Contents What is Pattern in Casting What is Pattern A pattern in casting is a replica of the object to be cast. It is used to create a mold, which is filled with molten metal to produce the final cast product. The pattern is typically designed to be easily removable from the mold after casting. pattern in casting Type of pattern Wood: This is the most common type of pattern material and is relatively inexpensive and easy to work with. However, it is not as durable as other materials and can warp or rot over time. Metal: Metal patterns are more durable and long-lasting than wood patterns, but they are also more expensive and difficult to work with. Plastic: Plastic patterns are lightweight, easy to work with, and have a good level of dimensional accuracy. They can be used for low to medium volume casting. Resin: Resin patterns are similar to plastic patterns, but they are more durable and heat-resistant. They are also more expensive than plastic patterns. Machined patterns: Thes...
What is Tensile Strength Test
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| tensile test |
Tensile Strength Test
A tensile strength test, also known as a tension test, is a method used to determine the mechanical properties of materials, particularly their ability to withstand tension or pulling forces.
The test is performed by applying a controlled tensile load to a specimen of the material being tested, typically a cylindrical or rectangular shaped sample, until the specimen fails or breaks.
The maximum load or force that the specimen can withstand before breaking is known as the ultimate tensile strength (UTS) of the material.
The test can also provide information on the material's elongation and ductility properties.
The test is widely used in engineering and manufacturing to evaluate the performance of materials such as metals, plastics, and composites in various applications.
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| tensile testing |
Stress
In a tensile strength test, stress is the force applied to a material per unit area of the cross-sectional area of the specimen being tested. Stress is typically measured in units of pounds per square inch (psi) or newtons per square meter (N/m^2). The load or force applied to the specimen during the test causes the specimen to stretch or deform, and the stress is directly proportional to the amount of deformation.
The material's ability to withstand the applied stress without breaking is known as its tensile strength. When the stress exceeds the tensile strength of the material, the specimen will eventually break or fail. The point at which the material breaks is known as the ultimate tensile strength (UTS) of the material, which is the highest stress that the material can withstand before breaking. The UTS is an important mechanical property of the material, and it is often used to compare the strength of different materials or to evaluate the quality of a particular batch of materials.
The definition of elongation and its relation
Elongation is a measure of how much a material stretches or deforms when a tensile load is applied to it. It is typically expressed as a percentage of the original length of the specimen before the test. Elongation is related to the concept of strain, which is a dimensionless measure of deformation. Strain is the ratio of the change in length of the specimen to its original length.
During a tensile strength test, as the load is applied to the specimen, the specimen will begin to stretch and elongate. As the load continues to increase, the specimen will continue to elongate until it reaches its breaking point. The maximum elongation at the point of failure is known as the ultimate elongation.
Elongation is an important mechanical property of a material as it is related to the ductility of the material, ductility is the ability of a material to deform significantly without breaking. Materials that have a high elongation at the point of failure are considered to be more ductile than materials with low elongation.
In summary, elongation is a measure of how much a material stretches under a tensile load, it is related to the strain, which is the change in length of the specimen divided by its original length, and it is an important property that reflects the ductility of a material.
Relationship between tensile strain and cross-sectional area
In a tensile strength test, the relationship between tensile strain and cross-sectional area is an important factor to consider. The tensile strain is the ratio of change in length of the specimen to its original length, it is dimensionless.
As the load is applied to the specimen during the test, it will begin to stretch and elongate. The amount of deformation or strain that occurs is directly proportional to the cross-sectional area of the specimen. In other words, the larger the cross-sectional area of the specimen, the less strain will be required to produce a given amount of elongation.
This relationship is described by the equation of engineering stress, which is the load applied to the specimen divided by the cross-sectional area of the specimen. The stress is directly proportional to the load and inversely proportional to the cross-sectional area.
It is important to note that the cross-sectional area of the specimen needs to be carefully selected and standardized in order to obtain accurate and comparable results from tensile strength tests.
load deformation curve
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| load deformation curve |
A load-deformation curve, also known as a stress-strain curve, is a graph that shows the relationship between the load applied to a specimen during a tensile strength test and the corresponding deformation or strain of the specimen. The curve is typically plotted with the load or stress on the y-axis and the deformation or strain on the x-axis.
The curve typically has several distinct regions:
The initial linear elastic region, where the material is behaving elastically and the relationship between stress and strain is linear. The slope of this region is known as the Young's modulus of the material.
The yield point, where the material begins to deform plastically and the curve becomes non-linear. At this point, the material is said to have yielded.
The strain-hardening region, where the material continues to deform plastically and the stress increases with increasing strain.
The ultimate tensile strength (UTS), where the material reaches its maximum stress and begins to fail.
The necking region, where the cross-sectional area of the specimen begins to reduce as the specimen continues to stretch and elongate.
The fracture region, where the specimen breaks.
The load-deformation curve provides a wealth of information about the mechanical properties of the material, such as its elastic modulus, yield strength, ultimate tensile strength, ductility, and toughness. It's a powerful tool to evaluate the performance of a material under tension and to compare the strength of different materials or to evaluate the quality of a particular batch of materials.
nominal and true stress strain curve
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| true stress strain curve |
In a tensile strength test, the load-deformation curve can be plotted in two ways: as a nominal stress-strain curve or as a true stress-strain curve.
The nominal stress-strain curve is plotted using the original cross-sectional area of the specimen as the denominator in the stress equation (Stress = Load/Original Area). This means that the stress is calculated based on the original area of the specimen, regardless of any changes in the area that may occur during the test. The resulting curve is a representation of the load applied to the specimen as a function of the deformation of the specimen, as the cross-sectional area is constant.
