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Questions and Answers
What is stress represented by in the broad sense?
What is stress represented by in the broad sense?
A force, called traction, acting on a finite area occupying an arbitrary position within the medium.
What is the limiting value of the ratio of a force acting on an elementary area, as the area diminishes to zero?
What is the limiting value of the ratio of a force acting on an elementary area, as the area diminishes to zero?
The stress (T), defined as: T = lim (F/ΔA)
What are the components of stress (T) that can be resolved into, and what do they represent?
What are the components of stress (T) that can be resolved into, and what do they represent?
The normal component (Tz), and two tangential components (Tx and Ty), representing normal stress and shearing stresses, respectively.
What is the normal component of stress (T) also known as?
What is the normal component of stress (T) also known as?
How many stress components are needed to completely define the stress at a given point?
How many stress components are needed to completely define the stress at a given point?
What is the significance of the nine stress components in describing the stress system within a body?
What is the significance of the nine stress components in describing the stress system within a body?
What is the role of the elementary area (ΔA) in the definition of stress?
What is the role of the elementary area (ΔA) in the definition of stress?
What is the importance of resolving the stress (T) into its components?
What is the importance of resolving the stress (T) into its components?
What is the name of the strains that involve purely translational displacement?
What is the name of the strains that involve purely translational displacement?
What is the name of the strains that involve purely rotational deformation?
What is the name of the strains that involve purely rotational deformation?
What are the three types of strain components mentioned in the text?
What are the three types of strain components mentioned in the text?
What is the approximate seismic wavelength for a 30Hz frequency at a speed of 1830m/S?
What is the approximate seismic wavelength for a 30Hz frequency at a speed of 1830m/S?
What is an example of a no-strain change?
What is an example of a no-strain change?
What is the range of wavelengths for typical speech sound waves?
What is the range of wavelengths for typical speech sound waves?
What is the name of the types of strains that involve a decrease in volume?
What is the name of the types of strains that involve a decrease in volume?
What is the result of an external force on an elastic medium?
What is the result of an external force on an elastic medium?
What is the name of the types of strains that involve an increase in length?
What is the name of the types of strains that involve an increase in length?
What type of changes are created in an elastic medium due to an external force?
What type of changes are created in an elastic medium due to an external force?
What is the figure number that shows types of simple strains and no-strain changes?
What is the figure number that shows types of simple strains and no-strain changes?
Who is the author of the reference cited in the text?
Who is the author of the reference cited in the text?
What is the property of an elastic medium that allows it to return to its original condition after the removal of an external force?
What is the property of an elastic medium that allows it to return to its original condition after the removal of an external force?
What is the condition under which rock media in nature are considered perfectly elastic?
What is the condition under which rock media in nature are considered perfectly elastic?
What is the typical frequency of seismic waves in the context of applied geophysics?
What is the typical frequency of seismic waves in the context of applied geophysics?
What is the purpose of understanding seismic wavelengths in the context of applied geophysics?
What is the purpose of understanding seismic wavelengths in the context of applied geophysics?
What is the primary goal of a petroleum geoscientist specialist in fulfilling oil and gas industrial needs?
What is the primary goal of a petroleum geoscientist specialist in fulfilling oil and gas industrial needs?
What is the significance of CLO2 in the context of hydrocarbon resource exploration?
What is the significance of CLO2 in the context of hydrocarbon resource exploration?
What is the key capability required for PO2 in petroleum geoscience?
What is the key capability required for PO2 in petroleum geoscience?
What is the primary objective of PO3 in geology, geophysics, and reservoir?
What is the primary objective of PO3 in geology, geophysics, and reservoir?
What is the role of research evidence in petroleum geoscience according to PO5?
What is the role of research evidence in petroleum geoscience according to PO5?
What is the focus of PEO2 in terms of sustainability?
What is the focus of PEO2 in terms of sustainability?
What is the characteristic of a body that exhibits a proportional strain under stress?
What is the characteristic of a body that exhibits a proportional strain under stress?
What is the term used to describe the behavior of a body beyond the elastic limit, where deformation becomes irrecoverable?
What is the term used to describe the behavior of a body beyond the elastic limit, where deformation becomes irrecoverable?
What is the point at which a body can no longer sustain the applied stress and breaks up?
What is the point at which a body can no longer sustain the applied stress and breaks up?
What mathematical equation governs the linear stress-strain relationship in an isotropic and elastic body under small strain?
What mathematical equation governs the linear stress-strain relationship in an isotropic and elastic body under small strain?
What is the term used to describe the limit beyond which the material may still be elastic, but with no more linear relationship?
What is the term used to describe the limit beyond which the material may still be elastic, but with no more linear relationship?
What type of body exhibits linear stress-strain behavior up to a certain stress limit?
What type of body exhibits linear stress-strain behavior up to a certain stress limit?
What is the characteristic of a body under increasing stress, where the deformation becomes large with decreasing stress?
What is the characteristic of a body under increasing stress, where the deformation becomes large with decreasing stress?
What is the type of body that exhibits a linear stress-strain relationship under increasing stress up to a certain point?
What is the type of body that exhibits a linear stress-strain relationship under increasing stress up to a certain point?
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Study Notes
Course Overview
- The course aims to equip students with knowledge and skills in applied geophysics, specifically in hydrocarbon resource exploration.
- Course learning outcomes (CLOs) include evaluating the suitability of geophysical techniques, assessing their advantages and limitations, and appraising the sustainability of emerging techniques.
Seismic Waves
- Seismic waves have wavelengths, e.g., 30Hz @ 1830m/S, or 60Hz @ 3660m/S, which are significantly longer than typical speech sound waves (25mm to 17m).
- Seismic waves are created by applying an external force to an elastic medium, causing internal opposing forces that resist deformations and return to their original condition after the force is removed.
- Rocks in nature are considered perfectly elastic, meaning they resist changes in volume and shape and return to their original condition after removal of the external force.
Theory of Elasticity
- Elasticity is the property of resisting changes in volume and shape and returning to original conditions after removal of the external force.
- Stress is a force acting on a finite area within a medium, defined as the limiting value of the ratio of a force (F) acting on an elementary area (ΔA) that is diminishing to zero.
- Stress can be resolved into components parallel and perpendicular to the area, including normal stress (Tz) and tangential or shearing stresses (Tx and Ty).
Stress and Strain
- The stress system within a body is completely defined by nine stress components, which constitute the stress tensor at a given point.
- Strain components (eab) can be written down as follows: Group 1 (exx, eyy, ezz) involves purely translational displacement resulting in compressional or dilatational strain, and Group 2 (exy, exz, eyz) involves purely rotational deformation resulting in shear strain.
- Common types of strains include compression, bulk contraction, tension, and shear strains.
Types of Strain
- Fig. 5 shows simple types of elastic deformation (strain) and no-strain changes, such as rigid body translation and rotation.
- The linear stress-strain relationship is governed by Hooke's law, which describes the behavior of perfectly elastic bodies under small strain.
Elastic and Plastic Behavior
- Bodies under stress exhibit deformation depending on the applied load and physical properties.
- Elastic bodies exhibit a proportional strain, and perfectly elastic bodies exhibit a linear relationship.
- Beyond the elastic limit, the deformation becomes irrecoverable, and the body behavior is described as plastic.
- The behavior of a ductile solid-body under an increasing extensional stress is shown in Fig. 9.
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