Variation of the instantaneous modulus of elasticity of certain types of plastics under long-time static loads

A brief overview of the features of the fatigue resistance of some steels is given with the selection of terms, concepts and numerical data necessary for the subsequent compilation and verification of the equivalence criterion in relation to assessing the ability of structural materials to resist fatigue for a long time under the action of certain combinations of alternating and static loads. Keywords: regular loading cycle, extremely stressed state, static stressed state, bending, torsion, biaxial static tension. [email protected]

Modelling variation in wood stiffness of Pinus ponderosa using static bending and acoustic measurements

Forestry An International Journal of Forest Research ◽

10.1093/forestry/cpaa030 ◽

2020 ◽

Author(s):

Damon Vaughan ◽

David Auty ◽

Joseph Dahlen ◽

Andrew J Sánchez Meador ◽

Kurt H Mackes

Keyword(s):

Pinus Ponderosa ◽

Ponderosa Pine ◽

Modulus Of Elasticity ◽

Forest Restoration ◽

Radial Profile ◽

Standing Tree ◽

Static Modulus ◽

Wood Stiffness ◽

Long Time ◽

Static Modulus Of Elasticity

Abstract Wood removed in Southwestern US forest restoration treatments currently has limited markets and thus low value. One important property of wood in structural products is its stiffness (measured as modulus of elasticity), which is known to vary systematically within trees. Directly measuring wood stiffness is expensive, time consuming and destructive. Therefore, we tested samples of ponderosa pine (Pinus ponderosa var. scopulorum Engelm.) from northern Arizona destructively in bending and also non-destructively using acoustic velocity (AV) methods. In total, we tested multiple pith-to-bark small clear (2.54 × 2.54 × 40.64 cm) samples from up to four heights in 103 trees. We first measured the standing-tree AV of sample trees, then the AV of small clear samples, and finally measured wood stiffness using three point static bending tests. We found that a Michaelis–Menten curve was a good fit to the radial profile of wood stiffness, with a steep increase outward from the pith that approached an asymptote. The AV of small clear samples, coupled with measured volumetric density values, approximated the static modulus of elasticity values with high accuracy (r2 = 0.86). At the stand level, a model predicting standing tree AV from tree morphology fit the data well (r2 = 0.77). Results indicate that southwestern ponderosa pine contains outerwood with relatively high stiffness that could be suitable for structural products. However, when assessed using wood stiffness, the trees take a long time to reach maturity (~50 years) and thus the corewood proportion is large. AV measurements are a good way to assess variability within and among stands and thus could be employed to segregate the resource by expected stiffness values. Segregation could help identify stands not suitable for structural uses and direct them toward more appropriate products.

Studying the Effect of Temperature, Static Load and Nanodimensional Defects on the Mechanical Properties of Polyethylene Film at Uniaxial Extension

Materials Science Forum ◽

10.4028/www.scientific.net/msf.992.325 ◽

2020 ◽

Vol 992 ◽

pp. 325-330

Author(s):

Anatoliy I. Kupchishin ◽

Marat N. Niyazov ◽

Buvkhan G. Taipova

Keyword(s):

Mechanical Properties ◽

Radiation Dose ◽

Electron Irradiation ◽

Modulus Of Elasticity ◽

Static Load ◽

Uniaxial Extension ◽

Exponential Model ◽

Effect Of Temperature ◽

Static Loads ◽

Different Temperatures

The dependence of strain on temperature in polyethylene under various static loads and exposure doses has been studied experimentally. After electron irradiation with doses of 10, 30, 50, 70, and 100 kGy, significant changes in the mechanical properties were observed, which are caused by the formation of nanodefects in the material’s structure. With increasing radiation dose, PE deformation at different temperatures decreases due to destruction in the structure of the polymer material. At the same time, the return deformation increases with increasing dose, indicating a change in the modulus of elasticity (E). The increase in E occurs due to the decrease in the distance between macromolecules in the irradiated structure of the sample. The obtained curves for both non-irradiated and irradiated material are described in an exponential model satisfactorily.

Hubungan antara Posisi Kerja dan Usia dengan Keluhan Muskuloskeletal pada Pekerja Penyapu Jalan di Kecamatan Wenang Kota Manado

Medical Scope Journal ◽

10.35790/msj.1.1.2019.26635 ◽

2019 ◽

Vol 1 (1) ◽

Author(s):

Brigita G. Imbar ◽

Lerry F. Suoth ◽

Afnal Asrifuddin

Keyword(s):