On the other hand, the true stress-strain curve is plotted using the instantaneous cross-sectional area of the specimen as the denominator in the stress equation (Stress = Load/Instantaneous Area). This means that the stress is calculated based on the current area of the specimen, taking into account any changes in the area that may occur during the test. This curve represents the actual behavior of the material and it is a function of the load and the current cross-sectional area.
The nominal stress-strain curve is useful for materials that do not exhibit significant changes in cross-sectional area during the test, such as metals. However, for materials that exhibit significant changes in cross-sectional area, such as polymers, the true stress-strain curve is more informative and accurate.
In summary, the nominal stress-strain curve is a representation of the load applied to a specimen as a function of the deformation of the specimen, assuming that the cross-sectional area is constant. The true stress-strain curve is a representation of the actual behavior of the material, taking into account any changes in cross-sectional area that may occur during the test.
Drawing method and application range of true stress strain curve
The true stress-strain curve is a graph that shows the relationship between the true stress and the true strain of a material during a tensile strength test. The true stress is calculated using the instantaneous cross-sectional area of the specimen as the denominator in the stress equation (Stress = Load/Instantaneous Area) instead of the original cross-sectional area. The true strain is calculated as the natural logarithm of the ratio of the final length to the initial length of the specimen.
To draw the true stress-strain curve, the specimen is first stretched to a certain elongation. Then, the load and the cross-sectional area are measured. The true stress is calculated as the load divided by the current cross-sectional area, and the true strain is calculated as the natural logarithm of the ratio of the current length to the initial length. This process is repeated for various loads and elongations. The data points are then plotted on a graph with true stress on the y-axis and true strain on the x-axis.
The true stress-strain curve is useful for materials that exhibit significant changes in cross-sectional area during a tensile strength test, such as polymers, elastomers, and biological materials. These materials often exhibit nonlinear behavior, and the true stress-strain curve can provide a more accurate representation of their mechanical properties, such as the modulus of elasticity, yield strength, and ultimate tensile strength.
In summary, the true stress-strain curve is a graph that shows the relationship between the true stress and the true strain of a material during a tensile strength test, it is calculated using the instantaneous cross-sectional area of the specimen and it's useful for materials that exhibit significant changes in cross-sectional area during a tensile strength test, such as polymers, elastomers and biological materials.
tensile test test equipment
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| Tensile testing machine |
- Tensile testing machine: This is the primary piece of equipment used to apply the load to the specimen and measure the deformation. There are different types of tensile testing machines available, including mechanical, hydraulic, and electronic machines. They usually consist of a frame, a load cell, and a means of gripping and holding the specimen.
- Specimen: The test requires a sample of the material to be tested, which is typically in the form of a cylindrical or rectangular shaped sample.
- Grips or fixtures: These are used to hold the specimen in place during the test. The grips or fixtures can be either mechanical or pneumatic.
- Extensometer: This device is used to measure the deformation of the specimen during the test. It can be either mechanical or optical, and it is attached to the specimen to measure the elongation.
- Data acquisition system: This equipment is used to collect and store the data generated during the test, such as the load and deformation data. It can be a computer-based system or a standalone data logger.
- Software: A software that allows the operator to control the test, collect the data, and analyze the results.
- Calibration equipment: To ensure accurate results, the testing machine and other equipment must be calibrated regularly. This can include weights and gauges for calibrating the load cell, and measurement equipment for calibrating the extensometer.
Tensile test sequence
Preparation: This includes selecting the appropriate specimen, preparing the specimen by cleaning and conditioning it, and preparing the testing equipment.
Sample alignment: The sample is aligned and mounted in the grips or fixtures of the testing machine in such a way that it will be tested in the direction of the applied load.
Zeroing and calibration: The testing machine and other equipment are zeroed and calibrated to ensure accurate results. This includes zeroing the load cell and the extensometer.
Test setup: The test is set up by adjusting the machine's parameters and selecting the appropriate test speed and load range. The extensometer is attached to the specimen to measure the deformation.
Test initiation: The test is initiated by applying a load to the specimen. The load and deformation are continuously measured and recorded.
Test termination: The test is terminated when the specimen reaches its breaking point or when the maximum load is reached.
Data analysis: The data collected during the test is analyzed to determine the mechanical properties of the material, such as the ultimate tensile strength, the yield strength, and the modulus of elasticity.
Report: The results of the test are reported and documented. The report usually includes the test conditions, the mechanical properties of the material, and a load-deformation curve.
Tensile test result calculation method
The results of a tensile strength test are typically calculated using the following methods:
Ultimate Tensile Strength (UTS): The maximum load or force that the specimen can withstand before breaking is known as the ultimate tensile strength (UTS) of the material. It is calculated by dividing the maximum load measured during the test by the original cross-sectional area of the specimen.
Yield Strength: The yield strength of a material is the stress at which the material begins to deform plastically. It is calculated by finding the point on the load-deformation curve where the material begins to deviate from linear behavior.
Modulus of Elasticity: The modulus of elasticity is a measure of a material's ability to resist deformation under load. It is calculated by finding the slope of the linear elastic portion of the load-deformation curve (i.e., the initial straight-line portion of the curve before the material begins to yield).
Elongation: The elongation of a material is a measure of how much it stretches or deforms when a tensile load is applied to it. It is usually expressed as a percentage of the original length of the specimen before the test. It is calculated by dividing the increase in the length of the specimen by the original length of the specimen, and multiplying by 100.
Reductions in area: Reduction in area is the percentage of area that is reduced after the specimen is stretched until it breaks. It is a measure of ductility of a material. It is calculated by dividing the minimum cross-sectional area of the specimen after the test by the original cross-sectional area of the specimen and multiplying by 100.
These are the most common calculations performed on tensile test, depending on the test requirements other calculations may be performed.
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