LAB Manual MT LAB I - Patrical material PDF

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Material Testing Lab Manual

EXPERIMENT NO: 1

Marks...............

DATE ………………….

TORSION PENDULUM TEST AIM To determine the shear modulus of the material of the given wire. EQUIPMENTS 1. Torsion Pendulum.

4. Venire Calipers.

2. Cylindrical wire.

5. Screw gauge.

3. Stop watch.

6. Meter scale.

SPECIMEN Steel wire, brass wire. TORSION PENDULUM APPARATUS The torsion pendulum apparatus consists of a (1) Torsion pendulum in the foam of disc and a thin wire (2) A bracket for suspending for suspending the Pendulum. There are two identical cylindrical weights which can be mounted on the disc; for changing the moment of inertia of the pendulum. PRINCIPLE OF THE TEST For small oscillations of the disc, it is in simple harmonic motion and the formula for simple pendulum holds good.

Where T= period of oscillation in sec. Department of Civil Engineering

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Material Testing Lab Manual

I = Mass moment of inertia of the rotating system about the longitudinal axis of wire. L= Length of the wire between its grips. N = Modulus of rigidity (Shear modulus). J = Polar moment of Inertia =

𝜋𝑑 4 32

d= diameter of the given wire in the test, N is found out as given below if other quantities are known. Suffices 1 and 2 refer to conditions when no cylindrical weight is added on to the disc and when known cylindrical weights are added. We have,

————– (2)

————-(3) From which it follows:

————-(4)

———(5) Where W = Total weight of cylinders added to the disc. Department of Civil Engineering

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Material Testing Lab Manual

g= Acceleration due to gravity. r= Radius of cylindrical weights. R = distance from centre of cylinder of the cylindrical weight to centre of wire Thus from equations (4) and (5)

PROCEDURE The wire for the test is tightened at its bottom to the disc and its top to the bracket. The disc is turned, trough a small angle and released without the cylindrical weights on it. Time for a number oscillation (Say20) is measured with a stop watch. Now, the cylindrical weights are mounted on the disc and the new time for the same number of oscillations of the disc is measured. Test is carried out for different lengths of the wire. OBSERVATIONS Observations are recorded in Table. CALCULATIONS

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Material Testing Lab Manual

OBSERVATIONS AND CALCULATIONS

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Material Testing Lab Manual

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Material Testing Lab Manual

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Material Testing Lab Manual

RESULT Modulus of rigidity (N) of the material of the given wire (steel) = ______________________ N/mm2 Modulus of rigidity (N) of the material of the given wire (steep =-_________N/mm2

QUESTIONS – DO YOU KNOW? 1. What are the tests that can be used for finding modulus rigidity of materials? 2. The period of oscillation increases as the length of pendulum. Is this statement correct or not? 3. What is the different between plane moment of Inertia and polar moment of inertia? 4. What is the use of cylindrical weights in Torsion Pendulum? 5. Define mass moment of Inertia? 6. What is the type of stress developed in the specimen subjected to torsion?

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Material Testing Lab Manual

EXPERIMENT NO: 2

Marks...............

DATE ………………….

SPRING TEST AIM To determine the modulus of rigidity (Shear modulus) of the material of the spring. EQUIPMENT I. Spring Testing Machine, 2. Dial gauge. DESCRIPTION OF THE MACHINE The spring testing machine has two uprights fixed to a rigid base and three cross heads. The upper and lower cross heads are rigidly attached to the uprights while the middle one is made to move on finely finished gunmetal bearings over the uprights. To the middle cross head is attached the loading cradle where tire weights for loading the spring during the test are placed. The spring for tension test is held on hooks between the upper and middle cross heads while that for compression test is placed on collar between the middle and lower cross heads .Clutch mechanisms are provided to help holding the middle cross heads for fixing the spring. Thus also an attachment with a fine adjustment device to fix the dial gauge for measuring extensions of the spring. SPECIMEN I: Close coiled spring 2. Open coil spring.

