COMPRESSIVE BEHAVIOR OF SOFT MUSCLE TISSUES

GROUP ME7SHUBHAM SHRIVASTAVA 2011225VIVEK KUMAR 2011237RAVI MEENA 2011213

INTRODUCTION

Muscles provide structural support to the bones and modify the impact between bones and external loads on the body.

Muscle tissues account for about 40-50% of body mass and an understanding of its deformation behavior is very important for human body impact biomechanics research.

In the project results of compressive loading of freshly slaughtered Ovine muscle tissue sample using a UTM testing rig is reported.

HUMAN BODY COMPOSITION

50%

15%

16%

15%4%

BIOLOGICAL COMPOSITION

Soft Muscle TissuesBonesSkinFatOthers

% of Human Body Weight

MUSCULAR SYSTEM OF HUMAN BODY

The muscular system is responsible for the movement of the human body.

Attached to the bones of the skeletal system are about 700 named muscles that make up roughly half of a person’s body weight.

Muscle tissue is also found inside of the heart, digestive organs, and blood vessels.

SOFT TISSUES

A group of tissues which binds, supports and protects our human body and structures such as organs is soft tissue.

TENDON AND LIGAMENT

Tendons act as muscle to bone linkage while Ligaments join one bone to the another one.

They are subjected to tension and there primarily purpose is to transmit the load.

In complex joints such as the knee, ligaments help to stabilise the joint (preventing undesired motions).

These are highly elastic material and very strong in tension.

Cont..

CARTILAGE AND FASCIA Cartilage is a flexible connective

tissue found in the joints between bones, the rib cage, the ear, the nose etc.

It is not as hard and rigid as bone but is stiffer and less flexible than muscle.

A fascia is a layer of fibrous tissue that surrounds muscles, group of muscles, blood vessels, and nerves.

It binds some structures together, while permitting others to slide smoothly over each other.

TISSUE MATERIALS

COLLAGEN

Collagen is the main structural protein of the various connective tissues

It is the main component of connective tissues, making up 25% to 35% of the whole body protein content.

ELASTIN

Elastin is a protein in connective tissue that is elastic and allows many tissues in the body to resume their shape after stretching or contracting.

Elastin load-bearing tissue in the bodies of vertebrates and used in places where mechanical energy is required to be stored.

Only biological part which shows linear elastic behavior

KERATIN

Fibrous structural protein making up the outer layer of human skin.

MUSCLE TYPES

VISCERAL MUSCLE Controlled by the unconscious part of the brain, so known as involuntary

muscle.

Weakest muscle found inside of organs like the stomach, intestines, and blood vessels.

Also known as ‘Smooth Muscle’

CARDIAC MUSCLE Cardiac muscle is found only in the heart Tissues.

It is also an involuntary muscle

Cont..

SKELETAL MUSCLE► Skeletal muscle is the only voluntary muscle tissue in the human body

► 80-90 % of the muscles are skeletal muscles

► Every physical action that a person consciously performs (e.g. speaking, walking, or writing) requires skeletal muscle.

► Most skeletal muscles are attached to two bones across a joint.

The function of skeletal muscle is move parts of the body.

PROPERTIES OF SOFT MUSCLE TISSUE

NONLINEAR VISCOELASTIC► The stress strain curve is non linear and

during loading and unloading it follows different paths.

► Soft muscle tissues shows time dependent stress–strain behaviour.

► It shows different behaviour for different value of strain rates.

Cont..

INHOMOGENEOUS AND ANISOTROPIC► It has the different behaviour in fiber and cross fiber direction.

Cross fiber direction Fiber Direction

Cont..

CROSS LINKED STRUCTURE

► Soft tissues shows the cross link properties like polymers.

► In polymers a cross-link is a bond that links one polymer chain to another.

► In Soft tissues cross-linking occurs in collagen fibers.

FACTORS ON WHICH THE MECHANICAL PROPERTIES DEPEND

AGE

Tissues becomes harder and less elastic as we get older

Different behavior for different age soft tissue sample

SPECIES

For different species the mechanical behavior is different

Porcine muscle tissue are stronger as compare to ovine muscle tissue

STRAIN RATE

If we increase the strain rate value we need larger forces to get same deformation

PHYSICAL ENVIRONMENT

Higher stresses are developed if the temperature is decreased

BEHAVIOUR OF TISSUE AGAINST TENSILE LOADING

[Phase-I]: The stress-strain curve is approximately linear and lower value of force achieves large deformations.

