Strength Ratio Research Articles

Influence of Fault Dip Angle and Strength on Fault Slip Characteristics of Gas Storage

The alternating stress caused by periodic high-pressure injection and extraction in gas storage can potentially induce fault slippage, compromising the sealing integrity of faults within these storages sites. Understanding the mechanical behavior of faults under alternating stress is crucial for ensuring the long-term stability and safety of gas storage operations. To explore the impact of fault dip angle and fault gouge strength on fault slip characteristics, fault samples were prepared with uniaxial compressive strengths of 20.1, 30.2, 42.4, and 51.4 MPa at two distinct dip angles. Triaxial compression experiments were conducted under alternating stress conditions corresponding to operational pressures at a specific gas storage site in China. The results indicate that faults with dip angles of 30° and 45° tend to fail at their weakest points. The increasing strength of fault gouges shifts failure mechanisms from interfacial failure between gouges and the surrounding rock towards internal gouge failure, often accompanied by shear failure across sections, resulting in characteristic “X”-shaped conjugate shear failures. The decrease in the ratio of bedrock strength to fault gouge strength elucidates the observed phenomena of an initial reduction followed by increased fault deformation. Transition points for faults with 30° and 45° dips occur around the strength ratios of 1.7/1 and 1.2/1, respectively. Fault damage exhibits a negative correlation with fault gouge strength and a positive correlation with fault dip angle. Samples with a higher-strength fault gouge at a 30° dip angle generally incur less damage compared to those with a lower-strength fault gouge at a 45° dip angle. Moreover, higher maximum static friction coefficients denote greater fault resistance to slipping, with 30° faults consistently demonstrating superior resistance compared to 45° faults. Additionally, a higher-strength fault gouge consistently enhances slip resistance under identical dip angles.

Sustainable soil stabilization of expansive soil subgrades through lime-fly ash admixture

Expansive soils, known for their significant volume changes with moisture variation, pose severe challenges for construction and pavement integrity. This study investigates the stabilization of expansive subgrade soils using a lime-fly ash mixture, aiming to enhance engineering properties and reduce associated risks. Soil samples from Nashik, Maharashtra, India, were analyzed for their geotechnical properties, revealing high plasticity and expansive nature. The study utilized different proportions of lime-fly ash mixtures to assess improvements in the stabilized soils' Unconfined Compressive Strength (UCS) and California Bearing Ratio (CBR). Laboratory tests, including granulometry, SEM, and XRF, indicated significant changes in the soil's physical and chemical composition. The stabilization process showed a marked reduction in the Free Swell Index (FSI) and swelling pressure attributed to flocculation. The optimum mix ratio of 1:4 (lime: fly ash) demonstrated the most substantial improvement, with UCS increasing to 224 kPa and CBR values reaching 8%. Additionally, the elastic modulus of the stabilized subgrade showed considerable enhancement, indicating better load-bearing capacity and durability. A flexible pavement design was implemented on both untreated and treated subgrades, demonstrating a 28% cost reduction for the stabilized section. This research underscores the effectiveness of using a sustainable lime-fly ash blend in mitigating the challenges posed by expansive soils, offering a cost-effective and environmentally friendly solution for road construction. The findings provide a robust framework for engineers to improve the stability and longevity of pavements on expansive soils.

Experimental Study to Investigate the Performance-Related Properties of Modified Asphalt Concrete Using Nanomaterials Al2O3, SiO2, and TiO2.

