In-plane shear behavior of 3D warp-knitted spacer fabrics: Part II—Effect of structural parameters

2017 ◽  
Vol 48 (4) ◽  
pp. 772-801 ◽  
Author(s):  
Veerakumar Arumugam ◽  
Rajesh Mishra ◽  
Maros Tunak ◽  
Jiri Militky
Keyword(s):  
Shear Stress ◽  
Energy Absorption ◽  
Layer Structure ◽  
Structural Parameters ◽  
Strain Curve ◽  
Shear Behavior ◽  
Plane Shear ◽  
Yarn Diameter ◽  
Deformation Properties ◽  
Spacer Fabrics

The objective of this work is to study the in-plane shear behavior of 3D warp-knitted spacer knitted fabrics by using a picture frame fixture. This part aims to investigate the effects of structural parameters on the shear stress and energy absorption of warp-knitted spacer fabrics. A group of warp-knitted spacer fabrics was produced on a double-needle bar Raschel machine by varying their structural parameters including spacer yarn fineness, fabric thickness, and outer layer structure. The effects of fabric structural parameters on the shear properties of the spacer fabrics were tested and analyzed based on the nonlinear behavior of shear stress versus shear angle and the deformation mechanism. During loading process, the series of surface images were acquired in certain interval at different positions. These images were processed in image analysis software to obtain the full-field displacement and shear angles at chosen points on the surface of test specimen. The potential shear behavior of the fabric was identified with support of the shear stress–strain curve, work done, and efficiency at different shear stages. The regression model was used to establish the elastic deformation properties to obtain the shear results. Advance statistical evaluation and two-way analysis of variance are used to analyze the significance of various factors such as thickness, spacer yarn diameter, and surface structures on energy absorption at maximum shear load and deformation.

scholarly journals An Experimental Study Of The Compression Properties Of Polyurethane-Based Warp-Knitted Spacer Fabric Composites

2017 ◽  
Vol 17 (3) ◽  
pp. 199-205 ◽  
Author(s):  
Si Chen ◽  
Xue-pei Zhang ◽  
Hong-xia Chen ◽  
Xiao-ping Gao
Keyword(s):  
Energy Absorption ◽  
Inclination Angle ◽  
Stress Level ◽  
Layer Structure ◽  
Structural Parameters ◽  
Fabric Thickness ◽  
Compression Properties ◽  
Spacer Fabric ◽  
Fabric Composites ◽  
Spacer Fabrics

AbstractThe present work has reported the compression properties of polyurethane-based warp-knitted spacer fabric composites (PWSF). In order to investigate the effect of structural parameters of fabric on the compression performance of composites, a series of warp-knitted spacer fabrics (WSF) with different structural parameters including spacer yarn inclination angle, thickness, fineness of spacer yarns, and outer layer structure have been involved. The produced composites have been characterized for compression properties. The energy-absorption performance during the compression process has been determined as a function of the efficiency and the compression stress obtained from compression tests. The results show that the composites based on spacer fabrics having smaller spacer yarns inclination angle, higher fabric thickness, finer spacer yarn, and larger mesh in outer layers perform better with respect to energy-absorption properties at lower stress level, whereas at higher stress level, the best energy-absorption abilities are obtained in case of spacer fabrics constructed of larger spacer yarn inclination angle, lower fabric thickness, coarser spacer yarn, and smaller mesh in surface layers.

scholarly journals An Experimental Study on Mechanical Behavior of Parallel Joint Specimens under Compression Shear

2018 ◽  
Vol 2018 ◽  
pp. 1-12
Author(s):  
Fei Wang ◽  
Ping Cao ◽  
Yu Chen ◽  
Qing-peng Gao ◽  
Zhu Wang
Keyword(s):  
Shear Stress ◽  
Shear Strength ◽  
Failure Mode ◽  
Shear Failure ◽  
Strain Curve ◽  
Shear Loading ◽  
Plane Shear ◽  
Joint Spacing ◽  
Dip Angle ◽  
Joint Inclination

In order to investigate the influence of the joint on the failure mode, peak shear strength, and shear stress-strain curve of rock mass, the compression shear test loading on the parallel jointed specimens was carried out, and the acoustic emission system was used to monitor the loading process. The joint spacing and joint overlap were varied to alter the relative positions of parallel joints in geometry. Under compression-shear loading, the failure mode of the joint specimen can be classified into four types: coplanar shear failure, shear failure along the joint plane, shear failure along the shear stress plane, and similar integrity shear failure. The joint dip angle has a decisive effect on the failure mode of the specimen. The joint overlap affects the crack development of the specimen but does not change the failure mode of the specimen. The joint spacing can change the failure mode of the specimen. The shear strength of the specimen firstly increases and then decreases with the increase of the dip angle and reaches the maximum at 45°. The shear strength decreases with the increase of the joint overlap and increases with the increase of the joint spacing. The shear stress-displacement curves of different joint inclination samples have differences which mainly reflect in the postrupture stage. From monitoring results of the AE system, the variation regular of the AE count corresponds to the failure mode, and the peak value of the AE count decreases with the increase of joint overlap and increases with the increase of joint spacing.

