Motion Posture and Kinematics of Cylindrical Tubes Under Sliding Detonation in Explosion Welding

1. Definition and Fundamental Principles

1.1 Sliding Detonation Phenomenon

Sliding detonation (also referred to as sliding-mode detonation or oblique detonation) is a distinct regime observed during explosion welding of cylindrical or tubular components. Unlike the classical normal-impact explosion welding mode—where the flyer plate strikes the base plate at a controlled collision angle (typically 10°–25°)—sliding detonation occurs when the detonation front propagates along the interface between the flyer and base material at a velocity exceeding the local Chapman-Jouguet (C-J) detonation velocity. In this regime, the flyer material does not undergo direct normal impact; instead, it is driven tangentially along the base surface by the expanding detonation gases, producing a high-velocity sliding motion that generates plastic instabilities at the interface.

The motion posture of a cylindrical tube during sliding detonation refers to the complete kinematic description of the tube's orientation, velocity vector, angular displacement, and deformation state as the detonation wave propagates around or along its circumference. This includes:

• Translational velocity — the linear speed of the tube center of mass
• Angular velocity — rotational motion about the tube axis or transverse axes
• Impact angle evolution — how the local collision angle between the tube outer surface and base material changes as the detonation front advances
• Radial and axial displacement — deformation of the tube geometry under explosive loading

1.2 Physical Mechanism

The fundamental mechanism governing tube motion under sliding detonation can be described by the following sequence:

1. Detonation initiation — A shaped charge or initiation device detonates at one end of the assembly, generating a high-pressure gas jet that accelerates the cylindrical tube toward the base material.
2. Initial impact and transition — The tube contacts the base plate at a designed impact angle. If the impact velocity exceeds a critical threshold (typically >400 m/s for steel-on-steel systems), the interface undergoes rapid plastic deformation.
3. Sliding regime establishment — The detonation front transitions from a normal impact mode to a sliding mode. The detonation gases exert a predominantly tangential force on the tube, pushing it along the base surface at supersonic velocities relative to the material sound speed.
4. Wave interaction — The sliding detonation generates complex wave systems including reflected shear waves, transmitted longitudinal waves, and Mach reflections within both the flyer and base materials.
5. Interface bonding — At the critical conditions, the sliding motion produces a periodic instability (Kelvin-Helmholtz type) at the interface, ejecting oxide films and creating fresh metal-to-metal contact under high pressure, resulting in metallurgical bonding.

2. Category and Business Positioning

2.1 Technical Knowledge Classification

This technical entry falls under the category of fundamental process physics and kinematic modeling within the explosion welding technology domain. It represents a critical knowledge asset that bridges theoretical detonation physics with practical manufacturing execution. The study of tube motion posture under sliding detonation is classified as a process development and qualification enabler—it does not directly produce a product but provides the analytical foundation upon which reliable, repeatable explosion welding of tubular components is built.

2.2 Positioning Within Cladding Technology Shanxi Co., Ltd. Capability Framework

The company operates three primary technology routes: TIG/MIG weld overlay, hydraulic explosive bonding, and explosion welding. This technical knowledge asset is specifically positioned within the explosion welding route, serving as the theoretical backbone for:

• Design of explosion welding assemblies for pipes and tubes
• Prediction and control of weld quality across different tube diameters and wall thicknesses
• Qualification of new material combinations for explosion-welded tubing
• Troubleshooting of bonding defects in cylindrical geometries

3. Technical Purpose and Value

3.1 Engineering Purpose

The primary engineering purpose of understanding tube motion posture under sliding detonation is to predict and control the local collision conditions at every point along the tube circumference. Since explosion welding quality is directly determined by local impact velocity, impact angle, and interface pressure, accurate knowledge of the tube's kinematic state during detonation is essential for ensuring uniform bonding quality around the entire circumference of a welded tube.

3.2 Quantitative Value to Operations

This knowledge delivers measurable operational value through:

• Reduced scrap rates — By predicting where bonding failures will occur before the shot is fired, process parameters can be adjusted proactively rather than reactively after inspection reveals defects.
• Faster qualification cycles — Analytical models of tube motion reduce the number of trial shots required to qualify a new material combination or geometry, saving significant material and facility time.
• Extended parameter windows — Understanding the kinematics allows engineers to push the boundaries of achievable tube sizes, wall thicknesses, and material combinations with confidence.
• Customer confidence — Documented process understanding supports WPS qualification packages and provides technical substantiation for customer audits and regulatory submissions.

