External Compressive Force Research Articles

Design of an Overhead Crane in Steel, Aluminium and Composite Material Using the Prestress Method

The present research describes a design of an overhead crane using different materials with a prestress method, which corresponds to an external compression force with the aim of reducing the displacement of the beam due to the external load. This study concerns a bridge crane with a span length of 10 m, with a payload equal to 20,000 N and an estimated fatigue life of 50,000 cycles. Three different materials are studied: steel S355JR, aluminium alloy 6061-T6 and carbon fibre-reinforced polymer (CFRP). These materials are analysed with and without the contribution of the prestress method. In reference to the prestressed steel solution (which has a weight equal to 79% of the non-prestressed configuration), this study designed an aluminium solution that is 50.7% of the weight of the steel one and a composite solution that is always 20.3% of the steel configuration. In combining the methods, i.e., the materials and prestress, compared to the non-prestressed steel solution with a weight evaluated to be 758 kg, the weight of the aluminium configuration is equal to 40% of the traditional one, and the composite value is reduced to 16%, with a weight of 121 kg.

The effect of compressive force in bone tissue induced by implants of different primary stabilities on macrophage polarization and bone regeneration

Dental implants with different primary stabilities give rise to distinct stress distributions at the implant-bone interface after placement and exert mechanical force on the cells in the bone tissue. This study aimed to investigate whether the mechanical forces in peri-implant bone participate in the body’s immune response and influence macrophage polarization. Therefore, an in vivo rat implantation model with different primary implant stabilities was established. The osteoimmune response and macrophage polarization were investigated, and the osseointegration of the implants was evaluated. In an in vitro experiment, an external compressive force was applied to RAW264.7 cells, and the polarization phenotype was observed. MC3T3-E1 cells were cultured in macrophage-conditioned medium to investigate the regulatory effect of the macrophage-secreted cytokines on the osteogenic differentiation of osteoblasts. In vivo experimental results indicated that the primary stability of implants is positively correlated with the mechanical force. The osteoimmune response was significantly amplified by compressive force generated from implants. This compressive force first induced both M1 and M2 macrophage polarization and then accelerated the progression of the transition to M2 macrophages in the bone repair phase. In vitro, compressive force significantly upregulated the M1 and M2 macrophage polarization. In addition, the suppressive effect of macrophages on the osteogenesis of MC3T3 cells was relieved by cytokines secreted by macrophages under compressive force loading, which promoted their osteogenesis. Overall, these results clarify that compressive force from different primary stabilities is an important influencing factor regulating the osteoimmunne response and macrophage polarization in addition to maintaining the implant.

Bone Health In Patients With Inflammatory Bowel Disease (IBD)

Metabolic bone disease is prevalent in persons with immune-mediated inflammatory diseases, including inflammatory bowel disease (IBD). Within these conditions the most common are osteoporosis and reduced bone mineral density (BMD), often termed osteopenia in adult patients, and refer to a decreased mineralization of the bone matrix. This decreased mineralization weakens the resistance of the bone to external forces, thus increasing the risk of fractures when external compressive or deforming forces are applied. Osteoporosis is asymptomatic in the absence of a fracture, and diagnosis generally occurs through the use of programmatic screening (most commonly dual energy x-ray absorption [DEXA]) or incidentally following the occurrence of a fracture. Osteoporosis is defined as a DEXA-measured BMD at the lumbar spine or proximal femur which falls more than 2.5 standard deviations below the mean value for healthy young adults (known as a T-score). BMD decreases of a lesser degree (a T-score falling between -1 and -2.5) are referred to as osteopenia. Osteoporosis is a major public health concern, owing to the significant morbidity and mortality that is attributed to fractures. While fractures may represent a time-limited hardship among persons in otherwise good health and function, major osteoporosis-related fractures, especially those of the femur and spine, can lead to permanent disability and premature mortality. In Canada, approximately 150 people per 100,000 suffer a hip fracture per year, which confers a 3-fold higher risk of mortality.

High Pressure 3 × 30 Minute Compression Methods for Advanced Lower Limb Lymphedema Patients.

