V29 - AERO - Lead Story 1
The MTS Alignment Solution helps ensure test system compliance with numerous industry standards, including ASTM E1012, GES400 (Nadcap), GE450 and ISOTC 164SC5WG11.

Precise Alignment in High Temperature Fatigue Testing

By their nature, fatigue tests of all varieties are highly sensitive to load train misalignment. Any amount of concentric or angular misalignment will have a significant effect on the fatigue life of the specimen, thus compromising the quality of test data.

This is why so many fatigue tests — particularly low-cycle fatigue (LCF), high-cycle fatigue (HCF) and thermomechanical fatigue (TMF) — must meet such strict alignment requirements from regulatory agencies such as ASTM, Nadcap and others. Valid test data requires both precise alignment as well as reliable confirmation of the same. Unfortunately, industry standards only dictate how much bending strain is permissible and how to measure it. They do not specify what method should be used to achieve it.

Test labs can choose from a range of options for ensuring alignment accuracy. Traditional approaches, which involve the careful placement and adjustment of shims, can be extremely time-consuming. Test engineers or assistants can easily spend an entire day completing the process for a single system, which means productivity grinds to a halt. This is a considerable challenge for any lab, but especially for contract test labs dealing with aggressive customer deadlines.

MTS introduced our first alignment tools to address this challenge more than 15 years ago, and the solution has been continuously enhanced since that time. As a result, the MTS Alignment Solution helps test teams verify system alignment in about 30 minutes. For large labs, the MTS solution gives test engineers the ability to verify the alignment of every system in the time it might normally take to align just one. Today, thousands of MTS load frames incorporate our alignment fixture and hundreds of labs use our proven methodology to achieve and validate alignment faster and more easily than with conventional approaches.

The MTS Alignment Solution includes an alignment fixture, software, a data acquisition and conditioning unit, and a variety of strain-gaged specimens. With the fixture attached to any MTS servohydraulic load frame, the software guides the user through the precise sequence of concentric and angular adjustments required to bring all bending strains within a 5% envelope.

To make the process as easy and accurate as possible, the software incorporates three kinds of user feedback: an on-screen image of the fixture and its eight adjustment points; a graphical representation of the bending strain; and a spoken direction (such as “turn C3”).

The design of the fixture allows adjustments to be made while the load train is preloaded, eliminating the risk of small changes in alignment that can occur during preloading. In addition, continual scanning of bending strains enables verification and alignment during load cycling.

Once correct alignment is achieved, the software generates a report to validate it. In fact, reports can be run before any adjustments are made. This can be preferable for maintaining consistency of test results over time when systems are not perfectly aligned but nevertheless within the acceptable envelope dictated by the relevant standard.

To accommodate as many different fatigue tests as possible, the MTS Alignment Solution comes with a selection of round and flat standardized, strain-gaged specimens. This variety allows test engineers to validate alignment using the same type of specimen that will be used in the actual fatigue test, with the same configuration of grips, fixturing and extensometers. The solution can also utilize customer-provided 4, 6, 8, and 9 gage specimens.

Learn more today about how the MTS Alignment Solution help your lab reduce the variability in test data, eliminate sources of uncertainty and meet rigorous industry standards.

>> MTS Alignment Solution


MTS Systems

14000 Technology Drive
Eden Prairie, MN USA

Tel: 952.937.4000
Tel: 800.328.2255
Fax: 952.937.4515
Email: info@mts.com