” “With the help of Keithley 2700 programmable electrometer and the 3D-digital image correlation(3D-DIC), monotonic and cyclic tests were carried out.” The monotonic test found that the off-axis sensor is more sensitive to shear failure than the on-axis sensor because of its lower shear strength. In addition, the qualitative relationship between shear damage and relative resistance was established by selecting crucial moments. In the cyclical test, the relative resistance of off-axis sensors presented a cyclic mode under cyclic load. Furthermore, the relative resistance under the first 20 cyclic loads was similar to that under monotonic loads. “Furthermore, the relative resistance under the first 20 cyclic loads was similar to that under monotonic loads, which shows that the sensor has superior sensing ability. Finally, the quantitative relation between shear damage and relative resistance was established.” “That means MWCNT@GF sensors can be used to reasonably evaluate the damage state and further evaluate the service performance, reliability and remaining life of the structure.”

Muscle Localized Phase Angle Is Related To Lower Limb Strength In Amateur Female Soccer Players

Muscle Localized Phase Angle Is Related To Lower Limb Strength In Amateur Female Soccer Players

Effects of Detraining on Physical Capacity and Its Relationship With Depressive Symptoms, Quality of Life and Sedentary Behavior in Community-Dwelling Older Adults: A Longitudinal Study.

Detraining is the partial or complete loss of physical training-induced adaptations as a result of exercise interruption or reduction. The COVID-19 pandemic led to the discontinuation of many older adult exercise programs and led to increased depressive symptoms (DS), increased sedentary behavior (SB), and decreased quality of life (QoL). To evaluate the effects of detraining, in the pandemic, on physical capacity and its relationship with DS, QoL, and SB of community-dwelling older adults. The physical capacity (static balance, dynamic balance, and lower limb and handgrip strength) of 35 participants was assessed prepandemic and after 18 and 24 months of the pandemic. DS, QoL, and SB were evaluated only at 18-month period. The analysis of variance for repeated measures or the Friedman and Pearson or Spearman tests were used for statistical analysis. There was a decline in dynamic balance (p < .001) and strength in the lower limbs (p < .001) in the first 18months, as well as maintenance in the following 6months. The reduction in dynamic balance during the 18months of the pandemic was associated with greater DS (p = .015; r = .414) and worse QoL (p = .024; r = -.381) in this period. More time spent on SB (p = .024; r = .386) in the 18th month was associated with worse dynamic balance in the following 6months. Detraining in the pandemic setting led to long-lasting harmful effects, which can last for 2years, on the physical capacity of community-dwelling older adults. Our findings highlight how periods of detraining can interfere in physical and mental health of older adults.

Optimizing the microstructure, mechanical, and optical properties of recycled zirconia for dental applications

Efficient recycling of dental zirconia residues from computer-aided design/manufacturing processes is crucial for sustainable development in dentistry. This study employed ball milling to modify recycled zirconia powder (RZP). Initial RZP and ball-milled RZP (RZP-BM) were pre-sintered at 1000–1150 °C and then final sintered at 1500 °C. Initial RZP had irregular shapes, while RZP-BM showed finer and more uniform morphology, higher packing density, and improved de-agglomeration after 6 h of ball milling. For pre-sintered zirconia, RZP-BM samples achieved properties comparable with commercial zirconia at 1100 °C, whereas initial RZP required 1150 °C. For final sintered zirconia, initial RZP samples exhibited lower Vickers microhardness, density, strength, and transmittance, with numerous defects in its microstructure. RZP-BM samples showed significant improvement in mechanical and optical properties, comparable with commercial zirconia. This study establishes a viable approach for recycling dental zirconia residues, enhancing its properties for potential reuse as dental materials.

Effects of age, elastin density, and glycosaminoglycan accumulation on the delamination strength of human thoracic and abdominal aortas

Aortic dissection is a life-threatening condition caused by layer separation. Despite extensive research, the relationship between the aortic wall's structural integrity and dissection risk remains unclear. Glycosaminoglycan (GAG) accumulation and elastin loss are suspected to play significant roles. We investigated how age-related changes in aortic structure affect dissection susceptibility. Peeling tests were performed on longitudinal and circumferential thoracic (TA) and abdominal aortic (AA) strips from 35 donors aged 13–76 years (mean 38 ± 15 years, 34 % female). GAG, elastin, collagen, and smooth muscle cell (SMC) contents were assessed using bidirectional histology. Young TAs resisted longitudinal peeling better than circumferential, with delamination strengths of 65.4 mN/mm and 44.2 mN/mm, respectively. Delamination strength decreased with age in both directions, more rapidly longitudinally, equalizing at ∼20–25 mN/mm in older TAs. Delamination strength in AAs was 22 % higher than in TAs. No sex differences were observed. GAG density increased, while elastin density decreased by 2.5 % and 4 % per decade, respectively. Collagen density did not change with age, while SMC density decreased circumferentially. GAGs partially mediated the reduction in longitudinal delamination strength due to aging, while circumferential strength reduction was not mediated by changes in either GAG or elastin densities. This study explains why aortic dissections are more common in TAs, especially in older individuals, and why they typically propagate spirally. TAs exhibit lower delamination strength compared to AAs and experience strength reduction with age, a phenomenon linked to increased GAG accumulation and elastin loss. These findings enhance our understanding of the pathophysiological mechanisms behind aortic dissection. Statement of significanceThis work explores the age-dependent relationships between delamination strength in human aortas and wall structural content. We investigated 35 human aortas from donors aged 13 to 76 years, providing new insights into the biomechanical and histological factors that influence aortic dissection risk. Our findings elucidate how variations in elastin, glycosaminoglycan, collagen, and smooth muscle cell densities impact the structural integrity of the aorta, contributing significantly to the understanding of aortic dissection mechanisms.

