Maximum Pulling Force Research Articles

Prolonged high force high repetition pulling induces trabecular bone loss and microcracks, while low force high repetition pulling induces bone anabolism

We have an operant rat model of upper extremity reaching and grasping in which we examined the impact of performing a high force high repetition (High-ForceHR) versus a low force low repetition (Low-ForceHR) task for 18 weeks on the radius, compared to age-matched controls. High-ForceHR rats performed at 4 reaches/min and 50% of their maximum voluntary pulling force for 2 hrs/day, 3 days/wk. Low-ForceHR rats performed at 6% maximum voluntary pulling force. High-ForceHR rats showed decreased trabecular bone volume in the distal radius and increased catabolic indices (microcracks and increased osteocyte apoptosis), compared to controls. In contrast, Low-ForceHR rats showed increased trabecular bone volume, and no microcracks or osteocyte apoptosis. Thus, prolonged performance of an upper extremity reaching and grasping task is loading-dependent with high force loading leading to accumulation of bone microdamage. The target grasp force (1.27N) of the High-ForceHR rats was 50% of their mean maximum voluntary force of 2.45N, easily below the predicted maximum acceptable force (MAF) of 1.64N (predicted from published equations). The presence of microcracks and bone loss leads us to suggest that the published equations over-estimated the MAF on these tissues by 1.3 fold.

Stepping boundary of external force-controlled perturbations of varying durations: Comparison of experimental data and model simulations

This study investigated the stepping boundary – the force that can be resisted without stepping – for force-controlled perturbations of different durations. Twenty-two healthy young adults (19–37 years old) were instructed to try not to step in response to 86 different force/time combinations of forward waist-pulls. The forces at which 50% of subjects stepped (F50) were identified for each tested perturbation durations. Results showed that F50 decreased hyperbolically when the perturbation’s duration increased and converged toward a constant value (about 10%BW) for longer perturbations (over 1500 ms). The effect of perturbation duration was critical for the shortest perturbations (less than 1 s).In parallel, a simple function was proposed to estimate this stepping boundary. Considering the dynamics of a linear inverted pendulum + foot model and simple balance recovery reactions, we could express the maximum pulling force that can be withstood without stepping as a simple function of the perturbation duration. When used with values of the main model parameters determined experimentally, this function replicated adequately the experimental results.This study demonstrates for the first time that perturbation duration has a major influence on the outcomes of compliant perturbations such as force-controlled pulls. The stepping boundary corresponds to a constant perturbation force-duration product and is largely explained by only two parameters: the reaction time and the displacement of the center of pressure within the functional base of support. Future work should investigate pathological populations and additional parameters characterizing the perturbation time-profile such as the time derivative of the perturbation.

THE INFLUENCE OF THE MOISTURE CONTENT OF WOOD ON THE STRENGH PROPERTIES OF NAILED CONNECTIONS

Objectives It is known that the moisture content of wood has a significant effect on the joint strength of elements of wooden structures. However, there has been little research in establishing a specific relationship between the moisture content of wood and the nailed joint strength of wooden elements. The aim of the study is to determine the influence of capillary (free) and bound (hygroscopic) wood moisture on the strength of nailed connections during pull-out. Methods Conducting experimental studies. Results Three series of samples were tested. For each sample the maximum nail pulling force was determined, with the ultimate pulling resistance calculated according to the formula supplied by the appropriate Rules and Regulations. The samples of the first series were tested with wood having low moisture content. The samples of the second series were moistened prior to the test by being immersed in water for 24 hours to gain capillary moisture. The samples of the third series were moistened prior to the test hygroscopic moisture absorption by being placed in a desiccator above water for a long time without direct contact. Conclusion In the course of the study, it was found that both capillary and hygroscopic moisture significantly affects the strength of nailed connections, and that the effect on the maximum pulling force is not determined by the type of moisture, but by its value. The samples of the first series indicated the greatest nail pulling resistance. The samples of the second series had nail pulling resistance less by 48%. In the third series, the strength of the nailed connection was reduced by 31% as compared to the dry wood. The results of the study confirm the necessity of taking into account the humidity during the design and operation of nailed connections.