4. Key Process and Implementation Points

4.1 Critical Kinematic Parameters

The following parameters must be characterized and controlled for reliable explosion welding of cylindrical tubes in the sliding detonation regime:

Parameter	Symbol	Typical Range (Steel/Steel)	Measurement Method	Criticality
Tube impact velocity	Vimp	400–700 m/s	High-speed photography, strain gauges	Critical
Design impact angle	α	10°–25°	Geometric design calculation	Critical
Sliding detonation velocity	Vsd	2,000–4,000 m/s	Particle velocity interferometry	High
Local collision velocity	Vc	150–400 m/s	Computational modeling (SPH/FEA)	Critical
Interface pressure	Pinterface	10–30 GPa	Computational modeling	High
Tube angular velocity	ω	Variable (geometry-dependent)	High-speed imaging analysis	Medium
Gap clearance (initial)	g	5–15 mm (for tubes)	Precision assembly measurement	High
Charge-to-flyer mass ratio	λ	0.10–0.30	Charge design calculation	Critical

4.2 Kinematic Modeling Approach

The motion posture of a cylindrical tube during sliding detonation is typically analyzed using a multi-physics computational framework. The implementation follows these steps:

1. Geometric setup — Define the tube outer diameter (OD), inner diameter (ID), wall thickness (t), length (L), and the base plate geometry. Account for initial gap clearance between tube outer surface and base plate.
2. Material property definition — Input elastic-plastic constitutive models (Johnson-Cook, Cowper-Symonds, or similar hydrodynamic equations of state) for both tube and base materials, including density, yield strength, strain rate sensitivity, and sound speed.
3. Detonation loading model — Represent the detonation pressure profile as a function of distance and time. For sliding detonation, apply a moving load that travels along the tube axis or circumference at the sliding detonation velocity.
4. Boundary and contact conditions — Define the tube-base contact interface with appropriate friction and bonding criteria. The bonding criterion typically requires local collision velocity above a threshold (material-specific, often 150–250 m/s for steel systems).
5. Simulation execution — Run the coupled detonation-structural analysis using software such as AUTODYN, LS-DYNA, or Abaqus Explicit. Extract the tube's translational and rotational kinematics as functions of time.
6. Post-processing — Map the local collision velocity and angle distributions around the tube circumference and along its length to identify potential bonding failure zones.

4.3 Geometric Configuration Analysis

The kinematic behavior of a cylindrical tube differs fundamentally depending on the assembly configuration. Three primary configurations are encountered in industrial practice:

Configuration	Description	Sliding Direction	Key Kinematic Challenge	Typical Application
Tube-on-plate (axial)	Cylindrical tube placed axially on a flat base plate	Along tube axis	Uniformity of impact angle around circumference	Explosion-welded pipe ends, tube-to-plate joints
Tube-on-tube (coaxial)	Smaller tube inserted inside or placed outside a larger tube	Around circumference	Non-uniform gap, eccentricity sensitivity	Bimetallic pipe fabrication
Tube-on-plate (radial)	Tube placed radially against a flat or curved base	Around tube circumference	Variable collision angle with tube curvature	Clad pipe manufacturing

4.4 Influence of Tube Geometry on Motion Posture

Several geometric factors significantly influence the tube's motion posture during sliding detonation:

• Diameter-to-length ratio (D/L) — Tubes with low D/L ratios (long, slender tubes) tend to exhibit greater angular deviation during detonation, leading to non-uniform impact angles along the tube length. Tubes with high D/L ratios (short, stubby tubes) maintain more predictable kinematics but may experience higher radial deformation.
• Wall thickness ratio (t/D) — Thin-walled tubes (t/D < 0.05) are susceptible to excessive radial collapse under detonation loading, which can alter the local impact angle and reduce collision velocity below the bonding threshold. Thick-walled tubes (t/D > 0.15) maintain geometry better but require more charge mass and exhibit higher angular momentum during sliding.
• Eccentricity — Any deviation from concentric alignment between tube and base creates asymmetric loading. Even 1–2 mm eccentricity in large-diameter tubes can produce significant variation in local impact conditions around the circumference.
• Tube end condition — Open-ended tubes experience different internal pressure dynamics than closed-ended tubes during detonation, affecting the radial component of motion.

