Mechanical and Physical Testing

1. Introduction

Manufacturing quality control depends on reliable mechanical and physical measurements. Tensile strength, dimensional tolerance, surface finish, material hardness, and fastener torque are quantities that determine whether a part ships or gets scrapped. The instruments that produce these measurements -- universal test machines, coordinate measuring machines, profilometers, hardness testers, and torque sensors -- traditionally operate through vendor-specific software with no common programming interface.

S1 Foundry eliminates this fragmentation. Five handler libraries abstract the vendor protocols behind consistent .NET interfaces. A module layer (S1.Modules.MechanicalTest) unifies all five families under a single IHardwareModule contract with 11 message handlers. Twelve TestStand step types expose the full capability set as drag-and-drop sequence building blocks. The result is that test programs written against these abstractions are portable across 15 instruments from 15 vendors, and new equipment can be deployed without rewriting test logic.

This guide covers each measurement domain in depth: the physical principles, the workflow mechanics, the standards that govern them, and the practical details of integrating each instrument family through the S1 platform.

2. Universal Test Machine (UTM) Testing

Universal testing machines apply controlled force to a specimen and measure its response. The three primary test modes -- tensile, compression, and flexure -- characterize material strength, elasticity, and ductility. UTM testing is governed by ASTM E8/E8M (metals tensile), ASTM D638 (plastics tensile), ASTM E9 (compression), and ASTM D790 (flexure), among others.

Supported Platforms

Tensile Testing Workflow

A tensile test grips a specimen at both ends and pulls it apart at a controlled crosshead speed until fracture. The handler manages the full sequence:

1. Specimen setup -- Configure gauge length, specimen geometry (rectangular or round cross-section), and grip type. The handler sends dimension data to the UTM controller for real-time stress calculation.
2. Test configuration -- Set crosshead speed (mm/min), preload force, data acquisition rate, and termination criteria (maximum extension, force drop percentage, or absolute force limit).
3. Execution -- The RunTensileTestAsync method starts the crosshead and streams load-displacement data pairs at the configured sample rate. The handler buffers data locally for post-test analysis while the UTM controller records internally.
4. Break detection -- When specimen fracture occurs, the UTM controller detects the sudden load drop and halts the crosshead. The handler captures the break point and returns the final data set.
5. Result extraction -- Ultimate tensile strength (UTS), yield strength (0.2% offset method), elongation at break, reduction of area, and Young's modulus are calculated from the raw load-displacement curve.

Compression Testing

Compression tests apply a compressive force to a specimen between two platens. The handler supports both force-controlled and displacement-controlled modes. Specimen geometry configuration includes cylindrical and prismatic shapes with automatic Euler buckling detection for slender specimens. Compressive strength, yield point, and elastic modulus are extracted from the force-displacement curve.

Flexure Testing

Three-point and four-point bending tests measure flexural strength and modulus. The handler configures span length, loading nose radius, and support roller positions. For three-point bending per ASTM D790, the specimen rests on two supports and is loaded at the midpoint. Four-point bending distributes load across two inner loading points, creating a uniform bending moment in the central region. The handler calculates flexural stress at the outer fiber and flexural strain from crosshead displacement and specimen geometry.

Data Acquisition

All UTM handlers stream force, displacement, and time data at configurable rates up to 1 kHz. The data stream is available through the GetTestDataAsync method, which returns the complete load-displacement-time array after test completion. Real-time data is also accessible during the test through event callbacks for live graph updates.

3. Coordinate Measuring Machine (CMM) Inspection

Coordinate measuring machines determine the physical geometry of objects by probing discrete points on their surfaces. CMM inspection verifies dimensional accuracy against engineering drawings and GD&T (Geometric Dimensioning and Tolerancing) specifications per ASME Y14.5. S1 Foundry provides a unified CMM handler that supports three major CMM platforms and covers the full inspection workflow from part alignment through measurement execution and report generation.

