Design and Manufacture of a Smart Macro-Structure with Changeable Effective Stiffness

2020 ◽  
Vol 12 (01) ◽  
pp. 2050001
Author(s):  
Mohammad Reza Hajighasemi ◽  
Majid Safarabadi ◽  
Azadeh Sheidaei ◽  
Mostafa Baghani ◽  
Majid Baniassadi
Keyword(s):  
Young’S Modulus ◽  
Periodic Structure ◽  
Young's Modulus ◽  
Strain Curve ◽  
Unit Cell ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Fused Deposition ◽  
Nonlinear Stress ◽  
A Cell

Smart materials are being utilized in many fields and different external stimuli are used to change specific properties of these materials. In this research, a novel method was developed to design a structure with the desired nonlinear effective Young’s modulus. This method is geometric based where the structures are designed with a gap between them. These structures exhibit nonlinear elastic response. Wide range of structures with desired stress–strain curve can be generated using this approach. First, a unit cell was designed and later used to create a periodic structure. Numerical simulations have been exploited to prove the efficiency of the method. A prototype was manufactured by the Fused Deposition Modeling (FDM) 3D printing method. The compression test was performed on the structure. Both simulations and experimental results proved that the effective Young’s modulus of the structure can be increased up to 142%. Second, the designed unit cell was optimized using Genetic Algorithm (GA) to achieve a cell with desired nonlinear stress–strain curve. This cell was optimized considering five effective geometric parameters to alter the effective Young’s modulus of the cell. Finally, a periodic structure was created by repeating a cell with two different gap’s distances. A structure with a desired stress–strain curve was designed using the same method.

Polysilicon Tensile Testing With Electrostatic Gripping

1998 ◽  
Vol 518 ◽  
Author(s):  
W. N. Sharpe ◽  
K. Turner ◽  
R. L. Edwards
Keyword(s):  
North Carolina ◽  
Young’S Modulus ◽  
Tensile Testing ◽  
Young's Modulus ◽  
Strain Curve ◽  
Electrostatic Forces ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Force Displacement

AbstractTechniques and procedures are described for tensile testing of polysilicon specimens that are 1.5 or 3.5 νm thick and have various widths and lengths. The specimens are fixed to the wafer at one end and have a large free end that can be gripped by electrostatic forces. This enables easy handling and testing and permits the deposition of 18 specimens on a one-centimeter square portion of a wafer. The displacement of the free end is monitored, which allows one to extract Young's modulus from the force-displacement record. Some of the wider specimens have two gold lines applied so that strain can be measured interferometrically directly on the specimen to record a stress-strain curve.The specimens were produced at the Microelectronics Center of North Carolina (MCNC). When compared with earlier results of wider MCNC specimens that were 3.5 μm thick, the Young's modulus is smaller and the strength is slightly larger.

Experimental Setup for the Determination of Mechanical Solder Materials Properties at Elevated Temperatures

2010 ◽  
Vol 638-642 ◽  
pp. 3793-3798
Author(s):  
Wolfgang H. Müller ◽  
Holger Worrack ◽  
Jens Sterthaus
Keyword(s):  
Mechanical Properties ◽  
Young’S Modulus ◽  
Elevated Temperatures ◽  
Young's Modulus ◽  
Linear Optimization ◽  
Strain Curve ◽  
Stress And Strain ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Non Linear

The fabrication of microelectronic and micromechanical devices leads to the use of only very small amounts of matter, which can behave quite differently than the corresponding bulk. Clearly, the materials will age and it is important to gather information on the (changing) material characteristics. In particular, Young’s modulus, yield stress, and hardness are of great interest. Moreover, a complete stress-strain curve is desirable for a detailed material characterization and simulation of a component, e.g., by Finite Elements (FE). However, since the amount of matter is so small and it is the intention to describe its behavior as realistic as possible, miniature tests are used for measuring the mechanical properties. In this paper two miniature tests are presented for this purpose, a mini-uniaxial-tension-test and a nanoindenter experiment. In the tensile test the axial load is prescribed and the corresponding extension of the specimen length is recorded, both of which determines the stress-strain- curve directly. The stress-strain curves are analyzed by assuming a non-linear relationship between stress and strain of the Ramberg-Osgood type and by fitting the corresponding parameters to the experimental data (obtained for various microelectronic solders) by means of a non-linear optimization routine. For a detailed analysis of very local mechanical properties nanoindentation is used, resulting primarily in load vs. indentation-depth data. According to the procedure of Oliver and Pharr this data can be used to obtain hardness and Young’s modulus but not a complete stress-strain curve, at least not directly. In order to obtain such a stress-strain-curve, the nanoindentation experiment is combined with FE and the coefficients involved in the corresponding constitutive equations for stress and strain are obtained by means of the inverse method. The stress-strain curves from nanoindentation and tensile tests are compared for two mate-rials (aluminum and steel). Differences are explained in terms of the locality of the measurement. Finally, material properties at elevated temperature are of particular interest in order to characterize the materials even more completely. We describe the setup for hot stage nanoindentation tests in context with first results for selected materials.

