Modification Of Material Properties Research Articles

Influence of Selective Laser Heat Treatment Pattern Position on Geometrical Variation

Selective laser heat treatment allows local modification of material properties and can have a wide range of applications within the automotive industry. Enhanced formability and strength are possible to achieve. As the process involves selective heating, positioning of the heat treatment pattern in local areas is vital. Pattern positioning is often suggested based on the part design and forming aspects of the material to avoid failures during manufacturing. Along with improving material properties in desired local areas, the process also produces unwanted distortion in the material. Such effects on variation should be considered and minimized. In this paper, the heat treatment pattern is offset from its original position and its effect on geometrical variation is investigated. Boron steel blanks are selectively laser heat treated with a specific heat treatment pattern and then cold formed to the desired shape. Two heat treatment pattern dimensions are examined. Geometrical variation at the blank level and after cold forming, and springback after cold forming are observed. Results show that pattern offsetting increases the effect on geometrical variation. Therefore, correct positioning of the heat treatment pattern is important to minimize its effect on geometrical variation along with enhancement in the material properties. Knowledge from this study will contribute to various stages of the geometry assurance process.

T6 Heat Treatment Impact on the Random Frequency Vibration Stress of Al–Si–Mg Alloys

Recent studies show an interest on the static and dynamic mechanical properties in applications where both influence the overall performance of mechanical systems. This study explores the impact of the T6 heat treatment in the elastic and damping properties of Al–Si–Mg alloys. Consequently, the role of such properties is characterized by the stresses that are developed in resonant structures. Experimental testing shows that, due to pinning length modifications, the heat treatments generate a progressive increase in Young’s modulus and a reduction in loss factor. Recurring to finite element analysis, it is concluded that such modifications in material properties generate a reduction in resonant stress after solution treatment. This stress tends to increase as the artificial ageing progresses. A model, based on an exponential decay function, is proposed to describe the variation of resonant stress as the elastic and damping properties are changed during the T6 treatment.

Buildings with environmental quality management, part 3: From log houses to environmental quality management zero-energy buildings

The discussion in this article starts in the 1920s, that is, at the time of the humble beginnings of building science and brings us to 2020s with the development of net-zero energy buildings. The knowledge accumulated by explaining observed failures in the practice of construction slowly formed a basis for moving toward a predictive capability and to an integration of modeling and testing. Furthermore, we have learned that interactions between energy efficiency, indoor environmental quality, and moisture management are so critical that the three issues must be considered simultaneously. Effectively, a change in the low energy is needed to ensure durability of materials and cost considerations for these buildings. At this stage, one could observe a clear change in the mind-set of the scientific community. Forty years after construction of the first 10 passive homes, we made a shocking observation—an adequate technology has been developed, but our lack of vision prevents effective use of this technology. Again, we need to modify our vision and change the design paradigm to balance comfort, building durability, and cost-effectiveness. If the quest for sustainable buildings is our ultimate objective, then we should learn more from the surrounding nature; termites appear to master the art of hygrothermal control better than humans because they can optimize transient conditions to maintain a stable interior comfort zone. Thus, in the article to follow a new compact building envelope design package is proposed, applicable to different climates with specific modifications of critical hygrothermal material properties. This approach is called the Environmental Quality Management. This will be the second step for a building science (physics) needed to become a leading force in the transition to sustainable built environments.

Mechanical behavior of metastatic vertebrae are influenced by tissue architecture, mineral content, and organic feature alterations.

