Design Verification Report DVR-001 Rev. A

The full technical report, as HTML: mechanism and governing inequalities, the ten-method capability matrix, the modelled DIN 25201-4 Annex B series at F_V = 70,0 kN and n = 12, stage 1 relaxation, thermal cycling, re-use and the costed verification programme. Every ISOKLAMP CFR figure in this report is model-predicted. The same content is available as a PDF download.

Status of this report. All ISOKLAMP CFR performance figures are model-predicted from closed-form bolted-joint mechanics (VDI 2230 Sheet 1) and finite-element analysis. No physical testing of ISOKLAMP hardware has been performed. Baseline figures for other locking methods are reconstructions calibrated against published data. Patent applications are in preparation; none has been filed. ISOKLAMP CFR is not certified to 3-A, EHEDG, NSF, ATEX, DNV or any other scheme.

§1 Scope

This report documents the design verification of ISOKLAMP CFR, a two-part preload-recovering washer occupying the envelope of an ISO 7089 or ISO 7093 plain washer. It covers the mechanism, the governing inequalities, the modelled performance case against nine incumbent securing methods, and the physical verification programme required to convert the modelled case into evidence.

§2 The two failure modes

A bolted joint loses clamp force by rotational self-loosening, in which the nut turns relative to the bolt, and by non-rotational relaxation, in which the stack gets shorter through embedment, coating creep, gasket relaxation and thermal ratcheting while the nut does not move. Published measurements put non-rotational losses at 10 to 40 % of preload within 200 load cycles, with no measurable nut rotation (Jiang, Zhang & Lee, ASME J. Mech. Des. 125(3), 2003), and 41 % in a single 20 → 120 °C thermal cycle with nut rotation of order 5 × 10⁻⁴ degrees (Eraliev et al., Adv. Mech. Eng. 13(8), 2021).

Every locking device on the market addresses the first mode only. Non-rotational preload loss →

§3 Capability matrix

Ten methods, assessed on rotation arrest and relaxation recovery. The full matrix is reproduced on the locking methods compared page.

Capability summary, §3. ISOKLAMP CFR figures are model-predicted; baselines are calibrated reconstructions.
Method	Stops rotation	Recovers preload	Residual at N = 2 000
Unsecured plain washer	No	No	0,0 %
Split spring washer	No	No	0,0 %
Nylon-insert nut	Partly	No	4,0 % ± 3,1
Double nut	Partly	No	23,4 % ± 14,0
Serrated flange nut	Partly	No	48,6 % ± 9,2
Anaerobic threadlocker	Yes	No	62,3 % ± 18,0
All-metal locknut	Yes	No	71,8 % ± 6,4
Thread-form nut	Yes	No	85,3 % ± 4,1
Wedge-locking washer pair	Yes	No	92,1 % ± 1,4
ISOKLAMP CFR	Yes	Yes	99,4 % ± 0,6

§4 Mechanism and governing inequalities

Two coaxial hardened rings share a multi-start helical ramp of lead angle α_c = 4,5°. A pre-wound constant-torque spiral biases the drive ring up that ramp.

(1) α_c > α_t → 4,50° > 2,48° (M16 × 2,0)
(2) tan α_c < µ_r → 0,079 < 0,11–0,16
(4) Δh = r_m · θ · tan α_c
(5) ΔF_V = Δh · (1/δ_S + 1/δ_P)⁻¹
(6) θ_max = h_reserve / (r_m · tan α_c)

Inequality (1) arrests rotational loosening; inequality (2) makes the axial take-up one-way, so each recovered increment of stack height is latched. Mechanism in detail →

Ramp geometry: 4,5 degree ramp lead angle against 2,48 degree thread lead angle — Figure 13 — ramp geometry.

Half-section of the assembled ISOKLAMP CFR washer — Figure 12 — half-section, assembled.

§5 Modelled Junker series

DIN 25201-4:2010-03 Annex B, M16 × 2,0 cl. 10.9, F_V = 70,0 kN, t_s = ±0,60 mm, f = 12,5 Hz, N = 2 000, n = 12 per configuration. Pass criterion clause B.6: more than 80 % residual with a gradient that does not indicate subsequent complete loss.

Master Junker curve for ten securing methods — Figure 1 — model-predicted, n = 12.

Recovery signature showing clamp force stepping back up after each disturbance — Figure 3 — recovery signature, model-predicted.

§6 Stage 1 relaxation

Residual clamp force against imposed stack shortening. At 150 µm the rigid stack is at 0,0 %, the Belleville stack at 68,7 % and ISOKLAMP CFR at 97,0 %, model-predicted.

§7 Thermal cycling

Preload retention over thermal cycles between 20 and 120 °C. Model-predicted; baselines calibrated to Eraliev et al., Adv. Mech. Eng. 13(8), 2021. n = 5.
Thermal cycle	Plain washer	Wedge-locking pair	Belleville stack	ISOKLAMP CFR
1	85,0 %	86,8 %	94,5 %	98,9 %
5	66,7 %	69,3 %	84,4 %	97,1 %
10	56,9 %	59,9 %	78,3 %	95,9 %
20	51,3 %	54,5 %	74,4 %	95,1 %

§8 Stiffness and load factor

Table 3 — load factor Φ by configuration. ISOKLAMP figure is model-predicted.
Configuration	Compliant direction	Load factor Φ
Rigid stack	None	0,21
Belleville stack	Both, permanently	0,82
ISOKLAMP CFR	One, then latched	0,27

§9 Verification programme

The programme required to convert this modelled case into evidence: an accredited DIN 25201-4 Annex B series against competitor articles bought on the open market; a thermal-cycling series to the Eraliev protocol; a long-duration relaxation series on representative gasketed and composite stacks; ramp-friction drift after environmental exposure; and indicator legibility after UV, caustic and wash-down ageing. Results will be published in full, whichever way they go.

§10 Principal technical risk

Ramp-friction drift after long exposure. The one-way latch depends on tan α_c < µ_r; if µ_r falls below 0,079 in service — through lubricant ingress, wear polishing or fretting products — the take-up ceases to be one-way. This is the single biggest open question in the design and it is why the exposure series exists.