For materials scientists and researchers, understanding the intricate relationship between a material’s microstructure and its mechanical properties is paramount. Electron backscatter diffraction (EBSD) offers a window into the crystallographic orientation of materials, while micromechanical testing provides insights into their mechanical behavior. Combined, these techniques can reveal a wealth of information about deformation mechanisms, damage initiation, and overall material performance.

Step-by-Step Process to Couple EBSD with Micromechanical Testing

1. Sample Preparation: The Foundation of Accurate Results

The first step in this methodical approach is preparing the sample for both EBSD and micromechanical testing. Achieving a mirror finish through polishing is essential for EBSD, as it ensures accurate data collection. Additionally, etching the sample will reveal its microstructure, allowing for clearer analysis. For micromechanical testing, the sample should be meticulously cut and shaped to the desired geometry, ensuring that it fits the testing apparatus and provides reliable results.

2. EBSD Analysis: Deciphering Crystallographic Orientation

Once the sample is prepared, it’s time to perform the EBSD analysis. This technique determines the crystallographic orientation of the material, a crucial piece of information for materials scientists. By understanding this orientation, professionals can predict and identify the deformation mechanisms that might occur during subsequent micromechanical tests.

3. Micromechanical Testing: Probing Mechanical Behavior

With the EBSD data in hand, researchers can proceed with micromechanical testing. Techniques such as nanoindentation, microcompression, or microtensile testing are employed to study the material’s deformation and fracture behavior. One of the significant advantages of coupling these techniques is the ability to observe material behavior in real-time using EBSD, providing a dynamic view of the deformation processes.

4. Data Analysis: Correlating Microstructure with Mechanical Properties

The final step involves a thorough analysis of the results. By correlating the EBSD data with observations from micromechanical testing, researchers can draw connections between the material’s crystallographic orientation and its mechanical behavior. This correlation offers invaluable insights into the microstructure and mechanical properties of materials at the microscale, enhancing the depth and breadth of understanding for materials scientists.

The Role of Alemnis in Advancing Micromechanical Testing

Alemnis AG stands at the forefront of micro- and nanomechanical property measurement. With a suite of instruments designed for in-situ material testing, we are committed to advancing the field and providing tools that enable researchers to delve deeper into the intricacies of material behavior. By offering solutions that facilitate the coupling of EBSD with micromechanical testing, we play a pivotal role in the ongoing exploration of materials at the micro and nano scales.

In the ever-evolving field of materials science, the coupling of electron backscatter diffraction with micromechanical testing represents a significant leap forward. By enabling more comprehensive characterization of materials, this combination paves the way for breakthroughs in understanding deformation processes and material performance.

At Alemnis, we recognize the potential of this synergy and invite researchers and professionals to explore our range of instruments.

Understanding stress relaxation is essential for ensuring the long-term integrity and reliability of various materials under different conditions and is crucial for those designing structural applications. In this blog post, we look at the concept of stress relaxation, its occurrence in viscoelastic materials, and its importance in the design and application of materials.

Stress Relaxation: Definition and Phenomenon

Stress relaxation is the gradual reduction in stress over time while maintaining a constant strain. It is commonly observed in viscoelastic materials, particularly polymers, which show time-dependent relaxation when subjected to stress or strain. When a stress relaxation experiment is conducted, a sample is rapidly strained to a fixed length at a constant temperature, and the stress is recorded as a function of time. During the experiment, the length of the sample remains constant, allowing stress relaxation to occur at a molecular level through molecular relaxation and viscous flow.

Stress Relaxation vs. Creep

It is important to differentiate stress relaxation from creep, as they are distinct phenomena. Creep involves the constant application of stress while adding an increasing amount of strain. Creep experiments are conducted by subjecting a material to a constant stress and recording the resulting strain over time. In contrast, stress relaxation experiments involve applying a constant strain and monitoring the stress response over time. These differing experimental setups highlight the unique characteristics of stress relaxation and creep in materials.

Factors Influencing Stress Relaxation

Various factors influence the rate of stress relaxation in polymers, including the type of polymer, the presence of fillers, strain levels, strain rates, and temperature. Additionally, the polymer’s stress relaxation behavior can be significantly impacted by the nature and composition of the polymer. 

It’s also important to know that the stress relaxation rate depends on the strain levels and strain rates applied to the material. Higher strain levels and faster strain rates typically lead to more rapid stress relaxation. Temperature also plays a vital role in stress relaxation, as higher temperatures generally result in faster relaxation.

