µTS:  Micro Test System

 

受限于可见光波长的衍射极限,光学显微镜分辨率只能达到250nm。而数字图像相关(DIC)技术,则是一种可达到0.1像素位移解析度的功能强大的图像后处理技术。两相结合可获得可见光条件下的分辨率为25nm的2D全场位移数据。通过这种方式,可以在不需要AFM或SEM的情况下进行纳米长度尺度研究。此外,还可发挥光学显微镜快速图像采集的优势。

The wavelength of visible light limits optical microscope resolution to 250 nm. Digital Image Correlation (DIC) is a powerful post-processing technique for resolving feature displacements down to 0.1 pixels. Combining DIC and optical microscopes gives 25 nm resolution of the full 2D displacement field. In this way, nano length scale research can be conducted without the need for an AFM or SEM. Moreover, optical microscopy offers the advantage of fast image acquisition.

 

在光学显微镜下进行材料原位试验的主要挑战是试件的离面运动。要实现25nm位移场分辨率所需的高放大率也意味着景深会很小。几微米的离面运动也足以导致图像失焦。Psylotech的μTS独特的结构设计专门用于限制试验过程中试件的离面位移。使得这一精密仪器非常适合于以下应用:

The primary challenge with in situ materials testing under optical microscopes is out-of-plane specimen deflection. The high magnifications needed to achieve 25 nm displacement field resolution also mean a small depth of field. A few microns out-of-plane motion causes the image to go out of focus. Psylotech's µTS is specifically designed to keep a sample in- plane during testing. The result is a sophisticated instrument well suited for:
 

 

 

 

 

 

连续模型通过多尺度试验验证有限元分析

• 微型试件测试,用以促进材料开发,而所需试件样本数量可以很少

前所未有的多功能性,可用于实现新的实验技术测试

• Continuum Model Validation of finite element analysis through multi-scale testing
• Miniature Sample Testing to facilitate material development where quantities can be low
• Unprecedented Versatility to enable implementation of new experimental techniques testing

 

 

连续模型验证 Continuum Model Validation

 

在有限元分析(FEA)中,为实现合理的计算时间,通过假定材料的机械性能是均匀的,用以限制单元的尺寸Psylotech的μTS是一种可跨越6个尺度量级的验证连续模型工具。通过数字图像相关(DIC)和优化的显微镜光学系统,可在力学性能测试过程保持全场位移分辨率低至0.1像素。这意味着位移场中的分辨率高达25 nm,应变场中的分辨率高达0.01%。

 

以一个复材铺层为例。 通常,FEA假定均匀的各向异性材料行为。 在给定的铺层测试中必须在多个方向上通过实验确定。 如果铺层被修改或基质材料被改变时,应该进行新的测试以重新定义材料特性。 多尺度试验提供了一种工具,可以更好地理解纤维之间以及纤维和基质之间的相互作用。 通过更小尺度的测试数据,可以对任何分层的连续属性进行建模,跳过额外的实验步骤并加快组件开发时间。 此外,更好地理解小尺度相互作用和小尺度失效机制可以从根本上改善材料性能。

In finite element analysis (FEA), material mechanical properties are presumed uniform to limit the size of elements for reasonable computation times. Psylotech's µTS is a tool to validate continuum models over 6 length scales. Through digital image correlation (DIC) and optimized microscope optics, the full displacement field can be monitored down to 0.1 pixel resolution during a mechanical test. This means up to 25 nm resolution in the displacement field and 0.01% resolution in the strain field, depending on camera resolution.
Consider the example of a composite layup. Typically, FEA presumes uniform, anisotropic material behavior. Tests on a given layup must be experimentally determined in multiple directions. If the layup is modified or the matrix material is changed, new tests should be conducted to re-define material properties. Multi-scale testing offers a vehicle to better understand the interaction between fibers as well as between fibers and the matrix. With test data on smaller scales, continuum properties for any layup can be modeled, skipping an extra experimentation step and accelerating component development time. Moreover, better understanding of small scale interactions and small scale failure mechanisms can lead to fundamentally improved materials.

