Automatic Concrete Sounder Connor Murphy ELM /24/14

Presentation Order Background Standard Testing Procedure Electronic Testing Procedure Problem Proposed Solution System Diagram Time Delay (1) Time Delay (2) Mechanical Timing Mechanism Electrical Programming (1) Programming (2) Project Goals Chronology Budget Questions?

Background As concrete structures deteriorate, the concrete must be monitored Some testing requires sample of the concrete but this is destructive Non-destructive evaluation (NDE) is a more popular method to test concrete. Examples of testing techniques for concrete and other materials include Existing Testing Technology Ground penetrating radar Infrared evaluation Sounding

Standard Testing Procedure Standard testing for bridges in Vermont is hammer and chain sounding Hammer strike against the concrete results in a sound whose pitch and ring tell whether the concrete is good or bad Technician sounds out “bad sections of concrete” to mark area of concrete to be replaced.

Speed of sound through materials Sound travels at a given speed through different materials A Person yells to two people, one person 10 ft away and one 100 ft away The speed of sound in air is 1000 ft/s The sound will reach the person who is 10ft away faster than the person who is 100ft away The time it took for the sound to travel is the time delay Time delay 10ft away = (10 ft)/(1000ft/s)=.01s Time delay 100ft away = (100 ft)/(1000ft/s)=.1s 10ft 100ft

Problem Create an automated concrete sounder Device must be able to determine concrete depth and delaminations (cracks) Device must be portable Must be easy to use

Proposed Solution Solution will use a time delay based on the pulse echo standard Sound input will be a mechanized hammer; the start of measured time delay MEMs microphone will record concrete sound; this marks the end of the time delay Kinetis micro-controller will measure time delay and convert an outputted time in seconds Hammer and microphone will both be on top side of bridge

System Diagram Initially Micro controls hammer Reads, records data from microphones Exports data to excel file on laptop Hammer Mechanism Microphones Concrete Slab Kinetis Micro Cart

Time Delay (Thickness measurement) Concrete Slab Sound Paths -Concrete -Air only Time (ms) Voltage Time (ms) Voltage Time (ms) Voltage Time Delay Copper Plate Slide Hammer Scope Ch2 Scope Ch1 Scope Ch2 Scope Ch1 Scope Ch2 Scope Ch1

Timing Mechanism Used for timing when hammer hits copper plate Hammer completes circuit when contacting copper plate Normally open contact drives circuit low upon the hammer striking the copper Energy In: Potential E=mhg E=(.7kg)(.1524m)(9.807m/s) E= 1.04 J/s Copper Plate Hammer Slug m=.7kg h= 6in =.1524m To Micro Time (ms) Voltage Hammer hits plate

Time delay (Sound speed measurement) To determine the speed of sound through concrete a time delay between 2 mic.s will be used That speed can then with the time delay of the concrete to determine concrete depth The speed of sound is 10 times faster through concrete than air – Concrete carries sound 10 times the distance air does in the same time Distance = 1ft V= 1ft/ t 1 Velocity = Displacement/time Can then be used: Thickness= V*t 2 Displacement= Velocity * time

Mechanical Device tentatively to be contained on rolling cart. Weights to improve coupling between hammer and microphone on cart and bridge surface Specific plans to be developed for cart Cart will be similar in size to the chain drag cart shown Weights Cart Hammer Mechanism

Electrical MEMs microphones Comes with amplifier built in Requires 3V and ground Signal out sits at.8V when no sound acts upon mic. Kinetis USB, with 5V power and ground A/D converter to read signal out of mic. Hammer Timing circuit will be simple switch involving hammer and copper plate USB Kinetis Micro 3V A/D Hammer Mechanism Driver External PS, to be sized Microphone

Programming Input pulse from hammer Read from microphones & hammer circuit Convert time delays to inches Output mic. Data to computer Programming is in initial stages 4 general action concepts Programming will be in C Timing will be very critical so sound waves don’t interfere with one another

Programming Input pulse from hammer Hammer/ plate switch inititates program Read from microphones & hammer circuit Data captured through A/D from microphone Convert time delays to inches Will eventually correlate sound wave time delay with concrete thickness Output mic. data to computer Data sent to computer Computer logs data in Excel Where Desired sound wave Cancelation wave Unwanted reflected/ transmitted wave Hammer Microphone Concrete Bridge Slab

Project Goals Chronology

Budget

Questions?

Speed of sound through materials Terms MB - Main Bang BE – Back Echo FE – Flaw Echo Four Concrete test depths An evolutionary step of hammer sounding is to automate the hammer and investigate physics creating the pitch and ring variance in concrete.