Microphone features.
The characteristics of the microphone depend on the material to be measured and the size of the specimen. For example, a concrete cylinder with a diameter of 100mm and a length of 200mm, presents flexion and torsional frequencies between 3000 and 6000Hz depending on the stiffness of the material. Therefore, an ordinary microphone with a frequency range of 0 to 16kHz is sufficient. However, longitudinal frequencies can be between 11000Hz and 20000Hz, so to capture these frequencies one would need a microphone with a wider range between 0 to 20khz or greater. This shows that commercial and cheap microphones could already be used at least to characterize the dynamic Young's modulus with the first flexional frequency. On the other hand, larger concrete cylinders may present lower frequency values for longitudinal frequencies, so microphones with a frequency range from 0 to 16kHz could work to identify longitudinal frequencies. The sound acquisition card for the microphone can be an ordinary card with a measurement range of 0 to 48khz. It is recommended to use unidirectional microphones to avoid picking up sound from other directions.
Manual for the Construction of the Support
Download the instructions in PDF.
(Only available in Portuguese)
Step 1 - Profiles cutting, stripes and solid stainless steel bars.
Below is a list of the length of the cuts to be made in the profiles, strips and the stainless steel bar.
List of cuts of profiles, strips and steel bar
Step 2 - Making screw threads and holes in all profiles
Figure 32. Position of threads and holes in profiles.
First the screw threads are made on the faces of all profiles with the help of the "Desandador - Vira Macho - M8", so, with the help of a machine, the profiles of aluminum are drilled in the following points for the passage of a 'Chave Allen Longa com Ponta Boleada - 5mm''
• For (2) 250 mm profiles and (2) 200 mm profiles drill as shown in Figure 32.a and 32.b;
• For the same (2) 250 mm profiles drill as indicated in Figure 32.c;
• For (2) 120 mm profiles, drill as shown in Figure 32.d and 32.e;
• For (2) 50 mm profiles, drill as shown in Figure 32.f;
The importance of cleaning immediately after drilling is emphasized in order to ensure that the residues do not obstruct the passage of the solid stainless steel round bar.
Step 3 - Assembling the skeleton
Figure 33 - Lateral skeleton of the support.
The lateral skeleton (Figure 33.a and 33.c) consists of: (1) 250 mm piece, (3) 200 mm, (1) 120 mm and (1) 80 mm. To assemble the skeleton, first place the M8 x 16mm Allen Head Bolt on the faces of the (2) 200 mm pieces - Connector 30 Screw, unite them and tighten with the help of the Long Allen Wrench with Rounded Tip - 5mm on one side with (1) 250 mm piece and on the other side with (1) 200 mm piece, just on the face of the 200 mm piece join and tighten with (1) 120 mm piece which in turn joins ( 1) 80 mm piece. In order to give greater resistance to the piece, (1) Angle Kit 38x38x28mm for Base Profile 30 - with Nuts and Screws is placed at the intersection of the 250 mm and 120 mm pieces (Figure 33.b).
Step 4 - Inserting the screws for the galvanized steel tensioner
In all 3/16 steel cable tensioners, one of the hooks is removed and replaced by the 3/16 mm round head screw screw, and fits in the (2) 300 mm pieces, and the hooks are placed on the hooks. Clamps for 1/8 "steel cable (Figure 34.a).
Step 5 - Joining the side and front skeletons
With the help of the (2) 300 mm pieces with the Allen Head Bolt M8 x 16mm - Connector 30 Screw on both sides, the connection of the side skeletons with the other aluminum parts is made and thus the skeleton is ready ( Figure 34.b).
Figure 34 - Skeleton assembly
Step 6 - Placing the stainless steel bars
All 25 mm x 3/4 "short thread weld PVC adapters are cut, leaving only the thread for use (Figure 35.a), which is placed (2) threads on the (3) bars 340 mm and then on (1) 340 mm bar and (2) 320 mm bars at one end respectively, the saw is cut at 45 ° (Figure 35.b) and welded. Before making the welding, put the PVC threads in. Finally, let the bar cool as shown in Figure 35.c.
Figure 35 - Mounting the stainless steel bars on the skeleton.
Step 7 - Mounting the tensioners
The cable is tied hook to hook, then fastened and fastened with the help of clamps.
Step 8 - Finishing the finishes
Finally, the feet are assembled, the closing covers and finishing strips are installed.
Figure 36 - Finishing support with finishes