Molecular dynamics simulations of the effect of temperature and strain rate on the plastic deformation of body centred cubic iron nanowires

2021 ◽  
pp. 1-19
Author(s):  
Qian Wu ◽  
Yong Wang ◽  
Tao Han ◽  
Hongtao Wang ◽  
Laihui Han ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Plastic Deformation ◽  
Strain Rate ◽  
Yield Stress ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Strain Curve ◽  
Dislocation Slip ◽  
Stress Strain Curve ◽  
Stress Strain

Abstract The tensile tests of BCC Fe nanowires were simulated through molecular dynamics methods. The temperature and strain rate effects on the mechanical properties as well as the orientation-dependent plastic deformation mechanism were analyzed. For [001]-oriented BCC Fe nanowires, as the temperature increased, the yield stress and Young's modulus decreased. While the yield stress and Young's modulus increased as the strain rate increased. With the increase of temperature, when the temperature was less than 400 K, the twin propagation stress decreased dramatically, and then tended to reach a saturation value at higher temperatures. Under different temperatures and strain rates, the [001]-oriented Fe nanowires all deformed by twinning. The oscillation stage in the stress-strain curve corresponds to the process from the nucleation of the twin to the reorientation of the nanowire. For [110]-oriented Fe nanowires, the plastic deformation is dominated by dislocation slip. The independent events such as the nucleation, slip, and annihilation of dislocations are the causes of the unsteady fluctuations in the stress-strain curve. The Fe nanowires eventually undergo shear damage along the dominant slip surface.

scholarly journals Effect of Nanopores on Mechanical Properties of the Shape Memory Alloy

Micromachines ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 529
Author(s):  
Chunzhi Du ◽  
Zhifan Li ◽  
Bingfei Liu
Keyword(s):  
Mechanical Properties ◽  
Constitutive Model ◽  
Shape Memory ◽  
Young’S Modulus ◽  
Residual Strain ◽  
Surface Effect ◽  
Young's Modulus ◽  
Strain Curve ◽  
Stress Strain ◽  
Strength Limit

Nanoporous Shape Memory Alloys (SMA) are widely used in aerospace, military industry, medical and health and other fields. More and more attention has been paid to its mechanical properties. In particular, when the size of the pores is reduced to the nanometer level, the effect of the surface effect of the nanoporous material on the mechanical properties of the SMA will increase sharply, and the residual strain of the SMA material will change with the nanoporosity. In this work, the expression of Young’s modulus of nanopore SMA considering surface effects is first derived, which is a function of nanoporosity and nanopore size. Based on the obtained Young’s modulus, a constitutive model of nanoporous SMA considering residual strain is established. Then, the stress–strain curve of dense SMA based on the new constitutive model is drawn by numerical method. The results are in good agreement with the simulation results in the published literature. Finally, the stress-strain curves of SMA with different nanoporosities are drawn, and it is concluded that the Young’s modulus and strength limit decrease with the increase of nanoporosity.

Numerical Modeling of Macroscopic Behavior of Particulate Composite with Crosslinked Polymer Matrix

2011 ◽  
Vol 465 ◽  
pp. 129-132
Author(s):  
Luboš Náhlík ◽  
Bohuslav Máša ◽  
Pavel Hutař
Keyword(s):  
Young’S Modulus ◽  
Polymer Matrix ◽  
Young's Modulus ◽  
Numerical Models ◽  
Strain Curve ◽  
Particulate Composite ◽  
Material Behavior ◽  
Particulate Composites ◽  
Stress Strain ◽  
Crosslinked Polymer

Particulate composites with crosslinked polymer matrix and solid fillers are one of important classes of materials such as construction materials, high-performance engineering materials, sealants, protective organic coatings, dental materials, or solid explosives. The main focus of a present paper is an estimation of the macroscopic Young’s modulus and stress-strain behavior of a particulate composite with polymer matrix. The particulate composite with a crosslinked polymer matrix in a rubbery state filled by an alumina-based mineral filler is investigated by means of the finite element method. A hyperelastic material behavior of the matrix was modeled by the Mooney-Rivlin material model. Numerical models on the base of unit cell were developed. The numerical results obtained were compared with experimental stress-strain curve and value of initial Young’s modulus. The paper can contribute to a better understanding of the behavior and failure of particulate composites with a crosslinked polymer matrix.