The dual nature of asphalt binder necessitates improvements to mitigate rutting and fatigue since it performs as an elastic material under the regime of rapid loading or cold temperatures and as a viscous fluid at elevated temperatures. The present investigation assesses the effectiveness of Nano Alumina (NA), Nano Silica (NS), and Nano Titanium Dioxide (NT) at weight percentages of 0, 2, 4, 6, and 8% in asphalt cement to enhance both asphalt binder and mixture performance. Binder evaluations include tests for consistency, thermal susceptibility, aging, and workability, while mixture assessments focus on Marshall properties, moisture susceptibility, resilient modulus, permanent deformation, and fatigue characteristics. NS notably improves binder viscosity by about 138% and reduces penetration by approximately 40.8% at 8% nanomaterial (NM) content, significantly boosting hardness and consistency. NS also enhances Marshall stability and decreases air voids, increasing the mix's durability. For moisture resistance, NS at 8% NM content elevates the Tensile Strength Ratio (TSR) to 91.0%, substantially surpassing the 80% standard. Similarly, NA and NT also show improved TSR values at 8% NM content, with 88.0% and 84.1%, respectively. Additionally, NS, NA, and NT reduce permanent deformation by 82%, 69%, and 64% at 10,000 cycles at 8% NM content, illustrating their effectiveness in mitigating pavement distress. Notably, while higher NM content generally results in better performance across most tests, the optimal NM content for fatigue resistance is 4% for NS and 6% for both NA and NT, reflecting their peak performance against various types of pavement distresses. These results highlight the significant advantages of nanoparticles in improving asphalt's mechanical properties, workability, stability, and durability. The study recommends further field validation to confirm these laboratory findings and ensure that enhancements translate into tangible improvements in real-world pavement performance and longevity.

Experimental and numerical study on the material constraint effect in pipeline steel welded joint

An in-depth analysis of the material constraint effect is crucial for accurately determining the constitutive relationship and safety evaluation of pipeline steel welded joint. Therefore, this work combines experiments and finite element simulations to study the constraint effect. Through the welding method, the weld specimens with different sizes and strength mismatch conditions are prepared. The microstructure and hardness distribution of the specimens are measured, and tensile tests based on the digital image correlation (DIC) technology are conducted. Finite element models of the weld specimens with different sizes and material parameters are established, followed by tensile simulations and detailed analysis. Based on the experiments and numerical simulations, the tensile strain responses, stress-strain curves, and material parameters of different weld specimens are obtained. The results show that the smaller the weld width, the more significant the effect of the material constraint. For undermatched welds, the calculated stress of the weld metal (WM) increases with the decrease of the weld width. Additionally, the calculated stress of WM also increases with the decrease of the mismatch coefficient, where the mismatch coefficient refers to the ratio of the yield strength of WM to that of the base metal (BM). Conversely, for overmatched welds, the calculated stress of WM decreases with the decrease of the weld width. The material constraint effect is also influenced by the mismatch condition of the weld. An increase in the mismatch coefficient reduces the effective range of the stress-strain curve obtainable for WM. To analyze the effect of the mismatch condition, it is necessary to comprehensively compare the yield strength and strain hardening capacity of each material. The width-to-thickness ratio of the weld specimen has little effect on the calculated stress of WM. The finite element simulation method can be used to correct the stress-strain curves obtained from the tests to achieve accurate constitutive relationships.

Thermodynamics and dynamics of coupled complex SYK models.

It has been known that the large-q complex SYK model falls under the same universality class as that of van der Waals (mean-field) and saturates the Maldacena-Shenker-Stanford bound, both features shared by various black holes. This makes the SYK model a useful tool in probing the fundamental nature of quantum chaos and holographic duality. This work establishes the robustness of this shared universality class and chaotic properties for SYK-like models by extending to a system of coupled large-q complex SYK models of different orders. We provide a detailed derivation of thermodynamic properties, specifically the critical exponents for an observed phase transition, as well as dynamical properties, in particular the Lyapunov exponent, via the out-of-time correlator calculations. Our analysis reveals that, despite the introduction of an additional scaling parameter through interaction strength ratios, the system undergoes a continuous phase transition at low temperatures, similar to that of the single SYK model. The critical exponents align with the Landau-Ginzburg (mean-field) universality class, shared with van der Waals gases and various AdS black holes. Furthermore, we demonstrate that the coupled SYK system remains maximally chaotic in the large-q limit at low temperatures, adhering to the Maldacena-Shenker-Stanford bound, a feature consistent with the single SYK model. These findings establish robustness and open avenues for broader inquiries into the universality and chaos in complex quantum systems. We provide a detailed outlook for future work by considering the ``very" low-temperature regime, where we discuss relations with the Hawking-Page phase transition observed in the holographic dual black holes. We present preliminary calculations and discuss the possible follow-ups that might be be taken to make the connection robust.

