SEM111 Materials Assignment 1 Trimester 1 2016 Lecturer: Akif Kaynak-186283

SEM111 Materials Assignment 1 Trimester 1 2016 Lecturer: Akif Kaynak

Stress/Strain Practical:

Aims:

The aim of this practical is to carry out tensile tests on selected metal and polymer samples with a view to understanding stress versus strain behaviour, Hooke’s Law, Young’s modulus, ultimate stress, yield, ductile and brittle behaviour and structure-property relationships . You will compare your tensile data with that published in literature.

 

 

 

1. Outline of your report
2. Aims
3. Introduction

Define:

1. Hooke’s Law,
2. Young’s Modulus,
3. Ultimate Stress,
4. Yield stress,
5. Breaking stress,
6. Breaking strain,
7. Ductile Material,
8. Brittle Material

 

 

 

 

 

 

2. Experimental Procedures:

 

Using the information below and your observations during the prac session explain experimental procedures in your own words. You may use some of the information given below as well as what you have observed during the laboratory session.

Include the graphical output we obtained during the experiments.

 

The following information is on the PASCO apparatus for stress strain measurements:

The PASCO AP-8214A Stress/Strain Apparatus illustrates the relationship between stress and strain for various materials. The apparatus stretches a test coupon (and breaks it in some cases) while measuring the amount of stretch and force experienced by the test coupon. Data acquisition software can be used to generate a plot of force versus displacement and also a plot of stress versus strain.

The Stress/Strain Apparatus requires a ScienceWorkshop or PASPORT interface, DataStudio software, a Rotary

Motion Sensor (RMS), and a Force Sensor. Included with the apparatus are four types of metal test coupons and four types of plastic test coupons. Also included are a tee handle with a socket that fits the hex nuts on the coupon clamps, a bar for calibrating the apparatus, and spare hex nuts for the coupon clamps.

1. Analysis of your results

 

1. Extract the Young’s modulus from the graphs. Young’s modulus for each sample is calculated during the practical by using the straight line fitting within the software.

 

1. Read Ultimate stress (tensile strength), yield stress, breaking stress, breaking strain and percentage elongation at break (if the sample is broken).

 

 

1. For metal samples if there is no clear yield point determine the 0.2% offset yield stress.

 

1. Tabulate Young’s modulus, Ultimate stress (tensile strength), Yield stress , 0.2% offset yield stress, breaking stress, breaking strain, percentage elongation at break for all the samples you tested.

 

1. Include values for the above from literature for comparison on the same table

 

 

1. Comment on the results and possible sources of error.

 

1. Comment on the ductile versus brittle behavior from your results. Ie which samples exhibited ductility and which ones failed in a brittle manner.

 

 

1. Comment on the strength of materials, compare and contrast them. Compare metals and polymers with respect to their general tensile behaviour.

Give reasons for the observed behavior.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2. In this section you will perform some calculations on a problem to test your learning in this prac:

 

Material samples, called specimens, often are tested using a tensile testing machine. A specimen is prepared in an ASTM (American Standards for Testing and Materials) standard shape, often like the one shown below and loaded into the machine. The machine applies a uniaxial load to the specimen at a slow, constant rate. The increasing load and associated deformation are measured at many points until the specimen fractures. Engineers use this data to calculate properties like the yield stress, ultimate stress, and failure stress. They also might use this data to construct a stress-strain diagram for the material.

 

 

 

 

• FORCES IN A TENSION TEST

 

Suppose you need to design a tension test machine capable of testing specimens that have nominal ultimate stresses as high as σu = 650 MPa. How much force must the machine be capable of generating? (express your answer in kN) Assume the testing specimen has the ASTM shape shown.

 

 

 

 

 

1. DEFORMATION IN A TENSILE TEST

If the maximum nominal strain is ϵ_f = 0.5 just before the test specimen fractures and the test machine operates by moving only one grip, how far must that grip be designed to travel? The total length of the deforming part of the specimen (gauge length) is 50 mm. In other words, what is the value of ?

 

 

 

1. INTERPRETATION OF DATA

 

You have built the majority of the tension testing machine, but much of the instrumentation is still being assembled. To test the machine, you perform a test on a steel specimen with known properties. The machine provides you with the given load data, and you manually record the lengths between the marks on the specimen at each point using an extensometer to obtain the table of data shown below.

