Strain Gauges Were Used As A MUSICAL INSTRUMENT Engineering Essay

Abstract

In our day to day life we meet impact launching. There are a lot of things happening relating to impact loading theory. This report is approximately development a screening rig for impact loading of beams for lab use.

The aim of this task is to design a ready to manufacture product which may be used for the purpose of laboratory experiments and compare the true results from experiments with the theoretical results from calculations.

Main factor is to measure the instantaneous deflection in cantilever beam. So these purpose stress gauges were used as a musical instrument. For design the rig Good Works software were used in the drawings.

Summary

This record is job goal at Greenwich University in United Kingdom. It really is about development a testing rig for calculating deformation and stresses caused by impact loading on beams for lab use.

The project started with the thought of affecting the impact loads on the standard steel beams and deformation and stress. The aim of this task is to development of a lab rig for calculating deformation and tensions caused by impact loading. This is used for the intended purpose of laboratory experiments and comperes the true results from the tests with the theoretical results from the calculations.

The specimens to be used were 1. 3 meter long 8 standard cantilever beams that i choose for end this job. The initiation step in this project was to research theory behind the impact loading and deformations and stress according to the impact loading. The next step was design and dimensions a evaluation rig which is suitable for lab use. The elevation and the maximum weight were chosen corresponding to laboratory use conditions, health insurance and safety issues. The third step was to measure the falling height of the weight onto the test test and gauge the instantaneous maximum deflection of the beam. In this case, the procedure of falling level was not very important but measuring the deflection of the beam with optimum approach was most important. A dimension system is used considering this factor.

In the project, Good Works software was mainly used in the design, drawings and strength and stress analyses.

Table of Contents

Chapter 1

1. Introduction

1. 1 backgrounds

This job research was made for Greenwich University College of engineering Mechanical Executive technology Department for my final year project to development of a laboratory rig for measuring deformation and strains caused by impact launching.

One of the most important things in this job is to use the theoretical record given in the executive dynamics and materials selection subject about impact loading and materials in reality. The main idea of this project is to development of a laboratory rig for calculating deformation and stresses caused by impact loading trials rig which is ideal for laboratory conditions. Because the screening machine will be employed by students, it should be as safe as is possible and at the same time should be practical and simple to use.

The Task

The goal of the research is to design an experimental rig for measure the deformation in cantilever beam at the mercy of impact loads. The picture below shows an example design of the assessment rig. Detailed drawings of most components and assemblies are available in Appendix Drawings.

Figure 1 Sketch of evaluating machine

The following parts need to assemble

Support Blocks

Bottom Plate

Rope

Testing Beam

Falling Part

Rulers

The goal is to find answers to the problems by providing answers to the next questions

How shall a assessment rig for impact launching be designed?

How can different lots apply to different sizes tests beams in various experiments?

How can the screening beam be set in a versatile way?

How can the movements of the dish be provided?

How can the beam deflection be assessed?

Best options for the issues above shall be chosen. As well as the evaluation machine will be designed ready to create. Since this is a genuine project, processing of the evaluation machine should also be affordable.

1. 3 The Objectives

The objectives of the task are to development of a rig to measure the instantaneous maximum deflection caused by impact loading examining machine for laboratory use. This article shall contain pursuing chapters.

Research about the impact loading

Research about deflection and stress

Designing of the rig

Dimensioning of the rig

Calculating the minimum amount and maximum insert that can be put on the screening beam

Fixing of the trials beam. The evaluation beam should be dependable, flexible and this also fixation shouldn't stop the free bending of the beam

Measuring the deflection of the beam and dropping height of the load precisely

Designing the evaluation rig to be safe

1. 4 Restrictions and Assumptions

Some elements of this research are assumed and chosen scheduled to time limitation and the main purpose of the study. The main goal is to create and sizing the impact loading testing rig. For this purpose the focused domains are design and assemblage. But since it is a genuine project it contains lots of other factors (welds etc). In which to stay the primary field these factors are assumed.

H beam assemble with the bottom dish using with bolts and nuts

For the design all the materials which is chosen ss 1035 metallic.

