Ageing of climbing ropes with and without hydrophobic coating

2021 ◽  
pp. 175433712110628
Author(s):  
Daniel Sedláček ◽  
Martina Roso ◽  
Leano Viel ◽  
Nicola Perotto ◽  
Barnaby Caven ◽  
...  
Keyword(s):  
Prolonged Exposure ◽  
Radial Pressure ◽  
Polyamide 6 ◽  
Drop Test ◽  
Maximum Force ◽  
Breaking Force ◽  
Hydrophobic Coating ◽  
The Core ◽  
Negative Effect ◽  
Static Tensile

The effects of 4 months of weather exposure on the ageing of dynamic climbing ropes made of polyamide 6 were studied and differences between ropes with and without hydrophobic coating were examined. The polyamide degradation of the rope yarns was studied using infrared spectroscopy and a quasi-static tensile test. The number of falls to failure and the maximum force on the climber in a fall were evaluated with a drop test according to the UIAA 101 standard. Moreover, changes in the length of the ropes due to weathering were measured. The following results were found. After 4 months of weathering, sheath yarns of the coated rope showed a greater decrease in breaking force than those of the uncoated rope, which might be due to reactions of polyamide with radicals formed during the photo-induced oxidation of the coating. In contrast, the core yarns from the uncoated rope showed a greater decrease in breaking force than those from the coated rope, probably due to prolonged exposure of the uncoated core to water with possibly dissolved atmospheric acids. Furthermore, the decrease in the number of falls to failure was greater in the uncoated than in the coated rope. This difference was explained by a mechanism of changes in radial pressure of the sheath on the core. Regarding the maximum force on the climber, no significant changes due to ageing were observed during the drop test. Thus, it was concluded that 4 months of weather exposure do not pose a safety risk for climbing ropes, but the negative effect of coating on the ageing of polyamide might be detrimental when it comes to static personal safety equipment, such as slings or accessory cords.

scholarly journals Adhesion Studies during Generative Hybridization of Textile-Reinforced Thermoplastic Composites via Additive Manufacturing

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 3888
Author(s):  
Johanna Maier ◽  
Christian Vogel ◽  
Tobias Lebelt ◽  
Vinzenz Geske ◽  
Thomas Behnisch ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Polyamide 6 ◽  
Thermoplastic Composites ◽  
Efficient Production ◽  
Angle Measurements ◽  
Small Series ◽  
Contact Angle Measurements ◽  
Static Tensile ◽  
Pre Treatment ◽  
Manufacturing Technologies

Generative hybridization enables the efficient production of lightweight structures by combining classic manufacturing processes with additive manufacturing technologies. This type of functionalization process allows components with high geometric complexity and high mechanical properties to be produced efficiently in small series without the need for additional molds. In this study, hybrid specimens were generated by additively depositing PA6 (polyamide 6) via fused layer modeling (FLM) onto continuous woven fiber GF/PA6 (glass fiber/polyamide 6) flat preforms. Specifically, the effects of surface pre-treatment and process-induced surface interactions were investigated using optical microscopy for contact angle measurements as well as laser profilometry and thermal analytics. The bonding characteristic at the interface was evaluated via quasi-static tensile pull-off tests. Results indicate that both the bond strength and corresponding failure type vary with pre-treatment settings and process parameters during generative hybridization. It is shown that both the base substrate temperature and the FLM nozzle distance have a significant influence on the adhesive tensile strength. In particular, it can be seen that surface activation by plasma can significantly improve the specific adhesion in generative hybridization.

Effect of prolonged exposure to continuous heat and humidity similar to long haul live export voyages in Merino wethers

2011 ◽  
Vol 51 (2) ◽  
pp. 135 ◽  
Author(s):  
C. A. Stockman ◽  
A. L. Barnes ◽  
S. K. Maloney ◽  
E. Taylor ◽  
M. McCarthy ◽  
...  
Keyword(s):  
Prolonged Exposure ◽  
Physiological Responses ◽  
Heat Exposure ◽  
High Heat ◽  
Controlled Environment ◽  
Physiological Changes ◽  
Bicarbonate Concentration ◽  
The Core ◽  
Continuous Heat ◽  
Live Export

