scholarly journals Prediction of Crashworthiness for Extruded Magnesium Materials

2015 ◽  
Vol 651-653 ◽  
pp. 1009-1014
Author(s):  
Dirk Steglich ◽  
X. Tian
Keyword(s):  
Deformation Behaviour ◽  
Compressive Loading ◽  
Yield Function ◽  
Loading Conditions ◽  
Compression Tests ◽  
Axial Deformation ◽  
Strain Anisotropy ◽  
Buckling Modes ◽  
Strength Differential ◽  
Plastic Potential

To assess the crashworthiness of simple wrought magnesium structures, the axial deformation behaviour of different square tubes produced from magnesium alloys AZ31 and ZE10 were numerically investigated under quasi-static compressive loading conditions. Finite-element simulations were conducted to predict and assess the plastic buckling and crush behaviour. The necessary data to determine parameters for the plastic potential were taken from compression tests conducted along different orientations. The yield function Hill48 was selected, despite its inability to capture the strength differential effect. The modelling approach pursued is justified by considering the mechanical loading conditions, the fabrication process of the profiles and its implication on strain anisotropy, balancing achievable accuracy and computational efforts. The simulation results revealed that the material work hardening rates evidenced in uniaxial compression tests influenced the buckling modes as well as the energy dissipation.

scholarly journals Mechanical properties and stress–dilatancy relationships of unsaturated soil under various cyclic loading conditions

2019 ◽  
Vol 15 (7) ◽  
pp. 1799-1813
Author(s):  
Win Tun Tun ◽  
Tomotaka Sato ◽  
Hirotaka Saito ◽  
Yuji Kohgo
Keyword(s):  
Mechanical Properties ◽  
Cyclic Loading ◽  
Potential Function ◽  
Unsaturated Soils ◽  
Triaxial Compression ◽  
Saturated Soils ◽  
Loading Conditions ◽  
Compression Tests ◽  
Plastic Potential ◽  
Plastic Potential Function

AbstractMost studies investigating the effect of cyclic loading on soil properties have been conducted for saturated soils. Embankments such as fill dams, roads and railways are usually constructed by unsaturated geo-materials and retained under unsaturated conditions during their in-service periods. Then when the stabilities of the embankments against dynamic motions such as earthquakes and traffic loads are evaluated, it is necessary to account for the cyclic properties of unsaturated soils. However, there are few studies investigating mechanical properties of unsaturated soils under cyclic loadings. There are two objectives in this paper. One objective is to investigate cyclic properties of an unsaturated silt under various cyclic loading conditions, while the other is to investigate the stress–dilatancy relationships; the relation of plastic strain increment ratio,  − dεvp/dγp, versus stress ratio, q/p′; and to derive the plastic potential function of the unsaturated silt. Cyclic triaxial compression tests under various loading conditions were performed using the unsaturated silt. The material used is an artificial silty soil named DL clay. It was found from the series of the tests that the stiffness of the soil increased with an increase in suction and the number of cyclic loadings. The total volume reductions in the specimens decreased with an increase in suction. When the numbers of cyclic loadings and suction increased, the dilation also increased. Each unique stress–dilatancy relationship could be found in both loading and unloading processes. The relationships were similar to those of saturated soils under cyclic loadings. A unique plastic potential function could also be derived from the stress–dilatancy relationships.

Dynamic and Quasi-Static Compressive Deformation Behaviour of Polyimide Foam at Various Elevated Temperature

2014 ◽  
Vol 566 ◽  
pp. 158-163 ◽  
Author(s):  
A. Yosimoto ◽  
Hidetoshi Kobayashi ◽  
Keitaro Horikawa ◽  
Keiko Watanabe ◽  
Kinya Ogawa
Keyword(s):  
Compressive Strength ◽  
Room Temperature ◽  
Deformation Behaviour ◽  
Testing Machine ◽  
Negative Temperature ◽  
Strain Rates ◽  
Compression Tests ◽  
Hopkinson Pressure Bar ◽  
Universal Testing ◽  
Pressure Bar

In order to clarify the effect of strain rate and test temperature on the compressive strength and energy absorption of polyimide foam, a series of compression tests for the polyimide foam with two different densities were carried out. By using three testing devices, i.e. universal testing machine, dropping weight machine and sprit Hopkinson pressure bar apparatus, we performed a series of compression tests at various strain rates (10-3~103s-1) and at several test temperatures in the range of room temperature to 280 ̊C. At over 100 s-1, the remarkable increase of flow stress was observed. The negative temperature dependence of strength was also observed.

