An analytical approach of filament bundle swinging dynamics, Part II: identifying equivalent dynamic constitutive parameters of filament bundles

2021 ◽  
pp. 004051752110592
Author(s):  
Xunxun Ma ◽  
Yongxing Wang ◽  
Shujia Li ◽  
Shengze Wang ◽  
He Ye
Keyword(s):  
Elastic Modulus ◽  
High Speed ◽  
Excitation Frequency ◽  
Bundle Method ◽  
Dynamic Elastic Modulus ◽  
Loading Test ◽  
Filament Bundles ◽  
Viscoelastic Coefficient ◽  
Constitutive Parameters ◽  
Filament Bundle

A filament bundle is a type of yarn, which is composed of nearly parallel and highly oriented polymer monofilaments. Due to its nonlinearity both in material constitutive properties and structure, the filament bundle possesses nonlinear viscoelastic properties. It is important to study the dynamic behavior of the filament bundle accurately during its high-speed movement. Therefore, an accurate expression of the constitutive relation of the filament bundle is an essential prerequisite for its dynamic simulation and analysis. Continued the previous study in Part I: modeling filament bundle method, in this paper, an approach was proposed to identify the equivalent dynamic constitutive parameters of the filament bundle considering frequency-dependent characteristics. Firstly, the identification formulas of the dynamic elastic modulus and viscoelastic coefficients were derived based on the Kelvin model. Then, a testing method of the cross-sectional parameters of the filament bundle under a certain tension was proposed, and the testing device was developed to obtain the area of the filament bundle; The dynamic loading test of the bundle filament was conducted in a DMA Q800 dynamic mechanical tester. Thirdly, the equivalent dynamic elastic modulus and viscoelastic coefficients were obtained through the experimental test. Finally, an analytical method was proposed to verify the correctness of experimental results through simulation. The results show that the excitation frequency has a significant influence on the dynamic elastic modulus and viscoelastic coefficient, and the curves of the equivalent dynamic elastic modulus and viscoelastic coefficient present nonlinear variation characteristics.

An analytical approach of filament bundle swinging dynamics, Part I: Modeling filament bundle by ANCF

2019 ◽  
Vol 89 (21-22) ◽  
pp. 4607-4619
Author(s):  
Yongxing Wang ◽  
Shujia Li ◽  
Xunxun Ma ◽  
Dayu Zhang ◽  
Pei Feng ◽  
...  
Keyword(s):  
Large Deformation ◽  
Dynamic Behavior ◽  
High Speed ◽  
Nonlinear Differential Equations ◽  
Viscoelastic Body ◽  
Factors Affecting ◽  
Air Resistance ◽  
Wide Range ◽  
Filament Bundles ◽  
Filament Bundle

A filament bundle is a kind of filament assembly with less twist or nontwist. It is a viscoelastic body and has a large aspect ratio. Its large deformation during motion over a wide range is a universal phenomenon in many textile processes. The dynamic viscoelasticity of the filament bundle, gravity, and air resistance are three important factors affecting the filament bundle's dynamic behavior. Taking account of these factors, a filament bundle dynamics analysis method is proposed in a series of three papers. This paper, the first in the series, presents an approach to model the dynamics of the flexible filament bundle with viscoelasticity and to analyze its dynamic behavior under the action of gravity and air resistance. The filament bundle element (FBE) is established based on absolute nodal coordinate formulation (ANCF), in which slope vectors and global coordinates are applied. The approach presented in this paper is well suited for the analysis of large deformation motions of filament bundles. As an example, a dynamic model was established to predict the filament bundle's trace during its swinging through large displacements under the action of gravity and air resistance, taking into account the filament bundle viscosity. The nonlinear differential equations of the filament bundle system were solved using MATLAB. Furthermore, the swing traces of the filament bundle in a closed Plexiglas box with different vacuum degrees were recorded using a high-speed camera to prove the validity of the established filament bundle model based on ANCF.

