Ultimate Tensile Force Research Articles

The Behavior of Post-installed Rebar Connectors in Steel Frame Retrofitted Concrete Structures Under Combined Shear and Tension

To investigate the response of post-installed rebar connectors in steel frame retrofitted concrete structures under combined shear and tension, seven shear-and-tensile tests were conducted. The bearing capacity, stiffness, and hysteresis behavior of the connectors were investigated during the tests. Both Monotonic and cyclic load regimes were applied in the loading process. The results show that with the increase of the loading angle, the deformation capacity, the yield force, ultimate tensile force, and tensile stiffness of the specimen decrease, while the maximum shear force and shear stiffness of the specimen increase. The bearing capacity, stiffness, and energy dissipation performance of the specimen under a monotonic load is greater than that under the coupled shear-and-pull load. The bearing capacity, stiffness, hysteresis curve, and failure status of the specimens are not affected by different loading regimes. At the end, the design formula of anchor bolt for this type of connectors from the design code of China, United States, and Japan were compared. Formulas to calculate the shear strength under combined shear and tension is developed.

Application of Friction Riveting technique for the assembly of electronic components on printed circuit boards (PCB)

This study focuses on the effects of reducing the diameter of rivets used in Friction Riveting due to the need for downscaling when joining assemblies on a smaller scale. The Friction Riveting process has shown promising feasibility for a variety of material combinations and applications in the transportation industry. Recent research has explored the potential application of this technique in electronics, specifically for the assembly of printed circuit boards (PCBs), using AA-2024-T351 rivets on thin glass-fiber-reinforced epoxy substrates (FR4). The joint formation of joints produced with PCBs was investigated in terms of process temperature evolution, microstructural changes, and mechanical properties. Joints were obtained at process temperatures ranging from 285 ºC to 368 ºC. The use of 4 mm rivets resulted in extensive delamination, weak joint mechanisms, and cracking, impaired by the different coefficients of thermal expansion of the materials involved. Reducing the rivet diameter to 3 mm significantly improved joint quality. A further reduction to 2.5 mm minimized delamination but led to insufficient anchorage and cracking. Joints produced with a 3 mm rivet diameter achieved the highest ultimate tensile force of 276 N. This study sets the foundation for applying the Friction Riveting process to practical PCB assemblies, demonstrating that optimizing the process parameters to the diameter-to-thickness ratio can balance sufficient rivet anchoring, minimize delamination, and reduce cracking.

Biomechanical and Histological Study of Retrieved LARS Synthetic Ligaments

Background: Synthetic grafts have been used for a number of years in anterior cruciate ligament (ACL) reconstruction surgery. One of the more recent additions to the stable of synthetic ligaments is the Ligament Augmentation and Reconstruction System (LARS) ligament. Purpose: To analyze the biomechanics and histology of LARS grafts retrieved due to failure of the device. Study Design: Descriptive laboratory study. Methods: A total of 22 LARS ligament grafts that were explanted from patients were sent for analysis. Five new, unused samples of the standard LARS ACL graft were also analyzed. Biomechanical testing was performed: ultimate tensile force, force versus displacement, and stress versus strain were recorded. Histopathological examination was performed looking for degree of fibrous tissue ingrowth as well as the presence of a foreign body reaction. Results: Of the 22 grafts retrieved, 14 were used for ACL grafts, 1 for a lateral collateral ligament graft, 2 for medial collateral ligament grafts, 4 for gluteal tendon augmentation, and 1 for a supraspinatus augmentation. A severe foreign body reaction was found in 86% of the grafts (18/22) and a mild foreign body reaction in the remaining 14% (4/22). Tissue ingrowth was minimal in the majority of ACL grafts; the other grafts showed moderate tissue ingrowth. Maximal tensile force was significantly higher for the new ACL grafts (mean ± SD, 1667 ± 845 N) compared with the retrieved grafts (897 ± 395 N; P < .05). Conclusion: This study demonstrated that the vast majority of retrieved LARS artificial ligaments had a florid foreign body reaction. There was minimal tissue ingrowth in ACL grafts and moderate ingrowth in other grafts. Retrieved grafts had a decreased ultimate tensile force, which increased their risk of rupture. Clinical Relevance: Surgeons should be cautious in choosing to use these grafts in reconstructive surgery for patients.