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Material Testing Lab Manual

PROCEDURE 1. Tension Test. (Test on close coil spring). Fix the close coiled spring to the hooks between the upper and the middle cross heads with the help of clutch mechanism. Release the clutches and let the spring hang freely between hooks. Fix the dial gauge and adjust it to read zero on the dial. Load the spring by placing one calibrated tire weight, on the cradle and note the corresponding deflection from the dial gauge. Place the tire weights one by one, noting the dial gauge reading every time a weight is placed. Continue the observation while unloading the spring also. 2. Compression Test (Test on open coiled spring). Fix the spring on the bearing collars between the middle and lower cross heads with the help of the clutch mechanisms. Release the clutch and let the spring rest freely between the collars. Adjust the dial gauge to read zero on the dial. Load the spring and note its deflection in the same way as for the tension spring. OBSERVATIONS Record the observation taken in table GRAPH Plot the variation of deflection with load for both the close coiled and open coiled spring.

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Material Testing Lab Manual

Load — Deflection Graph

CALCULATIONS 1. Close coiled spring

R = Mean radius of the spring n = No. of Coils. d = diameter of the wire. N = Shear modulus of the spring materials. W = Load applied. = Deflection

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Material Testing Lab Manual

2. Open coiled spring

Where N, R, n, d, W & are as above. P

α = 2πR , α is the helix angle. E = Modulus of Elasticity of the spring Material P=

L n

Stiffness of spring =

𝑊 𝛿

= ∆𝑊 ∆𝛿

Take E= 2×105 N/mm2 and complete the calculation.

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Material Testing Lab Manual

1. Close coiled spring DIAL GAUGE READINGS SL NO:

LOAD(Kg) LOADING

UNLOADING

DEFLECTION(mm)

Physical Constants Sl No:

Name

Unit

1

Outer Diameter (D0)

(mm)

2

Diameter of wire (d)

(mm)

3

Number of turns (n)

4

Length (L)

Value

(mm)

Calculations

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Material Testing Lab Manual

GRAPH SHEET

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Material Testing Lab Manual

2.Open coiled spring DIAL GAUGE READINGS SL NO:

LOAD(Kg) LOADING

UNLOADING

DEFLECTION(mm)

Constants Sl No:

Name

Unit

1

Outer Diameter (D0)

(mm)

2

Diameter of wire (d)

(mm)

3

Number of turns (n)

Value

Calculations

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Material Testing Lab Manual

RESULT Shear modulus of the material of Close coiled spring = _____________ N/mm2 Shear modulus of the material of Open coiled spring = ______________ N/mm SPRING A spring is defined as an elastic body, whose function is to distort when loaded and to recover its original shape when the load is removed. Springs are load bearing elastic objects that are used to store and transfer mechanical energy. They are usually made from a low alloy, medium or high carbon steel. Their relatively high yield strength allows them to return to their original shape and size after a temporary deformation. There are several types of springs, including helical springs, flat springs and torsion springs among others. Helical springs. The helical springs are made up of a wire coiled in the form of a helix and are primarily intended for compressive or tensile loads. The cross-section of the wire from which the spring is made may be circular, square or rectangular. Helical compression springs have applications to resist applied compression forces or in the push mode, store energy to provide the "push". Different forms of compression springs are produced. The helical springs are said to be closely coiled when the spring wire is coiled so close that the plane containing each turn is nearly at right angles to the axis of the helix and the wire is subjected to torsion. In other words, in a closely coiled helical spring, the helix angle is very small; it is usually less than 10 degree. The major stresses produced in helical springs are shear stresses due to twisting. The load applied is parallel to or along the axis of the spring. In open coiled helical springs, Department of Civil Engineering