Furthermore, external factors alone do not determine stress relaxation as it is also influenced by the intrinsic properties of the material. This includes its alloy, temper, and orientation. Considering these factors is crucial in accurately predicting and designing materials for specific applications.

Importance of Stress Relaxation in Design and Applications

Understanding stress relaxation is paramount when designing and selecting materials for structural applications because prolonged exposure to stress can result in irreversible deformation in plastic materials, compromising their structural integrity.

The data obtained from stress relaxation testing is particularly valuable in failure analysis and predicting material behavior under specific loading conditions. By accounting for stress relaxation, engineers can accurately model and simulate the long-term performance of materials, improving the overall reliability and safety of structural components.

Alemnis: Stress Relaxation Measurement Solutions

As scientific experts, it is essential to recognize the significance of stress relaxation and its implications in various industries. At Alemnis, we are dedicated to providing leading micro- and nanomechanical property measurement instruments in a range of material science applications.

Our Alemnis Standard Assembly (ASA) is a unique and powerful solution used reliably for stress relaxation measurements. It can be used in in-situ, ex-situ, in synchrotron, and Micro CT configurations in true displacement mode for understanding compression artifacts, load drops, strain rate jumps, and sudden load excursions in real-time.  

To ensure your stress relaxation measurements are accurate and reliable, contact Alemnis today, and let us show you the solution.

Creep testing and fatigue testing are two highly regarded methods used to assess the behavior of materials under varying loading conditions. Creep testing measures the gradual rate of deformation of a material under constant load and temperature conditions. Fatigue testing, on the other hand, involves subjecting a material or structure to cyclic loading. Experts must understand how these two methods are different, as they are necessary for evaluating the long-term performance and reliability of materials in various industries. In this blog post, we will look into the differences between fatigue testing and creep testing, including their underlying principles, testing procedures, and failure mechanisms.

Fatigue Testing

Fatigue testing is a method of mechanical testing conducted by adding cyclic loading to a structure. This method generates data on fatigue life and cracks, identifies critical areas, and assesses the safety of structures prone to fatigue. Fatigue occurs when a material undergoes fluctuating stresses and strains, eventually leading to cracks or a complete fracture. Fatigue tests aim to simulate real-world conditions and predict the material’s endurance under repetitive loading cycles. This method is common in the transport industry for testing components manufactured for automobiles and aircraft, as well as in the medical industry for testing implant materials.

Creep Testing

Creep testing assesses the progressive deformation of a material under constant load and temperature conditions. Creep is the tendency of materials to deform when subjected to long-term stress, especially at elevated temperatures. To perform a creep test, a constant stress is applied while maintaining a constant temperature. The corresponding strain is then recorded over time. Creep testing is crucial for understanding material behavior in high-temperature applications like jet engines and power plants.

Distinguishing Factors

The primary difference between fatigue and creep testing lies in the type of loading and the failure mechanisms involved. Fatigue testing looks at cyclic loading and how cracks or fractures are likely to develop due to fluctuating stresses and strains. In contrast, creep testing focuses on the material’s deformation under constant load and temperature conditions over extended periods. While both methods assess material performance, they address different aspects of long-term durability and reliability.

What is Creep Fatigue?

The term ‘creep fatigue’ often appears when discussing fatigue or creep testing. Creep fatigue, which involves crack elongation over time, may occur when materials are subjected to stress and extreme temperatures. It is important to note that surface finish and heat treatment factors can significantly impact fatigue life.

How is Creep Fatigue Tested?

To test for metal creep or fatigue, specialized procedures are employed. However, the earliest stages of creep are not visible to the naked eye and occur on a molecular level. Creep-to-fail testing is the most reliable method to determine the long-term performance of products with metal components. Different testing techniques can be utilized, such as flexural and compression creep tests. One commonly employed method is the tensile creep test.

Fatigue testing and creep testing serve different purposes in evaluating material behavior under specific loading conditions. While fatigue testing focuses on cyclic loading and crack propagation, creep testing assesses the deformation of materials under constant load and temperature conditions. Both testing methods are indispensable for comprehending the long-term performance and reliability of materials in diverse applications. By employing appropriate testing techniques, manufacturers can ensure the integrity of their products and meet the demands of various industries.

Alemnis: Providing Mechanical Testing Instruments

Alemnis is a pioneering company that empowers groundbreaking academic research in material science through its state-of-the-art micro- and nanomechanical property measurement instruments. Our cutting-edge products are designed to meet the diverse testing needs of researchers in various environments.