Introduction: In advanced lymphedema of lower limbs, stage III bandaging under the routinely applied pressure of 40-60 mmHg remains largely ineffective. This is caused by skin and subcutaneous tissue stiffness due to fibrosis. Edema fluid accumulates deep in the subcutaneous tissue. Evacuating this fluid requires a high external compression force to overcome the resistance of fibrous tissue. We aimed to investigate the effectiveness of the compression method, with high pressure lasting for 3 days. Methods and Results: Twenty-one patients with lower limb lymphedema, stage III, of the postinflammatory type were included. Patients with acute inflammatory symptoms, venous thrombosis, profuse varicose veins, diabetes, and cardiac insufficiency with edema were excluded. A 10-cm-wide rubber bandage was applied to the foot and calf. The interface pressure measured using PicoPress ranged from 58 to 120 mmHg. Skin and deep tissue tonometry, skin water concentration, leg circumference, and drop of interface pressure were measured. Ultrasound examination was done before and after each compression session. The calf circumference decreased by 15.9 ± 5.4%, deep tissue stiffness by 58.9 ± 18.9%, skin stiffness by 69.6 ± 13.5%, and skin water concentration by 43.8 ± 11.5%. Interface pressure dropped to 66.3 mmHg (28-110 mmHg); ultrasonography images showed less fluid in the tissue. Conclusions: High-pressure 30-minute leg compression can remove excess edema fluid within 3 days and enable adjustment of nonstretch compression stockings. This method is more effective in advanced lymphedema at the beginning of therapy than the standard 30-50-mmHg bandaging as it provides an immediate effect.

Towards a self-healing aluminum metal matrix composite: Design, fabrication, and demonstration

This paper presents a novel approach to designing and synthesizing a self-healing aluminum-based metal matrix composite (MMC) at the macro-scale. The composite comprises an Al 5083 matrix embedded with low melting point particles (LMPPs) that act as healing agents. A two-step electroless micro-encapsulation process is developed to create LMMPs with a diffusion and thermal barrier designed to protect the Zn-8Al core with a Co-P shell. The MMC is fabricated using spark plasma sintering. Following controlled total fracture under tension, external compressive force is applied during heat treatment to heal the fracture effectively. The evolution of phases and interfaces is characterized using electron microscopy, and transient liquid phase bonding (TLPB) is identified as the fracture-healing mechanism, facilitated in areas with sufficiently high Zn concentration to fill the crack. The design can be expanded to incorporate other matrix and LMMP materials, mechanical crack volume reduction by integrating shape memory alloy (SMA) reinforcement during MMC synthesis, and processing of the self-healing MMC using Directed Energy Deposition additive manufacturing.

Molecular Compressive Force Sensor for Mapping Forces at the Cell-Substrate Interface.

Mechanical forces are crucial for biological processes such as T cell antigen recognition. A suite of molecular tension probes to measure pulling forces have been reported over the past decade; however, there are no reports of molecular probes for measuring compressive forces, representing a gap in the current mechanobiology toolbox. To address this gap, we report a molecular compression reporter using pseudostable hairpins (M-CRUSH). The design principle was based on a pseudostable DNA structure that folds in response to an external compressive force. We created a library of DNA stem-loop hairpins with varying thermodynamic stability, and then used Förster Resonance Energy Transfer (FRET) to quantify hairpin folding stability as a function of temperature and crowding. We identified an optimal pseudostable DNA hairpin highly sensitive to molecular crowding that displayed a shift in melting temperature (Tm) of 7 °C in response to a PEG crowding agent. When immobilized on surfaces, this optimized DNA hairpin showed a 29 ± 6% increase in FRET index in response to 25% w/w PEG 8K. As a proof-of-concept demonstration, we employed M-CRUSH to map the compressive forces generated by primary naïve T cells. We noted dynamic compressive forces that were highly sensitive to antigen presentation and coreceptor engagement. Importantly, mechanical forces are generated by cytoskeletal protrusions caused by acto-myosin activity. This was confirmed by treating cells with cytoskeletal inhibitors, which resulted in a lower FRET response when compared to untreated cells. Furthermore, we showed that M-CRUSH signal is dependent on probe density with greater density probes showing enhanced signal. Finally, we demonstrated that M-CRUSH probes are modular and can be applied to different cell types by displaying a compressive signal observed under human platelets. M-CRUSH offers a powerful tool to complement tension sensors and map out compressive forces in living systems.

