Material Data for Modelling Density Distributions in Green Parts

2011 ◽  
Vol 672 ◽  
pp. 207-214
Author(s):  
C. Shang ◽  
I. Csaba Sinka ◽  
J. Pan
Keyword(s):  
Constitutive Models ◽  
Powder Materials ◽  
Density Distributions ◽  
State Variable ◽  
Hardening Law ◽  
Deformation Plasticity ◽  
Powder Pressing ◽  
Die Compaction ◽  
Complex Parts ◽  
Cam Clay

Die compaction of powders is a process which involves filling a die with powder, compaction using rigid punches to form a dense compact and ejection from the die. The process can be treated as a large deformation plasticity problem. The challenge is to develop and implement appropriate constitutive models that capture the evolution of the powder from a loose state into a dense compact. In this paper we describe data analysis procedures and calibrate classic incremental plasticity models, such as Cam-Clay, Drucker-Prager cap models. The complexity of the models is increased from models with a hardening law to more complex constitutive models using density as state variable. The compaction behaviour of a range of powder materials is characterized experimentally. Numerical simulation of the compaction of simple parts and complex parts is demonstrated. The merits of various models are evaluated in terms of the balance between complexity and practicality. The discussion is illustrated with case studies exploring the applicability of the models specific to various powder pressing scenarios.

Compression and consolidation characteristics of structured natural clay

2004 ◽  
Vol 41 (6) ◽  
pp. 1250-1258 ◽  
Author(s):  
J -C Chai ◽  
N Miura ◽  
H -H Zhu ◽  
Yudhbir
Keyword(s):  
Numerical Analysis ◽  
Void Ratio ◽  
Natural Clay ◽  
Hardening Law ◽  
Modified Cam Clay ◽  
Calculated Load ◽  
Natural Clays ◽  
Consolidation Behavior ◽  
Better Than ◽  
Cam Clay

The compression and consolidation behavior of some structured natural clays are discussed. It is shown that for some structured natural clays, the relation between void ratio (e) and mean effective stress (p′) is more linear in a ln(e + ec) – ln(p′) plot (where ec is a soil parameter) than in an e – ln(p′) plot. It is proposed that for structured natural clay with a sensitivity value greater than 4, a linear ln(e + ec) – ln(p′) relation can be used in settlement and consolidation calculation. The effect of introducing a linear ln(e + ec) – ln(p′) relation on the calculated load–settlement curve and consolidation behavior of structured clays is discussed. The linear ln(e + ec) – ln(p′) relation was incorporated into the modified Cam–clay model by modifying the hardening law of the model. It is shown that using the linear ln(e + ec) – ln(p′) relation simulated the consolidation behavior of the structured natural clays better than using the linear e – ln(p′) relation.Key words: structured natural clay, compression, consolidation, constitutive model, numerical analysis.

scholarly journals Validation of a simple hypoplastic constitutive model for overconsolidated clays

2020 ◽  
Author(s):  
Shun Wang ◽  
Wei Wu
Keyword(s):  
Laboratory Tests ◽  
Constitutive Models ◽  
Standard Laboratory ◽  
Hypoplastic Model ◽  
Proposed Model ◽  
Modified Cam Clay ◽  
Overconsolidated Clays ◽  
Hypoplastic Constitutive Model ◽  
Comparison With Experiments ◽  
Cam Clay

AbstractHypoplastic constitutive models are able to describe history dependence using a single nonlinear tensorial function with a set of parameters. A hypoplastic model including a structure tensor for consolidation history was introduced in our previous paper (Wang and Wu in Acta Geotechnica, 2020, 10.1007/s11440-020-01000-z). The present paper focuses mainly on the model validation with experiments. This model is as simple as the modified Cam Clay model but with better performance. The model requires five parameters, which are easy to calibrate from standard laboratory tests. In particular, the model is capable of capturing the unloading behavior without introducing loading criteria. Numerical simulations of element tests and comparison with experiments show that the proposed model is able to reproduce the salient features of normally consolidated and overconsolidated clays.

Soil mechanics: breaking ground

2007 ◽  
Vol 365 (1861) ◽  
pp. 2985-3002 ◽  
Author(s):  
Itai Einav
Keyword(s):  
Grain Size ◽  
Critical State ◽  
Void Ratio ◽  
Soil Mechanics ◽  
Constitutive Models ◽  
Energy Balance Equation ◽  
Constitutive Modelling ◽  
Alternative Theory ◽  
Fitting Parameters ◽  
Cam Clay

In soil mechanics, student's models are classified as simple models that teach us unexplained elements of behaviour; an example is the Cam clay constitutive models of critical state soil mechanics (CSSM). ‘Engineer's models’ are models that elaborate the theory to fit more behavioural trends; this is usually done by adding fitting parameters to the student's models. Can currently unexplained behavioural trends of soil be explained without adding fitting parameters to CSSM models, by developing alternative student's models based on modern theories? Here I apply an alternative theory to CSSM, called ‘breakage mechanics’, and develop a simple student's model for sand. Its unique and distinctive feature is the use of an energy balance equation that connects grain size reduction to consumption of energy, which enables us to predict how grain size distribution (gsd) evolves—an unprecedented capability in constitutive modelling. With only four parameters, the model is physically clarifying what CSSM cannot for sand: the dependency of yielding and critical state on the initial gsd and void ratio.

scholarly journals Modeling strain and density distributions during high-pressure torsion of pre-compacted powder materials

2016 ◽  
Vol 5 (3) ◽  
pp. 179-186 ◽  
Author(s):  
Roman Kulagin ◽  
Yajun Zhao ◽  
Yan Beygelzimer ◽  
Laszlo S. Toth ◽  
Michail Shtern
Keyword(s):  
High Pressure ◽  
High Pressure Torsion ◽  
Powder Materials ◽  
Density Distributions