5. Applicable Standards and Acceptance Criteria

5.1 Design and Process Standards

The following standards provide the framework for explosion welding process design and qualification, within which the understanding of tube motion posture under sliding detonation provides the technical justification:

• ASTM A419 — Standard Specification for Exploded-Welded Steel Clad Plate (provides the acceptance framework for bonded area percentage and bond quality)
• ASTM A514 — Standard Specification for Exploded-Welded Steel Clad Plate, Pipe, and Tube (specifically addresses tubular geometries)
• NB/T 20805 — Technical Specification for Exploded-Welded Steel Clad Plate (Chinese nuclear industry standard)
• GB/T 21095 — Technical Requirements for Exploded-Welded Clad Steel Plates and Pipes
• ASME BPV Section III, Appendix Q — Qualification requirements for explosion welding in nuclear pressure vessel applications
• ISO 14224 — Non-destructive testing methods for explosion welding (provides NDT methodology reference)
• NACE MR0175/ISO 15156 — Materials for use in H₂S-containing environments (material selection constraint for explosion-welded tubing in oil and gas)

5.2 Bond Quality Acceptance Criteria

The ultimate acceptance criteria for explosion-welded tubes, which the motion posture analysis helps ensure, include:

Acceptance Criterion	Requirement	Verification Method	Standard Reference
Minimum bonded area	≥95% of nominal interface area	Macrographic examination of cross-sections	ASTM A419 / ASTM A514
Bond quality (no defects)	No cracks, voids, or delamination at interface	MT/PT/UT inspection of interface	ASME BPV Section III, Appendix Q
Shear bond strength	Exceed base material shear strength (minimum 200 MPa typical)	Shear coupon testing	ASTM A419
Transverse weld strength	Exceed specified minimum (material-dependent)	Tensile transverse coupon testing	ASTM A514
Hardness profile	No excessive hardening beyond 350 HV in base material near interface	Microhardness traverse	Company WPS / Customer specification

5.3 Kinematic Acceptance Parameters for Process Qualification

While standards do not directly specify kinematic parameters, the following internal qualification parameters are derived from motion posture analysis and serve as process control indicators:

• Minimum local collision velocity at all interface points: ≥150 m/s (steel-on-steel), ≥100 m/s (dissimilar metal systems)
• Maximum local collision velocity at all interface points: ≤800 m/s (to prevent spatter and excessive dilution)
• Uniformity of collision velocity around circumference: variation ≤±20% of mean value
• Predicted bonded area percentage: ≥97% (internal target exceeding standard minimum of 95%)

6. Common Risks and Controls

6.1 Kinematic Risks Specific to Sliding Detonation of Tubes

Risk	Cause	Consequence	Control Measure
Non-uniform bonding around circumference	Eccentricity, asymmetric charge, tube rotation during detonation	Partial bonding failure at specific angular positions	Precision assembly fixtures with concentricity ≤0.5 mm; symmetric charge arrangement
Insufficient collision velocity	Excessive tube mass, inadequate charge mass, large initial gap	Complete bonding failure; tube rebounds without bonding	Charge-to-flyer mass ratio optimization; gap clearance verification; velocity prediction via computational model
Excessive collision velocity	Over-designed charge, insufficient tube mass, small gap	Material spatter, interface melting, dilution zone formation	Maximum velocity limit enforcement; charge mass upper bound calculation
Tube radial collapse	Thin wall thickness, high detonation pressure, low D/t ratio	Altered local impact geometry; reduced collision velocity	Minimum wall thickness requirement; reinforcement rings; computational pre-analysis
Tube axial displacement (slip)	Insufficient axial restraint, asymmetric detonation initiation	Non-uniform impact angle along tube length; localized bonding failure	Axial clamping fixtures; detonation initiation at geometric center; restraint design analysis
Angular deviation (tube rotation)	Asymmetric loading, tube-end effects, charge asymmetry	Variable collision angle along circumference and length	Symmetric charge geometry; kinematic simulation pre-check; angular restraint devices
Detonation front instability	Cellular detonation structure in charge material, geometry effects	Fluctuating interface pressure; inconsistent bonding quality	Charge material selection and quality control; detonation velocity characterization