Our flagship product, the Alemnis Standard Assembly (ASA), offers superior accuracy and flexibility for both in-situ and ex-situ nanomechanical testing. This system is an ideal solution for long-term creep experiments, such as for example for holding constant loads for several hours throughout X-ray diffraction studies due to its high stability. 

Contact a member of Alemnis today to learn more about fatigue and creep testing.

Nanoindentation is a ubiquitous analytical technique used to investigate a wide range of material properties. With increasingly compact geometries and high-resolution, nanoindenters can explore the mechanical properties of microscale samples to obtain results that are analogous to the macroscale, bulk material. The cost and convenience benefits of this are self-evident.

Nanoindenters can be leveraged in a choice of materials science test methods and applications. They are also increasingly pivotal in preliminary testing that enables further, more detailed mechanical analyses downstream.

Elastic modulus, for instance, is a key property underlying a range of dynamic behavioral mechanics including fracture toughness which is commonly calculated according to the Dukino and Swain equation. In brief, this considers fracture toughness a function of an applied indentation load, average crack length, the ratio of hardness to elastic modulus, and a geometric constant.

In this blog post, Alemnis will briefly explore how nanoindenters can be used to determine the elastic modulus of materials.

What is Elastic Modulus?

First, let us offer a short definition of elastic modulus. Often referred to as Young’s modulus, after British scientist Thomas Young, the elastic modulus of a material is a measure of its ability to resist bending or compressive forces and is consequently connected to both hardness and stiffness. Elastic moduli are determined as the ratio of tensile stress to strain within the material’s elastic limits for compressive and tensile loads; essentially comprising a measure of the force required to cause reversible (elastic) deformation. 

Nanoindenters are used to probe materials and measure malleability/brittleness in relation to linear elasticity on a stress-strain graph. This is critical for gaining a thorough understanding of material performance under pre-defined use conditions and forecasting various dynamic deformation mechanics or modes of failure.

How Do Nanoindenters Determine Elastic Modulus?

To measure the elastic moduli of materials, nanoindenters bring a probe tip into contact with the surface at minuscule loads, typically just a few micronewtons (µN). This load is ramped up at user-defined rates to a maximum point and then decreased back down to zero at the same rate. Conventional indentation tests acquire load-displacement curves that are indicative of various mechanical properties. By observing the unloading curve, analysts can observe the elastic recovery of sample materials, which is a fundamental parameter in calculating elastic modulus.

Alemnis Nanoindenters

At Alemnis, we have developed a class-leading nanoindentation unit that pushes the frontiers of nanomechanical testing. The Alemnis Standard Assembly (ASA) exceeds traditional nanoindenters in terms of measurement accuracy and experiment flexibility. If you would like more information about measuring the elastic moduli of your materials with our innovative nanoindenter, simply contact a member of the team today.

The high strain rate behavior of materials is of enormous interest to product developers and the wider research community. Strain rate testing intersects an extremely wide range of market segments and is relevant to a variety of application areas, providing unique insights into how ceramics, electronics arrays, polymers, and so on, can withstand severe loading events.

At the macroscale, there are numerous proven methodologies for ultra-high strain rate testing (impact experiments, Kolsky pressure bar, etc.). However, the micro- and nanoscales remain comparatively unexplored due to the inherent limitations of the established testing methods. One of the foremost techniques used to explore the mechanical properties of sample materials is nanoindentation. Though incredibly valuable, nanoindentation tests typically employ quasi-static loading, which limits available strain rates to fairly low levels (<10^-2s^-1).

Read More: A Guide to High Strain Rate Testing

How to Achieve Ultra-High Strain Rates via Nanoindentation

The problem with high strain rate testing of materials via nanoindentation is that conventional micromechanical indenters with strain gage sensors, or load cells, have low resonant frequencies and poor sampling rates. This has the tandem effect of increased signal noise and low resolution due to slow feedback loops. Resolving load-displacement data at strain rates above 10^-2s^-1 requires a high data acquisition rate and extremely precise actuation frequencies. Only piezoelectric actuation and sensing offer that level of control for micromechanical testing.

Additionally, ultra-high strain rate testing via nanoindentation is facilitated by novel test methods like micropillar compression. Using a piezo-based nanoindenter and a microscale pillar of lithographically-generated or extracted sample material, it is possible to achieve strain rates up to 10,000 s^-1. Owing to the sample’s extremely small dimensions relative to various test parameters (actuation velocity, inertia, wave travel time, etc.), fatigue, impact, and dynamic deformation phenomena can be acquired at ultra-high strain rates without interference.

