Rajaprakash Ramachandramoorthy

Max Planck Institute for Sustainable Materials | MPIE · Department of Structure and Nano-/ Micromechanics of Materials

An equimolar NiCoFeCrGa high entropy alloy having dual-phase homogeneous components was studied, where the constituent phases exhibit distinct mechanical properties. Micropillars with various diameters were created from two differently heat treated samples, then they were compressed at slow strain rates, that revealed the material's limited sensiti...

Understanding the mechanical properties of metals at extreme conditions is essential for the advancement of miniaturized technologies. As dimensions decrease, materials will experience higher strain rates at the same applied velocities. Moreover, the interplay effects of strain rates and temperatures are often overlooked and could have critical eff...

Compressed sensing is an image reconstruction technique to achieve high-quality results from limited amount of data. In order to achieve this, it utilizes prior knowledge about the samples that shall...

Compressed sensing is an image reconstruction technique to achieve high-quality results from limited amount of data. In order to achieve this, it utilizes prior knowledge about the samples that shall be reconstructed. Focusing on image reconstruction in nanotomography, this work proposes enhancements by including additional problem-specific knowled...

Additive manufacturing of pure copper (Cu) via laser-powder bed fusion (L-PBF) is challenging due to the low energy absorptivity under infra-red laser. As a result, 3-dimensional architectures, known for excellent load-bearing and energy absorption capabilities, have not been fabricated in pure Cu, so far. This study, for the first time, Cu lattice...

Lattice structures composed of periodic solid frames and pores can be utilized in energy absorption applications due to their high specific strength and large deformation. However, these structures typically suffer from post-yield softenings originating from the limited plasticity of available material choices. This study aims to resolve such an is...

Template-assisted electrodeposition is a promising microscale additive manufacturing technique allowing to deposit pure metals with high resolution. To allow the application-relevant design of metamaterials, it is necessary to establish microstructure-mechanical property relationships under extreme conditions. In this work, a novel process based on...

The ability to predict the micro-scale strength and plasticity of fused-silica micro-components is crucial as their miniaturization and applications in harsh environments advance. This study focusses on the micro-mechanical behavior of fused silica micropillars at high temperatures and variable strain rates. 160 micropillars with a diameter of 1.6...

Microscale dynamic testing is vital to the understanding of material behavior at application relevant strain rates. However, despite two decades of intense micromechanics research, the testing of microscale metals has been largely limited to quasi-static strain rates. Here we report the dynamic compression testing of pristine 3D printed copper micr...

Microscale dynamic testing is vital to the understanding of material behavior at application relevant strain rates. However, despite two decades of intense micromechanics research, the testing of microscale metals has been largely limited to quasi-static strain rates. Here we report the dynamic compression testing of pristine 3D printed copper micr...

Tungsten carbide cobalt hardmetals are commonly used as cutting tools subject to high operation temperature and pressures, where the mechanical performance of the tungsten carbide phase affects the wear and lifetime of the material. In this study, the mechanical behaviour of the isolated tungsten carbide (WC) phase was investigated using single cry...

The paper deals with experiments on 3D printed lattices in a Split Hopkinson Pressure Bar. An energy-based evaluation of the measured wave signals enables us to compare the damping properties of two different copper lattice structures.

The increased risk of fracture in the elderly associated with metabolic conditions like osteoporosis poses a significant strain on health care systems worldwide. Due to bone's hierarchical nature, it is necessary to study its mechanical properties and failure mechanisms at several length scales. We conducted micropillar compression experiments on c...

High strain rate micromechanical testing can assist researchers in elucidating complex deformation mechanisms in advanced material systems. In this work, the interactions of atomic-scale chemistry and strain rate in affecting the deformation response of a Zr-based metallic glass was studied by varying the concentration of oxygen dissolved into the...

Shear-based material removal processes significantly influence the quality of workpiece surface and implicitly the component functional performance. An in-situ SEM nano-cutting enabled the study of crystal flow and lattice rotation occurring below the cutting edge in a polycrystalline Nickel superalloy. When nano-cutting within single grains a defo...