Forecasting supercritical behavior of drill strings in horizontal wells

The determining factor in the current changes in the world energy balance and its structure, as well as the global development of the oil and gas industry, is currently the technological factor. As a result, fundamentally new categories of horizontal and inclined wells appeared and developed. They give a multiple increase in flow rates, as they increase the production area many times over. They are used in the development of offshore projects, in swampy and very difficult areas, to increase oil recovery, restoration of inactive wells.
 New technologies based on the method of horizontal drilling have revolutionized the practice and theory of world oil production, as they have allowed the destruction of offshore oil and gas fields without the construction of expensive offshore foundations and platforms.
 When drilling horizontal wells, as a rule, the main cause of emergencies is the loss of stability of the drill string, its bifurcation protrusion and the maximum frictional interaction with the well wall. The issues of theoretical modeling of the phenomenon of unstable protrusion of columns are associated with significant difficulties, the main of which is due to the need to set the Sturm-Liouville boundary value problem on a large length of drill string. Because for deep wells, the drill string becomes geometrically similar to a human hair, many traditional mathematical methods used to integrate solving equations become poorly convergent in these cases.
 Based on the theory of curvilinear flexible rods, the problem of theoretical modeling of supercritical states of drill strings taking into account their contact interaction with the walls of oil and gas wells is set. Analytical solutions of the problem are constructed, which determine the critical values of external tensile or compressive longitudinal force and torque at a given difference in the diameters of the cavity and the drill string, the zones of supercritical states of drill strings are established.

Cubic-architectured tungsten sulfide @ Cu-Fe bimetallic electrodes for dye-sensitized solar cells, hybrid supercapacitors, and piezoelectric nanogenerators

Designing an efficient multifunctional electrode material for energy conversion, generation, and storage application was cutting-edge in energy research for the advanced integrated device. In that view, WS2 @CuFe nano box composites were constructed using the Kirkendall effect and employed as the electrode in dye-sensitized solar cells (DSSCs), asymmetric supercapacitors (ASC), and piezoelectric nanogenerators (PENG). The WS2 @CuFe − 2 nano boxes were employed as the counter electrode in DSSC and attained a power conversion efficiency of 5.4%, surpassing the performance of platinum counter electrode device (4.4%). In ASC, benefiting from the nano box morphology, the intensive utilization of surface area by electrolytes, and the synergistic contribution of WS2 @CuFe − 2 nano box results in an outstanding specific capacitance of 467 F/g at 1 A/g current density. The WS2 @CuFe − 2 //AC device owing to the induced surface area provides a high energy density of 44.45 Wh/kg and a high-power density of 1420 W/kg with columbic efficiency of 98.62%. The PENG was investigated for practical application by applying an external compression force of 50 N, which delivered an impressive self-charging potential of 167 mV generated by the piezoelectric compartment. The results prove the comprehensive application of WS2 @CuFe nano boxes serving as the all-in-one electrode for constructing sophisticated neoteric electronic devices.

Preparation and Load-Bearing Capacity of Lattice Cell Warren Truss Slot Resin-Stiffener-Reinforced Foam Sandwich Material

This study optimized and proposed a Warren truss slot-hole structure with a double-sided, square shallow slot and vertical and horizontal corrugated symmetry, achieved with inclined holes based on the stability and a good bearing capacity of an inclined strut truss structure. The tetrahedral truss lattice cells were obverse and reverse-staggered in the central core of the structure. Compared with the double-sided, square shallow groove cylindrical straight hole, the resin consumption of the Warren truss slot holes was similar to that of a vacuum-assisted resin infusion; however, the external flat compression force of the Warren truss slot holes on the resin stiffener structure doubled, and its bending contact force increased by approximately 1.5 times. Furthermore, the resulting Warren truss-slotted resin structure exhibited a late failure time. Compared with the double-sided, square shallow groove cylindrical straight hole foam-core sandwich composite, the Warren truss slot resin-stiffener-reinforced sandwich composite exhibited an increase of 4.7 kN in the flat compression load, an improvement of ~40% in flat compressive strength performance, an increase of ~0.58 kN in the bending load, and an improvement of ~60% in the bending strength, demonstrating its better bearing strength performance.

