Mechanical and Tensile Testing
Mechanical testing measures the properties of a material under an applied dynamic or static force. Designed to ensure that materials are suitable for their intended applications, mechanical testing includes methods such as tensile strength, compression strength, impact resistance, fracture toughness and fatigue.
The results of tensile testing are critical for material comparison, quality control, alloy development, certifying the integrity of a product, and process limitations. A standard tensile test is used to measure several characteristics of a metal including Young’s modulus (modulus of elasticity), yield strength, tensile strength, and elongation at failure. Additionally, tensile testing can be used to measure formability parameters such as r-, n- and m-values.
Whether your mechanical testing requirements are driven by a PPAP/First Article Inspection, customer part specification, ASTM specification, field failure or manufacturing defect, Secat can help you understand the process and interpret the results!
Types of Mechanical Testing Machines
At Secat, mechanical testing is conducted on an impressive range of machines including:
The MTS 810 material testing system provides unparalleled capabilities for performing a wide variety of tests on materials, components, and finished goods. The innovative design of the load frame provides reliable service for all types of testing laboratory environments. It provides precise control over testing conditions, which are critical for adhering to ASTM E8 standards. Our MTS 810 Servo Hydraulic Testing System has capacity up to 100 kN (22 kip).
Testing can be conducted at ambient and elevated temperature. Built-in software allows the data collection and treatment to be processed with high speed and accuracy. The bi-axial extensometers obtain Poisson’s ratio and R-Value with high accuracy and provide superior performance in linearity, repeatability, hysteresis, low activation force.
Various mechanical properties may all be determined by tensile testing:
- Ultimate Tensile Strength
- Yield Strength
- Elongation
- n-value
- r- value
- Poisson’s Ratio
- True Stress and Strain Curve
- Engineering Stress and Strain
- the Elastic Modulus
- the Fracture Stress
- etc.
Applications
- Tensile / Compression testing at ambient and elevated temperature
- High and low cycle fatigue testing
- Indirect tension testing
- Peel/tear/friction testing
- Thermal-mechanical fatigue testing
- Electronic components testing
- Biomechanics and biomaterials testing
- Paints and coatings testing
- Bend testing
Features & Capabilities
- Versatile: Performs a variety of static and dynamic tests.
- Accurate: With integral base plate actuator for very high stiffness, exceptional side load resistance and excellent force train alignment.
- Precise: Factory laser alignment improves axial alignment and reduces specimen bending at all crosshead heights.
- Productive: Optional unit-mounted control modules speed, crosshead positioning, and specimen loading.
- Modular: Configure the system with your choice of actuators, servovalves, and service manifolds.
MTS Insight Electromechanical Testing Systems integrate an elegantly simple and reliable electromechanical drive system, state-of-the-art control electronics, and an intuitive user-interface to deliver highly accurate and repeatable results. There are two load cells available: 500N (110 lbf) or 2kN (450 lbf), providing reliable low force testing of smaller specimens. This system is ideal for lower force testing of components, for example, aluminum foil samples.
The Secat Laboratory has recently installed a MTS Landmark 370.25 Servohydraulic Test System to its meet its full spectrum of static and dynamic material test requirements. With a force capacity of 250 kN and a rated dynamic force of 55 kip, the new equipment provides a significant upgrade to Secat’s testing capabilities.
With the increased load capacity, this system is ideal for testing components and materials such as plastics, elastomers, aluminum, composites, steel, super alloys and more. The equipment delivers a broad array of testing capabilities for both low and high force static and dynamic testing. By selecting from a variety of force capacities, servovalve flow ratings, pump capacities, software and accessories, the system can be easily configured to meet Secat’s customers’ specific material or component testing needs.
The MTS Landmark System leverages MTS TestSuite Software to provide test definition, test execution and report generation for virtually all types of material tests, including tension, bending and compression testing, fatigue life studies and fracture growth studies.
Secat’s MTS system is ideal for the exacting demands of material fatigue testing. Highly stiff integrated actuator beams, hydraulic grips, high-resolution force transducers, and precision alignment fixtures combine to deliver tightly controlled and consistent through-zero specimen loading. Driven by MTS TestSuite software, the system can perform highly accurate and repeatable low-cycle, high-cycle and advanced low-cycle fatigue testing.
The Fatigue Analyzer software allows Secat to glean new insight from post-test data. Some of the fatigue tests that can be performed are – constant amplitude, variable amplitude, block loading, low cycle fatigue, high cycle fatigue.
In addition to the fatigue testing, the system can be readily configured to perform linear elastic and elastic-plastic fracture toughness testing. The system load frame can be used for both pre-cracking and fracture testing and equipped with a selection of standard compliant grips and precision clip-on displacement gauges.
The highly configurable test system features the test space and performance flexibility required to perform both static and dynamic component testing. The system can be equipped with fixtures for single and multiple specimens, as well as a full selection of extensometers that are versatile enough to measure displacement from a variety of locations on a specimen.
Using the new test system Secat will be able to analyze and test:
• Low cycle fatigue
• Advanced low cycle fatigue
• Fatigue crack growth
• Fracture toughness
• Crack propagation
• Component strength and durability
• Environmental testing
• Thermal mechanical fatigue
• Tension
• Compression
• Bending
• Stress relaxation
A new CNC mill has been installed at Secat which provides greater flexibility, improves sample quality, and adds long-term potential to our capabilities. A Haas TM-1 tool room mill was chosen as the replacement based on rigidity, machining envelope, and feed rates. The TM-1 has a machinable size of 30” travel on the X axis, 12” travel on the Y axis, and 16” travel on the Z axis, with a 200 ipm maximum cutting rate and 4,000 rpm spindle speed from a 7.5 hp drive.