Assessment of Springback Behaviour of 800-1200 MPa Dual-Phase Steel Grades

2021 ◽  
Vol 883 ◽  
pp. 151-158
Author(s):  
Ulas Durmaz ◽  
Sebastian Heibel ◽  
Thomas Schweiker ◽  
Marion Merklein
Keyword(s):  
Young’S Modulus ◽  
Elastic Strain ◽  
Bauschinger Effect ◽  
Young's Modulus ◽  
Strain Curve ◽  
Uniaxial Tensile ◽  
Dual Phase ◽  
Stress Strain ◽  
Dual Phase Steels ◽  
Microplastic Strain

Springback occurs in sheet metal forming due to elastic strain recovery after removal of process forces respectively after opening of the tool. For this reason, a precise description of springback requires the elastic stress-strain relationship described by the Young’s modulus as well as the internal stress distribution of the part before unloading. In this context, the Bauschinger effect influences the stress state before springback due to premature plastification during load reversal or load path change. As is well known, the stress-strain curve of a material during unloading is non-linear because of additional microplastic strain, which is reflected in a decrease of the Young’s modulus. The aim of this work is to characterize the aforementioned phenomena and their effect on springback for three dual-phase steels namely DH800, DH1000 and DP1200LY. For this purpose, cyclic tensile-compression tests as well as loading and unloading loops within uniaxial tensile tests are performed at different plastic strains. To evaluate the springback behavior of the investigated materials, two different hat-profiles geometries are investigated. By comparing the springback of dual-phase steels on part level, the significance of different material influences with regard to springback is evaluated. The results show that the investigated dual-phase steels exhibit a pronounced Bauschinger effect and a considerable amount of microplastic strain with increasing total strain. However, the comparison between the springback of the hat-profiles and the determined material parameters proves a significant influence of the elastic strain on springback, while microplastic strain and the Bauschinger effect have a minor influence.

Evaluation of yield strength by ultrasonic reconstruction of quadratic nonlinear Stress–Strain curve

2020 ◽  
Vol 112 ◽  
pp. 102242
Author(s):  
Jongbeom Kim ◽  
Chang-Soo Kim ◽  
Kyung-Cho Kim ◽  
Kyung-Young Jhang
Keyword(s):  
Yield Strength ◽  
Strain Curve ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Nonlinear Stress

Nonlinearity in the Dynamic Properties of Rubber

1957 ◽  
Vol 30 (1) ◽  
pp. 218-241 ◽  
Author(s):  
A. R. Payne
Keyword(s):  
Second Harmonic ◽  
Dynamic Properties ◽  
Strain Curve ◽  
Resonance Curve ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Positive Displacement ◽  
Static Modulus ◽  
Nonlinear Stress ◽  
Newtonian Liquids

Abstract The first two sections of this paper deal with the necessity for amending the classical Newtonian equations by assuming a nonlinear stress-strain curve in order to account for the presence of a considerable amount of second harmonic of the test frequency in the restoring forces in a rubber, in both forced-vibration and positive-displacement dynamic testers. The nonlinear stress-strain curve is applied also to a damped free-vibration curve of the Yerzley type, and is shown to account for the asymmetry of the envelope of the vibration curve. The latter part of the paper obtains a relationship between the dynamic modulus of loaded rubbers and amplitude of vibration, leading to equations analogous to those used in rheology to deal with rate of shear effects in non-Newtonian liquids, and to explain the effects of fillers on the static modulus and hardness of vulcanized rubbers. A resonance curve from a resonant vibrator is analyzed and the variation of modulus with amplitude is shown to exhibit the typical thixotropic effect associated with loaded rubbers subjected to vibrations. The last section discusses how the decrease of modulus with increasing amplitude can be attributed to two different mechanisms: (1) thixotropic breakdown of filler structure, (2) in compression, nonlinearity of the stress-strain curve.

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