Uniaxial tensile behavior of half-grouted sleeve connections with concrete cover after exposure to elevated temperatures

This study presents the tensile behavior of a half-grouted sleeve connection (HGSC). A total of 15 prism samples of grout are subjected to a series of tests before and after exposure to various temperatures. A total of 75 eccentric HGSC specimens with a 40 mm concrete cover and 15 central HGSC specimens without a concrete cover were fabricated for uniaxial tensile loading tests. A pseudo-transient heating regimen was applied to HGSC specimens with concrete covers; the specimens were heated to the desired temperature and left there for a duration of 0 min. This study systematically investigates the tensile properties of post-fire HGSC specimens to assess the combined effects of peak environmental temperature (20 °C, 200 °C, 400 °C, 600 °C, 800 °C), concrete cover depth (0 mm, 40 mm), concrete strength grade (C30, C35, C40, C45, C50), and concrete spalling (burst or unburst). The failure mode, load–displacement curves, sleeve strain distribution, and heat transfer are employed to characterize the response of the HGSC specimens, which is subsequently discussed. It is discovered that, although concrete compressive strength plays a minor role, temperature, concrete cover, and explosive spalling significantly influence certain post-fire tensile parameters of the HGSC. Based on the results, there is considerable potential for determining the ultimate tensile force in HGSC specimens with concrete covers and the remaining compressive strength of grout using ultrasonic pulse velocity detection. Furthermore, a comparative accuracy analytical model, incorporating the influence of tangential strain derived from the experimental results, is established based on confinement stress.

In Vitro Characterisation of 3D Printable Filaments Subjected to Edible Liquids: An Analysis of Fused Deposition Modelling for Intraoral Applicability.

To evaluate the influence of edible liquids on the characteristic properties of 3D printable materials compared to conventionally used dental resin acrylic. Dental polymethyl methacrylate (PMMA) specimens were fabricated from preformed molds while polylactic acid (PLA) and polyethylene terephthalate glycol (PETG) specimens were 3D printed using fused deposition modelling at 0.1 mm layer thickness. All specimen forms adhered to ISO 37:2017 and ISO 604:2002 specifications. Specimens underwent controlled immersion for 180 hr into different media (no immersion (control), oil, soda, milk, and caffeine). Changes in mass (g), plastic deformity (N/mm2), ultimate tensile stress (N), flexural deformity (N/mm2), and break force (N) were evaluated using analysis of variance. There was an increase in mass for all specimens following immersion with significant interactions between immersion media and the materials. The materials exhibited significant differences in plastic deformity (F (df) = 156.632(2), P < 0.001), ultimate tensile stress (F (df) = 109.521(2), P < 0.001), and break force (F (df) = 319.785 (2), P < 0.001) with no significant interactions with immersion media (P > 0.05) on both accounts. Materials showed no significant differences in flexural deformity (F (df) = 2.693(2), P = 0.074) but with significant interactions (F (df) = 4.984(8), P < 0.001) between acrylic and immersion media. Commercially available 3D printable PLA and PETG filaments printed at 0.1 mm thickness possess approximately half the mechanical resilience as dental PMMA with comparable flexural deformity after exposure to edible liquids.

Experimental investigation and design method of the general anchorage zone in the ring beam of prestressed concrete containment vessels

Ring beam is the main anchorage zone of the tendons in the nuclear power prestressed concrete containment vessel (PCCV). Its safety is crucial and has a great influence on the overall performance of PCCV. In this paper, two half-scale ring beams were tested to investigate the mechanical performance of the anchorage zone in the PCCV under multidirectional pressure. The effect of working condition with different tension sequences was investigated. Additionally, a half axisymmetric plane model of the containment was established by the finite element simulation to further predict the experimental responses and propose the local reinforcement design in the anchorage zone of the ring beam. The results showed that the ultimate load of the specimens under both working conditions was greater than the nominal ultimate tensile force. The original reinforcement design could meet the bearing capacity requirements, but there was still room for optimization. The ring beam was generally under pressure in the anchorage area, while the splitting force appeared in the under-anchor area, and the spalling force appeared in the corner area of the tooth block, which could be targeted for local strengthening design.