Prolonged high force high repetition pulling induces osteocyte apoptosis and trabecular bone loss in distal radius, while low force high repetition pulling induces bone anabolism.

We have an operant rat model of upper extremity reaching and grasping in which we examined the impact of performing a high force high repetition (High-ForceHR) versus a low force low repetition (Low-ForceHR) task for 18weeks on the radius and ulna, compared to age-matched controls. High-ForceHR rats performed at 4 reaches/min and 50% of their maximum voluntary pulling force for 2h/day, 3days/week. Low-ForceHR rats performed at 6% maximum voluntary pulling force. High-ForceHR rats showed decreased trabecular bone volume in the distal metaphyseal radius, decreased anabolic indices in this same bone region (e.g., decreased osteoblasts and bone formation rate), and increased catabolic indices (e.g., microcracks, increased osteocyte apoptosis, secreted sclerostin, RANKL, and osteoclast numbers), compared to controls. Distal metaphyseal trabeculae in the ulna of High-ForceHR rats showed a non-significant decrease in bone volume, some catabolic indices (e.g., decreased trabecular numbers) yet also some anabolic indices (e.g., increased osteoblasts and trabecular thickness). In contrast, the mid-diaphyseal region of High-ForceHR rats' radial and ulnar bones showed few to no microarchitecture differences and no changes in apoptosis, sclerostin or RANKL levels, compared to controls. In further contrast, Low-ForceHR rats showed increased trabecular bone volume in the radius in the distal metaphysis and increased cortical bone area its mid-diaphysis. These changes were accompanied by increased anabolic indices, no microcracks or osteocyte apoptosis, and decreased RANKL in each region, compared to controls. Ulnar bones of Low-ForceHR rats also showed increased anabolic indices, although fewer than in the adjacent radius. Thus, prolonged performance of an upper extremity reaching and grasping task is loading-, region-, and bone-dependent, with high force loads at high repetition rates inducing region-specific increases in bone degradative changes that were most prominent in distal radial trabeculae, while low force task loads at high repetition rates induced adaptive bone responses.

Size-dependent formation of membrane nanotubes: continuum modeling and molecular dynamics simulations.

Membrane nanotubes play important functional roles in numerous cell activities such as cellular transport and communication. By exerting an external pulling force over a finite region in a membrane patch, here we investigate the size dependence of the membrane nanotube formation under the continuum and atomistic modeling frameworks. It is shown that the membrane undergoes a discontinuous shape transition as the size of the pulling region and the membrane tension increase. A formula characterizing the nonlinear relationship between the maximum static pulling force and pulling size is identified. During the membrane extraction, lipids in the upper and lower leaflets exhibit different behaviors of structural rearrangements. Moreover, our computational simulations indicate that the steady state pulling force increases linearly with the pulling velocity as well as the size of the pulling region.

A STUDY OF HEMPCRETE PROPERTIES USING NATURAL HYDRAULIC LIME – MIX DESIGN, MECHANICAL PROPERTIES, AND MICROSTRUCTURE

In the article, an analysis of tensile strength fiber hemp and hemp fiber linkage analysis in the cement matrix is presented. The average tensile strength of the fibers of untreated hemp amounts to 764 MPa and the calculated modulus of elasticity amounts to 30 GPa. A test of pulling fibers from the cement matrix has shown that when increasing the length linkage, the maximum pulling force increases while the clamping strength does not significantly change. In the laboratory, a mixture of hemp concrete where a portion of mineral aggregate was replaced with hemp hurd was prepared. Results of the examination of the microstructure of hardened lime binder have shown that the hardened NHL mixture is porous and vapor-permeable while the hardened HL mixture is thick and compact. The goal was to create a prototype hemp concrete mixture that can be used for production of prefabricated elements with tensile strength between 10 and 25 MPa.

Attainment and retention of force moderation following laparoscopic resection training with visual force feedback.