Diminished vertebral mechanical behavior with metastatic involvement is typically attributed to modified architecture and trabecular bone content. Previous work has identified organic and mineral phase bone quality changes in the presence of metastases, yet limited work exists on the potential influence of such tissue level modifications on vertebral mechanical characteristics. This work seeks to determine correlations between features of bone (structural and tissue level) and mechanical behavior in metastatically involved vertebral bone. It is hypothesized that tissue level properties (mineral and organic) will improve these correlations beyond architectural properties and BMD alone. Twenty-four female athymic rats were inoculated with HeLa or Ace-1 cancer cells lines producing osteolytic (N = 8) or mixed (osteolytic/osteoblastic, N = 7) metastases, respectively. Twenty-one days post-inoculation L1-L3 pathologic vertebral motion segments were excised and μCT imaged. 3D morphometric parameters and axial rigidity of the L2 vertebrae were quantified. Sequential loading and μCT imaging measured progression of failure, stiffness and peak force. Relationships between mechanical testing (whole bone and tissue-level) and tissue-level material property modifications with metastatic involvement were evaluated utilizing linear regression models. Osteolytic involvement reduced vertebral trabecular bone volume, structure, CT-derived axial rigidity, stiffness and failure force compared to healthy controls (N = 9). Mixed metastases demonstrated similar trends. Previously assessed collagen cross-linking and proline-based residues were correlated to mechanical behavior and improved the predictive ability of the regression models. Similarly, collagen organization improved predictive regression models for metastatic bone hardness. This work highlights the importance of both bone content/architecture and organic tissue-level features in characterizing metastatic vertebral mechanics. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:3013-3022, 2018.

Characterization and performance analysis of Li-doped ZnO nanowire as a nano-sensor and nano-energy harvesting element

A complete investigation of the effect of Li doping on the physical, material, electromechanical and piezoelectric properties of ZnO nanowires (NWs) is presented. Low temperature hydrothermal growth technique is used to grow vertically aligned crystalline ZnO NWs doped with different concentrations of Li. Characterization techniques reveal considerable physical, material and electromechanical property modifications of the ZnO NWs due to the incorporation of Li dopants. Atomic Force Microscope is utilized to apply controlled amount of force on the fabricated NWs to assess their piezoelectric response. More than twenty two-fold improvement is observed in sensitivity due to the combined effect of modifications in NW geometry and piezoelectric properties with the addition of Li. Finite element method simulations were performed to decouple the individual effect of Li doping on the NW size and on the piezoelectric coefficient and to see how much each effect plays a role in the sensitivity improvement. It is estimated that the changes in the material and electromechanical properties alone are responsible for more than seven-fold improvement in the sensitivity. The impact of ‘kick-out’ diffusion mechanism of Li in ZnO is one of the major factors responsible behind this sensitivity improvement. It is also observed that there is an optimum level of Li doping concentration which can lead to the best piezoelectric performance by the ZnO NWs. The novelty of this work lies on the detailed analyses to illustrate the physics and impact of Li dopants in ZnO NW structures from a piezoelectric point of view towards improving their application as a nano-sensing and nano-energy harvesting element.

On the interaction between welding residual stresses: A numerical and experimental investigation

The interaction of weld induced residual stresses is an important issue for multi-pass and repair welding operations; effective prediction of the magnitude and location of peak residual stresses can lead to improved lifing predictions and greater understanding of the performance of components in service; however, the interaction of existing residual stress field with new ones imposed by fusion welding processes has received little attention to date. This study presents a numerical and experimental investigation into the interaction of bead-on-plate welds in thick plates of IN718 with the aim of evaluating the effects of pre-existing weld residual stresses on the final global residual stress distribution. Sequentially coupled thermo-mechanical finite element (FE) models, which have been validated through temperature measurements, optical macrography and residual stress measurements, performed using the neutron diffraction technique, have been used to investigate the interactions. The results show good correlation between the experimental and model residual stress fields, demonstrating that the FE models are capable of predicting the redistribution of existing residual stress fields subjected to fusion welding processes and that this can be achieved with the use of parent material properties throughout, without considering any material property modifications which may occur due to microstructural changes in and around the weld region. It can also be seen from the results that, even with the relatively thick plates used in the study, a plane-stress state exists in the plates with a normal stress of approximately zero in all cases.

