If the load is removed at this point the metal will not spring back to its original length and it is said to have taken a permanent set. The yield stress is the stress at the yield point; that is, the load at B divided by the original cross-section area of the specimen. From C to D extension is no longer proportional to the load, and if the load is removed little or no spring back will occur.
Due to this relatively greater loads the material is showing plastic properties. The ultimate tensile stress is calculated by dividing the load at D by the original cross-sectional area of the specimen.
Although a useful figure for comparing the relative strengths of materials, it has little practical value since engineering equipment is not usually operated so near to the breaking point.
From D to E the specimen appears to be stretching under reduced load conditions. The specimen finally work hardens to such an extent that it breaks at E. In general, values of load and extension are of limited use since they apply to one particular size of specimen and it is more usual to plot the stress-stain curve.
Therefore ductility is usually expressed, for practical purposes, as the percentage; Elongation in gauge length of a standard test piece at the point of fracture when subjected to a tensile test to destruction. The increase in length is determined by fitting the pieces of the fractured specimen together carefully and measuring the length at failure. Currently, he is working in the sheet metal industry as a designer.
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This site uses Akismet to reduce spam. Learn how your comment data is processed. Introduction to Pressure Vessels Vessels, tanks, and pipelines that carry, store, or receive fluids are called pressure vessels.
A pressure vessel is defined as a container with a pressure Knuckle Joint A knuckle joint is used to connect two rods which are under the action of tensile loads.
Discuss the mechanical properties obtained from the tensile test for each sample. ABS is an amorphous blend consisting of three monomers which are acrylonitrile, butadiene and styrene.
The addition of acrylonitrile helps in the increasing of the chemical and thermal enhancement. Butadiene contributes in the increasing of toughness and strength to the plastic. Lastly, the styrene will add the sleek and glossy to the plastic. In other words, ABS has good rigidity, toughness, low creep, low weight, good dimensional stability and good resistance to acid and alkali.
Finally, ABS also has a high abrasion resistance as its mechanical properties. The difference in strength exceeds the difference in density, giving HDPE a higher specific strength. It is also harder and more opaque and can withstand higher temperatures. LDPE has mechanical properties such as that it can be elongated very long before it fractured.
LDPE is made in translucent or opaque variations, it is quite flexible and tough but it is easily breakable. In addition, LDPE also has high impact strength at low temperatures. Which stress-strain curve shows brittle property and which curve shows the ductile property? The stress-strain curve that shows the material with the most brittle properties is the ABS stress-strain curve refer to attachments.
This is because the stress-strain curve shows that it takes only 5mm of the tensile extension before the sample completely fractures. In addition, its maximum load is less than N. It proves that the ABS sample to have the most brittle property compares to the other samples.
The stress-strain curve that shows the material with the most ductile properties is the LDPE stress-strain curve refer to attachment. As illustrated on the graph, it shows that the tensile extension is stretched to its maximum although the load is less than N.
However, the sample did not fracture even when it was stretched to the maximum. Discuss any possible error occurred during experiment. Error which may be occurred during this experiment includes parallax error during reading of measurement. We are advice to measure the test specimen parameters more than twice using vernier caliper to ascertain the reading. Besides, zero error may also occur due to the lack of vernier caliper calibration. In order to avoid this to happens, we are advice to check the vernier caliper before measuring.
If the vernier caliper is not showing absolute zero reading when it is totally closed, we have to minus or add the particular value in each of the measurements. Moreover, the consideration of putting the test specimen on the universal testing machine —Instron Series is also important.
We have to make sure the test specimen is tied orderly at grips for holding test specimen firmly at fixed head in order to avoid the specimen became loosen from that machine during the experiment. Tensile testing is one of the simplest and most widely used mechanical tests.
By measuring the force required to elongate a specimen to breaking point, material properties can be determined that will allow designers and quality managers to predict how materials and products will behave in their intended applications.
This is due to the chemical stress cracking which is a typical example of brittle fracture. In such a case, there are no undulations on the fracture surface and it takes on a smooth appearance.
Brittle fracture is caused by a combination of a force or stress which is less than the material strength and some other factor i. This has less hardness, stiffness and strength compared to HDPE, but better ductility. ABS is a light weight material and has the ability to be an injection molded and extruded which makes it useful in manufacturing products such as drain- waste-vent piping systems, musical instruments such as recorders, plastic clarinets, and piano movements.
Other than that, it is used to make golf club heads due to its good shock absorbance, automotive trim components, automotive bumper bars, medical devices for blood access, enclosures for electrical and electronic assemblies, protective headgear, whitewater canoes, buffer edging for furniture and joinery panels, luggage and protective carrying cases, small kitchen appliances, and toys, including Lego bricks. The limitations of ABS are such that ABS will crack and craze when subjected to petroleum-based cutting and tapping oils, it is flammable and under UV exposure, it will eventually cause the parts to become very brittle.
However, this cannot be avoided by coating or painting on the ABS. HDPE is commonly used to make toys, utensils, film, pipe and processing equipment. It is also used to make wire and cable insulations. However, its limitations are such as a high thermal expansion. It also has poor weathering resistance and subject to poor cracking.
Subsequently, it is very difficult to bond with, flammable as well as poor temperature capability. LDPE can be used to make variety of type of applications. It can be used to make packaging, transportations and protection such as shrink film for books, bundling and pallets, overwrap film for towels, tissues, and film for bakery goods, meat, coffee, frozen foods, liquid packaging, liners, bags and shoppers.
Next, it can also be used to make agricultural applications such as greenhouse and tunnel as well as the silage. Finally, it is used to make electrical cables which are the insulators, semiconductor layers, coax and HFFR cables.