Ask Question, Ask an Expert

+1-415-315-9853

info@mywordsolution.com

Ask Mechanical Engineering Expert

problem1.
 
A pressure vessel is to be treated to generate compressive residual stresses on it inner surface. This involves increasing the pressure until taking 75% of the wall thickness goes into the plastic range. The external diameter of the vessel is 250mm and the internal diameter is 120mm, so that it must be regarded as a thick cylinder. The yield stress of the material is approximately 400MPa.

(a)  find out the internal pressure required

(i)  to cause first yield

(ii)  to cause yield one third of the way through the wall thickness

(iii)  to cause yield all the way across the wall

(b) Sketch a curve of internal pressure versus radius of yielded zone boundary for the cylinder. Comment on the factor of safety against plastic collapse associated with the target amount of yield, taking into account the assumptions inherent in the calculations.

problem2.
 
As part of the fitting of the mooring lines to a wave energy device, the pin-jointed structure shown in Figure is to be subjected to a small degree of plastic deformation by applying a force, F, in the direction shown. The structure is made from two members, each of cross-sectional area 50mm2, using a high strength steel whose elastic-plastic stress-strain relationship is

472_stress stain relationship.jpg

(a)  find out the load, F, required causing first yield in members AC and BC.

(b)  Find the deflection, u, for a load, F, of 35kN and determine the residual plastic strain in the members after removal of the load. 

problem3.

A lifting shackle in a glass-making factory is made from a special high-temperature stainless steel.  It is expected that the shackle will experience a tensile load of 5kN and the design allows for a maximum creep strain of 1% over the design life of 10,000 operating hours.  The supplier of the alloy has measured the stress exponent, n, to be 4.5, the activation energy, QC , to be 110,000 J/mol and the pre-exponential constant, K2 , to be 2 ×10-8 (the constants K2 and n are in MPa, % and hour units).

(a) find out the minimum required cross-sectional area of the shackle if operating at 800oC.

(b) If the temperature were to be increased to 900oC and the load and cross-sectional area kept the same, what would be the time to 1% strain what would the creep strain be after 10,000 hours?

problem4.

A new high temperature alloy has been developed with creep properties as follows:  stress exponent, m = 4.5, activation energy, Q = 110,000 J/mol and pre-exponential constant, A = 2×10-8. The constants A and m are in MPa, % and hour units. Take E = 200GPa for the alloy and the Universal Gas Constant R = 8.314J/molK.

a) In one potential application, the alloy is to be used where it is subject to a constant tensile load of 5kN and service temperature of 800oC and the design allows for a maximum creep strain of 1% over the design life of 10,000 operating hours. 

(i) find out the minimum required cross-sectional area of the blade. 

(ii)  If the temperature were to be increased to 900oC and the load and cross-sectional area kept the same, what would be the time to 1% strain what would the creep strain be after 10,000 hours?

b)  In another application, the alloy is to be used for making bolts holding down the flange on a pressure vessel operating at 450oC. The bolts are preloaded to a stress of 400 MPa.

(i) Assuming the flange to be rigid, find the time taken for the stress to relax to half the preload value.

(ii) find out in remaining stress in the bolts after 100 hours.

c)  For a third application, the alloy is to be used in bending in a component of rectangular cross-section of breadth, b = 20mm and depth, d = 50mm. If a bending moment, M, of 1kNm is applied, the elastic stress distribution across the section, σ = My/I, is as shown in Figure. Using the elastic stress as a basis, sketch the stress distribution across the section if the alloy were to be used at an elevated temperature so that creep is occurring.   NB: Only use the positive values of  y  for your calculations, and sketch the remainder using symmetry.

727_symmentris.jpg


problem5.
 
A large hydraulic cylinder is to be treated using autofrettage, taking 80% of the wall thickness into the plastic range. The external diameter of the vessel is 200mm and the internal diameter is 100mm, so that it must be regarded as a thick cylinder. The yield stress of the material is approximately 450MPa.

(a)  find out the internal pressure required

(i)  to cause first yield

(ii)  to cause yield half-way through the wall thickness

(iii)  to cause yield all the way across the wall

(iv) Sketch a curve of internal pressure versus radius of yielded zone boundary for the cylinder. Comment on the factor of safety against plastic collapse associated with the target amount of yield, taking into account the assumptions inherent in the calculations.

(b)  prepare down the four equations which describe the hoop and radial stresses in the elastic and plastic zones of a pressurised thick cylinder. Hence, sketch the stress distribution across the wall of the cylinder indicating values of stress in MPa. Using this sketch, briefly describe the process of yielding and plastic failure of a thick-walled cylinder as the pressure increases.

problem6.
 
