Measuring the Young’s Relaxation Modulus of PDMS Using Stress Relaxation Nanoindentation

2009 ◽  
Vol 1222 ◽  
Author(s):  
Ping Du ◽  
Hongbing Lu ◽  
Xin Zhang
Keyword(s):  
Stress Relaxation ◽  
Reaction Force ◽  
Relaxation Modulus ◽  
Experimental Tests ◽  
Constitutive Law ◽  
Time Data ◽  
Flat Punch ◽  
Pdms Film ◽  
Bending Tests

AbstractThe Young’s relaxation modulus of Polydimethylsiloxane (PDMS) film specimens was measured by the nanoindenter with a flat punch indenter. In the stress relaxation test, the initial ramp part was carefully considered to develop an accurate viscoelastic contact model. This model was used to fit the load-time data from the experimental tests. The resulting relaxation function was expressed by a general Maxwell equation. In addition, a case study of PDMS micropillar bending tests was performed, and the viscoelastic constitutive law was applied to develop an analytical solution of the reaction force. The results show that the reaction force calculated from the corrected model is generally agreed well with the experimental data.

scholarly journals APPLICATION OF DOMAIN INTEGRATED DESIGN METHODOLOGY FOR BIO-INSPIRED DESIGN- A CASE STUDY OF SUTURE PIN DESIGN

2021 ◽  
Vol 1 ◽  
pp. 487-496
Author(s):  
Pavan Tejaswi Velivela ◽  
Nikita Letov ◽  
Yuan Liu ◽  
Yaoyao Fiona Zhao
Keyword(s):  
Cross Sections ◽  
Design Methodology ◽  
Reaction Force ◽  
Integrated Design ◽  
Total Deformation ◽  
Insertion Force ◽  
Force Reaction ◽  
The Moment ◽  
Work Done

AbstractThis paper investigates the design and development of bio-inspired suture pins that would reduce the insertion force and thereby reducing the pain in the patients. Inspired by kingfisher's beak and porcupine quills, the conceptual design of the suture pin is developed by using a unique ideation methodology that is proposed in this research. The methodology is named as Domain Integrated Design, which involves in classifying bio-inspired structures into various domains. There is little work done on such bio-inspired multifunctional aspect. In this research we have categorized the vast biological functionalities into domains namely, cellular structures, shapes, cross-sections, and surfaces. Multi-functional bio-inspired structures are designed by combining different domains. In this research, the hypothesis is verified by simulating the total deformation of tissue and the needle at the moment of puncture. The results show that the bio-inspired suture pin has a low deformation on the tissue at higher velocities at the puncture point and low deformation in its own structure when an axial force (reaction force) is applied to its tip. This makes the design stiff and thus require less force of insertion.

STRESS RELAXATION OF MAGNETORHEOLOGICAL FLUIDS

2002 ◽  
Vol 16 (17n18) ◽  
pp. 2655-2661
Author(s):  
W. H. LI ◽  
G. CHEN ◽  
S. H. YEO ◽  
H. DU
Keyword(s):  
Stress Relaxation ◽  
Viscoelastic Model ◽  
Relaxation Modulus ◽  
Damping Function ◽  
Mr Fluids ◽  
Large Step ◽  
Linear Viscoelastic ◽  
Predicted Values ◽  
Two Parameters ◽  
Step Strain

In this paper, the experimental and modeling study and analysis of the stress relaxation characteristics of magnetorheological (MR) fluids under step shear are presented. The experiments are carried out using a rheometer with parallel-plate geometry. The applied strain varies from 0.01% to 100%, covering both the pre-yield and post-yield regimes. The effects of step strain, field strength, and temperature on the stress modulus are addressed. For small step strain ranges, the stress relaxation modulus G(t,γ) is independent of step strain, where MR fluids behave as linear viscoelastic solids. For large step strain ranges, the stress relaxation modulus decreases gradually with increasing step strain. Morever, the stress relaxation modulus G(t,γ) was found to obey time-strain factorability. That is, G(t,γ) can be represented as the product of a linear stress relaxation G(t) and a strain-dependent damping function h(γ). The linear stress relaxation modulus is represented as a three-parameter solid viscoelastic model, and the damping function h(γ) has a sigmoidal form with two parameters. The comparison between the experimental results and the model-predicted values indicates that this model can accurately describe the relaxation behavior of MR fluids under step strains.