All other areas are weld jointly. Weld thickness in the look were assumed 10mm

8 different stranded screening beams receive below

Beam material

Cross section (mm)

Length(mm)

Young's modulus(Gpa)

Moment of inertia

Height

deflection

aluminium

50*50

40*40

steel

50*50

brass

Polyester fibre glass

Table 1 beam type

Chapter 2

2. Books review

2. 1 Impact Loading

A moving body dazzling a structure provides a out of the blue applied dynamic pressure that is called impact. Additionally it is called shock, sudden or impulsive launching. In our true to life many examples of the impact loading may be seen. Some of them are as follows

Driving a nail

Razing of properties with an impact ball

Automobile wheels dropping into potholes

Breaking up concrete with an air hammer

Automobile collisions

Dropping of cartoons by freight handlers

Impact loads may be split into three categories

Rapidly moving loads of essential constant, as produced by vehicle crossing a bridge

Suddenly applied loads, such as those in an explosion, or from combustion within an engine cylinder

Direct impact tons, as produced by a pile drivers, drop forge or vehicle crash

Impact lots may be labeled in a few categories

Compressive impact (Generating a nail)

Tensile impact (Starting a movements of an automobile which is tugging another car)

Torsional impact ( Jamming of the shaft for any reason)

Bending impact ( Falling of an object on the beam)

Combination of the listed above

2. 2 Impact Launching in Daily Life

In our life daily we undoubtedly deal with many impact loading applications. Sometimes we either notice them or not. Impact loading applications in everyday activity can sometimes be profitable and helpful (e. g. Driving a vehicle a nail, pneumatic nailing tool, etc), but usually it can be an undesired situation (collision of two cars, dropping a mass from a height onto something, fill resulting from the blow of your hammer etc. )

http://www. musclecars. faketrix. com/content/crashes-pics/page-2/large/head-on-car-crash-two-vehicles-collide. jpg http://www. dreamstime. com/hammering-nail-thumb4065755. jpg

Picture 2 Collision of two auto mobile Picture 3 travelling the nail

Diving panel analyse is basic idea in my case. How much force has to give when diver jumps easily. Then only divers understand how much deflection made from the diving panel and give back its original possession. Then divers can protect them self. As well as diving table designers also need to consider about the utmost deflection of the board.

http://craig. backfire. ca/img/diving-boards. png

Picture diving plank (http://craig. backfire. ca/pages/autos/cutting-springs)

Here we can suppose weight as divers weight (everybody different weight) and elevation as divers jumps vertical distance from the plank.

In this case we can use the plastic-type material for creating. But plastic materials have relatively low modulus of elasticity in comparison with metallic or aluminium. This is a downside when the framework requires high rigidity. Often to increase their rigidity reinforcing materials are added, as i described in beam analysing calculations and beam chart (table ). Polyester is thermoplastic with a great balance of properties and can be low priced. It is trusted with glass to produce fiberglass components. it is also produced thermoplastic formulation. Polyester fiberglass has

Good impact strength

Good thermal stability

Light weight

Low cost

Good tensile strength

Flex and stress cracking

We can analyse with spring of the impact loading because all materials have some elasticity. Below picture shows there may be x distance shows deflection when impact insert is applied. Here we can believe F as a abruptly applied load (falling weight).

http://craig. backfire. ca/img/spring-equation. png

Picture Spring and coil original level and after fill applied (http://craig. backfire. ca/pages/autos/cutting-springs)

2. 3 Stress

2. 4 Deflection

The energy balance procedure is easy to extend to effect on the beam a fowling mass. In cases like this energy to be consumed is the inbound kinetic energy with the additional work done by the weight behaving through the beam deformation. The static deflection of the beam is under the weight. The quantity in the parentheses is the powerful amplification the factor by which a load is amplified when all of a sudden imposed. Since the displacement and weight are proportional the effective drive taken by the beam during impact is the merchandise of the strong amplification and the weight. Insert suddenly applied from leftovers produces twice the strain and twice the displacement as the same weight steadily applied.

