Modeling of the impact of rigid ellipsoidal blocks by means of an elastic-visco-plastic constitutive model 

2021 ◽  
Author(s):  
Giuseppe Dattola ◽  
Giovanni Battista Crosta ◽  
Claudio Giulio di Prisco
Keyword(s):  
Constitutive Model ◽  
Three Dimensional ◽  
Impact Angle ◽  
Material Point ◽  
Lumped Mass ◽  
Mountain Areas ◽  
Block Motion ◽  
The Impact ◽  
Constitutive Parameters

<p>Rockfall is one of the most common hazards in mountain areas causing severe damages to structures/infrastructures and, human lives. For this reason, numerous are the papers published in the last decades on this subject, both introducing reliable approaches to simulate the boulder trajectory and defining design methods for sheltering structures. As is well known, the most popular strategy to simulate the block trajectory and velocity is based on the lumped mass material point approach. This is capable of describing the block trajectory, before either its natural arrest or impact against an artificial/natural obstacle, by suitably considering its interaction with soil/rock materials, interaction always dynamic, very often highly dissipative and defined, according to its nature, as sliding, rolling or impact.</p><p>In this framework, this study focusses on impacts and, in particular, on the role of block geometry in affecting the block kinematic response. The problem is approached numerically; by modifying a previously conceived elastic-viscoplastic constitutive model, based on the macro-element concept. and capable of satisfactorily simulating impacts of spherical blocks.</p><p>The modified constitutive model relaxes the assumption of spherical block by assuming an ellipsoidal shape and by allowing for the boulder rotation. These two changes make the problem more complex but allow to model more realistically the impact. For the sake of simplicity, the results shown in this work consider the block motion to be planar, but the model already allows to include general three dimensional conditions.</p><p>In this work, the model is briefly outlined and the procedure for calibrating the model constitutive parameters described. Then, the results of an extensive parametric analysis, employing constitutive parameters calibrated on experimental data taken from the literature, are discussed. In particular, the role of (i) the inner block orientation, and (ii) the inner impact angle is considered in terms of both kinematic variables and restitution coefficients. Finally, interpolation functions to compute restitution coefficients, once both block shape and inner impact block orientation are known, are provided.</p>

NUMERICAL SIMULATION OF HUMAN HEAD IMPACT USING THE MATERIAL POINT METHOD

2013 ◽  
Vol 10 (04) ◽  
pp. 1350014 ◽  
Author(s):  
SHUANGZHEN ZHOU ◽  
XIONG ZHANG ◽  
HONGLEI MA
Keyword(s):  
Constitutive Model ◽  
Brain Tissue ◽  
Three Dimensional ◽  
Material Point Method ◽  
Human Head ◽  
Material Point ◽  
Point Method ◽  
Skull Bone ◽  
Ball Impact ◽  
The Impact

In this paper, a three-dimensional material point human head model is constructed from the computed tomography (CT) scanned images of an adult male volunteer, and used to study the dynamic response of human head under the impact of a three-dimensional cylindrical lead projectile with a speed of 6.4 m/s. The model consists of skull bone, brain tissue and membrane of human head, which is close to the real one. The skull and membrane are modeled by an elastic constitutive model, and the brain tissue is modeled by an anisotropic viscoelastic constitutive model. These constitutive models have been implemented in our three-dimensional explicit material point method code, MPM3D, and is verified by comparing its numerical results for a ball impact problem with those obtained by LS-DYNA. The simulation results help illustrate the response of skull bone, membrane and brain tissues subjected to impact, which contributes to the understanding of the biomechanics and mechanisms of head injury.

A Sociocultural Perspective on Negotiating Digital Identities in a Community of Learners

2013 ◽  
pp. 210-224 ◽  
Author(s):  
Anna Peachey ◽  
Greg Withnail
Keyword(s):  
Social Interaction ◽  
Identity Development ◽  
Three Dimensional ◽  
Digital Identity ◽  
Sociocultural Perspective ◽  
Regular Feature ◽  
Virtual World Environments ◽  
The Impact ◽  
Digital Identities

Three dimensional virtual world environments are becoming an increasingly regular feature of the education landscape, providing the opportunity for richly graphical augmented and immersive learning activities. Those who participate in these experiences must mediate through an avatar, negotiating and managing the complexities of this new variation of digital identity alongside their more familiar identity as learner and/or teacher/facilitator. This chapter describes some key moments in the construction of digital identities as a lecturer and a student in the Open University’s community in Second LifeTM. The authors explore experiences in relation to the impact of trust and consistency from a sociocultural perspective, privileging the role of social interaction and context where meaning is socially produced and situationally interpreted, concluding that social interaction is pivotal to any meaningful identity development that takes place. The chapter ends with thoughts for future issues surrounding digital identity in relation to lifelong learning.

