Stress-strain Pattern Research Articles

Non-Linear Biomechanical Evaluation and Comparison in the Assessment of Three Different Piece Dental Implant Systems for the Molar Region: A Finite Element Study.

The widely available options of different manufacturers in dental implant systems have complicated the selection criteria process for periodontists, necessitating careful consideration of various factors when selecting suitable solutions for individual patient needs. Optimal implant selection requires careful consideration of the patient-specific factors, implant design, and surgical technique. Understanding the biomechanical behavior of implant-tissue interactions is crucial for achieving successful and long-lasting implant therapy. To adequately address this issue and improve the rigorous selection criteria from a biomechanically numerical approach, this research aims to analyze the stress distribution fields, strain patterns, and load transfer displacements within the implant system and the implant-biological interface (gingival and bony tissues) of titanium three-piece to two-one-piece ceramic implant systems. Thus, three different commercially available dental implants designed to be placed in the jaw molar region were considered for evaluation through the finite element method under both oblique and occlusal loading conditions. The results have exhibited an increasing trend to highlight the outstanding behavior of two-piece ceramic implants to dissipate the stress distribution better (6 and 2 times lower than the three- and one-piece systems under occlusal loads and almost 5 and 1.3 times more efficient for oblique loading, respectively), minimize peak stress values (below 100 MPa), and reduce strain peak patterns compared with the other two evaluated designs. On the other hand, the effects generated in biological tissues are strongly associated with implant geometry features. This biomechanical approach could provide a promising strategy for predicting micro-strains and micromotion in implant system pieces and geometries. Hence, these findings contribute to a deeper understanding of the biomechanics spectrum in the behavior of dental implant systems and emphasize the importance of carefully selecting appropriate material systems for accurate patient-specific biomechanical performance.

Investigating the Construction Procedure and Safety Oversight of the Mechanical Shaft Technique: Insights Gained from the Guangzhou Intercity Railway Project

Currently, subway and underground engineering projects are vital for alleviating urban congestion and enhancing citizens’ quality of life. Among these, excavation engineering for foundation pits involves the most accidents in geotechnical engineering. Although there are various construction methods, most face issues such as a large footprint, high investments, resource waste, and low mechanization. Addressing these, this paper focuses on a subway foundation pit project in Guangzhou using mechanical shaft sinking technology. Using intelligent cloud monitoring, we analyzed the stress–strain patterns of the cutting edge and segments. The results showed significant improvements in construction efficiency, cost reduction, safety, and resource conservation. Based on this work, this paper makes the following conclusions: (1) The mechanical shaft sinking method offers advantages such as small footprint, high mechanization, minimal environmental impact, and cost-effectiveness. The achievements include a 22.22% reduction in construction time, a 20.27% decrease in investment, and lower worker risk. (2) Monitoring confirmed that all cutting edge and segment values remained safe, demonstrating the method’s feasibility and rationality. (3) Analyzing shaft monitoring data and field uncertainties, this study proposes recommendations for future work, including precise segment lowering control and introducing high-precision total stations and GPS technology to mitigate tunneling and assembly inaccuracies. The research validates the mechanical shaft sinking scheme’s scientific and logical nature, ensuring safety and contributing to technological advancements. It offers practical insights, implementable suggestions, and significant economic benefits, reducing project investment by RMB 41,235,600. This sets a benchmark for subway excavation projects in South China and beyond, providing reliable reference values. Furthermore, the findings provide valuable insights and guidance for industry peers, enhancing overall efficiency and sustainable development in subway construction.