Skeletal Muscles ◽

P Value ◽

Musculoskeletal Complaints ◽

Weak Correlation ◽

Static Loads ◽

The Road ◽

Long Time ◽

Body Map ◽

R Value ◽

Spearman Test

Abstract: Musculoskeletal complaints could occur in parts of skeletal muscle ranging from very mild to very severe. If skeletal muscles receive static loads for a long time, muscle pain can occur. Street sweeper is a person whose job is to clean the road by using a broom. This study was aimed to determine whether there were relationships between work position and age and musculoskeletal complaints among street sweepers at Kecamaatan Wenang, Manado. This was a descriptive study. We used REBA for measuring work position; interview for age; and Nordic body map for musculoskeletal complaints. The Spearman test of the correlation between work position and musculoskeletal complaints obtained a p-value of 0.003 and an r-value of 0.381 with sufficiently weak correlation. Moreover, the Spearman test of the correlation between age and musculoskeletal complaints showed a p-value of 0.000 and an r-value of 0.529 with a moderate correlation. In conclusion, there was a relationship between work position and musculoskeletal complaints as well as between age and musculoskeletal complaints among street sweeper at Kecamatan Wenang, Manado.Keywords: work position, age, musculoskeletal complaints Abstrak: Keluhan muskuloskeletal dirasakan oleh seseorang atau pekerja mulai dari keluhan sangat ringan sampai sangat hebat. Jika otot menerima beban statis untuk waktu yang cukup lama, maka dapat terjadi nyeri otot. Penyapu jalan bertugas untuk membersihkan jalanan dengan menggunakan sapu. Penelitian ini bertujuan untuk mengetahui adanya hubungan antara posisi kerja dan usia dengan keluhan muskuloskeletal pada pekerja penyapu jalan di Kecamatan Wenang Kota Manado. Jenis penelitian ialah deskriptif. Instrumen yang digunakan untuk pengukuran posisi kerja ialah REBA, sedangkan untuk pengukuran usia ialah wawancara dan untuk pengukuran keluhan muskuloskeletal menggunakan nordic body map. Hasil uji korelasi Spearman antara posisi kerja dan keluhan muskuloskeletal mendapatkan nilai p=0,003 dan nilai r=0,381 dengan kolerasi cukup lemah. Selain itu hasil uji korelasi antara usia dengan keluhan muskuloskeletal mendapatkan nilai p=0,000 dan nilai r=0,529 dengan korelasi sedang. Simpulan penelitian ini yaitu terdapat hubungan bermakna antara posisi kerja dan usia dengan keluhan muskuloskeletal pada pekerja penyapu jalan di Kecamatan Wenang.Kata kunci: posisi kerja, usia, keluhan musculoskeletal

Biomechanical Tissue Properties as an Indicator of Organ Vitality Prior to Transplantations

The International Journal of Artificial Organs ◽

10.1177/039139889401700707 ◽

1994 ◽

Vol 17 (7) ◽

pp. 408-411 ◽

Cited By ~ 1

Author(s):

E. Shtengold ◽

E. Godin ◽

K. Affeld

Keyword(s):

Mechanical Properties ◽

Steady State ◽

Theoretical Analysis ◽

Modulus Of Elasticity ◽

Local Deformation ◽

Warm Ischemia ◽

Tissue Properties ◽

New Apparatus ◽

Instantaneous Modulus ◽

Cylindrical Element

An organ's vitality prior to transplatation can be evaluated by analysis of its mechanical properties. A new apparatus was designed to measure these properties. The organ to be tested is placed in a reservoir with saline and submitted to the load of a cylindrical element. The load is applied in a stepwise mode and results in a small local deformation of the organ. This deformation is identical to the displacement of the cylinder and is measured as a function of time. This is compared to a theoretical analysis of the deformation of a viscoelastic halfspace. This theory was used to interpret the results of experiments which were carried out on eight rabbit kidneys. The instantaneous modulus of elasticity reaches a maximum within 15 minutes, then decreases and reaches a steady state after 30 minutes of warm ischemia. The method is easy to apply and appears to be useful for the quantification of an organ's vitality and in particular recognizes the level of the organ's edema before transplantation

Compressive and Tensile Elastic Properties of Concrete: Empirical Factors in Span Reinforced Structures Design

Materials ◽

10.3390/ma14247578 ◽

2021 ◽

Vol 14 (24) ◽

pp. 7578

Author(s):

Alexander Sergeevich Korolev ◽

Anastasia Kopp ◽

Denis Odnoburcev ◽

Vladislav Loskov ◽

Pavel Shimanovsky ◽

...

Keyword(s):

Elastic Properties ◽

Modulus Of Elasticity ◽

Elasticity Modulus ◽

Steel Reinforcement ◽

Linear Deformation ◽

Elastic Deformations ◽

Non Linear ◽

Instantaneous Modulus

Concretes with the same strength can have various deformability that influences span structures deflection. In addition, a significant factor is the non-linear deformation of concrete dependence on the load. The main deformability parameter of concrete is the instantaneous modulus of elasticity. This research aims to evaluate the relation of concrete compressive and tensile elastic properties testing. The beam samples at 80 × 140 × 1400 cm with one rod Ø8 composite or Ø10 steel reinforcement were experimentally tested. It was shown that instantaneous elastic deformations under compression are much lower than tensile. Prolonged elastic deformations under compression are close to tensile. It results in compressive elasticity modulus exceeding the tensile. The relation between these moduli is proposed. The relation provides operative elasticity modulus testing by the bending tensile method. The elasticity modulus’s evaluation for the reinforced span structures could be based only on the bending testing results. A 10% elasticity modulus increase, which seems not significant, increases at 30–40% the stress of the reinforced span structures under load and 30% increases the cracking point stress.