Role of Through Silicon Via in 3D Integration: Impact on Delay and Power

2020 ◽  
pp. 2150051
Author(s):  
Shivangi Chandrakar ◽  
Deepika Gupta ◽  
Manoj Kumar Majumder
Keyword(s):  
Power Dissipation ◽  
Three Dimensional ◽  
Propagation Delay ◽  
Model Parameters ◽  
3D Integration ◽  
Coupling Behavior ◽  
Power Delay Product ◽  
Silicon Vias ◽  
The Impact

The metal–semiconductor (MES)-based through silicon vias (TSV) has provided attractive solutions over conventional metal–insulator–semiconductor (MIS) TSVs in recent three-dimensional (3D) integration. This paper aims a comprehensive performance analysis of MIS and MES structures considering different TSV shapes such as cylindrical, tapered, annular, and square. At 32[Formula: see text]nm technology, a CMOS-based coupled driver-via-load (DVL) setup is introduced wherein each via is represented an equivalent RLGC model of MIS- and MES-based TSV shapes. The proposed electrical model accurately considers the impact of micro bump and inter-metal dielectric (IMD) effects at 32[Formula: see text]nm technology as per the fabrication house. A 3D electromagnetic (EM) structural wave simulation is performed to validate the RLGC model parameters of different TSV structures for an operating frequency of up to 20[Formula: see text]GHz. The proposed DVL setup is used to analyze the propagation delay, power dissipation, and dynamic crosstalk for different MIS- and MES-based TSV shapes. A significant improvement in the cross-coupling behavior can be obtained using the MES-based tapered TSV compared to the other MIS structures. Additionally, the power delay product (PDP) of the tapered MES is reduced by 92.4% compared to the conventional MIS-based cylindrical TSV.

scholarly journals The Role of Nanoparticle Shapes and Structures in Material Characterisation of Polyvinyl Alcohol (PVA) Bionanocomposite Films

Polymers ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 264 ◽  
Author(s):  
Mohanad Mousa ◽  
Yu Dong
Keyword(s):  
Polyvinyl Alcohol ◽  
Three Dimensional ◽  
Halloysite Nanotubes ◽  
Mechanical And Thermal Properties ◽  
Cloisite 30B ◽  
Bionanocomposite Films ◽  
The Impact ◽  
Nanoparticle Shapes ◽  
Selection Of

Three different types of nanoparticles, 1D Cloisite 30B clay nanoplatelets, 2D halloysite nanotubes (HNTs), and 3D nanobamboo charcoals (NBCs) were employed to investigate the impact of nanoparticle shapes and structures on the material performance of polyvinyl alcohol (PVA) bionanocomposite films in terms of their mechanical and thermal properties, morphological structures, and nanomechanical behaviour. The overall results revealed the superior reinforcement efficiency of NBCs to Cloisite 30B clays and HNTs, owing to their typical porous structures to actively interact with PVA matrices in the combined formation of strong mechanical and hydrogen bondings. Three-dimensional NBCs also achieved better nanoparticle dispersibility when compared with 1D Cloisite 30B clays and 2D HNTs along with higher thermal stability, which was attributed to their larger interfacial regions when characterised for the nanomechanical behaviour of corresponding bionanocomposite films. Our study offers an insightful guidance to the appropriate selection of nanoparticles as effective reinforcements and the further sophisticated design of bionanocomposite materials.

Fixed-time three-dimensional guidance law with input constraint and actuator faults

2020 ◽  
pp. 095441002097197
Author(s):  
Peng Li ◽  
Qi Liu ◽  
Chen-Yu He ◽  
Xiao-Qing Liu
Keyword(s):  
Fault Tolerant ◽  
Sliding Mode ◽  
Input Saturation ◽  
Three Dimensional ◽  
Impact Angle ◽  
Actuator Faults ◽  
Input Constraint ◽  
Guidance Law ◽  
The Impact ◽  
Impact Angle Constraint

This paper investigates the three-dimensional guidance with the impact angle constraint, actuator faults and input constraint. Firstly, an adaptive three-dimensional guidance law with impact angle constraint is designed by using the terminal sliding mode control and nonhomogeneous disturbance observer. Then, in order to solve the problem of the input saturation and actuator faults, an adaptive anti-saturation fault-tolerant three-dimensional law is proposed by using the hyperbolic tangent function based on the passive fault-tolerant control. Finally, the effectiveness of the designed guidance laws is verified by using the Lyapunov function and simulation.