Arthroscopic dual-bone tunnel repair for palmer type IB injuries of the triangular fibrocartilage complex

BackgroundTriangular fibrocartilage complex (TFCC) injuries, especially Palmer type IB, pose surgical management challenges due to associated distal radial ulnar joint (DRUJ) instability. Traditional surgeries entail risks of complications. Arthroscopic repair presents advantages but lacks consensus on optimal techniques. To evaluate arthroscopic dual-bone tunnel repair in patients with Palmer type IB TFCC injuries of the wrist.MethodsIn this retrospective case series, grip strength ratio, joint range of motion, pain visual analogue scale (VAS), modified Mayo wrist score, and Disabilities of the Arm, Shoulder, and Hand (DASH) scores were assessed before and 12 months after surgery.ResultsThe cohort consisted of 45 patients. At 12 months, the grip strength ratio improved from 0.71 ± 0.08 to 0.93 ± 0.05 (P < 0.001), and wrist joint rotation increased from 126.78 ± 13.28° to 145.76 ± 8.52° (P < 0.001). VAS (1.60 ± 0.58 vs. 6.33 ± 0.91, P < 0.001), DASH (12.96 ± 3.18 vs. 46.87 ± 6.62, P < 0.001), and modified Mayo wrist (88.11 ± 4.43 vs. 63.78 ± 7.99, P < 0.001) scores all improved after surgery. The overall complication rate was 4.44%.ConclusionArthroscopic dual-bone tunnel repair appears to be an effective intervention for alleviating wrist pain, restoring stability, and enhancing joint function in patients with TFCC Palmer type IB injuries.

2-dimensional impact-damping electrostatic actuators with elastomer-enhanced auxetic structure

Biomimetic robots yearn for compliant actuators that are comparable to biological muscle in both functions and structural properties. For that, electrostatic actuators have been developed to imitate bio-muscle in features of fast response, high power, energy-efficiency, etc. However, those actuators typically lack impact damping performance, making them vulnerable and unstable in real applications. Here, we present auxetic electrostatic actuators that address this issue and demonstrate muscle-like performance by using elastomer-enhanced auxetics and electrostatic zipping mechanism. The proposed actuators contract linearly on applied voltage, producing large actuation strength (15 N) and contraction ratio (59%). Fabricated from readily available materials, our prototypes can quickly attenuate vibrations caused by impacts and absorb shock energy in 0.3 s. Furthermore, leveraging their 2-dimensional working mode and self-locking mechanism, a stiffness-changing muscle for a robotic arm and an active tensegrity device exemplify the potential applications of auxetic electrostatic actuators to a wide range of bionic robots.

Modeling and design optimization of the performance of stone matrix asphalt mixtures containing low-density polyethylene and waste engine oil using the response surface methodology

In recent years, the use of waste plastic materials such as low-density polyethylene (LDPE) to modify asphalt binders and enhance mixture performance has garnered significant attention. One major concern with using such materials is the higher production temperature required, which necessitates the use of a bitumen extender agent, such as waste engine oil (WEO), to reduce the viscosity and mixing temperature. Therefore, using these stabilizing additives can reduce the consumption of virgin binder, especially for Stone Matrix Asphalt (SMA) mixtures, which require higher asphalt content. This study aimed to optimize the design of SMA modified by LDPE and WEO to minimize the optimum asphalt content (OAC) and mixing temperature while maximizing SMA performance. To achieve this, Response Surface Methodology (RSM) was utilized to develop the necessary models for optimizing design and predicting performance. The selected independent variables (factors) for the design include LDPE content, WEO content, OAC, and mixing temperature. Meanwhile, the responses (dependent variables) consist of Marshall stability, rut depth, tensile strength ratio, and resilient modulus, which were used to determine the best mix design. The findings demonstrated that the suggested models for the output variables can predict performance with a higher level of confidence. The Analysis of variance (ANOVA) demonstrated that predictive models were significant and well-fitted, with a coefficient of determination (R2) of higher than 0.80, an adequate precision value of greater than 4, and a low p-value (less than 0.05). The error percentage between the RSM-predicted and actual values was less than 5 %, indicating that RSM-established models can accurately and efficiently predict the SMA performance. The best mix design of the SMA mixture modified by LDPE and WEO was found to be 10 % LDPE, 3.91 % WEO, 5.92 % OAC, and mixing temperature of 152.24°C with a combined desirability of 82.8 %.