 

 

微试件测试 Miniature Sample Testing

 

In novel materials research and development, sample yields can be too small to produce full scale ASTM samples. Consider the case of high cost nano-particle reinforced composites. Presuming five specimens are tested to produce statistically relevant data, machined dog-bone samples could prove cost prohibitive. With local strain measurement from the DIC, The µTS can perform accurate tests on significantly smaller samples, offering quality data when less material is available for testing.

 

 

前所未有的多功能性 Unprecedented Versatility

 

Psylotech's µTS includes a wide range of features which separate it from any other under-microscope system currently on the market today. These features allow for new possibilities in material testing applications in addition to novel experimental techniques. Some of them include:

1. Large Grip Variety
As a versatile universal testing system, the µTS accommodates many mechanical tests. Grip options include: Arcan, tension, film tension, compression and beam bending. These grips also accommodate fracture mechanics testing.

 

 

2. Ball Screw Servo Actuator
A low friction, direct drive, ball screw actuator facilitates precision motion control, compared to lead screw actuators and covers 8 orders of magnitude in speed. With peak speed performance approaching a standard servohydraulic universal test frame, the µTS is effective for step-load and load control experiments. The system can also operate in cross-head displacement control or motor drive shaft position control.
 
     
3. High Resolution Load Cell
Psylotech uses a capacitive dual range load cell with higher sensitivity compared to strain gauged sensors. With higher sensitivity and a similar signal to noise ratio, the proprietary sensor technology has 100x higher resolution such that a 1600 N cell can offer sub-mN resolution. High resolution reduces the need to install smaller range load cells for low force tests. Keeping the load cell installed improves lab efficiency, eliminating installation and load train realignment time.
 
     
4. High Resolution Cross-head Displacement Sensor
Psylotech uses an inductive displacement sensor for measuring local strains directly at the cross-head. With a range of 25 mm and resolution of 25 nm, this tool allows for very small, controlled moves as close to the specimen as possible. The support posts on either side of the system can be adjusted depending on the gauge length of the specimen. Custom post lengths available upon request.
 
     
5. X-Stage Option
An available X-Stage option makes it possible to keep the area of interest centered within the field of view of the microscope objective throughout the test. This is achieved via the control software which slaves the X- Stage to the moving cross-head by a user adjustable ratio. The µTS mounts directly on top of the X-Stage, all mounting hardware included. The X-Stage is capable of covering the full primary stage travel.
 
     
6. LabVIEW Control Software
Keeping with the theme of giving experimentalists a tool to develop new techniques, Psylotech offers the user access to the LabVIEW source code, including the closed loop control. Advanced users can make adjustments to suit their specific needs or personal preference.
 
     
7. Temperature Chamber
Validating thermomechanical models is accelerated with an optical microscope compatible temperature control module. The chamber allows
-100C to +200C tests with precise and accurate DIC, load and cross-head displacement measurements. Stability is better than .5C and fast ramp speeds cover the entire temperature range in minutes. Liquid nitrogen hookups are integrated with a high flow rate blower that ensures even temperature distribution around the specimen.
 

 

  Specifications  
Force Capacity  100N 1.6kN 4.5kN 10kN
High Res. Resolution  50µN 800µN N/A 5mN
Stroke (mm)  25 40 28 100
Positioning Control (nm)  <5 <5 <5 <5
Minimum Rate (nm/s)  12.5 12.5 5 25
Maximum Rate (mm/s)  100 100 40 140
        Peak Acceleration (m/s²)  10 10 0.6 7
Envelope L×W×H (mm)   220×100×54   300×100×54   180×100×71   650×200×123 
Mass (kg)  2.2 2.5 1.5 23
Control Loop (Hz)  500
Power Requirement  120/240V@50/60Hz

* Custom force capacities and strokes available upon request.
• The µTS includes the load frame, a set of grips, electronics hub and control computer.
• For optimal results, the µTS package is complemented with a high quality microscope, camera and digital image correlation software (see below)