Tectonic Activity Analysis of the Laji-Jishi Shan Fault Zone: Insights from Geomorphic Indices and Crustal Deformation Data

Fault segmentation plays a critical role in assessing seismic hazards, particularly in tectonically complex regions. The Laji-Jishi Shan Fault Zone (LJSFZ), located on the northeastern margin of the Tibetan Plateau, is a key structure that accommodates regional tectonic stress. This study integrates geomorphic indices, cross-fault deformation rate profiles, and 3D crustal electrical structure data to analyze the varying levels of tectonic activity across different segments of the LJSFZ. We extracted 160 drainage basins along the strike of the LJSFZ from a 30 m resolution digital elevation model and calculated geomorphic indices, including the hypsometric integral (HI), stream length-gradient index (SL), and channel steepness index (ksn), to assess the variations in tectonic activity intensity along the strike of the LJSFZ. The basins were categorized based on river flow directions to capture potential differences across the fault zone. Our results show that the eastern basins of the LJSFZ exhibit the strongest tectonic activity, demonstrated by significantly higher SL and ksn values compared to other regions. A detailed segmentation analysis along the northern Laji Shan Fault and eastern Jishi Shan Fault identified distinct fault segments characterized by variations in SL and ksn indices. Segments with high SL values (>500) correspond to higher crustal uplift rates (~3 mm/year), while segments with lower SL values exhibit lower uplift rates (~2 mm/year), as confirmed by cross-fault deformation profiles derived from GNSS and InSAR data. This correlation demonstrates that geomorphic indices effectively reflect fault activity intensity. Additionally, 3D crustal electrical structure data further indicate that highly conductive mid- to lower-crustal materials originating from the interior of the Tibetan Plateau are obstructed at segment L3 of the LJSFZ. This obstruction leads to localized intense uplift and enhanced fault activity. These findings suggest that while the regional stress–strain pattern of the northeastern Tibetan Plateau is the primary driver of the segmented activity along the Laji-Jishi Shan belt, the direction of localized crustal flow is a critical factor influencing fault activity segmentation.

The Stiffness of the Ascending Aorta Has a Direct Impact on Left Ventricular Function: An In Silico Model.

During systole, longitudinal shortening of the left ventricle (LV) displaces the aortic root toward the apex of the heart and stretches the ascending aorta (AA). An in silico study (Living Left Heart Human Model, Dassault Systèmes Simulia Corporation) demonstrated that stiffening of the AA affects myocardial stress and LV strain patterns. With AA stiffening, myofiber stress increased overall in the LV, with particularly high-stress areas at the septum. The most pronounced reduction in strain was noted along the septal longitudinal region. The pressure-volume loops showed that AA stiffening caused a deterioration in LV function, with increased end-systolic volume, reduced systolic LV pressure, decreased stroke volume and effective stroke work, but elevated end-diastolic pressure. An increase in myofiber contractility indicated that stroke volume and effective stroke work could be recovered, with an increase in LV end-systolic pressure and a decrease in end-diastolic pressure. Longitudinal and radial strains remained reduced, but circumferential strains increased over baseline, compensating for lost longitudinal LV function. Myofiber stress increased overall, with the most dramatic increase in the septal region and the LV apex. We demonstrate a direct mechanical pathophysiologic link between stiff AA and reduced longitudinal left ventricular strain which are common in patients with HFpEF.

Structural Performance Evaluation of Cross Dapped Connection for Vertical Wall to Wall Connection of Precast Wall Panel

In the context of Industrialised Building Systems (IBS), precast concrete buildings are composed of multiple structural members that are interconnected through different techniques. The adoption of precast concrete wall panels has gained significant traction in contemporary construction methodologies. Nevertheless, the utilization of dapped connections specifically designed for non-load bearing applications in precast walls incorporating recycled concrete aggregate (RCA) remains largely unexplored and limited in practice. This research proposes a new wall-to-wall connection for precast wall panels to enhance the constructability of IBS for non-load bearing walls. The novel Cross Dapped (CD) design enables horizontal panel installation in confined areas with existing structural frames, while ensuring the connection’s strength as a non-load bearing wall to prevent failure. Uniformly distributed loads are applied until sample failure, recording compressive load patterns, deflection, stress-strain patterns, and crack patterns on the wall surface. The CD connection demonstrates applicability for precast wall-towall connections, improving IBS constructability with its innovative design and locking system. Overall, this research explores and proposes an efficient and structurally sound wall-to-wall connection design for precast wall panels of non-load bearing system, facilitating the adoption of IBS methods, and improving the overall quality and constructability of building systems.