6.2 Risk Mitigation Through Kinematic Understanding

The study of tube motion posture under sliding detonation directly enables proactive risk mitigation through the following mechanisms:

1. Predictive modeling — Before any physical trial shot, computational models predict the complete kinematic trajectory of the tube, identifying potential failure zones in advance.
2. Design optimization — Geometric parameters (gap, charge mass, tube dimensions) are iteratively optimized in simulation to achieve uniform collision conditions across the entire tube surface.
3. Failure mode analysis — When bonding defects are observed, the kinematic model is used to back-calculate the actual impact conditions and identify the root cause (e.g., insufficient velocity at 3 o'clock position due to eccentricity).
4. Process window definition — Systematic variation of input parameters in simulation establishes the allowable ranges for each parameter, defining the robust process window for production.

7. Application Across the Company's Three Technology Routes

7.1 Primary Application: Explosion Welding

This technical knowledge is most directly applicable to the company's explosion welding operations. Specific applications include:

• Bimetallic pipe fabrication — Designing explosion welding assemblies for clad pipes where a carbon steel tube is bonded to a stainless steel or nickel-alloy tube using sliding detonation. The kinematic model ensures uniform bonding around the entire circumference and along the full pipe length.
• Tube-to-plate explosion welding — Joining process tubes to heat exchanger plates or pressure vessel heads using explosion welding. Understanding tube motion posture is critical for achieving reliable bonding at the tube-to-plate interface.
• Multi-layer tube welding — Sequential explosion welding of multiple tube layers (e.g., carbon steel + 304L transition + 6Mo overlay) where each layer's kinematics must be independently characterized.
• Large-diameter tube explosion welding — For tubes exceeding 500 mm OD, the kinematic complexity increases significantly due to charge asymmetry effects and tube deformation, making motion posture analysis essential.

7.2 Secondary Application: Hydraulic Explosive Bonding

While hydraulic explosive bonding primarily involves flat plate configurations, the principles of detonation-driven material motion are shared. The knowledge of tube kinematics contributes to hydraulic explosive bonding in the following ways:

• Curved plate bonding — When bonding curved sheets (preformed to cylindrical shape for subsequent tube fabrication), the kinematic understanding of curved flyer behavior under detonation is directly transferable.
• Water-coupled detonation effects — The hydraulic medium modifies the loading profile compared to air-coupled explosion welding. Understanding how the detonation-driven motion of curved geometries changes in the presence of a water medium extends the kinematic knowledge base.
• Process parameter correlation — Kinematic models developed for air-coupled tube explosion welding provide a baseline against which hydraulic coupling modifications can be quantified.

7.3 Indirect Application: TIG/MIG Weld Overlay

The connection to TIG/MIG weld overlay technology is indirect but valuable:

• Weld overlay on explosion-welded tubes — When a transition layer or additional overlay is deposited by TIG/MIG welding onto an explosion-welded tube, understanding the explosion welding interface quality (which depends on kinematic control) is essential for predicting residual stress states and crack susceptibility in the subsequent weld overlay.
• Hybrid process design — In composite processes combining explosion welding with weld overlay (explosion-welded base + TIG overlay transition), the kinematic quality of the explosion weld determines the starting condition for the weld overlay, affecting dilution, residual stress, and final mechanical properties.
• Defect prevention — Understanding where explosion welding bonding quality may be marginal (based on kinematic analysis) allows targeted weld overlay reinforcement at those locations.

8. Contribution to Qualification Building, Product Delivery, and Customer Value

8.1 Qualification Building

The technical knowledge of tube motion posture under sliding detonation directly strengthens the company's qualification capabilities:

• WPS development — Welding Procedure Specifications for explosion welding of tubes require documented justification for all parameters. Kinematic analysis provides the technical basis for selecting impact angle, charge mass, gap clearance, and tube geometry within each WPS.
• PQR substantiation — Performance Qualification Records benefit from pre-shot kinematic predictions that can be compared against post-shot inspection results, demonstrating process understanding and control.
• New material system qualification — When qualifying a new material combination (e.g., 2205 duplex stainless steel tube on carbon steel base), the kinematic model can be adapted to predict bonding feasibility without extensive trial shots, accelerating the qualification timeline.
• Regulatory submissions — For nuclear (NB/T) and pressure vessel (ASME) applications, regulators require demonstrated process understanding. Documented kinematic analysis of tube motion posture provides the technical rigor expected in qualification packages.

