Evaluation of Material Properties of Copper Thin Films by Micro-indentation Tests

AbstractA model is developed to predict the magnitude and pattern of stress due to drying of polymer films. This model combines diffusion-and-convection equation with large deformation elasto-viscoplasticity, utilizing concentration dependent elastic and viscoplastic material properties to better represent the behavior of drying thin films.The results show that the highest stress occurs at film surface where the concentration depletion is the highest. The magnitude of this stress is induced by increasing mass transfer across the film surface but reduced by increasing diffusion coefficient. The edge effect is significant but local, limited to about four film thicknesses. Similarly, change in substrate induces extra stress.

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ELASTO-PLASTIC PROPERTIES OF Mo-MODIFIED Ti DEDUCED FROM INDENTATION TESTS AND FINITE ELEMENT ANALYSIS

Surface Review and Letters ◽

10.1142/s0218625x18502256 ◽

2019 ◽

Vol 26 (07) ◽

pp. 1850225

Author(s):

YONG MA ◽

ZHAO YANG ◽

SHENGWANG YU ◽

BING ZHOU ◽

HONGJUN HEI ◽

...

Keyword(s):

Finite Element ◽

Surface Treatment ◽

Load Capacity ◽

Indentation Test ◽

Element Analysis ◽

Plastic Properties ◽

Polynomial Expression ◽

Indentation Tests ◽

Graded Material ◽

Micro Indentation

The aim of this paper is to establish an approach to quantitatively determine the elasto-plastic parameters of the Mo-modified Ti obtained by the plasma surface alloying technique. A micro-indentation test is conducted on the surface under 10[Formula: see text]N. Considering size effects, nanoindentation tests are conducted on the cross-section with two loads of 6 and 8[Formula: see text]mN. Assuming nanoindentation testing sublayers are homogeneous, finite element reverse analysis is adopted to determine their plastic parameters. According to the gradient distributions of the elasto-plastic parameters with depth in the Mo-modified Ti, two types of mathematical expressions are proposed. Compared with the polynomial expression, the linear simplified expression does not need the graded material to be sectioned and has practical utility in the surface treatment industry. The validation of the linear simplified expression is verified by the micro-indentation test and corresponding finite element forward analysis. This approach can assist in improving the surface treatment process of the Mo-modified Ti and further enhancing its load capacity and wear resistance.

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Comparison of biphasic material properties of equine articular cartilage estimated from stress relaxation and creep indentation tests

Current Directions in Biomedical Engineering ◽

10.1515/cdbme-2021-2092 ◽

2021 ◽

Vol 7 (2) ◽

pp. 363-366

Author(s):

Thomas Reuter ◽

Christof Hurschler

Keyword(s):

Articular Cartilage ◽

Stress Relaxation ◽

Material Properties ◽

Soft Tissues ◽

Sensitivity Analyses ◽

Creep Model ◽

Fe Model ◽

Relaxation Model ◽

Marquardt Algorithm ◽

Indentation Tests

Abstract Mechanical parameters of hard and soft tissues are explicit markers for quantitative tissue characterization. In this study, we present a comparison of biphasic material properties of equine articular cartilage estimated from stress relaxation (ε = 6 %, t = 1000 s) and creep indentation tests (F = 0.1 N, t = 1000 s). A biphasic 3D-FE-based method is used to determine the biomechanical properties of equine articular cartilage. The FE-model computation was optimized by exploiting the axial symmetry and mesh resolution. Parameter identification was executed with the Levenberg- Marquardt-algorithm. Additionally, sensitivity analyses of the calculated biomechanical parameters were performed. Results show that the Young’s modulus E has the largest influence and the Poisson’s ratio of ν ≤ 0.1 is rather insensitive. The R² of the fit results varies between 0.882 and 0.974 (creep model) and between 0.695 and 0.930 (relaxation model). The averaged parameters E and k determined from the creep model yield higher values in comparison to the relaxation model. The differences can be traced back to the experimental settings and to the biphasic material model.

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Size Scale Dependence of Deformation in NiTi

10.1115/imece2000-1683 ◽

2000 ◽

Author(s):

Ken Gall ◽

Martin L. Dunn ◽

Yiping Liu ◽

Paul Labossiere ◽

Huseyin Sehitoglu ◽

...

Keyword(s):

Thin Films ◽

Mechanical Properties ◽

Shape Memory ◽

Quantitative Information ◽

Scale Dependence ◽

Micro Electro Mechanical Systems ◽

Testing Techniques ◽

Shape Memory Materials ◽

Mems Testing ◽

Micro Indentation

Abstract Recent work [1-5] has suggested that a lucrative future for shape memory materials such as NiTi is in the area of micro-electro-mechanical systems (MEMS). To design MEMS and predict their behavior during service, we must have quantitative information on the mechanical properties of scaled down NiTi materials. One way of obtaining the mechanical properties of scaled down materials is with unique MEMS testing fixtures. Although this approach is favorably analogous to macroscopic testing techniques it is not always feasible owing to the difficulty of handling the microscopic samples. Many smart material actuators are deposited thin films [1-5] and separating the films from their substrate and subsequently testing them is beyond our current MEMS processing and handling tools. An alternative method to quantify the properties of microscale materials is through micro-indentation, which has been previously applied to NiTi polycrystals [6]. Although micro-indentation is simple to accomplish, interpretation and quantification of the results is not as straightforward, as will be demonstrated in this work.

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