Cyclic testing of six-strand suture techniques for zone 2 flexor tendon lacerations

BackgroundBiomechanical analysis using cyclic testing for repaired flexor tendons is a clinically relevant method. The aim of this study was to evaluate the tensile properties of two six-strand suture techniques, the triple looped suture and Yoshizu #1 suture techniques using cyclic testing under simulating early active mobilization conditions. MethodsTwenty-five flexor digitorum profundus tendons harvested from fresh frozen human cadaver hands were repaired in zone 2 utilizing one of three repair techniques: the 2-strand modified Kessler (MK) technique as a control, the triple looped suture (TLS) and Yoshizu #1 suture (Y1) techniques. In each suture technique, 4-0 monofilament nylon sutures were used for core sutures and 6-0 monofilament nylon sutures for circumferential running sutures. Cyclic testing was performed using 20 N with 600 cycles at 1 Hz. ResultsFive out of eight specimens in the MK group ruptured during cyclic testing. Thus, this group was excluded from analysis. On the other hand, all tendons in the TLS and Y1 groups tolerated cyclic testing. Average gaps of the TLS and Y1 groups were 0.5 ± 0.8 mm and 1.9 ± 2.2 mm, respectively. All tendons in the TLS group and six out of nine tendons in the Y1 group formed gaps less than 2 mm. Two tendons in the Y1 group formed a gap of 3.8 and 6.6 mm had breakage of peripheral sutures at the first cycle. Mean ultimate tensile force of the TLS and Y1 group measured after cyclic tensing, were 66.2 ± 9.0 N and 65.9 ± 13.1 N, respectively. No statistical difference between the two groups was found in gap and ultimate tensile forces. ConclusionsThis study suggested that the TLS and Y1 techniques have tensile properties to allow early active mobilization. None of tendons repaired with the TLS technique had gaps more than 2 mm.

An experimental study on ballistic limit: the effect of hole drilling on the mechanical properties of a polymeric composite plate produced by the resin transfer molding method

The high fracture strength and exceptional impact resistance of polymer-based composites are of paramount importance to various industries like aerospace, automotive, and construction. The resin transfer molding (RTM) process is used to produce composite samples of superior quality, minimal porosity, and reduced lamination defects. In the present study, the RTM method was employed to fabricate glass fiber-reinforced composites, aiming to investigate their specific mechanical properties and structural performance. The study initially determined the ballistic limit of the produced samples. Subsequently, experimental investigations were carried out to examine the impact of hole drilling on the tensile strength, flexural strength, and impact resistance of the samples. The results revealed that the produced polymer plate demonstrated a ballistic limit with a pressure of 11 bar and a speed of 104 m/s, leading to ball restriction in the plate. The sample without holes showed the highest fracture force, while samples with three and five holes exhibited reduced fracture forces. Additionally, bending force and impact resistance were lower in samples with multiple holes compared to the sample without holes. The impact resistance of the sample with five holes was the lowest among all configurations. The study revealed that the presence of three holes arranged in a row has a lesser impact on reducing the ultimate tensile force compared to the effect of five holes. Moreover, the bending test results indicated that sample failure occurred on the side under tension, resulting in higher bending forces than tensile forces.