Effects of TiO2 nanobelts addition on microstructure and physical properties of vitrified bonds

Titanium dioxide (TiO2) is commonly used additive to improve the strength, hardness and coefficient of expansion properties of vitrified bonds. In this work, TiO2 nanobelts were prepared through hydrothermal method, and the effect of TiO2 nanobelts content on the microstructure and physical properties of vitrified bonds and vitrified bond CBN composites were systematically investigated. When the content of 0.2 wt% TiO2 nanobelts and sintered at 660 °C, as-prepared nano-vitrified bonds exhibited the beneficial performance improvement. Specifically, the obtained coefficient of thermal expansion, flexural strength, microindentation hardness, and mobility are 5.37 × 10−6 °C−1, 85.96 MPa, 853.19 MPa, and 140.6 %, respectively. Moreover, the vitrified bonds with 0.2 wt% TiO2 nanobelts addition is further used to optimize the performance of cubic boron nitride (CBN) composites. When sintered at 720 °C, the CBN composite samples depicted the excellent flexural strength, rockwell, porosity, and grinding ratio of 63.27 MPa, 61.5 HRB, 48.9 %, and 22.3, respectively. It can be attributed to the positive contribution of nano-vitrified bonds on the physical properties of CBN composites. This work is expected to contribute to the research on improving the performance of vitrified bonds with nano additives, and further obtain excellent performance nano-vitrified bond materials for the design and manufacturing of high-performance superhard abrasive tools.

Directional fracture patterns of excavated jointed rock mass within rough discrete fractures

The influence of the fractures on the anisotropic mechanical behavior of excavated fractured rock mass is important for the stability of rock tunnels. Rough joints were generated using fractal principles, and the Monte Carlo method was employed to create joint network faces. Biaxial compression numerical simulations were conducted using the discrete element method to analyze the behavior of the rock mass containing these networks. Quantitative analysis was carried out to evaluate the strength variability and total number of cracks in the jointed rock mass. A linear regression analysis was conducted to establish the relationship between rock strength and excavation size. The findings demonstrate significant disparities between the linear and fractal models regarding rock damage mode, stress–strain curves, and crack evolution patterns. Tensile rupture and local shear damage were found to be the primary fracture modes for the fractured rock tunnels, forming a V-shaped damage zone within the central tunnel. The shape of this zone was influenced by fracture direction and excavation ratio. Excavation at the center of the rock mass substantially impacted the variability of rock strength and the occurrence of internal cracks. An increase in the slope ratio led to a greater variability of rock mass strength, transitioning from nearly isotropic to weakly anisotropic behavior. The total number of cracks exhibited a W-shaped trend, initially increasing and later decreasing as the slope ratio decreased. Additionally, a clear linear correlation was observed between rock strength and excavation ratio at the center of the rock mass.

Comparison of post-impact residual strength ratio between hybrid filament-wound cylinder and hybrid plate specimen

The filament-wound (FW) cylinders possess numerous benefits as a high-pressure storage device but are susceptible to impact loads. The presence of post-impact residual strength in an operating FW cylinder has the potential to accelerate the onset of failure. Ensuring the structural integrity and safety of the equipment requires thorough impact testing, which can be expensive and time-consuming, resulting in limited use. This article presents an innovative and cost-effective approach for conducting low-velocity impact testing on a hybrid Al/CFRP filament-wound cylinder by utilizing a simple hybrid Al/CFRP plate specimen. The main focus is to conduct low-velocity impact testing on both types of specimens, followed by post-damage testing that includes tensile tests on the hybrid plate specimen and burst tests on the FW cylinder. The results of laboratory experiments were compared to explicit and implicit numerical models conducted in a broad spectrum of impact energy range and found to be consistent. Using a parameter known as the post-impact residual strength ratio, it is possible to determine the expected impact loading conditions on the hybrid plate specimen that are equivalent to those experienced by the FW-cylinder. This low-cost impact testing method offers a practical and feasible solution to ensure the dependability and safety of FW cylinders throughout their operational lifespan.