Remember the assumptions

The beam stiffness is the same for static and dynamic loading.

The beam mass is ignored.

Deformation occurs without energy damage. Energy exchanges between kinetic energy of the mass and pressure energy of the beam.

Deflection depending on

Force applied

Object geometry

Material properties

The appropriate method of measuring deflection and stress I got analysed different kinds of equipment they involve some negatives so finally I used to be choose strain measure as measuring musical instruments. There are various kinds of sensors available whenever we choose the sensors have to consider about environmental factors, economic factors and sensor characteristics there are

Temperature range

Humidity effect

Corrosion

Size

Power consumption

Cost availability

Life time

Sensitive

Rage

Error

accuracy

According to I will analyse three types of sensors.

Linear changing displacement transducer

Dial gauge

Strain gauge

2. 4. 1 Liner varying displacement transducer

Liner adjustable displacement transducer used to assess very small displacements in a seismometer that measures moves in the earth's crust due to earthquakes. It includes a middle primary coil and two external supplementary coils. The magnetic main moves openly without coming in contact with bobbins, with the null (zero) position, it extends halfway into each supplementary coil.

Advantages

Infinite resolution

High pattern life

High accuracy

Good in hostile environment

Disadvantage

Can't gauge the stress

Require high frequency

Very complicated

2. 4. 2 Dial gauge

Dial measure is the tool used to effectively measure a little distance. The measurements effect is displayed in an impressive way through dial. It is available in digital model and analogue model. This used to check on the variant in tolerance during the inspection procedure for machined part, measure the deflection of the beam.

Advantage

More accurate

Low cost

Disadvantage

Can't gauge the stress

Not exact unless attached to a base

2. 4. 3 Tension gauge

To measure the instantaneous deflection in this task were used strain measure. It is a musical instrument can gauge the deflection as well as stress. This has more advantages and dis advantages.

Advantage

It can use in steel

Cost effective

Non corrosive

Sensitive

Small and light

Wide range

Disadvantage

Have to be careful when installing

Expensive control equipment

Temperature can be effect on sensor

Relatively new technology

More detail relating to this strain gauge described in section 3

2. 5 Cantilever Beam deflection

In this research I've chosen cantilever beam as an experimental beam. Below picture shows how the beam will deflect according to impact launching.

When we done impact computation we made some assumptions there are

The mass of the materials is ignored

The damping of the specimen and friction are neglected

The stiffness of the specimen is same both static and strong load

Picture 2 cantilever beam deflection

http://www. advancepipeliner. com/Resources/Others/Beams/Beam_Deflection_Formulae. pdf

Where;

p- Load

L- Length of the beam

h- Height fallen the load

- Maximum deflection of the beam

Equations

description

symbol

unite

Static deflection

mm

Maximum deflection

mm

Height

h

mm

length

L

mm

Moment of inertia

I

mass

m

kg

Table explanation of symbol

Weight is fell from a elevation h onto the free end of an cantilever metal beam. According to that there is a tiny deflection x

Here maximum deflection brought on by impact fill.

Maximum deflection is depending on static deflection and impact factor. Maximum deflection will be product of static deflection and impact factor.

The formula of the static deflection shown below

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [1]

Where;

P- Load

L- Length of the beam

E- Young's modulus

I - Minute of inertia (where; b-width d-depth)

The formula of impact factor shown below

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [2]

Where;

K= impact factor

h- Weight fell from height

- Static deflection

The maximum deflection of the cantilever beam is

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [3]

Minimum static deflection

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [4]

Where;

M - Weight

C- Section of the beam ( b*L where b- width L-Legnth)

Moment of inertia

Maximum stress

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . [5]

Where;

K- Impact factor

Above equations are being used for calculate the instantaneous maximum deflections and maximum stress resulting from the impact launching.

Calculation

3 Design of the evaluation rig

The intention of the research is to create an impact loading evaluating rig. Like all the design procedures, this design has many criteria, assumptions and limitations.