Effect of Ultrasonic Vibration on Tensile Mechanical Properties of Mg-Zn-Y Alloy

Ultrasonic vibration assisted (UVA) plastic forming technology has proven to be a highly effective processing method, particularly for materials that are challenging to deform. In this research, UVA tensile tests were carried out on Mg98.5Zn0.5Y1 alloy at different vibration frequencies and amplitudes. The experimental results indicate that, compared with conventional tensile tests, the yield strength and tensile strength of Mg98.5Zn0.5Y1 alloy exhibit a decrease. Furthermore, the application of ultrasonic vibration demonstrates an ability to enhance the material’s elongation and plasticity. In order to further predict the stress-strain relationship in the metal tensile process, a hybrid constitutive model coupling the frequency and amplitude of ultrasonic vibration was developed based on the modified Johnson Cook model. The calculated results of the constitutive equation are in good agreement with the experimental results, indicating that the established constitutive equation can accurately predict the trend of alloy stress change at different amplitudes and frequencies. It establishes a theoretical foundation for scrutinizing the deformation mechanisms of the alloy under ultrasonic vibration. Furthermore, Abaqus finite element analysis software was employed to simulate and analyze the UVA tensile process, elucidating the impact of ultrasonic vibration on stress distribution, strain patterns, and material flow in the tensile behavior of Mg98.5Zn0.5Y1 alloys.

Experimental Investigation on Strength and Stiffness Properties of Laminated Veneer Lumber (LVL).

This study presents a testing campaign aimed at evaluating the strength and stiffness properties of laminated veneer lumber (LVL) specimens. LVL is an engineered wood product composed of thin glued wood veneers whose use in construction for structural applications has increased due to its sustainability and enhanced mechanical performance. Despite LVL's growing popularity, there is a lack of comprehensive information regarding stress-strain responses, failure modes, and the full set of strength and stiffness properties. These are particularly essential when LVL is employed in pure timber structures or composite systems such as steel-timber or timber-concrete load-bearing elements. This research aims to bridge this knowledge gap, focusing on crossbanded LVL panels, known as LVL-C, crafted from Scandinavian spruce wood, which is an LVL product with 20% of crossbanded veneers. The study explores LVL-C mechanical behavior in three primary orthogonal directions: longitudinal, tangential, and radial. A series of mechanical tests, including compression, tension, shear, and bending, was conducted to provide a thorough assessment of the material's performance. In compression tests, different behaviors were observed in the three directions, with the longitudinal direction exhibiting the highest stiffness and strength. Tensile tests revealed unique stress-strain responses in each direction, with gradual tension failures. Shear tests showcased varying shear stress-strain patterns and failure modes, while bending tests exhibited significant strength and stiffness values in flatwise bending parallel to the grain and flatwise bending perpendicular to the grain. This paper summarizes the comprehensive testing results and discusses the obtained strength and stiffness properties of LVL-C panels, providing valuable insights into their mechanical behavior for engineering applications.

Three-dimensional laser scanning and numerical investigation on the influence of freeze-thaw and hang-wall mining on the instability of an open-pit slope

The instability of the open-pit slope and associated disasters of complex orebodies such as hanging-wall mining are the key problems to be solved urgently in the development of western resources. In this work, taking the hanging-wall mining in the open-pit mine of Hejing iron mine, for example, the disaster mechanism influenced by the coupling freeze-thaw and hanging-wall mining is systematically studied by 3D laser scanning and numerical simulation. Firstly, the rock mass structure information such as dip, dip angle, spacing, and equivalent trace length characteristics was obtained using 3D intelligent recognition technology. Then, numerical simulation is employed to reveal the influence of freeze-thaw and excavation sequences on the overall stability of the open-pit slope. The stress, displacement, plasticity zone, and maximum shear strain patterns are revealed in detail. The results show that the excavation engineering will lead to frequent increase and unloading of the internal stress of the rock mass, and the gradual increase of the goaf area will cause great damage to the rock mass. The slope failure mode is strongly impacted by freeze-thaw weathering and orebody excavation.