Supported Platforms

Point Probing

The fundamental CMM operation is capturing a single point in 3D space. The handler provides ProbePointAsync, which commands the probe head to approach the specified nominal coordinates, touch the surface, and return the measured X, Y, Z position along with the probe deflection vector. Touch-trigger and scanning probe modes are both supported -- touch-trigger captures discrete points while scanning mode collects continuous point clouds along a defined path.

Multi-point measurements build on single-point probing. The handler accepts lists of nominal probe positions for circle fitting (minimum 3 points), plane fitting (minimum 3 points), cylinder fitting (minimum 5 points), and sphere fitting (minimum 4 points). Least-squares and minimum-zone fitting algorithms are applied to determine best-fit geometric features from the probed data.

Part Alignment

Before measurement begins, the part's physical position on the CMM table must be established relative to the part coordinate system defined in the CAD model or engineering drawing. The AlignPartAsync method executes a three-step alignment:

1. Level -- Probe a plane (typically the bottom face) to establish the primary datum. The handler fits a plane to the probed points and defines the Z-axis perpendicular to it.
2. Rotate -- Probe a line or cylinder along a datum feature to establish angular orientation. The fitted line direction defines the X-axis or Y-axis rotation.
3. Origin -- Probe a point or feature to set the coordinate system origin. This typically corresponds to a datum intersection point.

The alignment routine stores the resulting 4x4 transformation matrix, which maps machine coordinates to part coordinates for all subsequent measurements. Re-alignment is supported without restarting the inspection program -- the handler recalculates the transformation and applies it retroactively to pending features if requested.

GD&T Evaluation

GD&T tolerances per ASME Y14.5 (and ISO 1101 for international projects) define the acceptable variation of geometric features. The CMM handler evaluates the following GD&T characteristics from probed data:

• Flatness -- Maximum deviation of a plane from true flat, computed as the distance between two parallel planes that contain all probed points.
• Cylindricity -- Radial deviation of a cylindrical surface from a perfect cylinder, evaluated as the difference between the minimum circumscribed and maximum inscribed cylinders.
• Perpendicularity -- Angular deviation of a feature axis or surface from true perpendicular to a datum, projected onto a tolerance zone.
• Parallelism -- Deviation of a surface or axis from true parallel to a datum plane or axis.
• Concentricity -- Deviation of the center points of a feature from the axis of a datum feature.
• True position -- Combined deviation of a feature's actual position from its nominal position, expressed as a diameter tolerance zone (MMC, LMC, or RFS material conditions supported).
• Runout -- Total indicator reading (TIR) when a feature is rotated around a datum axis. Both circular runout and total runout are computed.
• Profile -- Deviation of a surface or line profile from the nominal shape, evaluated as a bilateral or unilateral tolerance zone around the CAD nominal.

Part Program Execution

The handler supports loading and executing saved part programs (measurement routines) stored on the CMM controller. The ExecuteProgramAsync method loads a program by name, runs all measurement steps, and returns the complete result set including feature dimensions, GD&T evaluations, and pass/fail dispositions. This enables fully automated inspection cycles where the S1 test sequence selects the appropriate part program based on the part number scanned at the station.

4. Surface Metrology

Surface finish directly affects part performance -- friction, wear, fatigue life, sealing capability, and appearance are all governed by the microgeometry of the machined surface. The S1 surface profiler handler controls contact-type stylus profilometers and optical (non-contact) interferometric profilers to capture surface topography data and extract standardized roughness and waviness parameters.

Supported Instruments

Roughness Parameters

The handler computes the following ISO 4287 / ISO 21920 roughness parameters from the acquired surface profile after applying the appropriate Gaussian filter to separate roughness from waviness:

Waviness Parameters

Waviness describes longer-wavelength surface deviations caused by machine tool vibration, workpiece deflection, or thermal distortion. The handler applies a configurable Gaussian cutoff filter (lambda-c, typically 0.8 mm for finishing operations) to separate the roughness profile from the waviness profile. Waviness parameters (Wa, Wq, Wt) are computed from the filtered waviness profile using the same mathematical definitions as their roughness counterparts.