 

 

L (mm)	50.03	50.06	50.89	52.03	53.34	54.92	57.12	62.13	64.51	66.91	68.59	69.04
P (kN)	15.61	31.54	35.01	39.28	43.77	48.04	52.36	55.03	52.49	48.09	43.64	41.90

 

Use these results to plot the stress versus strain curve for the above sample and determine:

• Why is stress versus strain diagram is preferable to force versus extension diagram?

 

• Plot the above data using computer

 

• Yield stress

 

• Yield strain

 

• Ultimate stress (tensile strength)

 

• Young’s modulus

 

• Modulus of resilience

 

 

 

1. Using the information in the following graph of a\the sample with a gauge length of 50 mm and diameter 10 mm.

 

 

• if the sample was strained to a value of 0.0035 and released what would be the elastic recovery?

 

• Given that the Poisson’s ratio of this material is 0.29, if we applied a stress of 300 MPa, what would be change in its diameter?

 

• Using the graph below evaluate the approximate Modulus of Resilience of this material.

Note:

1. Your prac must be entirely your own work, otherwise no marks will be given.
2. The report must be type written including the calculations and the graphs.
3. Include the graphical outputs from the prac session
4. Include the plot from question 5C (should be computer plotted)
5. All the calculations should be worked out individually, and work copied from classmates will be marked as zero.

 

STRESS VERSUS STRAIN EXPERIMENTS

DATA COLLECTED IN JULY 2015 (T2) and also additional data from T1 2015 and T2 2014 are included for comparison and fill in the missing samples.

Stress versus strain

SAMPLE 1 Annealed steel

E= 135 GPa

Things to report:

Young’s modulus E= 275 MPa

Yield stress=250 MPa

Max stress= 280 MPa

Max strain, breaking strain=  0.32 (32 % stretch)

Nylon  66, E=1.39 GPa

 

Strain at break= 0.22

Percentage strain at break= 22%

Tensile strength=60 MPa

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

sample 4 (Polypropylene PP, data from last year 2015 T2)

Polypropylene

PP

Dimensions: crosssection =2.482 mm^2

Gauge length= 19 mm

Aim

The aim of this practical is to carry out tensile tests on selected metal and polymer samples with a view to understanding stress versus strain behavior, Hooke’s Law, Young’s modulus, ultimate stress, yield, ductile and brittle behavior and structure-property relationships. Once all the data of stress and strain are collected various stress and strain relationship curves to be compared.

 

Introduction

Stress is the reaction of a framework to a related nervousness. At the point when a material is stacked with constrain, it creates an anxiousness, which then factors a material to curve. Designing pressure is characterized because the measure of twisting towards the connected energy partitioned with the aid of the underlying length of the material. Stress strain diagram is a habit of material when it’s subjected to stack. On this chart anxieties are plotted alongside the vertical pivot and as an aftereffect of these hassles, referring to lines is plotted along the extent hub. As regarded beneath in the nervousness strain curves.

1. Hooke’s law

According to Hooke’s law stress is directly proportional to strain within the elastic limit as-

 

 

Where-

E = modulus of elasticity

 

1. Young’s modulus

Young’s modulus, which is otherwise referred to as the versatile modulus, is a mechanical property of direct bendy strong substances. It characterizes the connection between anxiousness and pressure in a fabric. The Young’s modulus is a number that measures an article or substance’s imperviousness to being distorted flexibly when vigor is attached to it. The Young’s modulus of an item is characterized as the incline of its stress–strain bend in the versatile twisting region: A stiffer fabric may have a bigger versatile modulus.

Young’s modulus =

 

1. Ultimate stress

The maximum value of stress in a stress-strain curve is known as ultimate stress. It is the maximum value of stress to which a material can withstand beyond this the material fails/breaks.

 

1. Yield stress

Yield stress of a material is the value of stress at the yield point. A yield point in a stress-strain curve is the point to which a material ceases to be elastic.

 

1. Breaking stress

Breaking stress is the value of stress where the material/specimen breaks into two parts i.e. the stress point where failure occurred.

 

1. Breaking strain

Breaking strain is the value of strain where the material/specimen breaks into two parts i.e. the strain point where failure occurred.

