Miniature Samples Research Articles

Mechanical Property Characterization of Cryo-Rolled Copper by Miniaturized Disk Bend and Nanoindentation Technique

The present study reports mechanical behavior of severe plastically deformed pure Cu under cryogenic conditions by miniaturized disk bend test (MDBT) and nanoindentation technique. MDBT is a useful technique to determine mechanical property of miniature samples under multiaxial state of stress. The samples were severely deformed by cryo-rolling upto 75% and 95% reduction. Microstructure evolution of cryo-rolled samples has been characterized using optical and EBSD technique. MDBT was performed on cryo-rolled 10-mm disk of ~200-μm thickness. Nanoindentation tests were also performed on the cryo-rolled samples. The hardness values obtained from nanoindentation tests were compared with yield stress obtained from MDBT. The present study established a good quantitative correlation between the two techniques. Mechanical dynamic parameters; strain rate sensitivity (m) and activation volume (V*) determined by MDBT and nanoindentation techniques showed close agreement in the results.

Investigations Into the Influence of Weld Zone on Formability of Fiber Laser-Welded Advanced High Strength Steel

In this study, two different dual phase steel grades DP980 and DP600, and IFHS steel sheets were laser welded by a 2-kW fiber laser. The weld quality of these three different LWBs was assessed with the help of microstructure, micro-hardness and transverse tensile tests. Tensile testing of longitudinal and miniature samples was performed to evaluate the mechanical properties of the weld zone. Formability of parent materials and LWBs were assessed in bi-axial stretch forming condition by Erichsen cupping test. To validate the weld zone properties, 3-D finite element models of Erichsen cupping test of LWBs was developed, and the failures in the deformed cups were predicted using two theoretical forming limit diagrams. It was observed that hardness of the fusion zone and HAZ in laser welded DP600 and IFHS steels was more compared to the respective parent metal. However, 29% reduction in hardness was observed at the outer HAZ of DP980 steel weldments due to tempering of martensite. Reduction of formability was observed for all the LWBs with two distinct failure patterns, and the maximum reduction in formability was observed in the case of DP980 LWBs. The presence of the soft zone is detrimental in forming of welded DP steels.

Evaluation of high temperature mechanical strength of Cr–Mo grade steel through small punch test technique

Remaining life assessment (RLA) of high temperature components calls for estimation current mechanical properties of the component material. For determination of mechanical properties of in-service components, large volumes of samples are required to be cut from components. The sample() removal warrants post-sampling repair by welding and mandatory post weld heat treatment. The time and the efforts involved in these exercises often limits the RLA to less reliable levels relying on the material’s original properties at the time of fabrication leading to over prediction.Research is being carried out for estimation of mechanical properties of materials by destructive testing of miniature samples under various modes. Small punch test (SPT) technology is one such technique which has generated significant interest of the researchers. However challenges exist to establish procedure of testing and development of field implementable characteristic co-relation between SPT parameters and material properties. Though reports are available on room temperature (RT) properties on variety of materials to a great extent, studies on estimation of high temperature properties through SPT are sparingly available. An attempt has been made to develop correlations between SPT parameters and high temperature mechanical properties of Cr–Mo grade material. This paper describes salient features of the test setup developed and used for conducting test at high temperature, experimental results on one of the Cr–Mo grade material followed by development of correlation equation for estimating tensile properties.

137 Controlling freezing using infrared radiation

Controlling ice growth is a significant tool in many fields such as preventing frost damage to plants, improving cryo-preservation of cells, tissues and organs, the frozen food industry, and cryopreservation procedures. We suggest a control of ice growth in super-cooled solutions by a combination of infrared (IR) radiation and antifreeze materials, such as antifreeze proteins (AFPs), for the purpose of cryobiology and food science. AFPs, which are part of the ice-binding proteins family, inhibit the growth of an ice crystal. As a result, the freezing temperature is reduced below the melting point. The hypothesis is that ice crystals can be stabilized in super-cooled solution by the use of the difference in the IR absorption of ice and water. Additional super-cooling can be achieved by AFPs. We use a homemade temperature-controlled system that allows fine control of the temperature of small amounts of liquid enclosed in a microdevice (Celik, Drori et al., 2013). The system includes an IR radiation to selectively heat and melt ice, due to the ability of IR radiation to heat ice more than water when a particular wavelength is chosen (Ullman, 2001). To measure the temperature within the device, we use a near-IR (NIR) camera and a band filter. This method is based on the temperature dependence of the NIR absorption of water (Kakuta, Fukuhara et al., 2011). Initial results show the ability to melt ice within microfluidic devices. We also were able to measure temperature field within the water using the IR camera. Simulation guided experiments are developed to show the control of ice growth using IR radiation in coexistence of ice crystals in super-cooled water. The combination we propose to control ice within miniature samples with an IR radiation and AFPs, opens the possibility of a new method for cryopreservation of cells and tissues. Source of funding: The Israel Science Foundation (ISF). Conflict of interest: None declared. ido.braslavsky@mail.huji.ac.il

