PSI - Issue 52

A.D. Cummings et al. / Procedia Structural Integrity 52 (2024) 762–784 A. Cummings / Structural Integrity Procedia 00 (2023) 000–000

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9

Drop orientation study

Material modelling

Lid down

Base down

Side down

All components Elastic-plastic (hardening) (quasi-static (Q-S))

0°

90°

180°

Drop orientation [°]

Stress [MPa]

Stress [MPa]

Stress [MPa]

Package Body Drop orientation [°]

Drop orientation [°]

Drop orientation [°]

Lid bolts

Lid

Stress analysis (1. characterisation)

1. Region of interest elastic model 2. Regions controlling load path(s) elastic-plastic (hardening) (dynamic/Q-S)

Bending

Membrane

dt Stress [MPa]

Stress [MPa]

Stress [MPa]

Thickness [mm]

Time [ms]

Thickness [mm]

Stress analysis (2. classification)

All areas elastic plastic (hardening) (dynamic/Q-S)

Determine plastic collapse (L r,uncracked ) by successively reducing yield in region of interest. F y = 9.5, 0.9, ..., 0.1. When/if section yielding occurs stress is classified as primary and F y = L r,uncracked

Determine K mat

Determine L r,cracked

Determine K I

Annex N (optional)

Charpy energy data Annex J estimate - Size, temperature corrections

Annex M K I

Annex P L r,cracked

Low constraint effects, T-stress

Annex L Dynamic effects

K mat

K r

K r

L r

Pass/fail

Fig. 2. Overview of assessment approach

The final stage is to apply the stresses to determine the fracture ratio:-

K I K mat

K r =

(8)

And the cracked body plastic collapse ratio:-

P P L

σ ref σ y

(9)

L r =

=

Typically this is done with Annex M and P of BS7910 (2019). A further option is to adjust K mat if the stress triaxiality in the vicinity of the flaw is low. In fracture mechanics terminology this condition is called low constraint and occurs when the hydrostatic stress ahead of the crack tip is low. For example shallow flaws have lower constraint conditions than deep flaws but the master curve approach