Peak Compressive Stress Research Articles

Experimental study on axial compressive properties of bamboo scrimber after high temperature

This study examines the uniaxial compressive mechanical properties of after high temperature bamboo scrimber, taking into account the combined effects of temperature, constant temperature duration, and moisture content. A series of 46 uniaxial compression tests were conducted on bamboo scrimber under various conditions to investigate the failure modes after high temperatures. The analysis focuses on the changes in compressive elastic modulus and peak stress of bamboo scrimber parallel and perpendicular to the grain, in relation to temperature, constant temperature duration, and moisture content. The findings reveal that below 180℃, diagonal shear failure and Y-type shear failure are the primary failure modes for specimens parallel to the grain, while diagonal shear failure predominates for specimens perpendicular to the grain. Above 180℃, bond failure and eccentric crushing become the main failure modes for specimens parallel and perpendicular to the grain, respectively. The peak compressive stress decreases significantly beyond 180℃, with a slower decrease observed as moisture content increases. Constant temperature duration has a notable impact on peak stress, with longer durations resulting in lower peak stress at the same temperature. Although temperature has a lesser effect on the elastic modulus compared to peak stress, empirical formulas were derived to establish the relationship between compressive elastic modulus and peak stress reduction coefficient with variations in temperature, constant temperature duration, and moisture content based on the experimental data.

Large Rupture Strain Cotton Ropes Hybridized with Affordable Fiberglass Chopped Strand Mat Sheets for Enhanced Compressive Behavior of Reinforced Concrete Columns

The hybrid confinement system combines various fiber types within a single matrix, allowing for the adjustment of volumetric ratios to optimize confinement performance. Synthetic FRPs are more expensive and have a higher carbon footprint due to significant CO2 emissions during production. In response, this study presents an innovative hybrid confinement approach using two natural materials: cotton ropes and FSMS (CFS) to improve concrete strength and ductility. Specimens, standardized at 300 mm height and 150 mm diameter with longitudinal steel bars and stirrups, were divided into two groups based on CFS configurations. The stress-strain response of CFS-confined concrete displayed distinctive behavior: an initial parabolic phase leading to peak compressive stress (ultimate strength), followed by a linearly degrading phase. Across all subgroups, CFS confinement significantly enhanced ultimate strength and corresponding compressive strains, with Subgroup 2A achieving the highest improvements of 246% in ultimate strength and 1477% in strain. Moreover, the ductility gain was reported as high as 20 for CFS-confined concrete. A non-proportional enhancement in the compressive behavior was observed with the increase in confinement ratio. Predictive models were developed for the idealized two-branch response of CFS-confined concrete, encompassing expressions based on nonlinear regression for ultimate strength, corresponding strain, ultimate strain, and elastic modulus. Two existing models were modified to trach each branch of the response. Integrating these two adjusted models closely replicated the experimental compressive curves.

Mechanical Properties of Ultra-High-Performance Concrete with Amorphous Alloy Fiber: Surface Modification by Silane Coupling Agent KH-550.

Amorphous alloy fiber has the advantages of high tensile strength and high corrosion resistance compared with steel fiber, but its interfacial bonding with cement matrix is poor and requires surface modification treatment. In this study, the surface modification of amorphous alloy fiber was carried out by using silane coupling agent KH-550 solution, and its effect on the mechanical properties of ultra-high-performance concrete was investigated. The results showed that the amorphous alloy fibers modified with 15% concentration silane coupling agent KH-550 solution can effectively improve the mechanical properties of the ultra-high-performance concrete, where the interfacial bond strength with the cement matrix reached 3.29 MPa and the roughness reached 3.85. The compressive strength, flexural strength, tensile strength, and peak stress of the ultra-high-performance concrete mixed with modified amorphous alloy fibers could reach up to 133.6 MPa, 25.5 MPa, 8.32 MPa, and 114.26 MPa, respectively, which were 2.9%, 6.3%, 10.9%, and 4.3% higher than those of the ultra-high-performance concrete with unmodified amorphous alloy fibers. As the surface of the fiber was modified, its properties changed and the bonding effect with the cement matrix was better, which in turn improved the mechanical properties of the ultra-high-performance concrete.

