scholarly journals Probing the in-plane liquid-like behavior of liquid crystal elastomers

2021 ◽  
Vol 7 (25) ◽  
pp. eabe9495
Author(s):  
Haruki Tokumoto ◽  
Hao Zhou ◽  
Asaka Takebe ◽  
Kazutaka Kamitani ◽  
Ken Kojio ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Mechanical Energy ◽  
True Stress ◽  
Sectional Area ◽  
Cross Sectional ◽  
True Stresses ◽  
State Of Matter ◽  
Liquid Crystal Elastomers ◽  
Isotropic Solids ◽  
Strain Direction

When isotropic solids are unequally stretched in two orthogonal directions, the true stress (force per actual cross-sectional area) in the larger strain direction is typically higher than that in the smaller one. We show that thiol-acrylate liquid crystal elastomers with polydomain texture exhibit an unusual tendency: The true stresses in the two directions are always identical and governed only by the area change in the loading plane, independently of the combination of imposed strains in the two directions. This feature proves a previously unidentified state of matter that can vary its shape freely with no extra mechanical energy like liquids when deformed in the plane. The theory and simulation that explain the unique behavior are also provided. The in-plane liquid-like behavior opens doors for manifold applications, including wrinkle-free membranes and adaptable materials.

Tensile and Compressive Creep Behavior of Magnesium Alloy AZ91D

2013 ◽  
Vol 313-314 ◽  
pp. 98-102
Author(s):  
Supamard Sujatanond ◽  
Yoshiharu Mutoh ◽  
Yukio Miyashita ◽  
Yuichi Otsuka
Keyword(s):  
Magnesium Alloy ◽  
Creep Curve ◽  
Estimation Method ◽  
True Stress ◽  
Cross Sectional Area ◽  
Secondary Creep ◽  
Sectional Area ◽  
Cross Sectional ◽  
Compressive Creep ◽  
Alloy Az91d

Tensile and compressive creep tests of the extruded magnesium alloy AZ91D were carried out in vacuum at 150°C under constant engineering stresses ranged from 60 to 150 MPa. From the test results, the secondary creep rate in tension was found to be significantly higher than that in compression. Moreover, the estimation method of creep curve under a constant true stress was proposed by considering the reduction of cross sectional area during tensile loading where the specimen cross-sectional area and length were measured periodically until the end of creep test. The creep curve under a constant true stress obtained in the present study was still different between tensile and compressive loadings. Therefore, it should be noted that the different creep curves and creep exponents should be used in the creep deformation analysis of structures.

Biomechanical simulation of an amputated forearm with and without a prosthesis

2000 ◽  
Vol 214 (3) ◽  
pp. 287-299 ◽  
Author(s):  
Y Meimoun ◽  
J Mizrahi
Keyword(s):  
Mechanical Energy ◽  
Dynamic Performance ◽  
Interesting Case ◽  
Rigid Bodies ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Biomechanical Simulation ◽  
Flexion Moment ◽  
Muscle Cross Sectional Area

In this study a computer simulation was developed for analysing the performance of a below-elbow amputated forearm, with and without a prosthesis. The upper extremity was represented in terms of two rigid bodies, the arm and the forearm. Five muscles, three elbow flexors and two elbow extensors, were included in the model. The muscle model used was the five-component model, including the contractile, parallel, series and viscous elements and the muscle mass. Dynamic and static simulations were conducted, with and without prosthesis, to study parametrically the effects of stump length, tendon distal transfer, tendon or muscle shortening and muscle physiological cross-sectional area. The performance measures which were the most affected included flexion moment of the forearm about the elbow, muscle moment, force in the joint, flexion rate and mechanical energy. The simulation presented an interesting case when the amputation site is more proximal than the anatomical insertion point of a muscle, necessitating shortening of the muscle to avoid the situation where it exerts no force. It was also found that, of the changeable parameters, the most beneficial changes in the forearm parameters for improved dynamic performance were: (a) tendon distal transfer and (b) increase of the muscle cross-sectional area, the latter achievable by means of physical training.