Numerical and Experimental Characterizations of Damping Properties of SMAs Composite for Vibration Control Systems

Shape memory alloys (SMAs) are very interesting smart materials not only for their shape memory and superelastic effects but also because of their significant intrinsic damping capacity. The latter is exhibited upon martensitic transformations and especially in martensitic state. The combination of these SMA properties with the mechanical and the lightweight of fiberglass-reinforced polymer (FGRP) is a promising solution for manufacturing of innovative composites for vibration suppression in structural applications. CuZnAl sheets, after laser patterning, were embedded in a laminated composite between a thick FGRP core and two thin outer layers with the aim of maximizing the damping capacity of the beam for passive vibration suppression. The selected SMA Cu66Zn24Al10 at.% was prepared by vacuum induction melting; the ingot was subsequently hot-and-cold rolled down to 0.2 mm thickness tape. The choice of a copper alloy is related to some advantages in comparison with NiTiCu SMA alloys, which was tested for the similar presented application in a previous study: lower cost, higher storage modulus and consequently higher damping properties in martensitic state. The patterning of the SMA sheets was performed by means of a pulsed fiber laser. After the laser processing, the SMA sheets were heat treated to obtain the desired martensitic state at room temperature. The transformation temperatures were measured by differential scanning calorimetry (DSC). The damping properties were determined, at room temperature, on full-scale sheet, using a universal testing machine (MTS), with cyclic tensile tests at different deformation amplitudes. Damping properties were also determined as a function of the temperature on miniature samples with a dynamical mechanical analyzer (DMA). Numerical modeling of the laminated composite, done with finite element method analysis and modal strain energy approaches, was performed to estimate the corresponding total damping capacity and then compared to experimental results.

An improved miniature mixed-mode delamination setup for in situ microscopic interface failure analyses

Precise characterization of interface delamination in miniature interface structures is an ongoing challenge with the advent of miniaturization and multi-functionality in the electronics industry. Accurate numerical prediction of the interface behaviour is necessary to minimize delamination failures. Successful prediction requires (i) accurate determination of the interface properties like the critical energy release rate (CERR) over the full range of mode mixities and (ii) simultaneous in situ microscopic visualization of the delamination mechanism. These requirements were recently addressed by the development of the miniature mixed-mode bending (MMMB) setup (Kolluri et al 2009 Int. J. Fract.). In this paper an improved MMMB setup is presented, which overcomes the main limitations of the original design. Specifically, the improved design (i) can access a significantly larger range of interface systems due to its increased limits of maximum accessible load and stroke in all mode mixities, (ii) has significantly higher accuracy in load–displacement measurement due to its reduced clearance at the connectors, which is particularly relevant for miniature samples, and (iii) has a high reproducibility due to a newly added setup alignment tool. The measurement concept is validated on (industrially relevant) copper lead frame–moulding compound epoxy interface structures. The load–displacement curves and corresponding CERR values obtained from experiments over the full range of mode mixities are discussed in relation to the delamination mechanism observed during real-time in situ visualization. Specifically, the measured increase in the CERR towards mode II is related to a more discrete or jerky crack growth behaviour observed in the mode II dominant tests. Finally, the potential of the methodology for interface parameter characterization is illustrated.