 

1. Ductile material

A ductile material is a material which has ability to extend its length easily up-to certain point.

 

1. Brittle material

A brittle material is a material which does not possesses ability to extend its length easily and breaks.

 

 

The tip perhaps screwed right into a strung maintains, or it perhaps stuck; butt closures maybe utilized, or the preserve area maybe held between wedges. The most primary worry in the choice of a greedy system is to assurance that the instance can also be held on the most severe load without slippage or disappointment within the snatch phase. Bowing must be minimized. Essentially the most recognized checking out machines are all inclusive analyzers, which test materials in pressure, pressure, or bowing. Their essential ability is to make the stress-strain bend portrayed in the accompanying section on this part. Trying out machines are both electromechanical alternately water driven. The key contrast is the method wherein the heap is hooked up. Electromechanical machines rely on a variable-speed electric engine; an apparatus curb framework; and one, two, or 4 screws that move the crosshead up or down. This movement stacks the example in pressure or strain. Crosshead rates can be modified by means of altering the percent of the engine. A chip established shut circle servo framework can also be actualized to precisely control the cost of the crosshead. Water powered trying out machines are headquartered on either a solitary or double performing cylinder that moves the crosshead up or down. Be that as it will, most

static water pushed checking out machines have a single acting cylinder or ram. In a bodily worked desktop, the administrator modifies the outlet of a weight remunerated needle valve to control the fee of stacking. In shut circle water pushed servo framework, the needle valve is supplanted through an electrically worked servo valve for specific control.

 

Experimental procedure

PASCO’s smaller Stress/strain equipment demonstrates the anxiousness amid the whole method of extending and breaking a fabric. The instance is extended with the aid of turning the handle by way of hand until the specimen breaks. The vigor used to prolong the example is measured using a force sensor. Confirm both the nervousness and the adjustment lengthy of the specimen using a each PASCO Interface and application. On this investigation, understudies experiment an assortment of substances through extending them unless disappointment beneath the elastic burden. The specimen is put within the holder and solidly held on both finishes. By means of turning the hand wrench, the illustration is expanded in one measurement. Amid the extending, the force Sensor measures the linked vigor via the 5 to 1 lever arm. This enables the finest reasonable power within the examination to be 250 N. whilst, the Rotary movement Sensor measures the stretch of the example regular. Utilizing PASCO Capstone, the nervousness can be ascertained and charted versus each different. The incline of the anxiety strain diagram in the flexible discipline is known as younger’s Modulus. The transfer amongst flexible and plastic twisting is often called the Yield factor; this point may also be effectively made up our minds from the PASCO Capstone chart. ­

 

Figure: AP-8221 stress-strain apparatus

At the heart of the Stress/strain equipment is a extremely good hand wrench that makes it possible for the patron to provide the vigor expected to prolong and ultimately spoil the gave experiment coupons of quite a lot of substances. Retaining in mind the top purpose to precisely gauge the powers incorporated an energy sensor is utilized. After all, its point of confinement is 50 N, a quantity readily surpassed by means of the strengths anticipated to interrupt a component of the materials. That’s the rationale the Stress/strain equipment makes use of a metallic bar with a 5:1 mechanical favorable position, increasing probably the most severe compel that the sensor can read to 250 N.

A power belt interfaces the hand wrench to a rotating action sensor which deciphers the transform of the wrench into the evaluating trade long of the specimen. Both PASPORT and Science Workshop sensors might be utilized with the Stress/stress apparatus. Stress is hooked up to the instance with the aid of turning the manage by using hand until the specimen breaks. The energy used to lengthen the illustration is measured using a force Sensor associated with a PASCO Interface. A steel lever offers a 5-to-one mechanical favorable role, increasing probably the most extreme compel that the sensor can learn to 250 N. The anxiety is ascertained using Capstone or SPARKvue programming with the aid of taking the vigor over the move-sectional range. No alteration is rolled out for any growth in the pass-sectional range amid extending.