Effect of Cure State on Stress Relaxation in 3501-6 Epoxy Resin

1997 ◽  
Vol 119 (3) ◽  
pp. 262-265 ◽  
Author(s):  
S. R. White ◽  
A. B. Hartman
Keyword(s):  
Stress Relaxation ◽  
Epoxy Resin ◽  
Creep Compliance ◽  
Numerical Technique ◽  
Matrix Material ◽  
Relaxation Modulus ◽  
Master Curves ◽  
Creep Tests ◽  
Three Point Bending ◽  
Direct Inversion

Little experimental work has been done to characterize how the viscoelastic properties of composite material matrix resins develop during cure. In this paper, the results of a series of creep tests carried out on 3501–6 epoxy resin, a common epoxy matrix material for graphite/epoxy composites, at several different cure states is reported. Beam specimens were isothermally cured at increasing cure temperatures to obtain a range of degrees of cure from 0.66 to 0.99. These specimens were then tested in three-point bending to obtain creep compliance over a wide temperature range. The master curves and shift functions for each degree of cure case were obtained by time-temperature superposition. A numerical technique and direct inversion were used to calculate the stress relaxation modulus master curves from the creep compliance master curves. Direct inversion was shown to be adequate for fully cured specimens, however it underpredicts the relaxation modulus and the transition for partially cured specimens. Correlations with experimental stress relaxation data from Kim and White (1996) showed that reasonably accurate results can be obtained by creep testing followed by numerical conversion using the Hopkins-Hamming method.

Innovative real-time sensing of flow dynamics in groundwater and sediments to map contaminant spreading

2021 ◽  
Author(s):  
Goedele Verreydt ◽  
Niels Van Putte ◽  
Timothy De Kleyn ◽  
Joris Cool ◽  
Bino Maiheu
Keyword(s):  
Surface Water ◽  
Groundwater Flow ◽  
Real Time ◽  
Flow Direction ◽  
Flow Dynamics ◽  
Sensor Data ◽  
Time Data ◽  
Mass Fluxes ◽  
First Case

<p>Groundwater dynamics play a crucial role in the spreading of a soil and groundwater contamination. However, there is still a big gap in the understanding of the groundwater flow dynamics. Heterogeneities and dynamics are often underestimated and therefore not taken into account. They are of crucial input for successful management and remediation measures. The bulk of the mass of mass often is transported through only a small layer or section within the aquifer and is in cases of seepage into surface water very dependent to rainfall and occurring tidal effects.</p><p> </p><p>This study contains the use of novel real-time iFLUX sensors to map the groundwater flow dynamics over time. The sensors provide real-time data on groundwater flow rate and flow direction. The sensor probes consist of multiple bidirectional flow sensors that are superimposed. The probes can be installed directly in the subsoil, riverbed or monitoring well. The measurement setup is unique as it can perform measurements every second, ideal to map rapid changing flow conditions. The measurement range is between 0,5 and 500 cm per day.</p><p> </p><p>We will present the measurement principles and technical aspects of the sensor, together with two case studies.</p><p> </p><p>The first case study comprises the installation of iFLUX sensors in 4 different monitoring wells in a chlorinated solvent plume to map on the one hand the flow patterns in the plume, and on the other hand the flow dynamics that are influenced by the nearby popular trees. The foreseen remediation concept here is phytoremediation. The sensors were installed for a period of in total 4 weeks. Measurement frequency was 5 minutes. The flow profiles and time series will be presented together with the determined mass fluxes.</p><p> </p><p>A second case study was performed on behalf of the remediation of a canal riverbed. Due to industrial production of tar and carbon black in the past, the soil and groundwater next to the small canal ‘De Lieve’ in Ghent, Belgium, got contaminated with aliphatic and (poly)aromatic hydrocarbons. The groundwater contaminants migrate to the canal, impact the surface water quality and cause an ecological risk. The seepage flow and mass fluxes of contaminants into the surface water were measured with the novel iFLUX streambed sensors, installed directly in the river sediment. A site conceptual model was drawn and dimensioned based on the sensor data. The remediation concept to tackle the inflowing pollution: a hydraulic conductive reactive mat on the riverbed that makes use of the natural draining function of the waterbody, the adsorption capacity of a natural or secondary adsorbent and a future habitat for micro-organisms that biodegrade contaminants. The reactive mats were successfully installed and based on the mass flux calculations a lifespan of at least 10 years is expected for the adsorption material.  </p>

Move Real-Time Data Analytics to the Cloud: A Case Study on Heron to Dataflow Migration

2021 ◽  
Author(s):  
Huijun Wu ◽  
Xiaoyao Qian ◽  
Aleks Shulman ◽  
Kanishk Karanawat ◽  
Tushar Singh ◽  
...  
Keyword(s):  
Real Time ◽  
Data Analytics ◽  
Time Data ◽  
Real Time Data

scholarly journals Stress relaxation of the infusion tube with a pressure sensor

2018 ◽  
Vol 232 ◽  
pp. 04021
Author(s):  
Aoru Xie
Keyword(s):  
Stress Relaxation ◽  
Stress Distribution ◽  
Contact Pressure ◽  
Pressure Sensor ◽  
Reaction Force ◽  
Infusion Tube

We studied stress relaxation of the infusion tube with a pressure sensor using FEA method. The stress distribution in the tube, the contact pressure on the wall of the pressure sensor, the decay of the reaction force on the wall of the pressure sensor were determined, respectively. Due to the stress relaxation of the infusion tube, the reaction force generated by the tube deformation was decreased by over 75% as compared with the original reaction force in the first several seconds after the infusion tube was set into the pressure sensor.

scholarly journals Experimental Investigations of Interactions between Sand Wave Movements, Flow Structure, and Individual Aquatic Plants in Natural Rivers: A Case Study of Potamogeton Pectinatus L.

