scholarly journals The Breakage of Shape-Anisotropic Particles under Normal Contact with Different Particle Shape Parameters

2021 ◽  
Vol 11 (16) ◽  
pp. 7319
Author(s):  
Yanwei Zhang ◽  
Qiwei Jian ◽  
Jian Zhou ◽  
Qinglin Huang ◽  
Lin Li ◽  
...  
Keyword(s):  
Particle Shape ◽  
Normal Force ◽  
Cone Angle ◽  
Particle Breakage ◽  
Sphere Diameter ◽  
Shape Parameters ◽  
Normal Contact ◽  
The Relationship ◽  
Force Displacement ◽  
Contact Diameter

This paper elaborates the cone–hemispherical gypsum particle breakages under normal contact with different particle shape parameters (contact diameter d, cone angle θ and sphere diameter D) and proposes a simple quantitative approach to discriminate breakage modes. The effects of the particle shape parameters on particle breakage are investigated through analyzing breakage processes, breakage modes and force–displacement curves. Three breakage modes are formed during the breakage experiments: peeling, peeling–splitting and splitting, corresponding to three different normal force–displacement curves. The formation of a conical core is deemed as the precondition for particle splitting. The particle breakage mode transfers from peeling to splitting with the increase in contact diameter d and cone angle θ, but a decrease in sphere diameter D. The critical normal force Fcr is positively linearly related to contact diameter d and cone angle θ, but the relationship between Fcr and sphere diameter D heavily depends on the breakage mode. Furthermore, the critical contact diameter dcr described by cone angle θ and sphere diameter D is proposed to discriminate breakage modes of the cone–hemispherical gypsum particles.

scholarly journals Micromechanism of the Breakage of Two Spherical Gypsum Particles under Normal–Tangential Contact Conditions

2021 ◽  
Vol 11 (9) ◽  
pp. 4039
Author(s):  
Yiran Niu ◽  
Lin Li ◽  
Yanwei Zhang ◽  
Shicai Yu ◽  
Jian Zhou
Keyword(s):  
Tangential Force ◽  
Coarse Grained ◽  
Spherical Particles ◽  
Contact Conditions ◽  
Normal Contact ◽  
Tangential Contact ◽  
Theoretical Predictions ◽  
Tangential Forces ◽  
Predicted Values ◽  
The Relationship

Contact breakage of particles makes a large difference in the strength of coarse-grained soils, and exploring the characteristics within the process of the breakage is of great significance. Ignoring the influence of particle shape, the micromechanism of two spherical particles breaking under normal–tangential contact conditions was investigated theoretically and experimentally. Through theoretical analysis, the breakage form, the shape and size of the conical core, and the relationship between the normal and tangential forces at crushing were predicted. Particle contact tests of two gypsum spheres were carried out, in which the breakage forms, features of the conical cores and the normal and tangential forces at crushing were recorded for comparison with the predicted values. The test results and the theoretical predictions showed good agreement. Both the analysis and test demonstrate that the presence of tangential forces causes the conical core to assume the shape of an oblique cone, and the breakage form to change. Moreover, with increasing normal contact force, the tangential force needed for crushing increases gradually first and then decreases suddenly.

scholarly journals Effect of Multi-Impact on QIQH Carbon/Epoxy Composite Laminate

Proceedings ◽  
2018 ◽  
Vol 2 (8) ◽  
pp. 511
Author(s):  
Adadé Seyth Ezéckiel Amouzou ◽  
Olivier Sicot ◽  
Ameur Chettah ◽  
Shahram Aivazzadeh
Keyword(s):  
Composite Structures ◽  
Epoxy Composite ◽  
Impact Damage ◽  
Ultrasonic Control ◽  
Impact Tests ◽  
Post Impact ◽  
Testing Techniques ◽  
Force Time ◽  
The Relationship ◽  
Force Displacement

This work is motivated by increasingly used of composite structures under severe loading conditions. During their use, these materials are often subjected to impact as for example, in the aeronautical field the fall of hailstone on structure composites. In fact, the low energy traditional impact tests don’t allow to see the evolution of the damage and don’t permit also to compare the best tolerance to impact between different stratifications. The multi-impact tests made it possible to find a solution to this problem. In this work, multi-impact tests are performed on three carbon/epoxy stratifications. The final goal is to predict the durability of the composite structures during impact loading for their design. This study brings to light the response of multi-impact tests through force-time and force-displacement curves obtained experimentally. On the other hand, a parameter D has introduced following the experimental results. This made it possible to rank the three stratifications from their tolerance to multi-impact tests. To evaluate the post impact damage, ultrasonic testing techniques are used. The results allow to find the relationship between the damaged surface obtained by the ultrasonic control and the parameter D and to rank the three laminates configurations.