T-STUB COMPONENT BEHAVIOR OF THE BEAM TO COLUMN BOLTED FLANGE CONNECTION BASED ON A NUMERICAL ANALYSIS AND EN 1993-1-8 DESIGN CODES

Nodal joints uniting separate elements of steel structures are the most important parts of the whole structure. For the tensile zone of a connection, the study of its stress-strain state up to the limit of exhaustion of its bearing capacity is of greatest interest. There exist different design approaches to obtain the ultimate capacity of a tension-zone of a steel joint, both numerical and analytical methods. In the presented paper this has been realized using a general-purpose finite element analysis package. The application of numerical methods for modelling the tensile performance of the T-component makes it possible to compensate for the lack of data on full-scale experimental studies. Despite the widespread use of finite element analysis packages, there are still no clear guidelines for creating numerical models of such connections. Numerical analysis has taken into account important effects such as the nonlinear behavior of the material and the contact interaction of its individual elements. Finite element analyses should represent the reality in an accurate way while not being too time consuming to be set up and run. That means appropriate parameters and phenomena, such as element types or loading procedure, should be compiled in a way suitable to the problem at hand, so that the discrepancy between reality and model is sufficiently small. A FE-model with wrong representation of reality can be solved correctly with FEA, but will thereby provide inaccurate results. Therefore, one needs understanding about FE parameters and their influence on time to execute the procedure effectively. When these conditions are met, the possibility to analyze larger number of T-stubs with less user modification opens up. The analytical method for the calculation of the properties of a bolted joint established by the structural Eurocodes proposes the T-stub as a component for the characterization of the tension and compression zones in moment joints. Using the component method, which is the basis for the calculation of joints according to the EN 1993-1-8 design codes, the value of the ultimate tensile force for the T-shaped component of the dimensions adopted in the work was obtained; the obtained values of the ultimate forces were further used in the numerical experiment. Keywords: end-plate connection, numerical model, T-stub component, bolt connection.

Determination of the Contact Resistance of Planar Contacts: Electrically Conductive Adhesives in Battery Cell Connections

This study presents a method to analyze the electrical resistance of planar contacts. The method can determine whether the contact resistance of the joint exhibits linear or non-linear behavior. By analyzing the current distribution over a planar contact, it can be determined whether an area-based contact resistance is justified or if other parameters define the contact resistance. Additionally, a quantitative evaluation of the factors that affect the measurement accuracy, including the positioning, the measurement equipment used, and the influence of the current injection on the sense pin was conducted. Based on these findings, the electrical contact resistance and the mechanical ultimate tensile force of a silver-filled epoxy-based adhesive are analyzed and discussed. The layer thickness and the lap joint length were varied. Overall, the investigated adhesive shows a low contact resistance and high mechanical strength of the same magnitude as that of well-established joining techniques, such as welding, press connections, and soldering. In addition to evaluating the mechanical and electrical properties, the electric conductive adhesive underwent an economic assessment. This analysis revealed that the material costs of the adhesive significantly contribute to the overall connection costs. Consequently, the effective costs in mass production are higher than those associated with laser beam welding.

Bearing capacity of footings on geosynthetic-reinforced soils under combined loading

In this study, the ultimate bearing capacity of shallow strip footings resting on a geosynthetic-reinforced soil mass subjected to inclined and eccentric combined loading is rigorously examined through the well-established method of lower bound limit analysis (LA) in conjunction with finite element (FE) and second-order cone programming (SOCP). Lower bound limit analysis formulation is modified to consider the ultimate tensile force of the geosynthetic layer in the soil mass so as to account for both pullout (sliding) and rupture (structural) modes of reinforcement failure. The effects of several parameters, including the embedment depth (u) and the ultimate tensile strength (Tu) of the geosynthetic layer along with load inclination angle (α) and load eccentricity (e), on the bearing capacity ratio (BCR) and failure envelopes of the overlying shallow foundation are examined and discussed. The results generally show a marked increase in the ultimate bearing capacity of the surface footing against combined loading with the inclusion of a single geosynthetic layer. Results also reveal that a second intermediate reinforcement might be required to bear a dual performance against both vertical concentric and combined loading scenarios so as to more effectively support the footing.

