Transition from Straight to Fractal Cracks due to Projectile Penetration

2013 ◽  
Vol 592-593 ◽  
pp. 765-768
Author(s):  
Zoltán Halász ◽  
Frank van Steeden ◽  
Ferenc Kun
Keyword(s):  
High Speed ◽  
Theoretical Study ◽  
Geometrical Structure ◽  
Element Model ◽  
Crack Pattern ◽  
External Boundary ◽  
Discrete Element Model ◽  
Two Dimensional ◽  
Crack Network ◽  
Fractal Cracks

We present a theoretical study of the fracture of two-dimensional disc-shaped samples due to projectile penetration focusing on the geometrical structure of the crack pattern. The penetration of a cone is simulated into a plate of circular shape using a discrete element model of heterogeneous brittle materials varying the speed of penetration in a broad range. As the cone penetrates a destroyed zone is created from which cracks run to the external boundary of the plate. Computer simulations revealed that in the low speed limit of loading two cracks are generated with nearly straight shape. Increasing the penetration speed the crack pattern remains regular, however, both the number of cracks and their fractal dimension increases. High speed penetration gives rise to a crack network such that the sample gets fragmented into a large number of pieces. We give a quantitative analysis of the evolution of the system from simple cracking through fractal cracks to fragmentation with a connected crack network.

Numerical Analysis of Bridge Expansion-Induced Rail Deformation of Ballast Truck

2014 ◽  
Vol 580-583 ◽  
pp. 3208-3214 ◽  
Author(s):  
Zhen Wei Xiong ◽  
Xin Ling Liang ◽  
Xian Xing Dai ◽  
Ping Wang
Keyword(s):  
Granular Flow ◽  
Element Model ◽  
Discrete Element Model ◽  
Board Structure ◽  
Vertical Deformation ◽  
Two Dimensional ◽  
Running Safety ◽  
Bridge Plate ◽  
Ballast Track ◽  
The Relationship

when the ballast track stretch with the bridge, ballast which is near expansion joint will move confusedly. As a result, rail produced vertical deformation. The deformation will affect the running safety and comfortability of train. At present, there are two kinds of treatments which are cover board structure and baffle structure to deal ballast’s movement. Aiming at the different modes of stretching when the two kinds of structures and different arrangement condition of bridge plate are applied, the rail-sleeper-ballast discrete element model is developed by the method of two-dimensional granular flow. The relationship between rail deformation and bridge expansion is analyzed on the foundation of the model. Results show as flows: when bridge extends or shortens, rail always produced upwarp deformation. Bridge plate should arrange asymmetrically. Like this, the rail deformation decrease by 40%. And adopting the baffle structure can effectively reduce the influence of bridge expansion in ballast truck.

Design and Test of a Double-Curved Guiding Groove for a High-Speed Precision Seed-Metering Device

2020 ◽  
Vol 63 (5) ◽  
pp. 1349-1360
Author(s):  
Pan Xue ◽  
Yujun Hao ◽  
Wan Jiao ◽  
Jie Ren ◽  
Feifei Yang ◽  
...  
Keyword(s):  
Inclination Angle ◽  
High Speed ◽  
Element Model ◽  
Discrete Element ◽  
Travel Speed ◽  
Curved Surface ◽  
Discrete Element Model ◽  
Release Point ◽  
Seed Spacing ◽  
Seed Metering Device

HighlightsThe instability of the seed release point in a seed-metering device is proved theoretically.A double-curved guiding groove at the seed-release point improves the seed-metering uniformity.A discrete element model was used to examine effects of the design parameters on the metering performance.The critical parameters for the double-curved guiding groove design were determined.Abstract. The instability of the seed release point in a seed-metering device is one of the main causes of the non-uniformity of seed spacing. To improve the seed spacing uniformity, a double-curved guiding groove (DGG) was designed based on the prerelease adaptive principle. The DGG was used at the seed release point of an existing high-speed precision soybean seed-metering device with a double-setting plate. The results showed that the prerelease curved surface of the DGG was capable of guiding seeds to be released at the same seed release point at all times, and the adaptive curved surface of the DGG prevented any changes in seed velocity caused by friction or collisions between seeds and the meter, thereby improving the seed spacing uniformity significantly. A discrete element model was developed and validated with laboratory tests. Through simulations using the model, the primary and secondary factors of the DGG impacting the qualified rate of seed metering (QRM) and the coefficient of variation of the seed spacing uniformity (CVU) were identified and were, in descending order, the spacing of prerelease (SPR), the starting position of prerelease (SPP), the inclination angle of the seed outlet (ASO), and the inclination angle of the receiving cup (ABR). Regression equations of the QRM and CVU with the two main impacting factors were then established. For a planter travel speed of 10 km h-1, the optimal SPR was 10 mm, and the optimal SPP was 40°, where the QRM was 100% and the CVU was 16.61%. When compared to seed metering without the DGG, the CVU was reduced by 2.55%, showing that the DGG significantly improved the uniformity of seed spacing. Keywords: Double-curved guiding groove, Discrete element method, Seed-metering device, Travel speed, Uniformity.

