Tensile testing is a destructive test process used to provide information about the strength and ductility of a material or to meet acceptance test requirements. The tensile test, also known as a tension test, involves applying an ever-increasing load to a test sample up to the point of failure. The process creates a stress/strain curve showing how the material reacts throughout the tensile test. The data generated during tensile testing is used to determine mechanical properties of materials and provides a quantitative measurement of tensile strength, yield strength and ductility or stiffness.
At Laboratory Testing Inc., tensile test equipment is available for both metals and polymers, and for evaluating high performance materials at elevated temperatures such as nickel alloys destined for jet engines and power generation gas turbines, and for steel and other materials used in high temperature service. The various test machines have maximum load capacities of 100 pounds on up to 400,000 pounds to test the smallest fasteners or huge bolts.
The following capabilities are available:
- Wedge tensile
- Axial tensile
- Full-size tensile test (ductility)
- Yield strength tensile testing
- Elevated temperature tensile testing to 1800°F
- Tensile testing of welds and castings
- Full-size yield testing of fasteners
Tensile testing at LTI is generally performed in accordance with ASTM E8, standard test methods for tension testing of metallic materials. This standard describes two types of samples, flat and round. Both types of specimens are machined to specification in our Machine Shop for tensile testing performed at our laboratory or for direct purchase by our customers.
The Tensile Test Process
Tensile testing can be carried out on various test samples including machined specimens, fasteners and bolts. The sample is securely held by top and bottom grips attached to the tensile or universal testing machine. During the tension test, the grips are moved apart at a constant rate to stretch the specimen. The force on the specimen and its displacement is continuously monitored and plotted on a stress-strain curve until failure.
Elevated Temperature Tensile Testing is a proven method of evaluating the behavior of materials under a combination of heat and tension. When performing an elevated temperature tensile test, the specimen is placed inside a furnace on our test carousel, which is capable of processing up to three specimens at a time. Our computer-controlled system heats the specimen to the required temperature, then allows it to soak. Next, the specimen is loaded into the test frame, where an extensometer in the latest design measures the strain on the specimen as the load is increased.
Tensile testing generates data that is used to determine tensile strength, yield strength and ductility, as expressed by percent elongation or reduction in area. The tensile strength is defined as the maximum load divided by the original cross-sectional area of the test sample or the maximum tensile stress carried by the specimen. The yield strength is related to the load at which time permanent (plastic) deformation or yielding is observed to begin. The usual ductility measurements are elongation, defined as the strain at the point of fracture, and reduction in area at the point of fracture of the test sample. The highest stress achieved before the specimen breaks is typically recorded as the ”ultimate strength” or UTS in the results.
These measurements are calculated by the technician after the test specimen has broken. The test sample is put back together to measure the final length, then this measurement is compared to the pre-test or original length to obtain elongation. The original cross section measurement is also compared to the final cross section to obtain reduction in area.
- Types of Tensile Testing – full-size, axial, wedge, yield, elevated temperature, weld and casting
- Tensile Profile – tensile strength test, yield strength, ductility or elongation to failure
- Equipment Capacity – up to 400,000 lb. load
- Machined Specimens – round and flat tensile prepared at LTI
- ASTM A370
- ASTM B557
- ASTM E8
- ASTM E21
- EN 2002-1
- EN 10002-1
- ISO 6892-1
- ASTM F606
- ASTM F835
- ISO 898-1
- ISO 898-2