This experiment investigated the physiological responses of Merino wethers (n = 12) to prolonged high heat and humidity similar to that experienced during long haul, live export voyages from Australia to the Middle East. Merino wethers were randomly assigned to individual pens in rooms with a controlled environment, and exposed to gradually increasing temperatures, and two exposures of 3–4 days of sustained high heat and humidity, up to a maximum of 31°C wet bulb temperature (37°C dry bulb and 67% relative humidity). There was 1 day at thermoneutral temperatures separating the heat exposures. The core temperatures and respiratory rates of Merino wethers increased during both heat exposures, with open-mouthed panting observed during both exposures. Plasma partial pressure carbon dioxide (pCO2) and bicarbonate concentration (HCO3–) decreased, and plasma pH increased during the second heat exposure. Both pCO2 and HCO3– returned to normal immediately following the heat exposures. Feed intake was maintained during the heat exposures. There were no large alterations in blood electrolyte concentrations attributable to the effects of the heat. The results show that Merino wethers experienced significant physiological changes during exposure to prolonged and continuous high heat and humidity, but maintained most aspects of homeostasis despite being hyperthermic and recovered quickly when conditions returned to thermoneutral.

On vortex boundary layers

1985 ◽  
Vol 400 (1819) ◽  
pp. 253-261 ◽  
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Three Dimensional ◽  
Radial Pressure ◽  
Outer Flow ◽  
The Core ◽  
Dimensional Boundary ◽  
Radial Pressure Gradient ◽  
Potential Vortex ◽  
Vortex Axis

Flow visualization is used to study the flow that results when a potential vortex rotates normal to a stationary horizontal disc. Viscosity is seen to remove the singularity on the vortex axis and lead to the development of a three-dimensional boundary layer. The flow remains laminar below a Reynolds number, Re , of about 10 4 , where Re is based on radius and velocity at the disc edge. With further increases in Re the boundary layer becomes turbulent but relaminarizes as it is advected radially inwards by the highly favourable radial pressure gradient associated with the outer flow. The radius of the zone of relaminarized fluid decreases with increasing Re . Close to the axis the flow effuses vertically to form the core of the vortex which, for Re < 10 4 , is observed to undergo a massive disruption, either of the axisymmetric or helical form. The sense of the helix was observed on some occasions to be with that of the outer flow and on others to be opposite that of the outer flow.

scholarly journals Analisis Penerimaan Core Banking System Berbasis Technology Readiness an Acceptance Model pada BPRS Bangun Drajat Warga di DIY (Analysis of Acceptance of Banking System Based on Technology Readiness and Acceptance Model in BPRS Bangun Drajat Warga at DIY)

2019 ◽  
Vol 3 (1) ◽  
pp. 57
Author(s):  
Sindu Rifai ◽  
Salamatun Asakdiyah ◽  
Rai Rake Setyawan
Keyword(s):  
Significant Influence ◽  
Research Method ◽  
Banking System ◽  
Ease Of Use ◽  
Technology Readiness ◽  
The Core ◽  
Negative Effect ◽  
Acceptance Model ◽  
Survey Approach ◽  
Special Region

The purpose of this study is to analyze the acceptance of the core banking system based on technology readiness and acceptance model on Bank Pembiayaan Rakyat Syariah Bangun Drajat Warga in the Special Region of Yogyakarta. Constructions used are optimism, innovativeness, discomfort, insecurity, easy of use and usefulness. This research method uses quantitative with a survey approach. The results of the study show that constructs of optimism and discomfort have a positive and significant effect on the perception of benefits and convenience in using the Core Banking System. The innovativeness construct has a positive and significant effect on the perception of the benefits of the core banking system, but for users, it has a negative effect and does not significantly influence the perception of ease of use of the Core Banking System. Insecurity, easy of use and usefulness constructs shows that there is no positive and significant influence on the perception of benefits and convenience in using the Core Banking System. 

scholarly journals Modification of Mechanical Properties of Aluminum Alloy Rods via Friction-Extrusion Method

Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5224
Author(s):  
Anna Wójcicka ◽  
Krzysztof Mroczka ◽  
Jerzy Morgiel
Keyword(s):  
Mechanical Properties ◽  
Outer Zone ◽  
Tensile Tests ◽  
The Core ◽  
Transmission Electron ◽  
Gradient Microstructure ◽  
The Face ◽  
Static Tensile ◽  
Friction Extrusion ◽  
Extrusion Method

