Mechanical testing methods are used to determine the properties of materials and products in different situations. Some common tests include the mechanical testing of joints, tensile tests, and the mechanical testing of stents. In addition, these tests can also be performed in situ. Depending on the type of test, some samples may be placed in an in-situ environment and tested using various electrical and X-ray measurements.
Tensile testing
Tensile testing is one of the most common mechanical testing techniques. It is used to measure many characteristics of materials, such as strength and ductility.
The tensile properties of a material are important for quality control. They are also used to predict behavior under different forms of loading.
These tests are usually performed at room temperature or elevated temperatures. Tests are typically performed in a tensile testing machine, which is made up of a test frame with a load cell, application-specific grips, and a testing software. Using a tensile test machine can help determine the behavior of a material under normal and cyclic loads.
The tensile strength of a material is the maximum stress that the material can withstand. This value is calculated by dividing the peak tension force by the cross sectional area. In a tensile test, the load is increased steadily.
Tensile strength can vary with the type of specimen and the test standard. The strength of steel is often lower than the strength at break, for example. However, it is not the shape of the bar that causes the strength.
Tensile testing can be done with a handheld force gage. It is important to select a test fixture that will accurately apply the desired forces. Failure to do so can result in an inaccurate measurement of the tensile strength.
Tensile tests can be performed with a variety of fixtures and setups. If the fixtures are not properly designed or maintained, the tensile measurements could be incorrect. A flaw in the equipment can be dangerous or costly.
In addition to the strength of a material, tensile testing can also measure properties such as Young’s Modulus and Poisson’s Ratio. Both of these properties are measures of the material’s stiffness and ability to withstand plastic deformation.
Inplane shear tests
Inplane shear tests measure forces acting in shear within the plane of a laminate. This is a type of test used in the reinforced plastics industry.
Shear tests can be a good means of testing new materials. They are important for both quality control and specification purposes. Because different materials behave differently under different conditions, a variety of test methods are used. These include tensile, compression, and tension tests.
For testing in-plane shear, a specimen is cut from a plate at a specified angle to the fiber direction. It is then loaded edgewise in a supporting jig. The load is applied until the sample fails. A compressive force is then applied to the specimen to determine the in-plane shear strength.
Shear strength is a critical design characteristic of many types of fasteners. For applications with crushing loads, it is essential to obtain accurate shear strength data. Several organizations recommend the +/-45 deg tensile shear test. However, this test is not a reliable quantitative method.
Inplane shear is a complex process to induce, which can be costly. To avoid this, symmetric shapes are typically preferred. Some test fixtures are specialized to ensure accurate measurement of in-plane shear properties.
Two procedures are used to determine in-plane shear strength of high-modulus fiber-reinforced composites. One procedure involves clamping two laminates between two pairs of loading rails. The other procedure consists of applying a tensile or compressive force to a third pair of rails in the center of the specimen.
Shear tests are widely used in the reinforced plastics industry. Tests are performed to determine the strength of the reinforcement to the resin bond in polyester. Also, the modulus of elasticity is determined.
In situ XRD and 4PP experiments
In situ X-ray diffraction (XRD) and four-point probe (4PP) experiments are effective mechanical testing methods for brittle materials. They allow for direct measurements of fracture stress and cosines of fracture onset strains (COS). It has been shown that these techniques are suitable for studying the electro-mechanical behavior of metal films on polymer substrates. Combined with optical observation methods, they are also able to detect “hot spots” in material microstructure that can lead to the accumulation of damage. This information can be used to better understand the mechanisms of failure and to improve processing and design methods for longer lasting products.
Several experiments have been performed using these techniques to determine the electro-mechanical properties of thin films. One example is the use of a 100-nm ITO film on PET for tensile straining. The tensile strength was tested as well as the thickness and grain size.
Another example is the use of in situ XRD to study the electro-mechanical behavior of low modulus b-type Ti alloys. These low modulus b-type Ti alloys have peculiar deformation behaviors. An in situ synchrotron X-ray diffraction technique was also used to study the same materials.
Combined in situ electro-mechanical fragmentation testing can be very useful to assess the electrical and mechanical failure mechanisms in flexible electronic devices. However, there are many materials that are not fully understood. A better understanding of the mechanisms of multilayer brittle fracture would be beneficial for the development of robust and durable devices.
Other in situ tests can also be used to observe the occurrence and evolution of mechanical damage. Confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) are two in situ methods that can be combined. Besides the ability to assess the density and density distribution of a crack, CLSM can provide a high-resolution three-dimensional view of the microstructure. Similarly, SEM can examine the local spatial displacements of individual grains.
In situ electrical measurements
The use of in situ electrical measurements as part of mechanical testing methods has been growing in recent years. These methods can provide insights into the deformation and fracture of microstructures. A variety of materials can be studied for their electrical properties. In addition, these techniques can be used to study mechanical failure mechanisms in both macro and nanoscale samples.
For instance, researchers have recently developed a new imaging technique for in situ fragmentation studies. This method can be combined with other in situ techniques to provide more detailed information about the fracture process.
Another in situ measurement that has been popular is infrared thermography. It can be used to inspect a building or HVAC installation and to detect energy leaks.
Another technique for in situ characterization of nanoscale specimens is scanning electron microscopy. It can be used to study the nanoscale structure of materials, as well as their electrical, mechanical, and thermal characteristics.
X-ray microscopy is another technique that can be used for in situ characterization of nanoscale materials. Besides being useful for studying the dimensions of individual nanoscale specimens, X-ray microscopy can be combined with other in situ techniques to better understand the combined electro-mechanical behavior of multilayers.
One common method for determining the combined electro-mechanical behavior of materials is the fragmentation test. It can be combined with other in situ techniques to determine the overall deformation and fracture mechanisms of brittle layers.
A newer technique that can be used in in situ characterization of nanomaterials is the confocal laser scanning microscopy (CLSM). CLSM can be used to image virtually any surface. It can also be used to measure reflectivity and interface adhesion.
Post-processing mechanical properties of stents
In the last few decades, many research lines have been explored in the field of stents. Research has been focused on developing new materials and manufacturing processes. However, few studies have been performed on the post-processing of mechanical properties of stents.
During the process of stent development, it is important to understand the role of different geometrical aspects in stent behavior. Some of these geometrical parameters include the stent’s geometry, radial strength, and the shape of the stent.
The three-point bending test is a method for quantifying the stent’s flexibility. It is applied on the external surface of a cylindrical stent. This technique is also used to evaluate the stent’s radial stiffness.
An artery tree stent must have adequate radial stiffness to resist radial compressive forces of the artery. Similarly, a woven design of a stent is highly dependent on the axial fixation of the ends.
In order to increase the radial strength of the stent, researchers have developed various methods. One is the use of two different extrusion processes. Another is the use of a micro-EDM. Both methods are effective but have certain disadvantages.
Currently, the most promising technique is the SL process. But further works are needed in this area to understand its benefits and disadvantages.
In addition to radial strength, a TS should be able to maintain its strength in vivo. Therefore, the goal of this study was to reduce the amount of force required to bend the stent.
After calculating the stent’s geometry, a three-point bending model was created. During simulation, a downward displacement of the upper pin was applied to induce a bend in the stent.