When I design the rig i have to conceder about following factors

Safety reliability

Cost effectiveness

User friendly

Dimensions of the all machine

Tolerances

Total mass which produce impact loading

Cost

Many components were made for the testing rig. These components are; falling part, columns, assisting block installing and connecting plate with them sub-designs. These components are defined below.

The accurate dimensions and in depth drawings were not given in this chapter. All the related drawings and dining tables can be found in Appendix Drawings and Appendix Data Sheets

3. 1 Bottom Plate

3. 2 Support Blocks

3. 3 Rope

3. 4 Screening Beam

3. 5 Falling Part

3. 6 Rulers

3. 7 pressure gauge

The tension in a material is determined by calculating small displacements that occur when the beam is subjected to an impact fill. Bonded metallic tension gages are the most frequent method used to assess deflection. The electric resistance of these gages changes when deformed credited to impact weight. Gauge duration is the most important factor to consider when choosing a pressure gage because the measure averages the measured stress over this size. Metallic foil pressure measure (SGD-6/120-LY1130) is shown in Number.

http://www. sensorland. com/Images/HowPic44-Strain%20Gauge. gif

Picture strain gauge (http://www. circuitstoday. com/strain-gauge)

The below picture is shows agreement of beam deflection measuring methods. The beam deflection will display on strain gauge signal. Below beam testing different way of produce the impact weight but this is a basic notion of our trials rig can measure the deflection.

http://www. kostic. niu. edu/Strain-gage. gif

Picture Measuring deflection strain measure (http://www. kostic. niu. edu/strain_gages. html )

In bonding tension gauges elements to a beam surface, it's important that the gauges go through the same stress as the object. With an adhesive material inserted between the receptors and the beam surface, the installation is delicate to creep anticipated to degradation of the relationship, temperature affects, and hysteresis triggered by thermo elastic stress. Because many glues and epoxy resins are inclined to creep, it is important to work with resins designed specifically for tension gauges.

A bonded metallic tension gauge will not provide appropriate measurements if not properly attached to the test specimen. The adhesive between measure and specimen is in charge of moving the strains produced in the specimen to the measure. It is crucial that the specimen prepare yourself properly to guarantee the adhesive performs its mechanical function.

Strain gages won't perform effectively unless they are really properly adhered to a specimen that has received proper surface planning. To ensure this important period of the laboratory is completed properly, a manual entitled, Student Manual for Pressure Gage Technology, prepared by the manufacturer of any risk of strain gages, Vishay Measurements Group, Inc. , will be provided.

The most important factor is determining tension gauge locations. You will find three ways to look for the locations.

Experience

Finite element research prediction

Theoretical prediction

Procedure to install any risk of strain gauge

The below picture shows how can place the strain gaugehttp://www. straingage. com/strain_gages/images/straingage. gif

Picture placing the strain measure on the beam

(http://www. straingage. com/strain_gages/what_strain. html)

Surface Preparation

Cleaning Surface

Remove grease and oil on the specimen surface by solvent, e. g. , Alcoholic beverages, Acetone, or various other degreasing agent

Abrading Surface

Use silicon-carbide newspaper to sand away uneven surface, paint, or rust and steady the gauging area.

Marking Layout Lines

Use a clean rule and an excellent pencil (2H or harder) or ball-point pen to attract the layout lines, usually a dash-cross, a mix skip the focusing on tension gage area, for positioning.

Conditioning

Re-clean the gaging area

Neutralizing

This is an optional step. A proper neutralizer provides the right pH level at the specimen surface for better bonding with adhesive.

Gauge bonding

Use proper catalyst and adhesive.

Handling and Prep of Gage -handle gages with tweezers and grasp gage at corner, away from gage grid area and solder tabs

Gage Copy- cellophane tape anchored at one end to box

Apply Catalyst on the gauge surface

Apply adhesive on the part surface

Immediately place thumb in the gauge and apply firm and steady strain on the measure for at least one minute

Tape Removal

Lead wire Attachment

Stripping Lead wire-Cut the lead wires to the desired length. Strip off 2 - 3 cm (1 in) insulation for connection.