Simulation of Fully Sintering Dental Zirconia Milling Process Based on Discrete Element Method

2013 ◽  
Vol 568 ◽  
pp. 49-54
Author(s):  
H.B. Wu ◽  
Q.P. Sun ◽  
Dun Wen Zuo
Keyword(s):  
High Speed ◽  
Cutting Tool ◽  
Cutting Speed ◽  
Element Model ◽  
Discrete Element ◽  
Milling Process ◽  
Discrete Element Model ◽  
Surface Cracks ◽  
Coating Technology ◽  
Cutting Speeds

Discrete element model of fully sintering dental zirconia was constructed and calibrated. Based on the model, the dynamic process of low-speed milling of zirconia was simulated, and the effects of different cutting speeds, cutting widths and federates on the formation of surface cracks were also analyzed. Results show that residue cracks number and maximum depth increases significantly with increase of the cutting width, while the influence of cutting speed and federates is not distinct. That shows the possibility of high-speed machining on fully sintering dental zirconia with development of coating technology of cutting tool.

A Theoretical Approach to Bow Deck Wetness of a High-Speed Ship

1990 ◽  
Vol 34 (03) ◽  
pp. 163-171 ◽  
Author(s):  
Ken Takagi ◽  
Akihiro Niimi
Keyword(s):  
Froude Number ◽  
Theoretical Approach ◽  
Analytical Method ◽  
High Speed ◽  
Theoretical Study ◽  
Two Dimensional ◽  
Long Wavelength ◽  
High Froude Number ◽  
Self Similar ◽  
Deck Wetness

A theoretical study of the phenomenon of deck wetness is presented and effects of the flare shape are discussed. It is shown that two-dimensional (2D) self-similar flow is applicable to the analysis of deck wetness on the assumption of long wavelength and high Froude number. The 2D self-similar flow which includes effects of the deck is calculated by an analytical method. Calculated results are compared with experimental results obtained at the limit of long wavelength, that is, in still water. Calculated results are used to determine the most suitable flare angle, and it is shown that increased flare is more effective than a knuckle to reduce bow deck wetness.

Tool-Chip Friction and Two-Dimensional Numerical Simulation Analysis of High-Speed Milling AISI304

2015 ◽  
Vol 1089 ◽  
pp. 377-380
Author(s):  
Lin Lin Guo ◽  
Guang Hui Li ◽  
Ning Xia Yin ◽  
Guang Yu Tan
Keyword(s):  
Finite Element ◽  
High Speed ◽  
Simulation Analysis ◽  
Chip Morphology ◽  
Element Model ◽  
Simulation Method ◽  
State Theory ◽  
Friction Model ◽  
Two Dimensional ◽  
High Speed Milling

The physical friction system model was established between the tool and the chip based on the analysis of tri-bological behavior of high speed milling process of the end mill. The finite element simulation method was employed to study the tool-chip friction model, and the two-dimensional(2D) finite element model of milling was created. The numerical results revealed the chip morphology, stress and temperature distribution of the tool-chip contact surface. The tool temperature field distribution provided supports for tool-chip friction state theory and the 3D milling model.

The Numerical Analysis of Contaminant Migration from Sanitary Landfill Sites

1977 ◽  
Vol 12 (1) ◽  
pp. 233-255
Author(s):  
J.F. Sykes ◽  
A.J. Crutcher
Keyword(s):  
Contaminant Transport ◽  
Cross Section ◽  
Element Model ◽  
Sanitary Landfill ◽  
Saturated Porous Media ◽  
Two Dimensional ◽  
Contaminant Migration ◽  
Southern Ontario ◽  
Galerkin Finite Element ◽  
Chloride Concentrations

Abstract A two-dimensional Galerkin finite element model for flow and contaminant transport in variably saturated porous media is used to analyze the transport of chlorides from a sanitary landfill located in Southern Ontario. A representative cross-section is selected for the analysis. Predicted chloride concentrations are presented for the cross section at various horizon years.

Load Spectrum Compiling and Fatigue Life Estimation of the Automobile Wheel Hub

2020 ◽  
Vol 13 ◽  
Author(s):  
Xintian Liu ◽  
Yang Qu ◽  
Xiaobing Yang ◽  
Yongfeng Shen
Keyword(s):  
Fatigue Life ◽  
High Speed ◽  
Two Dimensional ◽  
Load Spectrum ◽  
One Dimensional ◽  
Life Estimation ◽  
Load Spectra ◽  
Fatigue Life Estimation ◽  
Program Load Spectrum ◽  
Program Load

Background:: In the process of high-speed driving, the wheel hub is constantly subjected to the impact load from the ground. Therefore, it is important to estimate the fatigue life of the hub in the design and production process. Objective:: This paper introduces a method to study the fatigue life of car hub based on the road load collected from test site. Methods:: Based on interval analysis, the distribution characteristics of load spectrum are analyzed. The fatigue life estimation of one - dimensional and two - dimensional load spectra is compared by compiling load spectra. Results:: According to the S-N curve cluster and the one-dimensional program load spectrum, the estimated range fatigue life of the hub is 397,100 km to 529,700 km. For unsymmetrical cyclic loading, each level means and amplitude of load were obtained through the Goodman fatigue empirical formula, and then according to S-N curve clusters in the upper and lower curves and two-dimensional program load spectrum, estimates the fatigue life of wheel hub of the interval is 329900 km to 435200 km, than one-dimensional load spectrum fatigue life was reduced by 16.9% - 17.8%. Conclusion:: This paper lays a foundation for the prediction of fatigue life and the bench test of fatigue durability of auto parts subjected to complex and variable random loads. At the same time, the research method can also be used to estimate the fatigue life of other bearing parts or high-speed moving parts and assemblies.

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