Vibration of prestressed beams: Experimental and finite-element analysis of post–tensioned thin-walled box-girders

In published works, very different explanations are given for the effect of prestressing on the beam dynamics, especially on the relationship between the vibrational effects caused by an external compressive force and those due to a prestressing force. To solve this conflict, free transverse vibrations of a post–tensioned thin-walled steel box-girder were investigated. Its fundamental frequencies were then measured for different values of prestressing. Subsequently, the experimental data were compared with a formula considering shear effects. The experimental data were also compared with two high-fidelity finite-element models assuming geometric nonlinearities. According to the obtained findings, and comparisons with tests reported in literature, the beam dynamics strongly depends on the contact of the cables with the surrounding section. If the tendons are not in contact with the surrounding cross-section, the beam dynamics due to an external compressive force is practically coincident to that caused by a prestressing force for low values of prestressing. In this case, the dynamics of prestressed beams are initially ruled by the compression-softening effect. For high values of prestressing, the beam would behave as a shallow arc with horizontal elastic supports. In this case, an increase of fundamental frequency is observed, but the yield stress would be exceeded. Conversely, in thin-walled steel girder-bridges with tendons in contact with the cross-section or draped with a deviator, the fundamental frequency is practically unaffected by prestressing. Thus, the fundamental frequency cannot be used as indicator for identifying long-term phenomena of prestressing losses, such as anchorage slips, tendon friction and relaxation.

Pressure does not affect fibrotic function of dermal fibroblast through an in vitro 3D hydrogel culture model.

Pressure therapy has been used for the prevention and treatment of hypertrophic scars for decades. However, the cellular and molecular mechanisms of this treatment modality have not been fully elaborated, leading to long-lasting controversies regarding its clinical effectiveness. In this current study, we adopted an in vitro 3D culture and compression model to explore the effect of pressure force on fibroblasts, in order to further explain the working mechanism of compression force during pressure treatment. Human dermal fibroblasts were cultured in the 3D culture hydrogel and treated with 1.5atm of external compression force through a syringe tube device, for 4, 8, and 20 h respectively. RNA-seq identified 437 differentially regulated genes after an 8-h compression intervention compared with control cells, among which 256 genes were up-regulated and 181 genes were down-regulated. Further q-PCR analysis confirmed that early growth response 1(EGR1)and c-fos were down-regulated after an 8-h compression intervention. However, the down-regulation of EGR1 and c-fos at the mRNA level does not lead to altered protein synthesis through western blot, for both 8 and 20-h time points after pressure intervention. Genes closely related to the fibrotic function of fibroblasts including type I collagen (COL1), type III collagen (COL3), transforming growth factor β1(TGF-β1), matrix metallopeptidase 1 (MMP1), matrix metallopeptidase 1 (TIMP1), connective tissue growth factor (CTGF), α smooth muscle actin (α-SMA), and fibronectin 1 (FN1), were also unaffected after pressure treatment for 8h. The current study indicated that in our 3D hydrogel culture model, pressure does not directly affect the fibrotic function of dermal fibroblast in vitro. Indirect regulation including reducing oedema, blood perfusion, and tension could be a more possible mechanism of pressure therapy.

Peak tibial acceleration should not be used as indicator of tibial bone loading during running

ABSTRACT Peak tibial acceleration (PTA) is a widely used indicator of tibial bone loading. Indirect bone loading measures are of interest to reduce the risk of stress fractures during running. However, tibial compressive forces are caused by both internal muscle forces and external ground reaction forces. PTA might reflect forces from outside the body, but likely not the compressive force from muscles on the tibial bone. Hence, the strength of the relationship between PTA and maximum tibial compression forces in rearfoot-striking runners was investigated. Twelve runners ran on an instrumented treadmill while tibial acceleration was captured with accelerometers. Force plate and inertial measurement unit data were spatially aligned with a novel method based on the centre of pressure crossing a virtual toe marker. The correlation coefficient between maximum tibial compression forces and PTA was 0.04 ± 0.14 with a range of −0.15 to +0.28. This study showed a very weak and non-significant correlation between PTA and maximum tibial compression forces while running on a level treadmill at a single speed. Hence, PTA as an indicator for tibial bone loading should be reconsidered, as PTA does not provide a complete picture of both internal and external compressive forces on the tibial bone.