Process Intensification Principles Applied to Thermal Energy Storage Systems—A Brief Review

Process intensification (PI) technologies represent all approaches leading to size reduction and efficiency improvement of process equipment. Thermal Energy Storage (TES) systems are key elements in renewable and recovery thermal energy deployments and their performance can benefit from PI principles. This study covers a brief analysis and state of the art of several PI technologies applied to TES systems. All sensible, latent and thermochemical storage systems are covered. Two surface-to-volume ratios closely related to component size and system performance are first analysed. They theoretically show how PI principles may inspire the performance enhancement of TES systems. Then, a brief synthesis on successful PI applications in sensible, latent and thermochemical storages is given. Their approaches mainly consist of thermal stratification preservation, modular design, heat and mass transfer enhancement as well as material properties modification. Finally, potential TES system improvement directions based on PI principles are recommended.

Effect of modifications in mineralized collagen fibril and extra-fibrillar matrix material properties on submicroscale mechanical behavior of cortical bone.

A key length scale of interest in assessing the fracture resistance of bone is the submicroscale which is composed of mineralized collagen fibrils (MCF) and extra-fibrillar matrix (EFM). Although the processes through which the submicroscale constituents of bone contribute to the fracture resistance in bone have been identified, the extent of the modifications in submicroscale mechanical response due to the changes in individual properties of MCFs and EFM has not been determined. As a result, this study aims to quantify the influence of individual MCF and EFM material property modifications on the mechanical behavior (elastic modulus, ultimate strength, and resistance to failure) of bone at the submicroscale using a novel finite element modeling approach that incorporate 3D networks of MCFs with three different orientations as well as explicit representation of EFM. The models were evaluated under tensile loading in transverse (representing MCF separation) and longitudinal (representing MCF rupture) directions. The results showed that the apparent elastic modulus at the submicroscale under both loading directions for all orientations was only affected by the change in the elastic modulus of MCFs. MCF separation and rupture strengths were mainly dependent on the ultimate strength of EFM and MCFs, respectively, with minimal influence of other material properties. The extent of damage during MCF separation increased with increasing ultimate strength of EFM and decreased with increasing fracture energy of EFM with minimal contribution from elastic modulus of MCFs. For MCF rupture, there was an almost one-to-one linear relationship between the percent change in fracture energy of MCFs and the percent change in the apparent submicroscale fracture energy. The ultimate strength and elastic modulus of MCFs had moderate to limited influence on the MCF rupture fracture energy. The results of this study quantified the extent of changes that may be seen in the energy dissipation processes during MCF rupture and separation relative to the changes in the individual constituents of the tissue. This new knowledge significantly contributes to improving the understanding of how the material property alterations at the submicroscale that can occur due to diseases, age-related changes, and treatments affect the fracture processes at larger length scales.

Effects of material properties on warpage in fused deposition modeling parts

Fused deposition modeling (FDM) offers many advantages over conventional manufacturing methods, but it is limited by the number of materials available. Extending FDM technology to semicrystalline polymers has been challenging due to the crystallization that occurs during cooling which results in FDM part warpage. Previous work used process simulation models to study the effects of material parameters and FDM process variables on the part warpage seen using polypropylene (PP). In this work, the process simulation models were adapted to investigate warpage of FDM parts made with a high-performance semicrystalline polymer, polyphenylene sulfide (PPS). Material parameters in the PPS process simulation models were individually changed to the PP values to investigate which material parameters cause PP to exhibit higher warpage than PPS. Material parameters of interest included coefficient of thermal expansion (CTE), thermal conductivity, heat capacity, and Young’s modulus. Additional material parameters based on material property modification through the addition of fillers were investigated in order to establish the relationship between material parameters and warpage values. The simulation models suggested that the CTE has the largest impact on FDM part warpage. Decreasing the CTE in the simulation model resulted in a decrease in the FDM part warpage by the same factor.