Laparoscopic training with visual force feedback can lead to immediate improvements in force moderation. However, the long-term retention of this kind of learning and its potential decay are yet unclear. A laparoscopic resection task and force sensing apparatus were designed to assess the benefits of visual force feedback training. Twenty-two male university students with no previous experience in laparoscopy underwent relevant FLS proficiency training. Participants were randomly assigned to either a control or treatment group. Both groups trained on the task for 2weeks as follows: initial baseline, sixteen training trials, and post-test immediately after. The treatment group had visual force feedback during training, whereas the control group did not. Participants then performed four weekly test trials to assess long-term retention of training. Outcomes recorded were maximum pulling and pushing forces, completion time, and rated task difficulty. Extreme maximum pulling force values were tapered throughout both the training and retention periods. Average maximum pushing forces were significantly lowered towards the end of training and during retention period. No significant decay of applied force learning was found during the 4-week retention period. Completion time and rated task difficulty were higher during training, but results indicate that the difference eventually fades during the retention period. Significant differences in aptitude across participants were found. Visual force feedback training improves on certain aspects of force moderation in a laparoscopic resection task. Results suggest that with enough training there is no significant decay of learning within the first month of the retention period. It is essential to account for differences in aptitude between individuals in this type of longitudinal research. This study shows how an inexpensive force measuring system can be used with an FLS Trainer System after some retrofitting. Surgical instructors can develop their own tasks and adjust force feedback levels accordingly.

The king of snakes: performance and morphology of intraguild predators (Lampropeltis) and their prey (Pantherophis).

Across ecosystems and trophic levels, predators are usually larger than their prey, and when trophic morphology converges, predators typically avoid predation on intraguild competitors unless the prey is notably smaller in size. However, a currently unexplained exception occurs in kingsnakes in the genus Lampropeltis Kingsnakes are able to capture, constrict and consume other snakes that are not only larger than themselves but that are also powerful constrictors (such as ratsnakes in the genus Pantherophis). Their mechanisms of success as intraguild predators on other constrictors remain unknown. To begin addressing these mechanisms, we studied the scaling of muscle cross-sectional area, pulling force and constriction pressure across the ontogeny of six species of snakes (Lampropeltiscaliforniae, L.getula, L.holbrooki, Pantherophisalleghaniensis, P.guttatus and P.obsoletus). Muscle cross-sectional area is an indicator of potential force production, pulling force is an indicator of escape performance, and constriction pressure is a measure of prey-handling performance. Muscle cross-sectional area scaled similarly for all snakes, and there was no significant difference in maximum pulling force among species. However, kingsnakes exerted significantly higher pressures on their prey than ratsnakes. The similar escape performance among species indicates that kingsnakes win in predatory encounters because of their superior constriction performance, not because ratsnakes have inferior escape performance. The superior constriction performance by kingsnakes results from their consistent and distinctive coil posture and perhaps from additional aspects of muscle structure and function that need to be tested in future research.

Extracellular protonation modulates cell-cell interaction mechanics and tissue invasion in human melanoma cells

Detachment of cells from the primary tumour precedes metastatic progression by facilitating cell release into the tissue. Solid tumours exhibit altered pH homeostasis with extracellular acidification. In human melanoma, the Na+/H+ exchanger NHE1 is an important modifier of the tumour nanoenvironment. Here we tested the modulation of cell-cell-adhesion by extracellular pH and NHE1. MV3 tumour spheroids embedded in a collagen matrix unravelled the efficacy of cell-cell contact loosening and 3D emigration into an environment mimicking physiological confinement. Adhesive interaction strength between individual MV3 cells was quantified using atomic force microscopy and validated by multicellular aggregation assays. Extracellular acidification from pHe7.4 to 6.4 decreases cell migration and invasion but increases single cell detachment from the spheroids. Acidification and NHE1 overexpression both reduce cell-cell adhesion strength, indicated by reduced maximum pulling forces and adhesion energies. Multicellular aggregation and spheroid formation are strongly impaired under acidification or NHE1 overexpression. We show a clear dependence of melanoma cell-cell adhesion on pHe and NHE1 as a modulator. These effects are opposite to cell-matrix interactions that are strengthened by protons extruded via NHE1. We conclude that these opposite effects of NHE1 act synergistically during the metastatic cascade.