Scan Configuration

The ConfigureScanAsync method accepts scan length, scan speed, stylus force (for contact profilometers), sampling interval, and filter cutoff wavelength. For optical profilers, the method additionally accepts objective magnification, measurement mode (PSI or VSI), and stitching parameters for large-area scans. After configuration, RunScanAsync captures the surface profile data and computes all requested parameters.

5. Hardness Testing

Hardness quantifies a material's resistance to localized plastic deformation. It is the single most commonly performed mechanical test in manufacturing quality control because it is fast, non-destructive (or minimally destructive), and correlates well with tensile strength. S1 Foundry supports four indentation hardness methods, each suited to different material types and thickness ranges.

Supported Instruments

Rockwell Hardness

Rockwell testing (ASTM E18, ISO 6508) measures hardness by the depth of penetration of an indenter under a defined load. The test applies a minor load (10 kgf) to seat the indenter, then a major load (60, 100, or 150 kgf depending on scale), then returns to the minor load. The permanent depth increase determines the hardness number. Common scales:

• HRC -- Diamond cone indenter, 150 kgf major load. Used for hardened steels, tool steels, and hard alloys (typically 20-70 HRC range).
• HRB -- 1/16" steel ball indenter, 100 kgf major load. Used for softer metals: brass, copper, annealed steel (typically 20-100 HRB range).
• HRA -- Diamond cone indenter, 60 kgf major load. Used for tungsten carbide, thin hardened steel, and cemented carbides.
• HR15N, HR30N, HR45N -- Superficial Rockwell scales with reduced loads for thin materials and case-hardened surfaces.

The handler's MeasureRockwellAsync method accepts the scale designation and returns the hardness value, the indentation depth in micrometers, and the test validity status based on the instrument's internal verification.

Vickers Hardness

Vickers testing (ASTM E384, ISO 6507) presses a square-based diamond pyramid indenter into the surface under loads from 10 gf (micro-Vickers) to 50 kgf (macro-Vickers). The hardness number is calculated from the mean diagonal length of the resulting square indentation measured optically. Vickers testing is scale-independent -- the same HV number is obtained regardless of load, provided the material is homogeneous and the indentation is large enough relative to the surface finish.

Micro-Vickers (loads below 1 kgf) is used for thin coatings, individual grains in metallographic specimens, and case depth measurement in carburized or nitrided parts. The handler supports automated traverses for hardness depth profiles -- a sequence of indentations at specified spacings from the surface into the core, producing the hardness gradient curve required by ASTM E384 Section 9 (effective case depth determination).

Brinell Hardness

Brinell testing (ASTM E10, ISO 6506) uses a tungsten carbide ball indenter (1, 2.5, 5, or 10 mm diameter) under loads from 1 to 3000 kgf. The hardness number is derived from the applied load divided by the curved surface area of the indentation. Brinell testing is preferred for coarse-grained or heterogeneous materials (castings, forgings, rough surfaces) where the large indentation averages out local variations.

The handler measures the indentation diameter optically from two perpendicular measurements, computes the mean diameter, and calculates HBW (tungsten carbide ball designation per current standards). Load and ball diameter combinations must satisfy the standard force/diameter-squared ratio for the material class being tested.

Knoop Hardness

Knoop testing (ASTM E384, ISO 4545) uses an elongated diamond pyramid indenter that produces an asymmetric indentation with a 7:1 length-to-width ratio. The shallow indentation depth makes Knoop testing suitable for thin coatings, brittle materials (ceramics, glass), and near-edge measurements where a Vickers indentation would crack the specimen. The hardness number is calculated from the long diagonal of the indentation.

Hardness Scale Conversion

The handler includes ASTM E140 hardness conversion tables for approximate conversion between Rockwell, Vickers, Brinell, and Knoop scales. Conversions are approximate because the different test methods measure fundamentally different material responses, but the ASTM E140 tables provide standardized conversion values for carbon and alloy steels that are widely accepted in industry.