Progressive collapse assessment of Osmangazi Suspension Bridge due to sudden hanger breakage under different loading conditions

The design life of suspension bridges can expire in a shorter time than the estimated time due to many factors such as strong winds, earthquakes, heavy tonnage vehicle loads, vehicle crashes etc. Small cracks/damages that may occur due to corrosion and fatigue effects, especially in steel elements, may increase over time and cause sudden breakages. It has been seen in the past years that hangers, which are one of the slender structural elements, can break with the tearing of the plates, especially at the hanger-deck connection points. The creation of various damage/accident scenarios during the design of these structures, which are of high importance in terms of both the country's economy and life safety, will enable quick decision-making during possible events. For this purpose, scenarios for different loading condition and different number of hanger breakage situations were created for the Osmangazi Suspension Bridge with a main span of 1550 m, which was put into service in Turkey in 2016, and progressive collapse analyses were made. The analyses, which was started by removing only one hanger, taking into account the dead load and dead load + vehicle load of the bridge, continued until the bridge collapsed. After each removed hanger, the internal force and displacement values of the hangers, cables, deck and towers of the bridge were obtained and compared with each other. The results obtained show that large force and displacement values occur in the field where the hanger is breakage, but the other parts of the bridge are not affected by this event. As the number of hangers breakage increases, the tensile strength of the hanger immediately adjacent to the hanger breakage may exceed the ultimate tensile force that the hanger can bear. This situation causes the hanger to start to break automatically and the bridge to collapse.

Friction riveting of FR4 substrates for printed circuit boards: Influence of process parameters on process temperature development and joint properties

This work investigates the influence of Friction Riveting processing conditions on FR4-PCB substrate/AA2024 rivet joints in terms of process temperature evolution, joint formation, and joint physical-chemical and mechanical properties. The joints were manufactured using 4 mm diameter AA-2024-T3 rivets and FR4 laminates of 1.5 mm thickness with single or double copper-clad layers. The evolution of process temperature evolution was recorded on the FR4 substrate surface and correlated with the resulting joint formation. Most joints obtained with double copper clad layers developed process temperatures above 300 °C, whereas joints produced with a single copper clad presented slightly lower temperatures, but still above 250 °C. Rivet anchoring was achieved for both FR4 material combinations in the configuration of a single-base laminate, as well as two and even three overlapped laminates. Thermogravimetric analyses revealed that above 300 °C intensive thermal degradation occurs on FR4 materials (with 30% mass change), followed by decomposition, resulting in non-uniform heat distribution throughout the thickness. The joint ultimate tensile force was higher for double copper-clad layers and the joints achieved within more than one laminate, showing higher anchoring efficiency.

The effect of printing parameters on tensile properties of thermoplastics prepared by fused deposition modeling (FDM) based additive manufacturing technique

The additive manufacturing technique (AMT) has significantly surpassed the prototype as well as the end engineering application. One of the most widely used AMT techniques for thermoplastics is fused deposition modeling (FDM). In this study, FDM was used to evaluate the mechanical properties of a 3D-printed specimen as a function of raster orientation and layer thickness using thermoplastics such as Nylon 6 (semicrystalline) and ABS (amorphous). The samples were printed with raster orientation angles of 0, 90, +45/-45, and 0/90 degrees with a layer thickness of 0.1, 0.2, 0.3, and 0.4 mm. Modulus of elasticity, ultimate tensile strength, maximum force, and maximum elongation were investigated to determine optimal parameters. The result shows that 90 degree raster orientation and 0.1 mm later thickness gives the highest values of ultimate tensile strength. At higher layer thickness up to 0.4 mm and +45/-45 degree shows the highest ultimate tensile strength. Also, Nylon 6 shows the highest tensile toughness compared to ABS. The work focus on the effect of printing parameters on tensile behaviour of amorphous and crystalline polymers prepared by FDM, which is one of the present global precision manufacturing sector.

A combination of omega-3 and exercise reduces experimental Achilles tendinopathy induced with a type-1 collagenase in rats.

