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Mechanics of Deformable Bodies: Stresses and Thin-Walled Pressure Vessels - Prof. Pangilin, Exercises of Mechanics

An in-depth exploration of the mechanics of deformable bodies, focusing on the concepts of stresses and thin-walled pressure vessels. It covers the development of internal forces, types of stresses (normal and shear), and the analysis of thin-walled pressure vessels subjected to internal pressure. Several sample problems to illustrate the application of the principles discussed. It serves as a comprehensive resource for students and professionals studying the mechanics of materials, particularly in the areas of stress analysis and pressure vessel design.

Typology: Exercises

2023/2024

Uploaded on 04/29/2024

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STRESSES
MECHANICS OF DEFORMABLE BODIES
STRESSES
Rigid Bodies- do not deform (stretch, compress, or bend) when subjected to load.
Deformable Bodies - any body that changes its shape and/or volume while being
acted upon by any kind of external force.
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STRESSES

MECHANICS OF DEFORMABLE BODIES

STRESSES

Rigid Bodies- do not deform (stretch, compress, or bend) when subjected to load. Deformable Bodies - any body that changes its shape and/or volume while being acted upon by any kind of external force.

STRESSES

Development of Internal Forces In strength of materials, we make an additional investigation of the internal distribution of the forces. This is done by passing an exploratory section through the body, exposing the internal forces acting on the section that are necessary to maintain equilibrium of either segment. In general, the internal forces reduce to a resultant force and moment, which are resolved into components that are normal (perpendicular) and tangent to the section.

STRESSES

Development of Internal Forces N Axial Force,P. This component measures the resistance to pulling or pushing action perpendicular to the section. Vx,Vz Shear forces, v. These are components of the total resistance to sliding the portion to one side of the section. My Torque, T. This component measures the resistance to twisting the member. Mx, Mz Bending Moment, M. Measures the resistance to bending the member about the y and z axes.

STRESSES

Sample Problem 1. Below is an I-Beam subjected to a load P = 300 kN normal to the cross-section and located along the centroid, the I beam has the following properties tf =50 mm d = 300 mm bf = 100 mm tw = 60 mm Determine the average Normal Stress.

STRESSES

Sample Problem 2. A hollow steel tube with the exterior diameter of 120mm and inside diameter of 100mm is subjected to an axial stress of 400 kN. Determine the axial stress on the tube.

STRESSES

Sample Problem 3. An aluminum bar ( Cross-Sectional Area = 1125 mm^2 ) is fastened between steel bar (Cross-Sectional Area = 1000 mm^2 ) and a bronze bar (Cross-Sectional Area = 750 mm^2 ).

  1. Determine the stress of bronze
  2. Determine the stress of aluminum
  3. Determine the stress of steel

STRESSES

Sample Problem 4. The lap joint shown in Fig. P-126 is fastened by four ¾-in.-diameter rivets. Calculate the maximum safe load P that can be applied if the shearing stress in the rivets is limited to 14 ksi and the bearing stress in the plates is limited to 18 ksi. Assume the applied load is uniformly distributed among the four rivets.

STRESSES

Sample Problem 1. The lap joint shown below is fastened by four rivets of 3/4-in. diameter. Find the maximum load P that can be applied if the working stresses are 14 ksi for shear in the rivet and 18 ksi for bearing in the plate. Assume that the applied load is distributed evenly among the four rivets, and neglect friction between the plates.

STRESSES

Sample Problem 2. Referring to Fig. P-121, compute the maximum force P that can be applied by the machine operator, if the shearing stress in the pin at B and the axial stress in the control rod at C are limited to 4000 psi and 5000 psi, respectively. The diameters are 0.25 inch for the pin, and 0.5 inch for the control rod. Assume single shear for the pin at B.

STRESSES

Sample Problem 3. What force is required to punch a 20-mm-diameter hole in a plate that is 25 mm thick? The shear strength is 350 MN/m^2.

STRESSES

Sample Problem 4. In the clevis shown in Fig. 1-11b, find the minimum bolt diameter and the minimum thickness of each yoke that will support a load P = 14 kips without exceeding a shearing stress of 12 ksi and a bearing stress of 20 ksi.

Thin-Walled Pressure Vessel

Two Types of Stresses A tank or pipe carrying a fluid or gas under a pressure is subjected to tensile forces, which resist bursting, developed across longitudinal and transverse section. The general condition is : 𝑝𝐴௧௔௡௞ = 𝜎𝐴௥௘௦௜௦௧௔௡௖௘

