It is tensile deformation process where alloys undergo plastic deformation without formation of neck and give rise to high percentage of elongation. It’s given by a constitutive equation. σ=Kε ̇m where σ is the true flow stress, k is a constant and ε ̇ is strain rate and m is the stain rate of sensitivity. Stain rate sensitivity should be greater than .33 for achieving superplastic deformation. But, for most of metals and alloys the m value is less than 0.2 that is this is why this behavior is not achieved easily for most of metals and alloys. The major area of superplastic behavior includes in metals, ceramics, intermetallic and composites. For making it cost effective and near net shape forming process for commercial applications, extensive …show more content…
At the deformation temperature the grains are highly unstable so grain growth is major problem and that can be solved by the presence of second phase. Shape, size and distribution of second phase play important role for controlling cavitation and growth during deformation [6]. Maehara has shown elongation of around 2000% at a stain rate of 2×10-3s-1 in the temperature range of 950-1000°C. He proposed different mechanism for in this type of case. The presence of hard particles can lead to recrystallization in soft matrix. The σ phase acts as heterogeneous nucleation sites for recrystallization. Soft particles in hard matrix are not beneficial but reverse of this can be advantageous for superplasticity provided optimum quantity of second phase is maintained for …show more content…
Grain boundary sliding is dominant mechanism in superplasticity, high angle grain boundary is preferred over lower angle grain boundary. Equiaxed grains show better superplasticity than that of elongated grain; the grains along the transverse direction is fine but has limited superplasticity when tested along the longitudinal direction. The direction perpendicular to longitudinal direction i.e. transverse direction has poor elongation due to problem of cavitation; strain accommodation is difficult in the case of textured grain [6]. We know that m= ln σ/lnε ̇. Dependency of the value of m on strain rate is such that the m and ε ̇ curve has a dome-like shape. The maximum value mmax corresponds to the optimum strain rate ε ̇ optimal for superplastic deformation for the given average grain size and temperature of deformation. The region II could be divided into region II (a) (left of the maximum) and II (b) (right of the maximum). This is because physical mechanisms operating in the two regions are different. Also, in region II (a), an increase in strain rate increases the m value, while in region II (b), a strain rate increase will decrease the m value. Evidently, the necking resistance in the two regions resulting from such strain rate changes would be different [6]. The value m depends upon a number of factors: strain, strain rate, structure
3D printing is primarily for rapid part prototyping and small-run production in a variety of industries. In the meantime, the term additive manufacturing has come to represent the use of 3D printing to create metallic components and final parts, differentiating from conventional subtractive manufacturing processes. 3D printing uses computer-generated designs to create build paths that reproduce a digital model through consolidation of materials with an energy source. The process typically uses a laser, a binder or an electron beam that solidifies material as it is directed along scanned over a pre-placed layer or the build path of material. This method has been used successfully with metals, polymers and ceramics. Metals are still in their infancy in terms of finished part production. Metallic parts produced with 3D printing frequently require additio...
We use metals to construct all kinds of structures, from bridges to skyscrapers to elevators. The strength as well as durability of materials that are crafted out of metal make the materials ideal not only for construction but also for many other applications.
Elastic strain region at small and big end of connecting rod is shown in figure no. 10. The maximum and minimum equivalent strain values are 0.00033975 and 2.1407e-10 respectively. Due to applied pressure there will be change in original dimensions of the connecting rod and hence strain developed can be
Higher content of ytrrium was found that distributed on the grain boundary. This result made the depletion of the grain interior (Winubst and Burggraaf, 1988). This appearance represent nonuniform distribution of stabilizer should have smaller grain size than critical grain size of uniform distribution of stabilizer in order to prevent the effect of the grain size inducing the degradation.
But the grain size ranges between 3 μm to 6 μm, 3 μm to 8 μm and 4 μm to 9 μm for 4 mm, 6 mm and 8 mm plates respectively. Higher polygon pin face edges approach circular pin, this vanishes the pulse formation in stirring. This leads to distorted grains due to decrease in dynamic area or lack of sweeping between tool and material. Whereas a low number of polygon pin face edges generates higher dynamic area. This shows the coarse grains relatively. The grain size ranges between 5 μm to 7 μm, 6 μm to 8 μm and 7 μm to 9 μm for 4 mm, 6 mm and 8 mm plates
This is another property which relates the fatigue to tensile property of any material. It can be defined as the ratio of the endurance limit (Se) to the ultimate strength (Su) of the material of any structure. The value of fatigue ratio ranges from 0.25 to 0.60. It’s value solely depends upon the type of the material.
Nitinol is a metal amalgam made up of nickel and titanium, these two components are available in equivalent nuclear rate. Nitinol amalgams show two firmly related and extraordinary properties: shape memory effect (SME) and superelasticity. Shape memory is the capacity of nitinol to experience misshapening at one temperature, then recuperate its unique, undeformed shape after warming over its "change temperature". Superelasticity happens at a restricted temperature extend simply over its change temperature; for this situation, no warming is important to bring about the undeformed shape to recuperate, and the material shows tremendous flexibility, some 10-30 times that of standard metal.
High compressive stresses and the development of high temperature close to the cutting edge causes plastic deformation of cutting edge
A group of polymer chains can be organised together in a fiber. How the polymer chains are put together is important, as it improves the properties of the material. The flexibility, strength and stiffness of Kevlar fiber, is dependent on the orientation of the polymer chains. Kevlar fiber is an arrangement of molecules, orientated parallel to each other. This orderly, untangled arrangement of molecules is described as a “Crystalline Structure”. A manufacturing process known as ‘Spinning’ is needed to achieve this Crystallinity structure. Spinning is a process that involves forcing the liquefied polymer solution through a ‘die’ (small holes).
(1) The development of carbon-embedded plastics, otherwise called “composits,” is an important new technology because (2) it holds the key for new aircraft and spacecraft designs. This is so because (3) these composits are not only stronger than steel but lighter than aluminum.
There are issues with the theories though that causes them to be slightly unreliable. Strains can be measured in numerous ways. Every study of general strain theory can look at completely different strains and measure them in different ways. Looking at different strains while implementing different measurement techniques makes determining the accuracy and validity of strain theory to become difficult. Theories need to be empirically tested and replicated to determine their value.
Mechanical Engineering 130.2 (2008): 6 - 7. Academic Search Complete. Web. The Web. The Web.
Some steel containers are made through deforming the steel by means of extruding, forging, spin forming, ...
This is the textbook for my materials science and engineering class. It contains information about the behaviors and properties of materials such as metals and polymers. This source will prove useful because in the field of tensegrity, the type of material used to make a structure is very important. In the field of engineering/tensegrity, this source is considered as a reference
In summary, the rate of cooling from the austenite phase is the main determinant of final structure and properties.