Non-contact ultrasonic vibration-assisted laser metal deposition manufacturing Fe-based powder: Numerical simulation and experimental investigation

Fe-based powder was manufactured on 42CrMoA steel substrate using non-contact ultrasonic vibration-assisted(UVA) laser metal deposition(LMD) process with different exciting distances(d), and the temperature field and stress field distribution, microstructure and mechanical properties of the deposited layers were investigated. The results show that the distribution of temperature field was more uniform, especially at the bottom of the molten pool, and the gradient of temperature field decreased. Compared with the condition without UVA, the residual stress peak value of the tensile stress area decreased significantly after UVA applied. When d=80 mm, the peak tensile stress and compressive stress were 90.5 MPa and 72.6 MPa, respectively, which were reduced by 45.6 % and 25.2 % compared with the condition without UVA. The length of the columnar crystals and the region of the columnar crystals decreased at the interface after UVA applied. The application of UVA can significantly improved the microhardness of deposition layer. With the reduction of the residual stress at the interface and the improvement of uniformity, the tensile properties of the deposit were also significantly improved. The highest tensile strength was 1281.3 MPa when d=80 mm, which was 30.12 % higher than that without UVA.

Multiple-stage dynamic responses and failure behaviors of surrounding rocks subjected to development blasting: Exponential and triangular paths

During the development blasting of circular tunnels, the detonation of multiple blastholes arranged on concentric circles induces a complex dynamic response in the surrounding rocks. This process involves multiple blast loadings, static stress unloadings, and stress redistributions. In this study, the dynamic stresses of the surrounding rocks during development blasting, considering multiple blasting-unloading stages with exponential paths and triangular paths (linear simplified paths of exponential paths), are solved based on the dynamic theory and the Fourier transform method. Then, a corresponding discrete element model is established using particle flow code (PFC). The multiple-stage dynamic stress and fracture distribution under different in situ stress levels and lateral coefficients are investigated. Theoretical results indicate that the peak compressive stresses in the surrounding rocks induced by both triangular and exponential paths are equal, while the triangular path generates greater additional dynamic tensile stresses, particularly in the circumferential direction, compared to the exponential path. Numerical results show that the exponential path causes less dynamic circumferential tensile damage and forms fewer radial fractures than the triangular path in the first few blast stages; conversely, it exacerbates the damage and instability in the final blast unloading stage and forms more circumferential fractures. Furthermore, the in situ stress determines which of the two opposite effects is dominant. Therefore, when using overly simplified triangular paths to evaluate the stability of surrounding rocks, potential overestimation or underestimation caused by different failure mechanisms should be considered. Specifically, under high horizontal and vertical stresses, the static stress redistribution with layer-by-layer blasting suppresses dynamic circumferential tensile and radial compressive damage. The damage evolution of surrounding rocks in multi-stage blasting under different in situ stresses is summarized and classified according to the damage mechanism and characteristics, which can guide blasting and support design.

Chondrogenic potential of superficial versus cartilage layer cells of the temporomandibular joint condyle in photopolymerizable gelatin-based hydrogels.

The objectives of this study were to compare the chondrogenic potential of cells derived from different layers of Mandibular condyle cartilage and to gain further understanding of the impact of chondrogenic cues when embedded into a novel hydrogel scaffold (PGH, a polymer blend of poly (ethylene glycol), gelatin, and heparin) compared to a gelatin hydrogel scaffold (GEL). Cartilage layer cells (CLCs) and fibroblastic superficial layer cells (SLCs) were harvested from the mandibular condyle of boer goats obtained from a local abattoir. After expansion, cells were seeded into PGH and GEL hydrogels and cultured in chondrogenic media for 3 weeks. Scaffolds were harvested at 0, 1, and 3 week(s) and processed for gross appearance, histochemical, biochemical, and mechanical assays. In terms of chondrogenesis, major differences were observed between scaffold materials, but not cell types. Glycosaminoglycan (GAG) staining showed GEL scaffolds deposited GAG during the 3 week period, which was also confirmed with the biochemical testing. Moreover, GEL scaffolds had significantly higher compressive modulus and peak stress than PGH scaffolds at all time points with the largest difference seen in week 3. It can be concluded that GEL outperformed PGH in chondrogenesis. It can also be concluded that materials play a more important role in the process of chondrogenesis than the tested cell populations. Fibroblastic SLCs were shown to have similar chondrogenic potential as CLCs cells, suggesting a rich pool of progenitor cells in the superficial fibroblastic layer capable of undergoing chondrogenesis given appropriate physical and chemical cues.