Numerical Simulation of Sheet Metal Forming Processes Using a New Yield Criterion

2007 ◽  
Vol 344 ◽  
pp. 833-840 ◽  
Author(s):  
Dan Sorin Comsa ◽  
Dorel Banabic
Keyword(s):  
Yield Criterion ◽  
Plastic Anisotropy ◽  
Equivalent Stress ◽  
Constitutive Models ◽  
Cold Forming ◽  
Material Parameters ◽  
Numerical Tests ◽  
Hardening Law ◽  
Asymptotic Function ◽  
New Formulation

The paper is focused on the development of a new phenomenological yield criterion able to describe the inelastic response of sheet metals subjected to cold forming. The model consists in two components: the equivalent stress and the hardening law. The equivalent stress is a function incorporating 8 material parameters. Due to these parameters, the new formulation is able to describe four normalized yield stresses (y0, y45, y90, yb) and four coefficients of plastic anisotropy (r0, r45, r90, rb). The hardening law is defined as a linearly asymptotic function containing 4 material parameters. The numerical tests presented in the last section of the paper prove the capability of the elastoplastic constitutive models based on the new yield criterion to model the earing as well as the wrinkling phenomena accompanying the deep-drawing process.

The Variable Threshold Rod Experiment: A Comparison of Measured and Computed Deformations

1993 ◽  
Vol 115 (2) ◽  
pp. 211-219 ◽  
Author(s):  
P. R. Dawson ◽  
P. S. Follansbee
Keyword(s):  
Boundary Conditions ◽  
Cold Working ◽  
Constitutive Models ◽  
Simple Extension ◽  
Inhomogeneous Deformation ◽  
Sensitive Test ◽  
Variable Model ◽  
Variable Threshold ◽  
State Variable ◽  
State Variable Model

A novel experiment has been developed to induce inhomogeneous deformations under simple extension boundary conditions. By appropriate prior cold working of stock material and fabrication of test specimens with tailored dimensions, the location of the deformation zones along the gage length of tensile specimens was controlled. By design, the deformations were chosen to concentrate either toward the harder or softer ends of the specimens. The experiment provides a sensitive test to judge the ability of constitutive models to replicate the behavior of metals undergoing inhomogeneous deformation. A comparison of experimental results with simulated response using an isotropic state variable model is presented.

scholarly journals Peculiarities of obtaining high-quality products of titanium alloys manufactured by direct laser deposition technology Особенности получения качественных изделий из титановых сплавов, изготовленных технологией прямого лазерного выращивания

2019 ◽  
Vol 13 (8) ◽  
pp. 722-733
Author(s):  
M.O. Gushchina ◽  
O.G. Klimova-Korsmik ◽  
S.A. Shalnova ◽  
A.M. Vildanov ◽  
E.A. Valdaytseva
Keyword(s):  
Processing Parameters ◽  
Laser Deposition ◽  
Powder Materials ◽  
Additive Technology ◽  
Direct Laser Deposition ◽  
Direct Laser ◽  
The Right ◽  
Complex Parts ◽  
Unique Individual ◽  
Deposition Technology

The additive technology of direct laser deposition (DLD) belongs to the class of 3D printing methods for metal parts and constructions. It is promising for the manufacture of large-sized complex parts for the aviation and shipbuilding industries. Methods of additive production dictate serious requirements for the properties of building powders, but with the right choice of system and taking into account all the processes that occur when a selected source acts on powder materials, unique individual material properties can be achieved. In this work, the influence of powder quality, protect atmosphere as well as processing parameters on the structure and properties of deposited parts manufactured Ti-6Al-4V investigated. Аддитивная технология прямого лазерного выращивания (ПЛВ) относится к классу методов 3D печати металлических изделий. Она является перспективной для изготовления крупногабаритных сложнопрофильных изделий авиационной и судостроительной промышленностей. Методы аддитивного производства диктуют серьезные требования к свойствам используемых порошков, но при правильном выборе системы и с учетом всех процессов, протекающих при воздействии выбранного источника на порошковые материалы можно добиться уникальных индивидуальных свойств материала. В данной работе представлены результаты исследований влияния качества порошков, качества атмосферы и технологических режимов процесса на структуру и свойства конечных изделий, изготовленных методом прямого лазерного выращивания из титанового сплава ВТ6. Кроме того, показана принципиальная возможность повторного использования титановых порошков для достижение более высоких экономических показателей процесса.

scholarly journals Study on arching effect in the embankment over pile - reinforced soft soil

2020 ◽  
Vol 61 (HTCS6) ◽  
pp. 19-25
Author(s):  
Hung Van Pham ◽  
Huy Quang Dang ◽  
Lam Phuc Dao ◽  
Long Khac Nguyen ◽  
Keyword(s):  
Stress Reduction ◽  
Soft Soil ◽  
Constitutive Models ◽  
Pile Group ◽  
3D Numerical Modeling ◽  
Soil Arching ◽  
Modified Cam Clay ◽  
Stress Concentration Ratio ◽  
Pile Group Effect ◽  
Cam Clay

The paper employes 3D numerical modeling to analyze the soil arching mechanism within embankment by FLAC3D code, based on the finite difference method (FDM). To consider the pile group effect, the 3D mesh of four pile has been created. Related to the constitutive models, the embankment is used Mohr - Coulomb model, the soft soil is represented by modified Cam - clay model, and footing and piles are employed by elasticity model. The numerical results focus on the soil arching phenomena in terms of stress distribution on piles and soft soil, the stress concentration ratio and the stress reduction ratio. Additionally, the axial force along pile and the settlements of embankment, soft soil and pile are studied.

Sign in / Sign up

Export Citation Format

Share Document