# Role of Piezoelectric Elements in Finding the Mechanical Properties of Solid Industrial Materials
## 4 Conclusions  
Many corporations and factories need PE in finding the mechanical properties of solid materials especially when the purchase orders of their needed materials have non-uniform shapes or long specimens such as long shafts or wide and thick plates where long or wide materials cannot be tested within the tensile test devices. In addition, the need it to lower the costs of these types of test which are mostly non-destructive. A number of impressions can be gained from this review. A quick in-depth analysis on all the research that has been reviewed in the art of using piezoelectric elements in finding the mechanical properties of solid materials, which amounted to 121 studies, reveals that the PE frequencies in this kind of tests did not exceed 15 MHz and most of the research used PE frequencies less than 500 kHz. In addition, most of the dimensions of the samples that were used did not exceed 100 mm. In addition, in this review three tables were classified based on the range of PE frequencies \begin{table}
\begin{tabular}{c c c} \hline \hline
**Material Type** & **Range of Frequency of PE** & **Dimension of Samples (mm)** \\ \hline Plexiglas, glass, metallic glass & 300 kHz to 8 MHz & \\ \hline Polycrystaline metals Aluminium, & 10 Hz to 2000 kHz (bulk wave), & \\ copper, Al\({}_{2}\)O\({}_{3}\) & 1 MHz to 3.5 MHz (surface wave) & 200 \(\times\) 25 \(\times\) 2, 152 \(\times\) 50 \(\times\) 4 \\ \hline Ice & 1 Hz to 1000 Hz & 394 \(\times\) 76 \\ \hline Polymer & 1 Hz to 20 Hz & 8 to 20 (circle diameter) \\ \hline IN738 IC nickel base & 2.25–15 MHz & 150 \(\times\) (22.5–30) \\ \hline Stainless steel 316L & 100 Hz to 15 MHz & \\ \hline Tetrahedral amorphous carbon & 100 kHz to 2000 kHz & \\ diamond & 100 kHz to 5 MHz & 1.9–5.65 \\ \hline Famil specimen & 1 MHz to 10 MHz & \\ \hline Silica aerogels & 405 kHz & \\ \hline Paper of writing & 0.9 MHz to 1.7 MHz & 80–300 g/m\({}^{3}\) \\ \hline Fe\({}_{4}\)Sb\({}_{12}\), Co\({}_{4}\)Sb\({}_{12}\), didymium alkaline & 10 MHz & 10 (diameter) and 10 (height) \\ \hline Seismogenic rock, concert, bulk of & \multirow{2}{*}{75 kHz to 1 MHz} & \multirow{2}{*}{60 \(\times\) 13 \(\times\) 5} \\ cereal grains & & \\ \hline Epoxy-impregnated Kevlar & 1 kHz to 1.5 kHz & 25 \(\times\) 1.4 \(\times\) 1.1 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Different types of material with suitable frequency ranges for PE. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Frequency (\(f_{r}\))** & **Rough Description of** \\
**Range in MHz** & **Type of Application** & **the Samples** \\ \hline Less than 0.5 & Piezo-spectroscope, shaker load cell, filter for interface noise, emitter only, pickup sensor only, shock wave generator, active and passive velocity transducer, polyvinylidene fluoride & Most dimensions for length, width and depth \\  & (PVDF), Piezo-scanner, load cell, monitor to the constant load, dynamometer, strain gauge, accelerometers & are less than 100 mm. \\ \hline \(0.5<\)\(f_{r}\) \(<\) 2 & PVDF, Piezo-electroscope, and pickup sensor & Weight loads ranged \\ \hline \(2<\)\(f_{r}\) \(<\) 5 & Shaker load cell, pickup sensor only, monitor for constant load and PVDF. & between 4 N to 200 Grain size (0.3 \(\upmu\)m to 1.5 \(\upmu\)m) \\ \hline \(5<\)\(f_{r}\) \(<\) 15 & High-speed actuator, PVDF. & \\ \hline \end{tabular}
\end{table} 
Table 3: Types of applications for PE according to frequency range. for each test, type of test such as impact tests, toughness tests, etc. and classification of tests according to material properties. On the other hand, many technical advantages in using PEs can be concluded, as follows:  
1. Most of the ultrasonic creep tests have preferred of using PVDF because it can sense: (a) the low and high vibrations; (b) the slight changes in stress for more than 10 years and 100 million pressure cycles; (c) and can be used in a wide temperature range (\(-40\)\({}^{\circ}\)C to \(+160\)\({}^{\circ}\)C). 2.