Primary Creep Characterization in Porcine Lumbar Spine Subject to Repeated Loading.

Low back pain (LBP) is a common medical condition worldwide, though the etiology of injuries causing most LBP is unknown. Flexion and repeated compression increase lumbar injury risk, yet the complex viscoelastic behavior of the lumbar spine has not been characterized under this loading scheme. Characterizing the non-injurious primary creep behavior in the lumbar spine is necessary for understanding the biomechanical response preceding injury. Fifteen porcine lumbar spinal units were loaded in repeated flexion-compression with peak compressive stresses ranging from 1.41 to 4.68MPa. Applied loading simulated real loading exposures experienced by high-speed watercraft occupants. The strain response in the primary creep region was modeled for all tests using a generalized Kelvin-Voigt model. A quasilinear viscoelastic (QLV) approach was used to separate time-dependent (creep) and stress-dependent (elastic) responses. Optimizations between the models and experimental data determined creep time constants, creep coefficients, and elastic constants associated with this tissue under repeated flexion-compression loading. Average R2 for all fifteen models was 0.997. Creep time constants optimized across all fifteen models were 24s and 580s and contributed to 20 ± 3% and 30 ± 3% of the overall strain response, respectively. The non-transient behavior contributed to 50 ± 0% of the overall response. Elastic behavior for this porcine population had an average standard deviation of 24.5% strain across the applied stress range. The presented primary creep characterization provides the response precursor to injurious behavior in the lumbar spine. Results from this study can further inform lumbar injury prediction and kinematic models.

Strain-rate effect on mechanical properties of rock-like specimens with narrow crack under uniaxial compression

Uniaxial compression tests were carried out on rock-like specimens containing prefabricated narrow crack under various strain rates. Experimental observations and numerical results show that narrow crack will close or partially close or expand under low compressive stress. Due to the unidirectional loading of loading device, the deformation degree of crack tip near the loading end was different with that of crack tip near the bearing end. With the increase of strain rate, the cracking modes can be divided into 3 categories, near vertical splitting failure affected by horizontal crack (α = 0°), anti-N-wing crack (15°≤α ≤ 60°) and wing crack (60°<α ≤ 90°). Both of the initiation angle θ1 of crack tip near the loading end and θ2 of crack tip near the bearing end decreased with the increase of α and strain rate. Specially, when α = 90°, both θ1 and θ2 rose with the increase of strain rate. Moreover, the value of θ2 was greater than that of θ1 under the same α value because of the different deformation characteristics at two tips. Besides, the mechanical properties of fissured rock including peak compressive stress, residual compressive stress, strain at peak stress, elastic modulus and post-peak softening modulus were significantly influenced by the strain rate and inclination angles.

Ultrasonic Non-Destructive Detection Method for Residual Stress in Rotary Forging Aluminum Alloy Plates.

Aluminum alloy plates are widely used to manufacture large-scale integral structure parts in the field of aerospace. During the forming and processing of aluminum alloy plates, different degrees of residual stress are inevitably produced. Fast and accurate detection of residual stress is very essential to ensuring the quality of these plates. In this work, the longitudinal critically refracted (LCR) wave detection method based on a one-transmitter and double-receiver (OTDR) transducer and the finite element simulation were employed to obtain the residual stress. Aluminum alloy plates with different deformation amounts were fabricated by rotary forging to obtain different residual stress states. Results reveal that the plate formed by rotary forging is in a stress state of central tension and edge compression. As the deformation increases from 20% to 60%, the peak residual tensile stress increases from 156 MPa to 262 MPa, and there is no significant difference in the peak compressive stress. When the deformation reaches 60%, the difference in the residual stresses at different depths is less than 13%, which indicates that the plastic deformation zone basically penetrates the entire longitudinal cross-section of the plate. The maximum deviation between measurement and FE is 61 MPa, which means the experimental data are in good agreement with the FE results.

