The Name of God
Shiraz University
School of Mechanical Engineering
Department of Solid Mechanics
Machine Design II
First Examination
Open Notes & Book
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Exam . Date : 1400/07/29
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Exam . Time: 9:11:30
1- Static Weldment Joint Design: 25 Points
The ½-in cantilever plate is made of AISI 1018 HR steel and welded with a h=0.25-in fillet wed
as shown in the figure. An E7010 electrode was used. Find the safety factor:
1-1)
Use the conventional method for the weld metal.
1-2)
Use the conventional method for the attachment (cantilever plate) metal.
1-3)
Use a welding code for the weld metal.
2- Fatigue Weldment Joint Designs: 25 Points
The load on the plate shown, varies from 22 to 44 kN and the arrangement is such that the line of
action of F passes through the centroid G of the weld group, thereby avoiding eccentric loading,
Determine:
2-1. The ratio of L1/L2.
2-2. The lengths of L1 and L2 of 10 mm fillet welds made with of E6010 electrode for infinite life.
3 – Helical Compression Spring Design: 25 Points
A helical compression spring is to be designed as to satisfy the following requirements.
A force of 6000 N is required to compress spring 40 mm to the solid height.
In the service the spring is compressed so that its deflection varies from 12 mm to 28 mm.
The frequency of the load on the spring is 20 cycles/sec.
Outside diameter will be 60 mm and the spring index is considered to be not less than 4.
The spring is to be made of Hard-drawn wire and it is peened.
Determine all the specifications of the spring which will operate safety for the given
requirements.
4 – Helical Coil Torsion Spring Design: 25 Points
The rat trap shown in the figure uses two opposite-image torsion springs. The wire has a diameter
of 0.075-in that made of music wire, and the outside diameter of the spring in the position shown
is 0.5 in. Each spring has 10 turns. Use of a fish scale revealed a force of about 10 lbf is needed
to set the trap.
4-1. Find the probabable configuration of the spring prior to assembly.
4-2. Find the maximum stress in the spring when the trap is set.
4-3.Estimate the static factor of safety.