Water ◽  
2018 ◽  
Vol 10 (9) ◽  
pp. 1166 ◽  
Author(s):  
Łukasz Przyborowski ◽  
Anna Łoboda ◽  
Robert Bialik
Keyword(s):  
Flow Velocity ◽  
Three Dimensional ◽  
Potamogeton Pectinatus ◽  
Sand Wave ◽  
Experimental Investigations ◽  
Cross Sectional ◽  
Bending Tests ◽  
Long Duration ◽  
Elevation Changes

Long-duration measurements were performed in two sandy bed rivers, and three-dimensional (3D) flow velocity and bottom elevation changes were measured in a vegetated area and in a clear region of a river. Detailed flow velocity profiles downstream and upstream of a single specimen of Potamogeton pectinatus L. were obtained and the bed morphology was assessed. Potamogeton plants gathered from each river were subjected to tensile and bending tests. The results show that the existence of the plants was influenced by both bottom and flow conditions, as the plants were located where water velocity was lower by 12% to 16% in comparison to clear region. The characteristics of the flow and sand forms depended on the cross-sectional arrangement of the river, e.g., dunes were approximately four times higher in the middle of the river than in vegetated regions near the bank. Furthermore, the studied hydrophytes were too sparse to affect water flow and had no discernible impact on the sand forms’ movements. The turbulent kinetic energy downstream of a single plant was reduced by approximately 25%. Additionally, the plants’ biomechanical characteristics and morphology were found to have adjusted to match the river conditions.

A Direct Experimental Determination of the Elastic Contribution of Chain Entangling in a Tightly Crosslinked Elastomer

1982 ◽  
Vol 55 (1) ◽  
pp. 62-65
Author(s):  
W. Batsberg ◽  
O. Kramer
Keyword(s):  
Stress Relaxation ◽  
Elastic Equilibrium ◽  
Relaxation Modulus ◽  
Chain Scission ◽  
Experimental Result ◽  
Strained State ◽  
Equilibrium Stress ◽  
Linear Chains ◽  
Network Methods

Abstract The experimental result, that the equilibrium force is nearly equal to the pseudoequilibrium force immediately prior to quenching and irradiation, allows the following conclusions: (1) Chain scission during crosslinking is not a serious problem. (2) The network of highly entangled linear chains is effectively at elastic equilibrium immediately prior to crosslinking in the strained state. This would not be the case if the entangled structure remained untrapped. (3) The effect of chain entangling in tightly crosslinked elastomers is large, also at elastic equilibrium. In fact, it is almost quantitatively equal to the pseudo-equilibrium stress relaxation modulus of the uncrosslinked linear polymer. This result is in agreement with the results from the Langley and the two-network methods.

scholarly journals PROFIL FIJAI WARGA BELAJAR PROGRAM KESETARAAN PAKET A SANGGAR KEGIATAN BELAJAR (SKB)

2020 ◽  
Vol 2 (2) ◽  
pp. 111-115
Author(s):  
Putri Mardayani ◽  
Rufran Zulkarnain ◽  
Suardi Jasma
Keyword(s):  
Data Collection ◽  
Qualitative Method ◽  
Family Background ◽  
Traffic Light ◽  
Time Data ◽  
Light Traffic ◽  
Data Presentation ◽  
Traffic Lights ◽  
Data Validity

This study was aimed at describing the profile of Fijai, a student of program kesetaraan paket A Sanggar Kegiatan Belajar of Bengkulu municipality(case study on Fijai who is also a clown). This study used qualitative method. Data collection was done by interview , documentation, and observation. The subjects of this study included Fijai's parents and Fijai's tutor at program kesetaraan paket A Sanggar Kegiatan Belajar of Bengkulu municipality. Data validity was examined using triangulation of subject, technique and time. Data were analyzed through three steps which were data reduction, data presentation, and conclusion drawing. From the results, Fijai's profile was as follows. Firstly, how was Fijai's family background? His parents did not have a job except to help him work as a clown. Fijai got Rp 2,500,000/month from his job as a clown. Secondly, how was his study at program kesetaraan paket A Sanggar Kegiatan Belajar of Bengkulu municipality? He always attended the class once a week. Thirdly,how did he do his job as a clown? He started his job from 10 A.M. until 5 P.M. He moved around while doing his job, sometimes at Suka Merindu traffic light, traffic light near the roundabout, and other traffic lights. Fourthly,how was his parents' response on his education and his job as a clown? His parents agreed with his education at SKB and his job as a clown did not disturb his education. Fively,how was his tutor's response on his education and his job as a clown? According to his tutor he had highly enthusiasm in studying, he always attended the class once a week. Sixly, how was his achievement in package A program? His achievement was increasing per semester. Keywords : The profile of Fijai, student, package A equivalence program

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