List of top Mechanical Engineering Questions

Consider the surface roughness profile as shown in the figure. 

The center line average roughness (\(R_a\), in \(\mu m\)) of the measured length \(L\) is

In a machining operation, if a cutting tool traces the workpiece such that the directrix is perpendicular to the plane of the generatrix as shown in the figure, the surface generated is 

The loading and unloading response of a metal is shown in the figure. The elastic and plastic strains corresponding to 200 MPa stress, respectively, are 

In a grinding operation of a metal, specific energy consumption is 15 J/mm³. If a grinding wheel with a diameter of 200 mm is rotating at 3000 rpm to obtain a material removal rate of 6000 mm³/min, then the tangential force on the wheel is ________\ \text{N (round off to two decimal places).}
The XY table of a NC machine tool is to move from P(1,1) to Q(51,1); all coordinates are in mm. The pitch of the NC drive leadscrew is 1 mm. If the backlash between the leadscrew and the nut is 1.8°, then the total backlash of the table on moving from P to Q is ________\ \text{mm (round off to two decimal places).}
Consider a single machine workstation to which jobs arrive according to a Poisson distribution with a mean arrival rate of 12 jobs/hour. The process time of the workstation is exponentially distributed with a mean of 4 minutes. The expected number of jobs at the workstation at any given point of time is ________\ \text{(round off to the nearest integer).}
A 200 mm wide plate having a thickness of 20 mm is fed through a rolling mill with two rolls. The radius of each roll is 300 mm. The plate thickness is to be reduced to 18 mm in one pass using a roll speed of 50 rpm. The strength coefficient \(K\) of the work material flow curve is 300 MPa and the strain hardening exponent, \(n\) is 0.2. The coefficient of friction between the rolls and the plate is 0.1. If the friction is sufficient to permit the rolling operation then the roll force will be ________\ \text{kN (round off to the nearest integer).}
An orthogonal cutting operation is performed using a single point cutting tool with a rake angle of 12° on a lathe. During turning, the cutting force and the friction force are 1000 N and 600 N, respectively. If the chip thickness and the uncut chip thickness during turning are 1.5 mm and 0.75 mm, respectively, then the shear force is ______ N (round off to one decimal place).
A right solid circular cone standing on its base on a horizontal surface is of height \(H\) and base radius \(R\). The cone is made of a material with specific weight \(w\) and elastic modulus \(E\). The vertical deflection at the mid-height of the cone due to self-weight is given by
The resistance spot welding of two 1.55 mm thick metal sheets is performed using welding current of 10000 A for 0.25 s. The contact resistance at the interface of the metal sheets is 0.0001 \(\Omega\). The volume of weld nugget formed after welding is 70 mm\(^3\), the thermal efficiency of the welding process is ________ % (round off to one decimal place).
A true centrifugal casting operation needs to be performed horizontally to make copper tube sections with outer diameter of 250 mm and inner diameter of 230 mm. The value of acceleration due to gravity, \(g = 10 \, \text{m/s}^2\). If a G-factor (ratio of centrifugal force to weight) of 60 is used for casting the tube, the rotational speed required is _________ rpm (round off to the nearest integer).
Robot Ltd. wishes to maintain enough safety stock during the lead time period between starting a new production run and its completion such that the probability of satisfying the customer demand during the lead time period is 95%. The lead time period is 5 days and daily customer demand can be assumed to follow the Gaussian (normal) distribution with mean 50 units and a standard deviation of 10 units. Using \(\phi^{-1}(0.95) = 1.64\), where \(\phi\) represents the cumulative distribution function of the standard normal random variable, the amount of safety stock that must be maintained by Robot Ltd. to achieve this demand fulfillment probability for the lead time period is _________ units (round off to two decimal places).
The correct sequence of machining operations to be performed to finish a large diameter through hole is
In modern CNC machine tools, the backlash has been eliminated by
What are the number of numbers possible divisible by 3 if we choose 4 numbers from the set S = {4,5,7,8,9}