A suspended walkway in an underground cavern consists of a deck supported by three tie rods placed symmetrically about the centre as shown below:

2344_symmtrically diagram.jpg

The rods are each of cross-sectional area 100mm2, are made of steel (E = 200GPa) and can be assumed to behave in an elastic-perfectly plastic fashion. The central, longer rod yields at a stress (σ y,c) of 500MPa and the outer, shorter rods yield (σ y,o) at 250MPa.

The walkway is to be designed so that an alarm is triggered when the first rods yield, but before general yield in the suspension.  It is therefore important to now the downward displacement, δ, as a function of stress in the rods.

(a) Find the walkway loads and the corresponding downward displacements at which yield first occurs and at which all members have yielded.

(b) Construct the load displacement diagram and select an alarm trigger point.

(c) What is the residual displacement once a load triggering the alarm has been removed?

(d) Determine the residual displacement once a load above general yield has been removed.

Mechanical Engineering, Engineering

  • Category:- Mechanical Engineering
  • Reference No.:- M9672

Have any Question? 


Related Questions in Mechanical Engineering

Calculate the first-order correction to the energy of a

Calculate the first-order correction to the energy of a ground-state harmonic oscillator subject to an anharmonic potential of the form ax 3 +bx 4 where a and b are small (anharmonicity) constants. Consider the three cas ...

An isotopically enhanced sample has ndi moles of deuterated

An isotopically enhanced sample has nDI moles of deuterated hydrogen iodide and nHI moles of common HI at 398 K. Comparison of the infrared intensities of the v = 1 S 2 transition inds a ratio of 0.100 for DI molecules ( ...

1 develop three scenarios for comparable circular cylinders

1. Develop three scenarios for comparable circular cylinders of radius R and square tubes of side H that allow one to say R ∼ H. (Hint: What geometric attributes of the cylinder and tube might be made equal?) 2. If a str ...

Projectdesign a tube bank that will increase the

Project Design a tube bank that will increase the temperature of a 1200 CFM flow of air from 35°F to 100°F. Assume a constant pressure of 1atm. Each tube will have a diameter of 0.5in and a length of 24in. The tube confi ...

For the experimental pump data given belowqflow rate

For the experimental pump data given below: Q F low Rat e ( ???? /s) ???? Total Pressure (kPa) P IN Shaft power (kW) 0.0000 504.82 1.190 0.0004 481.50 1.318 0.0008 476.70 1.573 0.0012 471.50 1.828 0.0017 461.00 2.083 0.0 ...

There are 3 x 103 spheres in a box calculate the number of

There are 3 x 10 3 spheres in a box. Calculate the number of different combinations for the spheres in order to have 1100 spheres in the front third of the box. Assuming that the distribution is normal, calculate the pro ...

A gas sample is known to be a mixture of ethane and butane

A gas sample is known to be a mixture of ethane and butane. A bulb having a 230.0 cm 3 capacity is filled with the gas to a pressure of 97.5 X 10 3 Pa at 23.1°C. If the mass of the gas in the bulb is 0.3554 g, what is th ...

Water flows steadily through the piping junction entering

Water flows steadily through the piping junction, entering section 1 at 0.0013 m 3  /s. The average velocity at section 2 is 2.1 m/s. A portion of the flow is diverted through the showerhead, which contains 100 holes of ...

The top figure shows a diagram of the bones and biceps

The top figure shows a diagram of the bones and biceps muscle of a person's arm supporting a mass. The lower figure shows a biomechanical model of the arm, in which the biceps muscle AB is represented by a bar with pin s ...

Hot air rises but what happens to it as it rises through

Hot air rises, but what happens to it as it rises through our atmosphere? Given the number density function Eq. 14.33 and the temperature curve plotted in Fig. 14.3 to the surrounding atmosphere, calculate the Final temp ...

  • 4,153,160 Questions Asked
  • 13,132 Experts
  • 2,558,936 Questions Answered

Ask Experts for help!!

Looking for Assignment Help?

Start excelling in your Courses, Get help with Assignment

Write us your full requirement for evaluation and you will receive response within 20 minutes turnaround time.

Ask Now Help with Problems, Get a Best Answer

WalMart Identification of theory and critical discussion

Drawing on the prescribed text and/or relevant academic literature, produce a paper which discusses the nature of group

Section onea in an atwood machine suppose two objects of

SECTION ONE (a) In an Atwood Machine, suppose two objects of unequal mass are hung vertically over a frictionless

Part 1you work in hr for a company that operates a factory

Part 1: You work in HR for a company that operates a factory manufacturing fiberglass. There are several hundred empl

Details on advanced accounting paperthis paper is intended

DETAILS ON ADVANCED ACCOUNTING PAPER This paper is intended for students to apply the theoretical knowledge around ac

Create a provider database and related reports and queries

Create a provider database and related reports and queries to capture contact information for potential PC component pro