This study aimed to evaluate the effectiveness of omega-3 supplementation with exercise in acollagenase-induced Achilles tendinopathy (AT) ratmodel. Experimental groups (healthy control (HC), AT, exercise (Ex), omega-3 (W), and Ex+W) were randomly allocated. After a week of adaptation, oral omega-3 was initiated for 8 weeks (5 days/week). The exercise groups performed treadmill running for 30 min/day (5 days/week, 20 m/min, 8 weeks) following one week of adaptation (10 m/min, 15 min/day). Matrix metalloproteinase-13 (MMP-13), interleukin-1 beta (IL-1β), tumor necrosis factor-alpha (TNF-α), and total antioxidant-oxidant status (TAS) levels were determined in serum samples. Tendon samples were obtained for biomechanical, histopathological, and immunohistochemical assessments. Ultimate tensile force, yield force, stiffness values, collagen type-I alpha 1 expression, and serum TAS significantly decreased (P < 0.05) in AT vs. HC. These values and expression significantly increased in the Ex+W group vs. AT. Serum MMP-13, IL-1β, and TNF-α levels decreased in all treatment groups vs. AT. The most significant decrease was found in the Ex+W group (P < 0.01). Histopathologically, the improvement in degeneration was statistically significant in the Ex+W group (P < 0.05). Immunohistochemically, MMP-13, IL-1β, TNF-α, and nitric oxide synthase-2 expression was decreased in all treatment groups vs. AT. In conclusion, omega-3 and exercise might be recommended in AT patients.

Probabilistic risk assessment for the piping of a nuclear power plant: Uncertainty and sensitivity analysis by using SINTAP procedure

For the purpose of probabilistic fracture mechanics estimation in the field of reliability analysis of pressure vessels and piping, a probabilistic method by using SINTAP (Structural INTegrity Assessment Procedures for European Industry) is developed. Monte Carlo simulation (MCS) is applied to investigate the influence of both the uncertainties of random parameters and inspection strategies on the failure probability (FP). A sensitivity analysis with regard to the above-mentioned aspects is conducted to identify the most significant parameters and efficient countermeasures to reduce failure risk in specially-assumed cases. The results of this study point out that the thickness and the inner radius of the pipe have the strongest impact on the FP of the pipe, followed by the bending moment, weld residual stress (WRS), crack length, initial crack depth, yield strength (YS), ultimate tensile strength (UTS), flow strength, fracture toughness, inner pressure and axial force. Compared with the detection quality and the inspection start time, selecting an appropriate inspection interval is a more effective method to reduce the failure risk. All these results provide a reference for the design of piping systems and guide the selection of in-service inspection (ISI) strategies with suitable flaw-detection capabilities and inspection frequencies.

Comparison of the mechanical properties and anchoring performance of polyvinylidene fluoride and polypropylene barbed sutures for tendon repair.

Polyvinylidene fluoride (PVDF) has been considered as an alternative suture material to replace polypropylene (PP) due to its superior biocompatibility and mechanical properties, but it has never been examined for use in barbed sutures, particularly for tendon repair. This study fabricated size 2–0 PVDF and PP bidirectional barbed sutures and compared their mechanical properties and anchoring performance in patellar tendons. The mechanical properties were evaluated via tensile testing, and the anchoring performance of the barbed sutures was assessed by a tendon suture pullout test. Sixty porcine patellar tendons were harvested, transected to mimic a full‐thickness injury, and repaired using a cross‐locked cruciate suturing technique. The ultimate tensile force was 60% higher for the PVDF barbed sutures (22.4 ± 2.1 N) than for the PP barbed sutures (14.0 ± 1.7 N). The maximum pullout force was 35% higher for PVDF barbed sutures (70.8 ± 7.8 N) than for PP barbed sutures (52.4 ± 5.8 N). The force needed to form a 2‐mm gap, indicative of repair failure, was similar between the PVDF (29.2 ± 5.0 N) and PP (25.6 ± 3.1 N) barbed sutures, but both were greater than the 2‐mm‐gap forces for non‐barbed sutures of the same size. In this study, PVDF barbed sutures provided better mechanical properties and improved tissue anchoring performance compared to the barbed PP sutures for porcine patellar tendon repair, demonstrating that PVDF monofilament sutures can be barbed and used effectively for tendon repair.

