$12$:$31$

$5$G

$19$

$...$et$01-$xythos.content.blackboardcdn.com

$2$ of $3$

A leaf spring shown in the figure below, is to be made of AISI $1060$ Q&T $(425C)$ heat treated steel that is machined to required size after heat treatment. The dimensions of the leaf spring are $b=10mm,L=100mm$ and thickness hmm $.$ It is subject to a sequence of $3$ varying loads $($one cycle each$)$ varying as shown below in $10$ seconds.

$0N$ to $(\frac{10}{3}{P}_0)N$

$0N$ to $(\frac{210}{3}{P}_0)N$

$0N$ to $(10P_0)N$

where last non $-$ zero digit of your student ID$).$

If your student ID is $2021003560,$ then $P_0=6.$

Draw the bending moment diagram

$[3$ Marks$]$

Identify the critical point along the length and on the cross$-$section.

$[3$ Marks$]$

Identify the component of stress that is to be calculated here by drawing the cartesian coordinate system.

$[2$ Marks$]$

Determine all the required material properties.

$[7$ Marks$]$

Find $ma\frac{x}{m}in$ stress, stress amplitude and mean stress.

$[5$ Marks$]$

Choose Gerber fatigue theory, Palmgren$-$Miner rule and yield criteria to determine the thickness $h$ in mm for $60$ days of life $($i$.$e$.60$ days of continuous application of $3$ load sequences$)$ for a factor of safety $n=4.$ Use MatLab built$-$in solvers $($solve or vpasolve$)$ to solve non$-$linear equations.

$[30$ Marks$]$

$2$

Instructor: Dr$.$ Raguraman Kannan

Table A$-21$ Mean Mechanical Properties of Some Heat$-$Treated Steels

$[$These are typical properties for materials normalized and annealed. The properties for quenched and tempered $($Q&T$)$ steels

are from a single heat. Because of the many variables, the properties listed are global averages. In all cases, data were obtaine

from specimens of diameter $0\mathrm{.}505$ in $,$ machined from $1-$in rounds, and of gauge length $2$ in $.$ Unless noted, all specimens wer

oil$-$quenched.$]$

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