Manfred Kahmann
SAIBT 2014 Tutorial Assignment 1
Engineering Materials
- Main classes of materials
Metals and Alloys
Inorganic materials made out of one or more metallic components. They generally have a crystalline structure and are great warm and electrical conduits. Numerous metals have high quality and high versatile module. They uphold their great quality at high and low temperatures. They likewise have a sufficient elasticity, which is critical for some building provisions. They could be fortified by alloying and a high temperature medication. They are minimum impervious to erosion.
Pottery and Glasses
Inorganic materials comprising of both metallic and non-metallic components fortified together artificially. They could be crystalline, non-crystalline or mixture of both. Largely they have high dissolving focuses and high substance secure qualities. They have high hardness, high moduli and high temperature quality. Anyway, since they are extremely fragile, they cannot be utilized on a par with metals. Ceramics are normally poor in electricity conduction. Ceramics have a high quality on packing.
Polymers
Organic materials, which comprise of long atomic chains or systems holding carbon. Most polymers are non-crystalline, yet some comprise of mixtures of both crystalline and non-crystalline locales. They for the most part have low densities and low inflexibility. Their mechanical properties may differ significantly. Most polymers are poor electrical conduits because of the way of the nuclear holding. The majority of them are erosion safe, however, cannot be utilized at high temperatures. They have a great quality to weight proportion for the most part.
Composites
Materials where two or a greater amount of the above materials are united on plainly visible level. They comprise of a grid and fortification. They are intended to consolidate the best properties of each of its parts (Jackson 1988).
- Yield strength
Yield strength is the stress required to prepare a little specified measure of plastic twisting. The yield quality acquired by a counterbalancing strategy is ordinarily utilized for designing purposes because it dodges the viable troubles of measuring as far as possible or corresponding breaking point.
Elasticity is characterized as an anxiety, which is measured as energy for every unit range. For some non-homogeneous materials, it could be accounted for as energy or as a power for every unit width. It is a serious property; consequently, its esteem does not rely on upon the extent of the test example. Nonetheless, it is reliant on different variables, for example, the planning of the example, the vicinity or overall of surface imperfections, and the temperature of the test environment and material. Resistances are infrequently utilized as a part of the outline of bendable parts; however, they are essential in weak parts (Ashby 2005).
- Carbon and low-alloy steel: chemical composition
Carbon steel will be steel in which the fundamental interstitial alloying constituent is carbon in the reach of 0.12–2.0%. The American Iron and Steel Institute (AISI) characterizes carbon steel as the accompanying: “Steel is recognized to be carbon steel when no base substance is specified or needed for cobalt,chromium, nickel,molybdenum, titanium, niobium, tungsten, zirconium, or vanadium or any potential component to be added to get a craved alloying impact; when the specified least for copper does not surpass 0.40 percent; or when the most extreme substance specified for any of the accompanying components does not surpass the rates noted: 1.65, 0.60, and 0.60 of manganese, silicon, and copper respectively. Low-composite steels are normally used to accomplish better hardenability, which thus enhances its other mechanical properties like the Young's modulus.
- Hardness Testing vs. Tensile Testing
The reason hardness testing is regularly performed in inclination to tensile testing is that it is much faster and less costly and sensibly precise. The relationship is not so much straight for all materials. Restorative gadget producers face exceptional tests in this respect. The ordinarily little size of their parts example forces specific test limits.
In addition, hardness test is not as destructive as tensile test. In this regard, it is possible to reuse the material, which has undergone the tensile test other than the one, which has undergone tensile testing. In tensile test, a test piece is broken into two parts whereas in hardness test and indentation is impressed on material without much damage on it.
Fracture toughness is an attribute of material relating to the ability of material to resist propagation of a crack. This attribute is measured through loading a test piece and intentionally introducing manageable crack of a known length. A tensile force is then exerted and its extension measured for the calculation of Kc. It is determined through loading a test piece containing a deliberately introduced contained crack of length or a surface crack of length. On the other hand, Charpy test measures the impact resistance of a material when it is suddenly loaded through a pendulum force. The advantages of fracture toughness over Charpy test are as outlined below;
- A Charpy test result has a single result output per test because the fracture resistance is measured through a one-off test, which may lead to damage of test piece. This implies that if more data is required, subsequent tests must be carried out on as much number of test pieces as number of results required. On the other hand, fracture toughness can collect multiple data in a single test.
- Fracture toughness test can examine the uniformity of material composition because the test is continuous over a length of the test piece, unlike Charpy test where the source of information is localized at where the fracture occurs.
Notwithstanding the nature of example utilized, the broadly useful of the different sorts of indent sturdiness tests is to model the conduct of real structures so that the research centre test effects might be utilized to foresee administration execution. A normal characteristic of these strength tests is to prepare crack in steels under precisely controlled research centre conditions. The effects of the tests might be nearly related with administration execution to create levels of material property acknowledgement. The advancement of direct versatile crack mechanics makes it conceivable to portray the break conduct in structural parameters that might be utilized specifically by the specialist, in particular, stretch and blemish size. In addition, crack mechanics could be utilized to dissect the development of little, breaks to discriminating the size.
Theoretically, the specialist can then quantitatively secure suitable anxiety levels and assessment necessities so that cracks cannot happen. Moreover, break mechanics can produce into record the results of temperature and stacking rate on anxiety structures, which hold imperfections. Consequently, break mechanics has a few exceptionally unmistakable favourable circumstances contrasted and conventional score durability test.
- Force - Extension Curve
Cross-Section area=π×7×7mm2=153.93mm2
Yield Strength=100kN153.93mm2=0.6496kN/mm2
Tensile Strength=100kN153.93mm2=0.6496kN/mm2
Elastic Modulus=StressStrain=0.6496kN/mm20.0232.48kN/mm2
% Elongation=51-5050×100=2%
References
Ashby, MF 2005, Engineering materials 1 an introduction to properties, applications and
design. Oxford, Elsevier Butterworth-Heinemann.
Jackson, N 1988, Civil engineering materials. Basingstoke, Macmillan Education.