Experimental study on the mechanical properties and uniaxial compressive constitutive relationship of sea sand coral concrete

The use of seawater, sea sand and coral to formulate concrete for marine engineering construction is an effective measure for rationally allocating resources and alleviating resource shortages. To promote the engineering application of marine concrete, it is necessary to study the mechanical properties and microstructure of marine concrete. In this study, sea sand coral concrete (SSCC) with strength grades of C20–C40 was prepared, and the compressive and flexural tests were conducted to observe the stress process and damage morphology of the specimens and to establish a constitutive model for SSCC under uniaxial compression. In addition, the microstructures of the SSCC hydration products and interfacial transition zone (ITZ) were observed via X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that the damage surface of the SSCC occurred directly through the coral aggregate, and the damage process was sudden and brief. Under uniaxial compression, the trend of the rising section of the stress-strain curve of SSCC with different strength grades are basically the same, but the shape of the descending section vary greatly, and the higher the strength grade is, the steeper the slope of the descending section. Quantitative relationships between compressive strength, elastic modulus, peak strain and peak stress and cube compressive strength were established. Based on the experimental results, a two-stage uniaxial compression constitutive model for SSCC was proposed, and the established constitutive model can effectively predict the stress-strain behavior of SSCC. In addition, the XRD patterns show that the early hydration rate of SSCC is faster than that of ordinary concrete (OC), which leads to a faster early strength development of SSCC. The SEM images show that the coral aggregate binds better to the cement matrix than the crushed gravel aggregate does and that the microstructure of the SSCC is denser than that of OC.

Multi-scale damage mechanism of hierarchically structured high-strength martensitic steels under shock loading

The multi-scale damage behaviors and underlying mechanisms of hierarchically structured high-strength martensitic steels are investigated via plate-impact recovery experiments, postmortem characterizations. Plate-impact experiments were conducted at compressive peak stresses ranging from approximately 5.5 to 11.0 GPa, and the tensile strain rates are ∼105 s −1. Significant improvement in the spall strength of the heat-treated martensitic steel is achieved (5.4 GPa), about 80% higher compared to the as-received bainite steel. The spall failure of the investigated martensitic steel exhibited a mixed-mode combination of brittle (micro-cracks) and ductile (voids) characteristics, known as quasi-cleavage spallation. As the impact velocity increased, voids nucleated successively at different types of boundaries as follows: boundaries between enriched and depleted zones, prior austenite grain boundaries, packet boundaries, block boundaries and lath boundaries. Shear cracking was found to be an important mechanism to accommodate the severe plastic deformation during spallation, giving the strict geometric constraints due to void nucleation tending to occur at grain boundaries. Additionally, molecular dynamics simulations considering realistic hierarchical structure of martensitic steel have been developed to validate the experimental results. These findings and simulation methods contribute a better understanding of the spall behavior of martensitic steels, as well as guidance for future design of high-strength martensitic steels with exceptional reliability and safety under extreme conditions.

Mechanical damage mechanism investigation on CFRP strengthened recycled red brick concrete

Abstract Three reinforcement ratios (0, 50, and 100%) of carbon fiber reinforced plastics (CFRP) were selected to improve the mechanical properties of recycled brick concrete in this study. Utilizing axial compression test, X-ray diffractometer analysis, the evolution of parameters such as compressive strength, peak stress, and elastic modulus of reclaimed concrete were analyzed. The reclaimed brick concrete’ stress distribution and damage mechanism were revealed. The aggregate internal failure and CFRP reinforcement effect mechanism are discussed. The finite element model of red brick concrete reinforced by CFRP under uniaxial compression is established. The constitutive model for CFRP-reinforced recycled brick concrete is proposed.

