PE Industrial flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Dimensional homogeneity

A valid physical equation carries identical units on both sides. Checking units this way exposes algebra errors and confirms that conversion factors were applied correctly before any numbers are computed.

Factor of safety

Ratio of material failure strength to allowable design stress. A value of 2 means the member is sized to carry twice the expected service load, covering uncertainty in loads and properties.

Root-sum-square tolerance stack

Assembly tolerance equal to the square root of the summed squared component tolerances. Valid when component variations are independent and roughly normal, giving a looser assembly tolerance than worst-case addition.

Capital recovery factor

The (A/P, i, n) factor converts a present sum into an equivalent uniform annual series. It equals i(1+i)^n divided by (1+i)^n minus one.

Internal rate of return

Discount rate at which a project's net present worth equals zero. A project is acceptable when its IRR is at least the minimum attractive rate of return.

MACRS depreciation

U.S. tax depreciation using declining-balance rates that switch to straight line. A half-year convention applies, and salvage value is ignored in the annual deduction.

Binomial distribution moments

For n independent trials each with success probability p, the mean is np and the variance is np(1-p). It models counts of defectives in a fixed-size sample.

Type I error

Rejecting a null hypothesis that is actually true. Its probability is alpha, the significance level, and it corresponds to a false alarm in a control chart or test.

Central limit theorem

As sample size grows, the distribution of sample means approaches normal with mean mu and standard error sigma over root n, regardless of the shape of the population distribution.

Shadow price

The dual variable of a linear program constraint. It is the objective improvement from relaxing that right-hand side by one unit, valid only within the reported sensitivity range.

Little's Law

In a stable steady-state system, the average number of items present equals the arrival rate times the average time spent in the system. Applies to queues, WIP, and inventories.

M/M/1 utilization

Ratio of arrival rate to service rate. When it is below one, average number in system equals utilization divided by one minus utilization; at or above one the queue grows without bound.

Chvorinov's rule

Solidification time of a casting is proportional to the square of its volume-to-surface-area ratio. A riser must have a larger ratio so it freezes after the casting it feeds.

Taylor tool life equation

Cutting speed times tool life raised to exponent n equals a constant. Higher speed shortens tool life; n is roughly 0.1 to 0.15 for high-speed steel and higher for carbide.

Blanking versus piercing

Both are sheet-metal shearing operations. Blanking cuts out the desired workpiece as the product, while piercing cuts a hole and the removed slug is scrap.

Economic order quantity

Order size minimizing the sum of annual ordering and holding cost. It equals the square root of two times annual demand times order cost divided by annual holding cost per unit.

Johnson's rule

Sequencing rule for a two-machine flow shop: take the shortest remaining processing time and schedule that job first if it is on machine one, otherwise last.

Critical ratio priority

Scheduling index equal to time remaining until due date divided by remaining processing time. Values below one signal jobs already late; the smallest ratio gets priority.

Load-distance score

Sum over department pairs of material flow multiplied by the distance between them. Used to compare alternative block layouts; the lower the score, the better the arrangement.

Line balancing cycle time

Available production time per period divided by required output rate. It sets the maximum total task time that may be assigned to any single workstation on the line.

From-to chart

Matrix recording the number of loads moved between each pair of departments. It drives flow-dominant layout design and supplies the flow values for load-distance scoring.

Process capability index Cpk

The smaller of the upper and lower specification distances from the process mean, divided by three sigma. It penalizes both excessive spread and off-center operation.

Taguchi loss function

Quality loss rises with the square of the deviation from target: loss equals a constant times that squared deviation. Conforming to specification limits is therefore not sufficient.

Operating characteristic curve

Plots the probability of accepting a lot against lot fraction defective for a given sampling plan. Steeper curves discriminate more sharply between acceptable and rejectable quality.

Standard time

Normal time multiplied by one plus the allowance factor, where normal time is observed time times performance rating. It is the basis for cost estimating and capacity planning.

Learning curve

Unit time falls by a constant percentage each time cumulative output doubles. The exponent equals the log of the learning rate divided by the log of two.

NIOSH lifting equation

Computes a recommended weight limit from a load constant times multipliers for horizontal and vertical location, asymmetry, coupling, frequency, and task duration.

Bullwhip effect

Amplification of demand variability as orders move upstream in a supply chain, driven by batch ordering, price promotions, forecast updating, and shortage rationing.

Safety stock formula

Buffer inventory equal to the service-level z factor times the standard deviation of demand times the square root of lead time, protecting against demand variability during replenishment.

Newsvendor critical ratio

Optimal in-stock probability for a single-period item equals underage cost divided by the sum of underage and overage costs; order the quantity matching that fractile of demand.

Hierarchy of controls

Order of hazard mitigation from most to least effective: elimination, substitution, engineering controls, administrative controls, and finally personal protective equipment.

OSHA incidence rate

Number of recordable injuries times 200,000 divided by total hours worked. The 200,000 constant normalizes the rate to a base of 100 full-time workers for one year.