A Modified Microplane Model Using Transformation Surfaces to Consider Loading History on Phase Transition in Shape Memory Alloys

2014 ◽  
Author(s):  
Milad Shirani ◽  
Reza Mehrabi ◽  
Masood Taheri Andani ◽  
Mahmoud Kadkhodaei ◽  
Mohammad Elahinia ◽  
...  
Keyword(s):  
Free Energy ◽  
Constitutive Model ◽  
Three Dimensional ◽  
Constitutive Models ◽  
Phenomenological Approach ◽  
Material Point ◽  
Loading History ◽  
Energy Potential ◽  
Microplane Model ◽  
Thermodynamic Driving Force

In most of the existing SMA constitutive models, it is assumed that transformation starts when a thermodynamic driving force reaches a specified amount regardless of loading history. In this work, a phenomenological approach is used to develop an enhanced one-dimensional constitutive model in which loading history is directly considered as one of the main parameters affecting the transformation start conditions. To generalize the model to three-dimensional cases, a microplane formulation based on volumetric-deviatoric is employed. A free energy potential is defined at the microplane level, integrated over all orientations at a material point to provide the macroscopic free energy. Experiments are carried out on Nitinol superelastic tubes to validate the newly proposed constitutive model. In these experiments, interruptions are applied during transformations to show the effects of loading history on transformation start conditions. Numerical results are compared with the experimental data to demonstrate the accuracy of the enhanced model.

Review and Assessment of Ratcheting Considerations for Design and Analysis

2010 ◽  
Author(s):  
Yogendra S. Garud
Keyword(s):  
Kinematic Hardening ◽  
Structural Response ◽  
Material Point ◽  
Multiaxial Loading ◽  
Key Characteristics ◽  
Response Versus ◽  
Material Creep ◽  
Plastic Shakedown ◽  
The Impact

This paper presents theoretical, practical, and computational considerations of significance in assessing the strain ratcheting under combined cyclic loads. Different aspects of ratcheting are covered comparing uniaxial versus multiaxial loading. Since ratcheting and (elastic or plastic) shakedown are generally influenced by the same underlying factors, the conditions under which shakedown is more likely to be the end result are reviewed with reference to the material response versus the structural response. A simple two-bar model is used to illustrate the key characteristics of ratcheting and the essential factors or conditions responsible for the ratcheting. For example, the role of material strain hardening vs. kinematic hardening, and the effects of non-symmetry in loading or material yielding are examined. The role of structural constraint in determining the actual ratcheting response of components as compared to the material (point) response is discussed. Based on the review and assessment of these observations the resulting practical considerations in limiting the impact of ratcheting are discussed. The ratcheting considerations in this paper are limited to the time independent deformation or plasticity, excluding the additional effect of time-dependent phenomena such as the material creep or stress relaxation.

The Impact of Example Modality and Physical Interactions on Design Creativity

2014 ◽  
Vol 136 (9) ◽  
Author(s):  
Christine A. Toh ◽  
Scarlett R. Miller
Keyword(s):  
Engineering Design ◽  
Three Dimensional ◽  
Idea Generation ◽  
Controlled Study ◽  
First Year ◽  
Design Creativity ◽  
Physical Interactions ◽  
2D And 3D ◽  
The Impact

Interacting with example products is an essential and widely practiced method in engineering design, yet little information exists on how the representation (pictorial or physical) or interaction a designer has with an example impacts design creativity. This is problematic because without this knowledge we do not understand how examples affect idea generation or how we can effectively modify or develop design methods to support example usage practices. In this paper, we report the results of a controlled study with first year engineering design students (N = 89) developed to investigate the impact of a designer's interaction with either a two-dimensional (2D) pictorial image or a three-dimensional (3D) product (through visual inspection or product dissection activities) and the resulting functional focus and creativity of the ideas developed. The results of this study reveal that participants who interacted with the physical example produced ideas that were less novel and less functionally focused than those who interacted with the 2D representation. Additionally, the results showed that participants who dissected the product produced a higher variety of ideas than those that visually inspected it. These results contribute to our understanding of the benefits and role of 2D and 3D designer-product interactions during idea development. We use these findings to develop recommendations for the use of designer-product interactions throughout the design process.