Analyzing elastoplastic behavior and residual strength ratios in steel tubular braces under compression: a numerical investigation

Analyzing elastoplastic behavior and residual strength ratios in steel tubular braces under compression: a numerical investigation

Stress–strain behaviour and degradation mechanism of low–carbon MgO–C refractories at 900–1100 °C: role of TiB2–BN–AlN waste

The use of boron–containing additives often raises concerns when exposed to high temperatures. In this study, the high temperature stress–strain behavior and degradation mechanism of low–carbon MgO–C refractories containing TiB2–BN–AlN waste were investigated. Stress–strain curve, peak axial stress, Young’s modulus, cohesion, and residual strength ratio after thermal shock tests were thoroughly analyzed. The findings suggest that the mechanical properties of refractories remain unimpaired within the temperature range of 900–1100 ℃, and can even be enhanced through the synergistic effect of TiB2–BN–AlN waste and Al powder. The optimized axial stress increased from 55.0 to 62.0 MPa at 1100 ℃, while the cohesion increased from 10.0 to 13.8 MPa, respectively. The observed enhancement can be primarily attributed to the effective healing of pores and cracks, reduction in oxidation, and improved material cohesion. However, the excessive incorporation of boron–containing waste may compromise the performance of refractories, leading to instability or degradation.

Influence of cooling bed temperature on microstructural, mechanical properties and surface quality of high-strength seismic-resistant rebar

High-strength seismic-resistant rebar is essential in construction engineering, yet balancing its strength, plasticity, seismic resistance, and surface quality poses challenges. This research explores niobium-vanadium-nitrogen composite reinforced steel, examining how cooling bed temperature affects its microstructure, mechanical properties, and surface quality using advanced microscopy techniques. The research reveals that the steel's microstructure primarily consists of ferrite and pearlite. As cooling bed temperatures decrease, both the proportion and colony size of pearlite, along with ferrite size, show a declining trend. Specifically, reducing the cooling bed temperature from 1100 °C to 900 °C results in a decrease in yield strength, tensile strength, and tensile-to-yield strength ratio by 6 MPa, 27 MPa, and 0.03, respectively. Meanwhile, elongation after fracture, total elongation at maximum force, and strength-ductility balance improve by 3.8%, 1.5%, and 1.93%, respectively. At a cooling bed temperature of 1100 °C, significant blistering occurs on the steel surface. Significant blistering at 1100 °C vanishes at 1000 °C and 900 °C, with diminished silicon enrichment in the surface oxide scale. A cooling bed temperature of 1000 °C ± 20 °C is recommended for optimal performance. This study provides a temperature control strategy for the properties of high-strength seismic-resistant rebar rated at 650 MPa and above, contributing valuable insights to the field of advanced construction materials.

Research on Solidification Methods and Stabilization Mechanisms of Sulfate Saline Soils

In cold regions, saline soils can cause dissolution, settlement, and salt expansion of the roadbed under the influence of freeze–thaw cycles, so they need to be stabilized during road construction. In this study, lime, fly ash (FA), and polyacrylamide (PAM) were used to stabilize sulfate saline soils, and the stabilized saline soils were subjected to the unconfined compressive strength test (UCS), splitting test, and freeze–thaw cycle tests (FTs). The stabilization mechanism of the three materials on saline soils was also studied via scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TG), and X-ray photoelectron spectroscopy (XPS). The test results showed that the addition of lime, FA, and PAM to saline soils can improve the mechanical properties and frost resistance of saline soils. After 28 d of curing, the UCS of FA-, PAM-, and lime-stabilized saline soils increased by at least 55%, 23%, and 1068%, respectively, and the splitting strength increased by at least 161%, 75%, and 2720%, respectively. After five freeze–thaw cycles, the residual strength ratios (BDRs) of the UCS of L2 (lime 8%), F2 (FA 11%), and P2 (PAM 1%) stabilized soils and saline soils were 71.78%, 56.42%, 39.05%, and 17.95%, respectively, and the decreasing trend tended to be stable. The saline soils stabilized by lime and FA were chemically stabilized, and their mechanical properties and frost resistance were better than the physical stabilization of PAM.