Study on the Cement-Improved Loess under the Vibratory Load by Dynamic Tests

2013 ◽  
Vol 838-841 ◽  
pp. 1302-1308 ◽  
Author(s):  
Jia Ding Wang ◽  
Shu Jun Peng ◽  
Wan Li Xie
Keyword(s):  
Elastic Modulus ◽  
Dynamic Characteristics ◽  
High Speed ◽  
Dynamic Deformation ◽  
Damping Ratio ◽  
Test Method ◽  
Dynamic Elastic Modulus ◽  
Dynamic Tests ◽  
Long Time ◽  
Orthogonal Test Method

In this paper based on the foundation construction of Datong Xian high-speed railway, a large number of test samples have been taken. The order and contribution rate of every experiment factor like cement commingle ratio, depths, water dipping conditions, compacting factor and vibration frequency on the dynamic characteristics of cement-improved loess such as dynamic elastic modulus, dynamic deformation, damping ratio by dynamic triaxial test, which orthogonal test method has been applied to. The dynamic load was calculated according to the train vibration attenuation rule of different depth. The dynamic characteristics of cement-improved loess such as dynamic deformation, dynamic elastic modulus, damping ratio were got form the dynamic tests of long time and large number of cycles. The results showed that with the increase of cement ratio, the dynamic characteristics of cement-improved loess are more better, there is no optimal ratio of cement.

scholarly journals Mechanical properties of lightweight foam concrete filler for roadbed of high-speed railway

2021 ◽  
Vol 14 (10) ◽  
Author(s):  
De-Gou Cai ◽  
Shao-Wei Wei ◽  
Yang-Sheng Ye ◽  
Qian-Li Zhang ◽  
Zhong-Guo Li ◽  
...  
Keyword(s):  
Elastic Modulus ◽  
Fly Ash ◽  
Frost Resistance ◽  
High Speed ◽  
Ash Content ◽  
Dynamic Elastic Modulus ◽  
Filling Material ◽  
Foam Concrete ◽  
High Speed Railway ◽  
Lightweight Foam

AbstractA high-speed railway has high requirements for line smoothness, and uneven settlement control is the primary factor considered in the design and operation of the subgrade. The emergence of lightweight subgrade structures meets the needs of the development of the high-speed railway. As a kind of filling material with good performance, lightweight foam concrete can effectively reduce the load and excessive settlement of subgrade and effectively reduce the cost of foundation treatment. This paper studied the dynamic characteristics of lightweight foam concrete with different wet densities and water-bearing states under train loading. The effects of wet density and fly ash content on the compressibility, impermeability, and frost resistance of lightweight foam concrete were analyzed in detail. The results show that the lightweight foam concrete still has high residual strength after compression, which is about 60% of its peak strength. Under different mix ratios, the critical dynamic stress of the lightweight foam concrete is generally 0.2–0.3 times the unconfined compressive strength, and the dynamic elastic modulus increases with the increase of wet density and cyclic stress amplitude. With the fly ash content increasing, the volume water absorption of lightweight foam concrete decreases first and then increases, and the critical value of fly ash content is 40%. The frost resistance of lightweight foam concrete gradually increases with the increase of wet density, and the dynamic elastic modulus of the sample with 279 kg·m−3 density lost 41.1% after 20 freeze–thaw cycles. When the content of fly ash is 20%, the frost resistance of lightweight foam concrete is equivalent to that of pure cement.

scholarly journals An Improved Lagrangian-Inverse Method for Evaluating the Dynamic Constitutive Parameters of Concrete

Materials ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 1871
Author(s):  
Xinlu Yu ◽  
Yingqian Fu ◽  
Xinlong Dong ◽  
Fenghua Zhou ◽  
Jianguo Ning
Keyword(s):  
High Speed ◽  
Inverse Method ◽  
Image Correlation ◽  
Analysis Method ◽  
Stress Strain ◽  
Optical Techniques ◽  
Element Simulation ◽  
Non Linear ◽  
Constitutive Parameters ◽  
Inverse Analysis Method