Friction Control for Vibration Suppression

1999 ◽  
Author(s):  
L. Gaul ◽  
R. Nitsche
Keyword(s):  
Normal Force ◽  
Vibration Suppression ◽  
Piezoelectric Element ◽  
Friction Model ◽  
Space Structures ◽  
Control Law ◽  
Large Space ◽  
Normal Contact ◽  
Friction Control ◽  
Frictional Interface

Abstract Friction damping in bolted joint connections of large space structures turned out to be a major source of damping (Gaul and Bohlen, 1987). For vibration suppression, the joints are designed such that the normal force in a frictional interface is controlled which improves damping performance. The use of active control to vary the normal contact force in a joint by means of a piezoelectric element is explored. A model consisting of two elastic beams connected by a single active joint is considered. A friction model with velocity dependent dynamics is used to describe the friction phenomena. A control law for friction dampers which maximizes energy dissipation instantaneously by controlling the normal force at the friction interface is proposed. The effect of displacement- and velocity-induced friction dynamics is considered for the design of the control law. We arrive at a dynamic controller which prevents frictional energy stored as potential energy in a bristle model from being returned to the system.

scholarly journals Design, Experiment, and Improvement of a Quasi-Zero-Stiffness Vibration Isolation System

2020 ◽  
Vol 10 (7) ◽  
pp. 2273 ◽  
Author(s):  
Shuai Wang ◽  
Wenpen Xin ◽  
Yinghao Ning ◽  
Bing Li ◽  
Ying Hu
Keyword(s):  
Vibration Isolation ◽  
Damping Ratio ◽  
Excitation Amplitude ◽  
Isolation System ◽  
Vibration Isolation System ◽  
Linear Spring ◽  
Isolation Effects ◽  
Magnetic Rings ◽  
The Relationship ◽  
Force Displacement

This paper proposes a new kind of quasi-zero-stiffness (QZS) isolation system that has the property of low-dynamic but high-static stiffness. The negative stiffness was produced using two magnetic rings, the magnetization of which is axial. First, the force–displacement characteristic of the two coupled magnetic rings was developed and the relationship between the parameters of the magnetic rings and the stiffness of the system was investigated. Then, the dynamic response of the QZS was analyzed. The force transmissibility of the system was calculated and the effects of the damping ratio and excitation amplitude on the isolation performance were investigated. The prototype of the QZS system was developed to verify the isolation effects of the system based on a comparison with a linear vibration isolation platform. Lastly, the improvement of the QZS system was conducted based on changing the heights of the ring magnets and designing a proper non-linear spring. The analysis shows the QZS system after improvement shows better isolation effects than that of the non-improved system.

Contact Model of Two Rough Surfaces Based on a Visco-Elasto-Adhesive Interaction

2010 ◽  
Author(s):  
Ali Sepehri ◽  
Kambiz Farhang
Keyword(s):  
Normal Force ◽  
Rough Surfaces ◽  
Mathematical Formulation ◽  
Contact Model ◽  
Force Component ◽  
Adhesive Interaction ◽  
Normal Contact ◽  
Rate Dependent ◽  
Statistical Consideration ◽  
Adhesive Forces

Mathematical formulae are derived for normal contact force component between two nominally flat rough surfaces. The development of the contact model is based on the asperity level interaction in which adhesive forces between two asperities as well as elastic and rate-dependent forces are included. Statistical consideration of rough surfaces yields the mathematical formulation of total normal force due to adhesion, elastic and rate-dependent properties of the surfaces in contact.

scholarly journals The effect of particle shape on the deformation and stress reduction of a gravel soil due to wetting

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Reza Mahinroosta ◽  
Vahid Oshtaghi
Keyword(s):  
Particle Size ◽  
Shear Stress ◽  
Particle Size Distribution ◽  
Normal Stress ◽  
Size Distribution ◽  
Stress Reduction ◽  
Particle Shape ◽  
Particle Breakage ◽  
Direct Shear ◽  
Particle Shapes

AbstractThis paper investigates the effect of particle shape on the stress reduction and collapse deformation of gravelly soil using a medium-scale direct shear test apparatus under different relative densities, normal stress, and shear stress levels. A new method based on the Micro-Deval test was introduced to produce sub-angular particles from angular particles. Therefore, two series of soil specimens were obtained with the same rock origin, particle size distribution, and relative density but different particle shapes. In addition to traditional direct shear tests on dry and wet specimens, a specific test procedure was applied to explore the stress reduction and collapse of soil specimens due to wetting. The results of the tests, including shear stress–shear displacement and vertical displacement-shear displacement, were compared. The results showed that the stress reduction and settlement due to wetting increased with vertical and shear stress levels in both types of particle shapes, with higher values in angular particle shapes. The particle breakage of the soil specimens was also studied quantitatively using the change in the particle size distribution before and after the test. It was shown that the wetting of the samples had more impact on the particle breakage in angular gravel than sub-angular gravel, which increased linearly with the normal stress.