Evolution of microstructure and mechanical properties along the thickness direction of 500 MPa HSLA steel heavy plates

High strength heavy plates with large thickness are demanded for the construction of large-span bridge projects. However, there is a lack of understanding on the microstructure evolution and mechanical properties through the entire thickness of heavy plates with yield strength over 500 MPa, especially manufactured by the thermo-mechanical control processing (TMCP) and tempering (T) process. In this research, the microstructure and mechanical property evolution through the thickness was investigated for the 85 mm thick, 500 MPa grade heavy steel plate manufactured by TMCP + T. The results show that the microstructure throughout the thickness predominantly consists of granular bainite (GB) and polygonal ferrite (PF). The yield strength and tensile strength at 1/8t, 1/4t, 3/8t and 1/2t (t, the thickness) are 659.4 MPa, 520.6 MPa, 500.3 MPa and 494.0Mpa, and 739.2 MPa, 642.9 MPa, 627.8 MPa and 625.2 MPa, respectively. Yield and tensile strength both significantly decline from 1/8t to 1/2t. The strengthening mechanisms at different thickness were analyzed, and grain refinement has the most significant contribution. In addition, the mechanical properties of ferrite/bainite heterostructure were analyzed by Cyclic load-unload-reload (LUR) tests. The hetero-deformation induced (HDI) stress increases from 1/8t to 1/2t. At 1/8t, HDI hardening is higher but occurs over a narrower strain range compared to that at 1/2t. The impact energy at −40 °C for 1/8t, 1/4t, 3/8t and 1/2t are 182.7 J, 213.0 J, 242.2 J and 253.7 J, respectively. It was discerned that PF undergoes plastic deformation and absorbs a large amount of energy, constituting the primary rationale for the enhanced impact toughness at 1/2t compared to 1/8t. Through this research, not only the microstructure and mechanical property evolution through the thickness was revealed, but also the ferrite/bainite microstructure was found a promising heterostructure to obtain high strength, high toughness and low yield ratio for heavy plates.

Factors that interfere with immediate return to activity following volar locking plate fixation for distal radius fractures.

In the present study, the clinical findings that interfere with the immediate return to activity following volar locking plate (VLP) fixation for distal radius fractures were investigated. A total of 95 patients who underwent VLP fixation for distal radius fracture between July, 2014 and January, 2022 were divided into a good group (good score and outcome; n=86; 22 males and 64 females; median age, 61 years) and a poor group (poor score and outcome; n=8; 8 females; median age, 63.6 years) according to the quartiles of the disabilities of the arm, shoulder and hand (Q-DASH) score, at 1 month following VLP fixation. The duration from injury to surgery, the direction of fracture dislocation and radiographic parameters [radial inclination (RI), volar tilt (VT) and ulnar variance (UV)] at the time of injury were examined. Radiographic parameters (RI, VT and UV), the range of motion of the wrist joint, grip strength ratio and visual analog scale (VAS) at 1 month following VLP fixation were also examined. These parameters were compared among both groups. Moreover, logistic regression analysis was performed to determine whether these factors were independently associated with a poor Q-DASH score at 1 month following VLP fixation. At the time of injury, fracture displacement was significantly higher in the poor group (VT, -23.8˚; UV, 4.2 mm) than the good group (VT, -6.5˚; P=0.02; UV, 1.3 mm; P=0.01). No differences in the other parameters were observed between the groups. At 1 month following VLP fixation, the grip strength ratio (17.2%) in the poor group was significantly lower than that in the good group (43.8%, P<0.001), while the VAS score (5.6) in the poor group was significantly higher than that in the good group (2.4, P<0.001). Logistic regression analysis revealed that VT and UV at injury (P<0.05), grip strength ratio (P<0.001) and pain (VAS score) (P<0.001) were all independently associated with a poor Q-DASH score. On the whole, the present study suggests that large amounts of fracture displacement, weakness of grip strength and post-operative pain can be factors interfering with the return to activity immediately following VLP fixation.