8.2 Product Delivery Enhancement

This knowledge contributes to product delivery through:

• First-shot success rate improvement — By predicting kinematic conditions before the shot, the probability of achieving acceptable bonding on the first attempt increases, reducing production cycle time and cost.
• Scrap reduction — Early identification of potential bonding failure zones allows parameter adjustment before production shots, minimizing material waste.
• Size and geometry flexibility — Understanding how tube geometry affects kinematics enables the company to accept a wider range of customer tube specifications (diameter, wall thickness, length) with confidence.
• Quality consistency — Kinematic models provide a quantitative basis for setting process control limits, ensuring consistent quality across production batches.

8.3 Customer Value Creation

The technical depth represented by this knowledge asset translates to tangible customer value:

• Technical credibility — Customers in demanding industries (nuclear, oil and gas, chemical) value suppliers who demonstrate deep process understanding. The ability to explain and predict kinematic behavior during explosion welding builds trust and competitive differentiation.
• Risk reduction — Customers face significant consequences from bonding failure in service (leaks, corrosion, structural failure). Kinematic-based process control reduces this risk, providing customers with greater confidence in the delivered product.
• Design support — The company can offer customers early-stage design support, predicting whether a proposed tube geometry and material combination is feasible for explosion welding before the customer commits to procurement.
• Accelerated project timelines — Faster qualification and higher first-shot success rates translate to shorter project schedules, a direct value proposition for customers with time-critical projects.
• Cost optimization — Reduced scrap and fewer trial shots translate to lower delivered cost, providing customers with competitive pricing without compromising quality.

9. Implementation Recommendations

9.1 Immediate Actions

1. Document the kinematic analysis methodology — Formalize the computational modeling approach for tube motion posture into a standard operating procedure (SOP) for the company's explosion welding engineering team.
2. Establish a kinematic database — Compile all historical explosion welding shots with tubular components, recording input parameters (geometry, charge mass, gap) and output results (bonding quality, observed kinematic effects) to build a reference database for rapid future predictions.
3. Train the engineering team — Conduct internal technical training sessions covering the fundamentals of sliding detonation kinematics, ensuring all engineers involved in explosion welding process design understand the underlying physics.

9.2 Medium-Term Development

1. Develop a proprietary prediction tool — Create a user-friendly software tool that allows process engineers to input tube geometry and material parameters and receive predicted kinematic conditions and bonding feasibility assessment.
2. Validate models against experimental data — Conduct a series of instrumented trial shots with high-speed imaging and strain measurement to validate computational predictions and refine the kinematic models.
3. Extend to dissimilar metal systems — Adapt the kinematic analysis framework to cover dissimilar material combinations (steel/nickel, steel/titanium, steel/copper) where material-specific bonding thresholds and deformation behaviors must be accounted for.

9.3 Long-Term Strategic Value

1. Publish technical literature — Present findings at industry conferences and publish in technical journals to establish the company as a thought leader in explosion welding kinematics.
2. Pursue patent protection — Identify novel kinematic control methods or predictive algorithms that can be protected through intellectual property filings.
3. Develop customer-facing technical service — Offer kinematic analysis as a value-added service to customers during the design phase, differentiating the company from competitors who rely solely on trial-and-error approaches.

10. Conclusion

The study of metal cylindrical tube motion posture under sliding detonation represents a critical knowledge asset for Cladding Technology Shanxi Co., Ltd.'s explosion welding capabilities. This technical understanding bridges the gap between detonation physics and manufacturing execution, enabling predictive process design, reduced qualification cycles, improved first-shot success rates, and enhanced product quality consistency.

By systematically applying kinematic analysis to explosion welding of tubular components, the company can extend its service envelope to more challenging geometries and material combinations, reduce production costs through lower scrap rates, and provide customers with greater confidence in the reliability of explosion-welded products. This knowledge asset, while rooted in fundamental physics, delivers directly actionable value across the company's qualification, manufacturing, and customer relationship functions.

The investment in deepening and operationalizing this technical knowledge—through documentation, tool development, team training, and model validation—will compound in value as the company's explosion welding capabilities grow, providing a durable competitive advantage in the high-value bimetallic tube and pipe market.