The adjustment lengthy of the example is measured utilizing a Rotary movement Sensor. The resolution is 0.007 mm. The strain is figured via partitioning the adjustment lengthy through the first length. The product naturally ascertains stress by means of keeping apart the related power via the pass-sectional territory and the stress by way of partitioning the adjustment long through the primary size. Knowledge focuses are taken always making a chart progressively. A right away bend attack of the underlying straight line gives young’s Modulus while coordinating underneath the bend decides the material’s force. The Stress/strain equipment is installed on a hard aluminum plate.

 

The test coupon specifications for Ap-8222 plastic test coupon are as follows:

Item	HIPS	Nylon 6 (+15% glass)	ABS	Polypropylene
Color code	Orange	Black	Blue	White
Cross-sectional area	2.482 mm2	2.482 mm2	2.482 mm2	2.482 mm2
Tensile strength	23 MPa/3410 psi	98 MPa/14000 psi	47 MPa/6800 psi	34 MPa/4900 psi
Tensile elongation	40%	2.5%	20%	9%
Modulus of elasticity	2000 MPa/280000 psi	2900 Mpa/420000 psi	2300 MPa/380000 psi	1900 MPa/239000 psi

 Theory

The connection between the anxiousness that a designated fabric showcases is referred to as that designated material’s stress–strain bend. It is exciting for every material and is determined with the aid of recording the measure of disfigurement at unmistakable interims of malleable or compressive stacking. These bends uncover a tremendous number of the properties of a material.

Brittle materials

Brittle substances, which contains cast-iron, glass, and stone, are portrayed by the way that crack occurs with no detectable prior exchange within the rate of elongation. Brittle materials, for instance, cement or carbon fiber don’t have a yield point, and don’t pressure-solidify. On this manner, a definitive first-rate and breaking quality is the same. Usual brittle materials like glass do not exhibit any plastic miss-happening yet fall flat even as the twisting is bendy. One of the most attributes of a brittle disappointment is that the 2 damaged components may also be reassembled to create the equal shape as the first phase as there won’t be a neck association like on account of malleable substances.

A fashioned stress–stress bend for a brittle fabric will likely be direct. For a few materials, for example, concrete, rigidity is irrelevant contrasted with the compressive nice and it is authorized zero for some designing functions. Glass filaments have a stress extra grounded than metal, but mass glass ordinarily does now not. That is an immediate effect of the anxiety drive variable related with imperfections in the fabric. Because the extent of the example gets better, the span of imperfections likewise develops. Typically, the pliancy of a rope is consistently now not exactly the combination of the rigid features of its individual filaments.

 

Ductile materials

Low carbon metal for probably the most section indicates a chiefly direct stress–pressure relationship as much as an extraordinarily a lot characterized yield factor. The direct parcel of the bend is the bendy locale and the incline is the modulus of flexibility or younger’s Modulus. After the yield factor, the bend more often than not diminishes fairly in view of separations getting far away from Cottrell airs. As disfigurement proceeds with, the anxiety increments via advantage of stress solidifying except it achieves a definitive ductile nervousness. Until this point, the go-sectional territory diminishes regularly and haphazardly in mild of Poisson constrictions. The actual crack point is within the equal vertical line because the visual damage point.

Be that as it will, previous this point a neck structures the place the neighborhood move-sectional territory turns out to be altogether littler than the primary. The share of the pliable vigor to the genuine go-sectional neighborhood on the tightest district of the neck is often called the specific anxiousness. The percentage of the elastic vigor to the primary cross-sectional zone is known as the building stress. Within the event that the stress–pressure bend is plotted so far as genuine push and exact stress the anxiety will preserve on rising unless disappointment. Ultimately the neck gets to be precarious and the illustration breaks. On the off chance that the instance is subjected to logically expanding pliable compel it achieves a definitive ductile nervousness and later on necking and lengthening happen rapidly unless crack. On the off chance that the example is subjected to always increasing length it’s conceivable to look at the dynamic necking and stretching, and to quantify the diminishing tractable power within the illustration.

It is engaging to characterize a flexible factor of confinement as the stress at which plastic distortion first happens what’s extra, a corresponding utmost as the anxiousness at which the anxiousness stress bend first goes amiss from linearity. In spite of everything, neither one of the most definitions is particularly precious, considering the fact that estimation of the anxiety at which plastic disfigurement first occurs or the fundamental deviation from linearity is watched relies on upon how precisely strain can be measured. The littler the plastic strains that can be detected and the littler the deviations from linearity can be recognized, the littler the bendy and relative cutoff elements.