Cushioning properties of weft-knitted spacer fabrics

2017 ◽  
Vol 88 (14) ◽  
pp. 1628-1640 ◽  
Author(s):  
Tong Zhao ◽  
Hairu Long ◽  
Tianqi Yang ◽  
Yanping Liu
Keyword(s):  
Human Body ◽  
Structural Parameters ◽  
Testing Machine ◽  
Three Dimensional ◽  
Structural Features ◽  
Practical Significance ◽  
Absorption Energy ◽  
Yarn Diameter ◽  
Spacer Fabrics ◽  
Compression Resistance

Three-dimensional spacer fabrics which have a sandwich structure are formed in a single knitting process without any additional joining treatment. They consist of two separate multifilament outer layers connected by arrays of spacer monofilaments. This paper presents an experimental study on the relationships between the cushioning properties and structural parameters of weft-knitted spacer fabrics in order to lay a foundation for the development of seamless shaped impact protectors for human body impact protection. Sixteen spacer fabrics of different structural parameters were knitted on a computerized flat knitting machine and tested on a universal mechanical testing machine. The cushioning properties of the spacer fabrics were analyzed in terms of their structural features, compression stress–strain curves, energy absorption, and compression resilience. It was found that multifilament fineness, spacer yarn diameter, and spacer yarn pattern should be matching in order to form effective binding structures between the outer layers and spacer monofilaments. The results also showed that spacer fabrics knitted with a shorter spacer yarn span distance, coarser monofilaments, and higher spacer yarn density have better compression resistance and absorption energy but inferior compression resilience if their binding structures are effective. This study has practical significance in promoting the application of this type of fabric as a cushion material for human body protection.

A normalizing relation for granular materials

1990 ◽  
Vol 27 (1) ◽  
pp. 68-78 ◽  
Author(s):  
Colin L. Y. Wong
Keyword(s):  
Shear Stress ◽  
Granular Material ◽  
Granular Materials ◽  
Volume Change ◽  
Void Ratio ◽  
Axial Strain ◽  
Strain Curve ◽  
Shear Behavior ◽  
Stress Strain ◽  
Testing Procedures

It is hypothesized that a normalized shear stress – strain curve for granular materials can be obtained by accounting fully for the effects of volume change. In this sense, volume change behavior is a factor that controls the shear stress – strain behavior of a granular material. This hypothesis is applied to Rowe's stress-dilatancy theory to include slip, rolling, rearrangement, and crushing strains, and a theoretical normalizing relation is obtained. The relation is demonstrated to be reasonably correct for the published test data utilized in this study. Differing fabrics of a granular material at the same void ratio can be corrected for by the normalizing relation. The hypothesis is also applied to simple shear behavior and an empirical normalizing relation is obtained.On the basis of the success of the normalizing relation, it is suggested that the volume change rate at 4% axial strain may be, in relation to shear behavior, a more appropriate characterizing parameter than void ratio. However, owing to the long-standing use and acceptance of void ratio, the concept of a reference void ratio, determined by specific sample preparation and testing procedures, is introduced as a characterizing parameter for granular materials. Key words: volume change, dilatancy, normalization, fabric, stress, strain, deformation, sand, granular material.

scholarly journals A New S-Shape Specimen for Studying the Dynamic Shear Behavior of Metals

Metals ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 838 ◽  
Author(s):  
Ali Arab ◽  
Yansong Guo ◽  
Qiang Zhou ◽  
Pengwan Chen
Keyword(s):  
Shear Stress ◽  
Digital Image Correlation ◽  
Digital Image ◽  
Strain Curve ◽  
Shear Behavior ◽  
Image Correlation ◽  
Specimen Geometry ◽  
Dynamic Shear ◽  
Stress Strain Curve ◽  
Stress Strain

A new S-shaped specimen geometry is developed in this study to investigate the shear behavior of materials under dynamic shear condition. Traditionally, hat-shaped geometry is used to study the dynamic shear of materials by a conventional split Hopkinson pressure bar apparatus. However, in this geometry, the force equilibrium on the two sides of the sample is difficult to fulfill, and the stress field in the shear region is not homogeneous. Hence, the calculated shear stress–strain curve from this geometry is not precise. To overcome this problem, the new S-shaped specimen is designed to achieve accurate shear stress–strain curve. This geometry can be used in a wide range of strain rates and does not require additional machining process for microstructure observation. The new S-shaped specimen is successfully coupled with digital image correlation method because of the flat surface. Digital image correlation results indicate that the fracture patterns of the new S-shaped specimen occur with maximum shear strains in the shear region in the middle of the sample. This result is also validated by finite element model simulation. The new S-shaped specimen geometry can be used to study the dynamic shear behavior of various metals.

scholarly journals Mechanical Properties Of 3D-Structure Composites Based On Warp-Knitted Spacer Fabrics