Page Kidney From Ruptured Mycotic Pseudoaneurysm of Renal Artery: An Unusual Complication of Infective Endocarditis

Page kidney is an uncommon but potentially reversible cause of secondary hypertension characterized by external compressive force leading to renal hypoperfusion and elevated renin level. Renal artery mycotic aneurysms from infective endocarditis are exceedingly rare. The most feared complication is rupture, which can result in subcapsular hematoma and Page kidney. Early recognition and treatment are crucial to preserving renal function. Imaging and clinical findings aid diagnosis. Angiotensin-converting enzyme inhibitors are usually the first-line treatment of hypertension. Here, we present a rare patient case of ruptured mycotic pseudoaneurysm of the renal artery that complicated infective endocarditis and resulted in Page kidney.

Adhesive behavior between dissimilar materials subjected to thermo-elastic loadings with normal-tangential coupling effect

The temperature difference always exists between contacting objects in various thermal bonding technologies, where the adhesion strength is found to be very sensitive to the temperature. In this paper, the anisothermal adhesive contact between an elastic cylinder subjected to the external force with an inclined angle and an elastic substrate is investigated based on the non-slipping JKR model, where the coupling effect between the normal and tangential tractions within the contact region is taken into consideration. The stated problem is reduced to a system of coupled singular integral equations, which can be solved with the analytical function theory. The full analytical solutions of the oscillatory stress fields are obtained for the first time by taking the series expansion of the integrand induced by the thermoelastic effect, which is of substantial significance. The relationship between the contact size and the external loadings is established by virtue of the Griffith energy balance criterion. The difference between the oscillatory and non-oscillatory solutions of stress fields is discussed in detail. Numerical results demonstrate that the oscillatory solution cannot be well approximated by the corresponding non-oscillatory solution for the cases of large Dundurs’ index and external compressive force. Furthermore, it is found that both the thermoelastic effect and the inclined angle of the applied force have significant influences on the adhesive contact behaviors. The presence of temperature difference between contacting objects can either enhance or weaken the adhesion effect, which is related to the inclined angle of the external force. The results obtained from this paper may provide a new insight into the influence mechanism of the temperature on adhesion behaviors.

About the self-sensing behavior of smart concrete and its interaction with the carbon fiber percolation status, sand connectivity status and grain size distribution

The addition of conductive fibers to ordinary cementitious matrix permits to reduce its electrical resistivity, and consequently create its self-sensing behavior. This guarantees to the smart concrete a multifunctional behavior, where it satisfies the structural and self-sensing expectations simultaneously.This study intends to provide a better understanding of the self-sensing behavior of smart concrete function of the connectivity of carbon fibers, sand particles structure and its grain size distribution. The results showed that for cement paste, over carbon fiber volume fraction range, sensibility presented two local peaks. For mortar, in presence of diluted sand and partially connected sand, local peaks persisted. In presence of 50 % of sand volume fraction, sensibility to external compression forces was significantly reduced.

Effect of elastic disorder on single-electron transport through a buckled nanotube

We study transport properties of a single electron transistor based on elastic nanotube. Assuming that an external compressive force is applied to the nanotube, we focus on the vicinity of the Euler buckling instability. We demonstrate that in this regime the transport through the transistor is extremely sensitive to elastic disorder. In particular, built-in curvature (random or regular) leads to the ``elastic curvature blockade'': appearance of threshold bias voltage in the $I$-$V$ curve which can be larger than the Coulomb-blockade-induced one. In the case of a random curvature, an additional plateau in dependence of the average current on a bias voltage appears.

Externally applied force helps reduce bowstring effect of flexors in patients with carpal tunnel release surgery

BackgroundPatients with severe carpal tunnel syndrome (CTS) undergo carpal tunnel release (CTR) surgery to alleviate pressure in the carpal tunnel. However, the subsequent lack of the transverse carpal ligament (TCL) causes the bowstring phenomenon of the flexor tendons and increases the potential incidence of trigger finger. ObjectiveThis study aimed to investigate the effects of various compressive forces on the flexor tendon and identify the appropriate force needed to mitigate the bowstring effect of those flexors. DesignCross-sectional repeated measures comparison. MethodThirteen CTS patients who underwent CTR surgery were asked to flex the middle finger while applying different external compressive forces, just contact, 4N, and 8N force, over the carpal tunnel. Images of the flexor tendon within the carpal tunnel and at the metacarpal phalangeal (MCP) joint were recorded via ultrasound. ResultResults show that the compression force limited the volar migration of the flexor tendon under maximal voluntary contraction (MVC) conditions. Entrance angles between the flexor tendon and metacarpal bone also decreased as the external compressive force increased. ConclusionsFindings of this study may indicate that applying compression force on the carpal tunnel is useful for CTS patients and can inhibit the volar shift of the flexor digitorum superficialis (FDS) tendon after surgery, which may further prevent trigger finger.