Let’s All Pull Together: Principles for Sharing Large Loads in Microrobot Teams

We present a simple statistical model to predict the maximum pulling force available from robot teams. The expected performance is a function of interactions between each robot and the ground (e.g., whether running or walking). We confirm the model with experiments involving impulsive bristlebots, small walking and running hexapods, and 17 g μTug that employ adhesion instead of friction. With attention to load sharing, each μTug can operate at its individual limit so that a team of six pulls with forces exceeding 200 N.

往復式及び回転式シェーバーによる人工毛切断挙動観察

The shaver is a popular electronic utility for male to cut their beard, hair and so on. It is roughly divided two shaving system as oscillating or rotating motion of an inner blade. The cutting hairs mechanism is also assumed that inner blade edge just cut hairs at the moment of contact between inner blade and hairs. However, the hairs were likely to pull into the shaver and a pulling force generated which we felt in use. The detail cutting motion and pulling force was observed and measured to clarify the differences between oscillation and rotation type by a high speed camera. Each shaving system showed same tendency that the inner blade penetrated to the hair at the first, then both the inner blade and hair moved together to the outer blade. Finally, the inner and outer blade cut the hair by scissor action with pulling force generation simultaneously. As regards oscillation shaver, it was indicated that the inner blade hit the hair several times before the hair was completely cut. The maximum pulling force was approximately 0.15 N and the average was 0.04 which was higher than rotation type of 0.13 N as maximum and 0.03 N as average. Finally, the relation between the inner blade speed and pulling force of rotating type shaver was investigated, and the rotating type showed lower pulling force generation nevertheless of its lower inner blade speed (1.18 m/s) than oscillation type (2.3 m/s).

Out of die ultraviolet cured pultrusion for automotive crash structures

In this paper the out of die ultraviolet (UV) cured pultrusion for manufacturing impact automotive energy absorbing parts has been analysed. Aspects such as the UV source, pultrusion process variables and final mechanical and physical properties of the pultruted parts have been studied. The measured maximum pulling force in the die was approximately 80 N. The parts cured with high intensity UV LED sources present low void concentration and almost no expansion at the exit of the die. The parts cured with the traditional UV arc lamp have an expansion of 20% of the expected thickness and hence, high void concentration. The less expansion at the exit of the die is translated into an improvement of 26% in the interlaminar properties and in 8% in the energy absorbing capability of the UV LED cured parts.

Tensile failure mechanisms of individual junctions assembled by two carbon nanotubes

The tensile mechanical behaviors of junctions between carbon nanotubes (CNTs) were experimentally and theoretically studied. For sidewall-contact junctions, we found that tensile failure stress can be enhanced by radial deformation of CNTs. Meanwhile, a re-formation mechanism of junctions expected to contribute to interfacial toughness was found, for which a theoretical prediction was presented. For end-contact junction, it is found that the maximum pulling force is dependent on the diameters and wall numbers of CNTs. Most importantly, the interaction strength between two open-ends of CNTs was first experimentally estimated to be 21 MPa. This study would be helpful not only in understanding the failure behaviors, but also in quantifying the mechanical properties of the CNT-based fibers, films and blocks.

Calculation of optimal jaw geometry for an electronic bond pull test

A bond pull test is used to determine the strength of the bond of an electronic interconnect to a circuit board. A standard test consists of clamping and pulling the interconnect with a pair of microscopic jaws. In a successful test, the maximum pulling force registered by the jaws will be the failure load of the interconnect to circuit board bond. However, if the interconnect itself deforms before the bond has failed, then this would constitute an unsuccessful test. This paper reports on a theoretical analysis of the optimal geometry for gripping of a cylindrical interconnect. Upper and lower-bound plasticity models have been used to determine the jaw proportions that will maximize the load for the deformation of the interconnect and that should, therefore, be most likely to allow successful measurement of the bond strength. This theoretical analysis is compared to 2D and 3D non-linear finite element calculations. The 2D finite element models are axi-symmetric approximations of a pull test on a cylindrical interconnect. 3D finite element models take into account the actual jaw geometry and allow simulation of both clamping and pulling stages. The maximum calculated pull forces for both 2D and 3D simulations are in good agreement with the plasticity theory. Preliminary validation of the theory and finite element results has been accomplished through experimental clamping and pulling tests on cylindrical metal rods.