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Material Testing Lab Manual

the spring wire is coiled in such a way that there is a gap between the two consecutive turns, as a result of which the helix angle is large. Terms used in Compression Springs The following terms used in connection with compression springs Solid length (Ls). When the compression spring is compressed until the coils come in contact with each other, then the spring is said to be solid. The solid length of a spring is the product of total number of coils and the diameter of the wire. Free length (Lo). The free length of a compression spring is the length of the spring in the free or unloaded condition. Load(P) The force applied to a spring that causes a deflection. Deflection Motion of spring ends or legs under the application or removal of an external load . Wire Diameter (d) – The diameter of the wire that is wound into a helix. Spring Index (C) - The ratio of mean coil diameter to wire diameter. A low index indicates a tightly wound spring (a relatively large wire size wound around a relatively small diameter mandrel giving a high rate). C=

D d

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Material Testing Lab Manual

Coil Diameter (D) - The mean diameter of the helix, i.e., (D outer + Dinner)/2. Active Coils (Na) - The number of coils which actually deform when the spring is loaded, as opposed to the inactive turns at each end which are in contact with the spring seat or base. Total Coils (Nt)- The number of coils or turns in the spring. Pitch (p) - The distance from center to center of the wire in adjacent active coils. Compression Spring Rate: The change in load per unit of deflection. Spring rate is determined by the amount of force, in Kg, required to constrict a spring by one mm. Pitch Angle α- The angle between the coils and the base of the spring. The pitch angle is calculated from the equation

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Material Testing Lab Manual

EXPERIMENT NO: 3

Marks............................... DATE ………………….

VERFICATION OF CLERK MAXWELL’S RECIPROCAL THEOREM AIM To verify clerk- Maxwell’s Reciprocal Theorem and to determine the Young’s modulus of beam arterial of the apparatus EQUIPMENT REQUIRED 1. Clerk-Maxwell’s reciprocal’ theorem apparatus 2. Tire weight 3. Dial gauge THE THEOREM Clerk-Maxwell’s reciprocal theorem state that in a linearly elastic structure, the deflection at any point A due to a load applied at some other point B will be equal to the deflection at B when the same load is applied at A. THE APPARATUS Clerk-Maxwell’s reciprocal theorem apparatus consists of a rigid frame and a light beam. The beam is provided with simple end supports over the rigid frame in the form of a hinge at one end and a roller at other end. There is a tire rod assembly to load the beam using tire- weights (Weight of this assembly is made equal to that of one tire weight). There is also a traveling pedestal to support the dial gauge for measuring deflections.

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Material Testing Lab Manual

PROCEDURE Place the beam correctly over the supports. Mount the dial gauge on the pedestal, place it under the beam exactly at mid- span and adjust it to read zero on the scale. Hung the tire rod assembles exactly at quarter-span and notes the dial gauge reading. Place the tire weights one by one, noting the dial gauge reading every time a weight is placed. Continue the observations while unloading the beam also. Repeat the process after interchanging the positions of the dial gauge and the tire rod assemble. OBSERVATIONS Record the observations in the tabular form. GRAPH Plot a graph with deflection on X- axis and load on Y- axis for both the case. CALCULATIONS The deflection at quarter point due to at the center is given by

Where 𝛿 is the deflection, W- the load, L- the span, I is the moment or inertia of the section the beam and E- the Young’s of the beam. Hence E can be found out. VERIFICATION 1. Compare the deflection under different loads in case (1) with those in case (2). They will be found to be the same, thus verifying the theorem.