Excavating hidden adsorption sites in metal-organic frameworks using rational defect engineering

Metal–organic frameworks are known to contain defects within their crystalline structures. Successful engineering of these defects can lead to modifications in material properties that can potentially improve the performance of many existing frameworks. Herein, we report the high-throughput computational screening of a large experimental metal–organic framework database to identify 13 frameworks that show significantly improved methane storage capacities with linker vacancy defects. The candidates are first identified by focusing on structures with methane-inaccessible pores blocked away from the main adsorption channels. Then, organic linkers of the candidate structures are judiciously replaced with appropriate modulators to emulate the presence of linker vacancies, resulting in the integration and utilization of the previously inaccessible pores. Grand canonical Monte Carlo simulations of defective candidate frameworks show significant enhancements in methane storage capacities, highlighting that rational defect engineering can be an effective method to significantly improve the performance of the existing metal–organic frameworks.

Detection of charges at the interphase of polymeric nanocomposites

The use of nanoscale filler in polymeric insulating materials can lead to a modification of macroscopic material properties which is attributed to the properties of the interphase between the nanoscale filler particles and the surrounding polymer. In the present study, the interphase of two kinds of nanoscale silica particles embedded in silicone rubber was investigated with Electrostatic Force Microscopy (EFM). The phase signal measured above the particle and the adjacent polymer show a parabolic dependence on the tip voltage and a characteristic shift between each other. By numerical simulation with a 3D model it could be shown that the presence of a charge at the particle would result in such a parabolic dependence on the tip voltage, and that the vertical and horizontal shift depend on the charge magnitude. From electrostatic considerations it is known that charges could be present subject to a number of unknown parameters like contact potential differences, capacitive coupling and other measurement parameters. By eliminating the unknown parameters in the relevant formulae it could be shown that charges are present at particles, thus giving evidence that an electric double layer around the particles in polymeric nanocomposites exist.

Sensitivity of the Drift-Diffusion Approach in Estimating the Power Conversion Efficiency of Bulk Heterojunction Polymer Solar Cells

There are numerous theoretical approaches to estimating the power conversion efficiency (PCE) of organic solar cells (OSCs), ranging from the empirical approach to calculations based on general considerations of thermodynamics. Depending on the level of abstraction and model assumptions, the accuracy of PCE estimation and complexity of the calculation can change dramatically. In particular, PCE estimation with a drift-diffusion approach (widely investigated in the literature), strongly depends on the assumptions made for the physical models and optoelectrical properties of semiconducting materials. This has led to a huge deviation as well as complications in the analysis of simulated results aiming to understand the factors limiting the performance of OSCs. In this work, we intend to highlight the complex relation between mobility, exciton dynamics, nanoscale dimension, and loss mechanisms in one framework. Our systematic analysis represents key information on the sensitivity of the drift-diffusion approach, to estimate how physical parameters and physical processes bind the PCE of the device under the influence of structure, contact, and material layer properties. The obtained results ultimately led to recommendations for putting effort into certain properties to get the most out of avoidable losses, presented the impact and importance of modification of material properties, and in particular, recommended to what degree the design of new material could improve OSC performance.

The investigation of boron-doped diamond absorbance spectrum

The trend of using of radiation with shorter wave length in leading high technological processes demands the detected search of materials for the solid-state electronics equipment and optical systems of an ultra violet and vacuum ultra violet spectral range. Diamond photodetectors of ultra violet radiation have the advantage of their opponents due to their unique properties, such as high sensitivity at the range of 190–250 nm and low sensitivity to the solar irradiation. The modification of semiconductive diamond material properties by the doping to get photodetectors with the different width of photosensitivity range is of a great interest. Due to this fact the spectroscopic investigation of artificial diamonds doped with boron took place for the definition of their applicability to produce the wide-spectral photosensitive equipment. The samples of thin diamond films were cut out in a crystallography plane (001). Sample transmission spectra were measured by vacuum infrared Fourier transform spectrometer at the range of 400–7000 cm-1. As a result it was explored that diamond based detectors doped with boron could be applied for the detection of infrared irradiation at the average infrared spectral range, however it is necessary to optimize the doping level of diamond materials to reach the compromise between the sensitivity and the speed capability of produced diamond photodetectors.