Creep of Eight Years Old Cement Paste

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.825.41 ◽

2016 ◽

Vol 825 ◽

pp. 41-44

Author(s):

Pavel Padevět ◽

Petr Bittnar

Keyword(s):

Portland Cement ◽

Cement Paste ◽

Material Properties ◽

Modulus Of Elasticity ◽

Very Old ◽

Long Time ◽

Old Cement Paste

The paper presents research of shrinkage of the cement paste. The tested specimens wereprepared eight years ago from Portland cement CEM II and water. The observation was focused onthe evolution of creep in long time and for very old material. The material properties like a compressionstrength and Modulus of elasticity were observed according with the creep.

The Advantages of High-density Polymer CAD/CAM Interim Restorations in Oral Implantology

Materiale Plastice ◽

10.37358/mp.17.1.4779 ◽

2017 ◽

Vol 54 (1) ◽

pp. 32-36 ◽

Cited By ~ 2

Author(s):

Claudia Florina Andreescu ◽

Doina Lucia Ghergic ◽

Oana Botoaca ◽

Horia Mihail Barbu ◽

Ioan Sebastian Cernusca Mitariu ◽

...

Keyword(s):

Flexural Strength ◽

Polymethyl Methacrylate ◽

Modulus Of Elasticity ◽

Fracture Resistance ◽

Computer Assisted ◽

Computer Assisted Design ◽

Long Time ◽

Cad Cam ◽

Oral Implantology

Fabrication of temporary restorations is an essential part in dentistry and especially in oral implantology. Polymethyl methacrylate is used for a long time as material for temporary restorations and many improvements has been done to increase its properties, especially fracture resistance. Crosslinking and computer-assisted design/computer-assisted machining permit fabrication of long-term temporary restorations with flexural strength high enough and good modulus of elasticity that do not fracture easily under functional loads.

200kv superconducting cryo electron microscope

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100127645 ◽

1987 ◽

Vol 45 ◽

pp. 642-643

Author(s):

M. Iwatsuki ◽

Y. Kokubo ◽

Y. Harada ◽

J. Lehman

Keyword(s):

Electron Microscope ◽

Structure Analysis ◽

Organic Materials ◽

Strong Interactions ◽

Specimen Preparation ◽

Great Effort ◽

Electron Microscopic ◽

Crystal Fields ◽

Special Skill ◽

Long Time

In recent years, the electron microscope has been significantly improved in resolution and we can obtain routinely atomic-level high resolution images without any special skill. With this improvement, the structure analysis of organic materials has become one of the interesting targets in the biological and polymer crystal fields.Up to now, X-ray structure analysis has been mainly used for such materials. With this method, however, great effort and a long time are required for specimen preparation because of the need for larger crystals. This method can analyze average crystal structure but is insufficient for interpreting it on the atomic or molecular level. The electron microscopic method for organic materials has not only the advantage of specimen preparation but also the capability of providing various information from extremely small specimen regions, using strong interactions between electrons and the substance. On the other hand, however, this strong interaction has a big disadvantage in high radiation damage.

A Stationary Solution of High-Energy Electron Reflection (HEER) for An Arbitrary Surface

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100135472 ◽

1990 ◽

Vol 48 (2) ◽

pp. 374-375

Author(s):

YIQUN MA

Keyword(s):

Stationary Solution ◽

High Energy ◽

Bloch Wave ◽

Dynamical Theory ◽

High Energy Electron ◽

Bulk Materials ◽

Periodic Surface ◽

Electron Transmission ◽

Electron Reflection ◽

Long Time

For a long time, the development of dynamical theory for HEER has been stagnated for several reasons. Although the Bloch wave method is powerful for the understanding of physical insights of electron diffraction, particularly electron transmission diffraction, it is not readily available for the simulation of various surface imperfection in electron reflection diffraction since it is basically a method for bulk materials and perfect surface. When the multislice method due to Cowley & Moodie is used for electron reflection, the “edge effects” stand firmly in the way of reaching a stationary solution for HEER. The multislice method due to Maksym & Beeby is valid only for an 2-D periodic surface.Now, a method for solving stationary solution of HEER for an arbitrary surface is available, which is called the Edge Patching method in Multislice-Only mode (the EPMO method). The analytical basis for this method can be attributed to two important characters of HEER: 1) 2-D dependence of the wave fields and 2) the Picard iteractionlike character of multislice calculation due to Cowley and Moodie in the Bragg case.