Fracture Behavior of the Hot Rolled Strip’s Surface Scale Layer from Different Impacts Angles

2022 ◽  
Vol 905 ◽  
pp. 67-72
Author(s):  
Shang Wang ◽  
Rui Can Hao ◽  
Hua Gang Liu ◽  
Xiao Chen Wang ◽  
Quan Yang
Keyword(s):  
Finite Element ◽  
Three Dimensional ◽  
Element Model ◽  
Impact Angle ◽  
Rolled Strip ◽  
Shot Blasting ◽  
Cracking Behavior ◽  
Scale Layer ◽  
Hot Rolled ◽  
The Impact

In order to improve the energy efficiency of shot blasting impact descaling, a three-dimensional finite element impact descaling model was established. Based on the finite element model, the cracking behavior of the scale layer on hot rolled strip from different impacts angles was simulated. The results of finite element calculation and theoretical analysis show that: (1)Under the premise of constant velocity, the descaling area increases with the increase of impact angle, but the increasing rate tends to be moderate. (2)The depth of the impact tunnel and the residual compressive stress surface (-200 MPa) increase as the impact angle goes bigger. The ideal range of impact angle for shot blasting descaling should be 60°-75°.

Analytical thermochronometric models of Earth’s crust during the late accretionary bombardment epoch (4.5-3.5 Ga)

2020 ◽  
Author(s):  
Stephen J. Mojzsis ◽  
Oleg Abramov
Keyword(s):  
Age Distribution ◽  
Three Dimensional ◽  
Plate Boundary ◽  
Impact Angle ◽  
Asteroid Belt ◽  
Size Frequency Distribution ◽  
Frequency Distributions ◽  
The Earth ◽  
Size Frequency ◽  
The Impact

<p>Late accretionary bombardments in the first billion years of solar system history strongly affected the initial physical and chemical states of the Earth. Evidence of ancient impacts can be preserved in the oldest known terrestrial zircons with ages up to ca. 4.4 Ga. Here, we use the Hadean zircon record to directly assess the thermal effects of impact bombardment on the early Earth’s crust, couple the results to models of closure temperature-dependent diffusive loss and U-Pb age-resetting in zircon, derive zircon ages, and compare them to published ages.</p><p>The impact bombardment model consists of (i) a stochastic cratering model which populates the surface with craters within constraints derived from the lunar cratering record, the size/frequency distribution of the asteroid belt, and dynamical models; (ii) analytical expressions that calculate a temperature field for each crater; and (iii) a three-dimensional thermal model of the terrestrial lithosphere, where craters are allowed to cool by conduction and radiation. Equations for diffusion in zircon are coupled to these thermal models to estimate the amount of age-resetting.</p><p>We present modeling results for the Earth between 4.5 Ga and 3.5 Ga based new mass-production functions. Mean surface temperatures and geothermal gradients were assumed as 20 °C and 70 °C/km. Total delivered mass was estimated at 0.0013(M<sub>planet</sub>), or 7.8 × 10<sup>21</sup> kg. The size-frequency distributions of the impacts were derived from dynamical modeling. We begin model runs with a global magma ocean, which would have been formed by the Moon-forming impact. Mean impactor density of 3000 kg/m<sup>3</sup> and impactor velocity distribution from [1,2] was used, and impact angle of each impactor was stochastically generated from a gaussian centered at 45 degrees. The typical impact velocity of the Earth is ~21 km s<sup>-1</sup>.</p><p>It is important to note that the model age outputs we report omit normal processes of generation of zircon-saturated magmas that were operative in the Hadean. We find that as the impact flux decreases with time and becomes negligible for the purposes of thermal modeling by ca. 3.5 Ga. We find that the probability of randomly selecting a zircon of a given age increases with increasing age, predicting a large number of very old zircons. This contrasts with the actual age distribution of Hadean zircons, which, for >4 Ga, indicates the opposite case: the probability of selecting a zircon of a given age decreases with increasing age. We interpret this discrepancy to mean that impacts were not the dominant process in determining the ages of Hadean zircons. This is consistent with observations that the majority of Hadean zircons had formation temperature significantly lower than those expected for melt sheets and thermobarometry measurements suggesting formation of some Hadean zircons in a plate boundary environment.</p><p>[1] Mojzsis, S.J. et al. (2019). Astrophys. J., 881, 44. [2] Brasser, R. et al. (2020) Icarus 338, 113514. </p>

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