Experimental investigation of the compressive and shear behaviours of grouted and hollow masonry constructed with PVA fibre-reinforced mortar and grout

Polyvinyl alcohol (PVA) fibres are ultra-high-performance fibres that can be used to reinforce cementitious composites. This study experimentally investigated the compression and shear behaviours of grouted and hollow masonry constructed with fibre-reinforced mortar (FRM) used for the joints and/or PVA fibre-reinforced grout (FRG). In this regard, the effect of increasing the fibre content of 6 mm PVA fibres in the FRM on the behaviour of masonry was investigated. Moreover, the effect of changing the fibre length (8 mm and 13 mm PVA fibres) and the fibre content of 13 mm PVA fibres in the FRG on the behaviour of masonry was investigated. This was accomplished by constructing and testing 31 masonry prisms and 29 masonry assemblages. The behaviour of PVA-reinforced masonry was evaluated based on compressive strength, shear strength, modulus of elasticity, modulus of rigidity, compressive strain at peak compressive stress, shear strain at peak shear stress, compression ductility index and compression toughness. In addition, the compression and shear stress-strain curves, failure modes and crack propagation of PVA-reinforced masonry were compared with unreinforced masonry. It was concluded that using PVA fibres in the grout minimized the masonry face shell spalling, and most of the post-peak deterioration appeared in the form of masonry cracks and less face shell spalling compared with unreinforced masonry. In addition, using PVA-FRM only or PVA-FRM with PVA-FRG could increase the compressive strength of grouted masonry. In contrast, using PVA-FRM did not change the compressive strength of hollow masonry. Furthermore, all grouted assemblages with PVA-FRM and PVA-FRG (except for assemblages with 13 mm PVA-FRG with a fibre content of 0.10% by weight of grout) have similar average shear strength compared with unreinforced assemblages. Finally, As the fibre content of 6 mm PVA fibres in the FRM of hollow assemblages increased, the shear strength and the modulus of rigidity decreased. This study highlights the improvements and drawbacks of using PVA Fibres in mortar and grout on the compressive and shear performances of hollow and grouted masonry.

Experimental study on mechanical properties of sprayed ECC under quasi-static and cyclic loading

The tunnel lining will be subjected to the cyclic action of high ground stress during service. However, there is a lack of research on the damage evolution mechanism of sprayed engineered cementitious composites (ECC) under cyclic loading. Herein, we studied the strain rate effect and fatigue damage evolution mechanism of sprayed ECC by conducting compression and bending tests at different quasi-static strain rates and high-stress cyclic loading-unloading compression and bending tests. The results show that with the increase of strain rate, the compressive peak stress and bending strength of sprayed ECC show an upward trend, as well as the increase of the change rate. At 8.3 × 10−3 s−1, the compressive SGF is 1.52, with an energy storage limit density of 0.501MJ/m3. At 2.1 × 10−2 s−1, the bending SGF is 1.52, with a peak fracture energy of 49.29 J. In addition, under the compression test, the tensile shear failure of specimens develops from finer double shear planes to coarser multiple shear planes. Under the bending test, the position of the main crack of specimen is gradually transferred from the mid-span to both sides. Under high stress cycle test, the input energy and dissipation energy of the two tests have the similar trend, showing “U” type. The variation of elastic energy and dissipation energy conversion rate exhibits a “U” type with different directions. At the last loading, the dissipation energy conversion rate of compression test is 46.8%, while that of bending test is 70.4%. The damage variable of specimen increases significantly with the increase of the number of cycles, accompanied by an increase in the degree of breakage. In addition, the damage variables based on deformation characteristics are higher than those based on energy characteristics.