2015 ◽  
Vol 15 (2) ◽  
pp. 127-137 ◽  
Author(s):  
Si Chen ◽  
Hai-ru Long ◽  
Ying-hao Liu ◽  
Feng-chao Hu
Keyword(s):  
Mechanical Properties ◽  
Mechanical Performance ◽  
Layer Structure ◽  
Structural Parameters ◽  
3D Structure ◽  
Three Dimension ◽  
Different Types ◽  
Spacer Fabrics ◽  
Flexible Polyurethane ◽  
The Impact

Abstract In this paper, the mechanical properties (compression and impact behaviours) of three-dimension structure (3D-structure) composites based on warp-knitted spacer fabrics have been thoroughly investigated. In order to discuss the effect of fabric structural parameters on the mechanical performance of composites, six different types of warp-knitted spacer fabrics having different structural parameters (such as outer layer structure, diameter of spacer yarn, spacer yarn inclination angle and thickness) were involved for comparison study. The 3D-structure composites were fabricated based on a flexible polyurethane foam. The produced composites were characterised for compression and impact properties. The findings obtained indicate that the fabric structural parameters have strong influence on the compression and impact responses of 3D-structure composites. Additionally, the impact test carried out on the 3D-structure composites shows that the impact loads do not affect the integrity of composite structure. All the results reveal that the product exhibits promising mechanical performance and its service life can be sustained.

Finite Element Analysis of Tire/Rim Interface Forces Under Braking and Cornering Loads

1992 ◽  
Vol 20 (2) ◽  
pp. 83-105 ◽  
Author(s):  
J. P. Jeusette ◽  
M. Theves
Keyword(s):  
Finite Element ◽  
Shear Stress ◽  
Contact Pressure ◽  
Element Model ◽  
Shear Stresses ◽  
Detailed Knowledge ◽  
Stress Distributions ◽  
Element Analysis ◽  
Plane Shear ◽  
Normal Contact

Abstract During vehicle braking and cornering, the tire's footprint region may see high normal contact pressures and in-plane shear stresses. The corresponding resultant forces and moments are transferred to the wheel. The optimal design of the tire bead area and the wheel requires a detailed knowledge of the contact pressure and shear stress distributions at the tire/rim interface. In this study, the forces and moments obtained from the simulation of a vehicle in stationary braking/cornering conditions are applied to a quasi-static braking/cornering tire finite element model. Detailed contact pressure and shear stress distributions at the tire/rim interface are computed for heavy braking and cornering maneuvers.

scholarly journals A Monotonic Smeared Truss Model to Predict the Envelope Shear Stress—Shear Strain Curve for Reinforced Concrete Panel Elements under Cyclic Shear

2021 ◽  
Vol 2 (1) ◽  
pp. 174-194
Author(s):  
Luís Bernardo ◽  
Saffana Sadieh
Keyword(s):  
Shear Stress ◽  
Reinforced Concrete ◽  
Shear Strain ◽  
Peak Load ◽  
Strain Curve ◽  
Fiber Reinforced Polymers ◽  
Shear Stresses ◽  
Cyclic Shear ◽  
Concrete Panels ◽  
Truss Model

In previous studies, a smeared truss model based on a refinement of the rotating-angle softened truss model (RA-STM) was proposed to predict the full response of structural concrete panel elements under in-plane monotonic loading. This model, called the “efficient RA-STM procedure”, was validated against the experimental results of reinforced and prestressed concrete panels, steel fiber concrete panels, and reinforced concrete panels externally strengthened with fiber-reinforced polymers. The model incorporates equilibrium and compatibility equations, as well as appropriate smeared constitutive laws of the materials. Besides, it incorporates an efficient algorithm for the calculation procedure to compute the solution points without using the classical trial-and-error technique, providing high numerical efficiency and stability. In this study, the efficient RA-STM procedure is adapted and checked against some experimental data related to reinforced concrete (RC) panels tested under in-plane cyclic shear until failure and found in the literature. Being a monotonic model, the predictions from the model are compared with the experimental envelopes of the hysteretic shear stress–shear strain loops. It is shown that the predictions for the shape (at least until the peak load is reached) and for key shear stresses (namely, cracking, yielding, and maximum shear stresses) of the envelope shear stress–shear strain curves are in reasonably good agreement with the experimental ones. From the obtained results, the efficient RA-STM procedure can be considered as a reliable model to predict some important features of the response of RC panels under cyclic shear, at least for a precheck analysis or predesign.

In-plane shear behavior of masonry walls strengthened with steel fiber-reinforced concrete overlay

2018 ◽  
Vol 19 (5) ◽  
pp. 553-570 ◽  
Author(s):  
M. A. Najafgholipour ◽  
S. M. Dehghan ◽  
A. R. Kamrava
Keyword(s):  
Reinforced Concrete ◽  
Steel Fiber ◽  
Shear Behavior ◽  
Fiber Reinforced Concrete ◽  
Masonry Walls ◽  
Fiber Reinforced ◽  
Steel Fiber Reinforced Concrete ◽  
Plane Shear
Sign in / Sign up

Export Citation Format

Share Document