High Tensile Forces Research Articles

Interfacial Morphology and Mechanical Properties of Aluminium to Copper Sheet Joints by Electromagnetic Pulse Welding

This study investigated joining of Al to Cu sheets by electromagnetic pulse welding, which is a solid-state welding process that uses electromagnetic forces to join materials. The interfacial morphology and mechanical properties of the Al/Cu joints were analysed and related to the welding process parameters and weld properties. The centre section of the Al/Cu joints evolved from a non-welded to a welded zone. The welded zone started with a wavy interface, consisting of thick interfacial layers with defects and evolved to a relatively flat interface without an interfacial layer. The interfacial layer thickness is determined by both the discharge energy and the stand-off distance. A higher tensile force, up to 4.9 kN, was achieved at a higher energy and a lower stand-off distance of 2 mm. The tensile force is directly related to the weld width, since a higher tensile force is achieved for a higher weld width. In addition, the presence of interfacial layers can contribute to a small extent to a higher tensile force.

Tensile Strength of Embedded Anchor Groups: Tests and Strength Models

Steel column bases in seismically braced frames and other similar structures must be designed for high uplift or tensile forces. A common detail for this connection involves anchors embedded in the footing with a plate at their lower end, also embedded in the footing. This detail is increasingly prevalent in construction practice because it is exempt from the strength calculations of ACI 318 Appendix D. However, no experimental data or validated design guidelines are available to support the design of this detail. As a consequence, approaches from other similar situations (such as punching shear of slabs) are adapted for this purpose. To address this practical need, this paper presents tension tests on two full-scale specimens featuring this anchorage detail. The main variable examined in the experiments is the embedment depth, such that two depths (12 and 18 in.) are tested. The test specimens exhibit a classic concrete failure cone extending upward from the edges of the embedded base plate. The experimental data provide evidence that the anchorage detail provides an effective means to carry high-tensile loads. The data are evaluated against three strength models, including the ACI 318 Appendix D method, the ACI 318 punching shear equation and the concrete capacity design (CCD) method. It is determined that the ACI 318 Appendix D method is significantly conservative (average test-predicted ratio of 1.34) because it does not consider the beneficial effects of the embedded plate. On the other hand, the punching shear method has an average test-predicted ratio of 0.62. The CCD method shows the most promise, with an average test-predicted ratio of 0.99. Limitations of the study include the small size of the test set and the minimal reinforcement in the specimens.

Pitfalls during biomechanical testing - Evaluation of different fixation methods for measuring tendons endurance properties.

The goal of the study was to find a proper technique to fix tendon grafts into an INSTRON loading machine. From 8 human cadavers, 40 grafts were collected. We removed the bone-patella tendon-bone grafts, the semitendinosus and gracilis tendons, the quadriceps tendon-bone grafts, the Achilles tendons, and the peroneus longus tendons from each lower extremity. We tested the tendon grafts with five different types of fixation devices: surgical thread (Premicron 3), general mounting clamp, wire mesh, cement fixation, and a modified clamp for an INSTRON loading machine. The mean failure load in case of surgical thread fixation was (381N ± 26N). The results with the general clamp were (527N ± 45N). The wire meshes were more promising (750N ± 21N), but did not reach the outcomes we desired. Easy slippages of the ends of the tendons from the cement encasements were observed (253N ± 18N). We then began to use Shi's clamp that could produce 977N ± 416N peak force. We combined Shi's clamp with freezing of the graft and the rupture of the tendon itself demonstrated an average force of 2198 N ± 773N. We determined that our modified frozen clamp fixed the specimens against high tensile forces.

Catalysts of plant cell wall loosening.

The growing cell wall in plants has conflicting requirements to be strong enough to withstand the high tensile forces generated by cell turgor pressure while selectively yielding to those forces to induce wall stress relaxation, leading to water uptake and polymer movements underlying cell wall expansion. In this article, I review emerging concepts of plant primary cell wall structure, the nature of wall extensibility and the action of expansins, family-9 and -12 endoglucanases, family-16 xyloglucan endotransglycosylase/hydrolase (XTH), and pectin methylesterases, and offer a critical assessment of their wall-loosening activity