The elaboration of a modified friction-extrusion method aimed at obtaining 2017A aluminum rods of gradient microstructure is described. This was achieved by cutting spiral grooves on the face of the stamp used for alloy extrusion. The experiments were carried out at a constant material feed (~10 mm/min) and a range of tool rotation speeds (80 to 315 rpm). The microstructure observations were carried out using light microscopy (LM) and both scanning and transmission electron microscopy (SEM and TEM). The mechanical properties were assessed through hardness measurements and static tensile tests. The performed investigations show that material simultaneous radial and longitudinal flow, enforced by friction of the rotating tool head and extrusion, results in the formation of two zones of very different microstructures. At the perpendicular section, the outer zone stands out from the core due to circumferential elongation of strings of particles, while in the inner zone the particles are arranged in a more uniform way. Simultaneously, the grain size of the outer zone is refined by two to four times as compared with the inner one. The transfer from the outer zone to the core area is of gradient type. The hardness of the outer zone was found to be ~10% to ~20% higher than that of the core.

The Deduction of the Integral and the Estimation of the Local Core Rotation Ratio by Telemetric Pressure Measurements in a Two Cavity Test Rig

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
Wieland Uffrecht ◽  
André Günther
Keyword(s):  
Heat Transfer ◽  
Gas Turbines ◽  
Operation Mode ◽  
Radial Pressure ◽  
Pressure Measurements ◽  
Test Rig ◽  
The Core ◽  
Rotating Cavity ◽  
Cavity System ◽  
Core Rotation

The heat transfer in rotating cavities, as found in the internal air system of gas turbines, is mainly governed by the flow passing through these specific machine structures. The core rotation ratio represents the circumferential velocity, and is thought to be an influential flow parameter for heat transfer in rotating cavities with radial flow-through. Therefore, this paper focuses on deducing the core rotation ratio and the estimation of its local distribution using telemetric pressure measurements. The local core rotation ratio depends on the radial pressure distribution in a rotating cavity system. Thus, an integral core rotation ratio can be determined from pressure measurements in the rotating cavity system. A flow structure-based approximation of the measurements allows an estimation of the radial distribution of the core rotation ratio in the rotating cavity. The results of the measurements with varied flow rates and revolving speeds are presented, as well as a discussion of the fit parameters and their dependency on the operation mode of the test rig.

Study on the Properties of Melamine Cyanurate Modified Polyamide 6 Nanocomposites with Different Dimensional Siliciferous Particles

2014 ◽  
Vol 789 ◽  
pp. 169-173 ◽  
Author(s):  
Li Li Li ◽  
Zhi Hao Wu ◽  
Shuai Shuai Jiang ◽  
Tian Ze Wu ◽  
Shou Yang Lu ◽  
...  
Keyword(s):  
Flame Retardancy ◽  
Testing Machine ◽  
Polyamide 6 ◽  
Halloysite Nanotubes ◽  
Sem Images ◽  
Limiting Oxygen Index ◽  
Melamine Cyanurate ◽  
Universal Testing Machine ◽  
Universal Testing ◽  
Negative Effect

Different dimensional siliciferous particles including silica (0D), halloysite nanotubes (HNTs,1D) and montmorillonite (MMT,2D) were melt blending with certain amount of melamine cyanurate and polyamide 6(PA6) by a twin-screw extruder. Characterization of the PA6 composites has been investigated using scan electron microscopy (SEM), thermal gravimetric analyzer (TGA), universal testing machine and limiting oxygen index instrument. SEM images indicate that the nanoparticles were uniformly dispersed in the PA6 but there was some aggregation of MCA in the composites. The incorporation of silica exerted a negative effect on the flame retardancy of PA6/MCA composite, whereas adding HNTs and MMT lead to the improvements of LOI value of 30.4 and 30.9 respectively. TGA results show that PA6/MCA/silica, PA6/MCA/HNTs and PA6/MCA/OMMT exhibit two degradation stages. Higher Tmax1 and Tmax2 appeared comparing with PA6/MCA. Char residue of PA6/MCA/OMMT at 600°C were elevated most. HNTs and OMMT can increase the tensile strength and elongation of PA6/MCA by universal testing machine results, even higher than pure PA6, showing enhanced effects of these 1D and 2D fillers. These could enhance strength of the char and finally increase the flame retardancy of PA6.