Tinning Lead cables: Coat the non-insulated elements of the lead wires with solder.

Tinning Gage: Place the solder on the copper tabs of the gauge.

Attaching Lead cable: Position the non-insulated conductors directly on the surface of the solder pillow. Press the solder pencil on the conductor and motivate it into the solder pillow

Removing Rosin: Use solvent to clean the gaging area. Remove the tape fastened on the lead wires.

Anchoring Lead wire: Secured the business lead wiring to the specimen (when possible) with a durable tape

Quarter bridge pressure gauge circuit

http://www. sensorland. com/Images/SG-002. gif

Picture strain gauge connected into Wheatstone bridge

(http://www. circuitstoday. com/strain-gauge)

The strain measure is linked into a Wheatstone bridge circuit with a mixture of four a single gauge (1 / 4 bridge). Within the one fourth circuits, the bridge is completed with precision resistors. Typically, the rheostat arm of the bridge (R2 in the diagram) is set at a value equal to the strain measure resistance without force applied. Both ratio arms of the bridge (R1 and R3) are established equal to one another. Thus, without force put on the strain gauge, the bridge will be symmetrically balanced and the voltmeter will point out zero volts, representing zero drive on the strain gauge.

4 test procedure

5 Material selections

Stress and Strain are linearly related to the other person by Hooke's legislation. Young's Modulus is a tightness regular that relates stress and pressure, and is a property of the material. The curve shows stress versus tension for different types of materials. Each material has a linear region called the elastic region. The slope of those lines depends upon Young's Modules. As stress raises, the material gets into a plastic material region, meaning the materials will deform and no longer return to its original condition completely when stress is removed. The curves end abruptly when the materials breaks. Remember that the ceramic material breaks before stepping into the plastic region, and steel has an increased Young's Modulus than aluminium.

SSCURVE

Graph stress vs strain

Above graph shows clearer about young's modulus about material

In rig design main factor is using materials. So have to consider about the materials selection. The performance of the technical component is bound by the properties of the material of which it is made, and by the designs to which this materials can be produced. Under some circumstances a material can be chosen satisfactorily by specifying amounts for specific properties. An example is the young's modulus indices are governed by the look objectives. Component form is also an important awareness. Beams are lighter than solid ones for the same bending tightness and beams may be on top of that. Information regarding section form can be contained in the performance index to permit simultaneous selection of material and shape. A lot of the rig design ductile materials are using.

http://www-g. eng. cam. ac. uk/125/now/mfs/tutorial/non_IE/metals. jpg

Graph Young's modulus vs density graph

Above graph shows young's modulus vs density we can see the ductile materials shows higher young's modulus and good density too. So I have chosen metal materials for my development of assessment rig. And I also equate to same group materials such as aluminium and brass to get more research for the beam design. And additional I also equate to one of the amalgamated material to beam design.

Graph durability vs cost http://www-g. eng. cam. ac. uk/125/now/mfs/tutorial/non_IE/strength_generics. jpg

Above graph shows durability compare with cost. Cost factor also one of the major factor whenever we design or development. In order that I choose this graph to described about materials selection.

5. 1 beam materials

For the beam design I have choose metal as a materials because it's have higher young's modulus. To help expand I also compare with more materials such as aluminium, brass and amalgamated material which we can use in our tests procedure.

Reason for choosing metal as a material

Advantages

High strength per unite of weight (smaller weight of framework)

More durability

Ability to be rolled into various size and shape

Very high young's modulus

Uniformity

Ductility

Possible reuse and recyclable

Steel won't crack, reduce, splinter, creep, divide, warp, or swell.

Steel studs are non-flammable, and won't add gasoline to a fireplace.

User family

Disadvantage

High maintenance cost

Fatigue

Brittle fracture

Advantages for steel equate to aluminium

Low cost

Low co2 emission

5. 2 assessment rig materials

The same materials using for design the rig.

6 Assembling process

6. 1 welding

6. 2 bolts and nut

7 simulations express

8 Garnt chart

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