Measuring the Strength of the Horned Passalus Beetle,Odontotaenius disjunctus: Revisiting an Old Topic with Modern Technology

Over a century ago, a pioneering researcher cleverly devised a means to measure how much weight the horned passalus beetle, Odontotaenius disjunctus (Illiger) (Coleoptera: Passalidae), could pull using a series of springs, pulleys, and careful observation. The technology available in modern times now allows for more rigorous data collection on this topic, which could have a number of uses in scientific investigations. In this study, an apparatus was constructed using a dynamometer and a data logger in an effort to ascertain the pulling strength of this species. By allowing beetles to pull for 10 min, each beetle's mean and maximum pulling force (in Newtons) were obtained for analyses, and whether these measures are related was determined. Then, whether factors such as body length, thorax size, horn size, or gender affect either measure of strength was investigated. Basic body measurements, including horn size, of males versus females were compared. The measurements of 38 beetles (20 females, 18 males) showed there was no difference in overall body length between sexes, but females had greater girth (thorax width) than males, which could translate into larger muscle mass. A total of 21 beetles (10 females, 11 males) were tested for pulling strength. The grand mean pulling force was 0.14 N, and the grand mean maximum was 0.78 N. Despite the fact that beetles tended to pull at 20% of their maximum capacity most of the time, and that maximum force was over 5 times larger than the mean force, the 2 measures were highly correlated, suggesting they may be interchangeable for research purposes. Females had twice the pulling strength (both maximum and mean force) as males in this species overall, but when the larger thorax size of females was considered, the effect of gender was not significant. Beetle length was not a significant predictor of pulling force, but horn size was associated with maximum force. The best predictor of both measures of strength appeared to be thorax size. There are a multitude of interesting scientific questions that could be addressed using data on beetle pulling strength, and this project serves as a starting point for such work.

Evaluation of the influence of chemical softening on the properties of cellulose-origin textiles

The present research has explored the influence made by chemical softening with liquid household chemical softeners on changes in the structure and hand properties of the cellulose-origin textiles manufactured from cotton, bamboo and viscose spun yarns. Effectiveness of technological treatment has been analysed via application of an experimental method based on the pulling of a disc-shaped specimen through the central nozzle of KTU-Griff-Tester device. Analysis of the obtained results has demonstrated that washing of textiles leads to decrease in the hand parameters thereof such as the maximum pulling force (P max), tangent of the slope angle of the typical pulling curve H–P initial part (tgα), pulling work (A) and complex hand parameter (Q) as well as in mechanical thickness ratio (Δδ) compared to the ones of the unwashed (control) textiles independent of the fibre content and manufacturing type thereof. Hand properties of the textiles under investigation have been shown to improve after chemical softening compared to the washed textiles, but they have never been comparable to the ones of the untreated (control) textiles. Chemical softening with the cationic softeners “Wansou” (V), “Pflege Weichspuler” (P) and “Surcare” (Sr) containing 5–15% of PAM has determined the best hand of the textiles under discussion compared to other chemical softeners.

New flexible endoscopic full-thickness suturing device: a triple-arm-bar suturing system

A reliable full-thickness suturing device is necessary for pure natural orifice transluminal endoscopic surgery (NOTES). The present study focused on assessing the reliability of a new suturing device. A total of 60 single sutures were tested to close 5-cm incisions in 8-cm square pieces of resected swine stomach. Each incision was sutured by an over-the-scope clip (OTSC; n = 20), a single hand-sewn stitch (n = 20), or a single triple-arm-bar suturing system (TBSS) stitch. The maximum pulling force durability (MPD) of each suture was tested. To assess the reliability of the TBSS for endoscopic full-thickness resection (EFTR), 60 EFTRs of 50 mm diameter were performed on excised swine stomachs. After EFTR, full-thickness sutures were made using 3-stitch OTSCs (n = 20), 10-stitch hand-sewn sutures (n = 20), or 10-stitch TBSS sutures (n = 20). Outcomes were the MPD test for both single stitch and multiple stitch applications and the suturing time for single-stitch sutures. In the single-stitch MPD tests, there were significant differences between OTSCs and hand-sewn sutures (P = 0.0002) and between OTSCs and TBSS sutures (P = 0.0001), but no significant difference between hand-sewn and TBSS sutures. The multiple-stitch sutures revealed significant differences between OTSCs and hand-sewn sutures (P = 0.0039), and between OTSCs and TBSS sutures (P = 0.013). There was no significant difference between hand-sewn and TBSS sutures. There were significant differences in suture times between OTSC, hand-sewn sutures, and TBSS sutures (P < 0.05). Both single-stitch and multiple-stitch sutures using TBSS have similar strength to hand-sewn sutures. TBSS is a reliable suturing device.