Root tensile strength of terrace hedgerow plants in the karst trough valleys of SW China: Relation with root morphology and fiber content

Root tensile strength is commonly affected by root morphology and fiber content, which combinedly affect the effectiveness of terrace hedgerow on controlling soil erosion in sloping farmland. However, the relationships between these root characteristics are still elusive. This study aimed to compare the root tensile strength, root morphologies, and root fiber contents, and quantify their differences among different plant species. Complete root systems of three terrace hedgerow plant species, i.e., O. bodinieri, V. villosa, and D. lablab L. were sampled for detecting root morphologies and fiber contents at different slope positions on a representative hillslope in karst trough valley. Single root specimens were collected to measure root tensile properties for these three plant species. Results showed that most root morphological parameters were the highest in O. bodinieri, followed by D. lablab L. Three plant species presented the same dominant diameter class as < 1.0 mm, and root volumes as < 1.50 cm3. Cellulose with contents closing to 50% was the main fiber type, and increased significantly linearly with the increasing root diameter in both O. bodinieri and V. villosa. The highest tensile strength and Young's modulus were found in D. lablab L., while the best ultimate tensile force and ultimate elongation were displayed in O. bodinieri. Root diameter showed negative power relationships with tensile strength and Young's modulus, a positive power relationship with ultimate tensile force, and a positive linear relationship with ultimate elongation. Our results will deepen the understanding of the terrace hedgerow functions for controlling soil erosion worldwide.

喀斯特坡地2种地埂篱根-土复合体抗剪和抗冲性能综合评价

PDF HTML阅读 XML下载 导出引用 引用提醒 喀斯特坡地2种地埂篱根-土复合体抗剪和抗冲性能综合评价 DOI: 10.5846/stxb202010292774 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点研发计划项目（2016YFC0502303）；中央高校基本业务费专项资金项目（XDJK2018B044）；岩溶环境重庆市重点实验室开放课题项目（Cqk201803）；西南大学资源环境学院"光炯"项目（202008） Comprehensive evaluation of shear strength and anti-scourability of root-soil complex of two grass hedgerows in karst slope land Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:分析喀斯特地区不同地埂篱根系的形态和力学特性，量化其根-土复合体抗剪和抗冲性能的强弱，探寻该地区地埂篱根系固土抗蚀性能的评价因子，为喀斯特坡地水土流失治理中植被恢复措施的科学应用提供参考。选取重庆酉阳龙潭槽谷为研究区，分上、中、下坡分别布设拉巴豆和光叶苕子2种地埂篱，采用根系扫描仪和电子万能试验机测定其根系形态和力学参数，应变控制式直剪仪测定复合体抗剪强度，原状土冲刷水槽法测定复合体抗冲指数。结果表明：（1）抗剪复合体中，拉巴豆平均根长密度和根表面积密度分别高出光叶苕子59.32%和16.86%；抗冲复合体中，拉巴豆平均根长密度、根表面积密度和根体积密度较之光叶苕子高出30.48%、57.78%、92.98%；拉巴豆根系极限抗拉力和抗拉强度均显著高于光叶苕子。（2）2种地埂篱根系均能增强土壤的抗剪和抗冲性能，其中拉巴豆和光叶苕子复合体粘聚力较之对照土体分别增强了113.06%-124.37%和51.56%-87.12%，抗冲指数最高达到对照土体的2.81倍和2.45倍。（3）不同坡位，下坡2种植物的根长密度显著高于上、中坡；拉巴豆根系抗拉特性在下坡表现最优，光叶苕子在上坡表现更好；拉巴豆复合体粘聚力和抗冲指数均表现为下坡 > 中坡 > 上坡。（4）主成分分析显示，2种地埂篱下坡的根-土复合体抗剪和抗冲性能综合评分最高，根表面积密度、根系抗拉强度、根系木质素含量对根-土复合体抗剪和抗冲性能的贡献度最高，可作为表征复合体抗剪和抗冲性能的重要参数。 Abstract:Grass hedgerows are beneficial for preventing soil erosion on karst slopes, and their roots play a vital role. This paper aimed to analyze the morphological and mechanical properties of the root system of different hedgerows, to quantify the shear strength and anti-scourability of the root-soil complex, to explore the evaluation factors of the soil erosion resistance of the hedgerows in karst area and to provide reference for the scientific application of plant restoration measures in soil erosion control on karst slopes. Dolichos lablab L. and Vicia villosa hedgerows were planted on the upper, middle and down slopes of karst bedding slope in Youyang, Chongqing. The physical properties, root morphology and fiber content, tensile properties, shear strength index and anti-scouring index of the root-soil complex were measured. (1) The mean root length density and root surface area density of Dolichos lablab L. were 59.32% and 16.86% higher than those of Vicia villosa in the shear complex. The mean root length density, root surface area density and root volume density of Dolichos lablab L. were 30.48%, 57.78% and 92.98% higher than those of Vicia villosa in the souring complex. The ultimate tensile force and tensile strength of Dolichos lablab L. root were significantly higher than those of the Vicia villosa. (2) The roots of the two kinds of grass hedgerows could enhance the shear strength and anti-scourability of soil. Compared with the control check, the cohesion of Dolichos lablab L. and Vicia villosa complex was 113.06%-124.37% and 51.56%-87.12%, respectively, and the anti-scouring index was 2.81 and 2.45 times higher than the control check. (3) In different slope positions, the root length density was significantly higher in the lower slope than in the upper and middle slope. The tensile strength of Dolichos lablab L. root was the best in the downslope and the Vicia villosa was the best in the upslope. The cohesion and anti-scouring index of Dolichos lablab L. complex were both downslope > middle slope > upslope. (4) The principal component analysis showed that the comprehensive scores of the shear strength and anti-scourability of the root-soil complex of the two kinds of grass hedgerows were the highest in the down slope. Root surface area density, root tensile strength and root lignin content had the highest contribution to the shear strength and anti-scourability performance of the root-soil complex, which could be used as important parameters to characterize the shear strength and anti-scourability of the root-soil complex. When grass hedgerow measures are implemented in karst areas, planting on the low slope should be carried out in order to give full play to the soil and water conservation effect. 参考文献 相似文献 引证文献

