Nov_Dec_AMP_Digital

A D V A N C E D M A T E R I A L S & P R O C E S S E S | N O V E M B E R / D E C E M B E R 2 0 2 0 3 2 and analyzing them afterwards. A typi- cal system includes a camera, lighting, and software package to control image capture and to conduct post-test anal- ysis. Integrated DIC systems, which use existing video extensometers, have re- cently been introduced to provide a streamlined package tailored for the materials testing market. Though DIC has been a very popular stand-alone re- search technique for years, its capabili- ties have only recently been integrated with commercially available video ex- tensometers with a simplified user in- terface, making the powerful analytical tool available for any capable material testing operator. Conventional methods of measur- ing strain using extensometers or strain gauges have been limited to measuring a single component of the average strain over an extended length (extensome- ters) or at a limited number of pre-de- fined locations (strain gauges). Digital image correlation on the other hand can measure all the components of the strain tensor over the surface of a spec- imen or component simultaneously. Af- ter the full field strain distribution has been determined, it can be displayed as a color-coded map. The strain map can provide information about testing phe- nomena such as discontinuous yield- ing, shear strain, localized necking, or locate strain hot spots. This helps users to validate FEA models, find weakness- es in design and common failure points, and see strains that an extensometer would not be able to measure. It is also a useful tool for teaching. In addition, virtual strain gauges and extensom- eters can be placed on the map post- test and replayed time and time again. This technique can be used for almost any material and any industry. Plastic, metal, composite, rubber, foam, tex- tiles, and other materials have all been successfully tested using digital image correlation. SOFTWARE DEVELOPMENTS Major recent testing machine soft- ware developments include the use of touch operation and database in- tegration to allow easy interrogation and management of results along with traceability and security features. Con- trolling a testing machine through a touchscreen provides a simpler and more efficient means of operation than using traditional fixed hardware and computers. The simplified operation reduces training requirements and the possibility of errors at the same time, improving productivity. Managing the results of testing is important, and testing machine soft- ware needs to have the capability of au- tomatically communicating test data and results to other systems. Verification of the testing machine measurement systems (e.g., for force and strain) is an essential requirement for most testing. These verifications are an essential part of producing trust- worthy data. Until recently the same level of assurance has not been avail- able for the test methods and analy- sis, but Bluehill Universal software can now incorporate security and trace- ability features which helps ensure the reliability of test data. These features include multiple levels of security to control access to different parts of the system (e.g., an operator may only have the rights to run a test with all param- eters fixed, whereas the lab manager may have the ability to produce and up- date test methods). The security is fur- ther enhanced by the ability to sign off Sheet metal testing using a non-contact video extensometer for measurement of axial and average width strain. 2D strain map produced by digital image correlation software.