{ "node": { "id": "term:power-spectral-density", "type": "Term", "label": "Power spectral density", "properties": { "id": "power-spectral-density", "name": "Power spectral density", "abbr": "PSD", "aka": [ "PSD vibration profile", "random vibration", "acceleration spectral density", "ASD" ], "section": "topic-testing", "definition": "The way a random vibration profile is specified: acceleration intensity per unit frequency, in g²/Hz, across a band such as 5–200 Hz. The square root of the area under the curve gives the overall level in g rms. SAE J2380 and ISO 12405 use PSD profiles to stand for road vibration, whereas UN 38.3 uses a sine sweep.", "formula": "g_rms = √(∫ PSD(f) df)", "unit": "g²/Hz", "related": [ "vibration-test", "iso-12405", "transport-regulations", "un-r100-part-2" ], "example": { "title": "Integrate a flat vibration band", "text": "An illustrative one-sided acceleration PSD of 0.01 g²/Hz from 10 to 110 Hz has area 1 g² and therefore 1 g RMS. A peak PSD value alone does not determine RMS without the bandwidth." }, "url": "https://lemonergy.com/learn/glossary/power-spectral-density/", "mentions": [ "sae-j2380" ] } }, "edges": [ { "id": "edge:5450", "source": "term:power-spectral-density", "target": "topic:topic-testing", "type": "belongsTo", "properties": { "sourceFile": "terms.json" } }, { "id": "edge:5451", "source": "term:power-spectral-density", "target": "term:vibration-test", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:5452", "source": "term:power-spectral-density", "target": "term:iso-12405", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:5453", "source": "term:power-spectral-density", "target": "term:transport-regulations", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:5454", "source": "term:power-spectral-density", "target": "term:un-r100-part-2", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:mentions/power-spectral-density/sae-j2380", "source": "term:power-spectral-density", "target": "term:sae-j2380", "type": "mentions", "properties": { "sourceFile": "terms.json", "method": "build_glossary.mention_index + mentions", "field": "definition", "meaning": "Text mention; not a causal claim" } }, { "id": "edge:5456", "source": "term:power-spectral-density", "target": "visual:vibration-spectrum", "type": "illustratedBy", "properties": { "sourceFile": "visual-pages.json" } } ], "neighbors": [ { "id": "topic:topic-testing", "type": "Topic", "label": "Testing methods", "properties": { "id": "topic-testing", "name": "Testing methods", "lede": "The measurements and test procedures that characterise a cell or pack, from capacity and pulse tests to abuse and environmental tests.", "context": "Record specimen, state, instrument, temperature and timing.", "example": "Resistance immediately after a current step can differ from a ten-second value because slower polarization contributes.", "lesson_url": "https://lemonergy.com/learn/fundamentals/capacity-and-c-rate/", "lesson_label": "Open capacity measurements" } }, { "id": "term:vibration-test", "type": "Term", "label": "Vibration and shock test", "properties": { "id": "vibration-test", "name": "Vibration and shock test", "section": "topic-testing", "definition": "Shaking a cell or pack on a vibration table to a profile standing for years of road use, and striking it with defined mechanical shocks, then checking for loose connections, leaks and loss of isolation. UN 38.3, R100 and ISO 12405 each specify a profile.", "related": [ "transport-regulations", "un-r100-part-2", "iso-12405", "abuse-testing", "thermal-shock-test", "power-spectral-density" ], "url": "https://lemonergy.com/learn/glossary/vibration-test/", "mentions": [ "un-r100" ] } }, { "id": "term:iso-12405", "type": "Term", "label": "ISO 12405", "properties": { "id": "iso-12405", "name": "ISO 12405", "section": "topic-standards-vehicle", "definition": "The international standard for testing lithium-ion battery packs and systems in electric vehicles, covering performance, reliability and abuse at pack level. Part 4 is the current performance specification.", "related": [ "iec-62660", "pack", "testing", "un-r100", "iso-6469" ], "url": "https://lemonergy.com/learn/glossary/iso-12405/", "mentions": [ "lithium-ion" ] } }, { "id": "term:transport-regulations", "type": "Term", "label": "UN 38.3", "properties": { "id": "transport-regulations", "name": "UN 38.3", "aka": [ "UN transport test", "lithium battery shipping" ], "section": "topic-standards-vehicle", "definition": "The United Nations test sequence that every lithium cell and battery must pass before it can be shipped: altitude, thermal cycling, vibration, shock, external short, impact or crush, overcharge and forced discharge. Air shipment of cells also caps state of charge at 30 %.", "related": [ "shipping-soc", "abuse-testing", "iec-62133", "altitude-simulation-test" ], "url": "https://lemonergy.com/learn/glossary/transport-regulations/", "mentions": [ "overcharge", "state-of-charge" ] } }, { "id": "term:un-r100-part-2", "type": "Term", "label": "R100 Part II", "properties": { "id": "un-r100-part-2", "name": "R100 Part II", "aka": [ "REESS tests", "R100 Annex 8" ], "section": "topic-standards-vehicle", "definition": "The part of UN R100 that tests the battery system as a unit: vibration, thermal shock and cycling, mechanical shock and crash impact, fire resistance, external short circuit, overcharge and over-discharge protection, over-temperature protection and, from the 03 series, thermal propagation. Each test ends with a check that there is no fire, explosion, electrolyte leakage or loss of isolation.", "related": [ "un-r100", "un-r100-03", "abuse-testing", "propagation-test", "insulation-resistance" ], "url": "https://lemonergy.com/learn/glossary/un-r100-part-2/", "mentions": [ "electrolyte", "overcharge", "over-discharge", "thermal-propagation", "external-short-circuit", "short-circuit" ] } }, { "id": "term:sae-j2380", "type": "Term", "label": "SAE J2380", "properties": { "id": "sae-j2380", "name": "SAE J2380", "section": "topic-standards-vehicle", "definition": "SAE’s procedure for vibration-durability testing of an electric-vehicle battery module or pack, usually on several samples. For large batteries — typically over 200 kg and part of the vehicle structure — it recommends a profile derived from measurements on the actual vehicle. Crash, pothole and abuse shocks are left to SAE J2464.", "related": [ "vibration-test", "sae-j2464", "pack", "module", "sae-j1797" ], "url": "https://lemonergy.com/learn/glossary/sae-j2380/", "mentions": [] } }, { "id": "visual:vibration-spectrum", "type": "Visual", "label": "Area under PSD determines RMS acceleration", "properties": { "title": "Area under PSD determines RMS acceleration", "summary": "A flat illustrative vibration band makes the integral easy to inspect.", "readout": "Band width is 180 Hz. Variance = 1.8 g²; RMS acceleration = 1.342 g.", "formula": "g_rms = √∫ PSD(f) df", "note": "One-sided rectangular teaching spectrum. No resonances, random time history or standard-specific profile is generated.", "software": { "status": "reference", "label": "Reference concept", "body": "This illustrates a spectral-density definition. It does not reproduce a transport-test standard, compute structural response or establish qualification.", "href": "../chapter-1/" }, "html": "
Authored one-sided acceleration PSD
Authored one-sided acceleration PSDFrequency (Hz) versus PSD (g²/Hz). 20–200 Hz flat band. Interpretation follows the graphs.000.00362.50.0061250.0091880.012250Frequency (Hz)PSD (g²/Hz)
20–200 Hz flat band
" } } ] }