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Section 3 / loads and margins

Loads and Margins

Limit and ultimate loads, reserve factors, margin of safety reports, and consistent calculation templates.

04

Mohr's circle, principal stresses and von Mises, Tresca and maximum-principal margins with the plane-stress yield locus.

Mohr's circle with principal stress points.
Open Mohr's Circle & Failure → 🔒 Login required
05

Stress-strength interference reliability of a series system of items with redundancy, mission failure probability and failure rate.

Overlapping stress and strength distributions.
Open Structural Reliability → 🔒 Login required
06

Hertz contact for ball and line contacts, including a cylinder in a groove: contact patch, peak pressure, subsurface shear and yield margin.

A cylinder pressed against a surface with a pressure distribution.
Open Hertz Contact Stress → 🔒 Login required
07

Miles equation and spectrum integration for a single-degree-of-freedom item: RMS and 3-sigma acceleration, displacement, equivalent static load and stress margin.

Random acceleration spectrum with a resonant response peak.
Open Random Vibration (Miles) → 🔒 Login required
08

Helical compression spring rate, stress and solid height, and Belleville washer stack load-deflection with series and parallel stacking.

A coil spring and a stack of disc springs.
Open Spring Design → 🔒 Login required
09

Fatigue life scatter factor from test data at a chosen reliability and confidence, and the Gumbel estimate of a rare maximum load.

A bell curve with a tail and a lower limit marked.
Open Scatter & Extreme Value → 🔒 Login required
10

Block fatigue damage with a two-point S-N curve, Goodman mean-stress correction, notch factor and Miner summation, with life and margin.

An S-N curve with load levels marked.
Open S-N Fatigue & Miner → 🔒 Login required
11

Cycles to grow a crack from its initial to its critical length using the Paris law, with scatter factor and margin.

A crack growing across a plate with the crack length against cycles.
Open Crack Growth (Paris) → 🔒 Login required
12

One table of margins of safety from many checks: lowest margin, its line, count of negative margins and a bar plot.

A bar chart of margins of safety for several checks.
Open Margin of Safety Summary → 🔒 Login required
13

Local notch-root stress and strain past yield from Kt, the nominal stress and a Ramberg-Osgood curve using Neuber's rule.

A stress-strain curve crossed by a constant-product hyperbola.
Open Neuber Notch Plasticity → 🔒 Login required
14

Convert a point or vector between two 3D coordinate systems with an origin shift and three rotations; gives the rotation matrix.

Two sets of 3D axes rotated relative to each other.
Open Coordinate Transformation → 🔒 Login required
15

Combined-load margin of safety from a general interaction equation with two or three ratios and their exponents.

A curved interaction boundary between two load ratios.
Open Interaction Curve Margin → 🔒 Login required
16

Median-rank Weibull fit of failure lives: shape, characteristic life, B10, mean life and reliability at a chosen life.

A Weibull probability plot with a straight line fit.
Open Weibull Reliability → 🔒 Login required
17

Peak force, deflection, impact factor and deceleration for a weight dropped onto a linear spring-like structure.

A weight dropping onto a spring.
Open Drop Impact Load → 🔒 Login required
18

Principal stresses, maximum shear, von Mises and Tresca stress and yield margins from the six components of a 3D stress state.

A stress cube with principal stresses.
Open 3D Principal Stress → 🔒 Login required
19

Reliability of series, parallel or k-of-n arrangements, with the weakest component and the part reliability needed for a target.

Blocks arranged in series and in parallel.
Open System Reliability → 🔒 Login required
20

Contact pressure, PV value, Archard wear volume and depth, and time to reach an allowable wear depth for a sliding contact.

A block sliding on a surface with worn depth marked.
Open Sliding Wear & PV → 🔒 Login required
21

Hoop and radial centrifugal stress in a solid disc or a disc with a hole, and the speed at first yield.

A spinning disc with a central hole.
Open Rotating Disc Stress → 🔒 Login required
22

Combined stiffness, deflection, load sharing and stored energy for springs or load paths in series or in parallel.

Springs connected in series and in parallel.
Open Spring Network → 🔒 Login required
24

Natural frequency, magnification and transmissibility of a damped mass on a spring.

A damped mass on a spring.
Open SDOF Vibration → 🔒 Login required
25

Von Mises stress and margins in a round tube under axial load, bending, torque and shear.

A round tube with combined loads.
Open Tube Combined Loads → 🔒 Login required
26

Rated life in revolutions and hours for a rolling bearing, with reliability factor and required load rating.

A rolling bearing.
Open Bearing Life → 🔒 Login required
27

Convert stress and pressure, force, length and moment between common engineering units.

Unit conversion.
Open Unit Converter → 🔒 Login required
29

First lateral critical speed of a shaft on two supports with a disc at mid-span, and separation from running speed.

A shaft carrying a disc between two bearings.
Open Shaft Critical Speed → 🔒 Login required
31

Principal strains and stresses, maximum shear and von Mises stress from a rectangular strain gauge rosette.

A strain gauge rosette on a surface.
Open Strain Rosette → 🔒 Login required
34

Mean, standard deviation and normal-distribution A-basis and B-basis values from a list of test results.

A spread of test results with a lower bound.
Open Sample Statistics → 🔒 Login required
36

Worst-case and statistical tolerance stack-up with the gap range and margin against a required gap.

A chain of dimensions with a gap.
Open Tolerance Stack-Up → 🔒 Login required
37

Strut stroke and gear load needed to absorb a sink speed, with the margin on the available stroke.

A landing gear strut and tire.
Open Landing Gear Stroke → 🔒 Login required
40

Overall ratio, output speed, torque and power of a two-stage spur gear train.

Four gears in two stages.
Open Gear Train Ratio → 🔒 Login required
41

Push and pull force, speed, power and rod stress of a double-acting hydraulic cylinder.

A hydraulic cylinder with a rod.
Open Hydraulic Actuator → 🔒 Login required
43

Peak acceleration, amplification and displacement of an item hit by a half-sine shock pulse.

A half-sine shock pulse and an item on a spring.
Open Shock Pulse Response → 🔒 Login required
46

Bending stress, rate and deflection of a round-wire helical torsion spring with yield margin.

A helical torsion spring with two legs.
Open Torsion Spring → 🔒 Login required
49

Notch sensitivity and fatigue notch factor from the stress concentration, radius and strength.

A notched bar with a stress concentration at the root.
Open Fatigue Notch Factor → 🔒 Login required
55

Torsional natural frequency of two discs on a shaft, with separation from operating speed.

Two discs joined by a twisting shaft.
Open Torsional Vibration → 🔒 Login required
63

Flywheel inertia, stored energy, equivalent ring weight and rim stress.

A flywheel on a shaft.
Open Flywheel Energy → 🔒 Login required
71

Load against deflection of a single coned disc spring.

A coned disc spring in cross section.
Open Disc Spring → 🔒 Login required
79

Dynamic pressure, wind force and overturning moment on a flat surface.

A sign panel in a strong wind.
Open Wind Load Force → 🔒 Login required