Effect of residual volume after surgery of the discoid lateral meniscus on tibiofemoral joint biomechanics: a finite element analysis

BackgroundThe purpose of this study was to investigate the influence of different residual meniscus volume on the biomechanics of tibiofemoral joint after discoid lateral meniscus (DLM) surgery by finite element analysis.MethodsA knee joint model was established based on CT and MRI imaging data. The DLM model was divided into five regions according to conventional meniscectomy, with volumes of 15%, 15%, 15%, 15%, 15%, and 40% for each region. Additionally, the DLM model was divided into anterior and posterior parts to obtain ten regions. The DLM was resected according to the design scheme, and together with the intact discoid meniscus, a total of 15 models were obtained. Finite element analysis was conducted to assess shear and pressure trends on the knee joint.ResultsThe study observed significant changes in peak shear stress and compressive stress in the lateral meniscus and lateral femur cartilage. As the meniscus volume decreased, there was an increase in these stresses. Specifically, when the meniscus volume reduced to 40%, there was a sharp increase in shear stress (302%) and compressive stress (152%) on the meniscus, as well as shear stress (195%) and compressive stress (157%) on the lateral femur cartilage. Furthermore, the model grouping results showed that preserving a higher frontal volume in the meniscus model provided better biomechanical advantages.ConclusionThe use of finite element analysis has demonstrated that preserving more than 55% of the meniscus volume is necessary to prevent a significant increase in joint stress, which can potentially lead to joint degeneration. Additionally, it is crucial to preserve the front volume of the DLM in order to achieve improved knee biomechanical outcomes.

Microcracking treatment mechanism of semi-rigid base asphalt pavement with discrete-continuous coupling simulation

The microcracking treatment employs the falling weight to break the semi-rigid base into interlocking blocks to prevent reflective cracks in asphalt pavement. To study the microcracking treatment mechanism, the semi-rigid base microcracking simulation was performed through a discrete-continuous coupling model. After that, the coupling model was verified through a test road in Shaanxi Province, China, and the impact of convex points properties was studied. The results showed that the coupling model exhibited a peak compressive stress calculation error of less than 10% and effectively simulated the semi-rigid base cracking. Besides, the properties of convex points significantly impacted cracking. An appropriate area of convex points could effectively reduce upper layer cracks while inducing a greater number of cracks in the lower layer of the base. The three-convex falling weight produced significant cracks, and the semi-rigid base was microcracked into interlocking blocks. With convex points inner tangent circle radius increasing and length ratio decreasing, the number of upper layer cracks in the base grew while the number of lower layer cracks decreased. However, an increased length ratio could improve the horizontal extension capability of cracks. These findings contribute to improving the microcracking effect in engineering. After trail impact, if there is no apparent cracking on the semi-rigid base surface, it is recommended to use a three-convex point falling weight, slightly reduce the convex points area, and increase the inner tangent circle radius and length ratio. In the case of severe cracking, it is recommended to increase the number of convex points and their area, decrease the inner tangent circle radius and length ratio, or use a flat-bottomed falling weight.

Exploring the impact of heat treatment on the microstructural and compressive properties of Al-SiC-MWCNTs hybrid nanocomposites foams

The current study focused on the investigation of the microstructural and compressive properties of Al-SiC-MWCNT hybrid composite foams after the implementation of heat treatment. The samples were prepared with varying weight percentages of SiC and MWCNTs, with fixed porosity 86 % (relative density = 0.14). Initially, samples were subjected to solutionizing at 480 °C for 10h, followed by rapid water quenching. Subsequently, artificial aging was conducted by applying three different temperatures (150 °C, 180 °C, and 220 °C) for varying durations, ranging from 2 to 10h. The results revealed that significant improvement in mechanical properties and maximum peak compressive stress and microhardness were achieved between 6 and 8h and 8 and 10h, at the aging temperatures of 220 °C and 180 °C respectively. However, in the case of aging at 150 °C, mechanical properties also increased but at a slow rate, but no clear peak values were observed even after 10h of aging. It was observed that in case of HCF (both MWCNTs and SiC added as reinforcement) the plateau stress increased up to 30 to 40 %, whereas in case of AF, CF1, and CF2 foams the properties improved by 20 to 30 %. Also, by utilizing the established Gibson model, the plateau stresses were predicted and validated with experimental results.