To keep a strategic distance from this issue, the onset of the flexibility is customarily portrayed through a steadiness yield fine, which can also be measured with extra noteworthy reproducibility. It can be found by way of constructing a straight line parallel to the underlying direct parcel of the anxiety strain bend, however steadiness through 0.002 or 0.2%. The yield best is the anxiety at which this line converges the nervousness strain bend. The rationale is that if the material had been stacked to this nervousness and after that emptied, the emptying means would had been along this counterbalance line and would have induced a plastic stress of 0.2%. Different counterbalance strains are once in a whilst utilized. The upside of characterizing yield first-class alongside these lines is that such a parameter is with ease imitated and does not rely vigorously on the affectability of estimation.

Right here and there, for alleviation, yielding in metals is characterized by the anxiety required to achieve a indicated all out pressure as a substitute than a predefined counterbalance pressure. Regardless, the groundwork has to be clarified to the consumer of the information.

 

 

 

 

 

Data collection

1. Mount a coupon

• Remove the calibration bar from the bolts. Replace the spring, clamp top, concave washer, convex washer, flat washer and hex nut onto the bolts.
• Place one end of a coupon under one of the clamp tops.
• Adjust the crank so that the opposite end of the coupon can slip easily under the other clamp.
• Tighten both nuts with the tee handle with socket. With no force applied to the coupon, as little twist as possible should be visible in the coupon.
• The clamps should hold the coupon tightly enough that it will not slip when force is applied.
• However, over tightening the nuts will damage the bolts.

 

 

2. Place the lever arm in the starting position

• Turn the crank counter clock-wise and pull the lever arm away from the force sensor so that there is a small gap between the end of the force sensor attachment and the lever arm.

 

3. Collect data

• Press the tare or zero button on the force sensor.

 

 

 

Data analysis

Stress–strain investigation is a designing order that utilizations numerous methods to make a decision the burdens and strains in substances and buildings subjected to strengths. In continuum mechanics, anxiousness is a physical amount that communicates the interior powers that neighboring particles of a nonstop material follow on each other, whilst pressure is the measure of the disfigurement of the material. Stress examination is an principal challenge for usual, mechanical and airplane design experts required within the configuration of buildings of all sizes, for illustration, passages, scaffolds and dams, flying machine and rocket our bodies, mechanical elements, and even plastic cutlery and staples. Stress examination is likewise utilized as part of the support of such structures, and to study the motives for general disappointments.

Often, the beginning stage for nervousness investigation are a geometrical depiction of the structure, the houses of the substances utilized for its parts, how the ingredients are joined, and probably the most severe or run of the mill compels that are relied upon to be linked to the constitution. The yield know-how is commonly a quantitative depiction of how the connected powers spread all by way of the structure, bringing about burdens, traces and the diversions of the whole constitution and every section of that structure. The investigation may just don’t forget powers that adjust with time, for illustration, motor vibrations or the heap of moving cars. All things regarded, the hassles and distortions will likewise be elements of time and area. In building, stress investigation is typically an equipment versus an objective in itself; a definitive objective being the configuration of structures and old rarities that may stand up to a predetermined burden, utilizing the base measure of fabric or that fulfills any other optimality paradigm.

Stress investigation perhaps performed via usual scientific programs, explanatory numerical demonstrating or computational reenactment, trial checking out, or a mixture of systems. The term stress investigation is utilized all via this text for curtness, however it ought to be comprehended that the lines, and redirections of constructions are of an identical value and fact be instructed, an examination of a structure may just begin with the figuring of diversions or traces and end with estimation of the burdens.

