What is rigidity?
Stiffness refers to the ability of a material, component or structure to resist deformation under external forces.
The stiffness of a material is measured by the amount of external force required to produce a unit deformation.
The stiffness of isotropic materials depends on their elastic modulus E and shear modulus G (see Hooke's Law).
The stiffness of a structure depends not only on the modulus of elasticity of the constituent materials, but also on factors such as its geometric shape, boundary conditions and the form of external forces.
Analyzing the stiffness of materials and structures is an important task in engineering projects. Stiffness analysis is necessary for structures that require rigid deformation limits, such as aircraft wings and precision components.
Many structures, such as buildings and machines, also need to control their rigidity to avoid vibrations, chatter or instability.
Furthermore, for devices such as spring scales and ring force meters, it is necessary to control their stiffness to a certain reasonable value to ensure their specific functions. In displacement-based structural analysis, the stiffness of each part of the structure must be analyzed to determine its deformation and stress.
Stiffness refers to the ability of a part to resist elastic deformation under load. The stiffness (or rigidity) of a part is generally expressed as the force or torque required to produce a unit deformation, and its magnitude depends on the geometric shape of the part and the material properties (i.e. modulus of elasticity).
Stiffness requirements are particularly important for machine parts that can affect the quality of their operation when elastic deformation exceeds a certain limit, such as machine tool spindles, guides, and lead screws.
What is strength?
The ability of metallic materials to resist permanent deformation and fracture under external forces is called strength.
Depending on the nature of external forces, there are mainly yield strength, tensile strength, compressive strength, flexural strength, etc.
Commonly used strength indicators in engineering are yield strength and tensile strength, which can be measured by a tensile test.
Strength refers to the ability of a part to resist fracture or excessive residual deformation after being subjected to a load. In other words, strength is an important indicator of a component's load-carrying capacity (i.e., resistance to failure).
Resistance is the fundamental requirement that mechanical components must meet. The strength of mechanical parts can generally be divided into static strength, fatigue strength (bending fatigue, contact fatigue, etc.), fracture strength, impact strength, high and low temperature strength, strength under corrosive conditions, and creep , bond strength, and other items.
Experimental resistance research is a comprehensive study, mainly studying the stress state of components and predicting the conditions and timing of failures and damage.
Strength refers to the ability of a material to resist external forces without being destroyed (irreversible deformation is also considered destruction).
According to the type of force, it can be divided into the following categories:
(1) Compressive strength – the ability of materials to withstand pressure.
(2) Tensile strength – the ability of materials to resist tensile force.
(3) Flexural strength – the ability of materials to withstand external bending forces.
(4) Shear strength – the ability of materials to withstand shear forces.
Conclusion
In conclusion, strength and stiffness are two important properties of materials that are often confused with each other. While strength refers to the ability of a material to resist deformation or failure under an applied load, stiffness is the ability of a material to resist deformation and maintain its shape under an applied load. The difference between these two properties is crucial when designing structures or selecting materials for specific applications.
Understanding the relationship between strength and stiffness can help engineers and designers make informed decisions about which materials to use in different applications. For example, a material that is very strong but not very rigid may be appropriate for a load-bearing application, while a material that is very rigid but not very strong may be more suitable for a high-precision application where dimensional stability is criticism.
In summary, both strength and stiffness are important properties of materials, but they are not the same thing. By understanding the differences between these properties, engineers and designers can select the best materials for their specific applications and ensure the success of their projects.