Novel hybrid XGBoost-based soft computing models for predicting penetration resistance of buried pipelines in cohesive soils

In this paper, both the finite element limit analysis (FELA) and soft computing techniques of four hybrid XGBoost (XGB) models, namely, GA-XGB, optimized with Genetic Algorithms; SMA-XGB, optimized with Slime Mould Algorithms; PSO-XGB, optimized with Particle Swarm Optimization; ACO-XGB, Ant Colony Optimization; and one Genetic Programing model (GP), are employed to develop surrogate models for predicting the undrained penetration resistance of buried pipelines embedded in clays. The penetration resistance of pipelines is caused by internal and external pressures, resulting in a force that acts on the pipeline in the downward and inclined directions at the same time. The penetration resistance factor (N) of a buried pipeline is determined based on four dimensionless variables, namely, the buried depth ratio (H/D), the inclination angle of the applied load (β), the soil strength or overburden ratio (γH/c), and the adhesion factor at soil-pipeline interfaces (α). The findings of this study are presented and summarized in the form of charts for dimensionless penetration resistance factors (N) and failure mechanisms of pipelines. Furthermore, the results from this study are compared with the results from previous studies and agrees well with those of previous studies. According to the results of the four developed hybrid XGBoost-based models, SMA-XGB outperforms GA-XGB, PSO-XGB, and ACO-XGB with no symptoms of overfitting, while the GP model resulted in an adequately accurate model with the advantage of a closed-form equation; its determination correlation coefficient of training and testing equals 0.98 (R2 = 0.980).

Microstructure and Mechanical Properties of As-Cast Al-10Ce-3Mg-xZn Alloys.

The microstructure and mechanical properties of as-cast Al-10Ce-3Mg-xZn (x = 0, 1, 3, 5 wt.%) alloys were systematically investigated, with a focus on the effect of Zn on the Al11Ce3 reinforcing phase in the alloy. The results showed that the Al-10Ce-3Mg alloy consists of α-Al, a Chinese-script Al11Ce3 eutectic phase, and a massive Al11Ce3 primary phase. With the addition of Zn content, most of the Zn atoms are enriched in the Al11Ce3 phase to form the acicular-like Al2CeZn2 phase within the Al11Ce3 phase. Increasing the Zn content can increase the volume fraction of the Al11Ce3 phase. Compared to the alloy without Zn addition, the microhardness and elastic modulus of the Al2CeZn2-reinforced Al11Ce3 phase in the alloy with 5 wt.% Zn increased by 18.9% and 9.0%, respectively. Moreover, the room-temperature mechanical properties of Al-10Ce-3Mg alloys were significantly improved due to the addition of Zn element. The alloy containing 5 wt.% Zn had the best tensile properties with an ultimate tensile strength of 210 MPa and a yield strength of 171MPa, which were 21% and 77% higher than those of the alloy without Zn, respectively. The alloy containing 5 wt.% Zn demonstrated a superior retention ratio of tensile strength at 200-300 °C, indicating that the alloy has excellent heat resistance. The improvement in the mechanical properties is primarily attributed to second-phase strengthening and solid solution strengthening.

Influence of Build Orientation and Part Thickness on Tensile Properties of Polyamide 12 Parts Manufactured by Selective Laser Sintering.

The use of additive manufacturing to rapidly test and evaluate solutions to engineering problems has been demonstrated. Selective laser sintering (SLS) is a subset of additive manufacturing that is particularly well suited to producing structural thin wall models and end use parts which can improve the ability to prototype and manufacture certain designs at a substantially lower cost and time compared to current methods. However, a more comprehensive understanding of the material properties of these parts is warranted. The presented research investigates the influence of print orientation and sample thickness on the material properties of printed SLS parts. This novel work involves holding a hatch pattern constant across SLS prints using polyamide 12 material to isolate the anisotropic effects of orientation and thickness. An evaluation of ultimate tensile strength, modulus of elasticity, strain at failure, yield strength, and Poisson's ratio, and scanning electron microscope fractography are conducted. Transverse strain and Poisson's ratio are a key aspect that provide insight into the feasibility of building numerical orthotropic models. These data are used to calculate the degree of anisotropy due to both thickness and orientation. The results support the future use of SLS printing and modeling of thin-walled structures, such as scaled structural ship modeling. The presented data provide guidance on the impact of print orientation and thickness that will aid in manufacturing structural parts with intentionally tuned material properties.