Analysis of results

1. Young’s modulus for each sample is as follows:

Polyethylene E = 783 MPa

Acrylonitrile butadiene polystyrene (ABS) E = 943 MPa

Nylon 66 E = 1.39 GPa

Polypropylene E = 1.56 GPa

High impact polystyrene E = 1.87 GPa

 

1. Ultimate stress are:

Polyethylene = 34 MPa

Acrylonitrile butadiene polystyrene (ABS) = 68 MPa

Nylon 66 = 75 MPa

Polypropylene = 35 MPa

High impact polystyrene = 48 MPa

 

Yield stress:

Polyethylene = 34 MPa

Acrylonitrile butadiene polystyrene (ABS) = 54 MPa

Nylon 66 = 36 MPa

Polypropylene = 28 MPa

High impact polystyrene = 38 MPa

 

Breaking stress:

Polyethylene = 21 MPa

Acrylonitrile butadiene polystyrene (ABS) = 64 MPa

Nylon 66 = 60 MPa

Polypropylene = 17.5 MPa

High impact polystyrene = 46 MPa

 

Breaking strain:

Polyethylene = 1.0

Acrylonitrile butadiene polystyrene (ABS) = 1.17

Nylon 66 = 0.16

Polypropylene = 1.18

High impact polystyrene = 1.18

 

 

1. Tabulating all the data

Property	Polyethylene	ABS	Nylon 66	Polypropylene	HIPS
Young’s modulus (GPa)	0.783	0.943	1.39	1.56	1.87
Ultimate stress (Mpa)	34	68	75	35	48
Yield stress (MPa)	34	54	36	28	38
Breaking stress (Mpa)	21	64	60	17.5	46
Breaking strain	1	1.17	0.16	1.18	1.18
Actual E (GPa)	0.791	0.95	1.40	1.5	1.9
% error	1.01	0.736	0.714	4	1.57

 

 

The error possibilities in an experiment are inherent thing and can never be removed completely i.e. a factor of error will always be present in the calculated values. In these experimental values the error factor is below 4% for each and every plastic sample.

All of the above plastic samples i.e. polyethylene, ABS, nylon 66, polypropylene and high impact polypropylene the behavior observed is ductile. All these plastics have capability to stretch easily.

The strength of the materials varies from material to material and the highest strength among the tested materials is of HIPS (high impact polypropylene).

 

 

Sample testing and calculations

Material examples, referred to as examples, most of the time are tried making use of a pliable checking out computing device. An example is hooked up in an ASTM (American requirements for checking out and materials) normal shape, quite often just like the one regarded beneath and stacked into the computer. The laptop applies a uni-axial burden to the instance at a average, constant price. The expanding load and related disfigurement are measured at numerous focuses unless the illustration breaks. Engineers make use of this knowledge to compute residences just like the yield stress, extreme anxiousness, and disappointment stress. They likewise may just utilize this expertise to construct an anxiety stress chart for the fabric.

Ductile checks are performed for a few explanations. The aftereffects of elastic checks are utilized as part of picking substances for designing applications. Ductile properties each every so often are incorporated into material details to warranty exceptional. Elastic homes most likely are measured amid improvement of recent substances and systems, in order that wonderful materials and strategies may also be checked out. At last, ductile houses most of the time are utilized to assume the conduct of a fabric below forms of stacking rather than uni-axial strain.

 

Tensile testing

The first-rate of a fabric more often than not is the essential drawback. The pleasant of interest maybe measured concerning either the anxiety fundamental to purpose tremendous plastic distortion or the finest anxiety that the fabric can face up to. These measures of pleasant are utilized, with fitting alert, in constructing plan. Additionally of interest is the fabric’s flexibility, which is a measure of how a lot it can be disfigured earlier than it cracks. As soon as in a at the same time is pliability fused especially in outline; or possibly, it’s incorporated into material determinations to warranty first-rate and sturdiness. Low flexibility in a pliable experiment ordinarily is joined with the aid of low imperviousness to crack underneath extraordinary forms of stacking. Versatile homes likewise possibly of interest, be that as it should, distinctive ways need to be utilized to quantify these residences amid elastic trying out, and more certain estimations can be made by using ultrasonic techniques.

It has developed closures or shoulders for grasping. The principal part of the example is the gage segment. The move-sectional zone of the gage subject is lessened in appreciate to that of the leisure of the illustration in order that distortion and disappointment shall be limited in this locale. The gage size is the district over which estimations are made and is targeted inside the reduced area. The separations between the finishes of the gage discipline and the shoulders need to be sufficiently notable in order that the larger finishes don’t oblige disfigurement within the gage discipline, and the gage size have to be unusual in appreciate to its measurement. Whatever else, the stress state shall be extra intellect boggling than easy pressure. Nitty gritty depictions of common instance shapes are given in Chapter 3 and in ensuing materials on tractable checking out of distinctive substances.