Effect of europium(II) stearate on the mechanical properties and the oxidation resistance of UHMWPE

The objective of this pilot study is to investigate the effect of europium(II) stearate additive on the mechanical properties and oxidation resistance of an ultra-high molecular weight polyethylene (UHMWPE), which has been used as an articulating surface in prosthetic devices for many years. It is hypothesized in this study that combining the UHMWPE with lanthanide stearates could enhance oxidation resistance, leading to better preservation of the material’s mechanical integrity. Compression molded UHMWPE was doped at 0, 375 and 750 ppm of europium(II) stearate, γ -irradiated to 35 kGy in a nitrogen atmosphere, and accelerated aged in accordance with the ASTM standard F2003-02. Non-irradiated and nonaged samples were used as controls. Miniature samples were comparatively tested for mechanical properties using the small punch test. Oxidation indices (OIs) were obtained through the FTIR spectroscopy on thin film sections of all irradiated samples. The UHMWPE doped with the europium(II) stearate had the same small punch test curve shape as the conventional UHMWPE control; the ultimate displacement remained unchanged (approximately 4.33±0.02 mm), while the ultimate load and work-to-failure exhibited only small changes (<7.5% and <5.0%, respectively). The doped material was more resistant to oxidation than the control material, retaining 83% of its as-irradiated work-to-failure after irradiation and accelerated aging, versus only 53% for the control. Accelerated aging changed the average oxidation index of the control group from 0.07 to 0.40; whereas the average oxidation indices changed from 0.03 to 0.15 and from 0.05 to 0.13 for the 375 ppm and the 750 ppm doped condition, respectively.

The microstructure, tensile, and shear deformation behavior of an AZ31 magnesium alloy after extrusion and equal channel angular pressing

The shear punch testing (SPT) technique and the uniaxial tension tests were employed to evaluate the mechanical properties of the equal channel angularly pressed (ECAPed) AZ31 magnesium alloy. After extruding, the material was ECAPed for 1, 2, and 4 passes using route B C. The grain structure of the material was refined from 20.2 to 1.6 μm after 4 passes of ECAP at 200 °C. The 4 pass ECAPed alloy showed lower yield stress and higher ductility as compared to the as-extruded condition, indicating that texture softening has overcome the strengthening effects of grain refinement. The same trends in strength and ductility were also observed in shear punch testing. Similar shear strength and ductility values of the samples taken perpendicular to the extrusion direction (ED) and normal direction (ND) after 4 passes of ECAP indicated that {0 0 0 2} basal planes were inclined (∼45°) to the extrusion axis. The shear punch testing technique was found to be a useful method for verifying directional mechanical properties of the miniature samples of the ECAPed magnesium alloys.

Study of an ultrafine w-EDM technique

A precision ultrafine w-EDM (wire electrical discharge machining) technique specifically for machining intricate parts and structures is developed in this paper. A thumb-sized and versatile w-EDM device equipped with a complete control system for wire tension (ultrafine tungsten wire of 13 µm diameter) is designed and employed for the study of ultrafine w-EDM. The tension of the wire electrode is controlled by magnetic repulsive force to steady the wire during machining. Ultrafine wire cutting can be conducted in vertical-, horizontal- or slantwise-wire arrangements. Via some experiments, optimal machining conditions including discharge capacitance, feed rate, wire tension and the appropriate design for the w-EDM device are obtained. Two miniature samples including a micro of Taipei's landmark 101 building and a micro relay are fabricated and the feasibility of the proposed approach is verified. It is confirmed that the ultrafine w-EDM technique using an ultrafine tungsten wire of 13 µm was realized successfully.

A Remote, Non-destructive Laser Ultrasonic Material Evaluation System with Simplified Optical Fibre Interferometer Detection

An optical non-contact ultrasonic testing system is presented. It uses broadband surface acoustic wave impulses generated with a cylindrical lens focused laser line source. The detection of the ultrasound is achieved by a simple and yet effective design of optical fibre interferometer which provides good sensitivity and manoeuvrability. The effectiveness of the fibre interferometer is demonstrated by accurately measuring the broadband surface waves on various common metal structures. The measurement system’s ability for surface material evaluation is also demonstrated from fitting experimental surface wave dispersion curves with theoretical simulations. This measurement system can test small localised areas and miniature samples that were previously difficult to examine.

A method of using miniature samples for determining mechanical properties of metal of power-generating equipment at thermal power stations in Estonia

Devices for taking miniature samples of metal are described together with techniques for measuring mechanical properties of the metal of power-generating equipment using miniature samples.