Estimation of stature and sex from calcaneal measurements in Chinese

The calcaneus is a compact bone that is able to withstand high tensile forces and keep intact. Measurements of the calcaneus have been shown to be sexually dimorphic and used for stature estimation in different populations. In the present study, eight measurements for every calcaneal were taken from X-ray film of 293 Chinese, including five linear and three angular measurements. Discriminant function score equations were generated for use in sex determination, and five linear parameters were measured and matched against stature. The average accuracy of sex classification was 89.1% for the stepwise method, 78.2 to 82.3% for the direct method with linear measurements, and 52.6 to 58.7% for the direct method with angular measurements. However, the range of the standard errors of estimate is high in comparison with that obtained for stature estimation based on intact long bones and previous studies with the calcaneus in other populations. This paper provides indications that the calcaneus is an important bone for sex diagnosis and it could be effectively used as alternatives in forensic cases. However, the equations presented for stature estimation in this study should be used with caution in forensic cases when only the calcaneus is available for stature estimation.

Mechanical Actuation Systems for the Phenotype Commitment of Stem Cell-Based Tendon and Ligament Tissue Substitutes.

High tensile forces transmitted by tendons and ligaments make them susceptible to tearing or complete rupture. The present standard reparative technique is the surgical implantation of auto- or allografts, which often undergo failure.Currently, different cell types and biomaterials are used to design tissue engineered substitutes. Mechanical stimulation driven by dedicated devices can precondition these constructs to a remarkable degree, mimicking the local in vivo environment. A large number of dynamic culture instruments have been developed and many appealing results collected. Of the cells that have been used, tendon stem cells are the most promising for a reliable stretch-induced tenogenesis, but their reduced availability represents a serious limitation to upscaled production. Biomaterials used for scaffold fabrication include both biological molecules and synthetic polymers, the latter being improved by nanotechnologies which reproduce the architecture of native tendons. In addition to cell type and scaffold material, other variables which must be defined in mechanostimulation protocols are the amplitude, frequency, duration and direction of the applied strain. The ideal conditions seem to be those producing intermittent tension rather than continuous loading. In any case, all physical parameters must be adapted to the specific response of the cells used and the tensile properties of the scaffold. Tendon/ligament grafts in animals usually have the advantage of mechanical preconditioning, especially when uniaxial cyclic forces are applied to cells engineered into natural or decellularized scaffolds. However, due to the scarcity of in vivo research, standard protocols still need to be defined for clinical applications.

Analysis of geomembrane whale due to liquid flow through composite liner

When defects occur in geomembrane liner (GL), leaking water could infiltrate dry soil below, replace the pore air and may generate geomembrane whale (GW). An analytical solution is proposed in this paper to analyse the geometry and tensile force of axisymmetric GW. Parametric studies are also conducted to identify the influences from key factors and provide predicting charts for practical usage. It is concluded from the parametric studies that the maximum height and tensile force of GW can be achieved when the GW is just about to be submerged by external water. For a given level of external water, the height, width and tensile force of GW versus volume of leaking water curves are bilinear in a log–log graph, with a higher slope before a turning point but a smaller slope after that, whereas gas pressure in GW has reverse trends. It is also observed in this paper that GL with higher tension stiffness has a strong capacity to confine the gas pressure and thus generate lower and wider GW with higher tensile force and internal gas pressure.

A Wireless Sensor for Real-Time Monitoring of Tensile Force on Sutured Wound Sites.

A new wireless sensor was designed, fabricated, and applied for in situ monitoring of tensile force at a wound site. The sensor was comprised of a thin strip of magnetoelastic material with its two ends connected to suture threads for securing the sensor across a wound repair site. Since the sensor was remotely interrogated by applying an ac magnetic field and capturing the resulting magnetic field, it did not require direct wire connections to an external device or internal battery for long-term use. Due to its magnetoelastic property, the application of a tensile force changed the magnetic permeability of the sensor, altering the amplitude of the measured magnetic field. This study presents two sensor designs: one for high and one for low-force ranges. A sensor was fabricated by directly adhering the magnetoelastic strip to the suture. This sensor showed good sensitivity at low force, but its response saturated at about 1.5N. To monitor high tensile force, the magnetoelastic strip was attached to a metal strip for load sharing. The suture thread was attached to the both ends of the metal strip so only a fraction of the applied force was directed to the sensor, allowing it to exhibit good sensitivity even at 44.5N. The sensor was applied to two ex vivo models: a sutured section of porcine skin and a whitetail deer Achilles tendon. The results demonstrate the potential for in vivo force monitoring at a wound repair site.

Histological analysis of the structural composition of ankle ligaments.