Tungsten carbide cobalt hardmetals are commonly used as cutting tools subject to high operation temperature and pressures, where the mechanical performance of the tungsten carbide phase affects the wear and lifetime of the material. In this study, the mechanical behaviour of the isolated tungsten carbide (WC) phase was investigated using single cry...

Two-photon lithography (TPL) enables the fabrication of metamaterials exhibiting unprecedented mechanical performance. Such lattice structures consist of micron-scale geometric features and are designed to achieve their envisioned properties through stretching and bending of individual trusses. Here, we present for the first time a comprehensive st...

Given the push towards miniaturization in electronics it is vital to develop techniques capable of fabricating metal microarchitectures. Unfortunately, owing to the resolution limits macroscale additive manufacturing techniques cannot be used to manufacture mesoscale parts with sub-micron resolution. Here we present a novel dual-templating techniqu...

In this work, we demonstrate that template-assisted electrodeposition is a viable route for fabricating fully metallic 3D micro-architectures with tailored properties. Firstly, we show that the process can be controlled with the aid of a 3D time-dependent electrodeposition simulation and that design feasibility can be investigated prior to the expe...

In this work, we demonstrate that template-assisted electrodeposition is a viable route for fabricating fully metallic 3D micro-architectures with tailored properties. Firstly, we show that the process can be controlled with the aid of a 3D time-dependent electrodeposition simulation and that design feasibility can be investigated prior to the expe...

Glass is recently envisioned as a stronger and more robust alternative to silicon in MEMS applications including high frequency resonators and switches. Identifying the dynamic mechanical properties of microscale glass is thus vital for understanding their ability to withstand shocks and vibrations in such demanding applications. But despite nearly...

Nanomechanical experiments on 1-D and 2-D materials are typically conducted at quasi-static strain rates of 10⁻⁴/s, while their analysis using molecular dynamic (MD) simulations are conducted at ultra-high strain rates of 10⁶/s and above. This order of magnitude difference in the strain rates prevents a direct one-on-one comparison between experime...

Electrospun carbon nanofibers, produced from polyacrylonitrile (PAN) nanofiber precursors, with their superior mechanical properties, are promising candidates for manufacturing advanced polymer composites. Here, we report a series of tensile tests performed in situ under scanning electron microscope (SEM)/transmission electron microscope (TEM) obse...

In bird flight, the majority of the wing surface consists of highly refined and hierarchically organized feathers. They are composed of barbs that stem from the feather shaft and barbules that branch from barbs, forming a rigid feather vane. Barbules provide adhesion within the vane through an interlocking hook-and-groove mechanism to allow for the...

Time-dependent mechanical characterization of nanowires is critical to understand their long-term reliability in applications such as flexible-electronics and touch screens. It is also of great importance to develop a theoretical framework for experimentation and analysis on the mechanics of nanowires under time-dependent loading conditions such as...

The characterization of nanomaterials under high strain rates is critical to understand their suitability for dynamic applications such as nanoresonators and nanoswitches. It is also of great theoretical importance to explore nanomechanics with dynamic and rate effects. Here we report in situ scanning electron microscope (SEM) tensile testing of bi...

Recent major improvements to the transmission electron microscope (TEM) including aberration-corrected electron optics, light-element-sensitive analytical instrumentation, sample environmental control, and high-speed and sensitive direct electron detectors are becoming more widely available. When these advances are combined with in situ TEM tools,...

Studies of carbon nanotube (CNT) based composites have been unable to translate the extraordinary load-bearing capabilities of individual CNTs to macroscale composites such as yarns. A key challenge lies in the lack of understanding of how properties of filaments and interfaces across yarn hierarchical levels govern the properties of macroscale yar...

Laser transmission welding is a method of joining plastics, where a laser beam of near-infrared wavelength passes through the laser transparent part and hits the laser absorbent part, which has been made absorbent using additives such as carbon black. The absorbed laser energy is converted into heat, which welds the interface of the two parts by me...

Laser transmission welding is a method of joining plastics, which benefits from the infrared transparency in majority of thermoplastics. During the process, a laser beam passes through the laser transparent part and hits the laser absorbent part, which has been made absorbent using additives such as carbon black. The absorbed laser energy is then c...