Effect of a Parasitic Nematode,Chondronema passaliLeidy (Incertae sedis), on the Size and Strength of the Horned Passalus,Odontotaenius disjunctusIlliger (Coleoptera: Passalidae)

The horned passalus, Odontotaenius disjunctus (Illiger), is host to a variety of parasites, including a little-studied nematode, Chondronema passali (Leidy), that can number in the thousands in a single beetle. We attempted to determine the effects of this parasite on two measures of host fitness, physical strength and body size of adult beetles collected from hardwood logs at two sites in Georgia, USA. For a subset of the beetles, we measured their individual pulling strength using a dynamometer and data-logging apparatus. We also recorded the live weight of all beetles and from another subset a composite measure of body size based on digital images. Beetles were dissected and nematode infection status was assessed for all beetles. Of all beetles examined in this study (49 females, 44 males), we detected C. passali in 63 (67.7%) individuals. Prevalence in males did not differ from females. Infections ranged from 10 to over 1,000 individual nematode larvae per beetle. There was no significant effect of infection on maximum pulling force after accounting for body size and gender. Beetles with nematode infections weighed significantly more than those without nematodes and were significantly larger in body size. These results suggest the effects of this parasite are minimal to the host, and infections may even confer an advantage via the increase in size. Based on a review of the relevant literature, this appears to be a rare phenomenon among the many insect-nematode parasite relationships.

Theoretical prediction and experimental verification of pulling carbon nanotubes from carbon fiber prepared by chemical grafting method

This article reports on experiments for measuring pulling forces and displacements of a carbon nanotube (CNT) grafted on carbon fibers (CFs) and modeling for predicting the pulling force–displacement curves. In the experiments, the pulling force and displacement for different grafting configurations are measured. In the present analytical model, a power function relationship between a curvature radius and critical failure angle of the CNT was firstly established on the basis of the experimental data, and then the critical failure angle, maximum pulling forces and displacements were determined by using a free length, initial grafting length, initial grafting angle, the Hamaker constant and friction coefficient between the CNT and CF. By using the present model, pulling mechanical behaviors of CNTs with different grafting configurations are investigated and verified with results obtained from images taken in the experiment.

Psychophysical basis for maximum pushing and pulling forces: A review and recommendations

The objective of this paper was to perform a comprehensive review of psychophysically determined maximum acceptable pushing and pulling forces. Factors affecting pushing and pulling forces are identified and discussed. Recent studies show a significant decrease (compared to previous studies) in maximum acceptable forces for males but not for females when pushing and pulling on a treadmill. A comparison of pushing and pulling forces measured using a high inertia cart with those measured on a treadmill shows that the pushing and pulling forces using high inertia cart are higher for males but are about the same for females. It is concluded that the recommendations of Snook and Ciriello (1991) for pushing and pulling forces are still valid and provide reasonable recommendations for ergonomics practitioners. Regression equations as a function of handle height, frequency of exertion and pushing/pulling distance are provided to estimate maximum initial and sustained forces for pushing and pulling acceptable to 75% male and female workers.At present it is not clear whether pushing or pulling should be favored. Similarly, it is not clear what handle heights would be optimal for pushing and pulling. Epidemiological studies are needed to determine relationships between psychophysically determined maximum acceptable pushing and pulling forces and risk of musculoskeletal injuries, in particular to low back and shoulders. Relevance to industryThis article provides a concise discussion of important factors relevant to designing and analyzing pushing/pulling tasks. Regression equations to estimate initial and sustained pushing and pulling forces acceptable to 75% male and female workers are provided and can be used to design and analyze pushing and pulling tasks common in industry.