Thin-Walled Pressure Vessel

Tangential/Circumferential Stress Tangential Stress is sometimes called Circumferential Stress of Girth Stress or Hoop Stress. 𝜎௧ − 𝑇𝑎𝑛𝑔𝑒𝑛𝑡𝑖𝑎𝑙 𝑆𝑡𝑟𝑒𝑠𝑠 𝑖𝑛 𝑃𝑎 𝑜𝑟 𝑝𝑠𝑖 𝑝 𝑜𝑟 𝑝௜ − 𝐼𝑛𝑡𝑒𝑟𝑛𝑎𝑙 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 𝑖𝑛 𝑃𝑎 𝑜𝑟 𝑝𝑠𝑖 𝐷 − 𝐷𝑖𝑎𝑚𝑒𝑡𝑒𝑟 𝑜𝑓 𝑡ℎ𝑒 𝑣𝑒𝑠𝑠𝑒𝑙 𝑖𝑛 𝑚𝑒𝑡𝑒𝑟𝑠 𝑜𝑟 𝑖𝑛𝑐ℎ𝑒𝑠 𝑡 − 𝑡ℎ𝑖𝑐𝑘𝑛𝑒𝑠𝑠 𝑜𝑓 𝑡ℎ𝑒 𝑣𝑒𝑠𝑠𝑒𝑙 𝑤𝑎𝑙𝑙 𝑖𝑛 𝑚. 𝑜𝑟 𝑖𝑛. 𝑁𝑜𝑡𝑒 ∶ 𝑖𝑓 𝑒𝑥𝑡𝑒𝑟𝑛𝑎𝑙 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒, 𝑝௢ 𝑒𝑥𝑖𝑠𝑡𝑠 𝒑 = 𝒑𝒊 − 𝒑𝒐 Pressure for a fluid of depth,h 𝒑 = 𝝆 𝒈 𝒉 𝝈𝒕 = 𝒑𝑫 𝟐𝒕 𝒐𝒓 𝝈𝒕 = (𝒑𝒊 − 𝒑𝒐)𝑫 𝟐𝒕

Thin-Walled Pressure Vessel

Longitudinal Stress Consider the free body diagram in the transverse section of the tank, the force, F, acting at the rear end of the tank must be equal to the total longitudinal stress on the wall PT=σl Awall. Since it is compared to D, the area of the wall is closed to π D t. 𝝈୪ = 𝒑 𝑫 4𝒕 𝝈𝒍= (𝒑𝒊 − 𝒑𝒐)𝑫 𝟒𝒕 𝝈𝒕 = 𝟐𝝈𝒍 𝜎௟ − 𝐿𝑜𝑛𝑔𝑖𝑡𝑢𝑑𝑖𝑛𝑎𝑙 𝑆𝑡𝑟𝑒𝑠𝑠 𝑖𝑛 𝑃𝑎 𝑜𝑟 𝑝𝑠𝑖 𝑝 𝑜𝑟 𝑝௜ − 𝐼𝑛𝑡𝑒𝑟𝑛𝑎𝑙 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒 𝑖𝑛 𝑃𝑎 𝑜𝑟 𝑝𝑠𝑖 𝐷 − 𝐷𝑖𝑎𝑚𝑒𝑡𝑒𝑟 𝑜𝑓 𝑡ℎ𝑒 𝑣𝑒𝑠𝑠𝑒𝑙 𝑖𝑛 𝑚𝑒𝑡𝑒𝑟𝑠 𝑜𝑟 𝑖𝑛𝑐ℎ𝑒𝑠 𝑡 − 𝑡ℎ𝑖𝑐𝑘𝑛𝑒𝑠𝑠 𝑜𝑓 𝑡ℎ𝑒 𝑣𝑒𝑠𝑠𝑒𝑙 𝑤𝑎𝑙𝑙 𝑖𝑛 𝑚. 𝑜𝑟 𝑖𝑛. 𝑁𝑜𝑡𝑒 ∶ 𝑖𝑓 𝑒𝑥𝑡𝑒𝑟𝑛𝑎𝑙 𝑝𝑟𝑒𝑠𝑠𝑢𝑟𝑒, 𝑝௢ 𝑒𝑥𝑖𝑠𝑡𝑠 𝒑 = 𝒑𝒊 − 𝒑𝐨 Pressure for a fluid of depth,h 𝒑 = 𝝆 𝒈 𝒉

Thin-Walled Pressure Vessel

Sample Problem 1 From CE Board May 2011 - A water tank 3m in diameter ang 6 m in height is made from steel having a thickness of 12mm. When the tank is filled with water, determine the circumferential stress.

Thin-Walled Pressure Vessel

Sample Problem 4 The Tank shown in the figure is fabricated from steel plate,

  1. Determine the maximum longitudinal stress caused by an internal pressure of 1.2 MPa if the steel plate has a thickness of 10mm.
  2. Determine the maximum circumferential stress caused by an internal pressure of 1.2 MPa if the steel plate has a thickness of 10mm.
  3. Determine the minimum thickness of plate which may be used if the stress is limited to 40 MPa and the internal pressure is 1.5MPa.

Thin-Walled Pressure Vessel

Sample Problem 5 A Spherical tank for storing gas under pressure is 25 m in diameter and is made of structural steel 15 mm thick. The yield point of the material is 250 MPa, and a safety factor of 2.5 is adequate.

  1. Determine the maximum permissible internal pressure, assuming the welded seams between the various plates are as strong as the solid metal.
  2. Determine the permissible pressure if the seams are 75% as strong as the solid metal.
  3. Determine the thickness of the spherical tank if it has an allowable tensile stress of 150 MPa , if it is subjected to an internal pressure of 0.30 MPa.