Deformation and strength properties of some rocks in southern Ontario

1979 ◽  
Vol 16 (1) ◽  
pp. 108-120 ◽  
Author(s):  
K. Y. Lo ◽  
M. Hori
Keyword(s):  
Deformation Behaviour ◽  
Strength Properties ◽  
Compression Tests ◽  
Underground Structures ◽  
Southern Ontario ◽  
Analysis And Design ◽  
Rock Types ◽  
Anisotropic Elastic ◽  
Geological Formations ◽  
Independent Parameters

Uniaxial compression tests were performed on sedimentary rocks of five different geological formations at various sites in southern Ontario. The deformation behaviour is analysed in terms of the cross-anisotropic elastic theory and typical sets of five independent parameters for each rock unit have been obtained. It is shown that some of the rock types are significantly anisotropic both in deformation and strength behaviour. The practical relevance of the results in the analysis and design of underground structures in these rocks is discussed.

Non-linear influence of hydrostatic pressure on the yielding of asymmetric anisotropic sheet metals

2016 ◽  
Vol 23 (2) ◽  
pp. 159-180
Author(s):  
Farzad Moayyedian ◽  
Mehran Kadkhodayan
Keyword(s):  
Hydrostatic Pressure ◽  
Potential Functions ◽  
Face Centered Cubic ◽  
Sheet Metals ◽  
Strength Differential ◽  
Plastic Potential ◽  
Yield Functions ◽  
Non Linear ◽  
Data Points ◽  
Face Centered

The objective of the current research is the investigation into possible non-linear influence of hydrostatic pressure on yielding of asymmetric (exhibiting the so-called “strength-differential effect”) anisotropic sheet metals. To reach this aim, two yield functions are developed, called here “non-linear pressure sensitive criteria I and II,” (NPC-1 and NPC-2). In addition, the non-associated flow rules are employed for these new criteria. The yield functions are defined as non-linearly dependent on hydrostatic pressure, while the plastic potential functions are introduced to be pressure insensitive. To calibrate these criteria, the yield functions need 10 directional experimental yield stresses and the plastic potential functions need eight Lankford coefficients data points. Four well-known anisotropic sheet metals with different structures, namely AA 2008-T4, a Face Centered Cubic material (FCC), AA 2090-T3, a Face Centered Cubic material (FCC), AZ31, a hexagonal closed packed material (HCP) and high-purity [Formula: see text]-titanium (HCP) are considered as case studies. Finally, it is observed that NPC-1 and NPC-2 are more successful than previous criteria in anticipating directional strength and mechanical properties.

Atomistic Simulation Study of Mechanical Deformation of Al-Mg-Si Alloys

2021 ◽  
Vol 52 ◽  
pp. 149-163
Author(s):  
Hanae Chabba ◽  
Driss Dafir
Keyword(s):  
Deformation Behaviour ◽  
Compressive Loading ◽  
Embedded Atom Method ◽  
Stress Strain ◽  
Elasticity Limit ◽  
Embedded Atom ◽  
High Elasticity ◽  
Strain Relationship ◽  
Atomic Simulations ◽  
Strain Responses