Behavior of geomaterial composite using sugar cane bagasse ash under compressive and flexural loading

The sugar industry produces a huge quantity of sugar cane bagasse ash in India. Dumping massive quantities of waste in a non-eco-friendly manner is a key concern for developing nations. The main focus of this study is the development of a sustainable geomaterial composite with higher strength capabilities (compressive and flexural). To develop this composite, sugarcane bagasse ash (SA), glass fiber (GF), and blast furnace slag (BF) are used. Ash generated from burning sugar cane in the sugar industry is known as sugar cane bagasse. To check the suitability of this secondary waste for use in civil engineering and to minimize risk to the environment in the development of sustainable growth, a sequence of compressive and flexural strength tests was performed on materials prepared using sugar cane bagasse ash (SA) reinforced by glass fiber (GF) in combination with blast furnace slag (BF) and cement (CEM). The effects of the mix ratios of glass fiber to bagasse ash (0.2%–1.2%), blast furnace slag to the weight of bagasse ash (10%), cement binding to bagasse ash (10%–20%), and water to sugar cane bagasse ash (55%) regarding the flexural strength, compressive strength, density, tangent modulus, stress–strain pattern, and load–deflection curve of the prepared materials were studied. According to the findings, compressive strength achieved a maximum strength of 1055.5 kPa and ranged from 120 to 1055.5 kPa, and the flexural strength achieved a maximum strength of 217 kPa and ranged from 80.1 to 217 kPa at different mix ratio percentages. The value of the initial tangent modulus for the cube specimens ranged between 96 and 636 MPa. For compression specimens with 20% cement, the density decreased from 1320.1 to 1265 kg/m3, and the flexural strength decreased from 1318 to 1259.6 kg/m3. With limitation in lower percentages of C/SA, the specimen cannot sustain its shape even after curing period. In comparing the previous research with the present experimental work, it was observed that the material proposed here is lightweight and can be utilised as a filler substance in weak compressible soils to improve their load-bearing capacity.

Dynamic mechanical behavior, microstructure evolution, and restoration mechanism of a β‐Ti alloy during hot compression deformation

AbstractMetastable β titanium alloys are promising materials for lightweight and energy‐efficient applications due to their high strength and low density. Thermal–mechanical processing (TMP) is one of the most effective ways to improve the mechanical properties of such alloys. This paper describes a systematic TMP investigation on a new metastable β titanium alloy, including its dynamic mechanical behavior, and microstructure evolution, via isothermal compression tests and electron back‐scattered diffraction characterizations. The results show that the compression stress increases with an increase in the strain rate and a decrease in the temperature. After yielding, the compression stress–strain pattern shows flow‐softening behavior at a low temperature and a high strain rate, while sustaining a steady flow state at a high temperature and a low strain rate. The temperature‐rise effect contributes to a large degree of flow softening at high strain rates. After the correction for temperature rise, the stress–strain constitutive relationships are established, showing that the compression behavior varies in different phase regions. Based on the microstructure characterizations, it is found that the dynamic recovery and dynamic recrystallization dominate the hot deformations in β phase region and at low strain rates, while the deformation band as an additional product is found in α + β phase region and at high strain rates. The results contribute to a better understanding of the TMP for the considered alloy and may also represent a useful database for β‐Ti alloy applications in lightweight mechanical systems.

An analysis of digging anchor machine stability and track wear under digging conditions

To analyse the stability of a digging anchor machine under digging conditions, the dynamics model of the anchor machine and the interaction mechanics model between its tracks and the roadway floor are constructed with a Sandvik MB670-1 digging anchor machine in the context of the Zhang Jiamao 5–2 coal seam of the Shaanxi Coal and Chemical Industry Group. The discrete element method (DEM) and multibody dynamics (MBD) two-way coupling algorithm is used to simulate the cutting process of a full coal seam and coal rock containing gangue by using a digging anchor machine in a roadway. The changes in the cutting depth of the digging anchor machine drum, the sliding distance of the track and the stress‒strain pattern of the roadway floor are obtained. Finally, through shear slip testing, the stress distribution and deformation pattern of the roadway floor under different grouser parameters of the digging anchor machine track shoe, as well as the wear characteristics of the track shoe, are obtained. The results of this study can provide a theoretical basis for the control and reliability of the digging anchor machine and the life fatigue prediction of its tracks.

