November_December_2021_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 1 2 8 to configuring the test’s fixture separa- tion, an important parameter specified in many of the most common ASTM and ISO test standards. When fixture sepa- ration is inconsistently configured, labs should expect nontrivial variations in displacement or strain data collected. This problem is worsened when labs have multiple technicians using slight- ly different techniques to position the crosshead manually. Some providers have developed solutions to automate crosshead posi- tioning to ensure the fixture separation is precisely repeated by any technician operating the system. One simple im- plementation links the crosshead po- sition to the relevant test method, so when the technician selects a test method, the systemknows exactlywhere to move. AUTOMATED FIXTURE COLLISION DETECTION Any time a test operator posi- tions the crosshead during setup, there is a risk that the fixtures will acciden- tally collide. An unintended collision can cause serious damage to fixtures, force transducers (or load cells), or the test frame itself. Although most labs at- tempt to mitigate this risk by training technicians to remain vigilant when manually operating the system, errors happen, and nearly every lab has ex- perienced the pain of breaking fixtures and the cost associated with replace- ment and system downtime. To prevent undesired collisions, some equipment suppliers have engi- neered features into their systems to automatically stop the crosshead when irregular force is detected during test setup. Further, the system automati- cally returns to a safer state by return- ing to a crosshead position when force is within an acceptable range. While thorough training is always recom- mended, collision detection features, such as this one, help labs protect their investments. AUTOMATED GRIP PRESSURE CONTROL Pneumatically actuated grips have been widely adopted as the preferred gripping solution for many tensile test- ing applications due to their superior throughput and clamping force repeat- ability. However, pneumatic grips are also one of the leading causes of safe- ty incidents while operating a materials testing system due to pinched fingers. Traditionally, shields that mount to the grip itself are offered to mitigate this risk. Unfortunately, shields are not us- able for all specimen types and can eas- ily be removed and lost over the life of the system. Pneumatic grips also require tech- nicians to manually adjust the inlet pressure with an air regulator. Differ- ent materials require different clamp- ing pressures, so technicians must remember to adjust the regulator ac- cordingly. This adjustment adds time to the test process while also introducing undesired variability if one technician sets the pressure more precisely than another. To address these established con- cerns, suppliers have developed auto- mated air kits that are integrated into the system and communicate with the software. Now the system itself can ad- just pneumatic pressure, eliminating any manual interaction. When techni- cians are inserting specimens, grips au- tomatically close at a reduced pressure and speed to create a safer test process. Also, test methods configured in the system’s software can be linked to grip pressures, eliminating any wasted time and variability. Automated crosshead positioning features ensure the fixture separation is precisely repeated by any technician operating the system. Built-in collision detection features automatically stop the crosshead when an irregular force is detected during test setup.