Predicting unsaturated soil strength of coarse-grained soils for mobility assessments

Accurately estimating surficial soil moisture and strength is integral to determining vehicle mobility and is especially important over large spatial extents at fine resolutions. While methods exist to estimate soil strength across landscapes, they are empirical and rely on class average soil behavior. The Strength of Surficial Soils (STRESS) model was developed to estimate moisture-variable soil strength with a physics-based approach. However, there is a lack of field data from a diverse landscape to evaluate the STRESS model. To test the STRESS model, a field study was conducted in northern Colorado. Soil moisture and strength were measured on 10 dates. Data from the surficial layer (0–5 cm) were used to test the STRESS model and determine if soil strength trends could be estimated from topographical and soil textural differences. High variability was observed in soil strength measurements stemming from fine-scale terrain features and user variability. Observations show lower soil strengths for greater soil moistures, steeper slopes, higher vegetation, and lower soil fines content. STRESS estimated rating cone index values with a mean relative error of 37.5 %, while a pre-existing model had a mean relative error of 47.4 %. The STRESS model outperforms the current RCI prediction method, but uncertainty remains large.

The effect of percussion and manual activation massage on explosive strength and balance in young adult males: A crossover pilot study

BackgroundRecently, the usage of percussive vibration machines in physiotherapy and sports has increased rapidly. Numerous manufacturers claim they can enhance physical performance. However, there is minimal peer-reviewed research on their efficacy. Therefore, this study aimed to investigate the effect of percussion massage (PM) on muscular performance, particularly explosive strength and balance. Moreover, this is the first study to evaluate the potential PM impact on balance. Materials and methods18 young male participants aged 20.89 ± 3.43 years with a BMI of 25.08 ± 3.95 completed three measurements with two interventions - PM by Theragun device (TG), activation massage (AM), and assessment without activation (WA). The targeted area was m. triceps surae, hamstrings, and m. quadriceps femoris of the dominant leg. Single-leg squat jump (SJ), countermovement jump (CMJ), and Y-balance tests (YBT) were performed. One-Way Repeated Measures ANOVA was utilized to analyze the data. The level significance threshold was set to p ≤ 0.05. ResultsNo statistically significant difference was reported between TG, AM, and WA in the height of the squat jump and countermovement jump (p > 0.05). Furthermore, no significant changes were recorded in the YBT performance score (p > 0.05). ConclusionsNo improvement was reported in the monitored physical parameters when the PM by Theragun or manual AM was applied for 90 s right before the muscular performance. Therefore, we do not recommend the short-term stimulative application of PM and AM before athletic performance when lower limb explosive strength or balance improvements are the objective.

Lower Limb Power And Reactive Strength In Ultramarathon Running: Comparing Finishers And Non-finishers

Lower Limb Power And Reactive Strength In Ultramarathon Running: Comparing Finishers And Non-finishers

Effects Of O2O Multi-model Training On Depression, Aerobic Fitness And Lower Limb Strength In Older

Effects Of O2O Multi-model Training On Depression, Aerobic Fitness And Lower Limb Strength In Older

Femtosecond laser joining of Stellite and stainless steel

This research explores the practicality of fusing Stellite 6, a cobalt-chromium alloy known for its high performance, with stainless steel, utilizing various laser welding approaches. The primary challenge addressed is the joining of dissimilar materials, which presents obstacles such as divergent melting points and disparate coefficients of thermal expansion. The aim is to achieve a metallurgical bond between Stellite and stainless steel that retains desirable properties. The study employs both continuous wave and femtosecond laser welding techniques, subjecting the resultant joints to rigorous analysis to assess their impact on the properties of the bond. Initial tensile testing delineated the intrinsic mechanical characteristics of the materials, revealing that while Stellite exhibits a lower ultimate tensile strength, it compensates with greater elongation compared to stainless steel. The use of continuous wave laser welding proved to be capable of creating the bond; however, it also precipitated a considerable decline in the tensile strength of the Stellite component as a result of the thermal processing involved. In contrast, femtosecond laser welding emerged as a more effective method, enhancing the joint’s overall strength and ductility. This improvement is attributed to the femtosecond laser’s precise control over thermal exposure, which confines the heat to the intended weld zone, thereby safeguarding the adjacent material from damage. Further insights were gleaned from Scanning Electron Microscopy, which showed a preferable intergranular fracture in samples welded with the femtosecond laser—a feature typically associated with ductile failure modes. The femtosecond laser welding approach culminated in a joint efficiency of 53.7%, mirroring the innate yield strength of the Stellite wire. This outcome suggests that such welded joints possess the requisite robustness for practical deployment, thus underscoring the potential of femtosecond laser welding in applications requiring the joining of Stellite to stainless steel.