The dynamic constitutive behaviors of concrete-like materials are of vital importance for structure designing under impact loading conditions. This study proposes a new method to evaluate the constitutive behaviors of ordinary concrete at high strain rates. The proposed method combines the Lagrangian-inverse analysis method with optical techniques (ultra-high-speed camera and digital image correlation techniques). The proposed method is validated against finite-element simulation. Spalling tests were conducted on concretes where optical techniques were employed to obtain the high-frequency spatial and temporal displacement data. We then obtained stress–strain curves of concrete by applying the proposed method on the results of spalling tests. The results show non-linear constitutive behaviors in these stress–strain curves. These non-linear constitutive behaviors can be possibly explained by local heterogeneity of concrete. The proposed method provides an alternative mean to access the dynamic constitutive behaviors which can help future structure designing of concrete-like materials.

Studies the Properties of Polyaspartic Polyurea Coated Concrete under Coaction of Salt Fog and Freeze-Thaw

2012 ◽  
Vol 455-456 ◽  
pp. 781-785
Author(s):  
Ping Lu ◽  
Xin Mao Li ◽  
Xue Qiang Ma ◽  
Wei Bo Huang
Keyword(s):  
Elastic Modulus ◽  
Frost Resistance ◽  
Dynamic Elastic Modulus ◽  
Freeze Thaw ◽  
Decrease Rate ◽  
Thaw Cycle ◽  
Freeze Thaw Cycle ◽  
Salt Fog

. This paper mainly studied the properties of PAE polyurea coated concrete under coactions of salt fog and freeze-thaw. After exposed salt fog conditions for 200d, T3, B2, F2 and TM four coated concrete relative dynamic elastic modulus have small changes, but different coated concrete variation amplitude is different. T3 coated concrete after 100 times of freeze-thaw cycle the relative dynamic elastic modulus began to drop, 200 times freeze-thaw cycle ends, relative dynamic elastic modulus variation is the largest, decrease rate is 95%, TM concrete during 200 times freeze-thaw cycle, relative dynamic elastic modulus almost no change, B2 concrete and F2 concrete the extent of change between coating T3 and TM. After 300 times the freeze-thaw cycle coated concrete didn't appear freeze-thaw damage phenomenon. Four kinds of coating concrete relative dynamic elastic modulus variation by large to small order: T3 coated concrete > B2 coated concrete >F2 coated concrete > TM coated concrete, concrete with the same 200d rule. Frost resistance order, by contrast, TM coated concrete > B2 coated concrete > F2 coated concrete > T3 coated concrete.

scholarly journals Use of Silica Fume and GGBS to Improve Frost Resistance of ECC with High-Volume Fly Ash

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Yushi Liu ◽  
Xiaoming Zhou ◽  
Chengbo Lv ◽  
Yingzi Yang ◽  
Tianan Liu
Keyword(s):  
Elastic Modulus ◽  
Sodium Chloride ◽  
Mass Loss ◽  
Frost Resistance ◽  
Chloride Solution ◽  
Sodium Chloride Solution ◽  
Tap Water ◽  
High Volume ◽  
Dynamic Elastic Modulus ◽  
Freeze Thaw