Stress Distribution Pattern in Zygomatic Implants Supporting Different Superstructure Materials.

The aim of this study was to assess and compare the stress–strain pattern of zygomatic dental implants supporting different superstructures using 3D finite element analysis (FEA). A model of a tridimensional edentulous maxilla with four dental implants was designed using the computer-aided design (CAD) software. Two standard and two zygomatic implants were positioned to support the U-shaped bar superstructure. In the computer-aided engineering (CAE) software, different materials have been simulated for the superstructure: cobalt–chrome (CoCr) alloy, titanium alloy (Ti), zirconia (Zr), carbon-fiber polymers (CF) and polyetheretherketone (PEEK). An axial load of 500 N was applied in the posterior regions near the zygomatic implants. Considering the mechanical response of the bone tissue, all superstructure materials resulted in homogeneous strain and thus could reconstruct the edentulous maxilla. However, with the aim to reduce the stress in the zygomatic implants and prosthetic screws, stiffer materials, such Zr, CoCr and Ti, appeared to be a preferable option.

The effect of silica fume admixture on the compressive strength of the cellular lightweight concrete

Foam concrete has practical and economic advantages in construction, including reducing the structure's weight by building foundations. The market demand for foam concrete such as Cellular Lightweight Concrete (CLC) block has increased recently. One way to reduce the density of CLC is to add air pores to the cement paste or mortar mixture. However, the addition of pores can reduce the strength of lightweight bricks. Therefore, there is a need for innovation to improve the quality of CLC block by replacing some of the cement with other added materials. This study aims to obtain a good quality CLC block using silica fume to replace partial cement in a mortar mixture. The specimens are a CLC block measuring 10 cm wide, 20 cm high and 60 cm long. Variation of mortar mixture using silica fume percentage of 0%, 0.5%, 1%, 5%, 10% and 15% of cement weight. The output data generated from this sample are compressive strength, displacement, stress, strain and the modulus of elasticity. The test results obtained the optimum CLC compressive strength of 1.03 MPa at 10% silica fume composition. This optimum compressive strength of CLC was simulated using the LUSAS finite element analysis to obtain the displacement and stress-strain patterns. Based on the LUSAS numerical analysis, the optimum compressive strength of the CLC block was 1.06 MPa. This study shows that adding 10% silica to the CLC mortar mixture can increase the compressive strength by 81.25% compared to mortar without silica fume.

Strength and post-freeze-thaw behavior of a marl soil modified by lignosulfonate and polypropylene fiber: An environmentally friendly approach

Lignosulfonate is one of the by-products in the paper and pulp industry that is widely produced around the world and its improper disposal or storage can pose irreparable risks to human health and the environment. Sustainable reuse of this industrial waste as a stabilizing agent not only provides a novel approach in the construction industry, but also prevents the loss of natural resources. In this study, an environmentally friendly strategy involving lignosulfonate as a binder along with the polypropylene (PP) fiber as a reinforcing material was adopted to enhance the characteristics of marl soils from detrimental impacts of freeze-thaw (F-T) cycles. To this end, the pure marl specimens were improved by various contents of lignosulfonate and polypropylene fiber solely and simultaneously and cured for different time intervals. The variables assessed in this study were lignosulfonate content, polypropylene fiber content, curing period as well as the number of F-T cycles. The results showed that the greatest improvement was observed in the samples containing 1.5% lignosulfonate and 0.6% PP fibers, showing the least amplitude of fluctuations in MR reduction upon the F-T cycles. Moreover, freeze-thaw weathering transformed the stress-strain pattern of the samples from strain-softening to hardening behavior as well as increased the ductility behavior. It was observed that the simultaneous application of lignosulfonate and PP fibers led to the complete bonding of soil particles and the formation of interlocking zones around the fiber strands, leading to stronger particle bonding. The results of the Fourier transform infrared (FTIR) test also verified the formation of ionic bonds owing to the inclusion of lignosulfonate in the marl soil and the presence of lignosulfonate in the distance between the mineral layers of the soil. Overall, the reuse of lignosulfonate as a non-traditional alternative to marl soil modification can play an effective role in enhancing the durability and mechanical characteristics as well as sustainable development.