Anisotropic thin films formation rate on PEDOT : PSS layer with high azimuthal anchoring

AbstractOriented organic layers have great potential for organic electronics devices because of the unique modification of material properties without extensive chemical synthesis. Such layers can be prepared by wet coating of anisotropic organic molecules on top of specific surface of alignment layer. One of the most important parameter that indicates alignment properties of the surface is the anchoring energy. In this paper, we investigate azimuthal anchoring energy of pure and glycerol‐doped PEDOT : PSS layers and study the influence of the alignment layer preparation on the order parameter of the top wet‐coated oriented organic emitter. We confirm that the azimuthal anchoring energy increase leads to improvement of both dichroic ratio and contrast ratio of polarized emitter layer rod‐coated on top of the PEDOT : PSS. Suggested mechanism of anisotropic emitter formation at wet deposition grounds possibility of linear deposition rate of 2 m/s on top of PEDOT : PSS layer with obtained azimuthal anchoring above >10−4 J/m2.

The effect of cutting conditions on power inputs when machining

Any technological process involving modification of material properties or product form necessitates consumption of a certain power amount. When developing new technologies one should take into account the benefits of their implementation vs. arising power inputs. It is revealed that procedures of edge cutting machining are the most energy-efficient amongst the present day forming procedures such as physical and technical methods including electrochemical, electroerosion, ultrasound, and laser processing, rapid prototyping technologies etc, such as physical and technical methods including electrochemical, electroerosion, ultrasound, and laser processing, rapid prototyping technologies etc. An expanded formula for calculation of power inputs is deduced, which takes into consideration the mode of cutting together with the tip radius, the form of the replaceable multifaceted insert and its wear. Having taken as an example cutting of graphite iron by the assembled cutting tools with replaceable multifaceted inserts the authors point at better power efficiency of high feeding cutting in comparison with high-speed cutting.

High fat-fed diabetic mice present with profound alterations of the osteocyte network

Diabetes mellitus is considered to be an independent risk factor for bone fragility fractures. Reductions in bone mass, observed only with type 1 diabetes mellitus, as well as modifications of bone microarchitectures and tissue material properties are landmarks of diabetes-related bone alterations. An interesting feature observed in type 2 diabetes mellitus (T2DM) is the augmented concentration in circulating sclerostin. This observation prompts us to hypothesize that modifications of osteocyte network and perilacunar mineralization occur in T2DM. As such, the aims of the present study were to ascertain by quantitative backscattered electron imaging, confocal microscopy and image analysis, modifications of perilacunar tissue mineral density, osteocyte morphology and osteocyte network topology in a mouse model of high fat-induced type 2 diabetes. As compared with lean control animals, diabetic mice exhibited a significant 48% decrease in perilacunar mineralization heterogeneity although mean perilacunar mineralization was unchanged. Furthermore, in diabetic animals, osteocyte volume was significantly augmented by 34% with no change in the overall number of dendrite processes. Finally, the network topology was profoundly modified in diabetic mice with increases in the mean node degree, mean node volume and hub numbers whilst the mean link length was reduced. Overall, it appeared that in diabetic animals, the dendritic network exhibited features of a scale-free network as opposed to the single-scale characteristic observed in lean controls. However, it is important to ascertain whether diabetic patients exhibit such modifications of the osteocyte network and whether anti-diabetic drugs could restore normal osteocyte and network parameters, thereby improving bone quality and protecting against fragility fractures.

