Load displacement

The plastic behaviour of a material is usually measured by conducting a tensile test. Tensile testing equipment is standard in all engineering laboratories. Such equipment produces a load/displacement (F/u) curve for the material, which is then converted to a nominal stress/nominal strain, or cT l , curve (Fig. 8.10), where... 

Fig. 10. Typical load-displacement graph for elasto-plastic indentation.

Like the AFM, load-displacement curves from nanoindentation can also be used to measure tip-sample adhesion. However, because the force resolution of nanoindentation is typically of order tens to hundreds of nanoNewtons, such experiments... 

Fig. 11. Load-displacement data and contact stiffness for poly-isoprene. Reprinted with permission from ref. [102],...

Asif, S.A.S., Wahl, K.J. and Colton, R.J., Nanoindentation and contact stiffness measurement using force modulation with a capacitive load-displacement transducer. Rev. Sci. Instrum., 70, 2408-2413 (1999). 

Since the early 1980s, the study of mechanical properties of materials on the nanometre scale has received much attention, as these properties are size dependent. The nanoindentation and nanoscratch are the important techniques for probing mechanical properties of materials in small volumes. Indentation load-displacement data contain a wealth of information. From the load-displacement data, many mechanical properties such as hardness and elastic modulus can be determined. The nanoindenter has also been used to measure the fracture toughness and fatigue properties of ul-... 

The two mechanical properties measured most frequently using indentation techniques are the hardness, H, and the elastic modulus, E. A t5pical load-displacement curve of an elastic-plastic sample during and after indentation is presented in Fig. 30, which also serves to define some of the experimental quantities involved in the measurement. 

The contact depth is also estimated from the load-displacement data using ... 

Once the contact area is determined from the load-displacement data, the hardness, H, and effective elastic modulus, Egff, follow from ... 

Fig. 40—Typical load-displacement curves during a loading/ unloading cycle. Applied load 1250 /liN, 1-Fe-N(5 nm)/Ti-N(2 nm), 2-Fe-N(20 nm)/Ti-N(2 nm).

T5q)ical load-displacement curves, with maximum applied load of 1,250 /aN are shown in Fig. 40. It can be observed that... 

Figure 41 shows the dependence of hardness of multilayer on contact depth. The contact depth, h., is estimated from the load-displacement data using [35,36] ... 

Fig. 22 Bending load-displacement curve of SA-Tyrannohex using chevron notch spacemen at room temperature...

In order to satisfy both requirements of load displacement and unbalance displacement with one sensor system, the sensor must have ... 

Figure 2. Typical Load-Displacement (left) and Potential-Drop-Crack-Length-Measurement (right) Records Acquired During Fracture Toughness Test of Forged Stainless Steel.

Fig. 43. Load displacement curves under uniaxial compression for the neat epoxy line a) and macroporous epoxy networks prepared via CIPS with 20 wt % cyclohexane line b)...

Fig. 47. Load-displacement curves of solvent-modified and macroporous epoxy networks prepared with 20 wt % cyclohexane via CIPS with SENB testing at 1 mm/min...

Fig. 49. Load-displacement curves of solvent-modified, semi-porous, and macroporous epoxies prepared with 22 wt % cyclohexane via kinetically controlled CIPS with 1 wt % catalyst...

As for the samples prepared without catalyst, the ability for energy absorption after crack propagation decreases strongly as the solvent is removed. This is reflected in Fig. 49, where the load displacement curves of solvent-modifled, semi-porous, and macroporous epoxies prepared with initially 22 wt % cyclohexane (( )=18.5%) are shown. The crack length is the same in all three cases. Therefore the decrease in maximum load is directly proportional to the decrease in Kj. It is also clearly seen that the fracture behavior changes drastically and that the surface under the load-displacement curve, which is used to calculate the fracture energy is signiflcantly lowered. 

The quantitative results of fracture energy, which are calculated from the total area under load-displacement curves, are presented in Fig. 50. It becomes obvious, that a brittle-tough transition exists at a volume fraction of around 10%. This brittle-tough transition is observed for solvent-modifled as well as semi-porous epoxies. A brittle behavior is observed in macroporous epoxies after complete solvent removal, thus giving low fracture energies similar to the neat epoxy for each porosity. 

Fig. 5.9. Load-displacement records of double-cantilever-beam tests on E-glass fiber-vinyl ester matrix composites, (a) 0.4 wt% epoxy silane (b) 0.01 wt% methacrylate silane (c) 0.4 wt% methacrylate silane (d) 1.0 wt% methacrylate silane. After Suzuki et al. (1993).

The load-displacement curves for the orthogonal interlock fabric composites show a non-linear unloading sequence and an appreciable permanent deformation after unloading, with the crack tip not completely closed (Guenon et al., 1987). These observations are attributed to the crack closure process of the three-dimensional fabric composites where through-the-thickness yarns break near the outer surface of the specimen. 

Fig. 18 a Schematic of probe tack measurements of a thin adhesive film along a temperature gradient, b Compilation of probe tack data during loading and unloading cycles for different temperatures. c Total adhesion energy, calculated from the area under the load-displacement curve shown in b divided by maximum contact area, as a function of temperature. The error bars represent one standard deviation of the data, which is taken as the experimental uncertainty of the measurement. (Reproduced with permission from [86])... 

Figure 5.21 (a) A typical load-displacement curve and (b) the deformation pattern of an elas-... 

Nanoindentation hardness, H, is defined as the indentation load divided by the projected contact area of the indentation. From the load-displacement curve, hardness at the peak load can be determined as... 

---