Evaluation of cytokines in protective effect of docosahexaenoic acid in experimental achilles tendinopathy rat model induced with type-1 collagenase

ABSTRACT Background We aimed to investigate the effectiveness of docosahexaenoic acid (DHA) as a treatment for Achilles tendinopathy (AT) induced with type-I collagenase in rats and compare it with collagen. Methods The AT model was induced with type I collagenase, and animals were randomly assigned to groups. Group 1:AT, Group 2: Collagen (7.2 mg/kg/day), Group 3:DHA (300 mg/kg/day), and Group 4:DHA (100 mg/kg/day). Right tendons of Group1 were used as a healthy control (HC). Oral treatments were applied for eight weeks. Serum tumor necrosis factor-alpha(TNF-α), matrix metalloproteinase-13 (MMP-13), and interleukin-1 beta(IL-1β) concentrations were determined by ELISA. Tendon samples were taken for histopathological evaluation and examined immunohistochemically with antibodies specific for Col1A1, TNF-α, MMP-13, IL-1β, and nitric oxide synthase-2(NOS-2). The ultimate tensile force (UTF) yield force(YF) and stiffness were measured by biomechanical assessments. Results UTF,YF and stiffness values were increased in all treatment groups compared to the AT control, a significant increase was found in Group 2 (p < 0.05). There was severe degeneration of tendon cells in the AT control. The tendon cells in samples from Groups 2-3 were less degraded, and this was statistically significant (p < 0.05). TNF-α, MMP-13, IL-1β, and NOS-2 expressions were significantly higher in the AT control compared to the HC. In all treatment groups, their concentrations were lower than in the AT control. Serum TNF-α, MMP-13, and IL-1β levels were lower in all treatment groups (Especially in Group3 (p < 0.001)) compared to Group1. Conclusion The efficacy of high-dose DHA as a treatment for AT was investigated from biochemical, histopathological, and biomechanical perspectives. The results showed that DHA could be an alternative treatment compound to collagen.