Currently, fused silica micropillars exist as a proof of concept for how ultra-high strain rate testing can be carried out for numerous other materials with unexplored high-strain rate properties.

Read our full, in-depth article on Ultra-High Strain Rate Testing with a case study on fused silica micropillar compression for more details.

Ultra-High Strain Rate Testing with Alemnis

Alemnis specializes in micro- and nanoscale indentation testing for a wide range of materials, leveraging our pioneering Alemnis Standard Assembly (ASA) with proprietary high- and ultra-high strain rate modules. For strain rates of 1,000 s^-1 and above

Alemnis offers four distinct configurations:

• VHS-1-1, for impact/fatigue testing at strain rates of up to 1,000 s^-1 using a piezo stack actuator with a normal load range of 1N.
• UHS-1-1, for impact/fatigue testing at ultra-high strain rates of >1,000 s^-1 using class-leading SmarTip actuation with a range of +/- 175V.
• UHS-1-3, for ultra-high strain rate tests with additional tri-axial sensing (normal and lateral force) with a lateral load range of +/- 0.1N.
• UHS-3-3, a complete ultra-high strain rate testing solution with tri-axial sensing and actuation enabling novel nanotribology applications.

Observing how materials respond to applied stress in their native state is fundamental to understanding their mechanical properties (creep deformation, fracture toughness, hardness, elastic modulus, etc.). Limited insights can be gained from structural and surface analysis of samples before and after a mechanical load has been applied, typically via indentation. However, this fails to yield accurate data regarding the real-time deformation behavior of samples under test.

In situ mechanical testing is the only way to observe the real-time mechanical performance of samples under applied loads. For instance, conducting nanoindentation in a scanning electron microscope (SEM) environment allows researchers to visualize key parameters of their mechanical tests, including the actual deformation mechanics of samples in real-time.

Read More: What Properties Can Be Measured By Nanoindentation?

In this article, Alemnis briefly explores how real-time materials characterization can be actualized using vacuum-compatible nanoindenters and complementary SEM-based imaging. 

In Situ Mechanical Testing: Challenges & Solutions

Indentation is a common mechanical testing method used to explore the physical properties of different sample types (alloys, ceramics, polymers, etc.). The basic principle involves the application of a mechanical load via a diamond probe tip to determine a sample’s resistance to deformation. Typically carried out ex-situ, various indentation methods have been used to investigate the elastic moduli and hardness scales of materials as a function of load-depth curves. However, conventional indentation is unsuitable for in situ mechanical testing.

Because surface observations are made after the fact, all conclusions drawn from load-depth data that pertain to specific deformation mechanics within the material are largely speculative. This complication is compounded by the rise of nanomechanical testing based on sub-micro scale (μm) indentation. In situ mechanical testing subsequently requires a powerful imaging tool that can offer nanoscale observations of sample mechanics in real-time.

With far superior spatial resolution than optical light-based microscopy, SEMs have significantly shifted the goalposts of modern materials characterization. Prior to the onset of SEM, researchers were limited to nominal magnification ranges of up to 1000x due to the limited resolving power of visible light. A focused electron beam offers magnifying capabilities of up to 50,000x which yields extremely high lateral resolution ranging down to just a few nanometres (nm). Yet the limited geometries and vacuum pressures of sample chambers make it impossible to couple SEM imagery with conventional nanoindenters. 

Small-scale, vacuum compatible nanoindentation modules are subsequently a prerequisite for in situ mechanical testing. This can yield a range of valuable results, providing accurate data regarding crack propagation, delamination, fracture onset, and more.

Real-Time Materials Characterization with Alemnis

Alemnis offers a unique solution for in situ mechanical testing of myriad sample types with real-time imaging via SEM. The Alemnis Standard Assembly (ASA) is a small footprint nanoindenter comprising a piezo actuated displacement head with an integrated sensor for completely closed-loop indentation testing. This module can be mounted and operated within the sample chamber of an SEM with sufficient space, enabling researchers to observe the real-time displacement of their samples down to a single nanometre.

If you would like to learn more about the unique Almenis solution for nanoindentation testing, read our previous blog post: What is a Nanoindenter?

We also provide custom mounting solutions and modifications for SEM integration. Contact a member of the Alemnis team today to learn about costing an ASA configuration with your SEM unit.