НЕСУЧА ЗДАТНІСТЬ ПОШКОДЖЕНИХ ЗАЛІЗОБЕТОННИХ ДВОТАВРОВИХ КОЛОН

Abstract. The article presents the results of experimental and theoretical studies of the work, the parameters of the stress-strain state and the methodology for calculating the residual bearing capacity of reinforced concrete I-section columns damaged during operation and combat operations. The analysis of the literature on this subject made it possible to study the main factors affecting the residual bearing capacity, namely: the depth of damage; the angle of inclination of the damage front; relative eccentricity of application of external compressive force. A three-factor three-level experimental design has been developed. The conducted field tests of prototypes of damaged reinforced concrete columns made it possible to determine the parameters of the stress-strain state of damaged elements and their actual residual bearing capacity. On the basis of the performed experimental-statistical modeling, the main factors influencing the residual bearing capacity of damaged elements have been established. The prerequisites for calculating damaged reinforced concrete I-beams are proposed and equilibrium equations are drawn up. The proposals set out in the article are based on the main provisions of the current norms and expand the effect of their use. The analysis of influence of various factors on bearing capacity of the damaged I-beam reinforced concrete columns is carried out. It was found that the columns can withstand a maximum destructive load of 1738 kN at an angle of inclination of the damage front of 60о and in the absence of relative eccentricity. And the least destructive load columns can withstand in the absence of the angle of the damage front, and the relative eccentricity will be 1/8 of the applied load. On the basis of the conducted researches the technique of definition of reliably substantiated residual bearing capacity of reinforced concrete compressed elements of a T-profile profile damaged in the course of operation is developed. This makes it possible to determine the possibility of further trouble-free operation of structures or the need for their reinforcement or reconstruction.

The composition of the material phase responsible for the self-healing of macro-cracks in asphalt mortar beams

ABSTRACT Self-healing of asphalt is assumed to be a flow process where bitumen flows into cracks to close them. Hence, the rheological behaviour of bitumen is one of the main factors affecting self-healing together with damage history, healing duration and pressure (external compressive forces or internal thermal expansion). Bitumen-filler interaction influences the flow and it is hypothesised that the material flowing into cracks during self-healing is a mixture of bitumen, filler and eventually fine aggregates. In the paper, the self-healing ratio was determined by mechanical testing and the self-healing was accelerated by an increase of temperature to 100°C. Material draining from asphalt mortar beams into a horizontal gap, representing a crack, was found to be a mixture of bitumen and aggregates with increasing self-healing observed with increasing bitumen and filler content. For the mortar mixture used in this study, a bitumen content of 5.4 wt% was identified to be the limit for self-healing.

Soft elastic hydrogel couplants for ultrasonography

Couplants play significant roles in ultrasonography. To ensure imaging quality, it is critical to maintain conformal contact of the couplant with both the skin surface and the ultrasound probe in clinical applications. In addition, either the probe or the couplant should not deform the skin surface significantly, which will result in an overestimated modulus of the tissue for elastography imaging. However, existing liquid gel couplants cannot bear external compressive force, while existing solid gel couplants cannot maintain a conformal contact with skin surface. Especially, the nonconformal contacts and deformation become more severe on body parts of locally high curvatures such as skin tumors, fingers, and elbows. Here we report a bilayer design of couplant for ultrasonography, composing of a stiff layer and a compliant layer of hydrogels. The bilayer hydrogel pad enables it to bear external compression, allowing the probe to move smoothly, conforming high curvature parts and releasing stress concentration. Our clinical experiments further show high quality imaging of thyroid nodules, skin tumors in elbows and fingers using the bilayer hydrogel pad, which represents a promising alternative for a range of applications in ultrasonic diagnosis.