The Next Generation Control (NGC) combined with a Wireless Intuitive Probing System (WIPS) allow for rapid zeroing of work coordinates, probing of specimen geometry, and rapid changeover in setups between types of samples. The NGC and WIPS system also ease training for new staff using the Visual Programming System (VPS) to rapidly setup work coordinates and simple program paths.
The TM-1 uses a CAT-40 taper tooling system which allows for larger, more rigid tooling and faster tooling changeouts than previously capable at Secat. The current tooling available at Secat consists of end mills specifically chosen for aluminum in diameters of 3/16”, 1/4”, and 1/2”. Also available are shell mills of 2” and 4” diameters for rapid facing of samples.
With the current tooling assortment, Secat can mill profiles, pockets, and face off material for evaluation and fixture making for other equipment within the lab. Work holding is achieved with either a Kurt DX-6 vise, using soft jaws for customizable holding of samples with a maximum size of 6” x 9”, or a multi-station tensile cutting fixture which can hold up to six 0.5” stacks of samples for machining at a time.
The current improvements to Secat’s machining capability are a 10x reduction in cutting time, ability to utilize additional tooling common in traditional milling operations, larger work envelope with more flexibility in types/sizes of samples, and fixturing. Previously, a standard tensile program path would take more than 10 minutes to machine a tensile dog-bone sample. The Haas TM-1 mill permits these samples to be machined in 1 minute.
Previously, Secat engineers were unable to perform facing operations in the old mill, but the TM-1 allows Secat to face material for Optical Emission Spectrometer (OES) evaluation or reduce the amount of manual grinding needed for macro etching evaluations in large samples. There is also now the ability to pocket mill as deep as 3” for milling out samples from a larger material section such as a billet casting slice or ingot slice. The larger envelope of the TM-1 allows machining of Forming Limit Curve (FLC) samples in-house which provides better control and faster turnaround times.
Long term growth potential with the TM-1 is centered around the flexibility of having a larger rigid CNC mill with all the capabilities of traditional milling as opposed to a tensile cutting centric designed mill. In addition to the previously mentioned improvements, the TM-1 allows Secat to enhance and expand its offerings.
Past experience has shown cases where potential projects have required special fixturing or dies. For instance, Secat made hemming bend fixtures and were requested to test components in their final form. Secat had to utilize outside sources for manufacture, with typical lead times of 3 months. In-house capability allows Secat to cut lead times drastically.
In addition, wear and damage on dies typically requires a 6 month lead time for replacement, but with the ability to rough out the dies in-house, and only utilize outside sources for finish grinding and heat treatment, the 6 month lead time is significantly reduced. Correspondingly, new dies that customers would like to experiment with can be made in a similar fashion. Testing out a square box deep draw to more accurately depict a finished product for a customer or changing the draw ratio of current dies housed at Secat would now only require the finish grinding and heat treatment to be done outside.
The TM-1 offers significant benefits to the previous CNC housed at Secat. Below is a bullet point summary of improvements.
• 10x reduction in machining time
• Improvement in machined surface quality and dimensional tolerances
• Expansion of tooling options and operations
• Ease of machine setups
• Reduction of setup time between types of samples and operations
• Greater flexibility in accommodating special requests
• Expansion of in-house sample preps
• Reduction in special fixture and die manufacture times
Hardness is the resistance to indentation of a material, and it is often determined by measuring the permanent depth or width of the indentation. Basically, when using a fixed force (load) and a given indenter, the smaller the indentation, the harder the material.
Micro-hardness is the hardness of a material as determined by forcing an indenter such as a Vickers or Knoop indenter into the surface of the material under typical forces of 15 to 1000 gf; usually, the indentations are so small that they must be measured with a microscope. Thus, it is useful for a variety of applications: testing very thin materials like foils, measuring individual macrostructural phases, measuring the depth of case hardening, or examining changes in local properties across a weld.
The Vickers micro-hardness test method is the most common micro-hardness technique and is based on using an equilateral diamond shaped indenter with an optical measurement system. The micro-hardness test procedure, ASTM E-384, specifies a range of light loads using a smaller diamond indenter to make an indentation which is measured and converted to a hardness value. It is very useful for testing on a wide type of materials, but test samples must be highly polished to enable measuring the size of the impressions.
The Knoop micro-hardness test method is similar to the Vickers method, except the indenter is rhombohedral shaped (i.e. the length of the diamond is longer than the width). The shape of this indenter makes this method more suitable for measuring the hardness of thin surface coatings and measuring surface gradients in hardness after, such as case hardness depths.
“Dog bone” shape samples were prepared and tested on an MTS 810 in accordance with ASTM E 8/ E 8M -15a. Yield strength, Ultimate Tensile Strength, Elongation, n-value, r-value, Modulus, Poisson Ratio were determined.
Tensile specimens of 7” long x0.5” width was made in the rolling direction using the foil cutter with twin blade. The tensile properties were tested with a calibrated Material Test System MTS Insight 2. A 2000N load cell was used in the 0-2000N calibration range. The cross-head speed was kept constant at 0.05 inches/minute throughout the test. The Yield Strength was at 0.2 % offset. The elongation recorded is the plastic elongation until fracture. The tests were performed in accordance with ASTM E 345-93 (Reapproved 2002).
The surfaces of hardness samples were prepared using sand paper. The hardness tests were performed utilizing the calibrated Rockwell Hardness on Rockwell Superficial 30-T scale using Mitutoyo HR-500 machine with 1/16” diameter tungsten carbide (W) ball indenter as per ASTM E18-16.