Various ankle ligaments have different structural composition. The aim of this study was to analyze the morphological structure of ankle ligaments to further understand their function in ankle stability. One hundred forty ligaments from 10 fresh-frozen cadaver ankle joints were dissected: the calcaneofibular, anterior, and posterior talofibular ligaments; the inferior extensor retinaculum, the talocalcaneal oblique ligament, the canalis tarsi ligament; the deltoid ligament; and the anterior tibiofibular ligament. Hematoxylin-eosin and Elastica van Gieson stains were used for determination of tissue morphology. Three different morphological compositions were identified: dense, mixed, and interlaced compositions. Densely packed ligaments, characterized by parallel bundles of collagen, were primarily seen in the lateral region, the canalis tarsi, and the anterior tibiofibular ligaments. Ligaments with mixed tight and loose parallel bundles of collagenous connective tissue were mainly found in the inferior extensor retinaculum and talocalcaneal oblique ligament. Densely packed and fiber-rich interlacing collagen was primarily seen in the areas of ligament insertion into bone of the deltoid ligament. Ligaments of the lateral region, the canalis tarsi, and the anterior tibiofibular ligaments have tightly packed, parallel collagen bundles and thus can resist high tensile forces. The mixed tight and loose, parallel oriented collagenous connective tissue of the inferior extensor retinaculum and the talocalcaneal oblique ligament support the dynamic positioning of the foot on the ground. The interlacing collagen bundles seen at the insertion of the deltoid ligament suggest that these insertion areas are susceptible to tension in a multitude of directions. The morphology and mechanical properties of ankle ligaments may provide an understanding of their response to the loads to which they are subjected.

Relationship between the peak time of hamstring stretch and activation during sprinting

The purpose of this study was to investigate the time series relationships between the peak musculotendon length and electromyography (EMG) activation during overground sprinting to clarify the risk of muscle strain injury incidence in each hamstring muscle. Full-body kinematics and EMG of the right biceps femoris long head (BFlh) and semitendinosus (ST) muscles were recorded in 13 male sprinters during overground sprinting at maximum effort. The hamstring musculotendon lengths during sprinting were computed using a three-dimensional musculoskeletal model. The time of the peak musculotendon length, in terms of the percentage of the running gait cycle, was measured and compared with that of the peak EMG activity. The maximum length of the hamstring muscles was noted during the late swing phase of sprinting. The peak musculotendon length was synchronous with the peak EMG activation in the BFlh muscle, while the time of peak musculotendon length in the ST muscle occurred significantly later than the peak level of EMG activation (p < 0.05). These results suggest that the BFlh muscle is exposed to an instantaneous high tensile force during the late swing phase of sprinting, indicating a higher risk for muscle strain injury.

Unwinding motion of cable by taking into consideration effect of bending on cable

One of the most important factors influencing the performance of wire-guided missiles is the ability to exchange information through a connected cable. Some of the problems that occur during the process of unwinding the cable from the spool package are tangling of the cable because of low tensile force at the guide-eyelet point and cutting of the cable because of high tensile force. Therefore, it is important to analyze the transient motion of the unwinding cable withdrawn from the spool package, while considering the effect of flexural rigidity on the cable. The unwinding system is defined with cylindrical coordinates, and Hamilton׳s principle in an open system is introduced to represent the mass change of the cable in the control volume. Using Hamilton׳s principle, which takes into consideration the Lagrangian, virtual work, and virtual momentum transport, the unwinding equation with high non-linearity can be derived using boundary conditions. Further, by assuming inextensibility, the tensile force can be derived for the spatial variable. To solve the unwinding equation numerically, Newmark implicit integration is utilized with the central finite-difference approximation for spatial variables. The motions of the cable can be ascertained on the basis of various initial tensile forces by considering the constant unwinding velocity at the guide-eyelet point in air and water. It can be concluded from these motions that fluid resistance is the dominant force on the cable when it is unwound in the water, and, in contrast, centrifugal force is dominant in the air. Further, it can be observed that the initial tensile force required when the cable is unwound in water is greater than that required in air, to avoid unwinding problems such as tangling and cutting of the cable.

POTENTIAL RISK FACTORS FOR HAMSTRING MUSCLE STRAIN INJURY DURING THE LATE SWING PHASE OF SPRINTING

BackgroundThe hamstring muscles are susceptible to strain injury during sprinting, and the biceps femoris long head (BFlh) is reportedly the most frequently injured muscle. Therefore, elucidation of the risk factors...