Fly ash (FA) has been an important ingredient for engineered cementitious composite (ECC) with excellent tensile strain capacity and multiple cracking. Unfortunately, the frost resistance of ECC with high-volume FA has always been a problem. This paper discusses the influence of silica fume (SF) and ground-granulated blast-furnace slag (GGBS) on the frost resistance of ECC with high volume of FA. Four ECC mixtures, ECC (50% FA), ECC (70% FA), ECC (30% FA + 40% SL), and ECC (65% FA + 5% SF), are evaluated by freezing-thawing cycles up to 200 cycles in tap water and sodium chloride solution. The result shows the relative dynamic elastic modulus and mass loss of ECC in sodium chloride solution by freeze-thaw cycles are larger than those in tap water by freeze-thaw cycles. Moreover, the relative dynamic elastic modulus and mass loss of ECC by freeze-thaw cycles increase with FA content increasing. However, the ECC (30% FA + 40% SL) shows a lower relative dynamic elastic modulus and mass loss, but its deflection upon four-point bending test is relatively smaller before and after freeze-thaw cycles. By contrast, the ECC (65% FA + 5% SF) exhibits a significant deflection increase with higher first cracking load, and the toughness increases sharply after freeze-thaw cycles, meaning ECC has good toughness property.

scholarly journals Study on the Mechanical Properties of Chlorine Saline Soil under the Interaction of Multiple Factors

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Anhua Xu ◽  
Pengcheng Wang ◽  
Jianhong Fang
Keyword(s):  
Elastic Modulus ◽  
Moisture Content ◽  
Mechanical Characteristics ◽  
External Environment ◽  
Confining Pressure ◽  
Dynamic Elastic Modulus ◽  
Dynamic Strain ◽  
Saline Soils ◽  
Loading Frequency ◽  
Failure Strength

The distribution of chlorine saline soils is extensive in Haixi region of Qinghai Province in Northwest China. Its natural and geographical conditions are unique, and the external environment varies greatly. To study the effects of variable external environment on the mechanical characteristics of chlorine saline soils, a number of unconsolidated undrained (UU) dynamic triaxial tests under different confining pressure, moisture content, and loading frequency were carried out. The dynamic stress–dynamic strain, failure strength, dynamic elastic modulus, and parameter of shear strength were analyzed. The triaxial test results demonstrated that the stress–strain curves of the soil were strain-hardening. The failure strength and dynamic elastic modulus increased with the increasing of confining pressure; the law with moisture content and loading frequency were inconsistent. The dynamic cohesion and dynamic friction angle increased with the increasing of loading frequency, but decreased with the increasing of moisture content. Besides, the significance analysis theory was used to analyze the effect degree of different factors. It found that the effects of confining pressure, loading frequency, and the interaction between confining pressure and frequency on mechanical characteristics were significant, but the moisture content had less effect.

scholarly journals Dynamic Triaxial Test and Microscopic Study of Solidified Muddy Soil With Different Mixing Ratios and Curing Ages

2021 ◽  
Vol 8 ◽  
Author(s):  
Zhou Chen ◽  
Haocheng Xu ◽  
Mayao Cheng ◽  
Hanwen Lu ◽  
Zhijian Wang ◽  
...  
Keyword(s):  
Elastic Modulus ◽  
Triaxial Test ◽  
High Speed ◽  
Dynamic Strength ◽  
Dynamic Strain ◽  
Hydration Reaction ◽  
Curing Agent ◽  
Mixture Ratio ◽  
Dynamic Triaxial Test ◽  
Curing Age

Aiming to explore the optimal mixture ratio and curing age of solidified muddy soil under dynamic load, the paper intends to investigate whether the solidified muddy soil can be used as filling of high-speed railway subgrade. Based on the dynamic triaxial test, the investigation measured the dynamic strain and dynamic elastic modulus of solidified muddy soil under different mix ratios and curing ages, and also observed the microscopic morphology of solidified muddy soil samples by using scanning electron microscope. The results show that the addition of cement and curing agent significantly increases the dynamic strength and elastic modulus of muddy soil, which effectively improve the dynamic characteristics of muddy soil. The curing effect of the curing agent is more obvious with the increase of the dosage of cement and curing agent under different mix ratio. The content of curing agent plays a leading role in the hydration reaction between cement, curing agent and soil particles. Additionally, in case of the same test conditions, when the ratio of cement mass to dry silt mass is 1:20, the ratio of diluent volume to dry silt mass is 1:20, with 28 days of curing age, its curing effect will reach the best.

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