Experimental study on mechanical behaviors of polyoxymethylene woven tube-reinforced cementitious composites

This paper aimed to investigate the mechanical performances of woven tube-reinforced cementitious composites. Polyoxymethylene fibers were used to form woven tubes. The integrated woven tube and splicing woven tube-reinforced cementitious composites were prepared with different textile structures. The compressive and bending properties of woven tube-reinforced cementitious composites were experimentally characterized through compression and bending tests, and the testing processes were recorded by camera. The results showed that both the integrated woven tube and the splicing woven tube could apparently enhance the compressive and bending properties. The compressive and bending strengths of the integrated woven tube-reinforced cementitious composite could reach 44 and 21 MPa, respectively. Due to low splicing strength, the splicing woven tube-reinforced cementitious composite was likely to split, which led to the disassembly. The integrated woven tube-reinforced cementitious composite had higher compressive and bending strengths than the splicing woven tube-reinforced cementitious composite. Moreover, the integrated woven tube-reinforced cementitious composite exhibited better energy absorption ability and integrity after testing than the splicing woven tube-reinforced cementitious composite. The energy absorption of the integrated woven tube-reinforced cementitious composite could reach over 7 MJ/m3 during compression. Under compression, the splicing woven tube-reinforced cementitious composite and pure cement only had one compressive peak stress, which was caused by the damage to the cement, whereas the integrated woven tube-reinforced cementitious composite had two compressive peak stresses: the second compressive peak stress was caused by fiber breakage. In general, the integrated woven tube is more suitable for reinforcing cement than the splicing woven tube.

Engineering the perfect mattress: The influence of substrate mechanics on deep tissue stresses in supine

BackgroundWith increasing global interest in sleep hygiene, sleep ergonomics is an area that has been largely understudied. During sleep individuals turn over during the night to restore blood flow in occluded blood vessels, indicating that control of local tissue pressure may play a role in improving sleep comfort. This study investigates the influence of mattress stiffness on tissue compressive stresses during supine lying. MethodsA subject-specific 3D finite element (FE) model of the pelvis area has been developed to simulate supine lying on substrates of varying firmness. Constitutive parameters for the adipose-skin tissue and muscle-organ tissue were calibrated using a novel application of the inverse finite element method. FindingsThe compressive stress was consistently greatest in the muscle interfacing the sacrum at 18.5 kPa on the soft foam, and 30.9 kPa on the firm foam. From soft to firm, the compressive stress increased by 67% at the sacrum, 20% at the ischium, 42% at the lesser trochanter, and 50% at the skin. InterpretationThe non-linearity of the foam substrate had a pressure distributing effect, relieving the peak compressive stresses at the sacrum, indicating that it may be possible to design arrays of foam substrates that can provide most efficient pressure relief.

Experimental study of shape memory alloy plates under cyclic tension–compression loading scenarios

Shape memory alloys (SMAs) have garnered significant attention for their potential in earthquake-resistant structures, primarily due to their superelastic effect and exceptional self-centring capabilities. However, the mechanical properties of SMA plates, especially under cyclic tension–compression loading, remain underexplored. This research aims to bridge this gap by designing and testing 33 SMA plates equipped with buckling-restrained devices. The study varied parameters such as specimen thickness (4 mm, 6 mm, and 8 mm), loading protocols (seven in total), and test temperatures (25 °C and 0 °C). The findings reveal that the stress–strain curves under cyclic tension–compression loading exhibited asymmetric characteristics. For instance, at 25℃, a 4 mm thick specimen at 4% strain had a compressive peak stress that was 22.2% higher than its tensile counterpart, and its compressive residual strain exceeded the tensile residual strain by 99.0%. Furthermore, when compared to SMA plates under cyclic tension-release loading, those under cyclic tension–compression loading had reduced tensile residual strains. At 0 °C, the peak stress saw a decrease ranging from 2.4 to 43.1%, while the residual strain surged by 11.9–591.4% compared to the tests at 25℃. This study provides novel insights into the behavior of SMA plates under varied conditions, emphasizing their potential for seismic applications.