Theoretical and Experimental Research on Tapping of GH4169 and TC4 with Modified-Tooth Taps

2008 ◽  
Vol 375-376 ◽  
pp. 221-225
Author(s):  
Yan Li Tang ◽  
Rong Di Han ◽  
Jia Bin Ju
Keyword(s):  
High Speed ◽  
Cone Angle ◽  
High Speed Steel ◽  
Friction Torque ◽  
Theoretical Principle ◽  
Outer Diameter ◽  
Machined Surface ◽  
Frictional Wear ◽  
Fundamental Reason ◽  
The Relationship

Based on the theoretical principle of tapping formation and simulation with modified-tooth tap, the relationship among the different geometric parameters of the tap was further analyzed. A series of modified-tooth taps and standard ones with a cutting cone angle of 7°30´and a outer diameter of M6, which were made from high-speed steel W9, were taken to do the comparative tapping test on nickel-based high-temperature alloy GH4169, titanium alloy TC4 and 45 steel. The test results indicated that the leading cause of difficult tapping in GH4169 and TC4 was the largeness of their friction torques which were about 35 % and 62 % of tapping torque respectively, where the frictional wear was a fundamental reason for tough tapping GH4169 and the spring back of machined surface for TC4.The obvious decreases of friction torque with the modified-tooth tap approximately 70% and 50% respectively for GH4169 and TC4 were attributed to its unique tapping formation principle of generating broaching but no remarkable effects on 45 steel in comparison with standard tap.

Experimental Study of Rockfill Particle Breakage

2014 ◽  
Vol 900 ◽  
pp. 445-448
Author(s):  
Zhi Hua Xu ◽  
Da Wei Sun
Keyword(s):  
Internal Friction ◽  
Large Scale ◽  
Reference Value ◽  
Friction Angle ◽  
Confining Pressure ◽  
Particle Breakage ◽  
Internal Friction Angle ◽  
Dam Construction ◽  
Confining Pressures ◽  
The Relationship

As the high concrete faced rockfill dams construction, grain breakage gradually become the factors that influence the high dam construction which can not be ignored. This text based on the master of rockfill of shuibuya dam as the experimental material, getting and analyzing the particle breakage data under different confining pressure through the large-scale triaxial test, and the results show that the particle breakage index increases with the increase of confining pressures. The relationship between particle breakage index and confining pressure can be expressed by formula;Particle breakage increase leading to reduced internal friction angle and the shear strength of rockfill, and the author newly introduced two broken variable to describe the relationship which can be expressed by the formula between the particle breakage and internal friction angle, it has certain reference value for establishing constitutive model considering particle breakage.

Shape Optimal Design of Contact Springs of Electronic Connectors

2002 ◽  
Vol 124 (3) ◽  
pp. 178-183 ◽  
Author(s):  
Yeh-Liang Hsu ◽  
Yuan-Chan Hsu ◽  
Ming-Sho Hsu
Keyword(s):  
Contact Force ◽  
Printed Circuit Boards ◽  
Normal Force ◽  
Optimization Techniques ◽  
Contact Forces ◽  
Design Parameters ◽  
Original Design ◽  
Insertion Force ◽  
Element Analysis ◽  
Normal Contact

An electronic connector provides a separable interface between two subsystems of an electronic system. The contact spring is probably the most critical component in an electronic connector. Mechanically, the contact spring provides the contact normal force, which establishes the contact interface as the connector is mated. However, connector manufacturers have a basic struggle between the need for high normal contact forces and low insertion forces. Designing connectors with large numbers of pins that are used with today’s integrated circuits and printed circuit boards often results in an associated rise in connector insertion force. It is possible to lower the insertion force of a connector by redesigning the geometry of the contact spring, but this also means a decrease in contact normal force. In this paper, structural shape optimization techniques are used to find the optimal shape of the contact springs of an electronic connector. The process of the insertion of a PCB into the contact springs of a connector is modeled by finite element analysis. The maximum insertion force and the contact normal force are calculated. The effects of several design parameters are discussed. The geometry of the contact springs is then parameterized and optimized. The required insertion force is minimized while the normal contact force and the resulting stress are maintained within specified values. In our example, the insertion force of the final contact spring design is reduced to 68.3% of that of the original design, while the contact force and the maximum stress are maintained within specified values.

Sign in / Sign up

Export Citation Format

Share Document