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An abrupt bond failure can produce a short force peak that is not represented by the highest value in a slowly recorded trace. The opposite problem is also possible: noise or mechanical ringing can create a high sample unrelated to the intended failure force. Peak qualification therefore covers the complete force-measurement chain, from sensor response through filtering and acquisition to the number stored in the result file.
Measurement purpose
Establish whether a reported short-event pull peak is supported by the force-channel response, sample timing and data-processing path.
Specimens and conditions
- Physical event
- Defined failure or proof-load event and the observation used to locate it in time
- Matched comparison
- Controlled specimen, grip and loading conditions when acquisition settings are compared
Equipment and records required
- Force acquisition: Known sensor/conditioning response, actual rate, filters and overload behaviour
- Capture verification: Suitable electrical and mechanical checks with explicit portions of the chain exercised
Method sequence
- Path review
Identify where the reported peak is calculated
Record: Sensor-to-result acquisition map
- Dynamic challenge
Evaluate event-duration, bandwidth and phase sensitivity
Record: Qualified capture conditions and limitations
- Result retention
Preserve the event waveform and export relationship
Record: Traceable peak with physical failure classification
Decision and uncertainty
Accept a peak only when the relevant event is captured and the reported number can be traced through a suitable measurement path; missed or clipped peaks remain unresolved.
Bandwidth, phase, noise, resonance, triggering and data reduction can affect peaks in different directions.
The mechanical-test method owner defines the event and rate; the measurement owner approves acquisition and capture verification.
Traceable outputs
| Record | Required contents |
|---|---|
| Acquisition qualification | Response, timing, filters, algorithms and dynamic checks |
| Specimen result | Qualified peak, event segment, failure observations and anomaly disposition |
Method review decisions
- Identify whether the reported peak comes from raw acquisition, filtered data or a separate peak-hold path.
- Test bandwidth and sample timing as different limitations.
- Retain a force-time segment that can distinguish a specimen event from noise or ringing.
Define which event and which signal establish the peak
State whether the test reports the maximum applied force before the first qualifying failure, a proof-load value or another defined event. A transient after a wire snaps may belong to release dynamics rather than the force that initiated failure. Retain the event timing and the physical observation needed to establish that distinction.
Identify the data channel used by the result calculation. A display refreshed several times per second can show a peak calculated internally from faster data, while an exported file may contain only reduced samples. Conversely, a smooth displayed trace can be interpolated without containing an independently measured value at its drawn maximum.
Trace bandwidth separately from numerical sample rate
The force sensor, mechanical attachment, amplifier and filters all influence the transient presented to the digitizer. A low-bandwidth stage can attenuate a short peak before sampling begins. Recording that attenuated signal more frequently does not restore the original force waveform.
An excessively wide measurement path can retain unwanted noise or resonant responses that contaminate a maximum-value statistic. Select and validate the bandwidth for the relevant force event rather than choosing the highest available setting automatically. Preserve filter type and settings with the data, including any filtering performed after acquisition.
Check the peak location between recorded samples
Even an otherwise ideal sampler observes only particular instants. If the true maximum falls between them, the largest recorded sample may be lower. The effect depends on the waveform shape, sample interval and relative timing; total test duration does not determine the duration of its sharpest meaningful event.
A two-millisecond pulse can lie entirely between samples separated by five milliseconds. Its absence from that record would not prove that it never occurred. Increasing the overall test record length adds more time outside the pulse but does not repair the local timing gap.
Use a bounded waveform example to estimate sampling sensitivity
Assume an ideal triangular force pulse with a ten-newton maximum and four-millisecond total base width. Its force rises linearly for two milliseconds and falls linearly for two milliseconds. For uniformly spaced ideal samples one millisecond apart, the maximum can lie halfway between samples, leaving the nearest sample 0.5 millisecond from the peak.
The corresponding worst-phase largest sample is 7.5 newtons. With 0.1-millisecond sample spacing it becomes 9.75 newtons under the same assumed triangle. These figures isolate sampling phase only; they do not include bandwidth, noise, ringing or the actual shape of a bond-pull event and are not universal acquisition-rate requirements.
Fsample,min = Fpeak (1 − Δt/T), for 0 ≤ Δt ≤ T
- T is the total base duration of a symmetric ideal triangular pulse.
- Δt is uniform sample spacing; the nearest sample can be Δt/2 from the maximum.
- Fsample,min is the worst relative-phase maximum among ideal samples spanning the pulse.
A fully captured symmetric triangle, ideal instantaneous samples, no analog filtering or noise, and zero baseline. The model demonstrates phase sensitivity, not an actual test waveform.
Verify peak hold, decimation and export independently
Determine whether a peak-hold value is captured before or after the filter used for the stored trace. If its measurement path differs, preserve enough evidence to validate that path and associate the peak with the same specimen event. A single number above every exported sample is not automatically wrong, but its origin must be explained.
Reducing a trace by keeping every tenth point can discard a short event. A min-max envelope preserves extrema over blocks but does not preserve every waveform detail or exact timing. Keep the original qualified acquisition where required and document the reduction used for charts or long-term storage.
| Observed discrepancy | Possible reason | Required investigation |
|---|---|---|
| Higher internal peak than exported maximum | Different acquisition or reduction paths | Trace result calculation and export rules |
| Peak rises when bandwidth is widened | Recovered event detail or added noise | Compare waveform and physical event evidence |
| Peak changes with sample timing | Inadequate temporal representation | Challenge phase sensitivity and acquisition settings |
| Large spike occurs after physical separation | Release dynamics or electrical interference | Align force history with the defined failure event |
| Repeated display looks smooth but sparse raw points remain | Display interpolation | Inspect original sample timing and reconstruction assumptions |
| Flat top at instrument range limit | Clipping or overload | Treat the true peak as unresolved and review the method |
Challenge the measurement chain without confusing electrical and mechanical checks
A controlled electrical signal can check amplifier, acquisition and software behaviour but may bypass the force sensor and mechanical path. A mechanical dynamic check exercises additional terms, yet needs its own suitable reference and safe implementation. State exactly which portion of the chain each verification addresses.
Compare relevant event durations and amplitudes across permitted settings using an authorized method. A static calibration supports the force scale under its stated conditions, not every transient response. Keep the reference uncertainty and timing information so a claimed capture error has a defensible basis.
Preserve specimen comparability while improving acquisition
Do not slow a mechanical test solely to fit a weak acquisition system without considering the test requirement and material rate sensitivity. A changed loading rate can change the physical failure response, so the resulting peak may no longer represent the intended comparison. Improve or select the measurement chain appropriately for the authorized test.
When comparing old and new acquisition settings, retain matched specimen construction, grip geometry, load rate and failure classification. A change in mean peak alone cannot distinguish improved capture from a different specimen population. Where the original record missed the event, do not claim that a later software calculation has recovered an exact historical force.
Release the peak with its event and acquisition evidence
The result package should identify force-channel configuration, actual sample interval, filters, record window, peak algorithm and export processing. Retain a relevant pre-event and post-event segment, including overload or anomalous observations. Link the force record to the inspected failure location rather than treating the peak as an independent material property.
ChipSimple can review bond and pad requirements within a project-specific mechanical test plan. The useful output is a force value captured by a suitable, documented chain and associated with a defined physical event. It is not merely the largest number that one display or file happened to contain.
Specify the pull-event capture requirement
Provide the force event and result path as well as the nominal test load.
- Bond or terminal construction and failure endpoint
- Expected event duration evidence and loading rate
- Sensor, conditioner and acquisition configuration
- Raw traces, internal peak and exported result examples
- Peak algorithm, trigger window and dynamic-check records
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