Engineering materials have to be tested for creep before they are used for any project. The low temperature creep apparatus fabricated for this project uses a simple levels to transmit a tensile stress to a specimen.The elongation of the specimen due to the tensile stress is measured using a dial gauge. A weight hanger and a stirrup are provided for the weights which are used to produce this tensile stress. To hold the specimen in place, loading pins are loading stirrups a re provided and a rest pin beeps the apparatus steady when not in for the setting up of the whole apparatus. Results of experiments carried out with the apparatus are provided and the general friends agree with those in the literature.
TABLE OF CONTENTS
CHAPTER ONE
Introduction 1
1.2 The purpose of the project 6
1.3 Demand for the equipment 6
1.4 Literature review 7
1.5 Kinds of phenomena 8
1.6 Examples 10
1.7 Mechanism 11
CHAPTER TWO
Description of apparatus and design theory 13
2.1 static equilibrium conditions 17
CHAPTER THREE
Calculation 21
3.1 Calculation the maximum load 24
CHAPTER FOUR
4.1 Experimental procedure and result 34
4.2 Method of assembly 36
CHAPTER FIVE
Costing 37
5.1 Direct Material Cost 37
5.2 Direct Labour Cost 38
5.3 Over – Head Cost 39
5.4 Total Cost of Apparatus 40
5.5 Possible Problems of Creep Testing
Machine and Recommendation 40
5.6 Recommendation 41
5.7 Conclusion 41
Reference 43
CHAPTER ONE
At constant stress, materials continue to deform for an indefinite period of time. This time, dependent deformation is termed creep. At temperature less than 40 percent of the absolute melting point, the extent of the creep may be negligible, but at temperature higher than this, it becomes increasingly necessary. It is for this reason that the creep test is commonly thought of as a high temperature test. A creep curve is a plot of the elongation of tensile specimen versus time, at a given temperature, under either a constant load or constant true stress.
A failure may also be due to a phenomenon called creep, which is the plastic flow of a material under load at elevated temperatures in addition, the actual shape of a part may be responsible for failure for example stress concentrations due to sudden charges in contour must be taken into account. The sive-angle specimen creep measuring apparatus or machine is a table tip apparatus measuring dimensionally 610 x 310 x 170mm and approximated weight of. This simple machine uses specimens of plastics. The design is based on a simple lever principle having a mechanical advantage of 80:1 which provides a steady and uniform tensile load. The extension of specimen under load is measured by a dial gauge. It is made up of a vertical column which is the main supporting frame, a level beam, a stop watch, an extensometers (or dial gauge) and a weight hanger.
To ensure correct loading of the specimen, the load beam is fitted with hardened steel knife edges load is applied by means of a set of weights which are added to the weight hanger as required. This apparatus is specially designed for teaching. Generally for satisfactory use of this equipment, a bench area of approximately 1 x 0.6m is recommended. It is compact and easily stored and ideal for classroom demonstrations.
This creep material measuring apparatus is in simple unit designed for demonstrating and investigating the creep characteristics of plastic specimen at room temperature.
Materials when subjected to stress deform with time. Under low temperatures, creep become negligible at stress below the yield strength and may require many life time to be detectable. Creep can take place and lead to fracture at static stresses much smaller than those which will break the specimen when loading quickly in the temperature range 0.5 – 0.7 of the melting point (1mk), the variation with time of extensions of a metal under different stresses is shown below.
Now three conditions are observed:
(a) &n
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