Pure chitosan microfibres for biomedical applications

Abstract Due to its excellent biocompatibility, Chitosan is a very promising material for degradable products in biomedical applications. The development of pure chitosan microfibre yarn with defined size and directional alignment has always remained a critical research objective. Only fibres of consistent quality can be manufactured into textile structures, such as nonwovens and knitted or woven fabrics. In an adapted, industrial scale wet spinning process, chitosan fibres can now be manufactured at the Institute of Textile Machinery and High Performance Material Technology at TU Dresden (ITM). The dissolving system, coagulation bath, washing bath and heating/drying were optimised in order to obtain pure chitosan fibres that possess an adequate tenacity. A high polymer concentration of 8.0–8.5% wt. is realised by regulating the dope-container temperature. The mechanical tests show that the fibres present very high average tensile force up to 34.3 N, tenacity up to 24.9 cN/tex and Young’s modulus up to 20.6 GPa, values much stronger than that of the most reported chitosan fibres. The fibres were processed into 3D nonwoven structures and stable knitted and woven textile fabrics. The mechanical properties of the fibres and fabrics enable its usage as textile scaffolds in regenerative medicine. Due to the osteoconductive properties of chitosan, promising fields of application include cartilage and bone tissue engineering.

Delayed closure of open abdomen in septic patients is facilitated by combined negative pressure wound therapy and dynamic fascial suture

The aim of this prospective controlled trial was the definition of the optimal timepoint for delayed closure after negative pressure wound therapy (NPWT) in the treatment of the open abdomen (OA) in septic patients after abdominal surgery. The delayed closure of the abdominal wall after abdominal NPWT treatment is often problematic due to the lateralization of the fascial edge leading to unfavorably high tensile forces of the adapting sutures in the midline. We present the results of an innovative combination of NPWT with a new fascial-approximation technique using dynamic fascial sutures (DFS) and delayed closure of the abdominal wall. Eighty-seven patients subjected to OA therapy following surgery for secondary peritonitis were treated with NPWT and DFS. In all patients, a running suture of elastic vessel loops was used to approximate fascial edges. This procedure was continued for the duration of NPWT until final closure of the abdomen with running suture in 55 patients (63.2 %) and interrupted suture technique in eight patients (9.2 %). An anterior component separation was performed in seven patients. Delayed closure was achieved in 68 patients (78.2 %) after 12.6 days [mean (SD) 25.1 (2-204)] days and 4.3 re-operations [mean (SD) 6.0 (1-43)]. Fifteen (17.2 %) superficial and two (2.3 %) deep wound infections occurred. In three (3.4 %) cases, entero-atmospheric fistulas had to be treated. We recorded no technique-specific complications. Four (5.9 %) incisional hernia were detected in a mean follow-up of 40.5 months (16-65). Mortality rate was 55.2 %. Using a new technique combining NPWT and DFS in the treatment of the OA, the delayed closure of the fascial edges by running suture can be achieved and the number of re-operations can be kept low. The technique was safe and led to a low incidence of incisional hernias. Extensive abdominal wall reconstruction was seldom required.

High Sensitivity Force and Pressure Measurements Using Etched Singlemode Polymer Fiber Bragg Gratings

Singlemode polymer fiber Bragg gratings (FBGs) are etched down to a diameter of 30 $\mu{\rm m}$ to be used for high sensitivity tensile force measurements. The singlemode polymer fiber and the Bragg gratings are fabricated using the in-house fabrication facility. The fabricated cladding etched polymer FBGs are characterized for low value tensile force measurements and the sensitivity of the sensors is measured and compared with the theoretically estimated values. A sensitivity of 643 nm/N is obtained for the polymer Bragg grating with a diameter of 30 $\mu{\rm m}$ . A pressure sensor based on a singlemode polymer fiber grating is also demonstrated. Low pressure in the range of 290–790 Pa is measured and the observed sensitivity of the pressure sensor is 1.32 pm/Pa. Given the bio-compatible nature of polymer fibers, such as high sensitivity force and pressure sensors can find applications in bio-medical field where high sensitivity low value force/pressure measurements are required.

Effect of load flank angle modifications on the structural integrity of buttress threaded connections

One of the main requirements of threaded &amp; coupled connections used in oil-producing wells is the ability to resist high tensile loads. In order to ensure integrity under ever-increasing loads, the geometric parameters of the connection can be modified. In this paper, an FEA study of a 4.5 inch casing connection is reported to examine the effects of a modified load angle in combination with high tensile forces. The focus is on two failure mechanisms: jump-out and plastically deformed zones. Furthermore, a relative motion of pin and box at the contact regions is observed. It is concluded that using a negative load flank might be beneficial in order to prevent jump-out. At the same time, the deformations at the roots of the last engaged threads of the pin appear to be larger and relative sliding increases. Despite an optimization against one failure mechanism, the connection might fail as a result of an inevitable reduction of resistance against another.