6. Torque Measurement

Torque measurement verifies the rotational force applied to fasteners, shafts, actuators, and rotary assemblies. Proper torque control prevents joint failure (under-torque) and material damage (over-torque). S1 Foundry supports both static torque sensors (reaction-type, measuring torque on a stationary assembly) and rotary torque transducers (inline, measuring torque on a rotating shaft).

Supported Instruments

Peak Torque Measurement

The simplest torque measurement captures the maximum torque applied during a tightening or breakaway operation. The handler's MeasurePeakTorqueAsync method monitors the torque signal and records the peak value, the angle at peak (if an angle encoder is connected), and the timestamp. Peak torque is compared against upper and lower specification limits to produce a pass/fail result.

For fastener verification, the handler supports both tightening torque (monitoring during assembly) and breakaway/prevailing torque (measuring the torque required to initiate rotation of an already-tightened fastener). These are distinct test modes with different trigger and termination logic.

Angle-Torque Curve Analysis

For critical joints, peak torque alone is insufficient. Angle-torque curve analysis captures the complete relationship between applied torque and rotation angle during tightening. The handler's RecordAngleTorqueCurveAsync method streams synchronized torque and angle data throughout the tightening operation and extracts the following characteristics:

• Snug torque -- The torque at which the fastener head seats against the joint surface, identified by the inflection point in the torque-angle curve where the slope increases sharply.
• Elastic clamping region -- The linear portion of the curve between snug torque and yield point, where the relationship between torque and angle is proportional.
• Yield point -- The torque and angle at which the fastener or joint begins to yield plastically, identified by the onset of slope decrease in the torque-angle curve.
• Final torque and angle -- The torque and cumulative angle at the end of the tightening operation.
• Clamp force estimation -- Derived from the torque-angle gradient in the elastic region combined with the known joint geometry and friction coefficients.

Threshold Evaluation

The handler supports configurable torque windows with upper and lower limits for peak torque, final torque, angle, and gradient. Each threshold produces an independent pass/fail evaluation, and the combined result determines the overall joint disposition. Threshold configurations can be stored as named profiles and recalled by part number, enabling automatic test setup when the barcode scanner identifies the assembly.

7. S1 Platform Integration Architecture

The mechanical testing capability follows the same three-layer architecture used throughout S1 Foundry: instrument handlers at the bottom, module abstraction in the middle, and TestStand step types at the top. This section describes how the layers connect and how test programs interact with the mechanical instruments.

Handler Layer

Each handler library implements a specific instrument interface and communicates with the physical instrument through its native protocol. Handler instances are created through the S1 configuration system, which specifies the instrument model, connection string, and any model-specific options. All handlers implement ConnectAsync / DisconnectAsync lifecycle methods and throw InvalidOperationException when operations are attempted on a disconnected instrument.

Handlers support null-transport simulation mode for offline development. In simulation mode, all methods return realistic default values without requiring physical instrument connectivity. This enables test sequence development and validation without the target equipment.

Module Layer

S1.Modules.MechanicalTest implements IHardwareModule and exposes 11 message handlers that cover all five instrument families through a single module endpoint. The 15-vendor factory resolves the correct handler implementation based on the configured instrument model. Message routing is based on the message type, and the module handles connection lifecycle, error recovery, and result formatting.

Message Handlers

8. TestStand Integration

Twelve TestStand step types are organized into five palettes (one per instrument family) plus a combined mechanical test palette that includes all twelve. Test engineers build inspection and material characterization sequences by placing step types into the TestStand sequence editor.

UTM Palette (3 step types)

CMM Palette (3 step types)

Surface Profiler Palette (2 step types)

Hardness Palette (2 step types)

Torque Palette (2 step types)

9. Supported Instruments

S1 Foundry supports 15 instruments across 5 mechanical testing families, spanning 15 vendors. The following table summarizes the complete instrument coverage.

10. Standards Reference

The following standards govern the test methods and data processing implemented by the S1 mechanical testing libraries. The handler implementations enforce the applicable specimen requirements, load ranges, measurement procedures, and reporting formats specified in these documents.