Bayesian Neural Network for Estimating Stress-Strain Behaviors of Frozen Sand

Accurately estimating the mechanical behavior of frozen soil plays a central role in frozen ground engineering. Owing to the nonlinear and uncertain nature, modeling the stress-strain behaviors of frozen soil has been challenging the physics-based models. This study proposed a data-driven approach on the Bayesian neural network (BNN) framework that can precisely estimate the stress-strain behaviors of frozen sand with minimum input requirements. First, a series of triaxial tests were conducted to explore the mechanical behaviors of frozen sand under different conditions of confining stress and temperature. The acquired data were utilized for training the BNN to learn the stress-strain patterns under various conditions. Complicated coupled effects of confining stress and temperature on the variation of stress-strain behaviors of frozen sand were identified by experiment results. The low root-mean-squared error of 0.036 and statistical analysis of the absolute error distribution demonstrated the excellent performance of the BNN in providing a pseudo-continuous stress-strain relationship of frozen. Furthermore, hypothesis cases were presented to analyze the limitations and the applicability of the proposed approach in practices. Given the simplification and flexibility, the BNN based approach is expected to be a versatile means for estimating the mechanical behavior of frozen soil.

Geomechanical modelling of fault-propagation folds: Estimating the influence of the internal friction angle and friction coefficient

The interplay between faulting and folding mechanisms has been recognised in extensional and contractional settings. Numerous investigations have documented that the analysis of structural aspects of fault-related folds is important for the exploration and exploitation of hydrocarbon resources and in seismic data interpretation. In this study, we used four series of 2-D elastic-plastic finite element models (A, B, C, and D) to investigate the influence of internal friction angle, friction coefficient, and an additional detachment on the fault slip and uplift gradients, stress-strain patterns, and structural evolution of fault-propagation folds (FPFs). We found that: 1) the stress-strain patterns are similar in different sections of a FPF; 2) the plastic strain is concentrated at the fault tip, fault surface, and forelimb of the FPF; 3) among the internal friction angle, friction coefficient, and additional detachment parameters, only additional detachment affects the stress-strain patterns at the crest and backlimb of the FPF; 4) to create a FPF, not only must the fault friction be less than the layers, but the layer friction also has to be less than a threshold; 5) increase in the internal friction angle, decrease in the friction coefficient, and generation of an additional detachment lead to the formation of tight folds whereas, decrease in the internal friction angle and increase in the friction coefficient create wide folds; and 6) the internal friction angle and friction coefficient are two key factors of the fault-related fold style.

Unconfined and Triaxial Compression Tests on Hollowed Cylindrical Sandstones to Explore the Infilling Effects on the Deformation and Mechanical Behaviors

In practical engineering, the mechanical properties of the surrounding rock often reflect the bearing capacity of the support. To investigate the relations between the surrounding rock and the support, solid specimens, hollowed cylinders, and hollowed cylinders filled with two kinds of cement mortars are tested under unconfined and conventional triaxial compressions. The effects of the infilling on the stress‐strain curves, deformation features, mechanical properties, and failure patterns are schematically investigated. The results show that under the triaxial compression condition, each infilled specimen exhibits obvious residual carrying capacity though a slight stress drop occurs after the peak stress. The cement mortar exerts a positive effect on the carrying capacity of the rock, and the infilling having a higher strength and stiffness contributes to a more pronounced enhancement of the overall strength of the specimens. Under the triaxial compression condition, merely a dominated shear fracture can be seen on the surfaces, and with relatively high confining pressure (σ3 = 20 and 30 MPa), both the rock and cement mortar were cut into two parts by the dominated shear fracture. The laboratory tests in this study provide a simple and feasible way of investigating the interaction of the support system with the surrounding rock.