Similar phenotypes of Girdin germ-line and conditional knockout mice indicate a crucial role for Girdin in the nestin lineage

Girdin is an Akt substrate and actin-binding protein. Mice with germ-line deletions of Girdin (a non-conditional knockout, (ncKO)) exhibit complete postnatal lethality accompanied by growth retardation and neuronal cell migration defects, which results in hypoplasia of the olfactory bulb and granule cell dispersion in the dentate gyrus. However, the physiological and molecular abnormalities in Girdin ncKO mice are not fully understood. In this study, we first defined the distribution of Girdin in neonates (P1) and adults (6months or older) using β-galactosidase activity in tissues from ncKO mice. The results indicate that Girdin is expressed throughout the nervous system (brain, spinal cord, enteric and autonomic nervous systems). In addition, β-galactosidase activity was detected in non-neural tissues, particularly in tissues with high tensile force, such as tendons, heart valves, and skeletal muscle. In order to identify the cellular population where the Girdin ncKO phenotype originates, newly generated Girdin flox mice were crossed with nestin promoter-driven Cre transgenic mice to obtain Girdin conditional knockout (cKO) mice. The phenotype of Girdin cKO mice was almost identical to ncKO mice, including postnatal lethality, growth retardation and decreased neuronal migration. Our findings indicate that loss of Girdin in the nestin cell lineage underlies the phenotype of Girdin ncKO mice.

Investigating Influencing Factors on the Ductility Capacity of a Fixed-Head Reinforced Concrete Pile in Homogeneous Clay

AbstractThis study performs parametric analyses on the displacement ductility capacity of a fixed-head reinforced concrete pile in homogeneous clay, considering the spread of plasticity in the pile. The parametric study regards the pile as a limited ductility structure, which conditionally allows the pile to have inelastic response during large loading. The variables considered include the pile section parameters andp-ymodel parameters. A large number of pushover analyses are conducted to examine the displacement ductility capacity of the pile. The results show that the plastic hinging will occur at the pile head region for a fixed-head pile, and the displacement ductility capacity of the pile is mainly influenced by the over-strength ratio of the pile section. Furthermore, the second plastic region may occur in ground when the axial force is in high tension. Based on the design concept of limited ductility structures, the high tensile force in pile should be avoided in pile design. A quantitative relationship between the displacement ductility capacity and over-strength ratio is suggested for engineering applications.

Experimental study on the cable rigidness and static behaviors of AERORail structure

This paper presented a new aerial platform-AERORail for rail transport and its structure evolution based on the elastic stiffness of cable; through the analysis on the cable properties when the cable supported a small service load with high-tensile force, summarized the theoretical basis of the AERORail structure and the corresponding simplified analysis model. There were 60 groups of experiments for a single naked cable model under different tensile forces and different services loads, and 48 groups of experiments for the cable with rail combined structure model. The experimental results of deflection characteristics were compared with the theoretical values for these two types of structures under the same conditions. It proved that the results almost met the classical cable theory. The reason is that a small deflection was required when this structure was applied. After the tension increments tests with moving load, it is verified that the relationships between the structure stiffness and tension force and service load are simple. Before further research and applications are made, these results are necessary for the determination of the reasonable and economic tensile force, allowable service load for the special span length for this new platform.

Investigation on overlap joining of AZ61 magnesium alloy: laser welding, adhesive bonding, and laser weld bonding

This paper presents the research on weldability of magnesium alloy AZ61 sheets by overlap laser welding, adhesive bonding, and laser seam weld bonding processes. Microstructures and mechanical properties of the joints are investigated. In overlap laser welding, the joint fractures at the interface between the sheets and maximum shear strength can reach 85% of that of the base metal. Off-center moment during tensile shear test can lead to the strength loss, while the weld edge can also influence the strength as a cracking source. Adhesive bonded joint can offer high tensile shear failure force but low peel strength. Laser weld bonded joint offers higher tensile shear failure force than either laser welded joint or adhesive bonded joint does, and the improved failure load is due to combined contribution of the weld seam and the adhesive. The weld seam can block the adhesive crack propagation, and the adhesive improves the stress distribution, so they can offer a synergistic effect.