Tensile and Compression

• ASTM E8/E8M -- Standard Test Methods for Tension Testing of Metallic Materials. Defines specimen geometry, grip requirements, crosshead speed ranges, and property calculations for metallic tensile testing.
• ASTM D638 -- Standard Test Method for Tensile Properties of Plastics. Covers specimen types I-V for thermoplastic and thermoset materials.
• ASTM E9 -- Standard Test Methods for Compression Testing of Metallic Materials at Room Temperature.
• ASTM D790 -- Standard Test Methods for Flexural Properties of Unreinforced and Reinforced Plastics. Three-point and four-point bending configurations.

Hardness

• ASTM E18 -- Standard Test Methods for Rockwell Hardness of Metallic Materials. Covers regular and superficial Rockwell scales.
• ISO 6508 -- Metallic materials -- Rockwell hardness test. The international equivalent to ASTM E18 with minor procedural differences.
• ASTM E384 -- Standard Test Method for Microindentation Hardness of Materials. Covers Vickers and Knoop methods at test forces from 1 gf to 1 kgf.
• ISO 6507 -- Metallic materials -- Vickers hardness test. Parts 1-4 covering test method, verification of testing machines, calibration of reference blocks, and tables of hardness values.
• ASTM E10 -- Standard Test Method for Brinell Hardness of Metallic Materials.
• ISO 6506 -- Metallic materials -- Brinell hardness test. International Brinell standard.
• ASTM E140 -- Standard Hardness Conversion Tables for Metals. Relationship among Brinell, Vickers, Rockwell, and Knoop hardness values.
• ISO 4545 -- Metallic materials -- Knoop hardness test.

Surface Metrology

• ISO 4287 -- Geometrical Product Specifications (GPS) -- Surface texture: Profile method -- Terms, definitions and surface texture parameters. Defines Ra, Rq, Rz, Rt, Rsk, Rku, and others.
• ISO 21920 -- GPS -- Surface texture: Profile. The replacement for ISO 4287 in the updated GPS framework, maintaining backward compatibility with traditional roughness parameters.
• ISO 4288 -- GPS -- Surface texture: Profile method -- Rules and procedures for the assessment of surface texture. Defines evaluation length, cutoff selection, and number of sampling lengths.
• ISO 16610-21 -- GPS -- Filtration -- Linear profile filters: Gaussian filters. Specifies the filter algorithm used to separate roughness and waviness components.

Dimensional and GD&T

• ASME Y14.5 -- Dimensioning and Tolerancing. The definitive North American standard for GD&T symbology, datum reference frames, and tolerance zone definitions.
• ISO 1101 -- Geometrical Product Specifications -- Geometrical tolerancing. The international equivalent to ASME Y14.5, with some differences in datum precedence rules and tolerance zone interpretation.

11. Best Practices and Common Pitfalls

Specimen Preparation

• Machine finish consistency. Surface roughness on tensile specimens directly affects measured elongation and reduction-of-area values. Ensure specimen gauge sections are prepared to a consistent finish (typically 0.8 um Ra or better) across all specimens in a batch to avoid introducing measurement variability from specimen preparation rather than material variation.
• Grip alignment. Misalignment in tensile grips introduces bending moments that cause premature failure and artificially low UTS values. Use self-aligning grips or verify alignment with a strain-gauged alignment specimen before running production tests.
• Hardness specimen flatness. Both surfaces of hardness specimens (the test surface and the support surface) must be parallel and flat. Rocking on the anvil during indentation will produce inconsistent readings. Grind or lap specimens to meet ASTM E18 surface preparation requirements.