Capturing the texture changes in a zirconium alloy during the allotropic phase transformation

High-energy synchrotron X-ray diffraction was used to measure in situ the texture of a cold-rolled zirconium alloy during α to β phase transformation. Miniature samples were heat treated by resistive heating, during which diffraction patterns were captured continuously using a two-dimensional X-ray detector. High-quality quantitative texture information was obtained from single diffraction images. Experimental data of the high-temperature β texture is presented, as well as evidence of recrystallization and β grain growth.

Mini-Tensile Experiments of Clock-Rolled Zirconium Plate

We present our efforts to measure the tensile strength of clock-rolled pure zirconium in the through-thickness (TT) direction of the plate. Although the plate is too thin to produce standard ASTM tensile samples in the TT orientation, such measurements are relevant to benchmarking our constitutive models of hardening and texture evolution. We have designed a fixture and sample to perform tensile tests on our 9 mm thick plate. The sample is a double-ligament mini-tensile sample: 8 × 8 × 1 mm overall; each ligament has a gage section of 1 × 1 × 3 mm. In contrast, our standard “macro” tensile sample is a flat dogbone with a gage section of 3 × 1.5 × 25 mm. We validate our design by comparing the results of mechanical tests performed on samples of both geometries. Although the hardening response is nearly identical, the flow stress of the miniature samples is offset by +25 MPa at the onset of plastic yield. We present our efforts to resolve the origin of this offset.

Microcharacterization of Damage in Materials for Advanced Nuclear Fission Plants

Miniature and sub-miniature samples were used for determination of mechanical properties of materials for advanced fission plants. Results from indentation and focused ion beam prepared micro-samples, punch tests and thin strip (irradiation) creep tests are shown. The results allow conclusions concerning materials damage. Irradiation damage profiles were determined with indentation. Results from micro-pillar tests showed a good agreement with results from conventional samples in case of oxide dispersion strengthened steels. Thin strip irradiation creep experiments revealed a negligible influence of dispersoid size/distribution on creep rates. Punch tests of fibre reinforced materials showed consistent results which still need quantitative analysis.

Miniaturized Samples for Bond Strength and Hermetic Sealing Evaluation for Transmission Laser Joints

Transmission laser bonded titanium coated glass/polyimide miniature samples were tested to find out bond strength and hermeticity. Bond strength was evaluated using a miniature lap shear specimen and by developing a pressure test specimen. The joint hermeticity was tested by Helium bomb test. Successful results from these tests and meaningful failure modes establish these tests as good methods to determine the integrity of the joints. This paper will analyze the results and provide the technical basis for utilizing these tests for reliable assessment of the quality of transmission laser joints.

Electrochemical lab on a chip for high-throughput analysis of anticancer drugs efficiency

We describe a new method for rapid, sensitive, and high-throughput detection of colon cancer cells' response to differentiation therapy, using a novel electrochemical lab-on-a-chip system. Differentiation-inducing agents such as butyric acid and its derivatives were introduced to miniature colon cancer samples within the nanovolume chip chambers. The efficacy of each of the differentiation-inducing agents was evaluated by electrochemical detection of the cellular enzymatic activity level, whereas reappearance of normal enzymatic activity denotes effective therapy. The results demonstrate the ability to evaluate simultaneously multiplex drug effects on miniature tumor samples (~15 cells) rapidly (5 minutes) and sensitively, with quantitative correlation between cancer cells' number and the induced current. The use of miniature analytical devices is of special interest in clinically relevant samples, in that it requires less tissue for diagnosis, and enables high-throughput analysis and comparison of various drug effects on one small tumor sample, while maintaining uniform biological and environmental conditions.

Metal/ceramic composites from freeze-cast ceramic preforms: Domain structure and elastic properties

Innovative metal/ceramic composites produced by melt infiltration of ceramic preforms prepared by a freeze-casting technique are examined in this study. These composites exhibit a characteristic hierarchical structure: On a mesoscopic length scale, lamellar domains with sizes up to several millimetres are observed. The aim of the present study was to analyze the anisotropic elastic properties of such a composite on different length scales. Experimental studies were carried out on samples containing about 44% alumina ceramic and 56% aluminium-based alloy (Al–12Si). Ultrasonic wave velocity measurements were carried out on macroscopic poly-domain samples as well as on miniature single-domain samples. The elastic constants derived from these measurements are discussed in light of elasticity models established for lamellar and for fibrous composites.