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2. Superpose the plot of load Vs deflection or case (I) with that of case (2). They will coincide, thereby, verifying the theorem again. OBSERVATIONS SL NO:

LOAD (Kg)

LOAD AT MID SPAN & DEFLECTION AT LOADING

QUARTER SPAN UNLOADING DEFLECTION (mm)

LOAD AT QUARTER SPAN & DEFLECTION LOADING

AT MID SPAN UNLOADING DEFLECTION (mm)

0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

Length of beam L = Breadth

b=

Depth

d=

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Material Testing Lab Manual

GRAPH SHEET

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Material Testing Lab Manual

CALCULATIONS The deflection at quarter point due to at the center is given by

Moment

of Inertia

I=

bd3 12

RESULT 1. Verification of Clerk-Maxwell’s reciprocal theorem -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------2. Young’s Modulus of the material of the beam =…………………………… INFERENCE QUESTION – DO YOU KNOW? 1. The law of reciprocal Theorem. 2. What is the type of supports provided in the Clerk-Maxwell’s apparatus? 3. Why the depth of beam is less than the width in Maxwell’s reciprocal apparatus?

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Material Testing Lab Manual

EXPERIMENT NO: 4.

Marks............. DATE ………………….

BRINELL HARDNESS TEST AIM To determine the Brinell Hardness number HB of the given specimen. EQUIPMENT Brinell hardness tester RAB-250, Brinell microscope and indenters (2.5mm and 5mm ball) DESCRIPTION OF MACHINE The Brinell Hardness Tester consists of a loading system, a main screw and a dial gauge. The loading system consisting of weights, leavers and a hydraulic dashpot and a plunger arrangement is enclosed in the cast iron body of the machine. The main screw is also protected from extraneous elements by a rubber bellow. It carries the test table on its top to hold the specimen and is actuated by a hand at the base. The machine is provided with two ball indenters (of sizes 2.5mm&5mm) to transmit the test load on to the specimen. THEORY AND PRINCIPLE The test consists of forcing a steel ball of diameter D under a load P into the specimen for a known time and measuring the mean diameter‘d’ of the impression left on the surface after removal of the load. The Brinell Hardness Number (BHN) is then calculated as load (in kg-f) dived by surface area of indention (in mm2) Depth of indentation (h) is given by,

1 ℎ = (𝐷 − √(𝐷 − 𝑑) 2 Department of Civil Engineering

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Material Testing Lab Manual

And therefore,

Where, D = Diameter of wall in mm P = Applied load in kg-f, and d = Diameter of indentation in mm. The test load P, to be applied depends on the diameter D of the indenter and the material of the specimen. The table may be used for reference. The test surface should be machined smooth and even. Thickness of specimen shall not be less than eight times the depth of indentation. PROCEDURE Set the machine to the required stage of test load. Choose the intentor to be used and fasten it to the machine. Place the specimen on the test table and, apply a miner load of 10-kg-f on it by turning the hand wheel and brining both the pointers on the dial gauge to the ‘set’ positions. Apply the major load (remaining part of the test load) on the specimen by turning the loading lever backwards. Maintain the load on the Department of Civil Engineering

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Material Testing Lab Manual

specimen exactly for the specified dwell time (15 second) and then released it by turning the loading lever forwards. Take out the specimen and measure the diameter of the indentation formed on it by using the Brinell Microscope. OBSERVATION AND CALCULATION

Specimen

Diameter of Intender(D)

Steel Brass

2.5 mm 5.0 mm

𝒉=

𝟏 [𝑫 𝟐

Applied Force P(Kgf) 30 D2 = 10 D2 =

h(mm)

BHN

− √(𝑫𝟐 − 𝒅𝟐 ) ]

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BRINELLS HARNESS TESTING MACHINE

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Brinell Hardness Number

Specimen

BHN

Average

Steel

Brass

RESULT Brinell hardness of given steel specimen is H B / 2.5 / 187.5/ = ———Brinell hardness of given brass specimen is HB / 2.5 / 187.5/= ———— INFERENCE

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Brinell Hardness Testing Hardness is a characteristic of a material, not a fundamental physical property. It is defined as the resistance to indentation, and it is determined by measuring the permanent depth of the indentation. When using a fixed force (load) and a given indenter, the smaller the indentation, the harder the material. Indentation hardness value is obtained by measuring the depth or the area of the indentation. The Brinell hardness number, which normally ranges from HB 50 to HB 750 for metals, will increase as the...