There are unique methods for holding the instance, some of which are represented in the following figure. The end possibly screwed into a strung hold, or it perhaps caught; butt closures perhaps utilized, or the preserve subject possibly held between wedges.

Probably the most significant worry in the decision of a retaining manner is to warranty that the instance will also be held on the finest load without slippage or disappointment in the keep discipline. Twisting has got to be minimized.

 

1. Forces in tensile testing
2. Deformation in tensile test

If the maximum nominal strain is ϵf = 0.5 just before the test specimen fractures and the test machine operates by moving only one grip, how far must that grip be designed to travel? The total length of the deforming part of the specimen (gauge length) is 50 mm.

 

 

 

 

1. Interpretation of data

You have built the majority of the tension testing machine, but much of the instrumentation is still being assembled. To test the machine, you perform a test on a steel specimen with known properties. The machine provides you with the given load data, and you manually record the lengths between the marks on the specimen at each point using an extensometer to obtain the table of data shown below.

 

 

1. The stress strain diagram is preferable over the force extension diagram because the stress strain diagram provides information about the ultimate stress, yield stress, breaking stress, breaking strain, elastic limit and the fracture point for a particular material whereas the force extension diagram does not provides these information. The force extension diagram only provides the information regarding the extension only when a certain force is applied to it.

 

1. The given data are as follows-

L (mm)	50.03	50.06	50.89	52.03	53.34	54.92	57.12	62.13	64.51	66.91	68.59	69.04
P (kN)	15.61	31.54	35.01	39.28	43.77	48.04	52.36	55.03	52.49	48.09	43.64	41.90

 

Now plotting these data as-

 

 

1. Yield stress, Yield strain, Young’s modulus, ultimate stress, modulus of resilience from the force extension curve the Yield stress cannot be determined. As this diagram does not contain any specific information about these parameters.

 

1. If the sample is strained to 0.0035 and then released then the elastic recovery will be-

• Length L = 50 mm

Diameter d = 10 mm

Elastic recovery

Elastic recovery

Therefore up-to the extension of 0.175 mm there will be elastic recovery.

 

• Poisson’s ratio and stress = 300 MPa

 

 

 

 

• The approximate modulus of resilience from the following graph is as follows:

Flexibility is the capability of a fabric to continue vitality when it is disfigured flexibly, and discharge that vitality after emptying. Evidence force is characterized as essentially the most severe vitality that can be retained inside so far as viable, without making a perpetual bending. The modulus of force is characterized as the most severe vitality that may be consumed per unit quantity without making a perpetual bending. It may be computed by coordinating the anxiousness stress bend from zero to so far as viable. In uni-axial strain,

Conclusion

In this experiment all the values of the required parameters are calculated. The plastics possess higher elasticity as compared to the metals. The modulus of resilience obtained from the given figure of stress and strain is 0.81. The curves for each sample of plastic is drawn from the computer software and analyzed in detailed. The other parameters like change in diameter or length is also calculated and all the data are within 4% of error with the actual value of respective variable.

 

 

 

 

 

References

Andresen, P. and Duquette, D. (1980). Slow strain rate stress corrosion testing at elevated temperatures and high pressures. Corrosion Science, 20(2), pp.211-223.

Andresen, p. And duquette, d. (1980). Cheminform abstract: slow strain rate stress corrosion testing at elevated temperatures and high pressures. Chemischer informationsdienst, 11(24).

Beavers, J. and Koch, G. (1992). Limitations of the Slow Strain Rate Test for Stress Corrosion Cracking Testing. CORROSION, 48(3), pp.256-264.

Chaney, R., Demars, K., Vaid, Y., Eliadorani, A., Sivathayalan, S. and Uthayakumar, M. (2001). Laboratory Characterization of Stress-Strain Behavior of Soils by Stress and/or Strain Path Loading. Geotech. Test. J., 24(2), p.200.

Chromčíková, M. and Liška, M. (2008). Stress Strain Testing of the Strand of E-Glass Fibers. AMR, 39-40, pp.165-168.

Dannis, M. (1962). Stress-strain testing of rubbers at high rates of elongation. Journal of Applied Polymer Science, 6(21), pp.283-296.

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