In-situ measurements of chondrocyte deformation under transient loading

Chondrocytes are responsible for the elaboration and maintenance of the extracellular (EC) matrix in articular cartilage, and previous studies have demonstrated that mechanical loading modulates the biosynthetic response of chondrocytes in cartilage explants. The goal of this study is to investigate the deformation behaviour of the chondrocyte and its microenvironment under transient loading, in order to address the relationship between the applied dynamic deformation and cellular strain. In-situ strain measurements were performed on cells in the middle (MZ) zone at early time points during ramp loading and at equilibrium. In this study, we characterized the behaviour of cartilage at the zonal and cellular levels under compressive loading using digital image analysis on miniature samples tested in a custom microscopy-based loading device. The experimental results indicate that significant strain amplification occurs in the microenvironment of the cell, with the minimum (compressive) principal strain found to be nearly 7X higher in the intracellular region (IC), and ~5X higher in the pericellular (PC) matrix than in the EC matrix at peak ramp. A similar strain amplification mechanism was observed in the maximum (tensile) principal strain, and this behaviour persisted even after equilibrium was reached. The experimental results of this study were interpreted in the context of a finite element model of chondrocyte deformation, which modelled the cell as a homogeneous gel, possessing either a spherical or ellipsoidal geometry, surrounded by a semi permeable membrane, and accounted for the presence of a PC matrix. The results of the FEA demonstrate significant strain amplification mechanism in the IC region, greater than had previously been suggested in earlier computational studies of cell-EC matrix interactions. Based on the FEA, this outcome is understood to result from the large disparity between EC matrix and intracellular properties. The results of this study suggest that mechanotransduction of chondrocytes may be significantly mediated by this strain amplification mechanism during loading.

Microstructural transformations and mechanical properties of cast NiAl bronze: Effects of fusion welding and friction stir processing

A plate of as-cast NiAl bronze (NAB) material was sectioned from a large casting. A six-pass fusion weld overlay was placed in a machined groove; a portion of the weld reinforcement was removed by milling and a single friction stir processing (FSP) pass was conducted in a direction transverse to the axis of and over the weld overlay. A procedure was developed for machining of miniature tensile samples and the distributions of strength and ductility were evaluated for the fusion weld metal; for the stir zone (SZ) produced by the friction stir processing; and for a region wherein friction stir processing had taken place over the fusion weld. A region of low ductility in the heat affected zone (HAZ) of the fusion weld and in the thermomechanically affected zone (TMAZ) of friction stir processed material was attributed to partial reversion of an equilibrium lamellar eutectoid constituent upon local heating above ∼800 °C and formation of non-equilibrium transformation products upon subsequent cooling. The adverse effect on ductility is worse in the heat affected zone of the fusion weld than in the thermomechanically affected zone of friction stir processing due to the lower heat input of the latter process. The implications of this work to engineering applications of friction stir processing are discussed.

Effects of platelet factors on biodegradation and osteogenesis in metaphyseal defects filled with nanoparticular hydroxyapatite—an experimental study in minipigs

There are no studies on the cellular activity in the early phase of biodegradation and bone healing of bone substitutes loaded with platelet factors (PLF). The purpose of this study was to evaluate the cellular effects of PLF in combination with nanoparticulate hydroxyapatite (HA) on the biodegradation and bone formation after 20 days. Autogenous PLFs were obtained by centrifugation of miniature pig blood samples and subsequent degranulation of platelets by calcium and thrombin. A cylindrical bone defect with a diameter of 8.9 mm was created in the distal femoral condyle of 20 miniature pigs. Four of the defects were left empty, 8 were filled with HA with loading and 8 with HA loaded with PLF. The distal femur was harvested after 20 days and TRAP-staining, cathepsin-K and CD44 staining and scanning electron microscopy were performed for cellular assessment of biodegradation was done. Histomorphometry of new bone formation and of biodegradation of HA material was performed. PLF loading of HA led to statistically significant more TRAP-positive cells with enhanced biodegradation of the nanoparticulate HA but no statistically enhanced new bone formation compared to unloaded HA. Furthermore, there was a higher number of CD44 and cathepsin-K positive cells by PLF-loading. In summary, PLF led to stimulation of the cellular process of the biodegradation of HA.