Pelvic Canal Narrowing Caused by Triple Pelvic Osteotomy in the Dog

1994 ◽  
Vol 07 (03) ◽  
pp. 110-113 ◽  
Author(s):  
D. L. Holmberg ◽  
M. B. Hurtig ◽  
H. R. Sukhiani
Keyword(s):  
Postoperative Complications ◽  
Pelvic Osteotomy ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Canal Width ◽  
Operative Complications ◽  
Post Operative Complications

SummaryDuring a triple pelvic osteotomy, rotation of the free acetabular segment causes the pubic remnant on the acetabulum to rotate into the pelvic canal. The resulting narrowing may cause complications by impingement on the organs within the pelvic canal. Triple pelvic osteotomies were performed on ten cadaver pelves with pubic remnants equal to 0, 25, and 50% of the hemi-pubic length and angles of acetabular rotation of 20, 30, and 40 degrees. All combinations of pubic remnant lengths and angles of acetabular rotation caused a significant reduction in pelvic canal-width and cross-sectional area, when compared to the inact pelvis. Zero, 25, and 50% pubic remnants result in 15, 35, and 50% reductions in pelvic canal width respectively. Overrotation of the acetabulum should be avoided and the pubic remnant on the acetabular segment should be minimized to reduce postoperative complications due to pelvic canal narrowing.When performing triple pelvic osteotomies, the length of the pubic remnant on the acetabular segment and the angle of acetabular rotation both significantly narrow the pelvic canal. To reduce post-operative complications, due to narrowing of the pelvic canal, overrotation of the acetabulum should be avoided and the length of the pubic remnant should be minimized.

DETERMINATION OF THE FUNCTION OF THE ROD’S CROSS-SECTIONAL AREA USING VIBRATION EIGENFREQUENCIES

2020 ◽  
Vol 0 (4) ◽  
pp. 19-24
Author(s):  
I.M. UTYASHEV ◽  
◽  
A.A. AITBAEVA ◽  
A.A. YULMUKHAMETOV ◽  
◽  
...  
Keyword(s):  
Cross Sectional Area ◽  
Variable Cross ◽  
Sectional Area ◽  
Longitudinal Vibrations ◽  
Cross Sectional ◽  
Method Error ◽  
Various Boundary Conditions ◽  
Elastic Fixation ◽  
Crosssectional Area

The paper presents solutions to the direct and inverse problems on longitudinal vibrations of a rod with a variable cross-sectional area. The law of variation of the cross-sectional area is modeled as an exponential function of a polynomial of degree n . The method for reconstructing this function is based on representing the fundamental system of solutions of the direct problem in the form of a Maclaurin series in the variables x and λ. Examples of solutions for various section functions and various boundary conditions are given. It is shown that to recover n unknown coefficients of a polynomial, n eigenvalues are required, and the solution is dual. An unambiguous solution was obtained only for the case of elastic fixation at one of the rod’s ends. The numerical estimation of the method error was made using input data noise. It is shown that the error in finding the variable crosssectional area is less than 1% with the error in the eigenvalues of longitudinal vibrations not exceeding 0.0001.

Changes in the parameters of nasal breathing and parameters of the upper respiratory tract during orthognathic operations in patients with II and III skeletal class of jaw anomalies

2020 ◽  
pp. 22-27
Author(s):  
S.Sh. Gammadaeva ◽  
M.I. Misirkhanova ◽  
A.Yu. Drobyshev
Keyword(s):  
Respiratory Tract ◽  
Nasal Cavity ◽  
Nasal Septum ◽  
Cross Sectional Area ◽  
Upper Respiratory Tract ◽  
Sectional Area ◽  
Nasal Breathing ◽  
Cross Sectional ◽  
Skeletal Class ◽  
Upper Respiratory

The study analyzed the functional parameters of nasal breathing, linear parameters of the nasal aperture, nasal cavity and nasopharynx, volumetric parameters of the upper airways in patients with II and III skeletal class of jaw anomalies before and after orthognathic surgery. The respiratory function of the nose was assessed using a rhinomanometric complex. According to rhinoresistometry data, nasal resistance and hydraulic diameter were assessed. According to the data of acoustic rhinometry, the minimum cross-sectional area along the internal valve, the minimum cross-sectional area on the head of the inferior turbinate and nasal septum and related parameters were estimated. According to the CBCT data, the state of the nasal septum, the inferior turbinates, the nasal aperture, the state of the nasal cavity, and the linear values of the upper respiratory tract (nasopharynx) were analyzed. The patients were divided into 4 groups according to the classification of the patency of the nasal passages by

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