Aluminum alloys have been attracting significant attention. Especially Al-Mg-Si alloys can exhibit an excellent balance between strength and ductility. Deformation mechanisms and microstructural evolution are still challenging issues. Accordingly, to describe how the type of phase influence mechanical behaviour of Al/Mg/Si alloys, in this paper atomic simulations are performed to investigate the uniaxial compressive behaviour of Al-Mg-Si ternary phases. The compression is at the same strain rate (3.1010 s−1); using Modified Embedded Atom Method (MEAM) potential to model the deformation behaviour. From these simulations, we get the total radial distribution function; the stress-strain responses to describe the elastic and plastic behaviors of GP-AlMg4Si6, U2-Al4Mg4Si4 and β-Al3Mg2Si6 phases. For a Detailed description of which phase influence hardness and ductility of these alloys; the mechanical properties are determined and presented. These stress-strain curves obtained show a rapid increase in stress up to a maximum followed by a gradual drop when the specimen fails by ductile fracture. From the results, it was found that GP-AlMg4Si6 & U2-Al4Mg4Si4 phases are brittle under uniaxial compressive loading while β-Al3Mg2Si6 phase is very ductile under the same compressive loading. The engineering stress-strain relationship suggests that β-Al3Mg2Si6 phase have high elasticity limit, ability to resist deformation and have the advantage of being highly malleable. Molecular dynamics software LAMMPS was used to simulate and build the Al-Mg-Si ternary system.

scholarly journals High-Temperature Flow Behaviour and Constitutive Equations for a TC17 Titanium Alloy

2019 ◽  
Vol 38 (2019) ◽  
pp. 168-177 ◽  
Author(s):  
Liu Shi-feng ◽  
Shi Jia-min ◽  
Yang Xiao-kang ◽  
Cai Jun ◽  
Wang Qing-juan
Keyword(s):  
Titanium Alloy ◽  
High Temperature ◽  
Constitutive Equation ◽  
Constitutive Equations ◽  
Deformation Behaviour ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Compression Tests ◽  
Average Absolute Relative Error ◽  
Wide Range

AbstractIn this study, the high-temperature deformation behaviour of a TC17 titanium alloy was investigated by isothermal hot compression tests in a wide range of temperatures (973–1223 K) and strain rates (0.001–10 s−1). Then, the constitutive equations of different phase regimes (α + β and single β phases) were developed on the basis of experimental stress-strain data. The influence of the strain has been incorporated in the constitutive equation by considering its effect on different material constants for the TC17 titanium alloy. Furthermore, the predictability of the developed constitutive equation was verified by the correlation coefficient and average absolute relative error. The results indicated that the obtained constitutive equations could predict the high-temperature flow stress of a TC17 titanium alloy with good correlation and generalization.

Modelling Tow Compression in Textile Preforms During Composites Processing

Aerospace ◽  
2004 ◽  
Author(s):  
P. Potluri ◽  
V. S. Thammandra ◽  
R. B. Ramgulam
Keyword(s):  
Deformation Behaviour ◽  
Compressive Loading ◽  
Final Part ◽  
Initial Part ◽  
Transverse Compression ◽  
Fiber Assembly ◽  
Compression Model ◽  
Out Of Plane ◽  
Composites Processing ◽  
Transfer Moulding

Fiber assemblies, in the form of woven, braided, nonwoven or knitted structures, are used as reinforcements in composites. These textile structures are subjected to in-plane membrane stresses such as tensile and shear, and out-of-plane stresses such as bending and transverse compression. Amongst various modes of deformation, transverse compaction behaviour is the least understood mode; however this mode is very important for composites processing using vacuum forming, resin transfer moulding, thermoforming and hot compaction methods. The present paper reports a computational approach to predicting the load-deformation behaviour of textile structures under compressive loading. During the compression of a random fiber assembly, fibers are subjected to kinematic displacements, bending and finally transverse compression of individual fibres. In the case of interlaced architectures, such as woven and braided structures, it is convenient to deal with deformations at meso-scale involving yarns or tows, and deal with inter-fiber friction and fibre compression at yarn/tow level. It can be seen from the load deformation graphs that the initial part is dominated by bending energy and the final part by compression energy. A combined yarn bending and compression model was in good agreement with the experimental curve during the entire load-deformation cycle. On the other hand, an elastica-based bending model predicts well during the initial part while tow compression model predicts well during the final part. Inter-fiber friction was initially ignored — this is being introduced in the refined model for both the dry and wet states.

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