What is the ultimate strength and how can it be determined?
www.nde-ed.org/EducationResources/CommunityCollege/Materials/Mechanical/Tensile.htm
At what point does permanent deformation occur? What materials are most resistant to permanent deformation?
Plastic behavior: This permanent deformation behavior occurs when the tensile (or compressive) uniaxial stress reaches sy.
Hard materials like diamond, nitrided steel and even most plastic are resistant to permanent deformation.
Thank you sir!
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The ultimate strength refers to the maximum stress a material or structure can withstand before it breaks or fails. It is an important property when designing and evaluating the structural integrity of various components in engineering.
To determine the ultimate strength of a material, several methods can be used:
1. Tensile Testing: This is the most common method to determine the ultimate strength of a material. A sample of the material is subjected to a controlled tensile force until it fractures. During the test, the applied force and resulting deformation are measured. From these measurements, stress-strain curves can be plotted, and the ultimate strength can be identified as the maximum stress achieved before fracture.
2. Compression Testing: For materials that fail under compression rather than tension, such as concrete or ceramics, compression testing is performed. Similar to tensile testing, the sample is subjected to a controlled compressive force until it breaks. The maximum compressive stress exhibited before failure is considered the ultimate strength.
3. Impact Testing: Some materials may fail under sudden impact or shock loads rather than gradual deformation. Impact testing involves striking a sample with a controlled amount of energy and measuring the resulting deformation or fracture. The maximum force or energy absorbed before failure indicates the ultimate strength in impact loading conditions.
4. Shear Testing: For materials or structures where shearing forces are critical, such as in bolts or welds, shear testing is used. The sample is subjected to a shear force until it breaks or undergoes significant deformation. The maximum shear stress before failure is considered the ultimate shear strength.
It's important to note that the ultimate strength of a material can vary depending on factors like temperature, rate of loading, and material defects. Therefore, conducting tests under relevant conditions is crucial to obtain accurate results.