[Phase-II]: Collagen fibers tend to line up with the load direction and gradually elongate.

[Phase -III]: The collagen fibers aligned with one another in the direction in which the load is applied. The straightened collagen fibers resist the load strongly.

EXPERIMENTS PERFORMED

COMPRESSION TEST OF SOFT RUBBER

SPECIFICATION OF SAMPLE

Length of sample = 17.6mm

Width of sample = 17.34mm

Thickness of sample = 11.48mm

Cross section area = 305.184mm^2

Density = 1.41gm/cc

EXPERIMENTAL PROGRESS

Enlarged Fracture View of Sample

RESULTS

Stress vs strain curve varies approximately linearly up to the strain limit of 0.18 and non-linear onward.

Young’s Modulus- 1.32 Mpa

Compressive Strength- 1.0467 MPa

Stress vs Strain Curve

COMPRESSION TEST OF SILICONE RUBBER

SPECIFICATION OF SAMPLE

Thickness of sample = 11.66mm

Diameter of cross section = 9.7 mm

Cross section area = 73.898 mm^2

Density of material = 1.21gm/cc

RESULTS

Stress vs Strain curve Stress vs stain varies approximate linearly with strain till the value of strain 0.343(mm/mm) but it is non-linear onward.

Young’s modulus is 2.969MPa.

COMPRESSION TEST OF SOFT MUSCLE TISSUE

SAMPLE SPECIFICATION

Cubical freshly slaughtered muscle tissue of dimension 2 x 2 x 1.5 (cm)

Cross section area (A) = 4cm^2

Thickness of the sample = 1.5cm

Direction of loading = Lateral to muscle fiber direction

EXPERIMENTAL SETUP

Fixed the sample in UTM between two acrylic sheets.

Applied the load in transverse direction (cross fiber direction).

Value of strain rate 0.0056/s

RESULTS

TRUE STRESS

(Nominal stress (1 + Nominal strain))

TRUE STRAIN

Log (1 + Nominal strain)

Young’s Modulus Range 12 KPa to 500 KPa

Curve is non linear

0 0.1 0.2 0.3 0.4 0.5 0.60

20

40

60

80

100

120True Stress vs True Strain Curve

True Strain (mm/mm)

Tru

e S

tres

s (K

Pa)

DISCUSSION

Soft muscle tissue is nonlinear, viscoelastic, anisotropic and inhomogeneous material. It is a very soft material which is incompressible.

Cross section area of the sample varies considerably during the experiment. So nominal stress vs strain curve and true stress vs strain curves are different from each other from the beginning.

The results for the nominal stress are not reliable for soft materials like muscle tissue so we have to go for true stress and true strain to study the behavior of soft muscle tissues.

Cont.. TRUE STRESS- STRAIN AND NOMINAL STRESS- STRAIN CURVE

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80

50

100

150

200

250

300

350

400Nominal vs True

NominalTRUE

Strain (mm/mm)

Str

ess

(KP

a)

Cont.. Comparison with previous work in this field

0 0.1 0.2 0.3 0.4 0.5 0.60

20

40

60

80

100

120

140

160

180

200

True Stress vs True Strain

Our Experimental ResultPietsch and B. Wheatley

True Strain (mm/mm)

Tru

e St

ress

(K

Pa)

APPLICATIONS AND FURTHER STUDY

We did the ANSYS analysis of human femur and human leg like model only by applying loads gradually and found out the results for stress and strain behavior.

These analysis can be further implemented and can be calculated more precisely considering impact loading

We can apply our study in the field of human body subjected to impact modeling i.e. vehicle crash,

For these applications we need to know a little about various cases of impact loading.

ANSYS ANALYSIS

LOADING SPECIFICATION

FEMUR LEG MODEL

STRESS ANALYSIS

CONCLUSION

We studied the mechanical properties of soft muscle tissues and performed the compression test of Ovine muscle tissue on UTM.

The stress–strain curve for soft tissue is time dependent so it shows different stress-strain curves for different value of strain rates.

Because of nonlinearity of the curve Hook’s law is not valid for soft muscle tissues So there is no exact value for the young’s modulus for muscle tissues but an approximate range can be defined.

There is considerable change in the cross section of the sample so nominal stress-strain values are not reliable. We have to go for True stress-strain values to study the behavior of soft muscle tissues.

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