nanoDMA^® III

Hysitron’s nanoDMA III is a powerful new dynamic testing technique used to perform nanoscale mechanical property measurements. nanoDMA III is equipped with newly developed CMX control algorithms to provide a truly continuous measurement of mechanical properties as a function of depth into a material’s surface. High bandwidth transducer and control electronics are fully optimized for nanoscale dynamic testing and provide industry-leading performance, sensitivity, and a broad dynamic range. Hysitron’s unique coupled AC/DC force modulation routine enables true nanoscale mechanical characterization and is not subjected to the slow feedback response times that plague other nanoscale dynamic stiffness techniques. TriboScan™ v.9 control software incorporates a flexible and intuitive graphical user interface to speed test setup and execution, enhanced data analysis and plotting capabilities, and in-situ drift correction capabilities for accurate results during long test durations. 

CMX Alogrithms
Hysitron’s powerful CMX algorithms lie at the core of nanoDMA III. CMX provides a quantitative and truly continuous measurement of mechanical properties—including hardness, storage modulus, loss modulus, complex modulus, and tan delta—as a function of indentation depth, frequency, and time. During a nanoDMA III experiment, a quasi-static force is applied to the indenter probe while simultaneously superimposing a small oscillatory force. A dedicated lock-in amplifier measures changes in phase and amplitude of the resulting force-displacement signal. The dynamic mechanical response of the transducer in contact with the sample is modeled using two Kelvin-Voigt mechanical equivalents, from which the contact stiffness and damping properties of the material can be accurately determined. The nanoDMA III force modulation technique with CMX enables thousands of mechanical property measurements to be continuously taken during a single test, increases sensitivity to nanoscale elasto-plastic deformation and creep, and allows for the viscoelastic properties of materials to be measured. 

In-Situ Drift Correction
nanoDMA III incorporates a unique reference frequency technique for thermal drift correction during the course of an experiment. Reference testing is primarily advantageous in two areas; frequency sweeps and creep testing. The reference frequency technique allows for the measurement of contact area without relying on the raw displacement data. The measured stiffness is proportional to the contact area and can therefore be used to accurately determine contact area and contact depth in-situ. This allows for long duration frequency sweeps and creep tests to be reliably performed.

Reference Creep Testing
In a typical indentation test, the contact area is calculated based on the measured indenter displacement, making long tests prone to error in property measurement due to thermal drift. In a reference creep test, the quasistatic force is held constant while a small oscillation is superimposed for continuous measurement of contact stiffness. The modulus of the material is measured at the beginning of the hold segment when thermal drift error is negligible. The measured modulus is then used to calculate the contact area continuously for the remainder of the test, allowing for a continuous and accurate measurement of mean contact pressure and penetration depth over long durations of time. This technique is insensitive to changes in drift rates and allows tests lasting 1 hour or more to be routinely and reliably performed.

Reference Frequency Sweeps
During a frequency sweep, the material’s modulus is measured at a user specified reference frequency near the beginning of a test. As the test progresses from one frequency to the next, the system alternates between the testing and reference frequency. By measuring the contact stiffness at the reference frequency the contact area can be directly determined without relying on the raw displacement signal of the nanomechanical testing system. This allows for relatively long tests to be performed that are insensitive to changes in drift rate. As a result, large ranges of frequencies can be covered reliably in a single test.