A Comparative Analysis of the Biomechanical Behaviour of Five Flexor Tendon Core Sutures

2004 ◽  
Vol 29 (6) ◽  
pp. 536-543 ◽  
Author(s):  
A. VIINIKAINEN ◽  
H. GÖRANSSON ◽  
K. HUOVINEN ◽  
M. KELLOMÄKI ◽  
P. ROKKANEN
Keyword(s):  
Yield Point ◽  
Flexor Tendon ◽  
Tendon Repair ◽  
Gap Formation ◽  
Linear Region ◽  
The Core ◽  
Polyester Suture ◽  
Static Tensile ◽  
Yield Force

Five core suture techniques were compared by static tensile testing in vitro. Fifty porcine tendons were used. The core sutures were performed with 3-0 or 4-0 braided polyester suture (Ticron®) and the over-and-over running peripheral sutures with 6-0 monofilament polypropylene (Prolene®). The core sutures were: (1) Pennington modified Kessler (3-0), (2) Double Pennington modified Kessler (3-0), (3) 4-strand Savage (3-0), (4) 4-strand Savage (4-0), and (5) 6-strand Savage (4-0). Repairs were compared as paired in regard to one variable: the number of core suture strands, the suture calibre, or the suture configuration. Biomechanical differences between the repair groups started during the linear region, with the yield force and stiffness increasing along with the number of core suture strands. All three variables influenced the strain at the yield point. Thus, the strength of the intact repair can be improved by modifying the core suture. In all repairs gap formation started near the yield point after failure of the peripheral suture. The yield force represents the strength of the intact repair composite and should be considered the strength of the tendon repair.

Measurement of the Spatial Redistribution of Water in Rabbit Achilles Tendon in Response to Static Tensile Loading

2004 ◽  
Vol 126 (5) ◽  
pp. 651-656 ◽  
Author(s):  
K. G. Helmer ◽  
J. Wellen ◽  
P. Grigg ◽  
C. H. Sotak
Keyword(s):  
Load Condition ◽  
Tensile Loading ◽  
Complex Model ◽  
Load Application ◽  
Steady Increase ◽  
Proton Density ◽  
The Core ◽  
Static Tensile Loading ◽  
Static Tensile

The redistribution of water in response to static tensile loading was investigated in rabbit Achilles tendons in vitro. The distribution of water was measured along a radially oriented line, using a one-dimensional proton-density map created from fits to diffusion-weighted magnetic resonance (MR) data. Water movements were measured during application of tensile loads of 5N (N=7) and 10N (N=6). Water distribution along the line was measured before loading and up to 42 min after load application. Static loading with either 5 or 10N loads caused a steady increase in proton density in the outside edge (rim) of the tendon. The 10N load lowered the proton density in the core of the tendon, but did so in a single step that was observed when the load was applied. The 5N load caused no change in proton density in the core region. The immediate redistribution from the core was statistically significant for the 10N load, but not the 5N load application. Statistically significant within-group proton-density increases were observed in the rim after 42 min postload for all tendons irrespective of load condition. The rate of proton-density postload increase at the rim region did not depend upon load. The rate for the 5N load case was 0.010±0.002 min−1 and 0.007±0.002 min−1 in the 10N case. Thus, while generally consistent with an extrusion model, the data show other features that argue for a more complex model.

Striking at the Core

2020 ◽  
pp. 380-398
Author(s):  
Frank Jake Kachanoff ◽  
Michael J. A. Wohl ◽  
Donald M. Taylor
Keyword(s):  
Well Being ◽  
Self Determination Theory ◽  
Psychological Needs ◽  
Integrated Model ◽  
Self Determination ◽  
The Core ◽  
Victim Group ◽  
Negative Effect ◽  
Group Members ◽  
Personal Level

This chapter presents an integrated model of psychological needs among victimized groups, building on self-determination theory. Extending the model of needs-based reconciliation and other work on needs among victim groups, the authors posit that collective victimization frustrates basic needs for relatedness, competence, and autonomy. They review empirical findings showing that the frustration of these needs on the collective level frustrates related needs on the personal level as well, and in turn have a negative effect on psychological well-being and willingness for reconciliation. The chapter focuses in particular on collective autonomy, which is central to many experiences of collective victimization as well as reconciliation attempts. In order to increase victim group members’ willingness to reconcile, it is important to take into consideration all three needs identified in this model and present apologies and other steps toward reconciliation in a way that satisfies these needs.

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