CHAPTER 3: Force and stress
CHAPTER 4: Deformation and strain
CHAPTER 8: Stress
CHAPTER 15: Geometry of Homogeneous Strain
CHAPTER 1: Stress and strain
I Introduction
II Strain
II.1 Macroscopic aspect of deformationIII. Stress
Deformation vs strain
Discontinuous, continuous heterogeneous, continuous homogeneous
II.2 The finite strain ellipsoid
The strain shape and strain intensity
II.3 State of strain:The Flinn Diagram
II.4 Strain regime
Pure shear vs simple shear
II.5 Strain history
Flow lines and incremental strain ellipsoid
III.1 State of stress at a point: The Stress ellipsoid
III.2 State of stress on a plane: Normal stress and shear stress
III.3 The Mohr's circle
III.4 State of stress
IV. Strain and Stress relationship
IV. Pure shear strain regime
IV. Simple shear strain regime
References
Glossary
The part dealing with Strain is poorly written. You cannot pretend writing a report on a subject if you do not understand the basics. There is an obvious lack of readings and a general lack of understanding here.
There is clearly a great deal of effort put into the part dealing with Stress. There are a few error but overall it is a good effort.
It is too clear that you didn't work together but separately each of
you focussing on his/her own section. Not the best way.
Introduction
This is not an introduction. You are allowed to make mistake,
you are even encouraged to make mistakes since it is a very efficient way
to learn.
However making the same mistake twice proves that you didn't learned
from it. Again... an introduction must include two things:
First it must explain the significance of the topic; second it must present
the organization of the report. Unless you provide me with a better
introduction you will have to face loosing 20 marks on this poor introduction
alone. Tough but fair...
...varies defoematons...each small circle has been deformaed ...Any modern word processor has a 'check spelling' tool, use it.
The figures presented in this introduction in particular the one showing the deformation of three circle of different radius need to be explained. In particular the point should be made that, when a circle is transformed into an ellipse, its deformation can be easily characterized by measuring the orientation of the long axis of the ellipsoid, and measuring the axial ratio (ratio between the long and small axis of the ellipse).
The heading 2.0 Strain, is missing.
The heading 2.1 of the Table of Content is not the same than the heading
2.1 of the report.
2.1
As described above strain is a result of stress being applied to
a rock or material. Did you read you own introduction? you didn't
mention that '...strain is a result of stress...'
...the amount of deformation is the strain...No, strain is refers
to the change in the shape (the distorsion component of deformation).
...There are four types of deformation...No, deformation includes
four components.
Faults and fractures are discountinuites and when ...I suggest you put a new heading before this section for instance 2.2 Macroscopic aspect of deformation. In this section you explain the readers what homogeneous strain is, along with discontinuous deformation, and continuous heterogeneous deformation.
If lines were drawn on this object they will be able to match a point on the deformed object...Lines matching a point ????? I don't get it.
If all the lines are the parallel then the deformation is said to be homogeneous deformation, if the lines are different lengths and not parallel then the object is said to have deformed heterogeneously. …You may achieve heterogeneous deformation and still get parallel lines. There is simple criterion for homogenous deformation that is, lines drawn on a objet before deformation are transformed into straight lines after homogeneous deformation (=> no strain gradient). If the deformation is heterogeneous these lines become are curved.
...three non-parrell faces... there are far too many of this spelling mistake.
2.2
This section does not make sense clearly you didn't read and understood
enough the concept of the finite strain ellipsoid. The Finite Strain
Ellipsoid is not defined in this section, you didn't mention that this
ellipsoid result from the HOMOGENEOUS DEFORMATION of an imaginary sphere
representing the undeformed state of a body. No l1, l2, and l3 do not represent
the elongation of the principal axes of the finite strain ellipsoid.
...deformatiom ...exstension... comonly refferred...itermediate...deformemed...all these in six lines only! Enough of this, please provide me with an edited version of your text, or face another penalty of 15 marks.
2.3
The Flinn diagram describes two main types of strain ellipsoids,
cigar and pancake... No, it represents every type.
...The insert graph is the one most commonly used in field geology
to plot areas of folding... NO
...The L stands for vertical exstension, the S for horozontal exstension...NO
The diagram above is just Flinn's diagram but in three dimensions...NO
2.4
Pure shear is the deformation in the x axis resulting in no change
of area...NO
2.5.1
...either the six components of strain...This report is
not for structural geologists, it is for your classmates. None of
them will understand what the six components of strain are.
...a bracipod... what the hell is that?
2.5.2
Infinitesimal strain is ...The total difference between the initial
and final strain is the finite strain. NO
The infinitesimal strain is all the strains that the object has
gone through to get to the finite strain. NO
While finite strain is the end position all the positions used to
get to the final position is the infinitesimal strain.
NO
Finite strain
Rotational ? simple shear
Non-rotational ? pure shear
Infinitesimal strain
Coaxial ? progressive pure shea
Non-coaxial ? progressive simple shear What the
point of this?
You use figures in section 2.5.2 that you clearly do not understand.
2.5.3
If we take a square and place a number of coloured points on it. As we rotate the object through a number of incremental movements we join each of the point together. We produce a pathway which the object has moved through. These are called flow lines. I believe we have understood what flow lines are, but you have great difficulties writing a simple, clear, and concise explanation. This is a very serious problem, how can you think and share with other the product of your reflection if you cannot express your thinking into a coherent oral or written format. The solution for this problem is quite simple, read, read, read, and read. First, the object does not necessarily 'rotates', it deforms. Second, the object does not 'move through' a pathway, it follows a deformation path.
The rotated simple shear has straight lines...Traduction: Flow lines in simple shear strain regime remain parallel to the shear direction.
What is the purpose of the last figure in 2.5.3 ? There is no explanation in the text and no legend.
3.1
constituent particlaes,...???
Stress is a vector only is you consider the stress acting on a surface. The stress on a point is a tensor.
...stress is often required over a large volume... I don't understand this.
As such, stress is usually treated in a model of small scale, such as a plane, cube or ellipsoid. ?????
3.2
Stress on a plane is a vector usually decomposed into a normal and a
tangential component. The tangential component is contained in the
plane (1)
normal to the plane and (2) containing the total stress vector.
3.3
infintiely...
If you treat a point as an infintiely small cube, it is obvious that
a cube has six faces, or threepairs of planes as faces. True
even if you do not treat a
point as an infinitely small cube. In fact, big or small, a cube
has always six faces.
The cube can be orientated in such a way that the major stress acting
on it, is normal to one of the planes, and also that no shear stresses
are caused,
only normal stresses. ...Traduction: The cube can be orientated
in such a way that the total stress vectors acting on the faces of the
cube are perpendicular to each faces. In such orientation there is
no shear stresses acting on any of the faces, and the stress tensor reduces
to...
this tensor is ok, however in any other orientation I am afraid that
the general tensor has a different diagonal than s11, s22, s33.
this
tensor cannot be reduced to the tensor above unless the value of s11, s22,
s33 are changed.
Too finish with this s11, s22, s33 are the principal axes of the stress ellipsoid only if all the others component are zeros. Then they are referred to as s1, s2, s3.
3.4
As with the last example? the cube, the stress ellipsoid is
another, more acurate way to study the state of stress at a point.
NO it is the same (by the way, aCCurate).
3.5.1
...represents the hyrodstatic component...