A multiple fascicle muscle force model of the human triceps surae

Muscle is typically modelled using a lump sum idealization, scaling a single fascicle to represent the entire muscle. However, fascicles within a muscle have unique orientations, which could result in forces exerted not only in the axis running along the tendon, but also the two perpendicular axes, describing the muscle's width and depth. The purpose of this research was to develop a geometric-based model of the soleus, medial gastrocnemius, and lateral gastrocnemius as distributed force systems which can predict three-dimensional forces. Measurements were taken from the triceps surae in two human cadavers (80 and 85 years old). These models predicted muscle volumes and ankle plantar flexor moments that were realistic considering the age of the cadavers. Small differences were observed in calcaneal tendon force and moment for the distributed force models compared to modelling muscle force using a lump sum idealization. The major finding of the distributed force models was that forces were present in the axes corresponding to the muscle's length, width, and depth. The forces in the width and depth axes may be relevant for evaluating how muscle shape changes during contraction, as well as to investigate stress-strain patterns along the muscle's proximal and distal aponeuroses.

Improvement of Bone Filler Materials Using Granular Calcium Sulfate Dihydrate-Gelatin-Polycaprolactone Composite

Calcium sulfate dihydrate (CSD) cement has been used as bone void filler and antibiotic carrier for many years. However, the main drawback of CSD cement is its brittleness that limits its handling property. Thus, the aim of this study is to fabricate granular CSD cement-gelatin-polycaprolactone (CSD-Gel-PCL) to improve handling property. To prepare CSD-Gel-PCL composite, granular CSD was prepared from calcium sulfate hemihydrate (CaSO4.0.5H2O; CSH) and distilled water with water/powder (W/P) ratio of 0.5. The CSD cement was crushed and sieved into 300-500 μm. The obtained granular CSD was then mixed with 3 wt.%, 5 wt.% and 7 wt.% gelatin solution which previously mixed with PCL (50 wt% PCL, 50 wt% gelatin), followed by freeze drying for 48 hours. The CSD granules were able to bind together after the addition of gelatin and PCL matrix. After freeze drying, the CSD granules were not easy to remove from the composite body. Scanning electron microscopy (SEM) analysis revealed that CSD granules were surrounded by polymer matrix in all 3 different specimens in which the higher gelatin concentration, the more the matrix found between the granules. Mechanical evaluation suggested that all of the specimens showed the same stress-strain curve pattern. The CSD-Gel-PCL composite with 7 wt% gelatin has the highest strength compared with the other specimens. Stress-strain curves indicated that combination of CSD granules, gelatin and PCL has produced bone filler with improved handling property.

Modeling the mechanical response of gas hydrate reservoirs in triaxial stress space

Exploitation of gas from deep-sea methane hydrate-bearing layers might lead to some geological disasters, including marine landslides and excessive settlement of marine ground. The first offshore gas production tests for methane hydrate-bearing sediments were carried out in eastern Nankai Trough. However, knowledge on mechanical behavior of gas hydrate reservoirs with similar gradation and minerology component to the marine sediment is still insufficient. Consequently, proper modeling of geomechanical properties of methane hydrate-bearing sediments is crucial for reservoir simulation and deep ocean ground stability analysis for long-term gas production in the future. This study conducted a series of triaxial shear tests to examine the shear response of methane hydrate-bearing sediments with a similar grading curve and minerology components to the hydrate-rich sediments in Nankai Trough. The test results demonstrated that the presence of hydrate mass between sand grains altered the stress-strain pattern from strain-hardening to postpeak strain-softening. A simple constitutive model based on several empirical relationships of granular materials is proposed to describe the stress-strain relationship of methane hydrate-bearing sediments under triaxial stress condition. This model can reproduce the enhancement of shear strength, initial stiffness, and dilation behavior of methane hydrate-bearing sediments containing different amounts of fines content with a rise in the methane hydrate saturation at a wide range of effective confining pressures. The numerical results indicate that the parameter A associated with initial stiffness of stress-strain curve and the parameter α related with dilation properties are jointly governed by the confining pressure, fines content, and hydrate saturation.