Measurement Configuration

• Crosshead speed selection. ASTM E8 specifies strain rate ranges for different material types. Running too fast produces artificially high strength values due to strain rate sensitivity; running too slow wastes throughput. Configure the handler's crosshead speed based on the applicable strain rate for the material being tested, not a default value.
• Profilometer cutoff wavelength. The Gaussian cutoff (lambda-c) must be selected based on the expected Ra range per ISO 4288 guidelines. Using an incorrect cutoff shifts roughness into waviness (or vice versa), producing inaccurate Ra values. The handler validates cutoff selection against the measured Ra and issues a warning when the ISO 4288 recommendation is violated.
• CMM probe qualification. Always qualify the probe tip (sphere diameter and stem correction) before running measurements. A stale probe qualification introduces systematic position errors in every measured point. The handler tracks qualification timestamp and can be configured to require re-qualification at a specified interval.
• Torque sensor range selection. Measure within 20-80% of the sensor's rated capacity for optimal accuracy. Operating near the bottom of the range amplifies noise; operating near the top risks overload damage. Select the sensor size to place your expected torque range in the middle of the measurement range.

Common Pitfalls

• Hardness conversion across material families. ASTM E140 conversion tables are validated only for carbon and alloy steels. Applying them to aluminum, titanium, or other non-ferrous materials produces unreliable conversions. Specify the correct hardness scale for the material rather than measuring on one scale and converting.
• Ignoring machine compliance in UTM testing. The crosshead displacement includes both specimen strain and machine frame deflection. For accurate elastic modulus determination, use an extensometer attached directly to the specimen gauge section rather than relying on crosshead displacement. The handler supports extensometer input for all UTM models.
• Insufficient probing points on CMM. Fitting a circle to three points or a plane to three points produces mathematically valid results but has no redundancy to detect outliers. Use at least 6 points for circles, 9 for planes, and 12 for cylinders in production measurement routines. The additional points provide statistical overdetermination and enable outlier detection.
• Profile scan length too short. ISO 4288 requires the evaluation length to contain at least five sampling lengths (cutoff lengths). A scan that is shorter than five times lambda-c cannot produce ISO-compliant roughness parameters. The handler enforces this minimum and rejects scans that are too short.
• Thermal drift during CMM measurement. Temperature changes during a long measurement routine cause both the part and the CMM structure to expand or contract, introducing position errors. Keep the measurement room within the temperature stability range specified by the CMM manufacturer (typically 20 +/- 1 degrees C) and allow parts to thermally soak before measurement.
• Neglecting indentation spacing in hardness traverses. ASTM E384 requires a minimum spacing of 2.5 times the indentation diagonal between adjacent Vickers indentations (3 times for Knoop). Indentations placed too close together are affected by the strain field of neighboring indentations, producing artificially elevated hardness readings. The handler enforces minimum spacing rules based on the measured indentation size.

Data Management

• Retain raw data. Store the complete load-displacement curve, surface profile, and individual probe point coordinates alongside the calculated summary values. Recalculation or reanalysis requires the raw data -- summary statistics alone cannot be reprocessed if a calculation parameter changes.
• Link measurements to material certificates. Each mechanical test result should reference the material heat number, specimen ID, and preparation method. This traceability chain connects the measured properties back to the material source and enables investigation when out-of-spec results occur.
• Calibration status checks. Configure the handler to verify that the instrument's calibration is current before allowing measurements. The handler reads the calibration due date from the instrument (where supported) or from the S1 configuration and blocks operation when calibration has expired.

12. Getting Started

Evaluating the mechanical testing capabilities requires the S1 Foundry platform and access to the target instruments (or their simulation modes for offline development).

Evaluation Steps

1. Download S1 Foundry from the downloads page. The installer includes all mechanical testing handler libraries, the MechanicalTest module, and the TestStand step type packages.
2. Install the TestStand palettes by running the included palette installer. The five mechanical testing palettes appear in the TestStand Insertion Palette after installation.
3. Configure an instrument driver in the S1 module configuration. Specify the instrument family, vendor, model, and connection string (TCP/IP address and port, GPIB address, or COM port).
4. Build a test sequence using the mechanical step types. Start with the example sequences included in the installation, which demonstrate tensile testing, CMM inspection, and hardness measurement patterns.
5. Run in simulation mode if physical equipment is not available. All handlers support null-transport simulation that returns realistic default values for offline sequence development and validation.

Documentation

• S1 Foundry product page -- Full platform overview with module catalog
• Downloads -- Platform installer, module catalog PDF, and technical datasheet