Optically and rheologically tailored polymers for applications in integrated optics

We demonstrate an epoxy acrylate based system on which various micro-optical applications can be realized. With this innovative and flexible material concept, it is possible to adjust viscosity (3mPas<η<46Pas) as required for different microstructuring processes e.g. inkjet printing, spin coating, and stereolithography and simultaneously precisely tailor refractive indices (1.518<nD,20<1.569) which is essential to implement optical sensor concepts. The practicability of this material system is demonstrated for optical waveguide production and selected applications. The fast and low cost modification of optical and rheological material properties is advantageous for the fabrication of micro-optical polymer devices including planar-optical polymer sensor networks.

Selected laser methods for surface structuring of biocompatible diamond-like carbon layers

Laser based surface structuring methods are among the fastest growing techniques and displace other surface treatments for applications such as marking, change of topography and microstructure. Such changes may lead to controlled modification of material properties, including their biocompatibility. The paper presents two laser techniques — picosecond Direct Laser Writing (DLW) and multi-beam Direct Laser Interference Lithography (DLIL). The purpose of the research was to create different shapes and dimensions of 2D and 3D periodical microstructures on the surface of thin diamond like carbon (DLC) coatings on different substrates. Resulting structures were further tested to find the influence of laser processing on the interaction of created scaffolds with the living cells in the direction of improvement of their directional growth and adhesion. The use of two different patterning methods (DLW and DLIL) allowed creation of structures with periods ranging between sub-microns to tens of microns, with different pattern resolutions, shapes (linear, dotted, crossed, hierarchical) and depths. Preliminary analyses have shown the possibility of high degree of control and improvement in the directional growth of smooth muscle cells and the proliferation of the endothelial cells, cultivated on migration channels created at DLC layers.

Validation of Shoulder Response of Human Body Finite-Element Model (GHBMC) Under Whole Body Lateral Impact Condition.

In previous shoulder impact studies, the 50th-percentile male GHBMC human body finite-element model was shown to have good biofidelity regarding impact force, but under-predicted shoulder deflection by 80% compared to those observed in the experiment. The goal of this study was to validate the response of the GHBMC M50 model by focusing on three-dimensional shoulder kinematics under a whole-body lateral impact condition. Five modifications, focused on material properties and modeling techniques, were introduced into the model and a supplementary sensitivity analysis was done to determine the influence of each modification to the biomechanical response of the body. The modified model predicted substantially improved shoulder response and peak shoulder deflection within 10% of the observed experimental data, and showed good correlation in the scapula kinematics on sagittal and transverse planes. The improvement in the biofidelity of the shoulder region was mainly due to the modifications of material properties of muscle, the acromioclavicular joint, and the attachment region between the pectoralis major and ribs. Predictions of rib fracture and chest deflection were also improved because of these modifications.

The effect of eigenstrain induced by ion beam damage on the apparent strain relief in FIB-DIC residual stress evaluation

FIB milling using Ga ions is known to be accompanied by implantation, multiplication of material defects, material property modification (e.g. amorphisation), inelastic shrinking/swelling and residual stress generation. These processes affect the reliability of the micro-ring-core method for residual stress evaluation. Safe use of this technique requires formulating approaches that provide quantitative criteria of the method's validity. In the present study this task is accomplished by proposing a numerical model based on eigenstrain. Parametric simulations were performed to identify the extent to which the FIB-DIC micro-ring-core measurements are affected. As an example of a real and relevant material system, the procedure was applied to silicon material. The curvature of an AFM cantilever due to FIB damage was monitored, and the eigenstrain magnitude determined by matching the model to observations. Using the resulting eigenstrain profile, parametric analysis was performed in terms of the pillar radius, and the elastic strain field calculated at the pillar surface that is monitored in the FIB-DIC micro-ring-core method. An important property of the model is its versatility that allows it to be adapted to different milling conditions and geometries to determine the ultimate spatial resolution limits of the FIB-DIC method.